JP2004259709A - Sidelight type surface light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively evade occurrence of brightness unevenness even if length of a light guide plate is made longer than the effective light emission area of a light source by applying this device to a sidelight type surface light source device using, for example, a light guide plate having oriented emitting nature in the sidelight type surface light source applied to a liquid crystal display device or the like. <P>SOLUTION: As for the light guide plate 42 which is formed of wedge profile or the like, the thickness is locally reduced, and furthermore, a light diffusion member is selectively arranged on the incident face side or the like of the outgoing face. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a sidelight type surface light source device applied to a liquid crystal display device and the like, and is applied to, for example, a sidelight type surface light source device using a light guide plate having directional emission. The present invention provides a light guide plate formed in a wedge shape or the like, by locally reducing the thickness, and further by selectively arranging a light diffusing member on an incident surface side of an emission surface, etc. Even if the length of the light guide plate is made longer than the effective light emitting area, it is possible to effectively avoid luminance unevenness.

  2. Description of the Related Art Conventionally, for example, in a liquid crystal display device, a liquid crystal panel is illuminated by a sidelight type surface light source device, thereby reducing the overall shape.

  That is, in the sidelight type surface light source device, a primary light source composed of a rod-like light source such as a cold cathode tube is arranged on the side of a plate-shaped member (that is, composed of a light guide plate), and illumination light emitted from the primary light source is transmitted to the light guide plate. From the end face of the light guide plate. Further, the sidelight type surface light source device is formed so as to deflect the illumination light and emit the illumination light toward the liquid crystal panel from the plane of the light guide plate, whereby the overall shape can be reduced in thickness.

  Such sidelight type surface light source devices include a type in which the light guide plate is formed with a substantially uniform plate thickness, and a type in which the thickness of the light guide plate is gradually reduced as the distance from the primary light source increases, The latter can emit illumination light more efficiently than the former.

  FIG. 15 is an exploded perspective view showing the configuration of the latter sidelight type surface light source device. The sidelight type surface light source device 1 includes a primary light source 3 on a side of a light scattering light guide 2 formed of a light guide plate. Is disposed, and the reflection sheet 4, the light-scattering light guide 2, and the prism sheet 5 as a light control member are laminated to be formed. The primary light source 3 is formed by surrounding a fluorescent lamp 7 formed of a cold-cathode tube with a reflector 8 formed of a reflecting member having a substantially semicircular cross section. Illumination light is incident on the end face.

  The reflection sheet 4 is formed of a sheet-like regular reflection member made of a metal foil or the like, or a sheet-shaped irregular reflection member made of a white PET film or the like.

  The light-scattering light-guiding member 2 is a light-guiding plate having a wedge-shaped cross-section, and is formed by uniformly mixing and dispersing light-transmitting fine particles having a different refractive index from a matrix made of, for example, polymethyl methacrylate (PMMA). You. As a result, as shown in FIG. 16, which is a cross section taken along the line AA, the light-scattering light guide 2 receives the illumination light L from the incident surface T formed on the end surface on the primary light source 3 side, and transmits light-transmitting fine particles. In the case where an irregular reflection member is applied to the reflection sheet 4 while the illumination light L is scattered by the reflection sheet 4, the reflection sheet 4 partially reflects irregularly, and the reflection sheet 4 side plane (hereinafter referred to as a slope) and the prism sheet 5 side plane. (Hereinafter, referred to as an emission surface) and propagates the illumination light L by being repeatedly reflected.

  During this propagation, the illumination light L gradually decreases its incident angle with respect to the exit surface each time it is reflected by the inclined surface, and a component having a critical angle or less with respect to the exit surface is emitted from the exit surface. The illuminating light L1 emitted from the emission surface is scattered by the illuminating light L being scattered by the light-transmitting fine particles inside the light-scattering light guide 2 and diffusely reflected by the reflection sheet 4 and propagated. Is emitted. However, as the illumination light L1 reflects and propagates on a slope formed to be inclined in the propagation direction with respect to the emission surface, the main emission direction is in the wedge-shaped tip direction as shown by the arrow B in an enlarged manner. It is formed inclined. That is, the light L1 emitted from the light guide plate has directivity, whereby the light scattering light guide 2 has directivity.

