JP2006059559A - Planar luminaire and method for manufacturing die for forming light guide plate used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar luminaire having a light guide plate capable of widely diffusing light without highly managing positioning precision between the light guide plate and a spot-like light source. <P>SOLUTION: In the planar luminaire, a plurality of wavy protrusions 21a, 21b project from the side end face 12a of the light guide plate 12 for extending in the thickness direction of the light guide plate 12, and have at least one portion of a side shape composed of a curved surface 26. At least one of two crossing angles α, β should be approximately 90° between sides 22, 24 and 26 of the wavy protrusions 21a, 21b and the side end face 12a of the light guide plate 12. As a result, the angle of refraction in light entering the light guide plate 12 from the spot-like light source is widened, and the light can be diffused to a wider range in the light guide plate 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sidelight type planar illumination device, and more particularly to a planar illumination device used as an illuminating means of a liquid crystal display device and a method for producing a mold for molding a light guide plate used therefor.

  A liquid crystal display device is widely used as a display means of today's electronic equipment, but since this liquid crystal display device is not a self-luminous type, there is an illumination means for ensuring visibility at night or in a dark place. Necessary. Conventionally, there is a planar illumination device as such an illuminating means, and as one form, a sidelight type planar illumination device has been widely used. The sidelight type planar illumination device is composed of a light guide plate having translucency and a bar-shaped light source or one or more point light sources arranged on a side end surface of the light guide plate. In recent years, a planar lighting device having a point light source capable of simplifying a driving circuit is used due to an increase in application examples to small electronic devices such as mobile phones.

  FIG. 9 schematically shows the light guide plate 12 and the plurality of point light sources 14 arranged on the side end face of the side light type planar illumination device 10. The conventional sidelight type planar illumination device has been pointed out as follows. That is, as shown in FIG. 9, the planar illumination device 10 using the point light source 14 has a certain directivity because the light emitted from the point light source 14 to the light guide plate 12 has a certain directivity. The vicinity of the point light source 14 of the light guide plate 12 illuminated by 14 is clearly divided into a bright part A and a dark part B. In recent years, the unevenness of brightness has tended to reduce the number of point light sources mounted along with the demand for higher light intensity of light emitting diodes (LEDs) used as point light sources and cost reduction of surface illumination devices. As a result, since the space | interval of the point light source arrange | positioned at the side end surface of the light-guide plate 12 spreads, it becomes a bigger problem.

Conventionally, as a measure for eliminating the difference between the bright part A and the dark part B and obtaining an average brightness, as shown in FIG. 10, on the side end surface 12 a of the light guide plate 12 facing the point light source 14. It has been proposed to provide a light incident prism 13 composed of a plurality of grooves (for example, see Patent Document 1). Further, in the example shown in FIG. 10, the shape of each groove constituting the light incident prism 13 is changed little by little around the point light source 14, thereby changing the traveling direction due to light refraction for each groove. The entire light prism 13 is designed to diffuse light over as wide a range as possible. As a result, the range in which the brightness unevenness indicated by the symbol W in FIG. 9 occurs is narrowed as much as possible, and the light emission of the planar illumination device 10 is made uniform.
Japanese Patent No. 3344483 (“Claim 1”, “Claim 2”, FIG. 8)

  However, a measure for changing the shape of each groove constituting the light incident prism 13 requires high positioning accuracy between the point light source 14 and the light incident prism 13 in order to obtain a desired light diffusion effect. Therefore, a structural design for surely positioning the light guide plate 12 and the point light source 14 has been indispensable. In addition, in order to form grooves with different shapes, it is essential to improve the accuracy and functionality of the processing machine, which causes the processing process to be complicated and costly to produce a planar lighting device. It was.

  The present invention has been made in view of the above problems, and does not manage the positioning accuracy between the light guide plate and the point light sources disposed on the side end surfaces thereof, and does not manage the light from a point light source in a wide range. It aims at providing the planar illuminating device provided with the light-guide plate which can be made to diffuse in.

  Furthermore, the present invention provides a light guide plate capable of diffusing light incident from a point light source over a wide range without highly managing the positioning accuracy between the light guide plate and the point light source disposed on the side end surface thereof. It is an object of the present invention to provide a mold manufacturing method capable of easily and inexpensively manufacturing a mold for molding.

