JP2010205613A - Light guide plate, backlight device, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate and a backlight device using the light guide plate capable of illuminating the whole face of a liquid crystal display face even in the case a distance between a point light source and the liquid crystal display face is made smaller in the backlight device having the side light type point light source and its light guide plate. <P>SOLUTION: One part of light incident to the light guide plate 100 is reflected on a reflecting face 131, returned to an incident light face 110, reflected further on a face to form a notch part 115 and the other incident light face 110, and proceeds in a direction to enter a curved cylindrical lens 123. The light to enter the curved cylindrical lens 123 proceeds bent so as to become to have a direction perpendicular to the light incident face. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide plate, a backlight device, and a liquid crystal display device, and more specifically, a light guide plate used in a liquid crystal display device using a point light source as a light source, and a backlight device and a liquid crystal display device using the light guide plate. About.

  Liquid crystal display devices are widely used as display devices for information communication terminals such as computers and television receivers. A liquid crystal display device is a device that controls the image to be displayed by changing the degree of light transmission by changing the orientation of liquid crystal molecules. Since the liquid crystal itself does not emit light, the liquid crystal display surface is illuminated from the back side. Therefore, there are a reflective type that reflects sunlight and indoor light and a lighting type device called a backlight. As the backlight type of lighting, there are mainly known a direct light type having a light source on the back side of the liquid crystal display surface and a side light type that illuminates the liquid crystal display surface by reflecting light illuminated from the side. Yes. In addition, a cold cathode fluorescent tube is generally used as the light source of the backlight, but in recent mobile communication terminal devices such as mobile phones and liquid crystal display devices used in car navigation devices, miniaturization and power saving are achieved. Therefore, LEDs (light emitting diodes) have been used as light sources (see Patent Document 1).

  FIG. 16 is a diagram schematically showing a cross section in the horizontal direction in a typical example of a conventional sidelight type backlight device. As shown in this figure, the backlight device 600 is emitted from a light source 601 using LEDs, a light guide plate 602 formed in a plate shape with a translucent resin, and the like, and a lower surface of the light guide plate 602. A reflection sheet 603 that reflects light back into the light guide plate 602, a diffusion sheet 604 that diffuses light emitted from the upper surface of the light guide plate 602, and a direction of light diffused by the diffusion sheet in a direction perpendicular to the liquid crystal display surface And two prism sheets 605 and 606 for refraction. Further, the light guide plate is generally provided with a reflecting / scattering member such as a groove for reflecting light, a projection, or a printed material on the lower surface of the light guide plate. In this figure, a V-shaped groove 607 is formed. .

  The light emitted from the light source 601 enters the light guide plate 602, for example, as indicated by the arrows in the figure, repeats total reflection on the lower and upper surfaces of the light guide plate 602, and is reflected by the V-shaped groove 607. Thus, the light is emitted from the upper surface of the light guide plate 602. The light emitted from the light guide plate 602 is diffused by the diffusion sheet 604, and the light direction is adjusted by the prism sheets 605 and 606, and then further proceeds to the upper liquid crystal display surface.

JP 2002-184225 A

  The backlight device as described above is widely used for illuminating the entire liquid crystal display surface. Here, when a point light source such as an LED is used, as shown in the top partial view schematically showing the light spreading from the light source in FIG. 17 into the light guide plate 602, the light is separated from the light source. Therefore, in a region closer to the light source than the distance L in the drawing, a dark portion as shown by the oblique lines appears between the light sources and the brightness is not uniform. Therefore, when used as illumination for a liquid crystal display screen, the distance from the point light source to the light output region 610 for emitting light from the light guide plate needs to be larger than this distance L, and it is difficult to reduce the size of the backlight device. I was doing something.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the distance between a point light source and a light output region in a backlight device having a side light type point light source and a light guide plate thereof.

