JP4201942B2 - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device having excellent visual angle characteristics in which the driving voltage of the liquid crystal can be decreased and the responding speed can be improved. SOLUTION: The device has a pair of substrates 12, 14, liquid crystal 16, a plurality of stripe electrodes 22a, 22b for every one pixel and an alignment film 24 formed on one substrate 14, a transparent electrode 18 and an alignment film 20 formed all over the other substrate 14, and a dielectric layer 36 formed between the transparent electrode and the alignment film on the other substrate. The surface of the dielectric layer is formed into a curved face in such a manner that the normal line vector at a certain point of the surface is more nearly parallel to the electric line of force penetrating that point of the surface of the dielectric layer than for a dielectric layer having a flat face.

Description

カラーフィルタ基板の製造に際して、ガラス基板１２の上にＣｒ薄膜を形成し、これをエッチングすることによりブラックマトリクスとする（図示せず）。従来のカラーフィルタ基板では、この上にカラーフィルタ層を形成するが、本発明では、この段階で、ＩＴＯなどの透明電極１８をスパッタリング法により形成する。カラーフィルタ層３８はＲＧＢ毎にフォトリソプロセスにて透明電極１８上に形成する。膜厚は凡そ２．０μｍとする。カラーフィルタ層３８の比誘電率は４に近いものである。次にカラーフィルタ層３８上に透明樹脂層３６ｘを設ける。この場合、透明電極樹脂層３６ｘは、ＴＦＴ基板側のトランスファー電極（図示せず）と、カラーフィルタ基板側の透明電極１８とを接続するためにスルーホールを形成するため、パターニング可能であることが望ましい。ここでは、ε＝３．３の比誘電率をもつポジ型レジストの透明樹脂を、ＲＧＢのカラーフィルタ層の上に、凡そ膜厚０．２μｍで形成する。透明樹脂塗布後、マスクを介して、スルーホールを形成したい部分に紫外線を照射し、現像液（例えばＴＭＡＨ水溶液）で現像を行う。
【００７３】
透明樹脂は、通常の透明レジスト（例えばシプレイＳ１８０８等）を形成した後に、フォトブリーチング工程により、色抜きを行って使用してもよい。次に、透明樹脂上に垂直配向膜を塗布する。
一方のＴＦＴ基板には、ゲートバスライン、データバスライン、及びＴＦＴを含むアクティブマトリクスと、第１及び第２のストライプ状の電極２２ａ、２２ｂと、垂直配向膜とを形成する。
【００７４】
このようにして形成された液晶パネルは、カラーフィルタ層３８と透明樹脂層３６ｘを合わせたｄ／εの値が約０．６となり、図３３におけるピークに近い状態になり、輝度向上の効果がある。また、この条件での面焼きつきもなく、高い電圧保持率を維持することができる。
図３５はさらに他の実施例を説明する図である。この実施例においては、カラーフィルタ基板１２は透明電極１８と配向膜２０との間に誘電体層３６ｙを有する。誘電体層３６ｙは、光学的に異方性を有するものである。つまり、図９の構成においては、誘電体層３６（図９には示されず）とは別に位相差フィルム４２が設けられているが、図３５の構成においては、誘電体層３６ｙは誘電体層３６としての機能と位相差フィルム４２の機能とを合わせもつものである。従って、位相差フィルム４２に関しての上記説明は誘電体層３６ｙにもあてはまる。式（１）〜（５）及び図１０〜１３も誘電体層３６ｙに適用される。ここでは、繰り返しの説明はしない。
【００７５】
誘電体層３６ｙは、光重合基を導入した高分子液晶やディスコティック液晶などで形成されることができる。図３６は、誘電体層３６ｙとして使用可能なディスコティック液晶の例を示す図である。例えば、誘電体層３６ｙの形成において、ガラス基板１２上に透明電極１８を形成し、透明電極１８上に誘電体層を配向させるための配向層（例えばＪＳＲ製のＡＬ３０４６）を形成する。この配向層の上に溶剤と混合したディスコティック液晶を塗布し、ホットプレート上で溶剤を揮発させた後、紫外線を照射して硬化させ、誘電体層３６ｙを形成する。加熱によって硬化させてもよい。さらに、誘電体層３６ｙの上に垂直配向膜２０を形成する。この実施例によれば、視角特性に優れた液晶表示装置を簡単に製造することができる。
【００７６】
比誘電率εと膜厚ｄとの間には、０．５＜ｄ／ε＜０．９の関係がある。
透明樹脂層の厚さはカラーフィルタ層の厚さよりも薄い。
配向層の上に主誘電体層を塗布して配向させ、光照射又は加熱により硬化させてある。
【００７７】
【発明の効果】
以上説明したように、本発明によれば、液晶の駆動電圧を低下でき、液晶分子の応答速度を向上させることができる。
【図面の簡単な説明】
【図１】電圧無印加時の本発明の液晶表示装置の基本形態を示す断面図である。
【図２】電圧印加時の図１の液晶表示装置を示す断面図である。
【図３】一方の基板に形成されるアクティブマトリクスの一部を示す平面図である。
【図４】図１の偏光子の吸収軸の関係を示す図である。
【図５】誘電体層がない場合の電界の形成を示す図である。
【図６】誘電体層がある場合の電界の形成を示す図である。
【図７】ストライプ状の電極を覆う絶縁体層を含む例を示す図である。
【図８】絶縁体層に開口部を設けた例を示す図である。
【図９】位相差フィルムを含む例を示す図である。
【図１０】位相差フィルムのない液晶表示装置の視角特性を示す図である。
【図１１】位相差フィルムのある液晶表示装置の視角特性を示す図である。
【図１２】Ｒ_XZ−Ｒ_YZ座標上でコントラストが１０となる等視角曲線を示す図である。
【図１３】Ｒ_LC−Ｒ_t の関係を示す図である。
【図１４】図３の変形例として一方の基板に形成されるアクティブマトリクスの一部を示す図である。
【図１５】図１４の第１のストライプ状の電極を示す平面図である。
【図１６】図１４の第２のストライプ状の電極を示す平面図である。
【図１７】図１と類似した液晶表示装置を示す断面図である。
【図１８】図２と類似した液晶表示装置を示す図である。
【図１９】図１７及び図１８の液晶表示装置の誘電体層の表面の近傍の部分を示す図である。
【図２０】図２１及び図２２の液晶表示装置の誘電体層の表面の近傍の部分を示す図である。
【図２１】電圧無印加時の本発明の一実施例の液晶表示装置を示す図である。
【図２２】電圧印加時の図２１の液晶表示装置を示す図である。
【図２３】図２１の液晶表示装置の変形例を示す図である。
【図２４】ゲートバスラインと第１のストライプ状の電極との間に生じる電界により液晶の配向が乱されることを説明するための液晶表示装置を示す図である。
【図２５】図２１の液晶表示装置の変形例を示す図である。
【図２６】図２１の液晶表示装置の変形例を示す図である。
【図２７】他の実施例の一方の基板に形成されるアクティブマトリクスの一部を示す平面図である。
【図２８】図２７のストライプ状の電極を有する基板を示す断面図である。
【図２９】図２８の基板の変形例を示す図である。
【図３０】本発明の他の実施例の液晶表示装置を示す図である。
【図３１】図３１の液晶表示装置の変形例を示す図である。
【図３２】図３１の液晶表示装置の変形例を示す図である。
【図３３】ｄ／εと透過率との関係を示す図である。
【図３４】カラーフィルタ層の厚さが２μｍのときの、誘電体層の透明樹脂層の厚さと画面の焼きつきとの関係を示す図である。
【図３５】本発明の他の実施例の液晶表示装置を示す図である。
【図３６】図３５の誘電体層として使用可能なディスコティック液晶を示す図である。
【符号の説明】
１２…基板
１４…基板
１６…液晶層
１８…透明電極
２０…配向膜
２２ａ、２２ｂ…ストライプ状の電極
２４…配向膜
３６…誘電体層
３６ｘ…透明樹脂層
３６ｙ…誘電体層
３８…カラーフィルタ
５０…絶縁体層
５０ｈ…開口部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device including a plurality of striped electrodes.
