JP2007128788A - Backlight unit and display equipment having same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a backlight unit by reducing the number of light sources and reducing the size of a light guide plate. <P>SOLUTION: At least one cutout section 12a is provided between a side center section 12c of the light guide plate 12 and a corner section 12e in the backlight unit of a display, and a light source 13 comprising LEDs is arranged at the cutout section 12a. The light incidence surface of the light of a light source at the cutout section 12a is inclined toward an orthogonal line 12d passing through the corner section 12e, and the inclination angle is increased toward the corner section 12e. The shape of the cutout section 12a is formed to be in an L cutout shape or a cut-down shape of the corner section 12e. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a backlight unit of a display device or a display device including a backlight unit, and particularly relates to minimization of the size of the backlight unit.

  Liquid crystal display devices have been widely used in personal computers, liquid crystal televisions, electronic notebooks, mobile phones, and other terminal display devices. In order to display a display image of the liquid crystal display device brightly and clearly, a backlight unit is provided on the lower surface side of the liquid crystal display panel. One of the conventional structures of this backlight unit is the structure shown in FIGS. Hereinafter, the structure of a conventional backlight unit will be described with reference to FIGS. 6 shows a cross-sectional view of the main part of a liquid crystal display device according to the prior art, and FIG. 7 shows an explanatory view for explaining the size of the light guide plate according to the number of light sources arranged in FIG.

  The backlight unit 8 shown in FIG. 6 is disposed and used on the lower surface side of the liquid crystal display panel 1, and the backlight unit 8 and the liquid crystal display panel 1 constitute a liquid crystal display device 10. The backlight unit 8 includes a light guide plate 2, an LED light source 3 disposed on one side of the light guide plate 2, a light diffusion sheet 4 disposed on the upper surface side of the light guide plate 2, and the light diffusion sheet 4. The first prism sheet 5 and the second prism sheet 6 provided on the upper side, and a reflection plate 7 provided on the lower surface side of the light guide plate 2. Here, the first prism sheet 5 and the second prism sheet 6 are striped prism sheets formed by connecting triangular prisms in a straight line and parallel to each other, and the first prism sheet 5 and the second prism sheet 6. Is used by stacking stripe prisms in a state of being orthogonal to each other.

  The operation of the backlight unit 8 having the above-described configuration is as follows. The light emitted from the light source 3 that is an LED is taken into the light guide plate 2 from the side surface of the light guide plate 2, and receives the action of the reflecting means provided on the lower surface of the light guide plate 2 toward the diffusion sheet 4 from the upper surface of the light guide plate 2. Exit. The light diffusing sheet 4 diffuses the incident light to make a uniform light quantity distribution state and radiates it toward the first prism sheet 5 and the second prism sheet 6. In the first prism sheet 5 and the second prism sheet 6, the diffused light is converted into vertical light and emitted toward the liquid crystal display panel 1. Further, the light that passes through the reflecting means provided on the lower surface of the light guide plate 2 and is emitted below the light guide plate 2 is reflected by the reflection plate 7 and enters the light guide plate 2 again. In this way, the light of the light source 3 is effectively used to illuminate the display image of the liquid crystal display panel 1 brightly.

  Here, the light source 3 that is an LED is disposed close to one side surface of the light guide plate 2. 7A, one light source 3 is disposed at the center of the side surface of the light guide plate 2, and FIG. 7B is a state where two light sources 3 are disposed on the side surface of the light guide plate 2. FIG. Is shown. Although an LED is used as the light source 3, the angle of the radiation region is limited because the LED has a directivity of light emission. That is, when the angle of the radiation region is called a directivity angle, the LED has a limited directivity angle. In FIG. 7A, if the light guide plate 2 is large, the entire light guide plate 2 cannot be covered due to the limited directivity angle, and light is not reachable in regions outside the directivity angle and the luminance is low. A shadow 2f appears. The dark shadow portion 2f looks very bad because the luminance is remarkably different from that in the region of high directivity angle. In order to obtain a width W that can be effectively used except for the shadow portion 2f, it is necessary to make the width W1 of the light guide plate 2 wide. On the other hand, as shown in FIG. 7B, in the case where two light sources 3 are arranged, the width of the light guide plate 2 is slightly widened in order to obtain a width W that can be effectively used except for the shadow portion 2f. The required width W2 is sufficient. That is, the relationship of the width W1 of the light guide plate 2 when one light source 3 is disposed> the width W2 of the light guide plate 2 when two light sources 3 are disposed. It is necessary to increase the number of light sources 3 in order to widen a bright area by reducing the area of the shadow portion 2 f without increasing the width of the light guide plate 2.

