Light guide plate and manufacturing method of the same

Abstract

To provide a light guide plate for a side edge type surface lighting device having a light source at a lateral face, enhanced in high light extraction efficiency and reduced in luminance unevenness, and a manufacturing method of the same.SOLUTION: A surface-curved inclined plane 11 of a recess viewed from a light distribution control surface Scont has a contour shape projected to the light distribution control surface Scont, of a first circular arc shape having an arc H1 of a length W and a camber L1, and a surface-curved inclined plane 12 of the recess viewed from the light distribution control surface Scont has a second circular arc shape having the arc H1 of the length W and a camber L2. L1 is greater than L2, and the first circular arc shape defined by the length W and the camber L1 is larger than the second circular arc shape defined by the length W and the camber L2. That is, a curvature of the first circular arc shape is larger than a curvature of the second circular arc shape. A contour shape of the surface-curved inclined plane 11 projected to a light incident face Sin, and a contour shape of the surface-curved inclined plane 12 projected to an opposite light incident face Sin' form a third circular arc shape defined by the arc H2 of the length W, and a depth d from the light distribution control surface Scont of a light guide plate 100.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light guide plate for a side-edge type surface illumination device having a light source on a side surface and used in a liquid crystal display (LCD) device or the like, and to a method for manufacturing the same. [Background technology]

[0002] Side-edge type surface illumination devices, which are advantageous in terms of thinness and light weight, are widely used as surface illumination devices for LCD devices.

[0003] FIG. 12 is a diagram showing a typical side edge type surface lighting device.

[0004] 12, the side edge type surface lighting device U is composed of a light guide plate 100 and a light source 200 such as a light emitting diode (LED) element, and illuminates, for example, an LCD panel 300. The light guide plate 100 is made of a light-transmitting material such as an acrylic resin or a polycarbonate resin, and has a light entrance surface S on which the light source 200 is provided. in , the light output surface S facing the LCD panel 300 out , Idemitsu surface S out The light distribution control surface S located on the opposite side of cont and the light entrance surface S in The opposite side to the light-receiving surface S in The light R1 from the light source 200 is guided to the light distribution control surface S cont The reflected light R2 is incident on the light output surface S. out The LCD panel 300 is illuminated from the

[0005] FIG. 13 shows a side-edge type surface lighting device using a first conventional light guide plate, where (A) is an overall cross-sectional view and (B) is a perspective view of triangular reflective dots in (A) (see Patent Document 1).

[0006] In FIG. 13A, the light distribution control surface S of the light guide plate 101 contThe triangular reflective dots 101a, which are triangular recesses in a side view, are provided on the light guide plate 101. The light R1 from the light source 200 is reflected by the inclined surfaces 1011 of the triangular reflective dots 101a of the light guide plate 101, and the reflected light R2 is incident on the light output surface S. out 13B, the triangular reflective dot 101a is composed of a combination of flat surfaces, and has two inclined surfaces 1011 and 1012 and two side surfaces 1013 and 1014.

[0007] FIG. 14 shows a side-edge type surface lighting device using a second conventional light guide plate, where (A) is an overall cross-sectional view and (B) is a perspective view of the round reflective dots of (A).

[0008] In FIG. 14A, the light distribution control surface S of the light guide plate 102 cont The light R1 from the light source 200 is reflected by the inclined surface 1022 of the round reflective dot 102a of the light guide plate 102, and the reflected light R2 is incident on the light output surface S. out 14B, the round reflective dot 102a has a truncated cone shape, and has a circular bottom surface 1021 and an inclined surface 1022 provided on the circumference of the circular bottom surface 1021. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2009-81094 A (Patent No. 5066741 A) [Patent Document 2] JP 2011-51285 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the first conventional light guide plate 101 shown in Fig. 13, as shown in Fig. 15(A), the inclined surface 1011 acts as an effective area as a reflecting surface for the light R1 from the light source 200, but since the inclined surface 1012 is located on the opposite side to the light source 200, the light R1 is unlikely to enter the inclined surface 1012, and the inclined surface 1012 becomes an ineffective area that cannot be expected to function as a reflecting surface. Also, as shown in Fig. 15(B), even if the light R1 from the light source 200 enters the side surfaces 1013 and 1014, the reflected light R2' does not travel toward the LCD panel 300. Therefore, the utilization efficiency of the light R1 from the light source 200 is low, that is, there is room for improvement in the light extraction efficiency. 15C, since the inclined surface 1011 is planar, when the light R1 from the light source 200 has multiple paths, particularly R1a, R1b, and R1c, the reflected light R2a, R2b, and R2c reflected by the inclined surface 1011 and heading toward the LCD panel 300 cannot be controlled to be diffused, which causes a problem of uneven brightness. Furthermore, since the triangular reflective dots 101a are linear, they tend to interfere with linear elements of the LCD panel 300, such as a wiring pattern, which can easily cause moire.

