JP2012043671A - Planar light source device - Google Patents
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本発明は、液晶表示パネルなどの照明に用いる面状光源装置に関する。 The present invention relates to a planar light source device used for illumination of a liquid crystal display panel or the like.
薄型テレビや薄型モニターなどの大型ディスプレイには、画像表示のための液晶表示装置が広く採用されている。これらの液晶表示装置には、自発光性がない液晶表示パネルを照射するためにバックライトユニットが用いられている。バックライトユニットとしては、例えば導光板と、該導光板の端面に配置したＬＥＤ光源を備え、光源からの光を導光して主面全体から液晶表示パネルへ向け照射するエッジタイプや、導光板を用いず、液晶パネルの直下にＬＥＤ光源を配置し、光拡散板や光学シートの主面全体から液晶パネルに向け照射する直下タイプがある。 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.
近年、液晶テレビの大画面化にともない、軽量化や薄型化に対する要望がより高くなってきているが、導光板を用いたエッジタイプでは、導光板自体の重量増によりテレビ自体の軽量化が困難になるとともに、表示画面の輝度上昇が困難になってきている。一方、導光板を用いない直下タイプでは、導光板がない分軽量化が可能であるが、ＬＥＤ光源の指向性が強いため、ＬＥＤ直上部分が非常に明るくなり著しい輝度ムラが生じ、出光面全体で輝度ムラの少ない照射光を得るためには、ＬＥＤ光源の配置間隔を狭くするか、光拡散板とＬＥＤ光源の距離を充分離す必要があり、薄型化やコスト削減が困難な状況にある。 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.
特許文献１には、光束制御部材をＬＥＤ素子上に取り付け、ＬＥＤ直上部分への指向性を緩和し、直下型バックライトの光源として用いた際の明暗を抑制する方法が開示されている。特許文献２には、ＬＥＤ光源をマトリックス上に配置した直下型バックライトユニットにおける輝度ムラ解消を目的として、表面に略逆多角錐または略逆多角錐台形状の凹部を有し、凹部形状を有する面を入光面とする全光線透過率が６５％〜１００％であり、凹部形状を有する面の反対面を入光面とした全光線透過率が３０％〜８０％である光拡散板を用いることが開示されている。
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
しかしながら、バックライトコスト削減のためのＬＥＤ光源数のさらなる削減や、あるいは液晶テレビのさらなる薄型化、具体的には、図２に示すような反射シート上に設置された複数個のＬＥＤ光源間の最も接近した間隔（L）と、ＬＥＤの頭頂部と光学シートの点光源側に面までの距離ではなく、反射シートと光学シートの点光源側の面までの最も接近した距離（D）の比であるL／Dが、２．５以上においても、輝度ムラを解消できるという課題に対しては、応えられていないのが現状である。 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.
すなわち、直下型バックライトの点光源として光束制御部材をＬＥＤ素子上に配置することによりＬＥＤの直上以外の範囲に広く配光することが可能となるが、ＬＥＤ光源側に配置される光拡散板とＬＥＤ光源との間隔を縮小、あるいはＬＥＤ光源の配置間隔を拡げていくと光束制御部材の形状に起因する明暗パターンが生じてしまい、従来の光拡散板や光学シートの構成では、さらなる液晶表示装置の薄型化やＬＥＤ光源数の削減が困難となっている。 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.
一方、バックライトユニットのさらなる薄型化、あるいはＬＥＤ光源の配置間隔拡大によるＬＥＤ使用数の削減化において求められる、上記のL／D≧２．５となるという厳しい条件下において、反射シート上に配置されたＬＥＤ光源に、略逆多角錐または略逆多角錐台形状の凹部を有し、凹部形状を有する面を入光面とする全光線透過率が６５％〜１００％、凹部形状を有する面の反対面を入光面とした全光線透過率が３０％〜８０％である光拡散板を用い、この拡散板上に熱可塑性フィルム表面に光拡散剤となる微粒子を塗布した従来タイプの“拡散シート”、従来から光拡散板に重ね合わせてきたプリズムシート、マイクロレンズシート、反射偏光シートなどを適宜重ね合わせるといった光学シート構成だけで、輝度ムラの大幅低減や解消することには、限界が生じるようになってきている。 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.
本発明は前述の課題に鑑みてなされたものであり、ＬＥＤ光源を配置した直下型バックライトにおいて、さらなる薄型化、あるいはさらなるＬＥＤ光源数削減を実現させた面状光源装置を提供することを目的とする。 The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a planar light source device that achieves further thinning or further reduction in the number of LED light sources in a direct type backlight provided with LED light sources. And
本発明は、前記課題を解決するための面状光源装置に関するものであり、反射シート上に配置された複数個のＬＥＤ（発光ダイオード）光源と、該ＬＥＤ光源から出射した光が入射する位置に、透明樹脂に光拡散剤が配合され、片面に凹凸形状を有する光学シート（Ａ）を1枚以上、凹凸形状の賦型面がＬＥＤ光源と反対向きになるように設置し、さらに光学シート（Ａ）の出光面に、透明樹脂に光拡散剤が配合された光学シート（Ｂ）を設置した光学シート構成を有することを特徴とする面状光源装置である。 The present invention relates to a planar light source device for solving the above-described problem, and a plurality of LED (light emitting diode) light sources arranged on a reflective sheet and a position where light emitted from the LED light source is incident. 1 or more optical sheets (A) having a concavo-convex shape on one side, with a light diffusing agent blended in a transparent resin, and arranged so that the concavo-convex shaping surface is opposite to the LED light source, A planar light source device having an optical sheet configuration in which an optical sheet (B) in which a light diffusing agent is blended in a transparent resin is installed on the light exit surface of A).
光学シート（Ａ）は、凹凸形状を有しない面を入光面とした際の全光線透過率が４０％〜７０％であり、かつ、凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上であることを必須とし、一方、光学シート（Ｂ）は、表裏いずれの面を入光面とした場合でも全光線透過率が５５〜７０％であることを必須としている。 The optical sheet (A) has a total light transmittance of 40% to 70% when a surface that does not have a concavo-convex shape is used as a light incident surface, and all of the surface that has a concavo-convex shape as a light incident surface. It is essential that the light transmittance is 80% or more. On the other hand, the optical sheet (B) has a total light transmittance of 55 to 70% regardless of whether the front or back surface is a light incident surface. Yes.