  However, the structure in which the light source 3 is disposed on one side surface of the light guide plate 2 requires an increase in the number of light sources 3 that are LEDs according to the size of the light guide plate 2. Will bring up. In addition, since the light source 3 is disposed on the side surface of the light guide plate 2, a space for the light source 3 is required, and the overall size of the backlight unit is increased.

  The present invention has been made in view of the above-described problems, and aims to reduce the number of light sources without lowering the luminance and to minimize the size of the backlight unit.

  As a means for solving the above-described problems, the backlight unit of the present invention is characterized in that the backlight unit includes a rectangular light guide plate and a light source provided on the lower surface side of the display panel. At least one notch portion is provided between the corner portion and the corner portion, and the light source is disposed in the notch portion.

  The backlight unit of the present invention is characterized in that the light incident surface of the light source in the cutout portion is inclined so as to face a diagonal direction passing through the corner portion.

  The backlight unit according to the present invention is characterized in that the inclination of the light incident surface of the notch is such that the inclination angle increases as approaching the corner.

  The backlight unit according to the present invention is characterized in that the notch has an L-shaped notch shape.

  In addition, the backlight unit of the present invention is characterized in that the notch provided in the corner has a shape obtained by cutting off the corner or an L-shaped notch.

  Further, the backlight unit of the present invention is characterized in that the light source is disposed in such a manner as to be embedded in the notch.

  The backlight unit of the present invention is characterized in that the light source is an LED.

  Further, the display device of the present invention is characterized in that in the display device having a backlight unit on the lower surface side of the display panel, the backlight unit uses the backlight unit having the features of the above invention and uses the number of light sources. In addition to reducing the size, the size of the backlight unit is reduced.

  As an effect of the invention, in the configuration of the backlight unit of the present invention, a notch portion is provided between the side center portion of the light guide plate and the corner portion, and a light source is provided in the notch portion. Further, the light entrance surface of the notch is inclined so as to be directed in the direction of a diagonal line passing through the corner, and the inclination angle increases as the angle approaches the corner. With such a configuration, when using a light source having directional characteristics to the radiated light, if the light incident surface is inclined so as to be directed in a diagonal direction passing through the corner, a wide area of the light guide plate is obtained. When the light source is within the directivity angle (referred to as the angle within the directivity area), and the inclination angle of the light entrance surface is increased from the center of the side toward the corner, the light entrance surface is constantly increased. It faces the direction of the diagonal line, and a wide area of the light guide plate is accommodated in the directivity angle of the light source. In this configuration, the light source is disposed at a position shifted in the direction of the corner of the light guide plate, and the entire light guide plate is illuminated from the oblique direction of the light guide plate. When a light source having directional characteristics for radiated light is used, if the entire light guide plate is illuminated from an oblique direction of the light guide plate, a wide area of the light guide plate can be accommodated within the directivity angle of the light source. As a result, the area in which the shadow portion outside the directivity angle appears appears very small, and the effective area that can be used by illuminating a wide area of the light guide plate with a small number of light sources can be widened.

  In addition, when the notch portion has an L-shaped notch shape, the processability is easy and the light guide plate can be easily manufactured.

  Moreover, the notch part provided in a corner part takes the shape which cut off the corner part, or the L-shaped notch shape. In any case, since the workability is easy, the light guide plate can be easily manufactured. In addition, the shape with the corners cut off provides a wide space at the corners, which is convenient for adjusting the position of the light source.

