JP2017224558A - Light guide film, edge light type backlight unit, and light guide film manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide film capable of increasing light utilization efficiency in spite of its thin average thickness.SOLUTION: A light guide film including synthetic resin as a main component and having average thickness of 100-600 μm is a light guide film for an edge light type backlight unit which causes a light ray emitted from an LED to be incident from at least one end surface, and emits it to an upper surface side. The end edge part on the end surface side is formed in a trumpet shape in which the thickness of the end edge part on the end surface side gradually increases toward the end surface side, and includes a concave streak groove on the end surface along a longitudinal direction. It is preferable that the upper surface of the end edge part is an inclined surface which forms an elevation angle toward the end surface side, and the lower surface is a plane flush with the other regions. It is preferable that the cross section of the concave streak groove is formed in a V-shape. It is preferable that the base angle of the V-shaped cross section of the concave streak groove is an acute angle.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a light guide film, an edge light type backlight unit, and a method for producing a light guide film.

  In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back side is widely used, and a backlight unit such as an edge light type or a direct type is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 13, the edge light type backlight unit 101 generally includes a reflection sheet 105 disposed on the top surface of the top plate 106 and a light guide plate 102 disposed on the top surface of the reflection sheet 105. And an optical sheet 104 disposed on the upper surface of the light guide plate 102 and a light source 103 that emits light toward an end surface of the light guide plate 102. In the edge light type backlight unit 101 of FIG. 13, for example, a plurality of LEDs are used as the light source 103, and the light emitted from the light source 103 and incident on the light guide plate 102 passes through the light guide plate 102. Propagate. A part of this propagating light is emitted from the lower surface of the light guide plate 102, reflected by the reflection sheet 105, and incident on the light guide plate 102 again.

  Such a liquid crystal display device is required to be thin and light in order to improve its portability and convenience, and accordingly, the liquid crystal display unit is also required to be thin. In particular, in an ultra-thin portable terminal in which the thickest part of the casing is 21 mm or less, the thickness of the liquid crystal display part is desired to be about 4 mm to 5 mm, and the edge incorporated in the liquid crystal display part The light type backlight unit is required to be thinner.

  In such an ultra-thin portable terminal edge light type backlight unit, since the thickness of the liquid crystal display unit is set to the above level, the light guide plate is required to be further thinned. ing. From such a point, as a light guide plate used in the edge light type backlight unit of such an ultra-thin portable terminal, instead of a conventional light guide plate having a relatively large wedge shape and a relatively large thickness, A thin light guide film having a substantially uniform thickness has been used.

  However, although this thin plate-shaped light guide film contributes to the thinning of the portable terminal, the thickness of the light guide film becomes thinner than the light source, so that the upper surface of the light emitted from the light source is not incident on the end face. The amount of light passing through the side or the lower surface side tends to increase. Therefore, according to the edge light type backlight unit using this light guide film, the luminance may be lower than that of the conventional liquid crystal display device.

  In view of such a problem, a light guide film in which a light adjusting portion for making light emitted from a light source incident on the end surface of the thin base film facing the light source has been proposed ( JP, 2010-123669, A). The light guide film described in this publication is said to be able to sufficiently take in the light emitted from the light source by increasing the thickness of the end face facing the light source by the light adjusting unit.

JP 2010-123569 A

  However, the present inventor has found that even when a liquid crystal display device having a light guide film in which the light adjusting parts are laminated as described above is used, the luminance may be lower than that of a conventional liquid crystal display device. . Further, as a cause of such a decrease in luminance, it has been found that the light incident on the light adjusting unit is emitted from the upper or lower surface of the light adjusting unit without being sufficiently propagated into the base film. .

  The present invention has been made in view of such circumstances, a light guide film that can increase the light use efficiency even if the average thickness is thin, an edge light type backlight unit including the light guide film, and The object is to provide a method for producing this light guide film.

  The light guide film according to the present invention, which has been made to solve the above problems, has a synthetic resin as a main component, has an average thickness of 100 μm or more and 600 μm or less, and emits light emitted from an LED from at least one end face. A light guide film for an edge-light type backlight unit that emits to the upper surface side, wherein the edge portion on the end surface side is formed in a trumpet shape that gradually increases in thickness toward the end surface side, and the longitudinal direction on the end surface It is characterized by having a concave groove along the line.

  The light guide film is formed in a trumpet shape in which the edge on the end face side where the light emitted from the LED enters is gradually increased in thickness toward the end face side, so the average thickness is as thin as 100 μm or more and 600 μm or less. Also, the light beam emitted from the LED can surely enter the end face. Furthermore, since the light guide film has a concave groove along the longitudinal direction on the end face, the light emitted from the LED is made incident on the concave groove by causing the light emitted from the LED to enter the concave groove. Further, the light guide film can be incident from a position closer to the light emission area. Therefore, the light guide film can increase the light use efficiency.

  It is preferable that the upper surface of the edge portion is an inclined surface with an elevation angle toward the end surface, and the lower surface is a flat surface that is flush with other regions. In this way, the end surface portion can be easily formed into a desired shape by making the upper surface of the end edge portion an inclined surface and the lower surface a plane that is flush with other regions. In addition, the light guide film can be easily incorporated into the backlight unit because the lower surface of the edge portion is flush with other regions.

  The cross section of the concave groove may be formed in a V shape. Thus, since the cross section of the groove is formed in a V shape, it is easy to control the refraction angle of the light incident on the groove, so that the light incident on the groove is inside. Easy to propagate.

  The base angle of the V-shaped cross section of the groove is preferably an acute angle. Thus, when the base angle of the V-shaped cross section of the groove is an acute angle, it is easy to propagate the light beam by suppressing the light beam from being reflected to the LED side at the interface of the groove groove. .

  The elevation angle of the upper surface of the groove groove relative to the lower surface of the end edge portion and a parallel surface may be larger than the depression angle of the lower surface of the groove groove. Thus, when the elevation angle of the upper surface of the concave groove is larger than the depression angle of the lower surface of the concave groove, the light incident on the end surface is refracted downward, and the light can easily propagate inside.

  It is preferable to further include a reflective layer laminated on at least the upper surface of the edge portion. As described above, the reflection layer is laminated on the upper surface of the edge portion so that the light beam incident on the reflection layer is reflected to the edge portion side, thereby causing the light caused by the emission of the light beam from the edge portion. It is possible to suppress a decrease in the utilization efficiency.

  Moreover, the edge light type backlight unit according to the present invention made to solve the above-described problems includes the light guide film and one or more LEDs disposed along at least one end face of the light guide film. And one or more optical sheets superimposed on the upper surface side of the light guide film.

  Since the edge light type backlight unit includes the light guide film that can increase the light use efficiency even if the average thickness is thin, the edge light type backlight unit can be thinned and can improve the light use efficiency. it can.

  In addition, the light guide film manufacturing method according to the present invention made to solve the above-mentioned problems has a synthetic resin as a main component, has an average thickness of 100 μm or more and 600 μm or less, and at least emits light emitted from the LED. A light guide film for an edge light type backlight unit that is incident from one end face and exits to an upper surface side, comprising: a step of heating a flat synthetic resin film; and at least a synthetic resin film after the heating step. And a step of pressing a convex mold along the longitudinal direction on one end face.

  The light guide film is produced by pressing the convex mold along the longitudinal direction of at least one end surface of the synthetic resin film after heating the flat synthetic resin film by the heating step. As described above, even if the average thickness is small, the light guide film that can increase the light use efficiency can be manufactured.