光学シート（Ａ）単独、あるいは複数枚重ね合わせるだけでは、上記のような厳しいL／D≧２．５という条件下での輝度ムラを低減や解消することは困難であるが、上記のような範囲内における非対称的な全光線透過率を有する光学シート（Ａ）の反射・偏向・光拡散作用と、光学シート（Ａ）とは異なる上記範囲内における対称的な全光線透過率を有する光学シート（Ｂ）の反射、偏向・光散乱作用が相乗的に作用することにより、ＬＥＤ光源配置間隔が従来の間隔よりも拡大あるいはＬＥＤ光源と光学シートの間隔が縮小化した厳しいL／D≧２．５という条件下においても大幅な輝度ムラ低減、解消を可能にさせている。このことは、上記のように光学シート（Ａ）単独、あるいは複数枚重ね合わせるだけでも、あるいは光学シート（Ｂ）単独、あるいは複数枚重ね合わせるだけでも、L／D≧２．５という条件下での輝度ムラを低減や解消することは困難であることから明白である。 It is difficult to reduce or eliminate the luminance unevenness under the strict L / D ≧ 2.5 condition as described above only by superimposing the optical sheet (A) alone or a plurality of sheets. Optical sheet having reflection, deflection and light diffusion action of optical sheet (A) having asymmetric total light transmittance within the range, and symmetrical total light transmittance within the above range different from optical sheet (A) As a result of the synergistic action of reflection, deflection and light scattering in (B), 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. Even under the condition of 5, it is possible to significantly reduce and eliminate luminance unevenness. This is because, as described above, the optical sheet (A) alone or a plurality of sheets are overlapped, or the optical sheet (B) alone or a plurality of sheets are overlapped, under the condition of L / D ≧ 2.5. It is obvious from the fact that it is difficult to reduce or eliminate the luminance unevenness.
また、本発明の面状光源装置を構成する光学シート（Ａ）は、片面に底面積が１００〜１００００００μｍ２であり、かつ底面から最高部または最深部までの高低差が１０〜５００μｍである凹凸パターンが賦型されていることを特徴とする。上記のような凹凸寸法により、凹凸形状による反射・偏向効果と拡散剤の光拡散効果との相乗効果を充分発揮させることができ、入光面による全光線透過率に差を生じさせ、反射シートへの戻り光量を調整することができ、光指向性のＬＥＤ光源からの出射光の輝度ムラパターンを緩和させることができる。 In addition, the optical sheet (A) constituting the planar light source device of the present invention has an uneven surface with a bottom area of 100 to 1000000 μm 2 on one side and a height difference from the bottom to the highest or deepest part of 10 to 500 μm. The pattern is shaped. Due to the uneven size as described above, the reflection / deflection effect due to the uneven shape and the light diffusion effect of the diffusing agent can be sufficiently exerted, causing a difference in the total light transmittance due to the light incident surface, and the reflection sheet The amount of light returning to can be adjusted, and the uneven brightness pattern of the light emitted from the light-directed LED light source can be alleviated.
また、本発明の面状光源装置を構成する光学シート（Ａ）は、一方の全面に有する少なくとも1種以上の切断楕円体凹凸形状、円錐凹凸形状、切断円錐凹凸形状、多角錐凹凸形状、切断多角錐凹凸形状から選択される凹凸形状を有することを特徴とする。凹凸形状がこのような回転対称軸を有する対称的斜面を有することにより、ＬＥＤ光源からの出射光を設置面の法線方向を中心に等方的に反射、偏向させることが可能となる。 In addition, the optical sheet (A) constituting the planar light source device of the present invention has at least one or more types of cut ellipsoidal uneven shape, conical uneven shape, cut conical uneven shape, polygonal pyramid uneven shape, cut on one entire surface. It has the uneven | corrugated shape selected from the polygonal pyramid uneven | corrugated shape, It is characterized by the above-mentioned. Since the concavo-convex shape has a symmetric inclined surface having such a rotationally symmetric axis, it becomes possible to reflect and deflect the light emitted from the LED light source isotropically around the normal direction of the installation surface.
また、本発明の面状光源装置は、点光源として設置面の法線から３０°以上に出射強度のピークを有する略回転対称の出射分布を有するレンズ付ＬＥＤであることを特徴とする。本発明に用いるＬＥＤ光源として、ＬＥＤ素子上にレンズなどの光束制御部材を配置し、ＬＥＤ光源設置面の法線方向ではなく横方向に高い出光強度を有するＬＥＤ光源を用いることにより、本発明の効果をより一層引出すことが可能となる。 The planar light source device of the present invention is a LED with a lens having a substantially rotationally symmetric emission distribution having a peak of emission intensity at 30 ° or more from the normal of the installation surface as a point light source. As the LED light source used in the present invention, a light beam control member such as a lens is arranged on the LED element, and the LED light source having a high light output intensity in the lateral direction instead of the normal direction of the LED light source installation surface is used. The effect can be further extracted.
また、本発明の面状光源装置は、反射シート上に設置された複数個のＬＥＤ光源間の最も接近した間隔（L）と、反射シートと光学シート（Ａ）の点光源側の面までの最も接近した距離（D）の関係は、L／D≧２．５であることを特徴とする。すなわち、ＬＥＤ光源を反射シート上に配置した面状光源装置において、光学シート（Ａ）および光学シート（Ｂ）からなる光学シート構成が存在することによって、輝度ムラを低減しつつ、ＬＥＤ光源の配置間隔を拡大化、あるいはＬＥＤ光源が設置されている反射シートと光学シート（Ａ）の距離を縮小化が可能となる。 Moreover, the planar light source device of the present invention includes the closest distance (L) between the plurality of LED light sources installed on the reflection sheet, and the point light source side surface of the reflection sheet and the optical sheet (A). The closest distance (D) relationship is characterized by L / D ≧ 2.5. That is, in the planar light source device in which the LED light source is disposed on the reflection sheet, the presence of the optical sheet configuration including the optical sheet (A) and the optical sheet (B) reduces the luminance unevenness, and the arrangement of the LED light source. The distance can be increased, or the distance between the reflection sheet on which the LED light source is installed and the optical sheet (A) can be reduced.
本発明の反射シート上に配置された複数個のＬＥＤを光源とする面状光源装置は、ＬＥＤ光源配置間隔が従来の間隔よりも拡大、あるいはＬＥＤ光源と光学シートの間隔が縮小しても、輝度ムラ低減化や解消が可能になる。このことにより、ＬＥＤ光源を配置した直下型バックライトにおいて、さらなる薄型化を促進できるとともに、低コスト化のためのさらなるＬＥＤ光源数削減が可能となる。 In the planar light source device using a plurality of LEDs arranged on the reflection sheet of the present invention as the light source, even if 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, Luminance unevenness can be reduced or eliminated. As a result, in the direct type backlight in which the 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.
