JP2004133139A - Stn type liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an STN (super twisted nematic) type liquid crystal display device in which a nematic liquid crystal prevailing in recent years and a retardation plate are used, and the phase of coloring light is compensated while maintaining a contrast ratio. <P>SOLUTION: The STN type liquid crystal display device 100 is provided with a liquid crystal cell 40 consisting of a nematic liquid crystal 10 with birefringent index of refraction Δn<SB>1</SB>and electrode substrates 20, 30 holding the liquid crystal 10; polarizers 50, 60 respectively opposed to the electrode substrates 20, 30; and the retardation plate 70 opposed to the front side polarizing plate 50 and the front side electrode substrate 20. The ratio of retardation Δn<SB>2</SB>*d<SB>2</SB>of the retardation plate 70 to retardation Δn<SB>1</SB>*d<SB>1</SB>is 0.67-0.73. The angle which an absorption axis of the polarizer 50 forms with a reference line is defined as 0°<α<25°, the angle which an absorption axis of the polarizer 60 forms therewith is defined as 60°<β<85°, the angle which an optical axis of the retardation plate 70 forms therewith is defined as 45°<γ<70°, and the cross angle between the absorption axis of the front side polarizer 50 and a rubbing axis of the electrode substrate 20 is defined as 30°<δ<55°. <P>COPYRIGHT: (C)2004,JPO

Description

【０１０２】
【表２】

【０１０３】
表２から、αが０°（比較例４）のときは、透過率Ｔ_ｏｆｆが２３％未満であり、コントラスト比が１０未満であり、ＳＴＮタイプ液晶表示装置１００の表示をカラー表示に好適なものとすることができず、当該表示のコントラスト比を向上させることができず、αが２５°以上（比較例７）のときは、色度度座標ｙが０．３４０より大きくなるので、当該表示に緑みをつけることが分かった。従って、少なくともαの範囲は０°＜α＜２５°とする必要があることが分かった。
【０１０４】
βが６０°以下（比較例１）のときは、コントラスト比が１０未満であり、当該表示のコントラスト比を向上させることができない一方、βが８５°以上（比較例２）のときは、透過率Ｔ_ｏｆｆが２３％未満であるので、当該表示をカラー表示に好適なものとすることができないことが分かった。従って、少なくともβの範囲は６０°＜β＜８５°とする必要があることが分かった。
【０１０５】
γが４５°以下（比較例８）のときは、透過率Ｔ_ｏｆｆが２３％未満であり、色度度座標ｙが０．３４０より大きくなるので、ＳＴＮタイプ液晶表示装置１００の表示をカラー表示に好適なものとすることができず、当該表示のコントラスト比を向上させることができず、さらに、当該表示に緑みをつける一方、γが７５°以上（比較例３）のときは、色度度座標ｘが０．３３０より大きく且つ色度度座標ｙが０．３４０より大きいので、当該表示に黄みをつけることが分かった。従って、γの範囲は４５°＜γ＜７０°とする必要があることが分かった。
【０１０６】
ネマティック液晶１０のレタデーションΔｎ_１＊ｄ_１が８３５〜８６５ｎｍｎｍの範囲から外れる（比較例９，１０）ときは、色度度座標ｘが０．３００より小さいので当該表示に青みをつけるか、又は色度度座標ｙが０．３４０より大きいので当該表示に緑みをつけることが分かった。例え、ネマティック液晶１０のレタデーションΔｎ_１＊ｄ_１が８４０〜８６０ｎｍの範囲内であっても、位相差板７０のレタデーションΔｎ_２＊ｄ_２が５７０〜６１０ｎｍの範囲を外れる（比較例１１，１２）ときは、色度度座標ｙが０．３４０より大きいので、当該表示に緑みをつけることが分かった。従って、レタデーションΔｎ_１＊ｄ_１は８４０〜８６０ｎｍの範囲内とすると共に、レタデーションｎ_２＊ｄ_２は５７０〜６１０ｎｍの範囲内とする必要があることが分かった。
【０１０７】
また、表１及び表２より、ネマティック液晶１０のレタデーションΔｎ_１＊ｄ_１が８３５〜８６５ｎｍであって、レタデーション比が０．６７〜０．７３のＳＴＮタイプ液晶表示装置１００において、０°＜α＜２５°，６０°＜β＜８５°，４５°＜γ＜７０°，３０°＜δ＜５５°とすれば、透過率Ｔ_ｏｆｆは２３％以上、色度度座標ｘは０．３００≦ｘ≦０．３３０、色度度座標ｙは０．３３０≦ｙ≦０．３４０、及びコントラスト比は１０以上となり、ＳＴＮタイプ液晶表示装置１００において近年主流となっているネマティック液晶及び位相差板を使用することができ、着色光の位相の十分な補正を行うことができると共に、当該ＳＴＮタイプ液晶表示装置１００を着色を感じさせず且つカラー表示に好適なものとすることができることが分かった。さらに、透過率Ｔ_ｏｆｆが２３％以上であって無着色のものであると鮮明となるので、第１の実施の形態に係るＳＴＮタイプ液晶表示装置１００をカラー表示に好適なものとすることができるのが分かった。
【０１０８】
次に、本発明の第２の実施例を説明する。
【０１０９】
本発明者は、第２の実施の形態に係るＳＴＮタイプ液晶表示装置１００について、レタデーションΔｎ_１＊ｄ_１、レタデーションΔｎ_２＊ｄ_２、及びレタデーション比、並びにα，β，γ、及びδが夫々異なる試験片を作製した（表２の実施例５０〜７０及び比較例２０〜２７）。α，β，γ、及びδは上述した第１の実施例と同様に、表偏光板５０、裏偏光板６０及び位相差板７０の貼り合わせ方向を調整することにより変更した。
【０１１０】
そして、作製した試験片においてコントラスト比を向上させることができることができるか否かを研究した。具体的には、作製した試験片について透過率Ｔ_ｏｆｆ，色度度座標ｘ，色度度座標ｙ、及びコントラスト比を夫々測定した。
【０１１１】
以下、測定結果を表３，表４、及び測定結果の一部を図６に示す。
【０１１２】
【表３】

【０１１３】
【表４】

【０１１４】
表３及び表４から、ネマティック液晶１０のレタデーションΔｎ_１＊ｄ_１が８３５ｎｍ〜８６５ｎｍであって、レタデーション比が０．６７〜０．７３のＳＴＮタイプ液晶表示装置１００において、１０°＜α＜２０°，７０°＜β＜８０°，１５°＜γ＜５０°，４０°＜δ＜５０°とすれば、透過率Ｔ_ｏｆｆは２０％以上且つコントラスト比は３０以上となり、ＳＴＮタイプ液晶表示装置１００において近年主流となっているネマティック液晶及び位相差板を使用しても着色光の位相の補正を行いつつコントラスト比を向上させることができ、ＳＴＮタイプ液晶表示装置１００を２色表示に好適なものとすることができることが分かった。
【０１１５】
また、表３及び図６（レタデーション比が夫々異なる実施例５０〜５４，５５〜５８，５９〜６４，６５〜７０）から、レタデーションの比が０．６８〜０．７３であって、２０°＜γ＜４０°（実施例５１〜５３，６０〜６２，６６〜６８）とすれば、コントラスト比が５０以上となるので、着色光の位相の補正を行いつつコントラスト比をより効果的に向上させることができることが分かった。さらに、透過率Ｔ_ｏｆｆが２０％以上、好ましくは２３％以上であってコントラスト比を３０以上、好ましくは５０以上に向上させたものはカラー表示がより鮮明となるので、第２の実施の形態に係るＳＴＮタイプ液晶表示装置１００をカラー表示に好適なものとすることができるのが分かった。
【０１１６】
【発明の効果】
以上詳細に説明したように、請求項１記載のＳＴＮタイプ液晶表示装置によれば、ネマティック液晶のレタデーションΔｎ_１＊ｄ_１が８３５ｎｍ〜８６５ｎｍであって、該Δｎ_１＊ｄ_１に対する前記位相差板のレタデーションΔｎ_２＊ｄ_２の比率が０．６７〜０．７３であるＳＴＮタイプ液晶表示装置において、基準線に対して、表偏光板の吸収軸がなす角の角度を０°＜α＜２５°、裏偏光板の吸収軸がなす角の角度を６０°＜β＜８５°、及び位相差板の光学軸がなす角の角度を４５°＜γ＜７０°、並びに表偏光板の吸収軸と当該表偏光板に対向する電極基板のラビング軸との交差角の角度を３０°＜δ＜５５°としたので、近年主流となっているネマティック液晶及び位相差板を使用することができると共に、着色光の位相の十分な補正を行うことができる。また、コントラスト比を１０以上とすることができる。
【０１１７】
請求項２記載のＳＴＮタイプ液晶表示装置によれば、角度を夫々５°＜α＜１５°，７０°＜β＜８５°，４５°＜γ＜５５°，３５°＜δ＜４５°としたので、コントラスト比を１５以上とすることができる。
【０１１８】
請求項３記載のＳＴＮタイプ液晶表示装置によれば、角度を夫々１０°＜α＜２０°，６５°＜β＜７５°，５０°＜γ＜６０°，４０°＜δ＜５０°としたので、コントラスト比を１５以上とすることができる。
【０１１９】
請求項４記載のＳＴＮタイプ液晶表示装置によれば、角度を夫々１０°＜α＜２５°，７０°＜β＜８５°，４５°＜γ＜７０°，４０°＜δ＜５５°としたので、コントラスト比を１５以上とすることができる。
【０１２０】
請求項５記載のＳＴＮタイプ液晶表示装置によれば、１５°＜α＜２５°，７５°＜β＜８５°，５０°＜γ＜６５°，４５°＜δ＜５５°としたので、コントラスト比を２０以上とすることができる。
【０１２１】
以上詳細に説明したように、請求項６記載のＳＴＮタイプ液晶表示装置によれば、ネマティック液晶のΔｎ_１＊ｄ_１が８３５ｎｍ〜８６５ｎｍであって、該Δｎ_１＊ｄ_１に対する前記位相差板のレタデーションΔｎ_２＊ｄ_２の比率が０．６７〜０．７３であるＳＴＮタイプ液晶表示装置において、基準線に対して、表偏光板の吸収軸がなす角の角度を１０°＜α＜２０°、裏偏光板の吸収軸がなす角の角度を７０°＜β＜８０°、及び位相差板の光学軸がなす角の角度を１５°＜γ＜５０°、並びに表偏光板の吸収軸と当該表偏光板に対向する電極基板のラビング軸との交差角の角度を４０°＜δ＜５０°としたので、近年主流となっているネマティック液晶及び位相差板を使用することができると共に、コントラスト比を、具体的には３０以上に向上させることができる。
【０１２２】
請求項７記載のＳＴＮタイプ液晶表示装置によれば、レタデーションの比が０．６８〜０．７３であって、位相差板の光学軸がなす角の角度を２０°＜γ＜４０°としたので、コントラスト比を５０以上とすることができる。
【０１２３】
