JP2011204371A - Surface light emitting unit and light diffusion sheet unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting unit and a light diffusion sheet unit, capable of eliminating uneven brightness depending on distance from an LED3, elongating arrangement interval of the LEDs3, and refraining from depending on the arrangement position of the LEDs3.SOLUTION: On an upper surface of a translucent sheet, a number of ridges are arrayed along a constant direction on the sheet surface of the translucent sheet. A plurality of ridges having different shapes from each other are arrayed to form one set. Sets of a plurality of ridges are further arrayed in a repeated manner on two optical sheets 1 and 2. They are so stacked as the constant direction along which the ridges run on the sheet surface is perpendicular to the light emission direction of a plurality of LEDs3 arranged in a matrix.

Description

  The present invention is used for a surface light emitting unit such as a backlight unit using two optical sheets in which a plurality of convex ridges or concave grooves are formed on the surface of a translucent sheet, and the surface light emitting unit. The present invention relates to a light diffusion sheet unit composed of two optical sheets.

  The backlight unit of a liquid crystal display used in a television receiver or a personal computer has a direct light system in which a light source is arranged on the back side of the liquid crystal panel and a light guide plate on the back side of the liquid crystal panel. For example, there is an edge light system in which a light source is arranged on the side. Conventionally, a linear light source composed of a straight tube type CCFL (cold cathode tube) is often used as the light source.

  A conventional direct-light-type backlight unit generally uses a plurality of line light sources composed of the CCFL arranged in parallel at intervals on the back side of the liquid crystal panel. However, in the line light source, since light is emitted radially around the axis of the line light source, luminance unevenness occurs in a direction orthogonal to the axis of the line light source as it is.

  Therefore, the applicant has already invented an invention in which an optical sheet in which a large number of convex ridges or concave grooves are arranged on the surface of the light transmissive sheet on the light output direction side is arranged between the line light source and the liquid crystal panel. Proposed (PCT / JP2008 / 072992). In the invention already proposed by the applicant, the ridges or grooves on the surface of the translucent sheet are formed in a direction along the axis of the line light source, and the arrangement of the ridges or grooves is a plurality of different shapes. In this case, a set of the flanges or groove portions arranged side by side is taken as one set, and a set of the plurality of flange portions or groove portions is repeatedly arranged side by side.

  According to the applicant's previously proposed invention, a general light diffusing film (herein, “light diffusing film” is a translucent sheet that is flat on both sides and has no unevenness between the line light source and the liquid crystal panel. It means a conventional optical sheet having a light diffusibility by a method such as containing a light diffusing agent, including a sheet-like or plate-like one). Therefore, compared to a case where an optical sheet in which a large number of conical or pyramid-shaped (quadrangular pyramidal) convex portions are arranged in the vertical and horizontal directions is additionally arranged on the surface of the translucent sheet (see, for example, Patent Document 1). Therefore, uneven brightness can be surely reduced. In addition, when a plano-convex linear Fresnel lens-shaped optical sheet is disposed between the line light source and the liquid crystal panel (see, for example, Patent Document 2), the distance from the line light source is long on the surface of the translucent sheet. The mounting position of the line light source is limited as in the case where an optical sheet in which a large number of concave triangular grooves (convex triangular ridges) are arranged so as to have a large base angle is arranged (see, for example, Patent Document 3). In addition, it is not possible to cope with a design change such as an increase or decrease in the number of line light sources, and there is no disadvantage that versatility is impaired.

  Incidentally, in recent backlight units of liquid crystal displays, the use of LEDs (light emitting diodes) as light sources has been put into practical use. Since LEDs have sufficient brightness, they are not arranged in close proximity on a straight line and used as a linear light source such as CCFL, but are arranged in a matrix or zigzag as a point light source on the back side of the liquid crystal panel. Is generally used.

Japanese Utility Model Publication No. 7-8805 JP 2005-338611 A JP 2007-114587 A JP 2005-38643 A JP 2008-66086 A

  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, so that only a general light diffusion film is arranged between the light source and the liquid crystal panel, In order to increase the front brightness, the addition of an optical sheet with a large number of conical or pyramidal protrusions arranged vertically and horizontally on the surface of the translucent sheet is even brighter than a line light source consisting of CCFLs. There arises a problem that unevenness increases.

  In addition, for this purpose, it has been proposed to use an optical sheet in which concave portions that diffuse light emitted from LEDs from the central portion to the peripheral portion to widen the light distribution are formed (for example, Patent Documents). 4), the use of such an optical sheet causes a problem that the arrangement positions of the point light sources are limited, or the design change such as increase or decrease in the number of arrangement of the point light sources cannot be dealt with, and the versatility is impaired. Furthermore, when a plano-convex Fresnel lens-shaped optical sheet is disposed between the point light source and the liquid crystal panel, or a concave triangular groove portion whose base angle increases as the distance from the point light source increases on the surface of the translucent sheet ( In the case where an optical sheet in which a large number of convex triangular ridges) are arranged concentrically is disposed, there is a problem that versatility is similarly impaired.

  In addition, even when an optical sheet having a plurality of ridges or grooves formed according to the applicant's proposed invention is used, luminance unevenness in the direction along the ridges of the ridges or the direction along the grooves of the ridges is certain. However, since the LED is arranged not as a line light source but as a point light source, there is a problem that luminance unevenness in the direction along the ridge or along the groove cannot be sufficiently solved.

  In addition, two lenticular lens sheets formed by arranging a plurality of lens portions that are part of an elliptical cylinder on the surface of the light-transmitting sheet on the light emission direction side of the LED in a direction along which each lens portion extends. An invention that has been arranged in an orthogonal manner has also been proposed in the past (see, for example, Patent Document 5). However, in the optical sheet in which a plurality of convex ridges having the same shape are formed in this way, two sheets are used. Even if they are arranged so as to be orthogonal to each other, there has actually been a problem that it is not sufficient to eliminate luminance unevenness. Moreover, in order to prevent such luminance unevenness, the arrangement interval of the LEDs has to be narrow, for example, about 15 mm, and the number of LEDs used increases, so a high output LED has a wide arrangement, for example, about 30 mm. There was also a problem that it was not possible to save energy and reduce costs by using a small number of intervals.

  The present invention provides an LED-like point by arranging two optical sheets having a plurality of convex ridges or concave groove portions having different shapes formed on the surface of the translucent sheet so as to overlap each other at different angles. Surface emitting unit and light diffusing sheet unit capable of eliminating unevenness of brightness according to the distance from the light source and widening the arrangement interval of the point light sources and not depending on the arrangement positions of these point light sources Is to provide.

