Light guide plate and manufacturing method thereof

Abstract

The light guide plate (1) is provided with a translucent flat plate, a light incident surface (Sin) is provided on an end surface of the flat plate, a main surface of the flat plate is set as a light emergent surface (Sout), a main surface on the opposite side of the light emergent surface (Sout) is set as a light distribution control surface (Scont), an end surface on the opposite side of the light incident surface (Sin) is set as a reverse light incident surface (Sin '), and concave approximately semi-spindle-shaped reflection points (1a) are provided on the light distribution control surface (Scont). The approximately semi-fusiform reflection point (1a) is provided with: a first curved inclined surface (11) provided on the light incident surface (Sin) side; and a second curved-surface-shaped inclined surface (12) that is provided on the light incident surface reverse side (Sin ') with respect to the first curved-surface-shaped inclined surface (11) and that is joined to the first curved-surface-shaped inclined surface (11), the first curved-surface-shaped inclined surface (11) being in a first circular arc shape when viewed from the light distribution control surface (Scont), the second curved-surface-shaped inclined surface (12) being in a second circular arc shape when viewed from the light distribution control surface (Scont), and the second curved-surface-shaped inclined surface (12) being in a third circular arc shape when viewed from the light incident surface (Sin). The first curved inclined surface (11) has a third arc shape when viewed from the light incident surface (Sin '), and the second curved inclined surface (12) has a third arc shape when viewed from the light incident surface (Sin').

Description

Technical Field

[0001] The present invention relates to a light guide plate for a side-shaped surface lighting device having a light source on the side, used in a liquid crystal display (LCD) device, etc., and a method for manufacturing the same. Background Art

[0002] As a surface lighting device for an LCD device, an edge type surface lighting device excellent in thinness and weight reduction is widely used.

[0003] Figure 12 This is a diagram showing a general side-shaped surface lighting device.

[0004] exist Figure 12 In the embodiment, the side surface lighting device U is composed of a light guide plate 100 and a light source 200 composed of a light emitting diode (LED) element, etc., for example, to illuminate an LCD panel 300. The light guide plate 100 is a flat plate made of a light-transmitting material such as acrylic resin, polycarbonate resin, etc., and has a light incident surface S provided with the light source 200. in , a light emitting surface S opposite to the LCD panel 300 out , located on the light-emitting surface S out The light distribution control surface S on the opposite side cont and the light incident surface S in The light-reflecting surface S on the opposite side in '. The light R1 from the light source 200 is set on the light distribution control surface S of the light guide plate 100 cont The reflected light R2 is reflected from the light emitting surface S out The LCD panel 300 is illuminated.

[0005] Figure 13 The side surface lighting device using the first conventional light guide plate is shown, (A) is an overall cross-sectional view, and (B) is a perspective view of a triangular reflection point of (A) (see: Patent Document 1).

[0006] exist Figure 13 In (A), on the light distribution control surface S of the light guide plate 101 cont A triangular concave portion is provided when viewed from the side, namely, a triangular reflection point 101a. The light R1 from the light source 200 is reflected by the inclined surface 1011 of the triangular reflection point 101a of the light guide plate 101, and the reflected light R2 is emitted from the light exit surface S out The LCD panel 300 is illuminated. Figure 13 As shown in (B), the triangular reflection point 101a is composed of a combination of planes, and has two inclined surfaces 1011 and 1012 and two side surfaces 1013 and 1014.

[0007] Figure 14Side triangular surface illumination device using a second existing light guide plate, (A) is an overall cross-sectional view, and (B) is a perspective view of the circular reflection points in (A).

[0008] In Figure 14 (A) of, on the light distribution control surface S of the light guide plate 102 cont There is provided a concave portion in the shape of a conical trapezoid, that is, a circular reflection point 102a. The light R1 from the light source 200 is reflected by the inclined surface 1022 of the circular reflection point 102a of the light guide plate 102, and the LCD panel 300 is illuminated with the reflected light R2 from the light emitting surface S out In addition, as Figure 14 (B) of shows, the circular reflection point 102a is in the shape of a conical trapezoid, having a circular bottom surface 1021 and an inclined surface 1022 provided on its circumference.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2009-81094 (Patent No. 5066741 Gazette)

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-51285 Summary of the invention

[0013] Problems to be solved by the invention

[0014] However, in Figure 13 the first existing light guide plate 101 shown, as Figure 15 (A) of shows, the inclined surface 1011 functions as an effective region ER as a reflection surface of the light R1 from the light source 200, but the inclined surface 1012 is located on the side opposite to the light source 200, so the inclined surface 1012 becomes an ineffective region NR where the light R1 is difficult to enter and its function as a reflection surface cannot be expected. In addition, as Figure 15 (B) of shows, even if the light R1 of the light source 200 is incident on the side surfaces 1013 and 1014, its reflected light R2' does not face the LCD panel 300. Therefore, the utilization efficiency of the light R1 of the light source 200 is low, that is, there is room for improvement in improving the light extraction efficiency. In addition, as Figure 15As shown in (C), the inclined surface 1011 is flat. Therefore, especially when the light R1 from the light source 200 has multiple paths such as R1a, R1b, and R1c, there is also a problem that it is impossible to control the reflected light R2a, R2b, and R2c reflected by the inclined surface 1011 and directed toward the LCD panel 300 to be diffused, which causes uneven brightness. Furthermore, since the triangular reflection point 101a is linear, there is also a problem that it is likely to interfere with the linear elements of the LCD panel 300, such as wiring patterns, and easily generate moiré fringes.