[0011] The problem of moire occurring easily is considered to be a problem especially in front-light type display devices. In the case of back-light type display devices, it is possible to make elements that adversely affect the appearance, such as moire, less noticeable by sandwiching a light diffusion sheet between the light guide plate and the LCD panel. However, in the case of front-light type displays, diffusing light makes even the display on the LCD panel difficult to see. Therefore, in the case of front-light type display devices, it is preferable to take measures to suppress the occurrence of moire.

[0012] On the other hand, in the second conventional light guide plate 102 shown in FIG. 14, as shown in FIG. 16, the inclined surface 1022-1 on the light source 200 side acts as an effective area as a reflecting surface of the light R1 from the light source 200, but the inclined surface 1022-2 on the opposite side to the light source 200 side is located on the opposite side to the light source 200, so the light R1 is difficult to enter the inclined surface 1022-2, and it becomes an ineffective area that cannot be expected to function as a reflecting surface. In addition, due to the existence of the circular bottom surface 1021, the ineffective area becomes even larger. Therefore, there is a problem that the utilization efficiency of the light R1 from the light source 200 is low, that is, the extraction efficiency is low, and the area occupied by the circular reflective dots 102 in a plan view becomes large, and the transmittance of the light guide plate 102 becomes small. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, the light guide plate according to the present invention has a flat shape, with an end surface of the flat plate as a light entrance surface, a main surface of the flat plate as a light exit surface, a main surface opposite the light exit surface as a light distribution control surface, and an end surface located opposite the light entrance surface as a counter-light entrance surface, and the light distribution control surface is provided with concave pseudo half spindle shaped reflective dots, and the pseudo half spindle shaped reflective dots are provided with a first curved inclined surface provided on the light entrance surface side and a second curved inclined surface provided on the counter-light entrance surface side with respect to the first curved inclined surface. and a second curved inclined surface coupled to the first curved inclined surface, wherein the first curved inclined surface has a first arc shape as viewed from the light distribution control surface, the second curved inclined surface has a second arc shape as viewed from the light distribution control surface, the first curved inclined surface has a third arc shape as viewed from the light incident surface, and the second curved inclined surface has a third arc shape as viewed from the anti-light incident surface, and the curvature of the first arc shape is greater than the curvature of the second arc shape.

[0014] In addition, the manufacturing method of a light guide plate according to the present invention is a manufacturing method of the above-mentioned light guide plate, which includes a concave dot mold machining step for forming a plurality of concave dots corresponding to a plurality of pseudo half spindle-shaped reflective dots in the mold and machining the concave dot mold. Effect of the Invention