  In the present invention, the “upper surface side” means the viewer side in the backlight unit, and the “lower surface side” means the opposite. “Main component” refers to a component having the largest content, for example, a component having a content of 50% by mass or more. The “average thickness” of the light guide film means an average value of thicknesses at arbitrary 10 points in a portion other than the edge portion formed in a trumpet shape. “Trumpet shape” means that the cross-sectional shape perpendicular to the longitudinal direction (direction perpendicular to the thickness direction) of the end surface facing the LED is formed so that the thickness gradually increases toward the end surface side. Further, “gradually increasing the thickness” includes a shape having a region having the same thickness in a part of the cross-sectional shape. The “cross section of the groove groove” refers to a cross section perpendicular to the extending direction of the groove groove.

  As described above, the light guide film of the present invention can improve the light utilization efficiency even if the average thickness is thin. In addition, the edge light type backlight unit of the present invention can reduce the thickness and increase the light use efficiency. Furthermore, the light guide film manufacturing method of the present invention can easily and reliably manufacture the light guide film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective view of a portable terminal according to a first embodiment of the present invention, where (a) shows a state where a liquid crystal display unit is opened, and (b) shows a state where the liquid crystal display unit is closed. It is a typical end view which shows the edge light type backlight unit of the portable terminal of FIG. It is a typical perspective view of the light guide film of the backlight unit of FIG. It is a typical partial enlarged end view of the light guide film of FIG. It is a typical enlarged view which shows the recessed part and raised part of the light guide film of FIG. 2, (a) is an end elevation, (b) is a bottom view. It is a typical side view for demonstrating the manufacturing method of the light guide film of FIG. It is a typical side view for demonstrating the manufacturing method of the light guide film of FIG. It is a typical end view which shows the light guide film which concerns on embodiment different from the light guide film of FIG. It is a typical top view of the light guide film of FIG. It is a typical end view which shows the light guide film which concerns on embodiment different from the light guide film of FIG.2 and FIG.8. It is a typical perspective view of the light guide film of FIG. It is a typical end view which shows the concave groove which concerns on other embodiment of this invention. It is typical sectional drawing which shows the conventional edge light type backlight unit.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First embodiment]
<Liquid crystal display device>
The liquid crystal display device 1 of FIG. 1 is configured as a portable terminal. The liquid crystal display device 1 includes an operation unit 2 and a liquid crystal display unit 3 connected to the operation unit 2 so as to be rotatable (openable and closable). In the liquid crystal display device 1, the thickness of the casing (casing) that entirely accommodates the components of the liquid crystal display device 1 (the thickest portion when the liquid crystal display unit 3 is closed) is 21 mm or less, and is extremely thin. It is a laptop computer (hereinafter sometimes referred to as “ultra-thin computer 1”).

  The liquid crystal display unit 3 of the ultra-thin computer 1 includes a liquid crystal panel 4 and an edge light type ultra-thin backlight unit that irradiates light toward the liquid crystal panel 4 from the lower surface side. In the liquid crystal panel 4, the periphery of the lower surface, the side surface, and the upper surface is held by the casing 5 for the liquid crystal display unit of the housing. Here, the casing 5 for the liquid crystal display unit includes a top plate 6 disposed on the lower surface (and the rear surface) of the liquid crystal panel 4, and an upper surface support member 7 disposed on the surface side around the upper surface of the liquid crystal panel 4. Have A casing of the ultra-thin computer 1 is provided with a casing 5 for a liquid crystal display section and a casing 5 for the liquid crystal display section so as to be pivotable via a hinge section 8, and a central processing unit (ultra-low voltage CPU) or the like. And a casing 9 for the operation section in which is incorporated.

  The average thickness of the liquid crystal display unit 3 is not particularly limited as long as the thickness of the housing is in a desired range, but the lower limit of the average thickness of the liquid crystal display unit 3 is preferably 2 mm, more preferably 3 mm, 4 mm is more preferable. On the other hand, the upper limit of the average thickness of the liquid crystal display unit 3 is preferably 7 mm, more preferably 6 mm, and even more preferably 5 mm. If the average thickness of the liquid crystal display unit 3 is less than the above lower limit, the strength of the liquid crystal display unit 3 may be reduced or the luminance may be reduced. On the other hand, if the average thickness of the liquid crystal display unit 3 exceeds the above upper limit, there is a possibility that the demand for thinning the ultra-thin computer 1 cannot be met.

<Backlight unit>
The backlight unit 11 of FIG. 2 is provided in the liquid crystal display unit 3 of the ultra-thin computer 1. The backlight unit 11 is an edge light type backlight unit that emits light emitted from the LED 13 from one end face of the light guide film 12 and emits the light to the upper surface side. The backlight unit 11 includes a light guide film 12, a plurality of LEDs 13 disposed along one end surface of the light guide film 12, and one or a plurality of optical sheets superimposed on the upper surface side of the light guide film 12. 14. The backlight unit 11 further includes a reflection sheet 15 that is disposed on the lower surface side of the light guide film 12 and reflects the light emitted from the lower surface of the light guide film 12 to the upper surface side. As will be described later, the light guide film 12 is formed in a trumpet shape in which an end edge portion 17 on the end face side facing the plurality of LEDs 13 gradually increases in thickness toward the end face side. The light guide film 12 is disposed so that the entire lower surface is included in the reflection sheet 15 in plan view. On the other hand, the optical sheet 14 is not superimposed on the upper surface side of the edge 17 of the light guide film 12. That is, the optical sheet 14 is superimposed on the upper surface of the light guide film 12 except at least the edge portion 17. By having such a configuration, the backlight unit 11 causes light beams emitted from the plurality of LEDs 13 to enter the end face of the light guide film 21 and propagate in the light guide film 12 and propagate in the light guide film 12. The light beam can be emitted upward from the upper surface other than the edge portion 17, and the emitted light can be incident on the lower surface of the optical sheet 14 substantially uniformly.

(Light guide film)
The light guide film 12 includes a flat plate-like (non-wedge-shaped) main body 16 having a uniform thickness, and an end edge portion 17 continuous from the end faces of the main body 16 on the side of the plurality of LEDs 13. The light guide film 12 enters the light beams emitted from the plurality of LEDs 13 from the end face of the edge portion 17 facing the plurality of LEDs 13 and emits the light toward the upper surface side. Specifically, the light guide film 12 emits light incident from the end face from the upper surface of the main body 16 (that is, the upper surface of the main body 16 is formed as a light emission region). The main body 16 and the end edge portion 17 are integrally formed of the same forming material (that is, the main body 16 and the end edge portion 17 are integrally formed, and an interface exists between the main body 16 and the end edge portion 17. do not do). The light guide film 12 is formed in a trumpet shape in which the end edge portion 17 gradually increases in thickness toward the end surface side. The light guide film 12 has a groove 18 along a longitudinal direction (a direction perpendicular to the thickness direction) on an end surface facing the plurality of LEDs 13 (an end surface on the side of the plurality of LEDs 13 of the end edge portion 17). As shown in FIG. 3, the concave groove 18 is formed across both ends in the longitudinal direction of the end face of the light guide film 12 facing the plurality of LEDs 13. In addition, the light guide film 12 has a plurality of recesses 19 that are recessed on the upper surface side on the lower surface. Further, the light guide film 12 has a sticking prevention portion on the lower surface. Specifically, the light guide film 12 has a plurality of raised portions 20 that exist around the plurality of recesses 19 and protrude to the lower surface side as the sticking prevention portion. The raised portion 20 is provided adjacent to the recessed portion 19, and the inner surface side of the raised portion 20 is continuous with the formation surface of the recessed portion 19.