請求項８記載のＳＴＮタイプ液晶表示装置によれば、裏偏光板側にバックライトを備えるので、当該ＳＴＮタイプ液晶表示装置は透過型となり、バックライトに応じた輝度を提供することができる。
【０１２４】
請求項９記載のＳＴＮタイプ液晶表示装置によれば、バックライトが裏偏光板側に積層されたので、明るい透過光による表示を行うことができる。
【０１２５】
請求項１０記載のＳＴＮタイプ液晶表示装置によれば、バックライトの照射光が白色であるので、表示の色純度を向上させることができる。
【０１２６】
請求項１１記載のＳＴＮタイプ液晶表示装置によれば、バックライトと表偏光板との間において介在する三原色のカラーフィルターを備えるので、表示をカラーとすることができる。
【０１２７】
請求項１２記載のＳＴＮタイプ液晶表示装置によれば、裏偏光板側に光反射板を備えるので、当該ＳＴＮタイプ液晶表示装置は反射型となり、バックライトを備える透過型のものよりも小型化することができる。
【０１２８】
請求項１３記載のＳＴＮタイプ液晶表示装置によれば、光反射板が裏偏光板側に積層されたので、明るい反射光による表示を行うことができる。
【０１２９】
請求項１４記載のＳＴＮタイプ液晶表示装置によれば、光反射板が可視光を反射するので、２色表示に好適なものとすることができる。
【０１３０】
請求項１５記載のＳＴＮタイプ液晶表示装置によれば、位相差板が高分子一軸延伸フィルムから成るので、容易に入手することができる。
【０１３１】
請求項１６記載のＳＴＮタイプ液晶表示装置によれば、所定のねじれ角θが２２０〜２５０°であるので、視野角を十分に確保することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係るＳＴＮタイプ液晶表示装置の構成図である。
【図２】図１のＳＴＮタイプ液晶表示装置１００における各ラビング軸の方向や光学軸の方向や各吸収軸の方向等の相対関係を示す図である。
【図３】（ａ）〜（ｄ）は、レタデーション比０．６８〜０．７１である場合における図２におけるα，β，γ、及びδの各々とコントラスト比との関係を示す図である。
【図４】図１のＳＴＮタイプ液晶表示装置１００の可視光の透過色を示すＸＹＺ表色系色度図である。
【図５】本発明の第３の実施の形態に係るＳＴＮタイプ液晶表示装置１００の構成図である。
【図６】本発明の第２の実施例における測定結果を示す図である。
【符号の説明】
１０　ネマティック液晶
２０　表電極基板
３０　裏電極基板
４０　液晶セル
５０　表偏光板
６０　裏偏光板
７０　位相差板
８０　バックライト
９０　光反射板
１００　ＳＴＮタイプ液晶表示装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an STN (Super Twisted Nematic) type liquid crystal display device, and particularly to an STN type liquid crystal display device which performs achromatic liquid crystal display using a phase difference plate.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a liquid crystal display device called an STN type has been used to perform screen display using liquid crystal. This STN type liquid crystal display device has a nematic liquid crystal having a positive dielectric anisotropy and a predetermined torsion angle θ, a liquid crystal cell including two electrode substrates sandwiching the nematic liquid crystal, and a liquid crystal cell outside the liquid crystal cell. And two polarizing plates each having an absorption axis (or a polarization axis) facing each of the two electrode substrates.
[0003]
In the manufacture of the liquid crystal cell, first, the surface of the two electrode substrates, which comes into contact with the nematic liquid crystal, is rubbed in a predetermined direction with a cloth or the like so that a rubbing axis in a predetermined direction is applied to the surface. Is performed by a rubbing method that gives Next, the two electrode substrates that have been subjected to the orientation treatment are opposed to each other so that a cell gap (predetermined interval) d of, for example, 6 μm is ensured. A nematic liquid crystal containing a biphenyl-based liquid crystal and an estercyclohexane-based liquid crystal as main components and to which a small amount of a rotatory substance is added is sandwiched. Thereafter, the peripheral edge of the gap is sealed with a sealing material. Generally, the liquid crystal molecules constituting the nematic liquid crystal are arranged in a helical structure. At this time, the nematic liquid crystal has a predetermined twist angle θ. For example, when the two electrode substrates are opposed to each other, if the cell gap d is 6 μm and the angle at which the rubbing axes given to the two electrode substrates intersect is 260 °, the nematic The twist angle θ of the liquid crystal is 260 °.
[0004]
In the nematic liquid crystal having a twist angle of 260 °, the birefringence Δn is, for example, 0.083, and the product of the birefringence Δn and the cell gap d, that is, the retardation Δn * d is 500 to 1200 nm. is there.
[0005]
Further, a polycarbonate film as a retardation plate having a predetermined retardation Δn * d and an optical axis in a predetermined direction, and having a retardation Δn * d of 180 to 700 nm is added to the configuration of the STN type liquid crystal display device. An STN type liquid crystal display device has been proposed (Patent Document 1). According to this proposal, the phase difference plate can correct the phase of the colored light that causes color to adhere to at least one of the background and the display unit of the conventional liquid crystal display device, and the display can be achromatic or colored. An STN type liquid crystal display device can be provided.
[0006]
[Patent Document 1]
Patent No. 3040072
[0007]
[Problems to be solved by the invention]
However, in recent years, the retardation Δn * d of the nematic liquid crystal has a range of 835 to 865 nm from the viewpoint of suppressing yellowing, and the retardation Δn * d has the retardation Δn * d of the retardation plate from the viewpoint of correcting the yellowing of the nematic liquid crystal. 570-610 nm is the mainstream. Therefore, in order to correct the phase of the colored light in the STN type liquid crystal display device using a nematic liquid crystal and a retardation plate, which has become mainstream in recent years, the retardation Δn * of the retardation plate with respect to the retardation Δn * d of the nematic liquid crystal. It is assumed that the range of the ratio of d is 0.67 to 0.73. Therefore, in order to control the contrast ratio of the STN type liquid crystal display device having the retardation ratio in this range, it is necessary to consider parameters other than the above ratio.
