JP2015055679A - Polarizing plate, manufacturing method of polarizing plate, image display unit, manufacturing method of image display unit and light transmissivity improvement method of polarizing plate - Google Patents
Polarizing plate, manufacturing method of polarizing plate, image display unit, manufacturing method of image display unit and light transmissivity improvement method of polarizing plate Download PDFInfo
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Description
本発明は、偏光板、偏光板の製造方法、画像表示装置、画像表示装置の製造方法及び偏光板の光透過率改善方法に関する。 The present invention relates to a polarizing plate, a method for manufacturing a polarizing plate, an image display device, a method for manufacturing an image display device, and a method for improving the light transmittance of a polarizing plate.
液晶表示装置は、省電力、軽量、薄型等といった特徴を有していることから、従来のＣＲＴディスプレイに替わり様々な分野で用いられている。特に、近年急速に普及している携帯電話やスマートフォン等のモバイル機器では、液晶表示装置が必須となっている。
このような液晶表示装置は、例えば、バックライト光源上に、観察者側とバックライト光源側とに一対の偏光板が、液晶セルを介してクロスニコルの関係となるように配置された構成が知られている。
そして、このような構成の液晶表示装置は、バックライト光源から照射された光が、バックライト光源側の偏光板、液晶セル及び観察者側の偏光板を透過し、表示画面にて映像が表示される。
Since the liquid crystal display device has features such as power saving, light weight, and thin shape, it is used in various fields in place of the conventional CRT display. In particular, a liquid crystal display device is indispensable for mobile devices such as mobile phones and smartphones that are rapidly spreading in recent years.
Such a liquid crystal display device has, for example, a configuration in which a pair of polarizing plates are arranged on a backlight source on the viewer side and the backlight source side so as to have a crossed Nicols relationship via a liquid crystal cell. Are known.
In the liquid crystal display device having such a configuration, the light emitted from the backlight source passes through the polarizing plate on the backlight source side, the liquid crystal cell, and the polarizing plate on the viewer side, and an image is displayed on the display screen. Is done.
通常、上記偏光板としては、偏光子と光透過性基材とが積層された構造を有し、上記偏光板の光透過性基材としては、トリアセチルセルロースに代表されるセルロースエステルからなるフィルムが用いられている（例えば、特許文献１参照）。これは、セルロースエステルは、透明性、光学等方性に優れ、面内にほとんど位相差を持たない（リタデーション値が低い）ため、入射直線偏光の振動方向を変化させることが極めて少なく、液晶表示装置の表示品質への影響が少ないことや、適度な透水性を有することから、偏光板を製造した時に偏光子に残留した水分を、光学積層体を通して乾燥させることができる等の利点に基づくものである。 Usually, the polarizing plate has a structure in which a polarizer and a light-transmitting substrate are laminated, and the light-transmitting substrate of the polarizing plate is a film made of a cellulose ester typified by triacetyl cellulose. Is used (see, for example, Patent Document 1). This is because cellulose ester is excellent in transparency and optical isotropy, and has almost no retardation in the plane (low retardation value). Based on advantages such as having little influence on the display quality of the device and having moderate water permeability, moisture remaining in the polarizer when manufacturing the polarizing plate can be dried through the optical laminate. It is.
しかしながら、セルロースエステルは透湿度が高すぎるため、耐湿試験を行うと褪色による透過率の上昇や、偏光度の低下をきたすこと等の問題があった。これを解決するために、シクロオレフィン樹脂を保護フィルムとして用いた偏光板が提案されている（例えば、特許文献２参照）。この他にも、耐久性向上のため、セルロースエステルフィルムに比べて安価で市場において入手が容易な、あるいは簡易な方法で製造することが可能な汎用性フィルムを保護フィルムとして用いることが望まれており、例えば、セルロースエステルフィルムの代わりとして、ポリエチレンテレフタレート等のポリエステルフィルムを利用する試みがなされている（例えば、特許文献３参照）。 However, since the moisture permeability of the cellulose ester is too high, the moisture resistance test has problems such as an increase in transmittance due to discoloration and a decrease in the degree of polarization. In order to solve this, a polarizing plate using a cycloolefin resin as a protective film has been proposed (see, for example, Patent Document 2). In addition to this, in order to improve durability, it is desired to use a versatile film as a protective film that is cheaper than the cellulose ester film, easily available in the market, or that can be manufactured by a simple method. For example, an attempt has been made to use a polyester film such as polyethylene terephthalate instead of the cellulose ester film (see, for example, Patent Document 3).
ところで、このような構成の液晶表示装置において、バックライト光源から照射された光を効率よく表示画面まで透過させることは、表示画面の輝度向上に重要である。特に、近年急速に普及しているスマートフォン等のモバイル機器では、バッテリーの持続時間に直接影響するため、より効率よくバックライト光源からの光を表示画面まで透過させることが求められている。
しかしながら、ポリエステルフィルムは、分子鎖中に分極率の大きい芳香族環を持つため固有複屈折が極めて大きく、優れた透明性、耐熱性、機械強度を付与させるための延伸処理による分子鎖の配向に伴って複屈折が発現しやすいという性質を有する。このため、ポリエステルフィルムのような面内に複屈折率を有する光透過性基材を、偏光子の保護フィルムとして用いた場合、透過率が低下してしまうことがあり、従来の液晶表示装置では、バックライト光源から照射された光の多くが表示画面に到達することができず、より光透過率の向上が求められていた。
By the way, in the liquid crystal display device having such a configuration, it is important to improve the luminance of the display screen to efficiently transmit the light emitted from the backlight light source to the display screen. In particular, mobile devices such as smartphones that are rapidly spreading in recent years have a direct effect on the battery duration, and therefore it is required to transmit light from the backlight light source more efficiently to the display screen.
However, the polyester film has an extremely high polarizability aromatic ring in the molecular chain, so the intrinsic birefringence is extremely large, and the molecular chain is oriented by stretching to give excellent transparency, heat resistance and mechanical strength. Along with this, birefringence is easily developed. For this reason, when a light-transmitting substrate having a birefringence in a plane such as a polyester film is used as a protective film for a polarizer, the transmittance may decrease. Therefore, much of the light emitted from the backlight source cannot reach the display screen, and further improvement in light transmittance has been demanded.
本発明は、上記現状に鑑み、面内に複屈折率を有する光透過性基材が用いられていても光透過率に優れる偏光板、該偏光板の製造方法、画像表示装置、画像表示装置の製造方法及び偏光板の光透過率改善方法を提供することを目的とする。 In view of the above situation, the present invention provides a polarizing plate excellent in light transmittance even when a light-transmitting substrate having an in-plane birefringence is used, a method for manufacturing the polarizing plate, an image display device, and an image display device It aims at providing the manufacturing method of this, and the light transmittance improvement method of a polarizing plate.
本発明は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とは、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置されていることを特徴とする偏光板である。 The present invention is a polarizing plate in which at least a light-transmitting substrate having a birefringence in the plane is provided on a polarizer, and the light-transmitting substrate having a birefringence in the plane and the polarization The polarizer is arranged so that the angle formed by the fast axis, which is the direction in which the refractive index of the light-transmitting substrate having a birefringence index in the plane is small, and the transmission axis of the polarizer does not become 90 °. It is the polarizing plate characterized by the above-mentioned.
本発明の偏光板は、上記光透過性基材の面内における屈折率が大きい方向である遅相軸方向の屈折率をｎｘとし、上記面内における屈折率が大きい方向である遅相軸方向と直交する方向である進相軸方向の屈折率をｎｙとし、上記光透過性基材の平均屈折率をＮとしたとき、上記光透過性基材は、下記式の関係を満たすことが好ましい。
ｎｘ＞Ｎ＞ｎｙ
また、本発明の偏光板において、上記面内に複屈折率を有する光透過性基材は、屈折率が大きい方向である遅相軸方向の屈折率（ｎｘ）と、上記遅相軸方向と直交する方向である進相軸方向の屈折率（ｎｙ）との差（ｎｘ−ｎｙ）が、０．０１以上であることが好ましい。
また、本発明の偏光板は、観察者側から、上記面内に複屈折率を有する光透過性基材、上記偏光子がこの順に積層された状態で、画像表示装置の表面に配置して用いられることが好ましい。
また、本発明の偏光板は、観察者側から、偏光子、面内に複屈折率を有する光透過性基材がこの順に積層された状態で、画像表示装置のバックライト光源側に配置して用いられることが好ましい。
In the polarizing plate of the present invention, the refractive index in the slow axis direction, which is the direction in which the in-plane refractive index is large, is nx, and the slow axis direction is in the direction in which the in-plane refractive index is large. When the refractive index in the fast axis direction which is a direction orthogonal to ny is ny and the average refractive index of the light transmissive substrate is N, the light transmissive substrate preferably satisfies the relationship of the following formula: .
nx>N> ny
In the polarizing plate of the present invention, the light-transmitting substrate having a birefringence in the plane has a refractive index (nx) in the slow axis direction that is a direction in which the refractive index is large, and the slow axis direction. The difference (nx−ny) from the refractive index (ny) in the fast axis direction, which is the orthogonal direction, is preferably 0.01 or more.
Further, the polarizing plate of the present invention is disposed on the surface of the image display device from the observer side in a state where the light-transmitting base material having a birefringence in the plane and the polarizer are laminated in this order. It is preferable to be used.
In addition, the polarizing plate of the present invention is disposed on the backlight source side of the image display device in a state where a polarizer and a light-transmitting base material having a birefringence in-plane are laminated in this order from the observer side. Are preferably used.
