JP5078724B2 - Condensing sheet, backlight unit, and liquid crystal display device - Google Patents

Condensing sheet, backlight unit, and liquid crystal display device Download PDF

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JP5078724B2
JP5078724B2 JP2008110824A JP2008110824A JP5078724B2 JP 5078724 B2 JP5078724 B2 JP 5078724B2 JP 2008110824 A JP2008110824 A JP 2008110824A JP 2008110824 A JP2008110824 A JP 2008110824A JP 5078724 B2 JP5078724 B2 JP 5078724B2
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linearly polarizing
polarizing layer
birefringent
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JP2009265124A (en
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邦昭 石橋
宮武　　稔
博之 武本
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Nitto Denko Corp
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Description

本発明は液晶表示装置に使用されるシート状の集光素子（集光シート）、前記の集光シートを備えたバックライトユニット、そして前記のバックライトユニットを備えた液晶表示装置に関する。   The present invention relates to a sheet-shaped condensing element (condensing sheet) used in a liquid crystal display device, a backlight unit including the condensing sheet, and a liquid crystal display device including the backlight unit.

従来、視野角を制御する液晶表示装置として、液晶セルの視認側の表面に光拡散素子を配置し、液晶セルの視認側とは反対側（代表的にはバックライト側）に集光素子を配置した液晶表示装置が知られている（特許文献１、２）。このような液晶表示装置に用いられる集光素子としては、直角プリズムやコリメートレンズなどが知られている。   Conventionally, as a liquid crystal display device for controlling the viewing angle, a light diffusing element is arranged on the surface on the viewing side of the liquid crystal cell, and a condensing element is provided on the opposite side (typically the backlight side) of the liquid crystal cell. Arranged liquid crystal display devices are known (Patent Documents 1 and 2). As a condensing element used in such a liquid crystal display device, a right-angle prism, a collimating lens, and the like are known.

しかしながら上記の集光素子は、レーザー用に小型のものを製造することはできても、液晶テレビに使用できるほどの大面積で薄手のシート状のものは実現が難しいという問題があった。また上記の集光素子は表面に凹凸加工が施されているため、集光素子を他の部材に積層し難いという問題もあった。そのため、かかる問題を解決したシート状の集光素子（集光シート）が望まれていた。
特開平５−３４１２７０号公報 特開平９−１９７４０５号公報 However, although the above-mentioned light condensing element can be manufactured as a small one for a laser, there is a problem that it is difficult to realize a thin sheet-shaped one having a large area that can be used for a liquid crystal television. In addition, since the light condensing element has an uneven surface, there is a problem that it is difficult to stack the light condensing element on another member. Therefore, a sheet-like light condensing element (light condensing sheet) that solves such a problem has been desired.
JP-A-5-341270 JP-A-9-197405

本発明の課題は、例えば液晶テレビなどに使用できる大面積の集光シートを実現することである。さらに表面が平滑で、他の部材に積層できる集光シートを実現することである。   The subject of this invention is implement | achieving the condensing sheet | seat of a large area which can be used for a liquid crystal television etc., for example. Furthermore, it is to realize a light collecting sheet that has a smooth surface and can be laminated on another member.

本発明の要旨は以下のとおりである。
（１）本発明の集光シートは、吸収型直線偏光層と負の複屈折層と反射型直線偏光層とを備え、前記吸収型直線偏光層の片側に、前記負の複屈折層と前記反射型直線偏光層とが交互に、それぞれ２層または３層積層されてなり、前記吸収型直線偏光層の透過軸方向と各前記反射型直線偏光層の透過軸方向とが互いに平行であることを特徴とする。
（２）本発明の集光シートは、前記負の複屈折層のうち、前記吸収型直線偏光層に最も近い負の複屈折層が負の二軸性複屈折層であることを特徴とする。
（３）本発明のバックライトユニットは、バックライトと、上記の集光シートとを備え、前記集光シートの前記吸収型直線偏光層が、前記バックライトから遠い側になるように配置されたことを特徴とする。
（４）本発明の液晶表示装置は、バックライトと、上記の集光シートと、液晶セルとをこの順に備え、前記集光シートの前記吸収型直線偏光層側が、前記液晶セルと対向するように配置されたことを特徴とする。 The gist of the present invention is as follows.
(1) The condensing sheet of the present invention includes an absorptive linearly polarizing layer, a negative birefringent layer, and a reflective linearly polarizing layer, and on one side of the absorptive linearly polarizing layer, the negative birefringent layer and the Two or three reflective linearly polarizing layers are alternately laminated, and the transmission axis direction of the absorbing linearly polarizing layer and the transmission axis direction of each reflective linearly polarizing layer are parallel to each other. It is characterized by.
(2) The condensing sheet of the present invention is characterized in that, among the negative birefringent layers, the negative birefringent layer closest to the absorption linearly polarizing layer is a negative biaxial birefringent layer. .
(3) The backlight unit of the present invention includes a backlight and the light collecting sheet, and is arranged so that the absorption linearly polarizing layer of the light collecting sheet is on the side far from the backlight. It is characterized by that.
(4) The liquid crystal display device of the present invention includes a backlight, the above-described light collecting sheet, and a liquid crystal cell in this order, so that the absorption linearly polarizing layer side of the light collecting sheet faces the liquid crystal cell. It is characterized by being arranged in.

本発明により、例えば液晶テレビなどに使用できるような大面積であって、表面が平滑で他の部材に積層できる集光シートが実現された。   According to the present invention, a condensing sheet having a large area that can be used for, for example, a liquid crystal television and having a smooth surface and can be laminated on another member has been realized.