[0008]
An object of the present invention is to provide an STN type liquid crystal display device which can use a nematic liquid crystal and a retardation plate, which have become mainstream in recent years, and can sufficiently correct the phase of colored light. .
[0009]
Another object of the present invention is to provide an STN type liquid crystal display device which can use a nematic liquid crystal and a retardation plate which have become mainstream in recent years and can improve a contrast ratio.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the STN type liquid crystal display device according to claim 1 has a predetermined twist angle θ and a predetermined birefringence Δn. ₁ A nematic liquid crystal having the formula: ₁ A liquid crystal cell comprising two electrode substrates sandwiched in the gap and having a rubbing axis in a predetermined direction, and a front polarizing plate having an absorption axis in a predetermined direction facing each of the electrode substrates outside the liquid crystal cell. And a predetermined retardation Δn that faces either one of the two electrode substrates outside the two electrode substrates and a back polarizer. ₂ * D ₂ And a retardation plate having an optical axis in a predetermined direction, wherein a retardation Δn of the nematic liquid crystal is provided. ₁ * D ₁ Is 835 nm to 865 nm, and the retardation Δn ₁ * D ₁ Of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, a reference line which is a line segment equally dividing a narrow angle side crossing angle among crossing angles formed by the rubbing axes is referred to as the above table. The angle of the angle formed by the absorption axis of the polarizing plate is α, the angle of the angle formed by the absorption axis of the back polarizing plate is β, and the angle of the angle formed by the optical axis of the retardation plate is γ, and the angle of the front polarizing plate is Assuming that the angle of the intersection between the absorption axis and the rubbing axis of the electrode substrate facing the front polarizing plate is δ, 0 ° <α <25 °, 60 ° <β <85 °, 45 ° <γ <70 ° , 30 ° <δ <55 °.
[0011]
According to the STN type liquid crystal display device of the first aspect, Δn of the nematic liquid crystal ₁ * D ₁ Is 835 nm to 865 nm, and the Δn ₁ * D ₁ Δn of the phase difference plate with respect to ₂ * D ₂ Is 0.67 to 0.73, the angle of the angle formed by the absorption axis of the front polarizer with respect to the reference line is 0 ° <α <25 °, and the absorption of the back polarizer is The angle formed by the axes is 60 ° <β <85 °, the angle formed by the optical axis of the phase difference plate is 45 ° <γ <70 °, and the absorption axis of the table polarizer is opposed to the table polarizer. Since the angle of the intersection angle of the electrode substrate with the rubbing axis is set to 30 ° <δ <55 °, it is possible to use a nematic liquid crystal and a retardation plate, which have become mainstream in recent years, and to obtain a sufficient phase of the colored light. Correction can be performed. Further, the contrast ratio can be 10 or more.
[0012]
The STN type liquid crystal display device according to the second aspect is the STN type liquid crystal display device according to the first aspect, wherein the angles are respectively set to 5 ° <α <15 °, 70 ° <β <85 °, and 45 ° <γ <. 55 °, 35 ° <δ <45 °.
[0013]
According to the STN type liquid crystal display device of the second aspect, the angles are respectively set at 5 ° <α <15 °, 70 ° <β <85 °, 45 ° <γ <55 °, and 35 ° <δ <45 °. Therefore, the contrast ratio can be set to 15 or more.
[0014]
The STN type liquid crystal display device according to a third aspect is the STN type liquid crystal display device according to the first aspect, wherein the angles are respectively set to 10 ° <α <20 °, 65 ° <β <75 °, and 50 ° <γ <. 60 °, 40 ° <δ <50 °.
[0015]
According to the STN type liquid crystal display device of the third aspect, the angles are respectively set to 10 ° <α <20 °, 65 ° <β <75 °, 50 ° <γ <60 °, and 40 ° <δ <50 °. Therefore, the contrast ratio can be set to 15 or more.
[0016]
The STN-type liquid crystal display device according to a fourth aspect is the STN-type liquid crystal display device according to the first aspect, wherein the angles are respectively set to 10 ° <α <25 °, 70 ° <β <85 °, and 45 ° <γ <. 70 °, 40 ° <δ <55 °.
[0017]
According to the STN type liquid crystal display device of the fourth aspect, the angles are respectively set to 10 ° <α <25 °, 70 ° <β <85 °, 45 ° <γ <70 °, and 40 ° <δ <55 °. Therefore, the contrast ratio can be set to 15 or more.
[0018]
The STN type liquid crystal display device according to a fifth aspect is the STN type liquid crystal display device according to the fourth aspect, wherein the angles are respectively set to 15 ° <α <25 °, 75 ° <β <85 °, and 50 ° <γ <. 65 °, 45 ° <δ <55 °.
[0019]
According to the STN type liquid crystal display device of the fifth aspect, since 15 ° <α <25 °, 75 ° <β <85 °, 50 ° <γ <65 °, and 45 ° <δ <55 °, the contrast is improved. The ratio can be 20 or more.
[0020]
In order to achieve the above object, the STN type liquid crystal display device according to claim 6 has a predetermined twist angle θ and a predetermined birefringence Δn. ₁ A nematic liquid crystal having the formula: ₁ A liquid crystal cell comprising two electrode substrates sandwiched in the gap and having a rubbing axis in a predetermined direction, and a front polarizing plate having an absorption axis in a predetermined direction facing each of the electrode substrates outside the liquid crystal cell. And a predetermined retardation Δn that faces either one of the two electrode substrates outside the two electrode substrates and a back polarizer. ₂ * D ₂ And a retardation plate having an optical axis in a predetermined direction, wherein a retardation Δn of the nematic liquid crystal is provided. ₁ * D ₁ Is 835 nm to 865 nm, and the retardation Δn ₁ * D ₁ Of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, a reference line which is a line segment equally dividing a narrow angle side crossing angle among crossing angles formed by the rubbing axes is referred to as the above table. The angle of the angle formed by the absorption axis of the polarizing plate is α, the angle of the angle formed by the absorption axis of the back polarizing plate is β, and the angle of the angle formed by the optical axis of the retardation plate is γ, and the angle of the front polarizing plate is Assuming that the angle of intersection between the absorption axis and the rubbing axis of the electrode substrate facing the front polarizing plate is δ, 10 ° <α <20 °, 70 ° <β <80 °, 15 ° <γ <50 ° , 40 ° <δ <50 °.
[0021]
According to the STN type liquid crystal display device of the sixth aspect, the retardation Δn of the nematic liquid crystal ₁ * D ₁ Is 835 nm to 865 nm, and the retardation Δn ₁ * D ₁ Of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, the angle formed by the absorption axis of the front polarizing plate with respect to the reference line is 10 ° <α <20 °, and the absorption of the back polarizing plate is The angle between the axes is 70 ° <β <80 °, the angle between the optical axes of the phase difference plates is 15 ° <γ <50 °, and the absorption axis of the table polarizer is opposed to the table polarizer. Since the angle of the crossing angle of the electrode substrate with the rubbing axis is set to 40 ° <δ <50 °, nematic liquid crystals and retardation plates, which have become mainstream in recent years, can be used and the contrast ratio can be reduced. Can be improved to 30 or more.
[0022]
The STN-type liquid crystal display device according to claim 7, wherein the ratio is 0.68 to 0.73, and the angle formed by the optical axis of the retardation plate is the angle of the STN-type liquid crystal display device according to claim 6. Is set to 20 ° <γ <40 °.
[0023]
According to the STN type liquid crystal display device of the seventh aspect, the retardation ratio is 0.68 to 0.73, and the angle formed by the optical axis of the retardation plate is set to 20 ° <γ <40 °. Therefore, the contrast ratio can be set to 50 or more.
[0024]
An STN type liquid crystal display device according to an eighth aspect is the STN type liquid crystal display device according to any one of the first to seventh aspects, wherein a backlight is provided on the back polarizing plate side.
[0025]
According to the STN-type liquid crystal display device of the present invention, since the backlight is provided on the back polarizing plate side, the STN-type liquid crystal display device is of a transmission type, and can provide luminance according to the backlight.