また、本発明は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板の製造方法であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有することを特徴とする偏光板の製造方法でもある。 The present invention also relates to a method for producing a polarizing plate in which at least a light-transmitting substrate having a birefringence in the plane is provided on a polarizer, the light-transmitting property having a birefringence in the plane. The angle formed by the fast axis that is the direction in which the refractive index of the light-transmitting base material having a birefringence in the plane is small and the transmission axis of the polarizer is 90 °. It is also a manufacturing method of the polarizing plate characterized by having the process of arrange | positioning so that it may not become.
また、本発明は、上述した本発明の偏光板を備えることを特徴とする画像表示装置でもある。
また、本発明は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板を備えた画像表示装置の製造方法であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有することを特徴とする画像表示装置の製造方法でもある。
Moreover, this invention is also an image display apparatus provided with the polarizing plate of this invention mentioned above.
The present invention also relates to a method of manufacturing an image display device including a polarizing plate in which at least a light-transmitting substrate having a birefringence index in a plane is provided on a polarizer, wherein the birefringence is in the plane. A light-transmitting base material having a refractive index and the polarizer, and a fast axis that is a direction in which the refractive index of the light-transmitting base material having a birefringence in the plane is small, and a transmission axis of the polarizer. It is also a method of manufacturing an image display device characterized by having a step of arranging so that the formed angle does not become 90 °.
また、本発明は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板の光透過率改善方法であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置することを特徴とする偏光板の光透過率改善方法でもある。
以下に、本発明を詳細に説明する。
なお、本発明では、特別な記載がない限り、モノマー、オリゴマー、プレポリマー等の硬化性樹脂前駆体も“樹脂”と記載する。
The present invention also relates to a method for improving the light transmittance of a polarizing plate in which at least a light-transmitting substrate having a birefringence in the plane is provided on a polarizer, the birefringence having the in-plane birefringence. The angle formed between the light transmitting substrate and the polarizer by the fast axis which is the direction in which the refractive index of the light transmitting substrate having a birefringence in the plane is small and the transmission axis of the polarizer is It is also a method for improving the light transmittance of a polarizing plate, which is arranged so as not to be 90 °.
The present invention is described in detail below.
In the present invention, unless otherwise specified, curable resin precursors such as monomers, oligomers, and prepolymers are also referred to as “resins”.
本発明者らは、光透過性基材と偏光子とが積層された偏光板について鋭意検討した結果、面内に複屈折率を有する光透過性基材を用いた場合、偏光板の光透過率には、該光透過性基材の屈折率の小さい方向である進相軸と偏光子の透過軸との間で角度依存性があることを見出した。
すなわち、本発明者らは、面内に複屈折率を有する光透過性基材の屈折率の小さい方向である進相軸と上記偏光子の透過軸とが特定の角度範囲となるように積層することで、該偏光板の光透過率を向上させることができることを見出した。そして、このような知見に基づき本発明者らは、更に鋭意検討した結果、従来、光学等方性材料として用いられてきたセルロースエステル等の材料からなる光透過性基材に対しても、敢えて複屈折率を持たせた光透過性基材とすることにより、光学等方性材料のまま用いるよりも、光透過率を向上させることができることを見出し、本発明を完成するに至った。
As a result of intensive studies on a polarizing plate in which a light-transmitting base material and a polarizer are laminated, the present inventors have found that when a light-transmitting base material having an in-plane birefringence is used, the light transmission of the polarizing plate It has been found that there is an angle dependency between the fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, and the transmission axis of the polarizer.
That is, the present inventors laminated the light transmitting base material having a birefringence in the plane so that the fast axis, which is the direction in which the refractive index is small, and the transmission axis of the polarizer are in a specific angle range. It has been found that the light transmittance of the polarizing plate can be improved. And based on such knowledge, the inventors of the present invention have further intensively studied. As a result, the present inventors also dare to make a light-transmitting substrate made of a material such as cellulose ester, which has been conventionally used as an optically isotropic material. It has been found that by using a light-transmitting substrate having a birefringence index, the light transmittance can be improved as compared with using an optically isotropic material as it is, and the present invention has been completed.
本発明の偏光板は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられている。
上記光透過性基材としては、面内に複屈折率を有するものであれば特に限定されず、例えば、ポリカーボネート、アクリル、ポリエステル等からなる基材が挙げられるが、なかでも、コスト及び機械的強度において有利なポリエステル基材であることが好適である。なお、以下の説明では、面内に複屈折率を有する光透過性基材をポリエステル基材として説明する。
なお、本発明の偏光板において、上記光透過性基材としては、従来、光学等方性材料として用いられていたセルロースエステル等からなる光透過性基材であっても、敢えて複屈折率を持たせることで使用することができる。
In the polarizing plate of the present invention, at least a light-transmitting substrate having a birefringence in the plane is provided on the polarizer.
The light-transmitting substrate is not particularly limited as long as it has a birefringence in the plane, and examples thereof include substrates made of polycarbonate, acrylic, polyester, etc. Among them, cost and mechanical properties are particularly important. A polyester substrate that is advantageous in strength is preferred. In the following description, a light-transmitting substrate having a birefringence in the plane will be described as a polyester substrate.
In the polarizing plate of the present invention, as the light-transmitting substrate, even if it is a light-transmitting substrate made of cellulose ester or the like conventionally used as an optically isotropic material, the birefringence index is intentionally increased. It can be used by having it.
本発明の偏光板において、上記ポリエステル基材の面内において屈折率が大きい方向（遅相軸方向）の屈折率（ｎｘ）と、上記遅相軸方向と直交する方向（進相軸方向）の屈折率（ｎｙ）との差ｎｘ−ｎｙ（以下、Δｎとも表記する）は、０．０１以上であることが好ましい。上記Δｎが０．０１未満であると、透過率向上効果が少なくなることがある。一方、上記Δｎは、０．３０以下であることが好ましい。０．３０を超えると、ポリエステル基材を過度に延伸する必要が生じるため、ポリエステル基材が裂け、破れ等を生じやすくなり、工業材料としての実用性が著しく低下することがある。
以上の観点から、上記Δｎのより好ましい下限は０．０５、より好ましい上限は０．２７である。上記Δｎの更に好ましい下限は０．０７、上限は０．２５である。
上記したΔｎを満たすことで、好適な光透過率の向上を図ることができる。
In the polarizing plate of the present invention, the refractive index (nx) in the direction in which the refractive index is large (the slow axis direction) in the plane of the polyester substrate, and the direction (the fast axis direction) perpendicular to the slow axis direction. The difference nx−ny (hereinafter also referred to as Δn) from the refractive index (ny) is preferably 0.01 or more. When Δn is less than 0.01, the effect of improving transmittance may be reduced. On the other hand, the Δn is preferably 0.30 or less. If it exceeds 0.30, it becomes necessary to stretch the polyester base material excessively, so that the polyester base material is likely to be torn and torn, and the practicality as an industrial material may be remarkably lowered.
From the above viewpoint, the more preferable lower limit of Δn is 0.05, and the more preferable upper limit is 0.27. The more preferable lower limit of Δn is 0.07, and the upper limit is 0.25.
By satisfying the above-described Δn, it is possible to improve a suitable light transmittance.
なお、本明細書において、光透過性基材が面内に複屈折性を有しているか否かは、波長５５０ｎｍの屈折率において、Δｎ（ｎｘ−ｎｙ）≧０．０００５であるものは、複屈折性を有しているとし、Δｎ＜０．０００５であるものは、複屈折性を有していないとする。複屈折率は、王子計測機器社製ＫＯＢＲＡ−ＷＲを用いて、測定角０°かつ測定波長５５２．１ｎｍに設定して、測定を行うことができる。このとき、複屈折率算出には、膜厚、平均屈折率が必要となる。膜厚は、例えば、マイクロメーター（Ｄｉｇｉｍａｔｉｃ Ｍｉｃｒｏｍｅｔｅｒ、ミツトヨ社製）や、電気マイクロメータ（アンリツ社製）を用いて測定できる。平均屈折率は、アッベ屈折率計や、エリプソメーターを用いて測定することができる。
なお、一般的に等方性材料として知られる、トリアセチルセルロースからなるＴＤ８０ＵＬ−Ｍ（富士フィルム社製）、シクロオレフィンポリマーからなるＺＦ１６−１００（日本ゼオン社製）のΔｎは、上記測定方法により、それぞれ、０．００００３７５、０．００００５であり、複屈折性を有していない（等方性）と判断した。
その他、複屈折率を測定する方法として、二枚の偏光板を用いて、光透過性基材の配向軸方向（主軸の方向）を求め、配向軸方向に対して直交する二つの軸の屈折率（ｎｘ、ｎｙ）を、アッベ屈折率計（アタゴ社製 ＮＡＲ−４Ｔ）によって求めることもできるし、裏面に黒ビニールテープ（例えば、ヤマトビニールテープＮｏ２００−３８−２１ ３８ｍｍ幅）を貼ってから、分光光度計（Ｖ７１００型、自動絶対反射率測定ユニット、ＶＡＲ−７０１０ 日本分光社製）を用いて、偏光測定：Ｓ偏光にて、Ｓ偏光に対して、遅相軸を平行にした場合と、進相軸を平行にした場合の５度反射率を測定し、反射率（Ｒ）と屈折率（ｎ）との関係を示す下記式（１）より、遅相軸と進相軸の各波長の屈折率（ｎｘ、ｎｙ）を算出することもできる。
Ｒ（％）＝（１−ｎ）２／（１＋ｎ）２ 式（１）
In the present specification, whether or not the light-transmitting substrate has birefringence in the plane is determined by Δn (nx−ny) ≧ 0.0005 at a refractive index of a wavelength of 550 nm. It is assumed that those having birefringence and those having Δn <0.0005 do not have birefringence. The birefringence can be measured by setting a measurement angle of 0 ° and a measurement wavelength of 552.1 nm using KOBRA-WR manufactured by Oji Scientific Instruments. At this time, for calculating the birefringence, the film thickness and the average refractive index are required. The film thickness can be measured using, for example, a micrometer (Digital Micrometer, manufactured by Mitutoyo Corporation) or an electric micrometer (produced by Anritsu Corporation). The average refractive index can be measured using an Abbe refractometer or an ellipsometer.
