JP6295525B2 - Light guide plate, backlight unit and display device - Google Patents

Description

  The present invention relates to a light guide plate that emits light in a planar shape with respect to a light output surface of a display device such as a liquid crystal display panel.

  In liquid crystal display devices that have come to be widely used as small and medium-sized display devices such as mobile phones, car navigation systems, and portable terminals, and medium and large-sized display devices such as personal computers, computer monitors, television receivers, and advertising billboards For a liquid crystal display panel, a light guide plate that emits light in a planar shape is often used. This light guide plate constitutes a backlight unit in combination with other optical sheets such as a diffusion sheet and a prism sheet. These other optical sheets play a role of increasing the brightness of the emitted light and making the surface uniform.

  A cross-sectional view of an example of the configuration of the backlight unit is illustrated in FIG. A light source 203 (for example, LED) is disposed in the vicinity of the light incident surface 4 of the light guide plate 202. Light incident from the light source 203 (here, LED) is guided inside the light guide plate 202. The light 209 guided inside the light guide plate 202 repeats total reflection between the light reflection surface 2 which is one surface of the light guide plate 202 and the other light exit surface 3. In general, a reflection sheet 204 is provided on the light reflection surface 2 side of the light guide plate 202, but most of the light 209 guided inside the light guide plate 202 is formed on the light reflection surface 2 of the light guide plate 202. The optical path is changed by the fine structure pattern 208, and the light is emitted as planar light from the light exit surface 3 side. The light 209 emitted from the light exit surface side is sent to, for example, the reflective polarizing film 207 through, for example, the diffusion sheet 205 and the prism sheet 206 for increasing the brightness of the emitted light and in-plane uniformity. Yes.

  In recent years, the light guide plate as described above is required to have higher brightness and thinner thickness. In order to realize high brightness and thinning, it is necessary to further refine the fine structure pattern formed on the surface in order to change the optical path. In the screen printing method conventionally used as a method for manufacturing a light guide plate, there is a limit to miniaturization of the pattern shape, and it is difficult to further increase the brightness and reduce the thickness.

  Therefore, various methods for providing a fine structure pattern shape to the light reflecting surface of the light guide plate have been proposed. As these fine structure patterns, a linear pattern or an individual pattern parallel to the light incident surface is disclosed (Patent Document 1, Patent Document 2).

  The linear pattern is produced by a method of directly patterning the light guide plate base material or a method of transferring the pattern pattern to the light guide plate base material using a patterned die. However, for point light sources such as LEDs, which are frequently used as the light source of recent backlight units, uneven brightness in which only the vicinity of the front surface of the point light source becomes bright in the vicinity of the light incident surface of the light reflecting surface is likely to occur. There is a problem. Also, in order to make the overall brightness uniform from the light incident surface to the anti-light incident surface, the ratio of the pattern area to the unit area when viewed in a plane can be changed within the surface, or the pattern shape It is necessary to change the depth. For example, in the area close to the light source, it is necessary to reduce the pattern area ratio as compared with the area far from the light source. In the case of a linear pattern, it is necessary to make adjustments such as increasing the interval between patterns and reducing the pattern opening width and pattern depth. However, at that time, a problem that the light emitted from the linear pattern becomes a bright line and is visually recognized with the naked eye (visible line appearance) is likely to occur.

  On the other hand, since individual patterns can easily change the arrangement and number of patterns, it is easier to improve brightness uniformity and prevent the appearance of bright lines compared to linear patterns. However, it may take time to process the pattern.

  Furthermore, as a combination of a linear pattern and a piece-like pattern, a light guide plate is also proposed in which two patterns are switched at a fixed position in the vicinity of the light incident surface (Patent Document 3). By combining individual and linear patterns, brightness can be made uniform in the vicinity of the light incident surface, and the pattern processing time can be shortened compared to all individual patterns. Cost reduction can be realized. However, since a linear pattern and a piece-like pattern are combined, brightness irregularity may occur due to a sudden change in the shape of the pattern at the boundary between the linear pattern and the piece-like pattern. .

Japanese Patent Laid-Open No. 06-313885 Japanese Patent Laid-Open No. 05-2106030 JP 2009-176562 A

  The present invention is based on the above-described problems of the prior art, and an object of the present invention is to provide a light guide plate that can make the luminance uniform and prevent the appearance of bright lines and can be manufactured at low cost. It is in.

In order to solve the above-mentioned problems of the prior art, the light guide plate according to the present invention is a light guide plate that emits light entering from a light incident surface that is a side end surface to the outside from a light exit surface,
Patterns described in the following (a) to (c) are provided on the light reflecting surface of the light guide plate as structures for reflecting light propagating through the light guide plate toward the light exit surface of the light guide plate. Formed,
In order from the side closer to the light incident surface of the light guide plate, the patterns are arranged in the order of individual patterns, wavy patterns, and linear patterns, and further in the order of individual pattern areas, wavy pattern areas, and linear pattern areas. The light guide plate is characterized by being arranged so that the pattern occupancy gradually increases.
(A) A linear pattern having one extending direction and having a height in the thickness direction of the light guide plate that is substantially constant over the entire length in the extending direction.
(B) A wavy pattern having the same extending direction as the linear pattern and having a portion in which the height in the thickness direction of the light guide plate continuously changes along the extending direction.
(C) A group of a plurality of independent patterns arranged at a predetermined interval from each other, each having a piece-like pattern having the same extending direction as the wavy pattern.

  By arranging individual patterns in areas with low pattern density, it is possible to reduce unevenness in brightness and the appearance of bright lines at the boundaries of different pattern shapes, and by using linear patterns in combination, the light guide plate or mold The processing time can be shortened, and as a result, the processing cost can be reduced. In addition, by arranging a wave pattern area between the individual pattern area and the linear pattern area, it is possible to suppress a sudden change (brightness change) in the amount of light extracted from the light exit surface and make the brightness uniform throughout. It becomes possible.