  In order to solve the above-described problems, a planar illumination device according to the present invention is a planar illumination device including a light guide plate and a point light source disposed on a side end surface of the light guide plate, from a side end surface of the light guide plate. A plurality of streak-like protrusions that protrude and extend in the thickness direction of the light guide plate, and at least a part of the side surface shape is a curved surface, and 2 of the side face of the streaky protrusion and the side end face of the light guide plate At least one of the two intersection angles is approximately 90 degrees.

  Furthermore, as one aspect of the present invention, the plurality of streak protrusions are configured such that side surfaces of two adjacent streak protrusions are mirror-symmetric.

  Furthermore, as one aspect of the present invention, each of the two intersection angles of the side surface of the streaky protrusion and the side end surface of the light guide plate is approximately 90 degrees.

  Further, the mold manufacturing method according to the present invention is a mold manufacturing method for molding a light guide plate provided with a plurality of streak-like projections protruding from a side end surface and extending in the thickness direction of the side end surface. The step of forming a plurality of grooves corresponding to the plurality of streak-like projections on the machining plane of the mold uses a wedge-shaped tool whose tip is processed into a curved surface, and the tool is used in the pitch feed direction of the tool or Including a step of grooving in the opposite direction with respect to the vertical direction of the machining plane by a predetermined angle, the predetermined angle of each of the machining surfaces of the plurality of grooves to be formed and the mold It is characterized in that at least one of two intersection angles with the processing plane is set to be approximately 90 degrees.

  Furthermore, as one aspect of the present invention, in the step of performing the grooving, the predetermined angle of the cutting tool with respect to a vertical direction of the processing plane in either one of a pitch feed direction of the cutting tool or an opposite direction thereof. A first step of performing a plurality of times of grooving by inclining, and a vertical direction of the machining plane in a direction different from the direction in the first step in the bite pitch feed direction or the opposite direction thereof And a second step of performing groove processing a plurality of times by inclining the predetermined angle with respect to the direction.

  Furthermore, as one aspect of the present invention, the second step is characterized in that groove processing is performed between adjacent grooves of the plurality of grooves grooved in the first step.

  Furthermore, as one aspect of the present invention, in the second step, the two intersection angles of the processing surfaces of the plurality of grooves to be formed and the processing plane of the mold are both approximately 90 degrees. The grooving is performed so as to overlap each of the plurality of grooves grooved in the first step.

  According to the planar illumination device according to the present invention, the streak-like protrusion is provided on the side end surface of the light guide plate on which the point light source is arranged, and the light entering the light guide plate from the point light source is curved or curved and flat. The light can be diffused in the width direction of the light guide plate by being refracted on the side surface of the streak-shaped projection portion constituted by the above. Moreover, at least one of the two intersection angles of the side surface of the streaky protrusion and the side end surface of the light guide plate is approximately 90 degrees, thereby widening the refraction angle of light entering the light guide plate from the point light source, Light can be diffused over a wider area within the light guide plate.

  Further, by configuring the plurality of streaky projections so that the side surfaces of two adjacent streaky projections are mirror-symmetric, the light incident from the point light source is directed to the front direction of the point light source. The light can be diffused symmetrically in the width direction of the light guide plate. In particular, it is possible to diffuse light in a wider range and symmetrically by configuring the two intersection angles of the side surface of the streak-like projection and the side end surface of the light guide plate to be approximately 90 degrees.

  As described above, in the planar lighting device according to the present invention, the relatively simple side end face shape of the light guide plate allows the light from the point light source to be managed without highly managing the positioning accuracy between the light guide plate and the point light source. Light can be diffused over a wide range, and the light distribution from the light guide plate can be made uniform.

  Further, according to the mold manufacturing method of the present invention, the cutting tool for processing the groove corresponding to the streak-like protrusion provided on the side end surface of the light guide plate is inclined in the pitch feed direction or the opposite direction. In order to perform processing, it is possible to easily form a groove having a processing surface that makes an angle of intersection of approximately 90 degrees with the processing plane of the mold using a normal wedge-shaped tool.