  The prism sheet 5 is arranged to correct the directivity. That is, the prism sheet 5 is formed of a translucent sheet material such as polycarbonate, and a prism surface is formed on the side surface of the light scattering / guiding member 2. The prism surface is formed by repeatedly forming projections having a triangular cross-section extending substantially parallel to the incident surface T of the light scattering guide 2 from the incident surface T side toward the wedge-shaped tip. Thus, the prism sheet 5 corrects the main emission direction of the emission light L1 to the front direction of the emission surface on the slope of the triangular projection. The prism sheet 5 further includes a prism surface in a groove direction substantially orthogonal to the groove direction of the prism surface formed on the light scattering light guide 2 side on the surface opposite to the light scattering light guide 2 side. In some cases, a so-called double-sided prism sheet having a formed configuration is used. As a result, in the sidelight type surface light source device 1, the emitted light can be efficiently emitted in the front direction as compared with the sidelight type surface light source device in which the light guide plate is formed with a substantially uniform plate thickness. I have.

  In addition, as the light guide plate having directivity as described above, a light guide plate formed into a wedge shape or a shape close to a wedge shape by a transparent member or a translucent member, or a light guide plate formed into a flat plate shape by a transparent member is used. In some cases, a predetermined matte surface, a microlens array, a scattering film, or the like is formed on the light emitting surface and / or the rear surface of the light guide plate. Also in the side light type surface light source device using such a light guide plate, emitted light can be emitted in the front direction by using the above-described prism sheet 5.

  By the way, the fluorescent lamp 7 has electrodes 7a and 7b formed at both ends, and in the vicinity of these electrodes 7a and 7b, a region where the fluorescent material is not applied is formed in the tube. Accordingly, the fluorescent lamp 7 has a drawback in that a region that does not emit illumination light is formed near both ends, and a region that emits illumination light (hereinafter referred to as an effective light emitting region) is shorter than the entire length.

For this reason, in this type of side light type surface light source device, there was a problem that the fluorescent lamp 7 having a short length could not be used. That is, when the length of the light guide plate is longer than the effective light emitting area of the fluorescent lamp, the brightness at both ends of the light guide plate on the incident surface side decreases, and brightness unevenness occurs in the longitudinal direction of the fluorescent lamp.
JP-A-63-33702 Japanese Utility Model Publication No. Sho 62-74282 JP-A-7-288023

  The present invention has been made in view of the above points, and aims to propose a sidelight type surface light source device that can effectively avoid luminance unevenness even if the length of the light guide plate is made longer than the effective light emitting area. Things.

  In order to solve such a problem, in the invention of claim 1, illumination light is incident from an incident surface of a plate-shaped member formed so as to become thinner as the distance from the incident surface increases, and the illumination light is deflected by the plate-shaped member. When applied to a side light type surface light source device that emits light from an emission surface, the plate-shaped member is formed such that the incidence surface is formed in a rectangular shape and the plate thickness is locally reduced.

  Further, in the invention of claim 2, in the configuration of claim 1, the plate thickness is set asymmetrically with respect to a virtual line passing through the center of the effective light emitting area of the light source and orthogonal to the incident surface. To do.

  Further, in the invention of claim 3, the invention is applied to a sidelight type surface light source device in which illumination light emitted from a rod-shaped light source enters from an incident surface of a plate member and is emitted from an exit surface of the plate member. A light diffusing member is selectively disposed on the incident surface side of the exit surface or the reflection surface facing the exit surface.

  Further, in the invention according to claim 4, in the configuration according to claim 3, the light diffusion member is arranged corresponding to an end of the light source, and diffuses light from the end of the light source toward the center. It is formed so that the degree is reduced.

  According to a fifth aspect of the present invention, in the configuration of the third or fourth aspect, the light diffusing members are arranged corresponding to both ends of the light source, and the light diffusing members at both ends are light diffusing members. It is formed so as to have different degrees.

  In the configuration according to claim 1, in the plate-like member formed so that the thickness becomes thinner as the distance from the incident surface increases, the illumination light incident from the incident surface is between the exit surface and the surface facing the exit surface. Propagation while repeating reflection at. At this time, each time the illumination light is repeatedly reflected, the incident angle with respect to the exit surface gradually decreases and propagates, and the component whose incident angle is equal to or smaller than the critical angle is emitted from the exit surface. Accordingly, when the plate thickness is locally reduced by the configuration of claim 1, the change in the incident angle due to reflection increases, and the number of reflections increases, so that the light is emitted from the emission surface when propagating over a certain distance. The amount of light increases. Therefore, by forming such a region on the incident surface side, the luminance at both ends can be improved, and even when a light source having a short length is used, luminance unevenness in the longitudinal direction of the light source can be effectively avoided.

  According to the configuration of claim 2, in the configuration of claim 1, the plate thickness is set asymmetrically with respect to a virtual line passing through the center of the effective light emitting area of the light source and orthogonal to the incident surface. Accordingly, the degree of improvement in luminance can be made different accordingly, and the difference in the amount of light depending on the end of the light source can be compensated.

