JP2004309598A - Retardation plate, elliptical polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation plate and an elliptical polarizing plate contributing to the improvement of contrast and the enlargement of the angle of view in the front direction of a liquid crystal display device. <P>SOLUTION: The elliptical polarizing plate has a first optical anisotropic layer and a second optical anisotropic layer. When the retardation values of the first and the second optical anisotropic layers are Re<SB>1</SB>and Re<SB>2</SB>, respectively, Re<SB>1</SB>and Re<SB>2</SB>satisfy the following expression (1). Furthermore, the first optical anisotropic layer is formed by fixing a nematic hybrid-aligned liquid crystal compound, and the polarizing plate is constituted by layering the retardation plate and a polarizing film. The expression (1) is 90 nm≥¾Re<SB>1</SB>/2-Re<SB>2</SB>¾(absolute value)≥10 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５７】
ラビング処理を施した配向膜の上に、下記の組成の塗布液をスピンコート塗布、乾燥、および加熱（配向熟成）し、さらに紫外線照射して厚さ２．４μｍの光学異方性層Ａを形成した。光学異方性層Ａはラビング方向に遅相軸を有しており、５５０ｎｍにおけるレターデーション値（Ｒｅ_Ａ）は２５５ｎｍであった。クリスタルローテーション法を応用して傾斜角を測定したところ、配向膜界面側のチルト角が５°で空気界面側のチルト角が４５°で、且つ平均チルト角が２５°のハイブリッド配向をしていることがわかった。この光学異方性層Ａと、厚さ８０μｍで表面をけん化処理したトリアセチルセルロースフィルムとを粘着剤で貼り合わせ、光学異方性層Ａをガラス基板から剥離した。ここで用いたトリアセチルセルロースフィルムは５８９．３ｎｍで測定したＲｔｈ値が２０ｎｍである負の光学異方性を有した。
光学異方性層Ａの塗布液組成
下記の棒状液晶性化合物（１） １４．５質量％
下記の増感剤 ０．１５質量％
下記の光重合開始剤 ０．２９質量％
メチルエチルケトン ８５．０６質量％
【００５８】
棒状液晶性化合物（１）
【化２】

【００５９】
【化３】

【００６０】
厚さ８０μｍのロール状ポリビニルアルコールフイルムを、ヨウ素水溶液中で連続して５倍に延伸し、乾燥して偏光膜を得た。ポリビニルアルコール（クラレ製ＰＶＡ−１１７Ｈ）３％水溶液を接着剤としてけん化処理したトリアセチルセルロースフィルムと貼り合わせ、両面がトリアセチルセルロースによって保護された偏光板を得た。このとき、片面のトリアセチルセルロースフィルムには、上記作製した光学異方性層Ａの転写されているフィルムを用いて、光学異方性層Ａの転写されている面とは反対側の面を偏光膜と貼り合せた。このとき、偏光板の透過軸と光学異方性層Ａのなす角は７５°であった。
【００６１】
一軸延伸したアートンフィルム（ＪＳＲ製）を光学異方性層Ｂとして用いた。光軸はフィルム平面と平行であり、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）は１１２ｎｍであった。したがって、Ｒｅ_Ａ／２−Ｒｅ_Ｂ＝１５．５ｎｍであった。このアートンフィルムと上記作製した光学異方性層Ａと偏光膜の積層体を、偏光膜、光学異方性層Ａ、光学異方性層Ｂの順になるように粘着剤で貼り合せ、楕円偏光板を得た。このとき、偏光板の透過軸と光学異方性層Ａおよび光学異方性層Ｂの遅相軸それぞれとのなす角は、それぞれ７５°および１５°であった。また、ネマチックハイブリッド配向を固定化した液晶性フィルムからなる光学異方性層Ａのチルト角は、偏光膜に近い方の界面で４５°であり、光学異方性層Ｂに近い方の界面で５°であった。
【００６２】
［実施例２］
厚さが４０μｍのトリアセチルセルロースフィルムの表面をけん化処理し、その上にポリビニルアルコールの希釈液を塗布し、厚さ１μｍの配向膜を形成した。ここで用いたトリアセチルセルロースフィルムは５８９．３ｎｍで測定したＲｔｈ値が２０ｎｍである負の光学異方性を有した。ラビング処理した該配向膜の上に、実施例１と同様に光学異方性層Ａの塗布液を塗布し、乾燥および加熱（配向熟成）し、さらに紫外線照射して厚さ２．４μｍの光学異方性層Ａを形成した。光学異方性層Ａはラビング方向に遅相軸を有しており、５５０ｎｍにおけるレターデーション値（Ｒｅ_Ａ）は２５５ｎｍであった。クリスタルローテーション法を応用して傾斜角を測定したところ、配向膜界面の傾斜が５°で空気界面側の傾斜が４５°で、且つ平均チルト角が２５°のハイブリッド配向をしていることがわかった。
【００６３】
一軸延伸したアートンフィルム（ＪＳＲ製）を光学異方性層Ｂとして用いた。光軸はフィルム平面と平行であり、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）は１１２ｎｍであった。したがって、Ｒｅ_Ａ／２−Ｒｅ_Ｂ＝１５．５ｎｍであった。このアートンフィルムと上記作製した光学異方性層Ａの形成されたトリアセチルセルロースフィルムを粘着剤で貼り合せた。このとき、光学異方性層Ａの形成された面とは反対側の面がアートンフィルムと接するように貼り合わせ、光学異方性層Ａと光学異方性層Ｂの遅相軸とのなす角は６０°であった。
【００６４】
厚さが４０μｍのトリアセチルセルロースフィルムにより両面が保護された偏光板と、上記作製した光学異方性層Ａと光学異方性層Ｂとの積層体を、偏光板、光学異方性層Ａ、光学異方性層Ｂの順になるように粘着剤で貼り合せ、楕円偏光板を得た。このとき、偏光板の透過軸と光学異方性層Ａおよび光学異方性層Ｂの遅相軸それぞれとのなす角は、それぞれ７５°および１５°であった。また、ネマチックハイブリッド配向を固定化した液晶フィルムからなる光学異方性層Ａのチルト角は、偏光膜に近い方の界面で４５°であり、光学異方性層Ｂに近い方の界面で５°であった。
【００６５】
［実施例３］
光学異方性層Ｂとして、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）が１４５ｎｍである一軸延伸したアートンフィルムを用いた以外は、実施例１と同様にして、偏光板、光学異方性層Ａおよび光学異方性層Ｂの積層体からなる楕円偏光板を得た。Ｒｅ_Ｂ−Ｒｅ_Ａ／２＝１７．５ｎｍであった。
【００６６】
［実施例４］
厚さ８０μｍのトリアセチルセルロースフィルムの表面をけん化処理し、その上にポリビニルアルコールの希釈液を塗布し、厚さ１μｍの配向膜を形成した。ラビング処理した該配向膜の上に、下記の組成の光学異方性層Ｂの塗布液を塗布し、乾燥、および加熱（配向熟成）し、さらに紫外線照射して厚さ１．０μｍの光学異方性層Ｂを形成した。ここで用いたトリアセチルセルロースフィルムは５８９．３ｎｍにおけるＲｔｈ値が５０ｎｍである負の光学異方性を有し、光学異方性層Ｃとして機能することがわかった。該光学異方性層Ｃの上に形成された光学異方性層Ｂは、ホモジニアス配向をした液晶分子が固定化されたフィルムであり、光軸は層平面に対して平行であることがわかった。また、５５０ｎｍで測定した光学異方性層Ｂのレターデーション値（Ｒｅ_Ｂ）は１１０ｎｍであった。
実施例１と同様にして作製した偏光板と光学異方性層Ａ（５５０ｎｍにおけるレターデーション値（Ｒｅ_Ａ）は２５５ｎｍであった）の積層体と、上記作製した光学異方性層Ｂと光学異方性層Ｃの積層体を、偏光板、光学異方性層Ａ、光学異方性層Ｂ、光学異方性層Ｃの順になるように貼り合わせ、楕円偏光板を得た。このとき、偏光板の透過軸と光学異方性層Ａおよび光学異方性層Ｂのそれぞれの遅相軸とのなす角は、それぞれ７５°および１５°であった。また、Ｒｅ_Ａ／２−Ｒｅ_Ｂ＝１７．５ｎｍであった。
光学異方性層Ｂの塗布液組成
上記の棒状液晶性化合物（１） １３．０質量％
上記の増感剤 ０．１３質量％
上記の光重合開始剤 ０．３９質量％
下記の添加剤 ０．１３質量％
メチルエチルケトン ８６．３５質量％
【００６７】
添加剤（配向制御剤）
【化４】

【００６８】
［比較例１］
光学異方性層Ｂとして、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）が１２８ｎｍである一軸延伸したアートンフィルムを用いた以外は、実施例１と同様にして、偏光板、光学異方性層Ａおよび光学異方性層Ｂの積層体からなる楕円偏光板を得た。このとき、Ｒｅ_Ｂ−Ｒｅ_Ａ／２＝０．５ｎｍであった。
【００６９】
［比較例２］
光学異方性層Ｂとして、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）が１２２ｎｍである一軸延伸したアートンフィルムを用いた以外は、実施例１と同様にして、偏光板、光学異方性層Ａおよび光学異方性層Ｂの積層体からなる楕円偏光板を得た。このとき、Ｒｅ_Ｂ−Ｒｅ_Ａ／２＝５．５ｎｍであった。
【００７０】
［比較例３］