[0015] According to the present invention, it is possible to provide a light guide plate in which a decrease in transmittance caused by the formation of reflective dots is reduced while a decrease in light extraction efficiency is suppressed. [Brief description of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view showing a side-edge type surface illumination device including an embodiment of a light guide plate according to the present invention. [Diagram 2] This shows details of the pseudo-half spindle-shaped reflective dot in Figure 1, where (A) is an oblique view, (B) is a plan view seen from the light distribution control surface, (C) is a side view, (D) is a front view seen from the light incident surface, and (E) is a rear view seen from the anti-light incident surface. [Diagram 3] 2 is a diagram for explaining the effect of the light guide plate of FIG. 1. FIG. [Figure 4] 2 shows the arrangement of pseudo half spindle-shaped reflective dots on the light distribution control surface side of light guide plate 1 in FIG. 1, where (A) is a top view, (B) is a graph showing the change in Y-direction pitch, and (C) shows the Y-direction pitch. [Diagram 5] FIG. 15 is a diagram illustrating a simulation comparing the brightness of a light guide plate with round reflective dots in FIG. 13 and a light guide plate with pseudo semi-spindle reflective dots in FIG. 1, in which (A) shows the brightness distribution of the emitted light from the light incident surface to the anti-light incident surface, (B) shows that the dot depths are all the same at 4 μm, and (C) shows the arrangement of the dots in a planar view of the light guide plate. [Figure 6] 2A to 2C are diagrams illustrating a method for manufacturing the light guide plate of FIG. [Figure 7] FIG. 2 is a diagram for explaining the precision roll machining process of FIG. 1. [Figure 8] 2A and 2B are diagrams for explaining the light distribution of the light guide plate of FIG. 1, where (A) is a polar coordinate display and (B) is a two-dimensional display. [Figure 9] FIG. 2 is a cross-sectional view showing a modification of the side edge type surface illumination device of FIG. [Figure 10] FIG. 10 shows details of the pseudo-half spindle-shaped reflective dot in FIG. 9, where (A) is an oblique view, (B) is a plan view seen from the light distribution control surface, (C) is a side view, (D) is a front view seen from the light incident surface, and (E) is a rear view seen from the anti-light incident surface. [Figure 11]10A to 10C are diagrams illustrating a method for manufacturing the light guide plate of FIG. [Figure 12] FIG. 1 is an overall perspective view showing a typical side edge type surface lighting device. [Figure 13] 1A and 1B show a side-edge type surface lighting device including a first conventional light guide plate, in which (A) is an overall perspective view, and (B) is an enlarged perspective view of the triangular reflective dots in (A). [Figure 14] 10A and 10B show a side-edge type surface lighting device including a second conventional light guide plate, in which (A) is an overall perspective view, and (B) is an enlarged perspective view of the round reflective dots in (A). [Figure 15] 14A to 14C are diagrams for explaining a problem with the light guide plate of FIG. 13. [Figure 16] 15A to 15C are diagrams for explaining a problem with the light guide plate of FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] FIG. 1 is a cross-sectional view showing a side-edge type surface illumination device including an embodiment of a light guide plate according to the present invention.

[0018] In FIG. 1, the light distribution control surface S cont In other words, the pseudo half spindle-shaped reflective dots 1a are formed on the asymmetric light-receiving surface S in The curved inclined surface 11 on the side and the light-opposite surface S in The light R1 from the light source 200 is reflected by the curved inclined surface 11 of the pseudo half spindle shaped reflective dot 1a, and the reflected light R2 is incident on the exit surface S. out The LCD panel 300 is illuminated from the

[0019] The details of the pseudo half spindle-shaped reflective dot 1a in Fig. 1 will be described with reference to Fig. 2. In Fig. 2, (A) is a perspective view, (B) is a plan view seen from the light distribution control surface, (C) is a side view, (D) is a front view seen from the light incident surface, and (E) is a rear view seen from the anti-light incident surface.

[0020] As shown in (A) and (B) of FIG. 2, the light distribution control surface S contThe curved inclined surface 11 of the recess as viewed from the side is the light distribution control surface S cont The contour shape projected onto the light distribution control surface S has a first arc shape having a chord H1 of length (the longitudinal width of the pseudo half spindle-shaped reflective dot) W and an arrow height (depth of the arc) L1. cont The curved inclined surface 12 of the recessed portion as viewed from the outside forms a second arc shape having a chord H1 of length W and an arrow height L2. In this case, L=L1+L2 is the light entrance surface S of the pseudo half spindle reflective dot 1a. in Here, L1>L2, and therefore the first circular arc shape defined by the length W and the arrow height L1 is greater than the second circular arc shape defined by the length W and the arrow height L2. In other words, the curvature of the first circular arc shape is greater than the curvature of the second circular arc shape. Also, FIG. 2C shows a pseudo half spindle reflective dot 1a on the light entrance surface S. in 2C, the contour of the curved inclined surface 11 is projected onto a plane (a side surface of the light guide plate 1) perpendicular to the light distribution control surface S cont The angle of the curved inclined surface 12 with respect to the normal is θ1, and the light distribution control surface S cont If the angle with respect to the normal is θ2, then θ1>θ2. Note that the first and second arc shapes also include crescent and half-moon shapes.

[0021] As shown in FIG. 2(D), the light incident surface S in The curved inclined surface 11, i.e., the light incident surface S in The contour shape of the curved inclined surface 11 projected onto the light guide plate 1 is a chord H2 of length W and a light distribution control surface S cont 2(E), the light-receiving surface S in The curved inclined surface 12 seen from the side of in The contour shape of the curved inclined surface 12 projected onto the line 11 also has the same third arc shape defined by a depth d having a chord H2 of length W. The third arc shape includes a crescent shape, a half moon shape, etc.

