JP2012094266A - Optical member and planar light source device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical member, as well as a planar light source device, capable of alleviating, or further, cancelling brightness unevenness against contraction of setting intervals of LED light sources and an optical sheet or enlargement of arrangement intervals of the LED light sources, in a direct backlight with a plurality of LED light sources arranged.SOLUTION: The optical member for a planar light source device with a plurality of LEDs (light-emitting diodes) set on a reflecting sheet as light sources is provided with at least two optical sheets with a quadrangular pyramid or an inverted quadrangular pyramid shape at an opposite face at an LED light source side, and the planar light source device uses the optical member.

Description

  The present invention relates to an optical member for a planar light source device used for illumination of a liquid crystal display panel or the like, and a planar light source device using the optical member.

  Liquid crystal display devices for displaying images are widely used for large displays such as thin televisions and thin monitors. In these liquid crystal display devices, a backlight unit is used to irradiate a liquid crystal display panel that does not have self-luminous properties. The backlight unit includes, for example, a light guide plate and an LED light source disposed on an end face of the light guide plate, guides light from the light source, and irradiates the entire main surface toward the liquid crystal display panel, or a light guide plate There is a direct type in which an LED light source is disposed directly under the liquid crystal panel without using the light, and the liquid crystal panel is irradiated from the entire main surface of the light diffusion plate or optical sheet.

  In recent years, with the increase in screen size of liquid crystal televisions, demands for weight reduction and thinning have increased, but with the edge type using a light guide plate, it is difficult to reduce the weight of the television itself due to the increase in the weight of the light guide plate itself. At the same time, it has become difficult to increase the brightness of the display screen. On the other hand, the direct type that does not use a light guide plate can be reduced in weight because there is no light guide plate, but because the directivity of the LED light source is strong, the portion directly above the LED becomes very bright, causing significant luminance unevenness, and the entire light exit surface In order to obtain irradiation light with little luminance unevenness, it is necessary to narrow the arrangement interval of the LED light sources or to sufficiently separate the distance between the light diffusion plate and the LED light source, and it is difficult to reduce the thickness and reduce the cost.

  Patent Document 1 discloses a method in which a light flux controlling member is attached on an LED element, the directivity to a portion directly above the LED is relaxed, and brightness and darkness when used as a light source of a direct type backlight is disclosed. In Patent Document 2, for the purpose of eliminating luminance unevenness in a direct type backlight unit in which an LED light source is arranged on a matrix, the surface has a concave portion of a substantially inverted polygonal pyramid or a substantially inverted polygonal truncated cone shape, and has a concave shape. A light diffusing plate having a total light transmittance of 65% to 100% with the surface as the light incident surface, and a total light transmittance of 30% to 80% with the opposite surface of the surface having the concave shape as the light incident surface. It is disclosed to use.

JP2009-117207A JP 2010-117707 A

  However, further reduction in the number of LED light sources for reducing the backlight cost, or further thinning of the liquid crystal television, specifically, between a plurality of LED light sources installed on a reflective sheet as shown in FIG. The ratio between the closest distance (L) and the distance between the top of the LED and the surface of the optical sheet on the point light source side, but the closest distance (D) between the reflective sheet and the surface of the optical sheet on the point light source side However, even if L / D is 2.5 or more, the present situation is that the problem that the luminance unevenness can be solved is not satisfied.

  That is, it is possible to distribute light widely in a range other than directly above the LED by arranging the light flux control member on the LED element as a point light source of the direct type backlight, but the light diffusion plate arranged on the LED light source side If the distance between the LED light source and the LED light source is reduced or the arrangement distance of the LED light source is increased, a light / dark pattern is generated due to the shape of the light flux controlling member. It is difficult to reduce the thickness of the apparatus and the number of LED light sources.

  On the other hand, the backlight unit is placed on the reflective sheet under the strict condition of L / D ≧ 2.5, which is required for further thinning the backlight unit or reducing the number of LEDs used by expanding the LED light source spacing. A surface having a concave portion having a substantially inverted polygonal pyramid or substantially inverted polygonal frustum-shaped concave portion, and having a surface having the concave shape as a light incident surface. A light diffusion plate having a total light transmittance of 30% to 80% with the opposite surface as the light incident surface, and a fine particle as a light diffusion agent coated on the surface of the thermoplastic film on the diffusion plate. Diffusion sheet ”, prism sheet, microlens sheet, reflective polarizing sheet, etc. that have been superposed on the light diffusing plate from the past. Thing is to, have come to limit occurs.

