JP2006294560A - Backlight - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backlight capable of easily smoothing luminance unevenness of light emitted from a surface light emitting part without excessively increasing a light reflecting part in the vicinity of an incident surface of a light guide plate.
A light exit surface (31a) of a light guide plate (31) is inclined with respect to a diffusion plate (32), and a gap (40) is formed between the light guide plate (31) and the diffusion plate (32). As a result, light emitted from the light exit surface 31a of the light guide plate 31 can be diffused to a sufficiently wide angle and incident on the diffuser plate 32, and the light reflecting portion 39 in the vicinity of the entrance surface 31c of the light guide plate 31 is excessively large. It is possible to easily smooth the luminance unevenness of the light emitted from the surface light emitting portion 38 in the vicinity of the incident surface 31c without making it uniform. Therefore, consumption of the light quantity in the vicinity of the incident surface 31c of the light guide plate 31 can be suppressed, and even when a point light source such as the LED 10 is used, the luminance of the entire surface light emitting unit 38 can be maintained at a high level. it can.
[Selection] Figure 2

Description

  The present invention relates to a backlight using a light emitting element such as a plurality of light emitting diodes as a light source.

  Conventionally, as a backlight suitable for a liquid crystal display panel or the like, a so-called edge light type in which light is incident from a side end surface of a light guide plate made of a transparent parallel plate, a wedge-shaped flat plate or the like has been widely used. Further, in this type of edge light type backlight, in recent years, a plurality of light emitting elements such as light emitting diodes (LEDs) arranged as light sources on the incident surface of a light guide plate has been proposed. By the way, when light emitting elements such as LEDs are used as light sources, each light emitting element is a point light source. Therefore, luminance unevenness of light emitted from the surface light emitting portion of the backlight is in a direction perpendicular to the light source (that is, This is likely to occur not only in the depth direction of the light guide plate as viewed from the above but also in the direction horizontal to the light source (that is, the arrangement direction of the light sources). Specifically, the luminance of the light emitted from the surface light emitting portion tends to be locally reduced, particularly in a region outside the LED placement portion in the vicinity of the incident surface of the light guide plate.

Therefore, for example, in Patent Document 1, light reflecting portions (light reflecting patterns) are arranged by dot printing or the like on the reflecting surface of the light guide plate, and the area ratio of each light reflecting portion is set in a direction perpendicular to each light source. A technique is disclosed in which the gap is formed so as to be separated and the gap is formed so as to be separated in the horizontal direction with respect to each light source.
JP 2001-43714 A

  However, as in the technique disclosed in Patent Document 1 described above, it is difficult to simultaneously adjust the luminance unevenness in the direction perpendicular to the light source and in the horizontal direction only by designing the area ratio of the light reflecting portion. There is. In particular, when the light reflecting part corresponding to the dark part is enlarged in order to eliminate the decrease in the brightness of the light emitted from the surface light emitting part (occurrence of a dark part) in the vicinity of the incident surface of the light guide plate, Consumption of the light quantity in the vicinity of the incident surface is increased, and there is a possibility that the luminance of the entire surface light emitting unit is lowered.

  The present invention provides a backlight capable of easily smoothing uneven brightness of light emitted from a surface light emitting unit without excessively increasing the size of a light reflecting unit in the vicinity of an incident surface of a light guide plate. Objective.

  The present invention provides a light guide plate having a light exit surface and a reflection surface facing each other and having an incident surface on at least one side end surface thereof, a plurality of point light sources arranged along the incident surface of the light guide plate, and the light guide plate An optical member disposed opposite to the light output surface, wherein the light output surface of the light guide plate is inclined with respect to the optical member, and the light guide plate and the optical member are inclined by the inclination of the light output surface. It is characterized in that a gap is formed between them.

  According to the backlight of the present invention, it is possible to easily smooth the luminance unevenness of the light emitted from the surface light emitting portion without excessively increasing the size of the light reflecting portion in the vicinity of the incident surface of the light guide plate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings relate to an embodiment of the present invention, FIG. 1 is an exploded perspective view of the backlight, FIG. 2 is a cross-sectional view of the main part of the backlight, and FIG. 3 shows an example of the behavior of light incident on the diffusion plate from the light guide plate. 4 is an explanatory diagram, FIG. 4 is a contour map of luminance distribution, FIG. 5 is a cross-sectional view of an essential part showing a modification of the backlight, and FIG. 6 is a perspective view showing a modification of the light guide plate.

  1 and 2, reference numeral 1 denotes a backlight suitable for a liquid crystal television or the like. The backlight 1 has a flat, substantially box-shaped case 2 having an upper surface opened. The case 2 is made of, for example, a resin molded product in which a rectangular back plate 2a and side walls 2b erected on each side of the back plate 2a are integrally formed by injection molding, and further, the short side direction of the back plate 2a At both end portions, partition walls 3 facing the side walls 2b are erected. The partition 3 defines the inside of the case 2 into a pair of LED storage chambers 5 and a light guide chamber 6 interposed between the LED storage chambers 5.

