JP2006049192A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of expanding an active area of a light emitting surface and emitting white light having a high degree of uniformity in color regardless of the type of LED arranged as a light source and having excellent productivity.
SOLUTION: Since the concave and convex portion 12a formed on the light incident surface of the light guide plate 12 is formed by a continuous curved surface, the light incident on the light guide plate 12 is refracted by the concave and convex portion 20, and the light incident surface. The light is spread in the direction along 12a and scattered in the light guide plate 12. Further, by making the curvature radius R1 of the concave portion 20a in the concavo-convex portion 20 larger than the curvature radius R2 of the convex portion 20b, it is possible to prevent the light incident rate of light entering the light guide plate 12 from decreasing. Furthermore, the light incident on the light guide plate 12 can be more sufficiently scattered by disposing two or more convex portions 20b of the concave-convex portion 20 with respect to the light output region T of the LED 14.
[Selection] Figure 2

Description

  The present invention relates to a surface light source device using an LED as a light source among surface light source devices used for a backlight of a liquid crystal display panel.

  An edge light type surface light source device using a light guide plate is used as a backlight of a liquid crystal display panel for small devices such as portable information terminals and digital cameras because the thickness of the device can be reduced.

  In recent years, liquid crystal display panels for small devices have been desired to save power. As shown in FIG. 5, the light source attached to the light guide plate (2) of the surface light source device (1) is also a conventional cold cathode. An LED (Light Emitting Diode) (3) that consumes less power than a tube has been put into practical use.

  However, the conventional light guide plate (2) has the following problems because the light incident surface (4) is formed flat. That is, the light emitted from the LED (3) as the light source has high directivity, and when the light incident surface (4) is flat, it is condensed by refraction. For this reason, when the surface light source device (1) is turned on, the end of the light exit surface (5), specifically, the light emitted from the LED (3) directly enters the light guide plate (2) from the LED (3). A dark portion (S) is generated in a portion where light does not enter. Since this dark part (S) cannot be used as a surface light source, there is a problem that the area that can be effectively used as a surface light source among the light emitted from the light exit surface (5), that is, the active area (A) becomes narrow. .

  There is also a problem that a bright line (B) is generated at a portion where the light beams of adjacent LEDs (3) intersect with each other and the light beam is mixed, making it impossible to obtain a surface light source with high uniformity. .

  Furthermore, as the LED (3) that emits white light, a 2 in 1 type in which two light emitting elements of blue and amber are arranged in parallel, or a 3 in 1 type in which three light emitting elements of red, green, and blue are arranged in parallel. When using an object, the light emitted from each element has a different running direction, so that when the light enters the light guide plate (2) from the light incident surface (4), the refraction directions of the light emitted from each element are mutually different. It will be different. For this reason, there is a problem that the color mixing of the light emitted from each element is worsened, and white light with a well-tuned color cannot be emitted from the light emitting surface (5).

  As a technique capable of solving such a problem, as shown in FIG. 6, a prism portion (7) having a substantially triangular cross section configured by combining only a flat surface or a combination of a flat surface and a curved surface is provided on the light incident surface (6). A technique for expanding the light incident on the light guide plate (8) to a wide angle has been proposed (see, for example, Patent Documents 1 and 2).

According to such a technique, the light entering the light guide plate (8) is refracted by the prism portion (7) and spread along the light incident surface (6), that is, wide angle, so that the dark portion (S). The area can be reduced, and the active area (A) of the light exit surface (9) can be enlarged.
JP 2003-288807 A JP 2004-79461 A

  However, in the light guide plate (8) provided with the prism portion (7) on the light incident surface (6) and simply refracting the light entering the light guide plate (8) and spreading it to a wide angle, the adjacent LED (3 The bright line (B) that occurs when the light emitted by (2) is mixed cannot be completely eliminated, and a surface light source with high uniformity cannot be obtained.

  In addition, when a 2in1 type LED or a 3in1 type LED is used as the LED (3) that emits white light, the color mixture of light emitted from each element cannot be improved, and it still remains from the light emitting surface (9). There was also a problem that uniform white light with a well-tuned color could not be emitted.

  Furthermore, even if the prism portion (7) as described above is provided, as shown in FIG. 7, the arrangement position of the LED (3) arranged along the light incident surface (6) of the light guide plate (8) When the shift occurs, the area of the dark portion (S) increases. When the dark part (S) extends into the active area (A), the surface light source device becomes a defective product. For this reason, when LED (3) is arrange | positioned, it had to arrange | position with very high positional accuracy, and there existed a problem that production efficiency could not be raised.