  The lower limit of the average thickness of the light guide film 12 (the average thickness of portions other than the edge portion 17 formed in a trumpet shape, that is, the average thickness of the main body 16) is 100 μm, preferably 150 μm, and preferably 200 μm. Is more preferable. On the other hand, the upper limit of the average thickness of the light guide film 12 is 600 μm, preferably 580 μm, and more preferably 550 μm. If the average thickness of the light guide film 12 is less than the lower limit, the strength of the light guide film 12 may be insufficient, and the light beams of the plurality of LEDs 13 cannot be sufficiently incident on the light guide film 12. There is a fear. On the contrary, if the average thickness of the light guide film 12 exceeds the upper limit, there is a possibility that the demand for thinning the backlight unit 11 may not be met.

  As shown in FIG. 4, the upper surface of the end edge portion 17 is an inclined surface 21 having an elevation angle toward the end surface facing the plurality of LEDs 13. Further, the light guide film 12 is configured such that the lower surface 22 of the edge portion 17 and the other region (the lower surface of the main body 16) are flush with each other. Thus, the light guide film 12 forms the end surface portion 17 in a desired shape by the upper surface of the edge portion 17 being the inclined surface 21 and the lower surface 22 being flush with other regions. easy. In addition, the light guide film 12 can be stably disposed on the upper surface side of the reflection sheet 15, for example, because the lower surface 22 of the edge portion 17 is flush with other regions. Incorporation into the light unit 11 is easy.

  The inclined surface 21 is a flat surface. The lower limit of the average inclination angle of the inclined surface 21 relative to the parallel surface with the lower surface 22 of the edge 17 is preferably 10 °, more preferably 20 °, and even more preferably 25 °. On the other hand, the upper limit of the average inclination angle of the inclined surface 21 is preferably 50 °, more preferably 45 °, and even more preferably 40 °. If the average inclination angle of the inclined surface 21 is less than the lower limit, the length of the edge portion 17 (in particular, the thickness on the side facing the plurality of LEDs 13) is sufficiently long (in particular, the thickness facing the plurality of LEDs 13). The length of the light emitting direction of the plurality of LEDs 13 must be increased, and the planar area of the light guide film 12 may become unnecessarily large. Conversely, if the average inclination angle of the inclined surface 21 exceeds the above upper limit, it may be difficult to guide the light beam reflected by the inclined surface 21 to the main body 16 side. The “average inclination angle” means an average value of the inclination angles of the plurality of LED 13 side edges and the opposite edge.

  The lower limit of the average length of the edge portion 17 (the average length in the light emission direction of the plurality of LEDs 13) is preferably 100 μm, more preferably 150 μm, and even more preferably 200 μm. On the other hand, as an upper limit of the average length of the edge part 17, 500 micrometers is preferable, 450 micrometers is more preferable, and 300 micrometers is more preferable. If the average length of the edge portion 17 is less than the above lower limit, the average inclination of the inclined surface 21 is sufficient to sufficiently increase the thickness of the edge portion 17 (particularly, the thickness facing the plurality of LEDs 13). It is necessary to increase the angle, and it may be difficult to guide the light beam reflected by the inclined surface 21 to the main body 16 side. Conversely, if the average length of the edge portion 17 exceeds the upper limit, the planar area of the light guide film 12 may become unnecessarily large.

The lower limit of the average thickness _{D 1} at a plurality of LED13 side edge of the edge portion 17, 300 [mu] m are preferred, more preferably 350 .mu.m, more preferably 400 [mu] m. On the other hand, the upper limit of the average thickness _{D 1,} preferably from 800 [mu] m, more preferably 750 [mu] m, more preferably 700 .mu.m. When the average thickness D ₁ is less than the above lower limit, it may be impossible to sufficiently incident rays emitted from a plurality of LED13 to the end faces of the plurality of LED13 side edge portion 17. Conversely, the average thickness D ₁ exceeds the upper limit, the light guide film 12 is likely to be unnecessarily thick. Note that “average thickness” refers to an average value of thicknesses at arbitrary 10 points.

The lower limit of the average distance D ₂ in the thickness direction of the inclined surface 21 (that is, the average distance in the thickness direction between the plurality of LED 13 side edges of the inclined surface 21 and the opposite edge thereof) is preferably 50 μm. 100 μm is more preferable, and 150 μm is more preferable. In contrast, the upper limit of the average distance _{D 2} of the thickness direction, 300 [mu] m is preferable, 250 [mu] m, and still more preferably 200 [mu] m. When the average distance D ₂ of the thickness direction is less than the above lower limit, while sufficiently thin body 16, fully incident rays emitted from a plurality of LED13 to the end faces of the plurality of LED13 side edge portions 17 There is a possibility that it cannot be made. Conversely, the average distance D ₂ of the thickness direction is more than the upper limit, the edge portion 17 becomes unnecessarily thick, there is a possibility that the edge portion 17 is easily damaged. “The average distance D ₂ in the thickness direction of the inclined surface” refers to the average value of the distances in the thickness direction of the inclined surface at arbitrary 10 points.

  The cross section of the groove 18 is V-shaped. Since the light guide film 1 has the V-shaped cross section of the groove 18 in this way, it is easy to control the refraction angle of the light incident on the groove 18. It is easy to propagate the light incident on 18 into the main body 16.

  The base angle of the V-shaped cross section of the groove 18 is preferably an acute angle. If the bottom angle of the V-shaped cross section of the groove 18 is an obtuse angle, the light beam is likely to be reflected to the plurality of LEDs 13 at the interface of the groove 18, and it may be difficult to incorporate the light inside. Further, if the base angle of the V-shaped cross section of the groove 18 is an obtuse angle, the inclination angle of the inclined surface 21 becomes too large, and it is difficult to guide the light beam reflected by the inclined surface 21 to the main body 16 side. There is. On the other hand, when the bottom angle of the V-shaped cross section of the groove 18 is an acute angle, the light beam is propagated to the inside while suppressing reflection of the light beam to the plurality of LEDs 13 at the interface of the groove groove 18. Easy to do.

  The lower limit of the base angle of the V-shaped cross section of the groove 18 is preferably 15 °, more preferably 30 °, and even more preferably 45 °. On the other hand, the upper limit of the base angle is preferably 80 °, more preferably 70 °, and even more preferably 60 °. If the base angle is less than the lower limit, the amount of light incident on the groove 18 is reduced, and the light beams emitted from the plurality of LEDs 13 may not be sufficiently propagated into the main body 16. On the other hand, if the base angle exceeds the upper limit, it is difficult to sufficiently allow the light beams emitted from the plurality of LEDs 13 to enter from the position on the main body 16 side, and as a result, the light utilization efficiency cannot be sufficiently increased. There is a fear. Further, if the base angle exceeds the upper limit, the inclination angle of the inclined surface 21 becomes too large, and it may be difficult to guide the light beam reflected by the inclined surface 21 to the main body 16 side.

