JP4936487B2 - Polarizer - Google Patents
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- JP4936487B2 JP4936487B2 JP2010160814A JP2010160814A JP4936487B2 JP 4936487 B2 JP4936487 B2 JP 4936487B2 JP 2010160814 A JP2010160814 A JP 2010160814A JP 2010160814 A JP2010160814 A JP 2010160814A JP 4936487 B2 JP4936487 B2 JP 4936487B2
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Description
本発明は、クロスニコルに配置した偏光子間において視角の変化により生じる偏光子の軸変化に基づく光漏れを広帯域の可視光域で防止して広視野角の液晶表示等を達成しうる偏光板に関する。 The present invention relates to a polarizing plate capable of preventing liquid leakage due to a change in the axis of the polarizer caused by a change in viewing angle between polarizers arranged in crossed Nicols and achieving a wide viewing angle liquid crystal display or the like in a wide visible light range. About.
偏光子ではそれをクロスニコルに配置したとき法線(正面)方向では正常に光が遮断される場合においても、方位を変えて斜視したときに光漏れが生じる問題点があった。これは斜視による見掛け角度の変化で偏光子間のクロスニコルの光軸関係がズレて崩れることによる。従来、斯かる方位角による光漏れ問題の解消を図ったものとしては、位相差が190〜320nmで後述するNzが0.1〜0.9の複屈折性を示す透明保護フィルムをその遅相軸が偏光子の吸収軸に対し平行となるように配置した偏光板が知られていた(特許文献1)。 When the polarizer is arranged in crossed Nicols, there is a problem that light leakage occurs when the azimuth is changed and the light is normally blocked even when the light is normally blocked in the normal (front) direction. This is because the crossed Nicols optical axis relationship between the polarizers shifts and collapses due to the change in the apparent angle due to the perspective. Conventionally, as a solution to the light leakage problem due to such an azimuth angle, a transparent protective film having a phase difference of 190 to 320 nm and Nz of 0.1 to 0.9, which will be described later, is shown as a slow phase. There has been known a polarizing plate in which the axis is parallel to the absorption axis of the polarizer (Patent Document 1).
前記の偏光板は、水分の侵入防止等による耐久性の向上を目的に偏光子の片面又は両面に接着する透明保護フィルムとして、それまでの複屈折性を殆ど示さないトリアセチルセルロース(TAC)フィルム等による等方性の透明保護フィルムに代えて、可視光に対し約1/2波長の位相差特性を示すフィルムを用いて視角変化による偏光子間の吸収軸等のズレを補償するようにしたものである。 The above polarizing plate is a triacetyl cellulose (TAC) film that exhibits almost no birefringence as a transparent protective film that adheres to one or both sides of a polarizer for the purpose of improving durability by preventing moisture from entering. Instead of an isotropic transparent protective film, etc., a film having a retardation characteristic of about ½ wavelength with respect to visible light is used to compensate for a shift in the absorption axis between polarizers due to a change in viewing angle. Is.
しかしながら斯かる補償対策では、波長分散に対処できない問題点があった。すなわち一般に位相差フィルムでは波長にて位相差が相違する波長分散が生じるため前記した1/2波長板としての機能は特定の波長光に対してのみ現れ、他の波長光に対しては1/2波長板として正確に機能せずそれらの波長光が直線偏光性に劣ることとなって着色問題が発生する。ちなみに位相差フィルムの特性を視感度が最高の波長550nm近傍の光の補償に最適化した場合、他の波長光では最適化条件よりズレて青色に着色し、液晶表示装置等に適用した場合にその着色問題が表示のニュートラル性の低下問題として表出する。
本発明は、クロスニコルに配置した偏光子を光軸からズレた方位より斜視しても光漏れを生じにくく、かつ波長分散による着色も生じにくくてニュートラル性に優れる偏光板の開発を課題とする。
However, such compensation measures have a problem that chromatic dispersion cannot be dealt with. That is, in general, in a retardation film, chromatic dispersion occurs in which the phase difference is different depending on the wavelength. Therefore, the function as the half-wave plate described above appears only for specific wavelength light, and for other wavelength light, 1 / It does not function correctly as a two-wavelength plate, and those wavelength lights are inferior in linear polarization, causing a coloring problem. By the way, when the characteristics of the retardation film are optimized to compensate for light near the wavelength of 550 nm where the visibility is the highest, when the other wavelength light is shifted from the optimization condition to blue and applied to a liquid crystal display device, etc. The coloring problem appears as a problem of deterioration in neutrality of display.
It is an object of the present invention to develop a polarizing plate that is excellent in neutrality because it hardly causes light leakage even when the polarizer arranged in crossed Nicols is obliquely viewed from the direction deviated from the optical axis and does not easily cause coloring due to wavelength dispersion. .
本発明は、偏光子の少なくとも片面に、波長550nmの光による面内位相差が190〜320nmである2層の位相差フィルムよりなる透明保護フィルムを、その各位相差フィルムの遅相軸が偏光子の吸収軸と平行関係となるように接着してなり、かつ面内の屈折率をnx、ny、厚さ方向の屈折率をnzとしてnx>ny及びNz=(nx−nz)/(nx−ny)としたとき、前記2層の位相差フィルムが当該Nzに基づいて0.8〜0.95のものと0.55〜0.7のものとの組合せからなることを特徴とする偏光板を提供するものである。 The present invention provides a transparent protective film comprising a two-layer retardation film having an in-plane retardation of 190 to 320 nm with light having a wavelength of 550 nm on at least one surface of the polarizer, and the retardation axis of each retardation film is a polarizer. And nx> ny and Nz = (nx-nz) / (nx-), where the in-plane refractive index is nx, ny, and the refractive index in the thickness direction is nz. ny), the two-layer retardation film is a combination of 0.8 to 0.95 and 0.55 to 0.7 based on the Nz. Is to provide.
