JP2013069575A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device compatible with dimensional changes of a light guide plate.SOLUTION: In the surface light source device including a light guide plate having an incident surface as one of the side faces and a first side face as well as a second side face connected to the incident surface, and a chassis fixing the light guide plate, a plurality of either first notches or protrusions are fitted to the first side face of the light guide plate, and a plurality of either second notches or protrusions are fitted to the second side face. The chassis is provided with a plurality of first engagement parts engaged with the plurality of either first notches or protrusions, respectively, and a plurality of second engagement parts engaged with the plurality of either second notches or protrusions, respectively. A gap between the first engagement part and either the first notch or protrusion in a normal direction of the incident surface is the narrowest for the first engagement part nearest to the incident surface, and a gap between the second engagement part and either the second notch or protrusion in a normal direction of the incident surface is the narrowest for the second engagement part nearest to the incident surface.

Description

  The present invention relates to an edge light type surface light source device, for example, a surface light source device used for a liquid crystal display device or the like.

  In a liquid crystal display device, since the liquid crystal display panel itself does not emit light, a surface light source device for supplying light to the liquid crystal display panel is required. There are two types of surface light source devices: a direct-type surface light source device in which a light source is installed on the back surface of a liquid crystal display panel, and an edge light type surface light source device in which a light source is installed on a side surface of the liquid crystal display panel. Edge light type surface light source devices are widely used because they are suitable for thinning.

  Such an edge light type surface light source device generally includes a light guide plate that emits light from the light source to the liquid crystal display panel side, and an LED (light emitting diode) or CCFL (cold cathode) disposed on the side of the light guide plate. A light source such as a tube), an optical sheet such as a prism sheet (having a groove structure having a ridge line parallel to the light incident surface) on the liquid crystal display panel side, and the like. A chassis to which these members are fixed as necessary is configured as a main component.

  The light guide plate is generally a substantially rectangular plate-like member (excluding a concave portion and a convex portion for attaching the light guide plate to the engaging portion of the chassis) that is slightly larger than the size of the display screen of the liquid crystal display device. A light exit surface that is a surface, a facing surface that faces the light exit surface, and a light incident surface that is at least one of the side surfaces sandwiched between the light exit surface and the facing surface. The light guide plate guides light incident from its light incident surface by repeatedly totally reflecting between the light exit surface and the opposing surface. Of the guided light, the light whose direction of travel has changed by entering a light scattering portion provided on the opposite surface and has exceeded the critical angle is emitted from the light exit surface and travels to the liquid crystal display panel side. .

  As a material for the light guide plate, a transparent plastic material having a high light transmittance, such as polymethyl methacrylate, polycarbonate, and a styrene / methyl methacrylate copolymer has been proposed. Among these, polymethyl methacrylate, which is a material with high transmittance and the least light loss in the light guide plate, is widely used, but polymethyl methacrylate has a dimensional change caused by changes in environmental conditions such as humidity and temperature. large.

  In a surface light source device using a light guide plate, the light guide plate and the light source are directly or indirectly fixed to the chassis so that the light source faces the light incident surface of the light guide plate. In terms of light utilization efficiency, it is preferable to reduce the distance between the light incident surface of the light guide plate and the light emitting surface of the light source (hereinafter also referred to as “clearance”). For the purpose of dealing with the above-described dimensional change of the light guide plate, it is desirable to ensure a certain amount of clearance.

  Furthermore, in order to fix the light guide plate to the chassis made of a different material (plastic material or metal material whose dimensional change is small due to environmental changes), it is not sufficient to simply secure the above-described clearance. It is desirable to adopt an allowable fixing method.

  As a fixing method that allows dimensional change, for example, as a countermeasure against thermal expansion of the light guide plate due to the heat of the fluorescent lamp, three tongues are provided on the short side of the light guide plate having a substantially rectangular light exit surface. The hole of the tongue side is a reference hole, the second tongue side located in the X direction from the reference hole has a long hole in the X direction, and the third tongue side located in the Y direction from the reference hole is A method has been proposed in which a long hole is provided in the Y direction so that the reference hole is engaged with the engagement protrusion of the chassis and positioned, and expansion and contraction in the XY direction is allowed (see, for example, Patent Document 1). .)

  As an example of the surface light source device used in the television receiver, a surface light source device shown in FIG. In this surface light source device, two opposing side surfaces of the light guide plate are light incident surfaces, and three notches are provided on each of the two side surfaces other than the light incident surface to engage with the engaging portions protruding from the chassis. It has a structure to be fixed. Here, the light guide plate is positioned with respect to the chassis by setting a narrow gap between the central cutout portion and the engagement portion engaged with the cutout portion. Further, by setting a wide gap between the notch portions at both ends and the engaging portion engaged with the notch portion, it is possible to cope with assembly variations and dimensional changes of the light guide plate.

JP 2002-250915 A

  In recent years, from the viewpoint of energy saving, liquid crystal display devices using edge light type surface light source devices using LEDs as point light sources have been widely adopted. Furthermore, in order to promote energy saving and cost reduction, it is necessary to reduce the number of LEDs used and to reduce the clearance between the light emitting surface of the LED, which is a point light source, and the light incident surface of the light guide plate. It is desired. However, in the surface light source device shown in FIG. 31, the clearance between the light incident surface of the light guide plate and the light emitting surface of the light source cannot be reduced to a certain extent. And this clearance needs to be ensured larger as the light guide plate becomes larger in a large liquid crystal television receiver.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source device corresponding to a dimensional change of a light guide plate, and capable of setting a clearance between a light emitting surface of a light source and a light incident surface of a light guide plate to be small. To do.

  As a result of studies to solve the above problems, the present inventor has provided notch portions or protrusion portions for position fixing on both side surfaces of the light incident surface of the light guide plate, and engages with the notches or protrusion portions. Set the gap in the normal direction of the light incident surface with the engaging portion of the chassis to be set small at the notch or protrusion closest to the light incident surface, and large at the other notch or protrusion. As a result, the present invention was completed. That is, according to one aspect of the present invention, a light exit surface that is a main surface, a facing surface that faces the light exiting surface, a light incident surface that is at least one of the side surfaces between the light exiting surface and the facing surface, and a light incident surface are connected. A surface light source device including a light guide plate having a first side surface and a second side surface, a light source unit arranged substantially parallel to a light incident surface, and a chassis for fixing the light guide plate and the light source unit. The first side surface of the light guide plate is provided with a plurality of first notches or projections, and the second side surface is provided with a plurality of second notches or projections, and the chassis Are a plurality of first engagement portions that respectively engage with the plurality of first notch portions or projection portions, and a plurality of second engagement portions that respectively engage with the plurality of second notch portions or projection portions. A first notch in which the first engaging portion is engaged with the first engaging portion. The gap in the normal direction of the light incident surface of the portion or the protrusion is the narrowest in the first engagement portion closest to the light incident surface, and the second engagement portion and the second engagement portion are The surface light source device is such that the gap in the normal direction of the light incident surface between the engaged second notch or protrusion is the narrowest in the second engagement portion closest to the light incident surface. Is the gist.

  According to the surface light source device of the present invention, even if the clearance between the light emitting surface of the light source and the light incident surface of the light guide plate is set small, it is possible to cope with dimensional changes due to the environment.

It is a schematic plan view which shows the engagement state of the surface light source device which concerns on 1st embodiment. It is a schematic plan view which shows the engagement state of the surface light source device which concerns on 2nd embodiment. It is the model top view and sectional drawing which show the engagement state of the surface light source device which concerns on 3rd embodiment. It is the model top view and sectional drawing which show the engagement state of the surface light source device which concerns on 4th embodiment. It is a schematic plan view which shows an example of the light-guide plate used with the surface light source device which concerns on 6th embodiment. It is a perspective schematic diagram of a light-guide plate. It is a plane schematic diagram which shows the some elliptical recessed part and convex part in the light-incidence surface of a light-guide plate. It is a perspective schematic diagram of LED. It is a surface profile figure which shows the specific example of the some recessed part or convex part in the light-incidence surface of a light-guide plate. It is a surface profile figure which shows the specific example of the some recessed part or convex part in the light-incidence surface of a light-guide plate. It is a microscope picture (AF) which shows the specific example of the some recessed part or convex part in the light-incidence surface of a light-guide plate. It is a microscope picture (GJ) which shows the specific example of the some recessed part or convex part in the light-incidence surface of a light-guide plate. It is a microscope picture of the specific example of a moth eye structure. It is a microscope picture of the specific example of the recessed part (groove | channel) which has a moth eye structure on the surface. It is a figure which shows an example of the method of providing a some recessed part or convex part in the light-incidence surface of a light-guide plate. It is a cross-sectional schematic diagram of a seal type. It is a plane schematic diagram of a seal type. It is a figure which shows the method of slitting in roll shape in preparation of a tape type | mold. It is a figure which shows the definition of FWMH. It is a plane schematic diagram which shows an example of the light-scattering process in the opposing surface of a light-guide plate. It is explanatory drawing of a dot density. It is a figure which shows an example of the light-scattering process in the opposing surface of a light-guide plate. It is a figure which shows an example of the light-scattering process in the opposing surface of a light-guide plate. It is a plane schematic diagram which shows arrangement | positioning of a light-guide plate and a point light source. It is a cross-sectional schematic diagram of the principal part of the display apparatus using the surface light source device which concerns on this embodiment. It is a schematic plan view of a liquid crystal display device. It is a figure which shows the structure of the television receiver using the surface light source device which concerns on this embodiment. It is a plane schematic diagram which shows the clearance of the light emission surface of the light source in the surface light source device of a comparative design example, and the light-incidence surface of a light-guide plate. It is a plane schematic diagram which shows the clearance of the light emission surface of the light source in the surface light source device of an implementation design example, and the light-incidence surface of a light-guide plate. It is a schematic cross section which shows the principal part of the surface light source device of an Example. It is explanatory drawing of the direction which observes a brightness nonuniformity in an Example and a comparative example. It is a schematic plan view which shows an example of the engagement state of the conventional surface light source device.

  Embodiments of the present invention (hereinafter referred to as “present embodiments” or “embodiments”) will be described in detail with reference to the drawings. However, the present embodiment is not limited to the following description, and various modifications can be made within the scope of the gist. In addition, the dimension ratio of drawing is not limited to the ratio of illustration.

  The surface light source device according to the present embodiment includes a light exit surface that is a main surface, a facing surface that faces the light exiting surface, a light incident surface that is at least one of the side surfaces between the light exiting surface and the facing surface, and light incident A light guide plate having a first side surface and a second side surface in contact with the surface is included. Furthermore, the surface light source device according to the present embodiment includes a light source unit including a plurality of point light sources arranged substantially parallel to the light incident surface of the light guide plate, and a chassis for fixing the light guide plate and the light source unit.

  The light guide plate has a plurality of first cutouts or protrusions on the light output surface, for example, on a side shared with the first side surface, and a plurality of second cutouts on the side shared with the second side surface. Has a notch or protrusion. Moreover, the chassis has a plurality of first engaging portions and a plurality of second engaging portions. The plurality of first engaging portions of the chassis are respectively engaged with the plurality of first notches or protrusions of the light guide plate. Further, the plurality of second engaging portions of the chassis are respectively engaged with the plurality of second cutout portions or protrusion portions of the light guide plate. Note that the chassis having a plurality of engaging portions is not limited to a single member, but includes a combination of a plurality of members, and is not limited to a single material. Moreover, it is not limited to the opposing surface member of a light emission surface.

  Here, the gap in the normal direction of the light incident surface between the first engagement portion and the first notch portion or the projection portion with which the first engagement portion is engaged is the light incident surface. The first engaging portion closest to the gap is narrower than the gap in the other first engaging portion. In addition, a gap in the normal direction of the light incident surface between the second engagement portion and the second cutout portion or the protrusion portion with which the second engagement portion is engaged is formed on the light incident surface. The closest second engaging portion is narrower than the gap in the other second engaging portion.