実施例２と同様にして、トリアセチルセルロースフィルムに光学異方性層Ａを形成した。実施例１と同様に、トリアセチルセルロースで両面が保護された偏光板の作製において、片面にこの光学異方性層Ａの形成されたトリアセチルセルロースを用いて、光学異方性層Ａの形成された面とは反対側の面が偏光膜と接するように貼り合せた。次いで、５５０ｎｍで測定したレターデーション値（Ｒｅ_Ｂ）が１２８ｎｍである一軸延伸したアートンフィルムを用いた以外は、実施例１と同様に、アートンフィルムを光学異方性層Ｂとして貼り合せ、楕円偏光板を作製した。このとき、Ｒｅ_Ｂ−Ｒｅ_Ａ／２＝０．５ｎｍであり、ネマチックハイブリッド配向を固定化した液晶フィルムからなる光学異方性層Ａのチルト角は、偏光膜に近い方の界面で５°であり、光学異方性層Ｂに近い方の界面で４５°であった。
【００７１】
［視野角測定］
反射型の液晶表示装置として、次のものを用いた。基板が０．７ｍｍの厚みのガラス、液晶セルのギャップが２．７μｍ、観察者側の電極がＩＴＯ電極、その対向電極が凹凸をつけたアルミ反射電極、液晶セルの配向膜がポリイミドで、ラビング角度（液晶のねじれ角度に等しい）が７０°のセルを作製し、この空隔部に、Δｎ＝０．０８６で、且つ誘電率異方性が＋１０．０のネマチック液晶を注入し、液晶セルを作製した。
これに、実施例１、２および４で作製した楕円偏光板を、光学異方性層Ｂの遅相軸方向が、液晶セルの上下基板のラビング方向のなす角の２等分線と平行になるようにそれぞれ配置して、液晶表示装置を作製した。また、実施例３で作製した楕円偏光板を、液晶セルの上下基板のラビング方向のなす角の２等分線と直交するように配置し、液晶表示装置を作製した。また、比較例１〜３で作製した楕円偏光板を、光学異方性層Ｂの遅相軸方向が、液晶セルの上下基板のラビング方向のなす角の２等分線と直交するようにそれぞれ配置して、液晶表示装置を作製した。
【００７２】
続いて、通常の室内蛍光灯照明下で、分光放射輝度計を用いて、作製したそれぞれの液晶表示装置の反射輝度の測定を行った。このときの観察角度は、液晶表示装置を水平に置いたまま、正面方向、または法線から５０°の方向に角度を固定し、液晶表示装置の方位を１５°毎に変えながら測定した。液晶表示装置のＯＮ時とＯＦＦ時のそれぞれの輝度を測定し、ＯＮ時とＯＦＦ時の輝度の比であるコントラスト比を算出した。下表には正面方向のコントラスト比と、極角５０°においてコントラスト比が最も小さくなった方位での値を記載した。
【００７３】
【表１】

【００７４】
【発明の効果】
本発明によれば、液晶表示装置等に用いたときに、正面方向において良好なコントラストが得られ、かつ、視野角特性の改善に寄与する位相差板、楕円偏光板およびそれら性能の改善された液晶表示装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の楕円偏光板の代表的な実施形態を示す断面図である。
【図２】図１の楕円偏光板の光学異方性層の遅相軸の方向と偏光膜の偏光透過軸または偏光吸収軸の方向とを示す平面図である。
【図３】本発明の楕円偏光板の好ましい態様を示す断面図であり、第１の光学異方性層では液晶分子のハイブリッド配向を示し、第２の光学異方性層の矢印は光軸の方向を示す。
【図４】本発明の楕円偏光板の他の実施形態を示す断面図である。
【符号の説明】
Ａ 第１の光学異方性層
Ｂ 第２の光学異方性層
Ｃ 第３の光学異方性層
ＬＣ 液晶性分子
Ｐ 偏光膜
ａ 第１の光学異方性層の遅相軸
ｂ 第２の光学異方性層の遅相軸
ｐ 偏光透過軸または偏光吸収軸
ｏ 第２の光学異方性層の光軸[0001]
BACKGROUND OF THE INVENTION
The present invention relates to various displays (for example, OA equipment, reflective and transflective liquid crystal display devices used for portable terminals), retardation plates and elliptically polarizing plates used for optical disk pickups, and reflective and transflective devices. The present invention relates to a liquid crystal display device such as a mold.
[0002]
[Prior art]
The λ / 4 plate has a great many applications, and is already used for a reflective LCD, a pickup for an optical disk, and a PS conversion element. However, even if it is referred to as a λ / 4 plate, most of them achieve λ / 4 at a specific wavelength. In order to achieve λ / 4 in a wider wavelength range, a technique of laminating two polymer films having optical anisotropy has been proposed (see, for example, Patent Documents 1 and 2). There has also been proposed a phase difference plate in which a polymer film having a phase difference of λ / 4 and a polymer film having a phase difference of λ / 2 are bonded together with a slow axis crossed (for example, Patent Documents). 3). Furthermore, a retardation plate is proposed in which at least two retardation plates having a retardation value of 160 to 320 nm are laminated so that their slow axes are not parallel or orthogonal to each other (for example, (See Patent Document 4). These retardation plates achieve λ / 4 in a wide wavelength region by using two polymer films. On the other hand, a broadband λ / 4 plate that has been thinned by laminating a plurality of optically anisotropic layers formed of liquid crystal molecules has also been disclosed (see, for example, Patent Documents 5 to 7).
[0003]
When a λ / 4 plate formed of a plurality of optically anisotropic layers is used in a reflective liquid crystal display device, it is designed to maintain about ¼ wavelength at normal incidence in order to obtain a dark display. . However, since the reflection type liquid crystal display device normally uses outside light such as room light or outdoor light, the light is not only incident vertically but rather is incident from an oblique direction. Even when the reflective liquid crystal display device is designed as described above, when light is incident obliquely, a deviation from a quarter wavelength occurs, and there is a problem that the contrast is lowered depending on the viewing angle. As a means for improving the viewing angle dependency, a technique including two compensators including a liquid crystalline film in which a nematic hybrid alignment is fixed is disclosed (for example, Patent Documents 6 and 7), but those nematic hybrid liquid crystal properties are disclosed. In a liquid crystal display device using a circularly polarizing plate including a film, residual retardation that occurs when a voltage is applied to the liquid crystal layer cannot be canceled, and good dark display cannot be obtained even in the front direction. There is a problem that high contrast cannot be obtained.