[0015] The above problem of easily generating moiré fringes is particularly regarded as a problem in a frontlight type display device. In the case of a backlight type display device, by sandwiching a light diffusion sheet between the light guide plate and the LCD panel, elements that have an adverse effect on the appearance, such as moiré fringes, can be made less obvious. However, in the case of a frontlight type, if the light is diffused, it becomes difficult to see the display of the LCD panel. Therefore, in the case of a frontlight type display device, it is preferable to take measures to suppress the occurrence of moiré fringes.

[0016] On the other hand, in Figure 14 the second conventional light guide plate 102 shown in Figure 16 as shown, the inclined surface 1022-1 on the light source 200 side functions as an effective region ER as a reflection surface of the light R1 from the light source 200. However, since the inclined surface 1022-2 on the side opposite to the light source 200 side is located on the side opposite to the light source 200, the inclined surface 1022-2 becomes an ineffective region NR where it is difficult for the light R1 to enter and its function as a reflection surface cannot be expected. In addition, due to the presence of the circular bottom surface 1021, the ineffective region NR becomes even larger. Therefore, there are problems such as low utilization efficiency of the light R1 of the light source 200, that is, low extraction efficiency, a large occupied area of the circular reflection point 102 when viewed from above, and a small transmittance of the light guide plate 102.

[0017] Means for solving the problems

[0018] In order to solve the above problems, the light guide plate of the present invention has a light-transmitting flat plate. An incident light surface is provided at an end surface of the flat plate, the main surface of the flat plate is set as an outgoing light surface, the main surface on the opposite side of the outgoing light surface is set as a light distribution control surface, and the end surface on the opposite side of the incident light surface is set as a reverse incident light surface. Among them, an approximately semi-spindle-shaped reflection point is provided in a concave shape on the light distribution control surface. The approximately semi-spindle-shaped reflection point has: a first curved surface-like inclined surface provided on the incident light surface side; and a second curved surface-like inclined surface provided on the reverse incident light surface side with respect to the first curved surface-like inclined surface and joined to the first curved surface-like inclined surface. When observed from the light distribution control surface, the first curved surface-like inclined surface has a first circular arc shape. When observed from the light distribution control surface, the second curved surface-like inclined surface has a second circular arc shape. When observed from the incident light surface, the first curved surface-like inclined surface has a third circular arc shape. When observed from the reverse incident light surface, the second curved surface-like inclined surface has a third circular arc shape. The curvature of the first circular arc shape is greater than the curvature of the second circular arc shape.

[0019] In addition, the manufacturing method of the light guide plate of the present invention is the manufacturing method of the above light guide plate, and it includes a concave point mold machining process for machining the mold to form a plurality of concave points corresponding to the plurality of approximately semi-spindle-shaped reflection points.

[0020] Advantages of the Invention

[0021] According to the present invention, it is possible to provide a light guide plate that suppresses a decrease in light extraction efficiency and reduces a decrease in transmittance caused by the formation of reflection points. Description of the Drawings

[0022] Figure 1 It is a cross-sectional view showing a side surface type surface illumination device including a first embodiment of the light guide plate of the present invention.

[0023] Figure 2 Shows Figure 1 Details of the approximate semi-spindle-shaped reflection point, (A) is a perspective view, (B) is a top view observed from the light distribution control surface, (C) is a side view, (D) is a front view observed from the incident light surface, and (E) is a rear view observed from the reverse incident light surface.

[0024] Figure 3 Is used to illustrate Figure 1 Effect of the light guide plate.

[0025] Figure 4 Shows Figure 1 Configuration of the approximate semi-spindle-shaped reflection point on the light distribution control surface side of the light guide plate 1, (A) is a top view, (B) is a graph showing the change in the Y-direction pitch, and (C) shows the Y-direction pitch.

[0026] Figure 5 Is to illustrate for Figure 13 The light guide plate with circular reflection points andFigure 1 A diagram of a simulation comparing the brightness of a light guide plate with approximate semi-spindle-shaped reflection points. (A) shows the brightness distribution of the emitted light from the light-incident surface to the light-emitting surface on the opposite side, and (B)-1 shows Figure 13 the depth of 4 μm of the circular reflection point 102a of Figure 1 the depth d = 4 μm in the Z direction of the similar semi-spindle-shaped reflection point 1a of Figure 13 the layout of the light guide plate with the circular reflection point 102a when viewed from above, and (C)-2 shows Figure 1 the layout of the light guide plate with the semi-spindle-shaped reflection point 1a when viewed from above.