[0002]
[Prior art]
The TN type liquid crystal display device is widely used as a display device of a personal computer, for example. However, the TN liquid crystal display device has a problem that the contrast is lowered when the screen is viewed in an oblique direction, or the brightness of the display is reversed. Accordingly, there is a need for a liquid crystal display device in which contrast does not decrease in the oblique viewing angle direction.
[0003]
Therefore, a liquid crystal display device that drives liquid crystal by a lateral electric field has been proposed. In this liquid crystal display device, a liquid crystal is sandwiched between a pair of substrates, and one substrate has a first electrode and a second electrode arranged in a comb-teeth shape. A voltage is applied between the electrodes. The other substrate does not have electrodes. A lateral electric field is formed between the first electrode and the second electrode in a direction substantially parallel to the substrate surface, and the liquid crystal is driven by this lateral electric field. In this liquid crystal display device, the contrast does not decrease in the oblique viewing angle direction.
[0004]
Furthermore, a liquid crystal display device that drives liquid crystal by an oblique electric field has been proposed. This liquid crystal display device includes a pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of striped electrodes formed on one substrate, and a transparent formed entirely on the other substrate. And an electrode. In this liquid crystal display device, an oblique electric field is formed which runs in an oblique direction from a striped electrode toward a solid transparent electrode. In this liquid crystal display device, contrast does not decrease in the oblique viewing angle direction, and disclination does not occur.
[0005]
[Problems to be solved by the invention]
The liquid crystal display device that drives the liquid crystal by the oblique electric field preferably uses a liquid crystal having a large Δε in order to obtain sufficient white luminance. However, the liquid crystal having a large Δε has problems such as high viscosity and slow response speed, low specific resistance, and low voltage holding ratio. Therefore, it is required to further reduce the driving voltage of the liquid crystal and improve the response speed.
[0006]
An object of the present invention is to provide a liquid crystal display device that has excellent viewing angle characteristics, can reduce the driving voltage of liquid crystal, and can improve response speed.
[0007]
[Means for Solving the Problems]
A liquid crystal display device according to the present invention includes a pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe-shaped electrodes and alignment films per pixel formed on one substrate, and the other. A transparent electrode and an alignment film formed on the substrate so as to substantially entirely cover the other substrate; and a dielectric layer provided on the other substrate between the transparent electrode and the alignment film. The normal vector at a point on the surface of the dielectric layer is more parallel to the electric field lines penetrating the point on the surface of the dielectric layer than when the surface of the dielectric layer is planar. The surface of the dielectric layer is formed in a curved shape. The transparent electrode is commonly opposed to a plurality of pixels on one substrate and covers substantially the entire display area.
[0008]
According to this configuration, the alignment of the liquid crystal molecules when no voltage is applied can be more smoothly shifted to a predetermined alignment when a voltage is applied. Accordingly, the driving voltage of the liquid crystal can be reduced and the response speed can be improved.
Furthermore, according to another aspect, a liquid crystal display device according to the present invention includes a pair of substrates, a liquid crystal sealed between the pair of substrates, and a plurality of stripes per pixel formed on one substrate. Electrodes and an alignment film, a transparent electrode and an alignment film formed on the other substrate so as to cover the other substrate substantially entirely, and the one substrate covering the striped electrode. The insulating layer has an opening on the striped electrode, and the side wall of the opening is tapered.
[0009]
Furthermore, according to another aspect, a liquid crystal display device according to the present invention includes a pair of substrates, a liquid crystal sealed between the pair of substrates, and a plurality of stripes per pixel formed on one substrate. Between the transparent electrode and the alignment film on the other substrate, and the transparent electrode and the alignment film formed on the other substrate so as to cover the other substrate substantially entirely. The dielectric layer is provided, and there is a relationship of 0.5 <d / ε between the relative dielectric constant ε and the film thickness d of the dielectric layer.
[0010]
Furthermore, according to another aspect, a liquid crystal display device according to the present invention includes a pair of substrates, a liquid crystal sealed between the pair of substrates, and a plurality of stripes per pixel formed on one substrate. Between the transparent electrode and the alignment film on the other substrate, and the transparent electrode and the alignment film formed on the other substrate so as to cover the other substrate substantially entirely. Provided with a dielectric layer, and the dielectric layer is composed of a color filter layer and a transparent resin layer, and is overlapped in this order from the transparent electrode.
[0011]
Furthermore, according to another aspect, a liquid crystal display device according to the present invention includes a pair of substrates, a liquid crystal sealed between the pair of substrates, and a plurality of stripes per pixel formed on one substrate. Between the transparent electrode and the alignment film on the other substrate, and the transparent electrode and the alignment film formed on the other substrate so as to cover the other substrate substantially entirely. The dielectric layer is provided, and the dielectric layer has optical anisotropy.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
1 to 16 are views showing a basic form of the liquid crystal display device of the present invention.
1 is a cross-sectional view showing the liquid crystal display device 10 when no voltage is applied, and FIG. 2 is a cross-sectional view showing the liquid crystal display device 10 shown in FIG. The liquid crystal display device 10 includes first and second opposing transparent glass substrates 12 and 14, a liquid crystal layer 16 sealed between the first and second substrates 12 and 14, and polarizers 26 and 28. Prepare.
[0013]
The first substrate 12 includes a solid transparent electrode 18 and a vertical alignment film 20 that are formed so as to cover substantially the entire surface of the first substrate 12. The second substrate 14 includes a plurality of first and second groups of striped electrodes 22 a and 22 b and a vertical alignment film 24 that extend alternately and parallel to each other. Different voltages are applied to the striped electrodes 22a, 22b of the first and second groups. In the embodiment, the first group of striped electrodes 22a is applied with an AC data voltage (for example, ± 5V), and the second group of striped electrodes 22b is applied with the same voltage as the solid transparent electrode 18. Is done. In this case, the solid transparent electrode 18 is applied with a voltage (ground) substantially in the middle of the AC data voltage.
[0014]
FIG. 3 shows a part of the active matrix formed on the second substrate 14. The active matrix has a gate bus line 30, a data bus line 32, and a TFT 34. A region surrounded by the gate bus line 30 and the data bus line 32 corresponds to one pixel. The first group of striped electrodes 22 a is connected to the TFT 34 and receives the AC data voltage of the data bus line 32. The second group of striped electrodes 22 b is connected to a common bus line 40 parallel to the gate bus line 30. The solid transparent electrode 18 is made of a substantially transparent material such as ITO or NESA, but the striped electrodes 22a and 22b are made of the same metal as the gate bus line 30 or the data bus line 32.
[0015]
FIG. 4 shows the relationship between the absorption axes 26 a and 28 a of the polarizers 26 and 28. The absorption shafts 26a and 28a are arranged in a crossed Nicols relationship, that is, orthogonal to each other. The absorption axes 26a and 28a are arranged at an angle of 45 degrees with respect to the gate bus line 30, the data bus line 32, and the striped electrode 22 shown in FIG.
[0016]
Further, a dielectric layer (insulator layer) 36 is disposed between the solid transparent electrode 18 and the vertical alignment film 20. The solid transparent electrode 18 is provided on the inner surface of the first substrate 12, and the dielectric layer 36 is provided on the solid transparent electrode 18. Basically, the dielectric layer 36 is provided between the solid transparent electrode 18 and the liquid crystal layer 16. Preferably, the dielectric layer 36 is a photo-curing resin, thermosetting resin, positive or negative resist, polyamic acid, other organic resin (eg, epoxy resin, acrylic resin, fluororesin, etc.), SiO, SiO₂, Consisting of one of the SiN groups.