[0022] Light distribution control surface S cont The first arc shape projected on the light guide plate extends in the depth direction from the chord H1 (the light incident surface S of the light guide plate). inThe light distribution control surface S has a curved surface that is smoothly connected to a third arc shape formed in a direction parallel to the direction of the light distribution control surface S. cont The second arc shape projected on the light guide plate extends from the chord H2 (same as the chord H1) in the depth direction (the light incident surface S of the light guide plate). in The third arc shape is formed in a direction parallel to the first arc shape (i.e., in a direction parallel to the first arc shape), and this curved surface forms the curved inclined surface 12.

[0023] As shown in FIG. 2, a pseudo half spindle reflective dot 1a which is a combination of curved inclined surfaces 11 and 12 is defined as follows. W: Light distribution control surface S of the curved inclined surfaces 11 and 12 cont The length of the contour chord H1 projected onto d: Light distribution control surface S of the light guide plate 1 of the curved inclined surfaces 11 and 12 cont Depth from θ1: Light distribution control surface S of the curved inclined surface 11 cont Angle of inclination with respect to the normal θ2: Light distribution control surface S of the curved inclined surface 12 cont The inclination angle with respect to the normal However, θ1>θ2 In this way, the pseudo half spindle reflective dot 1a is defined by four parameters W, d, θ1, and θ2, and the condition θ1>θ2. In this case, preferably, W=5~75μm, for example 30μm d=1~10μm, for example 4μm θ1=30~89°, for example 55° θ2=0~60°, for example 10° If W and d are too small, there will be a large variation due to processing accuracy, and uneven brightness will easily occur. If W and d are too large, the reflective dots will be visible, which is not preferable for use as a light guide plate, particularly as a light guide plate for a front light. If θ1 is less than 30°, the amount of light reflected by the curved inclined surface 11 and directed toward the exit surface may be reduced. In addition, if θ1 is 90°, no reflective dots will be formed. Furthermore, if θ2 exceeds 60°, the transparency of the light guide plate 1 may decrease, which is not preferable.

[0024] The arrow heights L1 and L2 of the curved inclined surfaces 11 and 12 are approximately given by the following equations. L1=d tan θ1 L2=d tan θ2 Therefore, the pseudo half spindle reflective dot 1a can also be defined by four parameters W, d, L1, and L2 and the condition L1>L2.

[0025] FIG. 3 is a diagram for explaining the effect of the pseudo half spindle reflective dot 1a of FIG.

[0026] As shown in FIG. 3A, the curved inclined surface 11 acts as an effective area as a reflecting surface for the light R1 from the light source 200, and the curved inclined surface 12 is located on the opposite side of the light source 200, so the light R1 from the light source 200 is unlikely to enter and becomes an ineffective area, but since the curved inclined surface 12 is smaller than the curved inclined surface 11, the ineffective area is small. Also, as shown in FIG. 3B, there is no side surface as in the case of the triangular reflective dot 101. Therefore, the utilization efficiency of the light R1 from the light source 200 is high, that is, the light extraction efficiency is high. Furthermore, compared to the triangular reflective dot 101, there are fewer linear components, so moire is less likely to occur on the LCD panel 300.

[0027] In addition, since there is no circular bottom surface 1021 as in the case of the round reflective dots 102a, the area occupied by the pseudo half spindle reflective dots 1a is small. Therefore, by forming the pseudo half spindle reflective dots 1a, which have a smaller area than the round reflective dots 102a, it is possible to realize a light guide plate with high transmittance while maintaining the brightness of the light guide plate at the same level as the conventional light guide plate with the round reflective dots 102a formed thereon.

[0028] Furthermore, as shown in FIG. 3B, when the light from the light source 200 has multiple paths, particularly R1a, R1b, and R1c, the reflected light R2a, R2b, and R2c reflected by the curved inclined surface 11 and heading toward the LCD panel 300 can be controlled to be diffused, thereby reducing brightness unevenness.

[0029] FIG. 4 is a diagram for explaining the arrangement of pseudo half spindle-shaped reflective dots on the light distribution control surface side of the light guide plate 1 in FIG. 1, where (A) is a top view, (B) is a graph showing the Y-direction pitch, and (C) shows the Y-direction pitch.

[0030] In FIG. 4A, when multiple pseudo half spindle-shaped reflective dots 1a are arranged, the light incident surface S in From the opposite light incident surface S in Since the light R1 from the light source 200 becomes weaker in the Y direction, the dot density is reduced according to the Y direction pitch in (B) and (C) of FIG. 4 to reduce the light R1 reaching the light incident surface S. in From the opposite light incident surface S in The pitch is uniform from 0 to 100. In this case, the position in the X direction is shifted so that the dots are not in the shadow of the previous dot in the Y direction. In this case, a staggered arrangement may also be used. Also, instead of changing the Y direction pitch, the Z direction depth d of the pseudo half spindle shaped reflective dots 1a may be changed or the arrow height (=L1+L2) may be changed. When changing the Z direction depth d or the arrow height L, the pseudo half spindle shaped reflective dots are made similar in shape so that the light distribution characteristics do not change locally.