本発明の面状光源装置に用いる光学シート（Ａ）は、透明樹脂に光拡散剤が配合され、片面に凹凸形状を有し、凹凸形状を有する面の反対側面を入光面とした際の全光線透過率が４０％〜７０％、かつ凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上であることを必須とする。 The optical sheet (A) used in the planar light source device of the present invention has a light diffusing agent blended with a transparent resin, has a concavo-convex shape on one side, and a side opposite to the surface having the concavo-convex shape as a light incident surface. It is essential that the total light transmittance is 40% to 70%, and the total light transmittance is 80% or more when the surface having an uneven shape is used as the light incident surface.
本発明の面状光源装置に用いる光学シート（Ａ）において、凹凸形状設置面の反対側面を入光面とする場合の全光線透過率が、４０％未満では凹凸形状による偏向特性が強くなり、出光側に光学シート（B）を重ね合わせても、光学シート（B）上にＬＥＤ光源の出光パターンに基づく明暗が残存してしまう。一方、７０％を越えると凹凸形状による偏向特性が弱まってしまい、出光側に光学シート（B）を重ね合わせても、ＬＥＤ光源間の直上部に高輝度領域が生じやすくなり好ましくない。さらに、凹凸形状設置面の反対側面を入光面とする場合の全光線透過率は４０％〜７０％であっても、凹凸形状設置面を入光面とする場合の全光線透過率が８０％未満になると、光学シート（Ａ）の出光側に光学シート（B）を重ね合わせても、輝度ムラの解消、あるいは低減が困難となる。 In the optical sheet (A) used in the planar light source device of the present invention, the total light transmittance when the opposite side of the concave and convex shape installation surface is the light incident surface is less than 40%, the deflection characteristics due to the concave and convex shape become strong, Even if the optical sheet (B) is overlaid on the light output side, the light and darkness based on the light output pattern of the LED light source remains on the optical sheet (B). On the other hand, if it exceeds 70%, the deflection characteristic due to the uneven shape is weakened, and even if the optical sheet (B) is overlapped on the light output side, a high luminance region is likely to be formed immediately above the LED light source, which is not preferable. Furthermore, even if the total light transmittance is 40% to 70% when the opposite surface of the uneven surface is the light incident surface, the total light transmittance when the uneven surface is the light incident surface is 80%. If it is less than%, even if the optical sheet (B) is superimposed on the light output side of the optical sheet (A), it becomes difficult to eliminate or reduce luminance unevenness.
本発明の面状光源装置に用いられる光学シート（Ａ）の片面に有する凹凸形状の寸法は、底面積が１００〜１００００００μｍ２であり、かつ底面から最高部または最深部までの高低差が１０〜５００μｍであることが好ましい。このような微細な凹凸形状によりＬＥＤ光源からの指向性の高い光を反射、偏向させ、高指向性による明暗を平準化し、さらにレンズ付ＬＥＤ光源からの深い入射角の光を、面状光源装置の正面方向へ偏向させることで輝度ムラ低減をもたらすことができるが、明暗の平準化度、凹凸形状の賦型精度や再現性という点から、底面積が１００〜１０００００μｍ２であり、かつ底面から最高部または最深部までの高低差が１５〜２００μｍであることがより好ましい。 The size of the uneven shape on one side of the optical sheet (A) used in the planar light source device of the present invention is such that the bottom area is 100 to 1000000 μm 2 and the height difference from the bottom surface to the highest part or the deepest part is 10 to 10. It is preferable that it is 500 micrometers. Such a fine concavo-convex shape reflects and deflects highly directional light from the LED light source, leveling the brightness and darkness due to the high directivity, and further converting light with a deep incident angle from the LED light source with lens into a planar light source device The brightness unevenness can be reduced by deflecting in the front direction, but the bottom area is 100 to 100,000 μm 2 from the bottom in terms of leveling of light and darkness, shaping accuracy and reproducibility of the uneven shape, and from the bottom It is more preferable that the height difference from the highest part or the deepest part is 15 to 200 μm.
本発明の面状光源装置に用いられる光学シート（Ａ）の片面に有する凹凸形状としては、切断楕円体凹凸形状、円錐凹凸形状、切断円錐凹凸形状、多角錐凹凸形状、切断多角錐凹凸形状など、底面積より凸部最高部の面積が小さく、あるいは底面積より凹部最深部の面積が小さく、いずれも底面から最高部や最深部にかけて順次に細くなっている形状が好ましく、用いる面状光源装置のＬＥＤ光源の出光特性、ＬＥＤ光源配置間隔、反射シートと光学シート（Ａ）の距離に応じて選択できる。しかしながら、いずれの形状であっても、偏向機能の一つとしてＬＥＤ光源からの指向性の高い光による明暗を平準化するために、入射光を反射シート側に戻すことが必要であることから、４５±１０°の傾斜面を有する凹凸形状が好ましい。なかでも、全面に高密度で形成できるという点から、４５±１０°の傾斜面を有する多角錐凹凸形状、あるいは切断多角錐凹凸形状が好ましく、光学シートの表面に凹凸形状を賦型するための金型加工の点や、賦型の再現性の点からは正四角錐凹凸形状、あるいは切断正四角錐凹凸形状が特に好ましい。これらの多角錐凹凸形状、あるいは切断多角錐凹凸形状の配列されている接合部、頭頂部、傾斜面間の接合部や傾斜面と切断面との接合面が曲面であっても問題なく使用でき、ＬＥＤ光源の種類や配置方法によっては、より好ましい場合がある。 Examples of the uneven shape on one side of the optical sheet (A) used in the planar light source device of the present invention include a cut ellipsoid uneven shape, a cone uneven shape, a cut cone uneven shape, a polygonal pyramid uneven shape, a cut polygonal pyramid uneven shape, and the like. The surface light source device to be used is preferably such that the area of the highest part of the convex part is smaller than the bottom area, or the area of the deepest part of the concave part is smaller than the bottom area, and all of them are gradually narrowed from the bottom surface to the highest part and the deepest part. The light output characteristics of the LED light source, the LED light source arrangement interval, and the distance between the reflective sheet and the optical sheet (A) can be selected. However, in any shape, it is necessary to return the incident light to the reflective sheet side in order to level the brightness and darkness of the highly directional light from the LED light source as one of the deflection functions. An uneven shape having an inclined surface of 45 ± 10 ° is preferable. Among them, a polygonal pyramid uneven shape having an inclined surface of 45 ± 10 ° or a cut polygonal pyramid uneven shape is preferable from the viewpoint that it can be formed at a high density on the entire surface, and for forming the uneven shape on the surface of the optical sheet. From the viewpoint of mold processing and the reproducibility of forming, a regular quadrangular pyramid uneven shape or a cut regular quadrangular pyramid uneven shape is particularly preferable. Can be used without any problems even if the joints between these polygonal pyramid uneven shapes or cut polygonal pyramid uneven shapes, the joints between the top and the inclined surfaces, and the bonded surfaces between the inclined surfaces and the cut surfaces are curved surfaces. Depending on the type and arrangement method of the LED light source, it may be more preferable.