1A and 1B show an example of a light guide plate according to an embodiment of the present invention. FIG. 1A is a plan view seen from the light reflecting surface side, and FIG. 1B is a side view. FIG. 2 is an example of a cross-sectional view perpendicular to the extending direction of the individual patterns, wavy patterns, and linear patterns of the light guide plate according to an embodiment of the present invention. In FIG. 2A, the cross section is a concave pentagonal shape. 2 (b), the cross section is a concave V-shape, FIG. 2 (c) is a concave oval shape, FIG. 2 (d) is a convex pentagon, and FIG. 2 (e) is a convex V shape. FIG. 2 (f) shows a case where the cross section is a convex elliptical shape. FIG. 3 shows an example of a concave piece pattern, FIG. 3 (a) is a plan view seen from the light reflecting surface side, and FIG. 3 (b) is along the extending direction and reflects light. It is sectional drawing perpendicular | vertical to a surface. A broken line indicates a light reflecting surface. FIG. 4 shows an example of a convex individual pattern. FIG. 4 (a) is a plan view seen from the light reflecting surface side, FIG. 4 (b) is along the extending direction, and light It is sectional drawing perpendicular | vertical to a reflective surface. A broken line indicates a light reflecting surface. FIG. 5 shows an example of a concave piece pattern having a rounded trapezoidal wave shape. FIG. 5A is a plan view seen from the light reflecting surface side, and FIG. 5B is an extending direction. FIG. 4 is a cross-sectional view taken along the line and perpendicular to the light reflecting surface. A broken line indicates a light reflecting surface. FIG. 6 shows an example of a concave wavy pattern, FIG. 6 (a) is a plan view seen from the light reflecting surface side, FIG. 6 (b) is along the extending direction and on the light reflecting surface. It is a vertical sectional view. A broken line indicates a light reflecting surface. FIG. 7 shows another example of the concave wavy pattern. FIG. 7A is a plan view seen from the light reflecting surface side, and FIG. 7B is along the extending direction and reflects light. It is sectional drawing perpendicular | vertical to a surface. A broken line indicates a light reflecting surface. FIG. 8 shows still another example of the concave wave pattern. FIG. 8 (a) is a plan view seen from the light reflecting surface side, FIG. 8 (b) is along the extending direction, and light It is sectional drawing perpendicular | vertical to a reflective surface. A broken line indicates a light reflecting surface. FIG. 9 shows an example of a concave wave pattern having a rounded trapezoidal wave shape. FIG. 9A is a plan view seen from the light reflecting surface side, and FIG. 9B is along the extending direction. 2 is a cross-sectional view perpendicular to the light reflecting surface. A broken line indicates a light reflecting surface. FIG. 10 shows another example of a concave wavy pattern having a rounded trapezoidal wave shape. FIG. 10 (a) is a plan view seen from the light reflecting surface side, and FIG. 10 (b) is an extending direction. FIG. 4 is a cross-sectional view taken along the line and perpendicular to the light reflecting surface. A broken line indicates a light reflecting surface. FIG. 11 shows still another example of a concave wavy pattern having a rounded trapezoidal wave shape. FIG. 11 (a) is a plan view seen from the light reflecting surface side, and FIG. 11 (b) is an extension. It is sectional drawing which follows a direction and is perpendicular | vertical to a light reflection surface. A broken line indicates a light reflecting surface. FIG. 12 shows an example of a concave linear pattern, FIG. 12 (a) is a plan view seen from the light reflecting surface side, FIG. 12 (b) is along the extending direction, and the light reflecting surface. FIG. A broken line indicates a light reflecting surface. FIG. 13 is a diagram showing the relationship between the pattern width at which bright lines appear and the distance between patterns. FIG. 14 is a diagram showing an example of the relationship between the pattern occupation ratio and the distance from the light incident surface. FIG. 15 is a diagram showing an example of the relationship between the pattern average height and the distance from the light incident surface. FIG. 16 is a diagram showing an example of the relationship between the length of the non-pattern part and the distance from the light incident surface. FIG. 17 is a plan view seen from the light reflecting surface side of an example in which the positions of the non-patterned portions of the individual pattern are arranged in a staggered manner along the direction perpendicular to the light incident surface. FIG. 18 is a plan view as seen from the light reflecting surface side of an example in which the positions of the non-patterned portions of the individual pattern are randomly arranged along the direction perpendicular to the light incident surface. FIG. 19 is a plan view as seen from the light reflecting surface side of an example in which the positions of the pattern bottoms in the extending direction of the wavy pattern are arranged in a staggered manner along the direction perpendicular to the light incident surface. FIG. 20 is a plan view as seen from the light reflecting surface side of an example in which the position of the pattern bottom in the extending direction of the wavy pattern is randomly arranged along the direction perpendicular to the light incident surface. FIG. 21 is a diagram showing an example of the relationship between the distance between patterns and the distance from the light incident surface. FIG. 22 is a schematic cross-sectional view showing an example of a backlight unit having the light guide plate of the present invention. FIG. 23 is a schematic cross-sectional view showing an example of a display device using a backlight unit having a light guide plate of the present invention. FIG. 24 is a schematic cross-sectional view showing an example of a thermal imprint apparatus. FIG. 25 is a schematic cross-sectional view showing another example of the thermal imprint apparatus. FIG. 26 is a schematic cross-sectional view illustrating an example of a flow of manufacturing a light guide plate by an injection molding method. FIG. 27 is a schematic cross-sectional view showing an example of an extrusion molding apparatus. FIG. 28 is a schematic cross-sectional view showing an example of an optical imprint apparatus. FIG. 29 is a schematic cross-sectional view showing an example of the configuration of the backlight unit. FIG. 30 shows the distance in the direction perpendicular to the light incident surface and away from the light incident surface, the distance between the patterns, and the pattern occupancy rate for the light guide plate manufactured in Example 1 from the individual pattern closest to the light incident surface. FIG. FIG. 31 shows the first to third examples and comparative example 1 in the direction perpendicular to the light incident surface and away from the light incident surface, starting from the individual pattern closest to the light incident surface in the central portion of the light guide plate in the extending direction. It is the figure which showed the change of the brightness | luminance (cd / m < ² >) measured at a distance and 10 mm space | interval from the starting point. FIG. 32 is a diagram showing a change in the pattern occupancy ratio in the portion corresponding to the wavy pattern region of the light guide plate of Example 1 for the light guide plates manufactured in Example 1 and Comparative Example 1.

  Hereinafter, the light guide plate of the present invention will be described in more detail with reference to the drawings.

The light guide plate of the present invention is a light guide plate that emits light from a light incident surface that is a side end surface to the outside from a light exit surface.
The light reflecting surface facing the light exit surface of the light guide plate is a structure for reflecting light propagating inside the light guide plate toward the light exit surface side of the light guide plate, and the following (a) to (c) ) Pattern is formed,
In the same plane, in the direction perpendicular to the extending direction, the patterns are arranged in the order of individual patterns, wavy patterns, and linear patterns from the side closer to the light incident surface of the light guide plate. The light guide plate is characterized in that the pattern occupying ratio is gradually increased in the order of the area, the wavy pattern area, and the linear pattern area.
(A) A linear pattern having one extending direction and having a height in the thickness direction of the light guide plate that is substantially constant over the entire length in the extending direction.
(B) A wavy pattern having the same extending direction as the linear pattern and having a portion in which the height in the thickness direction of the light guide plate continuously changes along the extending direction.
(C) A group of a plurality of independent patterns arranged at a predetermined interval from each other, each having a piece-like pattern having the same extending direction as the wavy pattern.

  An example of a light guide plate according to an embodiment of the present invention is shown in FIG. In the present invention, the pattern is defined as a structure showing the uneven shape provided on the light reflecting surface 2 of the light guide plate 1. The extending direction is defined as the longitudinal direction of the pattern formed along one direction, and the direction of the arrow indicated by 31 in FIG. 1 is the extending direction. The pattern height 27 is the height or depth of the irregularities formed on the light reflecting surface 2 in a cross section perpendicular to the pattern extending direction 31.

  Here, an example of a cross-sectional shape perpendicular to the pattern extending direction 31 is shown in FIG. FIG. 2A shows a concave pentagonal shape. In FIG. 2B, it is a concave V-shape. In FIG. 2 (c), it is a concave elliptical shape. In FIG.2 (d), it is a convex pentagon shape. FIG. 2 (e) shows a convex V-shape. FIG. 2 (f) shows a convex elliptical shape. The shape of the cross section perpendicular to the pattern extending direction 31 is not limited to the shapes of FIGS. 2A to 2F, and may be other shapes. Moreover, the shape of the pattern in the light guide plate 1 does not have to be either a concave shape or a convex shape, and may be a combination of a concave shape and a convex shape. Furthermore, it is not necessary to unify the cross-sectional shape, and the cross-sectional shape may be changed for each pattern in the light guide plate 1. However, in consideration of the ease of manufacturing the light guide plate described later, it is preferable to unify the concave shape or the convex shape.

  The individual pattern 11 refers to each independent pattern in a state where a plurality of patterns are arranged in the extending direction 31 of the light reflecting surface 2 having the pattern. Further, in the individual pattern 11, the aggregate of the plurality of individual patterns 11 arranged at a predetermined interval from each other is a plurality of pieces with a certain non-pattern part 32 interposed in the extending direction 31. It means an aggregate in which the piece-like patterns 11 are arranged. FIG. 3 shows an example of the concave individual pattern 11, FIG. 3 (a) is a plan view seen from the light reflecting surface 2 side, FIG. 3 (b) is along the extending direction 31, and FIG. 3 is a cross-sectional view perpendicular to the light reflecting surface 2. FIG. 4 shows an example of the convex individual pattern 11, FIG. 4 (a) is a plan view seen from the light reflecting surface 2 side, FIG. 4 (b) is along the extending direction 31, Further, it is a cross-sectional view perpendicular to the light reflecting surface 2. The shape of the individual pattern 11 is not limited to these, and may be other shapes. The individual pattern 11 includes a pattern top 41 that is the highest position in the pattern with respect to the light reflecting surface 2, and a transition portion 42 that connects the pattern top 41 and the non-pattern portion 32. The height from the light reflecting surface 2 to the pattern top 41 is defined as the maximum height 44.

  The wavy pattern 12 is a wavy pattern having a portion in which the pattern height 27 continuously changes along the extending direction 31.

  FIGS. 6 to 8 show examples of the concave wavy pattern 12, and FIG. 6A is a plan view seen from the light reflecting surface 2 side, and FIG. FIG. 2 is a cross-sectional view perpendicular to the light reflecting surface 2. In the wavy pattern 12, the pattern top 41 and the pattern low portion 43, which is the lowest position of the wavy pattern 12, with respect to the light reflecting surface 2 are connected by the transition portion 42. Note that the height from the light reflecting surface 2 to the pattern low portion 43 is defined as a minimum height 45. In the example shown in FIG. 6, the pattern top 41 and the pattern bottom 43 having a straight line parallel to the light reflecting surface 2 are connected to the tapered transition 42. The pattern top part 41 and the pattern bottom part 43 do not necessarily have a straight line part, and the pattern bottom part 43 is sharp as shown in FIG. 7, or both the pattern top part 41 and the pattern bottom part 43 are sharp as shown in FIG. Or you may. The shape of the wave pattern 12 is not limited to these, and may be other shapes. 6 to 8 show only the concave wave pattern 12, the present invention can also be applied to the convex wave pattern 12. Further, the wavy pattern 12 only needs to have a portion in which the pattern height 27 continuously changes along the extending direction 31. That is, it may have a portion where the pattern height 27 continuously changes along the extending direction 31 and a portion where the pattern height 27 is constant, and the height in the thickness direction continuously over the entire length of the extending direction 31. It may have changed.

