JP2013084343A - Backlight device, liquid crystal display and television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sidelight type backlight device as well as a liquid crystal display with high luminance and high light utilization efficiency, and a television receiver.SOLUTION: The backlight device includes: a light guide body; a light emission area provided on a top face of the light guide body; a light-reflecting face provided to a given side face of the light guide body, and a concave part or a convex part formed between the light emission area and the light-reflecting face on an underside of the light guide body. A sidewall of the concave part or the convex part is a light-incident face set to oppose the light-reflecting face, the plurality of light sources are arranged in opposition to the sidewall, and light emitted from the light sources is guided from the light-incident face into the light guide body to be reflected at the light-reflecting face and emitted from the light emission face.

Description

  The present invention relates to a sidelight type backlight device, a liquid crystal display device, and a television receiver including a light source and a light guide.

  Conventionally, backlight devices used in liquid crystal display devices include a sidelight type backlight device in which a light source is disposed on the side of a light guide, and a direct type backlight device in which a light source is disposed directly under a liquid crystal panel. is there. Sidelight-type backlight devices are used in medium- and small-sized liquid crystal display devices and particularly liquid crystal display devices that require a thin shape. Conventionally, the cold cathode fluorescent lamp (CCFL) has been the mainstream as the light source of these backlight devices, but recently, environmental issues have been regarded as important, and LEDs are switching to mercury-free LEDs with low power consumption.

  For example, Patent Literature 1 discloses a sidelight type backlight device using LEDs. As shown in FIG. 6, Patent Document 1 discloses a light guide 7 having a predetermined side as a light incident surface 7a in a holder case 300 disposed on the back side of a liquid crystal panel, and the light incident surface 7a side. Is a backlight device for a liquid crystal panel that houses a chip-type LED 9 disposed in the, and irradiates the liquid crystal panel with light emitted from the chip-type LED 9 via a light guide 7. In Patent Document 1, the chip-type LED 9 is disposed such that the light emitting surface 91 side is opposite to the light incident surface 7a, and light reflecting means is provided on a specific side surface of the holder case 300 facing the light incident surface 7a. By providing 320, the light emitted from the chip-type LED 9 is reflected by the light reflecting means 320 and enters the light guide, so that no bright spot from the backlight source appears on the edge of the display portion of the liquid crystal panel. ing.

JP 2006-47339 A

  In the sidelight type backlight device of Patent Document 1, the light reflecting means 320 is provided in the holder case 300, and the cost of the backlight device is high because the parts cost and manufacturing cost of the light reflecting means 320 are increased. There was a problem. Further, the gap between the light reflecting means 320 and the light incident surface 7a is a space (air layer), and the light emitted from the chip LED 9 is reflected by the light reflecting means 320 and is incident on the light guide. In the meantime, a loss of light emitted from the chip LED 9 occurs due to scattering by the air layer or a part of the light being reflected by the light incident surface 7a. There was a problem that decreased.

  Further, the light reflected by the light reflecting means 320 is blocked by the chip-type LED 9 and is not incident on the light incident surface 7a, causing a partial shadow and causing uneven brightness at the display end. . By devising the uneven surface of the light reflecting means 320 or forming a lens surface on the light incident surface 7a, the chip shadow portion can be reduced, but there is a problem that the price of the backlight device further increases.

  The backlight device according to the present invention includes a light guide, a light emission area provided on the upper surface of the light guide, a light reflection surface provided on a predetermined side surface of the light guide, a light emission area, and light reflection. A concave portion or a convex portion is formed on the lower surface of the light guide, and a side wall of the concave portion or the convex portion is a light incident surface provided so as to face the light reflecting surface. The light source is arranged such that light emitted from the light source is guided into the light guide from the light incident surface, reflected by the light reflecting surface, and emitted from the light emitting region.

  According to the backlight device of the present invention, loss of light emitted from the light emitting diode can be prevented, the brightness of the irradiation light of the backlight device can be improved, and uneven brightness can be prevented.

