JP5360448B1 - Surface lighting device - Google Patents

Abstract

In a planar illumination device including a light guide plate manufactured by injection molding, the quality of illumination light is improved.
A planar illumination device 10 surrounds a light source 52, a light guide plate 12 configured to emit light emitted from the light source 52 as planar light, and outer peripheral side surfaces 16 to 19 of the light guide plate 12. And a housing frame 32 having side walls 36-39. Projections 22 and 24 for positioning the light guide plate 12 on the housing frame 32 are formed on the outer peripheral side surfaces 17 and 19 of the light guide plate 12. The light guide plate 12 is ejected by providing an inlet at a side end of the projection 22. Molded. As a result, the cross section of the cut trace 23 at the inlet can be moved away from the outer peripheral side surface 17, and the influence of abnormal light emission of this cross section on the illumination light can be reduced.
[Selection] Figure 1

Description

  The present invention relates to a planar illumination device, and more particularly to a planar illumination device suitable as a backlight of a liquid crystal display device.

  Currently, sidelight type planar illumination devices are widely used as backlights for liquid crystal display devices. This type of planar illumination device includes a light guide plate having a main surface that is approximately the same size as the screen, and a light source disposed on a side end surface of the light guide plate, and receives light incident from the side end surface of the light guide plate. By emitting from the main surface, the screen is illuminated uniformly.

  The light guide plate of such a planar illumination device is generally manufactured by injection molding using a resin material (see, for example, Patent Document 1). Here, an example of the manufacturing process of the light guide plate described in Patent Document 1 will be described with reference to FIG. In FIG. 4, the light guide plate 102 is molded by injecting and injecting a heat-melted resin into the mold 110 and then cooling and solidifying the injected resin. At this time, since the molded product includes an inflow port 108 of a resin unnecessary as a product, the light guide plate 102 is completed by cutting the inflow port 108 after the molded product is taken out from the mold 110 (see FIG. The dashed-dotted line C shown in 4 has shown the typical cutting line). Such cutting processing of the inlet 108 is conventionally performed using a laser beam or a hot nipper for cutting a resin material.

JP 2009-69714 A

  Conventionally, the light guide plate 102 manufactured by injection molding is completed through the cutting process of the inflow port 108 as described above. Therefore, the finished product of the light guide plate 102 has a cut mark obtained by cutting the inflow port 108. 109 (so-called gate mark) is formed. And, since the cut surface is usually rough, the light incident on the light guide plate from the light source is scattered by the cut surface, resulting in a specific bright spot near the cut mark of the light guide plate (hot spot), or There is a problem that abnormal light emission occurs such that a light column may be seen when the vicinity of the cut mark is viewed, and as a result, the quality (quality) of illumination light emitted from the normal light emitting area of the light guide plate is deteriorated.

  An object of this invention is to improve the quality of illumination light in the planar illuminating device provided with the light-guide plate manufactured by injection molding in view of the said subject.

  The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further, while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

(1) A planar illumination device comprising a light source, a light guide plate configured to emit light emitted from the light source as planar light, and a housing frame having a side wall surrounding an outer peripheral side surface of the light guide plate in the outer peripheral side surface of the light guide plate, the projections of the light guide plate for positioning the housing frame is formed, the light guide plate is injection-molded an inlet provided on the side end portion of the projection The shape of the connection portion of the inflow port with the side end portion of the projection is slightly smaller than the shape of the side end portion of the projection, and the outer peripheral surface of the inflow port on the exit surface side of the light guide plate is The planar illumination device is provided so as to be flush with the outer peripheral surface of the light guide plate on the light exit surface side of the protrusion .

According to the planar illumination device described in this section, a protrusion for positioning the light guide plate on the housing frame is formed on the outer peripheral side surface of the light guide plate, and the light guide plate has an inlet at a side end portion of the protrusion. Since the cut surface of the cut trace formed by cutting the inlet after the injection molding of the light guide plate is moved away from the outer peripheral side surface of the light guide plate by the protrusion dimension of the projection. Even if abnormal light emission occurs, it is possible to reduce the adverse effect on the quality of the illumination light emitted from the light emitting area in the design of the light guide plate.
In addition, according to the planar illumination device described in this section, the shape of the connection portion with the side end of the projection of the inflow port is slightly smaller than the shape of the side end of the projection. When cutting the inlet after molding, even if burrs or deformations occur in the cut marks, the possibility that the resin bulge due to the burrs and / or deformation reaches the outer peripheral surface of the protrusion is eliminated or reduced. It is possible to reduce the adverse effect of the cutting trace on the positioning of the light guide plate with respect to the housing frame.
Further, in the planar illumination device described in this section, the outer peripheral surface of the light guide plate at the inlet is on the same side as the outer peripheral surface of the light guide plate on the output surface side of the projection. The gap between the outer peripheral surface on the light guide plate side of the inlet and the outer peripheral surface on the light guide plate side of the projection is eliminated, and the structure of the mold is simplified, and burrs caused by the step during injection molding are eliminated. The risk of occurrence is eliminated.