  The light guide plate of the present invention is a light guide plate used in a liquid crystal display device using a point light source as a light source, and has a light output surface having a light output region for emitting light used for display, and one side surface with respect to the light output surface. A light incident surface having a light source arrangement area where the point light source is arranged, and a part of the light incident from the light incident surface before entering the light exit area, on the light incident surface side. It is a light guide plate provided with the reflective surface to reflect.

  Here, the point light source means an LED light source or the like. In addition, the light exit area means an area that emits light toward the liquid crystal display screen. The light exit surface means a surface facing the liquid crystal display surface of the light guide plate, and is not limited to a flat surface. The light incident surface being one side surface of the light exit surface means a side light type.

  In the light guide plate of the present invention, the reflection surface may be formed by a non-through hole that opens toward the light exit surface.

  In the light guide plate of the present invention, the cross-sectional shape of the surface parallel to the light exit surface in the non-through hole may be a rectangle.

  In the light guide plate of the present invention, in the non-through hole, a part of the cross-sectional shape of the surface parallel to the light exit surface may be formed by an arc.

  In the light guide plate of the present invention, the non-through hole may have a taper that widens toward the light exit surface.

  In the light guide plate of the present invention, the reflection surface may be formed by a groove extending in parallel with the light incident surface on the light exit surface.

  In the light guide plate of the present invention, the light incident surface may have a reflective notch formed at a portion different from the light source arrangement region by a surface perpendicular to the light exit surface. Further, the light guide plate may be formed such that a plurality of the reflection notches are continuously formed. Furthermore, the reflection surface may be formed in a region extending in a direction perpendicular to the light incident surface from between the notch and the light source arrangement region.

  In the light guide plate of the present invention, a plurality of cylindrical lenses extending in a direction perpendicular to the light exit surface are continuously formed on the light incident surface in a portion different from the light source arrangement region. Can do.

  In the light guide plate of the present invention, the light exit surface extends in a direction perpendicular to the light entrance surface so as to cover the light exit region from a position between the position of the reflection surface and the light exit region. It is formed by a plurality of cylindrical lenses, and one of the plurality of cylindrical lenses is curved in a direction toward a light source arrangement surface on which the point light source of the light incident surface is arranged. Can do.

  In the light guide plate of the present invention, the light exit surface extends in a direction perpendicular to the light entrance surface so as to cover the light exit region from a position between the position of the reflection surface and the light exit region. The central angle of the circular arc of one of the plurality of cylindrical lenses is larger than the central angle of the circular arc of the other cylindrical lens in the vicinity of the light incident surface. , And can be.

  Moreover, the backlight apparatus of this invention is a backlight apparatus provided with the light guide plate in any one of the light guide plate of this invention mentioned above. Here, the backlight device covers the light guide plate except the light incident surface having the light source arrangement region where the point light source is arranged, and covers the light incident surface other than the light source arrangement region around the light guide plate. It may be further provided with a mold having a convex portion.

  Moreover, the liquid crystal display device of this invention is a liquid crystal display device provided with the light guide plate in any one of the light guide plate of this invention mentioned above. Here, the liquid crystal display device covers the light guide plate except the light incident surface having the light source arrangement region where the point light source is arranged, and covers the light incident surface other than the light source arrangement region around the light guide plate. It may be further provided with a mold having a convex portion.