本発明の集光シートは、負の複屈折層と反射型直線偏光層とが交互に、それぞれ２層または３層積層されたものである。この構成の集光シートは、バックライトからの入射光のうち、集光シートに垂直入射し、かつ各透過軸と平行な電界ベクトル振動面を有する透過偏光だけを出射することができるため、集光性に優れる。   In the light collecting sheet of the present invention, negative birefringent layers and reflective linearly polarizing layers are alternately laminated in two or three layers, respectively. A condensing sheet having this configuration can emit only transmitted polarized light that is perpendicularly incident on the condensing sheet and has an electric field vector oscillation plane parallel to each transmission axis, out of incident light from the backlight. Excellent light properties.

図１は本発明の集光シート１０の作用原理を模式的に示したものである。   FIG. 1 schematically shows the principle of operation of the light collecting sheet 10 of the present invention.

（ア）バックライト１１からの光（自然光）を、電界ベクトルの振動面が第２の反射型直線偏光層１２の透過軸に平行な偏光（ｐ１、ｐ２、ｐ３）と、透過軸に直交する偏光（ｒ１、ｒ２、ｒ３）とに分けて考える。第２の反射型直線偏光層１２の透過軸に平行な偏光（ｐ１、ｐ２、ｐ３）は第２の反射型直線偏光層１２を透過するが、透過軸に直交する偏光（ｒ１、ｒ２、ｒ３）は反射される。   (A) Light (natural light) from the backlight 11 is perpendicular to the transmission axis and polarized light (p1, p2, p3) in which the vibration plane of the electric field vector is parallel to the transmission axis of the second reflective linearly polarizing layer 12 Consider separately polarized light (r1, r2, r3). Polarized light (p1, p2, p3) parallel to the transmission axis of the second reflective linear polarizing layer 12 is transmitted through the second reflective linear polarizing layer 12, but polarized light (r1, r2, r3) orthogonal to the transmission axis. ) Is reflected.

（イ）第２の反射型直線偏光層１２を透過した偏光のうち、第２の負の複屈折層１３に垂直入射する偏光（ｐ１）は何ら偏光状態を変換されない。しかし第２の負の複屈折層１３に浅い角度で斜め入射する偏光（ｐ２）は、第２の負の複屈折層１３によって、振動面が第１の反射型直線偏光層１４の透過軸と直交するように変換される。一方、第２の負の複屈折層１３に深い角度で斜め入射する偏光（ｐ３）は、第２の負の複屈折層１３によって、振動面が第１の反射型直線偏光層１４の透過軸と平行となるように変換される。   (A) Of the polarized light transmitted through the second reflective linearly polarizing layer 12, the polarized light (p1) perpendicularly incident on the second negative birefringent layer 13 is not converted in any polarization state. However, the polarized light (p2) obliquely incident on the second negative birefringent layer 13 at a shallow angle has a vibration plane that is the same as the transmission axis of the first reflective linearly polarizing layer 14 by the second negative birefringent layer 13. Converted to be orthogonal. On the other hand, polarized light (p3) obliquely incident on the second negative birefringent layer 13 at a deep angle is transmitted through the transmission axis of the first reflective linearly polarizing layer 14 by the second negative birefringent layer 13. Is converted to be parallel.

（ウ）第２の負の複屈折層１３を透過した偏光のうち、振動面が第１の反射型直線偏光層１４の透過軸と平行な偏光（ｐ１、ｐ３）は第１の反射型直線偏光層１４を透過するが、振動面が第１の反射型直線偏光層１４の透過軸と直交する偏光（ｐ２）は第１の反射型直線偏光層１４により反射される。   (C) Of the polarized light transmitted through the second negative birefringent layer 13, polarized light (p1, p3) whose vibration plane is parallel to the transmission axis of the first reflective linear polarizing layer 14 is the first reflective straight line. Polarized light (p2) that passes through the polarizing layer 14 but whose vibration plane is orthogonal to the transmission axis of the first reflective linear polarizing layer 14 is reflected by the first reflective linear polarizing layer 14.

（エ）第１の反射型直線偏光層１４を透過した偏光のうち、第１の負の複屈折層１５に垂直入射する光（ｐ１）は何ら偏光状態を変換されない。しかし深い角度で斜め入射する偏光（ｐ３）は、第１の負の複屈折層１５によって、振動面が吸収型直線偏光層１６の透過軸と直交するように変換される。   (D) Of the polarized light transmitted through the first reflective linearly polarizing layer 14, the light (p1) perpendicularly incident on the first negative birefringent layer 15 is not converted in polarization state. However, the polarized light (p3) obliquely incident at a deep angle is converted by the first negative birefringent layer 15 so that the vibration plane is orthogonal to the transmission axis of the absorption linear polarizing layer 16.

（オ）第１の負の複屈折層１５を透過した偏光のうち、振動面が吸収型直線偏光層１６の透過軸と平行な偏光（ｐ１）は吸収型直線偏光層１６を透過するが、振動面が吸収型直線偏光層１６の透過軸と直交する偏光（ｐ３）は吸収型直線偏光層１６により吸収される。   (E) Of the polarized light transmitted through the first negative birefringent layer 15, polarized light (p 1) whose vibration plane is parallel to the transmission axis of the absorbing linear polarizing layer 16 is transmitted through the absorbing linear polarizing layer 16. Polarized light (p3) whose vibration plane is orthogonal to the transmission axis of the absorption linear polarization layer 16 is absorbed by the absorption linear polarization layer 16.

以上の結果、原理的には、バックライト１１から集光シート１０に垂直入射する光のみが集光シート１０を透過できる。図１の集光シート１０は負の複屈折層１３、１５と反射型直線偏光層１２、１４を２組備えたものであるが、負の複屈折層と反射型直線偏光層をさらにもう１組積層した構成とすると、より広い角度にわたって斜め方向の偏光を反射または吸収できるようになり、より一層優れた集光性を示す。   As a result, in principle, only light perpendicularly incident on the light collecting sheet 10 from the backlight 11 can pass through the light collecting sheet 10. The condensing sheet 10 in FIG. 1 includes two sets of negative birefringent layers 13 and 15 and reflective linearly polarizing layers 12 and 14, but further includes a negative birefringent layer and a reflective linearly polarizing layer. When the laminated structure is used, it becomes possible to reflect or absorb polarized light in an oblique direction over a wider angle, and to exhibit a further excellent light collecting property.