  Further, the first step of performing the groove processing by tilting the cutting tool in any one of the pitch feed direction and the opposite direction, and the second step of performing the groove processing by tilting in one direction different from the tilt direction in the first step. By performing the groove processing in this step, it is possible to easily form a plurality of grooves configured such that the processing surfaces of adjacent grooves are mirror-symmetric. Furthermore, by performing the groove processing in the second step so as to overlap the plurality of grooves formed in the first step, the two intersection angles of the mold processing plane and the processing surface are both approximately 90 degrees. A certain groove can be easily formed.

  As described above, according to the mold manufacturing method according to the present invention, a special tool, a processing device, or the like is used as a mold for forming a light guide plate having a side end face shape that diffuses light over a wide range. Therefore, it is possible to easily and cost-effectively manufacture, and as a result, it is possible to simplify the processing process and reduce the cost of the planar lighting device including such a light guide plate.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, parts that are the same as or correspond to those in the prior art are denoted by the same reference numerals, and detailed description thereof is omitted.
The planar illumination device 18 according to the present invention has the same overall configuration as that of the prior art (FIG. 9), and is disposed on the light guide plate 12 and the side end face 12a of the light guide plate 12 as shown in FIGS. The point light source 14 is provided. Further, the light guide plate 12 is provided with a plurality of streak projections 21 that protrude from the side end face 12 a and extend in the thickness direction of the light guide plate 12, and the light incident prism 20 is configured by the plurality of streak projections 21. ing. In addition, the streak-like protrusion part 21 shown in FIG. 2 shows the aspect schematically, and the specific shape and action of the streak-like protrusion part 21 are described below with reference to FIGS. Detailed description.

  FIG. 3A is an enlarged plan view showing a part of the side end face 12a of the light guide plate 12 in the first embodiment of the present invention, where the left-right direction of the paper surface is the width direction of the light guide plate 12 and the paper surface. The perpendicular direction is the thickness direction of the light guide plate 12. In the present embodiment, the light incident prism 20 includes two types of streaky protrusions 21a and 21b. As shown in FIG. 3B, the side surface shape of the streak-like protruding portion 21a is such that a pair of planes 22 and 24 that are asymmetrically inclined with respect to the side end surface 12a and a tip side of the pair of planes 22 and 24 are smooth. In this case, an intersection angle α (hereinafter referred to as a base angle of the streak projection) α between the streaky projection 21a and the side end surface 12a on the plane 24 side is approximately 90 degrees. Is set. Further, the curved surface 26 forming the tip of the streak-like projection 21a is an arc having a radius of curvature R of 0.035 mm, and the base angle β on the plane 22 side of the streak-like projection 21a is about 60 degrees.

  Further, the streak protrusion 21b is formed in the same side surface shape by the same configuration surfaces 22, 24 and 26 as the streak protrusion 21a, and the light incident prism 20 includes the streak protrusion 21a and the streak protrusion 21b. Are arranged so that the planes 22 and the planes 24 face each other alternately, so that the side surfaces of the adjacent streaky projections 21a and 21b are mirror-symmetrical. Furthermore, in the present embodiment, the streak-shaped protrusions 21a and 21b are arranged at the same pitch P via the flat portions 28 having a predetermined width. With this configuration, the light incident prism 20 as a whole is guided. A uniform structure is realized in the width direction of the optical plate 12. In the present embodiment, it is assumed that the cross-sectional shape of each of the streaky protrusions 21 a and 21 b is constant in the thickness direction of the light guide plate 12.

  As described above, the light incident prism 20 in the present embodiment has the base angle α on the plane 24 side of the two base angles of each of the streaky projections 21a and 21b set to approximately 90 degrees. The following actions and effects are exhibited.

  In general, the light incident prism provided on the side end surface of the light guide plate is intended to make the luminance distribution uniform by diffusing the light incident from the point light source in the width direction of the light guide plate. It largely depends on the shape of the light incident prism. FIG. 4A is a graph showing the intensity distribution of the light emitted from the light guide plate with respect to the light emission angle from the point light source with the front direction of the point light source being 0 degrees. ) Is a plan view showing a light incident prism shape corresponding to each of the three types of intensity ratio curves shown in FIG. The light incident prism shown in FIG. 4B is composed of a plurality of streak protrusions each having a side surface with an arcuate cross section, the radius of curvature R of the arc is 0.035 mm, and the pitch P of the streak protrusions. The ratio with the width X of the flat portion is 2: 1, but the base angle of each streaky projection is 42 degrees in the case of (a), 60 degrees in the case of (b), and (c). In some cases, the angle is 90 degrees. Moreover, the graph which expands and shows the intensity ratio in the wide emission angle area | region C is shown by the upper right of FIG. 4 (A). According to FIG. 4 (A), the distribution of the emitted light from the light guide plate shows a tendency that the point light source is less concentrated to the front and widened as the base angle of the streak-like projections increases, It can be seen that light is diffused in the widest range in the case of (c) where the base angle of the protrusion is 90 degrees and the cross-sectional shape of the side surface is a semicircle.