本発明の面状光源装置に用いる光学シート（Ａ）の出光面に有する凹凸形状が、正四角錐凹凸形状、あるいは切断正四角錐凹凸形状の場合には、光学シート（Ａ）表面の正四角錐凹凸形状、あるいは切断正四角錐凹凸形状の配列方向と、ＬＥＤ光源の配置間隔における最短方向が交差するよう、ＬＥＤ光源上に光学シート（Ａ）を設置することが、輝度ムラ低減や解消により効果的である。 When the irregular shape on the light exit surface of the optical sheet (A) used in the planar light source device of the present invention is a regular quadrangular pyramid irregular shape or a cut regular quadrangular pyramid irregular shape, the regular quadrangular pyramid irregular shape on the surface of the optical sheet (A) Alternatively, it is more effective to reduce or eliminate luminance unevenness to install the optical sheet (A) on the LED light source so that the arrangement direction of the cut regular square pyramid uneven shape and the shortest direction in the arrangement interval of the LED light source intersect. .
本発明の面状光源装置に用いる光学シート（Ａ）を構成する透明樹脂は、無色透明であり、かつ光学シートの主な構成要素として適度な強度を有するものであれば特に制限されない。例えば、ポリカーボネート樹脂；ポリメチルメタクリレートなどのアクリル系樹脂；ポリスチレン、ポリビニルトルエン、ポリ（ｐ−メチルスチレン）などのスチレン系樹脂；ＭＳ樹脂（メチルメタクリレートとスチレンの共重合体）；ノルボルネン系樹脂；ポリアリレート樹脂；ポリエーテルスルホン樹脂や、これらのうち２種以上の混合樹脂などを用いることができる。好適にはポリカーボネート樹脂、スチレン系樹脂またはノルボルネン系樹脂を用いる。中でもポリカーボネート樹脂は、透明性や耐熱性、加工性に優れており、且つそれらのバランスがよいので光学シート用の樹脂として特に好ましい。 The transparent resin constituting the optical sheet (A) used in the planar light source device of the present invention is not particularly limited as long as it is colorless and transparent and has an appropriate strength as a main component of the optical sheet. 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.
さらに、光学シート（Ａ）に用いる光拡散剤としては、有機系微粒子、無機系微粒子、有機−無機ハイブリッド系微粒子のいずれの微粒子でも使用でき、例えば、（メタ）アクリル系樹脂、スチレン系樹脂、アミノ系樹脂、ポリエステル系樹脂、シリコーン系樹脂、フッ素系樹脂、これらの共重合体などの有機系微粒子；ガラス、スメクタイト、カオリナイト、シリカ、アルミナ、酸化チタン、酸化ジルコニウムなどの無機系微粒子；アクリル−シリカなどの有機−無機ハイブリッド系微粒子などが挙げられる。これらの材質のうち、（メタ）アクリル系樹脂、シリコーン系樹脂、シリカが特に好適である。 Furthermore, as the light diffusing agent used in the optical sheet (A), any of organic fine particles, inorganic fine particles, and organic-inorganic hybrid fine particles can be used. For example, (meth) acrylic resins, styrene resins, Organic fine particles such as amino resin, polyester resin, silicone resin, fluorine resin, and copolymers thereof; inorganic fine particles such as glass, smectite, kaolinite, silica, alumina, titanium oxide, zirconium oxide; acrylic -Organic-inorganic hybrid fine particles such as silica. Of these materials, (meth) acrylic resins, silicone resins, and silica are particularly suitable.
光拡散剤の平均粒子径は０．３μｍ〜３０μｍが好ましく、これ以上小さくても、大きくても光拡散効果が大きく低下して好ましくなく、より好ましくは０．５μｍ〜１５μｍである。光拡散剤の最適配合量は、光学シート（Ａ）を構成する透明樹脂と光拡散剤の屈折率差、光拡散剤の粒子径によって大きく異なるが、光学シート（Ａ）においては、光拡散性を決定する要因として、光拡散剤による光拡散以外に、片面に設置されている凹凸形状による拡散効果も合わせて考慮する必要がある。したがって、凹凸形状を有する面の反対側面を入光面とした際の全光線透過率が４０％〜７０％、かつ凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上、より好ましくは８０％〜９５％になるよう、所定の凹凸形状における光拡散剤の種類と配合量を決定することが最も好ましい。 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. The optimum blending amount of the light diffusing agent varies greatly depending on the difference in refractive index between the transparent resin constituting the optical sheet (A) and the light diffusing agent, and the particle size of the light diffusing agent. In addition to the light diffusion by the light diffusing agent, it is necessary to consider the diffusion effect due to the uneven shape installed on one side. Accordingly, the total light transmittance is 40% to 70% when the opposite side of the surface having the uneven shape is the light incident surface, and the total light transmittance is 80% when the surface having the uneven shape is the light incident surface. As described above, it is most preferable to determine the type and blending amount of the light diffusing agent in the predetermined uneven shape so that it is more preferably 80% to 95%.
光学シート（Ａ）の製法としては、上記の透明熱可塑性樹脂と光拡散剤、さらに熱安定剤などを均一に配合した熱可塑性樹脂混合物を、所望の凹凸形状の反転形状が実質全面に彫刻加工された金型を用いて、押出成形、射出成形、プレス成形などにより得ることができる。なかでも押出成形による方法が、帯電防止性能や特定波長の光吸収層などの表面機能層を形成できるなど多層化が容易なことや、生産効率が高いなどの点で特に好ましい The optical sheet (A) can be produced by engraving a thermoplastic resin mixture in which the above-mentioned transparent thermoplastic resin, light diffusing agent, and heat stabilizer are evenly blended, with the desired concavo-convex shape inversion. Using the formed mold, it can be obtained by extrusion molding, injection molding, press molding or the like. Among these, the extrusion method is particularly preferable in terms of easy multilayering and high production efficiency, such as the formation of a surface functional layer such as an antistatic performance and a light absorption layer having a specific wavelength.
光学シート（Ａ）の形状寸法は、用いる面状光源装置の形状寸法に合わせて裁断、あるいは最終寸法に応じた金型を用い成形すればよく、厚さも、用いる面光源装置の寸法、用途によって、あるいは光学シートの設置位置によって異なるが、０．３ｍｍ〜４ｍｍが好ましい。さらに、液晶表示装置の薄型化が求められる場合には、０．２〜２ｍｍがより好ましい。 The shape dimension of the optical sheet (A) may be cut according to the shape dimension of the planar light source device to be used, or may be molded using a mold according to the final dimension, and the thickness depends on the size and application of the surface light source device to be used. Or, depending on the installation position of the optical sheet, 0.3 mm to 4 mm is preferable. Furthermore, when thinning of a liquid crystal display device is calculated | required, 0.2-2 mm is more preferable.