本発明によれば、視角の変化に対応して透明保護フィルムを形成する位相差フィルムの遅相軸等の光軸が変化して偏光子の吸収軸等の光軸変化を相殺する補償作用を示し、クロスニコルに配置した場合に偏光子の光軸方向と共にその光軸からズレた方位においても光漏れを抑制できると共に、位相差の波長分散も抑制できてニュートラル性(無着色性)に優れ直線偏向性が変化しにくい偏光板を得ることができ、それを用いて広い視野角でコントラスト等の表示品位に優れる液晶表示装置等を形成することができる。また偏光板は、位相差フィルムが透明保護フィルムを兼ねるため薄型軽量性にも優れている。 According to the present invention, the compensation action of offsetting the optical axis change such as the absorption axis of the polarizer by changing the optical axis such as the slow axis of the retardation film that forms the transparent protective film corresponding to the change in viewing angle. When placed in crossed Nicols, light leakage can be suppressed in the direction of the optical axis of the polarizer as well as in the direction shifted from the optical axis, and wavelength dispersion of the phase difference can also be suppressed, resulting in excellent neutrality (colorlessness). It is possible to obtain a polarizing plate whose linear deflection property is difficult to change, and to use it, it is possible to form a liquid crystal display device having a wide viewing angle and excellent display quality such as contrast. Moreover, since the retardation film serves as a transparent protective film, the polarizing plate is also excellent in thinness and lightness.
本発明による偏光板は、偏光子の少なくとも片面に、波長550nmの光による面内位相差が190〜320nmである2層の位相差フィルムよりなる透明保護フィルムを、その各位相差フィルムの遅相軸が偏光子の吸収軸と平行関係となるように接着してなり、かつ面内の屈折率をnx、ny、厚さ方向の屈折率をnzとしてnx>ny及びNz=(nx−nz)/(nx−ny)としたとき、前記2層の位相差フィルムが当該Nzに基づいて0.8〜0.95のものと0.55〜0.7のものとの組合せからなるものである。その例を図1に示した。1が偏光子、2、3が透明保護フィルムで、21、22が位相差フィルムであり、4は接着剤層である。 The polarizing plate according to the present invention comprises a transparent protective film comprising a two-layer retardation film having an in-plane retardation of 190 to 320 nm by light having a wavelength of 550 nm on at least one surface of a polarizer, and a slow axis of each retardation film. Are bonded so as to be in parallel with the absorption axis of the polarizer, and nx> ny and Nz = (nx−nz) / n where the in-plane refractive index is nx, ny, and the refractive index in the thickness direction is nz. When (nx-ny), the two-layer retardation film is composed of a combination of 0.8 to 0.95 and 0.55 to 0.7 based on the Nz. An example thereof is shown in FIG. 1 is a polarizer, 2 and 3 are transparent protective films, 21 and 22 are retardation films, and 4 is an adhesive layer.
偏光子としては、自然光を入射させた場合に直線偏光が透過する適宜なものを用いることができ特に限定はない。好ましく用いうる偏光子は、偏光度に優れる透過光が光透過率よく得られるものである。斯かる点よりは自然光を入射させた場合に直線偏光が透過すると共に他の光は吸収される吸収二色性偏光子が好ましく、特に薄型化や柔軟性による取扱性などの点より偏光フィルムからなるものが好ましい。なお吸収二色性偏光子は、液晶性二色性染料の塗布配向層などからなっていてもよい。 As the polarizer, an appropriate one that transmits linearly polarized light when natural light is incident can be used, and there is no particular limitation. A polarizer that can be preferably used is one that can obtain a transmitted light with excellent light transmittance with a high degree of polarization. From such a point, an absorbing dichroic polarizer that transmits linearly polarized light and absorbs other light when natural light is incident is preferable, particularly from a polarizing film in terms of thinness and handleability due to flexibility. Is preferred. The absorbing dichroic polarizer may be composed of a coating alignment layer of a liquid crystalline dichroic dye.
前記した偏光フィルムからなる吸収二色性偏光子としても適宜なものを用いうる。可視光域の広い波長範囲で直線偏光を得る点などよりは例えばポリビニルアルコールや部分ホルマール化ポリビニルアルコールの如きポリマーからなるポリビニルアルコール系フィルムにヨウ素又は/及びアゾ系やアントラキノン系、テトラジン系等の二色性染料を吸着方式等の適宜な方式で含有させて延伸配向処理したもの就中、一軸延伸処理したフィルムが好ましく用いうる。 Any suitable absorbing dichroic polarizer composed of the polarizing film described above can be used. From the point of obtaining linearly polarized light in a wide wavelength range in the visible light range, for example, a polyvinyl alcohol film made of a polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol is added to iodine or / and azo, anthraquinone, tetrazine, etc. Among those obtained by containing a chromatic dye by an appropriate method such as an adsorption method and subjected to stretching and orientation treatment, a uniaxially stretched film can be preferably used.
