JP2005055709A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which a voltage necessary for the acquisition of a black display state is reduced. <P>SOLUTION: A driving cell 10 retains a liquid crystal layer 15 in which liquid crystal molecules are twist aligned so as to exhibit a helical structure in the state of no electric field generation. Electrodes to generate an electric field with a direction inside a substrate surface in the liquid crystal layer 15 is formed. A compensation means 30 is disposed on one of the surfaces of the driving cell 10. The compensation means 30 includes a liquid crystal layer 35 in which liquid crystal molecules are twist aligned so as to exhibit a helical structure wherein a twist direction of the helical structure is opposite to that of the driving cell 10 and an orientation direction of a liquid crystal molecule located on the center of the liquid crystal layer 35 in the thickness direction perpendicularly intersects an orientation direction of a liquid crystal molecule located on the center of the liquid crystal layer 15 in the thickness direction of the driving cell 10. Polarizing plates 50, 51 are respectively disposed on both sides of a structural body including the driving cell 10 and the compensation means 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching twisted nematic (IT) mode liquid crystal display device.

  Patent Documents 1 to 3 disclose IT mode (or IPS mode) liquid crystal display devices. The IT mode operation will be briefly described below.

  A comb-shaped electrode is formed only on one of the pair of substrates sandwiching the liquid crystal layer. In a state where no electric field is applied, the liquid crystal molecules are twisted nematic (TN) aligned. When a voltage is applied to the electrode, an electric field in a direction parallel to the substrate surface is generated, and the liquid crystal molecules on the substrate side on which the electrode is formed receive a force in a direction that changes the major axis direction in the substrate surface. When a high voltage is applied to the electrodes, the twisted state of the molecules in the liquid crystal layer is eliminated, and it approaches a homogeneous alignment.

  Polarizing plates are arranged in crossed Nicols on both sides of the liquid crystal layer. If the major axis of the liquid crystal molecule when the twisted state of the molecule in the liquid crystal layer is eliminated is parallel to the transmission axis of any polarizing plate, black display is obtained. In addition, white display is obtained when no voltage is applied.

  In the IT mode, the major axis direction of the liquid crystal molecules is changed in a plane parallel to the substrate surface. Therefore, compared with the conventional TN mode liquid crystal display device that realizes black display by standing the liquid crystal molecules vertically to the substrate surface, Good viewing angle characteristics can be obtained.

Japanese Patent No. 2986756 Japanese Patent No. 3299190 Japanese Patent Laid-Open No. 10-54982

  In the IT mode liquid crystal display device, a high voltage is required to eliminate the twisted state of the liquid crystal molecules in the liquid crystal layer and obtain a good black display.

  An object of the present invention is to provide a liquid crystal display device capable of reducing a voltage necessary for obtaining a black display state.

  According to one aspect of the present invention, an electrode for generating an electric field in a substrate in-plane direction is formed on a liquid crystal layer that holds a liquid crystal layer that exhibits a helical structure by twist alignment of liquid crystal molecules in a state where no electric field is generated. A driving cell and a liquid crystal layer arranged on one surface of the driving cell and having a helical structure in which liquid crystal molecules are twisted and arranged, and the turning direction of the helical structure is the turning direction of the helical structure of the driving cell. Is a reverse direction, and the compensation means in which the orientation direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer is orthogonal to the orientation direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer of the driving cell And a polarizing plate disposed on each side of the structure including the driving cell and compensation means.

  According to another aspect of the present invention, there is provided a liquid crystal layer having a helical structure in which liquid crystal molecules having positive uniaxial optical anisotropy or positive biaxial optical anisotropy are twisted in a state where an electric field is not generated. A driving cell in which an electrode for holding and generating an electric field in the in-plane direction of the substrate is formed on the liquid crystal layer, and is disposed on one surface of the driving cell and has negative uniaxial optical anisotropy or negative biaxial optical Compensation means including a liquid crystal layer having a helical structure in which anisotropic liquid crystal molecules are twisted and having a helical structure in which the rotational direction of the helical structure is opposite to the rotational direction of the helical structure of the drive cell, and the drive cell There is provided a liquid crystal display device having polarizing plates disposed on both sides of the layer structure of the compensation means.

