JP2011216271A - Plane light-emitting unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane light-emitting unit capable of improving uniformity through restraint of luminance unevenness, even with a lengthened interval between light sources and with a shortened interval from each point light source to an optical sheet.SOLUTION: In the plane light-emitting unit, the point light sources 3 having an angle at which a luminance in a light distribution of irradiation light is maximum within a range of +30° to +80° and -30° to -80° are discretely arranged, and at their front face side, an optical sheet 2 having a number of concave parts 2b or convex parts having a slanted face or a tapered face at least on a light-emitting face of a translucent resin sheet 2a are formed in array. As the optical sheet, convex ridge parts or concave groove parts may be arrayed as one set, and a plurality of the sets may be arrayed. The point light sources 3 have directivity in a slanted direction and the optical sheet 2 irradiates light incident from a slant backside nearly toward a front direction, so that degradation of luminance at a middle part between the point light sources can be restrained to enhance uniformity of light.

Description

  The present invention relates to a surface light emitting unit in which an optical sheet is provided on the front side of discretely arranged point light sources, and more specifically, a surface light emitting unit capable of improving uniformity of surface light emission by suppressing luminance unevenness. About.

  There are two types of backlight units for liquid crystal displays used in television receivers and personal computers: one with a direct light system in which a light source is arranged on the back side of the liquid crystal panel, and one side with a light guide plate arranged on the back side of the liquid crystal panel. There is an edge light type in which a light source is arranged. Conventionally, these backlight units generally use a linear light source such as a CCFL (Cold Cathode Tube) as a light source. Recently, those using an LED (Light Emitting Diode) have been put into practical use. Since LEDs have sufficient luminance, they are often used in a matrix or zigzag manner as point light sources on the back side of the liquid crystal panel.

  However, the LED has a strong directivity in the light distribution characteristics, and the light distribution is particularly biased in the front direction of the light emitting surface. Therefore, a general light containing a light diffusing agent is interposed between the LED and the liquid crystal panel. It is difficult to suppress luminance unevenness only by disposing a diffusion film. In particular, there is a disadvantage that the luminance unevenness increases as the distance between the light sources of the LED becomes longer and the distance from the LED to the light diffusion film becomes shorter. It was. Therefore, until now, the distance between the light sources of LEDs has been shortened to typically 30 mm or less, and the distance from the LED to the light diffusion film has been set as long as possible to reduce luminance unevenness. If the distance is shortened, the number of LEDs used increases, leading to an increase in cost, and increasing the distance from the LED to the light diffusion film is contrary to the recent trend of thinning television receivers. There's a problem.

  On the other hand, as a backlight unit of a liquid crystal display device, LEDs with plastic lenses are arranged in a matrix on a wiring board, and a general light diffusion sheet is provided on the front side thereof. The thing which formed the fine pattern which exhibits a light-diffusion effect with the mixture of a diffusion dust, a pigment, and an adhesive agent is proposed (patent document 1).

  In the backlight unit of Patent Document 1, light from the LED is diffused by both the fine pattern of the plastic lens of the LED and the light diffusion sheet. Therefore, it is presumed that the luminance unevenness is reduced and the uniformity is improved. However, the effectiveness of the luminance uniformity cannot be confirmed because it has not been proved experimentally to the extent that the luminance uniformity is actually improved.

JP 2006-18261 A

  The present invention has been made under the above circumstances, and the problem to be solved is that the distance between the light sources of the point light sources is set long, and the distance from the point light source to the optical sheet that exhibits the light diffusion action is shortened. It is another object of the present invention to provide a surface light emitting unit capable of sufficiently suppressing unevenness in luminance and greatly improving the uniformity.

In order to solve the above problems, the surface emitting unit of the present invention is a surface emitting unit in which an optical sheet is provided on the front side of discretely arranged point light sources,
The point light source is a point light source in which the angle at which the luminance becomes maximum in the light distribution of the emitted light is in the range of + 30 ° to + 80 ° and −30 ° to −80 °,
The optical sheet is an optical sheet in which a large number of concave or convex portions having inclined surfaces or tapered surfaces are arranged on at least the light exit surface of the translucent resin sheet, or at least on the light exit surface of the translucent resin sheet, A plurality of convex ridges or concave groove portions are arrayed along a certain direction, and the arrangement of these ridge portions or groove portions is arranged in such a manner that a plurality of ridge portions or groove portions having different shapes are arranged side by side. One set is an optical sheet in which a set of a plurality of flanges or grooves is repeatedly arranged in a line.

In the surface light emitting unit of the present invention, it is desirable that a light diffusing agent is contained in the optical sheet.
And, the inclination angle of the inclined surface of the concave portion or the convex portion, the inclination angle of the ridge line of the tapered surface of the concave portion or the convex portion, and the inclination angle of the inclined surface of the flange portion or the groove portion are all 10 ° or more and 70 ° or less. Desirably, the radius of curvature of the rounded tip of the concave or convex portion is preferably less than 100 μm.
Moreover, the distance D between the light sources of the adjacent point light sources is 40 mm or more and 60 mm or less, and the ratio (L / D) between the distance L from the point light source to the optical sheet and the distance D between the light sources is 0.2. It is desirable to be in the range of ~ 0.63.

  In the surface light emitting unit of the present invention, the point light source does not exhibit a directivity that has an angle at which the luminance becomes maximum in the light distribution of the emitted light as in the conventional LED, which is near 0 °, that is, in the front direction. It is a point light source having a directivity in an oblique direction in which the angle at which the luminance becomes maximum in the light distribution is in the range of + 30 ° to + 80 ° and −30 ° to −80 °, and the optical sheet has at least a light exit surface By arranging the concave portions or convex portions having the inclined surface or the tapered surface on the upper side, or by arranging the groups of the flange portions or the groove portions side by side, the light incident from the oblique rear side is substantially directed in the front direction. Because it is designed to emit light, the difference between the brightness of the area directly in front of the point light source and the brightness of the area between the point light source and the point light source is reduced. Degree (surface The uniformity of light emission) is greatly improved.

  When the optical sheet contains a light diffusing agent, the light passing through the optical sheet is strongly diffused by the light diffusing agent, so that the luminance uniformity is further improved as shown in test data described later. .

  Further, the inclination angle of the inclined surface of the concave portion or the convex portion of the optical sheet, the inclination angle of the ridge line of the tapered surface of the concave portion or the convex portion, and the inclination angle of the inclined surface of the flange portion or the groove portion are all 10 ° or more and 70 °. If it is within the following range, most of the light incident on the optical sheet from obliquely behind can be emitted to the front side, so that the luminance uniformity can be reliably improved as shown in test data described later. And when the curvature radius of the rounded front-end | tip part of the said recessed part or a convex part becomes small, the tendency for a uniformity to become high is seen, and a high degree of uniformity can be obtained as a curvature radius is less than 100 micrometers.

  In the surface light emitting unit of the present invention, the distance D between adjacent point light sources is as long as 40 mm or more and 60 mm or less, and the ratio of the distance L from the point light source to the optical sheet and the distance D between the light sources (L / Even if the distance L is shortened by setting D) within the range of 0.2 to 0.63, a high degree of uniformity can be obtained as shown in the test data to be described later. It is possible to save energy and to cope with the recent thinning of liquid crystal television receivers.

It is a disassembled perspective view of the surface emitting unit which concerns on one Embodiment of this invention used as a backlight of a liquid crystal display. It is a partial explanatory view of the same surface light emitting unit. It is a fragmentary top view of the optical sheet used for a same surface light emission unit. It is the AA line expanded sectional view of FIG. It is a fragmentary sectional view which shows the other shape of the recessed part of an optical sheet. It is a fragmentary sectional view which shows other shape of the recessed part of an optical sheet. It is a fragmentary top view which shows the other example of an optical sheet. It is a fragmentary top view which shows another example of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is the elements on larger scale of the optical sheet. It is an action explanatory view of the optical sheet, (a) shows the upper part of the point light source of the optical sheet, (b) the part away from the point light source upper part of the optical sheet in the right direction, (c) The part further away in the right direction of the optical sheet is shown. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is a fragmentary sectional view showing other examples of an optical sheet. It is explanatory drawing of the measurement point of a brightness | luminance when calculating | requiring the uniformity of a surface emitting unit. It is a graph which shows the relationship between the inclination | tilt angle of the inclined surface of the recessed part of the light emission surface, and uniformity in the surface emitting unit of Examples 1-4. It is a graph which shows the relationship between the uniformity and L / D in the surface emitting unit of Examples 5-8, and the relationship between the uniformity and L / D in the surface emitting unit of Comparative Examples 1-4. It is a graph which shows the relationship between the uniformity in the surface emitting unit of Examples 9-11, and L / D, and the relationship between the uniformity in the surface emitting unit of Comparative Examples 5-7, and L / D.