1 is an overall perspective view of a light guide plate according to a first embodiment of the present invention. It is a partial top view of the light guide plate of FIG. It is a fragmentary sectional view which shows a part of cross section among the cross sections in line AA of FIG. It is a fragmentary sectional view which shows a part of cross section among the cross sections in line BB of FIG. It is a perspective view of a mold. 1 is a diagram schematically showing a configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the horizontal cross section of the liquid crystal display device which concerns on 1st embodiment of this invention. It is a partial top view of the light-guide plate which concerns on the 1st modification of 1st embodiment. It is a fragmentary sectional view of the light-guide plate which concerns on the 2nd modification of 1st embodiment. It is a partial top view of the light-guide plate which concerns on 2nd embodiment of this invention. It is a partial top view of the light-guide plate which concerns on the 1st modification of 2nd embodiment. It is a partial top view of the light-guide plate which concerns on the 2nd modification of 2nd embodiment. It is a fragmentary sectional view which shows a part of cross section among the cross sections in line CC of FIG. It is a partial top view of the light-guide plate which concerns on 3rd embodiment of this invention. It is a partial top view of the light-guide plate which concerns on 4th embodiment of this invention. FIG. 15 is a partial cross-sectional view showing a part of the cross section taken along line DD in FIG. 14. It is a figure which shows roughly the cross section of the horizontal direction of the conventional sidelight type backlight apparatus. It is the upper surface partial view which represented a mode that the light spreads in a light-guide plate from a light source typically.

  Hereinafter, first to fourth embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

  A light guide plate and a backlight device and a liquid crystal display device using the light guide plate according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 6B. FIG. 1 is an overall perspective view of a light guide plate 100 according to the first embodiment of the present invention. The light guide plate 100 is plate-shaped, has a thickness of 0.2 to 1.0 mm, and is integrally formed of a light transmissive member such as acrylic or polycarbonate. As shown in this figure, a light incident surface 110 on which light from an LED light source is incident includes three LED light source installation areas 111 for installing three LED light sources, and a rectangular hole 130 described later. And two cutout portions 115 for further reflecting the light reflected by the reflecting surface 131.

  The upper surface, which is the light exit surface 120 from which the light is emitted, is incident on the cylindrical lens portion 121 that guides the light incident from the light incident surface 110 further inside the light guide plate 100 and refracts the light at the time of light exit. A rectangular hole 130 having a reflection surface 131 that reflects a part of the light and returns it to the incident surface side such as the notch 115, and the height is adjusted to the height of the LED light source, and the light incident from the LED light source is guided to the light guide plate 100. And an inclined surface 122 that leads to the cylindrical lens part 121. Although not shown, the lower surface is provided with reflective dots provided by printing to reflect light reflected from the lower surface at an angle at which the light can be emitted from the upper surface.

  FIG. 2 shows a partial top view of the light guide plate 100 shown in FIG. In this figure, the LED light source 60 installed in the LED light source installation region 111 is indicated by a two-dot chain line. As shown in the figure, the cylindrical lens 123 in the vicinity of the opposite side of the notch 115 is curved in the direction toward the left and right LED light sources 60 in the vicinity of the light incident surface 110. This makes it easy for the light reflected by the reflecting surface 131 of the rectangular hole 130 to enter the cylindrical lens 123 when the light is reflected by the light incident surface 110 and returns to the vertical direction with respect to the light incident surface 110. It plays a role.

  Here, the traveling direction of the light emitted from the LED light source 60 will be described. As indicated by the arrows in the figure, a part of the light incident on the light guide plate 100 is reflected by the reflecting surface 131 and is incident on the light incident surface 110. The light is returned and further reflected by the surface forming the notch 115 and the other light incident surface 110, and proceeds in the direction of entering the curved cylindrical lens 123. The light that has entered the curved cylindrical lens 123 travels while being bent so as to be perpendicular to the light incident surface. Therefore, light can be guided to the vicinity of the light incident surface 110 between the two LED light sources 60, thereby reducing the distance between the LED light source 60 and the light output region 140.

  FIG. 3 is a partial cross-sectional view showing a part of the cross section taken along line AA in FIG. As shown in the figure, the rectangular hole 130 is a non-through hole, and the depth is set to 0.8D, which is 80% of the plate thickness. This is to prevent the back side portion of the rectangular hole 130 from becoming dark by allowing light to pass through the remaining 0.2D thickness portion.

  FIG. 4 is a partial cross-sectional view showing a part of the cross section taken along line BB in FIG. As shown in the figure, the cross section of the cylindrical lens portion 121 has a shape in which a plurality of cylindrical lenses having a circular arc shape whose upper surface is convex upward are arranged.