  Hereinafter, this embodiment will be described in more detail. Here, in FIGS. 1 to 5, the horizontal direction (the direction parallel to the light incident surface and the long side direction of the light exit surface) in the drawing is the width direction, the vertical direction in the drawing (the normal direction to the light incident surface, and The short side direction of the light exit surface) is referred to as the depth direction, and the length in the width direction and the length in the depth direction of the member are simply referred to as the width and the depth, respectively.

(1. First embodiment)
The first embodiment is the one shown in FIG. 1, in which the depth of the shape of the notch portion of the light guide plate is changed.

  The light guide plate has three first cutout portions on a first side surface adjacent to the light incident surface (here, the right side surface in FIG. 1 is taken as an example). The shape of the first notch closest to the light incident surface has a specific width (X11) and depth (Y11). On the other hand, the other two first cutouts have the same width (X12) as the width (X11) of the first cutout closest to the light incident surface, but the depth (Y12). Is larger than the depth (Y11) of the first notch closest to the light incident surface.

  In addition, the light guide plate has three second cutout portions on a second side surface (here, the left side surface in FIG. 1 as an example) adjacent to the light incident surface. The shape of the second notch closest to the light incident surface has a specific width (X21) and depth (Y21). On the other hand, the other two second cutouts have the same width (X22) as the width (X21) of the second cutout closest to the light incident surface, but the depth (Y22). Is larger than the depth (Y21) of the second notch closest to the light incident surface.

  The light guide plate mounting surface of the chassis that fixes the light guide plate and the light source unit has first engaging portions at positions corresponding to the three first cutout portions of the light guide plate. The engaging portion is a member protruding from the light guide plate mounting surface, and specifically, a boss or a screw can be used. The cross-sectional shapes of these engaging portions are substantially the same, and have a specific width (x1) and depth (y1). The value obtained by adding the width (x1) of the first engaging portion to the allowable amount of assembly position displacement in the width direction and the amount of dimensional change due to the environmental change of the light guide plate in the width direction is the first notch described above. This corresponds to the part width (X11). The depth (y1) of the first engaging portion is substantially the same as the depth (Y11) of the first notch portion closest to the light incident surface described above, as long as it can be engaged without applying an excessive force. .

  Moreover, the light guide plate mounting surface of the chassis has second engaging portions at positions corresponding to the three second cutout portions of the light guide plate. The cross-sectional shapes of these engaging portions are substantially the same, and have a specific width (x2) and depth (y2). The value obtained by adding the assembly displacement tolerance in the width direction and the dimensional change amount of the light guide plate in the width direction to the width (x2) of the second engagement portion is the width of the second notch portion described above. It corresponds to (X21). The depth (y2) of the second engaging portion is substantially the same as the depth (Y21) of the second notch portion closest to the light incident surface described above, as long as it can be engaged without applying an excessive force. .

  As a result of engaging the notch portion of the light guide plate and the engagement portion of the chassis, the depth direction of the first engagement portion closest to the light incident surface and the first notch portion There is almost no gap in the depth direction between the second engagement portion closest to the light incident surface and the second cutout portion, for example. On the other hand, in the depth direction of the other first engagement portion and the first cutout portion, and in the depth direction of the other second engagement portion and the second cutout portion, , A gap occurs. With this structure, in the depth direction, the light guide plate is based on a line (indicated by a one-dot chain line in FIG. 1) connecting the first engagement portion closest to the light incident surface and the second engagement portion. As a line, the dimensions change on both sides due to environmental changes. Therefore, since the distance between the light incident surface and the reference line is kept small, it is possible to set the clearance on the light incident surface side smaller than that in the conventional example shown in FIG.

  In addition, although the number of the 1st notch part (engagement part) and the number of the 2nd notch part (engagement part) were each demonstrated here in three examples, it is four or more, Is the same. Further, the number of the first notch portions and the number of the second notch portions may be different, but the distance between the reference line and the light incident surface described above is the same on the left and right. It is preferable. In addition, in both the first notch portion and the second notch portion, the shape of the notch portion other than the notch portion closest to the light incident surface has been described as being the same, but may be different. If they are different, it is preferable to set the gap in the depth direction between the notch and the engaging portion to be larger as the distance from the light incident surface increases.

(2. Second embodiment)
The second embodiment is the one shown in FIG. 2, in which the depth of the shape of the engaging portion of the chassis is changed. In addition, the description which overlaps with 1st embodiment mentioned above is abbreviate | omitted.

  The light guide plate has three first cutout portions on a first side surface adjacent to the light incident surface (here, the right side surface in FIG. 2 is taken as an example). The shape of these notches is substantially the same, and has a specific width (X1) and depth (Y1).

  In addition, the light guide plate has three second cutout portions on a second side surface adjacent to the light incident surface (here, the left side surface in FIG. 2 is taken as an example). The shape of these notches is substantially the same, and has a specific width (X2) and depth (Y2).

  The light guide plate mounting surface of the chassis has first engaging portions at positions corresponding to the three first cutout portions of the light guide plate. The engaging portion is a member protruding from the light guide plate mounting surface. The shape of the first engaging portion closest to the light incident surface has a specific width (x11) and depth (y11). On the other hand, in the shapes of the other two first engaging portions, the width (x12) is substantially equal to the width (x11) of the first engaging portion closest to the light incident surface, but the depth (y12). Is smaller than the depth (y11) of the first engaging portion closest to the light incident surface. The value obtained by adding the assembly displacement tolerance in the width direction and the dimensional change due to the environmental change of the light guide plate in the width direction to the width (x11) of the first engagement portion is the first notch described above. This corresponds to the width (X1) of the part. The depth (y1) of the first engaging portion is substantially the same as the depth (Y1) of the first notch portion closest to the light incident surface described above, as long as it can be engaged without applying an excessive force. .

  Moreover, the light guide plate mounting surface of the chassis has second engaging portions at positions corresponding to the three second cutout portions of the light guide plate. The shape of the second engaging portion closest to the light incident surface has a specific width (x21) and depth (y21). On the other hand, the widths (x22) of the other two second engaging portions are substantially equal to the width (x21) of the second engaging portion closest to the light incident surface, but the depth (y22). Is smaller than the depth (y21) of the second engaging portion closest to the light incident surface. The value of the width (x21) of the second engaging portion, including the allowable amount of assembly position deviation in the width direction and the amount of dimensional change due to the environmental change of the light guide plate in the width direction, is the width of the second notch portion described above. It corresponds to (X2). The depth (y2) of the second engaging portion is substantially the same as the depth (Y2) of the second notch portion closest to the light incident surface described above, within a range where the second engaging portion can be engaged without applying an excessive force.

  As a result of engaging the notch portion of the light guide plate and the engagement portion of the chassis, the depth direction of the first engagement portion closest to the light incident surface and the first notch portion There is almost no gap in the depth direction between the second engagement portion closest to the light incident surface and the second cutout portion, for example. On the other hand, in the depth direction of the other first engagement portion and the first cutout portion, and in the depth direction of the other second engagement portion and the second cutout portion, , A gap occurs. With this structure, in the depth direction, the light guide plate is based on a line (indicated by a one-dot chain line in FIG. 2) connecting the first engagement portion closest to the light incident surface and the second engagement portion. As a line, the dimensions change on both sides due to environmental changes. Therefore, since the distance between the light incident surface and the reference line is kept small, it is possible to set the clearance on the light incident surface side smaller than that in the conventional example shown in FIG.

(3. Third embodiment)
The third embodiment is the one shown in FIG. 3 in which the depth of the shape of the protrusion of the light guide plate is changed. In addition, the description which overlaps with 1st embodiment mentioned above is abbreviate | omitted.

  The light guide plate has three first protrusions on a first side surface adjacent to the light incident surface (here, the right side surface in FIG. 3 is taken as an example). The shape of the first protrusion closest to the light incident surface has a specific width (X11) and depth (Y11). On the other hand, as for the shape of the other two first notches, the width (X12) is substantially equal to the width (X11) of the first protrusion closest to the light incident surface, but the depth (Y12) is It is smaller than the depth (Y11) of the first protrusion closest to the light incident surface.

  In addition, the light guide plate has three second protrusions on a second side surface (here, the left side surface in FIG. 1 as an example) adjacent to the light incident surface. The shape of the second protrusion closest to the light incident surface has a specific width (X21) and depth (Y21). On the other hand, the other two second protrusions have the same width (X22) as the width (X21) of the second protrusion closest to the light incident surface, but the depth (Y22) is the same. It is smaller than the depth (Y21) of the second protrusion closest to the light surface.

  The light guide plate mounting surface of the chassis has first engaging portions at positions corresponding to the three first protrusions of the light guide plate. As the engaging portion, for example, a plate-like member having a concavo-convex shape for fixing the protruding portion of the light guide plate with the light guide plate mounting surface of the chassis between the upper and lower sides can be used. The cross-sectional shapes of the spaces in which the protrusions of these engaging portions enter are substantially the same, and have a specific width (x1) and depth (y1). The value obtained by adding the width (x1) of the first engaging portion to the allowable amount of assembly position deviation in the width direction and the amount of dimensional change due to the environmental change of the light guide plate in the width direction is the first protrusion described above. Corresponds to the width (X11). The depth (y1) of the first engagement portion is substantially equal to the depth (Y11) of the first protrusion closest to the light incident surface in a range that allows engagement without applying an excessive force.

  Moreover, the light guide plate mounting surface of the chassis has second engaging portions at positions corresponding to the three second protrusions of the light guide plate. The cross-sectional shapes of the spaces in which the protrusions of these engaging portions enter are substantially the same, and have a specific width (x2) and depth (y2). The value obtained by adding the assembly displacement tolerance in the width direction and the dimensional change amount of the light guide plate in the width direction to the width (x2) of the second engagement portion is the width (X21) of the second protrusion. It corresponds to. The depth (y2) of the second engaging portion is substantially the same as the depth (Y21) of the second projecting portion closest to the light incident surface in a range that allows engagement without applying an excessive force.

  As a result of engaging the projection portion of the light guide plate and the engagement portion of the chassis, a gap in the depth direction between the first engagement portion closest to the light incident surface and the first projection portion In addition, there is almost no gap in the depth direction between the second engagement portion closest to the light incident surface and the second protrusion, for example. On the other hand, there are gaps in the depth direction of the other first engagement portion and the first projection portion, and in the depth direction of the other second engagement portion and the second projection portion. Occurs. With this structure, in the depth direction, the light guide plate is based on a line (indicated by a one-dot chain line in FIG. 3) connecting the first engagement portion closest to the light incident surface and the second engagement portion. As a line, the dimensions change on both sides due to environmental changes. Therefore, since the distance between the light incident surface and the reference line is kept small, it is possible to set the clearance on the light incident surface side smaller than that in the conventional example shown in FIG.

(4. Fourth embodiment)
The fourth embodiment is the one shown in FIG. 4 in which the depth of the shape of the space serving as the engagement portion of the chassis is changed. In addition, the description which overlaps with 1st embodiment mentioned above is abbreviate | omitted.

  The light guide plate has three first protrusions on a first side surface adjacent to the light incident surface (here, the right side surface in FIG. 4 is taken as an example). The shapes of these protrusions are substantially the same, and have a specific width (X1) and depth (Y1).

  The light guide plate has three second protrusions on a second side surface (here, as an example, the left side surface in FIG. 4) adjacent to the light incident surface. The shape of these protrusions is substantially the same, and has a specific width (X2) and depth (Y2).

  The light guide plate mounting surface of the chassis has first engaging portions at positions corresponding to the three first protrusions of the light guide plate. The shape of the space in which the protrusion of the first engaging portion closest to the light incident surface enters has a specific width (x11) and depth (y11). On the other hand, in the shape of the space in which the projections of the other two first engaging portions enter, the width (x12) is substantially equal to the width (x11) of the first engaging portion closest to the light incident surface. However, the depth (y12) is larger than the depth (y11) of the first engaging portion closest to the light incident surface. The width of the first protrusion is obtained by adding the width (x11) of the first engaging portion to the allowable amount of assembly position deviation in the width direction and the amount of dimensional change due to the environmental change of the light guide plate in the width direction. It corresponds to (X1). The depth (y1) of the first engaging portion is substantially the same as the depth (Y1) of the first protrusion closest to the light incident surface, as long as it can be engaged without applying an excessive force.