(2) The planar illumination device according to (1) , wherein a cut mark obtained by cutting the inflow port is disposed at a side end portion of the protrusion. 2).

(3) In the planar illumination device according to (1) or (2), the light guide plate has a wedge shape whose thickness decreases from an incident surface side to an opposite outer peripheral side surface side of the light guide plate. A planar lighting device (claim 3).

  Since this invention was comprised as mentioned above, in the planar illuminating device provided with the light-guide plate manufactured by injection molding, it becomes possible to improve the quality of illumination light.

It is a top view which shows the principal part of the planar illuminating device in the reference example of this invention. In the spread illuminating apparatus in reference example of the present invention, in order to show the configuration of the protruding portion of the light guide plate, and an enlarged view showing an A portion of the light guide plate shown in FIG. 1, (a) is a plan view, (B) is a side view. In the planar illuminating device in one Embodiment of this invention, it is a figure which shows an example of a structure of the protrusion part of a light-guide plate, (a) is a top view, (b) is a side view. In the conventional planar illuminating device, it is a top view which shows an example of the injection molding process of a light-guide plate.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, each figure (FIGS. 1-3) which shows the whole or a part of a planar illuminating device is a schematic diagram which emphasizes the characteristic for description, Comprising: Relative of each part shown in figure is shown. The dimensions do not necessarily reflect the actual scale.

FIG. 1 is a plan view showing a main part of a planar illumination device in a reference example of the present invention.
A planar illumination device 10 shown in FIG. 1 is suitably applied as a backlight of a transmissive (or transflective) liquid crystal display device, and stores a light guide plate 12, a light source 52, and these members. Housing frame 32.

  The light guide plate 12 is a plate-like light guide formed by injection molding from a transparent resin material such as methacrylic resin or polycarbonate resin. In the planar lighting device 10, the light guide plate 12 is formed in a substantially rectangular shape in plan view, and is one of the four outer peripheral side surfaces 16 to 19 (in the illustrated example, the outer peripheral side surface 16. A light source 52 is also disposed on the incident surface. Further, the outer peripheral side surfaces 17 and 19 extending in the direction orthogonal to the incident surface 16 of the light guide plate 12 are provided with projections 22 and 24 projecting from the outer peripheral side surfaces 17 and 19, respectively. As will be described later, when the light guide plate 12 is housed in the housing frame 32, the light guide plate 12 is used for positioning and fixing with respect to the housing frame 32. In the planar illumination device 10, the light source 52 may be composed of a plurality of point light sources (for example, white light emitting diodes) arranged along the incident surface 16, as shown in FIG. Good.

In the planar lighting device 10, the light emitted from the light source 52 enters the light guide plate 12 through the incident surface 16, and a predetermined light emitting area set in one main surface 14 (or the main surface 14) of the light guide plate 12. ) From the surface. Hereinafter, the main surface 14 is also referred to as an emission surface, and the main surface 15 (see FIG. 2B) on the side facing the main surface 14 is also referred to as a back surface. In the spread illuminating apparatus 10, as shown in FIG. 2 (b), the back surface 15 of the light guide plate 12, the thickness of the light guide plate 12 becomes thinner toward the outer peripheral side surface 18 side opposite from the incident surface 16 side As described above, the light guide plate 12 is provided so as to be inclined with respect to the emission surface 14, and the light guide plate 12 has a so-called wedge shape.

  The housing frame 32 has side walls 36 to 39, and when the light guide plate 12 is housed in the housing frame 32, the outer peripheral side surfaces 16 to 19 are surrounded by the side walls 36 to 39. Of the side walls 36 to 39 of the housing frame 32, concave portions 42 and 44 are respectively provided on the side walls 37 and 39 that face the outer peripheral side surfaces 17 and 19 when the light guide plate 12 is accommodated in the housing frame 32. The light guide plate 12 is positioned and fixed with respect to the housing frame 32 by inserting the protrusions 22 and 24 into the recesses 42 and 44.

  In the example shown in FIG. 1, the side wall 36 facing the incident surface 16 of the light guide plate 12 and the incident surface 16 in a state where the light guide plate 12 is positioned and stored at a predetermined position with respect to the housing frame 32. A gap is formed between them, and the light source 52 is accommodated in this gap (for example, in a state where it is mounted on a circuit board such as an FPC not shown).