  As shown in FIG. 3, the light incident prism 20 in the present embodiment is configured by planes 22 and 24 and a curved surface 26 that are constituent surfaces of the streaky protrusions 21 a and 21 b, and a flat portion 28. 22, 24, 26, and 28 are light direction changing elements that have different functions for changing the angle of incident light, and by combining them, incident light to the light guide plate 12 is converted to the front of the point light source. It equalizes with good balance over a wide range from the direction to the wide angle direction. In addition, since the base angle α on the plane 22 side of the streaky protrusions 21a and 21b is set to approximately 90 degrees, as described above with reference to FIG. 4, the diffusion range of incident light to the light guide plate 12 Can be further widened. Moreover, although the shape of the single streaky projections 21a and 21b is asymmetric with respect to the width direction of the light guide plate 12, the side surfaces of the adjacent streaky projections 21a and 21b are arranged so as to be mirror-symmetrical. Thus, since the light incident prism 20 as a whole has a uniform structure in the width direction of the light guide plate 12, the positioning of the light guide plate 12 and the point light source 14 is not performed with high accuracy. Light can be diffused symmetrically with respect to the front direction of the light source 14.

  Usually, such a light guide plate is manufactured by injection molding of a transparent resin, and as its material, an acrylic resin, polycarbonate resin, amorphous polyolefin resin or the like excellent in balance between moldability and optical properties is suitable. Instead of this, polystyrene, polyester, polyolefin, fluorine-based transparent polymer, epoxy resin, or the like can be used. As for the method of manufacturing the light guide plate, injection molding is excellent in terms of productivity and product accuracy, but is not limited to this, and various resins such as hot press molding, extrusion molding, casting method, etc. A molding method is applicable.

  Further, in a mold used for manufacturing a light guide plate by resin molding, a so-called general-purpose tool 40 as shown in FIG. The total shape tool 30 is composed of a tool part 38 and a shank part 40 to which the tool part 38 is fixed. The tool part 38 includes a pair of planes 32 and 34 that are symmetrically inclined with respect to the center line m. The pair of flat surfaces 32 and 34 is formed in a wedge shape with a curved surface 36 that smoothly connects the tip ends. The present invention relates to a step of forming a groove corresponding to a streak-like protrusion having a base angle of approximately 90 degrees in the manufacture of a mold for forming a light guide plate. The method implemented using 30 is included. In addition, although the material of the bit part 38 is suitable for diamond, other materials can be used as long as the required tool hardness can be obtained.

  Here, an embodiment of a mold manufacturing method according to the present invention will be described by taking as an example a mold for molding the light guide plate 12 including the light incident prism 20 shown in FIG. At that time, the mold manufacturing method in the present embodiment is the same as the conventional mold manufacturing method except for the process of processing the molding surface of the streaky protrusions 21a and 21b. Illustration and description are omitted.

  6 (A) to 6 (C) illustrate a mold manufacturing method according to the second embodiment of the present invention, in which a total cutting tool 30 shown in FIG. FIG. 5 is a diagram schematically showing a process of forming grooves 51a and 51b corresponding to the streak-like protrusions 21a and 21b, in which the right direction of the paper surface is the pitch feed direction of the total shape tool 30, and the direction perpendicular to the paper surface is groove processing. The direction. In the present embodiment, the angle θ formed by the pair of flat surfaces 32 and 34 constituting the bite portion 38 is 30 degrees, and the cross section of the curved surface 36 is an arc having a radius of curvature R = 0.035 mm.