  The linear pattern 13 is a pattern whose maximum height 44 is always constant in the extending direction 31. FIG. 12 shows an example of the concave linear pattern 13, FIG. 12 (a) is a plan view seen from the light reflecting surface 2 side, FIG. 12 (b) is along the extending direction 31, and FIG. 3 is a cross-sectional view perpendicular to the light reflecting surface 2. The shape of the concave linear pattern 13 is not limited to these, and may be other shapes. Although only the concave linear pattern 13 is shown in FIG. 12, the present invention can be applied to the convex linear pattern 13.

Here, the gradual increase in the pattern occupancy is an area obtained by projecting a pattern occupying a unit area (1 cm ² ) of the light reflection surface 2 measured at intervals of 5 mm in a direction away from the light incident surface 4 onto the light reflection surface 2. It is defined as the proportion increasing. As an example of a preferable change in the pattern occupancy ratio, FIG. 14 shows a case where the pattern occupancy increase ratio gradually increases as the distance from the light incident surface 4 increases. The form in which the pattern occupancy rate increases is not limited to the above, and other forms may be used.

  When all the patterns of the light guide plate 1 are composed of the linear patterns 13, the inter-pattern distance 34 between adjacent patterns in the direction perpendicular to the extending direction 31 in the light reflecting surface 2 is increased as the light source 6 is approached. In the light exit surface 3, uniform brightness can be obtained. However, if the inter-pattern distance 34 is increased, the bright lines of each pattern are easily visible. According to the inventor's experimental study, in the case of the light guide plate 1 having a thickness of 3 mm, in the graph showing the relationship between the pattern width 28 and the inter-pattern distance 34 shown in FIG. It was. As shown in FIG. 13, in order to prevent the appearance of bright lines, the inter-pattern distance 34 is preferably about 280 μm or less when the pattern width 28 is 6 μm, and the inter-pattern distance 34 is about 240 μm or less when the pattern width 28 is 18 μm. It is preferable.

  If the area close to the point light source is configured by only the linear pattern 13, it is necessary to increase the inter-pattern distance 34 in order to make the entire luminance uniform, and as a result, the appearance of bright lines is likely to occur. In view of this, in the region close to the point light source, the appearance of the bright line can be suppressed by arranging the discrete patterns 11 scattered. However, when the light guide plate is composed of only the individual pattern 11 and the linear pattern 13, the shape of the cross section parallel to the pattern extending direction 31 is the boundary portion between the individual pattern 11 and the linear pattern 13 at the boundary portion. In this case, the light amount on the light exit surface 3 slightly changes, and this may be visually recognized as bright line unevenness. Therefore, by interposing the wavy pattern region 8 between the individual pattern region 7 and the linear pattern region 9, the boundary between the individual pattern 11 and the wavy pattern 12 and the boundary between the wavy pattern 12 and the linear pattern 13. The amount of light extracted from the light exit surface 3 at the part can be changed gently, and as a result, the appearance of bright lines can be prevented. Further, by gradually increasing the pattern occupancy as the distance from the light incident surface 4 increases, the light guide distance in the light guide plate 1 becomes longer, and the light path can be changed at a higher density at a portion where the light intensity is relatively weak. As a result, it is possible to contribute to uniform luminance distribution on the light exit surface 3 after the optical path conversion. FIG. 1 illustrates the case where there is one light incident surface 4. However, when there are three light incident surfaces 4 on both sides of the light guide plate 1 or three or more surfaces, the distance from these light incident surfaces 4. It is preferable that the pattern occupancy is gradually increased as it goes to the central portion of the light guide plate 1 where the distance increases. In this way, by gradually increasing the pattern occupancy as the distance from the light incident surface 4 increases, the light guide distance in the light guide plate 1 becomes longer, and the portion away from the point light source 6 where the light intensity is relatively weaker is more. The optical path can be changed at a high density, and as a result, the luminance distribution on the light exit surface 3 can be made uniform after the optical path change.

  In this manner, the individual pattern 11 is arranged in the vicinity of the light incident surface 4 close to the point light source 6, and the linear pattern 13 is arranged in a place far from the light incident surface 4, and the individual pattern 11 and the linear pattern 13 are arranged. The light-emitting surface 3 of the light guide plate 1 is disposed by interposing the wavy pattern 12 between them and arranging the individual pattern 11, the wavy pattern 12, and the linear pattern 13 so that the pattern occupancy gradually increases from the vicinity of the light incident surface 4. It is possible to prevent the appearance of bright lines in the light source and to make the entire luminance distribution of the light exit surface 3 uniform.

  The preferable ranges of the pattern height 27 and the pattern width 28 of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 are all 1 μm to 100 μm, and more preferably 5 μm to 50 μm. Moreover, the preferable range of the inter-pattern distance 34 is 1 μm to 500 μm, and more preferably 5 μm to 50 μm. If the pattern height 27 and the pattern width 28 are less than 1 μm, the effect of improving the brightness may not be obtained. On the other hand, if the pattern height is greater than 100 μm, the brightness unevenness and the bright line appearance may occur. The surface roughness of the flat portions of the light reflecting surface 2 and the light emitting surface 3 is preferably 0.2 μm or less in terms of arithmetic average roughness Ra defined by JISB0601 (2001). This is because when Ra exceeds 0.2 μm, part of the light that should be totally reflected by the flat portion of the light exit surface 3 may be emitted.

  Further, in the individual pattern 11, the wavy pattern 12, and the linear pattern 13, a preferable range of the pattern slope angle 29 formed by the pattern and the direction perpendicular to the extending direction 31 in the light reflecting surface 2 is 40 ° to 60 °. Yes, more preferably 45 ° to 55 °. In the range where the pattern slope angle 29 is less than 40 ° or greater than 60 °, the luminance in the visual field region may decrease on the light exit surface 3 side. In the individual pattern 11 and the wavy pattern 12, the preferred range of the pattern transition angle 47 formed by the non-pattern part 32 or the pattern bottom part 43 and the pattern transition part 42 is 30 ° or less, more preferably 20 ° or less. . By setting the pattern transition angle 47 to 30 ° or less, more preferably 20 ° or less, the processing speed can be significantly increased in view of the processing characteristics of the pattern described later. In addition, since the clearance angle of the cutting tool for processing can be reduced, it is possible to suppress the problem of pattern processing defects due to chipping of the cutting tool during processing. Furthermore, the pattern top portion 41 and the pattern bottom portion 43 and the transition portion 42 have different emission angles at the light exit surface 3, so that the luminance changes depending on the angle in the viewing area, but the pattern transition angle 47 is preferably 30 ° or less, more preferably By setting the angle to 20 ° or less, a difference in luminance change can be suppressed, which is preferable in view angle characteristics.

  In the individual pattern 11, it is preferable that the cross-sectional shape along the extending direction 31 of the pattern and perpendicular to the light reflecting surface 2 is a rounded trapezoidal wave shape.

  An example of an individual piece pattern having a rounded trapezoidal wave shape is shown in FIG. 5A is a plan view seen from the light reflecting surface 2 side, and FIG. 5B is a cross-sectional view along the extending direction 31 and perpendicular to the light reflecting surface 2. The rounded trapezoidal wave shape refers to a shape in which the pattern top portion 41 and the transition portion 42 and the transition portion boundary 46 between the transition portion 42 and the non-pattern portion 32 have an arc shape. The transition part 42 excluding the transition part boundary 46 may be a straight line, or the pattern top part 41 and the non-pattern part 32 may be directly connected by an arc. Moreover, the transition part boundary 46 does not need to be the circular arc of all the same radii, and may differ. Furthermore, the arc of the transition boundary 46 need not be composed of a radius having a single value, and may be a shape in which arcs of a plurality of radii are connected while continuously changing. All transition part boundaries 46 do not have to be arcs. The shape of the individual pattern 11 having a rounded trapezoidal wave shape is not limited to these, and may be other shapes. Further, FIG. 5 shows only the concave individual pattern 11 having a rounded trapezoidal wave shape, but may be a convex individual pattern 11 having a rounded trapezoidal wave shape.

  In the individual pattern 11, the processing speed can be significantly increased with almost no change in luminance characteristics by making the end of the transition portion 42 into a rounded trapezoidal wave shape having an arc shape. Furthermore, since the emission angle at the light exit surface 3 is different between the pattern top 41 and the transition portion 42 alone, the luminance may vary greatly depending on the angle in the field of view area. Since light is emitted also between the emission angles of 41 and the transition portion 42, a smooth luminance change is exhibited in the viewing region, which is preferable in view angle characteristics.

  Here, the radius of the arc is preferably 1 μm or more, more preferably 10 μm to 100 μm. If the radius of the arc is less than 1 μm, it may not contribute significantly to the improvement of the processing speed, and the effect on the viewing angle characteristic of obtaining a smooth luminance change in the viewing area may not be significant.

  In the wavy pattern 12, it is preferable that the cross-sectional shape along the extending direction 31 of the pattern and perpendicular to the light reflecting surface 2 is a rounded trapezoidal wave shape.