[0017]
In this configuration, as shown in FIG. 1, when no voltage is applied, the liquid crystal molecules are aligned substantially perpendicular to the substrate surface. As shown in FIG. 2, when a voltage is applied, an electric field (lines of electric force) from each of the first group of striped electrodes 22a toward the solid transparent electrode 18 is formed. Many electric fields (field lines) are indicated by arrows F_OAs shown in FIG. 1, the first electrode 20a runs diagonally from each of the first group of striped electrodes 22a toward the solid transparent electrode 18. Accordingly, the liquid crystal molecules having positive dielectric anisotropy can be applied to the oblique electric field F when a voltage is applied._OOriented parallel to
[0018]
Further, a lateral electric field F is generated from each of the first group of striped electrodes 22a toward each of the second group of striped electrodes 22b._TIs formed. This transverse electric field F_TIs an oblique electric field F directed from each stripe-shaped electrode 22a of the first group to the solid transparent electrode 18._OIt acts to help the formation of. That is, the oblique electric field F_ODecreases rapidly as the lateral distance from the first stripe-shaped electrode 22a increases, but with the help of the lateral electric field, the oblique electric field F_ODoes not become so weak as the distance from the striped electrode 22a increases.
[0019]
Liquid crystal molecules have an oblique electric field F_OIn parallel to the substrate surface and tilted in an oblique direction with respect to the substrate surface, birefringence occurs, and the polarization state of incident light is changed. Therefore, most liquid crystal molecules are smoothly aligned along an oblique electric field, and a display without disclination can be realized.
When the dielectric layer 36 is provided between the solid transparent electrode 18 and the liquid crystal layer 16, the oblique electric field F_OCan be further helped to achieve a good display. The effect of the dielectric layer 36 will be described with reference to FIGS.
[0020]
5 and 6 are diagrams for explaining the operation of the dielectric layer 36. FIG. FIG. 5 is a diagram showing the formation of an electric field when there is no dielectric layer 36, and FIG. 6 is a diagram showing the formation of an electric field when there is a dielectric layer 36. 5 and 6 show equipotential lines formed around the first striped electrode 22a. In FIG. 5, the electric field is too concentrated in the vicinity of each of the first group of striped electrodes 22 a, and the equipotential lines remain in the liquid crystal layer 16. Therefore, the action of the electric field in the normal direction of the transparent electrode 18 is strong in the liquid crystal layer 16, and the oblique electric field has a strong component in the normal direction and is not sufficiently inclined. Accordingly, the liquid crystal does not exhibit sufficient birefringence.
[0021]
In FIG. 6, equipotential lines extend from the liquid crystal layer 16 to the dielectric layer 36 to alleviate the concentration of the electric field in the liquid crystal layer 16. Therefore, the action of the electric field in the normal direction of the transparent electrode 18 is weakened in the liquid crystal layer 16. Therefore, the oblique electric field has a weak component in the normal direction and is sufficiently oblique. Accordingly, the liquid crystal molecules are sufficiently tilted sideways.
[0022]
FIG. 7 is a diagram showing an example in which insulator layers 50a and 50b are provided to cover the first and second striped electrodes 22a and 22b. In this example, the insulator layer 50a covers the second group of striped electrodes 22b, and the first group of striped electrodes 22a is formed on the insulator layer 50a. Covered. The alignment film 24 is provided on the insulator layer 50b. The insulator layers 50a and 50b in FIG. 7 can be provided during the TFT forming process by using, for example, SiN.
[0023]
In the liquid crystal display device without the insulator layers 50a and 50b, if a DC voltage component is applied between the stripe electrode 22a of the first group and the stripe electrode 22b of the second group, the screen burns. May occur. However, in the liquid crystal display device of FIG. 7, by providing the insulator layers 50a and 50b, it is possible to prevent image burn-in caused by a DC voltage component.
[0024]
However, when the insulator layers 50a and 50b cover the first and second striped electrodes 22a and 22b, the driving voltage of the liquid crystal becomes high.
In FIG. 8, after the insulator layers 50a and 50b are provided, some of the insulator layers 50a and 50b are locally removed. That is, the insulating layer 50b on and around the first group of striped electrodes 22a is removed by dry etching. Accordingly, the oblique electric field formed between the first group of stripe-shaped electrodes 22a and the entire transparent electrode 18 is not obstructed by the insulator layer 50, and the liquid crystal driving voltage is prevented from being lowered. Can do.
[0025]
After providing the insulator layer 50, a portion of the insulator layer 50 around the first group of stripe electrodes 22a and a portion of the insulator layer 50 around the second group of stripe electrodes 22b are formed. It is also effective to remove both.
FIG. 9 is a diagram showing the liquid crystal display device 10 to which at least one retardation film 42 is added. The at least one retardation film 42 can be provided at any position between the pair of polarizers 26 and 28.
[0026]
The retardation film 42 in this example is the main refractive index n of the retardation film 42._x, N_y, N_zOf these, the refractive index in the film surface direction is n_x, N_y(The refractive index in the direction perpendicular to the absorption axis of the adjacent polarizer is n_x, The refractive index in the parallel direction is n_y), The refractive index in the film normal direction is n_zWhen
n_x≧ n_z, N_y≧ n_z(However, n_x= N_y= N_z(Excluding) (1)
It is assumed that the relationship is established. Refractive index n_x, N_yFor example n_x> N_yWhen this relationship holds, the x direction is called the slow axis. Here, when the thickness of the retardation film 42 is d, R_xZ= (N_x-N_zD, R_YZ= (N_Y-N_z) D.
[0027]
FIG. 10 is a diagram showing viewing angle characteristics of a liquid crystal display device without the retardation film 42. A curve 46 is an isocontrast curve that gives a contrast of 10 when the liquid crystal panel is viewed in all directions. From the isocontrast curve 46, it can be seen that a good contrast can be obtained with a wider viewing angle than the viewing angle characteristic of the TN liquid crystal display device. In the isocontrast curve 46, the viewing angle at which the contrast becomes 10 in the directions of 45 degrees, 135 degrees, 225 degrees, and 315 degrees is 38 degrees.
[0028]
FIG. 11 is a diagram showing viewing angle characteristics of the liquid crystal display device of FIG. A curve 48 is an isocontrast curve that gives a contrast of 10 when the liquid crystal panel is viewed in all directions. In the isocontrast curve 48, the viewing angle at which the contrast is 10 in the directions of 45 degrees, 135 degrees, 225 degrees, and 315 degrees is about 70 degrees. Therefore, good viewing angle characteristics can be obtained by inserting the retardation film 42.
[0029]
First, in the configuration of FIG. 9, one retardation film 42 is inserted, and R_xZ, R_YZThe viewing angle characteristics were investigated with various changes. R_xZ, R_YZWas changed to obtain a viewing angle at which the contrast was 10 in a 45-degree azimuth.
FIG. 12 is a diagram showing an isometric angle curve with a contrast of 10. FIG. Curves with viewing angles of 70, 60, 50, and 40 degrees are R_xZ-R_YZPlotted in coordinates. In the liquid crystal display device having the striped electrodes 22a and 22b in FIG. 23, the viewing angle characteristics in the four directions are the same, and the same result can be obtained even in the orientations of 135 degrees, 225 degrees, and 315 degrees.
[0030]
As described above, in FIG. 10, the viewing angle at which the contrast is 10 in the azimuth of 45 degrees is 38 degrees. Accordingly, in the range where the viewing angle at which the contrast is 10 in FIG. 12 is 38 degrees or more, the effect of adding the retardation film 42 is obtained.
In FIG. 12, the viewing angle at which the contrast is 10 is 38 degrees or more._xZ, R_YZWhen the following conditions are satisfied.