It is a perspective view explaining the backlight apparatus and liquid crystal display device of a 1st Example. It is a top view explaining the principal part structure of the backlight apparatus of a 1st Example. It is sectional drawing explaining the principal part structure of the backlight apparatus of a 1st Example. It is sectional drawing explaining the principal part structure of the backlight apparatus of a 2nd Example. It is sectional drawing explaining the principal part structure of the backlight apparatus of a 3rd Example. It is a top view of the conventional sidelight type backlight device.

  Hereinafter, preferred embodiments of a backlight device of the present invention and a liquid crystal display device using the same will be described with reference to the drawings. In the following description, a case where the present invention is applied to a transmissive liquid crystal display device will be described as an example.

  FIG. 1 is a perspective view for explaining a backlight device and a liquid crystal display device according to a first embodiment of the present invention. As shown in FIG. 1, the liquid crystal display device 1 has a configuration in which a backlight device 2 and a liquid crystal panel 3 to which light from the backlight device 2 is irradiated are integrated.

  Further, in the liquid crystal display device 1, for example, a diffusion sheet 4, a prism sheet 5, and a polarizing sheet 6 are disposed between the backlight device 2 and the liquid crystal panel 3, and the backlight device 2 is formed by these optical sheets. The brightness of the light emitted from the liquid crystal panel 3 is adjusted, and the display performance of the liquid crystal panel 3 is improved.

  The backlight device 2 includes a light guide 7, a reflection sheet 8, and a plurality of light sources. The light guide 7 is formed in a substantially rectangular parallelepiped shape using, for example, a synthetic resin such as a transparent acrylic resin. A reflection sheet 8 is disposed on the lower surface side of the light guide 7. A plurality of light emitting diodes 9 serving as light sources are arranged outside the display area 10 of the light guide 7.

  FIG. 2 is a cross-sectional view showing an example of the backlight device 2 of the present invention. As shown in FIGS. 1 and 2, a light emitting region 7 c for emitting light to the display region 10 is provided on the upper surface of the light guide 7, and light reflection is performed on a predetermined side surface of the light guide 7. A surface 7b is provided. Further, a concave portion 71 formed in a groove shape in the direction of the light reflecting surface 7b is provided on the outer surface and the lower surface of the light guide 7 and the side wall of the concave portion 71 facing the light reflecting surface 7b. Is the light incident surface 7a.

  A reflecting member 8a is provided outside the light reflecting surface 7b. As the reflecting member 8a, the same member as the reflecting sheet 8 disposed on the lower surface of the light guide 7 can be used. For example, the reflection sheet 8 may be provided by extending from the lower surface of the light guide 7 to the light reflection surface 7b and removing the reflection sheet 8 only on the light incident surface 7a.

  Inside the recess 71 of the light guide 7, a plurality of light emitting diodes 9 are arranged with their respective light emitting surfaces 91 facing the light incident surface 7 a. Further, the light emitting diode 9 is installed with the light emitting surface 91 inclined upward so that the main light emitting direction of the light emitted from the light emitting diode 9 proceeds upward from the light incident surface 7a toward the light reflecting surface 7b. ing.

  In FIG. 2, in order to prevent the light emitted from the light emitting diode 9 from being unnecessarily reflected by the light incident surface 7 a, the light incident surface 7 a is also inclined so as to be parallel to the light emitting surface 91. Thus, a configuration is shown in which light emitted from the light emitting diode 9 is vertically incident on the light incident surface 7a.

  FIG. 3 is a plan view of the backlight device 2 of the present invention. The light emitted from the light emitting surface 91 of the light emitting diode 9 is introduced into the light guide 7 from the light incident surface 7a, travels inside, and enters the light reflecting surface 7b. Incident light is reflected by the light reflecting surface 7b or the outer reflecting member 8a depending on the angle of incidence on the light reflecting surface 7b, and travels inside the light guide 7 in the direction of the display area 10 (light emitting area 7c). returned.

