JP2011126182A - Uniaxially oriented laminated multilayer film, brightness improving member made of the film, composite member for liquid crystal display made of them, and liquid crystal display made of them - Google Patents

Uniaxially oriented laminated multilayer film, brightness improving member made of the film, composite member for liquid crystal display made of them, and liquid crystal display made of them Download PDF

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JP2011126182A
JP2011126182A JP2009287758A JP2009287758A JP2011126182A JP 2011126182 A JP2011126182 A JP 2011126182A JP 2009287758 A JP2009287758 A JP 2009287758A JP 2009287758 A JP2009287758 A JP 2009287758A JP 2011126182 A JP2011126182 A JP 2011126182A
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layer
refractive index
film
incident
polarized light
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Taro Oya
太郎 大宅
Mitsumasa Ono
光正 小野
Tetsuo Yoshida
哲男 吉田
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Teijin Ltd
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Teijin Ltd
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Priority to JP2009287758A priority Critical patent/JP2011126182A/en
Priority to CN201080057794.5A priority patent/CN102652063B/en
Priority to US13/515,709 priority patent/US8703252B2/en
Priority to KR1020127015358A priority patent/KR101758406B1/en
Priority to EP10837723.5A priority patent/EP2514592B1/en
Priority to PCT/JP2010/073065 priority patent/WO2011074701A1/en
Priority to TW099144524A priority patent/TWI524994B/en
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated multilayer film having a reflective polarization function in which the hue dislocation of transmitted polarized light by an incident angle in the oblique direction to light incident in the oblique direction simultaneously while polarization performance is raised further is not seen. <P>SOLUTION: In a uniaxially oriented laminated multilayer film of at least 251 layers of a constant layer thickness, first layers and second layers are laminated alternately. (1) A thermoplastic resin constituting the first layer has an average refractive index of 1.60-1.70, a refractive index n<SB>X</SB>in the uniaxial orientation direction (X direction) increases by orientation, and a refractive index n<SB>Y</SB>in its orthogonal direction (Y direction) and a refractive index n<SB>z</SB>in the film thickness direction (Z direction) are decreased by orientation. (2) A thermoplastic resin constituting the second layer has an average refractive index of 1.50-1.60, and refractive index differences in the X direction, the Y direction, and the Z direction before and after the orientation are 0.05 or below, respectively. With regard to a P polarization component, average reflectances to the incident polarized light at incident angles of 0° and 50° are at least 90%, respectively. With regard to an S polarization component, average reflectances to the incident polarized light at incident angles of 0° and 50° are 15% or below, respectively. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は一定の偏光成分を選択的に反射し、該偏光成分と垂直方向の偏光成分を選択的に透過する１軸延伸多層積層フィルム、それからなる輝度向上用部材、それらからなる液晶ディスプレイ用複合部材およびそれらからなる液晶ディスプレイ装置に関する。   The present invention relates to a uniaxially stretched multilayer laminated film that selectively reflects a certain polarization component and selectively transmits a polarization component perpendicular to the polarization component, a brightness enhancement member comprising the same, and a liquid crystal display composite comprising the same. The present invention relates to a member and a liquid crystal display device made of them.

さらに詳しくは、一定の偏光成分を選択的に反射し、該偏光成分と垂直方向の偏光成分を選択的に透過する偏光性能が従来より優れ、かつ斜め方向に入射した光に対して部分的な反射が発生することなく透過偏光の色相ずれが解消された１軸延伸多層積層フィルム、それからなる輝度向上用部材、それらからなる液晶ディスプレイ用複合部材およびそれらからなる液晶ディスプレイ装置に関する。   More specifically, the polarization performance of selectively reflecting a certain polarization component and selectively transmitting a polarization component in a direction perpendicular to the polarization component is superior to that of the prior art, and partially with respect to light incident in an oblique direction. The present invention relates to a uniaxially stretched multi-layer laminate film in which a hue shift of transmitted polarized light is eliminated without occurrence of reflection, a brightness improving member made of the same, a composite member for liquid crystal display made of them, and a liquid crystal display device made of them.

屈折率の低い層と屈折率の高い層とを交互に多数積層したフィルムは、層間の構造的な光干渉によって、特定波長の光を選択的に反射または透過する光学干渉フィルムとすることができる。また、このような多層積層フィルムは、膜厚を徐々に変化させたり、異なる反射ピークを有するフィルムを貼り合せたりすることで金属を使用したフィルムと同等の高い反射率を得ることができ、金属光沢フィルムや反射ミラーとして使用することもできる。さらには、このような多層積層フィルムを１方向にのみ延伸することで、特定の偏光成分のみを反射する偏光反射フィルムとしても使用でき、これらを液晶ディスプレイなどに使用することで、液晶ディスプレイなどの輝度向上フィルムとして使用できることが知られている。   A film in which a plurality of layers having a low refractive index and a layer having a high refractive index are alternately laminated can be an optical interference film that selectively reflects or transmits light of a specific wavelength by structural optical interference between the layers. . In addition, such a multilayer laminated film can obtain a high reflectivity equivalent to a film using metal by gradually changing the film thickness or by laminating films having different reflection peaks. It can also be used as a glossy film or a reflection mirror. Furthermore, by stretching such a multilayer laminated film only in one direction, it can also be used as a polarizing reflection film that reflects only a specific polarization component. By using these for a liquid crystal display or the like, a liquid crystal display or the like can be used. It is known that it can be used as a brightness enhancement film.

一般に層厚が０．０５〜０．５μｍの異なる屈折率を持った層で構成される多層光学フィルムは、一方の層を構成する層と他方の層を構成する層の屈折率差と膜厚および積層数により、特定の波長の光を反射する増反射といった現象がみられる。一般にその反射波長は、下記の式で示される。
λ＝２（ｎ１×ｄ１＋ｎ２×ｄ２）
（上式中、λは反射波長（ｎｍ）、ｎ１、ｎ２はそれぞれの層の屈折率、ｄ１、ｄ２はそれぞれの層の厚み（ｎｍ）を表わす） In general, a multilayer optical film composed of layers having different refractive indexes of 0.05 to 0.5 μm is different in refractive index and film thickness between a layer constituting one layer and a layer constituting the other layer. Depending on the number of stacked layers, a phenomenon such as increased reflection that reflects light of a specific wavelength is observed. In general, the reflection wavelength is expressed by the following equation.
λ = 2 (n 1 × d 1 + n 2 × d 2 )
(In the above formula, λ is the reflection wavelength (nm), n 1 and n 2 are the refractive indexes of the respective layers, and d 1 and d 2 are the thicknesses (nm) of the respective layers)

例えば特許文献１に示されている通り、一方の層に正の応力光学係数をもった樹脂を使用することで、１軸方向の延伸によりかかる層の屈折率を複屈折化させて異方性を持たせ、フィルム面内の延伸方向における層間の屈折率差を大きくし、一方でフィルム面内の延伸方向と直交方向における層間の屈折率差を小さくする方法により、特定の偏光成分のみを反射することができる。   For example, as shown in Patent Document 1, by using a resin having a positive stress optical coefficient in one layer, the refractive index of such a layer is birefringent by stretching in a uniaxial direction to make anisotropy. To increase the refractive index difference between layers in the stretching direction in the film plane, while reducing the refractive index difference between layers in the direction perpendicular to the stretching direction in the film plane. can do.

この原理を利用して、例えばＰ偏光を反射し、Ｓ偏光を透過するといった反射偏光フィルムを設計することができ、そのときの望ましい複屈折性は下記の式で表される。
ｎ１Ｘ＞ｎ２Ｘ、ｎ１Ｙ＝ｎ２Ｙ
（上式中、ｎ１Ｘ、ｎ２Ｘはそれぞれの層における延伸方向の屈折率、ｎ１Ｙ、ｎ２Ｙはそれぞれの層における延伸方向に直交する方向の屈折率を表す） Utilizing this principle, for example, a reflective polarizing film that reflects P-polarized light and transmits S-polarized light can be designed. The desired birefringence at that time is expressed by the following equation.
n1 X > n2 X , n1 Y = n2 Y
(In the above formula, n1 X and n2 X represent the refractive index in the stretching direction in each layer, and n1 Y and n2 Y represent the refractive index in the direction orthogonal to the stretching direction in each layer)

また、特許文献２、特許文献３には、屈折率の高い層にポリエチレン−２，６−ナフタレンジカルボキシレート（以下、２，６−ＰＥＮと称することがある）を使用し、屈折率の低い層に熱可塑性エラストマーやイソフタル酸を３０ｍｏｌ％共重合したＰＥＮを使用した多層フィルムが例示されている。これは、一方の層に正の応力光学係数を有する樹脂を使用し、他方の層に応力光学係数が非常に小さい（延伸による複屈折の発現が極めて小さい）樹脂を使用することで、特定の偏光のみを反射する反射偏光フィルムを例示したものである。   In Patent Documents 2 and 3, polyethylene-2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as 2,6-PEN) is used for the layer having a high refractive index, and the refractive index is low. The multilayer film which uses PEN which copolymerized 30 mol% of thermoplastic elastomers and isophthalic acid for the layer is illustrated. This is because a resin having a positive stress optical coefficient is used in one layer and a resin having a very low stress optical coefficient (extremely low birefringence due to stretching) is used in the other layer. The reflective polarizing film which reflects only polarized light is illustrated.

しかしながら、屈折率の高い層に２，６−ＰＥＮを使用した場合、かかる層において、延伸後の延伸方向に直交する方向（Ｙ方向）の屈折率とフィルム厚み方向（Ｚ方向）の屈折率に差異が生じるために、延伸を大きくして延伸方向（Ｘ方向）の層間の屈折率差を大きくし、偏光性能を高めようとすると、それに伴いＺ方向の層間の屈折率差が大きくなってしまい、斜め方向に入射した光に対する部分的な反射により透過光の色相ずれがさらに大きくなるといった問題点があった。   However, when 2,6-PEN is used for a layer having a high refractive index, the refractive index in the direction perpendicular to the stretching direction after stretching (Y direction) and the refractive index in the film thickness direction (Z direction) in such a layer. Due to the difference, if the stretching is increased to increase the refractive index difference between the layers in the stretching direction (X direction) to improve the polarization performance, the refractive index difference between the layers in the Z direction is increased accordingly. There is a problem that the hue shift of transmitted light is further increased by partial reflection of light incident in an oblique direction.

特開平０４−２６８５０５号公報JP 04-268505 A 特表平９−５０６８３７号公報Japanese National Patent Publication No. 9-506837 ＷＯ０１／４７７１１号パンフレットWO01 / 47711 pamphlet

本発明の目的は、従来の多層積層フィルムが有する上記の課題を解消し、従来よりもさらに偏光性能を高めつつ、同時に斜め方向に入射した光に対して斜め方向の入射角による透過偏光の色相ずれが見られない、反射偏光機能を有する多層積層フィルムを提供することにある。   The object of the present invention is to solve the above-mentioned problems of the conventional multilayer laminated film and to improve the polarization performance further than before, while simultaneously transmitting the hue of transmitted polarized light by the obliquely incident angle with respect to the light incident in the oblique direction. An object of the present invention is to provide a multilayer laminated film having a reflective polarization function, in which no deviation is observed.

本発明者等は、前記課題を解決するために鋭意検討した結果、高屈折率層を構成する第１層の樹脂として、従来は高屈折率で複屈折率性のポリエチレン−２，６−ナフタレンジカルボキシレートが多く用いられていたところ、ポリエチレン−２，６−ナフタレンジカルボキシレートの一軸延伸による各方向の屈折率の変化は、延伸方向（Ｘ方向）は増大するものの、Ｙ方向は延伸前後でほとんど屈折率が変化しないこと、一方Ｚ方向は低下する特徴を有している。そのため、延伸を大きくして延伸方向（Ｘ方向）の層間の屈折率差を大きくし、偏光性能を高めようとすると、それに伴いＺ方向の層間の屈折率差が大きくなるか、延伸後のＺ方向の層間の屈折率を一致させようとすると今度はＹ方向の層間の屈折率差が大きくなってしまい、偏光性能の向上と斜め方向の入射光に対する透過偏光の色相ずれの両立が難しいことを見出した。   As a result of intensive studies to solve the above problems, the present inventors have conventionally used a high refractive index and birefringent polyethylene-2,6-naphthalene as the first layer resin constituting the high refractive index layer. When dicarboxylate was often used, the change in refractive index in each direction due to uniaxial stretching of polyethylene-2,6-naphthalenedicarboxylate increased in the stretching direction (X direction), but the Y direction was before and after stretching. However, the refractive index hardly changes, while the Z direction has a characteristic of decreasing. Therefore, if the stretching is increased to increase the refractive index difference between the layers in the stretching direction (X direction) to improve the polarization performance, the refractive index difference between the layers in the Z direction increases accordingly, or Z after stretching If the refractive index between the layers in the direction is made to coincide, the difference in the refractive index between the layers in the Y direction will increase, and it will be difficult to achieve both improved polarization performance and a hue shift of transmitted polarized light with respect to obliquely incident light. I found it.

それに対し、高屈折率層を構成する第１層の樹脂として、ポリエチレン−２，６−ナフタレンジカルボキシレートに代えて、一軸延伸によりＸ方向の屈折率が増大する一方、Ｙ方向とＺ方向の両方向の屈折率がともに低下する特性を有する熱可塑性樹脂を用いることにより、一軸延伸後の第１層のＸ方向とＹ方向の屈折率差を従来より大きくすることが可能となる結果、偏光性能が向上することに加え、Ｙ方向とＺ方向の両方向について層間の屈折率差を小さくでき、本発明の課題である偏光性能の向上と斜め方向の入射角よる透過偏光の色相ずれ解消の両立化が可能となることを見出し、本発明を完成するに至った。   On the other hand, instead of polyethylene-2,6-naphthalenedicarboxylate, the refractive index in the X direction is increased by uniaxial stretching as the resin of the first layer constituting the high refractive index layer, while in the Y direction and the Z direction. As a result of using a thermoplastic resin having a characteristic in which the refractive index in both directions decreases, the difference in refractive index between the X direction and the Y direction of the first layer after uniaxial stretching can be made larger than before. In addition to improving the refractive index difference between the layers in both the Y direction and the Z direction, the improvement in polarization performance, which is the subject of the present invention, and the elimination of the hue deviation of transmitted polarized light due to the incident angle in the oblique direction are compatible. As a result, the present invention has been completed.

すなわち本発明によれば、本発明の目的は、第１層と第２層とが交互に積層された２５１層以上の１軸延伸多層積層フィルムであり、
１）第１層を構成する熱可塑性樹脂が平均屈折率１．６０以上１．７０以下であって、１軸延伸方向（Ｘ方向）の屈折率ｎXが延伸により増大し、フィルム面内で１軸延伸方向に直交する方向（Ｙ方向）の屈折率ｎYおよびフィルム厚み方向（Ｚ方向）の屈折率ｎZが延伸により低下する熱可塑性樹脂であり、
２）第２層を構成する熱可塑性樹脂が平均屈折率１．５０以上１．６０以下であって、Ｘ方向、Ｙ方向およびＺ方向のそれぞれの屈折率差が延伸前後で０．０５以下である熱可塑性樹脂であり、
３）第１層および第２層の各層の厚みが０．０１μｍ以上０．５μｍ以下であって、かつ第１層および第２層におけるそれぞれの最大層厚みと最小層厚みの比率がいずれも２．０以上５．０以下であり、
４）フィルム面を反射面とし、Ｘ方向を含む入射面に対して平行な偏光成分について入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ９０％以上であり、
５）フィルム面を反射面とし、Ｘ方向を含む入射面に対して垂直な偏光成分について、入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ１５％以下
である１軸延伸多層積層フィルム（項１）によって達成される。 That is, according to the present invention, an object of the present invention is a 251 or more uniaxially stretched multilayer laminated film in which the first layer and the second layer are alternately laminated,
1) The thermoplastic resin constituting the first layer has an average refractive index of 1.60 or more and 1.70 or less, and the refractive index n X in the uniaxial stretching direction (X direction) is increased by stretching. a thermoplastic resin having a refractive index n Z of the refractive index n Y and the film thickness direction (Y direction) perpendicular to the uniaxial stretching direction (Z-direction) is reduced by stretching,
2) The thermoplastic resin constituting the second layer has an average refractive index of 1.50 or more and 1.60 or less, and the respective refractive index differences in the X direction, Y direction and Z direction are 0.05 or less before and after stretching. A thermoplastic resin,
3) The thickness of each layer of the first layer and the second layer is 0.01 μm or more and 0.5 μm or less, and the ratio between the maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer is 2 0.0 or more and 5.0 or less,
4) The average reflectance of the wavelength 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degrees and 50 degrees with respect to the polarized light component parallel to the incident surface including the X direction is 90% or more with the film surface as the reflecting surface. Yes,
5) With respect to the polarized light component perpendicular to the incident surface including the X direction, with the film surface as the reflective surface, the average reflectance at a wavelength of 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degrees and 50 degrees is 15% or less, respectively. It is achieved by the uniaxially stretched multilayer laminated film (item 1).