  According to the third aspect of the present invention, when the light diffusing member is selectively disposed on the exit surface or the reflecting surface, the illumination light is scattered by the light diffusing member, and the illumination light on the exit surface is provided in the vicinity where the light diffusing member is disposed. Can be changed. That is, the incident angle of the illumination light can be corrected so that the components above the critical angle are included below the critical angle, and the brightness in the vicinity can be improved. Therefore, this can also effectively avoid luminance unevenness in the longitudinal direction of the light source.

  According to the configuration of claim 4, in the configuration of claim 3, the light diffusion member is disposed corresponding to an end of the light source, and a degree of light diffusion from the end of the light source toward the center. Is formed so as to decrease, it is possible to increase the amount of emitted light that decreases on the end side of the light source, and effectively avoid luminance unevenness.

  According to the configuration of claim 5, in the configuration of claim 3 or claim 4, the light diffusion members are arranged corresponding to both ends of the light source, and the light diffusion members at both ends are provided with a light diffusion degree. Are formed so as to be different from each other, it is possible to effectively avoid the uneven brightness by increasing the amount of emitted light that decreases at both ends of the light source differently.

  According to the present invention, luminance unevenness can be effectively avoided even if the length of the light guide plate is made longer than the effective light emitting region.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

  FIG. 1 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a first embodiment of the present invention. In FIG. 1, members such as the reflection sheet 4 are omitted, and the same components as those of the sidelight type surface light source device described above with reference to FIGS. Is omitted.

  In the sidelight type surface light source device 10, the length of the fluorescent lamp 11 including the rod-shaped light source including the electrodes 11a and 11b at both ends is shorter than the length of the incident surface of the light-scattering light guide 2 including the light guide plate. The light-scattering light guide 2 has a length extremely shorter than that of the light-scattering light guide 2.

  In the sidelight type surface light source device 10, an illumination light introducing unit 12 is arranged between the incident surface of the light scattering guide 2 and the fluorescent lamp 11, and the illumination light introducing unit 12, the fluorescent lamp 11 and the reflector 8, a primary light source is formed. Here, the illumination light introducing unit 12 spreads the illumination light of the fluorescent lamp 11 to both ends of the fluorescent lamp 11 and guides the illumination light to the incident surface of the light scattering light guide 2.

  Specifically, in the first embodiment, the illumination light introducing unit 12 is formed by a trapezoidal prism 12a and parallelogram prisms 12b and 12c. The lamp 11 is disposed substantially at the center of the incident surface such that both ends of the lamp 11 are on the slope side. On the other hand, the parallelogram prisms 12b and 12c are arranged on the slope of the trapezoidal prism 12a and on the end side of the entrance surface such that the slope and the slopes of the parallelogram prisms 12b and 12c are separated by a small interval. Is done.

  Similarly to the light scattering guide 2, the trapezoidal prism 12a is formed by uniformly mixing and dispersing light-transmitting fine particles having a different refractive index from a matrix made of, for example, polymethyl methacrylate (PMMA). You. On the other hand, the parallelogram prisms 12b and 12c are formed of, for example, a transparent member such as polycarbonate, and the angle formed by the bottom surface and the slope is selected to be a predetermined angle equal to the angle formed by the slope of the trapezoid prism 12a and the lower base. It has been made.

  Here, this angle is an angle that is sufficient for the parallelogram prisms 12b and 12c to completely reflect the light vertically incident from the upper surface on the inclined surface, so that the parallelogram prisms 12b and 12c pass the illumination light L2. The light enters from the upper surface and is sequentially reflected and emitted from the opposite slope. That is, the parallelogram prisms 12b and 12c are configured to bend the optical path of the illumination light L2 incident from the upper surface to both ends of the light-scattering light guide 2 by bending.

  On the other hand, the trapezoidal prism 12a scatters the illumination light L3 by the internal fine particles, and enters the illumination light L3 incident on the shaded portions of the slopes of the parallelogram prisms 12b and 12c generated by distributing the illumination light L2 to both sides. Are distributed and emitted.

  Further, as shown in FIG. 2, the trapezoidal prism 12a and the parallelogram prisms 12a and 12c are selected to have a thickness such that a step does not occur between the exit surface and the inclined surface of the light-scattering light guide 2, and the exit surface and the The emission surface and the surface corresponding to the slope are formed so that the angle does not suddenly change with respect to the slope. Accordingly, the trapezoidal prism 12a and the parallelogram prisms 12a and 12c prevent a space from being formed between the trapezoidal prism 12a and the parallelogram prisms 12a and 12c when the primary light source is held by the light scattering / guiding member 2 via the reflector 8. It is designed to effectively avoid uneven brightness of the emitted light due to the formation of the seed space.