  The surface light emitting unit according to claim 1 is formed by arranging a plurality of convex ridges or concave grooves along a certain direction on the sheet surface of the translucent sheet on one surface of the translucent sheet, and The arrangement of the flanges or groove portions is a set in which a plurality of flange portions or groove portions having different shapes are arranged side by side, and a group consisting of the plurality of flange portions or groove portions is further repeatedly arranged side by side. The two optical sheets thus arranged are arranged on the light emission direction side of a plurality of discretely arranged point light sources so that the respective flange portions or groove portions overlap each other in a certain direction along the sheet surface. And

  The surface light emitting unit according to claim 2, wherein at least one of the two optical sheets has one surface on which a plurality of the ridges or grooves of the translucent sheet are formed, the light emitting direction side of the point light source It is the surface which faces.

  The surface light emitting unit according to claim 3 is characterized in that a certain direction along which the flanges or grooves of the two optical sheets are along the sheet surface is different with an angle difference of 30 ° or more and 90 ° or less.

  The surface light emitting unit according to claim 4 is characterized in that, in the two optical sheets, the ridge widths or groove widths of the ridge portions or groove portions having different shapes in the respective groups are different from each other.

  In the surface light emitting unit according to claim 5, in the two optical sheets, each flange or groove having a different shape in each set has a triangular cross-sectional shape perpendicular to the direction along the flange or along the groove. The larger the sum of both inner angles of the base of the triangle, the wider the ridge width or groove width of these ridges or grooves.

  The surface light emitting unit according to claim 6 is characterized in that, in the two optical sheets, 2 or more and 10 or less flanges or grooves are arranged in each set.

  The light diffusing sheet unit according to claim 7 is composed of two optical sheets used for the surface emitting unit.

  According to the first aspect of the present invention, a plurality of sets of flanges or grooves having different shapes are repeatedly arranged on the surface of one optical sheet, and the surface of the other optical sheet has a direction different from that of the one optical sheet. Since a large number of ridges or grooves along the line are formed, even if the four distances along the sheet surface from the point light source are different, the light passing through the two optical sheets comes to face the front side to some extent, Luminance unevenness corresponding to the distance from each point light source arranged discretely can be eliminated. Then, by reducing the luminance unevenness, the arrangement interval of the point light sources can be widened. In addition, since the ridges or grooves of the two optical sheets do not depend on the position of the point light source, the influence of the positional deviation of these point light sources is not eliminated, and the number of point light sources is increased or decreased. It will be possible to respond to changes.

  Here, the sheet of the optical sheet means a member having a small thickness and a wide area, and actually includes what is called a film shape, a plate shape, or the like. The sheet surface means a virtual surface averaged by unevenness of the ridges or grooves on the surface of the optical sheet, which is usually a flat surface, but other than a flat surface that is slightly curved depending on the application. It may be arranged to be a surface.

  In addition, the fixed direction (the direction along the ridge or the direction along the groove) along which the ridges or grooves of the two optical sheets extend on the sheet surface is an independent fixed direction for each optical sheet, and these two optical sheets Due to the difference in the fixed directions above, these fixed directions are not parallel but have a twisted positional relationship and an angular difference occurs.

  In addition, each optical sheet may have a different arrangement order of the flanges or groove portions having different shapes for each set. It is only necessary that the same shape of ridges or grooves be present in each group, and the order of arrangement of these ridges or grooves is arbitrary, so even if this arrangement order is different, the effect of the present invention is achieved. There is no impact.

  In each optical sheet, the shape of each ridge or groove is symmetrical with respect to a plane orthogonal to the arrangement direction of the ridges or grooves (direction along the ridge or perpendicular to the groove on the sheet surface). It is preferable that In this way, since the shape of each ridge or groove is symmetrical, it is possible to prevent the occurrence of luminance unevenness depending on which side around the point light source. In addition, light from four point light sources can be used effectively between a plurality of point light sources.

  According to the invention of claim 2, at least one of the two optical sheets is arranged discretely because a large number of ridges or grooves are formed on the surface of the point light source facing the light emission direction. Luminance unevenness corresponding to the distance from each point light source can be further reduced.

  According to the invention of claim 3, since the direction along the ridges of the ridges of the two optical sheets or the direction along the grooves of the grooves has an angle difference of 30 ° or more, the ridges or grooves of one of the optical sheets lie along the ridges. In addition to eliminating unevenness in brightness according to the distance from the point light source in the direction perpendicular to the direction or along the groove, a sufficient angle of 30 ° or more with respect to this direction by the flange or groove of the other optical sheet Since luminance unevenness corresponding to the distance in the difference direction can be eliminated, the luminance unevenness can be eliminated in a wide angle range. In addition, the angle difference in the direction along the ridge or in the groove is limited to 90 ° or less in order to clarify that it is the minimum angle difference between the two directions on the sheet surface.

  According to the invention of claim 4, it is possible to adjust the width of the ridge or the groove width according to the shape of each ridge or groove. Here, if the ridge width or the groove width is wide, more light from the point light source can be taken into the ridge or groove. Therefore, if all the ridge widths or groove widths are equal, depending on the shape of each ridge portion or groove portion, the light utilization factor (total reflection of these ridge portions or groove portions with respect to all the light that the ridge portion or groove portion takes in) If there is a difference in the ratio of the light that faces the front side to some extent after passing through, the amount of light that passes through each flange or groove and that faces the front side to some extent is adjusted by adjusting the width of the collar or groove. It becomes possible to make it as uniform as possible.

  Here, the ridge width or groove width refers to the length (width) of the ridge or groove in the direction along the ridge along the sheet surface of the optical sheet or in the direction perpendicular to the groove.

  In addition, it is preferable that each collar part or groove part of the said optical sheet is a triangular shape whose vertical cross-sectional shape orthogonal to the direction along a collar or the direction along a groove | channel has both inner angles of a base side less than 90 degrees. In this manner, the collar portion has a triangular prism shape and the groove portion has a triangular cylinder inner surface shape, so that a large amount of light can enter and exit the optical sheet. The bottom side here is a hypothetical straight line connecting the slant sides of the ridges or grooves with both slant sides of the longitudinal cross-section and connecting the intersections between these slant sides and the sheet surface. A triangle is formed by the hypotenuse and the base.

  In addition, each flange or groove of the optical sheet has an isosceles triangle shape in the longitudinal cross section perpendicular to the direction along the flange or along the groove, and the difference in the shape of each flange or groove in each set is the difference between the two. It is preferable that the base angle of the equilateral triangle is different. In this way, the shape of each collar part or groove part is symmetrical, and in the case of the collar part, it becomes a triangular prism shape, and in the case of the groove part, it becomes a triangular cylinder inner surface shape. Depending on which side of the four sides the luminance unevenness is prevented, a lot of light can be incident on and emitted from the optical sheet. Here, the base angle of the isosceles triangle is an internal angle (both internal angles are equal) of the base of the isosceles triangle.

  According to the fifth aspect of the present invention, since the ridges or grooves of each set have a narrower apex angle and a sharper apex of the triangle in the longitudinal cross-sectional shape, the ridge width or groove width becomes wider, so that more light can be taken in. And, as the apex or groove with a smaller apex angle, the light utilization rate decreases, so that such an eaves or groove makes it possible to capture more light, so that each apex with a different apex angle. Alternatively, the amount of light passing through the groove and facing the front side to some extent can be made uniform.