[0027] Figure 6 is for explaining Figure 1 the manufacturing method of the light guide plate of

[0028] Figure 7 is for explaining Figure 1 the relationship between components used in the precision roll machining process of

[0029] Figure 8 is for explaining Figure 1 the light distribution of the light guide plate of

[0030] Figure 9 is a cross-sectional view showing the second embodiment of the side surface illumination device of the present invention.

[0031] Figure 10 represents Figure 9 the details of the approximate semi-spindle-shaped reflection point of

[0032] Figure 11 is for explaining Figure 9 the manufacturing method of the light guide plate of

[0033] Figure 12 is an overall perspective view showing a general side surface illumination device.

[0034] Figure 13 represents a side surface illumination device including a first existing light guide plate. (A) is an overall perspective view, and (B) is an enlarged perspective view of the triangular reflection point of (A).

[0035] Figure 14Indicates a side surface illumination device including a second existing light guide plate. (A) is an overall three-dimensional view, and (B) is an enlarged three-dimensional view of the circular reflection points in (A).

[0036] Figure 15 Is for explaining Figure 13 The figure of the problems of the light guide plate.

[0037] Figure 16 Is for explaining Figure 14 The figure of the problems of the light guide plate. Detailed implementation mode

[0038] Figure 1 Is a cross-sectional view showing a side surface illumination device including a first embodiment of the light guide plate of the present invention.

[0039] In Figure 1 In the light guide plate 1, an approximately semi-spindle-shaped concave portion having an asymmetric shape when viewed from the side is provided on the light distribution control surface S cont Of the approximately semi-spindle-shaped reflection point 1a. That is, the approximately semi-spindle-shaped reflection point 1a is composed of a curved inclined surface 11 on the side of the asymmetric incident light surface S in And a curved inclined surface 12 on the side of the anti-incident light surface S in '. The light R1 from the light source 200 is reflected by the curved inclined surface 11 of the approximately semi-spindle-shaped reflection point 1a, and the LCD panel 300 is illuminated by the reflected light R2 from the light exit surface S out .

[0040] Refer to Figure 2 To explain Figure 1 The details of the approximately semi-spindle-shaped reflection point 1a. In addition, in Figure 2 , (A) is a three-dimensional view, (B) is a top view observed from the light distribution control surface, (C) is a side view, (D) is a front view observed from the incident light surface, and (E) is a rear view observed from the anti-incident light surface.

[0041] As Figure 2 Shown in (A) and (B) of, the curved inclined surface 11 of the concave portion observed from the light distribution control surface S cont Projected onto the light distribution control surface S cont The obtained contour shape has a first circular arc shape with a chord H1 having a length (the width of the approximately semi-spindle-shaped reflection point in the length direction) of W and an arc height (the depth of the circular arc) of L1. In addition, the curved inclined surface 12 of the concave portion observed from the light distribution control surface S cont Has a second circular arc shape with a chord H1 having a length of W and an arc height of L2. In this case, L = L1 + L2 is from the incident light surface S of the approximately semi-spindle-shaped reflection point 1a inDepth of side view. Here, L1 > L2. Therefore, the first arc shape defined by the length W and the arc height L1 is larger than the second arc shape defined by the length W and the arc height L2. That is, the curvature of the first arc shape is greater than the curvature of the second arc shape. Additionally, Figure 2 (C) of in in is the contour shape obtained by projecting the approximate semi-spindle-shaped reflection point 1a onto the surface (the side surface of the light guide plate 1) perpendicular to the light incident surface S. In Figure 2 (C) of cont cont if the angle of the contour line of the curved inclined surface 11 with respect to the normal line of the light distribution control surface S is set as θ1, and the angle of the contour line of the curved inclined surface 12 with respect to the normal line of the light distribution control surface S cont is set as θ2, then θ1 > θ2. Additionally, the first and second arc shapes also include crescent shapes, semi-moon shapes, etc.

[0042] As Figure 2 (D) of in in shows, the curved inclined surface 11 observed from the light incident surface S, that is, the contour shape of the curved inclined surface 11 projected onto the light incident surface S in is a third arc shape defined by a chord H2 with a length of W and a depth d from the light distribution control surface S of the light guide plate 1. Additionally, as cont (E) of in Figure 2 shows, the curved inclined surface 12 observed from the anti-light incident surface S in ’, that is, the contour shape of the curved inclined surface 12 projected onto the anti-light incident surface S in ’ is also the same third arc shape defined by a depth d with a chord H2 having a length of W. Additionally, the third arc shape includes crescent shapes, semi-moon shapes, etc.

[0043] The first arc shape projected onto the light distribution control surface S cont has a curved surface that smoothly connects from the chord H1 to the third arc shape formed in the depth direction (the direction parallel to the light incident surface S of the light guide plate 1), and it constitutes the curved inclined surface 11. Similarly, the second arc shape projected onto the light distribution control surface S in has a curved surface that smoothly connects from the chord H2 (the same as the chord H1) to the third arc shape formed in the depth direction (the direction parallel to the light incident surface S of the light guide plate 1), and it constitutes the curved inclined surface 12. cont parallel to the light incident surface S of the light guide plate 1), and it constitutes the curved inclined surface 12. in parallel to the light incident surface S of the light guide plate 1), and it constitutes the curved inclined surface 12.