本発明の面状光源装置においては、光学シート（Ａ）のＬＥＤ光源とは反対側の出光面に光学シート（B）が重ね合わせられている光学シート構成を有することが必須であり、本発明の面状光源装置に用いる光学シート（B）は、透明樹脂に光拡散剤が配合され、表裏いずれの面を入光面とした場合でも５５〜７０％の全光線透過率を有するものである。 In the planar light source device of the present invention, it is essential to have an optical sheet configuration in which the optical sheet (B) is superimposed on the light exit surface of the optical sheet (A) opposite to the LED light source. The optical sheet (B) used for the planar light source device has a total light transmittance of 55 to 70% even when a light diffusing agent is blended with a transparent resin and the front or back surface is a light incident surface. .
光学シート（B）の表裏いずれかの面を入光面とした場合に、全光線透過率が５５％未満となると、光学シート（B）のＬＥＤ光源側に用いる光学シート（Ａ）の凹凸形状を有する面の反対側面を入光面とした際の全光線透過率が４０％〜７０％、かつ凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上であっても、低輝度部分の解消や低減が困難となり、また、光学シート（B）の表裏いずれの面を入光面とした場合に、全光線透過率が７０％を超えると、同じく光学シート（B）のＬＥＤ光源側に用いる光学シート（Ａ）の凹凸形状を有する面の反対側面を入光面とした際の全光線透過率が４０％〜７０％、かつ凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上であっても、高輝度部のパターンが残存しやすくなる。光学シート（B）の表裏いずれの面を入光面とした場合のより好ましい全光線透過率は、５５％〜６５％であり、ＬＥＤ光源配置間隔が従来の間隔よりも拡大、あるいはＬＥＤ光源と光学シートの間隔が縮小した面状光源装置においても、一層、輝度ムラの低減や解消がしやすくなる。 When either the front or back surface of the optical sheet (B) is a light incident surface, if the total light transmittance is less than 55%, the uneven shape of the optical sheet (A) used on the LED light source side of the optical sheet (B) The total light transmittance is 40% to 70% when the opposite side of the surface having the light incident surface is the light incident surface, and the total light transmittance is 80% or more when the surface having the irregular shape is the light incident surface. However, it is difficult to eliminate or reduce the low-brightness part. Also, when the front and back surfaces of the optical sheet (B) are used as the light incident surface, if the total light transmittance exceeds 70%, the optical sheet (B ) Of the optical sheet (A) used on the LED light source side is 40% to 70% in total light transmittance when the side opposite to the surface having the uneven shape is the light incident surface, and the surface having the uneven shape is the light incident surface. Even when the total light transmittance is 80% or more, the pattern of the high brightness portion is likely to remain. Become. The more preferable total light transmittance when the front and back surfaces of the optical sheet (B) are used as the light incident surface is 55% to 65%, and the LED light source arrangement interval is larger than the conventional interval, or Even in the planar light source device in which the interval between the optical sheets is reduced, it becomes easier to reduce or eliminate the luminance unevenness.
なお、光学シート（Ａ）の出光面上に、光学シート（B）の代替として、従来から液晶表示装置の面状光源装置に広く用いられている拡散性熱可塑性樹脂フィルム表面に微粒子を塗布した“拡散フィルム”や“拡散シート”を、１枚なしは複数枚用いても、全光線透過率が高すぎ、反射・偏向・光拡散における光学シート（Ａ）との相乗作用が見られず、指向性の高いＬＥＤ光源とする本発明の面状光源装置の光学シートには不適である。 In addition, as an alternative to the optical sheet (B), fine particles were coated on the surface of the diffusive thermoplastic resin film that has been widely used in the surface light source devices of liquid crystal display devices on the light exit surface of the optical sheet (A). Even if a single "diffuse film" or "diffuse sheet" is used, the total light transmittance is too high, and there is no synergistic effect with the optical sheet (A) in reflection, deflection, and light diffusion. It is unsuitable for the optical sheet of the planar light source device of the present invention which is a highly directional LED light source.
光学シート（B）の表裏面は、光学シート（Ａ）のような凹凸形状を有さず、鏡面、エンボス面のいずれかが好ましいが、片面のみエンボス面とする場合や、両面エンボス面とする場合においても、表裏いずれの面を入射面とした全光線透過率が上記の範囲内になるようにすることが必須である。 The front and back surfaces of the optical sheet (B) do not have an uneven shape like the optical sheet (A), and either a mirror surface or an embossed surface is preferable, but only one side is an embossed surface or a double-sided embossed surface. Even in this case, it is essential that the total light transmittance with the incident surface on either the front or back surface is within the above range.
光学シート（B）を構成する透明樹脂や配合される光拡散剤は、いずれも光学シート（Ａ）を構成するものと同様なものから選択でき、光拡散剤の最適配合量は、光学シート（B）を構成する透明樹脂と光拡散剤の屈折率差、光拡散剤の粒子径によって大きく異なるが、表裏いずれの面を入光面とした場合でも５５〜７０％の全光線透過率になるよう光拡散剤の種類と配合量を決定することが最も好ましい。 The transparent resin constituting the optical sheet (B) and the light diffusing agent to be blended can be selected from those similar to those constituting the optical sheet (A). The optimum blending amount of the light diffusing agent is the optical sheet ( Although it varies greatly depending on the refractive index difference between the transparent resin and the light diffusing agent and the particle size of the light diffusing agent constituting B), the total light transmittance is 55 to 70% when either the front or back surface is the light incident surface. Most preferably, the type and amount of the light diffusing agent are determined.
光学シート（B）の製法としては、光学シート（Ａ）と同様の透明熱可塑性樹脂と光拡散剤、さらに熱安定剤などを均一に配合した熱可塑性樹脂混合物を、所望の表面状態にすべく、エンボス、鏡面などの金型を用いて、押出成形、射出成型、プレス成形などにより得ることができる。なかでも押出成形による方法が、帯電防止性能や特定波長の光吸収層などの表面機能層を形成できるなど、多層化が容易なことや生産効率が高いなどの点で特に好ましい。 As a method for producing the optical sheet (B), the same thermoplastic resin mixture as the optical sheet (A), a light diffusing agent, and a thermoplastic resin mixture uniformly blended with a thermal stabilizer should be brought into a desired surface state. It can be obtained by extrusion molding, injection molding, press molding or the like using a mold such as embossing or mirror 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 surface functional layer such as antistatic performance and a light absorbing layer having a specific wavelength.
