JP2018141870A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display that has liquid crystal molecules easily moving for bright display, has high responsiveness in stopping display of an image, and provides an electric field in a lateral direction to move liquid crystal.SOLUTION: A liquid crystal display comprises: a first substrate 13A on which a first alignment film 16 is formed; a second substrate 13B on which a second alignment film 17 is formed; and a drive electrode layer 20A that provides an electric field in a lateral direction to liquid crystal molecules L. When displaying an image in a liquid crystal layer, the liquid crystal display drives the drive electrode layer at a first frequency, and when not displaying the image, drives the drive electrode layer at a second frequency. The liquid crystal molecules have different positive and negative dielectric anisotropy for the first frequency and the second frequency. The second alignment film has strong binding force to maintain an initial alignment direction of the liquid crystal molecules as compared with the first alignment layer. When the drive electrode layer is driven at the first frequency, on the first alignment layer, an alignment direction of the liquid crystal molecules is changed according to magnitude of the electric field. When the drive electrode layer is driven at the second frequency, on the first alignment layer, the liquid crystal molecules are aligned in the initial alignment direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid crystal display device.

  As a driving method of a liquid crystal display device, there are methods such as TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), FFS (Fringe Field Switching) and the like. Among these, the IPS mode and the FFS mode change the alignment direction of the liquid crystal molecules by applying an electric field in a direction parallel to the substrate (lateral direction) to the liquid crystal molecules filled between the two substrates. It is carried out. Such IPS liquid crystal display devices and FFS liquid crystal display devices have excellent visual characteristics and are applied to a wide range of devices such as mobile phones and televisions.

  In the existing liquid crystal display device, the alignment direction of the liquid crystal molecules is forced so that the liquid crystal molecules are aligned along a predetermined direction in a state where an electric field is not applied. When the application of the electric field is stopped for the liquid crystal molecules, the alignment of the liquid crystal molecules displaced by the electric field is restored to the original alignment state, that is, the alignment state when no voltage is applied.

  As a method of further constraining the alignment direction of liquid crystal molecules, a method of forming an alignment film made of polyimide or the like on a substrate and rubbing the surface of the alignment film in a predetermined direction with a cloth such as rayon or cotton (rubbing method), A technique (photo-alignment method) that irradiates polarized ultraviolet rays to generate anisotropy on the surface of the polyimide film is employed. By these treatments, the liquid crystal molecules near the alignment film are strongly bound to the alignment film and are aligned in a certain direction. In a configuration in which liquid crystal molecules are aligned in a certain direction by applying a strong binding force to the liquid crystal molecules with an alignment film formed by rubbing or photo-alignment, the application of an electric field is stopped to stop displaying images. Then, the alignment of the liquid crystal molecules displaced by the strong binding force of the alignment film quickly returns to the original alignment state.

  In an IPS mode and FFS mode liquid crystal display device having an alignment film formed by a rubbing method or a photo-alignment method, when an electric field is applied, liquid crystal molecules far from the alignment film are twisted in a spiral shape, resulting in birefringence. An image is displayed. However, since an electric field parallel to the substrate is hardly generated immediately above the electrode, the liquid crystal molecules are difficult to move even if they are far from the alignment film, and light transmission is inhibited, so that a bright display cannot be achieved.

  On the other hand, a method has been proposed in which the orientation direction of liquid crystal molecules is directed to a desired direction by an external field (electric field, magnetic field, etc.) and the state is maintained (memory). In order to realize such an operation, it is necessary to eliminate alignment forcing (anchoring) on the substrate surface. Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-215421) has been proposed as a related technology for a configuration that weakens anchoring. In the configuration disclosed in Patent Document 1, in a liquid crystal cell in which a polymer brush is formed on a substrate subjected to a planarization process, and a liquid crystal is sandwiched between the substrates, the Tg (glass transition temperature) of the coexisting portion of the polymer brush and the liquid crystal. ) And a temperature at which the shape of the coexisting part can be freely changed, thereby realizing a zero-plane anchoring state.

  In the liquid crystal display device described in Patent Document 1, since anchoring is weak, liquid crystal molecules easily move when an electric field is applied. Therefore, even if an electric field parallel to the substrate is hardly generated immediately above the electrode, the liquid crystal molecules can move, light is easily transmitted, and a bright display can be achieved.

  However, in the liquid crystal display device described in Patent Document 1, since the binding force to the liquid crystal molecules by the alignment film is weak, the orientation of the liquid crystal molecules is not affected even when the application of the electric field is stopped in order to stop the image display. It takes time to recover the original alignment state. From such a background, high responsiveness is desired when image display is stopped.