  With the above-described structure, low-voltage driving is possible as compared with the conventional IT mode liquid crystal display device.

  FIG. 1 is an exploded perspective view of the main part of the liquid crystal display device according to the first embodiment of the present invention. The liquid crystal display device according to the first embodiment includes a driving cell 10, a compensation cell 30, a polarizing plate 50 on the driving cell side, and a polarizing plate 51 on the compensation cell side.

  The drive cell 10 has the same configuration as that of a conventional IT mode liquid crystal cell, and includes an electrode substrate 11, a counter substrate 12, and a liquid crystal layer 15 held between the two. The liquid crystal layer 15 is filled with liquid crystal molecules 16 having positive uniaxial optical anisotropy. Electrodes 13 and 14 are formed on the opposing surface of the electrode substrate 11 at a certain distance. When a voltage is applied between the electrodes 13 and 14, an electric field having a component parallel to the substrate surface is generated in the liquid crystal layer 15. This electric field becomes weaker as it approaches the counter substrate 12 from the electrode substrate 11.

  The orientation direction of the liquid crystal molecules at an azimuth angle θ rotated counterclockwise toward the opposing surface of the electrode substrate 11 with the direction of the electric field generated in a direction parallel to the substrate surface generated by the electrodes 13 and 14 as a reference (0 °). Define the angle coordinates representing (long axis direction) and the like.

  An alignment film is formed on the opposing surfaces of the electrode substrate 11 and the counter substrate 12. Although not shown, a plurality of pixels are defined within the surface of the electrode substrate 11, and the electrodes 13 and 14 are arranged for each pixel.

  The alignment film on the electrode substrate 11 and the counter substrate 12 is rubbed. The rubbing direction D1 applied to the alignment film on the electrode substrate 11 is a direction having an azimuth angle of 270 °, and the rubbing direction D2 applied to the alignment film on the counter substrate 12 is a direction having an azimuth angle of 0 °. The liquid crystal molecules in contact with the alignment film are aligned parallel to the rubbing direction and tilted so that the end portion on the tip side of the arrow indicating the rubbing direction is lifted from the substrate.

  The liquid crystal molecules 16 in the liquid crystal layer 15 are twisted so that the end of the liquid crystal molecules on the electrode substrate 11 side lifted from the substrate corresponds to the end of the liquid crystal molecules on the counter substrate 12 side in contact with the substrate. And constitutes a helical structure. This helical structure turns left, the twist angle is 90 °, and the azimuth angle θ in the alignment direction of the liquid crystal molecules located at the center in the thickness direction is 225 °.

  The compensation cell 30 includes a lower substrate 31, an upper substrate 32, and a liquid crystal layer 35 sandwiched between both. The lower substrate 31 is in contact with the counter substrate 12 of the drive cell 10. An alignment film is formed on the opposing surfaces of the lower substrate 31 and the upper substrate 32 and subjected to a rubbing process. A rubbing direction D3 applied to the alignment film on the lower substrate 31 is a direction having an azimuth angle of 90 °, and a rubbing direction D4 applied to the alignment film on the upper substrate 32 is a direction having an azimuth angle of 0 °. .

  The liquid crystal molecules 36 in the liquid crystal layer 35 are twisted to form a helical structure. This helical structure turns clockwise, the twist angle is 90 °, and the azimuth angle θ in the alignment direction of the liquid crystal molecules located at the center in the thickness direction is 135 °. The alignment direction of the liquid crystal molecules positioned in the center with respect to the thickness direction of the liquid crystal layer 15 of the driving cell 10 and the alignment direction of the liquid crystal molecules positioned in the center with respect to the thickness direction of the liquid crystal layer 35 of the compensation cell 30 are orthogonal to each other. To do.

  The polarizing plate 50 is in close contact with the outer surface of the electrode substrate 11 of the driving cell 10, and the polarizing plate 51 is in close contact with the outer surface of the upper substrate 32 of the compensation cell 30. The azimuth angle θ in the transmission axis direction D5 of the polarizing plate 50 is 0 °, and the azimuth angle θ in the transmission axis direction D6 of the polarizing plate 51 is 90 °. That is, the polarizing plates 50 and 51 are in a crossed Nicols arrangement.