  The present invention has been made in view of the above-described problems, and an object thereof is a planar light source capable of realizing further thinning or further reduction in the number of LED light sources in a direct type backlight provided with LED light sources. An optical member for an apparatus and a planar light source device including the optical member are provided.

  In order to achieve the above goal, the present invention employs the following means. That is, the first invention is an optical member for a planar light source device that uses a plurality of LEDs (light emitting diodes) installed on a reflective sheet as a light source, and has a quadrangular pyramid shape or an inverted four on the opposite surface on the LED light source side. It has at least two optical sheets having a pyramid shape.

According to a second invention, in the optical member of the first invention, the quadrangular pyramid shape or the falling quadrangular pyramid shape of the optical sheet having the quadrangular pyramid shape or the falling quadrangular pyramid shape on the opposite surface on the LED light source side is independently In any case, the bottom area is 10 ² to 10 ⁶ μm ² , and the height difference from the bottom surface to the highest part or the deepest part is 10 to 500 μm.

According to a third invention, in the optical member of the first or second invention, the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the side of the LED light source used at least two is closest to the LED light source. The optical sheet (A) and the optical sheet (B) are installed farthest away from the LED light source, and the optical sheet (A) has an LED light source side as a light incident surface with respect to the optical sheet (B). The total light transmittance is high, and the total light transmittance is low when a surface having a quadrangular pyramid m ² m ² shape or a falling quadrangular pyramid shape is used as the light incident surface.

  According to a fourth aspect of the present invention, in the optical member of the third aspect, among the optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, an optical sheet (A ) Has a total light transmittance of 35% to 70% when the LED light source side is the light incident surface, and a total light beam when a surface having a quadrangular pyramid shape or a falling quadrangular pyramid shape is the light incident surface. The transmittance is 70% to 98%.

  According to a fifth aspect of the present invention, in the optical member of the third aspect, among the optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, the optical sheet (B ), The total light transmittance when the LED light source side is the light incident surface is 10% to 65%, and the total light when the surface having a quadrangular pyramid shape or a falling quadrangular pyramid shape is the light incident surface The transmittance is 75% to 100%.

  6th invention is related with the planar light source device provided with the some LED light source installed on the reflective sheet, and the optical member for deflecting and diffusing the light from an LED light source, As an optical member The optical member according to any one of the first to fifth inventions is used.

  7th invention is related with the planar light source device provided with the some LED light source installed on the reflective sheet, and the optical member for deflecting and diffusing the light from LED light source, The pointed light source of the surface light source device of the invention is a LED with a lens having a substantially rotationally symmetric emission distribution having an emission intensity peak at 30 ° or more from the normal of the installation surface.

  8th invention is related with the planar light source device provided with the some LED light source installed on the reflective sheet, and the optical member for deflecting and diffusing the light from an LED light source, In the surface light source device of any of the seventh aspect, the closest distance (L) between the plurality of LED light sources installed on the reflection sheet, and the optical sheet closest to the light reflection surface of the reflection sheet and the LED light source side The relationship between the distance (D) to the light incident surface from the LED light source is L / D ≧ 2.5.

  By using the optical member of the present invention in a planar light source device using a plurality of LEDs arranged on a reflection sheet as a light source, the LED light source arrangement interval is larger than the conventional interval, or the LED light source and the optical sheet Even if the interval is reduced, the luminance unevenness can be reduced or eliminated. In addition, the planar light source device using the optical member of the present invention can reduce or eliminate luminance unevenness even when the LED light source arrangement interval is larger than the conventional interval or the interval between the LED light source and the optical sheet is reduced. Therefore, as a direct type planar light source device in which LED light sources are arranged, it is possible to further reduce the thickness and further reduce the number of LED light sources for cost reduction.

In embodiment of this invention, it is a top view of the simple principal part which shows the planar light source which has arrange | positioned several LED light source. It is a simplified sectional view showing one example of an embodiment which arranged an optical member of the present invention on a plurality of LED light sources. It is a simplified sectional view showing another example of an embodiment which has arranged an optical member of the present invention on a plurality of LED light sources.