[0031] FIG. 5 is a diagram for explaining a simulation comparing the brightness of a light guide plate with circular reflective dots in FIG. 13 and a light guide plate with pseudo semi-spindle reflective dots in FIG. 1. FIG. 5(A) is a diagram for explaining a simulation comparing the brightness of a light guide plate with circular reflective dots in FIG. 13 and a light guide plate with pseudo semi-spindle reflective dots in FIG. in From the opposite light incident surface S in (B) shows that the dot depth is the same at 4 μm, and (C) shows the arrangement of dots in a plan view of the light guide plate. in When comparing between the 20mm and 170mm points, the pattern area A [mm 2 ] for the round reflective dot 102a, it is 7.68 x 10 -4 [mm 2 ], and for the pseudo-half spindle reflective dot 1a, it is 1.39 × 10 -4 [mm 2 ] and the same area (B = 1574 [mm 2The number of dots (N) in the circular reflective dot 102a is 66563 [mm 2 ], and the pseudo-half spindle reflective dot 1a has a resolution of 225438 [mm 2 ]. Therefore, the area ratio (the proportion of reflective dots in this area) = A × N ÷ B was 3.25% for the round reflective dots 102a and 1.99% for the pseudo half spindle reflective dots 1a. In other words, the pseudo half spindle reflective dots 1a have a higher light extraction efficiency per dot formation area than the round reflective dots 102a, and can realize a light guide plate with high transmittance while maintaining the brightness of the light guide plate at the same level as conventional light guide plates.

[0032] As a manufacturing method for the mold used to manufacture the light guide plate 1 of the pseudo half spindle shaped reflective dots 1a in Fig. 1, an ultra-precision machining method can be used in which a diamond bit is attached to a piezoelectric element device to form concave dots in the mold (see Patent Document 2). This method can make the surface of the reflective dots 1a a mirror surface, making it possible to perform accurate light distribution control using the pseudo half spindle shaped reflective dots 1a. In addition, the manufacturing equipment is less expensive than the equipment used for photolithography.

[0033] FIG. 6 is a diagram for explaining a method of manufacturing the light guide plate of FIG.

[0034] First, referring to the ultra-precision roll machining process shown in Fig. 6(A), a cylindrical mold 601 plated with copper, brass, or the like is rotated, and a diamond bit 602 is moved vertically and in the depth direction by a piezoelectric element device (FTS) 603 to form a concave dot corresponding to the pseudo semi-spindle-shaped reflective dot 1a. This results in a concave dot mold 601. The diamond bit 602 and piezoelectric element device 603 shown in Fig. 7 may be used in a processing machine such as a precision lathe or a precision plate cutting device.

[0035] Next, referring to the resin sheet inversion step shown in FIG. 6(B), the concave dots of the concave dot mold 601 are used as parents to perform dot inversion to obtain a convex dot resin sheet 604.

[0036] Next, referring to the electroforming inversion step shown in FIG. 6C, the convex dot resin sheet 604 is used as a parent and is electroforming-inverted to obtain a concave dot resin sheet 605.

[0037] 6(D), the concave dot resin sheet 605 is used as a parent and is electroformed and reversed to obtain a convex dot resin sheet 606. A plurality of convex dot resin sheets 606 are obtained to form a stamper (mass production pattern).

[0038] Next, referring to the rolling molding process shown in FIG. 6(E), the convex dot resin sheet 606 is rolled up around a mold to obtain a convex dot mold 607.

[0039] Finally, referring to FIG. 6F, a convex dot mold 607 is used to form a light distribution control surface S cont A plurality of pseudo half spindle shaped reflective dots 1a are simultaneously formed on the substrate.

[0040] According to the manufacturing method shown in Fig. 6, the concave dot surface of the concave dot mold 601 becomes a three-dimensional mirror surface by fine cutting with the diamond bit 602, and the pseudo half spindle shaped reflective dots 1a of the concave dot light guide plate 1 using this also become mirror surfaces, enabling light to be distributed with high precision. In addition, the piezoelectric element device 603 can move the diamond bit 602 back and forth in the depth direction by performing electrical control, and the diamond bit 602 can engrave the concave dots into the rotating mold 601 at high speed. Therefore, the concave dots can be machined on the mold 601 in a short time.