  Hereinafter, typical embodiments of a surface emitting unit according to the present invention will be described with reference to the drawings.

  The surface light emitting unit shown in FIG. 1 is used as a direct light type backlight unit in a liquid crystal display. This surface light emitting unit is provided in parallel with the wiring substrate 5 on the front side (upper side in FIG. 1) of the point light sources 3 arranged and mounted on the wiring substrate 5 in a matrix. The optical sheet 2 is arranged behind the liquid crystal panel 4 (downward in FIG. 1). Although not shown, between the optical sheet 2 and the liquid crystal panel 4, one or more conventionally known optical sheets other than the optical sheet used in the present invention, including a conventionally known light diffusion film, are arranged. May be.

  As the point light source 3, it is necessary to use the point light source 3 in which the angle at which the luminance is maximized in the light distribution of the emitted light is in the range of + 30 ° to + 80 ° and −30 ° to −80 °. A preferable representative example of such a point light source 3 is a lens-covered LED in which the LED is covered with a lens made of a transparent resin and the angle at which the luminance is maximized is adjusted within the above range. In this embodiment, as shown in FIG. 2, the cross-sectional shape of the lens 3b covering the white light emitting LED 3a is a flat semi-elliptical shape, so that the angles at which the luminance becomes maximum are around + 70 ° and around −70 °. A lens-covered LED adjusted to 1 is used. However, the conventional general LED is also covered with a lens to protect the element, but in the present specification, in order to provide the above light distribution characteristics as in the LED used in the present invention. Those covered with a lens are described as “lens-covered LED”, and those covered with a lens for protecting the element like a conventional general LED are described as “lens-less LED” or simply “LED”. To distinguish.

  Since the point light source 3 having an angle of maximum brightness of less than ± 30 ° has directivity in the front direction (0 °) in the light distribution characteristic like the conventional LED, the optical sheet 2 is provided on the front side of the point light source 3. However, the luminance of the area in the front direction of the point light source 3 is considerably higher than the luminance of the area in the middle of the point light source 3 and the point light source 3, and it is difficult to sufficiently suppress the luminance unevenness. On the other hand, the point light source 3 whose angle at which the luminance reaches a maximum exceeds ± 80 ° is incident on the optical sheet 2, particularly the incident light in the area directly in front of the point light source 3, and the emitted light from the optical sheet 2. Is considerably reduced, resulting in a disadvantage that the overall brightness is reduced.

  As the distance D between the light sources 3 and 3 adjacent to each other becomes shorter, the luminance unevenness decreases and the uniformity increases, but in the surface emitting unit of this embodiment, the distance D between the light sources is 40 mm or more and 60 mm. It is set below, and is considerably longer than the distance between light sources in the case of a conventional LED (usually 30 mm or less). The distance L from the point light source 3 to the optical sheet 2 (the distance L from the surface of the wiring board 5 on which the point light source 3 is mounted to the back surface of the optical sheet 2 as shown in FIG. 2) and the above-mentioned distance D between the light sources The distance L from the point light source to the optical sheet 2 is shortened so that the ratio (L / D) is in the range of 0.2 to 0.63. For this reason, the number of lens-covered LEDs mounted on the wiring board 5 as the point light source 3 is significantly reduced compared to the conventional case, and cost reduction and energy saving can be achieved, and the distance from the point light source 3 to the optical sheet 2 can be achieved. By shortening L, the liquid crystal display can be sufficiently reduced in thickness.

  In this surface light emitting unit, a point light source having an oblique directivity in the range of + 30 ° to + 80 ° and −30 ° to −80 ° at which the luminance in the light distribution is maximized is used as the point light source 3. For use, the distance D between the light sources is set to 40 mm to 60 mm as described above, and the ratio (L / D) between the distance L from the point light source 3 to the optical sheet 2 and the distance D between the light sources is 0.2. Even if it is set within the range of -0.63, the synergistic action with the specific optical sheet 2 described later can suppress luminance unevenness and increase the uniformity, but the distance D between the light sources is set to 60 mm. If the ratio (L / D) between the distance L from the point light source 3 to the optical sheet 2 and the distance D between the light sources is smaller than 0.2, there is a disadvantage that the uniformity of the luminance is lowered. On the other hand, when the distance D between the light sources is less than 40 mm and the L / D is more than 0.63, the uniformity of the brightness becomes considerably high, but the lens-covered LED mounted on the wiring board 5 as the point light source 3 is increased. Since the number is not much different from the conventional one, it is difficult to reduce costs and save energy, and since the distance L from the point light source 3 to the optical sheet 2 is not so shortened, it is difficult to cope with thinning of the liquid crystal display. The inconvenience arises.

  In the surface light emitting unit of this embodiment, the above-described lens-covered LED is used as the point light source 3, but the angles at which the luminance in the light distribution is maximized are + 30 ° to + 80 ° and −30 ° to −80 °. Of course, a point light source other than the lens-covered LED, for example, an incandescent light bulb, a light bulb type fluorescent lamp, a discharge lamp, etc., may be used as long as it is within the range. In addition, the LED 3a covered with the lens 3b may be a single element that emits white light as in this embodiment, or a combination of three elements of red light emission, green light emission, and blue light emission to emit white light by three-color synthesis. But you can.

  Further, in this embodiment, the point light sources 3 are arranged in the form of a matrix at equal intervals in the vertical and horizontal directions. However, the arrangement of the point light sources 3 may be a staggered arrangement obtained by rotating the matrix arrangement by 45 °. The arrangement pattern is not particularly limited as long as it is regularly and evenly arranged. Further, if the point light sources 3 are arranged so that the difference in density is relatively small and distributed almost on average, the arrangement may be random.

  As shown in FIGS. 3 and 4, the optical sheet 2 provided on the front side of the point light source 3 (upper side in FIGS. 1 and 2) is on at least the light exit surface (upper surface in FIG. 4) of the translucent resin sheet 2a. Further, the optical sheet is formed by arranging a large number of inverted concave quadrangular pyramid-shaped concave portions 2b having four inclined surfaces 2c each having an inverted isosceles triangle. The inclination angle θ (inclination angle with respect to the light exit surface) of the inclined surface 2c of the recess 2b is preferably in the range of 10 ° or more and 70 ° or less, and even if the inclination angle θ is less than 10 °, Even if it becomes larger than 70 °, the luminance unevenness becomes large, and it becomes difficult to obtain sufficient uniformity. As supported by test data (Table 1 and FIG. 22) of Examples described later, the luminance uniformity becomes maximum when the inclination angle θ of the inclined surface 2c is around 45 °, and the inclination angle θ is larger than this. Although the brightness uniformity decreases even if it becomes smaller or smaller, since a high uniformity of 95% or more is obtained when the tilt angle θ is 35 ° to 55 °, a more desirable range of the tilt angle θ of the inclined surface 2c. Is in the range of 30 ° to 60 °, and a highly desirable tilt angle θ is in the range of 35 ° to 55 °.

  The luminance uniformity referred to in the present invention is an intermediate portion between the point light source 3 and the point light source 3 with respect to the luminance B1 in the region directly in front of the point light source 3 (directly above) measured from the front (upper) of the optical sheet 2. The ratio (B2 / B1) of the luminance B2 of the area is expressed as a percentage. When the uniformity is 100%, the luminance B1 of the area in the front direction of the point light source 3 and the point light source 3 and the point light source 3 This means that the brightness B2 of the intermediate area is equal and there is no brightness unevenness.

  The size of the inverted regular quadrangular pyramid-shaped recess 2b is preferably set such that the length a of one side (upper side) thereof is about 30 to 600 μm. ) Is sufficiently refracted and diffused by the four inclined surfaces 2c of each recess 2b, and can be emitted to the front side with a substantially uniform light amount. When the length a of one side is shorter than 30 μm, it becomes difficult to form the inverted regular quadrangular pyramid-shaped recess 2b. When the length a of one side is longer than 600 μm, the light refraction and diffusing action are greatly reduced, resulting in uneven brightness. Since suppression becomes inadequate, neither is preferable. A more preferable side length a of the recess 2b is 100 to 500 μm, and a very preferable side length a is 130 to 250 μm.