  Thus, in the first embodiment, the parallelogram prisms 12a and 12c constitute a first optical block that bends the optical path of the illumination light emitted from the end of the light source and distributes the light to the end of the light-scattering light guide. The trapezoidal prism 12a constitutes a second optical block for diffusing the illumination light emitted from the light source toward the first optical block.

  In the above configuration, the illumination light emitted from the effective light emitting region of the fluorescent lamp 11 is directly or after being reflected by the reflector 8 and then incident on the incident surface of the light scattering guide 2 via the illumination light introducing portion 12. I do. At this time, the illumination light is spread to both end sides of the incident surface in the illumination light introduction unit 12 and guided to the incident surface of the light scattering light guide 2.

  Specifically, of the illumination light, the illumination light L2 emitted from the end of the effective light emitting area AR mainly enters from the upper surfaces of the parallelogram prisms 12a and 12c constituting the illumination light introduction unit 12, The light is split and emitted to both ends of the light-scattering light guide 2 by the parallelogram prisms 12a and 12c. Thus, even when the length of the light scattering light guide 2 is longer than the effective light emitting area of the fluorescent lamp 11, sufficient illumination light L2 is incident on the end of the light scattering light guide 2 and the corresponding area on the emission surface. Brightness increases.

  On the other hand, the illumination light L3 emitted from the vicinity of the center of the effective light emitting area AR mainly enters from the upper bottom side surface of the trapezoidal prism 12a constituting the illumination light introduction unit 12, and is scattered in the trapezoidal prism 12a. Then, the light is incident on the incident surface of the light scattering guide 2. As a result, in the light-scattering light guide 2, a sufficient amount of illumination light L3 can be incident on the shaded portions of the slopes of the parallelogram prisms 12b and 12c generated by distributing the illumination light L2 to both sides. Therefore, the uneven brightness of the emitted light can be effectively avoided.

  According to the above configuration, the illumination light introducing unit 12 is arranged between the incident surface of the light scattering guide 2 and the fluorescent lamp 11, and the illumination light of the fluorescent lamp 11 is Of the fluorescent lamp 11 in the longitudinal direction of the fluorescent lamp 11 even when the effective light emitting area AR of the fluorescent lamp 11 is shorter than that of the light scattering guide 2. Brightness unevenness can be effectively avoided. Accordingly, the overall shape of the sidelight type surface light source device 10 can be reduced accordingly.

  Further, since the illumination light introducing portion 12 is formed by the trapezoidal prism 12a and the parallelogram prisms 12b and 12c arranged on the slope of the trapezoidal prism 12a, the illumination light L2 emitted from the end of the effective light emitting area AR is formed. Are distributed to both ends of the parallelogram prisms 12a and 12c, and the illumination light L3 emitted from the vicinity of the center of the effective light emitting area AR is scattered in the trapezoid prism 12a to form the parallelogram prism. It can be distributed to the shaded portions of the slopes 12b and 12c, whereby even if the length of the fluorescent lamp 11 is extremely short, it is possible to effectively avoid luminance unevenness in the longitudinal direction of the fluorescent lamp 11.

  FIG. 3 is a plan view illustrating the sidelight-type surface light source device according to the second embodiment. In this side light type surface light source device 20, the fluorescent lamp 21 has a length including the electrodes 21a and 21b at both ends substantially equal to the light scattering light guide 22, and an effective light emitting area AR having a length equal to the light scattering light guide. A shorter one is applied.

  On the other hand, the light-scattering light guide 22 is formed such that the incident surface side protrudes toward the fluorescent lamp 21, and both ends of the incident surface extend obliquely toward the inside of the fluorescent lamp 21. I have. Thus, in the second embodiment, the illumination light introducing portion 23 is configured by the obliquely extending extensions 22a and 22b and the incident surface side region 22c enlarged to the fluorescent lamp 21 side.

  Here, the extended portions 22a and 22b are formed in substantially the same shape as the parallelogram prism in the first embodiment described above, so that the illumination light L2 emitted from the end of the effective light emitting area AR is diffused. The light is distributed to both ends of the scattering light guide 22.

  On the other hand, in the incident surface side region 22c enlarged toward the fluorescent lamp 21, the incident surface is formed on the mat surface (textured surface) by the mat surface treatment, and near the center of the effective light emitting region AR due to the mat surface and the internal fine particles. The emitted illumination light L3 is scattered, and the illumination light L3 is distributed to the shadow portions of the extended portions 22a and 22b at the original incident surface position.