[0004]
[Patent Document 1]
JP-A-10-68816
[Patent Document 2]
JP-A-10-90521
[Patent Document 3]
JP-A-10-68816
[Patent Document 4]
JP-A-10-90521
[Patent Document 5]
JP 2001-4837 A
[Patent Document 6]
JP 2000-32156 A
[Patent Document 7]
JP 2002-31717 A
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a retardation plate, an elliptically polarizing plate, and a liquid crystal with improved performance, which can provide good contrast in the front direction when used in a liquid crystal display device and contribute to the improvement of viewing angle characteristics. It is to provide a display device.
[0006]
[Means for Solving the Problems]
The object of the present invention has been achieved by the following means.
[1] It has a first optical anisotropic layer and a second optical anisotropic layer, and the retardation of each of the first and second optical anisotropic layers is Re. ₁ And Re ₂ When Re ₁ And Re ₂ Satisfies the following formula (1), and the first optically anisotropic layer is a layer formed by fixing a liquid crystalline compound having nematic hybrid alignment.
90nm ≧ | Re ₁ / 2-Re ₂ | (Absolute value) ≥ 10 nm (1)
[0007]
[2] The tilt angle of the first optical anisotropic layer is larger on the side farther than the side closer to the second optical anisotropic layer, and the optical axis of the second optical anisotropic layer is the layer. The retardation plate of [1] which is parallel to the plane.
[3] The retardation plate of any one of [1] or [2], wherein a third optical anisotropic layer having negative optical anisotropy is further laminated.
[4] The retardation plate according to [3], wherein the third optically anisotropic layer is a layer formed of at least one material selected from a liquid crystalline compound, triacetylcellulose, and cyclic polyolefin.
[5] When the retardation (Rth) in the thickness direction at a wavelength of 589.3 nm is expressed by the following formula, the Rth value of the third optical anisotropic layer is 30 to 150 nm. Phase difference plate.
Rth = {(nx + ny) / 2−nz} × d
(In the formula, nx and ny are in-plane main refractive indexes, nz is the main refractive index in the thickness direction, and d is the thickness (nm).)
[6] An elliptically polarizing plate including the retardation plate of any one of [1] to [5] and a polarizing film, wherein the polarizing film, the first optical anisotropic layer, and the second optical anisotropic layer Are stacked in this order.
[7] An elliptically polarizing plate comprising the retardation plate of any one of [3] to [5] and a polarizing film, wherein the polarizing film, the first optical anisotropic layer, and the second optical anisotropic layer And an elliptically polarizing plate in which the third optically anisotropic layer is laminated in this order.
[0008]
[8] A liquid crystal display device using the elliptically polarizing plate according to [6] or [7].
[9] A liquid crystal cell comprising a pair of upper and lower substrates whose opposite surfaces are each rubbed, and a twisted nematic liquid crystal layer sandwiched between the substrates and having a twist angle of 0 to 100 °, and [6] or [7 A liquid crystal display device comprising the elliptically polarizing plate according to claim 1, wherein the Re ₁ And Re ₂ Satisfies the formula (1), and the slow axis direction of the second optically anisotropic layer is substantially parallel to the bisector of the angle formed by the rubbing direction of the pair of upper and lower substrates apparatus.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
[Optical properties of retardation plate]
The retardation plate of the present invention includes a first optical anisotropic layer having a phase difference of substantially π at a wavelength of 550 nm and a second optical anisotropy of a phase difference of substantially π / 2 at a wavelength of 550 nm. With layers. The retardation plate made of this laminate preferably has a retardation value / wavelength value measured at wavelengths of 450 nm, 550 nm and 650 nm, all in the range of 0.2 to 0.3.
In the present invention, the retardation value at a wavelength of 550 nm of the first optically anisotropic layer is ½ wavelength. Specifically, the retardation value at a wavelength of 550 nm is preferably in the range of 200 to 300 nm.
On the other hand, the retardation value at a wavelength of 550 nm of the second optically anisotropic layer is ¼ wavelength. Specifically, the retardation value at a wavelength of 550 nm is preferably in the range of 80 to 190 nm.
[0010]
In the present invention, the retardation of the first and second optically anisotropic layers at a wavelength of 550 nm is represented by Re ₁ And Re ₂ When Re ₁ And Re ₂ Satisfies the following formula (1) or (2).
Re ₁ / 2-Re ₂ ≧ 10nm (1)
Re ₂ − Re ₁ / 2 ≧ 10nm (2)
By satisfying the expression (1) or (2), when this retardation plate is used in a liquid crystal display device, residual retardation that occurs when a voltage is applied to the liquid crystal layer can be canceled, and a good dark display can be achieved. Can be obtained. Re ₁ / 2-Re ₂ Is 10 nm or more, and the upper limit is preferably 90 nm or less, preferably 100 nm or less, and more preferably 60 nm or less.
[0011]
In addition, when used in a liquid crystal display device having a twisted nematic liquid crystal layer with a twist angle of 0 to 100 °, when the expression (1) is satisfied, the slow axis direction of the second optical anisotropic layer is the liquid crystal It is preferable to design so that it is substantially parallel to the bisector of the angle formed by the rubbing direction of the upper and lower substrates of the cell. When the expression (2) is satisfied, the slow axis direction of the second optically anisotropic layer is substantially orthogonal to the bisector of the angle formed by the rubbing direction of the upper and lower substrates of the liquid crystal cell. It is preferable to design. Here, substantially parallel means in the range of 0 ± 30 °, and substantially orthogonal means in the range of 90 ± 30 °.
[0012]
In the present invention, a third optical anisotropic layer having negative optical anisotropy may be laminated. The third optically anisotropic layer has negative refractive index anisotropy and satisfies the following mathematical formula (3). Moreover, when the retardation (Rth) in the thickness direction at a wavelength of 589.3 nm is expressed by the following mathematical formula (4), Rth (retardation in the thickness direction) of the third optical anisotropic layer is 10 to 200 nm. Is preferable, and it is more preferable that it is 30-150 nm. Moreover, it is preferable that nx and ny of the third optical anisotropic layer are substantially equal.
nx ≧ ny> nz (3)
Rth = {(nx + ny) / 2−nz} × d (4)
In the formula, nx and ny are in-plane main refractive indexes of the optically anisotropic layer, nz is the main refractive index in the thickness direction, and d is the thickness (nm) of the optically anisotropic layer.
[0013]
The retardation plate of the present invention is formed by laminating first and second optically anisotropic layers, and may further be laminated by a third optically anisotropic layer. When the retardation plate is composed of first to third optically anisotropic layers, it is preferable that the first, second, and third optically anisotropic layers are laminated in this order. Moreover, the elliptically polarizing plate of the present invention is obtained by further laminating a linearly polarizing film on the retardation plate, and the first optically anisotropic layer is more linearly polarized than the second optically anisotropic layer. It is most preferable that the layers are stacked so as to be close to each other.
[0014]
In the present invention, the first optically anisotropic layer is a layer formed by fixing a liquid crystalline compound having a nematic hybrid orientation (preferably an nematic hybrid orientation with an average tilt angle of 5 ° to 35 °) (hereinafter referred to as “liquid crystal”). In some cases, it is referred to as a “sensitive film”. Here, the nematic hybrid alignment referred to in the present invention means that the liquid crystalline compound is nematic aligned, and the angle (tilt angle) formed by the director of the liquid crystalline compound and the layer plane at this time is the upper surface and the lower surface of the layer. And different orientation forms. Therefore, the orientation is such that the tilt angle is different between the vicinity of the upper surface interface and the vicinity of the lower surface interface. And the tilt angle continuously changing between the lower surface and the lower surface.