  The lower limit of the angle α formed by the virtual plane parallel to the lower surface 22 of the edge 17 and the upper surface 23 of the groove 18 is preferably 10 °, more preferably 20 °, and even more preferably 25 °. On the other hand, the upper limit of the angle α is preferably 50 °, more preferably 45 °, and still more preferably 40 °. If the angle α formed is less than the above lower limit, the amount of light incident on the groove 18 is reduced, and there is a possibility that light beams emitted from the plurality of LEDs 13 cannot be sufficiently propagated inside the main body 16. On the contrary, when the angle α formed exceeds the upper limit, there is a high possibility that the light beam reflected by the upper surface 23 is emitted to the plurality of LEDs 13 side. If the angle α formed exceeds the upper limit, the inclination angle of the inclined surface 21 becomes too large, and it may be difficult to guide the light beam reflected by the inclined surface 21 to the main body 16 side.

  The lower limit of the angle β formed by the virtual surface parallel to the lower surface 22 of the edge 17 and the lower surface 24 of the groove 18 is preferably 5 °, more preferably 10 °, and even more preferably 15 °. On the other hand, the upper limit of the angle β is preferably 35 °, more preferably 30 °, and even more preferably 25 °. If the angle β formed is less than the lower limit, the amount of light incident on the concave groove 18 is reduced, and there is a possibility that light beams emitted from the plurality of LEDs 13 cannot be sufficiently propagated into the main body 16. Conversely, when the angle β formed above exceeds the upper limit, it may be difficult to form the lower surface 22 of the edge portion 17 and the other region (the lower surface of the main body 16) flush with each other.

  The elevation angle (the angle α made) of the upper surface 23 of the concave groove 18 with respect to the plane parallel to the lower surface 22 of the edge 17 is larger than the depression angle (the angle β made) of the lower surface 24 of the concave groove 18. preferable. The light guide film 12 has the elevation angle of the upper surface 23 of the groove 18 greater than the depression angle of the lower surface 24 of the groove 18 so that the light incident on the upper surface 23 is refracted downward and propagated inside the main body 16. easy.

  The concave groove 18 is formed in the central portion in the thickness direction of the end surface facing the plurality of LEDs 13. That is, the distance between the upper surface 23 and the inclined surface 21 of the groove 18 on the end surface facing the plurality of LEDs 13 is substantially equal to the distance between the lower surface 24 of the groove 18 and the lower surface 22 of the edge 17 on this end surface. . As described above, the groove 18 is formed in the central portion in the thickness direction of the end surface facing the plurality of LEDs 13, so that the light emitted from the plurality of LEDs 13 can be easily incident on the groove 18. Therefore, it is easy to propagate the light emitted from the plurality of LEDs 13 into the main body 16.

The lower limit of the average width _{D 3} of concave groove 18 at the end face facing the plurality of LED 13, 50 [mu] m are preferred, more preferably 100 [mu] m, more preferably 150 [mu] m. On the other hand, the upper limit of the average width _{D 3,} 300 [mu] m is preferable, 250 [mu] m, and still more preferably 200 [mu] m. When the average width D ₃ is less than the above lower limit, the amount of light incident is reduced to concave groove 18, there is sufficient possibility that can not be propagated to the interior of the body 16 of the light ray emitted from a plurality of LED13 . Conversely, the average width D ₃ is more than the upper limit, the edge portion 17 becomes unnecessarily thick, there is a possibility that the edge portion 17 is easily damaged. Note that the "average width D ₃ of concave groove 18 at the end face facing the plurality of LED" refers to the average value of the width of the concave groove at any 10 points in the end surface facing the plurality the LED.

As a lower limit of the ratio (D ₃ / D ₄ ) of the average width D ₃ to the average distance D ₄ between the inclined surface 21 and the upper surface 23 of the groove 18 on the end surface facing the plurality of LEDs 13, 0.5 is preferable. 0.7 is more preferable, and 0.9 is more preferable. On the other hand, the upper limit of the ratio (D ₃ / D ₄ ) is preferably 2.5, more preferably 2, and even more preferably 1.5. If the ratio (D ₃ / D ₄ ) is less than the lower limit, the amount of light incident on the groove 18 is reduced, and the light emitted from the plurality of LEDs 13 can be sufficiently propagated into the main body 16. It may not be possible. On the contrary, when the ratio (D ₃ / D ₄ ) exceeds the upper limit, the edge portion 17 becomes unnecessarily thick and the edge portion 17 may be easily damaged.

The lower limit of the ratio (D ₃ / D ₄ ) of the average width D ₃ to the average distance D ₅ between the lower surface 22 of the edge 17 and the lower surface 24 of the groove 18 on the end surface facing the plurality of LEDs 13 is 0. .5 is preferred, 0.7 is more preferred, and 0.9 is even more preferred. On the other hand, the upper limit of the ratio (D ₃ / D ₄ ) is preferably 2.5, more preferably 2, and even more preferably 1.5. If the ratio (D ₃ / D ₄ ) is less than the lower limit, the amount of light incident on the groove 18 is reduced, and the light emitted from the plurality of LEDs 13 can be sufficiently propagated into the main body 16. It may not be possible. On the contrary, when the ratio (D ₃ / D ₄ ) exceeds the upper limit, the edge portion 17 may be easily damaged.

The lower limit of the average depth of the groove 18 is preferably 30 μm, more preferably 50 μm, and even more preferably 100 μm. On the other hand, the upper limit of the average depth of the groove 18 is preferably 400 μm, more preferably 300 μm, and even more preferably 200 μm. If the average depth of the concave groove 18 is less than the above lower limit, while adjusting the base angle of the concave groove 18, it is difficult to sufficiently ensure the average width D ₃ of concave groove 18, a plurality of There is a possibility that the light beam emitted from the LED 13 cannot be sufficiently propagated inside the main body 16. Conversely, if the average depth of the groove 18 exceeds the upper limit, the end edge 17 may be easily damaged.

  Moreover, it is preferable that the average depth of the groove 18 is more than the average length of the edge part 17 (average length of the light emission direction of several LED13). The light guide film 12 allows the light beams emitted from the plurality of LEDs 13 to enter more from the main body 16 side when the average depth of the groove 18 is equal to or greater than the average length of the end edge portion 17 in this way. Therefore, it is easy to propagate the light emitted from the plurality of LEDs 13 to the inside of the main body 16, thereby making it easy to improve the light use efficiency.

  The upper surface 23 and the lower surface 24 of the groove 18 may be roughened. Since the upper surface 23 and the lower surface 24 of the groove 18 are roughened, the light can be appropriately scattered on the upper surface 23 and the lower surface 24, thereby facing the plurality of LEDs 13 of the light guide film 12. It is possible to suppress the occurrence of hot spots (regions with an extremely large amount of light compared to other regions) in the vicinity of the end face.

  When the upper surface 23 and the lower surface 24 of the groove 18 are roughened, the lower limit of the arithmetic average roughness (Ra) of the upper surface 23 and the lower surface 24 is preferably 1.5 μm, more preferably 1.7 μm, 2.0 μm is more preferable. On the other hand, the upper limit of the arithmetic average roughness (Ra) of the upper surface 23 and the lower surface 24 is preferably 4.0 μm, more preferably 3.8 μm, and even more preferably 3.5 μm. If the arithmetic average roughness (Ra) of the upper surface 23 and the lower surface 24 is less than the lower limit, the light scattering function may be insufficient, and the generation of hot spots may not be sufficiently suppressed. On the contrary, if the arithmetic average roughness (Ra) of the upper surface 23 and the lower surface 24 exceeds the upper limit, the light rays are excessively scattered, and the amount of light emitted from the inclined surface 21 or the lower surface 22 of the edge portion 17 may increase. is there. The “arithmetic average roughness (Ra)” refers to a value with a cutoff λc of 2.5 mm and an evaluation length of 12.5 mm in accordance with JIS-B0601: 1994.