[0031]
R_YZ≧ R_xZ-230nm
R_YZ≦ R_xZ+130 nm
R_YZ≤ -R_xZ+ 1060nm
When these conditions are rewritten, it becomes as follows.
−130 nm ≦ (n_x-N_y) D ≦ 230nm
((N_x+ N_y) / 2-n_z) D ≦ 530nm
Where R = (n_x-N_yD, R_t= ((N_x+ N_y) / 2-n_z) If d, the conditions that the retardation film 42 should satisfy are:
−130 nm ≦ R ≦ 230 nm (2)
R_t≦ 530nm
become.
[0032]
Δnd of liquid crystal panel_LC(D_LCIs changed by changing the thickness of the liquid crystal layer)._tAs a result of obtaining the optimum condition of R, the optimum condition of R is Δnd of the liquid crystal panel._LCAlways,
−130 nm ≦ R ≦ 230 nm (2)
It turns out that.
On the other hand, R_tIs the optimal condition for liquid crystal panel Δnd_LCDepends on. Δnd_LCAnd R_tWhen the relationship with the upper limit of the optimum condition was examined, the relationship shown in FIG. 13 was obtained. Δnd of liquid crystal panel_LC= R_LCThen R_tThe upper limit of the optimum condition is 1.6 x R_LCThere is a relationship. Therefore, R_tShould be in a range below this upper limit. That is,
R_t≦ 1.6 × R_LC
It is.
[0033]
The above is a consideration when one retardation film 42 is inserted between the pair of polarizers 26 and 28. This consideration is also extended when a plurality of retardation films are inserted between the pair of polarizers 26 and 28. For example, when the polarizers 26 and 28 have a structure in which a PVC film and a TAC film are laminated, the inner TAC film functions as a retardation film defined by the formula (1) of the present application. Therefore, when the retardation film and the retardation film 42 are added, three retardation films are inserted between the pair of polarizers 26 and 28.
[0034]
Therefore, the case where N retardation films were inserted between the pair of polarizers 26 and 28 was examined in the same manner as described above. R of R retardation films is R₁, R₂・ ・ ・ ・ ・ ・ R_NAnd R_tR_t1, R_t2・ ・ ・ ・ ・ ・ R_tNThen, it turned out that the optimal condition is when the following relations are satisfied simultaneously.
−130 nm ≦ R₁≦ 230nm (2)
...
−130 nm ≦ R_N≦ 230nm
R_t1+ R_t2+ ... R_tN≦ 1.6 × R_LC              (3)
The above is the condition for the viewing angle at which the contrast is 10 to be 38 degrees or more. When this was further expanded and the conditions under which the viewing angle at which the contrast becomes 10 were 50 degrees or more were examined, it was found that the following relationship was satisfied simultaneously.
[0035]
n_x≧ n_z, N_y≧ n_z(However, n_x= N_y= N_z(Excluding) (1)
−50 nm ≦ R₁≦ 150nm (4)
...
−50 nm ≦ R_N≦ 150nm
R_t1+ R_t2+ ... R_tN≦ 1.3 × R_LC              (5)
FIG. 11 shows a structure including three retardation films, Δnd_LC= R_LC= 330 nm, R = (n_x-N_yD = 50 nm, R_tShows an iso-contrast curve when = 200 nm. The retardation film 42 is a Japanese synthetic rubber ARTON film (R = 50 nm, R_t= 200 nm), and the slow axis was arranged to be orthogonal to the absorption axis of the adjacent polarizer.
[0036]
FIG. 14 is a plan view showing a modification (for one pixel) of the electrode of FIG. FIG. 15 is a plan view showing the first striped electrode 22a of FIG. FIG. 16 is a plan view showing the second striped electrode 22b of FIG. This pixel feature can be applied to other embodiments. As shown in FIG. 7, the first stripe-shaped electrode 22a and the second stripe-shaped electrode 22b are overlapped with each other through the insulator layer 50a.
[0037]
In the liquid crystal display device 10 of FIG. 14, one substrate 14 has an active matrix including gate bus lines 30, data bus lines 32, and TFTs 34. Furthermore, there is a common bus line 40. In a substantially rectangular pixel 52 surrounded by the gate bus line 30 and the data bus line 32, first and second groups of striped electrodes 22a and 22b are provided. The striped electrodes 22a of the first group are connected to the TFTs 34 by the first connection electrodes 22c. The striped electrodes 22b of the second group are connected to the common bus line 40 by the second connection electrodes 22d.
[0038]
14 and 15, the plurality of striped electrodes 22a of the first group are parallel to each other in the first sub-group straight line portion (element above the horizontal center line in FIGS. 14 and 15). , And a second sub-group linear portion parallel to each other and angled with respect to the first sub-group linear portion (element below the horizontal center line in FIGS. 14 and 15). All straight portions are at an angle of 2 ° to 88 ° with respect to the data bus line 32. Preferably, all straight portions are at an angle of 45 degrees with respect to the data bus line 32.
[0039]
The straight portion of the first subgroup and the straight portion of the second subgroup are arranged so as to form 90 degrees with each other. That is, the striped electrodes 22a of the first group have right-angled bent portions. The straight portion of the first subgroup is arranged symmetrically with the straight portion of the second subgroup with respect to the horizontal center line of FIGS. The straight portion of the first subgroup can also be arranged point-symmetrically with the straight portion of the second subgroup. Some of the straight portions of the first and second subgroups extend straight without bending from one long side of the generally rectangular pixel to the opposite long side.
[0040]
14 and 16, a plurality of striped electrodes 22b of the second group are formed by straight portions of the third subgroup parallel to each other (elements above the horizontal center line in FIGS. 14 and 16). , Including a straight portion of the fourth subgroup parallel to each other and angled with respect to the straight portion of the third subgroup (elements below the horizontal center line of FIGS. 14 and 16). The straight portion of the third subgroup and the straight portion of the fourth subgroup are arranged so as to form 90 degrees with each other. The straight portion of the third subgroup is arranged symmetrically with the straight portion of the fourth subgroup with respect to the horizontal center line of FIGS. Some of the straight portions of the third and fourth subgroups extend straight without bending from one long side of the generally rectangular pixel to the opposite long side.
[0041]
In one pixel, the first connection electrode 22c is provided in the peripheral portion of the pixel 52 (a region slightly inward of the gate bus line 30 and the data bus line 32 defining the pixel 52), and the stripe of the first group. The electrodes 22a are connected together, and a second connection electrode 22d is provided at the periphery of the pixel 52 to connect the striped electrodes 22b of the second group together. The first connection electrode 22c overlaps at least partially with the second connection electrode 22d via the insulator layer 50a.
[0042]
As shown in FIG. 14, the width of the second connection electrode 22d is larger than the width of the first connection electrode 22c, and the first connection electrode 22c is placed on the inner edge of the second connection electrode 22d. The first connection electrode 22c is located at a distance from the gate bus line 30 and the data bus line 32 in order to prevent the short circuit.
The first connection electrode 22c includes connection electrode portions 22cp and 22cq that connect the ends of the first and second straight portions of the first group of striped electrodes 22a together. The connection electrode portion 22cp extends in parallel with the gate bus line 30 at the periphery of the pixel 52, and connects the ends of the first and second straight line portions. The connection electrode portion 22cq extends in a fragmentary manner in parallel with the data bus line 32 in the peripheral portion of the pixel 52, and at least two straight portions of the first and second straight portions of the stripe-like electrodes 22a of the first group. Connect the end comrades.
[0043]
In particular, the connection electrode portion 22cq is provided in the peripheral portion of the pixel 52 in parallel with the data bus line 32. For example, the connection electrode portion extending in the longitudinal direction at the center of the pixel can be eliminated. The connection electrode portion extending in the longitudinal direction in the center of the pixel considerably lowers the aperture ratio of the pixel. However, by providing the connection electrode portion 22cq in the peripheral portion of the pixel 52, the aperture ratio of the pixel can be improved.