また本発明の１軸延伸多層積層フィルムは、好ましい態様として以下の少なくともいずれか１つを具備するものも包含するものである。
２．第２層を形成する熱可塑性樹脂が、イソフタル酸もしくは２，６−ナフタレンジカルボン酸を共重合したエチレンテレフタレート成分を主たる成分とする融点が２２０℃以下のポリエステルである上記１に記載の１軸延伸多層積層フィルム。
３．第１層と第２層のＸ方向の屈折率差が０．１０〜０．４５である上記１または２に記載の１軸延伸多層積層フィルム。
４．第１層と第２層のＹ方向の屈折率差および第１層と第２層のＺ方向の屈折率差がそれぞれ０．０５以下である上記１〜３のいずれかに記載の１軸延伸多層積層フィルム。
５．フィルム厚みが１５μｍ以上４０μｍ以下である上記１〜４のいずれかに記載の１軸延伸多層積層フィルム。
６．入射面に対して平行な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．１以下である上記１〜５のいずれかに記載の１軸延伸多層積層フィルム。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす）
７．入射面に対して垂直な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．０１以下である上記１〜６のいずれかに記載の１軸延伸多層積層フィルム。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす）
８．第１層の平均層厚みに対する第２層の平均層厚みの比が１．５倍以上５．０倍以下の範囲である上記１〜７のいずれかに記載の１軸延伸多層積層フィルム。
９．第１層と第２層との交互積層の少なくとも一方の最外層面上にさらにヒートシール層が設けられてなる上記１〜８のいずれかに記載の１軸延伸多層積層フィルム。
１０．ヒートシール層が第２層と同じ熱可塑性樹脂からなり、該熱可塑性樹脂の融点が第１層の熱可塑性樹脂の融点より２０℃以上低く、かつ厚み３〜１０μｍの層である上記９に記載の１軸延伸多層積層フィルム。
１１．液晶ディスプレイの輝度向上フィルムとして用いられる上記１〜１０のいずれかに記載の１軸延伸多層積層フィルム。 Moreover, the uniaxially stretched multilayer laminated film of the present invention includes a film having at least one of the following as a preferred embodiment.
2. 2. The uniaxial stretching according to 1 above, wherein the thermoplastic resin forming the second layer is a polyester having a melting point of 220 ° C. or lower, the main component being an ethylene terephthalate component copolymerized with isophthalic acid or 2,6-naphthalenedicarboxylic acid. Multi-layer laminated film.
3. 3. The uniaxially stretched multilayer laminated film according to 1 or 2 above, wherein the difference in refractive index between the first layer and the second layer in the X direction is 0.10 to 0.45.
4). The uniaxial stretching according to any one of the above 1 to 3, wherein a difference in refractive index in the Y direction between the first layer and the second layer and a difference in refractive index in the Z direction between the first layer and the second layer are each 0.05 or less. Multi-layer laminated film.
5). The uniaxially stretched multilayer laminated film according to any one of 1 to 4 above, wherein the film thickness is 15 μm or more and 40 μm or less.
6). 1 for the polarization component parallel to the incident surface, wherein the hue variations Δx and Δy represented by the following formulas (1) and (2) are both 0.1 or less: Axial stretched multilayer laminated film.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y)
7). 1 for the polarization component perpendicular to the incident surface, wherein the hue variations Δx and Δy represented by the following formulas (1) and (2) are both 0.01 or less: Axial stretched multilayer laminated film.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y)
8). The uniaxially stretched multilayer laminated film according to any one of 1 to 7 above, wherein the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is in the range of 1.5 to 5.0.
9. 9. The uniaxially stretched multilayer laminated film according to any one of 1 to 8 above, wherein a heat seal layer is further provided on at least one outermost layer surface of the alternate lamination of the first layer and the second layer.
10. The heat seal layer is made of the same thermoplastic resin as the second layer, and the melting point of the thermoplastic resin is 20 ° C. lower than the melting point of the thermoplastic resin of the first layer and is a layer having a thickness of 3 to 10 μm. A uniaxially stretched multilayer laminated film.
11. The uniaxially stretched multilayer laminated film according to any one of 1 to 10 above, which is used as a brightness enhancement film for a liquid crystal display.

また、本発明は本発明の１軸延伸多層積層フィルムからなる輝度向上用部材に関する。
さらに、本発明は本発明の輝度向上用部材の少なくとも一方の面に光拡散フィルムが積層されてなる液晶ディスプレイ用複合部材に関し、その好ましい態様として、輝度向上用部材と光拡散フィルムとがヒートシール層を介して積層されてなる液晶ディスプレイ用複合部材、光拡散フィルムを介して輝度向上用部材と反対側にさらにプリズム層を有する液晶ディスプレイ用複合部材も包含される。
その他本発明は、本発明の輝度向上用部材を含む液晶ディスプレイ装置、本発明の液晶ディスプレイ用複合部材を含む液晶ディスプレイ装置に関する。 Moreover, this invention relates to the member for a brightness improvement which consists of a uniaxially stretched multilayer laminated film of this invention.
Furthermore, the present invention relates to a composite member for a liquid crystal display in which a light diffusion film is laminated on at least one surface of the brightness enhancement member of the present invention. As a preferred embodiment, the brightness enhancement member and the light diffusion film are heat sealed. A composite member for a liquid crystal display that is laminated through layers, and a composite member for a liquid crystal display that further includes a prism layer on the opposite side of the brightness enhancement member through a light diffusion film are also included.
Others The present invention relates to a liquid crystal display device including the brightness enhancing member of the present invention and a liquid crystal display device including the composite member for a liquid crystal display of the present invention.

本発明によれば、本発明の１軸延伸多層積層フィルムは従来の反射偏光フィルムで見られた斜め方向の入射角による透過偏光の色相ずれが解消され、しかも従来よりも高い偏光性能を有することから、輝度向上フィルムとして用いた場合に高い輝度向上率が得られ、かつ高視野角で色相ずれの少ない視認性に優れた液晶ディスプレイを提供することができる。   According to the present invention, the uniaxially stretched multilayer laminated film of the present invention eliminates the hue shift of transmitted polarized light due to the oblique incident angle seen in the conventional reflective polarizing film, and has higher polarization performance than before. Therefore, when used as a brightness enhancement film, a high brightness improvement rate can be obtained, and a liquid crystal display excellent in visibility with a high viewing angle and little hue shift can be provided.

２，６−ＰＥＮの１軸延伸後の延伸方向（Ｘ方向）、延伸方向と直交する方向（Ｙ方向）、厚み方向（Ｚ方向）の屈折率（それぞれｎＸ、ｎＹ、ｎＺと示す）を図１に示す。Refractive index (represented as n X , n Y , and n Z respectively) in the stretching direction (X direction) after uniaxial stretching of 2,6-PEN, the direction orthogonal to the stretching direction (Y direction), and the thickness direction (Z direction). ) Is shown in FIG. 本発明における第１層用芳香族ポリエステル（Ｉ）の１軸延伸後の延伸方向（Ｘ方向）、延伸方向と直交する方向（Ｙ方向）、厚み方向（Ｚ方向）の屈折率（それぞれｎＸ、ｎＹ、ｎＺと示す）を図２に示す。In the present invention, the first layer aromatic polyester (I) has a uniaxially stretched stretch direction (X direction), a direction perpendicular to the stretch direction (Y direction), and a refractive index in the thickness direction (Z direction) (each of n X , N Y and n Z ) are shown in FIG. 本発明の１軸延伸多層積層フィルムのフィルム面を反射面とし、延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分（Ｐ偏光成分）、および延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分（Ｓ偏光成分）の波長に対する反射率のグラフの一例である。The film surface of the uniaxially stretched multilayer laminated film of the present invention is a reflective surface, and the polarization component (P-polarized component) parallel to the incident surface including the stretching direction (X direction) and the incident including the stretching direction (X direction) It is an example of the graph of the reflectance with respect to the wavelength of a polarized light component (S polarized light component) perpendicular | vertical with respect to a surface.

［１軸延伸多層積層フィルム］
本発明の１軸延伸多層積層フィルムは、第１層と第２層とが交互に積層された２５１層以上の１軸延伸多層積層フィルムである。ここで第１層は第２層より屈折率の高い層、第２層は第１層より屈折率の低い層をそれぞれ表す。
本発明の最大の特徴は、一定の層厚み構成で、１軸延伸多層積層フィルムを構成する第１層と第２層において、第１層に延伸によりＸ方向の屈折率が増大する一方、Ｙ方向とＺ方向の両方向の屈折率がともに低下する特性を有する、平均屈折率が１．６０以上１．７０以下の熱可塑性樹脂を用い、かつ第２層に等方性で延伸による屈折率変化の小さい、平均屈折率が１．５０以上１．６０以下の熱可塑性樹脂を用いることにある。ここで、延伸方向（Ｘ方向）の屈折率はｎＸ、延伸方向と直交する方向（Ｙ方向）の屈折率はｎＹ、フィルム厚み方向（Ｚ方向）の屈折率はｎＺと記載することがある。
以下、さらに本発明の１軸延伸多層積層フィルムについて詳述する。 [Uniaxially stretched multilayer laminated film]
The uniaxially stretched multilayer laminated film of the present invention is a uniaxially stretched multilayer laminated film having 251 layers or more in which the first layer and the second layer are alternately laminated. Here, the first layer represents a layer having a higher refractive index than the second layer, and the second layer represents a layer having a lower refractive index than the first layer.
The greatest feature of the present invention is that, in the first layer and the second layer constituting the uniaxially stretched multilayer laminated film with a constant layer thickness configuration, the refractive index in the X direction is increased by stretching the first layer, while Y The refractive index changes due to stretching by using a thermoplastic resin having an average refractive index of 1.60 or more and 1.70 or less and having a characteristic that the refractive index in both the Z direction and the Z direction decreases. Is to use a thermoplastic resin having a small average refractive index of 1.50 or more and 1.60 or less. Here, the refractive index in the stretching direction (X direction) is described as n X , the refractive index in the direction orthogonal to the stretching direction (Y direction) is expressed as n Y , and the refractive index in the film thickness direction (Z direction) is described as NZ. There is.
Hereinafter, the uniaxially stretched multilayer laminated film of the present invention will be described in detail.

［第１層］
本発明において、第１層を構成する熱可塑性樹脂は、平均屈折率１．６０以上１．７０以下であって、１軸延伸方向（Ｘ方向）の屈折率ｎＸが延伸により増大し、フィルム面内で１軸延伸方向に直交する方向（Ｙ方向）の屈折率ｎＹおよびフィルム厚み方向（Ｚ方向）の屈折率ｎＺが延伸により低下する熱可塑性樹脂である。 [First layer]
In the present invention, the thermoplastic resin constituting the first layer has an average refractive index of 1.60 or more and 1.70 or less, and the refractive index n X in the uniaxial stretching direction (X direction) is increased by stretching. refractive index n Y and the refractive index n Z in the film thickness direction (Z direction) in the direction perpendicular to the uniaxial stretching direction in the plane (Y-direction) is a thermoplastic resin to decrease by stretching.

反射偏光機能を有する多層積層フィルムの第１層として、これまでポリエチレン−２，６−ナフタレンジカルボキシレートが最も好適な材料として知られていたが、ポリエチレン−２，６−ナフタレンジカルボキシレートは、延伸前後でＹ方向の屈折率ｎＹがほとんど変化しない材料であるのに対し、本発明の第１層を構成する熱可塑性樹脂は延伸によりＹ方向の屈折率ｎＹがＺ方向の屈折率ｎＺと同様、延伸に伴い減少する点で最も特徴を有する。
従来は反射偏光機能を有する多層積層フィルムの第１層に用いられることが知られていなかった本発明の屈折率特性を有する熱可塑性樹脂を第１層に用い、さらに後述する第２層の熱可塑性樹脂と組み合わせて一定層厚みの多層積層フィルムにすることにより、これまで困難であった、偏光性能の向上と斜め方向の入射光に対する透過偏光の色相ずれの両立化が可能となる。さらに、偏光性能が従来よりも高くなるため、従来と同程度の偏光性能であればフィルム厚みを１／３程度に薄くでき、ディスプレイ厚みをより薄肉化することができる。 Polyethylene-2,6-naphthalene dicarboxylate has hitherto been known as the most suitable material as the first layer of the multilayer laminated film having a reflective polarization function. while the refractive index n Y in the Y direction before and after stretching is almost unchanged material, the refractive index n thermoplastic resin has a refractive index n Y in the Y direction by stretching of the first layer is a Z-direction of the present invention Like Z , it is most characteristic in that it decreases with stretching.
The thermoplastic resin having the refractive index characteristics of the present invention, which has not been conventionally used for the first layer of the multilayer laminated film having a reflective polarization function, is used for the first layer, and the second layer heat described later. By using a multilayer laminated film having a constant layer thickness in combination with a plastic resin, it is possible to achieve both improvement in polarization performance and hue shift of transmitted polarized light with respect to obliquely incident light, which have been difficult until now. Furthermore, since the polarization performance is higher than before, the film thickness can be reduced to about 1/3 and the display thickness can be further reduced if the polarization performance is comparable to the conventional one.

ここで、本発明における平均屈折率とは、第１層を構成する熱可塑性樹脂を単独で溶融させ、ダイより押出して未延伸フィルムを作成し、得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向における屈折率について、メトリコン製プリズムカプラを用いて波長６３３ｎｍで測定し、それらの平均値を平均屈折率として規定したものである。   Here, the average refractive index in the present invention means that the thermoplastic resin constituting the first layer is melted alone, extruded from a die to create an unstretched film, and the obtained film in the X direction, Y direction, Z The refractive index in each direction is measured at a wavelength of 633 nm using a Metricon prism coupler, and the average value thereof is defined as the average refractive index.

また、延伸による各方向の屈折率変化については、次の方法により求めることができる。すなわち、第１層を構成する熱可塑性樹脂を単独で溶融させてダイより押出し、未延伸フィルムを作成する。得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向について、メトリコン製プリズムカプラを用いて波長６３３ｎｍにおける屈折率を測定し、３方向の屈折率の平均値より平均屈折率を求め、延伸前の屈折率とする。
次に、延伸後の屈折率については、第１層を構成する熱可塑性樹脂を単独で溶融させてダイより押出し、１軸方向に１３５℃で５倍を施して１軸延伸フィルムを作成し、得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向について、メトリコン製プリズムカプラを用いて波長６３３ｎｍにおける屈折率を測定し、延伸後の各方向の屈折率とする。
かかる方法で得られた延伸前の屈折率と延伸後の各方向の屈折率とを比較し、延伸による屈折率変化の増減を確認することができる。 Moreover, about the refractive index change of each direction by extending | stretching, it can obtain | require by the following method. That is, the thermoplastic resin constituting the first layer is melted alone and extruded from a die to produce an unstretched film. For each of the X direction, Y direction, and Z direction of the obtained film, the refractive index at a wavelength of 633 nm is measured using a metricon prism coupler, the average refractive index is obtained from the average value of the refractive indexes in three directions, and stretched. The previous refractive index.
Next, for the refractive index after stretching, the thermoplastic resin constituting the first layer is melted alone and extruded from a die to create a uniaxially stretched film by applying 5 times at 135 ° C. in the uniaxial direction, For each of the X direction, Y direction, and Z direction of the obtained film, the refractive index at a wavelength of 633 nm is measured using a metricon prism coupler to obtain the refractive index in each direction after stretching.
By comparing the refractive index before stretching obtained by such a method with the refractive index in each direction after stretching, the change in the refractive index due to stretching can be confirmed.

第１層の熱可塑性樹脂の平均屈折率の下限値は、より好ましくは１．６１、さらに好ましくは１．６２である。また第１層の熱可塑性樹脂の平均屈折率の上限値は、より好ましくは１．６９、さらに好ましくは１．６８である。第１層の熱可塑性樹脂の平均屈折率がかかる範囲内にあることにより、延伸後の第２層との層間の各方向の屈折率差を所望の範囲にすることができる。一方、第１層の熱可塑性樹脂の平均屈折率が下限値に満たない場合、第２層との屈折率差が近くなり、延伸後のＸ方向の屈折率差を十分に大きくすることができない。また第１層の熱可塑性樹脂の平均屈折率が上限値を超える場合は延伸後の第２層との屈折率差が大きくなり、延伸後のＹ方向、Ｚ方向における層間の屈折率差を小さくし難い。   The lower limit value of the average refractive index of the thermoplastic resin of the first layer is more preferably 1.61, and still more preferably 1.62. The upper limit of the average refractive index of the thermoplastic resin of the first layer is more preferably 1.69, and still more preferably 1.68. When the average refractive index of the thermoplastic resin of the first layer is within such a range, the refractive index difference in each direction between the stretched second layer and the second layer can be set to a desired range. On the other hand, when the average refractive index of the thermoplastic resin of the first layer is less than the lower limit value, the refractive index difference with the second layer is close, and the refractive index difference in the X direction after stretching cannot be sufficiently increased. . When the average refractive index of the thermoplastic resin of the first layer exceeds the upper limit value, the refractive index difference with the second layer after stretching becomes large, and the refractive index difference between the layers in the Y direction and Z direction after stretching becomes small. It is hard to do.

第１層の熱可塑性樹脂のＸ方向における屈折率ｎＸは、延伸により０．２０以上増大することが好ましく、より好ましくは０．２５以上、さらに好ましくは０．２７以上である。該屈折率の変化がより大きい方が偏光性能を高めることができるが、延伸倍率が高すぎるとフィルム破断が生じる関係で、上限値は０．３５に制限され、さらには０．３０である。 The refractive index n X in the X direction of the thermoplastic resin of the first layer is preferably increased by 0.20 or more by stretching, more preferably 0.25 or more, and further preferably 0.27 or more. When the refractive index change is larger, the polarization performance can be improved. However, if the draw ratio is too high, the film breaks, and therefore the upper limit is limited to 0.35, and further 0.30.