[0041] FIG. 8 shows the light distribution of a light guide plate using the pseudo half spindle-shaped reflective dots 1a of FIG. 1, where (A) is a polar coordinate display and (B) is a two-dimensional display.

[0042] As can be seen from Fig. 8, when the angle θ1 of the curved inclined surface 11 is changed to 55°, 58°, 60°, and 65°, the light distribution characteristics change. In particular, in the manufacturing method, it is possible to change the angle θ1 of the curved inclined surface 11 by changing the cutting angle of the diamond bit 602 or by changing the inclination in the direction perpendicular to the cutting direction, thereby changing the light distribution characteristics. Therefore, it is possible to improve the efficiency of the backlight according to requirements.

[0043] For example, the larger θ1 is, the smaller the surface area S in Since the light distribution characteristic changes to the ' side, the eye point is located on the opposite side of the light entrance surface S from directly above the center of the light guide plate in the Y direction. in When the reflector is set on the side of the incident light, the reflected light R2 is directed toward the opposite light incident surface S by setting θ1 larger. in This allows more light to be emitted to the side, thereby improving the visibility of the display device at the eyepoint.

[0044] On the other hand, if the eye point is directly above the center of the light guide plate in the Y direction, the light incident surface S in When the reflector is set to the side of the incident light, the reflected light R2 is directed toward the incident light surface S by setting θ1 small. in This allows more light to be emitted to the side, thereby improving the visibility of the display device at the eyepoint.

[0045] More preferably, the reflectance is higher as θ1 is larger. Therefore, when the expected eye point is not directly above the center of the light guide plate in the Y direction, the light source 200 and the light entrance surface S in The efficiency of light utilization can be improved by setting the position of on the side opposite the eye point in the Y direction.

[0046] In addition, it is also possible to concentrate the light distribution toward the eyepoint of the display device by making the angle θ1A of the curved inclined surface 11 of the reflective dot close to the light source in the Y direction larger, making the angle θ1B of the curved inclined surface 11 of the reflective dot close to the area directly below the eyepoint smaller than θ1A, and making the angle θ1C of the curved inclined surface 11 of the reflective dot located after the area directly below the eyepoint in the Y direction smaller than θ1B.

[0047] Conversely, it is also possible to increase the viewing angle of the display device by making the angle θ1A of the curved inclined surface 11 of the reflective dot close to the light source in the Y direction smaller, making the angle θ1B of the curved inclined surface 11 of the reflective dot close to the area directly below the eyepoint larger than θ1A, and making the angle θ1C of the curved inclined surface 11 of the reflective dot located after the area directly below the eyepoint in the Y direction larger than θ1B.

[0048] FIG. 9 is a cross-sectional view showing a side-edge type surface illumination device including a modified example of the light guide plate of FIG.

[0049] In FIG. 9, the light distribution control surface S cont In other words, the pseudo half spindle-shaped reflective dots 1'a are provided on the asymmetric counter-light-entering surface S in The curved inclined surface 11 of the convex portion on the side ' and the light incident surface S in The light R1 from the light source 200 is reflected by the curved inclined surface 11 of the pseudo half spindle reflective dot 1'a, and the reflected light R2 is incident on the exit surface S. out The LCD panel 300 is illuminated from the

[0050] The details of the pseudo half spindle-shaped reflective dot 1'a in Fig. 9 will be described with reference to Fig. 10. In Fig. 10, (A) is a perspective view, (B) is a plan view seen from the light distribution control surface, (C) is a side view, (D) is a front view seen from the light incident surface, and (E) is a rear view seen from the anti-light incident surface.

[0051] As shown in (A) and (B) of FIG. 10, the light distribution control surface S cont The curved inclined surface 11' of the convex portion seen from the side is the light distribution control surface S cont The contour shape projected onto the light distribution control surface S has a first arc shape having a chord H1 of length (the longitudinal width of the pseudo half spindle-shaped reflective dot) W and an arrow height (depth of the arc) L1. cont The curved inclined surface 12' of the convex portion seen from the outside forms a second arc shape having a chord H1 of length W and an arrow height L2. In this case, L=L1+L2 is the light entrance surface S of the pseudo half spindle reflective dot 1'a. inHere, L1>L2, and therefore the first circular arc shape defined by the length W and the arrow height L1 is greater than the second circular arc shape defined by the length W and the arrow height L2. In other words, the curvature of the first circular arc shape is greater than the curvature of the second circular arc shape. Also, FIG. 10C shows a pseudo half spindle reflective dot 1'a on the light incident surface S. in In FIG. 10C, the contour of the curved inclined surface 11′ and the light distribution control surface S cont The angle with respect to the normal line of the curved inclined surface 12′ is θ1, and the contour line of the curved inclined surface 12′ and the light distribution control surface S cont If the angle with respect to the normal is θ2, then θ1>θ2. Note that the first and second arc shapes also include crescent and half-moon shapes.

