JP2005293963A - Side light type surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the appearance of a side light type surface light source device, by reducing the difference between light and shade seen near a light source for attenuating unevenness in intensity, and by effectively diffusing emission light. <P>SOLUTION: The side light type surface light source device comprises at least a light guide plate, having a light incidence surface and a light emission surface for emitting incidence light from the light incidence surface in a planar shape; a reflection member arranged at a surface side opposite to the light emission surface of the light guide plate; an optical member arranged at the light emission surface side of the light guide plate; and the light source for emitting light toward the light incidence surface of the light guide plate. In this case, the light transmissive member having difference in light transmittance is arranged between the light guide plate and the reflection member, and distribution in quantity of light incident from the surface opposite to the light incidence surface of the light guide plate is made homogeneous. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sidelight type surface light source device used for a liquid crystal backlight or the like, and more particularly to a surface light source device in which measures for improving the appearance near a light source are taken.

  FIG. 7 is an exploded perspective view showing the basic structure of a conventional sidelight type surface light source device, and FIG. 8 is a cross-sectional view seen from the direction of arrow A in FIG. Reference numeral 1 denotes a light source, for example, a light emitting diode (LED). The light source 1 is mounted on a flexible substrate 8, and the flexible substrate 8 on which the light source 1 is mounted is fixed to a side end portion (light incident surface) of the light guide plate 3 with a double-sided tape 7.

  Reference numeral 5 denotes a case, in which the reflecting member 2 is disposed at the bottom of the case 5, and the light guide plate 3 is disposed on the reflecting member 2. The light source 1 is disposed on the light incident surface side of the light guide plate 3, and the optical member 4 is disposed on the light exit surface side of the light guide plate 3. Reference numeral 6 denotes a chassis having an opening light emitting area 9, which covers the light emitting surface side of the light guide plate 3 so as to correspond to the opening light emitting area 9, thereby forming a sidelight type surface light source device.

  The reflection member 2 is formed in a sheet shape and is a member having a high reflectance. The reflection member 2 is formed by depositing metal particles such as silver on a polyester, polyolefin, or resin sheet, for example.

  The optical member 4 is formed by laminating several kinds of sheet-like members. In FIGS. 7 and 8, a diffusion sheet, a vertical prism sheet, and a horizontal prism sheet are stacked in this order on the light output surface of the light guide plate 3. Is arranged.

  The above-described sidelight type surface light source device includes a reflective member 2 (upper reflective surface) having a high reflectance on the surface side (the lower surface side of the light guide plate 3) facing the light emitting surface of the light guide plate 3 housed in the case 5. ), The light emitted from the light source 1 passes through the light guide plate 3 while being reflected upward by the reflecting member 2. The light launched from the light guide plate 3 passes through the optical member 4 to be adjusted in the emission direction, and is emitted from the opening light emitting area 9 of the chassis 6 to the outside. This device is used as a surface light source device of a liquid crystal display device (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2002-229022 (pages 5 to 6, FIG. 1)

  In the side light type surface light source device shown in the background art, in the opening light emitting area 9 of the chassis 6, a phenomenon in which the vicinity of the light source 1 appears bright and other peripheral parts appear dark, that is, the light emitting surface has a large brightness difference and uneven brightness. There was a problem that it was likely to occur. It is known that this is more likely to occur as the distance from the light incident end face of the light guide plate 3 to the opening light emitting area 9 is shorter and as the light guide plate 3 is thinner. However, recently there has been a strong demand for thinness of the light guide plate due to the thinning of the product, so no good solution has been found.

  An object of the present invention is to improve the appearance of a sidelight type surface light source device by reducing the brightness difference seen near the light source to attenuate luminance unevenness and effectively diffusing emitted light.

  A light guide plate having at least a light incident surface and a light emitting surface that emits light incident from the light incident surface in a planar shape, and a reflecting member disposed on a surface facing the light emitting surface of the light guide plate; In the side light type surface light source device configured by an optical member disposed on the light emitting surface side of the light guide plate and a light source that emits light toward the light incident surface of the light guide plate, the light guide plate and the reflection A sidelight characterized in that a light transmissive member having light transmittance between the members is disposed, and the light quantity distribution of light incident from the surface facing the light incident surface of the light guide plate is homogenized. A mold surface light source device is used.