図例の如く偏光子1の片面又は両面には透明保護フィルム2、3が接着積層されるが、本発明においてはその少なくとも片面における透明保護フィルム2は、波長550nmの光による面内位相差がいずれのものも190〜320nmであり、かつNzが0.8〜0.95のものと0.55〜0.7のものとの組合せによる2層の位相差フィルム21、22にて形成される。なお前記のNzは、位相差フィルムにおける面内の屈折率をnx、ny、厚さ方向の屈折率をnzとしてnx>nyとしたとき、式:Nz=(nx−nz)/(nx−ny)にて定義される。
As shown in the figure, transparent
前記において当該2層の位相差フィルムは、その各位相差フィルムの遅相軸が偏光子の吸収軸と平行関係となるように接着積層される。その遅相軸と吸収軸の平行関係は、作業精度等の点より完全な平行状態を意味するものではないが補償効果の点よりは交差角度が少ないほど好ましい。その場合の位相差フィルムの遅相軸、偏光子の吸収軸は正面(方位角:0)からの視角に基づく。Nzが相違する位相差フィルムの積層順序は任意であり、図例ではNz0.8〜0.95のもの21を介してNz0.55〜0.7のもの22が偏光子1に接着積層されており、この配置順序が補償効果の点より好ましい。なお前記の面内位相差は、△n=nx−nyとして、その屈折率差と位相差フィルムの厚さ(d)との積(△n・d)として算出することができる。 In the above, the two-layer retardation film is bonded and laminated so that the slow axis of each retardation film is parallel to the absorption axis of the polarizer. The parallel relationship between the slow axis and the absorption axis does not mean a completely parallel state from the viewpoint of work accuracy and the like, but it is preferable that the crossing angle is smaller than the compensation effect. In this case, the retardation axis of the retardation film and the absorption axis of the polarizer are based on the viewing angle from the front (azimuth angle: 0). The order of lamination of the retardation films having different Nz is arbitrary, and in the illustrated example, Nz 0.55 to 0.7 22 is bonded and laminated to the polarizer 1 via Nz 0.8 to 0.95 21. This arrangement order is preferable from the viewpoint of the compensation effect. The in-plane retardation can be calculated as a product (Δn · d) of the refractive index difference and the thickness (d) of the retardation film as Δn = nx−ny.
位相差フィルムは、例えば高分子フィルムを一軸又は二軸等の適宜な方式で延伸処理してなる複屈折性のフィルムなどとして得ることができる。光透過率に優れて配向ムラや位相差ムラの少ない位相差フィルムが好ましく用いられる。前記した位相差とNzの特性を示す位相差フィルムの形成は、例えば高分子フィルムに熱収縮性フィルムを接着し加熱によるその熱収縮性フィルムの収縮力の作用下に配向処理して厚さ方向の屈折率を制御する方法や、厚さ方向に電界を印加して配向を制御しつつ高分子フィルムを得てそのフィルムを延伸処理する方法などにより行うことができる。その場合に処理対象のフィルムのポリマー種や延伸条件、熱収縮性フィルムの種類や印加電圧等を変更することで位相差やNzを変化させることができる。なお通常の一軸等による延伸処理ではNzが0以下又は1以上となる。 The retardation film can be obtained, for example, as a birefringent film formed by stretching a polymer film by an appropriate method such as uniaxial or biaxial. A retardation film having excellent light transmittance and less alignment unevenness and retardation unevenness is preferably used. The above-mentioned retardation film showing the characteristics of retardation and Nz is formed by, for example, bonding a heat-shrinkable film to a polymer film and performing an orientation treatment under the action of the shrinkage force of the heat-shrinkable film by heating. The refractive index of the film can be controlled, or a polymer film can be obtained while applying an electric field in the thickness direction to control the orientation, and the film is stretched. In that case, the phase difference and Nz can be changed by changing the polymer type and stretching conditions of the film to be treated, the type of heat-shrinkable film, the applied voltage, and the like. Note that Nz is 0 or less or 1 or more in a normal uniaxial stretching process.
位相差フィルムを形成する前記の高分子は、適宜なものであってよく特に限定はない。就中、透明性に優れるものが好ましい。また応力の発生による位相差の変化を抑制する点より光弾性係数の小さいものが好ましい。ちなみにその例としてはポリカーボネートやポリアリレート、ポリスルホンやポリプロピレン等のポリオレフィン、ポリエチレンテレフタレートやポリエチレンナフタレート等のポリエステル、ビニルアルコール系ポリマーやノルボルネン系ポリマー、アクリル系ポリマーやスチレン系ポリマー、セルロース系ポリマーやそれらポリマーの2種又は3種以上を混合したポリマーなどがあげられる。 The polymer for forming the retardation film may be any appropriate one and is not particularly limited. Of these, those excellent in transparency are preferred. Moreover, the thing with a small photoelastic coefficient is preferable from the point which suppresses the change of the phase difference by generation | occurrence | production of stress. Examples include polycarbonates, polyarylates, polyolefins such as polysulfone and polypropylene, polyesters such as polyethylene terephthalate and polyethylene naphthalate, vinyl alcohol polymers, norbornene polymers, acrylic polymers, styrene polymers, cellulose polymers and those polymers. The polymer etc. which mixed these 2 types or 3 types or more are mention | raise | lifted.