  The LED storage chamber 5 stores, for example, a plurality of (for example, four) surface-mounted light emitting diodes (hereinafter referred to as LEDs) 10 which are point light sources as light sources. Specifically, a pair of substrate holding grooves 5a facing each other are recessed at both ends in the longitudinal direction of the LED storage chamber 5, and these substrate holding grooves 5a are arranged on the LED substrate 11 at regular intervals. The light source unit 20 mounted on the LED storage chamber 5 is held in the LED storage chamber 5. As shown in FIGS. 1 and 2, each LED 10 housed and held in the LED housing chamber 5 exposes its light emitting surface to the light guide chamber 6 through a communication groove 7 recessed in the partition wall 3. .

  Here, in the present embodiment, each LED 10 is a white LED that emits white light having a predetermined color temperature. Such an LED 10 may be configured, for example, by using three light emitters of R, G, and B in one package. For example, a single-color LED is coated with a fluorescent material to convert emitted light into white light. You may comprise so that it may convert.

  The light guide chamber 6 includes, for example, a planar rectangular reflective sheet 30 having a reflective surface 30a on one surface, a planar rectangular light guide plate 31 having a light exit surface 31a and a reflective surface 31b facing each other, and a planar rectangular shape. A diffusion plate 32 as an optical member having a shape and facing the light exit surface 31a of the light guide plate 31, and a planar rectangular lens sheet 33 having a diffusion sheet 34 attached to one surface, in order from the back plate 2a side. Stack and store.

  Reference numeral 36 in the figure denotes a bezel that is provided on the case 2. The bezel 36 has a rectangular opening 36a for exposing the diffusion sheet 34 affixed to the lens sheet 33 to the outside. As shown in FIG. By providing, the upper opening part of the LED accommodating chamber 5 is closed, and the edge part of the lens sheet 33 (and the diffusion sheet 34) is further sandwiched between the case 2. In the backlight 1 of the present embodiment, a region on the diffusion sheet 34 exposed to the outside from the opening 36 a of the bezel 36 functions as the surface light emitting unit 38.

  As shown in FIGS. 1 and 2, in the light guide plate 31 of the present embodiment, the two side end surfaces facing the LEDs 10 of each light source unit 20 are respectively set as incident surfaces 31 c on which light emitted from the LEDs 10 is incident. ing.

  In addition, the light guide plate 31 includes a plurality of light reflecting portions 39 on the reflecting surface 31b that reflects the light incident from each incident surface 31c and guides the light to the light exit surface 31a. In the present embodiment, each light reflecting portion 39 is a circular reflecting member formed on the reflecting surface 31b by, for example, dot printing or the like, and the area thereof is different depending on the arrangement position. Specifically, for example, the light reflecting portion 39 has a relatively large area as it is separated from the light emitting surface of the LED 10 in the vertical direction, and is spaced apart from the light emitting surface of the LED 10 in the horizontal direction. The thing has a relatively large area.

  Further, the light output surface 31a of the light guide plate 31 is inclined relative to the diffusion plate 32, and the light guide plate 31 forms a gap 40 between the light output plate 31a and the light diffusion plate 32 when the light output surface 31a is inclined. . In the present embodiment, the light exit surface 31a is inclined so as to maximize the thickness of the light guide plate 31 at each incident surface 31c and to decrease the thickness of the light guide plate 31 as the distance from the incident surface 31c increases. That is, in the present embodiment, the light exit surface 31a has a gentle V-shaped cross section as shown in FIG. Here, when setting the light guide plate 31, it is desirable that the thickness of the light guide plate 31 on the incident surface 31 c is made to coincide with the width of the light emitting surface of each LED 10 (width in the thickness direction of the light guide plate 31).

  In such a configuration, light incident on the light guide plate 31 from each LED 10 is reflected by each light reflecting portion 39 disposed at each position on the reflecting surface 31b and then emitted from the light exit surface 31a. At that time, as shown in FIG. 3, the light emitted from the light exit surface 31 a is refracted due to the difference in refractive index between the light guide plate 31 and air, and passes through the gap 40 before reaching the diffusion plate 32. Proceeds in the direction of refraction. Thereby, the emitted light from the light guide plate 31 can be diffused at a sufficiently wide angle and incident on the diffusion plate 32, and the luminance unevenness of the light emitted from the surface light emitting unit 38 can be easily smoothed. .