1: Reflective sheet 2: LED
3: Optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side 4: Optical sheet 5 having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, 6: Prism sheet, micro Optical sheets other than optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, such as a lens sheet and a reflective polarizing sheet
D: Distance from the reflecting sheet surface to the light incident surface of the optical sheet closest to the LED light source side
L: Minimum distance between LED placement intervals

  Hereinafter, an optical member according to an embodiment of the present invention and a planar light source device using the optical member will be described in detail. The optical member of the present invention has at least two optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side. It is also possible to superimpose via other optical sheets, and it is preferable to optimize the order of superposition according to the LED light source arrangement conditions of the planar light source device in which the optical member is used and the light output characteristics of the LED light source.

  FIG. 2 is a schematic sectional view showing an example of a planar light source device using the optical member of the present invention. A plurality of LED light sources 2 are arranged on the reflective sheet 1 at the closest interval (L), and at least two optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side above the reflective light source 1. The optical member of the present invention having an optical sheet configuration having one sheet is installed at a distance (D) between the light reflection surface of the reflection sheet and the light incident surface from the LED light source of the optical sheet closest to the LED light source side. FIG. 2 shows a case where the optical sheet (A) and the optical sheet (B) are continuously arranged, and the light from the LED which is a point light source is the optical sheet (A) and the optical sheet (B). The optical member included partially reflects to the light source side, partially diffuses and deflects, and luminance unevenness is reduced or eliminated on the light exit surface of the optical sheet farthest from the LED light source of the optical sheet configuration.

FIG. 3 is a schematic sectional view showing another example of the planar light source device using the optical member of the present invention.
Unlike FIG. 2, in the optical sheet configuration of the optical member of the present invention, the optical sheet (A) is disposed on the most LED light source side among all the optical sheets, while the optical sheet (B) is disposed on the outermost layer on the light output side. The optical sheet (B) in this case has a role of improving luminance in the front direction of the display device arranged in front of the planar light source device as well as eliminating luminance unevenness as the planar light source device. Plays.

  2 and 3 are merely examples of the optical sheet configuration that forms the optical member of the present invention. In the optical sheet configuration, an optical having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side is shown. By having at least two sheets, high reflectivity and deflection can be imparted, and a uniform light distribution and condensing effect can be realized by randomization. Due to these effects, in the planar light source device using a plurality of highly directional LEDs arranged on the reflection sheet as the light source, the LED light source arrangement interval is larger than the conventional interval, or the LED light source and the optical sheet Even if the interval is reduced, a planar light source with reduced or eliminated luminance unevenness can be obtained.

  The optical member of the present invention must have at least two optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side. Depending on the specifications of the LED light source and the planar light source device, such as the distance between the reflection sheet and the optical sheet where the light source is disposed, it is possible to achieve luminance unevenness elimination by using three or more. However, in the situation where the thinning of the liquid crystal display device to which the planar light source device is mounted is being promoted, it is required to reduce the number of optical sheets as much as possible, and on the opposite surface of the optical member on the LED light source side Two sheets of the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape are preferable.

The quadrangular pyramid shape or the falling quadrangular pyramid shape of the optical sheet having the quadrangular pyramid shape or the falling quadrangular pyramid shape on the opposite surface on the LED light source side of the optical member of the present invention has a bottom area of 10 ² to 10 ⁶ μm ^2. It is preferable that the difference in height from the bottom surface to the highest part or the deepest part is 10 to 500 μm. When the bottom area is less than 10 ² μm ² and the height difference from the bottom surface to the highest part or the deepest part is less than 10 μm, a quadrangular pyramid shape or a falling quadrangular pyramid shape is reproducibly formed on the optical sheet surface. It becomes difficult to reduce and eliminate stable luminance unevenness. In addition, when the bottom area exceeds 10 ⁶ μm ² and the height difference from the bottom to the highest or deepest part exceeds 500 μm, the reproducibility of the quadrangular pyramid shape or the falling quadrangular pyramid shape on the opposite surface of the shaped LED light source side Although it can be shaped well, even with the optical sheet configuration of the present invention, the luminance unevenness is reduced in the planar light source device in which the LED light source arrangement interval is larger than the conventional interval or the interval between the LED light source and the optical sheet is reduced. It becomes difficult to eliminate.