  Examples of a wavy pattern having a rounded trapezoidal wave shape are shown in FIGS. (A) of each figure is the top view seen from the light reflective surface 2 side, (b) is sectional drawing along the extending direction 31 and perpendicular | vertical to the light reflective surface 2. FIG. In the wavy pattern 12, the rounded trapezoidal wave shape refers to a shape in which the pattern top portion 41, the transition portion 42, and the transition portion boundary 46 between the transition portion 42 and the pattern low portion 43 have an arc shape. Moreover, the transition part boundary 46 may be a straight line, or the pattern top 41 and the pattern low part 43 may be directly connected by an arc. Furthermore, the transition part boundaries 46 do not have to be arcs having the same radius, and may be different. Moreover, the arc of the transition part boundary 46 does not need to be configured by a radius having a single value, and may be a shape in which arcs of a plurality of radii are connected while continuously changing. All transition part boundaries 46 do not have to be arcs. The shape of the wave pattern 12 having a rounded trapezoidal wave shape is not limited to these, and may be other shapes. 9 to 11 show only the concave wave pattern 12 having a rounded trapezoidal wave shape, it may be a convex wave pattern 12 having a rounded trapezoidal wave shape. In the wavy pattern 12, the end of the transition portion 42 is formed into a rounded trapezoidal wave shape with an arc shape, so that the processing speed is greatly increased without changing the luminance characteristic as in the case of the individual pattern 11. In addition, the viewing angle characteristics are preferable.

  Here, the radius of the arc is 1 μm or more, more preferably 10 μm to 100 μm, from the viewpoint of improving the processing speed and the effect on the viewing angle characteristics.

  In the present invention, as the average value of the extending direction 31 of the light guide plate 1 having at least one pattern height 27 of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 moves away from the light incident surface 4, It is preferable to increase gradually. As the distance from the light incident surface 4 increases, the average height in the thickness direction of the extending direction 31 of the light guide plate 1 gradually increases. The pattern of the entire section between both ends of the pattern including the non-pattern portion 32 in the extending direction 31 That is, the average value of the height 27 increases as the distance from the light incident surface 4 increases.

  As an example of a preferable change in the pattern average height, FIG. 15 shows a case where the rate of increase in the pattern average height gradually increases as the distance from the light incident surface 4 increases. In addition, the form of increase in the pattern average height is not limited to the above, and other forms may be used.

  As the distance from the light incident surface 4 increases, the light propagating through the light guide plate 1 sequentially hits the pattern from the area close to the light source and is emitted from the light output surface 3. Therefore, the intensity of the light increases relative to the distance from the light incident surface 4. To decrease. However, as the distance from the light incident surface 4 increases, the average value of the pattern height 27 is gradually increased so that the light from the light source easily hits the pattern and the probability of being emitted from the light exit surface 3 is increased. This can contribute to uniform luminance distribution on the light exit surface 3.

  In the present invention, the distance between the individual patterns 11 adjacent to each other in the extending direction 31 in the individual patterns 11 gradually decreases as the distance from the light incident surface 4 increases. It is preferable that the space | interval of each piece-like pattern 11 adjacent to the extending direction 31 of the piece-like pattern 11 in the position nearest to is 10 micrometers or less.

  The interval between the individual patterns 11 is the length of the non-pattern part 32 in the extending direction 31 of FIG. FIG. 16 shows an example of a preferable change in the length of the non-pattern portion 32 in the case where the decrement ratio of the non-pattern portion 32 gradually increases as the distance from the light incident surface 4 increases. In addition, the form of the reduction | decrease of the non-pattern part 32 is not necessarily limited to these, Other forms may be sufficient. As the distance from the light incident surface 4 is increased, the length of the non-patterned portion 32 is gradually reduced so that light can be easily extracted. Therefore, even if the light intensity is relatively weak at a portion away from the light incident surface 4, the luminance is uniform. Easy to keep in.

  In addition, by setting the length of the non-pattern part 32 to 10 μm or less, a change in luminance from the light exit surface 3 due to a sudden change in pattern shape at the boundary between the individual pattern 11 and the wave pattern 12 is suppressed. As a result, unevenness in luminance that can be visually recognized does not occur, and as a result, it is possible to achieve uniform luminance at the boundary between the individual pattern 11 and the wave pattern 12.

  In the present invention, the minimum height 45 in the extending direction 31 of the wavy pattern 12 gradually increases as the distance from the light incident surface 4 increases, and the wavy pattern 12 extends at the position closest to the linear pattern 13 in the wavy pattern 12. The difference between the minimum height 45 in the current direction 31 and the maximum height 44 of the linear pattern 13 is preferably 1 μm or less.

  By setting the difference between the minimum height 45 of the wavy pattern 12 and the maximum height 44 of the linear pattern 13 at the boundary between the wavy pattern 12 and the linear pattern 13 to 1 μm or less, the wavy pattern 12 and the linear pattern 13 Since a change in luminance from the light exit surface 3 due to a sudden change in pattern shape at the boundary is suppressed, luminance unevenness that is visually recognized is less likely to occur, and as a result, the luminance distribution from the wave pattern 12 to the linear pattern 13 It is possible to move without significant change.

  In the present invention, the position of the minimum height in the extending direction 31 of the individual pattern 11 and the wavy pattern 12 is arranged in a staggered or random manner along the direction perpendicular to the light incident surface 4. Is preferred. FIG. 17 is a plan view seen from the light reflection surface 2 side of an example in which the positions of the non-pattern portions 32 of the individual pattern 11 are arranged in a staggered manner along the direction perpendicular to the light incident surface 4. FIG. 18 is a plan view as seen from the light reflecting surface 2 side of an example in which the positions of the non-patterned portions 32 of the individual pattern 11 are randomly arranged along the direction perpendicular to the light incident surface 4. FIG. 19 is a plan view seen from the light reflecting surface 2 side of an example in which the positions of the pattern bottom 43 in the extending direction 31 of the wave pattern 12 are arranged in a staggered manner along the direction perpendicular to the light incident surface 4. FIG. 20 is a plan view seen from the light reflecting surface 2 side of an example in which the position of the pattern bottom 43 in the extending direction 31 of the wave pattern 12 is randomly arranged along the direction perpendicular to the light incident surface 4.

  Arranged in a zigzag form means a state in which they are arranged alternately, and arranged in a random form means that the extending direction 31 has regularity but is perpendicular to the light incident surface 4. It means a state of being randomly distributed in any direction.

  Since the positions of the non-pattern part 32 and the pattern bottom part 43 are arranged in a staggered or random manner along the direction perpendicular to the light incident surface 4, the extending direction of the individual pattern 11 and the wave pattern 12 A portion having a low luminance in 31 does not continue in a direction perpendicular to the light incident surface 4, thereby preventing the appearance of bright lines and contributing to uniform luminance distribution. The individual pattern 11 and the wavy pattern 12 may be a mixed arrangement of a staggered arrangement and a random arrangement.

  In the present invention, in the individual pattern 11, the wavy pattern 12, and the linear pattern 13, the inter-pattern distance 34 in the direction perpendicular to the light incident surface 4 is gradually decreased as the distance from the light incident surface 4 increases. It is preferable that the slope of the change in the inter-distance 34 substantially matches between adjacent patterns at the switching position of each pattern. The switching position is a boundary portion between the individual pattern 11 and the wavy pattern 12 and between the wavy pattern 12 and the linear pattern 13. As an example of a preferable change in the inter-pattern distance 34, FIG. 21 shows a case where the decrement rate of the inter-pattern distance 34 gradually increases as the distance from the light incident surface 4 increases. In addition, the form of reduction is not necessarily limited to these, and other forms of reduction may be used.

  By gradually decreasing the inter-pattern distance 34 from the light incident surface 4 to facilitate the optical path conversion to the light exit surface 3, it becomes easy to maintain high luminance in the entire light guide plate 1. Further, the appearance of the bright line at the switching position can be visually recognized by matching the change positions of the inter-pattern distance 34 at the switching position between the individual pattern 11 and the wavy pattern 12 and the switching position between the wavy pattern 12 and the linear pattern 13. This makes it difficult to maintain brightness uniformity.

  According to the backlight unit of the present invention, since the light guide plate 1 of the present invention is incorporated, the luminance is made uniform from the light exit surface 3 and the appearance of the bright line hardly occurs. A cross-sectional view of an example of a backlight unit having the light guide plate 1 of the present invention is shown in FIG. In the backlight unit 71, the light 78 that exits from the light source 73, enters the light guide plate 1 from the light incident surface 4, and is guided inside the light guide plate 1 includes the individual pattern 11, the wave pattern 12, and the linear pattern. The light path is changed by 13 and emitted as planar light from the light exit surface 3 side. The light 78 emitted from the light exit surface 3 side passes through the diffusion sheet 75, the prism sheet 76, and the reflective polarizing film 77, so that the brightness is increased and the brightness distribution is further uniformed. The structure of the backlight unit 71 is not limited to this.