[0044] As Figure 2 shows, the combination of the curved inclined surfaces 11 and 12, that is, the approximate semi-spindle-shaped reflection point 1a, is defined as follows.

[0045] W: The projection of the curved inclined surfaces 11 and 12 onto the light distribution control surface S contLength of the chord H1 of the obtained contour shape

[0046] d: Depth of the curved inclined surfaces 11 and 12 from the light distribution control surface S of the light guide plate 1 cont

[0047] θ1: Angle of inclination of the curved inclined surface 11 with respect to the normal of the light distribution control surface S cont

[0048] θ2: Angle of inclination of the curved inclined surface 12 with respect to the normal of the light distribution control surface S cont

[0049] where θ1 > θ2

[0050] Thus, the approximate semi-spindle-shaped reflection point 1a is defined by four parameters W, d, θ1, θ2 and the condition θ1 > θ2.

[0051] At this time, preferably

[0052] W = 5 μm to 75 μm, for example 30 μm

[0053] d = 1 μm to 10 μm, for example 4 μm

[0054] θ1 = 30° to 89°, for example 55°

[0055] θ2 = 0° to 60°, for example 10°.

[0056] If W and d are too small, the deviation due to processing accuracy is large, and brightness unevenness is likely to occur. If W and d are too large, the reflection point can be visually observed, which is not preferable for the use of the light guide plate, especially for the light guide plate for headlamps. In addition, if θ1 is less than 30°, the light reflected by the curved inclined surface 11 and directed toward the emission surface will decrease. Furthermore, when θ1 is 90°, no reflection point is formed. Moreover, if θ2 exceeds 60°, the transparency of the light guide plate 1 may sometimes decrease, so it is not preferable.

[0057] In addition, the arc heights L1 and L2 of the curved inclined surfaces 11 and 12 are approximately given by the following formula.

[0058] L1 = d · tan θ1

[0059] L2 = d · tan θ2

[0060] Therefore, the approximate semi-spindle-shaped reflection point 1a can also be defined by four parameters W, d, L1, L2 and the condition L1 > L2.

[0061] Figure 3 is a diagram for explaining Figure 1 the effect of the approximate semi-spindle-shaped reflection point 1a.

[0062] As​​​Figure 3 As shown in (A), the curved inclined surface 11 functions as an effective area as the reflecting surface of the light R1 from the light source 200. Since the curved inclined surface 12 is located on the side opposite to the light source 200, the light R1 of the light source 200 is difficult to enter, becoming an ineffective area. However, since the curved inclined surface 12 is smaller than the curved inclined surface 11, the ineffective area is small. In addition, as Figure 3 shown in (B), there is no side surface such as the case where there is no triangular reflection point 101. Therefore, the utilization efficiency of the light R1 of the light source 200 becomes high, that is, the light extraction efficiency becomes high. Furthermore, compared with the triangular reflection point 101, there are fewer linear components, so it is difficult to generate moiré fringes in the LCD panel 300.

[0063] In addition, since there is no circular bottom surface 1021 such as the case where there is no circular reflection point 102a, the occupied area of the approximate semi-spindle-shaped reflection point 1a is small. Therefore, by forming the approximate semi-spindle-shaped reflection point 1a with a smaller occupied area than the circular reflection point 102a, it is possible to realize a light guide plate that maintains the brightness of the light guide plate at the same level as the existing light guide plate formed with the circular reflection point 102a and has a high transmittance.

[0064] In addition, as Figure 3 shown in (B), especially when the light from the light source 200 has multiple paths of light R1a, R1b, and R1c, it is possible to control the reflected light R2a, R2b, and R2c reflected by the curved inclined surface 11 and directed toward the LCD panel 300 to be diffused, so that the brightness unevenness can be reduced.

[0065] Figure 4 is a diagram for explaining the arrangement of the approximate semi-spindle-shaped reflection points on the light distribution control surface side of the light guide plate 1. (A) is a top view, (B) is a graph showing the Y-direction pitch, and (C) shows the Y-direction pitch. Figure 1 In (A), when multiple approximate semi-spindle-shaped reflection points 1a are arranged, the X-direction pitch Px is set to a fixed value, for example, 0.154 mm. On the other hand, from the light incident surface S

[0066] In Figure 4 to the anti-light incident surface S in to the anti-light incident surface S in ’, the light R1 of the light source 200 becomes weak. Therefore, as Figure 4 shown in (A) and (B), by gradually decreasing the Y-direction pitch Py, the dot density is increased, and the light R1 that arrives is made to go from the light incident surface S in to the anti-light incident surface S in‘Becomes uniform. In this case, in the Y direction, the position in the X direction is offset by ΔX so that the points are not blocked by the previous points. In addition, in this case, a staggered configuration can also be adopted. Further, instead of changing the Y-direction pitch Py, the Z-direction depth d of the approximate semi-spindle-shaped reflection point 1a can be changed, or the arc height L (=L1 + L2) can be changed. When changing the Z-direction depth d or changing the arc height L, the approximate semi-spindle-shaped reflection point is set to a similar shape so that the light distribution characteristics do not change locally.