  The quadrangular pyramid shape or the falling quadrangular pyramid shape formed on the optical sheet surface efficiently reflects light from the LED light source such that each side surface has an inclination angle of 35 ° to 55 ° with respect to the optical sheet plane, Since a planar light source that can be deflected and luminance unevenness can be expressed, it is preferable, and the angle is more preferably 40 ° to 50 °. Further, the inclination angles of the four side surfaces forming the quadrangular pyramid shape or the falling quadrangular pyramid shape may be the same or different.

  The bottom area of the quadrangular pyramid shape or the falling quadrangular pyramid shape formed on the optical sheet having at least two optical members of the present invention and the height difference from the bottom surface to the highest portion or the deepest portion may be the same or different. .

  Of the optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, the optical sheet (A) installed closest to the LED light source is important for eliminating the strong directivity of the LED light source It is required to level the output angle dependency of the luminance distribution as much as possible by the reflection / deflection function and the light diffusion function by the quadrangular pyramid shape or the falling quadrangular pyramid shape formed on the optical sheet surface. . For these reasons, a surface having a total light transmittance of 35% to 70% when the LED light source side of the optical sheet (A) is used as a light incident surface, and a surface having a quadrangular pyramid shape or a falling quadrangular pyramid shape is used as the light incident surface. The total light transmittance at that time is preferably 70% to 98%. More preferably, the total light transmittance is 35% to 65% when the LED light source side is the light incident surface, and the total light transmittance when the surface having the quadrangular pyramid shape or the falling quadrangular pyramid shape is the light incident surface. 75% to 96%.

  On the other hand, among the optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, the optical sheet (B) installed farthest from the LED light source is a quadrangular pyramid formed on the optical sheet surface. The angle dependence of the luminance distribution is leveled by the reflection or deflection function by the shape or the falling quadrangular pyramid shape, and light having a deep light emission angle from the optical sheet installed on the LED light source side from the optical sheet (B) is surfaced It is also necessary to start up in the normal direction of the planar light source device and to collect light in the front direction as the planar light source device. From this, when the light incident surface is 10% to 65% when the LED light source side of the optical sheet (B) is used as the light incident surface, and the surface having the quadrangular pyramid shape or the falling quadrangular pyramid shape is used as the light incident surface. The total light transmittance is preferably 75% to 100%. More preferably, the total light transmittance is 12% to 60% when the LED light source side is the light incident surface, and the total light transmittance is when the surface having the quadrangular pyramid shape or the falling quadrangular pyramid shape is the light incident surface. 80% to 100%.

  Among them, the optical sheet (A) installed closest to the LED light source among the optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side is the furthest away from the LED light source. The total light beam having a high total light transmittance when the LED light source side is used as the light incident surface with respect to the installed optical sheet (B), and a surface having a quadrangular pyramid shape or a falling quadrangular pyramid shape as the light incident surface A planar light source device in which luminance unevenness is reduced or eliminated even when the transmittance of the LED light source is further expanded, or the distance between the reflection sheet and the optical sheet where the LED light source is disposed is further reduced. It becomes easy to realize.

  The optical member of the present invention uses at least two optical sheets having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, and among these, the optical sheet (A) is closest to the LED light source. It is installed and the optical sheet (B) is installed farthest from the LED light source, but it is an arrangement in an optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, and is used in combination. Even if the other optical sheet is installed closest to the LED light source, or installed farthest from the LED light source, the effect of the present invention is not impaired.

  Moreover, as an optical sheet other than the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side used for the optical member of the present invention, an existing microlens sheet, prism sheet, lenticular sheet, diffusion sheet, Depending on the specifications of the planar light source device in which the present optical member is used or the specifications of the liquid crystal display device, there are reflective polarizing sheets and the like, and these optical sheets can be used as appropriate.

  An optical sheet having a quadrangular pyramid shape or an inverted quadrangular pyramid shape on the opposite surface to the LED light source side is either a quadrangular pyramid shape or an inversion on one side of a sheet made of a transparent resin or on one side of a sheet in which a light diffusing agent is dispersed in the transparent resin. The shape is a quadrangular pyramid shape, and the opposite surface of the quadrangular pyramid shape or the falling quadrangular pyramid shape is a mirror surface, or an uneven shape such as an emboss or mat with an arithmetic average roughness of 0.5 to 50 μm. May be given.