In addition, Δn of TD80UL-M (manufactured by Fuji Film Co., Ltd.) made of triacetyl cellulose and ZF16-100 (made by Nippon Zeon Co., Ltd.) made of cycloolefin polymer, which is generally known as an isotropic material, is determined by the above measuring method. These were 0.0000375 and 0.00005, respectively, and were judged to have no birefringence (isotropic).
In addition, as a method for measuring the birefringence, two polarizing plates are used to determine the orientation axis direction (major axis direction) of the light-transmitting substrate, and refraction of two axes perpendicular to the orientation axis direction The rate (nx, ny) can also be determined by an Abbe refractometer (NAGO-4T manufactured by Atago Co., Ltd.), and a black vinyl tape (for example, Yamato vinyl tape No200-38-21 38 mm width) is attached to the back surface. , Using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit, VAR-7010, manufactured by JASCO Corporation), polarization measurement: S-polarized light, with slow axis parallel to S-polarized light Measure the reflectivity of 5 degrees when the fast axis is parallel, and from the following formula (1) showing the relationship between the reflectivity (R) and the refractive index (n), each of the slow axis and the fast axis The refractive index (nx, ny) of the wavelength can also be calculated.
R (%) = (1-n) 2 / (1 + n) 2 formula (1)
また、平均屈折率は、アッベ屈折率計や、エリプソメーターを用いて測定することができ、光透過性フィルムの厚み方向の屈折率ｎｚは、上記の方法によって測定した、ｎｘ、ｎｙを用いて、下記式（２）より、計算できる。
平均屈折率Ｎ＝（ｎｘ＋ｎｙ＋ｎｚ）／３ 式（２）
The average refractive index can be measured using an Abbe refractometer or an ellipsometer, and the refractive index nz in the thickness direction of the light-transmitting film is measured by the above method, using nx and ny. It can be calculated from the following equation (2).
Average refractive index N = (nx + ny + nz) / 3 Formula (2)
ここで、ｎｘ、ｎｙ、ｎｚの算出方法を、具体例を挙げて説明する。
なお、ｎｘは、光透過性基材の遅相軸方向の屈折率、ｎｙは、光透過性基材の進相軸方向の屈折率、ｎｚは、光透過性基材の厚み方向の屈折率である。
（３次元屈折率波長分散の算出）
まずは、シクロオレフィンポリマーを例に挙げて、３次元屈折率波長分散の算出方法を具体的に説明する。
面内に複屈折率を有さないシクロオレフィンポリマーフィルムの平均屈折率波長分散を、エリプソメーター（ＵＶＩＳＥＬ 堀場製作所）を用いて測定し、その結果を図１に示した。この測定結果より、面内に複屈折率を有さないシクロオレフィンポリマーフィルムの平均屈折率波長分散を、ｎｘとｎｙ、ｎｚの屈折率波長分散とした。
このフィルムを延伸温度１５５℃で自由端一軸延伸して、面内に複屈折率を有するフィルムを得た。膜厚は、１００μｍであった。この自由端一軸延伸したフィルムを、複屈折測定計（ＫＯＢＲＡ−２１ＡＤＨ、王子計測機器）により、入射角０°及び４０°のリタデーション値を４波長（４４７．６ｎｍ、５４７．０ｎｍ、６３０．６ｎｍ、７４３．４ｎｍ）で測定した。
各波長での、平均屈折率（Ｎ）と、リタデーション値とを元に、複屈折測定計付属の３次元波長分散計算ソフトを用いて、Ｃａｕｃｈｙ又はＳｅｌｌｍｅｉｅｒの式などを用いて、３次元屈折率波長分散を算出し、その結果を図２に示した。なお、図２中、ｎｙはｎｚとほぼ重なって示されている。この結果より、面内に複屈折率を有するシクロオレフィンポリマーフィルムの３次元屈折率波長分散を得た。
（分光光度計を用いた屈折率ｎｘ、ｎｙ、ｎｚの算出）
ポリエチレンテレフタレートを例に挙げて、分光光度計を用いた屈折率ｎｘ、ｎｙ、ｎｚの算出方法を具体的に説明する。
面内に複屈折率を有さないポリエチレンテレフタレートの平均屈折率波長分散は、上記３次元屈折率波長分散の算出方法と同様に行った。
面内に複屈折率を有するポリエチレンテレフタレートの屈折率波長分散（ｎｘ、ｎｙ）は、分光光度計（Ｖ７１００型、自動絶対反射率測定ユニットＶＡＲ−７０１０ 日本分光社製）を用いて算出した。測定面とは反対面に、裏面反射を防止するために測定スポット面積よりも大きな幅の黒ビニールテープ（例えば、ヤマトビニールテープＮｏ２００−３８−２１ ３８ｍｍ幅）を貼ってから、偏光測定：Ｓ偏光にて、光透過性基材の配向軸を平行に設置した場合と、配向軸に対して直交する軸を平行に設置した場合との５度分光反射率を測定した。結果を図３に示す。反射率（Ｒ）と屈折率（ｎ）との関係を示す上記式（１）より、屈折率波長分散（ｎｘ、ｎｙ）を算出した。より大きい反射率（上記式（１）により算出された屈折率）を示す方向をｎｘ（遅相軸ともいう）とし、より小さい反射率（上記式（１）により算出された屈折率）を示す方向をｎｙ（進相軸ともいう）とした。ここで、配向軸とは、光源の上に、クロスニコル状態に設置された二枚の偏光板の間に、面内に複屈折率を有するフィルムを挟み、フィルムを回転させ、光漏れがもっとも少ない状態の時、偏光板の透過軸、又は、吸収軸と同一方向が、フィルムの配向軸とすることができる。また、屈折率ｎｚは、上記平均屈折率（Ｎ）と上記式（２）とにより算出できる。
Here, a calculation method of nx, ny, and nz will be described with a specific example.
Nx is the refractive index in the slow axis direction of the light transmissive substrate, ny is the refractive index in the fast axis direction of the light transmissive substrate, and nz is the refractive index in the thickness direction of the light transmissive substrate. It is.
(Calculation of three-dimensional refractive index wavelength dispersion)
First, a calculation method of three-dimensional refractive index wavelength dispersion will be specifically described by taking a cycloolefin polymer as an example.
The average refractive index wavelength dispersion of a cycloolefin polymer film having no in-plane birefringence was measured using an ellipsometer (UVISEL Horiba, Ltd.), and the results are shown in FIG. From this measurement result, the average refractive index wavelength dispersion of the cycloolefin polymer film having no in-plane birefringence was defined as the refractive index wavelength dispersion of nx, ny, and nz.
The film was uniaxially stretched at a free temperature at a stretching temperature of 155 ° C. to obtain a film having a birefringence in the plane. The film thickness was 100 μm. This free-end uniaxially stretched film was measured with a birefringence meter (KOBRA-21ADH, Oji Scientific Instruments) with four retardation values (447.6 nm, 547.0 nm, 630.6 nm) at an incident angle of 0 ° and 40 °. 743.4 nm).
Based on the average refractive index (N) and retardation value at each wavelength, the three-dimensional refractive index using the Couchy or Sellmeier equation, etc., using the three-dimensional chromatic dispersion calculation software attached to the birefringence meter. The chromatic dispersion was calculated and the result is shown in FIG. In FIG. 2, ny is shown substantially overlapping with nz. From this result, a three-dimensional refractive index wavelength dispersion of a cycloolefin polymer film having an in-plane birefringence was obtained.
(Calculation of refractive indices nx, ny and nz using a spectrophotometer)
Taking polyethylene terephthalate as an example, a method of calculating refractive indexes nx, ny, and nz using a spectrophotometer will be specifically described.
The average refractive index wavelength dispersion of polyethylene terephthalate having no in-plane birefringence was performed in the same manner as the above-described method for calculating the three-dimensional refractive index wavelength dispersion.
The refractive index wavelength dispersion (nx, ny) of polyethylene terephthalate having a birefringence in the plane was calculated using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit VAR-7010, manufactured by JASCO Corporation). Polarization measurement: S-polarized light after a black vinyl tape (for example, Yamato vinyl tape No200-38-21 38 mm width) having a width larger than the measurement spot area is pasted on the surface opposite to the measurement surface to prevent back surface reflection. Then, the 5-degree spectral reflectance was measured when the alignment axis of the light-transmitting substrate was installed in parallel and when the axis orthogonal to the alignment axis was installed in parallel. The results are shown in FIG. The refractive index wavelength dispersion (nx, ny) was calculated from the above formula (1) showing the relationship between the reflectance (R) and the refractive index (n). A direction indicating a larger reflectance (refractive index calculated by the above equation (1)) is nx (also referred to as a slow axis), and a smaller reflectance (refractive index calculated by the above equation (1)) is indicated. The direction was ny (also called fast axis). Here, the orientation axis is a state in which a film having a birefringence in-plane is sandwiched between two polarizing plates placed in a crossed Nicol state on a light source, the film is rotated, and light leakage is minimized. In this case, the transmission axis of the polarizing plate or the same direction as the absorption axis can be used as the orientation axis of the film. The refractive index nz can be calculated from the average refractive index (N) and the above equation (2).