  In addition, in place of such a triangle, in the two optical sheets, the vertical cross-sectional shape perpendicular to the ridge direction of each ridge portion or the groove direction of the groove portion is a square in which both inner angles of the bottom are 90 ° or less. It can also be set as the above polygon or the circular arc shape below a semicircular arc. In this way, in the case of the flange portion, it becomes a semi-polygonal columnar shape or a semi-cylindrical shape, and in the case of the groove portion, it becomes a semi-polygonal cylinder inner surface shape or a semi-cylindrical inner surface shape. It is possible to ensure that the light is directed to the front side to some extent at any one or two or more buttocks or grooves of each set.

  According to the invention of claim 6, since there are two or more different ridges or grooves in each group, it is ensured that light is directed to the front side to some extent in any one of the ridges or grooves in each group. Can do. Moreover, since the number of the ridges or grooves in each group is 10 or less, the range of one set of the ridges or grooves can be sufficiently narrowed, and uneven brightness can be suppressed for each group. In addition, if 3 or more and 5 or less collar parts or groove parts are arranged in each group, light can be more reliably directed to the front side, and luminance unevenness for each group can be further suppressed.

  According to the seventh aspect of the present invention, there is provided a light diffusion sheet unit that eliminates uneven brightness according to the distance from each point light source that is discretely arranged and does not depend on the position and number of point light sources. Will be able to.

1 is an exploded perspective view showing a configuration of a backlight unit according to an embodiment of the present invention. 1 is a partially enlarged longitudinal sectional front view of two optical sheets used in a backlight unit, showing an embodiment of the present invention. 1 is a partially enlarged vertical cross-sectional side view of two optical sheets used in a backlight unit, showing an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged vertical cross-sectional front view showing a set of eaves in an upper optical sheet, showing an embodiment of the present invention. 1 shows an embodiment of the present invention, and is a partially enlarged longitudinal sectional front view of a center position (a), a position (b) separated in the right direction, and a position (c) further separated in the right direction in the upper optical sheet. FIG. FIG. 10 is a partially enlarged longitudinal sectional front view of an upper optical sheet, showing another embodiment of the present invention, in which the ridge width of each ridge portion is different. FIG. 10 is a partially enlarged longitudinal sectional front view of an upper optical sheet in which the heights of the flanges are aligned, showing another embodiment of the present invention. FIG. 9 is a partially enlarged longitudinal sectional front view of an upper optical sheet in which another embodiment of the present invention is shown and the height of each flange portion is raised. FIG. 10 is a partially enlarged longitudinal sectional front view of an upper optical sheet, showing another embodiment of the present invention, in which the longitudinal sectional shape of each collar portion is an isosceles trapezoid. FIG. 10 is a partially enlarged longitudinal sectional front view of an upper optical sheet, showing another embodiment of the present invention, in which the arrangement order of the ridges of each set is irregularly changed. FIG. 11 is a partially enlarged longitudinal sectional front view of an upper optical sheet, showing another embodiment of the present invention, in which the ridges of each set are dispersed and biased left and right. FIG. 9 is a partially enlarged longitudinal sectional front view of an upper optical sheet, showing another embodiment of the present invention, in which the ridges of each set are distributed and biased left and right and the arrangement order is irregularly changed. . FIG. 5 is a partially enlarged longitudinal sectional front view of an upper optical sheet having two resin sheets, showing another embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged front view illustrating a configuration of a backlight unit according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged plan view illustrating an arrangement of LEDs in a backlight unit according to an embodiment of the present invention. It is a graph which shows the Example of this invention, Comprising: The angle difference of the direction along a ridge, and the relationship between uniformity. FIG. 5 is a schematic diagram illustrating an embodiment of the present invention and illustrating a state in which an upper optical sheet and an LED substrate in a backlight unit are rotated. It is an Example of this invention and is a graph which shows the relationship between an angle difference with an LED board, and a uniformity degree by using the angle difference of the direction along a ridge as a parameter. It is an Example of this invention, Comprising: It is a graph which shows the relationship between the angle difference of the direction along a ridge, and a uniformity degree by using the angle difference with an LED board as a parameter.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS.

  In the present embodiment, as shown in FIG. 1, a backlight unit of a direct light type (surface emitting unit) in a liquid crystal display will be described. The backlight unit uses a light diffusing sheet unit in which two optical sheets 1 and 2 are stacked one above the other with a slight gap therebetween. A large number of LEDs 3 are arranged below (on the back side) of these two optical sheets 1 and 2. The liquid crystal panel 4 is disposed above (front side) above these two optical sheets 1 and 2. A light diffusion film (not shown) may be disposed between the two optical sheets 1 and 2 above the liquid crystal panel 4.

  The two optical sheets 1 and 2 are both made of a transparent resin sheet, and are arranged so that the planar sheet surfaces are horizontal. A large number of LEDs 3 are arranged in a matrix at equal intervals in the front-rear and left-right directions on a plane parallel to the sheet surfaces of the two optical sheets 1 and 2.

  As shown in FIG. 2, the upper optical sheet 1 of the two optical sheets 1 and 2 has a plurality of convex flanges 1a to 1c arranged in the left-right direction on the upper surface, as shown in FIG. Yes. 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. The lower surface of the optical sheet 1 is a flat surface along the sheet surface.

  As shown in FIG. 3, the lower optical sheet 2 has a large number of convex flanges 2 a to 2 c that are arranged in the front-rear direction on the upper surface. The flanges 2a to 2c on the upper surface of the optical sheet 2 are convex upwards in which the longitudinal cross-sectional shape on the surface along the up and down direction is an isosceles triangle, and these flanges 2a to 2c are The isosceles triangle has three different shapes with different base angles. And the arrangement | sequence of these collar parts 2a-2c is what arranged the set S which arranged three kinds of collar parts 2a-2c from which a base angle differs in the back-and-forth direction, and repeated and arranged in the front-and-rear direction over many more groups. It has become. The lower surface of the optical sheet 2 is a flat surface along the sheet surface.

The structure in each group S of the collar parts 1a-1c of the upper optical sheet 1 is demonstrated based on FIG. One set S includes a ridge portion 1a of the base angle theta ₁ is 55 °, 3 types of ridges of the ridge portion 1b of the base angle theta ₂ is 45 °, base angle theta ₃ is a ridge 1c of 25 ° 1a to 1c are arranged from right to left one by one. 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 configuration of each set S of the flange portions 2a to 2c of the lower optical sheet 2 is also different in that the arrangement direction is changed from left to right in the upper optical sheet 1, but is the same in other cases. is there. Accordingly, the direction along the flanges of the flanges 1a to 1c of the optical sheet 1 and the flanges 2a to 2c of the optical sheet 2 are orthogonal to each other due to the positional relationship of torsion.