[0026]
An STN type liquid crystal display device according to a ninth aspect is the STN type liquid crystal display device according to the eighth aspect, wherein the backlight is laminated on the back polarizing plate side.
[0027]
According to the STN type liquid crystal display device of the ninth aspect, since the backlight is laminated on the back polarizing plate side, it is possible to perform display with bright transmitted light.
[0028]
An STN type liquid crystal display device according to a tenth aspect is the STN type liquid crystal display device according to the eighth or ninth aspect, wherein the irradiation light of the backlight is white.
[0029]
According to the STN type liquid crystal display device of the tenth aspect, since the irradiation light of the backlight is white, the color purity of the display can be improved.
[0030]
The STN type liquid crystal display device according to claim 11, wherein the three primary colors interposed between the backlight and the front polarizer in the STN type liquid crystal display device according to any one of claims 8 to 10. It is characterized by having a filter.
[0031]
According to the STN-type liquid crystal display device of the eleventh aspect, since the three primary color filters interposed between the backlight and the front polarizer are provided, the display can be colored.
[0032]
An STN type liquid crystal display device according to a twelfth aspect is the STN type liquid crystal display device according to any one of the first to seventh aspects, wherein a light reflector is provided on the back polarizing plate side.
[0033]
According to the STN type liquid crystal display device of the twelfth aspect, since the light reflecting plate is provided on the back polarizing plate side, the STN type liquid crystal display device is of a reflective type, and is smaller than a transmissive type having a backlight. be able to.
[0034]
The STN type liquid crystal display device according to a thirteenth aspect is characterized in that, in the STN type liquid crystal display device according to the twelfth aspect, the light reflection plate is laminated on the back polarizing plate side.
[0035]
According to the STN type liquid crystal display device of the thirteenth aspect, since the light reflecting plate is laminated on the back polarizing plate side, it is possible to perform display with bright reflected light.
[0036]
The STN type liquid crystal display device according to claim 14 is the STN type liquid crystal display device according to claim 12 or 13, wherein the light reflection plate reflects visible light.
[0037]
According to the STN type liquid crystal display device of the present invention, since the light reflecting plate reflects visible light, it can be suitable for color display.
[0038]
According to a fifteenth aspect of the present invention, in the STN type liquid crystal display device according to any one of the first to fourteenth aspects, the retardation plate is made of a polymer uniaxially stretched film.
[0039]
According to the STN type liquid crystal display device of the present invention, since the retardation plate is made of a uniaxially stretched polymer film, it can be easily obtained.
[0040]
The STN type liquid crystal display device according to claim 16 is the STN type liquid crystal display device according to any one of claims 1 to 15, wherein the predetermined twist angle θ is 220 to 250 °. And
[0041]
According to the STN type liquid crystal display device of the sixteenth aspect, since the predetermined twist angle θ is 220 to 250 °, a sufficient viewing angle can be secured.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventor has conducted intensive studies in order to achieve the above-mentioned object, and as a result, a predetermined twist angle θ and a predetermined birefringence Δn ₁ A nematic liquid crystal having the formula: ₁ A liquid crystal cell comprising two electrode substrates sandwiched in the gap and having a rubbing axis in a predetermined direction, and a front polarizing plate having an absorption axis in a predetermined direction facing each of the electrode substrates outside the liquid crystal cell. And a predetermined retardation Δn which faces one of the two electrode substrates on the outside of the back polarizer and the two electrode substrates. ₂ * D ₂ , And a retardation plate having an optical axis in a predetermined direction. ₁ * D ₁ Is 835 nm to 865 nm, and the retardation Δn ₁ * D ₁ Retardation Δn of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, a front polarizer is arranged with respect to a reference line which is a line segment equally dividing the crossing angle on the narrow angle side among the crossing angles formed by the rubbing axes. The angle of the angle formed by the absorption axis of 0 ° <α <25 °, the angle of the angle formed by the absorption axis of the back polarizer is 60 ° <β <85 °, and the angle of the angle formed by the optical axis of the retardation plate If 45 ° <γ <70 ° and the angle of intersection between the absorption axis of the front polarizer and the rubbing axis of the electrode substrate facing the front polarizer is 30 ° <δ <55 °, it has become mainstream in recent years. It has been found that a nematic liquid crystal and a retardation plate can be used, the phase of the colored light can be sufficiently corrected, and the contrast ratio can be 10 or more.
[0043]
Further, the present inventor has conducted intensive studies to achieve the above object, and as a result, a predetermined twist angle θ and a predetermined birefringence Δn ₁ A nematic liquid crystal having the formula: ₁ A liquid crystal cell comprising two electrode substrates sandwiched in the gap and having a rubbing axis in a predetermined direction, and a front polarizing plate having an absorption axis in a predetermined direction facing each of the electrode substrates outside the liquid crystal cell. And a predetermined retardation Δn which faces one of the two electrode substrates on the outside of the back polarizer and the two electrode substrates. ₂ * D ₂ , And a retardation plate having an optical axis in a predetermined direction. ₁ * D ₁ Is 835 nm to 865 nm, and the retardation Δn ₁ * D ₁ Retardation Δn of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, a front polarizer is arranged with respect to a reference line which is a line segment equally dividing the crossing angle on the narrow angle side among the crossing angles formed by the rubbing axes. The angle of the angle formed by the absorption axis of the polarizer is 10 ° <α <20 °, the angle of the angle formed by the absorption axis of the back polarizer is 70 ° <β <80 °, and the angle of the angle formed by the optical axis of the retardation plate is 15 ° <γ <50 °, and the angle of intersection between the absorption axis of the front polarizer and the rubbing axis of the electrode substrate facing the front polarizer is set at 40 ° <δ <50 °. It has been found that the nematic liquid crystal and the retardation plate can be used, and the contrast ratio can be specifically improved to 30 or more.
[0044]
Hereinafter, an STN type liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.
[0045]
FIG. 1 is a configuration diagram of an STN type liquid crystal display device according to a first embodiment of the present invention.
[0046]
In FIG. 1, the STN type liquid crystal display device 100 according to the first embodiment includes a nematic liquid crystal 10 and a nematic liquid crystal 10 having a cell gap d. ₁ A liquid crystal cell 40 including two electrode substrates 20 and 30 sandwiched in a gap between the liquid crystal cell 40 and a front polarizing plate 50 (for example, SQ-1852A manufactured by Sumitomo Chemical Co., Ltd.) facing the front electrode substrate 20 outside the liquid crystal cell 40; A back polarizing plate 60 (for example, SQ-1852A manufactured by Sumitomo Chemical Co., Ltd.) facing the back electrode substrate 30 outside the liquid crystal cell 40, and a front electrode substrate 20 outside the front electrode substrate 20 and inside the front polarizing plate 50. And a backlight 80 laminated on the outer surface of the back polarizing plate 60.
[0047]
In the STN type liquid crystal display device 100, the retardation Δn of the nematic liquid crystal 10 ₁ * D ₁ Is 835 nm to 865 nm, which has become mainstream in recent years. This is the retardation Δn ₁ * D ₁ Is out of the range of 835 nm to 865 nm, yellowing occurs and the contrast ratio decreases to less than 10.
[0048]
Note that the contrast ratio is the transmittance (23% or more) of visible light (wavelength 380 to 780 nm) when no voltage is applied to the transparent electrode (hereinafter referred to as “transmittance T”). _off ") When a voltage of 3 V is applied (hereinafter referred to as" transmittance T "). _on "). For example, the transmittance T _on Is as low as 2%, the contrast ratio becomes 10 or more, and the transmittance T _on Is high, the contrast ratio is less than 10.
[0049]
In the STN type liquid crystal display device 100, the Δn ₂ * D ₂ Is 570 nm to 610 nm, which has become mainstream in recent years. This is Δn ₂ * D ₂ Is out of the range of 570 nm to 610 nm, even if yellowing occurs in the nematic liquid crystal 10, the yellowing cannot be sufficiently corrected, and the transmittance T _off Is reduced to less than 23%.
[0050]
That is, in order to sufficiently correct the phase of the colored light, the ratio of the retardation Δn * d of the retardation plate to the retardation Δn * d of the nematic liquid crystal (hereinafter, referred to as “retardation ratio”) ranges from 0.67 to 0.67. It is assumed that it is 0.73. Therefore, in order to control the contrast ratio and the transmittance of the STN type liquid crystal display device 100 having the retardation ratio in this range, it is necessary to consider parameters other than the retardation ratio.