  The present invention provides a liquid crystal display device that moves a liquid crystal by applying a horizontal electric field that has a high response when stopping image display even if liquid crystal molecules are easy to move for bright display.

  The liquid crystal display device according to the present invention includes a first alignment film on which a first alignment film is formed, and a second alignment film disposed so as to face the first alignment film with a space therebetween. A second substrate formed, a liquid crystal layer disposed between the first alignment film and the second alignment film, and transmitting or blocking light by driving liquid crystal molecules; and the first A driving electrode layer that provides an electric field in a direction parallel to the first substrate and the second substrate to the liquid crystal molecules, and the driving at a first frequency when displaying an image on the liquid crystal layer. A driving circuit that drives the electrode layer and drives the driving electrode layer at a second frequency different from the first frequency when an image is not displayed on the liquid crystal layer, and the liquid crystal molecule includes the first liquid crystal molecule. When the driving electrode layer is driven at the frequency and the second frequency, the induction is different in polarity. The second alignment film has a stronger binding force to maintain the initial alignment direction with respect to the liquid crystal molecules when the electric field is applied, compared to the first alignment film. When the drive electrode layer is driven at the first frequency, on the first alignment film side, the alignment direction of the liquid crystal molecules is in a plane parallel to the first substrate and the second substrate, When the driving electrode layer is driven at the second frequency, the liquid crystal molecules are aligned in the initial alignment direction when the driving electrode layer is driven at the second frequency. It is the state that was done.

  The first frequency may be lower than the second frequency, and the liquid crystal molecules have a positive dielectric anisotropy when the drive electrode layer is driven at the first frequency, The driving electrode layer may have a negative dielectric anisotropy when driven at a second frequency.

  The first frequency may be higher than the second frequency, and the liquid crystal molecules have negative dielectric anisotropy when the drive electrode layer is driven at the first frequency, When the drive electrode layer is driven at a second frequency, it may have a positive dielectric anisotropy.

  The initial alignment direction may be the alignment direction of liquid crystal molecules when the electric field is not applied, and may be the same direction on the first alignment film side and the second alignment film side.

  When the drive electrode layer is driven at the first frequency, the displacement of the alignment direction of the liquid crystal molecules with respect to the initial alignment direction of the liquid crystal layer from the second alignment film toward the first alignment film The angle may be gradually increased.

  A chiral agent may not be added to the liquid crystal layer.

  In the present invention, in a liquid crystal display device that moves a liquid crystal by applying an electric field in the horizontal direction, even when the liquid crystal molecules are easy to move for a bright display, the responsiveness when stopping image display can be improved.

It is sectional drawing which shows schematic structure of the liquid crystal display device which concerns on 1st Embodiment of this invention. FIG. 2 is a cross-sectional view showing a distribution of alignment directions of liquid crystal molecules when an image is not displayed on the liquid crystal layer of the liquid crystal display device of FIG. 1. FIG. 2 is a plan view showing the alignment direction of liquid crystal molecules on the strong anchoring alignment film side of the liquid crystal display device of FIG. 1. FIG. 2 is a plan view showing the alignment direction of liquid crystal molecules on the weak anchoring alignment film side when a drive electrode layer is driven at a first frequency of the liquid crystal display device of FIG. 1. 2 is a graph showing dielectric anisotropy with respect to frequency of a two-frequency drive liquid crystal used in the liquid crystal display device of FIG. 1. FIG. 2 is a schematic cross-sectional view illustrating an example of a polymer brush formed on a substrate as a weak anchoring alignment film in the liquid crystal display device of FIG. 1. It is a table | surface which shows the experimental result which concerns on 1st Embodiment. It is sectional drawing which shows schematic structure of the liquid crystal display device which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows distribution of the orientation direction of the liquid crystal molecule at the time of the non-display of the image in the liquid crystal layer of the liquid crystal display device of FIG. It is a graph which shows the dielectric anisotropy with respect to the frequency of the dual frequency drive liquid crystal used with the liquid crystal display device of FIG. It is sectional drawing which shows schematic structure of the liquid crystal display device which concerns on the modification of this invention.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings.

[First Embodiment]
As alignment films for controlling the alignment direction of liquid crystal molecules, there are a strong anchoring alignment film that has a strong force to constrain the alignment direction of liquid crystal molecules and a weak anchoring alignment film that has a weak force to restrict the alignment direction of liquid crystal molecules. is there. The present invention is directed to a single-sided weak anchoring type in which a strong anchoring alignment film is employed for one of the opposing alignment films and a weak anchoring alignment film is employed for the other.