  The transparent resin constituting the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side is colorless and transparent, and has an appropriate strength as a main component of the optical sheet. Not limited. For example, polycarbonate resin; acrylic resin such as polymethyl methacrylate; styrene resin such as polystyrene, polyvinyl toluene, and poly (p-methylstyrene); MS resin (copolymer of methyl methacrylate and styrene); norbornene resin; poly Arylate resin; polyethersulfone resin, or a mixed resin of two or more of these can be used. A polycarbonate resin, a styrene resin, or a norbornene resin is preferably used. Among these, polycarbonate resin is particularly preferable as a resin for an optical sheet because it is excellent in transparency, heat resistance, and workability and has a good balance.

  As the light diffusing agent used for the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, any fine particles of organic fine particles, inorganic fine particles, and organic-inorganic hybrid fine particles can be used. Organic fine particles such as (meth) acrylic resin, styrene resin, amino resin, polyester resin, silicone resin, fluorine resin, and copolymers thereof; glass, smectite, kaolinite, silica, alumina, Examples thereof include inorganic fine particles such as titanium oxide and zirconium oxide; organic-inorganic hybrid fine particles such as acrylic-silica. Of these materials, (meth) acrylic resins, silicone resins, and silica are particularly suitable.

  The average particle diameter of the light diffusing agent is preferably 0.3 to 30 μm, and even if it is smaller or larger than this, the light diffusing effect is greatly reduced, which is not preferable, and more preferably 0.5 to 15 μm. Optimum blending amount of light diffusing agent is the diffusion effect due to the square pyramid shape or the falling quadrangular pyramid shape formed on the opposite side of the LED light source, the refractive index difference between the transparent resin and the light diffusing agent constituting the optical sheet, the light diffusion Although depending on the particle diameter of the agent, 0 to 20 parts by mass is preferably dispersed in the optical sheet. Dispersion of 20 parts by mass or more is not preferable because the reduction in luminance becomes large.

  As a dispersion form of the light diffusing agent, there are a form in which the light diffusing agent is uniformly dispersed in the entire optical sheet, a form in which a light diffusing agent dispersion layer is formed on the light incident surface side or the shaping surface side of a quadrangular pyramid shape or a falling quadrangular pyramid shape. .

  Among them, the optical sheet (B) installed farthest from the LED light source needs to perform a light collecting function in the front direction of the display device, and is refracted by a quadrangular pyramid shape or a falling quadrangular pyramid shape formed on the light emitting surface. The effect must be sufficiently exhibited, and it is preferable that the amount of dispersion of the light diffusing agent is smaller than that of the optical sheet (A). Depending on the required luminance level in the front direction of the display device, it is not necessary to disperse the light diffusing agent. There is also.

  As a method of manufacturing an optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, a thermoplastic resin mixture in which the above transparent thermoplastic resin, a light diffusing agent, a heat stabilizer and the like are uniformly blended is used. It can be obtained by extrusion molding, injection molding, press molding or the like using a mold in which a reverse shape of a desired uneven shape is engraved on substantially the entire surface. Among them, the extrusion method is particularly preferable from the viewpoints of easy multilayering and high production efficiency such as the formation of a light diffusing layer and a surface functional layer such as an antistatic performance and a light absorbing layer having a specific wavelength. .

  If the shape of the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side is cut according to the shape size of the planar light source device to be used, or if it is molded using a mold according to the final dimension The thickness is also preferably 0.2 mm to 4 mm, although the thickness varies depending on the size and use of the surface light source device to be used or the installation position of the optical sheet. Furthermore, when thinning of a liquid crystal display device is calculated | required, 0.2-2 mm is more preferable.

  In particular, since the optical sheet (A) is installed in the vicinity of the LED light source, it is necessary to play a supporting role in superimposing other optical sheets forming the optical sheet structure, and is affected by heat. It is preferable to have a thickness of 0.8 mm or more in order to avoid mechanical or thermal deformation.

  On the other hand, since the optical sheet (B) is placed away from the LED light source, it is preferable that the optical sheet (B) is thinner than the optical sheet (A), and preferably has a thickness of 0.3 mm to 1.5 mm.