  FIG. 2 shows electro-optical characteristics of the liquid crystal display device shown in FIG. The horizontal axis represents the applied electric field in the unit “V / mm”, and the vertical axis represents the light transmittance in the unit “%”. The light transmittance is a result obtained by simulation calculation. As a liquid crystal material, MLC2051 (refractive index anisotropy Δn = 0.11) manufactured by Merck Co., Ltd. having a positive dielectric anisotropy Δε was assumed. The polarizing plates 50 and 51 were assumed to be ideal without absorption.

A solid line a ₀ in the figure indicates a case where the thickness of the liquid crystal layer 15 of the driving cell 10 is equal to the thickness of the liquid crystal layer 35 of the compensation cell 30. Dashed lines a ₁₁ , a ₁₂ , and a ₁₃ indicate cases where the liquid crystal layer 35 of the compensation cell 30 is thicker by 0.1 μm, 0.2 μm, and 0.3 μm than the liquid crystal layer 15 of the driving cell 10, respectively. Dashed lines a ₂₁ , a ₂₂ , and a ₂₃ indicate cases where the liquid crystal layer 35 of the compensation cell 30 is thinner than the liquid crystal layer 15 of the driving cell 10 by 0.1 μm, 0.2 μm, and 0.3 μm, respectively. The retardation Δnd of the drive cell 10 when no electric field was applied was 0.4 μm.

  When the applied electric field is 0, black is displayed. When the thickness of the liquid crystal layer 15 of the driving cell 10 and the thickness of the liquid crystal layer 35 of the compensation cell 30 are equal, the light transmittance is zero when the applied voltage is zero. If the thickness of the liquid crystal layer 35 of the compensation cell 30 deviates from the thickness of the liquid crystal layer 15 of the driving cell 10, the light transmittance in the black display state is not zero, and the light transmittance increases as the amount of displacement increases. growing.

  Since the assumed refractive index anisotropy of the liquid crystal material is 0.11, when the amount of deviation in the thickness of the liquid crystal layer is 0.3 μm, the difference between the retardation of the compensation cell 30 and the retardation of the drive cell 10 is about 0.03 μm. It can be seen that if the difference between the retardation of the compensation cell 30 and the retardation of the driving cell 10 when no electric field is applied is 0.03 μm or less, a good black display can be obtained. Further, when the retardation difference is 0.03 μm or less, there is no significant difference in light transmittance in the white display state where a predetermined electric field is applied. Therefore, it is preferable that the difference between the retardation of the compensation cell 30 and the retardation of the driving cell 10 is 0.03 μm or less.

  In the conventional IT mode liquid crystal display device, it was necessary to generate a large electric field in order to perform a good black display. However, since the liquid crystal display device according to the above embodiment is a normally black display, the drive voltage is lowered. Can do.

FIG. 3 shows electro-optical characteristics when the retardation of the driving cell 10 and the retardation of the compensation cell 30 are equal. The horizontal axis represents the applied electric field in the unit “V / mm”, and the vertical axis represents the light transmittance in the unit “%”. Broken lines or solid lines b _{1 to} b ₆ in the figure indicate the light transmittance when the retardation Δnd is 0.40 μm, 0.47 μm, 0.80 μm, 1.20 μm, 1.60 μm, and 2.00 μm, respectively.

  In any of the retardations, there is no significant difference in light transmittance in the white display state. In the conventional IT mode liquid crystal display device, it was necessary to set the retardation in the vicinity of 0.49 μm in order to obtain a good white display (first minimum condition). In the liquid crystal display device according to the first embodiment, however, Provides a good white display over a wide range of retardation. Further, when the retardation was in the range of 0.40 to 2.00 μm, no significant difference was observed in the quality of black display.

  When the drive cell 10 is thickened, the response speed becomes slow. In order to maintain a response speed equivalent to that of a conventional IT mode liquid crystal display device, the retardation is preferably set to 0.3 μm to 1 μm.