[0015]
The first optical anisotropic layer, which is a liquid crystalline film in which a nematic hybrid alignment is fixed, in a retardation plate comprising a laminate of the first optical anisotropic layer and the second optical anisotropic layer of the present invention It is preferable that the tilt angle of the liquid crystal molecules forming the layer is larger on the side farther than the side closer to the second optical anisotropic layer, and the optical axis of the second optical anisotropic layer is parallel to the layer plane. Preferably there is.
[0016]
A liquid crystalline film having a nematic hybrid alignment fixed means that the liquid crystalline compound having a nematic hybrid alignment maintains the alignment under conditions in which it is actually used (for example, conditions in which a liquid crystal display element is used). It is a film in which the performance as a retardation plate is not lost. In such a liquid crystal film in which the nematic hybrid alignment is fixed, the directors of the liquid crystal molecules are oriented at different angles at all positions in the film thickness direction. Therefore, the optical axis does not exist when the film is viewed as a structure called a film.
[0017]
The average tilt angle as used in the present invention means the average value of the angle formed by the director of the liquid crystal molecules and the film plane in the film thickness direction of the liquid crystal film. In the liquid crystalline film in which the nematic hybrid orientation is fixed, the angle formed by the director and the film plane is usually 10 ° to 70 °, preferably 15 ° to 60 ° as an absolute value near one interface of the film. In the surface opposite to the surface, the absolute value is usually 0 ° to 50 °, preferably 0 ° to 30 °. The average tilt angle is in the range of 5 ° to 35 ° as an absolute value, preferably 7 ° to 33 °, more preferably 10 ° to 30 °. When the average tilt angle is out of the range of 5 ° to 35 °, the contrast is lowered. The average tilt angle can be obtained by applying a crystal rotation method.
[0018]
The liquid crystalline film in which the nematic hybrid alignment is fixed may be formed of any liquid crystalline compound as long as the above nematic hybrid alignment state is fixed. For example, a liquid crystalline film obtained by forming a low molecular weight liquid crystalline compound in a nematic hybrid alignment in a liquid crystal state and then fixing by photocrosslinking or thermal crosslinking, or a liquid crystalline film formed in a nematic hybrid alignment in a liquid crystal state and then cooled. By doing so, a liquid crystalline film obtained by fixing the orientation can be used. The liquid crystalline film as used in the present invention does not ask whether or not the film itself exhibits liquid crystallinity, and is obtained by forming a liquid crystalline compound such as a low molecular liquid crystalline compound or a high molecular liquid crystalline compound into a film. Including
[0019]
In the elliptically polarizing plate of the present invention, the first and second optically anisotropic layers and the polarizing film are laminated so that the whole is almost completely circularly polarized. By setting the optical orientation in this way, λ / 4 can be achieved in a wide wavelength region. For example, the angle between the slow axis of the first optical anisotropic layer and the slow axis of the second optical anisotropic layer is 60 °, the slow axis of the first optical anisotropic layer and the polarizing film The angle between the polarization axis (the direction in which the transmittance becomes maximum in the plane) is set to 15 °, and the angle between the slow axis of the second optical anisotropic layer and the polarization axis of the polarizing film is set to 75 °. Thus, circularly polarized light, that is, broadband λ / 4 can be achieved in the entire visible region. The angle between the slow axis of the first optical anisotropic layer and the slow axis of the second optical anisotropic layer is 60 °, and the slow axis of the first optical anisotropic layer is The angle between the polarizing axis of the polarizing film and the polarizing axis of the polarizing film may be set to 75 ° and 75 °, respectively. The allowable range of the above angle is within ± 10 °, preferably within ± 8 °, more preferably within ± 6 °, further preferably within ± 5 °, and more preferably ± 4 °. Is most preferably within.
[0020]
In the present specification, the broad band λ / 4 specifically means that the retardation value / wavelength value measured at wavelengths of 450 nm, 550 nm, and 650 nm are both in the range of 0.2 to 0.3. Means that. The retardation value / wavelength value is preferably in the range of 0.21 to 0.29, more preferably in the range of 0.22 to 0.28, and 0.23 to 0.27. Most preferably within the range.
[0021]
FIG. 1 is a schematic cross-sectional view showing a typical embodiment of an elliptically polarizing plate. The elliptically polarizing plate shown in FIG. 1 has a configuration in which a linearly polarizing film (P), a first optically anisotropic layer (A), and a second optically anisotropic layer (B) are laminated in this order. FIG. 2 is a plan view showing the direction of the slow axis of the optically anisotropic layer and the direction of the polarization transmission axis or polarization absorption axis of the linear polarizing film. In FIG. 2, the angle (in the same plane) of the slow axis (a) of the first optically anisotropic layer (A) and the slow axis (b) of the second optically anisotropic layer (B) ( α) is preferably 50 to 70 °. The angle (β) between the slow axis (a) of the first optically anisotropic layer (A) and the polarization transmission axis or polarization absorption axis (p) of the linear polarizing film is preferably 10 to 20 °. . 3 shows an example of the alignment state of the liquid crystalline molecules (LC) in the first optical anisotropic layer (A) and the light of the second optical anisotropic layer in the schematic cross-sectional view of FIG. It is the cross-sectional schematic diagram which showed an example of the direction of an axis | shaft with the arrow (o). In FIG. 3, in the first optically anisotropic layer (A), rod-like liquid crystalline molecules (LC) are nematic hybrid aligned at an average tilt angle of 5 ° to 35 °, and the second optically anisotropic layer ( The optical axis of B) is parallel to the layer plane.
FIG. 4 is a schematic cross-sectional view of one embodiment of the retardation plate of the present invention in which a third optically anisotropic layer (C) is further laminated. The third optically anisotropic layer (C) exhibits negative anisotropy. As described above, in the embodiment having the third optical anisotropic layer (C), the first optical anisotropic layer (A), the second optical anisotropic layer (B), and the third optical anisotropic layer (C). An embodiment in which the anisotropic layers (C) are laminated in this order is preferable, and this embodiment in which the polarizing film (P) is laminated so as to be closest to the first optical anisotropic layer (A) is preferable.
[0022]
[First optically anisotropic layer]
In the present invention, the first optically anisotropic layer is made of a liquid crystalline film having nematic hybrid alignment. The liquid crystalline compound constituting the first optically anisotropic layer is preferably a rod-like liquid crystalline compound or a discotic liquid crystalline compound, and more preferably a rod-like liquid crystalline compound. In the first optically anisotropic layer, the liquid crystalline compound is preferably fixed in a nematic hybrid alignment state, and more preferably fixed by a polymerization reaction. Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. It is more preferable to fix the alignment of the rod-like liquid crystal compound by polymerization. As the polymerizable rod-like liquid crystal compound, Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, WO 95/22586 No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, No. 7-110469, The compounds described in JP-A-11-80081 and JP-A-2001-328773 can be used.
[0023]
The optically anisotropic layer can be formed by applying a coating liquid containing a liquid crystalline compound and, if desired, the following polymerizable initiator and other additives on the alignment film. As the solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
[0024]
The aligned liquid crystal compound is fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction of the polymerizable group (P) introduced into the liquid crystal molecule. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
[0025]
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. Irradiation energy is 20mJ / cm ² ~ 50J / cm ² It is preferably 100 to 800 mJ / cm. ² More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.
[0026]
[Second optically anisotropic layer]
In the present invention, the second optically anisotropic layer may be a layer made of a liquid crystal compound that is hybrid-aligned similarly to the first optically anisotropic layer, but the optical axis is uniformly parallel to the layer plane. Is preferred. Such an optically anisotropic layer may be a liquid crystalline film obtained by aligning a liquid crystalline compound substantially horizontally (homogeneously), or may be a stretched polymer film.