  In the present invention, the number of collars arranged as one set is suitably 2 or more and 10 or less, more preferably 3 or more and 5 or less. 2 and 3 show only the region corresponding to one LED 3 in the optical sheets 1 and 2 in order to enlarge the protrusions of the flanges 1a to 1c and the flanges 2a to 2c for easy viewing. In this region, only nine sets of the collar parts 1a to 1c and the collar parts 2a to 2c are shown, but in reality, a larger number of groups are arranged for each LED 3, and the light emission of the elements of the LED 3 The collar width B shown in FIG. 4 is sufficiently narrower than the width of the portion. Furthermore, the number of sets in the region of the two optical sheets 1 and 2 corresponding to the single LED 3 does not necessarily have to be an integer.

According to the above arrangement, above the optical sheet 1 in the vicinity of the position E ₀ directly above the LED3 shown in FIG. 2, as shown in FIG. 5 (a), a large ridges light from the LED3 is base angle The part 1a and the collar part 1b are often emitted in the left-right direction or totally reflected, but the light emitted from the collar part 1c having the smallest base angle is almost upward. Further, in the vicinity of the position E ₁ apart a little lateral direction with respect to the right above the LED3, as shown in FIG. 5 (b), the maximum ridge portion 1a and a minimum of ridges 1c of the light base angle from the LED3 In this case, the light is emitted while being inclined in the left-right direction, but the light emitted from the flange portion 1b having an intermediate base angle is substantially upward. Then, further in the vicinity of the position E ₂ from directly above the LED3 far away in the left-right direction, as shown in FIG. 5 (c), the light is left in small ridge 1b and ridges 1c of the base angle from the LED3 The light emitted from the flange 1a having the largest base angle is substantially upward. In FIG. 5, refraction of incident light on the lower surface of the optical sheet 1 is omitted.

  Similarly to the above, also in the lower optical sheet 2, near the position directly above the LED 3, the light from the LED 3 is emitted in a slanting direction in the left-right direction at the flange portion 2 a or the flange portion 2 b having a large bottom angle. Although the total reflection often increases, the light incident on the flange 2c having the smallest base angle is almost upward. Also, in the vicinity of a position slightly away from the LED 3 in the front-rear direction, the light from the LED 3 is emitted in a tilted direction in the front-rear direction at the maximum flange 2a and the minimum flange 2c. The light incident on the flange 2b having an intermediate angle is almost upward. Further, in the vicinity of a position far from the LED 3 in the front-rear direction, the light from the LED 3 is emitted in a tilted direction in the front-rear direction at the flange portion 2b or the flange portion 2c with a small base angle. The light incident on the largest collar 2a is almost upward.

  Therefore, the two optical sheets 1 and 2 in the backlight unit of the present embodiment have a set S composed of three types of flanges 1a to 1c and 2a to 2c having different base angles of an isosceles triangle having a vertical cross section. Are arranged repeatedly in the front and back orthogonal directions, so that even if the distance from the LED 3 in the left-right direction or the front-rear direction is different, any one of the sets S of the upper optical sheet 1 in the left-right direction is different. The light incident on the parts 1a to 1c is substantially upward, and in the front-rear direction, the light emitted from any one of the flanges 2a to 2c of each set S of the lower optical sheet 2 is substantially upward. For this reason, since unevenness in luminance can be prevented according to the distance away from the LED 3 in the front / rear / right / left direction, the uniformity can be increased. In addition, since the decrease in luminance can be reduced even at positions far away from the LED 3, the degree of uniformity is not greatly reduced even if the distance between the LEDs 3 is widened, and the same degree of uniformity as before can be obtained. If it is sufficient, the distance between the LEDs 3 can be greatly increased, and the arrangement distance of the LEDs 3 used in the backlight unit can be increased to reduce the number of the energy savings and the cost.

  In addition, the two optical sheets 1 and 2 in the backlight unit of the present embodiment are formed by arranging a large number of sets S in which the three types of collars 1a to 1c and 2a to 2c are arranged in the left-right direction and the front-rear direction. Therefore, the arrangement positions of the LEDs 3 in the front / rear and left / right directions are arbitrary, and not only the influence of the positional deviation of the LEDs 3 is eliminated, but also the increase / decrease of the number of the LEDs 3 and the design change of the arrangement pattern can be dealt with. .

In the above-described embodiment, the case has been shown in which the three kinds of collar portions 1a to 1c and the collar widths 2a to 2c of each set S in the two optical sheets 1 and 2 are made constant. The width B does not necessarily have to be constant. That is, for example, like the upper optical sheet 1 shown in FIG. 6, the flange widths B _{1 to} B _{3 of the} flange portions _{1 a to 1} c may be different. In particular, as shown in FIG. 6, the larger the sum of both inner angles of the bases of the convex longitudinal cross-sectional shapes in the flanges 1 a to 1 c, that is, the larger the base angle of the isosceles triangle here. if such that ridge width _B 1 .about.B ₃ becomes wider, because the ridge width _B 1 .about.B ₃ more ridges 1a~1c the apex angle of the isosceles triangle is pointed small wider, three different types of apex angle The amount of light emitted from the collar portions 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. And also in the lower optical sheet 2, if the collar width B of the three kinds of collar portions 2a to 2c of each set S is adjusted in the same manner, the light emitted from these collar portions 2a to 2c and directed upward to some extent The amount of light can be made uniform to increase the degree of uniformity.

In addition, the two optical sheets 1 and 2 of the above embodiment differ in the heights of the convex shapes of the three types of collars 1a to 1c and collars 2a to 2c in each set S. The thickness may be aligned on a plane parallel to the sheet surface. For example, FIG. 7 shows a case where the heights of the three types of flanges 1a to 1c in each set S in the upper optical sheet 1 are aligned. However, in this case, contrary to the case shown in FIG. 6, the ridge widths B _{1 to} B of the ridge portions _{1 a to 1} c having a small apex angle of the triangle (triangle based on the original isosceles triangle) are small. _Since it becomes narrower by _3, there is a possibility that sufficient luminance cannot be obtained at a position where the distance in the left-right direction from the LED ₃ is far. Therefore, as shown in FIG. 8, with respect to the collar portion 1 b and the collar portion 1 c that are originally low in 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, the height B of the collar parts 1a-1c can be made constant, and the convex height can also be made uniform. And also in the lower optical sheet 2, the convex heights of the three types of flanges 2a to 2c of each set S can be similarly aligned.

The optical sheets 1 and 2 of two of the above embodiments, the base angle theta ₁ through? ₃ of the three ridges 1a~1c and ridge 2a~2c of each set S and the 55 ° and 45 ° 25 Although the case of ° is shown, these base angles θ _{1 to} θ ₃ only need to be different from each other, and therefore the specific angle values are arbitrary. However, 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 the maximum value of the base angle exceeds 70 ° and becomes too large, the height of the convex shape becomes too high when the ridge width B of the ridge portions 1a to 1c and the ridge portions 2a to 2c is sufficiently wide. As a result, the moldability of the optical sheets 1 and 2 becomes poor, and 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 angle of each of the flange portions 1a to 1c and each of the flange portions 2a to 2c is reduced, thereby eliminating luminance unevenness. The effect of increasing the uniformity is difficult to obtain sufficiently.