[0051]
At this time, the parameters that can be adjusted in the STN type liquid crystal display device 100 include the twist angle θ11 of the nematic liquid crystal 10 (FIG. 2), the rubbing axis direction 21 of the front electrode substrate 20, and the rubbing axis of the back electrode substrate 30. The direction 31, the direction 51 of the absorption axis of the front polarizing plate 50, the direction 61 of the absorption axis of the back polarizing plate 60, and the direction 71 of the optical axis of the retardation plate 70 are shown (FIGS. 1 and 2).
[0052]
FIG. 2 is a diagram showing a relative relationship between the direction of each rubbing axis, the direction of an optical axis, and the direction of each absorption axis in the STN type liquid crystal display device 100 of FIG.
[0053]
In FIG. 2, the intersection angle between the direction 51 of the absorption axis and the direction 21 of the rubbing axis is defined as δ, and the intersection angle on the narrow angle side among the intersection angles of the direction 21 of the rubbing axis and the direction 31 of the rubbing axis is equally divided. The line segment is used as the reference line 22. At this time, the rubbing axis direction 21 and the rubbing axis direction 31 are set such that the direction of the reference line 22 matches the longitudinal direction of the front electrode substrate 20 and the back electrode substrate 30.
[0054]
The light from the backlight 80 is polarized in the direction 61 of the absorption axis by passing through the back polarizing plate 60, further polarized by the twist angle θ11 by the liquid crystal cell 40, and transmitted through the front polarizing plate 50 to be polarized. Polarized in direction 51.
[0055]
Further, the angle between the reference line 22 and the direction 51 of the absorption axis is α, the angle between the reference line 22 and the direction 61 of the absorption axis is β, and the angle between the reference line 22 and the direction 71 of the optical axis is γ. It is said.
[0056]
In the STN-type liquid crystal display device 100, the angle formed by the reference line 22 and the direction 21 of the rubbing axis is + 30 °, and the angle formed by the reference line 22 and the direction 31 of the rubbing axis is -30 °. The angle θ11 is 240 °. To set the torsion angle θ11 to 250 °, the angle formed by the reference line 22 and the rubbing axis direction 21 is + 35 ° and the angle formed by the reference line 22 and the rubbing axis direction 31 is −35 °. Good.
[0057]
In FIG. 1, a nematic liquid crystal 10 is a mixture containing a cyclohexane-based liquid crystal as a main component and a small amount of a rotatory substance added as a chiral agent, and a predetermined liquid crystal selected from a range of 220 to 250 °. Torsion angle θ, for example 240 ° and a predetermined birefringence Δn ₁ , For example, 0.133. The nematic liquid crystal 10 has a cell gap d in the liquid crystal cell 40 by the front electrode substrate 20 and the back electrode substrate 30. ₁ For example, when the sheet is sandwiched by a gap of 6.4 μm, the retardation Δn ₁ * D ₁ Is 851 nm. At this time, since the torsion angle θ11 is 220 to 250 °, a sufficient viewing angle can be secured.
[0058]
The retardation plate 70 is made of a polymer uniaxially stretched film, for example, a polycarbonate uniaxially stretched retardation film (SEF460595, manufactured by Sumitomo Chemical Co., Ltd.), and has a predetermined retardation Δn. ₂ * D ₂ Is 570 to 610 nm, for example, 595 nm. Since the retardation plate 70 is made of a polymer uniaxially stretched film, it can be easily obtained.
[0059]
The backlight 80 (for example, a white fluorescent light source) emits white light with high luminance. Thereby, the color purity of the display can be improved. In addition, since the backlight 80 is stacked on the outer surface of the back polarizing plate 60, it is possible to perform display with bright transmitted light. Further, since the STN type liquid crystal display device 100 includes the backlight 80, the STN type liquid crystal display device 100 is of a transmissive type, and can provide luminance according to the backlight 80.
[0060]
FIGS. 3A to 3D are diagrams showing the relationship between each of the above α, β, γ, and δ and the contrast ratio when the retardation ratio is 0.68 to 0.71.
[0061]
FIG. 3A shows the relationship between α and the contrast ratio when the retardation ratio, β, γ, and δ are constant. From this relationship, it can be seen that if 0 ° <α <25 °, the contrast ratio can be 10 or more.
[0062]
FIG. 3B shows the relationship between β and the contrast ratio when the retardation ratio, α, γ, and δ are constant. From this relationship, it can be seen that if 60 ° <β <85 °, the contrast ratio can be 10 or more.
[0063]
FIG. 3C shows the relationship between γ and the contrast ratio when the retardation ratio, α, β, and δ are constant. From this relationship, it can be seen that if 45 ° <γ <70 °, the contrast ratio can be 10 or more.
[0064]
FIG. 3D shows the relationship between δ and the contrast ratio when the retardation ratio, α, β, and γ are constant. From this relationship, it can be seen that if 30 ° <δ <55 °, the contrast ratio can be 10 or more.
[0065]
Therefore, in the STN type liquid crystal display device 100 having a retardation ratio of 0.67 to 0.73, 0 ° <α <25 °, 60 ° <β <85 °, 45 ° <γ <70 °, 30 ° <δ. If <55 °, the contrast ratio can be 10 or more.
[0066]
According to the STN type liquid crystal display device 100 of FIG. 1, the nematic liquid crystal 10 and the retardation plate 70, which have become mainstream in recent years, can be used, and the retardation ratio is 0.67 to 0.73. Can be sufficiently corrected, and 0 ° <α <25 °, 60 ° <β <85 °, 45 ° <γ <70 °, and 30 ° <δ <55 °, so that the contrast ratio Can be 10 or more.
[0067]
Hereinafter, the manufacturing process of the liquid crystal cell 10 will be described.
[0068]
In the manufacture of the liquid crystal cell 10, first, an ITO transparent electrode formed of an ITO film (tin-containing indium oxide film) is formed on the surface, and is a plate having a thickness of 1.1 mm, a width of 100 mm, and a length of 40 mm. Electrode substrates 20 and 30 which are two glass substrates with ITO transparent electrodes are prepared.
[0069]
A polyimide alignment film is formed on the electrode substrates 20 and 30 by applying a polyimide alignment film on the surface on which the ITO transparent electrodes are formed. The ITO transparent electrode forming surface on which the polyimide alignment film is formed is rubbed in a certain direction (rubbing direction) using a rotating brush to which a cloth made of polyester fiber is adhered (rubbing method). Is subjected to an alignment process for forming an alignment groove (rubbing groove) for providing a rubbing axis in a certain direction, that is, a predetermined direction.
[0070]
Each of these rubbing axes has its own rubbing axis direction 21 and rubbing axis direction 31. At this time, the alignment grooves in each of the electrode substrates 20 and 30 are formed such that the intersection angle δ between the direction 51 of the absorption axis and the direction 21 of the rubbing axis is 30 ° <δ <55 °, for example, 40 °. .
[0071]
Next, the two electrode substrates 20 and 30 are placed in the cell gap (gap) d such that the ITO transparent electrode forming surface is on the inside. ₁ Are arranged so as to secure, for example, 6 μm, and a sealing member made of epoxy resin is arranged around the electrode substrates 20 and 30 by a screen printing method, so that the STN type liquid crystal cell 40 into which the nematic liquid crystal 10 can be injected is provided. To form
[0072]
After that, the nematic liquid crystal 10 is injected into the formed liquid crystal cell 40. As a result, the two electrode substrates 20, 30 sandwich the nematic liquid crystal 10 in the gap therebetween. Next, the periphery of the nematic liquid crystal 10 is sealed with a sealing material made of a sealing agent of a photocurable acrylic resin.
[0073]
At this time, since the liquid crystal molecules constituting the nematic liquid crystal 10 are arranged in a spiral structure, the nematic liquid crystal 10 has a predetermined twist angle θ11. For example, the angle between the reference line 22 and the rubbing axis direction 21 is + 30 °, the angle between the reference line 22 and the rubbing axis direction 31 is −30 °, and the cell gap d ₁ Is 6 μm, the twist angle θ of the nematic liquid crystal 10 is 240 °.