  A light guide plate having at least a light incident surface and a light emitting surface for emitting light incident from the light incident surface in a planar shape, a case for mounting the light guide plate, and a light emitting surface side of the light guide plate In the side light type surface light source device, which is composed of an optical member that is formed and a light source that emits light toward the light incident surface of the light guide plate, the inner surface of the case facing the surface facing the light output surface of the light guide plate The side light type surface light source device is characterized in that a reflection surface having a high and low reflectivity is formed on a light source, and a light amount distribution of light incident from a surface facing the light emitting surface of the light guide plate is homogenized. .

  Since the light transmissive member disposed on the side of the light guide plate facing the light exit surface is provided with a high or low transmittance, the distribution of the amount of light reflected back into the light guide plate can be adjusted. It is possible to reduce the brightness difference in the vicinity and improve luminance unevenness.

Since the reflection surface provided with the intensity of reflectivity is formed inside the case that is disposed on the side of the light guide plate that faces the light exit surface, the distribution of the amount of light that is reflected back into the light guide plate is returned. Since it can be adjusted, the difference in brightness near the light source can be reduced and the luminance unevenness can be improved. Furthermore, according to this configuration, since the reflective surface is provided on the case, it is not necessary to provide a reflective member separately from the case, the number of parts can be reduced by one, and the thickness of the device can be further reduced.

  By arranging a light transmissive member having light transmittance strength on the side of the light guide plate facing the light exit surface, or by forming a reflective surface having reflectance strength inside the case, By adjusting the amount of light that has not been sufficiently diffused in the past, the light amount distribution is homogenized, thereby reducing the difference in brightness near the light source and improving luminance unevenness.

  FIG. 1 is an exploded perspective view showing a side light type surface light source device according to a first embodiment of the present invention. 2 is a cross-sectional view seen from the direction of arrow A in FIG. Moreover, FIG. 3 is the schematic which looked at the light transmissive member 10 from the arrow B direction of FIG. Parts similar to those of the conventional configuration will be described using the same reference numerals (hereinafter the same). Reference numeral 1 denotes a light source, for example, a light emitting diode (LED). The light source 1 is mounted on a flexible substrate 8, and the flexible substrate 8 on which the light source 1 is mounted is fixed to the side end (light incident surface) side of the light guide plate 3 with a double-sided tape 7.

  Reference numeral 5 denotes a case, and the reflecting member 2 is disposed on the bottom of the case 5. The reflecting member 2 is a sheet-like member, for example, a metal particle such as silver deposited on a polyester, polyolefin, or resin sheet. A light-transmitting member 10 having light transmittance is provided on the surface of the light guide plate that faces the light exit surface to constitute a side light type surface light source device. The light transmissive member 10 is a sheet-like member, which is transparent or translucent, such as polyester. A light source 1 is disposed on the light incident surface side of the light guide plate 3, and an optical member 4 is disposed on the light exit surface side of the light guide plate 3. The optical member 4 is formed, for example, by laminating sheet-like members in the order of a diffusion sheet, a vertical prism sheet, and a horizontal prism sheet from the light emitting surface side of the light guide plate 3. Reference numeral 6 denotes a chassis having an opening light emitting area 9 that covers the light emitting surface side of the light guide plate 3 in correspondence with the opening light emitting area 9.

  In the side light type surface light source device having the above configuration, the light emitted from the light source 1 and transmitted through the light transmissive member 10 passes through the light guide plate 3 while being reflected upward by the reflecting member 2. Most of the light raised from the light guide plate 3 passes through the optical member 4 so that the light emission direction is adjusted, and is emitted from the opening light emitting area 9 to the outside of the sidelight type surface light source device. At this time, in the vicinity of the light source 1, the distribution of the amount of light that is reflected and returned again into the light guide plate is uniformly adjusted by the light transmissive member 10 that provides the light transmittance. With this configuration, it is possible to reduce the brightness difference near the light source 1 and improve luminance unevenness.

  In the light transmissive member 10, there are the following methods as specific examples for providing the light transmittance with a strength. One is a method of forming a gradation pattern 11 as shown in FIG. 3A on the transmission surface 10 a of the light transmissive member 10. One is a method of forming a gradation dot pattern 12 as shown in FIG. 3B on the transmission surface 10 a of the light transmissive member 10. The gradation pattern 11 and the gradation dot pattern 12 are formed such that the light transmittance is smaller as the distance from the light source is closer, and the light transmittance is larger as the distance is farther. As the formation method, for example, the surface roughness is changed by blasting the surface, the surface is shaded by applying ink by printing, or the surface is made into a very fine uneven rough surface. There is something to do.