The housing frame 32 may be formed from a resin material in which a light reflecting member (for example, a white pigment such as titanium oxide) is mixed into a transparent resin such as polycarbonate resin, or such light. You may comprise by the combination of the part shape | molded from the reflective resin material and the part which consists of metal materials, such as aluminum.
In the planar lighting device according to the present invention, the housing frame 32 may have a bottom wall facing the back surface 15 of the light guide plate 12 together with the side walls 36 to 39.

  In addition, the planar illumination device 10 may be one in which optical sheets such as a so-called prism sheet are laminated on the light exit surface 14 side of the light guide plate 12, and leaks on the back surface 15 side of the light guide plate 12. A reflection member for reflecting light may be disposed. In the planar illumination device 10, since well-known components can be used as these components, illustration and description thereof are omitted.

  Next, a configuration example of the protrusion 22 portion provided on the outer peripheral side surface 17 of the light guide plate 12 will be described with reference to FIG. The planar illumination device 10 is characterized in that the light guide plate 12 is injection-molded by providing a molten resin inlet (not shown) at the side end 25 of the positioning projection 22. is there. Therefore, the cut mark 23 formed by cutting the inlet after the injection molding process of the light guide plate 12 is disposed at the side end portion 25 of the protrusion 22.

  Further, as shown in FIG. 2, the shape of the cut mark 23 (and hence the shape of the connection portion with the side end portion 25 of the inflow port) is slightly smaller than the shape of the side end portion 25 of the protrusion 22. In addition, the cut mark 23 (and therefore the connection portion with the side end portion 25 of the inlet) is arranged such that the outer peripheral surfaces 23a to 23d are located inside the outer peripheral surfaces 22a to 22d of the protrusion 22. Has been.

  In the planar lighting device 10, the cut surface 27 of the cut mark 23 is moved away from the outer peripheral side surface 17 of the light guide plate 12, and thus the projection surface 22 by the protruding dimension of the projection 22, in the cut surface 27. Even if abnormal light emission occurs, it is possible to reduce an adverse effect on the quality of illumination light emitted from the emission surface 14 of the light guide plate 12 (or a light emission area defined on the emission surface 14).

  At this time, in the planar illumination device 10, the positioning projection 22 that is a component that originally protrudes from the outer peripheral side surface 17 is utilized to move the cutting surface 27 of the cutting trace 23 away from the emission surface 14. In the manufacturing process of the conventional light guide plate 102 shown in FIG. 4, compared with the case where the cutting position of the inflow port 108 shown by the broken line C is moved away from the outer peripheral side surface 102b, the original outline of the light guide plate 12 of the cut mark 23 itself is obtained. This is advantageous in that the quality of the illumination light can be improved while minimizing the protrusion of the light.

  Further, in the example shown in FIG. 2, the shape of the connection portion with the side end portion 25 of the inlet protrusion 22 is slightly smaller than the shape of the side end portion 25 of the protrusion 22, and the inlet protrusion 22 The connection portion with the side end portion 25 is disposed so that the outer peripheral surfaces 23a to 23d are all located inside the outer peripheral surfaces 22a to 22d of the protrusions 22. Therefore, the inlet is formed after the light guide plate 12 is injection molded. When cutting, even if burrs or deformations occur in a direction protruding from any of the outer peripheral surfaces 23 a to 23 d of the cutting trace 23, the possibility that the swell of the resin reaches the outer peripheral surfaces 22 a to 22 d of the protrusion 22 is eliminated. Alternatively, the quality of the illumination light can be improved without impairing the function of the protrusion 22 for positioning the light guide plate 12 with respect to the housing frame 32.

Next, with reference to FIG. 3, of the planar lighting device according to an embodiment of the present invention, example of the configuration of the inlet will be described. The planar lighting device in one embodiment of the present invention is the same as the planar lighting device 10 except for the configuration of the cutting trace 63, and the cutting trace 63 shown in FIG. 2 is a cut mark shown in FIG. 2 in that the outer peripheral surface 63a on the exit surface 14 side is provided so as to be flush with the outer peripheral surface 22a on the exit surface 14 side of the projection 22. 23.

  By adopting such a configuration, there is no step between the outer peripheral surface 63a of the inlet and the outer peripheral surface 22a of the projection 22, thereby simplifying the structure of the mold and causing the step during injection molding. This eliminates the possibility of burrs.

  Further, in the example shown in FIG. 3, among the outer peripheral surfaces 63 a to 63 d of the connection portion with the inlet projection 22, the outer peripheral surface 63 a on the emission surface 14 side is provided flush with the corresponding outer peripheral surface 22 a of the projection 22. The other outer peripheral surfaces 63b to 63d that are provided inside the corresponding outer peripheral surfaces 22b to 22d of the protrusions 22 have the following advantages. In the following description, the outer peripheral surfaces 63a to 63d of the connecting portion with the inflow port protrusion 22 are simply referred to as inflow port outer peripheral surfaces 63a to 63d.