First, in the first step shown in FIG. 6A, grooves 51a corresponding to the streaky protrusions 21a are formed on the processing plane 50a of the mold 50. In this step, the total cutting tool 30 is set to be inclined in the direction opposite to the pitch feed direction so that the vertical direction of the center line m and the machining plane 50a of the mold 50 forms an angle φ = θ / 2. In this embodiment, φ = 15 degrees because θ = 30 degrees. As a result, the plane 34 of the cutting tool portion 38 comes into contact with the machining plane 50a at an angle of 90 degrees when grooving is performed. A groove 51 a is formed such that the intersection angle γ between the machining surface 54 to be cut along and the machining plane 50 a of the mold 50 is approximately 90 degrees. With the above setting, the crossing angle δ between the machining surface 52 on the side of the groove 51a that is cut along the plane 32 of the cutting part 38 and the machining plane 50a is approximately 60 degrees, and the machining surface 52 and the machining surface 54 are It is smoothly connected to a machining surface 56 that is cut along the curved surface 36 of the portion 38.
In this step, after the completion of one grooving, the complete bite 30 is sent to the next position at a pitch P ′ twice the pitch P between the streaky projections 21a and 21b shown in FIG. A plurality of grooves 51a are obtained by repeating a series of steps in which similar groove processing is performed at that position.

Next, in the second step shown in FIG. 6B, grooves 51b corresponding to the streaky protrusions 21b are formed in the processing plane 50a of the mold 50. In this step, the total cutting tool 30 has its center line m and the vertical direction of the machining plane 50a of the mold 50 so that the plane 32 of the cutting part 38 forms an angle of 90 degrees with respect to the machining plane 50a. The angle φ is set to 15 degrees and tilted in the pitch feed direction. At this time, the processing position of the groove 51b in this step is set to an intermediate position between adjacent grooves of the plurality of grooves 51a formed in the first step. With such a setting, a groove 51b is formed such that the intersection angle γ between the machining surface 54 cut along the plane 32 and the machining plane 50a of the mold 50 is approximately 90 degrees. Also, with the above setting, the crossing angle δ between the machining surface 52 and the machining plane 50a cut along the plane 34 of the cutting tool 38 in the groove 51b is approximately 60 degrees. It is smoothly connected to a machining surface 56 cut along a curved surface 36 of 38.
In this step, after completion of one grooving, the overall cutting tool 30 is moved to the next position (that is, at a pitch P ′ twice the pitch P between the streaky protrusions 21a and 21b shown in FIG. A plurality of grooves 51b are obtained by repeating a series of steps of feeding the next groove 51a to an intermediate position between the grooves 51a and performing similar groove machining at that position.

By such first and second steps, as shown in FIG. 6C, grooves 51a and 51b respectively corresponding to the streaky protrusions 21a and 21b are formed on the processing plane 50a of the mold 50. By using the mold 50, the light guide plate 12 including the light incident prism 20 in the first embodiment of the present invention can be molded. As described above, in the present embodiment, without using a special tool or processing device, the line-shaped protrusion 30a having a base angle of about 90 degrees is used by using the total shape tool 30 having the wedge-shaped tool part 38. The mold for molding the light guide plate 12 provided with 21b can be processed easily and at low cost, and the processing process of the planar lighting device 18 can be simplified and the cost can be reduced.
In the present embodiment, for the sake of explanation, the inclination direction of the total cutting tool 30 is the direction opposite to the pitch feed direction in the first step and the pitch feed direction in the second step. It is good also as a direction opposite to a pitch feed direction in a process, and a pitch feed direction in a 2nd process. Further, instead of inclining the overall cutting tool 30 with respect to the machining plane 50 a of the mold 50, the machining plane 50 a of the mold 50 may be inclined with respect to the overall cutting tool 30.