  When the upper surface 23 and the lower surface 24 of the groove 18 are roughened, the lower limit of the ten-point average roughness (Rz) of the upper surface 23 and the lower surface 24 is preferably 1.5 μm, more preferably 1.7 μm. 2.0 is more preferable. On the other hand, the upper limit of the ten-point average roughness (Rz) of the upper surface 23 and the lower surface 24 is preferably 40 μm, more preferably 35 μm, and even more preferably 30 μm. If the ten-point average roughness (Rz) of the upper surface 23 and the lower surface 24 is less than the above lower limit, the light scattering function becomes insufficient, and the occurrence of hot spots may not be sufficiently suppressed. On the other hand, if the ten-point average roughness (Rz) of the upper surface 23 and the lower surface 24 exceeds the upper limit, the light rays are excessively scattered, and the amount of light emitted from the inclined surface 21 or the lower surface 22 of the edge 17 may increase. There is. The “ten-point average roughness (Rz)” refers to a value having a cutoff λc of 2.5 mm and an evaluation length of 12.5 mm in accordance with JIS-B0601: 1994.

  When the upper surface 23 and the lower surface 24 of the groove 18 are roughened, the lower limit of the ratio (Rz / Ra) of the ten-point average roughness (Rz) to the arithmetic average roughness (Ra) of the upper surface 23 and the lower surface 24 Is preferably 1. On the other hand, the upper limit of the ratio (Rz / Ra) is preferably 20, more preferably 15, and even more preferably 10. If the ratio (Rz / Ra) exceeds the above upper limit, it may be difficult to control the light scattering direction.

  The plurality of concave portions 19 are formed on the lower surface of the main body 16, but are not formed on the lower surface 22 of the end edge portion 17. The plurality of concave portions 19 function as light scattering portions that scatter incident light to the upper surface side. As shown in FIG. 5, each recess 19 is formed in a substantially circular shape in plan view. Moreover, each recessed part 19 is formed so that a diameter may be gradually reduced toward the upper surface side. The shape of the recess 19 is not particularly limited, and may be a hemispherical shape, a semi-ellipsoidal shape, a conical shape, a truncated cone shape, or the like. Especially, as a shape of the recessed part 19, a hemispherical shape or a semi-ellipsoidal shape is preferable. When the concave portion 19 is hemispherical or semi-ellipsoidal, the moldability of the concave portion 19 can be improved, and light incident on the concave portion 19 can be suitably scattered.

  As a minimum of average depth L of crevice 19 (refer to Drawing 5 (a)), 1 micrometer is preferred, 2 micrometers is more preferred, and 4 micrometers is still more preferred. On the other hand, as an upper limit of the average depth L of the recessed part 19, 10 micrometers is preferable, 9 micrometers is more preferable, and 7 micrometers is more preferable. If the average depth L of the recess 19 is less than the lower limit, the light scattering function may not be sufficiently obtained. Conversely, if the average depth L of the recesses 19 exceeds the upper limit, there is a risk of uneven brightness. “Depth L” refers to the distance from the average interface of the lower surface of the light guide film 12 to the bottom of the recess (deepest position), and “average depth L” refers to 10 arbitrarily extracted samples. The average value of the depth of the recess.

  As a minimum of average diameter D (refer to Drawing 5 (b)) of crevice 19, 10 micrometers is preferred, 12 micrometers is more preferred, and 15 micrometers is still more preferred. On the other hand, as an upper limit of the average diameter D of the recessed part 19, 50 micrometers is preferable, 40 micrometers is more preferable, and 30 micrometers is further more preferable. If the average diameter D of the recess 19 is less than the lower limit, the light scattering function may not be sufficiently obtained. On the other hand, if the average diameter D of the recesses 19 exceeds the upper limit, there may be luminance unevenness. Note that “the diameter D of the recess” means an intermediate value between the maximum diameter and the minimum diameter of the recess at the average interface on the lower surface of the light guide film 12, and “the average diameter D of the recess” is arbitrarily extracted 10 The average value of the diameter D of each recessed part is said.

  The raised portion 20 is formed continuously from a surface perpendicular to the thickness direction of the light guide film 12 on the lower surface of the light guide film 12. Specifically, the raised portion 20 is formed continuously from the flat surface of the lower surface of the light guide film 12. The raised portion 20 is formed in a substantially annular shape in plan view so as to surround the recessed portion 19. The light guide film 12 is formed in a substantially annular shape in plan view so that the raised portion 20 surrounds the concave portion 19, so that the reflective sheet 15 in which the concave portion 19 and the vicinity of the concave portion 19 are disposed on the lower surface side of the light guide film 12. Can be easily and reliably prevented.

  As a minimum of average height H (refer to Drawing 5 (a)) of upheaval part 20, 0.1 micrometers is preferred, 0.3 micrometers is more preferred, and 0.5 micrometers is still more preferred. On the other hand, the upper limit of the average height H of the raised portions 20 is preferably 5 μm, more preferably 4 μm, and even more preferably 3 μm. If the average height H of the raised portion 20 is less than the lower limit, the light guide film 12 and the reflective sheet 15 disposed on the lower surface side of the light guide film 12 may come into contact with each other at the portion other than the raised portion 20. As a result, the reflection sheet 15 may not be sufficiently damaged. Further, if the average height H of the raised portion 20 is less than the lower limit, the light guide film 12 and the reflective sheet 15 cannot be sufficiently prevented from being in close contact with each other, and the light guide film 12 and the reflective sheet 15 are incident on the close contact portion. There is a risk that luminance unevenness may occur due to the emitted light. Conversely, if the average height H of the raised portions 20 exceeds the above upper limit, the tips of the raised portions 20 are sharpened, and the damage prevention property on the upper surface of the reflective sheet 15 may be reduced. The “height H of the bulge” refers to the average value of the heights of any three points of the bulge, and the “average height H of the bulge” refers to the 10 bulges arbitrarily extracted. The average value of height.

  As a minimum of average width W (refer to Drawing 5 (b)) of upheaval part 20, 1 micrometer is preferred, 3 micrometers is more preferred, and 5 micrometers is still more preferred. On the other hand, the upper limit of the average width W of the raised portions 20 is preferably 15 μm, more preferably 12 μm, and even more preferably 10 μm. If the average width W of the raised portion 20 is less than the lower limit, the tip of the raised portion 20 is sharpened, and the scratch resistance to the upper surface of the reflective sheet 15 disposed on the lower surface side of the light guide film 12 is reduced. There is a fear. On the contrary, when the average width W of the raised portion 20 exceeds the upper limit, the contact area between the raised portion 20 and the reflection sheet 15 is increased, and there is a risk that unevenness in brightness is caused due to the light rays incident on the contact portion. There is. The “width of the raised portion” refers to the difference between the outer radius and the inner radius of the raised portion at the average interface on the lower surface of the light guide film. The width of the raised portion can be obtained, for example, by subtracting a value of ½ of the inner diameter from a value of ½ of the outer diameter at a portion where the outer diameter of the raised portion is maximum. The “average width of the raised portions” refers to an average value of the widths of 10 arbitrarily extracted raised portions.

  The light guide film 12 has flexibility. By having flexibility, the light guide film 1 can suppress damage to the reflection sheet 15 disposed on the lower surface side. Since the light guide film 1 is required to transmit light, the light guide film 1 is composed mainly of a transparent, particularly colorless and transparent synthetic resin.