  1 and 2 are cross-sectional views showing a schematic configuration of an IPS-driven liquid crystal display device 10 according to the first embodiment of the present invention. FIG. 1 shows liquid crystal molecules at the time of displaying an image on a liquid crystal layer. FIG. 2 shows the distribution of the alignment direction of the liquid crystal molecules when the image is not displayed on the liquid crystal layer. In the first embodiment of the present invention, an electric field is applied to the liquid crystal layer using a dual-frequency drive liquid crystal described later, both when an image is displayed and when it is not displayed. 1 and 2, the dotted line represents the electric field.

  As shown in FIGS. 1 and 2, the liquid crystal display device 10 includes a liquid crystal panel 11 and a backlight unit 12 that provides light to the liquid crystal panel 11.

  The backlight unit 12 uniformly irradiates light input from a light source (not shown) provided on the back surface of the liquid crystal panel 11 from the back surface 11r side of the liquid crystal panel 11 toward the front surface 11f side. For example, the backlight unit 12 propagates light input from a light source (not shown) provided at one end thereof in a direction parallel to the surface 11 f of the liquid crystal panel 11 and transmits the propagated light to the liquid crystal. A so-called edge light type that irradiates from the back surface 11r side of the panel 11 toward the front surface 11f side may be used. Alternatively, the backlight unit 12 may be a so-called direct type that irradiates light input from a light source provided on the back surface 11r side of the liquid crystal panel 11 from the back surface 11r side to the front surface 11f side of the liquid crystal panel 11. Good.

  The liquid crystal panel 11 includes a substrate (first substrate) 13A, a substrate (second substrate) 13B, a polarizing plate (first polarizing plate) 14A, a polarizing plate (second polarizing plate) 14B, and a drive electrode layer. 15, a weak anchoring alignment film (first alignment film) 16, a strong anchoring alignment film (second alignment film) 17, and a liquid crystal layer 18.

  The substrates 13A and 13B are each made of a substrate such as glass or resin, and are arranged in parallel with each other at a predetermined interval.

  The polarizing plate 14 </ b> A is provided on the side facing the backlight unit 12 or on the side opposite to the backlight unit 12 in the substrate 13 </ b> A disposed on the backlight unit 12 side. The polarizing plate 14 </ b> B is provided on the side opposite to the backlight unit 12 or the side facing the backlight unit 12 in the substrate 13 </ b> B disposed on the side away from the backlight unit 12.

  These polarizing plates 14A and 14B are arranged by the crossed Nicols method so that the transmission axis directions thereof are orthogonal to each other. For example, the transmission axis direction of one polarizing plate 14A, 14B is set to a direction X parallel to the substrate 13B.

  In this embodiment, the drive electrode layer 15 is provided on the substrate 13A on the backlight unit 12 side on the side away from the backlight unit 12. The drive electrode layer 15 has a plurality of electrode lines 20A arranged on the surface of the substrate 13A. Here, as shown in FIG. 3 and FIG. 4, each electrode line 20 </ b> A is formed in a straight line so that the long axis direction extends along the direction Y in a plane parallel to the surface of the substrate 13 </ b> A, for example. . In the drive electrode layer 15, such electrode lines 20A are arranged at regular intervals along a direction X orthogonal to the direction Y in a plane parallel to the surface of the substrate 13A.

  In such a drive electrode layer 15, when a predetermined voltage is applied to each electrode line 20A of the drive electrode layer 15, a direction in which the electrode lines 20A adjacent to each other are connected between the electrode lines 20A adjacent to each other. That is, an electric field in the direction X parallel to the substrates 13A and 13B is generated. In addition to FIGS. 1 and 2, the electric field is represented by a dotted line in FIG.

  In this embodiment, the weak anchoring alignment film 16 is formed on the side of the substrate 13A on the backlight unit 12 side away from the backlight unit 12, and the strong anchoring alignment film 17 is on the side away from the backlight unit 12. It is formed on the side of the substrate 13B facing the backlight unit 12.

  The strong anchoring alignment film 17 causes the liquid crystal molecules L of the liquid crystal layer 18 to substantially coincide with a predetermined alignment direction (direction Y in FIG. 1) in a plane parallel to the surfaces of the substrates 13A and 13B. Thus, the orientation direction is set. Compared with the weak anchoring alignment film 16, the strong anchoring alignment film 17 has a stronger restraining force to maintain the initial alignment direction with respect to the liquid crystal molecules when an electric field is applied. The weak anchoring alignment film 16 has a weak restraint force that maintains the initial orientation direction with respect to the liquid crystal molecules when an electric field is applied, and preferably has a restraint force of zero.