  The LED light source used in the planar light source device of the present invention is preferably a Lambertian type whose emission intensity peak is the normal direction of the LED light source installation surface, or a side emission type white LED whose direction is inclined from the normal line. However, a side emission type in which a lens or a light flux controlling member is installed on an LED chip is particularly preferably used because of the reduction in luminance unevenness of the planar light source device and the ease of eliminating it.

  Especially, it is preferable that it is LED with a lens in which a light distribution pattern has the substantially rotationally symmetrical output distribution which has the peak of an output intensity in the deep angle of 30 degrees or more from the normal line of a LED light source installation surface. Furthermore, using a LED with a lens having a substantially rotationally symmetric emission distribution with a light emission pattern having an emission intensity peak at a deep angle of 45 ° or more from the normal line of the LED light source installation surface, Even an enlarged planar light source device or a thin planar light source device in which the distance between the reflection sheet and the optical sheet on which the LED light source is disposed is reduced, which is more preferable because the luminance unevenness can be further reduced and reduced.

  The arrangement method of the LED light source is not particularly limited, and a parallel arrangement of a linear arrangement set, a lattice arrangement, a staggered arrangement, or the like is used.

  The reflection sheet used in the planar light source device of the present invention is a white sheet, and is made of a metal plate having a reflection function, a film, a metal foil, a film on which aluminum or the like is deposited, emitted light from the LED light source, LED light source It plays the role of leveling the incident angle to the optical sheet as well as returning the deflection or reflected light from the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite side of the side to the light exiting direction of the optical sheet again, Together with the optical sheet having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side, it plays an important role in eliminating or reducing luminance unevenness.

  In a direct type planar light source device using an LED light source, the level at which luminance unevenness can be substantially eliminated is closest to a plurality of LED light sources installed on a reflection sheet as shown in FIGS. L / D, which is the ratio of the distance (L) and the distance (D) between the light reflecting surface of the reflecting sheet and the light incident surface from the LED light source of the optical sheet closest to the LED light source side of the optical sheet configuration By using the optical sheet configuration of the present invention, it was possible to realize a planar light source device with L / D ≧ 2.5, which was difficult with the conventional optical sheet configuration.

  Next, the planar light source device according to the present invention will be specifically described with reference to experimental examples, examples, and comparative examples.

<Experimental example 1>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics) is blended with 0.1 parts by weight of a phosphorus-based antioxidant (“Irgaphos 168”: manufactured by BASF) as a heat stabilizer, and by extrusion molding, A falling regular square pyramid with a base of 150 μm, an inclination angle of each side with respect to the sheet plane of 45 °, a depth of 72 μm and a curved surface at the tip is formed concavely on one entire surface, and the opposite surface is a mirror surface of thickness 0 An optical sheet (P1) of 8 mm was obtained.

<Experimental example 2>
100 parts by mass of polycarbonate ("Iupilon E2000FN": manufactured by Mitsubishi Engineering Plastics), 0.05 part by mass of silicone fine particles ("Tospearl 120": manufactured by Momentive Performance) as a light diffusing agent, phosphorus-based oxidation as a thermal stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168" manufactured by BASF), and by extrusion molding, the bottom having a bottom of 150 μm, the inclination angle of each side with respect to the sheet plane being 45 °, and the depth being 72 μm is a curved surface. The inverted regular square pyramid thus formed was shaped into a concave shape on one entire surface, and an optical sheet (P2) having a thickness of 0.8 mm whose opposite surface was a mirror surface was obtained.

<Experimental example 3>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.1 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a heat stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168": manufactured by BASF), and by extrusion molding, the bottom having a bottom of 80 μm, the inclination angle of each side with respect to the sheet plane being 45 °, and the height of 37 μm being a curved surface The inverted regular square pyramid thus formed was shaped into a concave shape on one entire surface, and an optical sheet (P3) having a thickness of 0.8 mm was obtained in which the opposite surface was an embossed surface having a number average roughness (Ra) of 4.5 μm.

<Experimental example 4>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.1 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a heat stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168" manufactured by BASF), and by extrusion molding, the bottom having a bottom of 150 μm, the inclination angle of each side with respect to the sheet plane being 45 °, and the depth being 70 μm is a curved surface. The inverted regular square pyramid thus formed was shaped in a concave shape on one entire surface, and an optical sheet (P4) having a thickness of 1.5 mm having a mirror surface on the opposite surface was obtained.