  That is, the light exit surface 31 a of the light guide plate 31 is inclined with respect to the diffuser plate 32, and the gap 40 is formed between the light guide plate 31 and the diffuser plate 32, so that the light emitted from the light exit surface 31 a of the light guide plate 31 is emitted. The light can be diffused at a sufficiently wide angle so as to be incident on the diffusion plate 32, and the surface light emitting unit 38 is formed in the vicinity of the incident surface 31c without excessively increasing the size of the light reflecting unit 39 in the vicinity of the incident surface 31c of the light guide plate 31. The luminance unevenness of the light emitted from the light can be easily smoothed. Therefore, consumption of the light quantity in the vicinity of the incident surface 31c of the light guide plate 31 can be suppressed, and even when a point light source such as the LED 10 is used, the luminance of the entire surface light emitting unit 38 can be maintained at a high level. it can.

  At this time, the light exit surface 31a is inclined in a direction in which the plate thickness of the light guide plate 31 at the entrance surface 31c is maximized and the thickness is reduced as the distance from the entrance surface 31c increases. Even when the air gap 40 is formed between them, it is possible to accurately prevent the backlight 1 from being enlarged in the thickness direction. In addition, since the light guide plate 31 is made thinner as the light guide plate 31 is separated from the incident surface 31c due to the inclination of the light exit surface 31a, the light guide plate 31 can be reduced in weight, and the backlight 1 as a whole can be reduced in weight. Can be realized.

  4A includes a plurality of light reflecting portions 39 arranged in a predetermined pattern on the reflecting surface 31b of the light guide plate 31, and a gap 40 between the light emitting surface 31a and the diffusing plate 32. FIG. In the backlight 1 of this embodiment in which is formed, a simulation result of the luminance distribution of light emitted from the surface light emitting unit 38 in the vicinity of each LED 10 is shown. FIG. 4B shows a backlight having a plurality of light reflecting portions arranged in the same pattern on the reflecting surface of the light guide plate, and the light emitting surface and the diffusing plate are in close contact with each other. The simulation result of the luminance distribution of the light emitted from the surface light emitting part in the vicinity is shown. As is clear from these simulation results, by forming the gap 40 between the light exit surface 31a of the light guide plate 31 and the diffusion plate 32, the luminance distribution of the light emitted from the surface light emitting portion 38 is dramatically improved. I understand that I can do it.

  In the above-described embodiment, an example in which the present invention is applied to the backlight 1 in which the incident surfaces 31c are set on the pair of side end surfaces facing each other of the light guide plate 31 has been described, but the present invention is not limited thereto. A backlight having an incident surface set only on one side end surface of the light guide plate, a backlight having an incident surface set on two adjacent side end surfaces of the light guide plate, or three or more side end surfaces of the light guide plate The present invention can also be applied to a backlight or the like in which the incident surface is set. For example, as shown in FIG. 5, when the incident surface 31c is set only on one side end surface of the light guide plate 31, the light exit surface 31a is inclined from the incident surface 31c side toward the side end surface facing the incident surface 31c. As a result, it is possible to form a favorable gap 40 between the light guide plate 31 and the diffusion plate 32. For example, as illustrated in FIG. 6, when the incident surfaces 31 c are set on the four side end surfaces of the light guide plate 31, the light exit surfaces 31 a are inclined from the respective incident surfaces 31 c toward the center of the light guide plate 31, By forming the concave 31a on the reflecting surface 31b side, a good gap can be formed between the light guide plate 31 and the diffusion plate.

  In addition, the optical member facing the light exit surface 31a of the light guide plate 31 is not limited to the diffusion plate, and may be, for example, a lens sheet.

Exploded perspective view of backlight Cross section of the main part of the backlight Explanatory drawing which shows an example of the behavior of the light which injects into a diffuser from a light-guide plate Contour plot of luminance distribution Cross-sectional view of the main part showing a modification of the backlight The perspective view which shows the modification of a light-guide plate

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Back light, 10 ... Light emitting diode (point light source), 31 ... Light guide plate, 31a ... Light emission surface, 31b ... Reflection surface, 31c ... Incident surface, 32 ... Diffusing plate (optical member), 38 ... Surface light emission part, 39 ... light reflection part, 40 ... gap

Claims (2)

A light-emitting surface and a reflective surface face each other, and a light guide plate having an incident surface on at least one side end surface thereof, a plurality of point light sources arranged along the incident surface of the light guide plate, and a light-emitting surface of the light guide plate A backlight including an optical member disposed opposite to the optical member,
A backlight characterized in that a light output surface of the light guide plate is inclined with respect to the optical member, and a gap is formed between the light guide plate and the optical member by the inclination of the light output surface.   The light exit surface is inclined in a direction that maximizes the thickness of the light guide plate at the incident surface and decreases the thickness of the light guide plate as the distance from the incident surface increases. Item 10. The backlight according to item 1.

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