  The depth d of the deepest portion of the recess 2b is determined depending on the length a of one side of the recess 2b and the inclination angle θ of the inclined surface 2c. The depth d of the deepest portion is a translucent resin sheet. It is desirable to be within the range of 3/10 to 9/10 of the thickness t of 2a. When the depth is such a level, the tear strength of the translucent resin sheet 2a is not significantly reduced. Therefore, when the optical sheet 2 is handled or manufactured (in particular, the translucent resin sheet 2a is continuously extruded). It is possible to prevent the optical sheet 2 from being broken when the optical sheet 2 is manufactured by forming the recess 2b with an embossing roll while being molded.

  The thickness t of the translucent resin sheet 2a is not particularly limited, but is preferably about 0.1 to 3 mm in consideration of practical strength, the amount of resin used, and the like.

  The optical sheet 2 as described above is formed by, for example, a method of forming the recess 2b by press-molding the translucent resin sheet 2a, or forming the recess 2b with an embossing roll while continuously extruding the translucent resin sheet 2a. The optical sheet 2 manufactured by these methods is usually rounded at the tip 2d (deepest part) of the inverted square pyramid-shaped recess 2b as shown in FIG. When the optical sheet 2 having a rounded tip portion 2d with a large radius of curvature is used, the luminance uniformity tends to be slightly lower than when the optical sheet 2 having a tip portion 2d with a small radius of curvature is used. If the radius of curvature of the tip 2d is less than 100 μm, sufficient uniformity can be obtained. Therefore, it is desirable to manufacture the optical sheet 2 such that the radius of curvature of the rounded tip portion 2d of the recess 2b is less than 100 μm. The optical sheet manufactured by the former press molding method has a small radius of curvature of the tip portion 2d of about 10 to 40 μm, whereas the optical sheet manufactured by the combination of the latter continuous extrusion molding and embossing is Since the radius of curvature of the tip portion 2d is relatively large as about 40 to 80 μm, the former optical sheet manufactured by the press molding method is more advantageous in increasing the uniformity.

  Further, the concave portion 2b of the optical sheet 2 may be an inverted truncated quadrangular pyramidal concave portion having four inclined surfaces 2c and a flat tip portion 2e as shown in FIG. Here, the inverted truncated quadrangular pyramid shape refers to a shape obtained by horizontally cutting the top of the head of the inverted regular quadrangular pyramid. The size (area) of the flat tip portion 2e is preferably ¼ or less of the opening area of the concave portion 2b. When the flat tip portion 2e is larger than ¼, the light refraction and diffusion action by the inclined surface 2c are insufficient. Therefore, there is a disadvantage that the uniformity is lowered. A more preferable size of the flat tip 2e is 1/9 to 1/25 of the opening area of the recess 1.

  Although not shown, the concave portion 2b of the optical sheet 2 has an inverted regular triangular pyramid shape such as an inverted regular triangular pyramid shape or an inverted regular hexagonal pyramid shape having an inclined surface, or a horizontal top portion of the lower head portion thereof. It may be an inverted inverted truncated regular polygonal pyramid.

  In the optical sheet 2 described above, the concave portions 2b are arranged in the vertical and horizontal directions. However, like the optical sheet 2 shown in FIG. 7, the inverted square pyramid-shaped concave portions 2b having the inclined surfaces 2c are formed on the translucent resin sheet 2a. The light emitting surface (upper surface) may be arranged in an oblique manner at an angle of 45 °. Although not shown, the recesses 2b may be arranged in a staggered manner. Further, the array may be formed with a slight gap between the recess 2b and the recess 2b.

  Each of the concave portions 2b of the optical sheet 2 has the inclined surface 2c. However, the concave portions 2b having the tapered surface 2f may be arrayed as in the optical sheet 2 shown in FIG. That is, in the optical sheet 2 shown in FIG. 8, an inverted conical concave portion 2b having a tapered surface 2f is formed on the light exit surface of the translucent resin sheet 2a at an angle of 60 ° so as to be closely packed. Are arranged in a shape.

  The size of the inverted conical recess 2b is preferably set such that the diameter of the opening circle is 30 to 600 μm, and if this is the size, the recess 2b can be reliably formed, Light incident from the light incident surface (back surface) of the optical sheet 2 can be sufficiently refracted and diffused by the tapered surface 2f of each recess 2b, and can be emitted to the front side with a substantially uniform light amount. A more preferable diameter of the opening circle of the recess 2b is 100 to 500 μm, and a very preferable diameter is 130 to 250 μm.

  Further, in the inverted conical recess 2b, the inclination angle of the ridge line of the tapered surface 2f (inclination angle with respect to the light exit surface) is the same as the inclination angle θ of the inclined surface 2c of the inverted square pyramid recess 2b described above. Desirably, the angle is within a range of 10 ° or more and 70 ° or less. If the inclination angle is within this range, light incident from the light incident surface (back surface) of the optical sheet 2 is sufficiently refracted and diffused by the tapered surface 2f. Since it can be emitted to the front side, the uniformity of luminance can be improved. The more desirable inclination angle range of the ridgeline of the tapered surface 2f is 30 ° to 60 °, and the extremely desirable inclination angle range is 35 ° to 55 °.

  The depth of the deepest portion of the inverted conical recess 2b is 3/10 to 9 / of the thickness of the translucent resin sheet 2a, similar to the depth d of the inverted regular quadrangular pyramid recess 2b described above. The radius of curvature of the rounded tip of the inverted conical recess 2b is preferably less than 100 μm as described above. Further, instead of the inverted conical recess 2b, a frustoconical recess formed by horizontally cutting the top of the inverted conical lower end may be formed.

  As shown in FIG. 9, the optical sheet 2 disposed on the front side of the point light source 3 made of lens-covered LEDs has a large number of convex or inclined surfaces or tapered surfaces on at least the light exit surface of the translucent resin sheet 2a. The part 2g may be arranged. The convex portion 2g is provided with a convex shape obtained by vertically inverting the concave portion 2b having the inclined surface 2c or the tapered surface 2f described above, the size, the dimensions of each portion, the inclination angle of the ridgeline of the inclined surface or the tapered surface, The arrangement of the convex portions is the same as that of the concave portion 2b. Therefore, the optical sheet 2 in which the convex portions 2g are arranged and formed is also substantially refracted and diffused by the inclined surface or tapered surface of the convex portion 2g so that the light incident on the optical sheet 2 from the point light source 3 is almost directed to the front side. Since it can radiate | emit with a uniform light quantity, a brightness nonuniformity can be suppressed and a uniformity can be improved.

  In any of the optical sheets 2 described above, the concave portions 2b and the convex portions 2g are arrayed only on the light exit surface (upper surface) of the translucent resin sheet 2a, but the light incident surface (rear surface) of the translucent resin sheet 2a. Also, similar concave portions 2b and convex portions 2g may be formed in an array. When the optical sheet 2 in which the concave portions 2b and the convex portions 2g are arranged on both the light exit surface and the light entrance surface of the translucent resin sheet 2a is arranged on the front side of the point light source 3, the light refraction and diffusion action are strong. Therefore, a high degree of uniformity can be obtained as shown in test data (Table 5) of Examples described later.

  However, when the concave portions 2b or the convex portions 2g are arranged on both surfaces of the optical sheet 2 (translucent resin sheet 2a) as described above, the concave portions 2b or the convex portions 2g formed on the light incident surface of the optical sheet 2 are formed. When the inclination angle of the ridge line of the inclined surface 2c or the tapered surface 2f is increased, a part of the light emitted from the point light source 3 is totally reflected by the light incident surface of the optical sheet 2, and the incident light amount of the optical sheet 2 is reduced. Since the overall brightness is reduced, the concave portion 2b or convex portion 2g formed on the light incident surface of the optical sheet 2 has a concave portion 2b or convex portion 2g formed on the light exit surface of the optical sheet 2 with the inclination angle of the inclined surface or tapered surface. It is desirable to make it smaller than the inclination angle of the convex portion 2g.