  Moreover, according to the display device having the backlight unit 71 of the present invention, since the light guide plate 1 of the present invention is provided, the luminance is uniformized on the display surface and the bright line appearance does not occur. FIG. 23 shows a cross-sectional view of a liquid crystal display device as an example of a display device having a backlight unit. The light 78 emitted from the light exit surface 3 passes through the liquid crystal panel 82 after exiting the backlight unit. The liquid crystal panel 82 is configured by, for example, sealing a liquid crystal material between the array substrate 85 and the counter substrate 86 and then bonding a polarizing plate 83 and a polarizing plate 84 to the outer surfaces of the array substrate 85 and the counter substrate 86, respectively. Is done. The array substrate 85 is provided with pixel electrodes and switching elements corresponding to display pixels, and signal lines for supplying signals to the pixel electrodes and the switching elements. On the other hand, the counter substrate 86 is formed with a counter electrode of a transparent electrode material, and a color filter layer is formed so as to correspond to each pixel. In the liquid crystal panel 82, the switching element is driven based on a drive signal from an external circuit board (not shown), so that a pixel through which the light 78 emitted from the light exit surface 3 passes is selected and displayed as an image. The structure of the liquid crystal panel 82 is not limited to this.

  Examples of the use of the device equipped with the display device 81 include a mobile phone, a car navigation system, a mobile terminal, a personal computer, a computer monitor, a television receiver, an advertising billboard, and the like, but are not limited thereto. Further, the display device is not limited to the liquid crystal panel 82 and may be other types.

  In addition, although the example using the point light source 6 was shown in FIG. 1 as the light source 73, the light source does not need to be the point light source 6, for example, the line arrange | positioned in parallel with the light-incident surface 2 like a cold cathode tube etc. It may be a light source. In the case of a linear light source, if necessary, the arrangement of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 is appropriately changed to make the luminance uniform and the light source 73 as in the case of the point light source 6. The effect of preventing the appearance of bright lines can be obtained.

  Although various materials can be used as the material of the light guide plate 1 according to the present invention, particularly excellent light guide performance, optical path conversion performance on the light reflection surface 2, and excellent luminance characteristics on the light output surface 3 are obtained. Therefore, it is preferably formed from a resin mainly composed of polymethyl methacrylate, which is a kind of acrylic resin, or polycarbonate. The resin is not limited to these, and may be other thermoplastic resins or thermosetting resins. The individual patterns 11 of the light guide plate such as an injection molding method, an extrusion molding method, and a thermal imprint method described later. Even in the case where the formation of the wavy pattern 12 and the linear pattern 13 is accompanied by a heating step, a resin suitable for the molding method of each light guide plate 1 may be freely selected. In addition, it is preferable that the resin used for improving the light transmission property in the light guide plate 1 has high transparency.

  Examples of the material of the light guide plate other than polymethyl methacrylate or polycarbonate include thermoplastic resins such as polyester resin, polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, and cyclohexanedimethanol. Examples thereof include a polymerized polyester resin, an isophthalic acid copolymerized polyester resin, a spiroglycol copolymerized polyester resin, and a fluorene copolymerized polyester resin. Examples of the olefin-based resin include alicyclic olefin copolymer resins, and examples of other resins include polycarbonate, polystyrene, polyamide, polyether, polyesteramide, polyetherester, and polyvinyl chloride. Furthermore, a copolymer containing these components and a mixture of these resins can also be used. Examples of the thermosetting resin include acrylic resin, epoxy resin, unsaturated polyester resin, phenol resin, urea / melamine resin, polyurethane resin, silicone resin, and the like. Mixtures of the above can also be used.

  Further, when the light guide plate 1 is formed by directly forming the individual pattern 11, the wave pattern 12, and the linear pattern 13 on the light guide plate base material, glass may be used as the material of the light guide plate 1. . However, in that case, a highly transparent glass is preferable.

  The base material for a light guide plate applied to the present invention may be a sheet made of the above-mentioned resin or glass alone, or may be a laminate made of a plurality of resin layers. In this case, surface characteristics such as slipperiness and friction resistance, mechanical strength, and heat resistance can be imparted as compared with a single sheet. Thus, when it is a laminate composed of a plurality of resin layers, it is preferable that the entire sheet satisfies the above-mentioned requirements, but even if the entire sheet does not satisfy the above-mentioned requirements, a layer that satisfies at least the above-mentioned requirements is a surface layer. If it is formed, the surface can be easily formed.

  Next, a method for manufacturing the light guide plate 1 will be described. As a manufacturing method, direct processing using a cutting tool such as a cutting tool is performed on the base material for the light guide plate, and an in-process using a mold in which fine concavo-convex shapes corresponding to the individual pattern 11, the wavy pattern 12, and the linear pattern 13 are processed. Examples thereof include a printing method, an injection molding method, and an extrusion molding method.

  First, a direct cutting method of a base material for a light guide plate having a concave pattern, and a mold having a concave cross-sectional shape for manufacturing a light guide plate using an imprint method, an injection molding method, and an extrusion method A method will be described.

  First, using a processing tool having the same shape as the concave shape of the desired cross section on the shaping surface side of the base material for the light guide plate or the mold material, cutting with an ultra-precision processing machine capable of three-dimensional processing Thus, a concave cross section can be imparted to the shaping surface. Various types of ultra-precision processing machines are known, such as a planar (shaper) method, a fly-cut method, an end mill method, and a lathe processing method. In the present invention, the processing tool or the base material for light guide plate or the mold material is straightened along the shaping surface side of the above-mentioned base material for light guide plate or the mold material described later, which is the highest accuracy among them. Planer (Shaper) method that shapes the cross-sectional concave shape by moving the tool, and rotationally drives the processing bite, and moves the bite or the base material for the light guide plate or the mold material in the direction perpendicular to the rotation axis direction. A fly-cut method for shaping the shape is suitable. In the planar (shaper) method, the cutting tool is moved straight along the light guide plate base material or the mold material to form a concave cross-sectional shape, so that continuous and efficient processing is possible. Further, in the fly-cut method, since it is possible to process with relatively few burrs and burrs, it is preferable to use both according to the purpose.

  Examples of the material of the machining tool include carbon tool steel, cemented carbide, ceramics, diamond, cubic boron nitride, etc., but it has a highly accurate cross-sectional concave shape of nanometer level due to its crystal hardness and high thermal conductivity. More preferred are diamonds obtained over distance. In addition, it is more preferable to use single crystal diamond because the surface roughness of the cutting surface can be processed to be extremely small and desired optical characteristics can be easily obtained by using single crystal diamond. Is used.

  As the base material for the light guide plate in the case of cutting directly on the base material for the light guide plate, any material may be used as long as the cutting tool has good machinability and the deformation due to heat generated during the processing is small. Although thermosetting resin etc. are mentioned, it is not restricted to this, For example, substances with high transparency, such as glass, may be sufficient.

  In addition to the desired pattern processing accuracy and releasability of the light guide plate after shape transfer, the mold material may have the strength at the time of light guide plate molding, as long as it is an imprint method, injection molding method, or extrusion method. In addition, as long as it is a photoimprinting method, any material can be used as long as ultraviolet photosensitivity can be obtained. For example, a metal material containing stainless steel, nickel, copper, etc., silicone, glass, ceramics, resin, or a mold release on these surfaces Those coated with an organic film for improving the properties are preferably used. The concave shape of the fine cross section of the mold is formed corresponding to the pattern shape to be applied to the surface of the light guide plate 1 to which the shape is transferred.

  Next, using a bite, it corresponds to the individual concavo-convex pattern 11, the corrugated pattern 12, the linear pattern 13 or the fine concavo-convex shape corresponding to the individual pattern 11, the fine concavo-convex shape corresponding to the corrugated pattern 12, A method of manufacturing the fine uneven shape to be performed will be described.

  First, as a method of manufacturing the individual pattern 11 or the fine uneven shape corresponding to the individual pattern 11, the light reflecting surface 2 or the processing surface corresponding to the light reflecting surface 2 is parallel to the extending direction 31. While moving the cutting tool blade in the direction, move the cutting tool in the direction perpendicular to the processing surface, descending from the processing surface to the processing surface, stopping, rising from the processing surface to the processing surface, and then stopping. It is obtained by processing.

  As a manufacturing method of the corrugated pattern 12 or the fine concavo-convex shape corresponding to the corrugated pattern 12, the processing tool blade is moved in the extending direction 31, and the light reflecting surface 2 or the processing surface corresponding to the light reflecting surface 2 is perpendicular. The tool is obtained by moving the cutting tool in the order of descending, stopping, raising, and stopping in the machining surface.