  Moreover, the light guide plate mounting surface of the chassis has second engaging portions at positions corresponding to the three second protrusions of the light guide plate. The shape of the space in which the protrusion of the second engaging portion closest to the light incident surface enters has a specific width (x21) and depth (y21). On the other hand, in the shape of the space in which the projections of the other two second engaging portions enter, the width (x22) is substantially equal to the width (x21) of the second engaging portion closest to the light incident surface. However, the depth (y22) is larger than the depth (y21) of the second engaging portion closest to the light incident surface. The width of the second protrusion is obtained by adding the width (x21) of the second engaging portion to the allowable amount of assembly position deviation in the width direction and the amount of dimensional change due to the environmental change of the light guide plate in the width direction. It corresponds to (X2). The depth (y2) of the second engaging portion is substantially the same as the depth (Y2) of the second projecting portion closest to the light incident surface in a range that allows engagement without applying an excessive force.

  As a result of engaging the projection portion of the light guide plate and the engagement portion of the chassis, a gap in the depth direction between the first engagement portion closest to the light incident surface and the first projection portion In addition, there is almost no gap in the depth direction between the second engagement portion closest to the light incident surface and the second protrusion, for example. On the other hand, there are gaps in the depth direction of the other first engagement portion and the first projection portion, and in the depth direction of the other second engagement portion and the second projection portion. Occurs. With this structure, in the depth direction, the light guide plate is based on a line (indicated by a one-dot chain line in FIG. 4) connecting the first engagement portion closest to the light incident surface and the second engagement portion. As a line, the dimensions change on both sides due to environmental changes. Therefore, since the distance between the light incident surface and the reference line is kept small, it is possible to set the clearance on the light incident surface side smaller than that in the conventional example shown in FIG.

(5. Other embodiments)
In the above, an embodiment in which the depths of the plurality of notches or protrusions of the light guide plate take the same value and the depths of the engagement portions of the chassis take different values, and the plurality of notches of the light guide plate Alternatively, the embodiment has been described in which the depths of the protrusions have different values and the depths of the plurality of engaging portions of the chassis have the same value. However, even when the depths of the plurality of notches or protrusions of the light guide plate take different values and the depths of the engagement portions of the chassis take different values, the plurality of notches or portions of the light guide plate The gap between the depth of the protrusion and the depth of the plurality of engaging portions of the chassis is small at the notch or protrusion closest to the light incident surface, and is large at the other notch or protrusion. If the condition is satisfied, an embodiment of the present invention (hereinafter referred to as “fifth embodiment”) is obtained.

  The first to fifth embodiments have been described above in which the notch (or protrusion) of the light guide plate and the engagement portion of the chassis have a one-to-one correspondence.

  Furthermore, as a sixth embodiment, the light guide plate has notches (or protrusions) that do not correspond to the chassis engaging portions in addition to the notches (or protrusions) that correspond to the chassis engaging portions. May be.

  For example, in the light guide plate shown in FIG. 5, a surface light source device combined with a chassis having an engagement portion corresponding to the cutout portions of A1, A2, and A3, and a relationship corresponding to the cutout portions of B1, B2, and B3. It can be used for both a surface light source device combined with a chassis having a joint. Therefore, the light guide plate shown in FIG. 5 can be used in various surface light source devices, and it is possible to contribute to the reduction of the number of parts in a multi-product manufacturing line.

Next, members constituting the surface light source device according to the present embodiment will be described.
<1. Light guide plate>
Since the notch and the protrusion provided on the side surface adjacent to the light incident surface of the light guide plate used in the surface light source device according to the present embodiment are as described above, other elements are shown in FIG. This will be specifically described with reference to FIG. In FIG. 6, the description of the notch and the protrusion is omitted in order to avoid complication of the drawing.

<1.1 Concavity and convexity processing on the light incident surface of the light guide plate>
The light guide plate included in the surface light source device according to the present embodiment preferably has a plurality of concave portions and / or convex portions in at least a partial region of the light incident surface 12. By diffusing light through the plurality of concave portions and / or convex portions, it is possible to reduce luminance unevenness due to hot spots.

  Here, when a light guide plate is used in combination with a plurality of point light sources, a hot spot can be obtained with a uniform luminance at the center of the light exit surface (a place far away from the light source), but the light entrance surface of the light exit surface. In the vicinity, the portion directly facing between the point light sources is dark, while the portion facing the point light source is bright.

  The at least part of the light incident surface 12 provided with the plurality of concave portions and / or convex portions preferably includes at least a partial region of the light incident surface 12 that faces the point light source. It is more preferable that alignment is unnecessary. As the plurality of recesses and / or projections, the opening or the bottom surface is a plurality of recesses or projections having an anisotropic shape that is long in a direction perpendicular to the light exit surface (direction 14 in FIG. 6). Since it is excellent in the effect of diffusing light in the arrangement direction of point light sources (direction 15 in FIG. 6), it is more preferable.

  In the light guide plate 1 shown in FIG. 6, a plurality of recesses or projections having an anisotropic shape whose opening or bottom is long in a direction perpendicular to the light exit surface are provided on the light entrance surface 12 substantially perpendicular to the light exit surface 11. It is a groove.

  When the angle between the major axis of the opening (bottom) of the recess (convex) and the direction perpendicular to the light exit surface is 40 degrees or less (even if it is not 0 degree), the opening of the recess (convex) (Bottom surface) shall be “having a long anisotropic shape in a direction perpendicular to the light exit surface”, but the major axis of the opening (bottom surface) of the recess (convex portion) and the direction perpendicular to the light exit surface Is preferably 10 degrees or less, more preferably 8 degrees or less, more preferably 6 degrees or less, more preferably 4 degrees or less, and most preferably 0 degrees. is there. Here, the major axis of the opening (bottom surface) refers to the long side of the circumscribed rectangle that minimizes the area circumscribing the opening (bottom surface).

  The light incident surface may be provided with a concave portion (convex portion) whose opening (bottom surface) has a shape other than an anisotropic shape long in the direction perpendicular to the light outgoing surface. For example, a concave portion (convex portion) whose opening (bottom surface) has an isotropic shape such as a circle, or a concave portion whose opening (bottom surface) has an anisotropic shape but whose major axis is not parallel to the direction perpendicular to the light emitting surface. (Convex part) may be provided. However, the sum of the areas of the openings (bottom surfaces) of the recesses (projections) having an anisotropic shape with the opening (bottom surface) long in the direction perpendicular to the light exit surface is the opening of the other recesses (projections). It is preferable to exceed the total area of (bottom surface).

  The ratio of the major axis to the minor axis of the anisotropic shape (major axis / minor axis) is not limited, but is preferably 2 or more, more preferably 10 or more. Here, the minor axis and the major axis refer to the short side and the long side of the circumscribed rectangle having the smallest circumscribed area, respectively.

  The anisotropic shape is not limited, and specific examples thereof include a straight line (groove) as shown in FIG. 6 and a substantially elliptical shape as shown in FIG.

  The shape of the opening surface (bottom surface) of the concave portion (convex portion) can be determined by observing an arbitrary portion of the light incident surface with a microscope (such as a scanning electron microscope or a laser confocal microscope).

  The pitch in the direction parallel to the light exit surface of the concave portion (convex portion) is not limited, but the average pitch is preferably 100 μm or less, more preferably 65 μm or less, still more preferably 30 μm or less, and most preferably 15 μm. . The average pitch is preferably 580 nm (the central wavelength of visible light) or more, and more preferably 780 nm (the entire visible light region) or more.

  Since the light emitting surface size (width 102) of the LED shown in FIG. 8, which is a commonly used point light source, is about several millimeters, the average pitch in the direction parallel to the light emitting surface of the concave portion (convex portion) is such a value. If it sets to, sufficient number of recessed parts or convex parts can be allocated to the light emission surface of a point light source. Therefore, it is not necessary to strictly determine the accuracy of alignment between the point light source and the light incident surface of the light guide plate. Further, when the average pitch is set to such a value, the claw or the like is hardly caught on the concave portion or the convex portion during handling, and the handling property is improved. Furthermore, since the light diffused by the light guide plate included in the surface light source device according to the present embodiment is, for example, visible light (an electromagnetic wave of 380 nm to 780 nm), in order to sufficiently exhibit the diffusion effect by the concave portion or the convex portion, The average pitch is preferably a value as described above.

  Here, the pitch in the direction parallel to the light exit surface of the concave portion (convex portion) refers to the adjacent valley bottom (in the case of the concave portion) or peak in any cross section parallel to the light exit surface of the light incident surface with reference to FIG. This is the horizontal distance (in the direction parallel to the light incident surface) between the projections. If the valley bottom (mountain peak) is flat, the pitch is determined with the center as the valley bottom (peak peak).

  The average pitch in the direction parallel to the light exit surface of the recess (convex portion) is the pitch of the recess (convex portion) present at 100 μm arbitrarily extracted from any vertical cross section parallel to the light exit surface of the light entrance surface. Average value.

  The (average) pitch in the direction parallel to the light exit surface of the concave portion (convex portion) is observed and measured with a microscope (such as a scanning electron microscope or a laser confocal microscope) in an arbitrary cross section parallel to the light exit surface. Can be determined by

  The size (depth / height) of each recess (projection) is not limited to the numerical values exemplified here. For example, the minor axis of the opening (bottom surface) may be 580 nm to 100 μm, and 780 nm. It may be ˜60 μm or 1 to 20 μm. Further, the major axis of the opening (bottom surface) may be, for example, 5 μm or more and 2 cm or less.

  The depth (height) may be, for example, 500 nm to 100 μm, 700 nm to 50 μm, or 5 to 20 μm. The average depth (height) of the concave portion or convex portion is also preferably 500 nm to 100 μm, more preferably 700 nm to 50 μm, and further preferably 5 to 20 μm.

  Here, referring to FIG. 7, the depth of the concave portion is defined between the top of the higher mountain and the bottom of the concave portion among the peaks on both sides constituting each concave portion in an arbitrary cross section of the light incident surface. The distance in the direction perpendicular to the light incident surface, in other words, the difference in elevation between the top and bottom of the mountain. Moreover, the height of a convex part says the distance between the valley bottom of the deeper one of the troughs of the both sides which comprise each convex part, and the peak of a convex part. In addition, the average depth (height) of a recessed part or a convex part is made into the average value of the depth (height) of the recessed part (convex part) which exists in 100 micrometers extracted arbitrarily from the arbitrary vertical cross sections of a light-incidence surface. .

  The size of the concave portion (convex portion) can be determined by observing and measuring an arbitrary portion of the light incident surface with a microscope (such as a scanning electron microscope or a laser confocal microscope).

  However, when the shape of the recess (projection) is a groove (ridge), the length is preferably longer than the length of the light emitting surface of the point light source in the thickness direction of the light guide plate. That is, it is preferable that the length of the groove (畝) is not less than the size of the light emitting surface of the point light source and not more than the thickness of the light guide plate. In FIG. 6, the groove has a length that traverses the light incident surface 12 in the thickness direction of the light guide plate (from the light exit surface to the opposite surface). It does not have to cross the light surface 12.

  If at least one of the shape, size (depth, height) of the plurality of concave portions (convex portions) and the pitch in the direction 15 parallel to the light exit surface shown in FIG. 6 is randomly (irregularly) different. This is preferable because the effect of reducing luminance unevenness is improved.

  Here, being different at random means that a value (3 sigma) obtained by multiplying a standard deviation calculated from a plurality of measured values exceeds 10% of the average value.