<Experimental example 5>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.2 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a thermal stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168" manufactured by BASF), and by extrusion molding, the bottom having a bottom of 150 μm, the inclination angle of each side with respect to the sheet plane being 45 °, and the depth being 70 μm is a curved surface. The inverted regular square pyramid thus formed was shaped concavely on one entire surface, and an optical sheet (P5) having a thickness of 1.5 mm having a mirror surface on the opposite surface was obtained.

<Experimental example 6>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.3 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a heat stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168" manufactured by BASF), and by extrusion molding, the bottom having a bottom of 150 μm, the inclination angle of each side with respect to the sheet plane being 45 °, and the depth being 70 μm is a curved surface. The inverted regular quadrangular pyramid thus formed was concavely shaped on one entire surface, and an optical sheet (P6) having a thickness of 1.5 mm having a mirror surface on the opposite surface was obtained.

<Experimental example 7>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.2 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a thermal stabilizer Compounding 0.1 parts by weight of an inhibitor ("Irgaphos 168" manufactured by BASF) and by extrusion molding, the bottom having a bottom of 80 μm, the inclination of each side with respect to the sheet plane is 45 °, and the height of 32 μm is a curved surface. The formed regular square pyramid was convexly formed on one entire surface, and an optical sheet (P7) having a thickness of 1.5 mm having a mirror surface on the opposite surface was obtained.

<Experimental Example 8>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.5 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a heat stabilizer An optical sheet having a thickness of 0.8 mm, in which 0.1 parts by mass of an inhibitor (“Irgaphos 168”: manufactured by BASF) is blended, and both surfaces are embossed surfaces having an arithmetic average roughness (Ra) of 4.5 μm by extrusion molding. (Q1) was obtained.

<Experimental Example 9>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 1 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based antioxidant as a heat stabilizer ("Irgafos 168": manufactured by BASF) 0.1 parts by mass, and by extrusion molding, an optical sheet (Q2) having a thickness of 0.8 mm, both surfaces of which are embossed surfaces having an arithmetic average roughness (Ra) of 4.5 μm )

<Experimental example 10>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.5 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a heat stabilizer An optical sheet having a thickness of 1.5 mm in which 0.1 parts by mass of an inhibitor ("Irgaphos 168": manufactured by BASF) is blended and both surfaces are embossed surfaces having an arithmetic average roughness (Ra) of 4.5 μm by extrusion molding (Q3) was obtained.

<Experimental example 11>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 1 part by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based antioxidant as a heat stabilizer ("Irgafos 168": manufactured by BASF) 0.1 parts by mass, and by extrusion molding, an optical sheet (Q4) having a thickness of 1.5 mm whose both surfaces are embossed surfaces having an arithmetic average roughness (Ra) of 4.5 μm )

<Measurement of total light transmittance>
When the optical sheet (P7) from the optical sheet (P1) to which the quadrangular pyramid or the falling quadrangular pyramid produced in Experimental Examples 1 to 7 is formed is installed in a planar light source device, a mirror surface or embossing on the LED light source side Nippon Denshoku Kogyo Co., Ltd. has the total light transmittance with the light incident surface as the light incident surface and the total light transmittance with the light incident surface as the square pyramid or the falling quadrangular pyramid opposite to the LED light source side. Using a company-made turbidimeter NDH2000, the measurement was performed in accordance with JIS K7361. The results are shown in Table 1.

  In addition, for the optical sheets (Q1) to (Q4) in which the quadrangular pyramids or the falling quadrangular pyramids produced in Experimental Examples 8 to 11 are not shaped, the embossed surface on the LED light source side is used as the light incident surface. The total light transmittance and the total light transmittance with the embossed surface opposite to the LED light source side as the light incident surface were measured according to JIS K7361 as described above, and the results are shown in Table 1.