第１層の熱可塑性樹脂のＹ方向における屈折率ｎＹは、延伸により０．０５以上０．２０以下の範囲で低下することが好ましく、より好ましくは０．０６以上０．１５以下、さらに好ましくは０．０７以上０．１０以下である。該屈折率の低下量が下限値に満たない場合は、Ｙ方向の層間屈折率が一致するように両層の樹脂を選択すると、Ｘ方向の層間の屈折率差を大きくするに伴いＺ方向の層間の屈折率のずれが大きくなり、偏光性能の向上と斜め方向の入射光に対する透過偏光の色相ずれの両立化が困難であることがある。一方、該屈折率の低下量が上限値を超える場合は、配向性が高すぎて、機械的な強度が十分でないことがある。 The refractive index n Y in the Y direction of the thermoplastic resin of the first layer is preferably lowered in the range of 0.05 or more and 0.20 or less by stretching, more preferably 0.06 or more and 0.15 or less, and still more preferably. Is 0.07 or more and 0.10 or less. When the amount of decrease in the refractive index is less than the lower limit, if the resins in both layers are selected so that the interlayer refractive index in the Y direction matches, the difference in the refractive index between the layers in the X direction increases. The refractive index shift between the layers increases, and it may be difficult to achieve both improvement in polarization performance and hue shift of transmitted polarized light with respect to obliquely incident light. On the other hand, when the amount of decrease in the refractive index exceeds the upper limit, the orientation is too high and the mechanical strength may not be sufficient.

第１層の熱可塑性樹脂のＺ方向における屈折率ｎＺは、延伸により０．０５以上０．２０以下の範囲で低下することが好ましく、より好ましくは０．０６以上０．１５以下、さらに好ましくは０．０７以上０．１０以下である。該屈折率の低下量を下限値に満たない範囲にするためにはＸ方向を低配向にせざるを得ず、Ｘ方向の層間の屈折率差を十分に大きくすることができないことがある。一方、該屈折率の低下量が上限値を超える場合は、配向性が高すぎて、機械的な強度が十分でないことがある。 The refractive index n Z in the Z direction of the thermoplastic resin of the first layer is preferably lowered in the range of 0.05 to 0.20 by stretching, more preferably 0.06 to 0.15, and still more preferably. Is 0.07 or more and 0.10 or less. In order to make the amount of decrease in the refractive index less than the lower limit, the X direction must be lowly oriented, and the refractive index difference between the layers in the X direction may not be sufficiently large. On the other hand, when the amount of decrease in the refractive index exceeds the upper limit, the orientation is too high and the mechanical strength may not be sufficient.

第１層の延伸後のＹ方向屈折率ｎＹと延伸後のＺ方向屈折率ｎＺの屈折率差は、０．０５以下であることが好ましく、さらに好ましくは０．０３以下、特に好ましくは０．０１以下である。これら２方向の屈折率差が非常に小さいことにより、偏光光が斜め方向の入射角で入射しても色相ずれが生じない効果を奏する。かかる偏光光は特に、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分（以下、Ｓ偏光と称することがある）についての色相ずれの解消に効果的である。 The difference in refractive index between the Y-direction refractive index n Y after stretching of the first layer and the Z-direction refractive index n Z after stretching is preferably 0.05 or less, more preferably 0.03 or less, particularly preferably. 0.01 or less. Since the difference in refractive index between these two directions is very small, there is an effect that no hue shift occurs even when polarized light is incident at an oblique incident angle. In particular, such polarized light has a film surface as a reflection surface, and a hue shift with respect to a polarization component perpendicular to an incident surface including a stretching direction (X direction) of a uniaxially stretched film (hereinafter sometimes referred to as S-polarized light). It is effective in solving the problem.

かかる屈折率特性を有する熱可塑性樹脂として、具体的には以下に述べるような特定構造の共重合成分をジカルボン酸成分に有する芳香族ポリエステル（以下、芳香族ポリエステル（Ｉ）と称することがある）、ポリエチレン−２，７−ナフタレンジカルボキシレートなどが挙げられる。   As the thermoplastic resin having such refractive index characteristics, specifically, an aromatic polyester having a copolymer component having a specific structure as described below as a dicarboxylic acid component (hereinafter sometimes referred to as aromatic polyester (I)). And polyethylene-2,7-naphthalenedicarboxylate.

＜芳香族ポリエステル（Ｉ）＞
第１層を形成する熱可塑性樹脂の１つとして、特定構造の共重合成分をジカルボン酸成分に有する芳香族ポリエステル（Ｉ）が例示される。かかるポリエステルは、以下に詳述するジカルボン酸成分とジオール成分との重縮合によって得られる。
（ジカルボン酸成分）
本発明の芳香族ポリエステル（Ｉ）を構成するジカルボン酸成分（ｉ）として、５モル％以上５０モル％以下の下記式（Ａ）で表される酸成分、および５０モル％以上９５モル％以下の下記式（Ｂ）で表される酸成分で表わされる少なくとも２種の芳香族ジカルボン酸成分またはそれらの誘導体が用いられる。ここで、各芳香族ジカルボン酸成分の含有量は、ジカルボン酸成分の全モル数を基準とする含有量である。 <Aromatic polyester (I)>
As one of the thermoplastic resins forming the first layer, aromatic polyester (I) having a copolymer component having a specific structure as a dicarboxylic acid component is exemplified. Such a polyester is obtained by polycondensation of a dicarboxylic acid component and a diol component described in detail below.
(Dicarboxylic acid component)
As the dicarboxylic acid component (i) constituting the aromatic polyester (I) of the present invention, an acid component represented by the following formula (A) of 5 mol% or more and 50 mol% or less, and 50 mol% or more and 95 mol% or less At least two types of aromatic dicarboxylic acid components represented by the acid component represented by the following formula (B) or derivatives thereof are used. Here, the content of each aromatic dicarboxylic acid component is a content based on the total number of moles of the dicarboxylic acid component.

（式（Ａ）中、ＲＡは炭素数２〜１０のアルキレン基を表わす） (In the formula (A), R A represents an alkylene group having 2 to 10 carbon atoms)

（式（Ｂ）中、ＲＢはフェニレン基またはナフタレンジイル基を表わす） (In the formula (B), R B represents a phenylene group or a naphthalenediyl group)

式（Ａ）で表される酸成分について、式中、ＲＡは炭素数２〜１０のアルキレン基である。かかるアルキレン基として、エチレン基、プロピレン基、イソプロピレン基、テトラメチレン基、ヘキサメチレン基、オクタメチレン基等が挙げられる。 Regarding the acid component represented by the formula (A), R A is an alkylene group having 2 to 10 carbon atoms. Examples of the alkylene group include an ethylene group, a propylene group, an isopropylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group.

式（Ａ）で表される酸成分の含有量の下限値は、好ましくは７モル％、より好ましくは１０モル％、さらに好ましくは１５モル％である。また、式（Ａ）で表される酸成分の含有量の上限値は、好ましくは４５モル％、より好ましくは４０モル％、さらに好ましくは３５モル％、特に好ましくは３０モル％である。
従って、式（Ａ）で表される酸成分の含有量は、好ましくは５モル％以上４５モル％以下、より好ましくは７モル％以上４０モル％以下、さらに好ましくは１０モル％以上３５モル％以下、特に好ましくは１５モル％以上３０モル％以下である。 The lower limit of the content of the acid component represented by the formula (A) is preferably 7 mol%, more preferably 10 mol%, still more preferably 15 mol%. Further, the upper limit value of the content of the acid component represented by the formula (A) is preferably 45 mol%, more preferably 40 mol%, still more preferably 35 mol%, particularly preferably 30 mol%.
Therefore, the content of the acid component represented by the formula (A) is preferably 5 mol% or more and 45 mol% or less, more preferably 7 mol% or more and 40 mol% or less, and further preferably 10 mol% or more and 35 mol%. Hereinafter, it is particularly preferably 15 mol% or more and 30 mol% or less.

式（Ａ）で表される酸成分は、好ましくは６，６’−（エチレンジオキシ）ジ−２−ナフトエ酸、６，６’−（トリメチレンジオキシ）ジ−２−ナフトエ酸および６，６’−（ブチレンジオキシ）ジ−２−ナフトエ酸が好ましい。これらの中でも式（Ａ）におけるＲＡの炭素数が偶数のものが好ましく、特に下記式（Ａ−１）で表わされる６，６’−（エチレンジオキシ）ジ−２−ナフトエ酸が好ましい。 The acid component represented by the formula (A) is preferably 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, 6,6 ′-(trimethylenedioxy) di-2-naphthoic acid and 6 , 6 '-(Butylenedioxy) di-2-naphthoic acid is preferred. Among these, those having an even number of carbon atoms of RA in the formula (A) are preferable, and 6,6 ′-(ethylenedioxy) di-2-naphthoic acid represented by the following formula (A-1) is particularly preferable.

かかる芳香族ポリエステル（Ｉ）は、ジカルボン酸成分が５モル％以上５０モル％以下の式（Ａ）で表される酸成分を含有することを特徴とする。式（Ａ）で示される酸成分の割合が下限値に満たない場合は、１軸延伸によるＹ方向の屈折率の低下が生じにくいため、延伸フィルムにおけるＹ方向の屈折率ｎＹとＺ方向の屈折率ｎＺの差異が大きくなり、斜め方向の入射角で入射した偏光による色相ずれが改善し難い。また、式（Ａ）で示される酸成分の割合が上限値を超える場合は、非晶性の特性が大きくなり、延伸フィルムにおけるＸ方向の屈折率ｎＸとＹ方向の屈折率ｎＹとの差異が小さくなるため、反射偏光フィルムとして十分な性能を発揮しない。 Such aromatic polyester (I) is characterized in that the dicarboxylic acid component contains an acid component represented by the formula (A) in an amount of 5 mol% to 50 mol%. Wherein if the ratio of the acid component represented by (A) is less than the lower limit, 1 since the decrease in the refractive index in the Y direction by axial stretching hardly occurs, the Y direction in the stretched film refractive index n Y and Z directions the difference in refractive index n Z becomes large, it is difficult to improve the hue shift due polarized light incident at an incident angle of an oblique direction. Further, if the proportion of the acid component represented by the formula (A) exceeds the upper limit value, amorphous characteristics becomes large, the refractive index n Y in refractive index n X and Y direction of the X-direction in the stretched film Since the difference is small, it does not exhibit sufficient performance as a reflective polarizing film.

このように、式（Ａ）で表される酸成分を含有するポリエステルを用いることで、反射偏光フィルムとしての偏光性能を従来より高めつつ、斜め方向の入射角による色相ずれも生じない１軸延伸多層積層フィルムを製造することができる。   As described above, by using the polyester containing the acid component represented by the formula (A), uniaxial stretching that improves the polarization performance as a reflective polarizing film and does not cause a hue shift due to an incident angle in an oblique direction. A multilayer laminated film can be produced.

また、式（Ｂ）で表される酸成分について、式中、ＲＢはフェニレン基またはナフタレンジイル基である。
式（Ｂ）で表される酸成分として、テレフタル酸、イソフタル酸、２，６−ナフタレンジカルボン酸、２，７−ナフタレンジカルボン酸、またはこれらの組み合わせが挙げられ、特に２，６−ナフタレンジカルボン酸が好ましく例示される。 Further, the acid component of the formula (B), wherein, R B is a phenylene group or naphthalene-diyl group.
Examples of the acid component represented by the formula (B) include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, or a combination thereof, and particularly 2,6-naphthalenedicarboxylic acid. Is preferably exemplified.

式（Ｂ）で表される酸成分の含有量の下限値は、好ましくは５５モル％、より好ましくは６０モル％、さらに好ましくは６５モル％、特に好ましくは７０モル％である。また、式（Ｂ）で表される酸成分の含有量の上限値は、好ましくは９３モル％、より好ましくは９０モル％、さらに好ましくは８５モル％である。
従って、式（Ｂ）で表される酸成分の含有量は、好ましくは５５モル％以上９５モル％以下、より好ましくは６０モル％以上９３モル％以下、さらに好ましくは６５モル％以上９０モル％以下、特に好ましくは７０モル％以上８５モル％以下である。 The lower limit of the content of the acid component represented by the formula (B) is preferably 55 mol%, more preferably 60 mol%, still more preferably 65 mol%, particularly preferably 70 mol%. Further, the upper limit value of the content of the acid component represented by the formula (B) is preferably 93 mol%, more preferably 90 mol%, still more preferably 85 mol%.
Therefore, the content of the acid component represented by the formula (B) is preferably 55 mol% or more and 95 mol% or less, more preferably 60 mol% or more and 93 mol% or less, and further preferably 65 mol% or more and 90 mol% or less. Hereinafter, it is particularly preferably 70 mol% or more and 85 mol% or less.

式（Ｂ）で示される酸成分の割合が下限値に満たない場合は、非晶性の特性が大きくなり、延伸フィルムにおけるＸ方向の屈折率ｎＸとＹ方向の屈折率ｎＹとの差異が小さくなるため、反射偏光フィルムとして十分な性能を発揮しない。また、式（Ｂ）で示される酸成分の割合が上限値を超える場合は、式（Ａ）で示される酸成分の割合が相対的に少なくなるため、延伸フィルムにおけるＹ方向の屈折率ｎＹとＺ方向の屈折率ｎＺの差異が大きくなり、斜め方向の入射角で入射した偏光による色相ずれが改善し難い。
このように、式（Ｂ）で表される酸成分を含有するポリエステルを用いることで、Ｘ方向に高屈折率を示すと同時に１軸配向性の高い複屈折率特性を実現できる。 If the proportion of the acid component represented by the formula (B) is less than the lower limit value, amorphous characteristics becomes large, the difference between the refractive index n Y in refractive index n X and Y direction of the X-direction in the stretched film Therefore, sufficient performance as a reflective polarizing film is not exhibited. Moreover, since the ratio of the acid component shown by Formula (A) becomes relatively small when the ratio of the acid component shown by Formula (B) exceeds an upper limit, the refractive index n Y of the stretched film in the Y direction. And the difference in refractive index n Z in the Z direction becomes large, and it is difficult to improve the hue shift due to polarized light incident at an oblique incident angle.
Thus, by using the polyester containing the acid component represented by the formula (B), it is possible to realize a birefringence characteristic having a high uniaxial orientation while exhibiting a high refractive index in the X direction.

（ジオール成分）
本発明の芳香族ポリエステル（Ｉ）を構成するジオール成分（ｉｉ）として、９０モル％以上１００モル％以下の下記式（Ｃ）で表されるジオール成分が用いられる。ここで、ジオール成分の含有量は、ジオール成分の全モル数を基準とする含有量である。 (Diol component)
As the diol component (ii) constituting the aromatic polyester (I) of the present invention, a diol component represented by the following formula (C) of 90 mol% or more and 100 mol% or less is used. Here, the content of the diol component is a content based on the total number of moles of the diol component.

（式（Ｃ）中、ＲＣは炭素数２〜１０のアルキレン基を表わす） (In the formula (C), R C represents an alkylene group having 2 to 10 carbon atoms)

式（Ｃ）で表されるジオール成分の含有量は、好ましくは９５モル％以上１００モル％以下、より好ましくは９８モル％以上１００モル％以下である。
式（Ｃ）中、ＲＣは炭素数２〜１０のアルキレン基であり、かかるアルキレン基として、エチレン基、プロピレン基、イソプロピレン基、テトラメチレン基、ヘキサメチレン基、オクタメチレン基等が挙げられる。これらの中でも式（Ｃ）で表されるジオール成分として、エチレングリコール、トリメチレングリコール、テトラメチレングリコール、シクロヘキサンジメタノール等が好ましく挙げられ、特に好ましくはエチレングリコールである。式（Ｃ）で示されるジオール成分の割合が下限値に満たない場合は、前述の１軸配向性が損なわれる。 The content of the diol component represented by the formula (C) is preferably 95 mol% to 100 mol%, more preferably 98 mol% to 100 mol%.
In the formula (C), R C is an alkylene group having 2 to 10 carbon atoms, and examples of the alkylene group include an ethylene group, a propylene group, an isopropylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group. . Among these, preferred examples of the diol component represented by the formula (C) include ethylene glycol, trimethylene glycol, tetramethylene glycol, and cyclohexanedimethanol, and ethylene glycol is particularly preferred. When the ratio of the diol component represented by the formula (C) is less than the lower limit, the above-described uniaxial orientation is impaired.

（芳香族ポリエステル（Ｉ））
芳香族ポリエステル（Ｉ）において、式（Ａ）で表される酸成分と式（Ｃ）で表されるジオール成分で構成されるエステル単位（−（Ａ）−（Ｃ）−）の含有量は、全繰り返し単位の５モル％以上５０モル％以下であり、好ましくは５モル％以上４５モル％以下、さらに好ましくは１０モル％以上４０モル％以下である。 (Aromatic polyester (I))
In the aromatic polyester (I), the content of the ester unit (-(A)-(C)-) composed of the acid component represented by the formula (A) and the diol component represented by the formula (C) is , 5 mol% or more and 50 mol% or less of all repeating units, preferably 5 mol% or more and 45 mol% or less, more preferably 10 mol% or more and 40 mol% or less.

芳香族ポリエステル（Ｉ）を構成する他のエステル単位として、エチレンテレフタレート、トリメチレンテレフタレート、ブチレンテレフタレートなどのアルキレンテレフタレート単位、エチレン−２，６−ナフタレンジカルボキシレート、トリメチレン−２，６−ナフタレンジカルボキシレート、ブチレン−２，６−ナフタレンジカルボキシレートなどのアルキレン−２，６−ナフタレンジカルボキシレート単位が挙げられる。これらの中でも高屈折率性などの点からエチレンテレフタレート単位やエチレン−２，６−ナフタレンジカルボキシレート単位が好ましく、特にエチレン−２，６−ナフタレンジカルボキシレート単位が好ましい。   As other ester units constituting the aromatic polyester (I), alkylene terephthalate units such as ethylene terephthalate, trimethylene terephthalate, butylene terephthalate, ethylene-2,6-naphthalene dicarboxylate, trimethylene-2,6-naphthalene dicarboxylate And alkylene-2,6-naphthalenedicarboxylate units such as butyl and butylene-2,6-naphthalenedicarboxylate. Among these, ethylene terephthalate units and ethylene-2,6-naphthalenedicarboxylate units are preferable, and ethylene-2,6-naphthalenedicarboxylate units are particularly preferable from the viewpoint of high refractive index.