  In addition, since the light source is disposed in a notch portion so that the light source is accommodated in the size of the light guide plate, the backlight unit itself has the same size as the light guide plate. Can be combined into a compact and compact backlight unit. In addition, in terms of transportation and assembly, the unit has no irregularities in its outer shape, so that it is easy to handle.

  Further, by using the LED as the light source, the backlight unit can be reduced in size and the manufacturing cost can be reduced because it is small in size and low in cost. In addition, since it can be driven at a low voltage, the power consumption can be reduced and the life can be extended.

  By using a backlight unit with the above effects in the display device, the number of light sources is reduced and it is economical, and the display device combined with the display panel can be downsized by a compact and compact backlight unit. It becomes possible.

  Hereinafter, the best mode for carrying out the present invention will be described. First, the backlight unit according to the first embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 shows a side view of a display device including a backlight unit according to the first embodiment of the present invention. 2 is a plan view showing the arrangement of the light guide plate and the light source of the backlight unit in FIG. 1, and FIG. 3 is an enlarged view of a portion A in FIG.

  As shown in FIG. 1, the display device 20 includes a backlight unit 18 on the lower surface side of the display panel 11 and is used as a display device for a display device. The display panel 11 is a liquid crystal display panel in which liquid crystal is sealed in upper and lower transparent substrates. The backlight unit 18 includes a light guide plate 12, a light source 13 that is an LED disposed near a corner of the light guide plate, a light diffusion sheet 14 disposed on the upper surface side of the light guide plate 12, and the light diffusion sheet 14 The first prism sheet 15 and the second prism sheet 16 provided on the light guide plate 12, and the reflection plate 17 provided on the lower surface side of the light guide plate 12. Here, the first prism sheet 15 and the second prism sheet 16 are striped prism sheets formed by connecting triangular prisms in a straight line and parallel to each other, and the first prism sheet 15 and the second prism sheet 16. Is used in such a manner that striped prisms are arranged in a state of being orthogonal to each other and stacked.

  As shown in FIG. 2, the light guide plate 12 is provided with a notch 12a cut out in an L shape near the corner 12e, and a light source 13 serving as an LED is embedded in the notch 12a. It is arranged in a state. Here, 12f indicated by hatching indicates a dark portion having a poor appearance, and since the LED of the light source 13 has directivity characteristics, the light emission directivity angle (referred to as an angle within the directivity region) is used. It refers to the part where the light falls off and the light is low, the brightness is low, and it becomes dark. The brightness is lower than that in the area of high directivity angle, and it looks dark because it is dark. Moreover, 12c shown with the dashed-dotted line has pointed the side center part of the light-guide plate 12 by the side which arrange | positions the light source 13. As shown in FIG. Moreover, 12d shown with the dashed-two dotted line has shown the diagonal line connected with the corner | angular part 12e.

  The notch 12a in the first embodiment is provided at a position very close to the corner 12e. As shown in FIG. 3, the notch 12a has an L-shaped notch shape having sides 12g1 and 12g2 due to the notches. The side 12g1 is a light incident surface of the light source 13. Although not shown, the light incident from the light incident surface of the side 12g1 is guided deeply into the light guide plate 12 through a reflecting means such as a circular prism provided on the lower surface of the light guide plate 12, and The light is emitted from the upper surface toward the light diffusion sheet 14.

  The side 12g1 serving as the light incident surface of the light source 13 is provided with an inclination angle θ so as to be directed in the direction of a diagonal line 12d connected to the corner portion 12e. Since the position of the diagonal line 12d has the longest distance of the light guide plate 12 and hits a part having a large area, in order to illuminate the widest part greatly, the light incident surface is provided so as to face the direction of the diagonal line 12d. Yes. With such a configuration, it is possible to illuminate a wide area of the light guide plate with one light source.

  In the first embodiment, the notch 12a is provided at a position close to the corner 12e. However, in the present invention, the notch 12a is provided between the side center 12c and the corner 12e. And it forms with an inclination so that a light-receiving surface may face the direction of the diagonal 12d. When the cutout portion 12a is close to the side center portion 12c, the inclination angle θ is reduced, and when the cutout portion 12a is at the corner portion 12e, the inclination angle θ is increased. In this way, the area of the diagonal line 12d is sufficiently accommodated in the area of the directivity angle of the light source 13, and a wide area of the light guide plate 12 can be illuminated.