  The minimum value of the base angle is preferably 25 ° or less, and more preferably 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 flange portions 1a to 1c and each of the flange portions 2a to 2c is reduced, thereby eliminating luminance unevenness. Therefore, it is difficult to obtain the effect of increasing the uniformity. The minimum value of the base angle may be 0 °, and therefore any one ridge portion of each set S may be a surface parallel to the sheet surface.

  Further, in the two optical sheets 1 and 2 of the above-described embodiment, the longitudinal cross-sectional shape of each of the flange portions 1a to 1c and each of the flange portions 2a to 2c is an isosceles triangle or a shape based on the isosceles triangle. However, it is also possible to form an isosceles trapezoid in which the tops of these isosceles triangles are cut horizontally. FIG. 9 shows an example in which the longitudinal cross-sectional shape of the flange portions 1a to 1c of the upper optical sheet 1 is an isosceles trapezoid, but the same applies to the flange portions 2a to 2c of the lower optical sheet 2. 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.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where three types of collar parts 1a-1c and collar parts 2a-2c of each set S were arranged in the same order, these If the number of sets on the optical sheets 1 and 2 is sufficiently large, this arrangement order does not affect the effect of the present invention, so this arrangement order may be different for each set S. In this case, the arrangement order The differences are preferably irregular. FIG. 10 shows an example in which the arrangement order of the ridges 1a to 1c of each set in the upper optical sheet 1 is irregularly different for each set S, but also the ridges 2a to 2c of the lower optical sheet 2 It is the same.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where three types of collar parts 1a-1c and collar parts 2a-2c were arranged in each set S, four or more types of collars were shown. The parts may be arranged. Furthermore, even if only two types of collars are arranged, the effect of the present invention can be expected to some extent if the longitudinal cross-sectional shape is a polygon having a square shape or more.

  Moreover, the two optical sheets 1 and 2 of the said embodiment are the isosceles triangles whose longitudinal cross-sectional shape of each collar part 1a-1c and each collar part 2a-2c is symmetrical with respect to a perpendicular line, or this isosceles triangle However, the present invention is not necessarily limited to such a symmetrical shape. However, in order for the two optical sheets 1 and 2 to exhibit characteristics that do not depend on the positions of the respective LEDs 3 in the left-right direction or the front-rear direction, for example, the longitudinal cross-sectional shapes of the flange portions 1a to 1c of the upper optical sheet 1 are asymmetric In the case of the shape, it is not preferable that the left-right asymmetric shape is excessively biased rightward or leftward. If this bias is excessively large, depending on which side of the LED 3 is left or right when the optical sheet 1 is considered as a whole. There is also a risk of uneven brightness. Therefore, for example, in the case of the upper optical sheet 1, even if the vertical cross-sectional shapes of the individual flange portions 1 a to 1 c are left-right asymmetric, if the degree of deviation is quantified and the left-right direction is positive or negative, It is preferable to disperse and average the deviations so as to be as close to 0 as possible when the deviations of all the flanges 1a to 1c are totaled. That is, as shown in FIG. 11, if there are five types of collars 1a to 1e in each set S of the upper optical sheet 1, for example, the collars 1a and 1e are biased to the left by a certain amount, and the collar 1c Is symmetrical with no bias, and it is preferable that the biases 1b and 1d are balanced and averaged so that the ribs 1b and 1d are biased by a certain amount in the right direction. FIG. 12 shows a case where the arrangement order of these five types of collars 1a to 1e is different between adjacent sets S. In addition, it is preferable to disperse and average such asymmetrical bias in the lower optical sheet 2 as well.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment 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, convenience on manufacture and chamfering were shown. Etc., each corner may be slightly dull or rounded. For example, when the applicant actually manufactured the molds of the optical sheets 1 and 2, the apex portion of the triangle of the vertical cross-sectional shape of the heel part mold had an arc shape with a curvature radius of about 20 to 30 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, the optical sheets 1 and 2 were produced by filling the resin up to about 70% of the height of the triangle as a test, but almost no difference was found in the effect of the present invention. This is because it is important that the ridges of the optical sheets 1 and 2 have inclined surfaces composed of both oblique sides of the triangle, and the state of the details of the corners that are the boundary portions where these inclined surfaces contact is not important. Because. The same effect can be obtained when the vertical cross-sectional shape of the buttock is an isosceles trapezoid in FIG. 9 for the same reason.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where the convex collar part was arranged and formed in the upper surface, even if it is a thing in which a concave groove part is arranged and formed, this book is the same. The effects of the invention 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.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where the lower surface in which the collar part and a groove part were not formed was flat, the structure of the lower surface of this 1st optical sheet 1 is arbitrary. For example, light diffusibility may be improved by processing into a textured shape made of fine irregularities.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where the direction along the ridge of each ridge part, or the direction along the groove | channel of a groove part was mutually orthogonal, these ridge direction or the direction along a groove | channel is If they are different, they do not necessarily have to be orthogonal with an angle difference of 90 °. For example, there may be only an angle difference of 45 °. This is because the effect of reducing luminance unevenness due to the ridges or grooves of the two optical sheets 1 and 2 is not only in the direction along the ridges or in the direction perpendicular to the grooves but also in a certain angular range around them. This is because the degree of difference varies.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where a collar part and a groove part were formed in the upper surface, either one formed the collar part and the groove part in the lower surface, In addition, both the optical sheets 1 and 2 may have a flange or a groove formed on the lower surface. However, it is preferable that at least one of the optical sheets 1 and 2 has a flange or a groove formed on the upper surface.

  Moreover, in the said embodiment, although the case where the optical sheets 1 and 2 consist of a transparent resin sheet was shown, since it should just have the translucency which permeate | transmits light, it does not necessarily need to be transparent. The sheet thickness of the two optical sheets 1 and 2 is not particularly limited, and generally a sheet thickness of about 0.1 to 3 mm is appropriate, and a sheet thickness of 0.14 to 1.2 mm is suitable. Is more preferable.

  Examples of the resin sheet of the optical sheets 1 and 2 as described above include polycarbonate, polyester, polyethylene, polypropylene, polyolefin copolymer (for example, poly-4-methylpentene-1), polyvinyl chloride, cyclic polyolefin (for example, norbornene structure). Etc.), acrylic resins, polystyrenes, ionomers, styrene-methyl methacrylate copolymer resins (MS resins) and the like can be used. In particular, among resin sheets made of thermoplastic resin, those made of polycarbonate, polyester (especially polyethylene terephthalate), and cyclic polyolefin have good heat resistance and are deformed by heat radiation from LED 3 when used in a backlight unit. It is preferably used because it is less likely to cause wrinkles and wrinkles. Moreover, a resin sheet made of polycarbonate is very preferably used because the polycarbonate itself is a resin having good transparency, has low hygroscopicity, high luminance, and little warpage. Further, the resin sheet may be made of a light-transmitting thermosetting resin such as unsaturated polyester or epoxy resin. And this resin sheet can also use what mixed and alloyed two or more types of resin materials, and was compounded.