光学シート（B）の形状寸法も、用いる面状光源装置の形状寸法に合わせて裁断、あるいは最終寸法に応じた金型を用い成形すればよく、厚さも、用いる面光源装置の寸法、用途によって、あるいは光学シートの設置位置によって異なるが、０．１ｍｍ〜３ｍｍが好ましい。さらに、液晶表示装置の薄型化が求められる場合には、０．１〜１．５ｍｍがより好ましい。 The shape and size of the optical sheet (B) may be cut according to the shape and size of the planar light source device to be used, or may be molded using a mold corresponding to the final size, and the thickness depends on the size and use of the surface light source device to be used. Or, depending on the installation position of the optical sheet, 0.1 mm to 3 mm is preferable. Furthermore, when thinning of a liquid crystal display device is calculated | required, 0.1-1.5 mm is more preferable.
なお、本発明の面状光源装置に用いる光学シート（Ａ）は1枚に限定されることなく、反射シート上に配置されるＬＥＤ光源の出光特性、ＬＥＤ光源の配置間隔、反射シートと光学シート（Ａ）間の距離によっては、光学シート（Ａ）を複数枚重ね合わせた上に、光学シート（B）を重ね合わせることも、面状光源装置としての輝度ムラ解消に有効である。 In addition, the optical sheet (A) used for the planar light source device of the present invention is not limited to one, but the light emission characteristics of the LED light sources arranged on the reflective sheet, the arrangement interval of the LED light sources, the reflective sheet and the optical sheet Depending on the distance between (A), it is also effective to eliminate luminance unevenness as a planar light source device by overlapping a plurality of optical sheets (A) and then overlapping an optical sheet (B).
本発明の面状光源装置において、一枚以上の光学シート（Ａ）の出光面に光学シート（B）を重ね合わせた光学シート構成を有することが必須であるが、光学シート（B）の出光面にさらに、他の光学シートを重ね合わせることも可能である。これらの光学シートとしては、従来から面状光源装置に広く用いられている、プリズムシート、レンチキュラーシートなどのシリンドリカルレンズシート、マイクロレンズシートなどの偏向特性の大きな光学シート、輝度向上のための反射偏光シートなどがあり、これらを単独、あるいは複数枚、光学シート（B）の出光面に重ね合わせることにより、光学シート（Ａ）と光学シート（B）の相乗作用で、大幅に輝度ムラの低減や解消した面状光源装置の出光正面方向における一層の輝度向上をはることができる。 In the planar light source device of the present invention, it is essential to have an optical sheet configuration in which the optical sheet (B) is superimposed on the light output surface of one or more optical sheets (A). It is also possible to overlap another optical sheet on the surface. These optical sheets have been widely used in planar light source devices, such as cylindrical lens sheets such as prism sheets and lenticular sheets, optical sheets with large deflection characteristics such as microlens sheets, and reflected polarized light for improving luminance. There are sheets, etc., and by superimposing these alone or on the light exit surface of the optical sheet (B), the brightness unevenness can be greatly reduced by the synergistic action of the optical sheet (A) and the optical sheet (B). It is possible to further improve the luminance in the front direction of light emission of the planar light source device.
本発明の面状光源装置に用いるＬＥＤ光源は、出射強度のピークがＬＥＤ光源設置面の法線方向であるランバーシャンタイプ、法線から傾いた方向である側面放射タイプの白色ＬＥＤが好ましく用いられるが、面状光源装置の輝度ムラ低減や解消のし易さから、ＬＥＤチップ上にレンズ、あるいは光束制御部材を設置した側面放射型が特に好ましく用いられる。 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.
なかでも、配光パターンがＬＥＤ光源設置面の法線から３０°以上の深い角度に出射強度のピークを有する略回転対称の出射分布を有するレンズ付ＬＥＤであることが好ましい。さらに、配光パターンがＬＥＤ光源設置面の法線から４５°以上の深い角度に出射強度のピークを有する略回転対称の出射分布を有するレンズ付ＬＥＤを光源に用いることは、ＬＥＤ光源配置間隔の拡大化した面状光源装置、あるいはＬＥＤ光源が配置されている反射シートと光学シートの間隔が縮小した薄型面状光源装置においても、一層、輝度ムラ解消や低減をはかれることとなり、より好ましい。 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.
ＬＥＤ光源の配置方法としては、特に制約はなく、直線状配列セットの並列配置、格子状や千鳥状配置などが用いられる。 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.
本発明の面状光源装置に用いる反射シートは、白色シートであり、反射機能を有する金属板、フィルム、金属箔、アルミなどを蒸着したフィルムでできており、ＬＥＤ光源からの出射光、光学シート（Ａ）からの偏向あるいは反射光、光学シート（Ｂ）からの反射拡散光などを、再度光学シートの出光方向に戻すとともに反射方向の平準化役割を担っており、光学シート（Ａ）や光学シート（Ｂ）とともに輝度ムラ解消や低減に重要な働きをしている。 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 is vapor-deposited, emitted light from an LED light source, an optical sheet The deflected or reflected light from (A), the reflected diffused light from the optical sheet (B), etc. are returned again to the light exiting direction of the optical sheet, and are also responsible for leveling the reflecting direction. Together with the sheet (B), it plays an important role in eliminating or reducing luminance unevenness.
ＬＥＤ光源を用いた直下型面状光源装置において、実質的に輝度ムラ解消可能なレベルを、図２に示すように反射シート上に設置された複数個のＬＥＤ光源間の最も接近した間隔（Ｌ）と、反射シートと光学シート（Ａ）の点光源側の面までの最も接近した距離（Ｄ）の比であるL／Dで示すと、上記の光学シート（Ａ）と光学シート（Ｂ）の構成を有することにより、従来の光学シート構成では難易度が高かった、L／D≧２．５の面状光源装置の実現をも可能にすることができた。 In a direct type planar light source device using an LED light source, a level at which luminance unevenness can be substantially eliminated is set to a closest distance (L between the plurality of LED light sources installed on the reflection sheet as shown in FIG. ) And L / D, which is the ratio of the closest distance (D) between the reflecting sheet and the point light source side surface of the optical sheet (A), the optical sheet (A) and the optical sheet (B). Thus, it was possible to realize a planar light source device with L / D ≧ 2.5, which was difficult with the conventional optical sheet configuration.
次に、本発明に係る面状光源装置を、実験例、比較実験例、実施例、比較例により具体的に説明する。 Next, the planar light source device according to the present invention will be specifically described with reference to experimental examples, comparative experimental examples, examples, and comparative examples.