  FIG. 4 shows electro-optical characteristics when the relationship between the rubbing direction D1 of the alignment film on the electrode substrate 11 of the drive cell 10 and the direction of the applied electric field is shifted from 90 °. The horizontal axis represents the applied electric field in the unit “V / mm”, and the vertical axis represents the light transmittance in the unit “%”. The thickness of the liquid crystal layer 15 of the driving cell 10 and the liquid crystal layer 35 of the compensation cell 30 was 4 μm, and the helical angle of the helical structure was 90 °.

  In FIG. 4, the angle φ formed by the rubbing direction D1 of the alignment film on the electrode substrate 11 and the direction of the electric field in the direction parallel to the substrate surface generated by the electrodes 13 and 14 is 60 °, 70 °, 80 °, And the light transmittance in the case of 90 °. In any case, it can be seen that good black display and white display can be obtained.

FIG. 5 shows electro-optical characteristics when the helical angle θd of the helical structure of the drive cell 10 is changed. The horizontal axis represents the applied electric field in the unit “V / mm”, and the vertical axis represents the light transmittance in the unit “%”. The thickness of the liquid crystal layer 15 of the driving cell 10 and the liquid crystal layer 35 of the compensation cell 30 was 4 μm. The helical angle θc of the helical structure of the compensation cell 30 was made equal to the helical angle θd. Even if the twist angle of the helical structure is changed, the orientation direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 15 of the driving cell 10 is set to the direction of the azimuth angle of 225 °. Regarding the compensation cell 30 as well, the orientation direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 35 was fixed at 135 °.
For this reason, in any case, the alignment direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 15 of the driving cell 10 and the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 35 of the compensation cell 30. The orientation directions are orthogonal to each other.

  FIG. 5 shows the light transmittance when the helical angle θd of the helical structure of the drive cell 10 is 30 °, 60 °, 90 °, 120 °, 150 °, and 180 °. When the twist angle θd is smaller than 90 °, the maximum value of the light transmittance is lowered. Further, when the twist angle θd is larger than 90 °, the rise of the light transmittance becomes steep. In any case, a good black display state is obtained. Therefore, if the twist angle θd is greater than 0 ° and 180 ° or less, image display can be performed.

  In order to obtain a higher contrast, the helical angle θd of the helical structure of the drive cell 10 and the helical angle θc of the helical structure of the compensation cell 30 are made equal, and both are greater than 0 ° and 180 ° or less. It is preferable to do.

  FIG. 6 shows electro-optical characteristics when only the twist angle θc of the helical structure of the compensation cell 30 is changed. The horizontal axis represents the applied electric field in the unit “V / mm”, and the vertical axis represents the light transmittance in the unit “%”. The thickness of the liquid crystal layer 15 of the drive cell 10 and the liquid crystal layer 35 of the compensation cell 30 was 4 μm, and the twist angle θd of the helical structure of the drive cell 10 was 90 °. Further, even if the helical angle θc of the helical structure of the compensation cell 30 is changed, the alignment direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 35 is set to the direction of the azimuth angle 135 °. For this reason, in any case, the alignment direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 15 of the drive cell 10 and the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 35 of the compensation cell 30. The orientation directions are orthogonal to each other.

  As the torsion angle θc of the helical structure of the compensation cell 30 is reduced from 90 °, the light transmittance increases when no electric field is applied. In this case, as the electric field is strengthened, the light transmittance decreases and shows a minimum value, and then increases. A black display can be performed by applying an electric field showing a minimum value of light transmittance.

  When the torsion angle θc of the helical structure of the compensation cell 30 is 90 °, normally black display is obtained. By making the twist angle θc smaller than 90 °, normally white display can be performed. In order to ensure sufficient contrast when performing normal white display, the helical angle of the helical structure of the compensation cell 30 is preferably set to 30 to 60 °.

  Generally, normally white display is obtained by making the twist angle θc of the helical structure of the compensation cell 30 smaller than the twist angle θd of the helical structure of the drive cell 10. If the torsion angle θc of the helical structure of the compensation cell 30 is larger than the torsion angle θd of the helical structure of the drive cell 10, a good black display state cannot be obtained. For this reason, it is preferable to set the twist angle θc to be equal to or smaller than the twist angle θd.