[0067] Figure 5 is an illustration of Figure 13 the light guide plate with circular reflection points and Figure 1 the simulation diagram comparing the brightness of the light guide plate with approximate semi-spindle-shaped reflection points, (A) shows the brightness distribution of the outgoing light from the incident surface S in to the anti-incident surface S in ’, (B)-1 shows Figure 13 the Z-direction depth d = 4 μm of the circular reflection point 102a of Figure 1 the similar semi-spindle-shaped reflection point 1a of Figure 13 the light guide plate with a Z-direction depth d = 4 μm, (C)-1 shows Figure 1 the top view configuration of the light guide plate with the circular reflection point 102a of Figure 5 the light guide plate, (C)-2 shows Figure 5 the top view configuration of the light guide plate with the similar semi-spindle-shaped reflection point 1a of in According to (B)-1 and (B)-2 of 2 the light guide plates, the Z-direction depths of the reflection points are the same. In (A) of Figure 5 if a comparison is made in the interval where the brightness of both light guide plates is approximately the same, that is, between the location 20 mm from the incident surface S -4 to the location 170 mm, then regarding the pattern area A [mm 2 of each reflection point, according to (C)-1 of Figure 5 the circular reflection point 102a is 7.68×10 -4 [mm 2 , according to (C)-2 of 2 the approximate semi-spindle-shaped reflection point 1a is 1.39×10 Figure 5 In addition, regarding the number of points (N) within the same area (B = 1574 [mm 2 ), according to (C)-1 of Figure 5 the circular reflection point 102a is 66563 [mm 2. Therefore, regarding the area ratio (the proportion of reflection points within the area) = A × N ÷ B, the circular reflection point 102a is 3.25%, and the approximate semi-spindle-shaped reflection point 1a is 1.99%. That is, compared with the circular reflection point 102a, the approximate semi-spindle-shaped reflection point 1a has a higher light extraction efficiency with respect to the point formation area, and it is possible to achieve a light guide plate that maintains the brightness at the same level as the existing one and has a high transmittance.

[0068] As a method for manufacturing a mold used in the manufacture of the light guide plate 1 having the approximate semi-spindle-shaped reflection point 1a, an ultra-precision machining method (refer to: Patent Document 2) in which a diamond turning tool is mounted on a piezoelectric element device to form concave points in the mold can be used. This method can make the surface of the reflection point 1a a mirror surface, so accurate light distribution control based on the approximate semi-spindle-shaped reflection point 1a can be performed. In addition, it is less expensive than a device used for photolithography processing.

[0069] Figure 6 Figure 1 is a diagram for explaining

[0070] the manufacturing method of the light guide plate. Figure 6 Figure 7 First, referring to Figure 7 the ultra-precision roll machining process shown in (A) of Figure 7 and (A), (B) of , rotate the cylindrical mold 601 coated with copper, brass, etc. in the rotation direction F, and use the piezoelectric element device (FTS) 603 to move the diamond turning tool 602 in the vertical depth direction as shown by the arrow in (B) of

[0071] to form concave points corresponding to the approximate semi-spindle-shaped reflection point 1a. Thus, a concave point mold 601 is obtained. Instead of the diamond turning tool 602 and the piezoelectric element device 603 shown in (A) of Figure 6 , machining machines such as a precision lathe and a precision flat cutting device can also be used.

[0072] Next, referring to Figure 6 the resin sheet flipping process shown in (B) of , perform point flipping with the concave points of the concave point mold 601 as the master to obtain a convex point resin sheet 604.

[0073] Next, referring to Figure 6 the electroforming flipping process shown in (C) of , perform electroforming flipping with the convex point resin sheet 604 as the master to obtain a concave point resin sheet 605.

[0074] Next, referring to Figure 6Figure 6 In the roller die chemical process shown in (E), the bump die 607 is obtained by winding the bump resin sheet 606 around the die.

[0075] Finally, referring to Figure 6 (F), multiple approximate semi-spindle-shaped reflection points 1a are simultaneously formed on the light distribution control surface S of the light guide plate 1 using the bump die 607. cont

[0076] According to Figure 6 the manufacturing method shown, through the fine cutting using the diamond turning tool 602, the concave surface of the concave die 601 becomes a three-dimensional mirror surface, and the approximate semi-spindle-shaped reflection points 1a of the light guide plate 1 using the concave die 601 also become mirror surfaces, enabling high-precision light distribution. In addition, the piezoelectric element device 603 can reciprocate the diamond turning tool 602 in the depth direction through electrical control, and the diamond turning tool 602 can engrave concave points on the rotating die 601 at high speed. Therefore, the concave point processing of the die 601 can be performed in a short time.

[0077] Figure 8 Indicates the light distribution of the light guide plate using the Figure 1 approximate semi-spindle-shaped reflection points 1a. (A) is a polar coordinate display, and (B) is a two-dimensional display.