  There is no particular limitation on the region where the concave portion or the convex portion on the light incident surface is arranged, and it can be appropriately determined according to the light emission distribution and arrangement of the light source used in combination with the light guide plate. That is, in the light guide plate included in the surface light source device according to the present embodiment, it is preferable that the concave portion or the convex portion is provided at least in the region of the light incident surface facing the light emitting surface of each point light source, The light incident surface may have a portion (region) having no concave portion or convex portion.

  Moreover, although there is no limitation in the density of a recessed part or a convex part, about the area | region which opposes the light emission surface of a light source among the light-incidence surfaces of a light-guide plate, the sum total of the area of the opening part (bottom surface) of a recessed part (convex part). Occupy 25% or more (more preferably 50% or more, still more preferably 70% or more) of the region.

  Specific examples of the plurality of concave portions or convex portions are shown in FIGS. 9A, 9B, A to F in FIG. 10, and G to J in FIG. The plurality of grooves (groove structure) shown in FIG. 9A is anisotropic with a diffusion angle in a direction perpendicular to the groove (defined by FWHM described later) of 60 degrees and a diffusion angle in a direction parallel to the grooves of 1 degree. It has the following diffusion characteristics. The groove structure shown in FIG. 9B has anisotropic diffusion characteristics in which the diffusion angle in the direction perpendicular to the groove is 30 degrees and the diffusion angle in the direction parallel to the groove is 1 degree.

Diffusion angles, average pitches (average pitch in the direction perpendicular to the major axis direction (grooves) of the openings of the recesses), and the plurality of recesses or protrusions shown in FIGS. 10A to F and G to J in FIG. The average depth is shown in Table 1. In Table 1, “horizontal” means a direction perpendicular to the direction of the major axis of the opening of the recess (perpendicular to the groove), and “vertical” means a direction parallel to the major axis of the opening of the recess ( The direction (parallel to the groove).

  A moth-eye structure may be provided on the surface of the plurality of concave portions or convex portions for the purpose of reducing reflection on the light incident surface and efficiently using incident light. Here, the “moth eye structure” means that convex portions having substantially the same shape with a height of 1 μm or less are substantially periodic (for example, a square lattice shape, a rectangular lattice shape, a square quadrangular lattice shape, a triangular lattice shape (honeycomb)). Alternatively, it means a fine uneven structure provided in a hexagonal lattice pattern with a pitch of about 50 to 500 nm. The height may be 50 to 500 nm or 100 to 300 nm.

  Specific examples of the moth-eye structure and the recesses (grooves) having the moth-eye structure on the surface are shown in FIGS. 12 and 13, respectively.

  A plurality of concave portions or convex portions (hereinafter referred to as “opening portions” or “bottom portions”) having a long anisotropic shape in the direction perpendicular to the light exit surface on the light incident surface of the light guide plate included in the surface light source device / display device according to the present embodiment. , There is no limitation on the method for forming the concavo-convex structure. For example, (1) a method of injection molding a light guide plate using a mold having a concavo-convex pattern corresponding to the concavo-convex structure, and (2) a light incident surface of the light guide plate using a transfer mold having a concavo-convex pattern corresponding to the concavo-convex structure A method of transferring the concavo-convex structure to the top, or (3) a method of bonding a film having the concavo-convex structure to a light guide plate using a translucent adhesive or the like can be used.

  As a method of (1), for example, a stamper having a concavo-convex pattern corresponding to the concavo-convex structure is disposed at a position corresponding to the light incident surface of a mold for forming the light guide plate, and the light guide plate having the concavo-convex structure is injection molded from the beginning. can do. This method is suitable for manufacturing a light guide plate for a surface light source device used for a relatively small (about 32 type or less) image display device.

  As a method of (2), for example, after forming a light guide plate (raw sheet for light guide plate production) that does not have a concavo-convex structure by extrusion molding or cast molding, a light incident surface (surface that becomes a light incident surface) The concavo-convex structure can be transferred using a transfer mold having a concavo-convex pattern corresponding to the concavo-convex structure.

  FIG. 14 shows a specific example of this method. In the method of FIG. 14, a plurality of transparent substrates 41 cut to a predetermined size are stacked, and light incident on the transparent substrate while heating a transfer roller 42 having a concavo-convex pattern corresponding to the concavo-convex structure (here, a groove structure) on the surface. The uneven structure is transferred by pressing against the surface. According to this method, since transfer can be performed collectively on a plurality of light guide plates, mass production is possible and quality is improved.

Specific examples of the method (3) are as follows. A sealing mold, and b. Two types of tape-type methods will be described.
a. Seal type For example, an ultraviolet curable resin layer is applied on a transparent base film made of polyethylene terephthalate, polycarbonate, polystyrene, or the like, and an uneven structure is formed on the ultraviolet curable resin layer by a method using a speckle pattern described later. Thus, a layer having an uneven structure is formed. Although there is no limitation in the thickness of a base film, it can be 20-250 micrometers, for example, Preferably it is 50-125 micrometers.

  Next, an adhesive is applied to the surface of the base film opposite to the surface on which the concavo-convex structure is formed, and a release film made of polyethylene terephthalate or the like is bonded thereon, or an adhesive film with a release film is attached. A multilayer film in which the pressure-sensitive adhesive side is covered with a release film is produced by laminating the layers. A specific example of the layer structure of such a multilayer film is shown in FIG. Both 5a and 5b in FIG. 15 are multilayer films provided with a release film on one side. In the multilayer film 5a, a release film 51, an adhesive layer 52, a base film 53, and a layer 54 on which a concavo-convex structure (here, a groove structure) is formed are laminated in order from the bottom. Further, in the multilayer film 5b, an adhesive layer 55 and a mount film layer 56 are further provided on the layer 54 on which the concavo-convex structure is formed, and the release film 51, the adhesive layer 52, the base film 53, the concavo-convex are formed in this order from the bottom. A layer 54 having a structure, an adhesive layer 55, and a backing film 56 are laminated. The release film 51 and the mount film 56 serve as a seal mount or a protective film during the manufacture of the light guide plate, and the thickness thereof is not limited. For example, depending on the material, it should be 20 to 100 μm. Can do. However, in order to perform the half-cut processing more easily, the mount film is preferably 50 μm or more, and more preferably 75 μm or more. Moreover, the thickness of the adhesion layer can be 10-100 micrometers, for example. When considering the balance between performance and cost, it is preferably about 15 to 50 μm, and more preferably about 20 to 25 μm.

  Next, this multilayer film is cut in accordance with the length (width) of the light incident surface of the light guide plate. Next, in the case of the multilayer film 5a, only the release film 51 is left, and in the case of the multilayer film 5b, the mount film 56. And the adhesive layer 55, and the remaining layer is cut into half the same width as the light incident surface (half cut), thereby forming a film having a concavo-convex structure having the same size as the light incident surface of the light guide plate ( A seal sheet is produced in which a plurality of uneven structure seals) are formed on the release film 51 (in the case of the multilayer film 5a) or the mount film 56 (in the case of the multilayer film 5b). As described above, in the case of the multilayer film 5a, the blade of the cutting means enters from the side of the layer on which the concavo-convex structure is formed during the half-cut process, and thus there is an advantage that the risk of breaking the concavo-convex structure is small. On the other hand, in the case of the multilayer film 5b, the blade of the cutting means enters from the side of the adhesive layer 52 during the half-cut process, so that the adhesive layer can be reliably cut and the adhesives stick together again. There is an advantage that the problem “is difficult to occur”. Examples of the half-cutting method include, but are not limited to, a method of putting a Thomson blade in the cutting direction, a method of rolling a roll blade in the cutting direction, and a method of burning to a desired depth using a laser. In addition, there exists an advantage that cutting waste does not generate | occur | produce when a laser is used. A schematic front view of the seal sheet thus produced is shown in FIG. In FIG. 16, each vertical line indicates a groove 61.

  Then, in the manufacturing process of the light guide plate and the assembly process of the surface light source device having the light guide plate, in the case of the multilayer film 5a, the film (uneven structure seal) on which the uneven structure is formed is peeled off from the release film 51 one by one. It is bonded to the light incident surface of the light guide plate via the layer 52. In the case of the multilayer film 5b, the film (uneven structure seal) on which the uneven structure is formed is peeled off from the adhesive layer 55 one by one, and then the release film 51 is peeled off and bonded to the light incident surface through the adhesive layer 52. Finally, if necessary, the air between the film and the light incident surface may be brought into close contact by removing with a roller or the like.

  Prior to bonding, surface adhesion such as excimer UV treatment or corona treatment is applied to the adhesive layer 52 and / or the light incident surface to break the surface molecular bond, and immediately the adhesive layer and the light incident surface are brought into close contact with each other. By doing so, the bonding strength can also be improved. Furthermore, if such a surface treatment is used, it is possible to bond the base film of the film having a concavo-convex structure and the light guide plate without using an adhesive, thereby reducing cost and improving reliability. Can do.

  According to this seal-type method, the bonding operation to the light incident surface is facilitated, and the number of used (bonded) seals can be easily managed, so that the light guide plate can be easily manufactured. Furthermore, transportation of the light guide plate manufacturing material is facilitated.

  When manufacturing the seal sheet, the multilayer film (5a, 5b) is cut shorter than the length (width) of the light incident surface of the light guide plate, and two or more multilayer films (seal) are assembled when assembling the surface light source device. ) May be bonded to the light incident surface. At this time, the multilayer film (seal) covers 2 mm or more outside (up and down, left and right) from the area facing the light emitting surface of the light source on the light incident surface (the gap or seam between the films is in the area facing the light emitting surface). It is preferable to position and bond together.

b. Tape type b. A tape-type method will be described with reference to FIG.
a. In the same manner as in the case of the seal type, a multilayer film 71 having a layer in which an uneven structure is formed is manufactured. Next, this is cut into the same width as the thickness of the light incident surface to form a plurality of tapes, each wound on a reel (not shown) and processed into a roll 72. At this time, it is preferable to wind up with a reel having a structure sandwiched between two disks so that the wound tape does not cause axial misalignment. The diameter of the wound tape is preferably smaller than the outer diameter of the disk.

  Then, in the manufacturing process of the light guide plate and the assembly process of the surface light source device and the illuminating device having the light guide plate, a tape (tape film) having a layer having a concavo-convex structure is fed out from the roll 72 to enter the light guide plate After cutting to the length of the light surface, it is bonded to the light incident surface, or after being bonded to the light incident surface, it is cut to the length of the light incident surface. For bonding, a. The same method as described in the seal-type method can be adopted.

  According to this method, the length for cutting the tape may be determined when the tape is bonded to the light guide plate. Therefore, one type of roll (a roll of a tape-like film having a layer on which a concavo-convex structure is formed) can be of various sizes. Can be used for manufacturing a light guide plate having a large thickness, and the versatility of the roll is high. Further, it is easy to automate and speed up the process of bonding the multilayer film 71 to the light guide plate.

  As the pressure-sensitive adhesive used in the method (3), it is preferable to use a pressure-sensitive adhesive corresponding to the optical application. Specifically, it is preferable to select the type and thickness of the pressure-sensitive adhesive so that the total light transmittance of the pressure-sensitive adhesive layer is 90% or more and the haze is 1.0 or less.

  Commercially available adhesives include CS9621, HJ9150W (manufactured by Nitto Denko), DH425A (manufactured by Sanei Kaken), ZACROS TR-1801A (manufactured by Fujimori Kogyo), PD-S1 (manufactured by Panac), MO-3006C, MO-3012C (manufactured by Lintec) ) Etc. can be used.

  In addition, the multilayer film formed with the concavo-convex structure is disposed in the vicinity of the light source when it is attached to the light guide plate and incorporated in the surface light source device, so that it can withstand the influence of heat from the light source. It is preferable to paste using. The pressure-sensitive adhesive satisfying such conditions varies depending on the material of the base film. For example, when the film base material is polyethylene terephthalate and the light guide plate material is polymethyl methacrylate resin, and used in an environment of 85 ° C., among the above-mentioned adhesives, ZACROS TR-1801A, PD-S1, MO -3006C is preferred. The pressure-sensitive adhesive that can withstand even in a high temperature environment of 100 ° C. is PD-S1, ZACROS TR-1801A.