[0074]
Thereafter, a retardation plate 70 is provided on the display-side surface of the obtained liquid crystal cell 40, and a reference line 22 which equally divides the intersection angle on the narrow angle side among the intersection angles of the rubbing axis direction 21 and the rubbing axis direction 31. Is bonded to the surface of the liquid crystal cell 40 on the front electrode substrate 20 side such that γ, which is the angle between the optical axis direction 71 and the optical axis direction 71, is 45 ° <γ <70 °, for example, 50 °. In addition, the front polarizer 50 is adhered on the display side surface of the retardation plate 70, and the back polarizer 60 is adhered on the back electrode substrate 30 side surface of the liquid crystal cell 40 with an adhesive.
[0075]
At this time, the angle α formed by the reference line 22 and the direction 51 of the absorption axis of the front polarizer 50 is 0 ° <α <25 °, for example, 10 °, and the direction 61 of the reference line 22 and the absorption axis of the back polarizer 60 is set. The angle β is 60 ° <β <85 °, for example, 70 °, and the retardation of the liquid crystal cell 40 is Δn ₁ * D ₁ = 840 to 860 nm, for example, 851 nm, and the retardation of the retardation plate 70 is Δn ₂ * D ₂ = 570-610 nm, for example, 595 nm. Therefore, the retardation Δn of the liquid crystal cell 40 ₁ * D ₁ Of the phase difference plate 70 with respect to ₂ * D ₂ The retardation ratio is 0.67 to 0.73, for example, 0.699.
[0076]
FIG. 4 is an XYZ color system chromaticity diagram showing transmitted colors of visible light of the STN type liquid crystal display device 100 of FIG.
[0077]
In this XYZ color system chromaticity diagram, the uncolored area A in which the visible light transmission color of the STN type liquid crystal display device 100 measured by a spectrophotometer is uncolored has a chromaticity coordinate x of 0.300 to 0.300. 0.330, and the chromaticity coordinate y is 0.310 to 0.340.
[0078]
Further, in the region of the liquid crystal cell 40 that shows the transmitted color of visible light, the chromaticity coordinate x is, for example, 0.320, and the chromaticity coordinate y is, for example, 0.334. A is included. That is, in the STN type liquid crystal display device 100 shown in FIG. 1, the chromaticity coordinates x and the colors substantially coincide with the chromaticity coordinates x and the chromaticity coordinates y of the uncolored area A in the XYZ color system chromaticity diagram. Visible light of transmitted color having the degree coordinate y, in other words, visible light of non-colored or extremely light-colored transmitted color can be displayed. Therefore, the display of the STN type liquid crystal display device 100 is close to a white display, and coloring can not be greatly felt.
[0079]
Further, when a voltage, for example, 3 V is applied to the transparent electrodes on the front electrode substrate 20 and the back electrode substrate 30, black display can be performed with almost no visible light transmitted through the liquid crystal cell 40 only in the portion where the voltage is applied.
[0080]
The contrast ratio of the STN type liquid crystal display device 100 of FIG. 1 is as large as about 10 to 25, for example, 11 and, as described above, the visible light is uncolored or has a very light transmitted color. It has practical and necessary commercial value.
[0081]
According to the STN type liquid crystal display device 100 of FIG. 1, since the phase of the colored light can be sufficiently corrected, the achromatic STN type liquid crystal display device 100 can be suitable for color display. .
[0082]
Next, a second embodiment of the present invention will be described.
[0083]
The STN type liquid crystal display device 100 according to the second embodiment is different from the STN type liquid crystal display device 100 in FIG. And a two-color display composed of black and black display colors.
[0084]
The configuration of the STN-type liquid crystal display device 100 according to the second embodiment is the same as the configuration of the STN-type liquid crystal display device 100 in FIG. 1, and thus the same components are given the same reference numerals and description thereof is omitted. I do.
[0085]
In the STN-type liquid crystal display device 100 according to the second embodiment, each of α, β, and γ is 10 ° <α <20 °, 70 ° <β <80 °, and 40 ° <δ <50 °. is there. Accordingly, it is possible to use a nematic liquid crystal and a retardation plate, which have become mainstream in recent years, and to improve the contrast ratio, specifically, to 30 or more while correcting the phase of the colored light. Thereby, the STN type liquid crystal display device 100 can be made suitable for two-color display.
[0086]
In addition, when the above-mentioned retardation ratio is 0.68 to 0.73 and the above-mentioned γ is 20 ° <γ <40 °, the contrast ratio can be made 50 or more. This makes it possible to make the STN type liquid crystal display device 100 more suitable for two-color display. _off Is 23% or more, it can be suitable for color display.
[0087]
In the STN type liquid crystal display device 100 according to the first and second embodiments, the backlight 80 is laminated on the outside of the back polarizing plate 60, and further, between the backlight 80 and the front polarizing plate 50. , R (red), G (green), and B (blue) color filters (not shown) may be interposed. Thereby, the display of the STN type liquid crystal display device 100 can be colored. The display of the STN type liquid crystal display device 100 is in a normal white mode.
[0088]
Next, a third embodiment of the present invention will be described with reference to the drawings.
[0089]
FIG. 5 is a configuration diagram of an STN type liquid crystal display device 100 according to the third embodiment of the present invention.
[0090]
The STN type liquid crystal display device 100 according to the third embodiment has a backlight 80, whereas the STN type liquid crystal display device 100 according to the first and second embodiments has a backlight 80. It differs in preparing.
[0091]
5, the configuration of the STN type liquid crystal display device 100 according to the third embodiment is almost the same as the configuration of the STN type liquid crystal display device 100 in FIG. 1, and the same components are denoted by the same reference numerals. Their description is omitted.
[0092]
The light reflecting plate 90 is laminated by being attached on the outer surface of the back polarizing plate 60. Since the light reflecting plate 90 is laminated on the outside of the back polarizing plate 60, display with bright reflected light can be performed. The light reflecting plate 90 includes a resin base material 91 and an aluminum-deposited thin film 92 deposited on the upper surface of the resin base material 91. The aluminum-deposited thin film 92 reflects visible light so that the STN type liquid crystal display device 100 can be displayed.
[0093]
According to the STN type liquid crystal display device 100 of FIG. 5, since the light reflecting plate 90 is provided, the STN type liquid crystal display device 100 is of a reflection type, and can be made smaller than the transmission type of FIG. Further, since the light reflecting plate 90 is attached to the outside of the back polarizing plate 60, it is possible to perform display by bright reflected light. Further, since the light reflecting plate 90 reflects visible light, the STN type liquid crystal display device 100 can be suitable for two-color display. In the STN type liquid crystal display device 100 suitable for two-color display, when the power is turned off, the display is in a normal white mode.
[0094]
In the STN type liquid crystal display device 100 according to the third embodiment, the light reflecting plate 90 is bonded to the outside of the back polarizing plate 60, and further, between the light reflecting plate 90 and the front polarizing plate 50, Three primary color filters of R, G, and B may be interposed. Thereby, the display of the STN type liquid crystal display device 100 can be colored.
[0095]
Further, the metal deposited on the upper surface of the resin base material 91 in the light reflection plate 90 may be any metal as long as it can reflect visible light.
[0096]
【Example】
Hereinafter, examples of the present invention will be described.
[0097]
First, a first embodiment of the present invention will be described.
[0098]
The present inventor has proposed a retardation Δn for the STN type liquid crystal display device 100 according to the first embodiment. ₁ * D ₁ , Retardation Δn ₂ * D ₂ , And retardation ratios, and test pieces having different α, β, γ, and δ were prepared (Examples 1 to 45 and Comparative Examples 1 to 12 in Table 1). The retardation Δn of the nematic liquid crystal 10 (cyclohexane-based liquid crystal) ₁ * D ₁ Is the cell gap d of the liquid crystal cell 40 ₁ And the retardation Δn of the phase difference plate 70 ₂ * D ₂ Is the thickness d of the retardation plate 70 ₂ And the directions 51 and 61 of the absorption axes of the front polarizing plate 50 and the back polarizing plate 60, and the direction 71 of the optical axis of the retardation plate 70, and the angle formed by the reference line 22. The angles α, β, and γ, and the angle δ of the intersection angle between the direction 51 of the absorption axis of the front polarizing plate 50 and the direction 21 of the rubbing axis of the electrode substrate 20 facing the front polarizing plate 50 are the corresponding front polarization. When the plate 50, the back polarizing plate 60, and the retardation plate 70 were bonded to the liquid crystal cell 40 or the like, the direction was changed by adjusting the bonding direction.