  Therefore, the main problem of the present invention is that the active area of the light exit surface can be enlarged, and light with a high degree of uniformity and color tone can be emitted with high brightness regardless of the type of LED arranged as a light source. It is to provide an excellent surface light source device.

  The invention described in claim 1 includes: a light guide plate (12) having a light incident surface (12a) and a light exit surface (12b) orthogonal to the light incident surface (12a); and the light incident surface (12a). A surface light source device (10) having a plurality of LEDs (14) arranged along a plurality of parallel busbars in a direction perpendicular to the light exit surface (12b) on the light incident surface (12a). The extending concavo-convex portion (20) is provided with a continuous curved surface ".

  In this invention, the light (L) emitted from the light source LED (14) enters the light guide plate (12) from the light incident surface (12a) and is refracted by the concave and convex portions (20) to enter the light incident surface. It is expanded toward the direction along (12a) (that is, wide angle). For this reason, when the surface light source device (10) is turned on, the light emitted from the end of the light exit surface (12b), specifically, the LED (14), directly enters the light guide plate (12) from the LED (14). It is possible to reduce the area of the dark part (S) generated in the part that does not enter, and to enlarge the active area (A) of the light exit surface (12b).

  What should be noted here is that the concavo-convex portion (20) is formed of a continuous curved surface. With this configuration, light that has entered the light guide plate (12) through the light incident surface (12a) is scattered in the light guide plate (12). For this reason, the dark portion (S) can be made thin and inconspicuous, and the light (L) emitted by the adjacent LEDs (14) can be sufficiently mixed to prevent generation of bright lines, resulting in high uniformity. A surface light source can be obtained.

  The invention described in claim 2 is the surface light source device (10) according to claim 1, wherein “the radius of curvature (R1) of the concave portion (20a) in the concave and convex portion (20) is the radius of curvature of the convex portion (20b) ( R2) ”, which can prevent the light incident rate of light (L) entering the light guide plate (12) from decreasing. Therefore, the light emitted from the LED (14) can be sufficiently incident on the light guide plate (12), and light having a higher luminance than the light exit surface (12b) can be emitted.

  According to a third aspect of the present invention, in the surface light source device (10) according to the first or second aspect of the present invention, “two or more protrusions (20b) are arranged with respect to the light output region (T) of the LED (14). By this, when the light (L) from the LED (14) enters the light guide plate (12), the light (L) is more sufficiently scattered. Can do.

  For this reason, even when a 2 in 1 type LED (14) or a 3 in 1 type LED (14) is used as a light source, the light emitted from each element can be sufficiently mixed, and the color tone from the light exit surface (12b) It is possible to emit uniform and uniform light.

  Further, since the dark portion (S) can be made thinner and less conspicuous, the arrangement position of the LED (14) arranged along the light incident surface (12a) is slightly shifted, and the end portion of the light emitting surface (12b) Even if the area of the dark part (S) generated in the above is increased, there is no concern that this will be a defective product. For this reason, when arranging the LED (14), it is not necessary to arrange the LED (14) with extremely high positional accuracy, and the production efficiency can be increased.

  According to the present invention, since the uneven portion formed on the light incident surface of the light guide plate is constituted by a continuous curved surface, the light incident on the light guide plate is refracted by the uneven portion and is along the light incident surface. And is scattered in the light guide plate. For this reason, the active area on the light exit surface can be enlarged, the generation of bright lines can be prevented, and a surface light source with high uniformity can be obtained.

  In addition, by making the curvature radius of the concave portion in the concave and convex portion larger than the curvature radius of the convex portion, it is possible to prevent the light incident rate of the light entering the light guide plate from being lowered, and to emit light with higher brightness than the light exit surface. Can be emitted.

  Furthermore, by arranging two or more convex portions of the concavo-convex portion with respect to the light output region of the LED, light entering the light guide plate can be more sufficiently scattered. For this reason, even when a 2-in-1 type LED or a 3-in-1 type LED is used as the light source, uniform light with a well-tuned color can be emitted from the light exit surface. In addition, since the dark part generated on the light exit surface can be made thinner and less conspicuous, it is not necessary to arrange the LEDs with extremely high positional accuracy, and the production efficiency can be increased.

  Therefore, it is possible to expand the active area of the light exit surface, and can emit light with a high degree of uniformity in color with a high brightness, regardless of the type of LED arranged as a light source. Can be provided.