本発明の偏光板では、上記光透過性基材の面内における屈折率が大きい方向である遅相軸方向の屈折率をｎｘとし、上記面内における屈折率が大きい方向である遅相軸方向と直交する方向である進相軸方向の屈折率をｎｙとし、上記光透過性基材の平均屈折率をＮとしたとき、上記光透過性基材は、下記式の関係を満たすことが好ましい。
ｎｘ＞Ｎ＞ｎｙ
上記式を満たすことで、光学等方性フィルムの状態で偏光子の保護フィルムとして用いた場合と比較して、透過率を向上させることができる。
なお、本発明の偏光板は、面内に複屈折を有する光透過性基材の偏光子が積層されている側とは反対の面に、上記光透過性基材の進相軸方向の屈折率ｎｙよりも小さな屈折率を有する低屈折率層が設けられていてもよい。このような低屈折率層としては、屈折率が上記光透過性基材の進相軸方向の屈折率ｎｙよりも小さなものであれば特に限定されず、従来公知の材料からなるものが挙げられる。
In the polarizing plate of the present invention, the refractive index in the slow axis direction, which is the direction in which the in-plane refractive index is large, is nx, and the slow axis direction is in the direction in which the in-plane refractive index is large. When the refractive index in the fast axis direction which is a direction orthogonal to ny is ny and the average refractive index of the light transmissive substrate is N, the light transmissive substrate preferably satisfies the relationship of the following formula: .
nx>N> ny
By satisfy | filling the said Formula, the transmittance | permeability can be improved compared with the case where it uses as a protective film of a polarizer in the state of an optical isotropic film.
The polarizing plate of the present invention has a refractive index in the fast axis direction of the light-transmitting substrate on the surface opposite to the side on which the polarizer of the light-transmitting substrate having birefringence is laminated. A low refractive index layer having a refractive index smaller than the refractive index ny may be provided. Such a low refractive index layer is not particularly limited as long as the refractive index is smaller than the refractive index ny in the fast axis direction of the light-transmitting substrate, and includes those made of conventionally known materials. .
上記ポリエステル基材を構成する材料としては、上述したΔｎを充足するものであれば特に限定されないが、芳香族二塩基酸又はそのエステル形成性誘導体とジオール又はそのエステル形成性誘導体とから合成される線状飽和ポリエステルが挙げられる。かかるポリエステルの具体例として、ポリエチレンテレフタレート、ポリエチレンイソフタレート、ポリブチレンテレフタレート、ポリ（１，４−シクロヘキシレンジメチレンテレフタレート）、ポリエチレンナフタレート（ポリエチレン−２，６−ナフタレート、ポリエチレン−１，４−ナフタレート、ポリエチレン−１，５−ナフタレート、ポリエチレン−２，７−ナフタレート、ポリエチレン−２，３−ナフタレート）などを例示することができる。また、ポリエステル基材に用いられるポリエステルは、これらのポリエステルの共重合体であってもよく、上記ポリエステルを主体（例えば８０モル％以上の成分）とし、少割合（例えば２０モル％以下）の他の種類の樹脂とブレンドしたものであってもよい。上記ポリエステルとしてポリエチレンテレフタレート又はポリエチレンナフタレートが力学的物性や光学物性等のバランスが良いので特に好ましい。特に、ポリエチレンテレフタレート（ＰＥＴ）からなることが好ましい。ポリエチレンテレフタレートは汎用性が高く、入手が容易であるからである。本発明においてはＰＥＴのような、汎用性が極めて高いフィルムであっても、光透過率に優れる偏光板を得ることができる。更に、ＰＥＴは、透明性、熱又は機械的特性に優れ、延伸加工によりΔｎの制御が可能であり、固有複屈折が大きいため、比較的容易に複屈折率を持たせることができる。 The material constituting the polyester base material is not particularly limited as long as it satisfies the above-described Δn, but is synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Examples include linear saturated polyester. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene naphthalate (polyethylene-2,6-naphthalate, polyethylene-1,4-naphthalate). , Polyethylene-1,5-naphthalate, polyethylene-2,7-naphthalate, polyethylene-2,3-naphthalate) and the like. The polyester used for the polyester substrate may be a copolymer of these polyesters. The polyester is mainly used (for example, a component of 80 mol% or more), and a small proportion (for example, 20 mol% or less). It may be blended with these types of resins. Polyethylene terephthalate or polyethylene naphthalate is particularly preferable as the polyester because of good balance between mechanical properties and optical properties. In particular, it is preferably made of polyethylene terephthalate (PET). This is because polyethylene terephthalate is highly versatile and easily available. In the present invention, a polarizing plate having excellent light transmittance can be obtained even with a highly versatile film such as PET. Furthermore, PET is excellent in transparency, heat or mechanical properties, Δn can be controlled by stretching, and has a large intrinsic birefringence, so that it can have a birefringence relatively easily.
上記ポリエステル基材を得る方法としては、上述したΔｎを充足する方法であれば特に限定されないが、例えば、材料の上記ＰＥＴ等のポリエステルを溶融し、シート状に押出し成形された未延伸ポリエステルをガラス転移温度以上の温度においてテンター等を用いて横延伸後、熱処理を施す方法が挙げられる。
上記横延伸温度としては、８０〜１３０℃が好ましく、より好ましくは９０〜１２０℃である。また、縦延伸倍率は２．５〜６．０倍が好ましく、より好ましくは３．０〜５．５倍である。上記横延伸倍率が６．０倍を超えると、得られるポリエステル基材の透明性が低下しやすくなり、横延伸倍率が２．５倍未満であると、延伸張力も小さくなるため、得られるポリエステル基材の複屈折が小さくなり、透過率向上の効果が小さくなるためである。
また、本発明においては、二軸延伸試験装置を用いて、上記未延伸ポリエステルの縦延伸を上記条件で行った後、もしくは前に、該縦延伸に対する幅方向の延伸（以下、横延伸ともいう）を行ってもよい。この場合、上記横延伸は、延伸倍率が２倍以下であることが好ましい。上記横延伸の延伸倍率が２倍を超えると、Δｎの値を上述した好ましい範囲にできないことがある。
また、上記熱処理時の処理温度はしては、１００〜２５０℃が好ましく、より好ましくは１８０〜２４５℃である。
なお、ロール状の未延伸のポリエステルフィルムを縦方向のみに延伸させ、又は、横方向に僅かに延伸させた場合には、ポリエステル基材の進相軸が幅方向に沿って存在している。その一方で、ロール状の偏光子は、その延伸処理を非常に高精度に管理されながら製造されるため、特殊な場合を除き、長手方向に沿って吸収軸が存在している（幅方向に透過軸が存在）。このため、ロールツーロール法によってポリエステル基材と偏光子とを貼り合わせることによって、偏光子の透過軸方向とポリエステル基材の進相軸方法が沿った偏光板を作製することができる。
The method for obtaining the polyester base material is not particularly limited as long as it satisfies the above-described Δn. For example, a polyester such as the above-mentioned PET, which is a material, is melted and extruded into a sheet to form glass. The method of heat-processing after transverse stretching using a tenter etc. at the temperature more than transition temperature is mentioned.
The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. In addition, the longitudinal draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. When the transverse draw ratio exceeds 6.0 times, the transparency of the resulting polyester base material tends to be lowered, and when the transverse draw ratio is less than 2.5 times, the draw tension becomes small. This is because the birefringence of the substrate is reduced and the effect of improving the transmittance is reduced.
In the present invention, the unstretched polyester is stretched in the width direction with respect to the longitudinal stretching (hereinafter, also referred to as lateral stretching) after or before the unstretched polyester is longitudinally stretched under the above conditions using a biaxial stretching test apparatus. ) May be performed. In this case, the transverse stretching preferably has a stretching ratio of 2 times or less. When the draw ratio of the transverse stretching exceeds 2 times, the value of Δn may not be within the preferred range described above.
The treatment temperature during the heat treatment is preferably 100 to 250 ° C, more preferably 180 to 245 ° C.
In addition, when a roll-shaped unstretched polyester film is stretched only in the longitudinal direction or slightly stretched in the lateral direction, the fast axis of the polyester base exists along the width direction. On the other hand, a roll-shaped polarizer is manufactured while its stretching process is managed with very high precision, and therefore, there is an absorption axis along the longitudinal direction (in the width direction) except in special cases. There is a transmission axis). For this reason, a polarizing plate in which the transmission axis direction of the polarizer and the fast axis method of the polyester substrate are aligned can be produced by laminating the polyester substrate and the polarizer by the roll-to-roll method.
上記ポリエステル基材の厚みとしては、５〜３００μｍの範囲内であることが好ましい。５μｍ未満であると、上記ポリエステル基材の力学特性の異方性が顕著となり、裂け、破れ等を生じやすくなり、工業材料としての実用性が著しく低下することがある。一方、３００μｍを超えると、ポリエステル基材が非常に剛直であり、高分子フィルム特有のしなやかさが低下し、やはり工業材料としての実用性が低下するので好ましくない。上記ポリエステル基材の厚さのより好ましい下限は１０μｍ、より好ましい上限は２５０μｍであり、更に好ましい上限は２００μｍである。 The thickness of the polyester base material is preferably in the range of 5 to 300 μm. When the thickness is less than 5 μm, the anisotropy of the mechanical properties of the polyester base material becomes remarkable, and tearing, tearing and the like are likely to occur, and the practicality as an industrial material may be significantly reduced. On the other hand, if it exceeds 300 μm, the polyester base material is very rigid, the flexibility specific to the polymer film is lowered, and the practicality as an industrial material is also lowered, which is not preferable. The minimum with more preferable thickness of the said polyester base material is 10 micrometers, a more preferable upper limit is 250 micrometers, and a more preferable upper limit is 200 micrometers.