[0078] As can be seen from Figure 8 , if the angle θ2 of the curved inclined surface 12 is fixed at 10°, and on the other hand, the angle θ1 of the curved inclined surface 11 is changed to 55°, 58°, 60°, 65°, the light distribution characteristics change. In particular, in the manufacturing method, by changing the tool angle of the diamond turning tool 602 and changing the inclination in the direction orthogonal to the cutting direction, the angle θ1 of the inclined surface 11 on the curved surface can be changed, thereby enabling the light distribution characteristics to change. Therefore, the high efficiency of the backlight corresponding to the requirements can be achieved. In any case, the light distribution is superior to that in the case of using the circular reflection points 102a.

[0079] For example, the larger θ1 is, the more the light distribution characteristics change toward the anti-incident light surface S in ’. Therefore, when the eye point is set in the Y direction above the center of the light guide plate and closer to the anti-incident light surface S in ’, by setting θ1 larger, more reflected light R2 can be emitted toward the anti-incident light surface S in ’, and the visual recognition of the display device at the eye point can be improved. In any case, the light distribution is superior to that in the case of using the circular reflection points 102a.

[0080] On the contrary, when the eye point is set in the Y direction above the center of the light guide plate and closer to the incident light surface S in ​In the case of the side, by setting θ1 small, more reflected light R2 can be emitted toward the light incident surface S in side, and the visual recognition of the display device at the eye point can be improved.

[0081] More preferably, since the reflectance is high when θ1 is large, in the case where the assumed eye point deviates from directly above the center of the light guide plate in the Y direction, if the positions of the light source 200 and the light incident surface S in are set on the side in the direction opposite to the direction where the eye point is located in the Y direction, the light utilization efficiency is improved.

[0082] In addition, by increasing the angle θ1A of the curved inclined surface 11 of the reflection point closer to the light source in the Y direction, making the angle θ1B of the curved inclined surface 11 of the reflection point closer to the region directly below the eye point smaller than θ1A, and making the angle θ1C of the curved inclined surface 11 of the reflection point farther than the region directly below the eye point in the Y direction smaller than θ1B, the light distribution can also be concentrated toward the eye point of the display device.

[0083] Conversely, by decreasing the angle θ1A of the curved inclined surface 11 of the reflection point closer to the light source in the Y direction, making the angle θ1B of the curved inclined surface 11 of the reflection point closer to the region directly below the eye point larger than θ1A, and making the angle θ1C of the curved inclined surface 11 of the reflection point farther than the region directly below the eye point in the Y direction larger than θ1B, the viewing angle of the display device can also be increased.

[0084] Figure 9 is a cross-sectional view showing a side surface type surface illumination device according to a second embodiment of the light guide plate including the present invention.

[0085] In Figure 9 , on the light distribution control surface S of the light guide plate 1', cont there is provided an approximately semi-spindle-shaped convex portion which is asymmetric when viewed from the side, and an approximately semi-spindle-shaped reflection point 1'a. That is, the approximately semi-spindle-shaped reflection point 1'a is composed of a curved inclined surface 11' of the convex portion on the non-light incident surface S in ' side and a curved inclined surface 12' of the convex portion on the light incident surface S in side. The light R1 from the light source 200 is reflected by the curved inclined surface 11' of the approximately semi-spindle-shaped reflection point 1'a, and the LCD panel 300 is illuminated with the reflected light R2 from the light exit surface S out .

[0086] Refer to Figure 10 to illustrate Figure 9 the details of the approximately semi-spindle-shaped reflection point 1'a. In addition, in Figure 10In (A), it is a perspective view; in (B), it is a top view observed from the light distribution control surface; in (C), it is a side view; in (D), it is a front view observed from the light incident surface; in (E), it is a rear view observed from the anti-light incident surface.

[0087] As Figure 10 shown in (A) and (B) thereof, the projected contour shape of the curved inclined surface 11' of the convex portion observed from the light distribution control surface S cont onto the light distribution control surface S cont results in a first circular arc shape having a chord H1 with a length (the width of the approximate semi-spindle-shaped reflection point in the length direction) of W and an arc height (the depth of the circular arc) of L1. Additionally, the curved inclined surface 12' of the convex portion observed from the light distribution control surface S cont has a second circular arc shape having a chord H1 with a length of W and an arc height L2. In this case, L = L1 + L2 is the depth observed from the side of the light incident surface S of the approximate semi-spindle-shaped reflection point 1'a. Here, L1 > L2, so the first circular arc shape defined by the length W and the arc height L1 is larger than the second circular arc shape defined by the length W and the arc height L2. That is, the curvature of the first circular arc shape is greater than the curvature of the second circular arc shape. Additionally, in (C) thereof is the contour shape obtained by projecting the approximate semi-spindle-shaped reflection point 1'a onto a plane (the side surface of the light guide plate 1') perpendicular to the light incident surface S. In Figure 10 (C), if the angle of the contour line of the curved inclined surface 11' with respect to the normal of the light distribution control surface S in is set as θ1, and the angle of the contour line of the curved inclined surface 12' with respect to the normal of the light distribution control surface S Figure 10 is set as θ2, then θ1 > θ2. Additionally, the first and second circular arc shapes also include crescent shapes, semi-moon shapes, etc. cont cont cont cont