＜実験例1＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．１質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、深さが３８μｍの先端が曲面となった転倒正四角錐が凹状に一方の全面に賦型され、反対面が鏡面である厚さ１．５ｍｍの光学シート（A−１）を得た。
<Experimental example 1>
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 Falling with an inhibitor ("Irgafos 168" manufactured by BASF) 0.1 parts by mass, and by extrusion, the bottom is 80 μm, the inclination of each side is 45 °, the depth is 38 μm, and the tip is curved An optical sheet (A-1) having a thickness of 1.5 mm was obtained in which a regular quadrangular pyramid was formed in a concave shape on one entire surface and the opposite surface was a mirror surface.
＜実験例２＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．２質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、深さが３８μｍの先端が曲面となった転倒正四角錐が凹状に一方の全面に賦型され、反対面が鏡面である厚さ１．５ｍｍの光学シート（A−２）を得た。
<Experimental example 2>
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 Falling with an inhibitor ("Irgafos 168" manufactured by BASF) 0.1 parts by mass, and by extrusion, the bottom is 80 μm, the inclination of each side is 45 °, the depth is 38 μm, and the tip is curved An optical sheet (A-2) having a thickness of 1.5 mm, in which a regular quadrangular pyramid was concavely shaped on one entire surface and the opposite surface was a mirror surface, was obtained.
＜実験例３＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．１５質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、高さが３３μｍの先端が曲面となった正四角錐が凸状に一方の全面に賦型され、反対面が鏡面である厚さ１．５ｍｍの光学シート（A−３）を得た。
<Experimental example 3>
100 parts by mass of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 0.15 parts by mass of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus-based oxidation as a thermal stabilizer Inhibitor ("Irgafos 168": manufactured by BASF) 0.1 parts by mass, and by extrusion, the base is 80 μm, the slope of each side is 45 °, the tip is a curved surface with a curved surface at a height of 33 μm An optical sheet (A-3) having a thickness of 1.5 mm, in which a pyramid is convexly formed on one entire surface and the opposite surface is a mirror surface, was obtained.
＜実験例４＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．３質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、深さが３８μｍの先端が曲面となった転倒正四角錐が凹状に一方の全面に賦型され、反対面が鏡面である厚さ０．８ｍｍの光学シート（A−４）を得た。
<Experimental example 4>
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 Falling with an inhibitor ("Irgafos 168" manufactured by BASF) 0.1 parts by mass, and by extrusion, the bottom is 80 μm, the inclination of each side is 45 °, the depth is 38 μm, and the tip is curved An optical sheet (A-4) having a thickness of 0.8 mm, in which a regular quadrangular pyramid is formed in a concave shape on one entire surface and the opposite surface is a mirror surface, was obtained.
＜実験例５＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）２質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により両面が鏡面である厚さ０．８ｍｍの光学シート（B−１）を得た。
<Experimental example 5>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 2 parts by weight of silicone fine particles (“Tospearl 120”: manufactured by Momentive Performance) as a light diffusing agent, and phosphorus antioxidants as a heat stabilizer ("Irgafos 168": manufactured by BASF) 0.1 parts by mass was blended, and an optical sheet (B-1) having a thickness of 0.8 mm whose both surfaces are mirror surfaces was obtained by extrusion molding.
＜実験例６＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）３質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により両面が鏡面である厚さ０．８ｍｍの光学シート（B−２）を得た。
<Experimental example 6>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 3 parts 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 ("Irgaphos 168": manufactured by BASF) 0.1 parts by mass was blended, and an optical sheet (B-2) having a thickness of 0.8 mm whose both surfaces are mirror surfaces was obtained by extrusion molding.
＜比較実験例１＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．０５質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、深さが３８μｍの先端が曲面となった転倒正四角錐が凹状に一方の全面に賦型され、反対面が鏡面である厚さ１．５ｍｍの光学シート（C−１）を得た。
<Comparative Experimental Example 1>
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 Falling with an inhibitor ("Irgafos 168" manufactured by BASF) 0.1 parts by mass, and by extrusion, the bottom is 80 μm, the inclination of each side is 45 °, the depth is 38 μm, and the tip is curved An optical sheet (C-1) having a thickness of 1.5 mm, in which a regular quadrangular pyramid is formed in a concave shape on one entire surface and the opposite surface is a mirror surface, was obtained.
＜比較実験例２＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．５質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により、底辺が８０μｍ、各側面の傾斜度が４５°、深さが３８μｍの先端が曲面となった転倒正四角錐が凹状に一方の全面に賦型され、反対面が鏡面である厚さ１．５ｍｍの光学シート（C−２）を得た。
<Comparative Experiment Example 2>
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 Falling with an inhibitor ("Irgafos 168" manufactured by BASF) 0.1 parts by mass, and by extrusion, the bottom is 80 μm, the slope of each side is 45 °, and the depth is 38 μm. An optical sheet (C-2) having a thickness of 1.5 mm was obtained in which a regular quadrangular pyramid was formed in a concave shape on one entire surface and the opposite surface was a mirror surface.
＜比較実験例３＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）０．５質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により両面が鏡面である厚さ０．８ｍｍの光学シート（D−１）を得た。
<Comparative Experimental Example 3>
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 (D-1) having a thickness of 0.8 mm having both mirror surfaces was obtained by blending 0.1 part by mass of an inhibitor (“Irgaphos 168” manufactured by BASF) and extrusion molding.
＜比較実験例４＞
ポリカーボネート（「ユーピロンＥ２０００ＦＮ」：三菱エンジニアリングプラスチック社製）１００質量部に、光拡散剤としてシリコーン系微粒子（「トスパール１２０」：モメンティブパーフォーマンス社製）５質量部、熱安定剤としてリン系酸化防止剤（「イルガフォス１６８」：ＢＡＳＦ社製）０．１質量部を配合し、押出成形により両面が鏡面である厚さ０．８ｍｍの光学シート（D−２）を得た。
<Comparative Experimental Example 4>
100 parts by weight of polycarbonate (“Iupilon E2000FN”: manufactured by Mitsubishi Engineering Plastics), 5 parts 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 ("Irgaphos 168": manufactured by BASF) 0.1 parts by mass was blended, and an optical sheet (D-2) having a thickness of 0.8 mm with both surfaces being mirror surfaces was obtained by extrusion molding.
＜全光線透過率の測定＞
上記実験例１〜４、比較実験例１〜２で作製した光学シート（A−１）から光学シート（A−４）までと、光学シート（C−１）と光学シート（C−２）について、面状光源装置に設置時にＬＥＤ光源側となる鏡面側を入光面とする全光線透過率と、出光面となる凹凸形状が賦型された面を入光面とする全光線透過率を、ＪＩＳ K７１０５に準拠し測定し、その結果を表1に示した。
<Measurement of total light transmittance>
From optical sheet (A-1) to optical sheet (A-4) prepared in Experimental Examples 1 to 4 and Comparative Experimental Examples 1 and 2, and optical sheet (C-1) and optical sheet (C-2) The total light transmittance with the mirror surface, which is the LED light source side, as the light incident surface when installed in the planar light source device, and the total light transmittance with the irregular surface shape as the light exit surface as the light incident surface. Measured according to JIS K7105, the results are shown in Table 1.