また、上記ポリエステル基材は、可視光領域における透過率が８０％以上であることが好ましく、８４％以上であるものがより好ましい。なお、上記透過率は、ＪＩＳ Ｋ７３６１−１（プラスチック−透明材料の全光透過率の試験方法）により測定することができる。 The polyester base material preferably has a transmittance in the visible light region of 80% or more, more preferably 84% or more. In addition, the said transmittance | permeability can be measured by JISK7361-1 (The test method of the total light transmittance of a plastic-transparent material).
また、本発明において、上記ポリエステル基材には本発明の趣旨を逸脱しない範囲で、けん化処理、グロー放電処理、コロナ放電処理、紫外線（ＵＶ）処理、及び火炎処理等の表面処理を行ってもよい。 In the present invention, the polyester substrate may be subjected to surface treatment such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment without departing from the spirit of the present invention. Good.
上記偏光子としては特に限定されず、例えば、ヨウ素等により染色し、延伸したポリビニルアルコールフィルム、ポリビニルホルマールフィルム、ポリビニルアセタールフィルム、エチレン−酢酸ビニル共重合体系ケン化フィルム等を使用することができる。上記偏光子と上記光透過性基材とのラミネート処理においては、該光透過性基材にケン化処理を行うことが好ましい。ケン化処理によって、接着性が良好になる。 The polarizer is not particularly limited, and for example, a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, etc. dyed and stretched with iodine or the like can be used. In laminating the polarizer and the light transmissive substrate, it is preferable to saponify the light transmissive substrate. Adhesion is improved by the saponification treatment.
本発明の偏光板において、上記光透過性基材と上記偏光子とは、上記光透過性基材の屈折率が小さい方向である進相軸と上記偏光子の透過軸とのなす角度が、９０°とならないように積層されている。本発明の偏光板は、上記光透過性基材と上記偏光子とが上述のように配置されるため、光透過率を優れたものとすることができる。すなわち、上記光透過性基材の進相軸と上記偏光子の透過軸とのなす角度が上記範囲を外れる場合、具体的には、９０°である場合、本発明の偏光板の光透過率が極めて低いものとなる。
これは、以下の理由による。
すなわち、観測者側から、面内に複屈折率を有する光透過性基材、偏光子の順に積層されている偏光板の場合、偏光子の透過軸方向に振動し、該偏光子から出射した光は、その振動方向を保ったまま、光透過性基材を通過するが、例えば、この光が、光透過性基材から、空気界面に出る場合、下記式によって反射が起こる。なお、下記式中、ρは、反射率を示し、ｎａは、光の振動方向と同じ方向の光透過性基材の面内の屈折率を示す。
ρ＝（１−ｎａ）２／（１＋ｎａ）２
そして、上記偏光板の透過率τは、下記式によって求められるが、吸収率αは、材料が同じであるため、同じ値であることを考えれば、透過率τを大きくするためには、反射率ρを小さくすれば良い。
τ＝１−ρ−α
すなわち、上記面内に複屈折率を有する光透過性基材と上記偏光子とは、該光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が０°である場合、光は、光透過性基材の面内において、最も小さい屈折率と空気の屈折率との差によって反射が起こるため、反射率を最も小さくでき、透過率を上げることができる。一方、上記面内に複屈折率を有する光透過性基材と上記偏光子とは、該光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°である場合、光は、光透過性基材の面内において、最も大きい屈折率と空気の屈折率との差によって反射が起こるため、反射率がもっとも大きくなり、結果として、透過率が低下する。
In the polarizing plate of the present invention, the light transmissive substrate and the polarizer have an angle formed by a fast axis which is a direction in which the refractive index of the light transmissive substrate is small and the transmission axis of the polarizer, The layers are stacked so as not to be 90 °. In the polarizing plate of the present invention, since the light transmissive substrate and the polarizer are arranged as described above, the light transmittance can be improved. That is, when the angle formed by the fast axis of the light transmissive substrate and the transmission axis of the polarizer is out of the above range, specifically, when it is 90 °, the light transmittance of the polarizing plate of the present invention Is extremely low.
This is due to the following reason.
That is, from the observer side, in the case of a polarizing plate laminated in the order of a light-transmitting base material having a birefringence in the plane and a polarizer, it vibrates in the transmission axis direction of the polarizer and is emitted from the polarizer. The light passes through the light-transmitting substrate while maintaining its vibration direction. For example, when the light exits from the light-transmitting substrate to the air interface, reflection occurs according to the following formula. In the following formula, ρ represents the reflectance, and na represents the in-plane refractive index of the light-transmitting substrate in the same direction as the light vibration direction.
ρ = (1-na) 2 / (1 + na) 2
The transmittance τ of the polarizing plate can be obtained by the following equation. Since the material is the same, the absorption rate α is the same value. The rate ρ may be reduced.
τ = 1−ρ−α
That is, the light-transmitting substrate having a birefringence in the plane and the polarizer have a fast axis that is a direction in which the refractive index of the light-transmitting substrate is small and a transmission axis of the polarizer. When the angle formed is 0 °, light is reflected by the difference between the smallest refractive index and the refractive index of air in the plane of the light transmissive substrate, so that the reflectance can be minimized and the transmittance can be reduced. Can be raised. On the other hand, the light-transmitting substrate having a birefringence in the plane and the polarizer have a fast axis which is a direction in which the refractive index of the light-transmitting substrate is small and a transmission axis of the polarizer. When the angle formed is 90 °, light is reflected by the difference between the largest refractive index and the refractive index of air in the plane of the light-transmitting substrate, so that the reflectance becomes the largest, and as a result, The transmittance decreases.
本発明の偏光板において、上記光透過性基材と上記偏光子とは、上記光透過性基材の進相軸と上記偏光子の透過軸とのなす角度が、０°±２０°以下となるように積層されていることが好ましく、より好ましくは、０°±５°以下である。上記光透過性基材の遅相軸と上記偏光子の透過軸とのなす角度が上記範囲にあることで、平均屈折率を用いたものよりも、本発明の偏光板の光透過率が優れたものとなる。 In the polarizing plate of the present invention, the light-transmitting base material and the polarizer have an angle between a fast axis of the light-transmitting base material and a transmission axis of the polarizer of 0 ° ± 20 ° or less. It is preferable to be laminated so as to be, more preferably 0 ° ± 5 ° or less. The light transmittance of the polarizing plate of the present invention is superior to that using the average refractive index because the angle formed by the slow axis of the light transmissive substrate and the transmission axis of the polarizer is in the above range. It will be.
ここで、画像表示装置には、通常、一対の偏光板が偏光子の透過軸同士がクロスニコルの関係となるように配置されている。本発明の偏光板は、上記一対の偏光板のいずれであってもよい。すなわち、本発明の偏光板は、観察者側から、面内に複屈折率を有する光透過性基材、偏光子がこの順に積層された状態で、画像表示装置の表面に配置して用いられる構成であってもよく、観察者側から、偏光子、面内に複屈折率を有する光透過性基材がこの順に積層された状態で、画像表示装置のバックライト光源側に配置して用いられるものであってもよい。更に、上記一対の偏光板のいずれもが本発明の偏光板であってもよい。 Here, in the image display device, a pair of polarizing plates is usually arranged so that the transmission axes of the polarizers have a crossed Nicols relationship. The polarizing plate of the present invention may be any of the above pair of polarizing plates. That is, the polarizing plate of the present invention is used by placing it on the surface of an image display device in a state where a light-transmitting base material having a birefringence in-plane and a polarizer are laminated in this order from the observer side. It may be configured, and from the observer side, a polarizer and a light-transmitting base material having a birefringence index in the plane are laminated in this order and used on the backlight light source side of the image display device. May be used. Further, any of the pair of polarizing plates may be the polarizing plate of the present invention.
本発明の偏光板は、光透過性基材と偏光子とが、光透過性基材の進相軸と偏光子の透過軸とが特定の関係となるように積層されているため、光透過率が改善されたものとなる。このような本発明の偏光板による光透過率改善方法もまた、本発明の一つである。 In the polarizing plate of the present invention, the light-transmitting substrate and the polarizer are laminated so that the fast axis of the light-transmitting substrate and the transmission axis of the polarizer are in a specific relationship. The rate will be improved. Such a method of improving light transmittance by the polarizing plate of the present invention is also one of the present invention.
また、本発明の偏光板は、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とのなす角度が、９０°とならないように積層することで製造することができる。このような本発明の偏光板を製造する方法もまた、本発明の一つである。 Further, the polarizing plate of the present invention includes a light-transmitting base material having a birefringence in the plane and the polarizer, and a direction in which the refractive index of the light-transmitting base material having a birefringence in the plane is small. It can manufacture by laminating | stacking so that the angle which the fast axis which is and the transmission axis of the said polarizer may not become 90 degrees. Such a method for producing the polarizing plate of the present invention is also one aspect of the present invention.