  As the translucent resin sheet 2a of the optical sheet 2, polycarbonate, polyester, polyethylene, polypropylene, polyolefin copolymer (for example, poly-4-methylpentene-1), polyvinyl chloride, cyclic polyolefin (for example, norbornene structure) A material made of a light-transmitting thermoplastic resin such as acrylic resin, polystyrene, ionomer, styrene-methyl methacrylate copolymer resin (MS resin) is used. Among these, the translucent resin sheet 2a made of polycarbonate, polyester (particularly polyethylene terephthalate), and cyclic polyolefin has good heat resistance, and when used in a surface light emitting unit, from the point light source 3 (lens-covered LED). It is preferably used because it is difficult to cause deformation, wrinkles and the like due to heat radiation. Moreover, the translucent resin sheet 2a made of polycarbonate is very preferably used because the polycarbonate itself is a resin with good transparency, has low hygroscopicity, high brightness, and little warpage. The translucent resin sheet 2a may be made of a translucent thermosetting resin such as unsaturated polyester or epoxy resin, or two or more kinds of resin materials are mixed and alloyed to form a composite. It is also possible to use things.

  It is desirable for the light transmissive resin sheet 2a of the optical sheet 2 to contain a light diffusing agent. If the light diffusing agent is contained, the light passing through the optical sheet 2 (translucent resin sheet 2a) is strongly diffused by the light diffusing agent, so that there is an advantage that the luminance uniformity is further improved. There is no need to additionally provide another expensive light diffusion film or the like between the liquid crystal panel 4 and the liquid crystal panel 4.

  As the light diffusing agent, inorganic particles, metal oxide particles, organic polymer particles, and the like having different light refractive indexes from the material resin of the translucent resin sheet 2a are used alone or in appropriate combination. Inorganic particles include glass [A glass (soda lime glass), C glass (borosilicate glass), E glass (low alkali glass)], silica, mica, synthetic mica, calcium carbonate, magnesium carbonate, barium sulfate, talc, Particles such as montmorillonite, kaolin clay, bentonite, hectorite and silicone are used. As the metal oxide particles, particles such as titanium oxide, zinc oxide, and alumina are used, and as the organic polymer particles, particles such as acrylic beads, styrene beads, and benzoguanamine are used.

  The light diffusing agent has an average particle diameter of 0.1 to 100 μm, preferably 0.5 to 50 μm, more preferably 1 to 30 μm. A light diffusing agent having a particle size of less than 0.1 μm is likely to aggregate and thus has poor dispersibility. Even if the light diffusing agent can be uniformly dispersed, the light scattering efficiency is poor because the wavelength of light is large. Therefore, particles having a size of 0.5 μm or more, more preferably 1 μm or more are preferable. On the other hand, a light diffusing agent having a particle size larger than 100 μm causes light scattering to be non-uniform, light transmittance to be reduced, and particles to be visible with the naked eye. For this reason, particles of 50 μm or less, more preferably 30 μm or less, are preferable.

  Although content of a light-diffusion agent is not specifically limited, It is desirable to make it contain 0.05-5.0 mass%. If it is less than 0.05% by mass, the effect due to the inclusion of the light diffusing agent, that is, the effect of suppressing luminance unevenness accompanying the improvement of the light diffusing action is insufficient, and even if contained in a larger amount than 5.0% by mass. Since the improvement in the luminance unevenness suppressing effect corresponding to that is not seen, the material is wasted. The more preferable content of the light diffusing agent is 0.1 to 1.0% by mass.

  The light-transmitting resin sheet 2a of the optical sheet 2 includes a stabilizer necessary for molding, a lubricant, an impact modifier, an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a colorant, A fluorescent whitening agent or the like is appropriately contained.

  The surface light-emitting unit of the present invention is provided on the front side (upper side) of the point light source 3, instead of the optical sheet 2 described above, at least an optical sheet 1 as shown in FIGS. 10 to 20, that is, a translucent resin sheet. On the light-emitting surface, a plurality of convex ridges or concave groove portions are arrayed along a certain direction, and a plurality of ridges or groove portions having different shapes are arranged in the array of these ridge portions or groove portions. You may provide the optical sheet 1 which made the arranged thing one group, and arranged the group which consists of this some collar part or groove | channel further repeatedly.

  The optical sheet 1 shown in FIG. 10 has a plurality of convex collars 1a to 1c arranged in the left-right direction along the front-rear direction on the upper surface (light-emitting surface) of the translucent resin sheet. The flanges 1a to 1c on the upper surface of the optical sheet 1 are upward convex shapes in which the vertical cross-sectional shape on the surface along the vertical and horizontal directions is an isosceles triangle, and these flanges 1a to 1c are The isosceles triangle has three different shapes with different base angles. And the arrangement | sequence of these collar parts 1a-1c is the thing which arranged the set S which arranged three kinds of collar parts 1a-1c from which a base angle differs in the left-right direction, and repeated and arranged in the left-right direction over many more groups. It has become. Further, the lower surface (light incident surface) of the optical sheet 1 is a flat surface.

The configuration of each set S of the flange portions 1a to 1c of the optical sheet 1 will be described with reference to FIG. 11. One set S has a slope angle θ ₁ (hereinafter referred to as a base angle θ ₁ ) of 55 °. And a flange 1b having a slope inclination angle θ ₂ (hereinafter referred to as a base angle θ ₂ ) of 45 ° and a slope having a slope inclination angle θ ₃ (hereinafter referred to as a base angle θ ₃ ) of 25 °. Three types of flanges 1a to 1c with the part 1c are arranged one by one from the right to the left. In addition, the flange portions 1a to 1c are configured such that the flange widths B, which are the lengths of the portions corresponding to the bases of the isosceles triangles, are equal. Therefore, these ridges 1a~1c is higher and protrudes convexly uppermost ridge portion 1a having a maximum base angle theta _1, the lowest convex ridge portion 1c having the smallest base angle theta ₃ becomes convex ridge portion 1b having an intermediate base angle theta ₂ is the mid-height.

  The number of buttocks arranged as one set is suitably 2 or more and 10 or less, more preferably 3 or more and 5 or less. FIG. 10 shows only a region corresponding to one point light source 3 (lens-covered LED) in the optical sheet 1, and in order to enlarge the convex shape of each of the collar portions 1 a to 1 c for easy viewing, Although only nine sets of the collar portions 1a to 1c are shown, in practice, a larger number of groups are arranged for each point light source 3, and the diameter of the lens 3b of the point light source 3 is shown in FIG. The width B is sufficiently narrow. Furthermore, the number of sets in the region of the optical sheet 1 corresponding to this one point light source 3 is not necessarily an integer.

According to the above configuration, in the optical sheet 1, in the vicinity of the position E ₀ immediately above the point light source 3 shown in FIG. 10, the light from the point light source 3 is inclined at an inclination angle as shown in FIG. The ridge part 1a and the ridge part 1b having a large base angle (hereinafter referred to as a base angle) are often emitted in a left-right direction and are totally reflected, but the light emitted from the ridge part 1c having the smallest base angle is almost upward. It becomes. Further, in the vicinity of the position E ₁ apart a little lateral direction with respect to the right above the point light source 3, as shown in FIG. 12 (b), the light from the point light source 3 is maximum ridges 1a and minimal base angle In the collar part 1c, it inclines in the left-right direction, and it radiate | emits, but the light radiate | emitted from the collar part 1b with an intermediate base angle turns upward substantially. And, in yet around from just above the point light source 3 in the horizontal direction far away E _2, as shown in FIG. 12 (c), small ridges 1b and ridges of the light base angle from a point source 3 In 1c, it inclines in the left-right direction, and it radiate | emits, but the light radiate | emitted from the collar part 1a with the largest base angle turns upward substantially. In FIG. 12, the refraction of incident light on the lower surface of the optical sheet 1 is omitted.

When the point light source 3 is a conventional LED having a directivity (0 °) directivity in the light distribution characteristic or a light bulb having no directivity in the light distribution characteristic, the point light source 3 is far from right above the point light source 3 in the left-right direction. in the vicinity of a position away E _2, light by ridge 1a as described above be emitted substantially upward, since the amount of light incident on the vicinity of the position E ₂ is small, so that the luminance unevenness. However, in this surface light emitting unit, the point light source 3 is provided with a directivity in an oblique direction in which the angle at which the luminance in the light distribution is maximized is in the range of + 30 ° to + 80 ° and −30 ° to −80 °. Since the lens-covered LED is used, the amount of light incident near the position E ₂ far away is larger than the amount of light incident near the other positions E ₀ and E ₁ . Accordingly, the amount of light emitted almost upward from the vicinity of the respective positions E ₀ , E ₁ , E ₂ becomes substantially uniform, so that luminance unevenness is suppressed and the uniformity is improved.