[0052] As shown in FIG. 10(D), the opposite light incident surface S in ', that is, the curved inclined surface 11' seen from the opposite light-entering surface S in The contour shape of the curved inclined surface 11′ projected onto the light guide plate 1′ is a chord H2 of length W and a light distribution control surface S cont 10(E), the light-receiving surface S in The curved inclined surface 12' seen from the side, i.e., the light incident surface S in The contour shape of the curved inclined surface 12' projected onto the surface 12 also has the same third circular arc shape defined by a height h having a chord H2 of a length W. The third circular arc shape includes a crescent shape, a half moon shape, and the like.

[0053] As shown in FIG. 10, a pseudo half spindle reflective dot 1'a which is a combination of curved inclined surfaces 11' and 12' is also defined as follows. W: Light distribution control surface S of the curved inclined surfaces 11' and 12' cont The length of the contour chord H1 projected onto h: Light distribution control surface S of the light guide plate 1' of the curved inclined surfaces 11' and 12' cont Height from θ1: Light distribution control surface S of the curved inclined surface 11′ cont Angle of inclination with respect to the normal θ2: Light distribution control surface S of the curved inclined surface 12′ cont Angle of inclination with respect to the normal However, θ1>θ2 In this way, the pseudo half spindle reflective dot 1'a is also defined by four parameters W, h, θ1, and θ2, and the condition θ1>θ2. In this case, preferably, W=5~75μm, for example 30μm h=1~10μm, for example 4μm θ1=30~89°, for example 55° θ2=0~60°, for example 10° If W and h are too small, there will be a large variation due to processing accuracy, and uneven brightness will easily occur. If W and h are too large, the reflective dots will be visible, which is not preferable for use as a light guide plate, particularly as a light guide plate for a front light. If θ1 is less than 30°, the amount of light reflected by the curved inclined surface 11' and directed toward the exit surface may be reduced. In addition, if θ1 is 90°, no reflective dots will be formed. Furthermore, if θ2 exceeds 60°, the transparency of the light guide plate 1' may decrease, which is not preferable.

[0054] The arrow heights L1 and L2 of the curved inclined surfaces 11' and 12' are approximately given by the following equations. L1=h tan θ1 L2=h tan θ2 Therefore, the pseudo half spindle reflective dot 1'a can also be defined by four parameters W, h, L1, and L2 and the condition L1>L2.

[0055] The pseudo half spindle reflective dot 1'a in FIG. 9 has the same effect as the pseudo half spindle reflective dot 1a in FIG.

[0056] Fig. 11 is a diagram for explaining a method for manufacturing the light guide plate of Fig. 9. In Fig. 11, there are fewer electroforming reversal steps compared to the manufacturing method of Fig. 6. In other words, there is only one electroforming reversal step.

[0057] First, referring to the ultra-precision roll machining process shown in Fig. 11(A), a cylindrical mold 601 plated with copper, brass, etc. is rotated, and a diamond bit 602 is moved vertically and in the depth direction by a piezoelectric device (FTS) 603 to form a concave dot equivalent to the pseudo semi-spindle reflective dot 1'a. In this way, a concave dot mold 601 is obtained.

[0058] Next, referring to the resin sheet inversion step shown in FIG. 11(B), the concave dots of the concave dot mold 601 are used as parents to perform dot inversion to obtain a convex dot resin sheet 604.

[0059] 11(C), the convex dot resin sheet 604 is used as a parent and is electroformed and reversed to obtain a concave dot resin sheet 605. A plurality of concave dot resin sheets 605 are obtained to form a stamper (mass production pattern).

[0060] Next, referring to the roll molding process shown in FIG. 11(D), the recessed dot resin sheet 605 is rolled up around a mold to obtain a recessed dot mold 607'.

[0061] Finally, referring to FIG. 11(E), a concave dot mold 607′ is used to form a light distribution control surface S of the light guide plate 1′. cont A plurality of pseudo half spindle shaped reflective dots 1'a are simultaneously formed on the substrate.