  When performing normally white display, it is possible to perform better black display at a lower voltage (weak electric field) than when performing black display with a conventional IT mode liquid crystal display device.

  In the first embodiment, the compensation cell 30 is arranged on the counter substrate 12 side of the drive cell 10, but the same effect can be obtained even if the compensation cell 30 is arranged on the electrode substrate 11 side. In the first embodiment, the simulation is performed assuming a liquid crystal material having positive uniaxial optical anisotropy. However, a liquid crystal material having positive biaxial optical anisotropy may be used.

  In the first embodiment, a liquid crystal material having a positive dielectric anisotropy is used. However, a liquid crystal material having a negative dielectric anisotropy may be used. Even if the dielectric anisotropy is negative, the orientation direction in the plane parallel to the substrate surface can be changed by applying an electric field parallel to the substrate surface.

  The liquid crystal molecules in the liquid crystal layer 35 of the compensation cell 30 used in the first embodiment do not change their alignment state during operation. Therefore, instead of the compensation cell 30, an optical film made of a liquid crystal polymer or the like having equivalent optical characteristics may be used.

  FIG. 7 is an exploded perspective view of the main part of the liquid crystal display device according to the second embodiment. Hereinafter, differences from the configuration of the liquid crystal display device shown in FIG. 1 will be described. A quarter wavelength plate 52 is inserted between the drive cell 10 and the polarizing plate 50, and a quarter wavelength plate 53 is inserted between the compensation cell 30 and the polarizing plate 51. Other configurations are the same as those of the liquid crystal display device shown in FIG.

  As the quarter-wave plates 52 and 53, those having positive uniaxial optical anisotropy or positive biaxial optical anisotropy can be used. The slow axis in the plane of the quarter wavelength plate 52 is orthogonal to the transmission axis of the polarizing plate 50, and the slow axis in the plane of the quarter wavelength plate 53 is parallel to the transmission axis of the polarizing plate 51. . Conversely, the slow axis in the plane of the quarter-wave plate 52 is parallel to the transmission axis of the polarizing plate 50, and the slow axis in the plane of the quarter-wave plate 53 is You may make it orthogonally cross a transmission axis.

  FIG. 8 shows the viewing angle characteristics of the liquid crystal display device according to the second embodiment, and FIG. 9 shows the viewing angle characteristics of the liquid crystal display device according to the first embodiment. The viewing angle characteristics were calculated using an LCD MASTER one-dimensional simulator manufactured by Shintech Co., Ltd. Assuming ZLI-4792 manufactured by Merck Co., Ltd. as the liquid crystal material, and assuming G-1220DU manufactured by Nitto Denko Co., Ltd. as the polarizing plate, the retardation in the thickness direction is 70 nm as a quarter wavelength plate, in-plane A film having positive biaxial optical anisotropy with a direction retardation of 137.5 nm was assumed. The thickness of the liquid crystal layer of the drive cell 10 and the compensation cell 30 was 4.9 μm, and the helical angle of the helical structure was 90 °.

  The azimuth angle 0 ° shown in FIGS. 8 and 9 corresponds to the angular coordinate 315 ° shown in FIGS. 7 and 1. The outermost circumference corresponds to an inclination angle (polar angle) of 80 ° from the normal direction of the substrate. The solid line in the figure shows an isoluminance curve when no voltage is applied (when black is displayed).

  In the case of the second embodiment, it can be seen that the interval of the isoluminance curves is wider than that of the first embodiment, and the viewing angle characteristics are improved. When using what has biaxial optical anisotropy as a quarter wavelength plate, it is preferable to use a thing whose retardation of thickness direction is 40 to 60% of retardation of an in-plane direction.

  FIG. 10 is an exploded perspective view of the liquid crystal display device according to the third embodiment. Hereinafter, differences from the configuration of the liquid crystal display according to the first embodiment shown in FIG. 1 will be described. In the first embodiment, a liquid crystal material having a positive optical anisotropy is used for the compensation cell 30, but in the third embodiment, a negative uniaxial optical anisotropy or a negative biaxial optical anisotropy is used. An anisotropic liquid crystal material is used. The liquid crystal molecules have a discotic shape. The director direction of the liquid crystal molecules coincides with the optical axis direction of the liquid crystal molecules. Note that it is not always necessary to use a liquid crystal material in which both match.