The widths B of the three types of flanges 1a to 1c in each set S in the optical sheet 1 are not necessarily constant. For example, as in the optical sheet 1 shown in FIG. 13, the widths of the flanges 1a to 1c. B _{1 to} B ₃ may be different. In particular, as shown in FIG. 13, the larger the sum of the inner angles of the bases of the triangles having the convex longitudinal cross-sections at the flanges 1a to 1c, that is, the greater the base angle of the isosceles triangle, If B _{1 to} B ₃ are widened, the ridge widths B _{1 to} B ₃ become wider as the ridges _{1 a to 1} c of the isosceles triangle have a small apex angle, and therefore, three types of ridges having different apex angles The amount of light emitted from 1a to 1c and directed upward to some extent can be made uniform, and the uniformity can be increased. This is because the utilization of the higher ridges 1a~1c the vertical angle pointed small light decreases, but if thus wide ridge width B ₁ .about.B ₃ more ridges 1a~1c the vertical angle pointed small light This is because the amount of light that is emitted from the three types of flanges 1a to 1c having different apex angles and is directed upward to some extent can be made uniform.

In the optical sheet 1 described above, the convex heights of the three types of flanges 1a to 1c of each set S are different, but these heights are aligned on a plane parallel to the sheet surface. Also good. For example, FIG. 14 shows a case where the convex heights of the three types of collars 1a to 1c of each set S in the upper optical sheet 1 are aligned. However, in this case, contrary to the case shown in FIG. 13, the ridge widths B _{1 to} B ₃ of the ridges 1a to 1c having a small apex angle of the triangle (triangle based on the original isosceles triangle) are small. Therefore, the luminance may not be sufficiently obtained at a position where the distance from the point light source 3 in the left-right direction is long. Therefore, as shown in FIG. 15, with respect to the collar portion 1 b and the collar portion 1 c that originally have a low convex shape, the isosceles triangle is translated upward to increase the height, and a square based on the original isosceles triangle. By setting it as the above polygon, convex height can be arrange | equalized, making the collar width B of collar parts 1a-1c constant.

Further, the optical sheet 1 described above, the case base angle theta ₁ through? ₃ of the three ridges 1a~1c of each set S is 55 ° and 45 ° and 25 °, these base angle Since θ _{1 to} θ ₃ may be different from each other, the specific angle value is arbitrary. However, the range of this base angle is preferably 10 ° or more and 70 ° or less, similar to the inclination angle θ of the ridgeline of the concave surface 2b or convex portion 2g of the optical sheet 2 described above or the tapered surface. The maximum value of the base angle is preferably 40 ° or more and 70 ° or less, and more preferably 50 ° or more and 70 ° or less. If it exceeds 70 ° and becomes too large, when the ridge width B of the ridge portions 1a to 1c is made sufficiently wide, the convex height becomes too high and the moldability of the optical sheets 1 and 2 deteriorates. Handling becomes difficult. On the contrary, when the maximum value of the base angle is smaller than 55 °, particularly smaller than 40 °, the difference in the base angles of the flanges 1a to 1c is reduced, so that the effect of increasing the uniformity by eliminating luminance unevenness is sufficient. It becomes difficult to obtain.

  On the other hand, the minimum value of the base angle of each of the flanges 1a to 1c is preferably 10 ° or more and 25 ° or less, and more preferably 10 ° or more and 20 ° or less. If the minimum value of the base angle exceeds 20 °, and particularly exceeds 25 °, the difference in the base angle of each of the flanges 1a to 1c is reduced. It becomes difficult to obtain enough. In some cases, the minimum value of the base angle may be set to 0 °, and any one ridge portion of each set S may be a surface parallel to the sheet surface.

  Moreover, although said optical sheet 1 showed the case where the longitudinal cross-sectional shape of each collar part 1a-1c is a shape based on an isosceles triangle or this isosceles triangle, the top part of these isosceles triangles is horizontal. It is good also as an isosceles trapezoid shape cut out. In FIG. 16, the example which made the longitudinal cross-sectional shape of the collar parts 1a-1c of the optical sheet 1 the isosceles trapezoid shape is shown. Furthermore, it may be a shogi piece-shaped pentagon in which an isosceles triangle with a small base angle is placed on the top of the cut, or a hexagon or more polygon.

  In the optical sheet 1, the three kinds of collars 1a to 1c of each set S are arranged in the same order. However, if the number of sets on the optical sheet 1 is sufficiently large, this arrangement order is used. Does not affect the luminance unevenness preventing effect due to the light refraction / diffusion action, the arrangement order may be different for each set S, and the arrangement order in that case is preferably irregular. FIG. 17 shows an example in which the arrangement order of the flange portions 1 a to 1 c of each set in the optical sheet 1 is irregularly different for each set S.

  Moreover, although said optical sheet 1 showed the case where three types of collar parts 1a-1c were arranged in each set S, four or more types of collar parts may be arranged. Furthermore, even if only two types of collars are arranged, the desired effect can be obtained to some extent if the longitudinal cross-sectional shape is a polygon having a square shape or more.

  In addition, the optical sheet 1 described above is a case where the longitudinal cross-sectional shape of each of the flange portions 1a to 1c is an isosceles triangle symmetrical with respect to a vertical line or a shape based on the isosceles triangle. It is not limited to such a symmetrical thing. However, in order for the optical sheet 1 to exhibit characteristics that do not depend on the position of each point light source 3 in the left-right direction, for example, when the vertical cross-sectional shape of the flanges 1a to 1c of the optical sheet 1 is a left-right asymmetric shape, It is not preferable that the shape of the light source is excessively biased rightward or leftward. If this bias is excessively large, luminance unevenness may occur depending on the left or right side of the point light source 3 when the optical sheet 1 is considered as a whole. is there. Therefore, even if the vertical cross-sectional shapes of the individual flange portions 1a to 1c of the optical sheet 1 are asymmetrical, if the degree of the bias is quantified and the left-right direction is positive or negative, all the flange portions 1a of each set S It is preferable that the deviations are dispersed and averaged so as to be as close to 0 as possible when the deviations of ˜1c are totaled. That is, as shown in FIG. 18, if there are five types of collars 1a to 1e in each set S of the optical sheet 1, for example, the collars 1a and 1e are biased by a certain amount in the left direction, and the collar 1c is biased. Preferably, the flanges 1b and 1d are balanced and averaged such that the ribs 1b and 1d are biased by a certain amount in the right direction. FIG. 19 shows a case where the arrangement order of these five types of collars 1a to 1e is different between adjacent sets S.

  Moreover, although the said optical sheet 1 showed the case where each corner | angular part, such as a triangle, in the longitudinal cross-sectional shape of a collar part was pointed, in reality, a manufacturing convenience, chamfering, etc. are given. Each corner may be slightly dull or rounded. For example, when the applicant actually manufactured the mold of the optical sheet 1, the apex portion of the triangle of the vertical cross-sectional shape of the collar portion mold was an arc having a curvature radius of about 10 to 80 μm. Further, when the resin was molded using this mold, the resin was actually filled only up to about 90% of the height from the base of the triangle to the apex. Moreover, as a trial, the optical sheet 1 was made by filling the resin up to about 70% of the height of the triangle, but no significant difference was found in the effect of the present invention. This is because it is important that the collar portion of the optical sheet 1 has a slope formed by both oblique sides of a triangle, and the state of the details of the corner portion that is a boundary portion where these slopes contact is not important. For the same reason, the same effect can be obtained when the vertical cross-sectional shape of the buttocks in FIG. 16 is an isosceles trapezoid.

  In addition, the optical sheet 1 has been shown in the case where convex ridges are arranged on the upper surface (light-emitting surface), but the effect of the present invention is similarly obtained even when concave grooves are arranged. Can be obtained. In this case, the concave vertical cross-sectional shape can be arbitrarily used as the vertical cross-sectional shape of the above-mentioned convex ridge part upside down.