  First, the inlet is generally cut using a hot nipper for laser processing or resin cutting. In particular, the hot nipper sandwiches the member with two heated blades and performs cutting by melting and pressing the member while melting the member. It is suitably used for cutting the inlet. In such a cutting mechanism, it is advantageous to drive the two blades from the long side of the member because the cutting thickness is thin, and in the example shown in FIG. 3, when the inlet is cut by a hot nipper, The cutting process is performed in the thickness direction of the inlet by driving the two blades of the hot nipper from the outer peripheral surface 63a on the exit surface 14 side of the inlet and the outer peripheral surface 63d on the rear surface 15 side. is there. However, due to the characteristics of the hot nipper, burrs and deformation may occur slightly in the direction perpendicular to the blade drive direction. Therefore, as shown in the example shown in FIG. 3, the outer peripheral surfaces 63a to 63d of the inlet port Among these, the configuration in which the outer peripheral surfaces 63b and 63c whose normals are orthogonal to the driving direction of the hot nipper blades are provided on the inner side of the outer peripheral surfaces 22b and 22c of the protrusions 22, respectively, This is advantageous in reliably eliminating the possibility of adversely affecting the positioning with respect to the frame 32.

  Further, from the viewpoint described above, regarding the thickness direction of the inlet, not only the outer peripheral surface 63a on the emission surface 14 side but also the outer peripheral surface 63d on the back surface 15 side is the same as the outer peripheral surface 22d on the back surface 15 side of the protrusion 22. It can be made one. However, when the thickness of the inlet is too thick by investigation and examination by the present inventors, the release property of the inlet deteriorates when the molded product is taken out from the mold after injection molding of the light guide plate 12. I found out that Therefore, as in the example shown in FIG. 3, the configuration in which the outer peripheral surface 63d on the back surface 15 side of the inlet is provided on the inner side from the outer peripheral surface 22d on the back surface 15 side of the protrusion 22 is the outer periphery on the exit surface 14 side of the inlet. This is advantageous in that the surface 63a is flush with the outer peripheral surface 22a of the projection 22 on the exit surface 14 side, and the thickness of the inlet is kept at a good level of releasability.

  In this case, regarding the thickness direction of the inlet, the outer peripheral surface that is flush with the outer peripheral surface of the protrusion 22 is not the outer peripheral surface 63d on the back surface 15 side but the outer peripheral surface 63a on the emission surface 14 side. It is as follows. As described above, the light guide plate 12 has a wedge shape. In general, a mold for forming such a light guide plate 12 has an emission surface 14 side corresponding to the bottom surface of the mold cavity. Formed. Therefore, as in the example shown in FIG. 3, the outer peripheral surface that is flush with the outer peripheral surface of the protrusion 22 in the thickness direction of the inlet is not the outer peripheral surface 63d on the back surface 15 side, but the outer peripheral surface on the output surface 14 side. If it is 63a, the structure of the corresponding mold is only advantageous to simplify the structure of the mold because it only needs to be a flat surface including the bottom surface of the cavity up to the inlet.

However, and planar illumination device according to the present invention, in addition to the outer peripheral surface 63a of the exit surface 14 side of the inlet port, any one or more of the outer peripheral surface 63 b ~63d, corresponding respectively projection 22 it is intended to include a structure in which the outer peripheral surface 22 b ~22d flush to.

10: planar illumination device, 12: light guide plate, 14: exit surface, 15: back surface, 16-19: outer peripheral side surface, 22, 24: protrusion, 23, 63: cut mark, 25: side end, 32: housing Frame, 36-39: side wall, 42, 44: recess

Claims (3)

In a planar illumination device comprising: a light source; a light guide plate configured to emit light emitted from the light source as planar light; and a housing frame having a side wall surrounding an outer peripheral side surface of the light guide plate.
A protrusion for positioning the light guide plate on the housing frame is formed on an outer peripheral side surface of the light guide plate, and the light guide plate is injection-molded with an inlet at a side end portion of the protrusion , The shape of the connection portion of the inflow port with the side end of the projection is slightly smaller than the shape of the side end of the projection, and the outer peripheral surface of the inflow port on the light exit surface side is A planar illumination device, characterized in that the projection is provided so as to be flush with the outer peripheral surface of the light guide plate on the light exit surface side . Wherein the side edge portion of the projection, the planar lighting device according to claim 1, characterized in that the cutting mark cut the inlet is disposed. 3. The surface shape according to claim 1, wherein the light guide plate has a wedge shape whose thickness decreases from an incident surface side to an opposite outer peripheral side surface side of the light guide plate. Lighting device.

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