  FIG. 4 is an exploded perspective view showing a sidelight type surface light source device according to a second embodiment of the present invention. FIG. 5 is a cross-sectional view seen from the direction of arrow A in FIG. Moreover, FIG. 6 is the schematic which looked at the case 5 from the arrow B direction of FIG. The configuration of the second embodiment of the present invention omits the reflecting member as compared with the configuration shown in the prior art, but as an alternative, a reflective surface 5a having higher reflectivity than usual is formed inside the case 5. ing. In order to form a reflective surface having a high reflectance, there are the following methods as specific examples. One is a method of forming a glossy surface having a very high reflectivity by performing bright heat treatment or skin pass finishing after cold rolling a stainless steel plate. The other is a method in which the surface of the stainless steel plate is mirror-polished with a very fine abrasive. The other is a method of forming a glossy surface by depositing metal particles such as silver on a base material of a steel material such as stainless steel. The other is a method of forming a glossy surface by bonding a white reflective polyester layer to a base material of a steel material such as stainless steel. One is a method of forming a glossy surface by bonding a white reflective polyester layer to a base material of a resin material such as polycarbonate.

  With such a configuration, the light emitted from the light source 1 passes through the light guide plate 3 while being reflected upward by the inner reflection surface 5 a of the case 5. Most of the light raised from the light guide plate 3 passes through the optical member 4 so that the light emission direction is adjusted, and is emitted from the opening light emitting area 9 to the outside of the sidelight type surface light source device. At this time, in the vicinity of the light source 1, the distribution of the amount of light reflected and returned again into the light guide plate is uniformly adjusted by the inner reflection surface 5 a of the case 5 having a high and low reflectance. With this configuration, the difference in brightness near the light source 1 can be reduced and luminance unevenness can be improved.

  In the case 5, there are the following methods as specific examples for forming the inner reflection surface 5a having a high and low reflectivity. One is a method of forming a gradation pattern 11 as shown in FIG. One is a method of forming a gradation dot pattern 12 as shown in FIG. The gradation pattern 11 and the gradation dot pattern 12 are formed such that the closer to the light source, the smaller the reflectance and the farther the reflectance is. As the formation method, for example, the surface roughness is changed by blasting the surface, the surface is shaded by applying ink by printing, or the surface is made into a very fine uneven rough surface. There is something to do.

1 is an exploded perspective view showing a side light type surface light source device of the present invention (Example 1). Sectional view seen from the direction of arrow A in FIG. 1 (Example 1) FIG. 1 is a schematic view of a light transmissive member viewed from the direction of arrow B in FIG. An exploded perspective view showing a sidelight type surface light source device of the present invention (Example 2) Sectional view seen from the direction of arrow A in FIG. 3 (Example 2) Schematic of the case seen from the direction of arrow B in FIG. 4 (Example 2) An exploded perspective view showing a basic structure of a conventional sidelight type surface light source device Sectional view seen from the direction of arrow A in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Reflective member 3 Light guide plate 4 Optical member 5 Case 5a Reflective surface 6 Chassis 7 Double-sided tape 8 Flexible substrate 9 Opening light emission area 10 Light transmissive member 10a Transmissive surface 11 Gradient pattern 12 Gradient dot pattern

Claims (2)

  A light guide plate having at least a light incident surface and a light emitting surface that emits light incident from the light incident surface in a planar shape, and a reflecting member disposed on a surface facing the light emitting surface of the light guide plate; In the side light type surface light source device configured by an optical member disposed on the light emitting surface side of the light guide plate and a light source that emits light toward the light incident surface of the light guide plate, the light guide plate and the reflection A sidelight characterized in that a light transmissive member having light transmittance between the members is disposed, and the light quantity distribution of light incident from the surface facing the light emitting surface of the light guide plate is homogenized. Mold surface light source device. A light guide plate having at least a light incident surface and a light emitting surface for emitting light incident from the light incident surface in a planar shape, a case for mounting the light guide plate, and a light emitting surface side of the light guide plate In the side light type surface light source device, which is composed of an optical member that is formed and a light source that emits light toward the light incident surface of the light guide plate, the inner surface of the case facing the surface facing the light output surface of the light guide plate A side light type surface light source device characterized in that a reflection surface having a high and low reflectivity is formed, and a light amount distribution of light incident from a surface facing the light emitting surface of the light guide plate is homogenized.

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