[0044]
By providing the connection electrode portion 22cq in a piecewise manner in parallel with the gate bus line 30, the amount of the connection electrode portion 22cq near the gate bus line 30 is reduced, and the connection electrode portion 22cq and the gate bus line 30 are short-circuited. Reduce the possibility. The first connection electrode 22 c further includes a connection electrode portion 22 cr provided in a fragmentary manner along the horizontal center line of the pixel 52. The connection electrode portion 22cr is not particularly necessary, but the connection electrode portion 22cr prevents the liquid crystal alignment from being disturbed at the bent portions of the first and second striped electrodes 22a and 22b, thereby causing a dispersion. it can.
[0045]
The end of one straight line portion of the first group of striped electrodes 22a (indicated by a in FIG. 15) is located at the corner of the short side of the pixel, and the end of the other straight line portion (shown in FIG. 51). (shown as b) is located at the corner of the other short side of the pixel. A substantially continuous series from a straight portion having end a to most other straight portions and the connection electrode portion 22cq of the first connection electrode to another straight portion having end b. An electrical path is formed. That is, the connection electrode portion 22cq of the first connection electrode is provided only in the minimum portion necessary to achieve electrical connection of the first group of striped electrodes 22a.
[0046]
The second connection electrode 22d extends in parallel with the gate bus line 30 at the periphery of the pixel 52 to connect together the ends of the third and fourth straight portions of the second group of striped electrodes 22b. A connection electrode portion 22dp and a connection electrode portion 22dq extending in parallel with the data bus line 32 in the peripheral portion of the pixel 52 are provided. The second connection electrode 22d further includes a connection electrode portion 22dr that functions as an auxiliary capacitance electrode disposed along the horizontal center line of the pixel. The connection electrode portion 22dr can also prevent the occurrence of disclination due to disorder of the alignment of the liquid crystal at the bent portions of the first and second striped electrodes 22a and 22b. The connection electrode portion 22dr may be omitted. The second connection electrode 22d further has outward projections 22ds for connecting to similar connection electrodes of adjacent pixels at a plurality of points. These outward projections 22ds are a part of the common bus line 40 of FIG. That is, the second connection electrode 22d of one pixel is connected to the second connection electrode of the adjacent pixel by the plurality of common bus lines 40.
[0047]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIGS. 17 and 18 correspond to FIGS. 1 and 2 and show the alignment of liquid crystal molecules in more detail. FIGS. 19A and 19B are views showing a portion in the vicinity of the surface of the dielectric layer 36.
In the liquid crystal display device 10 shown in FIGS. 17 to 19B, the color filter substrate 12 has a transparent electrode 18 and a dielectric layer 36 covering the entire surface, and the TFT substrate 14 has first and second stripe shapes. Electrodes 22a and 22b. The first stripe electrode 22a is connected to the TFT 34 and receives a data voltage. The second striped electrode 22b is connected to the common bus line 40 and receives a common voltage. The surface of the dielectric layer 36 is flat and substantially parallel to the surface of the substrate. Further, the liquid crystal layer 16 has positive dielectric anisotropy, and the vertical alignment films 20 and 24 and the polarizing plates 26 and 28 are disposed. The polarizing plates 26 and 28 are affixed to the outside of both the substrates 12 and 14 so that the transmission axes are orthogonal to each other. The insulator layer is collectively indicated by 50.
[0048]
The liquid crystal molecules are aligned perpendicular to the substrates 12 and 14 when no voltage is applied (FIGS. 17 and 19A), and light does not pass through the liquid crystal panel. When a voltage is applied (FIGS. 18 and 19B), an oblique electric field F in which liquid crystal molecules are formed between the first stripe-shaped electrode 22a and the transparent electrode 18 is applied.₀The light is transmitted through the liquid crystal panel due to the birefringence effect of the liquid crystal 16. That is, if the surface of the dielectric layer 36 is flat, all liquid crystal molecules are aligned perpendicularly to the surface of the dielectric layer 36 as shown in FIG. When a voltage is applied, the liquid crystal molecules are subjected to an oblique electric field F as shown in FIG.₀, And obliquely with respect to the surfaces of the substrates 12 and 14. When the liquid crystal molecules are aligned obliquely with respect to the surfaces of the substrates 12 and 14, the liquid crystal molecules change from the state of FIG. 19A to the state of FIG. 19B because of the alignment regulating force of the vertical alignment film 20. It takes time to migrate. That is, the drive response of the liquid crystal is low and the drive voltage must be increased.
[0049]
FIGS. 20A to 22 are diagrams showing an embodiment of the present invention that solves the problems described with reference to FIGS. 17 to 19B. 20A to 22, the surface of the dielectric layer 36 is formed in a curved surface. The vertical alignment film 20 is also formed in a curved surface like the surface of the dielectric layer 36. The curved surface shape of the surface of the dielectric layer 36 is such that the normal vector at a certain point on the surface of the dielectric layer penetrates the same point on the surface of the dielectric layer 36 than when the surface of the dielectric layer 36 is flat. It is close to parallel to the line. That is, the surface of the dielectric layer 36 is inclined in a direction in which the normal vector of the surface of the dielectric layer 36 approaches parallel to the lines of electric force. FIG. 20A shows the arrangement of liquid crystal molecules when no voltage is applied. The liquid crystal molecules are aligned perpendicularly to the surface of the dielectric layer 36 and are obliquely aligned to the surfaces of the substrates 12 and 14 when no voltage is applied. Thus, by preliminarily tilting the liquid crystal molecules in the vicinity of the dielectric layer 36, when the voltage is applied as shown in FIG. 20B, the entire liquid crystal molecules are easily tilted, and thus the driving voltage of the liquid crystal is reduced. The response speed of liquid crystal molecules becomes high.
[0050]
That is, when the liquid crystal molecules are tilted from the state of FIG. 20A to the state of FIG. 20B, the liquid crystal molecules are tilted from the state of FIG. 19A to the state of FIG. 19B. However, since the amount of change in the alignment of the liquid crystal molecules is small and the influence of the alignment regulating force is small, the driving voltage of the liquid crystal can be lowered and the response speed of the liquid crystal molecules can be improved.
[0051]
Next, in FIG. 21, when the surface portion (for example, 36x) of the dielectric layer 36 corresponding to the gap between the first and second striped electrodes 22a and 22b is inclined, liquid crystal molecules are displayed when no voltage is applied. Is somewhat inclined with respect to the substrate surface, and there is a problem that light leaks and the contrast is lowered.
Therefore, as shown in FIG. 23, only the portions 36a and 36b corresponding to the first and second stripe-shaped electrodes 22a and 22b on the surface of the dielectric layer 36 are curved, and the first and second portions on the surface of the dielectric layer 36 are curved. A portion 36x corresponding to the gap between the second striped electrodes 22a and 22b is made parallel to the substrate surface. By doing so, the liquid crystal molecules positioned in the gap between the striped electrodes that affect the display are aligned vertically when no voltage is applied, and thus the above-described light leakage does not occur.
[0052]
On the other hand, a portion 36b on the surface of the dielectric layer 36 corresponding to the second stripe-shaped electrode 22b that receives the common voltage protrudes in a protruding shape, and the dielectric corresponding to the first stripe-shaped electrode 22a that receives the data voltage. The surface portion 36a of the layer 36 is recessed in a groove shape. Therefore, the portion 36a of the dielectric layer 36 facing the first stripe-shaped electrode 22a is the thinnest, and the portion 36b of the dielectric layer 36 facing the second stripe-shaped electrode 22b is the thickest. Further, both sides of the protruding portion 36b and the groove-like portion 36a are slopes. The width of the protruding portion 36b including the slope portion is the same as or narrower than the width of the second stripe-shaped electrode 22b, and the width of the groove-shaped portion 36a including the slope portion is the first stripe. Is the same as or narrower than the electrode 22a. Therefore, in this case, the region where the surface of the dielectric layer 36 is curved is only on the first and second striped electrodes 22a and 22b.