  In addition, it is preferable that the multilayer film in which the concavo-convex structure is formed is attached to the light incident surface with an adhesive or the like and integrated with the light guide plate. That is, simply disposing the film having the concavo-convex structure between the light incident surface of the light guide plate and the light source diffuses the incident light inside the light guide plate to a wide angle, There is a tendency that it becomes difficult to eliminate luminance unevenness derived from spots and other point light sources.

  In addition, in order to improve the optical performance, it is also useful to add silicon fine particles having an average particle diameter of about 2 μm to the inner layer in order to improve the optical performance in the method (3). In the examples, an ultraviolet curable resin having no such internal diffusion performance is used.

  The concavo-convex pattern or concavo-convex structure corresponding to the concavo-convex structure is applied to the mold (stamper), transfer mold (transfer roller) used in the methods (1) and (2) or the film used in the method (3). There is no limitation on the forming method. For example, it may be formed by machining such as cutting or sandblasting, or may be formed by laser speckle pattern exposure. The method using speckle pattern exposure is suitable for forming a fine three-dimensional structure of about 10 μm or less, which is difficult by machining, and it is easy to obtain an appropriate irregularity.

  Specifically, when speckle pattern exposure is used, a random uneven structure can be formed as follows.

  For example, a random speckle pattern or a striped speckle pattern is generated by interference exposure using laser light, and this is irradiated to a photosensitive material such as a photoresist. Next, when the exposed photosensitive material is developed by a known method, a random uneven structure corresponding to the speckle pattern is formed on the photosensitive material.

  Note that the random speckle pattern or striped speckle pattern can be generated by, for example, diffusing laser light with a diffusion layer having strong anisotropy. Normally, when the laser beam is diffused by the diffusion layer and irradiated to the exposed surface, speckles are generated as circular unevenness. However, if the diffusion layer has a strong anisotropy, the speckles have a speckled or striped pattern. be able to. Furthermore, a desired random spot / striped pattern can be obtained by appropriately changing the wavelength of the laser light, the conditions for diffusing the laser light, and the like. Specifically, it can be generated by the method disclosed in paragraphs [0047] to [0057] of JP-T-2004-508585.

  The metal mold or transfer mold having a concavo-convex pattern corresponding to the concavo-convex structure is a sub-master mold formed by the above-described concavo-convex structure, and the metal is deposited on the sub-master mold by a method such as electroforming. It can be produced by transferring a concavo-convex pattern corresponding to the concavo-convex structure.

  In addition, a method for producing a fine concavo-convex pattern using a speckle pattern by interference exposure is well known. Yes.

  Although there is no limitation on the thickness of the light guide plate (the distance between the light exit surface and the facing surface facing this), it can be, for example, about 2.0 to 5.0 mm.

  The material of the light guide plate included in the surface light source device according to this embodiment is not particularly limited as long as it is translucent. For example, polymethyl methacrylate, polycarbonate, polystyrene, methyl methacrylate-styrene copolymer, and the like. It is possible to use a highly transparent polymer material generally used as a material for these optical components and an inorganic material such as glass. Among these, polymethyl methacrylate having high transmittance is preferable.

  In addition, the light guide plate included in the surface light source device according to the present embodiment includes organic and inorganic dyes and pigments, matting agents, heat stabilizers, flame retardants, antistatic agents, antifoaming agents, and color-adjusting as necessary. Additives such as an agent, an antioxidant, an ultraviolet absorber, an impurity scavenger, a thickener, a surface conditioner, and a mold release agent may be contained within a range that does not impair the object of the present invention.

  The uneven structure (plural recesses or protrusions) in the light guide plate included in the surface light source device according to the present embodiment has an anisotropic shape in which openings (bottom surfaces) of the recesses (protrusions) are long in a specific direction. It is preferable to have a diffusion angle in a specific direction, that is, a direction perpendicular to the major axis direction of the opening (bottom surface) of the recess (projection) depending on the surface shape, and the specific direction An anisotropic diffusion characteristic in which the diffusion angle in the direction parallel to the minimum is the minimum.

  Although there is no limitation on the specific value of the diffusion angle (the diffusion angle (FWHM) of the emitted light when a light beam is incident perpendicularly to the light incident surface), the diffusion angle in the direction parallel to the light emitting surface is 30 ° to 30 °. It is preferably 120 °, more preferably 40 ° to 100 °, and still more preferably 50 to 90 °. On the other hand, the diffusion angle in the direction perpendicular to the light exit surface is recommended to be less than 10 °, preferably less than 5 °, more preferably less than 1 °, and most preferably less than 0.5 °. preferable.

  The diffusion angle in the direction perpendicular to and parallel to the light exit surface can be adjusted by appropriately changing the shape, depth (height), pitch, etc. of each concave portion (convex portion). When the groove structure is formed using a pattern, these can be adjusted by appropriately changing the conditions for diffusing the laser beam.

  Further, it is preferable that the diffusion characteristics are substantially constant in the entire region where the uneven structure of the light incident surface is formed.

  Here, as shown in FIG. 18, the “diffusion angle” means an angle (FWHM: Full Width Half Maximum) that is twice the angle (half-value angle) at which the transmitted light intensity is attenuated to half the peak intensity. This diffusion angle can be measured by, for example, Photon Inc. Transmission of light incident on the concavo-convex structure from the normal direction of the surface on which the concavo-convex structure is formed, using a variable angle color difference meter such as Photon manufactured by Photon or Beam Profiler NanoScan or GC5000L manufactured by Nippon Denshoku Industries Co., Ltd. It can be obtained by measuring the angular distribution of light intensity (distribution of the intensity of transmitted light with respect to the emission angle). In particular, NanoScan is most suitable for measurement with respect to the characteristics with FWHM of 1 ° or less. Here, the normal direction of the surface on which the concavo-convex structure is formed refers to the direction indicated by 16 in FIG.

  Note that the diffusion angle is theoretically (Snell's law), if the substrate does not have internal diffusion performance, it is not affected by the refractive index of the substrate, and the material that forms the surface on which the concavo-convex structure is formed. Depends on refractive index. For this reason, if the manufacturing method of (3) above is adopted as a method for forming the concavo-convex structure on the light incident surface of the light guide plate, even if the diffusion angle is measured with the film having the concavo-convex structure alone, this is used as the light guide plate. Even if the diffusion angle is measured in the state of the final form bonded together, the measurement result does not change. Further, if the production methods (1) and (2) are adopted, a thin piece cut by a plane parallel to the light incident surface may be produced and the diffusion angle thereof may be measured.

  In addition, when the surface facing the surface to be measured is not smooth, the surface is made smooth by cutting or the like, or the surface shape of the surface to be measured is the same refraction as the material forming the surface It can be measured by transferring to a material having a refractive index and using it (even if the unevenness is inverted, the angular distribution of transmitted light intensity does not change, so the diffusion angle does not change).

  Furthermore, it is preferable that the transmitted light intensity of the light is 90% or more of the peak intensity at the emission angle = 0 ° when the light beam is incident on the light incident surface on which the uneven structure is formed from the normal direction. .

  As described above, the surface shape of the light incident surface on which the concavo-convex structure is formed is such that the angular distribution of the transmitted light intensity of light when a light beam is incident from the normal direction does not have a plurality of peaks and changes gently. It is preferable that it is such.

  In the light guide plate used in the surface light source device according to the present embodiment, unevenness in brightness such as hot spots can be reduced by the diffusion characteristics derived from the surface shapes of the plurality of concave portions or convex portions as described above, for example.

  In the light guide plate used in the surface light source device according to the present embodiment, the diffusion characteristics are realized by the surface shape of the concavo-convex structure. Therefore, by controlling the surface shape, it is possible to stably obtain the highly accurate diffusion characteristics. it can. Further, in the present embodiment in which the diffusion characteristics are realized by the surface shape, the refraction causing the diffusion is air (refractive index of approximately 1) and the material (resin or resin composition) constituting the concavo-convex structure (refractive index of approximately 1. 3 to 1.6), the recess portion (see, for example, Japanese Patent Application Laid-Open No. 2008-34234) using the refraction between the pressure-sensitive adhesive and the filler. The diffusion angle in the direction perpendicular to the major axis direction of the opening (bottom surface) of the convex portion can be a large value.

<1.2 Light Scattering Processing on Opposing Surface of Light Guide Plate>
In the light guide plate included in the surface light source device according to the present embodiment, a partial region (hereinafter referred to as “region B”) in the vicinity of the light incident surface of the facing surface that faces the light shielding region shielded by the frame of the light emitting surface. 19), the light scattering degree of the partial region directly facing the point light source is configured to be lower than the light scattering degree of the partial region directly facing the part between the point light source and the point light source. It is preferable to have a light scattering process as shown.

  In the region B, by providing a light scattering process configured such that the light scattering degree of the partial region directly facing the point light source is lower than the light scattering degree of the partial region directly facing the portion between the point light source and the point light source In combination with the concavo-convex structure provided on the light incident surface, specifically, the light scattering process provided in the vicinity of the light incident surface of such a light exit surface and / or its opposite surface, and the light incident surface The concavo-convex structure complements each other where the effect of reducing the luminance unevenness is insufficient, so that the uniformity of the luminance of the light exit surface is dramatically improved, and the P / L described later can be increased.

  The “partial region directly facing the point light source (or the portion between the point light source)” means that the direction parallel to the light incident surface of the light exit surface is the X axis, and the direction perpendicular to the light incident surface is Y. A partial area having the same X coordinate as the point light source (or the part between the point light source and the point light source) when used as an axis. “The light scattering degree of the partial area directly facing the point light source is the point light source and the point light source. “Lower than (or approximately equal to) the light scattering degree of the partial region directly facing the portion between the light sources” means that the partial region (point) facing the point light source when comparing the partial regions having the same Y coordinate. The partial area in which the light scattering degree of the partial area having substantially the same X coordinate as that of the light source directly faces the part between the point light source and the point light source (the partial area having substantially the same X coordinate as the part between the point light source and the point light source) ) Is lower (or substantially equal) than the light scattering degree.

  The light scattering degree of the opposite surface is applied so that the light scattering degree of the partial area facing the point light source is lower than the light scattering degree of the partial area facing the part between the point light source and the point light source. The region B is preferably a belt-like partial region parallel to the light incident surface in the region facing the light shielding region of the light exit surface, but it is not necessarily required to start from the light incident surface side end (Y = 0). There is no.

  As a specific embodiment of the configuration in which `` the light scattering degree of the partial region directly facing the point light source is lower than the light scattering degree of the partial region directly facing the portion between the point light source and the point light source, for example, a. Light scattering processing is performed in a region other than the partial region directly facing the point light source (light scattering processing is performed on the partial region directly facing the portion between the point light source and the point light source), b. Light scattering is applied to substantially the entire region B so that the degree of light scattering is lower in the partial region facing the point light source than in the other partial regions (the portion facing the portion between the point light source and the point light source). For the region, the degree of light scattering is higher than that of other partial regions).

  There is no limitation in light scattering processing, and those generally employed in the technical field of light guide plates can be used. For example, a plurality of diffusive dot patterns made of a reflective or diffusive material may be provided by stacking or printing, or a plurality of three-dimensional dot patterns such as concavo-convex shapes may be formed. There is no limitation in the shape of a dot, For example, circular, a square, etc. are mentioned, The magnitude | size can be about 0.1-2.0 mm, for example.