図２は本発明の要件を備えない、負の複屈折層２２と反射型直線偏光層２１を１組積層した集光シート２０の作用原理を模式的に示したものである。この集光シート２０においては、反射型直線偏光層２１を透過した斜め方向の偏光（ｐ２、ｐ３）のうち、浅い角度の偏光（ｐ２）は吸収型直線偏光層２３で吸収することができるが、深い角度の偏光（ｐ３）は吸収することができずに透過してしまう。このため十分な集光性を得ることができない。   FIG. 2 schematically shows the principle of operation of the light collecting sheet 20 in which one set of the negative birefringent layer 22 and the reflective linearly polarizing layer 21 is not provided. In this condensing sheet 20, out of the obliquely polarized light (p 2, p 3) transmitted through the reflective linearly polarizing layer 21, shallow angle polarized light (p 2) can be absorbed by the absorbing linearly polarizing layer 23. Deep polarized light (p3) cannot be absorbed and is transmitted. For this reason, sufficient light condensing property cannot be obtained.

負の複屈折層と反射型直線偏光層を交互にそれぞれ４層以上積層した集光シート（図示しない）は、集光作用は高くなるが、各層の界面反射が大きすぎて透過強度が小さくなってしまうため、好ましくない。   A condensing sheet (not shown) in which four or more negative birefringent layers and reflective linearly polarizing layers are alternately laminated has a high condensing effect, but the interface reflection of each layer is too large and the transmission intensity decreases. This is not preferable.

［集光シート］
本発明の集光シートは図３（Ａ）および（Ｂ）に示すように、吸収型直線偏光層と負の複屈折層と反射型直線偏光層とを備える。吸収型直線偏光層の片側には、負の複屈折層と反射型直線偏光層とが交互に、それぞれ２層（図３（Ａ））または３層（図３（Ｂ））積層されている。吸収型直線偏光層の透過軸方向と各反射型直線偏光層の透過軸方向は互いに平行である。 [Condenser sheet]
As shown in FIGS. 3A and 3B, the condensing sheet of the present invention includes an absorption linearly polarizing layer, a negative birefringent layer, and a reflective linearly polarizing layer. On one side of the absorption type linearly polarizing layer, a negative birefringent layer and a reflective type linearly polarizing layer are alternately laminated in two layers (FIG. 3A) or three layers (FIG. 3B), respectively. . The transmission axis direction of the absorption linearly polarizing layer and the transmission axis direction of each reflective linearly polarizing layer are parallel to each other.

図３（Ａ）に示す本発明の集光シート１０は、吸収型直線偏光層１６の片側に、第１の負の複屈折層１５、第１の反射型直線偏光層１４、第２の負の複屈折層１３、第２の反射型直線偏光層１２が積層されてなる。   The condensing sheet 10 of the present invention shown in FIG. 3A has a first negative birefringent layer 15, a first reflective linearly polarizing layer 14, and a second negatively polarizing layer 16 on one side of the absorbing linearly polarizing layer 16. The birefringent layer 13 and the second reflective linearly polarizing layer 12 are laminated.

図３（Ｂ）に示す本発明の集光シート３０は、吸収型直線偏光層３７の片側に、第１の負の複屈折層３６、第１の反射型直線偏光層３５、第２の負の複屈折層３４、第２の反射型直線偏光層３３、第３の負の複屈折層３２、第３の反射型直線偏光層３１が積層されてなる。   The light collecting sheet 30 of the present invention shown in FIG. 3 (B) has a first negative birefringent layer 36, a first reflective linearly polarizing layer 35, and a second negatively polarizing layer 37 on one side of the absorbing linearly polarizing layer 37. The birefringent layer 34, the second reflective linearly polarizing layer 33, the third negative birefringent layer 32, and the third reflective linearly polarizing layer 31 are laminated.

本発明の集光シートは広い角度にわたって斜め方向の偏光を反射または吸収することができるため、優れた集光性を示す。また表面にレンズシートのような凹凸加工が施されていないため、他の部材と積層しやすく、かつ大面積化が可能である。   Since the condensing sheet of the present invention can reflect or absorb polarized light in an oblique direction over a wide angle, it exhibits excellent condensing properties. Further, since the surface is not subjected to uneven processing like a lens sheet, it can be easily laminated with other members, and the area can be increased.

本発明の集光シートは上記の部材を有するものであれば、他の部材が積層されていてもよい。他の部材としては、例えば粘着剤層やカバーシートなどが挙げられる。あるいは輝度をさらに高めるために、吸収型直線偏光層と第１の負の複屈折層との間に第４の反射型直線偏光層を配置してもよい。   As long as the condensing sheet of this invention has said member, the other member may be laminated | stacked. Examples of other members include a pressure-sensitive adhesive layer and a cover sheet. Alternatively, in order to further increase the luminance, a fourth reflective linearly polarizing layer may be disposed between the absorbing linearly polarizing layer and the first negative birefringent layer.

本発明の集光シートの厚みは、好ましくは５μｍ〜１０００μｍであり、さらに好ましくは５０μｍ〜５００μｍである。   The thickness of the light collecting sheet of the present invention is preferably 5 μm to 1000 μm, more preferably 50 μm to 500 μm.

本発明の集光シートは、好ましくは方位角４５°における輝度の半値角を６０°以下とすることが可能であり、さらに好ましくは５０°以下とすることが可能である。   In the condensing sheet of the present invention, the half-value angle of luminance at an azimuth angle of 45 ° can be preferably 60 ° or less, and more preferably 50 ° or less.