[0088] As Figure 10 shown in (D) thereof, the curved inclined surface 12' observed from the light incident surface S, that is, the projected contour shape of the curved inclined surface 12' onto the light incident surface S in has a third circular arc shape defined by a chord H2 with a length of W and a height h from the light distribution control surface S of the light guide plate 1'. Additionally, as in shown in (E) thereof, the curved inclined surface 11' observed from the anti-light incident surface S, that is, the projected contour shape of the curved inclined surface 11' onto the anti-light incident surface S cont ' also has the same third circular arc shape defined by a height h with a chord H2 having a length of W. Additionally, the third circular arc shape includes crescent shapes, semi-moon shapes, etc. Figure 10 in in in in in

[0089] As Figure 10As shown, an approximate semi-spindle-shaped reflection point 1'a, which is a joined body of curved inclined surfaces 11' and 12', is also defined as follows.

[0090] W: The projection of the curved inclined surfaces 11' and 12' onto the light distribution control surface S cont The length of the chord H1 of the obtained contour shape

[0091] h: The height of the curved inclined surfaces 11' and 12' from the light distribution control surface S of the light guide plate 1' cont Height

[0092] θ1: The inclination angle of the curved inclined surface 11' with respect to the normal of the light distribution control surface S cont Inclination angle

[0093] θ2: The inclination angle of the curved inclined surface 12' with respect to the normal of the light distribution control surface S cont Inclination angle

[0094] where θ1 > θ2

[0095] Thus, the approximate semi-spindle-shaped reflection point 1'a is also defined by four parameters W, h, θ1, θ2 and the condition θ1 > θ2. At this time, it is preferable that

[0096] W = 5 μm to 75 μm, for example 30 μm

[0097] h = 1 μm to 10 μm, for example 4 μm

[0098] θ1 = 30° to 89°, for example 55°

[0099] θ2 = 0° to 60°, for example 10°.

[0100] If W and h are too small, the deviation caused by processing accuracy is large, and brightness unevenness is likely to occur. If W and h are too large, the reflection point can be visually observed, which is not preferable for the use of the light guide plate, especially for the light guide plate for headlamps. In addition, if θ1 is less than 30°, the light reflected by the curved inclined surface 11' and directed toward the exit surface may become less. Furthermore, when θ1 is 90°, no reflection point is formed. Moreover, if θ2 exceeds 60°, the transparency of the light guide plate 1' may sometimes decrease, so it is not preferable.

[0101] In addition, the arc heights L1 and L2 of the curved inclined surfaces 11' and 12' are approximately given by the following formula.

[0102] L1 = h · tanθ1

[0103] L2 = h · tanθ2

[0104] Therefore, the approximate semi-spindle-shaped reflection point 1'a can also be defined by four parameters W, h, L1, L2 and the condition L1 > L2.

[0105] Figure 9 The approximate semi-spindle-shaped reflection point 1'a also has the same effect as that of Figure 1 the approximate semi-spindle-shaped reflection point 1a.

[0106] Figure 11 is a diagram for explaining Figure 9 the manufacturing method of the light guide plate. In Figure 11 , compared with the manufacturing method of Figure 6 , the electroforming turning process is less. That is, there is only one electroforming turning process.

[0107] First, referring to the ultra-precision roll machining process shown in (A) of Figure 11 , rotate the cylindrical mold 601 coated with copper, brass, etc., and use the piezoelectric element device (FTS) 603 to move the diamond turning tool 602 in the up and down depth directions to form concave points corresponding to the approximate semi-spindle-shaped reflection point 1'a. Thus, the concave point mold 601 is obtained.

[0108] Next, referring to the resin sheet turning process shown in (B) of Figure 11 , perform point turning with the concave points of the concave point mold 601 as the master to obtain the convex point resin sheet 604.

[0109] Next, referring to the electroforming turning process shown in (C) of Figure 11 , perform electroforming turning with the convex point resin sheet 604 as the master to obtain the concave point resin sheet 605. In addition, by obtaining a plurality of concave point resin sheets 605, embossing (mass production patterning) is performed.

[0110] Next, referring to the roll mold forming process shown in (D) of Figure 11 , wind the concave point resin sheet 605 around the mold to obtain the concave point mold 607'.

[0111] Finally, referring to (E) of Figure 11 , use the concave point mold 607' to simultaneously form a plurality of approximate semi-spindle-shaped reflection points 1'a on the light distribution control surface S of the light guide plate 1'. cont At the same time, a plurality of approximate semi-spindle-shaped reflection points 1'a are formed.

[0112] In addition, the present invention can be applied to any changes made within the obvious scope of the above-described embodiments.

[0113] Industrial Applicability

[0114] In addition to the light guide plate for the backlight of an LCD device, the light guide plate of the present invention can be used not only for a light guide plate for front light, such as an LCD device, but also for an electrophoretic display. Further, by changing the optical bevel shape of the dots, it can also be used as a backlight. Moreover, it can cause signs such as letters and patterns for signs to emit light, or can also distribute light in the front direction, so it can also be used in lighting devices for automobiles and the like.