透明保護フィルムないしそれを形成する位相差フィルムと偏光子の接着積層は保護効果の向上や光学軸のズレ防止、ゴミ等の異物の侵入防止などを目的とし、例えば透明接着層を介した接着方式などの適宜な方式にて行うことができその接着剤等についても特に限定はない。偏光子や透明保護フィルムの光学特性の変化防止等の点よりは硬化や乾燥の際に高温のプロセスを要しないものが好ましく、長時間の硬化処理や乾燥時間を要しないものが望ましい。斯かる点よりはポリビニルアルコール系接着剤や粘着剤が好ましく用いうる。なお図例では位相差フィルムと偏光子を接着する接着層の図示は省略している。 Adhesive lamination of transparent protective film or retardation film forming the polarizer and polarizer is aimed at improving the protective effect, preventing optical axis misalignment, preventing entry of foreign matters such as dust, etc. There are no particular limitations on the adhesive and the like. From the viewpoint of preventing changes in the optical properties of the polarizer and the transparent protective film, those that do not require a high-temperature process during curing and drying are preferable, and those that do not require a long curing process or drying time are desirable. From such points, polyvinyl alcohol adhesives and pressure-sensitive adhesives can be preferably used. In the example shown in the figure, an adhesive layer for bonding the retardation film and the polarizer is not shown.
前記の粘着剤には例えばアクリル系重合体やシリコーン系ポリマー、ポリエステルやポリウレタン、ポリエーテルや合成ゴムなどの適宜なポリマーを用いてなるものを用いることができる。就中、光学的透明性や粘着特性、耐候性などの点よりアクリル系粘着剤が好ましい。なお図例の如く接着層4、特に粘着層は、液晶セル等の被着体への接着を目的に偏光板の片面又は両面に必要に応じて設けることもできる。その場合、粘着層が表面に露出するときにはそれを実用に供するまでの間、セパレータ等を仮着して粘着層等の表面の汚染等を防止することが好ましい。 As the adhesive, for example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyether, a synthetic rubber, or a suitable polymer can be used. In particular, acrylic pressure-sensitive adhesives are preferred from the viewpoints of optical transparency, pressure-sensitive adhesive properties, weather resistance, and the like. As shown in the figure, the adhesive layer 4, particularly the adhesive layer, can be provided on one or both sides of the polarizing plate as required for the purpose of adhesion to an adherend such as a liquid crystal cell. In that case, when the pressure-sensitive adhesive layer is exposed on the surface, it is preferable to temporarily attach a separator or the like to prevent contamination of the surface of the pressure-sensitive adhesive layer or the like until it is put to practical use.
なお図例の如く補強、耐熱性や耐湿性の向上等の適宜な目的を有する透明保護フィルムは必要に応じ偏光子1の両面に設けうるものであるが、その場合に一方の透明保護フィルムを上記した位相差フィルムで形成しないときには、例えばTAC等の適宜な樹脂の塗布層や樹脂フィルムのラミネート層などとして従来に準じて形成することができる。 In addition, as shown in the figure, a transparent protective film having an appropriate purpose such as reinforcement, improvement in heat resistance and moisture resistance can be provided on both surfaces of the polarizer 1 as necessary. In that case, one transparent protective film is provided. When not formed with the above-mentioned retardation film, it can be formed according to the conventional manner, for example, as an appropriate resin coating layer such as TAC or a laminate layer of a resin film.
前記の場合の透明保護層は、上記した補償効果の維持の点より位相差が可及的に小さいことが好ましく、位相差がある場合にはNzが0若しくは1又はそれらの近傍であることが好ましい。さらにそのNzが0又はその近傍の透明保護層は、その進相軸が偏光子の吸収軸と平行関係となるように設けることが好ましく、Nzが1又はその近傍の透明保護層は、その遅相軸が偏光子の吸収軸と平行関係となるように設けることが好ましい。 In the transparent protective layer in the above case, it is preferable that the phase difference is as small as possible from the viewpoint of maintaining the compensation effect described above, and when there is a phase difference, Nz is 0 or 1 or in the vicinity thereof. preferable. Further, the transparent protective layer having Nz of 0 or its vicinity is preferably provided so that the fast axis is in parallel with the absorption axis of the polarizer, and the transparent protective layer having Nz of 1 or its vicinity is provided with its retardation. It is preferable to provide the phase axis in parallel with the absorption axis of the polarizer.
図2に本発明と従来例を対比して、視角の変化による偏光板の軸ズレの様子をポアンカレ球を用いた模式図として示した。(a)が本発明による偏光板、(b)及び(c)が従来例の偏光板であり、その(b)は位相差が190〜320nmでNzが0.1〜0.9の複屈折性を示す透明保護フィルムをその遅相軸が偏光子の吸収軸に対し平行となるように配置してなる特開平4−305602号公報に準拠した偏光板である。また(c)は透明保護フィルムに面内位相差が約30nm以下で、Nzが1〜30のものを用いた偏光板である。 FIG. 2 is a schematic diagram using a Poincare sphere in which the axial displacement of the polarizing plate due to the change in viewing angle is shown in comparison with the present invention and the conventional example. (A) is a polarizing plate according to the present invention, (b) and (c) are conventional polarizing plates, and (b) is a birefringence having a phase difference of 190 to 320 nm and Nz of 0.1 to 0.9. It is a polarizing plate based on JP-A-4-305602, in which a transparent protective film exhibiting properties is arranged so that its slow axis is parallel to the absorption axis of the polarizer. (C) is a polarizing plate using a transparent protective film having an in-plane retardation of about 30 nm or less and Nz of 1 to 30.