［吸収型直線偏光層］
本発明に用いられる吸収型直線偏光層は、入射光を２つの偏光成分に分けたとき、一方の偏光成分を透過し、他方の偏光成分を吸収する偏光子である。このような吸収型直線偏光層に特に制限はなく、例えばポリビニルアルコールフィルムを延伸し、ヨウ素で染色したものが用いられる。あるいは市販の吸収型直線偏光板（吸収型直線偏光子を透明保護フィルムで挟持したもの）でもよい。吸収型直線偏光層の厚みは、好ましくは１μｍ〜５００μｍであり、さらに好ましくは１０μｍ〜２００μｍである。 [Absorption type linearly polarizing layer]
The absorption linear polarizing layer used in the present invention is a polarizer that transmits one polarized component and absorbs the other polarized component when incident light is divided into two polarized components. There is no restriction | limiting in particular in such an absorption-type linearly-polarizing layer, For example, what stretched | stretched the polyvinyl alcohol film and dye | stained with the iodine is used. Alternatively, a commercially available absorption linear polarizing plate (a structure in which an absorption linear polarizer is sandwiched between transparent protective films) may be used. The thickness of the absorption linearly polarizing layer is preferably 1 μm to 500 μm, more preferably 10 μm to 200 μm.

［負の複屈折層］
本発明に用いられる負の複屈折層は、屈折率楕円体がｎｘ＝ｎｙ＞ｎｚの関係を満足する負の一軸性複屈折層、または屈折率楕円体がｎｘ＞ｎｙ＞ｎｚの関係を満足する負の二軸性複屈折層である。ここでｎｘは遅相軸方向の屈折率を表わし、ｎｙは遅相軸と直交する方向（進相軸方向）の屈折率を表わし、ｎｚは厚み方向の屈折率を表わす。 [Negative birefringent layer]
Negative birefringence layer used in the present invention has a refractive index ellipsoid n x = n y> n negative uniaxial birefringent layer satisfies the relationship of z, or refractive index ellipsoid n x> n y> It is a negative biaxial birefringent layer that satisfies the relationship of nz . Where n x represents a refractive index in a slow axis direction, n y represents a refractive index in a direction (a fast axis direction) perpendicular to the slow axis, n z represents the refractive index in the thickness direction.

上記の各負の複屈折層のＲｅ［５９０］およびＲｔｈ［５９０］は、それぞれ同一であってもよいし、異なっていてもよい。Ｒｅ［５９０］は波長５９０ｎｍにおける面内の位相差を表わし、Ｒｅ［５９０］＝（ｎｘ−ｎｙ）×ｄにより求められる。ここでｄは層の厚み（単位ｎｍ）である。またＲｔｈ［５９０］は波長５９０ｎｍにおける厚み方向の位相差を表わし、Ｒｔｈ［５９０］＝（ｎｘ−ｎｚ）×ｄにより求められる。 Re [590] and Rth [590] of each of the negative birefringent layers may be the same or different. Re [590] represents the phase difference in the plane at a wavelength of 590 nm, determined by Re [590] = (n x -n y) × d. Here, d is the thickness of the layer (unit: nm). The Rth [590] represents the phase difference in the thickness direction at a wavelength of 590 nm, determined by Rth [590] = (n x -n z) × d.

また図３（Ａ）および（Ｂ）の構成において各負の複屈折層は、負の一軸性複屈折層のみ、または負の二軸性複屈折層のみを用いてもよいし、両者を組み合わせて用いてもよい。好ましくは、第１および第２の負の複屈折層は負の二軸性複屈折層であり、第３の負の複屈折層は負の一軸性複屈折層である。その理由は、負の二軸性複屈折層を第１の負の複屈折層とすれば、負の二軸性複屈折層で偏光状態を変換した偏光をそのまま吸収型直線偏光層へ入射させることができるからである。   3A and 3B, each negative birefringent layer may use only a negative uniaxial birefringent layer or only a negative biaxial birefringent layer, or a combination of both. May be used. Preferably, the first and second negative birefringent layers are negative biaxial birefringent layers, and the third negative birefringent layer is a negative uniaxial birefringent layer. The reason is that if the negative biaxial birefringent layer is the first negative birefringent layer, the polarized light whose polarization state is converted by the negative biaxial birefringent layer is directly incident on the absorption linear polarizing layer. Because it can.

負の一軸性複屈折層のＲｅ［５９０］は１０ｎｍ未満である。またＲｔｈ［５９０］は、好ましくは５００ｎｍ〜６０００ｎｍであり、さらに好ましくは６００ｎｍ〜５０００ｎｍである。Ｒｔｈ［５９０］が大きすぎたり小さすぎたりすると、斜め方向の偏光の振動面が、第１の反射型直線偏光層ないし吸収型直線偏光層の透過軸と直交するように変換されないことがある。   Re [590] of the negative uniaxial birefringent layer is less than 10 nm. Rth [590] is preferably 500 nm to 6000 nm, and more preferably 600 nm to 5000 nm. If Rth [590] is too large or too small, the vibration plane of polarized light in the oblique direction may not be converted so as to be orthogonal to the transmission axis of the first reflective linear absorption layer or absorption linear polarization layer.

負の二軸性複屈折層のＲｅ［５９０］は１０ｎｍ以上であり、好ましくは１００ｎｍ〜２０００ｎｍであり、さらに好ましくは１５０ｎｍ〜１０００ｎｍである。Ｒｔｈ［５９０］は、好ましくは５００ｎｍ〜６０００ｎｍであり、さらに好ましくは１０００ｎｍ〜５０００ｎｍである。Ｒｅ［５９０］やＲｔｈ［５９０］が小さすぎると目的の集光性が得られない場合がある。一方、Ｒｅ［５９０］やＲｔｈ［５９０］が大きすぎると、位相差による干渉現象（モアレ縞）が発生する場合がある。   Re [590] of the negative biaxial birefringent layer is 10 nm or more, preferably 100 nm to 2000 nm, and more preferably 150 nm to 1000 nm. Rth [590] is preferably 500 nm to 6000 nm, and more preferably 1000 nm to 5000 nm. If Re [590] or Rth [590] is too small, the desired light collecting property may not be obtained. On the other hand, if Re [590] or Rth [590] is too large, an interference phenomenon (moire fringes) due to a phase difference may occur.