  The main components of the light guide film 12 are polycarbonate, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, polystyrene, methyl (meth) acrylate-styrene copolymer, polyolefin, cycloolefin polymer, cycloolefin copolymer, cellulose acetate, weather resistance And reactive vinyl chloride, active energy ray-curable resin, and the like. Especially, as a main component of the light guide film 12, a polycarbonate or an acrylic resin is preferable. Polycarbonate is excellent in transparency and has a high refractive index. Therefore, when the light guide film 12 contains polycarbonate as a main component, total reflection is likely to occur on the upper and lower surfaces of the light guide film 12, and light can be propagated efficiently. it can. In addition, since polycarbonate has heat resistance, it is difficult for the plurality of LEDs 13 to deteriorate due to heat generation. Furthermore, since polycarbonate has less water absorption than acrylic resin, dimensional stability is high. Therefore, the light guide film 12 can suppress aged deterioration by including polycarbonate as a main component. On the other hand, since acrylic resin has high transparency, light wear on the light guide film 12 can be reduced.

(LED)
The plurality of LEDs 13 are arranged along the end surface of the light guide film 12. The plurality of LEDs 13 are arranged such that the light-emitting surface faces (or abuts) the end surface of the light guide film 12.

(Optical sheet)
The one or more optical sheets 14 have optical functions such as diffusion and refraction with respect to light incident from the lower surface. Examples of the one or more optical sheets 14 include a light diffusion sheet having a light diffusion function and a prism sheet having a refraction function toward the normal direction.

(Reflective sheet)
The reflection sheet 15 is disposed on the lower surface side of the light guide film 12 so as to come into contact with the plurality of raised portions 20 formed on the lower surface of the light guide film 12. The reflection sheet 15 reflects the light beam emitted from the lower surface of the light guide film 12 to the upper surface side. As the reflection sheet 15, regular reflection is enhanced by depositing a metal such as aluminum or silver on the surface of a white sheet in which a filler is dispersed in a base resin such as polyester or a film formed from polyester. Specular sheet etc. are mentioned.

<Advantages>
The light guide film 12 is formed in a trumpet shape in which the end edge portion 17 on the end face side where the light beams emitted from the plurality of LEDs 13 are incident is gradually increased in thickness toward the end face side. Even if the average thickness is as small as 100 μm or more and 600 μm or less, the light emitted from the plurality of LEDs 13 can be reliably incident on this end face. Furthermore, since the light guide film 12 has the groove 18 along the longitudinal direction on the end face, a plurality of light beams emitted from the plurality of LEDs 13 are incident on the groove 18, so that The light beam emitted from the LED 13 can be made incident from a position closer to the light emission region of the light guide film 12 (on the main body 16 side). Therefore, the light guide film 12 can easily propagate the light emitted from the plurality of LEDs 13 to the inside of the main body 16 and can improve the light use efficiency.

  In the light guide film 12, since the main body 16 and the edge portion 17 are integrally formed of the same forming material, for example, after the main body is formed, the edge portion is separately formed by coating with an ultraviolet curable resin or the like. Compared to the above, the light utilization efficiency is excellent. In other words, if the edge portion is formed by applying an ultraviolet curable resin after the main body is formed, the main body may be yellowed by the ultraviolet rays. However, the light guide film 12 prevents the yellowing by preventing the yellowing. Can improve the efficiency of use.

  Even if the backlight unit 11 has a small average thickness (average thickness of the main body 16) as described above, the light emitted from the plurality of LEDs 13 can be easily propagated into the main body 16, and the light use efficiency can be improved. Since the light guide film 12 that can be increased is provided, the light guide film 12 can be reduced in thickness and the light use efficiency can be increased.

<Method for producing light guide film>
Next, a method for manufacturing the light guide film 12 will be described. The light guide film manufacturing method includes a step of heating a flat synthetic resin film (a film containing synthetic resin as a main component) (heating step), and at least one end face (back) of the synthetic resin film after the heating step. A step (pressing step) of pressing a convex mold along the longitudinal direction (the direction perpendicular to the thickness direction) on an end surface facing the plurality of LEDs in a state of being incorporated in the light unit.

(Heating process)
In the heating step, the flat synthetic resin film is heated to the glass transition temperature or higher of the main component of the synthetic resin film. Although the heating temperature in the said heating process is based also on the main component of the said synthetic resin film, as a minimum of the heating temperature in the said heating process, 130 degreeC is preferable and 150 degreeC is more preferable. On the other hand, the upper limit of the heating temperature in the heating step is preferably 250 ° C and more preferably 200 ° C. If the heating temperature is less than the lower limit, the synthetic resin film cannot be sufficiently heated, and it may be difficult to form a desired groove on the end surface of the synthetic resin film in the pressing step described later. . Conversely, when the heating temperature exceeds the upper limit, the synthetic resin film may be deteriorated. In addition, as an average thickness of the said synthetic resin film, 100 micrometers or more and 600 micrometers or less are preferable.

(Pressing process)
In the pressing step, a convex mold is pressed along the longitudinal direction on at least one end surface of the synthetic resin film in a heated state. With reference to FIG.6 and FIG.7, it demonstrates in full detail about the said press process. In the pressing step, as shown in FIG. 6, the convex mold 34 is placed on the end surface of the synthetic resin film 31 in a state where the upper and lower surfaces of the synthetic resin film 31 are pressed by a pair of flat molds 32 and 33. This is done by pressing. As for the metal mold | die 32 arrange | positioned at the upper surface of the synthetic resin film 31, the lower surface (pressing surface) of the said end surface side of the synthetic resin film 31 inclines upward (opposite side to a pressing surface) over this end surface. Specifically, the lower surface on the end surface side of the mold 32 is formed as an inverted shape of the inclined surface 21 described above. Further, the tip of the ridge-shaped mold 34 is formed as an inverted shape of the groove 18. In the pressing step, as shown in FIG. 7, the convex mold 34 is pressed against the end surface of the synthetic resin film 31 with the upper and lower surfaces of the synthetic resin film 31 pressed by the pair of molds 32 and 33. Thus, the concave groove 18 is formed as an inverted shape of the convex mold 34 at the end edge of the synthetic resin film 31 on the end face side. At the same time, in the pressing step, the upper portion of the groove 18 is raised upward by pressing the protruding die 34, and the upper surface of the raised portion is formed as the inclined surface 21. The shape of the groove 18 can be easily and reliably adjusted by adjusting the shape of the tip of the protrusion die 34.

  In the pressing step, only the groove 18 may be formed, but it is preferable to form a plurality of recesses 19 on the lower surface of the synthetic resin film 31 simultaneously with the formation of the groove 18. The plurality of recesses 19 can be formed by making the upper surface of the mold 33 disposed on the lower surface of the synthetic resin film 31 into an inverted shape of the plurality of recesses 19. Further, in the pressing step, it is also preferable to form the plurality of concave portions 19 and the plurality of raised portions 20 at the same time by forming the upper surface of the mold 33 as an inverted shape of the plurality of concave portions 19 and the raised portions 20.

  By the pressing step, the synthetic resin film 31 is formed as the light guide film 12 of FIG. In addition, although the said heating process and a press process may be performed separately, you may perform simultaneously by the hot press method.

<Advantages>
The light guide film manufacturing method makes it easy to propagate the light emitted from the plurality of LEDs 13 into the main body 16 even when the average thickness (the average thickness of the main body 16) is thin as described above. The light guide film 12 that can increase the efficiency can be manufactured easily and reliably.