  According to the second embodiment, both ends of the light-scattering light guide 22 corresponding to the end of the light source are obliquely extended toward the effective light-emitting area to form the illumination light introduction unit 23. Although not to the same extent, similar effects can be obtained. Further, since the light-scattering light guide 22 and the illumination light introducing portion 23 can be integrally formed, the overall configuration can be simplified accordingly.

  FIG. 4 is a plan view illustrating the sidelight-type surface light source device according to the third embodiment. Also in this side light type surface light source device 30, the fluorescent lamp 21 has a length including the electrodes 21a and 21b at both ends substantially equal to the light scattering light guide 32, and the length of the effective light emitting area AR is light scattering light guiding. It is adapted to be shorter than the body 32.

  On the other hand, the light-scattering light guide 32 has an extended portion 32a formed so that the incident surface protrudes toward the fluorescent lamp 21, and a slit 33 is formed radially in the extended portion 32a. That is, the extension portions 22a are formed with slits at a constant pitch from the center toward both ends, and as the slits 33 become more distant from the center, they are inclined to both end sides with respect to the incident surface of the extension portion 32a, and have a wedge-shaped tip. It is made to be formed deeply toward. The extension 22a is formed with slopes at both ends corresponding to the inclination of the slit that changes as the distance from the center increases.

  Thus, in this embodiment, a large number of trapezoidal prisms are formed on the incident surface of the light scattering guide 32 by these slits 33. Further, the inclination and depth of these slits 33 are gradually changed so that the shape and size of the trapezoidal prism gradually change from the center of the effective light emitting area toward the end, whereby the illumination incident from the fluorescent lamp 21 is obtained. The light is largely bent toward the end portion toward the end portion.

  That is, the extension portion 32 a reflects the illumination light outward by the end side surface of the slit 33, and reflects the illumination light reflected by the end side surface in the original direction by the central side surface of the slit 33. In addition, the extension 32a also scatters the illumination light due to the internal fine particles. Thus, the extension portion 32a operates to spread the illumination light incident from the incident surface toward both end sides of the light scattering light guide 32 and to guide the light to the original incident surface of the light scattering light guide 32.

  Thereby, in this embodiment, the illumination light introducing section 34 is constituted by the extension 32a in which the slit 33 is formed.

  According to the configuration of FIG. 4, the incident surface side of the light-scattering light guide 32 is extended to the fluorescent lamp 21 side, and a slit 33 is radially formed in the extended portion 32a, and the illumination light introducing portion is formed by the extended portion 32a. Even if it is configured, the same effect can be obtained, though not as much as in the first embodiment. Further, since the light-scattering light guide 32 and the illumination light introducing portion 34 can be integrally formed, the overall configuration can be simplified accordingly.

  FIG. 5 is a perspective view illustrating a light-scattering light guide applied to the sidelight-type surface light source device according to the fourth embodiment. The light scattering light guide 42 is applied to a side light type surface light source device in combination with a fluorescent lamp having a length including the electrodes at both ends substantially equal to the length of the light scattering light guide.

  Here, as shown in FIGS. 6 to 8, the light-scattering light-guiding member 42 sequentially takes a cross section from the wedge-shaped tip toward the incident surface side by a BB cross section, a CC cross section, and a DD cross section. While the incident surface 42a is kept in a rectangular shape, the slope side is formed so as to meander smoothly on the end side near the incident surface 42a, and thereby, the plate thickness at both ends near the incident surface 42a is It is made thin locally.

  That is, in the sidelight type surface light source device using the light scattering light guide, the illumination light incident from the end surface propagates while being repeatedly reflected between the emission surface and the inclined surface. At this time, every time the illumination light is repeatedly reflected, the incident angle with respect to the emission surface gradually decreases, and a component of which the incident angle becomes equal to or smaller than the critical angle is emitted from the emission surface. Therefore, in a region where the plate thickness is locally reduced, the angle of incidence is increased by locally changing the slope of the slope and by increasing the number of reflections when propagating over a certain distance as the plate thickness decreases. Changes, thereby increasing the amount of illumination light emitted from the emission surface.

  As a result, in the light scattering / guiding member 42, the amount of emitted light is increased at the end portion near the incident surface 42a from the region where the plate thickness is locally reduced, and the brightness at both ends is improved. ing. Furthermore, the illumination light at the wedge-shaped tip and at both ends, which are insufficient by locally increasing the amount of emitted light, is compensated for by the scattered light due to the internal fine particles, thereby effectively avoiding the uneven brightness.

  In addition, while the incident surface is maintained in a rectangular shape, the plate thickness is locally reduced at both ends near the incident surface 42a, so that illumination light incident from the incident surface is efficiently incident as before. Further, by forming the slope so as to meander smoothly, a sudden change in the slope due to the locally thinned plate thickness is prevented from being observed from the emission surface, thereby also effectively preventing luminance unevenness. .