[0053]
In the case of active matrix driving, a selection voltage is applied to the gate bus line 30 in a pulsed manner, and a voltage of minus several volts is normally applied when no pulsed voltage is applied. Therefore, a large electric field is generated between the gate bus line 30 and the first and second striped electrodes 22a and 22b (the first and second connection electrodes 22c and 22d and the common bus line 40) (FIG. 24). . Therefore, there is a problem that a sufficient distance is taken between the gate bus line 30 and the first and second striped electrodes 22a and 22b, a shielding electrode is required, and the aperture ratio is lowered.
[0054]
FIG. 24 is a diagram for explaining that the alignment of the liquid crystal is disturbed by the electric field generated between the gate bus line 30 and the second stripe electrode 22b. In FIG. 24, regions RA and RB are regions where the alignment of the liquid crystal is disturbed.
FIG. 25 is a diagram showing an example of preventing the alignment of the liquid crystal shown in FIG. 24 by curving the surface of the dielectric layer 36. The surface of the dielectric layer 36 balances the electric field generated between the gate bus line 30 and the second stripe-shaped electrode 22b with the alignment regulating force by the alignment film 20 on the dielectric layer 36. The liquid crystal molecules in the vicinity of the layer 36 (liquid crystal molecules in the region RC) are aligned perpendicular to the substrate. In this case, the thickness of the portion of the dielectric 36 corresponding to the gate bus line 30 is set to L.₁And the thickness of the portion of the dielectric 36 corresponding to the second striped electrode 22b is L₂Then, in region RC, L₁> L₂The surface of the dielectric layer 36 is curved so that
[0055]
Since a substantially constant common voltage is applied to the second striped electrode 22b, the voltage of the gate bus line 30 and the electric field generated by the common voltage may be balanced with the alignment regulating force. As for the first stripe-shaped electrode 22a, since an AC voltage is applied to the first stripe-shaped electrode 22a, it is assumed that a voltage substantially the same as the common voltage, which is an almost intermediate voltage, is applied. Balance the electric field and the orientation regulating force. As a result, the distance between the gate bus line and the striped electrode can be reduced, and the width of the shielding electrode can be reduced, so that the aperture ratio can be improved.
[0056]
FIG. 26 is a diagram showing that a lens effect can be additionally obtained by making the surface of the dielectric layer 36 a curved surface. The dielectric layer 36 in FIG. 26 has a concave lens shape. Therefore, the dielectric layer 36 has a function as a lens, and collects light directed toward the second stripe-shaped electrode 22b in the opening of the gap between the first and second stripe-shaped electrodes 22a and 22b. By shining, the substantial aperture ratio can be increased. At this time, the light is irradiated almost perpendicularly to the substrate from the substrate side on which the dielectric layer 36 is provided.
[0057]
A 15-inch XGA liquid crystal display device of the example of FIG. 23 was manufactured as follows. A dielectric layer 36 is formed on the transparent electrode 18 of one substrate 12, and a portion 36a of the dielectric layer 36 corresponding to the first stripe-shaped electrode 22a is formed in a groove shape by a photolithography process, and is thermally cured. After that, a further layer of resin was applied, and a portion 36b of the dielectric layer 36 corresponding to the second stripe-shaped electrode 22b was formed in a projection shape by a photolithography process and thermally cured. The resin used was NN700 (JSR). By applying heat, the corners of the protrusion-like part 36b or the groove-like part 36a are rounded to generate a slope. A vertical alignment film JALS204 (JSR) was applied. After forming the other board | substrate 14, both board | substrates 12 and 14 were bonded together and the liquid crystal inject | poured ZLI4535 (Merck Japan). In addition, a liquid crystal panel having a flat surface of the dielectric layer 36 was formed under the same conditions as described above. When both liquid crystal display devices were compared, the white brightness increased by 15% and the response speed improved by 10% at the same drive voltage without lowering the contrast.
[0058]
27 to 29 are diagrams showing another embodiment.
FIG. 27 shows an active matrix similar to FIG. As described with reference to FIG. 7, the liquid crystal display device having the active matrix includes the first and second striped electrodes 22a and 22b and the first and second striped electrodes 22a and 22b. Covering insulator layers 50a and 50b are provided.
[0059]
FIG. 28 shows the substrate 14 having the first and second striped electrodes 22a and 22b of FIG. 27, and the insulator layers 50a and 50b covering the first and second striped electrodes 22a and 22b are shown. ing.
The insulator layers 50a and 50b have an opening 50h on the second stripe-shaped electrode 22b, and the side wall of the opening 50h is forward tapered. That is, the opening 50h is formed so as to expand from the TFT substrate 14 side toward the color fill substrate 12 side (not shown). The contour of the opening 50h is also shown in FIG. Further, the color filter substrate 12 has a solid electrode 18 as shown in FIG.
[0060]
In FIG. 28, as described above, when a voltage is applied, an oblique electric field F is applied from the first stripe-shaped electrode 22 a toward the transparent electrode 18.₀Is formed, and the liquid crystal molecules have an oblique electric field F₀To be parallel to The lateral electric field formed between the first stripe-shaped electrode 22a and the second stripe-shaped electrode 22b is an oblique electric field F.₀It acts to help the alignment of the liquid crystal. However, the electric field near the second striped electrode 22b is not necessarily the oblique electric field F.₀The liquid crystal molecules are not in agreement with the oblique electric field F.₀The orientation of the liquid crystal is different from that of the liquid crystal. However, the liquid crystal molecules adjacent to the tapered wall 50i of the opening 50h are aligned perpendicular to the wall surface, and the alignment direction is an oblique electric field F.₀This coincides with the alignment of the liquid crystal along the line. Therefore, the alignment of the liquid crystal molecules is improved.
[0061]
FIG. 29 is a view showing a modification of the openings of the insulator layers 50a and 50b in FIG. An opening 50h is formed in the insulator layers 50a and 50b on the second stripe electrode 22b, and an opening 50j is formed in the insulator layers 50a and 50b on the first stripe electrode 22a. Yes. The ends of these openings 50h and 50j are narrower than the first and second striped electrodes 22a and 22b, respectively, and are hidden by these electrodes. As shown in FIG. 28, the liquid crystal molecules adjacent to the tapered wall 50i of the opening 50h are aligned perpendicularly to the wall surface when no voltage is applied. Therefore, when no voltage is applied, the alignment of the liquid crystal is disturbed at that portion, causing light leakage. It becomes. As shown in FIG. 29, by arranging the end portions of the openings 50h and 50j on the respective electrodes, it is possible to shield the disorder of the alignment of the liquid crystal due to the end portions of the openings and to improve the contrast.
[0062]
30 to 34 are diagrams for explaining still another embodiment. In this embodiment, the color filter substrate 12 has a dielectric layer 36 between the transparent electrode 18 and the alignment film 20.
In FIG. 30, the transparent electrode 18 is formed on the surface of the substrate 12, the color filter layer 38 (including R, G, and B components) is formed on the transparent electrode 18, and the transparent resin is formed on the color filter layer 38. The layer 36x is formed, and the alignment film 20 is formed on the transparent resin layer 36x. The dielectric layer 36 includes a color filter layer 38 and a transparent resin layer 36x.
[0063]
In FIG. 31, the color filter layer 38 is formed on the surface of the substrate 12, the transparent electrode 18 is formed on the color filter layer 38, the transparent resin layer 36x is formed on the transparent electrode 18, and the transparent resin layer 36x. An alignment film 20 is formed on the substrate. The dielectric layer 36 is made of a transparent resin layer 36x.