  The light scattering degree is, for example, the concentration of a reflective (diffusible) substance in a diffusive dot made of a reflective (diffusive) material (the higher the density, the higher the light scattering degree), and the shape of the uneven three-dimensional dot. (For example, the higher the height, the higher the light scattering degree), and the ratio of the area of the portion where the dots are formed (hereinafter referred to as “dot density”, represented by ρ. In the case where it changes stepwise, the dot density of the area is a perpendicular bisector of a line segment connecting the center of the dot 26 and the centers of the adjacent dots A to F as shown in FIG. It can be controlled by adjusting the ratio (%) of the area of the dot 26 to the area of the polygon 262 surrounded by 26a to 26f. The light scattering degree increases as the dot density increases. Dot density, for example, changes the area of each dot with a constant number of dots per unit area, or conversely changes the number of dots per unit area with a constant area of each dot (dot pitch) It is possible to make adjustments by changing both of them.

  As shown in FIG. 21, the area of the facing surface (hereinafter also referred to as “area A”) facing the display area that is not shielded by the frame of the light exit surface, including at least the area facing the display area, Light scattering processing is also applied to a region (a boundary area) which may be partly opposed). At this time, the range of the region A is preferably set so that a region C described later exists between the region A and the region B.

  In the region A, at least in the region facing the display region, the light scattering degree of the partial region directly facing the point light source, and the light scattering degree of the partial region directly facing the part between the point light source and the point light source Are preferably substantially equal.

  In the facing surface, the region C sandwiched between the region A and the region B is preferably a band-like region parallel to the light incident surface, and in that case, the width of the region C is preferably 0.2 mm or more, more preferably It is 0.5 mm or more, and most preferably 1 mm or more. Further, the upper limit of the width of the region C is preferably 3.0 mm or less, more preferably 2.0 mm or less, and most preferably 1.5 mm or less.

  In the region C, light scattering processing is not provided at least in a partial region directly facing a portion between the point light source and the light source processing may not be provided at all in the region C.

  In the example of FIG. 21, a partial area facing the point light source is located in a part of the area B (a strip-shaped area parallel to the light incident surface) in the vicinity of the light incident surface of the facing surface that faces the light shielding area of the light exit surface. Light scattering processing is performed so that the light scattering degree is lower than the light scattering degree of the partial area directly facing the part between the point light source and the light of the partial area directly facing the point light source. In the light scattering processing configured so that the scattering degree is lower than the light scattering degree of the partial area directly facing the part between the point light source and each point light source, each of the partial areas directly facing the point light source in the vicinity of the light incident surface By reducing the area of the dots, and by increasing the area of each dot in the partial area directly facing the portion between the point light source and the point light source near the light incident surface, the area of the partial region directly facing the light source in the vicinity of the light incident surface The light scattering degree of the partial area that directly faces the part between the light sources It is set to be lower than the degree.

  In the area A of the facing surface that faces the display area of the outgoing surface, the light scattering degree of the partial area that faces the point light source is approximately equal to the light scattering degree of the partial area that faces the part between the point light source and the point light source. Light scattering processing is applied so as to be equal. Specifically, when the light scattering degree is controlled by the dot density, the dot density ρ1 in the lowest dot density region and the highest dot density among the regions having the same distance from the light incident surface (regions having the same Y coordinate). The ratio (ρ2 / ρ1) of the dot density ρ2 in the high region is preferably ρ2 / ρ1 ≦ 1.2, more preferably ρ2 / ρ1 ≦ 1.1, and ρ2 / ρ1 = 1. Is most preferred.

  Light scattering processing configured such that the light scattering degree of the partial area directly facing the point light source is lower than the light scattering degree of the partial area directly facing the part between the point light source and the light shielding part / non-light shielding part (That is, the light scattering degree of the partial area directly facing the point light source is lower than the light scattering degree of the partial area directly facing the part between the point light source and the point light source) By arranging the light scattering processing thus configured in a region facing the light blocking region of the light exit surface, it is possible to prevent the luminance unevenness of the light exit surface from being viewed not only from the front but also from the diagonal.

  FIG. 22 shows another specific example of the light scattering processing of the opposing surface of the light guide plate. In the example of FIG. 22, in a partial region B (a strip-shaped area parallel to the light incident surface) in the vicinity of the light incident surface of the opposite surface that faces the light shielding region of the light exit surface, Dots are not formed, and dots are formed at a density that is twice to 20 times higher than the dot density in the area facing the display area only in the partial area that faces the part between the point light source and the point light source.

  In this way, by performing light scattering processing only on a partial region that directly faces the portion between the point light source and the point light source in the region B, a pseudo light source is generated between the point light source and the point light source. By overlapping the image of the point light sources on both sides, unevenness derived from the point light sources can be reduced.

  Further, in the example of FIG. 22, the light scattering degree of the partial area directly facing the point light source and the point light source in the display area and the surrounding area (the boundary area located at the boundary between the light shielding area and the display area) A light scattering process is performed so that the light scattering degree of the partial region that directly faces the portion between the point light source and the point light source is approximately equal to form a region A. And between the area | region A and the area | region B, the area | region C (band-like area | region parallel to a light-incidence surface) in which the light-scattering process is not provided exists.

  In addition, it is preferable that the area | region B starts from 1 mm or more outside from the line on the opposing surface facing the boundary line of the light-shielding area | region of a light emission surface, and a display area. By doing so, the above-described pseudo light source can be prevented from being visually recognized by the user when the surface light source device is used.

  In addition, the light scattering processing (light scattering processing to be a pseudo light source) applied to the partial region directly facing the portion between the point light source and the point light source in the region B is the center (intermediate between the point light source and the point light source). It is preferable to apply a gradation that increases the degree of light scattering toward. By doing so, the light arriving from the left and right point light sources strongly scatters toward the center part between the point light source and the point light source, and the natural pseudo-light source is not generated in the center of the pseudo light source scattering processed part. A light source unit can be provided.

  Here, with reference to FIG. 20, the dot density ρ (%) of a certain area refers to the center point of a specific dot (26) included in the area and the dots (A to F) adjacent to the specific dot. ) With the denominator being the area of a polygon (263) formed by a perpendicular bisector (26a-f) of a line segment connecting the center point of 26) The area ratio with the area of numerator as a molecule is expressed in%.

  In order to achieve further uniformity of the light emission distribution on the light exit surface, the light scattering degree near the light entrance surface and other light scattering processes will further increase the light scattering degree in the direction away from the light entrance surface. (For example, a gradation in which the dot area increases as the distance from the light incident surface increases, or a gradation in which the same size dots are disposed so that the pitch decreases as the distance from the light source increases).

  Further, in the case of a surface light source device for a display device, it is preferable that a uniform mountain-shaped light distribution with the highest luminance at the center of the screen is easy to visually recognize while improving the uniformity of the light output distribution. The light scattering processing provided on the light exit surface and / or the opposing surface may be further configured to increase the light scattering degree of the central portion.

  The light scattering process described above can be provided on the light exiting surface or both the opposing surface and the light exiting surface. However, when the light scattering processing is easy to be visually recognized, it is provided only on the opposing surface. It is preferable.

  Moreover, you may provide the groove structure which consists of a several groove | channel perpendicular | vertical to a light-incidence surface in the direction which does not perform light-scattering processing among a light emission surface and / or an opposing surface. Providing such a groove structure on the light exit surface and / or the opposing surface can suppress the spread of light emitted from the light exit surface, so that the light guide plate can be made suitable for local dimming.

<2. Surface light source device>
Next, the surface light source device according to the present embodiment will be described.

  FIG. 23 shows a schematic plan view of an example of the surface light source device according to the present embodiment.

  The surface light source device 9 according to the present embodiment includes a light guide plate 91, a plurality of point light sources 92 disposed in the vicinity of the light incident surface 93 of the light guide plate, and a light source unit arranged substantially parallel to the light incident surface. A chassis (not shown) for fixing the light guide plate and the light source unit, one or a plurality of optical sheets (not shown) laminated so as to cover the light emitting area of the light exit surface, and the optical sheet and the light absorbing sheet so as to face each other. And an arranged frame (not shown). FIG. 24 is a schematic cross-sectional view of the main part of an example of the surface light source device according to this embodiment.

<2-1. Point light source>
Although there is no limitation in a point light source, it is preferable to use LED (light emitting diode). Since the LED can obtain high-luminance light with low power consumption and emit light brightly even when the temperature is low, it is possible to provide a surface light source device and a lighting device having sufficient illuminance immediately after lighting. There is no limitation on the type of LED, for example, a one-chip type pseudo white LED that excites green and red phosphors by a blue LED, a multi-chip type that combines white / red / green / blue LEDs to produce white light, and the near ultraviolet One-chip type pseudo white LED that combines an LED and a red / green / blue phosphor may be used.

  As shown in the schematic diagram of FIG. 8, the LED 10 that can be used in the present embodiment has, for example, a box shape. The outer shape of the LED and the size of the light emitting surface are not limited, but the outer shape is about 5.6 mm (width) × 3.0 mm (height) × 1.0 mm (thickness), and the lateral width 102 of the light emitting surface 101 is 5 mm. The following are commonly used:

  The distance between the light emitting surface of the point light source and the light incident surface of the light guide plate is preferably 0.1 mm or more and 1.5 mm or less. More preferably, it is 0.1 mm or more and 1.0 mm or less. When the distance between the light incident surface and the light emitting surface is increased, the amount of light incident on the light guide plate is reduced by the inverse square law, and as a result, the total amount of light emitted from the light emitting surface is also reduced. Therefore, it is preferable that the distance between the light emitting surface of the point light source and the light incident surface of the light guide plate is short. On the other hand, since heat is generated around the point light source and the light guide plate expands due to the heat or moisture absorption, it is preferable to leave a gap that can withstand the expansion.

  Although there is no limitation on the arrangement method of the point light source, it is arranged on the straight line along the light incident surface of the light guide plate (parallel to the light emitting surface) at regular intervals (“equal interval” includes an error of ± 10%). It is preferable to do. In this case, the arrangement pitch P of the point light sources is generally, for example, about the width (outer shape) of the point light source to about 200 mm. From the viewpoint of preventing luminance unevenness, the point light sources should be arranged as densely as possible, and from the viewpoint of mounting restrictions on the substrate, a certain distance should be opened. The arrangement pitch of the point light sources is preferably 5 mm to 200 mm, more preferably 10 to 100 mm.

<2-2. Frame>
The surface light source device according to the present embodiment further includes an optical sheet laminated on the light exit surface of the light guide plate, and a light emitting region of the surface light source device disposed so as to face the outer edge portion of the light absorption sheet or the light exit surface. The plane shape defining the frame has a frame shape. The frame is made of a material that does not transmit the light from the point light source, and the display area is defined by, for example, an opening of the frame.

  The frame may be combined with the chassis to further include a cover portion that can accommodate the light guide plate and the point light source therein. In this case, the surface light source device can be made to have a clean appearance by hiding the point light source, the power supply device, and the like therein.

  The frame is configured such that the display area of the light exit surface of the light guide plate starts from the inside of the light entrance surface, and further, the area of the light exit surface located on the side closer to the light entrance surface than the display area includes stray light. In order to exclude the influence, a light absorbing sheet may be laminated.

  The region where the light scattering process is performed on the opposite surface of the light guide plate is outside the range facing the opening of the frame on at least one light incident surface side, preferably 0 to 10 mm (however, 0 mm is not included). , More preferably 1 to 6 mm, further preferably 1 to 4 mm, particularly preferably 2 mm. In this case, there is no possibility that the start line of the light scattering process can be visually recognized from the screen side, and there is a tendency that high in-plane (in the light emitting area) average luminance can be secured.

  23, the horizontal distance L between the light emitting surface of the point light source 92 and the display area 94, in other words, the area 94 when the area 94 corresponding to the display area is projected on the light guide plate 91, It is preferable that the distance L between the light incident surface 93 and the light incident surface 93 is designed to be secured to a certain level.

  Specifically, in the surface light source device according to the present embodiment, the horizontal distance L between the light emitting surface of the light source and the display area is set to L <P / 1.5 (with respect to the arrangement pitch P of the point light sources. Even when P / L> 1.5), luminance unevenness can be suppressed. Furthermore, it is good also as L <P / 2.5 (P / L> 2.5), L <P / 3.0 (P / L> 3.0), L <P / 4.0 (P / L) > 4.0).