  FIG. 5 shows the shape of the mold 150 that covers the side surface when the light guide plate 100 is incorporated into the backlight device. A resin such as white polycarbonate is used as the material of the mold. Light emitted from the side surface of the light guide plate 100 is reflected by the mold and returned to the light guide plate 100. The mold 150 includes a convex portion 151 at a portion where the LED light source 60 is not disposed at a portion that contacts the light incident surface 110 of the light guide plate 100, and is reflected by the reflective surface 131 of the rectangular hole 130. The light emitted from 110 is further returned to the light guide plate 100.

  FIG. 6A is a diagram schematically showing the configuration of the liquid crystal display device 900 according to the first embodiment of the present invention. As shown in this figure, the liquid crystal display device 900 includes a liquid crystal panel 800, a backlight device 180, and a control circuit 842. Here, the control circuit 842 is mounted on the flexible substrate 840, and controls the display of the liquid crystal panel 800 via the control line 854 and controls the LED light source 60 via the control line 855.

  On the other hand, the liquid crystal panel 800 includes two substrates, a TFT substrate 830 and a color filter substrate 820, and a liquid crystal composition is sealed between these substrates. The TFT substrate 830 is provided with a gate signal line 837 controlled by a drive circuit 832 and a drain signal line 835 controlled by the drive circuit 833, and these signal lines are cells that function as one pixel of a liquid crystal display device. 810 is formed.

  Here, a region surrounded by a two-dot chain line in FIG. 6A indicates a display region 815. Note that the liquid crystal panel 800 includes a number of cells 810 corresponding to the display resolution, but is simplified in FIG. 6A. The liquid crystal panel 800 includes an IPS (In Plane Switching) method in which electrodes are provided only on the TFT substrate 830, and a TN (Twisted Nematic) in which electrodes are provided on both the TFT substrate 830 and the color filter substrate 820. Any of a method and a VA (Vertical Alignment) method may be used.

  The backlight device 180 includes the light guide plate 100 in FIG. 1, the mold 150 in FIG. 5, the LED light source 60, and a flexible substrate 845 to which the LED light source 60 is attached. By adopting such a configuration of the backlight device 180, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 6B is a diagram showing a transverse cross section of the liquid crystal display device 900 according to the first embodiment of the present invention. As shown in this figure, in addition to the configuration shown in FIG. 6A, the liquid crystal display device 900 has a diffusion sheet 904 that uniformly diffuses the light emitted from the light guide plate 100, and the direction of the diffused light. Prism sheets 905 and 906 to be arranged, and polarizing plates 908 and 909 that allow light in only one direction to pass through are provided. By adopting such a configuration for the liquid crystal display device 900, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 7 is a partial top view of a light guide plate 200 according to a first modification of the first embodiment described above. As shown in this figure, the cylindrical lens portion 125 of the light guide plate 200 has a cylindrical lens 127 that is curved not only near the opposite side of the notch 115 but also near the back side of the rectangular hole 130. Even in such a configuration, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 8 is a partial cross-sectional view of a light guide plate 250 according to a second modification of the first embodiment described above. This partial sectional view is based on the same field of view as FIG. As shown in this figure, the light guide plate 250 includes a rectangular hole 135 including a reflective surface 136 provided on the inclined surface 122 instead of the rectangular hole 130 of the light guide plate 100. Even in such a configuration, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 9 is a partial top view of the light guide plate 310 according to the second embodiment of the present invention. As shown in this figure, the light guide plate 310 includes a cut surface 312 having a plurality of fine cutouts instead of the cutout portions 115 of the lightguide plate 100, and an LED instead of the inclined surface 122 of the lightguide plate 100. An inclined surface 315 provided only on the display area side of the light source installation area 111 is provided. Further, a cylindrical lens portion 317 that does not have the curved cylindrical lens 123 is provided. Other configurations are the same as those of the light guide plate 100.