<Examples 1 to 9 and Comparative Examples 1 to 6>
As shown in FIG. 1, nine white LEDs with a lens having an emission intensity peak at about 70 ° from the normal of the installation surface are arranged in a grid pattern at intervals of 70 mm on a 210 mm × 210 mm white reflective sheet. Each first optical sheet was placed so that the distance between the reflection sheet and the first optical sheet incident surface was 20 mm. With respect to the optical sheet (P1) to the optical sheet (P7) formed with the quadrangular pyramid or the falling quadrangular pyramid produced in the experimental examples 1 to 7, the concave or convex regular square pyramid existing on the light exit surface of each optical sheet is used. The arrangement direction was set so as to intersect at 45 ° with the shortest direction of the arrangement interval of the white LED with lens. Further, when two prism sheets were arranged, they were overlapped so that the prism forming surface was opposite to the LED light source side and the extending directions of the prisms were orthogonal to each other.

  As for the luminance unevenness, the light and darkness generated on the light exit surface of the uppermost optical sheet in each sheet configuration was visually evaluated, and these results are shown in Table 2.

  The microlens sheet is PTD837 (manufactured by SHINWHA INTERTECH), the prism sheet is BEFIII (manufactured by Sumitomo 3M), and the diffusion sheet is CH282 (SKC-HAAS, which has a PET film surface coated with fine particles. The total light transmittance when entering from the opposite surface of the light diffusion layer was 74%), and DBEF-D400 (manufactured by Sumitomo 3M) was used as the reflective polarizing film.

<Evaluation of uneven brightness>
Luminance unevenness evaluation was visually judged from the normal direction of the optical sheet arranged on the LED and ± 30 ° direction with respect to the normal direction, and was classified into the following five stages.

1: A bright and dark pattern with a clear boundary line can be confirmed. 2: A clear boundary line in the light and dark area is not recognized, but a bright and dark pattern is clearly recognized. 3: A light and dark pattern is recognized although it is faint. 4: The light / dark pattern is almost eliminated, but the overall brightness uniformity level is not reached. 5: The presence of the brightness / darkness region cannot be confirmed, and the brightness uniformity level is obtained as a whole.

  The optical member of the present invention and the planar light source device using the optical member are suitable for reducing the thickness and cost of the LED light source direct type liquid crystal display device.

Claims (8)

  An optical member for a planar light source device having a plurality of LEDs (light emitting diodes) installed on a reflective sheet as a light source, and having a quadrangular pyramid shape or a falling quadrangular pyramid shape on the opposite surface on the LED light source side An optical member for a planar light source device, characterized by having at least two. Each of the quadrangular pyramid shape or the falling quadrangular pyramid shape of the optical sheet has independently a bottom area of 10 ² to 10 ⁶ μm ² and a height difference from the bottom surface to the highest part or the deepest part is 10 to 500 μm. The optical member for a planar light source device according to claim 1. Among the optical sheets, the optical sheet (A) installed closest to the LED light source is the light incident surface on the LED light source side with respect to the optical sheet (B) installed farthest from the LED light source. 3. The surface according to claim 1, wherein the surface has a high total light transmittance and a low total light transmittance when a surface having a quadrangular pyramid shape or a falling quadrangular pyramid shape is used as an incident surface. Optical member for a light source device. Among the optical sheets, the total light transmittance is 35% to 70% when the LED light source side of the optical sheet (A) installed closest to the LED light source is the light incident surface, and the shape is a quadrangular pyramid or falls. 4. The optical member for a planar light source device according to claim 3, wherein a total light transmittance is 70% to 98% when a surface having a quadrangular pyramid shape is used as a light incident surface. Among the optical sheets, the total light transmittance when the LED light source side of the optical sheet (B) installed farthest from the LED light source is the light incident surface is 10% to 65%, and is a quadrangular pyramid shape or a falling four. 4. The optical member for a planar light source device according to claim 3, wherein the total light transmittance is 75% to 100% when a surface having a pyramid shape is used as a light incident surface.   A planar light source device comprising a plurality of LEDs (light emitting diodes) installed on a reflective sheet as a light source and the optical member according to claim 1. The planar light source device according to claim 6, wherein the LED light source is a lens-equipped LED having a substantially rotationally symmetric emission distribution having an emission intensity peak at 30 ° or more from a normal line of the installation surface.   The closest distance (L) between the plurality of LED light sources installed on the reflection sheet, the light reflection surface of the reflection sheet, and the light incident from the LED light source of the optical sheet closest to the LED light source side of the optical member The planar light source device according to any one of claims 6 to 7, wherein the relationship between the distance (D) and the surface is L / D≥2.5.

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