  On the surface of the lower substrate 31 and the upper substrate 32 of the compensation cell 30, the liquid crystal molecules are upright and are turning right with respect to the thickness direction. That is, the turning direction of the helical structure of the compensation cell 30 is opposite to the turning direction of the helical structure of the drive cell 10. The liquid crystal molecules on the surface of the lower substrate 31 are aligned so that their optical axes are oriented in the 0 ° direction, and the liquid crystal molecules on the surface of the upper substrate 32 are oriented so that their optical axes are oriented in the 90 ° direction. ing.

  The optical axis direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 35 of the compensation cell 30 is an azimuth angle of 45 °. Since the alignment direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer 15 of the driving cell 10 is also a direction having an azimuth angle of 45 °, both are parallel to each other.

  Hereinafter, a method for manufacturing the compensation cell 30 will be described. An alignment film is formed on the opposing surfaces of the lower substrate 31 and the upper substrate 32. As this alignment film, for example, a polyimide film shown in paragraph 319 of JP-A-9-26572 can be used. The alignment film is rubbed. The rubbing direction of the alignment film of the lower substrate 31 is a direction with an azimuth angle of 90 °, and the rubbing direction of the alignment film of the upper substrate 32 is a direction with an azimuth angle of 0 °.

  The discotic liquid crystal molecules in contact with the alignment film are almost upright with respect to the substrate surface, and the optical axis thereof is substantially orthogonal to the rubbing direction. As the discotic liquid crystal material, for example, a mixed liquid crystal compound having optical activity disclosed in JP-A-9-26572 can be used. At this time, adjusting the mixing ratio of the optically active material for adjusting the chiral pitch is a method known to those skilled in the art. By rubbing the alignment films on the upper and lower substrates, the alignment direction of the liquid crystal molecules in the vicinity of the upper and lower substrates is restricted, and a compensation cell having a twist angle of 90 ° between the upper and lower substrates is obtained.

  FIG. 11 shows the viewing angle characteristics of the liquid crystal display device according to the third embodiment. As the liquid crystal material having negative optical anisotropy, an ordinary light refractive index and an extraordinary light refractive index of ZLI-4792 manufactured by Merck Co., Ltd. were assumed to be interchanged. Other conditions are the same as in the simulations shown in FIGS. The meanings of azimuth and polar angles in FIG. 11 are the same as the meanings of azimuth and polar angles shown in FIG.

  The interval between the isoluminance curves shown in FIG. 11 is significantly wider than the interval between the isoluminance curves shown in FIGS. That is, it can be seen that the viewing angle characteristics are remarkably improved.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

  The present invention relates to a liquid crystal display device, and more particularly to an IT mode liquid crystal display device that changes the transmittance by rotating liquid crystal molecules in the in-plane direction of the substrate. With this liquid crystal display device, segment display and dot matrix display can be performed. This liquid crystal display device can be applied to both simple matrix driving and thin film transistor (TFT) driving.

1 is an exploded perspective view of a liquid crystal display device according to a first embodiment. 6 is a graph showing electro-optical characteristics of the liquid crystal display device according to the first embodiment for each difference in thickness of the liquid crystal layer between the driving cell and the compensation cell. It is a graph which shows the electro-optical characteristic of the liquid crystal display device by a 1st Example for every retardation of a drive cell and a compensation cell. 6 is a graph showing electro-optical characteristics of the liquid crystal display device according to the first embodiment for each angle formed by the alignment direction on the electrode substrate side of the driving cell and the electric field direction. 4 is a graph showing electro-optical characteristics of the liquid crystal display device according to the first embodiment for each twist angle of a helical structure of a drive cell and a compensation cell. 6 is a graph showing electro-optical characteristics of the liquid crystal display device according to the first embodiment for each helical angle of the helical structure of the compensation cell when the helical angle of the helical structure of the driving cell is fixed at 90 °. It is a disassembled perspective view of the liquid crystal display device by a 2nd Example. It is a graph which shows the viewing angle characteristic of the liquid crystal display device by a 2nd Example. It is a graph which shows the viewing angle characteristic of the liquid crystal display device by a 1st Example. It is a disassembled perspective view of the liquid crystal display device by a 3rd Example. It is a graph which shows the viewing angle characteristic of the liquid crystal display device by a 3rd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drive cell 11 Electrode substrate 12 Opposite substrate 13, 14 Electrode 15, 35 Liquid crystal layer 16, 36, 36A Liquid crystal molecule 30 Compensation cell 31 Lower substrate 32 Upper substrate 35 Liquid crystal layer 50, 51 Polarizing plate 52, 53 1/4 wavelength Board