前記のポアンカレ球では半径にて視角を表しており、偏光子の吸収軸Aが45度となるように配置して0度方向から見たときの視角の変化にて光軸の見掛け角度が変化する様子を太線で示している。ただしその軸変化は説明のため実際より大きくしている。なお図例では偏光子の吸収軸Aと、位相差フィルム(透明保護フィルム)の遅相軸Sについて示しているが、偏光子の透過軸と吸収軸、及び位相差フィルムの進相軸と遅相軸は常に直交状態を形成するものであるので当該透過軸と進相軸の関係でも図と同じように変化する。 In the Poincare sphere described above, the viewing angle is represented by the radius, and the apparent angle of the optical axis changes due to the change in viewing angle when viewed from the 0 degree direction by arranging the polarizer so that the absorption axis A of the polarizer is 45 degrees. This is shown in bold lines. However, the axis change is made larger than the actual for explanation. In the illustrated example, the absorption axis A of the polarizer and the slow axis S of the retardation film (transparent protective film) are shown, but the transmission axis and absorption axis of the polarizer, and the fast axis and slow of the retardation film. Since the phase axis always forms an orthogonal state, the relationship between the transmission axis and the fast axis also changes in the same manner as in the figure.
図2において偏光子の吸収軸Aは、視角の変化で徐々に平行になるように変化し元の角度から大きく変化する。これは(a)〜(c)のいずれの場合も同様である。一方、(c)の従来例において透明保護フィルムの遅相軸S3は、視角の変化に伴ってほぼいつも視角に対し水平方向に発生するので図の如く0度と見なしうる。しかも位相差は、視角の変化で徐々に大きくなる。位相差の最大値を約40nm程度とすると偏光子を透過した光αは、ポアンカレ球上で遅相軸S3を中心として回転変換を受け、そのとき波長により作用の大きさが相違して短波長の光ほど速く回り(波長分散)、図の如くαblueからαredと広がる。そのため偏光の直交関係が崩れて透過率は大きくなる(光漏れ)。 In FIG. 2, the absorption axis A of the polarizer changes so as to become parallel gradually as the viewing angle changes, and changes greatly from the original angle. This is the same in any of the cases (a) to (c). On the other hand, in the conventional example of (c), the slow axis S3 of the transparent protective film almost always occurs in the horizontal direction with respect to the viewing angle as the viewing angle changes, so that it can be regarded as 0 degrees as shown in the figure. Moreover, the phase difference gradually increases as the viewing angle changes. When the maximum value of the phase difference is about 40 nm, the light α transmitted through the polarizer undergoes rotational transformation around the slow axis S3 on the Poincare sphere, and the magnitude of the action varies depending on the wavelength, and the short wavelength. The light turns faster (wavelength dispersion) and spreads from αblue to αred as shown in the figure. For this reason, the orthogonal relationship of polarization is broken and the transmittance is increased (light leakage).
他方、(b)の従来例において透明保護フィルムの遅相軸S2は、Nzが0.1〜0.9であり、0.5以上(図例では0.75)では図の如く常に吸収軸Aの変化に対して元の角度との間になるように変化し、図例では遅相軸S2の視角による軸変化は常に吸収軸Aの変化の半分となる。その場合、正面方向では透明保護フィルムと偏光子の光軸が一致しているため位相差の影響はでないが、軸ズレに伴ってその影響が現れる。 On the other hand, in the conventional example of (b), the slow axis S2 of the transparent protective film has an Nz of 0.1 to 0.9, and when it is 0.5 or more (0.75 in the example), it is always an absorption axis as shown in the figure. It changes so as to be between the original angle with respect to the change of A, and in the example shown in the figure, the axial change due to the viewing angle of the slow axis S2 is always half of the change of the absorption axis A. In that case, in the front direction, since the optical axes of the transparent protective film and the polarizer coincide with each other, there is no influence of the phase difference, but the influence appears along with the axial deviation.
図2(b)の例での面内位相差は可視光の1/2波長程度であるので偏光子を透過した光αは、ポアンカレ球上で遅相軸S2を中心としてπの回転変換を受け、元の吸収軸Aの角度と等しい角度となるように補償される。しかしそのとき前記(c)の場合と同じく波長分散で短波長の光ほど速く回り、図の如くαblueからαredと広がるため例えば中心波長が550nmのときには青色光や赤色光で光漏れが発生することとなる。 Since the in-plane phase difference in the example of FIG. 2B is about ½ wavelength of visible light, the light α transmitted through the polarizer undergoes rotational transformation of π around the slow axis S2 on the Poincare sphere. And compensated so that the angle is equal to the angle of the original absorption axis A. However, as in the case of (c), the shorter wavelength light with wavelength dispersion rotates faster and spreads from αblue to αred as shown in the figure. For example, when the center wavelength is 550 nm, light leakage occurs with blue light or red light. It becomes.