  In the surface light source device, if the relationship between P and L can be designed as described above, a stylish display device in which the outer frame portion of the active area formed on the display panel called a frame is thin can be realized. Moreover, since the number of point light sources to be used can be reduced, power saving can be achieved. Note that the relationship between P and L in the conventional surface light source device is at most about P / L ≦ 1.4. In addition, although the magnitude | size of L is decided by balance with P as above-mentioned, it can be set to 0.1-30 mm, 0.1-20 mm, or 0.1-10 mm, for example.

  Even if the arrangement pitch P of the point light sources is changed or the horizontal distance L between the light emitting surface of the point light sources and the display area of the light guide plate is changed, if the P / L is the same value, the same luminance unevenness is obtained. Shows reduced performance.

<2-3. Optical sheet>
In the surface light source device according to the present embodiment, in addition to the light guide plate, the point light source, and the frame described above, one or a plurality of optical sheets generally employed in the edge light type surface light source device such as a diffusion sheet and a prism sheet. Is laminated on the light emitting area of the light exit surface of the light guide plate. Specifically, the diffusion sheet can be laminated on the light exit surface of the light guide plate. Furthermore, on the light exit surface of the light guide plate, in addition to the diffusion sheet, a polarizing sheet for avoiding optical loss in a prism sheet, a condensing sheet such as a lenticular lens sheet and a micro lens sheet, and a polarizing plate of a liquid crystal panel. Sheets can also be laminated.

  In particular, when a lens sheet having a groove structure having a ridge line substantially perpendicular to the light incident surface on which the LEDs are arranged is laminated on the light exit surface of the light guide plate, the luminance unevenness reducing effect according to the present embodiment is extremely high. The lens sheet is preferably a prism sheet in which the groove structure is configured by a substantially triangular prism. In addition, it is preferable to combine a lens sheet having a groove structure having a ridge line substantially parallel to the light incident surface on which the LEDs are disposed, since luminance unevenness when viewed from an oblique direction is improved. In this case, it is preferable to interpose a diffusion sheet between the prism sheet and the light guide plate because light scattering processing of the light guide plate becomes difficult to be visually recognized and fine unevenness is improved. Further, in order to prevent the optical sheet from being damaged due to interference with the display panel used in combination, a diffusion sheet is provided on the outermost side (the diffusion property is lower than the diffusion property of the diffusion sheet described above). It is preferable to dispose.

  The surface light source device according to the present embodiment has, on the surface thereof, a groove structure having at least a ridge line substantially perpendicular to the light incident surface on which the diffusion sheet and the LED are disposed, on the light exit surface side of the light guide plate. When four optical sheets of a prism sheet and a prism sheet having a groove structure having a ridge line substantially parallel to the light incident surface on which the LEDs are arranged and a diffusion sheet are laminated in this order, there is almost no luminance unevenness. In addition, a very high quality surface light source device can be obtained in which light scattering processing or the like provided on the light guide plate is not visually recognized.

  As the prism sheet and the diffusion sheet, those generally used in a surface light source device or the like can be used. For example, as a diffusion sheet (hereinafter referred to as “lower diffusion sheet”) in contact with the light exit surface of the light guide plate, the total thickness is 215 μm, and the breakdown is several μm to several on the display surface side on the 188 μm thick PET substrate. Transparent particles such as silica beads of the order of 10 μm are dispersed, and the beads are coated with a UV or thermosetting resin around 10 μm thick as a binder (wherein most of the beads are coated so as to protrude from the binder. Thus, an appropriate diffusibility and light condensing property are obtained. On the opposite side as viewed from the display surface side, a coating layer for preventing charging and adhesion is provided with a thickness of about 10 μm (the coating layer leads to conduction). This prevents problems due to close contact with the light plate, etc. A small amount of beads and a fatty acid salt for reducing the surface resistance are added to this coat layer.

  The diffusion sheet disposed on the display surface side (hereinafter referred to as “upper diffusion sheet”) has a total thickness of 220 μm, and the breakdown is several μm to several tens μm on the display surface side on the 188 μm thick PET substrate. Transparent particles such as silica beads of order are dispersed less than the lower diffusion sheet, and the beads are coated with UV or thermosetting resin around 10 μm thick as a binder (where many of the beads are coated so that they are embedded in the binder). This prevents damage due to interference with the panel, etc. while suppressing appropriate diffusibility.) In the same way as the lower diffusion sheet, it prevents charging and adhesion on the opposite side when viewed from the display surface side. The coating layer was provided with a thickness of about 10 μm (the coating layer prevents problems due to adhesion with the prism sheet, etc. In this coating layer, a small amount of beads, For. Upper diffusion sheet fatty acid salt to lower the surface resistance is added, from the viewpoint of preventing the adhesion to the panel, can be used often.) I shall take the same design or display surface side.

  As the prism sheet, for example, an optical sheet in which a UV curable resin is formed on a display surface side of a PET substrate having a thickness of 250 μm and a prism having a thickness of 15 μm to 20 μm and an apex angle of approximately 90 ° is formed at a pitch of approximately 50 μm. Can be used. On the opposite side when viewed from the display surface side, a coating layer for preventing charging and adhesion is provided in a thickness of 15 μm to 20 μm like the diffusion sheet, and adhesion with other laminated optical sheets and coefficient of friction are provided. It prevents problems such as damage caused by the increase. A small amount of beads and a fatty acid salt for reducing the surface resistance are added to this coat layer.

<2-4. Other components of surface light source device>
In addition to the components described above, the surface light source device according to the present embodiment can dispose a reflective sheet below the opposing surface of the light guide plate in order to improve the light utilization efficiency.

  In addition, as shown in FIG. 24, a chassis that houses a light guide plate and other members in combination with a frame is included.

  In addition, a power source that supplies power to the point light source may be included, and a control circuit that controls the amount of current and on / off may be included.

<3. Display device>
Next, a display device using the surface light source device according to this embodiment described in the schematic cross-sectional view of the main part in FIG. 24 will be described.

  The display device includes an active area that displays by adjusting light transmission of the surface light source device, a light shielding frame that defines the active area (hereinafter also referred to as “black matrix”), and a rear surface of the display panel. A surface light source device.

  Since the luminance unevenness occurs near the light entrance surface of the light guide plate and sufficient display quality cannot be guaranteed, the active area of the display panel should start from the inner side of the boundary line between the display area of the surface light source device and the light shielding area. It is preferable to be designed.

  The display panel is preferably a liquid crystal display panel. Conventionally used liquid crystal display panels can be used as the liquid crystal display panel. An example of the configuration is schematically shown in FIG. 25 and described below.

  FIG. 25 is a schematic front view of an example of the liquid crystal display panel 11. The outside of the dotted line 111 is a light shielding frame (black matrix) 113 and the inside is an active area 112. Panel wiring (not shown) and the like exist behind the light shielding frame (black matrix) 113. In FIG. 25, reference numerals 114 and 115 denote a source chip, which is a driver IC for applying a voltage to a source line (described later, not shown), and a voltage for applying a voltage to a gate line (described later, not shown). It is a gate chip which is a driver IC.

  In a transmissive liquid crystal display panel, generally, a large number of pixel electrodes arranged in a matrix on a transparent substrate are driven by active matrix elements arranged on the transparent substrate. An active matrix substrate in which an active matrix element and pixel electrodes are provided on a transparent substrate is provided with a liquid crystal layer in a stacked state, and a counter substrate is disposed so as to face the active matrix substrate with the liquid crystal layer interposed therebetween. ing. The counter substrate is a transparent substrate provided with a counter electrode, and this counter electrode is opposed to the display region in the liquid crystal layer.

  The active matrix element provided on the active matrix substrate is provided with a TFT (thin film transistor) as an active element connected to each pixel electrode. The active matrix element includes a plurality of gate lines arranged in parallel to each other along the row direction and a plurality of source lines arranged in parallel to each other along the column direction orthogonal to each gate line. Each TFT is disposed in the vicinity of the intersection between each gate line and each source line. Each TFT is connected to each of a gate line and a source line that form adjacent intersections.

  Each TFT is configured to be turned on by a gate signal supplied from a gate line to which each TFT is connected, and to supply a source signal supplied from a source line to which each TFT is connected to a pixel electrode connected thereto. Has been.

  In such a liquid crystal display panel, gate signals (horizontal synchronization) are usually line-sequentially arranged in the order along the column direction for each gate line arranged along the row direction on the active matrix substrate for each frame. Signal), and gate signals are continuously supplied to gate lines adjacent in the column direction.

  The display panel of the display device has a light shielding frame that defines an active area of the display device.

  The light shielding frame is made of a material that does not transmit the light from the point light source, and the region corresponding to the active area is an opening or a material that transmits the light from the point light source. Specific examples of such a light shielding frame include a glass substrate on which a color filter in which a light shielding agent such as carbon black is mixed only in a region (frame portion) other than the active area.

  The light shielding frame is configured such that the active area of the display device starts from the inside of the light incident surface of the light guide plate, and the active area is provided near the light incident surface of the light guide plate and / or the opposing surface. In addition, a region having a light scattering process configured so that the light scattering degree of the partial region facing the point light source is lower than the light scattering degree of the partial region facing the portion between the point light source and the point light source (described above) It is configured so as to start from the inner side (the side farther from the light incident surface of the light guide plate) than the region B).

  In other words, the region where the light scattering process is performed on the opposite surface of the light guide plate is outside of the line facing the inner frame of the light shielding frame on at least one light incident surface side, preferably 0 to 10 mm (however, 0 mm is not included), more preferably 1 to 6 mm, still more preferably 1 to 4 mm, and particularly preferably 2 mm outside. In this case, there is no possibility that the start line of the light scattering process can be visually recognized from the screen side, and high in-plane (in the active area) average luminance can be ensured.

  The display device using the surface light source device according to this embodiment can be used for various applications such as a portable information terminal and a monitor of a personal computer. For example, as shown in FIG. 26, the display device 121 according to this embodiment. Are combined with a front cabinet 122 provided with a speaker 1221; various circuit boards such as a TV tuner circuit board 123, a power circuit board 124, a control circuit board 125; a back cabinet 126, a stand 127, and the like. Can be manufactured.

The effects according to this embodiment will be described below based on specific design examples. The light guide plate is made of polymethyl methacrylate, and has the following physical properties, for example.
The coefficient of thermal expansion of Asahi Kasei Delpet (registered trademark: polymethyl methacrylate manufactured by Asahi Kasei Chemical Co., Ltd.) is 6 × 10 ⁻⁵ cm / cm · ° C. (measured by ASTM-D257). Moreover, the water absorption of polymethylmethacrylate is 0.3% (measured by ASTM-D570). Saturated water absorption is 0.4% at 20 ° C and 40% RH, 0.7% at 20 ° C and 60% RH, 1.1% at 20 ° C and 80% RH, and 1 at 20 ° C and 92% RH. There is data of 5% (Plastic Data Book 470-471 pages, published December 1, 1999, Industrial Research Council).
In the following examples and comparative examples, simply “gap” means a gap in the normal direction of the light incident surface of the light guide plate.

<Comparative design example>
A light guide plate having a light output surface depth of 409 mm was provided with a first notch and a second notch at the position shown in FIG. The engaging portion of the chassis is a circle having a cross-sectional shape of a diameter of 3.9 mmφ. The gap between the notch at the center of the light guide plate and the engagement portion at the center of the chassis is 0.1 mm, and the gap between the other notch portions of the light guide plate and the other engagement portions of the chassis is 2. 1 mm.

  When the thermal expansion is calculated when the temperature of the light guide plate increases by 40 ° C. from 20 ° C. to 60 ° C. due to environmental changes, it is 0.98 mm. Therefore, it expands by 0.49 mm in the vertical direction of the figure around the dotted line.