すなわち、本発明の偏光板の製造方法は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板の製造方法であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有することを特徴とする。
本発明の画像表示装置の製造方法において、上記面内に複屈折率を有する光透過性基材と偏光子としては、上述した本発明の偏光板と同様のものが挙げられる。
また、上記面内に複屈折率を有する光透過性基材と上記偏光子との積層は、公知の接着剤を介して行うことが好ましい。
That is, the method for producing a polarizing plate of the present invention is a method for producing a polarizing plate in which at least a light-transmitting substrate having a birefringence index in the plane is provided on a polarizer, and the birefringence is in the plane. A light-transmitting base material having a refractive index and the polarizer, and a fast axis that is a direction in which the refractive index of the light-transmitting base material having a birefringence in the plane is small, and a transmission axis of the polarizer. It has the process of arrange | positioning so that the angle made may not become 90 degrees, It is characterized by the above-mentioned.
In the method for producing an image display device of the present invention, examples of the light-transmitting substrate and the polarizer having a birefringence in the plane include those similar to the polarizing plate of the present invention described above.
Moreover, it is preferable to laminate | stack the transparent base material which has a birefringence in the said surface, and the said polarizer through a well-known adhesive agent.
上述した本発明の偏光板を備えてなる画像表示装置もまた、本発明の一つである。
本発明の画像表示装置は、液晶セルと、該液晶セルを背面から照射するバックライト光源とを備え、上記液晶セルのバックライト光源側に、本発明の偏光板が形成されてなる液晶表示装置（ＬＣＤ）であることが好ましい。
The image display device comprising the polarizing plate of the present invention described above is also one aspect of the present invention.
The image display device of the present invention comprises a liquid crystal cell and a backlight light source that irradiates the liquid crystal cell from the back, and the liquid crystal display device in which the polarizing plate of the present invention is formed on the backlight light source side of the liquid crystal cell. (LCD) is preferred.
また、本発明の画像表示装置は有機ＥＬであってもよい。上記有機ＥＬは、画像表示原理上、偏光子を必要としないが、外光反射防止の観点から、観測者側から面内に複屈折率を有する光透過性基材、偏光子、λ／４位相差板、有機ＥＬの順に積層した構成を用いる場合がある。
上記有機ＥＬの画像表示方式としては、白色発光層を用い、カラーフィルタを通すことで、カラー表示を得るカラーフィルタ方式、青色発光層を用い、その発光の一部を、色変換層を通すことによりカラー表示を得る色変換方式、赤色・緑色・青色の発光層を用いる３色方式、この３色方式にカラーフィルタを併用した方式などが挙げられる。発光層の材料としては、低分子であっても、高分子であってもよい。
The image display device of the present invention may be an organic EL. The organic EL does not require a polarizer on the principle of image display, but from the viewpoint of preventing external light reflection, a light-transmitting substrate having a birefringence in-plane from the observer side, a polarizer, λ / 4 A configuration in which a retardation plate and an organic EL are sequentially laminated may be used.
As an organic EL image display method, a white light emitting layer is used and a color filter is used to obtain a color display by using a color filter, a blue light emitting layer is used, and part of the light emission is passed through a color conversion layer. There are a color conversion method for obtaining a color display, a three-color method using red, green, and blue light-emitting layers, a method using a color filter in combination with the three-color method, and the like. The material of the light emitting layer may be a low molecule or a polymer.
本発明の画像表示装置は、いずれの場合も、テレビジョン、コンピュータ、電子ペーパー、タブレットＰＣなどのディスプレイ表示に使用することができ、特に、高精細画像用ディスプレイの表面に好適に使用することができる。 In any case, the image display device of the present invention can be used for display display of a television, a computer, electronic paper, a tablet PC, etc., and particularly preferably used for the surface of a high-definition image display. it can.
また、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板を備えた画像表示装置の製造方法も本発明の一つである。
すなわち、本発明の画像表示装置の製造方法は、少なくとも、面内に複屈折率を有する光透過性基材が偏光子上に設けられた偏光板を備えた画像表示装置の製造方法であって、上記面内に複屈折率を有する光透過性基材と上記偏光子とを、上記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、上記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有することを特徴とする。
本発明の画像表示装置の製造方法において、上記偏光板を構成する面内に複屈折率を有する光透過性基材及び偏光子としては、上述した本発明の偏光板で説明したものと同様のものが挙げられる。
In addition, a manufacturing method of an image display device including at least a polarizing plate in which a light-transmitting base material having a birefringence index in a plane is provided on a polarizer is also one aspect of the present invention.
That is, the manufacturing method of the image display device of the present invention is a manufacturing method of an image display device including at least a polarizing plate in which a light-transmitting base material having a birefringence index is provided on a polarizer. A light-transmitting substrate having a birefringence in the plane and the polarizer, a fast axis in a direction in which the refractive index of the light-transmitting substrate having a birefringence in the plane is small, and It has the process of arrange | positioning so that the angle which the transmission axis of a polarizer makes may not become 90 degrees, It is characterized by the above-mentioned.
In the manufacturing method of the image display device of the present invention, the light-transmitting substrate and the polarizer having a birefringence in the plane constituting the polarizing plate are the same as those described in the polarizing plate of the present invention described above. Things.
上述のように本発明の偏光板は光透過性基材と偏光子とが、光透過性基材の進相軸と偏光子の透過軸とが特定の関係となるように積層されているため、光透過率が改善されたものとなる。本発明の画像表示装置は、このような本発明の偏光板を備えたものであるため、本発明の画像表示装置も光透過率が改善されたものとなる。 As described above, in the polarizing plate of the present invention, the light-transmitting substrate and the polarizer are laminated so that the fast axis of the light-transmitting substrate and the transmission axis of the polarizer have a specific relationship. The light transmittance is improved. Since the image display device of the present invention includes the polarizing plate of the present invention, the image display device of the present invention also has improved light transmittance.
本発明の偏光板は、上述した構成からなるものであるため、面内に複屈折率を有する光透過性基材が用いられた場合であっても、光透過率に優れたものとなり、また、従来の面内に位相差を持たないトリアセチルセルロースに代表されるセルロースエステルからなるフィルムが用いられた偏光板であっても、あえて、複屈折率を持たせることで、透過率が優れたものとなる。 Since the polarizing plate of the present invention has the above-described configuration, even when a light-transmitting substrate having a birefringence in the surface is used, it has excellent light transmittance. Even a polarizing plate using a film made of cellulose ester typified by triacetyl cellulose that does not have a phase difference in the plane in the past has an excellent transmittance by providing a birefringence. It will be a thing.
以下に実施例及び比較例を掲げて本発明を更に詳しく説明するが、本発明はこれら実施例及び比較例のみに限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.
（光透過性基材の作製）
（面内に複屈折率を有さない光透過性基材Ａの作製）
セルロースアセテートプロピオネート（イーストマンケミカル社製ＣＡＰ５０４−０．２）を、塩化メチレンを溶剤として固形分濃度が１５％になるように溶解後、ガラス上に流延し、乾燥させ、光透過性基材Ａを得た。波長５５０ｎｍにおけるΔｎ＝０．００００２であり、平均屈折率Ｎ＝１．４８３８であった。
(Production of light-transmitting substrate)
(Preparation of light-transmitting substrate A having no in-plane birefringence)
Cellulose acetate propionate (CAP504-0.2 manufactured by Eastman Chemical Co., Ltd.) was dissolved in methylene chloride as a solvent so that the solid content concentration was 15%, then cast on glass, dried, and light transmissive. A substrate A was obtained. Δn at a wavelength of 550 nm was 0.00002, and the average refractive index N was 1.4838.
（面内に複屈折を有する光透過性基材ａの作製）
光透過性基材Ａを、１６０℃で１．５倍自由端一軸延伸して、面内に複屈折を有する光透過性基材ａを作製した。３次元屈折率波長分散を算出した結果、波長５５０ｎｍにおける屈折率ｎｘ＝１．４８４５、ｎｙ＝１．４８３５であり、ｎｚ＝１．４８３４であった。
(Preparation of light-transmitting substrate a having in-plane birefringence)
The light transmissive substrate A was uniaxially stretched 1.5 times at 160 ° C. to prepare a light transmissive substrate a having in-plane birefringence. As a result of calculating the three-dimensional refractive index wavelength dispersion, the refractive index at a wavelength of 550 nm was nx = 1.4845, ny = 1.4835, and nz = 1.4834.
（面内に複屈折率を有さない光透過性基材Ｂの作製）
光透過性基材Ｂとして、シクロオレフィンポリマーよりなる、日本ゼオン社製未延伸ゼオノアを準備した。波長５５０ｎｍにおけるΔｎ＝０．００００４であり、平均屈折率Ｎ＝１．５１７７であった。
(Preparation of light transmissive substrate B having no in-plane birefringence)
As the light-transmitting substrate B, an unstretched ZEONOR made of Nippon Zeon Co., Ltd. made of a cycloolefin polymer was prepared. Δn = 0.00004 at a wavelength of 550 nm, and the average refractive index N = 1.5177.
（面内に複屈折を有する光透過性基材ｂの作製）
光透過性基材Ｂを、１５０℃で１．５倍自由端一軸延伸して、面内に複屈折を有する光透過性基材ｂを作製した。３次元屈折率波長分散を算出した結果、波長５５０ｎｍにおける屈折率ｎｘ＝１．５１８６、ｎｙ＝１．５１７２であり、ｎｚ＝１．５１７３であった。
(Preparation of light-transmitting substrate b having birefringence in the plane)
The light transmissive substrate B was uniaxially stretched 1.5 times at 150 ° C. to produce a light transmissive substrate b having birefringence in the plane. As a result of calculating the three-dimensional refractive index wavelength dispersion, the refractive index at a wavelength of 550 nm was nx = 1.5186, ny = 1.5172, and nz = 1.5173.