Next, another aspect of the light guide plate 12 in the planar illumination device 18 according to the present invention will be described as a third embodiment of the present invention.
FIG. 7 is an enlarged plan view showing a part of the side end face 12a of the light guide plate 12 according to the third embodiment of the present invention. As in FIG. The thickness direction of the light guide plate 12 is the width direction of FIG. In the present embodiment, the light incident prism 60 is configured by one type of streak-like protrusion 61. The streaky projection 61 is composed of a pair of flat surfaces 62 and 64 and a pair of curved surfaces 66 and 68 smoothly connected to the respective flat surfaces 62 and 64, and the pair of curved surfaces 66 and 68 is the width of the streaky projection 61. Connected at the center of the direction. The side surface shape of the streak-like protrusion 61 is configured such that the constituent surfaces 62 and 66 and the constituent surfaces 64 and 68 are mirror-symmetrical. In addition, two base angles ( That is, the angles of intersection α) and β between the flat surfaces 62 and 64 and the side end surface 12a are set to 90 degrees. Each of the pair of curved surfaces 66 and 68 is an arc having a curvature radius of 0.035 mm.

  In this embodiment, since the side surface shape of the streaky projection 61 is mirror-symmetric, the side surfaces of the adjacent streaky projections 61 having the same shape are also mirror-symmetric. Further, the streak protrusions 61 are arranged at the same pitch P through the flat part 69 having a predetermined width. With such a configuration, the light incident prism 60 as a whole is uniform in the width direction of the light guide plate 12. A simple structure is realized. In the present embodiment, it is assumed that the cross-sectional shape of each streaky protrusion 61 is constant in the thickness direction of the light guide plate 12.

  With such a configuration, the light incident prism 60 in the present embodiment exhibits the same functions and effects as the light incident prism 20 in the first embodiment described above, but the light incident prism 60 in the present embodiment. FIG. 4B shows that the side surface shape of each of the streaky protrusions 61 is mirror-symmetrical and the two base angles α and β are both approximately 90 degrees. Since the side surface shape close to the semicircle shown in the above case is realized, a more remarkable effect can be obtained with respect to diffusing light incident from the point light source 14 in a wide range and symmetrically.

  Next, an embodiment of a mold manufacturing method according to the present invention will be described by taking as an example a mold for molding the light guide plate 12 including the light incident prism 60 shown in FIG. At that time, the mold manufacturing method in the present embodiment is the same as the conventional mold manufacturing method except for the process of processing the molding surface of the streaky protrusion 61, and therefore, other processes are illustrated and illustrated. Description is omitted.

  8 (A) to 8 (C) illustrate a mold manufacturing method according to a fourth embodiment of the present invention, in which a total cutting tool 30 shown in FIG. FIG. 8 is a diagram schematically showing a process of forming a groove 71 corresponding to the streak-like protrusion 61, where the right direction on the paper surface is the pitch feeding direction of the total cutting tool 30 and the direction perpendicular to the paper surface is the groove machining direction. In the present embodiment, the angle θ formed by the pair of flat surfaces 32 and 34 constituting the bite portion 38 is 30 degrees, and the cross section of the curved surface 36 is an arc having a radius of curvature R = 0.035 mm.

First, in the first step shown in FIG. 8A, a groove 71a is formed in the processing plane 70a of the mold 70. In this step, the total cutting tool 30 is set to be inclined in the direction opposite to the pitch feed direction so that the vertical direction of the center line m and the machining plane 70a of the mold 70 forms an angle φ = θ / 2. In this embodiment, φ = 15 degrees because θ = 30 degrees. As a result, the plane 34 of the cutting tool portion 38 comes into contact with the machining plane 70a at an angle of 90 degrees when the groove machining is performed. A groove 71a is formed such that the intersection angle γ between the machining surface 74 to be cut along and the machining plane 70a of the mold 70 is approximately 90 degrees. Further, according to the above setting, in the groove 71a, the crossing angle δ between the machining surface 72a on the side cut along the plane 32 of the bite portion 38 and the machining plane 50a is approximately 60 degrees, and the machining surface 72a and the machining surface 74 are It is smoothly connected to a machining surface 78 cut along the curved surface 36 of the bite portion 38.
In this step, after the completion of one grooving, the complete cutting tool 30 is sent to the next position at the same pitch P as the pitch P between the streaky protrusions 61 shown in FIG. A plurality of grooves 71a are obtained by repeating a series of steps of performing the above.