[Second Embodiment]
<Light guide film>
The light guide film 42 in FIG. 8 is used in the backlight unit 11 in FIG. 2 instead of the light guide film 12 in FIG. The light guide film 42 in FIG. 8 includes a reflective layer 43 that is laminated on the upper surface (the inclined surface 21) of the edge 17 of the light guide film 12 in FIG. The light guide film 42 in FIG. 8 is configured in the same manner as the light guide film 12 in FIG. Therefore, only the reflective layer 43 will be described below.

(Reflective layer)
As shown in FIG. 9, the reflective layer 43 is laminated on the entire surface of the inclined surface 21. On the other hand, the reflective layer 43 is not laminated on the upper surface of the main body 16. The light guide film 42 has the reflective layer 43 laminated on the entire surface of the inclined surface 21 and is not laminated on the upper surface of the main body 16, thereby accurately suppressing the emission of light rays from the edge 17 and the main body. A sufficient amount of light can be emitted from the upper surface of 16.

  The reflective layer 43 may be configured as a white layer in which a white pigment is dispersed in a binder, for example, or may be configured as a metal layer containing a metal as a main component. When the reflective layer 43 is configured as the white layer, the light guide film 42 can diffusely reflect light rays, thereby suppressing the occurrence of hot spots. On the other hand, when the reflective layer 43 is configured as the metal layer, the light guide film 42 can easily reflect the light beam specularly and thereby control the reflection direction of the light beam reflected by the reflective layer 43.

  When the reflective layer 43 is configured as the white part, the binder is not particularly limited. For example, acrylic resin, polyurethane, polyester, fluororesin, silicone resin, polyamideimide, epoxy resin, ultraviolet curable resin These can be used, and these can be used alone or in combination. In addition, the white pigment is not particularly limited, and examples thereof include titanium oxide (titanium white), zinc oxide (zinc white), lead carbonate (lead white), barium sulfate, calcium carbonate (white chalk), and the like. .

  The lower limit of the average particle size of the white pigment is preferably 100 nm, more preferably 200 nm, and even more preferably 300 nm. On the other hand, the upper limit of the average particle diameter of the white pigment is preferably 30 μm, more preferably 20 μm, and even more preferably 10 μm. When the average particle diameter of the white pigment is less than the lower limit, the reflectivity may be lowered. Conversely, if the average particle diameter of the white pigment exceeds the upper limit, the thickness of the reflective layer 43 may be unnecessarily increased. The “average particle diameter” means the average of the particle diameters of 30 particles randomly extracted from particles observed with an electron microscope with a magnification of 1000 times. The particle diameter is the Ferret diameter (parallel lines in a certain direction). And the interval when the projection image is sandwiched between them).

  As a minimum of the content rate of the white pigment, 3 mass% is preferred, 5 mass% is more preferred, and 7 mass% is still more preferred. On the other hand, as an upper limit of the content rate of the said white pigment, 30 mass% is preferable, 25 mass% is more preferable, and 20 mass% is further more preferable. If the content ratio of the white pigment is less than the lower limit, sufficient reflectivity may not be obtained. On the other hand, when the content ratio of the white pigment exceeds the upper limit, the white pigment may not be sufficiently fixed to the binder.

  The lower limit of the average thickness of the reflective layer 43 in the case of being configured as the white layer is preferably 20 μm, more preferably 50 μm, and even more preferably 75 μm. On the other hand, the upper limit of the average thickness is preferably 250 μm, more preferably 200 μm, and even more preferably 150 μm. If the average thickness is less than the lower limit, there is a high possibility that the white pigment will fall off the reflective layer 43. On the contrary, if the average thickness exceeds the upper limit, the reflective layer 43 becomes unnecessarily thick, which may violate the demand for thinning the light guide film 42.

  The reflective layer 43 includes an ultraviolet absorber, a flame retardant, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance aid, a phase difference reducing agent, a matting agent, an antibacterial agent, an antifungal agent, an antioxidant, You may include arbitrary components, such as a mold release agent and an antistatic agent.

  When the reflective layer 43 is the white layer, the reflective layer 43 can be laminated on the inclined surface 21 with, for example, an adhesive.

  When the reflective layer 43 is configured as the metal layer, the metal is not particularly limited. For example, a simple metal such as gold, silver, zinc, aluminum, copper, nickel, chromium, iron, titanium, zirconium , These alloys and oxides.

  The lower limit of the average thickness of the reflective layer 43 in the case of being configured as the metal layer is preferably 20 nm, and more preferably 30 nm. On the other hand, the upper limit of the average thickness is preferably 1000 nm, and more preferably 500 nm. If the average thickness is less than the lower limit, sufficient reflectivity may not be obtained. On the contrary, when the average thickness exceeds the upper limit, the production cost may increase.

  When the reflective layer 43 is the metal layer, the reflective layer 43 can be laminated on the inclined surface 21 by, for example, a known vapor deposition method.

<Advantages>
Since the light guide film 42 has the reflective layer 43 laminated on the inclined surface 21, the light utilization efficiency of the light caused by the emission of the light from the edge portion 17 is reflected by reflecting the light incident on the reflective layer 43. The decrease can be suppressed.

[Third embodiment]
<Light guide film>
The light guide film 52 in FIG. 10 is used in the backlight unit 11 in FIG. 2 instead of the light guide film 12 in FIG. The light guide film 52 in FIG. 10 has the same configuration as the light guide film 12 in FIG. 2 except that a wavy fine modulation structure is formed on the upper surface of the main body 53. The wavy fine modulation structure is formed over the entire upper surface of the main body 53 as shown in FIG. The ridge line direction in the wavy fine modulation structure and the end faces facing the plurality of LEDs are substantially parallel. As a result, the ridge line direction of the fine modulation structure is positioned substantially perpendicular to the traveling direction of the light beam propagating through the light guide film 52, so that the incident angle of the light beam on the upper surface varies due to the fine modulation structure. As a result, the light output from the upper surface of the light guide film 52 is improved. The “fine modulation structure” refers to a structure having fine undulation in one direction. In addition, this undulation does not need to have regularity as long as the ridge line and the valley line are continuous in one direction, and includes, for example, a shape in which a part of the ridge line and the valley line partially rises or falls.

  As a minimum of ridgeline interval p in the above-mentioned fine modulation structure, 1 mm is preferred, 10 mm is more preferred, and 20 mm is still more preferred. On the other hand, the upper limit of the ridge line interval p in the fine modulation structure is preferably 500 mm, more preferably 100 mm, and still more preferably 60 mm. If the ridge line interval p is less than the above lower limit, there is a possibility that light rays are emitted excessively from the upper surface of the light guide film 52. On the other hand, when the ridge line interval p exceeds the above upper limit, there is a possibility that the effect of improving the light output property of the light guide film 52 is low. In addition, although it is preferable that all the ridge line intervals p in the fine modulation structure are within the above range, some of the plurality of ridge line intervals p in the fine modulation structure may be outside the above range. Of the plurality of ridge line intervals, 50% or more, preferably 70% or more ridge line intervals may be within the above range.

  Moreover, as a minimum of the average height h of the ridgeline on the basis of the approximate virtual surface through which a plurality of valley lines in the fine modulation structure passes, 5 μm is preferable, 7 μm is more preferable, and 9 μm is further preferable. On the other hand, the upper limit of the average height h of the ridge line based on the approximate virtual plane through which the plurality of valley lines in the fine modulation structure passes is preferably 40 μm, more preferably 20 μm, and even more preferably 15 μm. If the average height h is less than the lower limit, the light guide film 52 may have a low effect of improving light output. On the other hand, when the average height h exceeds the upper limit, light may be emitted from the upper surface of the light guide film 52 too much.