また、上記実験例５〜６、比較実験例３〜４で作製した光学シート（B−１）と光学シート（Ｂ−２）、および光学シート（D−１）と光学シート（D−２）についても、両鏡面の各々を入光面とする全光線透過率を、ＪＩＳ K７１０５に準拠し測定し、その結果を表1に示した。 Moreover, the optical sheet (B-1) and optical sheet (B-2) which were produced in the said experimental examples 5-6 and comparative experimental examples 3-4, and the optical sheet (D-1) and optical sheet (D-2) Also, the total light transmittance with each of the mirror surfaces as the light incident surface was measured according to JIS K7105, and the results are shown in Table 1.
＜実施例１〜実施例８、および比較例１〜比較例８＞
設置面の法線から７０°に出射強度のピークを有するレンズ付白色ＬＥＤを、図１に示すように、１５０ｍｍ×１５０ｍｍの白色の反射シート上に９個、５０ｍｍ間隔で格子状に配置し、反射シートと一枚目の光学シート入光面との距離が１５ｍｍになるように、各一枚目の光学シートを設置した。ＬＥＤ光源側の一枚目に、光学シート（A−１）から光学シート（A−４）、および光学シート（C−１）、光学シート（C−２）を設置する場合には、各光学シートの出光面に存在する凹状ないしは凸状正四角錐の配列方向が、レンズ付白色LED配置間隔の最短方向と４５°で交差するように設置した。なお本実施例で使用したＬＥＤは、略回転対称の光の出射強度分布を有するレンズ付ＬＥＤである。
<Examples 1 to 8 and Comparative Examples 1 to 8>
As shown in FIG. 1, nine white LEDs with a lens having an emission intensity peak at 70 ° from the normal of the installation surface are arranged in a grid pattern at intervals of 50 mm on a 150 mm × 150 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 15 mm. When the optical sheet (A-1) to the optical sheet (A-4), the optical sheet (C-1), and the optical sheet (C-2) are installed on the first LED light source side, each optical The arrangement direction of the concave or convex regular quadrangular pyramids existing on the light exit surface of the sheet was set so as to intersect the shortest direction of the white LED with lens arrangement interval at 45 °. The LED used in this example is an LED with a lens having a substantially rotationally symmetric light emission intensity distribution.
輝度ムラについては、各シート構成における最上の光学シートの出光面に生じる明暗を目視にて評価し、これらの結果を表２に示した。 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.
なお、プリズムシートには、PETフィルム上にピッチ５０μｍ、頂角９０°の二等辺三角形断面を有するプリズム列が形成されたものを用い、反射偏光フィルムには、住友スリーエム社製のDBEFを、拡散シートには、微粒子が塗布された反対面を入光面とした際の全光線透過率が７５％であるPETフィルムをベースとした汎用タイプを用いた。 The prism sheet uses a PET film with a prism array having an isosceles triangular cross section with a pitch of 50 μm and apex angle of 90 °. The reflective polarizing film is a DBEF made by Sumitomo 3M Co., Ltd. As the sheet, a general-purpose type based on a PET film having a total light transmittance of 75% when the opposite surface coated with fine particles was used as the light incident surface was used.
＜輝度ムラ評価＞
輝度ムラ評価は、ＬＥＤ上に配置した光学シートの法線方向、および法線方向に対し±４５°方向から目視により判定し、下記の5段階に区分した。
１： 明確な境界線を有する明暗のパターンが確認できる。
２： 明暗領域の明確な境界線は認められないが、明暗パターンが明確に認められる。
３： 薄っすらとではあるが明暗パターンが認められる。
４： ほぼ明暗パターンは解消されているが、全体的な輝度均一レベルには至らず。
５： 明暗領域の存在が確認できず、全体的に輝度均一レベルが得られている。
<Evaluation of uneven brightness>
Luminance unevenness evaluation was visually judged from the normal direction of the optical sheet placed on the LED and ± 45 ° direction with respect to the normal direction, and was classified into the following five stages.
1: A bright and dark pattern having a clear boundary line can be confirmed.
2: A clear boundary between light and dark areas is not recognized, but a light and dark pattern is clearly recognized.
3: A light and dark pattern is recognized although it is thin.
4: The light / dark pattern is almost eliminated, but the overall brightness uniformity level is not reached.
5: The presence of a bright / dark region could not be confirmed, and a uniform luminance level was obtained overall.
本発明の面状光源装置は、ＬＥＤ光源直下型液晶表示装置の薄型化、コスト削減化に好適である。 The planar light source device of the present invention is suitable for reducing the thickness and cost of an LED light source direct type liquid crystal display device.
１：反射シート
２：ＬＥＤ
３：光学シート（Ａ）
４：光学シート（Ｂ）
D： 反射シート表面から光学シート（Ａ）の入光面までの距離
L： ＬＥＤ配置間隔の最短距離
1: Reflective sheet 2: LED
3: Optical sheet (A)
4: Optical sheet (B)
D: Distance from the reflecting sheet surface to the light incident surface of the optical sheet (A)
L: Minimum distance between LED placement intervals
Claims (5)
光学シート（Ａ）は、凹凸形状を有しない面を入光面とした際の全光線透過率が４０％〜７０％であり、かつ、凹凸形状を有する面を入光面とした際の全光線透過率が８０％以上であり、光学シート（Ｂ）は、表裏いずれの面を入光面とした場合でも全光線透過率が５５〜７０％であることを特徴とする面状光源装置。 An optical sheet having a plurality of LED (light emitting diode) light sources arranged on a reflection sheet and a light diffuser mixed with a transparent resin at a position where light emitted from the LED light sources is incident and having an uneven shape on one side ( An optical sheet (B) in which a light diffusing agent is blended with a transparent resin on the light exiting surface of the optical sheet (A), with one or more A) installed so that the concavo-convex shape molding surface is opposite to the LED light source Is a planar light source device having an optical sheet configuration,
The optical sheet (A) has a total light transmittance of 40% to 70% when a surface that does not have a concavo-convex shape is used as a light incident surface, and all of the surface that has a concavo-convex shape as a light incident surface. A planar light source device having a light transmittance of 80% or more, and the optical sheet (B) having a total light transmittance of 55 to 70% even when either the front or back surface is a light incident surface.
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| JP2010184645A JP2012043671A (en) | 2010-08-20 | 2010-08-20 | Planar light source device |
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|---|---|---|---|
| JP2010184645A JP2012043671A (en) | 2010-08-20 | 2010-08-20 | Planar light source device |
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