  When the water absorption amount of the light guide plate is increased by 0.4% from 0.4% to 0.8% due to a change in environmental humidity, the hygroscopic expansion is calculated as 0.4%, which is 1.63 mm. Therefore, it expands by 0.82 mm in the vertical direction in the figure around the dotted line.

  Therefore, when this design example is adopted, the clearance between the light incident surface of the light guide plate and the light emitting surface of the light source in a room temperature dry state is, for example, as an allowable environmental temperature change amount in addition to the assembly variation amount at the time of manufacture. It is necessary to ensure 0.82 mm, and in the following comparative example, it was set to 1.00 mm.

<Example design>
A light guide plate having the same light exit surface as that of the comparative design example having a depth of 409 mm was provided with a first cutout portion and a second cutout portion at the position shown in FIG. The engaging part of the chassis is a circle having a cross-sectional diameter of 3.9 mmφ. The clearance between the notch portion closest to the light incident surface of the light guide plate and the engagement portion closest to the light incident surface of the chassis is 0.1 mm, the other notch portions of the light guide plate and the other engagement of the chassis The gap between the two is 2.1 mm.

  The thermal expansion when the temperature of the light guide plate is increased by 40 ° C. from 20 ° C. to 60 ° C. due to environmental changes is 0.98 mm, as in the comparative design example. Therefore, centering on the dotted line portion, the expansion is 0.11 mm in the downward direction and 0.88 mm in the upward direction.

  When the moisture absorption of the light guide plate is increased by 0.4% from 0.4% to 0.8% due to environmental humidity change, the moisture absorption expansion is calculated as 0.4%. is there. Therefore, centering on the dotted line part, the figure expands 0.17 mm downward and 1.46 mm downward.

  Therefore, when this design example is adopted, the clearance between the light incident surface of the light guide plate and the light emitting surface of the light source in a room temperature dry state is, for example, as an allowable environmental temperature change amount in addition to the assembly variation amount at the time of manufacture. It would be sufficient to secure 0.17 mm, and in the following examples, it was set to 0.25 to 0.75 mm.

<Example>
As an example, a surface light source device shown in FIG. 29 was prepared.
A light guide plate (material: polymethyl methacrylate, thickness: 3.0 mm, short side length: 409 mm, long side length: 721 mm) of an implementation design example made of a substantially rectangular plate-like member was used. On the light incident surface (side surface on the long side) of the light guide plate, an average thickness in which a groove structure having the surface profile shown in FIG. 9A (average pitch: about 6 μm, average depth: about 4 μm) is formed is 125 μm. The polyethylene terephthalate film was affixed using a transparent double-sided adhesive sheet. On the opposite surface of the light guide plate, light scattering processing was performed in which circular diffusive dots having a diameter of 0.8 mm to 1.3 mm made of diffusing beads and a binder were provided in a staggered arrangement (in a triangular lattice pattern).

  As a point light source, LEDs (light emitting surface size 5.0 mm (width direction) × 3.0 mm (thickness direction), 36 LEDs) are arranged along the light incident surface of the light guide plate, and the arrangement pitch P is 16 mm and 18 mm. The distance (clearance: C) between the light plate and the light emitting surface of the LED was set to 0.25, 0.50, and 0.75 mm.

  A first prism sheet (the direction of the stripe is perpendicular to the direction in which the LEDs are arranged) and a second prism sheet (the stripe) on an area 4 mm or more away from the light entrance surface of the light guide plate (an area including the display area). The row direction was parallel to the direction in which the LEDs were arranged), and the diffusion sheets were laminated in this order.

  Further, a frame having an opening of a size of 395 mm × 700 mm and having a size that sufficiently covers the light guide plate and the LED is arranged on the light output plate side of the light guide plate (L = 8.3 mm). A device was made.

  Here, as shown in FIG. 29, the back side of the frame (surface facing the light exit surface of the light guide plate) is opposed to a part of the light exit surface in the vicinity of the light entrance surface (a region of 0 to 4 mm from the light entrance surface). The portion to be provided with a convex portion, the spacing between the frame and the vicinity of the light incident surface of the light guide plate by the convex portion is greater than the spacing between the frame and other regions. Is also narrower. The frame is made of black-colored plastic, and the sum of the reflectance of light having a wavelength of 555 nm at an incident angle of 5 ° and the transmittance of light having a wavelength of 555 nm at an incident angle of 0 ° is 5.756%. is there.

  With the surface light source device emitting light (with the point light source turned on), the front direction N (V = 0 °, H = 0 °), the oblique direction V (Vertical) = 60 ° and H ( (Horizontal) = 45 °), whether or not unevenness is visually recognized was evaluated. Here, as shown in FIG. 30, the above H is the inclination angle on the surface where the LEDs are arranged, and the above V is the inclination angle on the surface perpendicular to the surface where the LEDs are arranged, and a positive value is the display area. The direction that falls to the center.

  The evaluation results are shown in Table 1. In Table 1, ◯ indicates a state where periodic unevenness is not visually recognized, Δ indicates a state where slight periodic unevenness is visually recognized, and x indicates a state where periodic unevenness is visually recognized. In this example, the clearance is 0.50 to 0.75 mm when the pitch is 16 mm (P / L = 1.93), and the clearance is 0.8 when the pitch is 18 mm (P / L = 2.17). It was found that 25 to 0.50 mm was good, and that when the pitch was further expanded, the better region was shifted to the smaller clearance.

<Comparative example>
Using the light guide plate of the comparative design example made of a substantially rectangular plate-like member, the arrangement pitch P is 16 mm and 18 mm, and the distance (clearance: C) between the light guide plate and the light emitting surface of the LED is 1.00 mm. In the same manner as in the example except that it is installed in the front, the front direction N (V = 0 °, H = 0 °), the oblique direction V (Vertical) = 60 °, and H (Horizontal) = 45 are visually observed. It was evaluated whether unevenness was visually recognized from °).

  The evaluation results are shown in Table 1. In this comparative example, periodic unevenness was visually recognized from the oblique direction at both pitches of 16 mm and 18 mm.

From these results, when P / L is increased to around 2, it is possible to suppress unevenness by designing the light guide plate of the implementation design example to have a small clearance, but in the light guide plate of the comparative design example, However, it was difficult to suppress unevenness because the clearance could not be designed to be small.

  The surface light source device of the present invention can be used in various display devices such as notebook PCs, portable information terminals, desktop PC monitors, and digital cameras.

DESCRIPTION OF SYMBOLS 1 Light guide plate 11 Light exit surface 12 Light entrance surface 13 Groove 14 Light guide plate thickness direction 15 Direction parallel to light exit surface 16 Normal direction of light entrance surface 17 Notch portion 18 Projection portion 21 Chassis engagement portion 31 Light source unit 32 Clearance 41 between the light emitting surface of the light source and the light incident surface of the light guide plate Transparent substrate 42 Transfer roller 5a Multilayer film 5b having a layer in which a groove structure is formed Multilayer film 51 having a layer in which a groove structure is formed Release film 52 Adhesive Layer 53 Base film 54 Layer 55 in which groove structure is formed Adhesive layer 56 Mount film 61 Groove 71 Multilayer film 72 having a layer in which groove structure is formed Roll 9 Surface light source device 91 Light guide plate 92 Point light source 93 Light incident surface 94 Display Region 10 LED corresponding to the region
DESCRIPTION OF SYMBOLS 101 Light emission surface 102 Width of light emission surface 110 Liquid crystal display panel 112 Active area 113 Black matrix 114 Source chip 115 Gate chip 120 Television receiver 121 Display device 122 Front cabinet 1221 Speaker 123 TV tuner circuit board 124 Power supply circuit board 125 Control circuit board 126 Back cabinet 127 Stand 26 Specific dot 26a-f Vertical bisector 262 of the line segment which connects the center point of a specific dot and the center point of an adjacent dot Polygon AF surrounding a specific dot Adjacent dot L Horizontal distance P between the light emitting surface of the point light source and the display area

Claims (12)

A light exit surface that is a main surface, a facing surface that faces the light exit surface, a light incident surface that is at least one of the side surfaces between the light exit surface and the facing surface, and a first side surface connected to the light incident surface And a light source plate having a second side surface, a light source unit arranged substantially parallel to the light incident surface, and a chassis for fixing the light guide plate and the light source unit,
A plurality of first notches or protrusions are provided on the first side of the light guide plate, and a plurality of second notches or protrusions are provided on the second side. ,
The chassis includes a plurality of first engagement portions that respectively engage with the plurality of first cutout portions or protrusion portions, and a plurality of engagement portions that respectively engage with the plurality of second cutout portions or protrusion portions. A second engagement portion,
A gap in the normal direction of the light incident surface between the first engagement portion and the first cutout portion or the protrusion portion with which the first engagement portion is engaged is the light incident Narrowest at the first engagement portion closest to the surface,
A gap in the normal direction of the light incident surface between the second engagement portion and the second cutout portion or the projection portion with which the second engagement portion is engaged is the light incident Narrowest at the second engagement portion closest to the surface,
Surface light source device.   The cross-sectional areas of the plurality of first engaging portions are substantially the same, and the cross-sectional areas of the plurality of second engaging portions are substantially the same, and the first notch portion closest to the light incident surface is cut off. 2. The cross-sectional area of the second cutout portion closest to the light incident surface is smaller than the cross-sectional area of the other second cutout portion. The surface light source device described in 1.   The cross-sectional areas of the plurality of first engaging portions are substantially the same, and the cross-sectional areas of the plurality of second engaging portions are substantially the same, and the cross-sectional area of the first protrusion closest to the light incident surface. 2. The surface according to claim 1, wherein is larger than a cross-sectional area of the other first protrusion, and a cross-sectional area of the second protrusion closest to the light incident surface is larger than a cross-sectional area of the other second protrusion. Light source device.   The plurality of first cutout portions have substantially the same cross-sectional area, and the plurality of second cutout portions have substantially the same cross-sectional area, and the first engagement portion closest to the light incident surface is cut off. 2. The cross-sectional area of the second engaging portion closest to the light incident surface is larger than the cross-sectional area of the other second engaging portion. The surface light source device described in 1.   The cross-sectional areas of the plurality of first protrusions are substantially the same, the cross-sectional areas of the plurality of second protrusions are substantially the same, and the cross-sectional area of the first engaging part closest to the light incident surface is 2. The cross-sectional area of the second engaging portion that is smaller than the cross-sectional area of the other first engaging portion and closest to the light incident surface is smaller than the cross-sectional area of the other second engaging portion. Surface light source device. The shape of the light exit surface is substantially rectangular except for the notch and the protrusion, the light incident surface is one side including the long side of the rectangle, and the first side and the second side are Two sides including the short side of the rectangle,
The light incident surface is one side surface including the short side of the rectangle, and the first side surface and the second side surface are two side surfaces including the long side of the rectangle.
The surface light source device according to claim 1.   The surface light source device according to claim 1, wherein the light source unit includes a plurality of point light sources.   The surface light source device according to any one of claims 1 to 7, wherein the light incident surface has a plurality of concave portions or convex portions showing light diffusibility at least in part.   The surface light source device according to claim 1, wherein the light guide plate is made of polymethyl methacrylate resin. A gap in the normal direction of the light incident surface between the first engagement portion and the first cutout portion or the projection portion with which the first engagement portion is engaged is the light incident As the distance from the surface increases,
A gap in the normal direction of the light incident surface between the second engagement portion and the second cutout portion or the projection portion with which the second engagement portion is engaged is the light incident Increases as the distance from the surface increases,
The surface light source device according to claim 1.   The normal direction of the light incident surface of the first engagement portion closest to the light incident surface and the first cutout portion or the protrusion portion with which the first engagement portion is engaged The light incident surface of the gap, the second engagement portion closest to the light incident surface, and the second cutout portion or the protrusion portion with which the second engagement portion is engaged. The surface light source device according to claim 1, wherein both of the gaps in the normal direction are 0.1 mm or less. A display panel having an active area for displaying by adjusting light transmission;
The surface light source device according to claim 11 disposed on the back surface of the display panel;
A display device.