  In the optical sheet 1, the lower surface (light incident surface) on which the flange portion and the groove portion are not formed is flat. On the lower surface, a similar flange portion or groove portion is provided on the upper surface. Alternatively, it may be formed in a direction different from the groove (for example, an orthogonal direction), or fine graining may be performed. In this way, there is an advantage that luminance unevenness is further suppressed and the uniformity is further improved.

  It is desirable that the optical sheet 1 contains the above-described light diffusing agent in the same content as described above, and it is desirable to add the above-described various additives as appropriate. The thickness of the optical sheet 1 is desirably substantially the same as the thickness of the optical sheet 2 described above.

  In some cases, the optical sheet 1 may have a multilayer structure, and the type and blending amount of the light diffusing agent and various additives may be appropriately changed between the surface layer and the base material layer. FIG. 20 shows an optical sheet 1 having a two-layer structure in which a surface layer 12 is provided on a base material layer 11 and convex ridges are arranged on the surface layer 12.

  The optical sheet 1 as described above is formed by press-molding the translucent resin sheet made of the above-described material resin and arranging the ridges or grooves. Alternatively, the above-described optical resin 1 is injection-molded with the above-described material resin. Or the above-described material resin is continuously extruded to form the ridges or grooves in the extrusion direction, or the above-described material resin is continuously extruded to form the ridges or grooves with an embossing roll. Can be produced by a desired method such as a method of forming an array.

  Note that the optical sheet 1 and the optical sheet 2 described above are not necessarily flat sheets, and may be, for example, sheets that are slightly curved in accordance with the shape of the liquid crystal panel 4. In addition, the optical sheet 1 and the optical sheet 2 described above may be stacked on the front side of the point light source 3, and in that case, there is an advantage that the uniformity is further improved.

  In the surface light emitting unit in which the optical sheet 1 or 2 as described above is arranged on the front side (upper side) of the point light source 3, the point light source 3 has the maximum luminance in the light distribution of the emitted light as in the conventional LED. The angle is near 0 °, that is, does not show directivity biased in the front direction, and the angle at which the luminance in the light distribution is maximized is in the range of + 30 ° to + 80 ° and −30 ° to −80 ° The light source is a point light source having directionality, and the optical sheet 2 or 1 has at least the inclined surface 2c or the tapered surface 2f on the light exit surface and the convex portion 2g or the flange portion 1a. Since the light incident from obliquely behind can be emitted almost in the front direction by repeatedly arranging the array S of grooved portions 1e or S, the distance D between the point light sources 3 and 3 is increased as compared with the prior art. Even spotlight It can suppress that the brightness | luminance of the area | region of the intermediate part of the source 3 and the point light source 3 falls. Therefore, the distance D between the light sources 3 and 3 is set to be as long as 40 mm or more and 60 mm or less, and the ratio (L / D) between the distance L from the point light source 3 to the optical sheet 2 or 1 and the distance D between the light sources is described above. Even if the distance L is shortened within the range of 0.2 to 0.63, the difference between the brightness of the area directly in front of the point light source 3 and the brightness of the area in the middle of the point light source 3 and the point light source 3 is reduced. As shown in the test data of the examples to be described later, a high degree of uniformity can be obtained, so that the number of point light sources 3 can be reduced to reduce the cost and save energy. It is possible to fully meet the demands of

  By the way, the conventional LED direct-type backlight incorporated in the 40-inch liquid crystal display has LEDs arranged with a distance between light sources of 20 to 30 mm, so the number of LEDs used is around 700. For example, when the surface emitting unit of the present invention in which the distance between the lenses is increased to 55 mm and the lens-covered LEDs are arranged is used as a backlight, the number of lens-covered LEDs used is reduced to about 150. Can be planned.

  Such a surface light emitting unit is used by being installed behind the liquid crystal panel 4 as a backlight unit of a liquid crystal display such as a liquid crystal television receiver or a personal computer as described above. It can also be used as a unit, and can also be used as a surface illumination device or the like. When used as a surface illumination device or the like, the arrangement distribution of the point light sources 3 is biased in relation to the illumination effect, or the distance L between each point light source 3 and the optical sheets 1 and 2 is not necessarily the same. It is also possible to arrange them so that they do not exist.

  Next, more specific examples of the surface light emitting unit according to the present invention and an effect confirmation test performed on each example will be described.

[Examples 1 to 4]
As a point light source, a lens-covered LED (OSW, LW W5KM) having an angle of maximum luminance in the light distribution distribution near + 70 ° and −70 ° is set on the wiring board with a distance D between the light sources of 40 mm. They were arranged in a matrix of length and width. Then, on the front side (upper side) of the lens-covered LED, four types of optical sheets having different inclination angles of the concave portions are provided at a distance L of 25 mm from the surface of the wiring board on which the lens-covered LED is disposed. It installed in parallel with the wiring board, and comprised the surface light distribution unit of Examples 1-4.
In each of the four types of optical sheets used in Examples 1 to 4, inverted square pyramid-shaped concave portions each having a side length a of 130 μm are arranged vertically and horizontally on the light exit surface (upper surface) of a polycarbonate resin sheet having a thickness of 2 mm. In addition to forming 0.3 mass% of Tospearl 120S manufactured by Momentive Performance Materials Japan GK as a light diffusing agent, the optical sheet of Example 1 has an inclination angle of the inclined surface of the recess of 35 °. The optical sheet of Example 2 has an inclination angle of 45 °, the optical sheet of Example 3 has an inclination angle of 55 °, and the optical sheet of Example 4 has an inclination angle of 65 °.

For the surface emitting units of Examples 1 to 4, by using “EYESCALE III” manufactured by I-System Co., Ltd., by measuring the luminance uniformity under an environment of room temperature 23 ° C. and humidity 50% RH, The relationship between the inclination angle of the inclined surface of the concave portion of the optical sheet and the uniformity was investigated. As shown in FIG. 21, the measurement of the uniformity is performed in the regions A _{1 to} A ₄ directly above the four lens-covered LEDs (point light sources 3) adjacent to each other in the vertical and horizontal directions, and in the middle portion of these four lens-covered LEDs. the brightness from above the optical sheet at the measurement points in total 5 points directly above the area a ₅ is measured, calculated luminance ratio of the area a ₅ for each of the areas a ₁ to a ₄ a (%), respectively, of the four The calculation was performed by calculating the average value of the luminance ratio as the uniformity.

Table 1 shows the configurations of the surface light emitting units of Examples 1 to 4 and the calculated uniformity. And the graph which shows the relationship between the inclination | tilt angle of the inclined surface of the recessed part formed in the light emission surface of an optical sheet and uniformity is shown in FIG.
In Tables 1 to 8 below, “presence / absence of lens” means a lens for providing a light distribution characteristic in which the angles at which the luminance is maximized are near + 70 ° and −70 ° as described above. It means presence or absence.

  From Table 1 and FIG. 22, the surface emitting units of Examples 1 to 4 have the distance D between the light sources enlarged to 40 mm, and the distance L from the point light source to the optical sheet is shortened to 25 mm. Since the inclination angle of the inclined surface of the concave portion of the optical sheet is 35 ° to 65 °, a high degree of uniformity of 85% or more is obtained, and in particular, the inclination angle is 35 ° to 55 ° as in Examples 1 to 3. It can be seen that an extremely high homogeneity of 95% or more can be obtained. FIG. 22 also shows that the maximum value of uniformity is obtained when the inclination angle is set to around 45 °.

[Examples 5 to 8]
The lens-covered LEDs used in Examples 1 to 4 (manufactured by OSRAM, LW W5KM) were arranged in a matrix form vertically and horizontally on the wiring board with a distance D between light sources of 40 mm. An optical sheet having a thickness of 2 mm in which concave portions of an inverted regular quadrangular pyramid having an inclination angle of 55 ° (a length of one side is 130 μm) is formed on the front side (upper side) of the lens-covered LED vertically and horizontally. And an optical sheet containing 0.4% by mass of Tospearl 120S manufactured by Momentive Performance Materials Japan GK as a light diffusing agent, and the distance L from the wiring board on which the lens-covered LEDs are disposed. It changed and installed in parallel with the wiring board, and comprised the surface light distribution unit of Examples 5-8. In Example 5, the distance L from the lens-covered LED (wiring board) to the optical sheet is 25 mm (L / D = 0.63), and in Example 6, the distance L is 20 mm (L / D = 0.50). In Example 7, the distance L was 15 mm (L / D = 0.38), and in Example 8, the distance L was 10 mm (L / D = 0.0.25).
For the surface light distribution units of Examples 5 to 8, the uniformity was measured in the same manner as in Examples 1 to 4, and the relationship between L / D and the uniformity when the inter-light source distance D was 40 mm was examined. .
Table 2 below shows the configurations and uniformity of the surface emitting units of Examples 5 to 8. And the graph which shows the relationship between the uniformity of Examples 5-8 in case the distance D between light sources is 40 mm and L / D in FIG. 23 is published.