負の複屈折層は、好ましくは透明材料により形成される。負の複屈折層を形成する材料としては、イミド系樹脂、エステル系樹脂、セルロース系樹脂、カーボネート系樹脂、およびそれらの混合樹脂などが挙げられる。あるいは特開２００３−２８７６２３号公報に記載された、選択反射波長帯域が紫外線領域にあるコレステリック層を含む光学フィルムや、特開２００５−３３１５９７号公報に記載された、ポリイミドなどを含む光学フィルムを用いることもできる。   The negative birefringent layer is preferably formed of a transparent material. Examples of the material for forming the negative birefringent layer include imide resins, ester resins, cellulose resins, carbonate resins, and mixed resins thereof. Alternatively, an optical film including a cholesteric layer having a selective reflection wavelength band in the ultraviolet region described in JP-A No. 2003-287623, or an optical film including polyimide or the like described in JP-A No. 2005-331597 is used. You can also.

負の複屈折層の厚みは、好ましくは１μｍ〜２００μｍであり、さらに好ましくは２μｍ〜１００μｍである。   The thickness of the negative birefringent layer is preferably 1 μm to 200 μm, more preferably 2 μm to 100 μm.

［反射型直線偏光層］
本発明に用いられる反射型直線偏光層は、入射光を２つの偏光成分に分けたとき、一方の偏光成分を透過し、他方の偏光成分を反射する偏光子である。 [Reflective linearly polarizing layer]
The reflective linearly polarizing layer used in the present invention is a polarizer that transmits one polarized component and reflects the other polarized component when incident light is divided into two polarized components.

反射型直線偏光層として特に制限はなく、例えば特開２００６−１４５８８４号公報に記載されているような、複屈折性の誘電体材料と、等方性の誘電体材料とを交互に積層したものや、特開２００１−３０５３１２号公報に記載されているような、２種類の樹脂からなる共押し出しフィルムを一軸延伸したものが用いられる。あるいは市販の反射型直線偏光板（例、スリーエム社製 商品名「Ｄ−ＢＥＦ」）を用いてもよい。   There is no particular limitation on the reflective linearly polarizing layer. For example, a birefringent dielectric material and an isotropic dielectric material laminated alternately as described in JP-A-2006-14584 Alternatively, a uniaxially stretched co-extruded film made of two kinds of resins as described in JP-A-2001-305312 is used. Alternatively, a commercially available reflective linear polarizing plate (eg, trade name “D-BEF” manufactured by 3M) may be used.

反射型直線偏光層の厚みは、好ましくは５μｍ〜２００μｍであり、さらに好ましくは１０μｍ〜１００μｍである。   The thickness of the reflective linearly polarizing layer is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm.

［バックライトユニット］
図４に示す本発明のバックライトユニット４０は、バックライト１１と、本発明の集光シート１０とを備え、集光シート１０の吸収型直線偏光層１６が、前記バックライト１１から遠い側になるように配置されてなる。バックライト１１と集光シート１０との間には、好ましくはバックライト１１からの光を均一にするための拡散シート４１を備える。 [Backlight unit]
The backlight unit 40 of the present invention shown in FIG. 4 includes the backlight 11 and the light collecting sheet 10 of the present invention, and the absorption linearly polarizing layer 16 of the light collecting sheet 10 is on the side far from the backlight 11. It is arranged to become. A diffusion sheet 41 for making the light from the backlight 11 uniform is preferably provided between the backlight 11 and the light collecting sheet 10.

［液晶表示装置］
図５に示す本発明の液晶表示装置５０は、バックライト１１と、本発明の集光シート１０、３０と、液晶セル５１とをこの順に備え、集光シート１０、３０の吸収型直線偏光層側が、液晶セル５１と対向するように配置されてなる。本発明の液晶表示装置５０は、好ましくは液晶セル５１の、集光シート１０、３０とは反対側に、第２の吸収型直線偏光層５２と拡散層５３とを備える。 [Liquid Crystal Display]
The liquid crystal display device 50 of the present invention shown in FIG. 5 includes the backlight 11, the light collecting sheets 10 and 30 of the present invention, and the liquid crystal cell 51 in this order, and the absorption linearly polarizing layer of the light collecting sheets 10 and 30. The side is disposed so as to face the liquid crystal cell 51. The liquid crystal display device 50 of the present invention preferably includes a second absorption linearly polarizing layer 52 and a diffusion layer 53 on the opposite side of the liquid crystal cell 51 from the light collecting sheets 10 and 30.

［参考例１］
機械式攪拌装置、ディーンスターク装置、窒素導入管、温度計および冷却管を取り付けた反応容器（５００ｍｌ）内にて、２，２’−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパン酸二無水物［クラリアントジャパン（株）製］１７．７７ｇ（４０ｍｍｏｌ）に、２，２’−ビス（トリフルオロメチル）−４，４’−ジアミノビフェニル［和歌山精化工業（株）製］１２．８１ｇ（４０ｍｍｏｌ）を加えた。続いて、イソキノリン２．５８ｇ（２０ｍｍｏｌ）をｍ−クレゾール２７５．２１ｇに溶解させた溶液を加え、２３℃で１時間攪拌して（６００ｒｐｍ）、均一な溶液を得た。次に反応容器をオイルバスを用いて反応容器内の温度が１８０℃になるように加温し、温度を保ちながら５時間攪拌して黄色溶液を得た。さらに３時間攪拌を行なったのち、加温および攪拌を停止し、放冷して室温に戻すと、ポリマーがゲル状となって析出した。 [Reference Example 1]
2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid in a reaction vessel (500 ml) equipped with a mechanical stirrer, Dean-Stark device, nitrogen inlet tube, thermometer and cooling tube Anhydrous [Clariant Japan Co., Ltd.] 17.77 g (40 mmol), 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl [Wakayama Seika Kogyo Co., Ltd.] 12.81 g (40 mmol) was added. Subsequently, a solution in which 2.58 g (20 mmol) of isoquinoline was dissolved in 275.21 g of m-cresol was added, and the mixture was stirred at 23 ° C. for 1 hour (600 rpm) to obtain a uniform solution. Next, the reaction vessel was heated using an oil bath so that the temperature in the reaction vessel became 180 ° C., and stirred for 5 hours while maintaining the temperature to obtain a yellow solution. After further stirring for 3 hours, heating and stirring were stopped, and the mixture was allowed to cool and returned to room temperature.