In FIG. 32, the transparent electrode 18 is formed on the surface of the substrate 12, the color filter layer 38 is formed on the transparent electrode 18, and the alignment film 20 is formed on the color filter layer 38. The dielectric layer 36 is composed of a color filter layer 38. Furthermore, the substrate 12 is appropriately provided with a black matrix.
[0064]
When such a dielectric layer 36 is formed, sufficient brightness as a display cannot be obtained unless the value of the ratio (d / ε) between the thickness (d) and the relative dielectric constant (ε) is appropriate. In the case of the configuration shown in FIG. 31 in which the dielectric layer 36 is formed of the transparent resin layer 36x, screen burn-in may occur when a liquid crystal panel is manufactured and displayed.
In the case of the configuration of FIG. 32 in which the dielectric layer 36 is formed of the color filter layer 38, there is no problem of screen burn-in, but there is only a thin alignment film 20 between the liquid crystal layer 16 and the color filter layer 38. There is a problem that the voltage holding ratio of the liquid crystal panel is lowered due to contamination of the liquid crystal layer 16 by the color filter layer 38.
[0065]
The relative permittivity (ε) of the color filter has a higher value than that of the transparent resin. For example, the relative permittivity of the transparent resin is about 3 to 3.3, whereas the relative permittivity of the color filter is 3.5 to 4. Since the transparent electrode 18 is under the dielectric layer 36, the voltage applied to the liquid crystal from the transparent electrode 18 is affected by the dielectric layer 36. When the dielectric constants of the dielectric layer 36 are different, it is necessary to change the film thickness of the dielectric layer 36 in order to make the voltage applied to the liquid crystal the same. For example, when the relative dielectric constant is high, the film thickness may be increased accordingly. Specifically, when the relative dielectric constant ε1 and film thickness d1 of the dielectric layer 1 and the relative dielectric constant ε2 and film thickness d2 of the dielectric layer 2, the voltage applied to the liquid crystal layer is the same. , (D1 / ε1) = (d2 / ε2).
[0066]
As a result of actually examining many resins, it was found that the display luminance is related to the relative dielectric constant and film thickness of the dielectric layer 36.
FIG. 33 shows a value obtained by dividing the film thickness d by the relative dielectric constant ε, where the relative dielectric constant of the dielectric layer 36 is ε (unit f) and the film thickness is d (μm) (d / ε, unit is f / μm). ) Is the x-axis, and the relationship when the transmittance when 10 V is applied is the y-axis is shown.
[0067]
Luminance (transmittance) peaks when the value of d / ε is around 0.7 f / μm. When the value of d / ε exceeds 0.7 f / μm, the luminance slightly decreases. When the value of d / ε is 0.7 f / μm or less, the luminance decreases as the value of d / ε decreases. For this reason, it is preferable that the value of d / ε is 0.5 f / μm or more. When the value of d / ε is 0.7 f / μm or more, the transmittance of the dielectric layer itself may be lowered, and the luminance will be lowered. For this reason, it is important that the value of d / ε does not become too large, and the value of d / ε is preferably 0.9 f / μm or less.
[0068]
The screen burn-in of the dielectric layer 36 is related to the resistivity. The lower the resistivity of the dielectric layer 36, the smaller the degree of screen burn-in. As the thickness of the dielectric layer 36 increases, the resistivity increases and the degree of screen burn-in increases.
In the case where the dielectric layer 36 is composed of the transparent resin layer 36x, a certain thickness is required to satisfy the luminance. As a result, the resistivity becomes high and seizure tends to occur. On the other hand, when the dielectric layer 36 is composed of the color filter layer 38, it cannot be said that the conventional color filter layer 38 having a typical thickness has sufficient luminance. However, the resistivity is not so high and screen burn-in does not occur.
[0069]
Therefore, as shown in FIG. 30, when the dielectric layer 36 includes the color filter layer 38 and the transparent resin layer 36x, the above problems can be solved at the same time. In this case, the transparent resin layer 36x is preferably thinner than the color filter layer 38. In this case, the thickness of the dielectric layer 36 is thicker than the thickness of the dielectric layer 36 when the dielectric layer 36 is a single color filter layer 38, and the thickness is suitable for ensuring sufficient luminance. Become. In this case, the resistivity of the dielectric layer 36 is lower than the resistivity of the dielectric layer 36 when the dielectric layer 36 is a single transparent resin layer 36x, and screen burn-in does not occur. In addition, since the transparent resin layer 36x having a high density is provided outside the color filter layer 38, liquid crystal contamination by the color filter layer 38 is eliminated, and the problem that the voltage holding ratio is reduced is solved.
[0070]
When the dielectric layer 36 is composed of the color filter layer 38 and the transparent resin layer 36x, it is preferable that the thickness and the relative dielectric constant satisfy the following relationship as in the case of the single layer.
When the color filter layer 38 has a relative dielectric constant ε1 and a film thickness d1, and the transparent resin layer 36x has a relative dielectric constant ε2 and a film thickness d2, 0.5 <(d1 / ε1) + (d2 / ε2). ) Preferably, there is a relationship of 0.5 <(d1 / ε1) + (d2 / ε2) <0.9.
[0071]
FIG. 34 is a diagram showing the relationship between the thickness of the transparent resin layer 36x of the dielectric layer 36 and the screen burn-in when the thickness of the color filter layer 38 is 2 μm. Screen burn-in is the sum of squares of the difference in brightness before and after applying 3V DC to the liquid crystal panel (S_T) It can be seen that the greater the thickness of the transparent resin layer 36x, the greater the degree of image sticking. This is because the proportion of the transparent resin layer 36x in the dielectric layer 36 increases, the effect of the color filter layer 38 having a low resistance below the transparent resin layer 36x is reduced, and charges are easily accumulated. I think that the. That is, if the ratio of the color filter layer 38 used as the dielectric layer 36 and the transparent resin layer 36x to the color filter layer 38 having a high relative dielectric constant and a high resistivity is not increased, the effect of preventing burn-in can be obtained. Does not rise. The film thickness of the transparent resin layer 36x formed on the color filter layer 38 is desirably as thin as possible.
[0072]
Table 1 below shows the degree of surface burn-in and the voltage holding ratio when the present invention of FIGS. 30 to 32 is used.

In manufacturing the color filter substrate, a Cr thin film is formed on the glass substrate 12, and this is etched to form a black matrix (not shown). In a conventional color filter substrate, a color filter layer is formed thereon. In the present invention, at this stage, a transparent electrode 18 such as ITO is formed by sputtering. The color filter layer 38 is formed on the transparent electrode 18 by photolithography process for each of RGB. The film thickness is about 2.0 μm. The relative dielectric constant of the color filter layer 38 is close to 4. Next, a transparent resin layer 36 x is provided on the color filter layer 38. In this case, the transparent electrode resin layer 36x can be patterned because a through hole is formed to connect the transfer electrode (not shown) on the TFT substrate side and the transparent electrode 18 on the color filter substrate side. desirable. Here, a positive resist transparent resin having a relative dielectric constant of ε = 3.3 is formed on the RGB color filter layer with a film thickness of about 0.2 μm. After applying the transparent resin, the portion where the through hole is to be formed is irradiated with ultraviolet rays through a mask, and development is performed with a developer (eg, TMAH aqueous solution).
[0073]
The transparent resin may be used after forming a normal transparent resist (for example, Shipley S1808) and then performing color removal by a photo bleaching process. Next, a vertical alignment film is applied on the transparent resin.
On one TFT substrate, an active matrix including gate bus lines, data bus lines, and TFTs, first and second stripe-shaped electrodes 22a and 22b, and a vertical alignment film are formed.
[0074]
The liquid crystal panel thus formed has a d / ε value of about 0.6, which is a combination of the color filter layer 38 and the transparent resin layer 36x, and is in a state close to the peak in FIG. is there. Further, there is no surface burn-in under these conditions, and a high voltage holding ratio can be maintained.