[Comparative Examples 1-4]
For comparison, in place of the optical sheets of Examples 5 to 8, Examples 5 to 8 were used except that a light diffusion sheet having a thickness of 2 mm and containing 0.4% by mass of the same light diffusing agent was used. In the same manner, the surface emitting units of Comparative Examples 1 to 4 were configured. And the uniformity was similarly measured about these surface emitting units of Comparative Examples 1-4, and the relationship between L / D and uniformity when the distance D between light sources was 40 mm was investigated.
The structures and uniformity of the surface emitting units of Comparative Examples 1 to 4 are also shown in Table 2 below. And in FIG. 23, the graph which shows the relationship between the uniformity of Comparative Examples 1-4 in case the distance D between light sources is 40 mm, and L / D is also published.

[Examples 9 to 11]
Except that the inter-light source distance D was changed to 55 mm, the surface emitting units of Examples 9 to 11 were configured in the same manner as in Examples 5 to 7, and the degree of uniformity was similarly set for the surface emitting units of these Examples 9 to 11. By measuring, the relationship between L / D and uniformity when the inter-light source distance D was 55 mm was examined.
Table 3 below shows the configurations and uniformity of the surface light emitting units of Examples 9 to 11. And the graph which shows the relationship between the uniformity degree of Examples 9-11 in case the distance D between light sources is 55 mm in FIG. 24, and L / D is published.

[Comparative Examples 5 to 7]
For comparison, the optical sheets of Examples 9 to 11 were changed to Examples 9 to 11 except that a light diffusing sheet having a thickness of 2 mm and having both surfaces containing 0.4% by mass of the same light diffusing agent was used. In the same manner, surface emitting units of Comparative Examples 5 to 7 were configured. And the uniformity was similarly measured about these surface emitting units of Comparative Examples 5-7, and the relationship between the uniformity of Comparative Examples 5-7 and L / D when the distance D between light sources was 55 mm was investigated. .
The structures and uniformity of the surface emitting units of Comparative Examples 5 to 7 are also shown in Table 3 below. And in FIG. 24, the graph which shows the relationship between the uniformity of Comparative Examples 5-7 in case the distance D between light sources is 55 mm, and L / D is also published.

  From Table 2, Table 3, FIG. 23, and FIG. 24, it is the surface emitting unit of the Example using the optical sheet which formed the recessed part on the light-emitting surface even if the distance D between light sources is 40 mm or 55 mm. Regardless of whether or not it is a surface emitting unit of a comparative example using a flat light diffusing sheet on both sides, it can be seen that as L / D increases, the degree of uniformity increases. And the surface emitting unit of Examples 5-11 in which L / D using the optical sheet which formed the recessed part on the light emission surface in the range of 0.25-0.63 is 68.7-97.6%. The surface emitting units of Comparative Examples 1 to 7 having a uniformity and having a L / D in the range of 0.25 to 0.63 using a double-sided flat light diffusion sheet have a uniformity of 46.5. 88.5%, which is a significant reduction. From this, it can be seen that the recesses arranged in the optical sheets of Examples 5 to 11 act very effectively in improving the uniformity.

[Comparative Example 8]
Instead of the optical sheet used in the surface light emitting unit of Example 5, an inverted regular quadrangular pyramid-shaped concave portion (the length of one side a is 130 μm) on the light incident surface (rear surface) is 55 °. A surface emitting unit of Comparative Example 8 was constructed in the same manner as in Example 5 except that an optical sheet made of polycarbonate resin (thickness 2 mm) having a flat output surface (upper surface) was used. Then, the uniformity of the surface light emitting unit of Comparative Example 8 was measured in the same manner, and the luminance was measured and compared with the uniformity and luminance of the surface light emitting unit of Example 5.
Table 4 below shows the configuration, uniformity, and luminance of the surface emitting unit of Comparative Example 8, and the configuration, uniformity, and luminance of the surface emitting unit of Example 5.

  From Table 4, the optical sheet having the concave portions arranged on the light incident surface like the surface light emitting unit of Comparative Example 8 is arranged with the concave portions on the light emitting surface like the surface light emitting unit of Example 5. Although the degree of uniformity seems to be slightly higher than that using the formed optical sheet, the surface light emitting unit of Comparative Example 8 has the disadvantage that the overall luminance is greatly reduced by about 25% and darkens. I understand. This is because part of the light emitted from the lens-covered LED is totally reflected by the rear surface on which the concave portions of the optical sheet are arranged, and the amount of light incident on the optical sheet and the amount of light emitted from the exit surface of the optical sheet are reduced. It is thought from.

[Example 12]
Instead of the optical sheet used in the surface light emitting unit of Example 5, an inverted regular quadrangular pyramid-shaped concave portion (the length of one side a is 130 μm) having an inclination angle of 55 ° is formed vertically and horizontally on the light exit surface (upper surface). An optical sheet made of polycarbonate resin in which concave portions having an inverted regular square pyramid shape with an inclination angle of 25 ° (a length of one side is 130 μm) are formed vertically and horizontally on the light incident surface (back surface). A surface emitting unit of Example 12 was configured in the same manner as Example 5 except that 2 mm in thickness was used. And the uniformity was measured similarly about the surface emitting unit of this Example 12, and the effectiveness of forming a recessed part in both surfaces of an optical sheet compared with the surface emitting unit of Example 5 was investigated.
The configuration and uniformity of the surface emitting unit of Example 12 and the configuration and uniformity of the surface emitting unit of Example 5 are also shown in Table 5 below.

  From Table 5, as in the surface light emitting unit of Example 12, a concave portion having an inclined surface with an inclination angle (25 °) smaller than the inclined angle (55 °) of the inclined surface of the concave portion of the light exit surface is entered into the optical sheet. It can be seen that the arrangement formed on the light surface (rear surface) can remarkably increase the uniformity with almost no decrease in luminance. This is because the angle of inclination of the inclined surface of the recess formed on the incident surface of the optical sheet is small, so that the light emitted from the lens-covered LED is incident on the optical sheet with almost no total reflection at the incident surface of the optical sheet. Moreover, it is considered that light is refracted and diffused by the concave portions on both the incident surface and the exit surface of the optical sheet.

[Comparative Examples 9 to 10]
Instead of the lens-covered LED of the surface light emitting unit of Example 5, a conventional LED, that is, a lensless LED (the angle at which the luminance becomes maximum is near the front (0 °), and the angle is around + 70 ° and −70. A surface emitting unit of Comparative Example 9 was configured in the same manner as Example 5 except that an LED without a lens for imparting a light distribution characteristic in the vicinity of 0 ° (hereinafter the same) was used.
Moreover, it replaced with the lens covering LED of the surface emitting unit of the comparative example 1, and comprised the surface emitting unit of the comparative example 10 like the comparative example 1 except having used LED without a lens.
And the uniformity of the surface emitting units of Comparative Examples 9 to 10 was measured in the same manner, and the uniformity of the surface emitting units of Comparative Example 9 and Example 5 was compared, and the surfaces of Comparative Example 10 and Comparative Example 1 were compared. By comparing the uniformity of the light-emitting units, the presence or absence of LED lenses (lenses for providing light distribution characteristics where the angles at which the luminance is maximized is near + 70 ° and −70 °) and the light output of the optical sheet The effect of the presence or absence of concave portions on the surface was examined.
Table 6 below shows the configurations and uniformity of the surface emitting units of Comparative Examples 9 to 10, the configuration and uniformity of the surface emitting unit of Example 5, and the configurations and uniformity of the surface emitting unit of Comparative Example 1.