前記に対し図2(a)による本発明の偏光板における透明保護フィルム2を形成する位相差フィルム21の遅相軸S21は、位相差フィルムのNzが0.8〜0.95(図例では0.87)の間にあるので吸収軸Aの変化に対して元の角度との間で1/2より大きくなるように変化し、その視角による軸変化は常に吸収軸Aの変化の約3/4となる。
In contrast, the slow axis S21 of the
前記の場合、上記(b)のときと同様に位相差フィルム21と偏光子の軸ズレに伴って位相差の影響が現れ、偏光子を透過した光αがポアンカレ球上で遅相軸S21を中心としてπの回転変換を受け、波長分散でαblueからαredと広がると共に、視角により変化した吸収軸Aと元の角度との中間の角度となるように補償されて透明保護フィルムを形成する次の位相差フィルム22に入射する。
In the above case, as in the case of (b), the influence of the phase difference appears due to the axial shift between the
位相差フィルム22はNzが0.55〜0.7(図例では0.63)の間にあるのでその遅相軸S22は、吸収軸Aの変化に対して元の角度との間でその1/2より小さくなるように変化し、その視角による軸変化は常に吸収軸Aの変化の約1/4となる。位相差フィルム22においても偏光子との軸ズレに伴って位相差の影響が現れその遅相軸S22は、先の位相差フィルム21で回転変換を受けたαblue〜αredと元の吸収軸Aの角度との中間の角度となる。
Since the retardation film 22 has Nz between 0.55 and 0.7 (0.63 in the illustrated example), its slow axis S22 is between its original angle with respect to the change of the absorption axis A. It changes so that it becomes smaller than 1/2, and the axial change by the viewing angle is always about 1/4 of the change of the absorption axis A. Also in the phase difference film 22, the influence of the phase difference appears along with the axis deviation with respect to the polarizer, and the slow axis S 22 of αblue to αred that has undergone rotational transformation in the previous
前記の結果、先の位相差フィルム22で回転変換を受けたαblueからαredは、ポアンカレ球上で遅相軸S22を中心としてπの回転変換を受け、波長分散でαblueからαredに広がる。しかしこの場合の変化は、先に受けた変化を打ち消す働きをするものであり、そのため図の如く波長に関わらず吸収軸Aの元の角度にほぼ収束するように補償される。従って例えば中心波長を550nmとした場合にも青色光や赤色光で光漏れすることが防止される。 As a result, αblue to αred that have undergone rotational transformation in the above retardation film 22 undergoes rotational transformation of π around the slow axis S22 on the Poincare sphere, and spread from αblue to αred by wavelength dispersion. However, the change in this case has a function of canceling the change received earlier, so that it is compensated so as to converge to the original angle of the absorption axis A regardless of the wavelength as shown in the figure. Therefore, for example, even when the center wavelength is 550 nm, light leakage with blue light or red light is prevented.
本発明による偏光板は、例えば液晶表示装置の形成などの従来に準じた適宜な目的に好ましく用いうる。その実用に際しては片側又は両側に各種目的の保護層や表面反射の防止等を目的とした反射防止層又は/及び防眩処理層、光拡散層などの適宜な機能層を付与することもできる。反射防止層は、例えばフッ素系ポリマーのコート層や多層金属蒸着膜等の光干渉性の膜などとして適宜に形成することができる。また防眩処理層も例えば微粒子含有の樹脂塗工層やエンボス加工、サンドブラスト加工やエッチング加工等の適宜な方式で表面に微細凹凸構造を付与するなどにより表面反射光が拡散する適宜な方式で形成することができる。 The polarizing plate according to the present invention can be preferably used for an appropriate purpose according to the prior art, such as the formation of a liquid crystal display device. In practical use, an appropriate functional layer such as a protective layer for various purposes, an antireflection layer for the purpose of preventing surface reflection, and / or an antiglare treatment layer, a light diffusion layer, or the like can be provided on one side or both sides. The antireflection layer can be suitably formed, for example, as a light interference film such as a fluorine polymer coat layer or a multilayer metal vapor deposition film. The antiglare layer is also formed by an appropriate method that diffuses the surface reflected light, for example, by providing a fine uneven structure on the surface by an appropriate method such as a resin coating layer containing fine particles, embossing, sandblasting or etching. can do.
さらに光拡散層も前記防眩処理層に準じて形成することができる。なお前記の微粒子には、例えば平均粒径が0.5〜20μmのシリカや酸化カルシウム、アルミナやチタニア、ジルコニアや酸化錫、酸化インジウムや酸化カドミウム、酸化アンチモン等の導電性のこともある無機系微粒子や、ポリメチルメタクリレートやポリウレタの如き適宜なポリマーからなる架橋又は未架橋の有機系微粒子などの適宜なものを1種又は2種以上用いうる。なお防眩処理層や光拡散層は、透明保護フィルムの拡散化や粗面化等にてそれと一体化したものとして形成することもできる。 Furthermore, the light diffusion layer can also be formed according to the antiglare treatment layer. Examples of the fine particles include inorganic materials having an average particle diameter of 0.5 to 20 μm, such as silica, calcium oxide, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide. One kind or two or more kinds of fine particles, such as crosslinked or uncrosslinked organic fine particles made of a suitable polymer such as polymethyl methacrylate and polyureta can be used. The antiglare treatment layer and the light diffusion layer can also be formed as one integrated therewith by diffusing or roughening the transparent protective film.
一方、液晶表示装置は、従来の偏光板に代えて本発明による偏光板を用いてそれを液晶セルの片側又は両側に配置することにより形成することができる。その場合、2層の位相差フィルムにて形成した透明保護フィルムが偏光子と液晶セルの間に位置するように配置することが表示品位の向上等の点より好ましいが、これに限定するものではない。 On the other hand, the liquid crystal display device can be formed by using the polarizing plate according to the present invention instead of the conventional polarizing plate and disposing it on one side or both sides of the liquid crystal cell. In that case, it is preferable to arrange the transparent protective film formed of the two-layer retardation film so as to be positioned between the polarizer and the liquid crystal cell from the viewpoint of improvement of display quality, etc. Absent.