[0027]
The substantially horizontal (homogeneous) orientation of the liquid crystalline molecules means that the average angle between the director direction of the liquid crystalline molecules and the layer plane is in the range of 0 to 40 °, It means that the angle formed by the director and the layer plane is smaller than 5 °. The liquid crystalline molecules are preferably fixed in an aligned state, and more preferably fixed by polymerization. The immobilization method and the immobilizable liquid crystal molecule structure are the same as those described in the description of the immobilization of the hybrid alignment.
[0028]
The second optically anisotropic layer may be formed from a polymer film. The polymer film is formed from a polymer that can exhibit optical anisotropy. Examples of such polymers include polyolefins (eg, polyethylene, polypropylene, norbornene-based polymers), polycarbonate, polyarylate, polysulfone, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester and cellulose ester (eg, cellulose triacetate). Tate, cellulose diacetate). Moreover, a copolymer or a polymer mixture of these polymers may be used.
[0029]
The optical anisotropy of the polymer film is preferably obtained by stretching. The stretching is preferably uniaxial stretching. Uniaxial stretching is preferably longitudinal uniaxial stretching using the difference in peripheral speed between two or more rolls, or tenter stretching in which both sides of the polymer film are gripped and stretched in the width direction. In addition, using two or more polymer films, the optical properties of the entire two or more films may satisfy the above conditions. The polymer film is preferably produced by a solvent cast method in order to reduce unevenness in birefringence. The thickness of the polymer film is preferably 20 to 500 nm, and most preferably 40 to 100 nm.
[0030]
[Third optically anisotropic layer]
The retardation plate and the elliptically polarizing plate of the present invention may have a third optical anisotropic layer exhibiting negative optical anisotropy. The third optically anisotropic layer may be formed from a single layer or may be formed from multiple layers as long as the above mathematical formula (3) is satisfied. The third optically anisotropic layer may be a polymer film that exhibits optical anisotropy, or may be one that exhibits optical anisotropy by aligning a liquid crystalline compound. A laminate of them may be used. When the third optically anisotropic layer is a polymer film, examples of the material of the polymer film include triacetylcellulose, cyclic polyolefin, polyimide, and modified polycarbonate. These exhibit negative optical anisotropy. The material of the polymer film is not limited to the above material as long as the orientation state of the molecular chain is the same as the orientation state of the polymer molecular chain. Among them, a polymer film made of triacetyl cellulose or cyclic polyolefin is preferable. Moreover, you may express desired Rth by biaxially stretching a polymer film. Further, Rth may be adjusted by adding an additive to the polymer. JP-A 2000-1111914 and JP-A 2001-166144 are known as techniques for adjusting Rth of triacetyl cellulose.
[0031]
When the third optically anisotropic layer is formed from a liquid crystalline compound, it is preferably formed from a discotic liquid crystalline compound or a cholesteric liquid crystalline compound, and more preferably formed from a discotic liquid crystalline compound. By aligning the discotic liquid crystalline compound substantially horizontally with respect to the substrate, a layer exhibiting negative optical anisotropy can be formed. Such a technique is disclosed in Japanese Patent Laid-Open No. 11-352328. The term “substantially horizontal” means that the average angle formed by the optical axis of the discotic liquid crystalline molecule and the normal direction of the substrate is in the range of 0 ± 10 °. The average tilt angle of the discotic liquid crystal molecules may not be 0 ° (specifically, a range of 0 ± 10 °), or may be a hybrid alignment in which the tilt angle gradually changes. In addition, a twisting deformation may be added to the orientation state by adding a chiral agent or applying a shear stress.
[0032]
Preferable examples of the discotic liquid crystalline compound forming the third optically anisotropic layer are described in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981). ); Chemical Society of Japan, Quarterly Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. , Page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. JP-A-2001-4387 discloses a discotic liquid crystalline molecule having a polymerizable group.
[0033]
Cholesteric liquid crystalline molecules exhibit negative optical anisotropy due to helical twist alignment. Desired optical properties can be obtained by arranging the cholesteric liquid crystalline molecules in a spiral and controlling the twist angle and retardation value of the alignment. The twisted orientation of cholesteric liquid crystalline molecules can be achieved by using a known method. The liquid crystalline molecules are preferably fixed in an aligned state, and more preferably fixed by polymerization.
[0034]
The first, second and third optically anisotropic layers can be formed of a liquid crystalline compound or a polymer film. Examples of methods for producing these laminates include the following.
When all of the first, second, and third optically anisotropic layers are made of a liquid crystalline compound, three layers may be sequentially laminated on the same support, or after each is formed on the temporary support. These layers may be bonded together, or one layer formed on the temporary support may be transferred to one obtained by sequentially laminating two layers on the same support.
When the first optically anisotropic layer is made of a liquid crystal compound and the second and third optically anisotropic layers are made of a liquid crystal compound or a polymer film, the polymer film is used to form a layer made of the liquid crystal compound. It can be used as a support. For example, a polymer film having negative optical anisotropy, such as triacetyl cellulose, can be used as the third optical anisotropic layer, and also as a support for the second optical anisotropic layer made of a liquid crystal compound. Available. Further, a liquid crystal compound that forms the first optically anisotropic layer may be applied thereon. As another example, when a stretched polymer film is used as the second optical anisotropic layer, a liquid crystal compound that forms the first optical anisotropy can be applied to one surface of the film. In the lamination of the third optically anisotropic layer, a liquid crystal compound may be applied to the opposite surface, a liquid crystal layer formed on a temporary support may be transferred, or an optical anisotropy may be provided. A polymer film may be bonded.
[0035]
The polymer film used as the support on which the liquid crystal compound is applied can be used as either the second or third optically anisotropic layer, and can also be used as a protective film for the polarizer. It can also be used as a film that has both functions. Further, an isotropic film having no optical anisotropy may be used as a support or a protective film.
[0036]
The preferred form of the elliptically polarizing plate of the present invention is that the polarizing plate, the first and second optically anisotropic layers are in this order, or the polarizing plate, the first, second and third optically anisotropic layers are The layers are stacked in this order, and the order of stacking is not limited as long as the order is finally reached.
[0037]
The first optical anisotropic layer may be a liquid crystalline film in which a nematic hybrid alignment of a liquid crystalline compound is fixed, and the second optical anisotropic layer may be a similar liquid crystalline film. The liquid crystalline film is asymmetrical in the vertical direction with respect to the plane of the film because the inclination angle of the liquid crystal molecules is different between above and below in the thickness direction. Therefore, for example, when the liquid crystal molecule closer to the polarizing plate has a higher tilt angle or a lower tilt angle, the viewing angle improvement effect differs when used in a liquid crystal display device. Considering the optical parameters and required optical performance of the liquid crystal cell, use an optically anisotropic layer with a horizontal optical axis, an optically anisotropic layer with hybrid orientation, or their positional relationship It is preferable to optimize the direction of hybrid orientation, in-plane retardation of each layer, Rth, and the like.
[0038]
In forming the nematic hybrid aligned liquid crystal film, the tilt angle on the support side and the tilt angle on the air interface side can be controlled by selecting an air interface aligning agent added to the alignment film or the liquid crystal layer, and the support side has a low tilt angle. Thus, the air interface side can be set to a high tilt angle and vice versa. Furthermore, even if the same alignment film and air interface alignment agent are used, a hybrid alignment film in which the high tilt angle side and the low tilt angle side are turned upside down can be formed by transferring it to another substrate after being formed on a temporary support. Can be obtained.
[0039]
[Alignment film]
When the first, second and third optically anisotropic layers are formed from liquid crystalline molecules, it is preferable to use an alignment film in order to align the liquid crystalline molecules. For example, when the first, second and third optical anisotropic layers are sequentially formed on the same support, the support / alignment film / first optical anisotropic layer / alignment film / second Optical anisotropic layer / alignment film / third optical anisotropic layer, or support / alignment film / third optical anisotropic layer / alignment film / second optical anisotropic layer / alignment film / Like the first optically anisotropic layer, each optically anisotropic layer can be formed on an alignment film to control the alignment and to exhibit desired optical characteristics.