  Even in such a configuration, as indicated by the arrows in the figure, the light reflected by the reflecting surface 131 of the rectangular hole 130 is reflected by the notch surface 312 and returned to the light guide plate. Light can be guided to the vicinity of the light incident surface 110 between the two. Therefore, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 10 is a partial top view of the light guide plate 320 according to the first modification of the second embodiment described above. As shown in the figure, the light guide plate 320 includes a groove 321 having a reflective surface 322 parallel to the light incident surface 110 instead of the rectangular hole 130 of the light guide plate 310. Even in such a configuration, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 11 is a partial top view of a light guide plate 330 according to a second modification of the second embodiment described above. As shown in the figure, the cylindrical lens portion 331 of the light guide plate 330 has an angled lens portion in the vicinity of the opposite side of the notch surface 312 where the central angle of the circular arc of the cylindrical lens is larger than the central angle of the surrounding cylindrical lenses. 332.

  12 is a partial cross-sectional view showing a part of the cross section taken along line CC of FIG. As shown in the drawing, a contact angle R2 that is an angle with the light output plane of the angled lens portion 332 is larger than a contact angle R1 of the surrounding cylindrical lens. That is, this means that the central angle of the circular arc of the cylindrical lens of the angled lens portion 332 is larger than the central angle of the circular arcs of the other cylindrical lenses. Here, in this modification, R1 is 45 ° and R2 is 70 °. Thus, when light is emitted from the angled lens unit 332, a component parallel to the incident surface (a horizontal component in the drawing) can be reduced.

  FIG. 13 is a partial top view of a light guide plate 400 according to the third embodiment of the present invention. As shown in the figure, the light guide plate 400 includes a cylindrical lens reflecting portion 405 instead of the notch surface 312 of the light guide plate 310. Even in such a configuration, the distance between the LED light source 60 and the light output region 140 can be reduced.

  FIG. 14 is a partial top view of a light guide plate 500 according to the fourth embodiment of the present invention. As shown in the figure, the light guide plate 500 includes a semicircular hole 502 that is a substantially semicircular hole having a reflecting surface 501 instead of the rectangular hole 130. By doing in this way, since the thickness of a hole becomes large, the intensity | strength of the hole formation part of the metal mold | die used in the case of light-guide plate manufacture can be raised. Also, in the manufactured light guide plate 500, since the thickness of the hole is increased, the amount of light hitting from the side of the hole is increased, but by making it substantially semicircular, the light hitting from the side is minimized. Can be.

  FIG. 15 is a partial cross-sectional view showing a part of the cross section taken along line DD in FIG. As shown in this figure, the semicircular hole 502 has a taper that widens toward the light exit surface. Thereby, the hole formation part of the metal mold | die used in the case of light-guide plate manufacture can be easily extracted from a metal mold | die. Even in the configuration of the light guide plate 500, the distance between the LED light source 60 and the light output region 140 can be reduced.

  As described above, in any of the above-described embodiments, the distance between the LED light source 60 and the light output region 140 can be reduced in the backlight device having the sidelight type point light source and the light guide plate thereof.

  In the above-described plurality of embodiments, some combinations of the rectangular hole / semicircular hole, the cutout part / the notch surface / the cylindrical lens reflection part, the curved cylindrical lens / angled lens part, and the like are shown. These may be combined in any way.

  In the above-described embodiments, three LED light sources, two notches, four rectangular holes, and the like have been shown as examples, but these numbers may increase or decrease. Even if it does, it does not change the technical idea of the present invention.

  In the above embodiments, the point light source is an LED, but the present invention can be applied to other point light sources that are not LEDs.

  In the above embodiments, the hole having the reflecting surface has a depth of 80% of the plate thickness, but the depth of the hole or groove may be any other depth. It may be a hole or groove opened on the lower surface side opposite to the surface, or may be a through hole.