参考例
ポリビニルアルコールフィルムを温水中に浸漬して膨潤させた後、ヨウ素/ヨウ化カリウム水溶液中にて染色しホウ酸水溶液中で一軸延伸処理して偏光子を得た。これは、分光光度計にて単体透過率、平行透過率及び直交透過率を調べたところ透過率43.5%、偏光度99.9%のものであった。
Reference Example A polyvinyl alcohol film was immersed in warm water to swell, then dyed in an iodine / potassium iodide aqueous solution and uniaxially stretched in an aqueous boric acid solution to obtain a polarizer. When the single transmittance, parallel transmittance and orthogonal transmittance were examined with a spectrophotometer, the transmittance was 43.5% and the polarization was 99.9%.
実施例1
ポリカーボネート(PC)フィルムの両面に粘着層を介し熱収縮性フィルムを接着して155℃で一軸延伸処理し、波長550nmの光に基づく(以下同じ)面内位相差が272nmで、Nzが0.88の位相差フィルムAを得た。また同様に158℃で処理して面内位相差が265nmで、Nzが0.62の位相差フィルムBを得た。次に参考例で得た偏光子の片面にポリビニルアルコール系接着剤を介しTACフィルムを接着して透明保護層を形成した後、その偏光子の他面にポリビニルアルコール系接着剤を介し位相差フィルムAを接着し、その上にアクリル系粘着層を介し位相差フィルムBを重畳接着して透明保護フィルムを形成し、偏光板を得た。なおいずれの位相差フィルムもその延伸軸が遅相軸となっており、その遅相軸が偏光子の吸収軸と平行になるよう接着した。
Example 1
A heat-shrinkable film was adhered to both surfaces of a polycarbonate (PC) film via an adhesive layer, and uniaxially stretched at 155 ° C., and the in-plane retardation based on light having a wavelength of 550 nm (hereinafter the same) was 272 nm, and Nz was 0.1. 88 retardation films A were obtained. Similarly, the film was processed at 158 ° C. to obtain a retardation film B having an in-plane retardation of 265 nm and Nz of 0.62. Next, after forming a transparent protective layer by adhering a TAC film to one side of the polarizer obtained in the reference example via a polyvinyl alcohol-based adhesive, a retardation film is formed on the other side of the polarizer via a polyvinyl alcohol-based adhesive. A was adhered, and a retardation film B was superposed and adhered thereon via an acrylic adhesive layer to form a transparent protective film, thereby obtaining a polarizing plate. In each of the retardation films, the stretching axis was a slow axis, and the slow axes were bonded so as to be parallel to the absorption axis of the polarizer.
実施例2
153℃で一軸延伸処理して得た面内位相差が270nmで、Nzが0.92の位相差フィルムAと、同様に156℃で処理して得た面内位相差が267nmで、Nzが0.64の位相差フィルムBを用いたほかは、実施例1に準じて偏光板を得た。
Example 2
The in-plane retardation obtained by uniaxial stretching at 153 ° C. is 270 nm and N z is 0.92, and the in-plane retardation obtained by processing at 156 ° C. is 267 nm, and N z is A polarizing plate was obtained according to Example 1 except that the retardation film B of 0.64 was used.
実施例3
155℃で一軸延伸処理して得た面内位相差が249nmで、Nzが0.81の位相差フィルムAと、同様に158℃で処理して得た面内位相差が257nmで、Nzが0.69の位相差フィルムBを用いたほかは、実施例1に準じて偏光板を得た。
Example 3
An in-plane retardation obtained by uniaxial stretching at 155 ° C. is 249 nm and an Nz is 0.81, and an in-plane retardation obtained by processing at 158 ° C. is 257 nm, and Nz is A polarizing plate was obtained according to Example 1 except that the retardation film B of 0.69 was used.
実施例4
156℃で一軸延伸処理して得た面内位相差が260nmで、Nzが0.82の位相差フィルムAと、同様に160℃で処理して得た面内位相差が271nmで、Nzが0.58の位相差フィルムBを用いたほかは、実施例1に準じて偏光板を得た。
Example 4
The in-plane retardation obtained by uniaxial stretching at 156 ° C. is 260 nm and the retardation film A having Nz of 0.82 and the in-plane retardation obtained by similarly treating at 160 ° C. is 271 nm, and Nz is A polarizing plate was obtained according to Example 1 except that the retardation film B of 0.58 was used.
比較例1
位相差フィルムA、Bからなる透明保護フィルムに代えて、面内位相差が6nmで、Nzが8のTACフィルムからなる透明保護フィルムとしたほかは、実施例1に準じて偏光板を得た。
Comparative Example 1
A polarizing plate was obtained according to Example 1, except that the transparent protective film made of a TAC film having an in-plane retardation of 6 nm and Nz of 8 was used instead of the transparent protective film made of retardation films A and B. .
比較例2
位相差フィルムAに代えて、面内位相差が265nmで、Nzが1.01の位相差フィルムを用いたほかは、実施例1に準じて偏光板を得た。この位相差フィルムは、熱収縮性フィルムを接着せずにPCフィルムを159℃で一軸延伸処理したものである。
Comparative Example 2
Instead of the phase difference film A, a polarizing plate was obtained according to Example 1 except that a phase difference film having an in-plane retardation of 265 nm and Nz of 1.01 was used. This retardation film is obtained by uniaxially stretching a PC film at 159 ° C. without bonding a heat-shrinkable film.