  In addition, the said fine modulation structure can be formed by making the cross-sectional shape of T-die in an extrusion molding apparatus into the reverse shape of a cross-sectional shape perpendicular | vertical to the ridgeline of this fine modulation structure, for example.

<Advantages>
Since the light guide film 52 has a wavy fine modulation structure on the upper surface of the main body 53, the light output from the upper surface of the main body 53 can be improved as described above.

[Other Embodiments]
In addition, the manufacturing method of the light guide film which concerns on this invention, an edge light type backlight unit, and a light guide film can be implemented in the aspect which gave various change and improvement other than the said aspect. For example, the light guide film may be formed in a trumpet shape in which the edge portion on the end surface side facing the LED is widened on both the upper and lower surfaces. Further, the lower surface of the edge portion may be an inclined surface having a depression angle toward the end surface, and the upper surface may be a flat surface flush with the upper surface of the main body. Furthermore, you may have a plane site | part parallel to the upper surface and lower surface of a main body in a part of this edge part.

  The groove has a V-shaped cross section, but the cross section of the groove may have a shape as shown in FIG. 12, for example. In FIG. 12A, the cross section of the groove 61 is V-shaped, but the lower surface of the groove 61 is formed in parallel with the lower surface of the main body. Even when the lower surface of the groove 61 is formed in parallel with the lower surface of the main body, the light guide film uses light by sufficiently propagating the light incident on the groove 61 into the main body. Efficiency can be increased. In FIG.12 (b), although the cross section of the groove groove 62 is V-shaped, the bottom angle of this groove groove 62 is an obtuse angle. Moreover, in FIG.12 (b), the elevation angle of the upper surface and the depression angle of a lower surface of a concave groove on the basis of a parallel surface with the lower surface of a main body are equal. Even when the light guide film has such a configuration, the light use efficiency can be increased as compared with a conventional light guide film having no groove. In FIG.12 (c), the cross section of the groove 63 is formed in circular arc shape. The light guide film can improve the light use efficiency as compared with the conventional light guide film having no groove, even when the groove 63 has a circular cross section. In FIG. 12D, the cross section of the groove 64 is formed in a W shape (that is, a shape in which V-shaped grooves are continuously provided). In this light guide film, even when the groove 64 has a W-shaped cross section, light utilization efficiency is improved by sufficiently propagating the light incident on the groove 64 into the main body. be able to.

  In the light guide film, when a reflective layer is laminated on the upper surface of the edge portion, another reflective layer may be laminated on the lower surface of the edge portion. When the light guide film has a pair of reflective layers on the upper and lower surfaces of the edge portion, light can be prevented from being emitted from the upper and lower surfaces of the edge portion, so that the light use efficiency is remarkably improved. be able to. Further, the light guide film may have a reflective layer laminated only on the lower surface of the edge portion, for example.

  The light guide film may not have both a plurality of recesses and an annular ridge on the lower surface, and may have only a plurality of recesses on the lower surface, for example.

  When the wavy fine modulation structure is formed on the upper surface of the main body of the light guide film, the ridge line direction of the wavy fine modulation structure may be substantially perpendicular to the end faces facing the plurality of LEDs. Thereby, when the light beam propagating in the light guide film is reflected on the upper surface, the traveling direction of a part of the light beam is closer to the ridge line side, so that the light beam is easily collected on the ridge line direction side. In addition, since the light emitted from the upper surface is slightly diffused in the direction perpendicular to the ridge line by refraction at the fine modulation structure, the diffusibility of the emitted light is improved.

  The backlight unit preferably includes a plurality of LEDs, but may include only one LED. The backlight unit does not necessarily have a reflective sheet. In the backlight unit, for example, the top surface of the top plate may be formed as a reflective surface, and the light guide film may be directly superimposed on the top surface of the top plate.

  The backlight unit does not need to be a one-side edge light type backlight unit in which one or a plurality of LEDs are disposed only along one end surface of the light guide film, but on a pair of opposite end surfaces of the light guide film. It may be a double-sided edge light type backlight unit in which a plurality of LEDs are arranged along, or an all-around edge light type backlight unit in which a plurality of LEDs are arranged along each end face of the light guide film. Moreover, in this case, it is preferable that the light guide film is formed in a trumpet shape at each end face facing the plurality of LEDs, and a groove is formed on each end face.

  The backlight unit can be used for relatively large display devices such as personal computers and liquid crystal televisions, mobile phone terminals such as smartphones, and portable information terminals such as tablet terminals.

  As described above, since the light guide film of the present invention can improve the light use efficiency even if the average thickness is thin, it is suitably used for various liquid crystal display devices such as high-quality transmissive liquid crystal display devices. It is done.

1 Liquid crystal display (ultra-thin computer)
2 Operation part 3 Liquid crystal display part 4 Liquid crystal panel 5 Casing for liquid crystal display part 6 Top plate 7 Upper surface support member 8 Hinge part 9 Casing for operation part 11 Backlight unit 12, 42, 52 Light guide film 13 LED
DESCRIPTION OF SYMBOLS 14 Optical sheet 15 Reflective sheet 16,53 Main body 17 End edge part 18,61,62,63,64 Groove groove 19 Recessed part 20 Raised part 21 Inclined surface 22 Lower surface 23 Upper surface 24 Lower surface 31 Rigid resin film 32, 33 Mold 34 Projection mold 43 Reflective layer 101 Edge light type backlight unit 102 Light guide plate 103 Light source 104 Optical sheet 105 Reflective sheet 106 Top plate

Claims (8)

A light guide film for an edge-light type backlight unit that has a synthetic resin as a main component, has an average thickness of 100 μm or more and 600 μm or less, emits light emitted from an LED from at least one end surface, and emits the light to the upper surface side. There,
The edge part on the end face side is formed in a trumpet shape that gradually increases in thickness toward the end face side,
A light guide film having a groove on the end face along the longitudinal direction.   The light guide film according to claim 1, wherein the upper surface of the end edge is an inclined surface having an elevation angle toward the end surface, and the lower surface is a flat surface that is flush with other regions.   The light guide film according to claim 1 or 2, wherein a cross section of the concave groove is formed in a V shape.   The light guide film according to claim 3, wherein the bottom angle of the V-shaped cross section of the groove is an acute angle.   5. The light guide film according to claim 3, wherein an elevation angle of an upper surface of the concave groove with respect to a plane parallel to a lower surface of the edge portion is larger than a depression angle of the lower surface of the concave groove.   The light guide film according to any one of claims 1 to 5, further comprising a reflective layer laminated on at least an upper surface of the edge portion. The light guide film according to any one of claims 1 to 6,
One or more LEDs disposed along at least one end face of the light guide film;
An edge light type backlight unit comprising: one or a plurality of optical sheets superimposed on the upper surface side of the light guide film. A light guide film for an edge-light type backlight unit that has a synthetic resin as a main component, has an average thickness of 100 μm or more and 600 μm or less, and emits light emitted from an LED from at least one end face and emits the light to the upper surface side. A manufacturing method comprising:
Heating the flat synthetic resin film;
And a step of pressing a convex mold along the longitudinal direction to at least one end face of the synthetic resin film after the heating step.

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