反応容器内の黄色溶液にアセトンを加えてゲルを完全に溶解させ、希釈溶液（７重量％）を作製した。この希釈溶液を２Ｌのイソプロピルアルコール中に攪拌を続けながら少しずつ加えると、白色粉末が析出した。この粉末を濾取し、１．５Ｌのイソプロピルアルコール中に投入して洗浄した。さらにもう一度同様の操作を繰り返して洗浄した後、前記の粉末を再び濾取した。これを６０℃の空気循環式恒温オーブンで４８時間乾燥した後、１５０℃で７時間乾燥して、下記構造式（１）のポリイミド粉末を得た（収率８５％）。上記のポリイミドの重合平均分子量（Ｍｗ）は１２４，０００であった。

Figure 0005078724
Acetone was added to the yellow solution in the reaction vessel to completely dissolve the gel to prepare a diluted solution (7% by weight). When this diluted solution was gradually added to 2 L of isopropyl alcohol while stirring, a white powder was precipitated. This powder was collected by filtration and poured into 1.5 L of isopropyl alcohol for washing. Further, the same operation was repeated once again for washing, and then the powder was again collected by filtration. This was dried for 48 hours in an air circulation type constant temperature oven at 60 ° C. and then dried at 150 ° C. for 7 hours to obtain a polyimide powder of the following structural formula (1) (yield 85%). The polymerization average molecular weight (Mw) of the polyimide was 124,000.
Figure 0005078724

上記のポリイミド粉末をメチルイソブチルケトンに溶解し、１５重量％のポリイミド溶液を調製した。このポリイミド溶液を、厚み７５μｍのポリエチレンテレフタレートフィルム［東レ（株）製 商品名「ルミラーＳ２７−Ｅ」］の表面に、コンマコータにより一方向に塗工した。次に１２０℃の空気循環式恒温オーブンで２０分間乾燥して溶剤を蒸発させ、ポリエチレンテレフタレートフィルムを剥離して厚み５μｍのポリイミドからなる負の一軸性複屈折層を作製した。上記の負の一軸性複屈折層は、Ｒｅ［５９０］が１ｎｍ、またＲｔｈ［５９０］が２００ｎｍであった。   The above polyimide powder was dissolved in methyl isobutyl ketone to prepare a 15% by weight polyimide solution. This polyimide solution was applied in one direction with a comma coater on the surface of a 75 μm thick polyethylene terephthalate film [trade name “Lumirror S27-E” manufactured by Toray Industries, Inc.]. Next, it was dried in a 120 ° C. air circulating constant temperature oven for 20 minutes to evaporate the solvent, and the polyethylene terephthalate film was peeled off to produce a negative uniaxial birefringent layer made of polyimide having a thickness of 5 μm. The negative uniaxial birefringent layer had Re [590] of 1 nm and Rth [590] of 200 nm.

［参考例２］
参考例１で用いたポリイミド溶液を、厚み７５μｍのポリエチレンテレフタレートフィルム［東レ（株）製 商品名「ルミラーＳ２７−Ｅ」］の表面に、コンマコータにより一方向に塗工した。次に１５０℃の空気循環式恒温オーブンで２０分間乾燥して、そのまま塗工方向に１．０４倍延伸した。ポリエチレンテレフタレートフィルムを剥離して厚み７．８μｍのポリイミドからなる負の二軸性複屈折層を作製した。上記の負の二軸性複屈折層は、Ｒｅ［５９０］が８０ｎｍ、Ｒｔｈ［５９０］が３４５ｎｍであった。 [Reference Example 2]
The polyimide solution used in Reference Example 1 was applied in one direction with a comma coater on the surface of a 75 μm thick polyethylene terephthalate film [trade name “Lumirror S27-E” manufactured by Toray Industries, Inc.]. Next, it was dried for 20 minutes in an air circulation type thermostatic oven at 150 ° C., and stretched 1.04 times in the coating direction as it was. The polyethylene terephthalate film was peeled off to produce a negative biaxial birefringent layer made of polyimide having a thickness of 7.8 μm. The negative biaxial birefringent layer had Re [590] of 80 nm and Rth [590] of 345 nm.

［実施例１］
市販の吸収型直線偏光板（日東電工社製 商品名「ＮＰＦ−ＳＥＧ１２２４ＤＵ」）の片側に、アクリル系粘着剤を介して、参考例２で作製した負の二軸性複屈折層７枚（第１の負の複屈折層）／第１の反射型直線偏光層／参考例２で作製した負の二軸性複屈折層７枚（第２の負の複屈折層）／第２の反射型直線偏光層／参考例１で作製した負の一軸性複屈折層３枚（第３の負の複屈折層）／第３の反射型直線偏光層、をこの順に積層して集光シートを作製した。 [Example 1]
Seven negative biaxial birefringent layers prepared in Reference Example 2 with an acrylic adhesive on one side of a commercially available linear absorption polarizing plate (trade name “NPF-SEG1224DU” manufactured by Nitto Denko Corporation) 1 negative birefringent layer) / first reflective linearly polarizing layer / seven negative biaxial birefringent layers prepared in Reference Example 2 (second negative birefringent layer) / second reflective type A linearly polarizing layer / three negative uniaxial birefringent layers prepared in Reference Example 1 (third negative birefringent layer) / third reflective linearly polarizing layer are laminated in this order to produce a condensing sheet. did.