（面内に複屈折率を有さない光透過性基材Ｃの作製）
ポリエチレンテレフタレート材料を２９０℃で溶融して、ガラス上にて、ゆっくりと冷却し、光透過性基材Ｃを得た。波長５５０ｎｍにおけるΔｎ＝０．０００３５であり、平均屈折率Ｎ＝１．６１６７であった。
(Preparation of a light-transmitting substrate C having no in-plane birefringence)
A polyethylene terephthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate C. Δn at a wavelength of 550 nm was 0.00035, and the average refractive index N was 1.6167.
（面内に複屈折を有する光透過性基材ｃ１の作製）
光透過性基材Ｃを、１２０℃で４．０倍固定端一軸延伸して、面内に複屈折を有する光透過性基材ｃ１を作製した。分光光度計を用いて、屈折率波長分散（ｎｘ、ｎｙ）を計算した。波長５５０ｎｍにおける屈折率ｎｘ＝１．７０１、ｎｙ＝１．６０１５であり、ｎｚ＝１．５４７６であった。
(Preparation of light-transmitting substrate c1 having in-plane birefringence)
The light transmissive substrate C was uniaxially stretched 4.0 times at 120 ° C. to produce a light transmissive substrate c1 having birefringence in the plane. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.701, ny = 1.0165, and nz = 1.5476.
（面内に複屈折を有する光透過性基材ｃ２の作製）
光透過性基材Ｃを、１２０℃で２．０倍自由端一軸延伸して、面内に複屈折を有する光透過性基材ｃ２を作製した。分光光度計を用いて、屈折率波長分散（ｎｘ、ｎｙ）を計算した。波長５５０ｎｍにおける屈折率ｎｘ＝１．６５１１、ｎｙ＝１．５９９８であり、ｎｚ＝１．５９９２であった。
(Production of light-transmitting substrate c2 having birefringence in the plane)
The light transmissive substrate C was uniaxially stretched 2.0 times at 120 ° C. to produce a light transmissive substrate c2 having birefringence in the plane. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.511, ny = 1.5998, and nz = 1.5992.
（面内に複屈折を有する光透過性基材ｃ３の作製）
光透過性基材Ｃを、１２０℃で二軸延伸の倍率を調整して、面内に複屈折を有する光透過性基材ｃ３を作製した。分光光度計を用いて、屈折率波長分散（ｎｘ、ｎｙ）を計算した。波長５５０ｎｍにおける屈折率ｎｘ＝１．６６５２、ｎｙ＝１．６１５３であり、ｎｚ＝１．５６９６であった。
(Preparation of light-transmitting substrate c3 having in-plane birefringence)
The light transmissive substrate C was adjusted at a biaxial stretching ratio at 120 ° C. to prepare a light transmissive substrate c3 having in-plane birefringence. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.6652, ny = 1.6153, and nz = 1.5696.
（面内に複屈折を有する光透過性基材ｃ４の作製）
光透過性基材Ｃを、１２０℃で二軸延伸の倍率を調整して、面内に複屈折を有する光透過性基材ｃ４を作製した。分光光度計を用いて、屈折率波長分散（ｎｘ、ｎｙ）を計算した。波長５５０ｎｍにおける屈折率ｎｘ＝１．６７０８、ｎｙ＝１．６１８９であり、ｎｚ＝１．５６０４であった。
(Production of light-transmitting base material c4 having birefringence in the plane)
The light-transmitting substrate C was adjusted at a biaxial stretching ratio at 120 ° C. to prepare a light-transmitting substrate c4 having in-plane birefringence. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.6708, ny = 1.6189, and nz = 1.5604.
（面内に複屈折率を有さない光透過性基材Ｄの作製）
ポリエチレンナフタレート材料を２９０℃で溶融して、ガラス上にて、ゆっくりと冷却し、光透過性基材Ｄを得た。波長５５０ｎｍにおけるΔｎ＝０．０００４であり、平均屈折率Ｎ＝１．６８３３であった。
(Preparation of light transmissive substrate D having no in-plane birefringence)
A polyethylene naphthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate D. At the wavelength of 550 nm, Δn = 0.004, and the average refractive index N = 1.6833.
（面内に複屈折を有する光透過性基材ｄの作製）
光透過性基材Ｄを、１２０℃で４．０倍固定端一軸延伸して、面内に複屈折を有する光透過性基材ｄを作製した。分光光度計を用いて、屈折率波長分散（ｎｘ、ｎｙ）を計算した。波長５５０ｎｍにおける屈折率ｎｘ＝１．８４７２、ｎｙ＝１．６４６６であり、ｎｚ＝１．５５６１であった。
(Preparation of light-transmitting substrate d having birefringence in the surface)
The light transmissive substrate D was uniaxially stretched 4.0 times at 120 ° C. to produce a light transmissive substrate d having birefringence in the plane. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.8472, ny = 1.6466, and nz = 1.5561.
（偏光板透過率の計算）
透過率の計算は、２×２行列法や４×４行列法、拡張ジョーンズ行列法を用いて計算できる。実施例、比較例、参考例においては、シミュレーションソフト（ＬＣＤＭａｓｔｅｒ、シンテック社製）を用いて、偏光板の透過率を計算した。図４に偏光板の層構成を示す。図４の実施例及び比較例部分に、各光透過性基材の３次元屈折率波長分散を入れて上記計算を行った。面内に複屈折を有さないと判断した光透過性基材は、平均屈折率Ｎ＝ｎｘ＝ｎｙ＝ｎｚとし、面内に複屈折を有すると判断した光透過性基材は、実測値を用いた。各層の膜厚は、実施例、比較例、保護フィルム部分は８０μｍとし、偏光子部分は２０μｍとした。
図５は、光源のスペクトルである。入射する光の偏光状態は、液晶パネル透過後の偏光状態と同じとなるよう、直線偏光とし、偏光子の透過軸方向に振動する光とした。
図６に、用いた保護フィルムの屈折率波長分散を示し、保護フィルムは、等方性材料とした。
図７に、用いた偏光子の屈折率及び消衰係数を示した。なお、図７中、吸収軸方向と透過軸方向とはほぼ重なって示されている。
(Calculation of polarizing plate transmittance)
The transmittance can be calculated using a 2 × 2 matrix method, a 4 × 4 matrix method, or an extended Jones matrix method. In the examples, comparative examples, and reference examples, the transmittance of the polarizing plate was calculated using simulation software (LCD Master, manufactured by Shintec Co., Ltd.). FIG. 4 shows the layer structure of the polarizing plate. The above calculation was performed by putting the three-dimensional refractive index wavelength dispersion of each light-transmitting substrate into the Example and Comparative Example portions of FIG. The light-transmitting substrate determined to have no in-plane birefringence has an average refractive index N = nx = ny = nz, and the light-transmitting substrate determined to have in-plane birefringence is a measured value. Was used. The film thickness of each layer was set to 80 μm in the examples, comparative examples, and the protective film part, and 20 μm in the polarizer part.
FIG. 5 shows the spectrum of the light source. The polarization state of the incident light was linearly polarized so as to be the same as the polarization state after transmission through the liquid crystal panel, and the light oscillated in the transmission axis direction of the polarizer.
FIG. 6 shows the refractive index wavelength dispersion of the protective film used, and the protective film was an isotropic material.
FIG. 7 shows the refractive index and extinction coefficient of the polarizer used. In FIG. 7, the absorption axis direction and the transmission axis direction are substantially overlapped.
（実施例１）
光透過性基材ａの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
Example 1
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate a, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例１）
光透過性基材ａの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 1)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate a, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is 90 degrees, Transmittance was calculated.
（実施例２）
光透過性基材ｂの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
(Example 2)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate b, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例２）
光透過性基材ｂの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 2)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate b, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is 90 degrees, Transmittance was calculated.
（実施例３）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
(Example 3)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（実施例４）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が５度となるように設置し、偏光板の透過率を計算した。
Example 4
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 5 degrees. Transmittance was calculated.
（実施例５）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が２２．５度となるように設置し、偏光板の透過率を計算した。
(Example 5)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 22.5 degrees. The transmittance of the plate was calculated.
（実施例６）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が４５度となるように設置し、偏光板の透過率を計算した。
(Example 6)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 45 degrees. Transmittance was calculated.
（比較例３）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 3)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 90 degrees. Transmittance was calculated.
（実施例７）
光透過性基材ｃ２の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
(Example 7)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c2, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例４）
光透過性基材ｃ２の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 4)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive base material c2, the angle between the fast axis of the light transmissive base material and the transmission axis of the polarizer is set to 90 degrees. Transmittance was calculated.
（実施例８）
光透過性基材ｃ３の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
(Example 8)
Using the three-dimensional refractive index wavelength dispersion of the light-transmitting substrate c3, the angle between the fast axis of the light-transmitting substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例５）
光透過性基材ｃ３の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 5)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c3, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 90 degrees. Transmittance was calculated.
（実施例９）
光透過性基材ｃ４の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
Example 9
Using the three-dimensional refractive index wavelength dispersion of the light-transmitting substrate c4, the angle between the fast axis of the light-transmitting substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例６）
光透過性基材ｃ４の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 6)
Using the three-dimensional refractive index wavelength dispersion of the light-transmitting substrate c4, the angle between the fast axis of the light-transmitting substrate and the transmission axis of the polarizer is 90 degrees. Transmittance was calculated.
（実施例１０）
光透過性基材ｄの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、偏光板の透過率を計算した。
(Example 10)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate d, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. Transmittance was calculated.
（比較例７）
光透過性基材ｄの３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、偏光板の透過率を計算した。
(Comparative Example 7)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate d, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is 90 degrees, Transmittance was calculated.