  In addition, the optical sheets 1 and 2 of the above embodiment can be manufactured by using a press manufacturing method in which a resin sheet having flat surfaces on both sides is pressed with a mold, but other press manufacturing methods, casting methods, or the like, or injection You may produce by arbitrary manufacturing methods, such as the shaping | molding method of a shaping | molding method, the continuous shaping | molding method by the roll shaping | molding method by letting a mold roll pass, and the extrusion molding method.

  In addition, the resin sheets of the optical sheets 1 and 2 according to the above-described embodiments are stabilizers, lubricants, impact resistance improvers, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, colorants, fluorescents necessary for molding. A brightener or the like may be appropriately contained. Furthermore, in the optical sheets 1 and 2 having a multi-layer configuration, these additives may be appropriately changed in the kind and blending ratio of the additive between the base material layer and the surface layer, for example. FIG. 13 shows an example of a two-layer structure in which an upper optical sheet 1 is provided with a surface layer 12 as an upper layer of the base material layer 11 and convex ridges are arranged on the surface layer 12.

  Moreover, the light diffusing agent may be contained in the resin sheets of the optical sheets 1 and 2 of the above embodiment. As the light diffusing agent, inorganic particles, metal oxide particles, organic polymer particles, and the like having a different light refractive index from the resin material of the resin sheet 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 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. If such a light diffusing agent is contained, light can be sufficiently diffused in the optical sheets 1 and 2, so that it is not necessary to add an expensive light diffusing film or the like to the backlight unit.

  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, particularly particles of 30 μm or less are preferred.

  Moreover, in the said embodiment, although the case where the optical sheets 1 and 2 were a resin sheet was shown, since what is necessary is just a translucent sheet | seat (things, such as a film form and plate shape, etc.), thin glass etc. It may be. Furthermore, although the optical sheets 1 and 2 of the above-described embodiment have shown the case where the sheet surface is a flat surface, it may be a surface other than a flat surface, for example, slightly curved according to the shape of the liquid crystal panel 4.

  Moreover, although the two optical sheets 1 and 2 of the said embodiment showed the case where it was the same structure except the direction along the ridge of a collar part, or the direction along the groove of a groove part orthogonally crossed, for example, one side is a collar part. The structures of the optical sheet 1 and the optical sheet 2 may be different such that the other is a groove, the longitudinal cross-sectional shape of these flanges or grooves is different, or the material of the translucent sheet is different.

  In the above embodiment, the two optical sheets 1 and 2 are slightly used to make the backlight unit thin and to efficiently capture the light passing through the lower optical sheet 2 into the upper optical sheet 1. Although the case where the gaps are arranged so as to overlap each other with a gap is shown, the size of the gap is not necessarily limited. For example, the upper optical sheet 1 forms a flange or a groove on the upper surface, and the lower optical In the case where the sheet 2 has a flange or a groove formed on the lower surface and the facing surfaces of these optical sheets 1 and 2 are flat, they can be arranged in close contact with each other without a gap.

  Moreover, in the backlight unit of the said embodiment, although the case where only two optical sheets 1 and 2 were arrange | positioned above LED3 was shown, between these liquid crystal panels 4 above these optical sheets 1 and 2 was shown. Furthermore, one or more conventional optical sheets having a configuration different from that of a general light diffusing film and the optical sheets 1 and 2 can be arranged.

  In the above-described embodiment, the case where a large number of LEDs 3 are arranged in a matrix form with equal intervals in the front-rear and left-right directions has been shown. The arrangement pattern is not particularly limited as long as the LEDs 3 are regularly and evenly arranged. In addition, the arrangement pattern may be random as long as the density difference in which the LEDs 3 are arranged is relatively small and the distribution is almost average. Furthermore, many LED3 is arrange | positioned in the position shifted | deviated to the up-down direction not for the same horizontal plane but according to the sheet surface which is not the plane of the two optical sheets 1 and 2 or for other reasons. May be. Furthermore, there are no particular limitations as long as the number of LEDs 3 is plural.

  Moreover, although the case where LED3 was used as a light source was shown in the said embodiment, the kind of light source will not be ask | required if it is a point light source. The point light source is used to mean a surface light source such as an EL (electroluminescence) sheet or a line light source such as CCFL, and a small light bulb, a discharge tube, or the like can also be used as a point light source. In this case, not only a single element but also a plurality of elements arranged closely may be used. Furthermore, in the said embodiment, although normal LED3 which does not have a lens was used, LED with a lens can also be used.

  The two optical sheets 1 and 2 are arranged on the light emission direction side of the point light source. When the point light source is the LED 3, the light distribution characteristic has a strong directivity. Although it is on the light emission direction side, in the case of a normal small bulb or discharge tube, light is emitted at almost all solid angles, so any side from which light is emitted can be the light emission direction side. In addition, for example, two optical sheets 1 and 2 may be arranged above and below a small light bulb, a discharge tube, or the like to supply light to both the upper and lower sides. However, when a reflecting plate is used, the side opposite to the reflecting plate in a small light bulb, a discharge tube or the like is the light output direction side.

  Moreover, although the said embodiment showed the case where it uses as a backlight unit of the liquid crystal panel 4, it can also be used as backlight units other than the liquid crystal panel 4, and is not limited to a backlight, For example, a surface illuminating device etc. Can also be used. When the above-described embodiment is used for a surface illumination device or the like, the plurality of LEDs 3 may be biased in the distribution of distribution due to lighting effects or the like, or the distance between each LED 3 and the two optical sheets 1 and 2 may be increased. It is also possible to arrange them so that they are not necessarily the same.

  The light diffusing sheet unit composed of the two optical sheets 1 and 2 according to the above embodiment is used as a component of the surface light emitting unit according to the above embodiment, and is not limited to a light source, for example, a daylighting plate that captures natural light from outside. Etc. can also be used.

[Configuration of Examples and Comparative Examples]
The backlight units of Examples 1 to 10 using the various two optical sheets 1 and 2 shown in the above embodiment, and Comparative Example 1 using the various two optical sheets 1 and 2 of the conventional example. The result of measuring the uniformity of each of the two backlight units is shown below.

  In the backlight units of Examples 1 to 10 and Comparative Examples 1 and 2, a large number of LEDs 3 are arranged in a matrix on the LED substrate 5 below the two optical sheets 1 and 2, as shown in FIG. Yes. Here, the distance H between the light source sheets from each LED 3 to the upper two optical sheets 1 and 2 is 20 mm, and the distance D between the light sources, which is the distance between the adjacent LEDs 3 and 3 in the front-rear and right-and-left directions, is particularly refused. Unless otherwise, it is 30 mm.