  From Table 6, the surface light emitting unit of Example 5 and the surface light emitting unit of Comparative Example 9 both use the same optical sheet in which concave portions are arranged on the light emitting surface, but in Example 5, a lens-covered LED is used. In Comparative Example 9, a lensless LED is used, so that the surface emitting unit of Example 5 using a lens-covered LED has a much higher degree of uniformity than the surface emitting unit of Comparative Example 9. I understand. The surface emitting units of Comparative Example 1 and Comparative Example 10 both use the same diffusion sheet that is flat on both sides, but Comparative Example 1 uses a lens-covered LED, and Comparative Example 10 uses a lensless LED. Therefore, it can be seen that the surface emitting unit of Comparative Example 1 using the lens-covered LED has a higher degree of uniformity than the surface emitting unit of Comparative Example 10. This demonstrates that the use of lens-covered LEDs is extremely effective in increasing uniformity.

  Moreover, although the surface emitting units of Example 5 and Comparative Example 1 both use lens-covered LEDs, in Example 5, an optical sheet having concave portions arranged on the light-emitting surface is used. Since Comparative Example 1 uses a light diffusion sheet that is flat on both sides, the surface light emitting unit of Example 5 that uses an optical sheet in which concave portions are arranged on the light emitting surface is more suitable than the surface light emitting unit of Comparative Example 1. It can be seen that it has a high degree of uniformity. And although the surface emitting units of Comparative Example 9 and Comparative Example 10 both use lensless LEDs, Comparative Example 9 uses an optical sheet in which concave portions are arrayed on the light exit surface. Since Comparative Example 10 uses a light diffusion sheet that is flat on both sides, the surface emitting unit of Comparative Example 9 that uses an optical sheet in which concave portions are arranged on the light exit surface is more than the surface emitting unit of Comparative Example 10. It can be seen that it has a high degree of uniformity. From this, it is proved that the formation of the concave portions on the light exit surface of the optical sheet is extremely effective in increasing the uniformity.

  As described above, the uniformity of the surface light emitting unit of Example 5 using the optical sheet having the concave portions arranged on the light-emitting surface and the lens-covered LED is the highest, and Comparative Example 10 using the diffusion sheet and the lens-less LED having both flat surfaces. It can be seen that the uniformity of the surface emitting unit is the lowest. Further, the surface light emitting unit of Comparative Example 1 using a diffusion sheet and a lens-covered LED having flat surfaces on both sides is a surface light emitting unit of Comparative Example 9 using an optical sheet in which concave portions are arranged on the light emitting surface. Since the degree of uniformity is higher than that, it can be seen that the use of the lens-covered LED is more effective in increasing the degree of uniformity than the use of the optical sheet in which concave portions are arranged on the light-emitting surface.

[Example 13]
Instead of the optical sheet used in the surface light emitting unit of Example 5, five convex ridges (i.e., sections whose base angles are 55 °, 45 °, 35 °, 25 °, and 10 ° are isosceles triangles, respectively) Using a polycarbonate resin optical sheet (optical sheet having a cross-sectional shape shown in FIG. 18, thickness 2.0 mm) in which this group is further repeatedly arranged and arranged on the light-emitting surface. Then, the surface emitting unit of Example 13 was configured in the same manner as Example 5. And the uniformity was measured similarly about this surface emitting unit.
The structure and the uniformity of the surface emitting unit of Example 13 are shown in Table 7 below.

[Comparative Example 11]
For comparison, the surface light emitting unit of Comparative Example 11 was constructed in the same manner as in Example 13 except that a lensless LED was used instead of the lens-covered LED of the surface light emitting unit of Example 13, and the degree of uniformity was determined. Was measured in the same manner.
The configuration and uniformity of the surface emitting unit of Comparative Example 11 are also shown in Table 7 below.

  From Table 7, the surface emitting unit of Example 13 using the optical sheet in which five flanges having different base angles are repeatedly arranged as a set is arranged with a uniformity of 96.6% and inverted on the light emitting surface. It can be seen that the surface light emitting units of Examples 1 to 13 using the optical sheet in which regular quadrangular pyramid-shaped concave portions are arranged have the same degree of uniformity. And although the surface emitting unit of the comparative example 11 uses the same optical sheet as the surface emitting unit of Example 13, it uses LED without a lens as a point light source, Therefore A uniformity is 65. It has fallen significantly to 6%. From this, it can be seen that the use of a lens-covered LED as a point light source is extremely effective in increasing the uniformity.

[Example 14]
As an optical sheet, an optical sheet made of polycarbonate resin (thickness: 2 mm, light diffusion) in which concave portions of an inverted regular quadrangular pyramid having an inclination angle of 55 ° (the length of one side a is 200 μm) are arranged vertically and horizontally on the light exit surface. 0.4 mass% of the agent) was prepared by press molding. It was 17 micrometers when the curvature radius of the rounded front-end | tip part of this optical sheet was measured.
A surface light emitting unit of Example 14 was constructed in the same manner as in Example 5 except that the above optical sheet was used in place of the optical sheet of the surface light emitting unit of Example 5, and the uniformity was measured in the same manner.
The configuration and uniformity of the surface light emitting unit of Example 14 are shown in Table 8 below.

  In addition, in order to contrast with the surface emitting unit of Example 5, the structure and uniformity of the surface emitting unit of Example 5 are also shown in Table 8 below. The optical sheet used in the surface light emitting unit of Example 5 is an optical sheet made of polycarbonate resin in which concave portions having an inverted regular quadrangular pyramid shape whose inclination angle is 55 degrees (the length of one side is 130 μm) are arranged on the light emission surface. A sheet (thickness 2 mm, containing 0.4% by weight of a light diffusing agent), in which a concave portion is formed on one side (light emitting surface) with an embossing roll while continuously extruding the material resin. The radii of curvature at the tip end are relatively large at 60 μm.

  From Table 8, the surface emitting unit of Example 14 using the optical sheet produced by press molding and Example 5 using the optical sheet produced by continuous extrusion molding and embossing have substantially the same degree of uniformity. However, it can be seen that Example 14 using a press-molded optical sheet having a small curvature radius at the tip of the concave portion tends to exhibit a slightly higher degree of uniformity.

1 Optical sheet 1a, 1b, 1c, 1d, 1e ridge part θ ₁ , θ ₂ , θ ₃ base angle (inclination angle of slope of ridge part)
2 Optical sheet 2a Translucent resin sheet 2b Concave part 2c Inclined surface of concave part 2d Rounded tip part of concave part 2f Tapered surface 2g Convex part θ Inclination angle of inclined surface of concave part 3 Point light source (lens-covered LED)
3a LED
3b Lens 4 Liquid crystal panel 5 Wiring board S Set of collar part D Distance between light sources L Distance from point light source to optical sheet

Claims (5)

A surface emitting unit provided with an optical sheet on the front side of discretely arranged point light sources,
The point light source is a point light source in which the angle at which the luminance becomes maximum in the light distribution of the emitted light is in the range of + 30 ° to + 80 ° and −30 ° to −80 °,
The optical sheet is an optical sheet in which a large number of concave or convex portions having inclined surfaces or tapered surfaces are arranged on at least the light exit surface of the translucent resin sheet, or at least on the light exit surface of the translucent resin sheet, A plurality of convex ridges or concave groove portions are arrayed along a certain direction, and the arrangement of these ridge portions or groove portions is arranged in such a manner that a plurality of ridge portions or groove portions having different shapes are arranged side by side. A surface light-emitting unit characterized in that it is one of optical sheets in which a set of a plurality of flanges or grooves is repeatedly arranged side by side.   The surface light-emitting unit according to claim 1, wherein the optical sheet contains a light diffusing agent.   The inclination angle of the inclined surface of the concave portion or the convex portion, the inclination angle of the ridge line of the tapered surface of the concave portion or the convex portion, and the inclination angle of the inclined surface of the flange portion or the groove portion are all in the range of 10 ° or more and 70 ° or less. The surface emitting unit according to claim 1 or 2, wherein   The surface emitting unit according to any one of claims 1 to 3, wherein a radius of curvature of the rounded tip portion of the concave portion or the convex portion is less than 100 µm.   The distance D between adjacent point light sources is 40 mm or more and 60 mm or less, and the ratio (L / D) between the distance L from the point light source to the optical sheet and the distance D between the light sources is 0.2 to 0. 5. The surface emitting unit according to claim 1, wherein the surface emitting unit is within a range of .63.

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