  As indicated by the arrows in FIG. 3, the light path length to the display region 10 is long and guided so that the light emitted from the light emitting diode 9 reaches the display region 10 via the light incident surface 7a through the light reflecting surface 7b. Thus, since the light reaching the display area 10 is diffused to a sufficient width, it is possible to prevent the occurrence of bright spots that cause uneven light at the display area end 10a adjacent to the light emitting diode 9. . Furthermore, since the light from the light emitting diode 9 travels inside the light guide 7 from the light incident surface 7a to the display region 10, it is possible to prevent the light from being scattered by the air layer.

  Further, a reflecting member 8a is provided outside the light reflecting surface 7b. Even when light is incident on the light reflecting surface 7b at an angle equal to or larger than the critical angle θ, the light reflecting surface 7b is not transmitted through the outside. Since the light is reflected by the reflecting member 8, the light incident on the light reflecting surface 7b is totally reflected. Therefore, the light incident on the light reflecting surface 7b is not lost through the light reflecting surface 7b, and all the light emitted from the light emitting diode 9 can be used. Brightness can be improved.

  In this embodiment, the reflecting member 8a is provided outside the light reflecting surface 7b. However, when the incident angle of incident light is smaller than the critical angle θ and is totally reflected by the light reflecting surface 7b, the light reflecting surface. The reflection member 8a may not be provided outside the 7b.

  The light emitting diode 9 is installed with the optical axis inclined upward, and the light emitted from the light emitting surface 91 is incident on the light reflecting surface 7b from below and reflected upward. Therefore, the light reflected by the light reflecting surface 7b or the reflecting member 8a travels inside the light guide 7 above the light emitting diode 9 (upper part of the concave portion 71) and reaches the display area 10, and therefore from the light reflecting surface 7b. The problem that the returning light is blocked by the light emitting diode 9 and a shadow portion is formed can be solved.

  As described above, according to the backlight device according to the present invention, the light loss of the light emitting diode is prevented, so the brightness of the irradiation light of the backlight device is improved and the occurrence of uneven brightness in the display area is prevented. be able to.

  FIG. 4 is a cross-sectional view of the backlight device 2 according to the second embodiment of the present invention. In Example 2, the convex portion 72 is provided on the lower surface of the light guide 7. Since other configurations may be the same as those of the first embodiment, detailed description thereof is omitted.

  The light guide body 7 is provided with a convex portion 72 formed by extending a side surface portion on which the light reflecting surface 7b is provided on the lower surface side of the light guide body 7 so as to be convex, and is opposed to the light reflecting surface 7b. The side wall of the portion 72 is a light incident surface 7a.

  A reflecting member 8a is provided outside the light reflecting surface 7b. The same member as the reflection sheet 8 disposed on the lower surface of the light guide 7 can be used as the reflection member 8a. The reflection sheet 8 extends from the lower surface of the light guide 7 to the light reflection surface 7b. You may provide by removing the reflective sheet 8 only in the part of the entrance plane 7a.

  On the light incident surface 7a side of the convex portion 72 of the light guide 7, a plurality of light emitting diodes 9 are arranged with the respective light emitting surfaces 91 facing the light incident surface 7a. Further, the light emitting diode 9 is installed with the light emitting surface 91 inclined upward so that the main light emitting direction of the light emitted from the light emitting diode 9 proceeds upward from the light incident surface 7a toward the light reflecting surface 7b. ing.

  In FIG. 4, in order to prevent the light emitted from the light emitting diode 9 from being unnecessarily reflected by the light incident surface 7 a, the light incident surface 7 a is also inclined so as to be parallel to the light emitting surface 91. 1 shows a configuration in which light emitted from the light emitting diode 9 is vertically incident on the light incident surface 7a.

  The light emitted from the light emitting surface 91 of the light emitting diode 9 is introduced into the light guide 7 from the light incident surface 7a, travels inside, is reflected by the light reflecting surface 7b, and travels inside the light guide 7. Returned in the direction of the display area 10.