芳香族ポリエステル（Ｉ）として、特に、式（Ａ）で表されるジカルボン酸成分が式（Ａ−１）で表わされるジカルボン酸成分であり、
式（Ｂ）で表されるジカルボン酸成分が２，６−ナフタレンジカルボン酸由来の芳香族ジカルボン酸成分であり、ジオール成分がエチレングリコールであるポリエステルが好ましい。 As the aromatic polyester (I), in particular, the dicarboxylic acid component represented by the formula (A) is a dicarboxylic acid component represented by the formula (A-1),
A polyester in which the dicarboxylic acid component represented by the formula (B) is an aromatic dicarboxylic acid component derived from 2,6-naphthalenedicarboxylic acid and the diol component is ethylene glycol is preferred.

芳香族ポリエステル（Ｉ）は、Ｐ−クロロフェノール／１，１，２，２−テトラクロロエタン（重量比４０／６０）の混合溶媒を用いて３５℃で測定した固有粘度が０．４〜３ｄｌ／ｇであることが好ましく、さらに好ましくは０．４〜１．５ｄｌ／ｇ、特に好ましくは０．５〜１．２ｄｌ／ｇである。   The aromatic polyester (I) has an intrinsic viscosity of 0.4 to 3 dl / measured at 35 ° C. using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60). It is preferable that it is g, More preferably, it is 0.4-1.5 dl / g, Most preferably, it is 0.5-1.2 dl / g.

芳香族ポリエステル（Ｉ）の融点は、好ましくは２００〜２６０℃の範囲、より好ましくは２０５〜２５５℃の範囲、さらに好ましくは２１０〜２５０℃の範囲である。融点はＤＳＣで測定して求めることができる。   The melting point of the aromatic polyester (I) is preferably in the range of 200 to 260 ° C, more preferably in the range of 205 to 255 ° C, and still more preferably in the range of 210 to 250 ° C. The melting point can be determined by measuring with DSC.

該ポリエステルの融点が上限値を越えると、溶融押出して成形する際に流動性が劣り、吐出などが不均一化しやすくなることがある。一方、融点が下限値に満たないと、製膜性は優れるものの、ポリエステルの持つ機械的特性などが損なわれやすくなり、また本発明の屈折率特性が発現し難い。   If the melting point of the polyester exceeds the upper limit value, fluidity may be inferior when melt-extruded and molded, and discharge and the like may be made uneven. On the other hand, if the melting point is less than the lower limit, the film forming property is excellent, but the mechanical properties of the polyester are easily impaired, and the refractive index properties of the present invention are hardly exhibited.

一般的に共重合体は単独重合体に比べて融点が低く、機械的強度が低下する傾向にある。しかし、本発明のポリエステルは、式（Ａ）の酸成分および式（Ｂ）の酸成分を含有する共重合体であり、式（Ａ）の酸成分のみを有する単独重合体に比べて融点が低いものの機械的強度は同程度であるという優れた特性を有する。   In general, a copolymer has a lower melting point than a homopolymer and tends to decrease mechanical strength. However, the polyester of the present invention is a copolymer containing an acid component of the formula (A) and an acid component of the formula (B), and has a melting point compared to a homopolymer having only the acid component of the formula (A). Although it has a low mechanical strength, it has excellent properties.

芳香族ポリエステル（Ｉ）のガラス転移温度（以下、Ｔｇと称することがある。）は、好ましくは８０〜１２０℃、より好ましくは８２〜１１８℃、さらに好ましくは８５〜１１８℃の範囲にある。Ｔｇがこの範囲にあると、耐熱性および寸法安定性に優れたフィルムが得られる。かかる融点やガラス転移温度は、共重合成分の種類と共重合量、そして副生物であるジアルキレングリコールの制御などによって調整できる。
かかる芳香族ポリエステル（Ｉ）の製造方法は、例えばＷＯ２００８／１５３１８８号パンフレットの第９頁に記載されている方法に準じて製造することができる。 The glass transition temperature (hereinafter sometimes referred to as Tg) of the aromatic polyester (I) is preferably 80 to 120 ° C, more preferably 82 to 118 ° C, and still more preferably 85 to 118 ° C. When Tg is within this range, a film having excellent heat resistance and dimensional stability can be obtained. Such melting point and glass transition temperature can be adjusted by controlling the kind and copolymerization amount of the copolymerization component and dialkylene glycol as a by-product.
The method for producing the aromatic polyester (I) can be produced, for example, according to the method described on page 9 of the pamphlet of WO2008 / 153188.

（芳香族ポリエステル（Ｉ）の屈折率特性）
芳香族ポリエステル（Ｉ）を１軸延伸した場合の各方向の屈折率の変化例を図２に示す。図２に示すように、Ｘ方向の屈折率ｎＸは延伸により増加する方向にあり、Ｙ方向の屈折率ｎＹとＺ方向の屈折率ｎＺはともに延伸に伴い低下する方向にあり、しかも延伸倍率によらずｎＹとｎＺの屈折率差が非常に小さいことを特徴としている。 (Refractive index characteristics of aromatic polyester (I))
FIG. 2 shows an example of changes in the refractive index in each direction when the aromatic polyester (I) is uniaxially stretched. As shown in FIG. 2, the refractive index n X in the X direction is in a direction that increases by stretching, the refractive index n Y in the Y direction and the refractive index n Z in the Z direction are both in a direction that decreases with stretching, and refractive index difference regardless of the draw ratio n Y and n Z is characterized by very small.

また第１層は、かかる特定の共重合成分を含む芳香族ポリエステル（Ｉ）を用いて１軸延伸を施すことにより、Ｘ方向の屈折率ｎＸが１．８０〜１．９０の高屈折率特性を有する。第１層におけるＸ方向の屈折率がかかる範囲にあることにより、第２層との屈折率差が大きくなり、十分な反射偏光性能を発揮することができる。 In addition, the first layer is uniaxially stretched using the aromatic polyester (I) containing the specific copolymer component, so that the refractive index n X in the X direction is 1.80 to 1.90. Has characteristics. When the refractive index in the X direction in the first layer is within such a range, the refractive index difference from the second layer becomes large, and sufficient reflective polarization performance can be exhibited.

一方、第１層を構成するポリエステルが、ポリエチレン−２，６−ナフタレンジカルボキシレートの場合、図１に示すように、１軸方向の延伸倍率によらず、Ｙ方向の屈折率ｎＹは一定で低下がみられないのに対し、Ｚ方向の屈折率ｎＺは１軸延伸倍率の増加に伴い屈折率が低下する。そのためＹ方向の屈折率ｎＹとＺ方向の屈折率ｎＺの差が大きくなり、偏光光が斜め方向の入射角で入射した際に色相ずれが生じやすくなる。 On the other hand, when the polyester constituting the first layer is polyethylene-2,6-naphthalenedicarboxylate, as shown in FIG. 1, the refractive index n Y in the Y direction is constant regardless of the stretching ratio in the uniaxial direction. In contrast, the refractive index n Z in the Z direction decreases as the uniaxial stretching ratio increases. Therefore, the difference between the refractive index n Y in the Y direction and the refractive index n Z in the Z direction becomes large, and a hue shift is likely to occur when polarized light is incident at an oblique incident angle.

＜ポリエチレン−２，７−ナフタレンジカルボキシレート＞
第１層を形成する別の熱可塑性樹脂の１つとして、ポリエチレン−２，７−ナフタレンジカルボキシレート（以下、２，７−ＰＥＮと称することある）が例示される。かかるポリエステルは、ジカルボン酸成分として２，７−ナフタレンジカルボン酸を用い、ジオール成分としてエチレングリコールを用い、それらの重縮合によって得られる。また、全繰り返し単位量を基準として１０モル％以下、さらに好ましくは５モル％以下の範囲内で、共重合成分を有していてもよい。かかる共重合成分として、芳香族ポリエステル（Ｉ）で述べたジカルボン酸成分、ジオール成分の中から１種または２種以上用いることができる。 <Polyethylene-2,7-naphthalenedicarboxylate>
An example of another thermoplastic resin forming the first layer is polyethylene-2,7-naphthalenedicarboxylate (hereinafter sometimes referred to as 2,7-PEN). Such polyester is obtained by polycondensation using 2,7-naphthalenedicarboxylic acid as a dicarboxylic acid component and ethylene glycol as a diol component. Moreover, you may have a copolymerization component in the range of 10 mol% or less based on the total repeating unit amount, More preferably, it is 5 mol% or less. As the copolymer component, one or more of the dicarboxylic acid components and diol components described in the aromatic polyester (I) can be used.

２，７−ＰＥＮは、ポリエチレン−２，６−ナフタレンジカルボキシレートと同種の構成成分を有するが、カルボン酸の配位が異なることにより、延伸による結晶構造などが異なり、２，６−ＰＥＮではみられなかった延伸によるＹ方向の屈折率ｎＹの低下が生じるため、芳香族ポリエステル（Ｉ）と同様、偏光性能の向上と斜め方向の入射光に対する透過偏光の色相ずれを両立することができる。 2,7-PEN has the same constituents as polyethylene-2,6-naphthalenedicarboxylate, but due to the different coordination of carboxylic acid, the crystal structure due to stretching is different. In 2,6-PEN, since the decrease in the refractive index n Y in the Y direction by the stretching was not observed occurs, it is possible to achieve both hue deviation of the transmitted polarized light to the aromatic polyester (I) and similarly improve the diagonal direction of the incident light polarization performance .

［第２層］
（熱可塑性樹脂）
本発明において、第２層は平均屈折率１．５０以上１．６０以下であって、Ｘ方向、Ｙ方向およびＺ方向のそれぞれの屈折率差が延伸前後で０．０５以下である熱可塑性樹脂からなる。ここで平均屈折率とは、第１層を構成する熱可塑性樹脂の平均屈折率と同様、第２層を構成する熱可塑性樹脂を単独で溶融させ、ダイより押出して未延伸フィルムを作成し、得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向における屈折率について、メトリコン製プリズムカプラを用いて波長６３３ｎｍで測定し、それらの平均値を平均屈折率として規定したものである。 [Second layer]
(Thermoplastic resin)
In the present invention, the second layer has an average refractive index of 1.50 or more and 1.60 or less, and a difference in refractive index between the X direction, the Y direction, and the Z direction is 0.05 or less before and after stretching. Consists of. Here, the average refractive index is the same as the average refractive index of the thermoplastic resin constituting the first layer, the thermoplastic resin constituting the second layer is melted alone, and extruded from a die to create an unstretched film, The refractive index in each of the X direction, Y direction, and Z direction of the obtained film is measured at a wavelength of 633 nm using a metricon prism coupler, and the average value thereof is defined as the average refractive index.

また、延伸前後の屈折率差についても第１層での説明と同様、まず、第２層を構成する熱可塑性樹脂を単独で溶融させてダイより押出し、未延伸フィルムを作成する。得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向について、メトリコン製プリズムカプラを用いて波長６３３ｎｍにおける屈折率を測定し、３方向の屈折率の平均値より平均屈折率を求め、延伸前の屈折率とする。次に、延伸後の屈折率については、第２層を構成する熱可塑性樹脂を単独で溶融させてダイより押出し、１軸方向に１３５℃で５倍を施して１軸延伸フィルムを作成し、得られたフィルムのＸ方向、Ｙ方向、Ｚ方向それぞれの方向について、メトリコン製プリズムカプラを用いて波長６３３ｎｍにおける屈折率を測定して延伸後の各方向の屈折率を求め、延伸前後の各方向の屈折率差を比較して得られる。   As for the difference in refractive index before and after stretching, as in the case of the first layer, first, the thermoplastic resin constituting the second layer is melted alone and extruded from a die to produce an unstretched film. For each of the X direction, Y direction, and Z direction of the obtained film, the refractive index at a wavelength of 633 nm is measured using a metricon prism coupler, the average refractive index is obtained from the average value of the refractive indexes in three directions, and stretched. The previous refractive index. Next, for the refractive index after stretching, the thermoplastic resin constituting the second layer is melted alone and extruded from a die, and a uniaxially stretched film is formed by applying 5 times at 135 ° C. in the uniaxial direction, For each direction in the X direction, Y direction, and Z direction of the obtained film, the refractive index at a wavelength of 633 nm is measured using a Metricon prism coupler to determine the refractive index in each direction after stretching, and each direction before and after stretching. It is obtained by comparing the difference in refractive index.

第２層を構成する熱可塑性樹脂の平均屈折率は、好ましくは１．５３以上１．６０以下、さらに好ましくは１．５５以上１．６０以下、さらに好ましくは１．５８以上１．６０以下である。第２層がかかる平均屈折率を有し、しかも延伸前後の屈折率差の小さい等方性材料であることにより、第１層と第２層の層間における延伸後のＸ方向の屈折率差が大きく、かつＹ方向の屈折率差およびＺ方向の屈折率差が共に極めて小さい屈折率特性を得ることができ、その結果、偏光性能と斜め方向の入射角よる色相ずれの両立が可能となる。   The average refractive index of the thermoplastic resin constituting the second layer is preferably from 1.53 to 1.60, more preferably from 1.55 to 1.60, and even more preferably from 1.58 to 1.60. is there. Since the second layer is an isotropic material having such an average refractive index and a small difference in refractive index before and after stretching, the refractive index difference in the X direction after stretching between the first layer and the second layer is reduced. A refractive index characteristic that is large and has a very small difference in refractive index in the Y direction and extremely small difference in refractive index in the Z direction can be obtained. As a result, both the polarization performance and the hue shift due to the incident angle in the oblique direction can be achieved.

かかる屈折率特性を有する熱可塑性樹脂の中でも、１軸延伸における製膜性の観点から、結晶性ポリエステルであることが好ましい。かかる屈折率特性を有する結晶性ポリエステルとして、共重合ポリエチレンテレフタレート、共重合ポリエチレンナフタレンジカルボキシレート、またはこれら共重合ポリエステルと非晶性ポリエステルとのブレンドが好ましく、中でも共重合ポリエチレンテレフタレートが好ましい。かかる共重合ポリエチレンテレフタレートの中でも、イソフタル酸もしくは２，６−ナフタレンジカルボン酸を共重合したエチレンテレフタレート成分を主たる成分とするポリエステルが好ましく、特にイソフタル酸もしくは２，６−ナフタレンジカルボン酸を共重合したエチレンテレフタレート成分を主たる成分とする融点が２２０℃以下のポリエステルであることが好ましい。   Among thermoplastic resins having such a refractive index characteristic, a crystalline polyester is preferable from the viewpoint of film forming property in uniaxial stretching. As the crystalline polyester having such refractive index characteristics, copolymerized polyethylene terephthalate, copolymerized polyethylene naphthalene dicarboxylate, or a blend of these copolymerized polyester and amorphous polyester is preferable, and copolymerized polyethylene terephthalate is particularly preferable. Among such copolymerized polyethylene terephthalates, polyesters mainly composed of an ethylene terephthalate component copolymerized with isophthalic acid or 2,6-naphthalenedicarboxylic acid are preferred, and in particular, ethylene copolymerized with isophthalic acid or 2,6-naphthalenedicarboxylic acid. A polyester having a melting point of 220 ° C. or lower, mainly composed of a terephthalate component, is preferred.

また、共重合ポリエチレンテレフタレートの場合、上記成分以外の共重合成分としては、第２層のポリエステルを構成する全繰り返し単位を基準として１０モル％以下の範囲内で、イソフタル酸、２，６−ナフタレンジカルボン酸、２，７−ナフタレンジカルボン酸などのうちのメインの共重合成分以外の芳香族カルボン酸；アジピン酸、アゼライン酸、セバシン酸、デカンジカルボン酸等の脂肪族ジカルボン酸；シクロヘキサンジカルボン酸といった脂環族ジカルボン酸等の酸成分、ブタンジオール、ヘキサンジオール等の脂肪族ジオール；シクロヘキサンジメタノールといった脂環族ジオール等のグリコール成分を好ましく挙げることができる。   In the case of copolymerized polyethylene terephthalate, the copolymer components other than the above components may be isophthalic acid or 2,6-naphthalene within a range of 10 mol% or less based on all repeating units constituting the polyester of the second layer. Aromatic carboxylic acids other than the main copolymer component among dicarboxylic acids and 2,7-naphthalenedicarboxylic acids; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid; fats such as cyclohexanedicarboxylic acid Preferable examples include acid components such as cyclic dicarboxylic acids, aliphatic diols such as butanediol and hexanediol; and glycol components such as alicyclic diols such as cyclohexanedimethanol.

これらの中でも、比較的、延伸性を維持しながら融点を低下させやすいことから、イソフタル酸、２，６−ナフタレンジカルボン酸の２種の共重合成分が好ましい。なお、第２層を構成する熱可塑性樹脂の融点は、フィルムにする前の段階から低い必要はなく、延伸処理後に低くなっていれば良い。例えば、２種以上のポリエステルをブレンドし、これらを溶融混練時にエステル交換させたものであってもよい。   Among these, two copolymer components of isophthalic acid and 2,6-naphthalenedicarboxylic acid are preferable because the melting point is easily lowered while maintaining stretchability. In addition, the melting point of the thermoplastic resin constituting the second layer does not have to be low from the stage before forming the film, and may be low after the stretching treatment. For example, two or more kinds of polyesters may be blended and transesterified at the time of melt kneading.