FIG. 35 is a diagram for explaining still another embodiment. In this embodiment, the color filter substrate 12 has a dielectric layer 36 y between the transparent electrode 18 and the alignment film 20. The dielectric layer 36y is optically anisotropic. That is, in the configuration of FIG. 9, the retardation film 42 is provided separately from the dielectric layer 36 (not shown in FIG. 9), but in the configuration of FIG. 35, the dielectric layer 36y is a dielectric layer. The function as 36 and the function of the retardation film 42 are combined. Therefore, the above description regarding the retardation film 42 also applies to the dielectric layer 36y. Expressions (1) to (5) and FIGS. 10 to 13 are also applied to the dielectric layer 36y. A repetitive description will not be given here.
[0075]
The dielectric layer 36y can be formed of a polymer liquid crystal or a discotic liquid crystal into which a photopolymerization group is introduced. FIG. 36 is a diagram illustrating an example of a discotic liquid crystal that can be used as the dielectric layer 36y. For example, in the formation of the dielectric layer 36y, the transparent electrode 18 is formed on the glass substrate 12, and an alignment layer (for example, AL3046 made by JSR) for aligning the dielectric layer is formed on the transparent electrode 18. A discotic liquid crystal mixed with a solvent is applied on the alignment layer, the solvent is volatilized on a hot plate, and then cured by irradiating with ultraviolet rays to form a dielectric layer 36y. It may be cured by heating. Further, the vertical alignment film 20 is formed on the dielectric layer 36y. According to this embodiment, a liquid crystal display device having excellent viewing angle characteristics can be easily manufactured.
[0076]
There is a relationship of 0.5 <d / ε <0.9 between the relative dielectric constant ε and the film thickness d.
The transparent resin layer is thinner than the color filter layer.
A main dielectric layer is applied on the alignment layer, aligned, and cured by light irradiation or heating.
[0077]
【The invention's effect】
As described above, according to the present invention, the driving voltage of the liquid crystal can be lowered and the response speed of the liquid crystal molecules can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a basic form of a liquid crystal display device of the present invention when no voltage is applied.
FIG. 2 is a cross-sectional view showing the liquid crystal display device of FIG. 1 when a voltage is applied.
FIG. 3 is a plan view showing a part of an active matrix formed on one substrate.
4 is a diagram showing the relationship of absorption axes of the polarizer of FIG. 1. FIG.
FIG. 5 is a diagram illustrating the formation of an electric field in the absence of a dielectric layer.
FIG. 6 is a diagram showing the formation of an electric field when there is a dielectric layer.
FIG. 7 is a diagram showing an example including an insulator layer covering a striped electrode.
FIG. 8 is a diagram showing an example in which an opening is provided in an insulator layer.
FIG. 9 is a diagram showing an example including a retardation film.
FIG. 10 is a diagram showing viewing angle characteristics of a liquid crystal display device without a retardation film.
FIG. 11 is a diagram showing viewing angle characteristics of a liquid crystal display device having a retardation film.
FIG. 12 R_XZ-R_YZIt is a figure which shows the isometric angle curve in which contrast becomes 10 on a coordinate.
FIG. 13 R_LC-R_tIt is a figure which shows the relationship.
14 is a view showing a part of an active matrix formed on one substrate as a modification of FIG. 3; FIG.
15 is a plan view showing a first stripe-shaped electrode of FIG. 14; FIG.
16 is a plan view showing a second stripe-shaped electrode of FIG. 14; FIG.
17 is a cross-sectional view showing a liquid crystal display device similar to FIG.
18 is a diagram showing a liquid crystal display device similar to FIG.
19 is a view showing a portion in the vicinity of the surface of a dielectric layer of the liquid crystal display device of FIGS. 17 and 18. FIG.
20 is a diagram showing a portion in the vicinity of the surface of a dielectric layer of the liquid crystal display device of FIGS. 21 and 22. FIG.
FIG. 21 is a diagram showing a liquid crystal display device according to an embodiment of the present invention when no voltage is applied.
22 is a diagram showing the liquid crystal display device of FIG. 21 when a voltage is applied.
FIG. 23 is a diagram showing a modification of the liquid crystal display device of FIG.
FIG. 24 is a diagram showing a liquid crystal display device for explaining that the alignment of liquid crystal is disturbed by an electric field generated between a gate bus line and a first stripe electrode.
25 is a diagram showing a modification of the liquid crystal display device of FIG.
FIG. 26 is a diagram showing a modification of the liquid crystal display device of FIG.
FIG. 27 is a plan view showing a part of an active matrix formed on one substrate of another embodiment.
28 is a cross-sectional view showing a substrate having the striped electrode of FIG. 27. FIG.
FIG. 29 is a view showing a modification of the substrate of FIG.
FIG. 30 is a diagram showing a liquid crystal display device according to another embodiment of the present invention.
FIG. 31 is a diagram showing a modification of the liquid crystal display device of FIG.
32 is a diagram showing a modification of the liquid crystal display device of FIG.
FIG. 33 is a diagram showing a relationship between d / ε and transmittance.
FIG. 34 is a diagram showing the relationship between the thickness of the transparent resin layer of the dielectric layer and the screen burn-in when the thickness of the color filter layer is 2 μm.
FIG. 35 is a diagram showing a liquid crystal display device according to another embodiment of the present invention.
36 is a diagram showing a discotic liquid crystal that can be used as the dielectric layer of FIG. 35. FIG.
[Explanation of symbols]
12 ... Board
14 ... Board
16 ... Liquid crystal layer
18 ... Transparent electrode
20 ... Alignment film
22a, 22b ... Striped electrodes
24 ... Alignment film
36 ... Dielectric layer
36x ... Transparent resin layer
36y ... dielectric layer
38 ... Color filter
50. Insulator layer
50h ... opening

Claims (6)

A pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe electrodes and alignment films per pixel formed on one substrate, and the other substrate substantially on the other substrate A transparent electrode and an alignment film formed to cover the entire surface, and a dielectric layer provided on the other substrate between the transparent electrode and the alignment film,
The dielectric vector is such that the normal vector at a point on the surface of the dielectric layer is more parallel to the electric field lines penetrating through that point on the surface of the dielectric layer than when the surface of the dielectric layer is planar. A liquid crystal display device characterized in that the surface of the body layer is formed in a curved shape. A pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe electrodes and alignment films per pixel formed on one substrate, and the other substrate substantially on the other substrate A transparent electrode and an alignment film formed so as to cover the entire surface, and an insulator layer provided on the one substrate to cover the stripe-shaped electrode,
The liquid crystal display device, wherein the insulating layer has an opening on the striped electrode, and the side wall of the opening is tapered. A pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe electrodes and alignment films per pixel formed on one substrate, and the other substrate substantially on the other substrate A transparent electrode and an alignment film formed to cover the entire surface, and a dielectric layer provided on the other substrate between the transparent electrode and the alignment film,
A liquid crystal display device characterized in that there is a relationship of 0.5 <d / ε between a relative dielectric constant ε and a film thickness d of the dielectric layer. A pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe electrodes and alignment films per pixel formed on one substrate, and the other substrate substantially on the other substrate A transparent electrode and an alignment film formed to cover the entire surface, and a dielectric layer provided on the other substrate between the transparent electrode and the alignment film,
The dielectric layer includes a color filter layer and a transparent resin layer, and is laminated in this order from the transparent electrode. A pair of substrates, a liquid crystal sealed between the pair of substrates, a plurality of stripe electrodes and alignment films per pixel formed on one substrate, and the other substrate substantially on the other substrate A transparent electrode and an alignment film formed to cover the entire surface, and a dielectric layer provided on the other substrate between the transparent electrode and the alignment film,
A liquid crystal display device, wherein the dielectric layer is optically anisotropic. The liquid crystal display device according to claim 7, wherein the dielectric layer includes a main dielectric layer and an alignment layer for aligning the main dielectric layer.

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