  As a method for manufacturing the linear pattern 13 or the fine uneven shape corresponding to the linear pattern 13, the processing tool blade is processed with a constant depth with respect to the light reflecting surface 2 or the processing surface corresponding to the light reflecting surface 2. Can be formed. In addition, since there is no ascending or descending operation, it is possible to perform high-speed processing as compared with the production of the individual pattern 11 or the wavy pattern 12 or the fine concavo-convex shape corresponding to the individual pattern 11 or the wavy pattern 12. Shortening can be achieved.

  By adjusting the moving speed in the horizontal direction and the moving speed in the height direction during the ascent and descent operations of the machining tool blade with respect to the machining surface, a rounded trapezoidal wave shape can be obtained at the change position in the height direction.

  By using such a processing method and using the linear pattern 11 that can be processed at a high speed for the pattern of the light guide plate 1, the processing time of the light guide plate 1 or the mold can be shortened, resulting in a reduction in processing cost. It becomes possible.

  Next, a method for manufacturing the light guide plate 1 using the light guide plate forming mold described above will be described.

  First, a method for manufacturing the light guide plate 1 by the imprint method will be described. The light guide plate 1 formed by imprinting, for example, imparts the above-described uneven shape to the surface of a known thermoplastic resin film, sheet-like material, plate-like material (hereinafter referred to as a base substrate) or the like. can get. Here, the method for imparting the uneven shape as described above is not particularly limited, and examples thereof include a thermal imprint method and an optical imprint method.

  The thermal imprint method is to heat a mold having a fine concave cross section and a resin, press the mold against the resin, cool, and release the mold so that the cross section concave shape applied to the mold surface is transformed into the resin. This is a technique for transferring. The light guide plate 1 of the present invention can be manufactured using an apparatus as shown in FIGS. 24 and 25, for example. 24 and 25 show a light guide plate base material, with individual patterns 11, wavy patterns 12, and linear patterns 13 formed on one side to form a light reflecting surface 2, and if necessary, a fine pattern on the light emitting surface 3. An example of an apparatus for forming a structural pattern is shown. Although FIG. 25 shows a film that can be conveyed by roll-to-roll, it can also be applied to a sheet-like sheet by changing the conveyance unit. In addition, the base material for light-guide plates may be a single layer, and may be laminated | stacked.

  In the example shown in FIG. 24, for a light guide plate that is intermittently sent, a heated mold 104 having fine irregularities corresponding to the individual patterns 11, wavy patterns 12, and linear patterns 13 formed on the surface is heated. A press unit 105 for a pressure transfer process that presses against the base material 102 and thermoforms a predetermined fine structure pattern on the surface of the light guide plate base material 102 by pressurization is provided. One surface of the light guide plate base material 102 that has been intermittently sent by a conveying device (not shown) is thermoformed by the die 104 in the press unit 105 and is attached to the die 104 after the thermoforming. The light guide plate 1 having the individual pattern 11, the wave pattern 12, and the linear pattern 13 shape on the light reflecting surface 2 is obtained by releasing the mold 102. In the mold 104, the extending direction 31 of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 is not particularly limited. Further, a fine uneven shape corresponding to the shape of the individual pattern 11, the wave pattern 12, and the line pattern 13 of the light reflecting surface 2 of the present invention may be formed on the outer surface of the pressure plate 109.

  In the example illustrated in FIG. 25, the light guide plate base material 122 is pulled out from the light guide plate base material take-up roll 121, and the individual pattern 11, the wave pattern 12, and the linear pattern are formed on one surface of the light guide plate base material 122. 13 is continuously thermoformed. The light guide plate base material 122 is supplied onto a heated endless belt-shaped mold 124 by a heating roll 123. On the outer surface of the mold 124, fine concavo-convex shapes corresponding to the individual pattern 11, the wave pattern 12, and the linear pattern 13 are formed. The endless belt-shaped mold 124 and the light guide plate base material 122 laminated thereon are pressed against the mold surface 124 a on which the fine structure of the endless belt-shaped mold 124 is processed by the nip roll 125, and are used for the light guide plate. A fine structure pattern corresponding to the surface shape of the endless belt-shaped mold 124 is transferred onto one surface of the substrate 122. Thereafter, the light guide plate base material 122 is conveyed to the outer surface position of the cooling roll 126 while being in close contact with the surface of the endless belt-shaped mold 124. The light guide plate base material 122 is cooled by heat conduction through the endless belt-shaped mold 124 by the cooling roll 126, and then peeled from the endless belt-shaped mold 124 by the peeling roll 127 to become the light guide plate 128. . Thereafter, the light guide plate 128 is wound as a light guide plate winding roll 129. By such a process, the light guide plate 1 having the individual pattern 11, the wave pattern 12, and the linear pattern 13 can be continuously manufactured with high productivity.

  The direction of the fine concavo-convex shape corresponding to the extending direction 31 of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 formed on the outer surface of the endless belt-shaped mold 124 or nip roll 125 is not particularly limited.

  The light guide plate 1 of the present invention can also be manufactured by an injection molding method using an injection molding machine. A cross-sectional view of a process diagram showing an example of a method for manufacturing the light guide plate 1 using an injection molding machine will be described with reference to FIGS.

  First, as shown in FIG. 26A, light guide plate resin particles 131 as a material of the light guide plate 1 are supplied from a hopper 133 of an injection molding machine 132, heated and melted and mixed inside, and sequentially supplied to the vicinity of the nozzle 135. To do. When mixing a plurality of resin raw material particles as the light guide plate resin particles 131, they are uniformly mixed in this step. Next, as shown in FIGS. 26 (b) and 26 (c), the plasticized and melted molding material 134 stored in the vicinity of the nozzle 135 is passed through the nozzle 135 through the individual pattern 11, the wavy pattern 12, and the linear shape. A mold 136 that has been processed to have a fine concavo-convex shape corresponding to the pattern 13 is filled. The plasticized and melted molding material 134 filled in the mold 136 is held in the mold 136 for a certain time, and is cooled and solidified. After cooling in the mold 136 for a certain time in this way, the mold 136 is opened as shown in FIG. 26D, and the light guide plate 137 which is a molded product is taken out to complete one cycle of the molding process. In this state, since unnecessary portions such as a runner 138 are also formed on the light guide plate 137, the light guide plate 1 is cut later, and the cut portion is polished or the like as necessary to form the light guide plate 1.

  The injection molding conditions such as the resin melting temperature, the injection temperature, the pressure at the stage of injecting the molding material into the mold 136, and the pressure at the stage after the mold has been filled, are as follows: What is necessary is just to set suitably according to a mold size etc., and it does not specifically limit.

  The light guide plate 1 of the present invention can also be manufactured using an extrusion molding method in which a resin of a base material for a light guide plate is extruded from a die in a heated and melted state to produce an extruded resin plate. A schematic sectional view showing an example of the extrusion molding method will be described with reference to FIG. The present invention is not limited to these.

  First, the light guide plate resin particles 141 are introduced from the hopper 143 of the extruder 142. The resin particles 141 for the light guide plate are heated and melted in the extruder 142, and are fed to the die 144 while being kneaded. The light guide plate resin particles 141 pumped from the extruder 142 are spread and extruded into a plate shape by the die 144 while being heated and melted. The light guide plate base material 148 extruded from the die 144 is sandwiched between the first roll 145 and the second roll 146. Here, a pattern roll in which fine irregularities corresponding to the individual pattern 11, the wavy pattern 12, and the linear pattern 13 are formed on one surface of the first roll 145 or the second roll 146 is used.

  The base material 148 for the light guide plate sandwiched between the first roll 145 and the second roll 146 becomes the light guide plate 149 having the individual pattern 11, the wave pattern 12, and the linear pattern 13 of the present invention on the surface, After that, the light guide plate 149 is usually wound around the third roll 147 or a plurality of cooling rolls, and the temperature of the light guide plate 149 gradually decreases and solidifies. If it cut | disconnects by required length after solidification, it will become the light-guide plate 1. FIG.

  Further, in the roll having the pattern, the extending direction 31 of the individual pattern 11, the wavy pattern 12, and the linear pattern 13 may be any of the circumferential direction of the roll and the central axis direction of rotation.

  In addition, what is necessary is just to set suitably according to resin to be used about the melting temperature of resin at the time of manufacturing the light-guide plate 1 of this invention, extrusion temperature, extrusion pressure, etc., It does not specifically limit.

  In this extrusion molding method, the light guide plate 1 can also be manufactured from a base material for a light guide plate having a laminated structure composed of a plurality of resin layers by a coextrusion process.

  In FIG. 27, the mold having fine irregularities corresponding to the individual pattern 11, the wavy pattern 12, and the linear pattern 13 is a roll shape. For example, the light guide plate base material 148 extruded from the die 144 is a belt. The pattern may be thermoformed on one or both sides by pressing with a metal mold.

  Although the manufacturing method described above is extremely excellent from the viewpoint of productivity, it can be manufactured by the optical imprint method as another manufacturing method of the light guide plate 1 of the present invention. A schematic sectional view of the optical imprint method will be described with reference to FIG.