  According to the configuration shown in FIG. 5, while the incident surface 42a is maintained in a rectangular shape, the slope near the end surface near the incident surface 42a is smoothly meandered to locally increase the thickness of the light scattering light guide 42. Even if the thickness is reduced, the same effect as in the above-described embodiment can be obtained.

  FIG. 9 is a perspective view illustrating a sidelight-type surface light source device according to a fifth embodiment. Since the other configuration according to this embodiment is the same as the conventional configuration described above with reference to FIG. 15, the description of the other members will be omitted in FIG.

  In this embodiment, the light-scattering light guide 52 is formed so that the incident surface side protrudes toward the fluorescent lamp 21, and further, the end on the incident surface side protrudes toward the fluorescent lamp 21. ing. Thus, in this embodiment, the illumination light introducing portion 53 is constituted by the extended portions 52a and 52b extended at both ends and the incident surface side region 52c enlarged toward the fluorescent lamp 21 side.

  Here, the outer side surfaces of the extending portions 52a and 52b are formed so as to extend from the side surfaces of the light scattering guide 52. On the other hand, on the inner side surfaces of the extended portions 52a and 52b, a gentle curved surface is drawn and connected to the incident surface side region 52c, so that the illumination light introducing portion 53 has a gently concave region corresponding to the effective light emitting region. The light-scattering light guide 52 is formed so that the incident surface side is enlarged toward the fluorescent lamp 21 so as to change the shape, and illumination light is incident from the concave incident surface.

  That is, the illumination light emitted from the effective light emitting region includes a component emitted so as to spread to the end side, and such a component is compared with the illumination light emitted toward the front of the fluorescent lamp 21, The feature is that the amount of light per unit area is small. The illumination light introducing section 53 converges the component emitted so as to spread to the end side inward by the concave incident surface and condenses the component, and the light scattering guide 52 of the light scattering light guide 52 at the original incident surface position. The brightness is distributed to the end portions, thereby effectively avoiding luminance unevenness.

  According to the configuration shown in FIG. 9, even if the incident surface side of the light-scattering light guide 52 is enlarged to the fluorescent lamp side so that the portion corresponding to the effective light-emitting area gradually changes to a concave shape, The same effect as the example can be obtained.

  FIG. 10 is a perspective view illustrating a sidelight-type surface light source device according to a sixth embodiment. Since the other configuration according to this embodiment is the same as the conventional configuration described above with reference to FIG. 15, the description of the other components in FIG. 10 will be omitted.

  In this embodiment, the light scattering / guiding member 2 is configured such that a diffuser 61 made of a light diffusing member is attached to each of an incident surface side and both ends of the light emitting surface. Here, the diffuser 61 is formed by processing a white PET film into a right-angled triangular shape as shown in FIG. 11, and using a predetermined adhesive so that the right-angled portion coincides with a corner of the light-scattering light guide 2. Is attached to the light scattering light guide 2.

  Here, this adhesive is an adhesive having a refractive index extremely close to that of the light-scattering light guide 2 and a large transmittance used for bonding the optical glass. Thus, the light-scattering light guide 2 is configured to scatter the illumination light at both ends on the incident surface side.

  That is, in the illumination light emitted from the effective light emitting area AR, there is a component emitted so as to spread toward the end. However, since the effective issuance area AR of the fluorescent lamp 11 has an elongated shape substantially parallel to the incident surface, the illumination light emitted so as to spread toward the end first has a small light amount itself. In addition, there are many components having a large incident angle. As a result, in the conventional light-scattering light guide 2, the illumination light arriving at the end from the incident surface has very little emission from near the incident surface, and is gradually emitted as it propagates toward the wedge-shaped tip. .

  That is, in the conventional light-scattering light guide 2, although the illumination light is distributed at the end of the incident surface, these illumination light have a large incident angle with respect to the exit surface, and Almost no light was emitted. Thus, if the diffuser 61 is disposed at the end and the end-side illumination light is scattered as in this embodiment, the incident angle of the illumination light with respect to the emission surface can be converted into a wide angle distribution. In addition, the amount of light emitted from near the incident surface can be increased.

  However, if the amount of the diffused illumination light is excessively increased, the luminance level at the end portion is extremely increased, and the luminance unevenness occurs instead. Thus, in this embodiment, the shape of the diffuser 61 is set to a right-angled triangular shape, and the degree of diffusion increases toward both ends.