For the measurement of the uniformity of the backlight units of Examples 1 to 10 and Comparative Examples 1 and 2, "EYESCALE III" manufactured by I-System Co., Ltd. was used and measured in an environment of room temperature 23 ° C and humidity 50% RH. Went. As shown in FIG. 15, this measurement is performed with two optical sheets at a total of five measurement points: a region A ₀ directly above the LED ₃ and regions A _{1 to} A ₄ between the four surrounding LEDs 3. The brightness is measured from above 1 and 2, the ratio of the brightness of the area A ₀ and each of the areas A _{1 to} A ₄ is calculated, and the average value of these four brightness ratios is calculated as the uniformity. It was.

  The configuration of the two optical sheets 1 and 2 used in the backlight units of Examples 1 to 10 will be described. Each of the optical sheets 1 and 2 of Examples 1 to 10 is formed by forming a flange on one surface of a transparent polycarbonate resin sheet containing no light diffusing agent and flattening the other surface. . In Examples 1 to 10, all the directions along the ridges of the ridges of the upper optical sheet 1 and the ridges of the lower optical sheet 2 are orthogonal. And the optical sheets 1 and 2 of Examples 1-7 all have a collar portion formed on the upper surface.

  Table 1 shows the detailed configuration of the two optical sheets 1 and 2 used in the backlight units of Examples 1 to 7.

  As shown in Table 1, Examples 1 to 3 have the same configuration of the flange portions of the two optical sheets 1 and 2 except that the directions along the flanges are orthogonal. That is, the two optical sheets 1 and 2 of Example 1 each have three kinds of isosceles triangle longitudinal cross-sectional shapes with base angles of 55 °, 45 °, and 25 ° and a width of 200 μm. The two optical sheets 1 and 2 of Example 2 are both formed with an array of ridge portions, and the base angles are 70 °, 60 °, 45 °, and 25 °, and the ridge widths are 300 μm and 200 μm. The four optical sheets 1 and 2 of Example 3 have a base angle of 55, which is an array of four types of ridges having isosceles longitudinal cross-sectional shapes of 150 μm and 100 μm. A set of five types of ridges having an isosceles triangular longitudinal cross-sectional shape of と, 45 °, 35 °, 25 °, and 10 ° and a ridge width of 200 μm is arranged.

  In the fourth embodiment, the upper optical sheet 1 is formed by arranging a set of four types of collars having the same configuration as the two optical sheets 1 and 2 of the second embodiment. In this example, a set of five types of eaves portions having the same configuration as the two optical sheets 1 and 2 of Example 3 is arranged. Further, in the fifth embodiment, the upper optical sheet 1 is formed by arranging a set of five types of eaves parts having the same configuration as the two optical sheets 1 and 2 of the third embodiment. In this example, four sets of collars having the same configuration as the two optical sheets 1 and 2 of Example 2 are arranged.

  Each of the two optical sheets 1 and 2 of Examples 1 to 5 has a sheet thickness of 0.5 mm. On the other hand, the two optical sheets 1 and 2 of Example 6 are both formed by arranging a set of three types of collars having the same configuration as the two optical sheets 1 and 2 of Example 1. However, the sheet thickness is as thin as 0.14 mm. Further, the two optical sheets 1 and 2 of Example 7 are both formed by arranging a set of four types of eaves parts having the same configuration as the two optical sheets 1 and 2 of Example 2. The sheet thickness is as thick as 1.2 mm.

  The buttocks of the two optical sheets 1 and 2 of Examples 8 to 10 not shown in Table 1 have the same configuration as the buttocks of the optical sheets 1 and 2 of Example 2, but two in Example 2 Unlike the optical sheets 1 and 2, the upper surface of both of the optical sheets 1 and 2 is different from one or both of the optical sheets 1 and 2 only in that the lower surface is formed with a flange. Other configurations are the same as those in the second embodiment. That is, Example 8 forms a hook on the lower surface of both optical sheets 1 and 2, Example 9 forms a hook on the lower surface of only the lower optical sheet 2, and Example 10 Only the optical sheet 1 has a flange on the lower surface.

  Table 2 shows the detailed configuration of the two optical sheets 1 and 2 used in the backlight units of Comparative Examples 1 and 2.

  As shown in Table 2, the two optical sheets 1 and 2 of Comparative Example 1 both have a base angle of 45 ° and a ridge width on the upper surface of a transparent polycarbonate resin sheet containing no light diffusing agent. One type of eaves portion having an isosceles triangular vertical cross-sectional shape of 200 μm is formed in an array, and the lower surface is flat. The two optical sheets 1 and 2 of Comparative Example 2 are both commercially available lenticular lens sheets (manufactured by Dainippon Printing Co., Ltd.) in which one type of collar portion having a semi-elliptical longitudinal section is formed on the upper surface. H2K). The optical sheets 1 and 2 of Examples 1 to 10 and Comparative Example 1 other than Comparative Example 2 were all prepared by the applicant.

[Comparison of uniformity of Examples and Comparative Examples]
Table 3 shows the results of measuring the uniformity of the backlight units of Examples 1 to 5 and Comparative Examples 1 and 2.

  As can be seen from Table 3, Examples 1-5 have a uniformity of at least 79.7% of Example 3 and the highest uniformity reaches 97.7% of Example 4, so Compared to the low uniformity of 36.6% and 29.7% of Examples 1 and 2, a significantly superior uniformity can be obtained, and the luminance unevenness can be sufficiently reduced. This is only two optical sheets 1 and 2 of Comparative Examples 1 and 2 in which only the ridges having the same shape are repeatedly formed, whereas two optical sheets 1 of Examples 1 to 5 are used. , 2 is because the dependency on the difference in the distance from the LED 3 along the sheet surface is reduced by arranging three or more types of flanges having different shapes.

  Moreover, according to Table 3, it turned out that an extremely high degree of uniformity can be obtained by arranging 3 to 5 kinds of brim groups as in Examples 1 to 3. Furthermore, it was also found that, as in Examples 4 and 5, it is possible to obtain a higher degree of uniformity by arranging different types of brim groups on the two optical sheets 1 and 2.

[Effect of sheet thickness on uniformity]
The optical sheets 1 and 2 of Example 6 are obtained by reducing only the sheet thickness of the optical sheets 1 and 2 of Example 1, and the optical sheets 1 and 2 of Example 7 are the optical sheets 1 and 2 of Example 2. Only the sheet thickness of 2 is increased. Table 4 shows the results of measuring the uniformity of the backlight units of Example 6 and Example 7. For comparison, the uniformity of Example 1 and Example 2 shown in Table 3 is also shown.

  According to Table 4, the uniformity of Example 6 having a thinner sheet thickness than that of Example 1 is slightly improved, and the uniformity of Example 7 having a larger sheet thickness than that of Example 2 is slightly decreased. However, in any case, since the change in uniformity is small, it is found that there is no practical problem if the sheet thickness of the optical sheets 1 and 2 is at least in the range of 0.14 to 1.2 mm. It was.