  By adopting such a configuration, as shown in FIG. 2, the area of the shadow portion 12f indicated by diagonal lines becomes very small, and an effective area with high brightness can be taken very wide. Therefore, it is not necessary to make the light guide plate 12 so large and can be made small.

  Further, since the light guide plate 12 can be made small and the light source 13 is disposed in such a manner as to be embedded in the notch 12a, the size including the light source 13 can be made small. This can make the backlight unit 18 itself small. Therefore, in the display device provided with the backlight unit 18 of the present invention, a small and compact display device 20 can be obtained, and a brightly illuminated display can be seen. In addition, the display device can be downsized. Further, since the number of light sources 13 to be used is reduced, an effect of cost reduction is also produced.

  The light guide plate 12 having such a shape is formed by an injection molding method using a resin such as transparent polycarbonate with the notch 12a provided. The sides 12g1 and 12g2 of the notch 12a are finished to have a glossy surface by transfer from a mold formed on a mirror surface. Since the notch 12a is L-shaped, it is easy to mold. Although not shown, reflecting means such as a circular prism is provided on the lower surface of the light guide plate 12, which is also formed by a transfer method from a mold. The resin used for the light guide plate 12 is not limited to polycarbonate resin, and a resin excellent in heat resistance, moisture resistance, impact resistance, and chemical resistance can be used. For example, examples of such a resin include a polyimide resin, a polyethylene resin, a polyethylene terephthalate resin, and an acrylic resin.

  An LED is used as the light source 13. Small size, high brightness, and low cost. In addition, since it is driven at a low voltage, power consumption can be reduced. It is effective in reducing the size of the backlight unit and can achieve a long life.

  As the light diffusing sheet 14, a resin sheet in which light diffusing particles such as silica particles are dispersed, a resin sheet having fine irregularities on the surface, or the like is used. Transmits light and functions to diffuse light.

  The first prism sheet 15 and the second prism sheet 16 are striped prism sheets formed by connecting triangular prisms in a straight line and in parallel. The first prism sheet 15 and the second prism sheet 16 are formed by stacking stripe-shaped prisms so as to be orthogonal to each other, and are made of the same member. The light diffused in a uniform state by the light diffusing sheet 14 serves as vertical light to increase brightness.

  The reflection plate 17 functions to reflect the light transmitted through the light guide plate 12 and return the light into the light guide plate 12 again. Al metal plate with high reflectivity, metal plate with high reflectivity such as Ag, Ni, Cr, Pd, etc., sheet with metal vapor deposition film such as Al, Ag, sheet with Al foil, etc. A resin plate or the like having a white color tone can be used as the reflecting plate.

  The backlight unit 18 in the first embodiment is composed of a light guide plate 12, a light source 13 that is an LED, a light diffusion sheet 14, a first prism sheet 15, a second prism sheet 16, and a reflection plate 17. However, the backlight unit of the present invention is not particularly limited to this configuration. For example, the number of prism sheets used can be reduced by one, and a single prism sheet can be used. Further, it can be configured without using any prism sheet. In addition, the backlight unit may be configured using a storage case that has a reflection means instead of the reflection plate 17 and holds and stores these components.

  Next, a backlight unit according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a plan view showing the arrangement of the light guide plate and the light source of the backlight unit according to the second embodiment of the present invention.

  In FIG. 4, two cutout portions are provided between the side center portion 22 c and the corner portion 22 e of the light guide plate 22. One portion has an L-shaped cutout portion 22a1 near the left side of the side central portion 22c in the drawing, and the other portion has a cutout portion 22a2 with the corner portion 22e cut off at the corner portion 22e. Then, the LEDs of the light source 23 are disposed in a slightly embedded manner at the two notches 22a1 and 22a2. The side 22g1 is a light incident surface from the light source 23 in the notch 22a1, and the side 22g2 is a light incident surface from the light source 23 in the notch 22a2. The two light incident surfaces are provided with an inclination in a direction toward a diagonal line 22d passing through the corner portion 22e of the light guide plate 22, and the inclination angle θ of the light incident surface formed by the side 22g1 is small and formed by the side 22g2. The inclination angle θ of the light incident surface is large. Since the size of the light guide plate 22 is large, the entire light guide plate 22 is illuminated brightly with two LEDs.