  First, the photocurable resin 154 is applied from the die 153 onto one surface of the light guide plate substrate 152 drawn from the light guide plate substrate take-up roll 151. Then, while pressing the roll metal mold | die 155 which has the fine uneven | corrugated shape corresponding to the piece-shaped pattern 11, the wavy pattern 12, and the linear pattern 13 against a photocurable resin part, the direction opposite to the surface which pressed the roll metal mold | die 155 is carried out. Then, the ultraviolet light 157 emitted from the ultraviolet light generator 156 is irradiated to cure the photocurable resin 154. Thereafter, the roll mold 155 is released to form the light guide plate 158 having the individual patterns 11, the wavy patterns 12, and the linear patterns 13 on the surface. The light guide plate 158 is wound as a light guide plate winding roll 159. In addition, in FIG. 28, although the metal mold | die was roll shape, it may be flat form, for example. In addition, the direction of irradiating the ultraviolet light does not need to be opposite to the surface on which the roll mold 155 is pressed when the material of the mold is transparent such as glass.

  Examples of the photocurable resin 154 include a compound having at least one radical polymerizable property in the molecule or a compound having a cationic polymerizable property. The compound having radical polymerizability is a compound that undergoes a polymer or a crosslinking reaction by irradiation with active energy rays in the presence of a polymerization initiator that generates radicals by active energy rays. For example, the structural unit includes at least one ethylenically unsaturated bond, and includes other functional vinyl monomers in addition to a monofunctional vinyl monomer. Moreover, these oligomers, polymers, and mixtures may be used. Examples of the compound having at least one cationic polymerizability in the molecule include one or more compounds selected from a compound having an oxirane ring, a compound having an oxetane ring, and a vinyl ether compound.

  The light guide plate 1 having a convex pattern can also be manufactured using a mold obtained by processing a concave pattern. On the other hand, after manufacturing a mold having a concave pattern, an electroforming process is performed to manufacture a mold having a convex pattern, and the light guide plate 1 having the concave pattern is formed using this mold by, for example, an imprint method. Can be molded.

  When the light guide plate 1 is formed by the imprint method, the injection molding method, or the extrusion method, the lenticular or prism arranged in a stripe shape in the light exit surface 3 in a direction perpendicular to the light entrance surface 4. The pattern may be formed. By forming these patterns on the light exit surface 3, the appearance of bright lines is suppressed, and steep viewing angle characteristics are also eased.

  The embodiments according to the present invention have been described above with specific examples. However, the present invention is not limited to these specific examples.

After producing a light guide plate and disassembling a 32-inch liquid crystal television (UN32D6350RF manufactured by Samsung Electronics Co., Ltd.) as an optical evaluation, the light guide plate was incorporated into the backlight unit taken out and allowed to light for 30 minutes. Out of the brightness on the front surface of the light exit surface, the brightness is 10 mm apart in the direction perpendicular to the light entrance surface and away from the light entrance surface, starting from the piece-like pattern closest to the light entrance surface in the central portion of the light guide plate in the extending direction. cd / m ² ) was measured. For the measurement, a two-dimensional luminance meter CA-2000 (manufactured by Konica Minolta Sensing Co., Ltd.) was used.

Example 1
A light guide plate in which individual patterns, wavy patterns, and linear patterns have a concave V-shape with respect to the light reflecting surface is applied to an ultra-precision processing machine capable of three-dimensional processing with a tip angle of 80 °. The diamond method is applied, and the planar method is applied so that the processing direction of the individual patterns, wavy patterns, and linear patterns is extended on one side of a polymethyl methacrylate resin (PMMA) base material. It was manufactured by cutting.

  The dimensions of the prepared PMMA substrate were 3 mm thick, 405 mm long, and 710 mm wide so that it could be applied to a backlight unit used in optical evaluation. The extending direction is the horizontal direction.

  Regarding the design of pattern shape, the pattern widths of the individual pattern, wavy pattern, and linear pattern are all 8 μm, and the design values of the pattern slope angle of the individual pattern, wavy pattern are both on the light incident surface side and the light incident surface side. 50 ° and the pattern transition angle were 9 °. Also, the individual pattern located closest to the light incident surface is arranged at a distance of 5 mm from the light incident surface in the direction perpendicular to the light incident surface, and the individual pattern located closest to the light incident surface is the most similar to the individual pattern. The distance of the linear pattern at a position close to the anti-light-incident surface was 395 mm. Furthermore, the individual pattern and the wavy pattern are arranged in a pattern that periodically changes at a pitch of 0.2 mm in the extending direction, and are arranged in a staggered pattern for both patterns that are adjacent in the direction perpendicular to the light incident surface. .

The pattern occupancy rate is changed so as to gradually increase as the distance from the light incident surface increases, and the distance in the direction perpendicular to the light incident surface and away from the light incident surface is set to dmm starting from the individual pattern closest to the light incident surface. When the pattern occupancy at the distance dmm is defined as y, the value of the pattern occupancy at intervals of 5 mm from the individual pattern closest to the light incident surface is y = 8.4 × 10 ⁻²⁴ × d ⁸ +7 It was designed to satisfy 9.9 × 10 ⁻¹⁸ × d ⁶ + 2.7 × 10 ⁻¹² × d ⁴ + 3.8 × 10 ⁻⁷ × d ² +0.02. In order to satisfy this occupancy rate, the distance between patterns is vertical to the light incident surface, starting from the individual pattern where the distance between the individual patterns, wavy patterns, and linear patterns is closest to the light incident surface. The shape is such that the average height in the extending direction gradually increases as the distance from the light incident surface increases in the individual pattern and the wave pattern in the direction away from the light incident surface. Regarding the inter-pattern distance, the inclination of the change in the inter-pattern distance is substantially matched at the switching position between the individual pattern and the wavy pattern and at the switching position between the wavy pattern and the linear pattern. FIG. 30 shows changes in the distance perpendicular to the light incident surface and away from the light incident surface, the distance between the patterns, and the pattern occupancy rate, starting from the individual pattern that is closest to the light incident surface. By design, the boundary between the individual pattern and the wave pattern is 195.1 mm in the direction perpendicular to the incident surface and away from the incident surface, starting from the individual pattern closest to the incident surface. Among the patterns, the interval between the individual patterns adjacent to each other in the extending direction of the individual patterns at the position closest to the wave pattern is less than 0.1 μm. The boundary between the wavy pattern and the linear pattern is 250.0 mm in the direction perpendicular to the light incident surface and away from the light incident surface, starting from the individual pattern closest to the light incident surface. Among these, the difference between the minimum height in the extending direction of the wavy pattern at the position closest to the linear pattern and the maximum height of the linear pattern is less than 0.1 μm.

  The surface of the manufactured light guide plate is 1,000 times with a digital microscope (VHX-500, manufactured by Keyence Corporation), and 10 arbitrary points are taken out for each of the individual pattern, wavy pattern, and linear pattern. When the pattern width was measured, all the patterns were in the range of 7.9 to 8.1 μm. Further, among the individual patterns, when 10 points were taken and measured for the interval between the individual patterns adjacent to each other in the extending direction of the individual patterns at the position closest to the wave pattern, all 0.1 μm were measured. Was less than. As a result of measuring the distance between the patterns at intervals of 20 mm in the direction perpendicular to the light incident surface and away from the light incident surface, starting from the individual piece pattern closest to the light incident surface, the distance between patterns is ± 2 μm with respect to the design value. Was in the range.

  Subsequently, an inverted shape was collected using an impression material (Exafine Regular Type, manufactured by GC Corporation) at a part of each of the individual pattern, wavy pattern, and linear pattern on the surface of the light guide plate, and scanning electron The cross-sectional shape in the extending direction of each pattern was observed with a microscope (VE-7800 manufactured by Keyence Corporation) at a magnification of 2,000. First, for each of the individual pattern, wavy pattern, and linear pattern, 10 arbitrary points were taken out and the pattern width was measured. As a result, all patterns were in the range of 7.9 to 8.1 μm. Next, among the wavy patterns, the minimum height in the extending direction of the wavy pattern at the position closest to the linear pattern was measured by extracting 10 arbitrary points and found to be in the range of 4.6 to 4.8 μm. . Furthermore, when the shape of arbitrary 10 points was measured with respect to the transition part boundary shape of the individual piece pattern and the wavy pattern, all of them were arc shapes having a radius of 0.5 μm or less.

Then, as a result of measuring a brightness | luminance, it was 7,209-10,185 cd / m < ² >. The change in luminance is shown in FIG. Further, the liquid crystal panel was placed on the top and visually confirmed, but no luminance unevenness occurred.

(Example 2)
A light guide plate having the same pattern arrangement on a PMMA base material having the same dimensions as in Example 1 except that the transition part boundary between the piece-like pattern and the wave-like pattern is processed so as to have an arcuate rounded trapezoidal wave shape. Was made. By using the rounded trapezoidal wave shape, the processing speed of the individual pattern and the wave pattern could be increased, so that the processing time could be reduced by 5% compared to Example 1.