The material of the alignment film can be selected according to the required optical properties and the type of liquid crystalline molecules used. In addition, even if an alignment film is not separately provided between each optically anisotropic layer, it can be laminated on the optically anisotropic layer by adding molecules having an alignment film function to the components constituting the optically anisotropic layer. The optically anisotropic layer thus formed can be brought into a desired orientation state.
[0040]
The alignment film is formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroup, or an organic compound (eg, ω-tricosanoic acid, dioctadecyldimethyl) by the Langmuir-Blodgett method. It can be provided by means such as accumulation (LB film) of ammonium chloride and methyl stearate. Furthermore, an alignment film in which an alignment function is generated by application of an electric field or a magnetic field or light irradiation is also known. An alignment film formed by a polymer rubbing treatment is particularly preferable. The rubbing treatment is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.
[0041]
The type of polymer used for the alignment film is determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound. It is preferable to adjust the surface energy according to the inclination angle to be expressed. In the present invention, when the third optically anisotropic layer is formed of liquid crystalline molecules, it is preferable to use a polymer that does not reduce the surface energy of the alignment film. When the third optically anisotropic layer is formed using discotic liquid crystalline molecules, the rubbing treatment may not be performed and the alignment film may be omitted. However, for the purpose of improving the adhesion between the liquid crystalline molecules and the transparent support, an alignment film (described in JP-A-9-152509) forming a chemical bond with the liquid crystalline molecules at the interface may be used. When the alignment film is used for the purpose of improving adhesion, rubbing treatment need not be performed.
[0042]
In the first or second optically anisotropic layer, when the director of the rod-like liquid crystalline molecule is oriented at an angle larger than 45 ° with respect to the major axis direction of the transparent support, the direction orthogonal to the rubbing direction It is preferable to use an alignment film (hereinafter referred to as an orthogonal alignment film) in which directors of rod-like liquid crystal molecules are arranged. The orthogonal alignment film is described in JP-A Nos. 2002-62427 and 2002-268068.
[0043]
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm.
In any of the alignment films, after the liquid crystalline molecules are fixed in the aligned state, they can be transferred onto another support. The liquid crystal compound fixed in the alignment state can maintain the alignment state even without the alignment film. Therefore, the retardation plate of the present invention requires each optically anisotropic layer formed on a temporary support, in addition to the method of sequentially forming each optically anisotropic layer on the same support. If it exists, it can also be produced by a method of bonding using an adhesive or the like.
[0044]
Any alignment film preferably has a polymerizable group. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group.
[0045]
[Transparent support]
The retardation plate and the elliptically polarizing plate of the present invention may have a support, and the support is preferably a transparent support. As the transparent support, a glass plate or a polymer film, preferably a polymer film is used. That the support is transparent means that the light transmittance is 80% or more.
The thickness of the transparent support is preferably 10 to 500 μm, and more preferably 30 to 200 μm.
[0046]
In order to improve adhesion between the transparent support and the layer (adhesive layer, alignment film or optically anisotropic layer) provided thereon, surface treatment (for example, glow discharge treatment, corona discharge treatment, ultraviolet ray) is applied to the transparent support. Treatment, flame treatment, etc.).
An ultraviolet absorber may be added to the transparent support.
An adhesive layer (undercoat layer) may be provided on the transparent support. The adhesive layer is described in JP-A-7-333433. The thickness of the adhesive layer is preferably 0.1 to 2 μm, and preferably 0.2 to 1 μm.
[0047]
As the transparent support, it is preferable to use a polymer film having a small wavelength dispersion. The transparent support preferably has a small optical anisotropy. Specifically, the small chromatic dispersion means that the ratio of Re400 / Re700 is preferably less than 1.2. Specifically, the small optical anisotropy means that in-plane retardation (Re) is preferably 20 nm or less, and more preferably 10 nm or less. Examples of the polymer include cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate and cyclic polyolefin. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. As the cyclic polyolefin, a polymer obtained by hydrogenation reaction of a ring-opening polymer of tetracyclododecene or a ring-opening copolymer of tetracyclododecene and norbornene described in JP-B-2-9619 Can be used from the series of Arton (manufactured by JSR), Zeonex, and Zeonore (manufactured by Nippon Zeon). The polymer film is preferably formed by a solvent cast method.
[0048]
[Elliptically polarizing plate]
The retardation plate of the present invention is used as a λ / 4 plate used in a liquid crystal display device, a pickup for writing an optical disc, a λ / 4 plate used in a GH-LCD or a PS conversion element, or an antireflection film. It is particularly advantageously used as a λ / 4 plate. The λ / 4 plate is generally used in combination with a polarizing film. Therefore, if it is configured as an elliptically polarizing plate in which a retardation plate and a polarizing film are combined, it can be easily incorporated into a device for a purpose such as a reflection type or a transflective liquid crystal display device.
[0049]
The elliptically polarizing plate of the present invention comprises the above retardation plate and a linear polarizing film. Examples of the linear polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The polarizing axis (transmission axis) of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The polarizing film generally has a protective film. The transparent support can function as an optically anisotropic layer made of a polymer film, or can function as a protective film on one side of the polarizing film. When a protective film is used separately from the transparent support, it is preferable to use a cellulose ester film having high optical isotropy, particularly a triacetyl cellulose film or a cyclic polyolefin film, as the protective film. Specifically, high optical isotropy means that in-plane retardation (Re) is preferably 20 nm or less, and more preferably 10 nm or less. Furthermore, the thickness direction retardation (Rth) is preferably 50 nm or less, and more preferably 30 nm or less.
[0050]
[Liquid Crystal Display]
The liquid crystal display device of the present invention includes at least the elliptically polarizing plate, and includes a reflective, transflective, and transmissive liquid crystal display device. A liquid crystal display device generally includes a polarizing plate, a liquid crystal cell, and a retardation plate, a reflective layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, a color filter, etc. Although comprised from a member, in this invention, there is no restriction | limiting in particular except the point which makes it essential to use the said elliptically polarizing plate. Further, the use position of the elliptically polarizing plate is not particularly limited, and may be one place or a plurality of places. The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used. The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film. The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystalline compounds, high-molecular liquid crystalline compounds, and mixtures thereof that can constitute various liquid crystal cells. Moreover, a pigment | dye, a chiral agent, a non-liquid crystalline compound, etc. can also be added to these in the range which does not impair liquid crystallinity.
[0051]
In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later. As a method of the liquid crystal cell, a TN (twisted nematic) method, an STN (super twisted nematic) method, an ECB (electrically controlled birefringence) method, an IPS (in-plane switching) method, a VA (in-plane switching) method, a VA (in-plane switching) method, and a VA (in-plane switching) method. ), PVA (Patterned Vertical Alignment), OCB (Optically Compensated Birefringence), HAN (Hybrid Aligned Nematic), ASM (Axial Symmetrical Asymmetric l) Various methods, such as a display method using a halftone gray scale method, a domain division method, or a ferroelectric liquid crystal or an anti-ferroelectric liquid crystal. The driving method of the liquid crystal cell is not particularly limited, and a passive matrix method used for STN-LCD and the like, and an active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode and a TFD (Thin Film Diode) electrode, Any driving method such as a plasma addressing method may be used. A field sequential method that does not use a color filter may be used.