[Influence on uniformity by the surface forming the buttock]
In Example 2, the flanges are formed on the upper surfaces of both of the two optical sheets 1 and 2, but in Examples 8 to 10, one or both of the two optical sheets 1 and 2 are on the lower surface. Forms a buttock. The results of measuring the uniformity of the backlight units of Examples 8 to 10 are shown in Table 5. For comparison, the uniformity of Example 2 shown in Table 3 is also shown.

  According to Table 5, only the uniformity of Example 8 in which the flanges are formed on the lower surfaces of the two optical sheets 1 and 2 is slightly less than 90%. The uniformity of Examples 9 and 10 in which the ridges are formed on the upper and lower surfaces of No. 2 is higher than that of Example 2 and exceeds 90% together with Example 2. Accordingly, the surface forming the collar does not affect the uniformity so much in either case of the upper surface or the lower surface, but at least one of the two optical sheets 1 and 2 is used. It was found that Example 2 and Examples 9 and 10 in which the collar portion is formed on the upper surface (the surface facing the light emission direction side) are more preferable.

[Effect on uniformity by angle difference along the ridge]
In both Example 2 and Comparative Example 2, the directions along the ridges of the two optical sheets 1 and 2 are orthogonal. Therefore, only the upper optical sheet 1 of Example 2 and Comparative Example 2 is rotated on the sheet surface, and the angle difference in the ridge direction with respect to the lower optical sheet 2 is 0 ° (the ridge direction is parallel). ) To 90 ° (the direction along the ridge is orthogonal) The results of measuring the uniformity of the backlight unit are shown in Table 6, and a graph of Table 6 is shown in FIG.

  As is apparent from Table 6 and FIG. 16, in Example 2, a high degree of uniformity of 70% or more was obtained when the angle difference was 30 ° or more, and an extremely high degree of uniformity of 90% or more when the angle difference was 35 ° or more. It was found that the degree could be obtained stably. Further, in comparison with Comparative Example 2, the uniformity of Example 2 is superior when the angle difference is 30 ° or more, and when the angular difference is 70 ° or more, the uniformity of Comparative Example 2 sharply decreases. It was found that the uniformity of Example 2 was much better. Moreover, it was also found that Example 2 can obtain a high degree of uniformity in a wide angle range where the angle difference is 30 ° or more and 90 ° or less.

[Influence on uniformity due to angle difference with LED board and angle difference along ridge]
In the second embodiment, the directions along the ridges of the two optical sheets 1 and 2 are orthogonal to each other, and the LEDs 3 on the LED substrate 5 therebelow are arranged in a matrix on the matrix along the ridge direction. Therefore, as shown in FIG. 17, only the upper optical sheet 1 of Example 2 is rotated on the sheet surface, and the uniformity of the backlight unit is measured when the LED substrate 5 is also rotated on the substrate surface. The results are shown in Table 7, and Table 7 is a graph of the angle difference in the direction along the ridges of the optical sheets 1 and 2 as a parameter. FIG. 18 shows the angle difference between the optical sheet 2 and the LED substrate 5. A graph of the parameters is shown in FIG.

  According to Table 7 and FIG. 18, when the angle difference in the direction along the ridge is 0 °, the uniformity is 50% only when the angle difference from the LED substrate 5 is 45 ° (LEDs 3 are arranged in a staggered pattern). However, in any case, it was found that sufficient uniformity cannot be obtained. On the other hand, when the angle difference in the direction along the ridge is 30 ° or more, a high degree of uniformity can be obtained regardless of the angle difference with the LED substrate 5, and in particular, when the angle difference in the direction along the ridge is 60 ° or more. It was found that an extremely high uniformity can be obtained stably without depending on the angle difference with the LED substrate 5.

  According to Table 7 and FIG. 19, even if the angle difference with the LED substrate 5 changes from 0 ° (the LED 3 is a matrix) to 60 °, the angle difference between the Table 6 and the LED substrate 5 shown in FIG. As in the case of 0 °, a high degree of uniformity can be obtained if the angle difference in the direction along the ridge is 30 ° or more, and particularly if the angle difference in the direction along the ridge is 60 ° or more, It was found that a very high uniformity can be obtained stably without depending on the angle difference.

[Influence on uniformity when the distance between light sources is increased]
In the backlight unit of Example 2, the distance D between the light sources of the LEDs 3 is 30 mm (H / D = 0.66), and these LEDs 3 are normal ones having no lens, as shown in Table 3. A uniformity of 91.3% was obtained. Therefore, when these LEDs 3 were replaced with LEDs and the distance D between the light sources was increased to 55 mm (H / D = 0.36), a uniformity of 85.4% was obtained.

  In the backlight unit, when the H / D, which is the ratio of the distance H between the light source sheets and the distance D between the light sources, becomes smaller, for example, by increasing the distance D between the light sources, the uniformity decreases. However, by using the two optical sheets 1 and 2 of Example 2 and replacing the LED 3 with a lens, the H / D is 0.66 (= 20/30) to 0.36 (= 20 / It was found that even if it is almost halved to 55), there is no significant decrease in the uniformity, and a relatively high uniformity can be maintained.

1 optical sheet 1a collar 1b collar 1c collar 11 base layer 12 surface layer 2 optical sheet 2a collar 2b collar 2c collar 3 LED
4 LCD panel 5 LED board

Claims (7)

  On one surface of the translucent sheet, a large number of convex ridges or concave grooves along a certain direction on the sheet surface of the translucent sheet are formed, and the arrangement of these ridges or grooves is arranged. Two optical sheets in which a plurality of flanges or groove portions different in shape from each other are arranged side by side as one set, and a set of the plurality of flange portions or groove portions are arranged repeatedly side by side, A surface light emitting unit, wherein a plurality of discretely arranged point light sources are arranged so as to overlap each other with their flanges or grooves different in a certain direction along the sheet surface.   At least one of the two optical sheets is characterized in that one surface of the translucent sheet on which a plurality of the ridges or grooves are formed is a surface facing the light emitting direction side of the point light source. The surface emitting unit according to claim 1.   3. The fixed direction according to claim 1 or 2, wherein a certain direction along the sheet surface of each of the two optical sheets is different from each other by an angle difference of 30 ° or more and 90 ° or less. Surface emitting unit.   4. The surface light emission according to claim 1, wherein, in the two optical sheets, the flange widths or groove widths of the flange portions or the groove portions having different shapes in the respective sets are different from each other. 5. unit.   In the two optical sheets, each flange or groove having a different shape in each set has a triangular longitudinal cross-sectional shape perpendicular to the direction along the flange or the direction along the groove. 4. The surface emitting unit according to claim 1, wherein the larger the sum is, the wider the ridge width or groove width of these ridge portions or groove portions is.   6. The surface emitting unit according to claim 1, wherein, in the two optical sheets, 2 to 10 buttocks or grooves are arranged in each set.   A light diffusing sheet unit comprising two optical sheets used in the surface emitting unit according to claim 1.

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