（実施例１１）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が０度となるように設置し、更に、光透過性基材よりも観測者側に、図８に示した屈折率波長分散を有するハードコート層を設置し、偏光板の透過率を計算した。
(Example 11)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is set to 0 degree. The hard coat layer having the refractive index wavelength dispersion shown in FIG. 8 was installed on the observer side from the transmissive substrate, and the transmittance of the polarizing plate was calculated.
（比較例８）
光透過性基材ｃ１の３次元屈折率波長分散を用いて、光透過性基材の進相軸と、偏光子の透過軸とのなす角度が９０度となるように設置し、更に、光透過性基材よりも観測者側に、図８に示した屈折率波長分散を有するハードコート層を設置し、偏光板の透過率を計算した。
(Comparative Example 8)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate c1, the angle between the fast axis of the light transmissive substrate and the transmission axis of the polarizer is 90 degrees. The hard coat layer having the refractive index wavelength dispersion shown in FIG. 8 was installed on the observer side from the transmissive substrate, and the transmittance of the polarizing plate was calculated.
（参考例１）
光透過性基材Ａの３次元屈折率波長分散を用いて、偏光板の透過率を計算した。
(Reference Example 1)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate A, the transmittance of the polarizing plate was calculated.
（参考例２）
光透過性基材Ｂの３次元屈折率波長分散を用いて、偏光板の透過率を計算した。
(Reference Example 2)
Using the three-dimensional refractive index wavelength dispersion of the light-transmitting substrate B, the transmittance of the polarizing plate was calculated.
（参考例３）
光透過性基材Ｃの３次元屈折率波長分散を用いて、偏光板の透過率を計算した。
(Reference Example 3)
Using the three-dimensional refractive index wavelength dispersion of the light-transmitting substrate C, the transmittance of the polarizing plate was calculated.
（参考例４）
光透過性基材Ｄの３次元屈折率波長分散を用いて、偏光板の透過率を計算した。
(Reference Example 4)
Using the three-dimensional refractive index wavelength dispersion of the light transmissive substrate D, the transmittance of the polarizing plate was calculated.
（参考例５）
光透過性基材ｃ１のかわりに、光透過性基材Ｃの３次元屈折率波長分散を用いた以外は、実施例１１と同様の構成にて、偏光板の透過率を計算した。
(Reference Example 5)
The transmittance of the polarizing plate was calculated in the same configuration as in Example 11 except that the three-dimensional refractive index wavelength dispersion of the light transmissive substrate C was used instead of the light transmissive substrate c1.
実施例、比較例及び参考例に係る各評価結果を表１に示す。
透過率は、各材料ごとに、面内に複屈折を有さない場合の透過率を１００として、面内に複屈折を有する偏光板の透過率を示している。
Table 1 shows the results of evaluation according to Examples, Comparative Examples, and Reference Examples.
The transmittance indicates the transmittance of a polarizing plate having in-plane birefringence, where 100 is the transmittance when there is no in-plane birefringence for each material.
表１に示したように、実施例１と比較例１との比較、実施例２と比較例２との比較、実施例３〜６と比較例３との比較、実施例７と比較例４との比較、実施例８と比較例５との比較、実施例９と比較例６との比較、実施例１０と比較例７との比較及び、実施例１１と比較例８との比較より、光透過性基材の進相軸と偏光子の透過軸とが所定の角度範囲内にある実施例に係る偏光板は、当該角度範囲を外れる比較例に係る偏光板よりも光透過性に優れていた。
また、実施例１と参考例１との比較、実施例２と参考例２との比較、実施例３、７、８と参考例３との比較、実施例１０と参考例４との比較、及び、実施例１１と参考例５との比較より、面内に複屈折率を有する光透過性基材を用いた実施例に係る偏光板は、面内に複屈折率を有さない光透過性基材を用いた参考例に係る偏光板よりも、光透過性に優れていた。
ここで、実施例３、７、８、９と参考例３との比較より、実施例９は、光透過性基材の遅相軸方向の屈折率（ｎｘ）、進相軸方向の屈折率（ｎｙ）及び光透過性基材の平均屈折率（Ｎ）が下記式を満たすことができず、面内に複屈折を有さない光透過性基材を用いた参考例３に係る偏光板よりも劣っていた。
ｎｘ＞Ｎ＞ｎｙ
As shown in Table 1, comparison between Example 1 and Comparative Example 1, comparison between Example 2 and Comparative Example 2, comparison between Examples 3-6 and Comparative Example 3, and Example 7 and Comparative Example 4 Comparison between Example 8 and Comparative Example 5, Comparison between Example 9 and Comparative Example 6, Comparison between Example 10 and Comparative Example 7, and Comparison between Example 11 and Comparative Example 8, The polarizing plate according to the example in which the fast axis of the light-transmitting substrate and the transmission axis of the polarizer are within a predetermined angle range is superior to the polarizing plate according to the comparative example that is out of the angular range. It was.
Also, a comparison between Example 1 and Reference Example 1, a comparison between Example 2 and Reference Example 2, a comparison between Examples 3, 7, 8 and Reference Example 3, a comparison between Example 10 and Reference Example 4, From the comparison between Example 11 and Reference Example 5, the polarizing plate according to the example using the light-transmitting base material having the in-plane birefringence is light transmissive having no in-plane birefringence. The light transmittance was superior to the polarizing plate according to the reference example using the conductive substrate.
Here, from comparison between Examples 3, 7, 8, and 9 and Reference Example 3, Example 9 has a refractive index (nx) in the slow axis direction and a refractive index in the fast axis direction of the light-transmitting substrate. (Ny) and the average refractive index (N) of the light-transmitting substrate cannot satisfy the following formula, and the polarizing plate according to Reference Example 3 using a light-transmitting substrate that does not have birefringence in the plane Was inferior.
nx>N> ny
本発明の偏光板は、面内に複屈折率を有する光透過性基材が用いられた場合であっても、光透過率に優れたものとなり、また、従来の面内に位相差を持たないトリアセチルセルロースに代表されるセルロースエステルからなるフィルムが用いられた偏光板であっても、あえて、複屈折率を持たせることで、光透過率が優れたものとなり、液晶ディスプレイ（ＬＣＤ）の偏光板として好適に用いることができる。 The polarizing plate of the present invention has excellent light transmittance even when a light-transmitting substrate having a birefringence in the plane is used, and has a phase difference in the conventional plane. Even a polarizing plate using a film composed of a cellulose ester typified by triacetylcellulose has a birefringence, which makes it excellent in light transmittance, and is used for a liquid crystal display (LCD). It can be suitably used as a polarizing plate.
Claims (9)
前記面内に複屈折率を有する光透過性基材と前記偏光子とは、前記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、前記偏光子の透過軸とがなす角度が９０°とならないように配置されている
ことを特徴とする偏光板。 At least a polarizing plate in which a light-transmitting substrate having a birefringence in the plane is provided on a polarizer,
The light-transmitting substrate having a birefringence in the plane and the polarizer include a fast axis that is a direction in which the refractive index of the light-transmitting substrate having a birefringence in the plane is small, and the polarization A polarizing plate, characterized in that the angle formed by the transmission axis of the child is not 90 °.
ｎｘ＞Ｎ＞ｎｙ The refractive index in the slow axis direction, which is the direction in which the refractive index in the plane of the light transmissive substrate is large, is nx, and the phase advance is a direction orthogonal to the slow axis direction in which the refractive index in the plane is large The polarizing plate according to claim 1, wherein when the refractive index in the axial direction is ny and the average refractive index of the light-transmitting substrate is N, the light-transmitting substrate satisfies the relationship of the following formula.
nx>N> ny
前記面内に複屈折率を有する光透過性基材と前記偏光子とを、前記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、前記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有する
ことを特徴とする偏光板の製造方法。 At least a method for producing a polarizing plate in which a light-transmitting substrate having a birefringence in the plane is provided on a polarizer,
The light-transmitting substrate having a birefringence index in the plane and the polarizer, the fast axis in a direction in which the refractive index of the light-transmitting substrate having a birefringence index in the plane is small, and the polarization A method for producing a polarizing plate, comprising a step of arranging so that an angle formed by a transmission axis of a child does not become 90 °.
前記面内に複屈折率を有する光透過性基材と前記偏光子とを、前記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である進相軸と、前記偏光子の透過軸とがなす角度が９０°とならないように配置する工程を有する
ことを特徴とする画像表示装置の製造方法。 At least a method for producing an image display device comprising a polarizing plate in which a light-transmitting substrate having a birefringence index in a plane is provided on a polarizer,
The light-transmitting substrate having a birefringence index in the plane and the polarizer, the fast axis in a direction in which the refractive index of the light-transmitting substrate having a birefringence index in the plane is small, and the polarization A method of manufacturing an image display device, comprising a step of arranging so that an angle formed by a transmission axis of a child does not become 90 °.
前記面内に複屈折率を有する光透過性基材と前記偏光子とを、前記面内に複屈折率を有する光透過性基材の屈折率が小さい方向である遅相軸と、前記偏光子の透過軸とがなす角度が９０°とならないように配置する
ことを特徴とする偏光板の光透過率改善方法。 At least a method for improving the light transmittance of a polarizing plate in which a light-transmitting substrate having a birefringence index in a plane is provided on a polarizer,
The light-transmitting base material having a birefringence index in the plane and the polarizer, the slow axis in which the refractive index of the light-transmitting base material having a birefringence index in the plane is small, and the polarization A method for improving the light transmittance of a polarizing plate, characterized in that the angle formed by the transmission axis of the child is not 90 °.
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