[0115] Description of Reference Numerals

[0116] U: Side surface illumination device

[0117] 100, 101, 102, 1, 1': Light guide plate

[0118] S in : Light incident surface

[0119] S out : Light exit surface

[0120] S cont : Light distribution control surface

[0121] S in ’: Reverse light incident surface

[0122] 200: Light source

[0123] 300: Liquid crystal display (LCD) panel

[0124] 1a, 1’a: Approximately semi-spindle-shaped reflection points

[0125] 11, 12, 11’, 12’: Curved inclined surfaces

[0126] 601: Concave dot mold

[0127] 602: Diamond turning tool

[0128] 603: Piezoelectric element device

[0129] 604: Convex dot resin sheet

[0130] 605: Concave dot resin sheet

[0131] 606: Convex dot resin sheet

[0132] 607: Convex dot mold

[0133] 607’: Concave dot mold

[0134] 100a: Reflection point

[0135] 101a: Triangular reflection point

[0136] 1011, 1012: Inclined surfaces

[0137] 1013, 1014: Side

[0138] 102a: Circular reflection point

[0139] 1021: Circular bottom surface

[0140] 1022: Inclined surface

[0141] R1: Incident light

[0142] R2: Reflected light

Claims

1. A light guide plate, the light guide plate (1) having a light-transmissive flat plate, with a light incident surface (S in ) at an end face of the flat plate, setting a main surface of the flat plate as a light exit surface (S out ), setting a main surface on the opposite side of the light exit surface (S out ) as a light distribution control surface (S cont ), setting an end face on the opposite side of the light incident surface (S in ) as a reverse light incident surface (S in ’), wherein, On the light distribution control surface (S cont ), approximately semi-spindle-shaped reflection points are provided in a concave shape, The approximate semi-spindle-shaped reflection point (1a) has: A first curved inclined surface (11) provided on the side of the light incident surface (S in ); and A second curved inclined surface (12) disposed on the side of the anti-incident light surface (S in ’) relative to the first curved inclined surface (11), and the second curved inclined surface (12) is joined to the first curved inclined surface (11). Observed from the light distribution control surface (S cont ), the first curved inclined surface (11) has a first circular arc shape, Observed from the light distribution control surface (S cont ), the second curved inclined surface (12) has a second arc shape. Observed from the incident light surface (S in ), the first curved inclined surface has a third arc shape, Observed from the anti-incident light surface (S in ’), the second curved inclined surface (12) assumes the shape of the third circular arc.

2. A light guide plate, the light guide plate having a light-transmissive flat plate, with a light incident surface (S in ) at an end face of the flat plate, setting a main surface of the flat plate as a light exit surface (S out ), setting a main surface on the opposite side of the light exit surface (S out ) as a light distribution control surface (S cont ), setting an end face on the opposite side of the light incident surface (S in ) as a reverse light incident surface (S in ’), wherein, On the light distribution control surface (S cont ), an approximately semi-spindle-shaped reflection point (1’a) is provided in a convex shape, The approximate semi-spindle-shaped reflection point (1’a) has: A first curved inclined surface (11') disposed on the side of the anti-incident light surface (S in '); A second curved inclined surface (12') disposed on the light incident surface (S in ) side with respect to the first curved inclined surface (11'), and the second curved inclined surface (12') is joined to the first curved inclined surface (11'). Observed from the light distribution control surface (S cont ), the first curved inclined surface (11’) has a first arc shape, Observed from the light distribution control surface (S cont ), the second curved inclined surface (12’) is in the shape of a second circular arc, Observed from the anti-incident light surface (S in ’), the first curved inclined surface (11’) is in the shape of a third arc Viewed from the light incident surface (S in ), the second curved inclined surface (12') has the shape of the third circular arc.

3. The light guide plate according to claim 1 or 2, wherein, The arc height (L1) of the first arc shape is greater than the arc height (L2) of the second arc shape.

4. The light guide plate according to claim 1 or 2, wherein, When the angle of the first curved inclined surface (11, 11') with respect to the normal line of the light distribution control surface (S cont ) is θ1, and the angle of the second curved inclined surface (12, 12') with respect to the normal line of the light distribution control surface (S cont ) is θ2, θ1>θ2.

5. The light guide plate according to claim 4, wherein, θ1 ranges from 30° to 89°, and θ2 ranges from 0° to 60°.

6. The light guide plate according to claim 1 or 2, wherein, The width of the approximate semi-spindle-shaped reflection point (1a, 1’a) is 5 μm to 75 μm.

7. The light guide plate according to claim 1 or 2, wherein, The depth (d) or height (h) of the approximate semi-spindle-shaped reflection point (1a, 1’a) is 1 μm to 10 μm.

8. A method for manufacturing a light guide plate, which is the method for manufacturing the light guide plate according to claim 1 or 2, wherein, The manufacturing method of the light guide plate includes a concave point mold machining process for machining a mold to form a plurality of concave points corresponding to the plurality of approximate semi-spindle-shaped reflection points (1a, 1’a).

9. The method for manufacturing a light guide plate according to claim 8, wherein, The concave point mold machining process uses a cutting tool (602) and a piezoelectric element device (603) for driving the cutting tool (602).

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