Claims (11)

A driving cell in which liquid crystal molecules are twisted in a state where no electric field is generated and a liquid crystal layer having a helical structure is held, and an electrode for generating an electric field in a substrate in-plane direction is formed on the liquid crystal layer;
The liquid crystal layer is arranged on one surface of the drive cell and includes a liquid crystal layer in which liquid crystal molecules are twisted to show a helical structure, and the turning direction of the helical structure is opposite to the turning direction of the helical structure of the drive cell. Compensation means in which the alignment direction of the liquid crystal molecules positioned in the center with respect to the thickness direction of the liquid crystal layer is orthogonal to the alignment direction of the liquid crystal molecules positioned in the center with respect to the thickness direction of the liquid crystal layer of the drive cell;
A liquid crystal display device comprising polarizing plates disposed on both sides of a structure including the driving cell and compensation means. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules in the driving cell and the compensation unit have positive uniaxial optical anisotropy or positive biaxial optical anisotropy. 3. The liquid crystal display device according to claim 1, wherein a difference between the retardation of the driving cell and the retardation of the compensation unit in a state where no electric field is generated is 0.03 μm or less. The liquid crystal display device according to claim 1, wherein retardation of the compensation means and retardation of the driving cell in a state where no electric field is generated are 0.3 μm to 1 μm. The liquid crystal display device according to claim 1, wherein a helical angle of the helical structure of the compensation means is equal to or smaller than a helical angle of the helical structure of the drive cell. 5. The liquid crystal display device according to claim 1, wherein the helical angle of the helical structure of the driving cell is equal to the helical angle of the helical structure of the compensating means, and both are larger than 0 ° and not larger than 180 °. Furthermore, it is disposed between the driving cell and the polarizing plate on the driving cell side, and between the compensating means and the polarizing plate on the compensating means side, and is positive uniaxial optical anisotropy or positive biaxial The liquid crystal display device according to claim 1, further comprising a quarter-wave plate having optical anisotropy. The liquid crystal display device according to claim 7, wherein the quarter-wave plate has positive biaxial optical anisotropy, and the retardation in the thickness direction is 40% to 60% of the retardation in the in-plane direction. Liquid crystal molecules having positive uniaxial optical anisotropy or positive biaxial optical anisotropy hold a liquid crystal layer having a helical structure by twist alignment in a state where no electric field is generated. A driving cell in which an electrode for generating an inward electric field is formed;
A liquid crystal layer disposed on one surface of the drive cell and having a negative uniaxial optical anisotropy or a negative biaxial optical anisotropy and having a helical structure in which the liquid crystal molecules have a twist arrangement; Compensation means whose direction is opposite to the turning direction of the helical structure of the drive cell;
A liquid crystal display device comprising polarizing plates disposed on both sides of the layer structure of the driving cell and compensation means. The director direction of the liquid crystal molecules of the compensation means coincides with the optical axis direction of the liquid crystal molecules, and the alignment direction of the liquid crystal molecules located in the center with respect to the thickness direction of the liquid crystal layer of the compensation cell is the liquid crystal layer of the drive cell. The liquid crystal display device according to claim 9, wherein the liquid crystal display device is parallel to the alignment direction of liquid crystal molecules located in the center with respect to the thickness direction. Furthermore, it is disposed between the driving cell and the polarizing plate on the driving cell side, and between the compensating means and the polarizing plate on the compensating means side, and is positive uniaxial optical anisotropy or positive biaxial The liquid crystal display device according to claim 9, comprising a quarter-wave plate having optical anisotropy.

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