第１〜第３の反射型直線偏光層としては、いずれも日東電工社製 商品名「ＡＰＦ−３５」を用いた。吸収型直線偏光層の透過軸方向と、第１〜第３の反射型直線偏光層の透過軸方向は、それぞれ平行とした。吸収型直線偏光層の透過軸方向を０°としたとき、負の二軸性複屈折層（第１の負の複屈折層）の遅相軸方向は４５°とし、負の二軸性複屈折層（第２の負の複屈折層）の遅相軸方向は１３５°とした。この集光シートの各複屈折層の位相差値と集光性を表２に示す。   As the first to third reflective linearly polarizing layers, the product name “APF-35” manufactured by Nitto Denko Corporation was used. The transmission axis direction of the absorption linearly polarizing layer and the transmission axis direction of the first to third reflective linearly polarizing layers were parallel to each other. When the transmission axis direction of the absorptive linearly polarizing layer is 0 °, the negative biaxial birefringent layer (first negative birefringent layer) has a slow axis direction of 45 ° and a negative biaxial birefringent layer. The slow axis direction of the refractive layer (second negative birefringent layer) was set to 135 °. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例２］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を９枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を９枚用いた以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 2]
Nine negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and negative biaxial birefringent layers prepared in Reference Example 2 were used as the second negative birefringent layer. A condensing sheet was produced in the same manner as in Example 1 except that nine refractive layers were used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例３］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を１２枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を１２枚用いた以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 3]
Twelve negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and the negative biaxial birefringent layer prepared in Reference Example 2 was used as the second negative birefringent layer. A condensing sheet was produced in the same manner as in Example 1 except that 12 refractive layers were used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例４］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を２枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を２枚用いたことと、第３の複屈折層および第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 4]
Two negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and negative biaxial birefringent layers prepared in Reference Example 2 were used as the second negative birefringent layer. A condensing sheet was produced in the same manner as in Example 1 except that two refractive layers were used and the third birefringent layer and the third reflective linearly polarizing layer were not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例５］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を７枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を７枚用いたことと、第３の複屈折層および第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 5]
Seven negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and negative biaxial birefringent layers prepared in Reference Example 2 were used as the second negative birefringent layer. A condensing sheet was produced in the same manner as in Example 1 except that seven refractive layers were used and the third birefringent layer and the third reflective linearly polarizing layer were not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例６］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を９枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を９枚用いたことと、第３の複屈折層および第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 6]
Nine negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and negative biaxial birefringent layers prepared in Reference Example 2 were used as the second negative birefringent layer. A condensing sheet was produced in the same manner as in Example 1 except that nine refractive layers were used and the third birefringent layer and the third reflective linearly polarizing layer were not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［実施例７］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を１２枚、第２の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を１２枚用いたことと、第３の複屈折層および第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Example 7]
Twelve negative biaxial birefringent layers prepared in Reference Example 2 were used as the first negative birefringent layer, and the negative biaxial birefringent layer prepared in Reference Example 2 was used as the second negative birefringent layer. A condensing sheet was prepared in the same manner as in Example 1 except that 12 refractive layers were used and the third birefringent layer and the third reflective linearly polarizing layer were not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［比較例１］
第１の負の複屈折層として、参考例２で作製した負の二軸性複屈折層を７枚用いたことと、第２ならびに第３の負の複屈折層、および第２ならびに第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Comparative Example 1]
Seven negative biaxial birefringent layers produced in Reference Example 2 were used as the first negative birefringent layer, and the second and third negative birefringent layers, and the second and third layers. A condensing sheet was prepared in the same manner as in Example 1 except that the reflective linearly polarizing layer was not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

［比較例２］
第１〜第３の負の複屈折層、および第１〜第３の反射型直線偏光層を用いなかったこと以外は、実施例１と同様の方法で集光シートを作製した。この集光シートの各複屈折層の位相差値と集光性を表２に示す。 [Comparative Example 2]
A condensing sheet was produced in the same manner as in Example 1 except that the first to third negative birefringent layers and the first to third reflective linearly polarizing layers were not used. Table 2 shows the phase difference value and light condensing property of each birefringent layer of the light collecting sheet.

実施例１〜７、比較例１〜２の集光シートの主要部構成を表１に示す。

Figure 0005078724
Table 1 shows the main configuration of the light collecting sheets of Examples 1 to 7 and Comparative Examples 1 and 2.
Figure 0005078724

実施例１〜７、比較例１〜２の集光シートの各複屈折層の位相差値と集光性を表２に示す。

Figure 0005078724
Table 2 shows retardation values and light condensing properties of the birefringent layers of the light condensing sheets of Examples 1 to 7 and Comparative Examples 1 and 2.
Figure 0005078724

［測定方法］
［Ｒｅ［５９０］、Ｒｔｈ［５９０］の測定］
自動複屈折測定装置（王子計器社製 製品名「ＫＯＢＲＡ−２１ＡＤＨ」）を用いて測定した。 [Measuring method]
[Measurement of Re [590] and Rth [590]]
It measured using the automatic birefringence measuring apparatus (The product name "KOBRA-21ADH" by Oji Keiki Co., Ltd.).