  As in the first embodiment, the light emitted from the light emitting diode 9 is guided with a long optical path length to the display area 10 so as to reach the display area 10 from the light incident surface 7a via the light reflecting surface 7b. Thus, since the light reaching the display area 10 is diffused to a sufficient width, it is possible to prevent the occurrence of bright spots that cause uneven light at the display area end 10a adjacent to the light emitting diode 9. . Furthermore, since the light from the light emitting diode 9 travels inside the light guide 7 from the light incident surface 7a to the display region 10, it is possible to prevent loss of light scattered by an air layer or the like.

  Further, a reflecting member 8a is provided outside the light reflecting surface 7b. Even when light is incident on the light reflecting surface 7b at an angle equal to or larger than the critical angle θ, the light reflecting surface 7b is not transmitted through the outside. Since the light is reflected by the reflecting member 8a, the light incident on the light reflecting surface 7b is totally reflected. Therefore, the light incident on the light reflecting surface 7b is not lost through the light reflecting surface 7b, and all the light emitted from the light emitting diode 9 can be used. Brightness can be improved.

  In this embodiment, the reflecting member 8a is provided outside the light reflecting surface 7b. However, when the incident angle of incident light is smaller than the critical angle θ and is totally reflected by the light reflecting surface 7b, the light reflecting surface. The reflection member 8a may not be provided outside the 7b.

  Further, since the light totally reflected by the light reflecting surface 7b travels in the light guide 7 above the light emitting diode 9 and reaches the light emitting region 7c, the reflected light is blocked by the light emitting diode 9. A shadow portion does not occur, and uneven brightness in the display area end 10a can be prevented. In particular, in Example 3, since the light incident surface 7a is provided on the convex portion 72, the thickness of the light guide 7 above the light emitting diode 9 can be ensured with the same thickness as the light emitting region 7c, and thus the light reflecting surface 7b. The light reflected by can be effectively guided to the display area 10.

  FIG. 5 is a cross-sectional view of the backlight device 2 according to the third embodiment of the present invention. The difference from the first embodiment is the configuration of the reflecting surface 7b, and the other configurations may be the same as those of the first embodiment, and thus detailed description thereof is omitted.

  The reflecting surface 7b provided on the side surface of the light guide 7 is composed of a plurality of inclined surfaces (7b1, 7b2), and each inclined surface has an angle at which the light emitted from the light emitting diode 9 is smaller than the critical angle θ. It is inclined so as to be incident (reflected) on the inclined surface.

  The critical angle θ is the smallest incident angle at which total reflection occurs when light enters from a large refractive index to a small refractive index. The refractive index of the incident material is n1, and the refractive index of the incident material. Can be obtained from the equation θ = arc · sin (n2 / n1). For example, when the critical angle is obtained from the refractive indexes of acrylic (n1 = 1.49) and air (n2 = 1) used for the light guide 7, θ = 42.2 °.

  The arrangement relationship between the first inclined surface 7b1 and the optical axis of the light emitting diode 9 is set in consideration of the critical angle θ as described above. For example, as shown in FIG. Is preferably set so that the incident angle of light is equal to or smaller than the critical angle θ at the angle of the first inclined surface 7 b 1 in parallel with the light guide 7. The inclined surfaces 7b1 and 7b2 can be formed integrally with the light guide 7 using a mold used when the light guide 7 is molded. For this reason, in order to set the incident angle of light on each inclined surface with high accuracy, it is better to adjust the angle of the inclined surface as described above than to adjust the light axis of the light emitting diode 9 by inclining. The incident angle of light can be easily and accurately set to be equal to or smaller than the critical angle θ, and the working time required for assembling the backlight device 2 can be shortened.

  Light emitted from the light emitting surface 91 of the light emitting diode 9 is introduced into the light guide 7 from the light incident surface 7a, travels inside, and is sequentially reflected by the inclined surfaces 7b1 and 7b2 of the light reflecting surface 7b to emit light. The light travels inside the light guide 7 above the diode 9 (above the recess 71) and returns toward the display area 10.