  Hereinafter, the present invention will be described in detail according to illustrated embodiments. A surface light source device (10) of one embodiment of the present invention shown in FIG. 1 is used as a backlight for irradiating a liquid crystal display panel (not shown) of a small device such as a portable information terminal or a digital camera from the back side. In general, it is composed of a light guide plate (12), an LED (14), a reflector (16), a holder (18), and the like.

  The light guide plate (12) is a plate-like member obtained by molding a translucent resin having a small birefringence such as acrylic (PMMA resin) by an injection molding method or the like. A light incident surface (12a) is formed on at least one side end surface of the light guide plate (12), and an upper surface orthogonal to the light incident surface (12a) (meaning the upper surface in FIG. 1; the same applies hereinafter). ) Is formed with a light exit surface (12b). Further, a non-light emitting surface (12c) is formed on the lower surface (meaning the lower surface in FIG. 1; the same applies hereinafter) facing the light emitting surface (12b).

  In addition, a concavo-convex portion (20) in which a plurality of parallel bus bars extend in a direction orthogonal to the light exit surface (12b) is formed in the entire area of the light incident surface (12a).

  The concavo-convex portion (20) is formed of a continuous curved surface having no flat portion, and is configured such that the radius of curvature (R1) of the concave portion (20a) is larger than the radius of curvature (R2) of the convex portion (20b). Has been. In addition, the concavo-convex portion (20) is formed in such a size that two or more convex portions (20b) (9 in FIG. 2) are disposed with respect to the light output region (T) of the LED (14) described later. Has been.

  The non-light-emitting surface (12c) is provided with a predetermined optical pattern (22) composed of white printing dots or reflective grooves over the entire surface, and light guided toward the non-light-emitting surface (12c). Is efficiently turned in the direction of the light exit surface (12b).

  The LED (14) is a light source that emits white light, for example, a white LED that converts light emitted from a GaN-based blue LED into white light using a YAG (yttrium, aluminum, garnet) -based fluorescent material applied on the inner surface of the case. In addition, a 2 in 1 type LED in which two light emitting elements of blue and amber are arranged in parallel, a 3 in 1 type LED in which three light emitting elements of red, green, and blue are arranged in parallel correspond to this. The LED (14) is mounted on a flexible circuit board (FPC) (not shown), and a plurality of LEDs (three in FIG. 1 and three in FIG. 4) are provided along the light incident surface (12a) of the light guide plate (12). 4) are arranged.

  The reflector (16) is for reflecting light leaking from the non-light-emitting surface (12c) of the light guide plate (12) to the light guide plate (12) side, and is a regular reflection member such as a metal foil or the like. It is formed of a diffuse reflection member such as a white PET film.

  Each component configured as described above is housed in a housing-like holder (18) whose upper surface is made of an irregular reflection material such as white PET resin and has an open top surface. Here, by configuring the holder (18) with the irregular reflection material as described above, the light is guided in the light guide plate (12) from the side end surface other than the light incident surface (12a) to the outside of the light guide plate (12). The leaked light is reflected by the side surface of the holder (18) and returned to the light guide plate (12) again. Therefore, the light emitted from the LED (14) can be used efficiently without leakage. Further, since the bottom surface of the holder (18) functions as a reflecting plate, the above-described reflecting plate (16) can be omitted.

  The surface light source device (10) includes a diffusion sheet (not shown) that enhances the appearance and quality of light by relaxing the directivity of light emitted in a planar shape from the light exit surface (12b), and the LED (14) A reflector or the like that reflects light from the light and guides it to the light incident surface (12a) may be provided.

  Next, the operation of the surface light source device (10) of the present embodiment will be described. When the surface light source device (10) is placed on the back of the liquid crystal display panel (not shown) and the LED (14) is turned on, the light emitted from the LED (14) enters the light guide plate (12) from the light incident surface (12a). Shine. Part of the incident light is emitted directly from the light exit surface (12b), and the rest is between the light exit surface (12b) and the non-light exit surface (12c) toward the side end face facing the light entrance surface (12a). Proceed while reflecting.

  Here, when the light (L) from the LED (14) enters the light guide plate (12) from the light incident surface (12a), the light incident surface (20) is formed by the concave and convex portions (20), particularly the convex portions (20b). The light is refracted in the direction along 12a) (that is, at a wide angle). For this reason, when the surface light source device (10) is turned on, the light emitted from the end of the light exit surface (12b), specifically, the LED (14), directly enters the light guide plate (12) from the LED (14). It is possible to reduce the area of the dark part (S) generated in the part where light does not enter, and to enlarge the active area (A) of the light exit surface (12b) (see FIGS. 3 and 4).