[0099]
Then, it was studied whether or not the phase of the colored light can be sufficiently corrected in the prepared test piece. Specifically, the transmittance T _off The chromaticity coordinate x and the chromaticity coordinate y of the transmitted light in the XYZ color system chromaticity diagram and the contrast ratio were measured. In each of the test pieces, the twist angle θ11 of the nematic liquid crystal 10 in the liquid crystal cell 40 was in the range of 220 to 250 °.
[0100]
Hereinafter, the measurement results are shown in Tables 1 and 2.
[0101]
[Table 1]

[0102]
[Table 2]

[0103]
From Table 2, when α is 0 ° (Comparative Example 4), the transmittance T _off Is less than 23%, the contrast ratio is less than 10, the display of the STN type liquid crystal display device 100 cannot be made suitable for color display, and the contrast ratio of the display cannot be improved. When α is 25 ° or more (Comparative Example 7), since the chromaticity coordinate y becomes larger than 0.340, it is found that the display has a green tint. Therefore, it was found that at least the range of α needs to be 0 ° <α <25 °.
[0104]
When β is 60 ° or less (Comparative Example 1), the contrast ratio is less than 10, and the contrast ratio of the display cannot be improved. On the other hand, when β is 85 ° or more (Comparative Example 2), the transmission ratio does not increase. Rate T _off Is less than 23%, it was found that the display could not be made suitable for color display. Therefore, it was found that at least the range of β needs to be 60 ° <β <85 °.
[0105]
When γ is 45 ° or less (Comparative Example 8), the transmittance T _off Is less than 23% and the chromaticity coordinate y is larger than 0.340, so that the display of the STN type liquid crystal display device 100 cannot be made suitable for color display, and the contrast ratio of the display is improved. In addition, while the display is greenish, the chromaticity coordinate x is larger than 0.330 and the chromaticity coordinate y is 0 when γ is 75 ° or more (Comparative Example 3). .340, it was found that the display was yellowed. Therefore, it was found that the range of γ needs to be 45 ° <γ <70 °.
[0106]
Retardation Δn of nematic liquid crystal 10 ₁ * D ₁ Is out of the range of 835 to 865 nm (Comparative Examples 9 and 10), since the chromaticity coordinate x is smaller than 0.300, the display is bluish or the chromaticity coordinate y is larger than 0.340. Therefore, it was found that the display was greenish. For example, the retardation Δn of the nematic liquid crystal 10 ₁ * D ₁ Is within the range of 840 to 860 nm, the retardation Δn of the retardation plate 70 ₂ * D ₂ Is out of the range of 570 to 610 nm (Comparative Examples 11 and 12), since the chromaticity coordinate y is larger than 0.340, it is found that the display has a green tint. Therefore, the retardation Δn ₁ * D ₁ Is within the range of 840 to 860 nm, and the retardation n ₂ * D ₂ Has to be within the range of 570 to 610 nm.
[0107]
Also, from Tables 1 and 2, the retardation Δn of the nematic liquid crystal 10 is shown. ₁ * D ₁ Is 835 to 865 nm and the retardation ratio is 0.67 to 0.73, in the STN type liquid crystal display device 100, 0 ° <α <25 °, 60 ° <β <85 °, 45 ° <γ <70 ° , 30 ° <δ <55 °, the transmittance T _off Is 23% or more, the chromaticity coordinate x is 0.300 ≦ x ≦ 0.330, the chromaticity coordinate y is 0.330 ≦ y ≦ 0.340, and the contrast ratio is 10 or more. 100, it is possible to use a nematic liquid crystal and a retardation plate, which have become mainstream in recent years, and it is possible to sufficiently correct the phase of the colored light, and to make the STN type liquid crystal display device 100 not feel colored and It turned out that it can be suitable for color display. Further, the transmittance T _off Is not less than 23%, and it is clear that the STN type liquid crystal display device 100 according to the first embodiment is suitable for color display.
[0108]
Next, a second embodiment of the present invention will be described.
[0109]
The present inventor has proposed a retardation Δn for the STN type liquid crystal display device 100 according to the second embodiment. ₁ * D ₁ , Retardation Δn ₂ * D ₂ , And retardation ratios, and test pieces having different α, β, γ, and δ were prepared (Examples 50 to 70 and Comparative Examples 20 to 27 in Table 2). α, β, γ, and δ were changed by adjusting the bonding direction of the front polarizing plate 50, the back polarizing plate 60, and the retardation plate 70, as in the first embodiment described above.
[0110]
Then, it was studied whether or not the prepared test piece could improve the contrast ratio. Specifically, the transmittance T _off , Chromaticity coordinate x, chromaticity coordinate y, and contrast ratio were measured.
[0111]
Hereinafter, the measurement results are shown in Tables 3 and 4, and a part of the measurement results is shown in FIG.
[0112]
[Table 3]

[0113]
[Table 4]

[0114]
From Tables 3 and 4, the retardation Δn of the nematic liquid crystal 10 is shown. ₁ * D ₁ Is 835 nm to 865 nm and the retardation ratio is 0.67 to 0.73 in the STN type liquid crystal display device 100, 10 ° <α <20 °, 70 ° <β <80 °, 15 ° <γ <50 ° , 40 ° <δ <50 °, the transmittance T _off Is 20% or more and the contrast ratio is 30 or more. Even if a nematic liquid crystal and a retardation plate, which have recently become mainstream in the STN type liquid crystal display device 100, are used, the contrast ratio is improved while correcting the phase of the colored light. It was found that the STN type liquid crystal display device 100 could be suitable for two-color display.
[0115]
Also, from Table 3 and FIG. 6 (Examples 50 to 54, 55 to 58, 59 to 64, 65 to 70 having different retardation ratios), the retardation ratio is 0.68 to 0.73, and 20 ° If <γ <40 ° (Examples 51 to 53, 60 to 62, 66 to 68), the contrast ratio becomes 50 or more, so that the phase ratio of the colored light is corrected and the contrast ratio is more effectively improved. It turns out that it can be done. Further, the transmittance T _off Is 20% or more, preferably 23% or more, and the contrast ratio is improved to 30 or more, preferably 50 or more, because the color display becomes clearer, so that the STN type liquid crystal display according to the second embodiment is used. It has been found that the device 100 can be suitable for color display.
[0116]
【The invention's effect】
As described in detail above, according to the STN type liquid crystal display device of the first aspect, the retardation Δn of the nematic liquid crystal ₁ * D ₁ Is 835 nm to 865 nm, and the Δn ₁ * D ₁ Of the retardation plate with respect to ₂ * D ₂ Is 0.67 to 0.73, the angle of the angle formed by the absorption axis of the front polarizer with respect to the reference line is 0 ° <α <25 °, and the absorption of the back polarizer is The angle formed by the axes is 60 ° <β <85 °, the angle formed by the optical axis of the phase difference plate is 45 ° <γ <70 °, and the absorption axis of the table polarizer is opposed to the table polarizer. Since the angle of the intersection angle of the electrode substrate with the rubbing axis is set to 30 ° <δ <55 °, it is possible to use a nematic liquid crystal and a retardation plate, which have become mainstream in recent years, and to obtain a sufficient phase of the colored light. Correction can be performed. Further, the contrast ratio can be 10 or more.
[0117]
According to the STN type liquid crystal display device of the second aspect, the angles are respectively set at 5 ° <α <15 °, 70 ° <β <85 °, 45 ° <γ <55 °, and 35 ° <δ <45 °. Therefore, the contrast ratio can be set to 15 or more.
[0118]
According to the STN type liquid crystal display device of the third aspect, the angles are respectively set to 10 ° <α <20 °, 65 ° <β <75 °, 50 ° <γ <60 °, and 40 ° <δ <50 °. Therefore, the contrast ratio can be set to 15 or more.
[0119]
According to the STN type liquid crystal display device of the fourth aspect, the angles are respectively set to 10 ° <α <25 °, 70 ° <β <85 °, 45 ° <γ <70 °, and 40 ° <δ <55 °. Therefore, the contrast ratio can be set to 15 or more.
[0120]
According to the STN type liquid crystal display device of the fifth aspect, since 15 ° <α <25 °, 75 ° <β <85 °, 50 ° <γ <65 °, and 45 ° <δ <55 °, the contrast is improved. The ratio can be 20 or more.