［樹脂以外の成分］
本発明の１軸延伸多層積層フィルムは、フィルムの巻取り性を向上させるために、少なくとも一方の最外層に平均粒径が０．０１μｍ〜２μｍの不活性粒子を、層の重量を基準として０．００１重量％〜０．５重量％含有することが好ましい。不活性粒子の平均粒径が下限値よりも小さいか、含有量が下限値よりも少ないと、多層延伸フィルムの巻取り性を向上させる効果が不十分になりやすく、他方、不活性粒子の含有量が上限値を超えるか、平均粒径が上限値を超えると、粒子による多層延伸フィルムの光学特性の悪化が顕著になることがある。好ましい不活性粒子の平均粒径は、０．０２μｍ〜１μｍ、特に好ましくは０．１μｍ〜０．３μｍの範囲である。また、好ましい不活性粒子の含有量は、０．０２重量％〜０．２重量％の範囲である。 [Ingredients other than resin]
In order to improve the winding property of the film, the uniaxially stretched multilayer laminated film of the present invention is provided with inert particles having an average particle diameter of 0.01 μm to 2 μm in at least one outermost layer based on the weight of the layer. It is preferable to contain 0.001 to 0.5 weight%. If the average particle diameter of the inert particles is smaller than the lower limit value or the content is less than the lower limit value, the effect of improving the winding property of the multilayer stretched film tends to be insufficient, while the inclusion of the inert particles When the amount exceeds the upper limit value or the average particle diameter exceeds the upper limit value, deterioration of the optical properties of the multilayer stretched film due to the particles may become remarkable. The average particle diameter of the preferable inert particles is in the range of 0.02 μm to 1 μm, particularly preferably 0.1 μm to 0.3 μm. Moreover, content of a preferable inert particle is the range of 0.02 weight%-0.2 weight%.

１軸延伸多層積層フィルムに含有させる不活性粒子としては、例えばシリカ、アルミナ、炭酸カルシウム、燐酸カルシウム、カオリン、タルクのような無機不活性粒子、シリコーン、架橋ポリスチレン、スチレン−ジビニルベンゼン共重合体のような有機不活性粒子を挙げることができる。粒子形状は、凝集状、球状など一般的に用いられる形状であれば特に限定されない。   Examples of the inert particles included in the uniaxially stretched multilayer laminated film include inorganic inert particles such as silica, alumina, calcium carbonate, calcium phosphate, kaolin, and talc, silicone, crosslinked polystyrene, and styrene-divinylbenzene copolymer. Such organic inert particles can be mentioned. The particle shape is not particularly limited as long as it is a generally used shape such as agglomerated or spherical.

不活性粒子は、最外層のみならず、最外層と同じ樹脂で構成される層中に含まれていてもよく、例えば第１層または第２層の少なくとも一方の層中に含まれていてもよい。または、第１層、第２層と異なる別の層を最外層として設けてもよく、またヒートシール層を設ける場合は該ヒートシール層中に不活性粒子が含まれていてもよい。   The inert particles may be contained not only in the outermost layer but also in a layer composed of the same resin as the outermost layer. For example, the inert particles may be contained in at least one of the first layer and the second layer. Good. Alternatively, another layer different from the first layer and the second layer may be provided as the outermost layer, and when a heat seal layer is provided, inert particles may be included in the heat seal layer.

［１軸延伸多層積層フィルムの積層構成］
（積層数）
本発明の１軸延伸多層積層フィルムは、上述の第１層および第２層を交互に合計２５１層以上積層したものである。積層数が２５１層未満であると、延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分の平均反射率特性について、波長４００〜８００ｎｍにわたり一定の平均反射率を満足するすることができない。
積層数の上限値は、生産性およびフィルムのハンドリング性など観点から２００１層に制限される。積層数の上限値は、本発明の平均反射率特性が得られれば生産性やハンドリング性の観点からさらに積層数を減らしてもよく、例えば１００１層、５０１層、３０１層であってもよい。 [Lamination structure of uniaxially stretched multilayer laminated film]
(Number of layers)
The uniaxially stretched multilayer laminated film of the present invention is obtained by alternately laminating a total of 251 layers of the above-mentioned first layer and second layer. When the number of stacked layers is less than 251 layers, the average reflectance characteristics of the polarization component parallel to the incident surface including the stretching direction (X direction) may satisfy a certain average reflectance over a wavelength range of 400 to 800 nm. Can not.
The upper limit of the number of layers is limited to 2001 layers from the viewpoints of productivity and film handling. As long as the average reflectance characteristic of the present invention is obtained, the upper limit value of the number of layers may be further reduced from the viewpoint of productivity and handling properties, and may be, for example, 1001, 501 and 301 layers.

（各層厚み）
第１層および第２層は、層間の光干渉によって選択的に光を反射するために、各層の厚みは０．０１μｍ以上０．５μｍ以下である。各層の厚みは透過型電子顕微鏡を用いて撮影した写真をもとに求めることができる。 (Each layer thickness)
Since the first layer and the second layer selectively reflect light by optical interference between layers, the thickness of each layer is 0.01 μm or more and 0.5 μm or less. The thickness of each layer can be determined based on a photograph taken using a transmission electron microscope.

本発明の１軸延伸多層積層フィルムが示す反射波長帯は、可視光域から近赤外線領域であることから、上記層厚の範囲とすることが必要である。層厚みが０．５μｍを超えると反射帯域が赤外線領域になり、反射偏光フィルムとして有用性が得られない。一方、層厚みが０．０１μｍ未満であると、ポリエステル成分が光を吸収し反射性能が得られなくなる。
第１層の各層の厚みは、好ましくは０．０１μｍ以上０．１μｍ以下である。また第２層の各層の厚みは、好ましくは０．０１μｍ以上０．３μｍ以下である。 Since the reflection wavelength band shown by the uniaxially stretched multilayer laminated film of the present invention is from the visible light region to the near infrared region, it is necessary to set the layer thickness within the above range. When the layer thickness exceeds 0.5 μm, the reflection band becomes an infrared region, and usefulness as a reflective polarizing film cannot be obtained. On the other hand, when the layer thickness is less than 0.01 μm, the polyester component absorbs light and the reflection performance cannot be obtained.
The thickness of each layer of the first layer is preferably 0.01 μm or more and 0.1 μm or less. The thickness of each layer of the second layer is preferably 0.01 μm or more and 0.3 μm or less.

（最大層厚みと最小層厚みの比率）
本発明の１軸延伸多層積層フィルムは、第１層および第２層におけるそれぞれの最大層厚みと最小層厚みの比率がいずれも２．０以上５．０以下であり、好ましくは２．０以上４．０以下、より好ましくは２．０以上３．５以下、さらに好ましくは２．０以上３．０以下である。かかる層厚みの比率は、具体的には最小層厚みに対する最大層厚みの比率で表わされる。第１層、第２層におけるそれぞれの最大層厚みと最小層厚みは、透過型電子顕微鏡を用いて撮影した写真をもとに求めることができる。 (Ratio of maximum layer thickness to minimum layer thickness)
In the uniaxially stretched multilayer laminated film of the present invention, the ratio between the maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer is 2.0 or more and 5.0 or less, preferably 2.0 or more. It is 4.0 or less, more preferably 2.0 or more and 3.5 or less, and further preferably 2.0 or more and 3.0 or less. The ratio of the layer thickness is specifically represented by the ratio of the maximum layer thickness to the minimum layer thickness. The maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer can be obtained based on a photograph taken using a transmission electron microscope.

多層積層フィルムは、層間の屈折率差、層数、層の厚みによって反射する波長が決まるが、積層された第１層および第２層のそれぞれが一定の厚みでは、特定の波長のみしか反射することができず、延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分の平均反射率特性について、波長４００〜８００ｎｍの幅広い波長帯にわたって均一に平均反射率を高めることができない。また、最大層厚みと最小層厚みの比率が上限値を超える場合は、反射帯域が広がりすぎ、延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分の反射率が低下する。
第１層および第２層は、段階的に変化してもよく、連続的に変化してもよい。このように積層された第１層および第２層のそれぞれが変化することで、より広い波長域の光を反射することができる。 In the multilayer laminated film, the wavelength to be reflected is determined by the difference in refractive index between layers, the number of layers, and the thickness of the layer. However, when each of the laminated first and second layers has a constant thickness, only a specific wavelength is reflected. The average reflectance of the polarization component parallel to the incident surface including the stretching direction (X direction) cannot be increased uniformly over a wide wavelength range of 400 to 800 nm. Further, when the ratio between the maximum layer thickness and the minimum layer thickness exceeds the upper limit value, the reflection band is excessively widened, and the reflectance of the polarization component parallel to the incident surface including the stretching direction (X direction) decreases.
The first layer and the second layer may change stepwise or may change continuously. By changing each of the first layer and the second layer laminated in this way, light in a wider wavelength range can be reflected.

本発明の１軸延伸多層積層フィルムにおける多層構造を積層する方法は特に限定されないが、例えば、第１層用ポリエステルを１３７層、第２層用熱可塑性樹脂を１３８層に分岐させた第１層と第２層が交互に積層され、その流路が連続的に２．０〜５．０倍までに変化する多層フィードブロック装置を使用する方法が挙げられる。   The method for laminating the multilayer structure in the uniaxially stretched multilayer laminated film of the present invention is not particularly limited. For example, the first layer is obtained by branching 137 layers of polyester for the first layer and 138 layers of thermoplastic resin for the second layer. And a second layer are alternately laminated, and a method of using a multilayer feed block device in which the flow path continuously changes by 2.0 to 5.0 times is mentioned.

（第１層と第２層の平均層厚み比）
本発明の１軸延伸多層積層フィルムは、第１層の平均層厚みに対する第２層の平均層厚みの比が１．５倍以上５．０倍以下の範囲であることが好ましい。第１層の平均層厚みに対する第２層の平均層厚みの比の下限値は、より好ましくは２．０である。また、第１層の平均層厚みに対する第２層の平均層厚みの比の上限値は、より好ましくは４．０であり、さらに好ましくは、３．５である。 (Average layer thickness ratio of the first layer and the second layer)
In the uniaxially stretched multilayer laminated film of the present invention, the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is preferably in the range of 1.5 to 5.0 times. The lower limit value of the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is more preferably 2.0. The upper limit of the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is more preferably 4.0, and even more preferably 3.5.

第１層の平均層厚みに対する第２層の平均層厚みの比がかかる範囲にあることにより、反射波長の半波長で生じる２次反射を有効に利用できるため、第１層および第２層それぞれの最大層厚みと最小層厚みの比率を最小限に抑えることができ、光学特性の観点から好ましい。また、このように第１層と第２層の厚み比を変化させることにより、層間の密着性を維持したまま、また使用する樹脂を変更することなく、得られたフィルムの機械特性も調整することができ、フィルムが裂けにくくなる効果も有する。
一方、第１層の平均層厚みに対する第２層の平均層厚みの比がかかる範囲からはずれる場合、反射波長の半波長で生じる２次反射が小さくなってしまい、反射率が低下することがある。 Since the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is in such a range, secondary reflection occurring at a half wavelength of the reflection wavelength can be effectively used. Therefore, each of the first layer and the second layer The ratio of the maximum layer thickness to the minimum layer thickness can be minimized, which is preferable from the viewpoint of optical characteristics. In addition, by changing the thickness ratio of the first layer and the second layer in this way, the mechanical properties of the obtained film are also adjusted while maintaining the adhesion between the layers and without changing the resin used. And has an effect of making the film difficult to tear.
On the other hand, when the ratio of the average layer thickness of the second layer to the average layer thickness of the first layer deviates from this range, the secondary reflection that occurs at the half wavelength of the reflection wavelength becomes small, and the reflectance may decrease. .

（厚み調整層）
本発明の１軸延伸多層積層フィルムは、かかる第１層、第２層以外に、層厚みが２μｍ以上の厚み調整層を第１層と第２層の交互積層構成の一部に有していてもよい。かかる厚みの厚み調整層を第１層と第２層の交互積層構成の一部に有することにより、偏光機能に影響をおよぼすことなく、第１層および第２層を構成する各層厚みを均一に調整しやすくなる。かかる厚みの厚み調整層は、第１層、第２層のいずれかと同じ組成、またはこれらの組成を部分的に含む組成であってもよく、層厚みが厚いため、反射特性には寄与しない。一方、透過する偏光光には影響することがあるため、層中に粒子を含める場合は既述の粒子濃度の範囲内であることが好ましい。 (Thickness adjustment layer)
In addition to the first layer and the second layer, the uniaxially stretched multilayer laminated film of the present invention has a thickness adjusting layer having a layer thickness of 2 μm or more in a part of the alternately laminated structure of the first layer and the second layer. May be. By having the thickness adjusting layer having such a thickness as a part of the alternately laminated structure of the first layer and the second layer, the thickness of each layer constituting the first layer and the second layer can be made uniform without affecting the polarization function. Easy to adjust. The thickness adjusting layer having such a thickness may be the same composition as either the first layer or the second layer, or a composition partially including these compositions. Since the layer thickness is thick, the thickness adjusting layer does not contribute to the reflection characteristics. On the other hand, since it may affect the transmitted polarized light, when the particles are included in the layer, it is preferably within the range of the particle concentration described above.

［１軸延伸フィルム］
本発明の１軸延伸多層積層フィルムは、目的とする反射偏光フィルムとしての光学特性を満足するために、少なくとも１軸方向に延伸されている。本発明における１軸延伸には、１軸方向にのみ延伸したフィルムの他、２軸方向に延伸されたフィルムであって、一方向により延伸されたフィルムも含まれる。１軸延伸方向（Ｘ方向）は、フィルム長手方向、幅方向のいずれの方向であってもよい。また、２軸方向に延伸されたフィルムであって、一方向により延伸されたフィルムの場合は、より延伸される方向（Ｘ方向）はフィルム長手方向、幅方向のいずれの方向であってもよく、延伸倍率の低い方向は、１．０５〜１．２０倍程度の延伸倍率にとどめることが偏光性能を高める点で好ましい。２軸方向に延伸され、一方向により延伸されたフィルムの場合、偏光光や屈折率との関係での「延伸方向」とは、より延伸された方向を指す。
延伸方法としては、棒状ヒータによる加熱延伸、ロール加熱延伸、テンター延伸など公知の延伸方法を用いることができるが、ロールとの接触によるキズの低減や延伸速度などの観点から、テンター延伸が好ましい。 [Uniaxially stretched film]
The uniaxially stretched multilayer laminated film of the present invention is stretched in at least a uniaxial direction in order to satisfy the optical properties as the target reflective polarizing film. The uniaxial stretching in the present invention includes a film stretched in a biaxial direction in addition to a film stretched only in a uniaxial direction and a film stretched in one direction. The uniaxial stretching direction (X direction) may be either the film longitudinal direction or the width direction. Further, in the case of a film stretched in a biaxial direction and stretched in one direction, the direction (X direction) that is more stretched may be either the film longitudinal direction or the width direction. In the direction where the draw ratio is low, it is preferable that the draw ratio is about 1.05 to 1.20 times from the viewpoint of improving the polarization performance. In the case of a film stretched in a biaxial direction and stretched in one direction, the “stretch direction” in relation to polarized light and refractive index refers to a more stretched direction.
As the stretching method, known stretching methods such as heat stretching with a rod heater, roll heat stretching, and tenter stretching can be used, but tenter stretching is preferable from the viewpoint of reducing scratches due to contact with the roll and stretching speed.

［第１層と第２層の層間の屈折率特性］
第１層と第２層のＸ方向の屈折率差は０．１０〜０．４５であることが好ましく、さらに好ましくは０．２０〜０．４０、特に好ましくは０．２５〜０．３０である。Ｘ方向の屈折率差がかかる範囲にあることにより、反射特性を効率よく高めることができるため、より少ない積層数で高い反射率を得ることができる。
また、第１層と第２層のＹ方向の屈折率差および第１層と第２層のＺ方向の屈折率差は、それぞれ０．０５以下であることが好ましい。Ｙ方向およびＺ方向それぞれの層間の屈折率差がともに上述の範囲にあることにより、偏光光が斜め方向の入射角で入射した際に色相ずれを抑制することができる。 [Refractive index characteristics between the first layer and the second layer]
The X-direction refractive index difference between the first layer and the second layer is preferably 0.10 to 0.45, more preferably 0.20 to 0.40, and particularly preferably 0.25 to 0.30. is there. When the refractive index difference in the X direction is within such a range, the reflection characteristics can be improved efficiently, so that a high reflectance can be obtained with a smaller number of layers.
Moreover, it is preferable that the difference in refractive index in the Y direction between the first layer and the second layer and the difference in refractive index in the Z direction between the first layer and the second layer are 0.05 or less, respectively. Since the refractive index difference between the layers in the Y direction and the Z direction is both in the above-described range, hue deviation can be suppressed when polarized light is incident at an oblique incident angle.

［フィルム厚み］
本発明の１軸延伸多層積層フィルムは、フィルム厚みが１５μｍ以上４０μｍ以下であることが好ましい。従来の反射偏光機能を有する多層積層フィルムは、Ｐ偏光について９０％程度の平均反射率を得るためには、本発明より層数を多くする必要があり、１００μｍ程度の厚みが必要であったところ、本発明は第１層を構成する熱可塑性樹脂として延伸によりＹ方向の屈折率が低下する樹脂を用い、さらに既述の第２層の熱可塑性樹脂と組み合わせて一定層厚みの多層積層フィルムにすることにより、従来と同程度の偏光性能であれば層数を減らしても達成することが可能となり、フィルム厚みを１／３程度の４０μｍ以下に薄くできることを見出した点にも特徴がある。かかるフィルム厚みにより、ディスプレイ厚みをより薄肉化することができる。 [Film thickness]
The uniaxially stretched multilayer laminated film of the present invention preferably has a film thickness of 15 μm or more and 40 μm or less. In order to obtain an average reflectance of about 90% for the P-polarized light, the conventional multilayer laminated film having a reflective polarizing function needs to have a larger number of layers than the present invention, and a thickness of about 100 μm is required. The present invention uses a resin whose refractive index in the Y direction decreases as a result of stretching as the thermoplastic resin constituting the first layer, and further combines with the above-described second layer thermoplastic resin to form a multilayer laminated film having a constant layer thickness. Thus, if the polarization performance is about the same as that of the prior art, it can be achieved even if the number of layers is reduced, and the film thickness can be reduced to about 1/3 of 40 μm or less. With such a film thickness, the display thickness can be further reduced.