  That is, the diffuser 61 is selected such that the length W on the incident surface side is substantially equal to the length of the electrodes 11 a and 11 b of the fluorescent lamp 11 corresponding to the region where the amount of emitted light is increased. Further, the height H on the end side is selected according to the light amount to be increased, and the shape of the side connecting the base and the height is selected according to the light amount distribution to be further increased. By the way, in the case where a larger light amount increase is required on the end side compared to this embodiment, it is necessary to increase the height H and change the hypotenuse to a hyperbolic or arcuate shape to secure a desired luminance distribution. Can be.

  According to the configuration shown in FIG. 10, the diffuser 61 is selectively attached to the incident surface side of the light scattering guide 2 corresponding to the end of the light source, and the diffuser 61 scatters the illumination light. Accordingly, with a simple configuration, even if the length of the light guide plate is made longer than the effective light emitting area of the light source, it is possible to effectively avoid luminance unevenness.

  By the way, when the luminance unevenness at the end is reduced by the above-described embodiments 1 to 6, in the sidelight type surface light source device, a difference in luminance is perceived at both ends on the incident surface side.

  That is, as shown in FIG. 12, in the fluorescent lamp 11 applied to this type of side light type surface light source device, after the drive power output from the drive circuit 62 is boosted by the boost transformer T, the capacitor C Supplied via At this time, one electrode 11b of the fluorescent lamp 11 is grounded, so that unnecessary radiation is reduced.

  In this manner, the fluorescent lamp 11 has the ground-side electrode 11b set to the cold side L, the capacitor-side electrode 11a set to the hot side H, and the amount of illumination light emitted from the cold-side L end becomes higher than the hot-side H end. There is a disadvantage that the amount of emitted illumination light is smaller than that. Thus, in the sidelight type surface light source device, when the luminance unevenness at the end is reduced, the difference in the light amount between the cold side L and the hot side H is perceived as the difference in the luminance at the end.

  Therefore, in this embodiment, as shown in FIG. 13, the shape of the exit surface and the diffusers 66a and 66b disposed at both ends are set to different shapes, thereby effectively avoiding luminance unevenness, To prevent a difference in luminance.

  That is, the diffusers 66a and 66b are formed in the shape of a right triangular shape by cutting off the tip, and are set to the same height H. The tip of the hot diffuser 66a is cut larger than the cold diffuser 66b, and the length W2 is set to be shorter than the length W1 of the cold diffuser 66b. As a result, the cold-side diffuser 66b is formed so that the degree of diffusion is greater than that of the hot-side diffuser 66a, and the amount of outgoing light is increased by that amount to compensate for the decrease in luminance on the hot side. ing.

  According to the configuration shown in FIG. 13, diffusers 66a and 66b having different shapes and different degrees of diffusion are attached to the ends of the light-scattering light guide 2 corresponding to the ends of the light source. As a result, the difference in luminance at the end can be prevented in addition to the effect of the sixth embodiment.

  FIG. 14 is a perspective view of the sidelight type surface light source device according to the eighth embodiment. In this embodiment, the sidelight-type surface light source device 70 supplies illumination light to the large light diffusion / stray light guide 72 using two fluorescent lamps 11. In this case, the side light type surface light source device 70 has two fluorescent lamps 11 arranged linearly on the incident surface. Further, the diffusers 71a, 71b and 71c are arranged on the emission surface of the light-scattering light guide 72 corresponding to the electrodes 11a and 11b when the fluorescent lamp 11 is arranged in this manner, thereby effectively avoiding luminance unevenness. Further, a difference in luminance at the end portion is prevented.

  According to the configuration shown in FIG. 14, the diffusers 71a, 71b, and 71c are attached to the light scattering / guiding member 2 corresponding to the ends of the light source, so that the light source Even when the length of the light guide plate is longer than the substantial effective light emitting area, it is possible to effectively avoid luminance unevenness.

  In the above-described Examples 6, 7, and 8, a case has been described in which a diffuser is arranged by attaching a white PET film with an optical adhesive, but the present invention according to Claim 3 is not limited thereto. When various diffusion sheets are adhered with an optical adhesive, when a silver sheet made of a regular reflection member is adhered with a double-sided tape having light scattering properties, when white ink is adhered, locally roughened A similar effect can be obtained by arranging various light diffusing members such as a case where a reflecting member is arranged after the surface treatment.

  Furthermore, in Embodiments 6, 7, and 8 described above, the case where the diffuser is arranged on the emission surface side has been described. However, the present invention according to claim 3 is not limited to this, and instead or in addition to this. May be arranged on the slope side.