  60 LED light source, 100, 200, 250, 310, 320, 330, 400, 500 Light guide plate, 110 light entrance surface, 111 LED light source installation area, 115 notch, 120 light exit surface, 121, 125, 317, 331 cylindrical lens Part, 123, 127 curved cylindrical lens, 122, 315 inclined surface, 130, 135 rectangular hole, 131, 136, 322, 501 reflecting surface, 140 light emission region, 150 mold, 151 convex part, 180 backlight device, 312 step Surface, 321 groove, 332 angled lens, 405 cylindrical lens reflector, 502 semicircular hole, 800 liquid crystal panel, 810 cell, 815 display area, 820 color filter substrate, 830 TFT substrate, 840, 845 flexible substrate, 832, 83 3 driving circuit, 835 drain signal line, 837 gate signal line, 842 control circuit, 854, 855 control line, 900 liquid crystal display device, 904 diffusion sheet, 905, 906 prism sheet, 908, 909 polarizing plate.

Claims (16)

A light guide plate used in a liquid crystal display device using a point light source as a light source,
A light exit surface having a light exit area for emitting light used for display;
A light incident surface that is a side surface with respect to the light exit surface and has a light source arrangement region in which the point light source is arranged;
A light guide plate comprising: a reflection surface configured to reflect a part of light incident from the light incident surface toward the light incident surface before entering a part of the light exit region.   The light guide plate according to claim 1, wherein the reflection surface is formed by a non-through hole that opens toward the light exit surface.   The light guide plate according to claim 2, wherein in the non-through hole, a cross-sectional shape of a surface parallel to the light exit surface is a rectangle.   3. The light guide plate according to claim 2, wherein in the non-through hole, a part of a cross-sectional shape of a surface parallel to the light exit surface is formed by an arc.   The light guide plate according to claim 2, wherein the non-through hole has a taper that widens toward the light exit surface.   The light guide plate according to claim 1, wherein the reflection surface is formed by a groove extending in parallel with the light incident surface on the light exit surface.   2. The light guide plate according to claim 1, wherein the light incident surface has a notch for reflection formed in a portion different from the light source arrangement region by a surface perpendicular to the light output surface.   The light guide plate according to claim 7, wherein a plurality of the cutouts for reflection are continuously formed.   The light guide plate according to claim 7, wherein the reflection surface is formed in a region extending in a direction perpendicular to the light incident surface from between the notch and the light source arrangement region.   2. The guide according to claim 1, wherein a plurality of cylindrical lenses extending in a direction perpendicular to the light exit surface are continuously formed on a portion different from the light source arrangement region on the light entrance surface. Light board. The light exit surface is formed by a plurality of cylindrical lenses extending from the position between the reflection surface and the light exit region in a direction perpendicular to the light entrance surface so as to cover the light exit region,
2. The cylindrical lens according to claim 1, wherein any one of the plurality of cylindrical lenses is curved in a direction toward a light source arrangement surface on which the point light source of the light incident surface is arranged. Light guide plate. The light exit surface is formed by a plurality of cylindrical lenses extending from the position between the reflection surface and the light exit region in a direction perpendicular to the light entrance surface so as to cover the light exit region,
The center angle of an arc of any one of the plurality of cylindrical lenses is larger than the center angle of an arc of another cylindrical lens in the vicinity of the light incident surface. The light guide plate according to 1.   A backlight apparatus provided with the light-guide plate as described in any one of Claims 1-12.   A mold having a convex portion for covering the light incident surface other than the light source arrangement region and covering the light guide plate except the light incident surface having the light source arrangement region around which the point light source is arranged is further provided. The backlight device according to claim 13.   A liquid crystal display device provided with the light-guide plate as described in any one of Claims 1-12.   A mold having a convex portion for covering the light incident surface other than the light source arrangement region and covering the light guide plate except the light incident surface having the light source arrangement region around which the point light source is arranged is further provided. The liquid crystal display device according to claim 15.

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