［半値角の測定］
ＶＡモードの２０インチテレビ（ソニー社製 商品名「ＫＤＬ−２０Ｊ３０００」）から、液晶パネルを取り出し、液晶セルの裏面に貼着された光学フィルムを全て剥離して、代わりに各実施例の集光シートを、集光シートの吸収型直線偏光層側が液晶セルと対向するように配置した。このように作製した液晶パネルを元のテレビに組み込んで液晶表示装置を作製した。 [Measurement of half-value angle]
Remove the liquid crystal panel from the 20-inch TV in VA mode (product name “KDL-20J3000” manufactured by Sony Corporation), peel off all the optical films attached to the back of the liquid crystal cell, and collect the light from each example instead. The sheet was disposed so that the absorption linearly polarizing layer side of the light collecting sheet was opposed to the liquid crystal cell. A liquid crystal display device was manufactured by incorporating the liquid crystal panel thus manufactured into the original television.

この液晶表示装置に白画像を表示させて、コノスコープ（ＧｍｂＨ社製 商品名「ａｕｔｒｏｎｉｃ−ＭＥＬＣＨＥＲＳ」）を用いて、方位角４５°および１３５°の極角０°〜８０°輝度を測定し、法線方向の輝度（最大値）が半分になる角度を求めた。表１に示した値は、方位角４５°および１３５°の半値角の平均値である。   A white image is displayed on this liquid crystal display device, and using a conoscope (trade name “atronic-MELCHERS” manufactured by GmbH), polar angles of 0 ° to 80 ° of azimuth angle 45 ° and 135 ° are measured, The angle at which the luminance in the normal direction (maximum value) was halved was determined. The values shown in Table 1 are average values of half-value angles of azimuth angles of 45 ° and 135 °.

本発明の集光シートの作用原理の模式図Schematic diagram of the principle of operation of the light collecting sheet of the present invention 本発明の要件を備えない集光シートの作用原理の模式図Schematic diagram of the principle of operation of the light collecting sheet without the requirements of the present invention 本発明の集光シートの模式図Schematic diagram of the light collecting sheet of the present invention 本発明のバックライトユニットの模式図Schematic diagram of the backlight unit of the present invention 本発明の液晶表示装置の模式図Schematic diagram of the liquid crystal display device of the present invention

符号の説明Explanation of symbols

１０ 集光シート
１１ バックライト
１２ 第２の反射型直線偏光層
１３ 第２の負の複屈折層
１４ 第１の反射型直線偏光層
１５ 第１の負の複屈折層
１６ 吸収型直線偏光層
２０ 集光シート
２１ 反射型直線偏光層
２２ 負の複屈折層
２３ 吸収型直線偏光層
３０ 集光シート
３１ 第３の反射型直線偏光層
３２ 第３の負の複屈折層
３３ 第２の反射型直線偏光層
３４ 第２の負の複屈折層
３５ 第１の反射型直線偏光層
３６ 第１の負の複屈折層
３７ 吸収型直線偏光層
４０ バックライトユニット
４１ 拡散シート
５０ 液晶表示装置
５１ 液晶セル
５２ 第２の吸収型直線偏光層
５３ 拡散層 DESCRIPTION OF SYMBOLS 10 Light-condensing sheet 11 Backlight 12 2nd reflection type linear polarization layer 13 2nd negative birefringence layer 14 1st reflection type linear polarization layer 15 1st negative birefringence layer 16 Absorption type linear polarization layer 20 Condensing sheet 21 Reflective linear polarizing layer 22 Negative birefringent layer 23 Absorbing linear polarizing layer 30 Condensing sheet 31 Third reflective linear polarizing layer 32 Third negative birefringent layer 33 Second reflective straight line Polarizing layer 34 Second negative birefringent layer 35 First reflective linearly polarizing layer 36 First negative birefringent layer 37 Absorbing linearly polarizing layer 40 Backlight unit 41 Diffusion sheet 50 Liquid crystal display device 51 Liquid crystal cell 52 Second absorption type linearly polarizing layer 53 Diffusion layer

Claims (3)

吸収型直線偏光層と負の複屈折層と反射型直線偏光層とを備え、
前記吸収型直線偏光層の片側に、前記負の複屈折層と前記反射型直線偏光層とが交互に、それぞれ２層または３層積層されてなり、
前記負の複屈折層のうち、前記吸収型直線偏光層に最も近い前記負の複屈折層が、負の二軸性複屈折層であり、
前記負の二軸性複屈折層のＲｅ［５９０］が１００ｎｍ〜２０００ｎｍであり、Ｒｔｈ［５９０］が５００ｎｍ〜６０００ｎｍであり、
前記吸収型直線偏光層の透過軸方向と各前記反射型直線偏光層の透過軸方向とが互いに平行であることを特徴とする集光シート。 An absorption linearly polarizing layer, a negative birefringent layer, and a reflective linearly polarizing layer,
The negative birefringent layer and the reflective linearly polarizing layer are alternately laminated on one side of the absorbing linearly polarizing layer, and two or three layers are respectively laminated.
Among the negative birefringent layers, the negative birefringent layer closest to the absorption linearly polarizing layer is a negative biaxial birefringent layer,
Re [590] of the negative biaxial birefringent layer is 100 nm to 2000 nm, Rth [590] is 500 nm to 6000 nm,
The condensing sheet, wherein a transmission axis direction of the absorption linear polarization layer and a transmission axis direction of each of the reflection linear polarization layers are parallel to each other. バックライトと、請求項１に記載の集光シートとを備え、前記集光シートの前記吸収型直線偏光層が、前記バックライトから遠い側になるように配置されたことを特徴とするバックライトユニット。   A backlight comprising: a backlight; and the light collecting sheet according to claim 1, wherein the absorbing linearly polarizing layer of the light collecting sheet is disposed so as to be on a side far from the backlight. unit. バックライトと、請求項１に記載の集光シートと、液晶セルとをこの順に備え、前記集光シートの前記吸収型直線偏光層側が、前記液晶セルと対向するように配置されたことを特徴とする液晶表示装置。   A backlight, the condensing sheet according to claim 1, and a liquid crystal cell are provided in this order, and the absorbing linearly polarizing layer side of the condensing sheet is disposed so as to face the liquid crystal cell. A liquid crystal display device.
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