Next, in the second step shown in FIG. 8B, the groove 71 corresponding to the streaky protrusion 61 is formed again by overlapping the plurality of grooves 71a grooved in the first step. To complete. In this process, the total cutting tool 30 has its center line m and the vertical direction of the processing plane 70a of the mold 70 so that the plane 32 of the cutting section 38 forms an angle of 90 degrees with respect to the processing plane 70a. The angle φ is set to 15 degrees and tilted in the pitch feed direction. At this time, the overall cutting tool 30 is arranged so that the processing region overlaps with the groove 71a formed in the first step. By performing the groove processing with such setting, the processing of the groove 71a is performed. A part of the surface 72 a and the machining surface 78 is cut, and a machining surface 72 that is cut along the plane 32 of the bite portion 38 and a curved machining surface 76 that is cut along the curved surface 36 are newly formed. By this grooving, a machining surface 72 having an intersection angle δ with the machining plane 70a of the mold 70 of approximately 90 degrees, a curved machining surface 76 connected to the machining surface 72, and a machining plane 70a of the mold 70 are obtained. A groove 71 is completed in which a machining surface 74 having an intersection angle γ of approximately 90 degrees and a curved machining surface 78 coupled to the machining surface 74 are connected in a mirror-symmetric manner.
In this step, after the completion of one groove processing, the total cutting tool 30 is sent to the next position at a pitch P between the streaky protrusions 61 shown in FIG. 7, and the groove 71a formed at that position is sent to the next position. A plurality of grooves 71 are obtained by repeating a series of steps of performing similar groove processing.

By such first and second steps, as shown in FIG. 8C, a groove 71 corresponding to the streaky protrusion 61 shown in FIG. 7 is formed on the processing plane 70a of the mold 70, and this metal By using the mold 70, the light guide plate 12 including the light incident prism 60 in the third embodiment of the present invention is formed. As described above, even in the present embodiment, without using a special tool or processing equipment, using the general cutting tool 30 having the wedge-shaped cutting part 38, the two base angles are both streaks that are approximately 90 degrees. A mold for forming the light guide plate 12 having the protrusions 61 can be processed easily and at low cost, and the processing process of the planar lighting device 18 can be simplified and the cost can be reduced.
In the present embodiment, the inclination direction of the overall cutting tool 30 is the direction opposite to the pitch feed direction in the first step and the pitch feed direction in the second step. Conversely, in the first step, The pitch feed direction may be the direction opposite to the pitch feed direction in the second step.

  The light guide plate and the method for producing the mold thereof in the surface illumination device according to the present invention are particularly useful for the following reason. As described above with reference to FIG. 4, in order to diffuse light incident on the light guide plate in a wide-angle and symmetrical manner, the cross-section is a semicircular curved surface as shown in (c) of FIG. A streak having a side shape is most desirable. On the other hand, in the case of performing groove processing of a mold for forming a light guide plate using a general-purpose cutting tool, in order to form a groove corresponding to such a streak-like projection, for example, in a total cutting tool 30 shown in FIG. In order to make the curved surface 36 of the bite portion 38 into a semicircular shape, it is necessary to form a pair of planes 32 and 34 in parallel. However, making the bite portion into such a shape makes it difficult to process itself, and significantly deteriorates the mechanical strength and tool life of the bite portion. The present invention can obtain the same operation and effect as the streak-like projection portion having a side surface shape having a semicircular cross section by using a total shape bite having a wedge-like bite shape without such a problem. This is advantageous in that a streak-like projection is realized.

  In the first and third embodiments described above, the component surfaces forming the base angle of about 90 degrees of the streaky protrusions 21a, 21b, 61 are all the planes 24, 62, 64. Depending on conditions such as the desired height and width of the streaks 21a, 21b, 61, the tangential angle of about 90 degrees with respect to the side end face 12a of the light guide plate 12 without having the flat surfaces 24, 62, 64 in particular. One end of each of the curved surfaces 26, 66, and 68 may be directly connected to the side end surface 12a. Corresponding to this point, in forming the grooves 51a, 51b, 71 in the molds 50, 70 in the second and fourth embodiments, by adjusting the depth of the groove processing, Without forming the machining surfaces 54, 72, 74, one end of the curved machining surfaces 56, 76, 78 forming an intersecting angle of approximately 90 degrees with respect to the machining planes 50 a, 70 a is directly formed on the machining plane 50 a, Grooving can be applied to connect to 70a.