比較例3
152℃で一軸延伸処理して得た面内位相差が630nmで、Nzが0.91の位相差フィルムAと、同様に156℃で処理して得た面内位相差が515nmで、Nzが0.67の位相差フィルムBを用いたほかは、実施例1に準じて偏光板を得た。
Comparative Example 3
The in-plane retardation obtained by uniaxial stretching at 152 ° C. is 630 nm and N z is 0.91, and the in-plane retardation obtained by similarly treating at 156 ° C. is 515 nm, and N z is A polarizing plate was obtained according to Example 1 except that the retardation film B of 0.67 was used.
比較例4
位相差フィルムA、Bからなる透明保護フィルムに代えて、面内位相差が260nmで、Nzが0.75の位相差フィルムからなる透明保護フィルムとしたほかは、実施例1に準じて偏光板を得た。この位相差フィルムは、実施例1に準じ158℃で一軸延伸処理して得たものである。
Comparative Example 4
A polarizing plate according to Example 1 except that a transparent protective film made of a retardation film having an in-plane retardation of 260 nm and Nz of 0.75 was used instead of the transparent protective film made of retardation films A and B. Got. This retardation film is obtained by uniaxial stretching at 158 ° C. according to Example 1.
評価試験
実施例、比較例で得た偏光板について分光強度を図3に示した装置にて測定した。すなわち光源KとピンホールPとレンズRとで平行光線を形成し、それをグラントムソンプリズムGを介し実施例、比較例で得た偏光板からなるサンプルSに入射させてその透過光を分光器Bを介しディテクタDで受光して分光強度を測定した。なお測定では平行光線に対して垂直な回転軸γを介して回転βしうる回転ステージにサンプルSをその位相差フィルムからなる透明保護フィルム側を光源側として光線に対して垂直となるように、かつ偏光子の吸収軸が回転軸γに対して45度となるように取付けた。またグラントムソンプリズムGは、その透過軸がサンプルの吸収軸と平行となるように配置してクロスニコルの関係を形成した。
Evaluation Test Spectral intensity of the polarizing plates obtained in Examples and Comparative Examples was measured with the apparatus shown in FIG. That is, a parallel light beam is formed by the light source K, the pinhole P, and the lens R, and is incident on the sample S made of the polarizing plate obtained in the example and the comparative example via the Glan-Thompson prism G, and the transmitted light is spectroscope. Spectral intensity was measured by receiving light with detector D via B. In the measurement, the sample S is placed on a rotary stage that can be rotated β via a rotation axis γ that is perpendicular to the parallel light beam so that the transparent protective film side made of the retardation film is on the light source side and perpendicular to the light beam. The polarizer was attached so that the absorption axis of the polarizer was 45 degrees with respect to the rotation axis γ. The Glan-Thompson prism G was arranged so that its transmission axis was parallel to the absorption axis of the sample to form a crossed Nicols relationship.
前記により測定した分光強度と基準分光強度との比から透過率を算出し、その値より三刺激値を元にL、a、bを算出して黒色点との色差△E0を求めた。一方、サンプルを回転軸γを介し75度回転させて前記に準じ分光透過率を調べ、黒色点との色差△E75を求めると共に、それらの結果より回転角が0度の時と75度の時の色座標より色差△E75-0を算出した。なお前記の基準分光強度は、前記図3の装置においてグラントムソンプリズムGとサンプルSのない状態、従って光源K、ピンホールP、レンズR、分光器B及びディテクタDからなる状態での装置の分光強度に基づく。 The transmittance was calculated from the ratio of the spectral intensity measured as described above and the reference spectral intensity, and L, a, and b were calculated based on the tristimulus values, and the color difference ΔE0 from the black point was determined. On the other hand, the sample is rotated 75 degrees through the rotation axis γ, the spectral transmittance is examined in accordance with the above, and the color difference ΔE75 with respect to the black point is obtained, and when the rotation angle is 0 degrees and 75 degrees from these results. The color difference ΔE75-0 was calculated from the color coordinates. Note that the above-mentioned reference spectral intensity is the spectrum of the apparatus in the state shown in FIG. Based on strength.
前記の結果を表1に示した。 The results are shown in Table 1.
一方、比較例4では色差△E75が比較例1より小さくなっているものの、aとbの値が大きくて目視観察においても透過光が青紫色に抜けていた。これは青色や赤色の領域で最適に補償されていないことを意味する。また0度と75度の間における角度においてもその回転角が大きくなるほど色差△Eが徐々に大きくなり目視観察においても抜け(光漏れ)が徐々に大きくなっていることが確認された。これに対し実施例では殆ど無彩色に近く、aとbの値も比較例4より小さくて補償効果が可視光域の広い範囲で達成されていることがわかる。以上より本発明にて広帯域の可視光域にて視角変化による光漏れを防止しうる偏光板の得られていることがわかる。 On the other hand, in Comparative Example 4, although the color difference ΔE75 was smaller than that in Comparative Example 1, the values of a and b were large, and the transmitted light was lost to blue-violet even in visual observation. This means that the blue and red regions are not optimally compensated. Further, it was confirmed that the color difference ΔE gradually increased as the rotation angle increased at an angle between 0 ° and 75 °, and the omission (light leakage) gradually increased in visual observation. On the other hand, in Example, it is almost achromatic color, the value of a and b is also smaller than the comparative example 4, and it turns out that the compensation effect is achieved in the wide range of visible light region. From the above, it can be seen that a polarizing plate capable of preventing light leakage due to a change in viewing angle in a broadband visible light region is obtained in the present invention.
1:偏光子
2、3:透明保護フィルム
(21、22:位相差フィルム)
1:
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