[0121]
As described above in detail, according to the STN type liquid crystal display device of the sixth aspect, the Δn of the nematic liquid crystal ₁ * D ₁ Is 835 nm to 865 nm, and the Δn ₁ * D ₁ Of the retardation plate with respect to ₂ * D ₂ In the STN type liquid crystal display device having a ratio of 0.67 to 0.73, the angle formed by the absorption axis of the front polarizing plate with respect to the reference line is 10 ° <α <20 °, and the absorption of the back polarizing plate is The angle between the axes is 70 ° <β <80 °, the angle between the optical axes of the phase difference plates is 15 ° <γ <50 °, and the absorption axis of the table polarizer is opposed to the table polarizer. Since the angle of the crossing angle of the electrode substrate with the rubbing axis is set to 40 ° <δ <50 °, nematic liquid crystals and retardation plates, which have become mainstream in recent years, can be used and the contrast ratio can be reduced. Can be improved to 30 or more.
[0122]
According to the STN type liquid crystal display device of the seventh aspect, the retardation ratio is 0.68 to 0.73, and the angle formed by the optical axis of the retardation plate is set to 20 ° <γ <40 °. Therefore, the contrast ratio can be set to 50 or more.
[0123]
According to the STN-type liquid crystal display device of the present invention, since the backlight is provided on the back polarizing plate side, the STN-type liquid crystal display device is of a transmission type, and can provide luminance according to the backlight.
[0124]
According to the STN type liquid crystal display device of the ninth aspect, since the backlight is laminated on the back polarizing plate side, it is possible to perform display with bright transmitted light.
[0125]
According to the STN type liquid crystal display device of the tenth aspect, since the irradiation light of the backlight is white, the color purity of the display can be improved.
[0126]
According to the STN-type liquid crystal display device of the eleventh aspect, since the three primary color filters interposed between the backlight and the front polarizer are provided, the display can be colored.
[0127]
According to the STN type liquid crystal display device of the twelfth aspect, since the light reflecting plate is provided on the back polarizing plate side, the STN type liquid crystal display device is of a reflective type, and is smaller than a transmissive type having a backlight. be able to.
[0128]
According to the STN type liquid crystal display device of the thirteenth aspect, since the light reflecting plate is laminated on the back polarizing plate side, it is possible to perform display with bright reflected light.
[0129]
According to the STN type liquid crystal display device of the present invention, since the light reflecting plate reflects visible light, it can be suitable for two-color display.
[0130]
According to the STN type liquid crystal display device of the present invention, since the retardation plate is made of a uniaxially stretched polymer film, it can be easily obtained.
[0131]
According to the STN type liquid crystal display device of the sixteenth aspect, since the predetermined twist angle θ is 220 to 250 °, a sufficient viewing angle can be secured.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an STN type liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a relative relationship between directions of rubbing axes, directions of optical axes, directions of absorption axes, and the like in the STN type liquid crystal display device 100 of FIG.
FIGS. 3A to 3D are diagrams showing the relationship between α, β, γ, and δ in FIG. 2 and the contrast ratio when the retardation ratio is 0.68 to 0.71. .
FIG. 4 is an XYZ color system chromaticity diagram showing transmitted colors of visible light of the STN type liquid crystal display device 100 of FIG.
FIG. 5 is a configuration diagram of an STN type liquid crystal display device 100 according to a third embodiment of the present invention.
FIG. 6 is a diagram showing measurement results in a second example of the present invention.
[Explanation of symbols]
10 Nematic liquid crystal
20 Front electrode substrate
30 Back electrode substrate
40 liquid crystal cell
50 Front polarizing plate
60 Back polarizing plate
70 retardation plate
80 Backlight
90 Light reflector
100 STN type liquid crystal display

Claims (16)

A nematic liquid crystal having a predetermined twist angle θ and a predetermined birefringence Δn _1, and a liquid crystal cell including two electrode substrates each sandwiching the nematic liquid crystal in a gap having a thickness d ₁ and each having a rubbing axis in a predetermined direction. A front polarizing plate and a back polarizing plate that face each of the electrode substrates and have an absorption axis in a predetermined direction outside the liquid crystal cell; and any one of the two electrode substrates outside the two electrode substrates. A retardation plate facing one side and having a predetermined retardation Δn ₂ * d ₂ and an optical axis in a predetermined direction;
STN in which the retardation Δn ₁ * d _{1 of the} nematic liquid crystal is 835 nm to 865 nm, and the ratio of the retardation Δn ₂ * d ₂ of the retardation plate to the retardation Δn ₁ * d ₁ is 0.67 to 0.73. Type liquid crystal display device,
The angle of the angle formed by the absorption axis of the front polarizing plate is α with respect to a reference line which is a line segment equally dividing the crossing angle on the narrow angle side among the crossing angles formed by the rubbing axes, and the absorption of the back polarizing plate is The angle of the angle formed by the axes is β, and the angle of the angle formed by the optical axes of the phase difference plates is γ, and the intersection angle between the absorption axis of the front polarizing plate and the rubbing axis of the electrode substrate facing the front polarizing plate. Where δ is the angle of
0 ° <α <25 °
60 ° <β <85 °
45 ° <γ <70 °
30 ° <δ <55 °
An STN type liquid crystal display device, characterized in that: Each of the angles is 5 ° <α <15 °
70 ° <β <85 °
45 ° <γ <55 °
35 ° <δ <45 °
2. The STN type liquid crystal display device according to claim 1, wherein: Each of the angles is 10 ° <α <20 °
65 ° <β <75 °
50 ° <γ <60 °
40 ° <δ <50 °
2. The STN type liquid crystal display device according to claim 1, wherein: Each of the angles is 10 ° <α <25 °
70 ° <β <85 °
45 ° <γ <70 °
40 ° <δ <55 °
2. The STN type liquid crystal display device according to claim 1, wherein: The angles are 15 ° <α <25 °, respectively.
75 ° <β <85 °
50 ° <γ <65 °
45 ° <δ <55 °
5. The STN type liquid crystal display device according to claim 4, wherein: A nematic liquid crystal having a predetermined twist angle θ and a predetermined birefringence Δn _1, and a liquid crystal cell including two electrode substrates each sandwiching the nematic liquid crystal in a gap having a thickness d ₁ and each having a rubbing axis in a predetermined direction. A front polarizing plate and a back polarizing plate that face each of the electrode substrates and have an absorption axis in a predetermined direction outside the liquid crystal cell; and any one of the two electrode substrates outside the two electrode substrates. A retardation plate facing one side and having a predetermined retardation Δn ₂ * d ₂ and an optical axis in a predetermined direction;
STN in which the retardation Δn ₁ * d _{1 of the} nematic liquid crystal is 835 nm to 865 nm, and the ratio of the retardation Δn ₂ * d ₂ of the retardation plate to the retardation Δn ₁ * d ₁ is 0.67 to 0.73. Type liquid crystal display device,
The angle of the angle formed by the absorption axis of the front polarizing plate is α with respect to a reference line which is a line segment equally dividing the crossing angle on the narrow angle side among the crossing angles formed by the rubbing axes, and the absorption of the back polarizing plate is The angle of the angle formed by the axes is β, and the angle of the angle formed by the optical axes of the phase difference plates is γ, and the intersection angle between the absorption axis of the front polarizing plate and the rubbing axis of the electrode substrate facing the front polarizing plate. Where δ is the angle of
10 ° <α <20 °
70 ° <β <80 °
15 ° <γ <50 °
40 ° <δ <50 °
An STN type liquid crystal display device, characterized in that: The ratio is 0.68 to 0.73, the angle of the optical axis of the phase difference plate,
20 ° <γ <40 °
7. The STN type liquid crystal display device according to claim 6, wherein: The STN type liquid crystal display device according to claim 1, further comprising a backlight on the back polarizing plate side. 9. The STN type liquid crystal display device according to claim 8, wherein the backlight is laminated on the back polarizing plate side. 10. The STN type liquid crystal display device according to claim 8, wherein the irradiation light of the backlight is white. The STN type liquid crystal display device according to any one of claims 8 to 10, further comprising a color filter of three primary colors interposed between the backlight and the front polarizing plate. The STN type liquid crystal display device according to any one of claims 1 to 7, further comprising a light reflection plate on the back polarizing plate side. The STN type liquid crystal display device according to claim 12, wherein the light reflection plate is laminated on the back polarizing plate side. 14. The STN type liquid crystal display device according to claim 12, wherein the light reflecting plate reflects visible light. 15. The STN type liquid crystal display device according to claim 1, wherein the retardation plate is made of a polymer uniaxially stretched film. The STN type liquid crystal display device according to any one of claims 1 to 15, wherein the predetermined twist angle θ is 220 to 250 °.

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