It is a principal part top view of the planar illuminating device which concerns on this invention. It is a principal part perspective view of the planar illuminating device which concerns on this invention. FIG. 3 is a diagram illustrating a specific shape example of a light incident prism of the light guide plate illustrated in FIGS. 1 and 2 as the first embodiment of the present invention, where (A) is a plan view of the main part thereof, and (B) is light incident. It is a top view which shows the shape of the separate streak-shaped projection part which comprises a prism. (A) is the graph which showed the emitted light distribution of the light-guide plate with respect to the emission angle of the light from a point light source by intensity ratio, (B) respond | corresponds to three types of intensity ratio curves shown to (A), respectively. It is a top view which shows the incident light prism shape to do. It is a principal part side view which shows the total form bite which has a wedge-shaped bite part shape. FIG. 4 is a diagram schematically showing a step of forming a groove corresponding to the streaky protrusion shown in FIG. 3 in a mold manufacturing method for forming a light guide plate as a second embodiment of the present invention; Is a side view showing the first step, (B) is the second step, and (C) is a side view showing the mold produced by the steps (A) and (B). FIG. 10 is a plan view of a principal part showing another example of the specific shape of the light incident prism of the light guide plate shown in FIGS. 1 and 2 as the third embodiment of the present invention. FIG. 8 is a diagram schematically showing a step of forming a groove corresponding to the streaky protrusion shown in FIG. 7 in a mold manufacturing method for forming a light guide plate as a fourth embodiment of the present invention; Is a side view showing the first step, (B) is the second step, and (C) is a side view showing the mold produced by the steps (A) and (B). It is a top view which shows the basic composition of the planar illuminating device using the conventional point light source. It is a schematic diagram which shows the example of a countermeasure for eliminating the difference between a bright part and a dark part, and obtaining average brightness in the planar illumination device using the conventional point light source.

Explanation of symbols

12: Light guide plate, 14: Point light source, 18: Planar illumination device, 21a, 21b, 61: Streaky projection, 30: Total shape tool, 50, 70: Mold, 50a, 70a: Mold processing Plane, 51a, 51b, 71: groove, 54, 72, 74: groove processed surface

Claims (7)

In a planar illumination device comprising a light guide plate and a point light source disposed on a side end surface of the light guide plate,
A plurality of streak-shaped projections projecting from the side end surface of the light-guide plate and extending in the thickness direction of the light-guide plate and having at least a part of a side surface formed of a curved surface are provided. At least one of the two intersection angles with the side end surface of the light plate is approximately 90 degrees.   The planar illumination device according to claim 1, wherein the plurality of streak protrusions are configured such that side surfaces of two adjacent streak protrusions are mirror-symmetrical.   3. The planar illumination device according to claim 1, wherein the two intersection angles between the side surface of the streak-like projection and the side end surface of the light guide plate are both approximately 90 degrees. In a method for producing a mold for molding a light guide plate provided with a plurality of streak protrusions protruding from a side end surface and extending in the thickness direction of the side end surface,
The step of forming a plurality of grooves corresponding to the plurality of streak-like projections on the processing plane of the mold uses a wedge-shaped tool whose tip is processed into a curved surface, and the tool is fed to the pitch of the tool. Including a step of inclining a predetermined angle with respect to a vertical direction of the processing plane in a direction or the opposite direction to form a groove,
The predetermined angle is set such that at least one of two intersection angles between the processing surface of each of the plurality of grooves to be formed and the processing plane of the mold is approximately 90 degrees. Mold production method.   The grooving step includes grooving a plurality of times by inclining the cutting tool by the predetermined angle with respect to the vertical direction of the processing plane in one of the pitch feed direction of the cutting tool or the opposite direction. A first step to be applied, and the cutting tool at a predetermined angle with respect to a vertical direction of the processing plane in one direction different from the direction in the first step among the pitch feed direction of the cutting tool or the opposite direction. The method according to claim 4, further comprising a second step of inclining and performing groove processing a plurality of times.   6. The method for producing a mold according to claim 5, wherein in the second step, groove processing is performed between adjacent grooves of the plurality of grooves formed in the first step. In the second step, the groove processing is performed in the first step so that the two intersection angles of the processing surfaces of the plurality of grooves to be formed and the processing plane of the mold are both approximately 90 degrees. 6. The method for producing a mold according to claim 5, wherein groove processing is performed on each of the plurality of grooves formed.

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