  In the above-described embodiment, the case where the incident surface of the illumination light introducing unit is appropriately roughened by the matte surface treatment has been described. However, the method of roughening is not limited thereto, and the blasting process using sandpaper, In the case of forming a rough surface by a chemical etching process, various rough surface forming means can be widely applied. In addition to the case where the illumination light is diffused by roughening, a light diffusion material such as white ink may be attached to the incident surface, or a diffusion sheet or the like may be arranged to diffuse the illumination light incident from the incident surface. .

  Further, in the above-described first to fifth embodiments, the case where the illumination light introducing portion is formed in a symmetric shape has been described. However, the present invention is not limited to this, and the illumination light introducing portion may be formed in an asymmetric shape. In this case, as described above in the seventh embodiment corresponding to the sixth embodiment, different luminances can be corrected on the hot side and the cold side. In addition, it is possible to cope with the case where the fluorescent lamp is arranged shifted from the light guide plate.

  Further, in the above-described first to third and fifth embodiments, the illumination light introducing portion is arranged, and in the fourth embodiment, the plate thickness is locally reduced, and in the sixth to eighth embodiments, the diffuser is provided. Has been described above to reduce the uneven brightness, but the present invention is not limited to this, and these means may be combined.

  In the above-described embodiment, the case where the illumination light is incident from one end face is described. However, the present invention is not limited to this, and the present invention is also applicable to a sidelight type surface light source device configured to receive the illumination light from another end face. Can be widely applied.

  Further, in the above-described embodiment, the case where the present invention is applied to the surface light source device of the liquid crystal display device has been described. Can be widely applied.

  The present invention can be applied to, for example, a sidelight type surface light source device using a light guide plate having directional emission.

FIG. 2 is an enlarged plan view showing a light source side of the sidelight type surface light source device according to the first embodiment of the present invention. FIG. 2 is a side view of FIG. 1. FIG. 6 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a second embodiment of the present invention. FIG. 9 is an enlarged plan view showing a light source side of a sidelight type surface light source device according to a third embodiment of the present invention. FIG. 13 is a perspective view showing a light scattering light guide applied to a side light type surface light source device according to a fourth embodiment of the present invention. FIG. 6 is a cross-sectional view taken along a line BB of FIG. 5. FIG. 6 is a cross-sectional view taken along the line CC of FIG. 5. FIG. 6 is a cross-sectional view taken along the line DD of FIG. 5. It is a perspective view showing the light source side of the sidelight type surface light source device according to Example 5 of the present invention. It is a perspective view showing the light source side of the sidelight type surface light source device according to Example 6 of the present invention. It is a top view which expands and shows the light source side of FIG. FIG. 4 is a connection diagram for explaining a driving method of a fluorescent lamp. It is a top view which expands and shows the light source side of the side light type surface light source device concerning Example 7 of this invention. It is a perspective view showing the light source side of the sidelight type surface light source device according to Example 8 of the present invention. It is an exploded perspective view showing the conventional side light type surface light source device. FIG. 16 is a cross-sectional view of the sidelight type surface light source device of FIG. 15 taken along a line AA.

Explanation of reference numerals

1, 10, 20, 30, 50, 60, 70 side light type surface light source device, 2, 22, 32, 42, 52, 72 light scattering guide 4, reflection sheet 5, 5 Prism sheet, 7, 11, 21 Fluorescent lamp 8, Reflector 12, 23, 34, 53 Illumination light introducing section 12a Trapezoidal prism 12b, 12c Parallelogram prism 61 66a, 66b, 71a, 71b ... diffuser

Claims (5)

In a side light type surface light source device, which receives illumination light from an incident surface of a plate-shaped member formed so as to have a smaller thickness as the distance from the incident surface becomes smaller, and is deflected by the plate-shaped member and emitted from an emission surface,
The plate member,
The incident surface is formed in a rectangular shape,
A side light type surface light source device characterized in that the plate thickness is locally reduced. The plate thickness is
The sidelight type surface light source device according to claim 1, wherein the sidelight type surface light source device is set to be asymmetrical with respect to a virtual line passing through a center of an effective light emitting area of the light source and orthogonal to the incident surface. In the sidelight type surface light source device, the illumination light emitted from the rod-shaped light source is incident from the incident surface of the plate-shaped member, and is emitted from the emission surface of the plate-shaped member.
A side light type surface light source device, wherein a light diffusing member is selectively disposed on the incident surface side of the exit surface or the reflection surface facing the exit surface. The light diffusion member,
The side light according to claim 3, wherein the side light is arranged corresponding to an end of the light source, and is formed so that a degree of light diffusion decreases from an end of the light source toward a center. Mold surface light source device. The light diffusion member,
It is arranged corresponding to both ends of the light source,
The light diffusion members at both ends,
The sidelight type surface light source device according to claim 3, wherein the sidelight type surface light source device is formed to have different degrees of light diffusion.

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