[0052]
The elliptically polarizing plate in the present invention is preferably used for a reflection type and a transflective liquid crystal display device. The reflective liquid crystal display device has a configuration in which a reflector, a liquid crystal cell, and a polarizing plate are laminated in this order. The retardation plate is disposed between the reflecting plate and the polarizing film (between the reflecting plate and the liquid crystal cell or between the liquid crystal cell and the polarizing film). The reflector may share the liquid crystal cell and the substrate. The transflective liquid crystal display device includes an electro-liquid crystal cell, a polarizing plate disposed closer to the viewer than the liquid crystal cell, and at least one retardation plate disposed between the polarizing plate and the liquid crystal cell. And at least a transflective layer disposed behind the liquid crystal layer as viewed from the viewer, and at least one retardation plate and a polarizing plate behind the transflective layer as viewed from the viewer. Have In this type of liquid crystal display device, it is possible to use both a reflection mode and a transmission mode by installing a backlight.
[0053]
In the liquid crystal display device, at least one retardation plate and a polarizing plate function as an elliptical polarizing plate. The liquid crystal display device of the present invention uses at least one of the elliptically polarizing plates of the present invention.
[0054]
The phase difference plate and the elliptically polarizing plate of the present invention are not limited to the above uses, and can be used for various other uses. For example, it can be used for an antireflection film such as a host-guest type liquid crystal display device, a touch panel, an electroluminescence (EL) element, a reflection type polarizing plate, and the like.
[0055]
【Example】
The present invention will be described more specifically with reference to the following examples. The materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.
[Example 1]
(Production of retardation plate)
A glass substrate having a width of 100 mm and a length of 150 mm is spin-coated with a diluted solution of an alignment film (polymer having the following structural formula), heated at 80 ° C. for 1 hour, at 180 ° C. for 1 hour, and further at 250 ° C. for 1 hour. An alignment film having a thickness of 0.5 μm was formed.
[0056]
Polymer for alignment film
[Chemical 1]

[0057]
On the alignment film subjected to the rubbing treatment, a coating liquid having the following composition is spin-coated, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form an optically anisotropic layer A having a thickness of 2.4 μm. Formed. The optically anisotropic layer A has a slow axis in the rubbing direction and has a retardation value (Re _A ) Was 255 nm. When the tilt angle was measured by applying the crystal rotation method, the hybrid film was aligned with a tilt angle of 5 ° on the alignment film interface side, a tilt angle of 45 ° on the air interface side, and an average tilt angle of 25 °. I understood it. The optically anisotropic layer A and a triacetylcellulose film having a thickness of 80 μm and a saponified surface were bonded with an adhesive, and the optically anisotropic layer A was peeled from the glass substrate. The triacetylcellulose film used here had negative optical anisotropy with an Rth value measured at 589.3 nm of 20 nm.
Coating liquid composition of optically anisotropic layer A
The following rod-like liquid crystalline compound (1) 14.5% by mass
The following sensitizer 0.15% by mass
The following photoinitiator 0.29 mass%
Methyl ethyl ketone 85.06 mass%
[0058]
Rod-like liquid crystalline compound (1)
[Chemical 2]

[0059]
[Chemical 3]

[0060]
A roll-like polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizing film. A 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) was bonded to a saponified triacetyl cellulose film as an adhesive to obtain a polarizing plate having both surfaces protected by triacetyl cellulose. At this time, for the triacetyl cellulose film on one side, the surface opposite to the surface to which the optically anisotropic layer A is transferred is formed using the film to which the optically anisotropic layer A is transferred. Bonded with a polarizing film. At this time, the angle formed by the transmission axis of the polarizing plate and the optically anisotropic layer A was 75 °.
[0061]
A uniaxially stretched Arton film (manufactured by JSR) was used as the optically anisotropic layer B. The optical axis is parallel to the film plane, and the retardation value measured at 550 nm (Re _B ) Was 112 nm. Therefore, Re _A / 2-Re _B = 15.5 nm. The laminate of this Arton film and the optically anisotropic layer A and the polarizing film produced as described above was bonded with an adhesive so that the polarizing film, the optically anisotropic layer A, and the optically anisotropic layer B were in this order. I got a plate. At this time, the angles formed by the transmission axis of the polarizing plate and the slow axes of the optically anisotropic layer A and the optically anisotropic layer B were 75 ° and 15 °, respectively. Further, the tilt angle of the optically anisotropic layer A made of a liquid crystalline film in which nematic hybrid alignment is fixed is 45 ° at the interface closer to the polarizing film, and at the interface closer to the optically anisotropic layer B. It was 5 °.
[0062]
[Example 2]
The surface of a 40 μm thick triacetylcellulose film was saponified, and a diluted solution of polyvinyl alcohol was applied thereon to form an alignment film having a thickness of 1 μm. The triacetylcellulose film used here had negative optical anisotropy with an Rth value measured at 589.3 nm of 20 nm. On the alignment film subjected to the rubbing treatment, a coating solution for the optically anisotropic layer A was applied in the same manner as in Example 1, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form an optical film having a thickness of 2.4 μm. An anisotropic layer A was formed. The optically anisotropic layer A has a slow axis in the rubbing direction and has a retardation value (Re _A ) Was 255 nm. When the tilt angle was measured by applying the crystal rotation method, it was found that the orientation of the alignment film interface was 5 °, the air interface side tilt was 45 °, and the hybrid was aligned with an average tilt angle of 25 °. It was.
[0063]
A uniaxially stretched Arton film (manufactured by JSR) was used as the optically anisotropic layer B. The optical axis is parallel to the film plane, and the retardation value measured at 550 nm (Re _B ) Was 112 nm. Therefore, Re _A / 2-Re _B = 15.5 nm. This Arton film and the triacetyl cellulose film on which the optically anisotropic layer A prepared above was formed were bonded with an adhesive. At this time, bonding is performed so that the surface opposite to the surface on which the optically anisotropic layer A is formed is in contact with the ARTON film, and the slow axis of the optically anisotropic layer A and the optically anisotropic layer B is formed. The angle was 60 °.
[0064]
A laminate of a polarizing plate having both sides protected by a 40 μm thick triacetylcellulose film and the optically anisotropic layer A and the optically anisotropic layer B produced as described above is composed of a polarizing plate and an optically anisotropic layer A. And an optically anisotropic layer B were laminated with an adhesive so that an elliptically polarizing plate was obtained. At this time, the angles formed by the transmission axis of the polarizing plate and the slow axes of the optically anisotropic layer A and the optically anisotropic layer B were 75 ° and 15 °, respectively. Further, the tilt angle of the optically anisotropic layer A made of a liquid crystal film in which the nematic hybrid alignment is fixed is 45 ° at the interface closer to the polarizing film, and is 5 at the interface closer to the optically anisotropic layer B. °.
[0065]
[Example 3]
Retardation value measured at 550 nm (Re _B ) Is 145 nm, except that an uniaxially stretched arton film is used, and an elliptically polarizing plate comprising a laminate of a polarizing plate, an optically anisotropic layer A and an optically anisotropic layer B is obtained in the same manner as in Example 1. It was. Re _B -Re _A /2=17.5 nm.
[0066]
[Example 4]
The surface of a triacetyl cellulose film having a thickness of 80 μm was saponified, and a diluted solution of polyvinyl alcohol was applied thereon to form an alignment film having a thickness of 1 μm. On the alignment film subjected to the rubbing treatment, a coating solution of the optically anisotropic layer B having the following composition is applied, dried and heated (alignment aging), and further irradiated with ultraviolet rays to give an optical film having a thickness of 1.0 μm. An isotropic layer B was formed. The triacetylcellulose film used here has negative optical anisotropy with an Rth value at 509.3 nm of 50 nm, and was found to function as the optically anisotropic layer C. The optically anisotropic layer B formed on the optically anisotropic layer C is a film in which liquid crystal molecules having homogeneous alignment are fixed, and the optical axis is parallel to the layer plane. It was. The retardation value (Re of the optically anisotropic layer B measured at 550 nm _B ) Was 110 nm.