  By adopting the above configuration, even if the size of the light guide plate 22 is increased, the number of the light sources 23 is limited to a minimum increase, and the area of the shadow portion 22f is suppressed to be small, and a wide area of the light guide plate 22 is luminance. Can be used as a bright effective area. Therefore, the size of the light guide plate 22 can be reduced.

  In the second embodiment, two light sources 23 are used. However, the number may be set as appropriate according to the size of the light guide plate 22.

  Further, in the second embodiment, the cutout portion 22a2 of the corner portion 22e is a cutout-shaped cutout portion, but there is no problem even if it takes an L-shaped shape. The cut-off shape of the corner 22e is convenient in terms of position adjustment of the light source 23.

  The light guide plate 22 is formed by an injection molding method using a resin having excellent heat resistance, moisture resistance, impact resistance, and chemical resistance, such as polycarbonate resin, as in the light guide plate used in the first embodiment. To do. Two notches 22a1 and 22a2 are also formed at the time of injection molding. In addition, the two light incident surfaces of the side 22g1 and the side 22g2 are also finished to a glossy surface by transfer from the mold. If it is a glossy surface, light can be guided deep into the light guide plate 22 without causing light diffusion in the incident light. Although not shown, light reflecting means is provided on the lower surface of the light guide plate 22, and light is emitted from the upper surface of the light guide plate 22 by the reflecting means, or light is emitted toward the back of the light guide plate 22. The work such as guiding is done.

  The backlight unit of the second embodiment includes a light guide plate 22 having the arrangement structure shown in FIG. 4, a light source 23 that is an LED, a light diffusion sheet, a first prism sheet, a second prism sheet, a reflector, and the like. is doing. The light diffusion sheet, the first prism sheet, the second prism sheet, and the reflection plate have the same specifications as those used in the first embodiment, but are not necessarily limited to this configuration. For example, the number of prism sheets used may be reduced by one, and the prism sheet may be configured by one sheet. Further, it can be configured without using any prism sheet. Further, the backlight unit may be configured by using a storage case that has a reflection means instead of the reflection plate and holds and stores these components.

  Next, a backlight unit according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a plan view showing the arrangement of the light guide plate and the light source of the backlight unit according to the third embodiment of the present invention.

  The arrangement relationship between the light guide plate and the light source of the backlight unit according to the third embodiment is such that the light source 33, which is an LED, is completely embedded in the notch 32a provided in the light guide plate 32, as shown in FIG. The arrangement is taken. Therefore, the light source 33 that is an LED is disposed and accommodated in the size of the light guide plate 32. The cutout portion 32a is provided in the corner portion 32e in an L shape. The light source 33, which is an LED, is arranged in the L-shape so as to be embedded without protruding from the light guide plate 32. The side 32g1 of the notch 32a is a light incident surface for receiving light from the light source 33, and this light incident surface is formed in a state facing the direction of a diagonal line 32d passing through the corner 32e.

  Since the light guide plate 32 having the above-described configuration is in a state in which the light source 33 is completely embedded, the vertical width in the drawing needs to be large enough to prevent the light source 33 from popping out. However, the overall size of the backlight unit can be made the same as the size of the light guide plate 32, and the backlight unit can be compactly gathered with the same size as the light guide plate 32. As a backlight unit, there is no unevenness in the outer shape, so handling convenience in transportation and assembly is born.

  In the third embodiment, as shown in FIG. 5, one light source is used. However, even when the light guide plate is large and two or three light sources are required, the notch is deepened. All light sources are arranged so as not to protrude outside the light guide plate.