［平均反射率］
本発明の１軸延伸多層積層フィルムは、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分について入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ９０％以上であり、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分について、入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ１５％以下である。
ここで、入射面とは反射面と垂直の関係にあり、かつ入射光線と反射光線を含む面を指す。また、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分は、一般的にＰ偏光とも称される。また、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分は、一般的にＳ偏光とも称される。さらに入射角とは、フィルム面の垂直方向に対する入射角を表す。 [Average reflectance]
The uniaxially stretched multilayer laminated film of the present invention has a film surface as a reflection surface and a polarization component parallel to the incident surface including the stretching direction (X direction) of the uniaxially stretched film at an incident angle of 0 degrees and 50 degrees. About a polarized light component perpendicular to the incident surface including the stretching direction (X direction) of the uniaxially stretched film, the average reflectance of the wavelength of 400 to 800 nm with respect to the incident polarized light is 90% or more, respectively. The average reflectance at a wavelength of 400 to 800 nm with respect to the incident polarized light at incident angles of 0 degrees and 50 degrees is 15% or less, respectively.
Here, the incident surface refers to a surface that is perpendicular to the reflecting surface and includes the incident light beam and the reflected light beam. In addition, the polarization component parallel to the incident surface including the film surface as a reflection surface and including the stretching direction (X direction) of the uniaxially stretched film is generally referred to as P-polarized light. In addition, a polarized light component having a film surface as a reflection surface and perpendicular to an incident surface including a stretching direction (X direction) of a uniaxially stretched film is generally referred to as S-polarized light. Furthermore, the incident angle represents an incident angle with respect to a direction perpendicular to the film surface.

フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分について、入射角０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率は、さらに好ましくは９５％以上１００％以下であり、特に好ましくは９８％以上１００％以下である。
また、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して平行な偏光成分について、入射角５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率は、さらに好ましくは９３％以上９９％以下であり、特に好ましくは９５％以上９８％以下である。 With respect to the polarization component parallel to the incident surface including the stretching direction (X direction) of the uniaxially stretched film with the film surface as the reflecting surface, the average reflectance at a wavelength of 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degree is More preferably, it is 95% or more and 100% or less, and particularly preferably 98% or more and 100% or less.
In addition, with respect to the polarization component parallel to the incident surface including the stretching direction (X direction) of the uniaxially stretched film with the film surface as the reflecting surface, the average reflection at a wavelength of 400 to 800 nm with respect to the incident polarized light at an incident angle of 50 degrees. The rate is more preferably 93% or more and 99% or less, and particularly preferably 95% or more and 98% or less.

かかる入射角でのＰ偏光成分に対する波長４００〜８００ｎｍの平均反射率が下限値に満たない場合、反射偏光フィルムとしての偏光反射性能はもとより、反射した光の色相ずれが生じ、ディスプレイとした場合に着色が生じる。一方、かかる範囲内でより該平均反射率が高い方がより偏光反射性能が高まるものの、上限値を超える程度にまで高くすることは組成や延伸との関係で難しいことがある。   When the average reflectance at a wavelength of 400 to 800 nm with respect to the P-polarized light component at such an incident angle is less than the lower limit, not only the polarization reflection performance as a reflective polarizing film, but also the hue shift of the reflected light occurs, resulting in a display. Coloring occurs. On the other hand, the higher the average reflectance within this range, the higher the polarization reflection performance, but it may be difficult to increase it to an extent exceeding the upper limit due to the composition and stretching.

フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分について入射角０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率は、さらに好ましくは５％以上１２％以下であり、特に好ましくは８％以上１２％以下である。
また、フィルム面を反射面とし、１軸延伸フィルムの延伸方向（Ｘ方向）を含む入射面に対して垂直な偏光成分について入射角５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率は、さらに好ましくは５％以上１０％以下であり、特に好ましくは８％以上１０％以下である。 The average reflectance at a wavelength of 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degree with respect to the polarized light component perpendicular to the incident surface including the stretching direction (X direction) of the uniaxially stretched film with the film surface as the reflecting surface is More preferably, it is 5% or more and 12% or less, and particularly preferably 8% or more and 12% or less.
Moreover, the average reflectance of the wavelength 400-800 nm with respect to the incident polarized light at an incident angle of 50 degrees with respect to a polarized light component perpendicular to the incident surface including the stretching direction (X direction) of the uniaxially stretched film with the film surface as a reflecting surface. Is more preferably 5% or more and 10% or less, and particularly preferably 8% or more and 10% or less.

かかる入射角でのＳ偏光成分に対する波長４００〜８００ｎｍの平均反射率が上限値を越える場合、反射偏光フィルムとしての偏光透過率が低下するため、液晶ディスプレイなどの輝度向上フィルムのとして十分な性能を発現しない。一方、かかる範囲内でより該偏光反射率が低い方がよりＳ偏光成分の透過率が高くなるものの、下限値より低くすることは組成や延伸との関係で難しいことがある。   When the average reflectance of a wavelength of 400 to 800 nm with respect to the S-polarized light component at such an incident angle exceeds the upper limit value, the polarization transmittance as a reflective polarizing film is lowered, so that sufficient performance as a brightness enhancement film such as a liquid crystal display is obtained. Not expressed. On the other hand, although the transmittance of the S-polarized component is higher when the polarization reflectance is lower than the above range, it may be difficult to lower the lower limit than the lower limit.

かかるＰ偏光成分についての平均反射率特性を得るためには、各層厚み、積層数に加え、第１層および第２層を構成するポリマー成分として上述の特性を有するポリマーを用い、かつ延伸方向（Ｘ方向）に一定の延伸倍率で延伸して第１層のフィルム面内方向を複屈折率化させることにより、延伸方向（Ｘ方向）における第１層と第２層の屈折率差を大きくすることによって達成される。   In order to obtain an average reflectance characteristic for such a P-polarized component, in addition to the thickness of each layer and the number of layers, a polymer having the above-described characteristics is used as the polymer component constituting the first layer and the second layer, and the stretching direction ( In the X direction, the film is stretched at a constant draw ratio to increase the birefringence in the in-plane direction of the first layer, thereby increasing the refractive index difference between the first layer and the second layer in the stretching direction (X direction). Is achieved.

また、Ｓ偏光成分についての平均反射率特性を得るためには、第１層および第２層を構成するポリマー成分として上述の特性を有するポリマーを用い、かつ該延伸方向と直交する方向（Ｙ方向）に延伸しないか、低延伸倍率での延伸にとどめることにより、該直交方向（Ｙ方向）における第１層と第２層の屈折率差を極めて小さくすることによって達成される。   Further, in order to obtain an average reflectance characteristic for the S-polarized component, a polymer having the above-described characteristics is used as a polymer component constituting the first layer and the second layer, and a direction perpendicular to the stretching direction (Y direction) This is achieved by making the difference in the refractive index between the first layer and the second layer in the orthogonal direction (Y direction) extremely small.

［色相の変化量］
本発明の１軸延伸多層積層フィルムは、入射面に対して平行な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．１以下であることが好ましく、さらに好ましくは０．０９以下、特に好ましくは０．０８以下である。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす） [Hue change]
In the uniaxially stretched multilayer laminated film of the present invention, the amount of hue change Δx, Δy represented by the following formulas (1) and (2) is 0.1 or less for the polarization component parallel to the incident surface. It is preferably 0.09 or less, more preferably 0.08 or less.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y)

入射面に対して平行な偏光成分（Ｐ偏光）に係る色相ｘ、ｙは、フィルムのＰ偏光について０°および５０°入射角で測定した透過スペクトルをもとに、ＪＩＳ規格Ｚ８７２９に準じて標準光源Ｃに対するＣＩＥ表色系におけるＹ、ｘ、ｙを求めた値で表わされる。   The hues x and y related to the polarization component parallel to the incident surface (P-polarized light) are standard according to JIS standard Z8729 based on transmission spectra measured at 0 ° and 50 ° incident angles for P-polarized light of the film. Y, x, and y in the CIE color system for the light source C are represented by calculated values.

また、式（１）、式（２）で表わされる色相の変化量Δｘ、Δｙは、フィルム面に垂直方向（０度）の入射偏光成分とフィルム面に垂直な方向から５０度斜め方向の入射偏光成分との色相ｘ、ｙの変化量の大きさを表わしており、透過Ｐ偏光の色相ずれに相当する。
かかる色相の変化量Δｘ、Δｙが上限値を超える場合、斜め方向の入射角による透過Ｐ偏光の色相ずれが大きく、輝度向上フィルムとして用いた場合に高視野角での色相ずれが大きく、視認性が低下することがある。 Further, the hue change amounts Δx and Δy represented by the equations (1) and (2) are incident on the incident polarization component perpendicular to the film surface (0 degree) and incident obliquely by 50 degrees from the direction perpendicular to the film surface. This represents the magnitude of the amount of change in hue x and y with respect to the polarization component, and corresponds to the hue shift of transmitted P-polarized light.
When the hue change amounts Δx and Δy exceed the upper limit, the hue shift of the transmitted P-polarized light due to the incident angle in the oblique direction is large, and when used as a brightness enhancement film, the hue shift at a high viewing angle is large and the visibility is high. May decrease.

また、本発明の１軸延伸多層積層フィルムは、入射面に対して垂直な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．０１以下であることが好ましく、さらに好ましくは０．００５以下、特に好ましくは０．００３以下である。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす） In the uniaxially stretched multilayer laminated film of the present invention, the hue change amounts Δx and Δy represented by the following formulas (1) and (2) are both 0.01 or less with respect to the polarization component perpendicular to the incident surface. Preferably, it is 0.005 or less, particularly preferably 0.003 or less.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y)

入射面に対して垂直な偏光成分（Ｓ偏光）に係る色相ｘ、ｙは、フィルムのＳ偏光について０°および５０°入射角で測定した透過スペクトルをもとに、ＪＩＳ規格Ｚ８７２９に準じて標準光源Ｃに対するＣＩＥ表色系におけるＹ、ｘ、ｙを求めた値で表わされる。   The hues x and y related to the polarization component perpendicular to the incident surface (S-polarized light) are standard according to JIS standard Z8729 based on transmission spectra measured at 0 ° and 50 ° incident angles for S-polarized light of the film. Y, x, and y in the CIE color system for the light source C are represented by calculated values.

また、色相の変化量Δｘ、Δｙは、フィルム面に垂直方向（０度）の入射偏光成分とフィルム面に垂直な方向から５０度斜め方向の入射偏光成分との色相ｘ、ｙの変化量の大きさを表わしており、透過Ｓ偏光の色相ずれに相当する。
かかる色相の変化量Δｘ、Δｙが上限値を超える場合、斜め方向の入射角による透過Ｓ偏光の色相ずれが大きく、輝度向上フィルムとして用いた場合に高視野角での色相ずれが大きく、視認性が低下することがある。
かかる色相変化量は、第１層、第２層を構成する熱可塑性樹脂として、それぞれ上述の特定のポリエステルを用いることにより達成される。 The hue change amounts Δx and Δy are the change amounts of the hue x and y between the incident polarized light component perpendicular to the film surface (0 degree) and the incident polarized light component inclined at 50 degrees from the direction perpendicular to the film surface. It represents the magnitude and corresponds to the hue shift of transmitted S-polarized light.
When the hue change amounts Δx and Δy exceed the upper limit, the hue shift of the transmitted S-polarized light due to the incident angle in the oblique direction is large, and when used as a brightness enhancement film, the hue shift at a high viewing angle is large and the visibility is high. May decrease.
Such a hue change amount is achieved by using the above-described specific polyester as the thermoplastic resin constituting the first layer and the second layer, respectively.

［ヒートシール層］
本発明の１軸延伸多層積層フィルムは、第１層と第２層との交互積層の少なくとも一方の最外層面上にさらにヒートシール層を設けることができる。ヒートシール層を有することにより、例えば液晶ディスプレイの部材として他の部材と積層させる際に、加熱処理により、ヒートシール層を介して部材同士を貼り合せることができる。 [Heat seal layer]
In the uniaxially stretched multilayer laminated film of the present invention, a heat seal layer can be further provided on at least one outermost layer surface of the alternate lamination of the first layer and the second layer. By having a heat seal layer, when laminating | stacking with another member as a member of a liquid crystal display, for example, members can be bonded together via a heat seal layer by heat processing.

かかるヒートシール層として、該交互積層の最外層の融点と同程度か該融点以下の熱可塑性樹脂を用いることが好ましいが、交互積層と同時に形成できる利点として、第２層と同じ熱可塑性樹脂を用いることが好ましい。さらに、該熱可塑性樹脂の融点が第１層の熱可塑性樹脂の融点より２０℃以上低く、かつ厚み３〜１０μｍの層であることが好ましい。かかる融点でかつ該層厚みを有することにより、ヒートシール層として部材同士を強固に接着することができる。   As such a heat seal layer, it is preferable to use a thermoplastic resin having a melting point equal to or lower than the melting point of the outermost layer of the alternately laminated layers, but as an advantage that can be formed simultaneously with the alternately laminated layers, the same thermoplastic resin as the second layer is used. It is preferable to use it. Furthermore, it is preferable that the thermoplastic resin has a melting point of 20 ° C. or more lower than the melting point of the thermoplastic resin of the first layer and has a thickness of 3 to 10 μm. By having the melting point and the layer thickness, the members can be firmly bonded as a heat seal layer.

ヒートシール層として第２層と同じ熱可塑性樹脂を用いる場合、かかるヒートシール層は層厚みが３〜１０μｍであり、このような交互積層層を構成する層の最大厚みである０．５μｍに比して４倍以上の厚みの層は、波長４００〜８００ｎｍの波長帯での反射率に寄与しない層であり、第１層と第２層の交互積層とは区別される。
また、ヒートシール層としての特性を損なわない範囲で、第１の層および第２層のブレンド物を使用しても問題ない。 When the same thermoplastic resin as the second layer is used as the heat seal layer, the heat seal layer has a layer thickness of 3 to 10 μm, which is compared with 0.5 μm which is the maximum thickness of the layers constituting such an alternately laminated layer. Thus, the layer having a thickness of 4 times or more is a layer that does not contribute to the reflectance in the wavelength band of 400 to 800 nm, and is distinguished from the alternate lamination of the first layer and the second layer.
Moreover, even if it uses the blend of the 1st layer and the 2nd layer in the range which does not impair the characteristic as a heat seal layer, it is satisfactory.

［輝度向上フィルム］
本発明の１軸延伸多層積層フィルムは、Ｐ偏光成分を選択的に高反射し、該偏光成分と垂直方向のＳ偏光成分を選択的に高透過させ、かつ斜め方向に入射した光についての透過偏光の色相ずれが解消されることから、液晶ディスプレイの輝度向上フィルムとして好適に使用することができ、加工して輝度向上用部材にすることができる。特に従来よりも高い偏光性能を有することから、輝度向上フィルムとして用いた場合に高い輝度向上率が得られ、かつ高視野角で色相ずれの少ない視認性に優れた液晶ディスプレイを提供することができ、しかもフィルム厚みを４０μｍ以下にできる。 [Brightness enhancement film]
The uniaxially stretched multilayer laminated film of the present invention selectively reflects the P-polarized component with high reflection, selectively transmits the S-polarized component perpendicular to the polarized component, and transmits light incident in an oblique direction. Since the deviation of the hue of polarized light is eliminated, it can be suitably used as a brightness enhancement film for liquid crystal displays, and can be processed into a brightness enhancement member. In particular, since it has higher polarization performance than before, it can provide a high brightness improvement rate when used as a brightness enhancement film, and can provide a liquid crystal display excellent in visibility with a high viewing angle and little hue shift. Moreover, the film thickness can be made 40 μm or less.

［液晶ディスプレイ用複合部材］
本発明の１軸延伸多層積層フィルムを用いて作成された輝度向上用部材は、さらにその少なくとも一方の面に光拡散フィルムを積層し、液晶ディスプレイ用複合部材として使用されることが好ましい。また、輝度向上用部材と光拡散フィルムとはヒートシール層を介して貼り合せて積層されることが好ましい。従来は、８００層以上の層構成で使用され、複合部材としての合計厚みが１００ミクロン程度であったが、本発明の液晶ディスプレイ用複合部材の層構成を採用することにより、複合部材としての合計厚みを５０ミクロン程度に薄くすることが可能となり、液晶ディスプレイの薄肉化が可能となる。 [Composite materials for liquid crystal displays]
It is preferable that the brightness enhancement member prepared using the uniaxially stretched multilayer laminate film of the present invention is further used by laminating a light diffusion film on at least one surface thereof and used as a composite member for a liquid crystal display. Moreover, it is preferable that the brightness enhancement member and the light diffusion film are laminated by being bonded via a heat seal layer. Conventionally, it was used in a layer configuration of 800 layers or more, and the total thickness as a composite member was about 100 microns, but by adopting the layer configuration of the composite member for liquid crystal display of the present invention, the total as a composite member The thickness can be reduced to about 50 microns, and the liquid crystal display can be made thinner.

また、本発明の液晶ディスプレイ用複合部材は、輝度向上用部材の少なくとも一方の面に光拡散フィルムを積層し、該光拡散フィルムを介して輝度向上用部材と反対側にさらにプリズム層を有する層構成も好ましく例示される。かかる層構成を有することにより、従来の８００層以上の層構成の複合部材と比べて、ディスプレイの薄膜化が実現できると同時に輝度向上性能も高まる。   In the composite member for a liquid crystal display according to the present invention, the light diffusion film is laminated on at least one surface of the brightness enhancement member, and a prism layer is further provided on the opposite side of the brightness enhancement member via the light diffusion film. The configuration is also preferably exemplified. By having such a layer structure, the display can be made thinner and at the same time the brightness enhancement performance is enhanced as compared with the conventional composite member having a layer structure of 800 layers or more.