  When the manufactured light guide plate was measured in the same manner as in Example 1, the results were almost the same as in Example 1 except for a piece-like pattern and a rounded-trapezoidal wave-shaped portion at the boundary of the wavy pattern. As for the rounded trapezoidal wave shape at the transition part boundary of the individual piece pattern and the wavy pattern, as in Example 1, any 10 inverted shapes collected using an impression material (Exafine regular type manufactured by GC Corporation) When the points were measured, it was an arc shape with a radius of 9.8 to 10.2 μm.

Subsequently, as a result of measuring the luminance, it was 7,251 to 10,197 cd / m ² . The change in luminance is shown in FIG. Further, the liquid crystal panel was placed on the top and visually confirmed, but no luminance unevenness occurred.

(Example 3)
The light guide plate design, manufacturing method, and evaluation method are the same as those in Example 2, except that the arrangement of the individual pattern and the wave pattern is randomly arranged.

  The random arrangement of each individual pattern and wavy pattern is based on the staggered arrangement of the second embodiment, and the individual patterns and the wavy pattern are extended using random values generated using a random function. Were randomly moved in the range of ± 50 μm. About the manufactured light-guide plate, as a result of evaluating the shape of an individual piece pattern, a wavy pattern, and a linear pattern by the method similar to Example 2, it became the same result as Example 2. FIG. In addition, the surface is obtained by using a digital microscope (VHX-500, manufactured by Keyence Corporation) at intervals of 10 mm in the direction perpendicular to the light incident surface and away from the light incident surface, starting from the individual piece pattern closest to the light incident surface. When the shape was observed, the positional deviation in the extending direction of the individual patterns and the wavy patterns at the same distance from the light incident surface as in Example 2 was within ± 50 μm.

Subsequently, the luminance was measured and found to be 7,148 to 10,174 cd / m ² . The change in luminance is shown in FIG. Further, the liquid crystal panel was placed on the top and visually confirmed, but no luminance unevenness occurred.

(Comparative Example 1)
Of the pattern arrangement of Example 1, a pattern in which all the patterns of the wavy pattern were changed to a linear pattern having a pattern width of 8 μm was manufactured. Of the changes in the pattern occupancy ratios of Example 1 and Comparative Example 1, comparison in the wavy pattern region in Example 1 is shown in FIG.

  With respect to the processed light guide plate, the shape of the individual pattern and the linear pattern was measured in the same manner as in Example 1. As a result, both were the same as those in Example 1.

Then, as a result of measuring a brightness | luminance, it was 6,275-10,201cd / m < ² >. The change in luminance is shown in FIG. As a result of visual confirmation, the luminance, which had a tendency to decrease with increasing distance from the light incident surface, suddenly increased in the vicinity of the boundary between the piece-like pattern and the linear pattern, so that luminance unevenness was visually recognized. Moreover, since the luminance value was lower than that of Example 1 on the side close to the non-light-incident surface and the luminance was significantly reduced, luminance unevenness was visually recognized. Furthermore, when the liquid crystal panel was mounted from above and visually confirmed, luminance unevenness was visually recognized in the vicinity of the boundary between the individual pattern and the linear pattern and on the side close to the light-incident surface.

  The light guide plate of the present invention as described above is useful because it can be suitably used for the light output surface of a backlight unit (particularly a point light source) and can exhibit good performance particularly in a direct type backlight unit.

DESCRIPTION OF SYMBOLS 1 Light-guide plate 2 Light reflection surface 3 Light-emitting surface 4 Light-incidence surface 5 Anti-light-incidence surface 6 Point light source 7 Piece-shaped pattern area | region 8 Wave-like pattern area | region 9 Line-shaped pattern area | region 11 Piece-like pattern 12 Wave-like pattern 13 Line-like pattern 21 Pentagonal pattern 22 V-shaped pattern 23 Elliptical pattern 27 Pattern height 28 Pattern width 29 Pattern slope angle 31 Extension direction 32 Non-pattern part 34 Inter-pattern distance 41 Pattern top part 42 Transition part 43 Pattern low part 44 Maximum height 45 Minimum height 46 Transition portion boundary 47 Pattern transition angle 51 Pattern bright line appearance occurrence region 52 Pattern bright line appearance non-occurrence region 62 Pattern occupancy gradually increasing 64 Pattern average height gradually increasing 66 Non-pattern portion length gradually decreasing 68 Inter-pattern distance Gradual decrease 71 Backlight unit 72 Case 73 Light source 74 Reflective sheet 75 Diffuse G 76 Prism sheet 77 Reflective polarizing film 78 Light 81 Display device 82 Liquid crystal panel 83 Polarizing plate 84 Polarizing plate 85 Array substrate 86 Counter substrate 102 Light guide plate base material 104 Die 105 Press unit 109 Pressure plate 121 Light guide plate base material Winding roll 122 Light guide plate base material 123 Heating roll 124 Endless belt mold 124a Mold surface 125 on which fine structure is processed Nip roll 126 Cooling roll 127 Peeling roll 128 Thermoformed light guide plate 129 Light guide plate winding Roll 131 Light guide plate resin particles 132 Injection molding machine 133 Hopper 134 Plasticized and melted molding material 135 Nozzle 136 Mold 137 Light guide plate 138 produced by injection molding 141 Light guide plate resin particles 142 Extruder 143 Hopper 144 Die 145 First roll 146 Second 147 Third roll 148 Light guide plate base material 149 Light guide plate 151 manufactured by extrusion molding Light guide plate base material roll 152 Light guide plate base material 153 Die 154 Photocurable resin 155 Roll mold 156 Ultraviolet Light generator 157 Ultraviolet light 158 Light guide plate 159 Light guide plate winding roll 201 Backlight unit 202 Light guide plate 203 Light source 204 Reflective sheet 205 Diffusion sheet 206 Prism sheet 207 Reflective polarizing film 208 Fine structure pattern 209 Light

Claims (10)

In the light guide plate that emits the light entering from the light incident surface that is the side end surface to the outside from the light exit surface,
On the light reflecting surface facing the light exit surface of the light guide plate, the following (a) to (c) are provided as structures for reflecting the light propagating inside the light guide plate toward the light exit surface side of the light guide plate. ) Pattern is formed,
In order from the side closer to the light incident surface of the light guide plate, the patterns are arranged in the order of individual patterns, wavy patterns, and linear patterns, and further in the order of individual pattern areas, wavy pattern areas, and linear pattern areas. A light guide plate that is arranged so that a pattern occupancy gradually increases.
(A) A linear pattern having one extending direction and having a height in the thickness direction of the light guide plate that is substantially constant over the entire length in the extending direction.
(B) have the same extending direction as the linear pattern, a bout that is not spaced by extending direction, continuously varying height in the thickness direction of the light guide plate along the extending direction have a portion, and undulating pattern minimum height in the extending direction gradually increases as the distance from the light incident surface.
(C) A group of a plurality of independent patterns arranged at a predetermined interval from each other, each having a piece-like pattern having the same extending direction as the wavy pattern.   2. The light guide plate according to claim 1, wherein in the piece-like pattern, a cross-sectional shape along the extending direction of the pattern and perpendicular to the light reflecting surface is a rounded trapezoidal wave shape.   3. The light guide plate according to claim 1, wherein, in the wavy pattern, a cross-sectional shape along the extending direction of the pattern and perpendicular to the light reflecting surface is a rounded trapezoidal wave shape.   The average height in the extending direction of the light guide plate of at least one pattern selected from the group consisting of the individual pattern, the wavy pattern, and the linear pattern gradually increases as the distance from the light incident surface increases. The light guide plate according to claim 1. The distance between the individual patterns adjacent to each other in the extending direction in the individual patterns gradually decreases as the distance from the light incident surface increases.
The interval between the individual patterns adjacent to each other in the extending direction of the individual patterns at a position closest to the wave pattern among the individual patterns is 10 μm or less. The light guide plate according to any one of 4. Among previous SL wavy pattern, claim 1 in which the difference between the maximum height of the minimum height and the linear pattern in the extending direction of the wave pattern in a position closest to said linear pattern is characterized in that at 1μm or less The light guide plate according to any one of 5.   The position of the minimum height in the extending direction of the piece-like pattern and the wavy pattern is arranged in a staggered manner or a random manner along a direction perpendicular to the light incident surface. The light guide plate according to any one of 6. In the individual pattern, wavy pattern, linear pattern, the inter-pattern distance in the direction perpendicular to the light incident surface is gradually decreased as the distance from the light incident surface increases.
The light guide plate according to any one of claims 1 to 7, wherein inclinations of changes in distance between patterns substantially coincide with each other at a switching position of each pattern.   A backlight unit comprising the light guide plate according to claim 1. A display device comprising the backlight unit according to claim 9.