The polarizing plate and optically anisotropic layer A (retardation value at 550 nm (Re _A ) Was 255 nm), and the laminate of the optically anisotropic layer B and the optically anisotropic layer C produced above were combined with a polarizing plate, an optically anisotropic layer A, an optically anisotropic layer B, Bonding was performed in the order of the optically anisotropic layer C to obtain an elliptically polarizing plate. At this time, the angles formed by the transmission axis of the polarizing plate and the slow axes of the optically anisotropic layer A and the optically anisotropic layer B were 75 ° and 15 °, respectively. Re _A / 2-Re _B = 17.5 nm.
Coating liquid composition of optically anisotropic layer B
Said rod-like liquid crystalline compound (1) 13.0 mass%
Said sensitizer 0.13 mass%
The above photopolymerization initiator 0.39% by mass
The following additive 0.13 mass%
Methyl ethyl ketone 86.35% by mass
[0067]
Additive (alignment control agent)
[Formula 4]

[0068]
[Comparative Example 1]
Retardation value measured at 550 nm (Re _B ) Is 128 nm, and an elliptical polarizing plate comprising a laminate of a polarizing plate, an optically anisotropic layer A and an optically anisotropic layer B is obtained in the same manner as in Example 1 except that an uniaxially stretched arton film is used. It was. At this time, Re _B -Re _A /2=0.5 nm.
[0069]
[Comparative Example 2]
Retardation value measured at 550 nm (Re _B ) Is 122 nm, and an elliptical polarizing plate comprising a laminate of a polarizing plate, an optically anisotropic layer A and an optically anisotropic layer B is obtained in the same manner as in Example 1 except that an uniaxially stretched arton film is used. It was. At this time, Re _B -Re _A /2=5.5 nm.
[0070]
[Comparative Example 3]
In the same manner as in Example 2, the optically anisotropic layer A was formed on the triacetylcellulose film. As in Example 1, in the production of a polarizing plate protected on both sides with triacetylcellulose, the formation of optically anisotropic layer A was performed using triacetylcellulose having optically anisotropic layer A formed on one side. Bonding was performed so that the surface opposite to the formed surface was in contact with the polarizing film. Next, the retardation value measured at 550 nm (Re _B Except for using a uniaxially stretched arton film having a thickness of 128 nm, an arton film was bonded as the optically anisotropic layer B in the same manner as in Example 1 to produce an elliptically polarizing plate. At this time, Re _B -Re _A /2=0.5 nm, and the tilt angle of the optically anisotropic layer A made of a liquid crystal film in which the nematic hybrid alignment is fixed is 5 ° at the interface closer to the polarizing film, and the optically anisotropic layer B It was 45 degrees at the interface closer to.
[0071]
[Viewing angle measurement]
The following was used as a reflective liquid crystal display device. The substrate is 0.7 mm thick glass, the gap of the liquid crystal cell is 2.7 μm, the electrode on the observer side is ITO electrode, the counter electrode is an aluminum reflective electrode with irregularities, the alignment film of the liquid crystal cell is polyimide, and rubbing A cell having an angle (equal to the twist angle of the liquid crystal) of 70 ° is manufactured, and nematic liquid crystal having Δn = 0.086 and a dielectric anisotropy of +10.0 is injected into this space portion. Was made.
For this, the slow polarization direction of the optically anisotropic layer B is parallel to the bisector of the angle formed by the rubbing direction of the upper and lower substrates of the liquid crystal cell. A liquid crystal display device was manufactured by arranging each of the above. Further, the elliptically polarizing plate produced in Example 3 was arranged so as to be orthogonal to the bisector of the angle formed by the rubbing direction of the upper and lower substrates of the liquid crystal cell, to produce a liquid crystal display device. In addition, the elliptically polarizing plates produced in Comparative Examples 1 to 3 were each such that the slow axis direction of the optically anisotropic layer B was orthogonal to the bisector of the angle formed by the rubbing direction of the upper and lower substrates of the liquid crystal cell. The liquid crystal display device was manufactured by arranging.
[0072]
Subsequently, the reflection luminance of each of the manufactured liquid crystal display devices was measured using a spectral radiance meter under normal indoor fluorescent lamp illumination. The observation angle at this time was measured while the liquid crystal display device was placed horizontally, the angle was fixed in the front direction or in the direction of 50 ° from the normal line, and the orientation of the liquid crystal display device was changed every 15 °. The respective luminances of the liquid crystal display device when it was turned on and off were measured, and the contrast ratio, which is the ratio of the luminance when it was turned on and off, was calculated. The table below shows the contrast ratio in the front direction and the value in the direction where the contrast ratio is the smallest at a polar angle of 50 °.
[0073]
[Table 1]

[0074]
【The invention's effect】
According to the present invention, when used in a liquid crystal display device or the like, a favorable contrast is obtained in the front direction, and the retardation plate, the elliptically polarizing plate, which contributes to the improvement of viewing angle characteristics, and their performance are improved. A liquid crystal display device can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a typical embodiment of an elliptically polarizing plate of the present invention.
2 is a plan view showing the direction of the slow axis of the optically anisotropic layer of the elliptically polarizing plate of FIG. 1 and the direction of the polarization transmission axis or polarization absorption axis of the polarizing film. FIG.
FIG. 3 is a cross-sectional view showing a preferred embodiment of the elliptically polarizing plate of the present invention, in which the first optical anisotropic layer shows a hybrid orientation of liquid crystal molecules, and the arrow of the second optical anisotropic layer indicates the optical axis. Indicates the direction.
FIG. 4 is a cross-sectional view showing another embodiment of the elliptically polarizing plate of the present invention.
[Explanation of symbols]
A first optically anisotropic layer
B Second optically anisotropic layer
C Third optical anisotropic layer
LC Liquid crystalline molecules
P Polarizing film
a Slow axis of the first optically anisotropic layer
b Slow axis of the second optically anisotropic layer
p Polarization transmission axis or polarization absorption axis
o Optical axis of the second optically anisotropic layer

Claims (8)

When the first and second optical anisotropic layers have a first optical anisotropic layer and a second optical anisotropic layer, and the retardations of the first and second optical anisotropic layers are Re ₁ and Re ₂ , respectively, Re ₁ and A retardation plate in which Re ₂ satisfies the following formula (1), and the first optically anisotropic layer is a layer formed by immobilizing a nematic hybrid aligned liquid crystal compound.
90 nm ≧ | Re ₁ / 2-Re ₂ | (absolute value) ≧ 10 nm (1) The tilt angle of the first optical anisotropic layer is larger on the side farther than the side closer to the second optical anisotropic layer, and the optical axis of the second optical anisotropic layer is parallel to the layer plane. The phase difference plate according to claim 1. The phase difference plate according to claim 1, wherein a third optical anisotropic layer having a negative optical anisotropy is further laminated. The retardation plate according to claim 3, wherein the third optically anisotropic layer is a layer formed of at least one material selected from a liquid crystalline compound, triacetylcellulose, and cyclic polyolefin. The retardation film according to claim 3 or 4, wherein the retardation (Rth) in the thickness direction at a wavelength of 589.3 nm is expressed by the following formula, and the Rth value of the third optically anisotropic layer is 30 to 150 nm. .
Rth = {(nx + ny) / 2−nz} × d
(In the formula, nx and ny are in-plane main refractive indexes, nz is the main refractive index in the thickness direction, and d is the thickness (nm).) An elliptically polarizing plate comprising the retardation plate according to claim 1 and a polarizing film, wherein the polarizing film, the first optically anisotropic layer, and the second optically anisotropic layer are An elliptically polarizing plate laminated in this order. An elliptically polarizing plate comprising the retardation plate according to any one of claims 3 to 5 and a polarizing film, wherein the polarizing film, the first optical anisotropic layer, the second optical anisotropic layer, and An elliptically polarizing plate in which a third optically anisotropic layer is laminated in this order. A liquid crystal display device using the elliptically polarizing plate according to claim 6.

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