  Further, it should be noted that the concavo-convex portion (20) is composed of a continuous curved surface. With this configuration, the light (L) that has entered the light guide plate (12) through the light incident surface (12a) is scattered in the light guide plate (12). For this reason, the dark portion (S) can be made thin and inconspicuous, and the light (L) emitted by the adjacent LEDs (14) can be sufficiently mixed to prevent generation of bright lines, resulting in high uniformity. A surface light source can be obtained.

  Furthermore, since the radius of curvature (R1) of the concave portion (20a) in the concave and convex portion (20) is larger than the radius of curvature (R2) of the convex portion (20b), the light (L) that enters the light guide plate (12) It is possible to prevent the light incident rate from decreasing. Therefore, the light (L) from the LED (14) can be sufficiently incident into the light guide plate (12), and light having a higher luminance than the light exit surface (12b) can be emitted.

  Since two or more protrusions (20b) are arranged with respect to the light output region (T) of the LED (14), the light (L) from the LED (14) enters the light guide plate (12). When light is emitted, the light (L) can be more sufficiently scattered. For this reason, even when a 2in1 type LED (14) or a 3in1 type LED (14) is used as a light source, the light emitted by each element can be sufficiently mixed, and uniform light with a uniform color tone. Can be emitted from the light exit surface (12b). In addition, since the dark portion (S) can be made thinner and less conspicuous, the arrangement position of the LED (14) arranged along the light incident surface (12a) is slightly shifted, and the end of the light emitting surface (12b) Even if the area of the dark part (S) generated in the part increases, there is no concern that this will be a defective product. For this reason, when arranging the LED (14), it is not necessary to arrange the LED (14) with extremely high positional accuracy, and the production efficiency can be increased.

  Thus, according to the surface light source device (10) of the present embodiment, the active area (A) of the light exit surface (12b) can be enlarged, and the degree of uniformity is high regardless of the type of the LED (14) arranged as the light source. It is possible to provide a surface light source device that can emit light having a well-tuned color in a planar shape with high brightness and excellent in productivity.

  In the above-described example, as shown in FIG. 1, the case where the uneven portion (20) is provided in the entire area of the light incident surface (12a) is shown. However, the uneven portion (20) is provided on the light incident surface (12a). You may make it provide only in the part corresponding to the light emission area | region (T) of LED (14). By forming the concavo-convex portion (20) in this way, the processing range of the light incident surface (12a) can be reduced as well as the above-described operation and effect, and the surface light source device (10) (specifically Specifically, the light guide plate (12) can be manufactured more economically.

  The surface light source device of the present invention can enlarge the active area, improve the color mixing of the light emitted from the LED, and emit uniform light with a uniform color tone. In addition to the above, it can be applied to all kinds of backlights using LEDs as light sources. For example, it can be suitably used as a backlight for large liquid crystal display panels such as TV receivers and computer displays.

It is a disassembled perspective view which shows the surface light source device of one Example of this invention. It is a top view which expands and shows the principal part of the surface light source device of one Example in this invention. It is explanatory drawing which shows the effect | action of the surface light source device of one Example in this invention. It is a top view which shows the principal part of the surface light source device of one Example of this invention. It is a top view which shows the principal part of the conventional surface light source device (thing with a flat light-incidence surface). It is a top view which shows the principal part of the conventional surface light source device (what provided the prism part in the light-incidence surface). It is explanatory drawing which shows the effect | action of the conventional surface light source device.

Explanation of symbols

(10) ... Surface light source device
(12) ・ ・ ・ Light guide plate
(12a) ・ ・ ・ Light entrance surface
(12b) ・ ・ ・ Light emitting surface
(12c) ・ ・ ・ Non-light-emitting surface
(14) ... LED
(16) ... Reflector
(18) ・ ・ ・ Holder
(20) ・ ・ ・ Uneven portion
(20a) ・ ・ ・ Recess
(20b) ... Projection

Claims (3)

A light source plate having a light incident surface and a light exit surface orthogonal to the light incident surface, and a surface light source device comprising a plurality of LEDs arranged along the light incident surface,
The surface light source device, wherein the light incident surface is provided with concave and convex portions having a plurality of parallel buses extending in a direction orthogonal to the light exit surface in a continuous curved surface.   The surface light source device according to claim 1, wherein a radius of curvature of the concave portion in the concave and convex portion is larger than a radius of curvature of the convex portion.   The surface light source device according to claim 1, wherein two or more of the convex portions are disposed with respect to a light emission region of the LED.

Images