［１軸延伸多層積層フィルムの製造方法］
つぎに、本発明の１軸延伸多層積層フィルムの製造方法について詳述する。
本発明の１軸延伸多層積層フィルムは、第１層を構成する熱可塑性樹脂と第２層を構成する熱可塑性樹脂とを溶融状態で交互に少なくとも２５１層以上重ね合わせた状態で押出し、多層未延伸フィルム（シート状物とする工程）とする。このとき、積層された２５１層以上の積層物は、各層の厚みが段階的または連続的に２．０倍〜５．０倍の範囲で変化するように積層される。 [Method for producing uniaxially stretched multilayer laminated film]
Below, the manufacturing method of the uniaxially stretched multilayer laminated film of this invention is explained in full detail.
The uniaxially stretched multilayer laminated film of the present invention is extruded in a state where at least 251 layers or more of the thermoplastic resin constituting the first layer and the thermoplastic resin constituting the second layer are alternately superposed in the molten state. It is set as a stretched film (process made into a sheet-like material). At this time, the laminated body of 251 layers or more laminated | stacked so that the thickness of each layer may change in the range of 2.0 times-5.0 times in steps or continuously.

このようにして得られた多層未延伸フィルムは、製膜方向、またはそれに直交する幅方向の少なくとも１軸方向（フィルム面に沿った方向）に延伸される。延伸温度は、第１層の熱可塑性樹脂のガラス転移点の温度（Ｔｇ）〜Ｔｇ＋５０℃の範囲が好ましい。このときの延伸倍率は２〜１０倍であることが好ましく、さらに好ましくは２．５〜７倍、さらいに好ましくは３〜６倍、特に好ましくは４．５〜５．５倍である。延伸倍率が大きい程、第１層および第２層における個々の層の面方向のバラツキが、延伸による薄層化により小さくなり、多層延伸フィルムの光干渉が面方向に均一になり、また第１層と第２層の延伸方向の屈折率差が大きくなるので好ましい。このときの延伸方法は、棒状ヒータによる加熱延伸、ロール加熱延伸、テンター延伸など公知の延伸方法を用いることができるが、ロールとの接触によるキズの低減や延伸速度などの観点から、テンター延伸が好ましい。また、かかる延伸方向と直交する方向（Ｙ方向）にも延伸処理を施し、２軸延伸を行う場合は、１．０５〜１．２０倍程度の延伸倍率にとどめることが好ましい。Ｙ方向の延伸倍率をこれ以上高くすると、偏光性能が低下することがある。また、延伸後にさらに熱固定処理を施すことが好ましい。   The multilayer unstretched film thus obtained is stretched in the film forming direction or at least one axial direction (direction along the film surface) in the width direction perpendicular thereto. The stretching temperature is preferably in the range of the temperature (Tg) to Tg + 50 ° C. of the glass transition point of the thermoplastic resin of the first layer. The draw ratio at this time is preferably 2 to 10 times, more preferably 2.5 to 7 times, further preferably 3 to 6 times, and particularly preferably 4.5 to 5.5 times. The larger the draw ratio, the smaller the variation in the plane direction of the individual layers in the first layer and the second layer due to the thinning by stretching, and the light interference of the multilayer stretched film becomes uniform in the plane direction. This is preferable because the difference in refractive index between the layers and the second layer in the stretching direction becomes large. As the stretching method at this time, a known stretching method such as heat stretching with a rod heater, roll heating stretching, and tenter stretching can be used, but from the viewpoint of reduction of scratches due to contact with the roll and stretching speed, tenter stretching is performed. preferable. Moreover, when performing a extending | stretching process also in the direction (Y direction) orthogonal to this extending | stretching direction and performing biaxial stretching, it is preferable to limit to a draw ratio of about 1.05-1.20 times. If the stretch ratio in the Y direction is further increased, the polarization performance may be deteriorated. Moreover, it is preferable to perform a heat setting process after extending | stretching.

実施例をもって、本発明をさらに説明する。なお、実施例中の物性や特性は、下記の方法にて測定または評価した。   The invention is further described by way of examples. In addition, the physical property and characteristic in an Example were measured or evaluated by the following method.

（１）熱可塑性樹脂およびフィルムの融点（Ｔｍ）およびガラス転移点（Ｔｇ）
ポリマー試料またはフィルムサンプルを１０ｍｇサンプリングし、ＤＳＣ（ＴＡインスツルメンツ社製、商品名：ＤＳＣ２９２０）を用い、２０℃／ｍｉｎ．の昇温速度で、融点およびガラス転移点を測定する。 (1) Melting point (Tm) and glass transition point (Tg) of thermoplastic resin and film
10 mg of a polymer sample or a film sample was sampled, and a DSC (manufactured by TA Instruments, trade name: DSC2920) was used. The melting point and the glass transition point are measured at a temperature rising rate of.

（２）熱可塑性樹脂の特定ならびに共重合成分および各成分量の特定
フィルムサンプルの各層について、１Ｈ−ＮＭＲ測定より熱可塑性樹脂の成分ならびに共重合成分および各成分量を特定した。 (2) Identification of thermoplastic resin and identification of copolymer component and amount of each component For each layer of the film sample, the component of the thermoplastic resin, the copolymer component and the amount of each component were identified by 1 H-NMR measurement.

（３）各層の厚み
フィルムサンプルをフィルム長手方向２ｍｍ、幅方向２ｃｍに切り出し、包埋カプセルに固定後、エポキシ樹脂（リファインテック（株）製エポマウント）にて包埋した。包埋されたサンプルをミクロトーム（ＬＥＩＣＡ製ＵＬＴＲＡＣＵＴ ＵＣＴ）で幅方向に垂直に切断し、５ｎｍ厚の薄膜切片にした。透過型電子顕微鏡（日立Ｓ−４３００）を用いて加速電圧１００ｋＶにて観察撮影し、写真から各層の厚みを測定した。
また、得られた各層の厚みをもとに、第１層における最小層厚みに対する最大層厚みの比率、第２層における最小層厚みに対する最大層厚みの比率をそれぞれ求めた。
また、得られた各層の厚みをもとに、第１層の平均層厚み、第２層の平均層厚みをそれぞれ求め、第１層の平均層厚みに対する第２層の平均層厚みを算出した。
なお、最外層のヒートシール層は第１層と第２層から除外した。また交互積層中に２μｍ以上の厚み調整層が存在する場合は、かかる層も第１層と第２層から除外した。 (3) Thickness of each layer A film sample was cut into a film length direction of 2 mm and a width direction of 2 cm, fixed to an embedding capsule, and then embedded with an epoxy resin (Refotech Co., Ltd. Epomount). The embedded sample was cut perpendicularly in the width direction with a microtome (LETRAC ULCT UCT manufactured by LEICA) to form a thin film slice having a thickness of 5 nm. Using a transmission electron microscope (Hitachi S-4300), the film was observed and photographed at an acceleration voltage of 100 kV, and the thickness of each layer was measured from the photograph.
Moreover, based on the thickness of each obtained layer, the ratio of the maximum layer thickness to the minimum layer thickness in the first layer and the ratio of the maximum layer thickness to the minimum layer thickness in the second layer were determined.
Moreover, based on the thickness of each obtained layer, the average layer thickness of the first layer and the average layer thickness of the second layer were determined, respectively, and the average layer thickness of the second layer relative to the average layer thickness of the first layer was calculated. .
The outermost heat seal layer was excluded from the first layer and the second layer. Further, when a thickness adjusting layer having a thickness of 2 μm or more exists in the alternate lamination, such a layer was also excluded from the first layer and the second layer.

（４）フィルム全体厚み
フィルムサンプルをスピンドル検出器（安立電気（株）製Ｋ１０７Ｃ）にはさみ、デジタル差動電子マイクロメーター（安立電気（株）製Ｋ３５１）にて、異なる位置で厚みを１０点測定し、平均値を求めフィルム厚みとした。 (4) Total film thickness A film sample is sandwiched between spindle detectors (K107C manufactured by Anritsu Electric Co., Ltd.), and 10 points of thickness are measured at different positions using a digital differential electronic micrometer (K351 manufactured by Anritsu Electric Co., Ltd.). Then, the average value was obtained and used as the film thickness.

（５）各方向の延伸前、延伸後の屈折率および平均屈折率
各層を構成する個々の樹脂について、それぞれ溶融させてダイより押出し、キャスティングドラム上にキャストしたフィルムをそれぞれ用意した。また、得られたフィルムを１３５℃にて一軸方向に５倍延伸した延伸フィルムを用意した。得られたキャストフィルムと延伸フィルムについて、それぞれ延伸方向（Ｘ方向）とその直交方向（Ｙ方向）、厚み方向（Ｚ方向）のそれぞれの屈折率（それぞれｎＸ、ｎＹ、ｎＺとする）を、メトリコン製プリズムカプラを用いて波長６３３ｎｍにおける屈折率を測定して求め、延伸前、延伸後の屈折率とした。平均屈折率については、延伸前のそれぞれの屈折率の平均値を平均屈折率とした。 (5) Refractive index and average refractive index before stretching in each direction and average refractive index Each resin constituting each layer was melted and extruded from a die, and a film cast on a casting drum was prepared. Further, a stretched film was prepared by stretching the obtained film at 135 ° C. in a uniaxial direction 5 times. About the obtained cast film and stretched film, the respective refractive indexes in the stretching direction (X direction), the orthogonal direction (Y direction), and the thickness direction (Z direction) (referred to as n X , n Y , and n Z respectively). Was determined by measuring the refractive index at a wavelength of 633 nm using a metricon prism coupler, and the refractive index was determined before and after stretching. About average refractive index, the average value of each refractive index before extending | stretching was made into the average refractive index.

（６）反射率、反射波長
分光光度計（島津製作所製、ＭＰＣ−３１００）を用い、光源側に偏光フィルタを装着し、各波長でのアルミ蒸着したミラーとの相対鏡面反射率を波長４００ｎｍから８００ｎｍの範囲で測定する。このとき、偏光フィルタの透過軸をフィルムの延伸方向（Ｘ方向）と合わせるように配置した場合の測定値をＰ偏光とし、偏光フィルタの透過軸をフィルムの延伸方向と直交するように配置した場合の測定値をＳ偏光とした。それぞれの偏光成分について、４００−８００ｎｍの範囲での反射率の平均値を平均反射率とした。 (6) Reflectivity, reflection wavelength Using a spectrophotometer (manufactured by Shimadzu Corporation, MPC-3100), a polarizing filter is mounted on the light source side, and the relative specular reflectivity with respect to the aluminum-deposited mirror at each wavelength is measured from a wavelength of 400 nm. Measure in the range of 800 nm. In this case, the measured value when the transmission axis of the polarizing filter is aligned with the film stretching direction (X direction) is P-polarized light, and the transmission axis of the polarizing filter is disposed perpendicular to the film stretching direction. Was measured as S-polarized light. For each polarization component, the average reflectance in the range of 400 to 800 nm was defined as the average reflectance.

（７）色相
サンプルフィルムのＰ偏光およびＳ偏光それぞれについて、０°および５０°の入射角で測定した透過スペクトルから、ＪＩＳＺ８７２９に準じて標準光源Ｃに対するＣＩＥ表色系におけるＹ，ｘ，ｙを求めた。また、Ｐ偏光およびＳ偏光それぞれについて、０°および５０°のｘ、ｙについての差異（色相の変化量）を下記の式（１）、（２）により求めた。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす） (7) Hue For each of the P-polarized light and S-polarized light of the sample film, Y, x, and y in the CIE color system for the standard light source C are obtained from the transmission spectrum measured at an incident angle of 0 ° and 50 ° according to JISZ8729. It was. In addition, for each of P-polarized light and S-polarized light, a difference (amount of change in hue) for x and y at 0 ° and 50 ° was obtained by the following equations (1) and (2).
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y)

（８）輝度向上効果
積層体サンプルフィルムをＬＣＤパネル（三菱電機製Diamond Crysta RDT158V-N 2004年製）中の偏光板との間に挿入し、ＰＣにて白色を表示したときの正面輝度を５００ｍｍ離れた場所からトプコン製輝度計（BM-7）で測定し、サンプルフィルム挿入前の輝度に対するサンプルフィルム挿入後の輝度の上昇率を算出し、輝度向上効果を評価した。 (8) Brightness improvement effect The laminated sample film is inserted between the polarizing plates in the LCD panel (Diamond Crysta RDT158V-N 2004 manufactured by Mitsubishi Electric Corporation), and the front brightness when displaying white on the PC is 500 mm. The luminance was measured with a Topcon luminance meter (BM-7) from a remote location, and the rate of increase in luminance after inserting the sample film relative to the luminance before inserting the sample film was calculated to evaluate the effect of improving luminance.

（９）ヒートシール強度
フィルムのヒートシール面同士を合せて、チャック掴み代を残して、１４０℃、２７５ｋＰａにて２秒間圧着し、ラミネートサンプルを作成した。得られたラミネートサンプルを２５ｍｍ幅にスリットし、引張試験機（東洋ボールドウィン社製の商品名「テンシロン」）のクロスヘッドのチャックに掴み代を挟み、たるみの無いようにクロスヘッド位置を調整した。１００ｍｍ／分のクロスヘッド速度で引張り、ラミネートサンプルを剥離させて試験機に装着されたロードセルで荷重を測定して、ヒートシール強度（単位：Ｎ／２５ｍｍ）とした。 (9) Heat seal strength The heat seal surfaces of the films were put together, leaving a chuck grip, and pressure-bonded at 140 ° C. and 275 kPa for 2 seconds to prepare a laminate sample. The obtained laminate sample was slit to a width of 25 mm, and the position of the crosshead was adjusted so as not to sag by sandwiching the grip margin with the chuck of the crosshead of a tensile tester (trade name “Tensilon” manufactured by Toyo Baldwin). The laminate was pulled at a crosshead speed of 100 mm / min, the laminate sample was peeled off, and the load was measured with a load cell attached to a testing machine to obtain heat seal strength (unit: N / 25 mm).

［実施例１］
２，６−ナフタレンジカルボン酸ジメチル、６，６’−（エチレンジオキシ）ジ−２−ナフトエ酸、そしてエチレングリコールとを、チタンテトラブトキシドの存在下でエステル化反応およびエステル交換反応を行い、さらに引き続いて重縮合反応を行って、固有粘度０．６２ｄｌ／ｇで、酸成分の６５モル％が２，６−ナフタレンジカルボン酸成分（表中、ＰＥＮと記載）、酸成分の３５モル％が６，６’−（エチレンジオキシ）ジ−２−ナフトエ酸成分（表中、ＥＮＡと記載）、グリコール成分がエチレングリコールである芳香族ポリエステルを得た。これに真球状シリカ粒子（平均粒径：０．３μｍ、長径と短径の比：１．０２、粒径の平均偏差：０．１）を第１層の重量を基準として０．１０ｗｔ％添加したものを第１層用熱可塑性樹脂とし、第２層用熱可塑性樹脂として固有粘度（オルトクロロフェノール、３５℃）０．６２ｄｌ／ｇのイソフタル酸２０ｍｏｌ％共重合ポリエチレンテレフタレート（ＩＡ２０ＰＥＴ）を準備した。 [Example 1]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, and ethylene glycol are subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and Subsequently, a polycondensation reaction was performed, and the intrinsic viscosity was 0.62 dl / g, 65 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component (described as PEN in the table), and 35 mol% of the acid component was 6 mol%. , 6 '-(ethylenedioxy) di-2-naphthoic acid component (described as ENA in the table) and an aromatic polyester whose glycol component is ethylene glycol. To this, 0.10 wt% of spherical silica particles (average particle size: 0.3 μm, ratio of major axis to minor axis: 1.02, average deviation of particle size: 0.1) based on the weight of the first layer This was used as a thermoplastic resin for the first layer, and 20 mol% of isophthalic acid copolymerized polyethylene terephthalate (IA20PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g was prepared as the thermoplastic resin for the second layer. .

準備した第１層用ポリエステルおよび第２層用ポリエステルを、それぞれ１７０℃で５時間乾燥後、第１、第２の押出機に供給し、３００℃まで加熱して溶融状態とし、第１層用ポリエステルを１３７層、第２層用ポリエステルを１３８層に分岐させた後、第１層と第２層が交互に積層され、かつ第１層と第２層におけるそれぞれの最大層厚みと最小層厚みが最大／最小で２．２倍まで連続的に変化するような多層フィードブロック装置を使用して、第１層と第２層が交互に積層された総数２７５層の積層状態の溶融体とし、その積層状態を保持したまま、その両側に第３の押出機から第２層用ポリエステルと同じポリエステルを３層ダイへと導き、総数２７５層の積層状態の溶融体の両側にヒートシール層をさらに積層した。両端層（ヒートシール層）は、全体の１８％なるよう第３の押出機の供給量を調整した。その積層状態を保持したままダイへと導き、キャスティングドラム上にキャストして、第１層と第２層の平均層厚み比が１．０：２．６になるように調整し、総数２７７層の未延伸多層積層フィルムを作成した。   The prepared polyester for the first layer and polyester for the second layer are each dried at 170 ° C. for 5 hours, then supplied to the first and second extruders, heated to 300 ° C. to be in a molten state, and used for the first layer After branching the polyester to 137 layers and the second layer polyester to 138 layers, the first layer and the second layer are alternately laminated, and the maximum layer thickness and the minimum layer thickness of the first layer and the second layer, respectively. Using a multi-layer feedblock device in which the maximum value is continuously changed up to 2.2 times at the minimum, and a total of 275 layers of the melt in which the first layer and the second layer are alternately stacked, While maintaining the laminated state, the same polyester as the second layer polyester is led from the third extruder to the three-layer die on both sides thereof, and a heat seal layer is further provided on both sides of the melt in the laminated state of 275 layers in total. Laminated. The supply amount of the third extruder was adjusted so that both end layers (heat seal layers) were 18% of the whole. The laminated state is led to a die, cast on a casting drum, adjusted so that the average layer thickness ratio of the first layer and the second layer is 1.0: 2.6, and a total of 277 layers. An unstretched multilayer laminated film was prepared.