  The light guide plate 32 having the above-mentioned shape is excellent in heat resistance, moisture resistance, impact resistance, and chemical resistance such as polycarbonate resin, similar to the light guide plate used in the first and second embodiments described above. It is formed by an injection molding method using the obtained resin. The notch 32a is also formed at the time of injection molding, and the side 32g1 serving as the light receiving surface is also finished to a glossy surface by a transfer method from a mold. Although not shown in FIG. 5, light reflecting means is provided on the lower surface of the light guide plate 32.

  The backlight unit of the third embodiment includes a light guide plate 32 having the arrangement structure shown in FIG. 5, a light source 33 that is an LED, a light diffusion sheet, a first prism sheet, a second prism sheet, a reflector, and the like. is doing. The light diffusion sheet, the first prism sheet, the second prism sheet, and the reflection plate have the same specifications as those used in the first embodiment, but are not necessarily limited to this configuration. For example, the number of prism sheets used may be reduced by one, and the prism sheet may be configured by one sheet. Further, it can be configured without using any prism sheet. Further, the backlight unit may be configured by using a storage case that has a reflection means instead of the reflection plate and holds and stores these components.

  The backlight unit of the present invention has been described in detail above using the first to third embodiments. In the display device using the backlight unit of the present invention, the number of light sources to be used is very small as compared with the backlight unit described in the prior art, and a cost merit is obtained. In addition, since the size of the light guide plate can be reduced, the backlight unit itself can be miniaturized, and an effect that the display device of the display device can be made compact and compact can be produced. Moreover, since the high brightness | luminance area | region in a light-guide plate is obtained widely, the area | region which can be used effectively can also be taken widely. As a result, a dark shadow portion or the like having a low luminance does not appear on the display panel, and a bright display with a high overall luminance without luminance unevenness can be obtained.

1 is a side view of a display device including a backlight unit according to a first embodiment of the present invention. It is the top view which showed arrangement | positioning of the light-guide plate and light source of the backlight unit in FIG. It is an enlarged view of the A section in FIG. It is the top view which showed arrangement | positioning of the light-guide plate and light source of the backlight unit which concern on 2nd Embodiment of this invention. It is the top view which showed arrangement | positioning of the light-guide plate and light source of the backlight unit which concern on 3rd Embodiment of this invention. It is principal part sectional drawing of the liquid crystal display device in a prior art. It is explanatory drawing explaining the magnitude | size of the light-guide plate by the arrangement | positioning number of the light sources in FIG.

Explanation of symbols

11 Display panels 12, 22, 32 Light guide plates 12a, 22a1, 22a2, 32a Notch portions 12c, 22c Side center portions 12d, 22d, 32d Diagonal lines 12e, 22e, 32e Corner portions 12f, 22f Shadow portions 12g1, 12g2, 22g1, 22g2 , 32g1 Sides 13, 23, 33 Light source 14 Light diffusion sheet 15 First prism sheet 16 Second prism sheet 17 Reflector θ Inclination angle

Claims (8)

Provided on the lower surface side of the display panel, in a backlight unit having a rectangular light guide plate and a light source, at least one notch portion is provided between a side central portion and a corner portion of the light guide plate, and the notch portion A backlight unit having a light source. 2. The backlight unit according to claim 1, wherein a light incident surface of the light source at the cutout portion is inclined so as to face a diagonal direction passing through the corner portion. 3. The backlight unit according to claim 1, wherein an inclination angle of the light incident surface of the notch portion increases as the angle portion approaches. The backlight unit according to any one of claims 1 to 3, wherein the notch has an L-shaped notch shape. 5. The backlight unit according to claim 1, wherein the cutout portion provided in the corner portion has a shape obtained by cutting off the corner portion or an L-shaped cutout shape. 6. The backlight unit according to claim 1, wherein the light source is disposed so as to be embedded in the notch. The backlight unit according to claim 1, wherein the light source is an LED. In a display device including a backlight unit on the lower surface side of the display panel, the backlight unit uses the backlight unit according to any one of claims 1 to 7 and reduces the number of light sources used. A display device characterized by downsizing the backlight unit.

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