[0062] Incidentally, the present invention can be applied to any modifications within the obvious scope of the above-described embodiment. [Industrial Applicability]

[0063] The light guide plate according to the present invention can be used not only as a light guide plate for the backlight of an LCD device, but also as a light guide plate for a frontlight, for example, not only for an LCD device but also for an electrophoretic display. It can also be used as a backlight by changing the optical slope shape of the dots. Furthermore, it can be used to illuminate signs such as letters and pictures on a signboard, and can also distribute light in the front direction, so it can also be used in lighting devices for automobiles, etc. [Explanation of symbols]

[0064] U: Side edge type surface lighting device 100, 101, 102, 1, 1': Light guide plate S in :Light entrance surface S out :Idemitsu surface S cont :Light distribution control surface S in ': Anti-light incident surface 200: Light source 300: Liquid crystal display (LCD) panel 1a, 1'a: pseudo-half spindle reflective dot 11, 12, 11', 12': Curved inclined surface 601: Concave dot mold 602: Diamond Bit 603: Piezoelectric device 604: Convex dot resin sheet 605: Concave dot resin sheet 606: Convex dot resin sheet 607: Convex dot mold 607': Concave dot mold 100a:Reflective dots 101a: triangular reflective dot 1011, 1012: Inclined surface 1013, 1014: Side 102a: Round reflective dot 1021:Circular bottom 1022: Inclined surface R1: Incident light R2: Reflected light

Claims

1. A light guide plate having a flat plate shape, an end surface of the flat plate being a light entrance surface, a main surface of the flat plate being a light exit surface, a main surface opposite to the light exit surface being a light distribution control surface, and an end surface positioned opposite to the light entrance surface being a counter light entrance surface, The light distribution control surface is provided with a concave pseudo half spindle reflective dot, The pseudo half spindle reflective dot is a first curved inclined surface provided on the light incident surface side; a second curved inclined surface provided on the opposite light-entering surface side of the first curved inclined surface and coupled to the first curved inclined surface; Equipped with When viewed from the light distribution control surface, the first curved inclined surface has a first arc shape, When viewed from the light distribution control surface, the second curved inclined surface has a second arc shape, When viewed from the light entrance surface, the first curved inclined surface has a third arc shape, The light guide plate, when viewed from the opposite light-entering surface, the second curved inclined surface has the third arc shape.

2. A light guide plate having a flat plate shape, an end surface of the flat plate being a light entrance surface, a main surface of the flat plate being a light exit surface, a main surface opposite to the light exit surface being a light distribution control surface, and an end surface positioned opposite to the light entrance surface being a counter light entrance surface, The light distribution control surface is provided with a pseudo half spindle reflective dot in a convex shape, The pseudo half spindle reflective dot is a first curved inclined surface provided on the side opposite to the light-entering surface; a second curved inclined surface provided on the light incident surface side of the first curved inclined surface and connected to the first curved inclined surface; Equipped with When viewed from the light distribution control surface, the first curved inclined surface has a first arc shape, When viewed from the light distribution control surface, the second curved inclined surface has a second arc shape, When viewed from the opposite light-entering surface, the first curved inclined surface has a third arc shape, The light guide plate, when viewed from the light incident surface, the second curved inclined surface has the third arc shape.

3. The light guide plate according to claim 1 or 2, wherein an arrow height of the first arc shape is greater than an arrow height of the second arc shape.

4. When the angle of the first curved inclined surface with respect to the normal line of the light distribution control surface is θ1 and the angle of the second curved inclined surface with respect to the normal line of the light distribution control surface is θ2, θ1>θ2 3. The light guide plate according to claim 1, wherein

5. 5. The light guide plate according to claim 4, wherein θ1 is in the range of 30° to 89°, and θ2 is in the range of 0° to 60°.

6. 3. The light guide plate according to claim 1, wherein the pseudo half spindle reflective dots have a width of 5 μm to 75 μm.

7. 3. The light guide plate according to claim 1, wherein the pseudo half spindle reflective dots have a depth or height of 1 μm to 10 μm.

8. A method for producing the light guide plate according to claim 1 or 2, comprising the steps of: A method for manufacturing a light guide plate, comprising: a concave dot die machining step for machining a concave dot die by forming a plurality of concave dots in a die, the concave dots corresponding to a plurality of the pseudo half spindle shaped reflective dots.

9. The method for manufacturing a light guide plate according to claim 8 , wherein the concave dot mold machining step uses a cutting tool and a piezoelectric device for driving the cutting tool.

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