この多層未延伸フィルムを１３５℃の温度で幅方向に５．２倍に延伸し、１４０℃で３秒間熱固定処理を行った。得られたフィルムの厚みは３３μｍであった。
得られた１軸延伸多層積層フィルムの各層の樹脂構成、各層の特徴を表１に、また物性を表２に示す。
また、得られた１軸延伸多層積層フィルムを光拡散フィルム（恵和株式会社製：オパルスＢＳ−９１２）のバックコート面と１４０℃、２７５ｋＰａにて２秒間圧着して貼り合わせて積層体フィルムを得た。 This multilayer unstretched film was stretched 5.2 times in the width direction at a temperature of 135 ° C., and heat-set at 140 ° C. for 3 seconds. The thickness of the obtained film was 33 μm.
Table 1 shows the resin composition of each layer of the obtained uniaxially stretched multilayer laminated film, the characteristics of each layer, and Table 2 shows the physical properties.
Further, the obtained uniaxially stretched multilayer laminated film was bonded to the back coat surface of a light diffusion film (Eiwa Co., Ltd .: Opulse BS-912) by pressure bonding at 140 ° C. and 275 kPa for 2 seconds to bond the laminated film. Obtained.

［実施例２、３］
表１に示すとおり、各層の樹脂組成を変更した以外は、実施例１と同様にして１軸延伸多層積層フィルムを得た。得られた１軸延伸多層積層フィルムの物性を表２に示す。また、得られた１軸延伸多層積層フィルムを光拡散フィルム（恵和株式会社製：オパルスＢＳ−９１２）のバックコート面と１４０℃、２７５ｋＰａにて２秒間圧着して貼り合わせて積層体フィルムを得た。
なお、実施例２で第２層用ポリエステルとして用いたＮＤＣ２０ＰＥＴとは、実施例１の第２層用ポリエステルとして用いたイソフタル酸２０ｍｏｌ％共重合ポリエチレンテレフタレート（ＩＡ２０ＰＥＴ）の共重合成分を２，６−ナフタレンジカルボン酸に変更した共重合ポリエステルである。 [Examples 2 and 3]
As shown in Table 1, a uniaxially stretched multilayer laminated film was obtained in the same manner as in Example 1 except that the resin composition of each layer was changed. Table 2 shows the physical properties of the obtained uniaxially stretched multilayer laminated film. Further, the obtained uniaxially stretched multilayer laminated film was bonded to the back coat surface of a light diffusion film (Eiwa Co., Ltd .: Opulse BS-912) by pressure bonding at 140 ° C. and 275 kPa for 2 seconds to bond the laminated film. Obtained.
In addition, NDC20PET used as the second layer polyester in Example 2 is a copolymer component of 20 mol% isophthalic acid copolymerized polyethylene terephthalate (IA20PET) used as the second layer polyester in Example 1 with 2,6- It is a copolyester changed to naphthalenedicarboxylic acid.

［実施例４］
第１層用ポリエステルをポリエチレン−２，７−ナフタレンジカルボキシレートとし、第２層用ポリエステルを表１に示すとおりに変更し、層厚みを表１に示すように変更した以外は実施例１と同様の操作を行い、１軸延伸多層積層フィルムを作成した。得られた１軸延伸多層積層フィルムの各層の樹脂構成、各層の特徴を表１に、また物性を表２に示す。
また、得られた１軸延伸多層積層フィルムの片面に光拡散フィルム（恵和株式会社製：オパルスＢＳ−９１２）のバックコート面を、反対面にプリズムシート（三菱レーヨン製：「ダイヤアート」Yタイプ（M268Y））のバックコート面をはさみ１４０℃、２７５ｋＰａにて２秒間圧着して貼り合わせて積層体フィルムを得た。得られた積層体フィルムを用いて輝度向上効果を測定したところ、１９５％の輝度向上効果が得られた。 [Example 4]
Example 1 except that the polyester for the first layer was polyethylene-2,7-naphthalene dicarboxylate, the polyester for the second layer was changed as shown in Table 1, and the layer thickness was changed as shown in Table 1. The same operation was performed to prepare a uniaxially stretched multilayer laminated film. Table 1 shows the resin composition of each layer of the obtained uniaxially stretched multilayer laminated film, the characteristics of each layer, and Table 2 shows the physical properties.
In addition, a back coat surface of a light diffusion film (Eiwa Co., Ltd .: Opulse BS-912) is provided on one side of the obtained uniaxially stretched multilayer laminated film, and a prism sheet (Made by Mitsubishi Rayon: “Diaart” Y) The back coat surface of the type (M268Y) was sandwiched and bonded together at 140 ° C. and 275 kPa for 2 seconds to obtain a laminate film. When the brightness enhancement effect was measured using the obtained laminate film, a brightness improvement effect of 195% was obtained.

［比較例１］
第１層用熱可塑性樹脂を固有粘度（オルトクロロフェノール、３５℃）０．６２ｄｌ／ｇのポリエチレン−２，６−ナフタレンジカルボキシレート（ＰＥＮ）、第２層用熱可塑性樹脂を固有粘度（オルトクロロフェノール、３５℃）０．６２ｄｌ／ｇのテレフタル酸６４ｍｏｌ％共重合ポリエチレン−２，６−ナフタレンジカルボキシレート（ＴＡ６４ＰＥＮ）に変更し、表１に示す製造条件に変更する以外は実施例１と同様にして１軸延伸多層積層フィルムを得た。得られた１軸延伸多層積層フィルムの各層の樹脂構成、各層の特徴を表１に、また物性を表２に示す。
得られた１軸延伸多層積層フィルムは、Ｓ偏光の平均反射率が入射角０°、５０°ともに１５％を超えており、偏光性能が実施例に比べて低下した。またＰ偏光のΔｘの色相変化量が実施例に比べて大きく、色相ずれが生じた。 [Comparative Example 1]
The thermoplastic resin for the first layer is made of polyethylene-2,6-naphthalenedicarboxylate (PEN) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g, and the thermoplastic resin for the second layer is made of intrinsic viscosity (ortho Chlorophenol, 35 ° C.) Example 1 with the exception of changing to 0.62 dl / g terephthalic acid 64 mol% copolymerized polyethylene-2,6-naphthalenedicarboxylate (TA64PEN) and changing to the production conditions shown in Table 1. Similarly, a uniaxially stretched multilayer laminated film was obtained. Table 1 shows the resin composition of each layer of the obtained uniaxially stretched multilayer laminated film, the characteristics of each layer, and Table 2 shows the physical properties.
In the obtained uniaxially stretched multilayer laminated film, the average reflectance of S-polarized light exceeded 15% at both incident angles of 0 ° and 50 °, and the polarization performance was deteriorated as compared with Examples. Further, the amount of hue change of Δx of P-polarized light was larger than that of the example, and a hue shift occurred.

［比較例２］
表１に示すとおり、樹脂組成と製造条件を変更した以外は実施例１と同様にして、１軸延伸多層積層フィルムを得た。得られた１軸延伸多層積層フィルムの各層の樹脂構成、各層の特徴を表１に、また物性を表２に示す。得られたフィルムは実施例に比べて偏光性能が低下した。またＳ偏光の色相変化量が大きく色相ずれが生じた。 [Comparative Example 2]
As shown in Table 1, a uniaxially stretched multilayer laminated film was obtained in the same manner as in Example 1 except that the resin composition and production conditions were changed. Table 1 shows the resin composition of each layer of the obtained uniaxially stretched multilayer laminated film, the characteristics of each layer, and Table 2 shows the physical properties. The obtained film had lower polarization performance than the Examples. Further, the hue change amount of S-polarized light was large, and a hue shift occurred.

本発明によれば、本発明の１軸延伸多層積層フィルムは従来の反射偏光フィルムで見られた斜め方向の入射角による透過偏光の色相ずれが解消され、しかも従来よりも高い偏光性能を有することから、輝度向上フィルムとして用いた場合に高い輝度向上率が得られ、かつ高視野角で色相ずれの少ない視認性に優れた液晶ディスプレイが提供できる。   According to the present invention, the uniaxially stretched multilayer laminated film of the present invention eliminates the hue shift of transmitted polarized light due to the oblique incident angle seen in the conventional reflective polarizing film, and has higher polarization performance than before. Therefore, when used as a brightness enhancement film, a high brightness improvement rate can be obtained, and a liquid crystal display excellent in visibility with a high viewing angle and little hue shift can be provided.

Claims (17)

第１層と第２層とが交互に積層された２５１層以上の１軸延伸多層積層フィルムであり、
１）第１層を構成する熱可塑性樹脂が平均屈折率１．６０以上１．７０以下であって、１軸延伸方向（Ｘ方向）の屈折率ｎXが延伸により増大し、フィルム面内で１軸延伸方向に直交する方向（Ｙ方向）の屈折率ｎYおよびフィルム厚み方向（Ｚ方向）の屈折率ｎZが延伸により低下する熱可塑性樹脂であり、
２）第２層を構成する熱可塑性樹脂が平均屈折率１．５０以上１．６０以下であって、Ｘ方向、Ｙ方向およびＺ方向のそれぞれの屈折率差が延伸前後で０．０５以下である熱可塑性樹脂であり、
３）第１層および第２層の各層の厚みが０．０１μｍ以上０．５μｍ以下であって、かつ第１層および第２層におけるそれぞれの最大層厚みと最小層厚みの比率がいずれも２．０以上５．０以下であり、
４）フィルム面を反射面とし、Ｘ方向を含む入射面に対して平行な偏光成分について入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ９０％以上であり、
５）フィルム面を反射面とし、Ｘ方向を含む入射面に対して垂直な偏光成分について、入射角０度および５０度での該入射偏光に対する波長４００〜８００ｎｍの平均反射率がそれぞれ１５％以下
であることを特徴とする１軸延伸多層積層フィルム。 A uniaxially stretched multilayer laminated film having 251 layers or more in which the first layer and the second layer are alternately laminated,
1) The thermoplastic resin constituting the first layer has an average refractive index of 1.60 or more and 1.70 or less, and the refractive index n X in the uniaxial stretching direction (X direction) is increased by stretching. a thermoplastic resin having a refractive index n Z of the refractive index n Y and the film thickness direction (Y direction) perpendicular to the uniaxial stretching direction (Z-direction) is reduced by stretching,
2) The thermoplastic resin constituting the second layer has an average refractive index of 1.50 or more and 1.60 or less, and the respective refractive index differences in the X direction, Y direction and Z direction are 0.05 or less before and after stretching. A thermoplastic resin,
3) The thickness of each layer of the first layer and the second layer is 0.01 μm or more and 0.5 μm or less, and the ratio between the maximum layer thickness and the minimum layer thickness in each of the first layer and the second layer is 2 0.0 or more and 5.0 or less,
4) The average reflectance of the wavelength 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degrees and 50 degrees with respect to the polarized light component parallel to the incident surface including the X direction is 90% or more with the film surface as the reflecting surface. Yes,
5) With respect to the polarized light component perpendicular to the incident surface including the X direction, with the film surface as the reflective surface, the average reflectance at a wavelength of 400 to 800 nm with respect to the incident polarized light at an incident angle of 0 degrees and 50 degrees is 15% or less, respectively. A uniaxially stretched multilayer laminated film characterized by 第２層を形成する熱可塑性樹脂が、イソフタル酸もしくは２，６−ナフタレンジカルボン酸を共重合したエチレンテレフタレート成分を主たる成分とするポリエステルである請求項１に記載の１軸延伸多層積層フィルム。   The uniaxially stretched multilayer laminate film according to claim 1, wherein the thermoplastic resin forming the second layer is a polyester mainly composed of an ethylene terephthalate component copolymerized with isophthalic acid or 2,6-naphthalenedicarboxylic acid. 第１層と第２層のＸ方向の屈折率差が０．１０〜０．４５である請求項１または２に記載の１軸延伸多層積層フィルム。   The uniaxially stretched multilayer laminated film according to claim 1 or 2, wherein a difference in refractive index between the first layer and the second layer in the X direction is 0.10 to 0.45. 第１層と第２層のＹ方向の屈折率差および第１層と第２層のＺ方向の屈折率差がそれぞれ０．０５以下である請求項１〜３のいずれかに記載の１軸延伸多層積層フィルム。   The uniaxial axis according to any one of claims 1 to 3, wherein a difference in refractive index in the Y direction between the first layer and the second layer and a difference in refractive index in the Z direction between the first layer and the second layer are each 0.05 or less. Stretched multilayer laminated film. フィルム厚みが１５μｍ以上４０μｍ以下である請求項１〜４のいずれかに記載の１軸延伸多層積層フィルム。   The uniaxially stretched multilayer laminated film according to claim 1, wherein the film thickness is 15 μm or more and 40 μm or less. 入射面に対して平行な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．１以下である請求項１〜５のいずれかに記載の１軸延伸多層積層フィルム。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす） 6. The hue change amounts Δx and Δy represented by the following formulas (1) and (2) are both equal to or less than 0.1 for the polarization component parallel to the incident surface. Uniaxially stretched multilayer laminated film.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y) 入射面に対して垂直な偏光成分について、下記式（１）、（２）で表わされる色相の変化量Δｘ、Δｙがいずれも０．０１以下である請求項１〜６のいずれかに記載の１軸延伸多層積層フィルム。
Δｘ＝ｘ（０°）−ｘ（５０°） ・・・（１）
（上式（１）中、ｘ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｘを表わし、ｘ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｘを表わす）
Δｙ＝ｙ（０°）−ｙ（５０°） ・・・（２）
（上式（２）中、ｙ（０°）は入射角０度での該入射偏光の透過スペクトルの色相ｙを表わし、ｙ（５０°）は入射角５０度での該入射偏光の透過スペクトルの色相ｙを表わす） 7. The hue change amounts Δx and Δy represented by the following formulas (1) and (2) are both 0.01 or less for the polarization component perpendicular to the incident surface. Uniaxially stretched multilayer laminated film.
Δx = x (0 °) −x (50 °) (1)
(In the above formula (1), x (0 °) represents the hue x of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and x (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents hue x)
Δy = y (0 °) −y (50 °) (2)
(In the above formula (2), y (0 °) represents the hue y of the transmission spectrum of the incident polarized light at an incident angle of 0 degrees, and y (50 °) represents the transmission spectrum of the incident polarized light at an incident angle of 50 degrees. Represents the hue y) 第１層の平均層厚みに対する第２層の平均層厚みの比が１．５倍以上５．０倍以下の範囲である請求項１〜７のいずれかに記載の１軸延伸多層積層フィルム。   The ratio of the average layer thickness of the second layer to the average layer thickness of the first layer is in the range of 1.5 to 5.0 times, and the uniaxially stretched multilayer laminated film according to any one of claims 1 to 7. 第１層と第２層との交互積層の少なくとも一方の最外層面上にさらにヒートシール層が設けられてなる請求項１〜８のいずれかに記載の１軸延伸多層積層フィルム。   The uniaxially stretched multilayer laminated film according to any one of claims 1 to 8, wherein a heat seal layer is further provided on at least one outermost layer surface of the alternate lamination of the first layer and the second layer. ヒートシール層が第２層と同じ熱可塑性樹脂からなり、該熱可塑性樹脂の融点が第１層の熱可塑性樹脂の融点より２０℃以上低く、かつ厚み３〜１０μｍの層である請求項９に記載の１軸延伸多層積層フィルム。   The heat seal layer is made of the same thermoplastic resin as that of the second layer, and the melting point of the thermoplastic resin is 20 ° C. lower than the melting point of the thermoplastic resin of the first layer and has a thickness of 3 to 10 μm. The uniaxially stretched multilayer laminated film described. 液晶ディスプレイの輝度向上フィルムとして用いられる請求項１〜１０のいずれかに記載の１軸延伸多層積層フィルム。   The uniaxially stretched multilayer laminated film according to any one of claims 1 to 10, which is used as a brightness enhancement film for a liquid crystal display. 請求項１〜１１のいずれかに記載の１軸延伸多層積層フィルムからなる輝度向上用部材。   The member for brightness | luminance improvement which consists of a uniaxially stretched multilayer laminated film in any one of Claims 1-11. 請求項１２に記載された輝度向上用部材の少なくとも一方の面に光拡散フィルムが積層されてなる液晶ディスプレイ用複合部材。   A composite member for a liquid crystal display, wherein a light diffusion film is laminated on at least one surface of the brightness enhancement member according to claim 12. 輝度向上用部材と光拡散フィルムとがヒートシール層を介して積層されてなる請求項１３に記載の液晶ディスプレイ用複合部材。   The composite member for a liquid crystal display according to claim 13, wherein the brightness enhancement member and the light diffusion film are laminated via a heat seal layer. 光拡散フィルムを介して輝度向上用部材と反対側にさらにプリズム層を有する請求項１３または１４に記載の液晶ディスプレイ用複合部材。   The composite member for a liquid crystal display according to claim 13 or 14, further comprising a prism layer on the side opposite to the member for improving brightness via a light diffusion film. 請求項１２に記載の輝度向上用部材を含む液晶ディスプレイ装置。   A liquid crystal display device comprising the brightness enhancement member according to claim 12. 請求項１３〜１５のいずれかに記載の液晶ディスプレイ用複合部材を含む液晶ディスプレイ装置。   The liquid crystal display device containing the composite member for liquid crystal displays in any one of Claims 13-15.
JP2009287758A 2009-12-18 2009-12-18 Uniaxially oriented laminated multilayer film, brightness improving member made of the film, composite member for liquid crystal display made of them, and liquid crystal display made of them Withdrawn JP2011126182A (en)

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