  As in the first embodiment, the light emitted from the light emitting diode 9 is guided with a long optical path length to the display area 10 so as to reach the display area 10 from the light incident surface 7a via the light reflecting surface 7b. Thus, since the light reaching the display area 10 is diffused to a sufficient width, it is possible to prevent the occurrence of bright spots that cause uneven light at the display area end 10a adjacent to the light emitting diode 9. . Furthermore, since the light from the light emitting diode 9 travels inside the light guide 7 from the light incident surface 7a to the display region 10, it is possible to prevent loss of light scattered by an air layer or the like.

  In addition, the arrangement of the optical axis and the inclined surface is such that the light emitted from the light emitting surface 91 is incident (reflected) at an angle smaller than the critical angle θ by a plurality of inclined surfaces 7b1 and 7b2 provided on the light reflecting surface 7b. Is set, the light incident on the light reflecting surface 7b is totally reflected. Therefore, the light incident on the light reflecting surface 7b is not lost through the light reflecting surface 7b, and all the light emitted from the light emitting diode 9 can be used. Brightness can be improved.

  Further, since the light totally reflected by the light reflecting surface 7b travels in the light guide 7 above the light emitting diode 9 (above the recess 71) and reaches the light emitting region 7c, the reflected light is emitted from the light emitting diode. 9 does not cause a shadow portion, and uneven brightness of the display region end 10a can be prevented.

  In FIG. 5, the light reflecting surface 7b is configured by two inclined surfaces (7b1, 7b2), but the light reflecting surface 7b may be configured by two or more inclined surfaces. By increasing the inclined surfaces, the incident angle of light can be further reduced with respect to the critical angle θ on each inclined surface, and light can be reliably totally reflected on each inclined surface.

  Moreover, you may comprise the light reflection surface 7b by the curved surface (cylindrical surface, toroidal surface) from which the curvature radius of a vertical direction and a horizontal direction differs. By configuring the light reflecting surface 7b with a curved surface, the light reflecting direction can be finely adjusted or condensed.

  Although the first to third embodiments have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the reflecting member 8a shown in the configurations of the first and second embodiments can be provided in the configuration shown in the third embodiment.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Backlight apparatus 3 Liquid crystal panel 5 Prism sheet 6 Polarizing sheet 7 Light guide 7a Light incident surface 7b Light reflecting surface 7c Light emitting area 8 Reflecting sheet 8a Reflecting member 9 Light emitting diode 10 Display area 71 Concave part 72 Convex part 91 light emitting surface 130 light diffusing plate 320 light reflecting means 321 corrugated surface 322 light reflecting layer

Claims (8)

A light guide;
A light emitting region provided on the upper surface of the light guide;
A light reflecting surface provided on a predetermined side surface of the light guide;
A concave portion or a convex portion is formed on the lower surface of the light guide between the light emitting region and the light reflecting surface,
A side wall of the concave or convex portion is a light incident surface provided so as to face the light reflecting surface,
A plurality of light sources are arranged to face the side wall,
The light emitted from the light source is guided from the light incident surface into the light guide, reflected by the light reflecting surface, and emitted from the light emitting region.   The backlight device according to claim 1, wherein the light source is a light emitting diode.   The backlight device according to claim 2, wherein the light emitting diode is disposed such that a main light emitting direction is inclined obliquely upward.   The backlight device according to claim 1, wherein the light reflection surface includes an inclined surface.   5. The backlight device according to claim 1, wherein light emitted from the light emitting diode is incident on the light reflecting surface at a critical angle or less. 6.   The backlight device according to claim 1, wherein the light reflecting surface includes a reflecting member.   A liquid crystal display device using the backlight device according to claim 1.   A television receiver comprising: the liquid crystal display device according to claim 7; and a tuner unit that receives a television broadcast.