  The liquid crystal layer 18 is formed by filling a large number of liquid crystal molecules L between the weak anchoring alignment film 16 and the strong anchoring alignment film 17. The liquid crystal layer 18 is driven by changing the alignment direction of the liquid crystal molecules L by an electric field generated when a voltage is applied to each electrode line 20 </ b> A constituting the drive electrode layer 15. By changing the orientation of the liquid crystal molecules L in this way, the liquid crystal layer 18 partially transmits or blocks the light supplied from the backlight unit 12 to generate a display image.

  The liquid crystal display device 10 further includes a drive circuit 24. The drive circuit 24 drives the drive electrode layer 15 at a first frequency when an image is displayed on the liquid crystal layer 18, and the drive electrode at a second frequency different from the first frequency when an image is not displayed on the liquid crystal layer 18. Drive layer 15. Therefore, in this embodiment, an electric field is applied to the liquid crystal layer 18 when an image is displayed and when it is not displayed. However, when the drive circuit 24 does not drive the drive electrode layer 15 and does not apply an electric field to the liquid crystal layer 18, no image is displayed on the liquid crystal layer 18.

  The liquid crystal layer 18 is composed of a two-frequency drive liquid crystal, and the liquid crystal molecules L have dielectric anisotropy Δε having different positive and negative when the drive electrode layer 15 is driven at the first frequency and the second frequency. More specifically, as shown in FIG. 5, the liquid crystal molecules L have a positive dielectric anisotropy at a low frequency and a negative dielectric anisotropy at a high frequency. Such a dual frequency drive liquid crystal has, for example, two components having a chemical structure represented by the following formula.

  For the two-frequency driving liquid crystal having two exemplified components, when an electric field is applied at a frequency of 50 Hz, the dielectric anisotropy Δε is +6.1, and when an electric field is applied at a frequency of 10 kHz, the dielectric constant is anisotropic. The property Δε is −2.2. The crossover frequency is 150 Hz at 0 ° C., 10 kHz at room temperature, and 80 kHz at 50 ° C. The dual frequency drive liquid crystal constituting the liquid crystal layer 18 may include other components in addition to the above two components.

  In this embodiment, the first frequency for displaying an image is, for example, 50 Hz to 100 Hz, and the second frequency for stopping the display of an image is, for example, 100 kHz to 2000 kHz.

  FIG. 1 shows a distribution of orientation directions of liquid crystal molecules when the drive electrode layer 15 is driven at the first frequency (that is, when an image is displayed on the liquid crystal layer 18), and FIG. Shows the distribution of the alignment direction of the liquid crystal molecules when the drive electrode layer 15 is driven (that is, when no image is displayed on the liquid crystal layer 18). The initial alignment direction of the liquid crystal molecules when no electric field is applied to the liquid crystal layer 18 is the same as the direction shown in FIG. The initial alignment direction of the liquid crystal molecules is the same on the weak anchoring alignment film 16 side and the strong anchoring alignment film 17 side (that is, the liquid crystal molecules are homogeneous alignment).

  The strong anchoring alignment film 17 has a strong binding force for maintaining the initial alignment direction with respect to the liquid crystal molecules when an electric field is applied. Therefore, even if an electric field is generated by applying a voltage, the liquid crystal molecules L on the strong anchoring alignment film 17 side in the liquid crystal layer 18 have their major axis directions in a plane along the surfaces of the substrates 13A and 13B. The initial alignment state substantially matched with the alignment processing direction (direction Y) of the strong anchoring alignment film 17 is maintained. FIG. 3 shows the alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side. As is clear from the comparison between FIG. 1 and FIG. 2, the alignment of the liquid crystal molecules L on the strong anchoring alignment film 17 side regardless of whether the drive electrode layer 15 is driven at the first frequency or the second frequency. The direction hardly changes from the initial alignment direction.

  On the other hand, the weak anchoring alignment film 16 has a weak restraining force for maintaining the initial orientation direction with respect to the liquid crystal molecules when an electric field is applied, and preferably has a restraining force of zero. When an electric field is generated by applying a voltage at the first frequency (that is, when the drive electrode layer 15 is driven at the first frequency), when the applied voltage exceeds a threshold, FIG. As shown, on the weak anchoring alignment film 16 side, the alignment direction of the liquid crystal molecules L changes from the initial alignment direction according to the magnitude of the electric field in a plane parallel to the substrates 13A and 13B. This is because at the first frequency, the liquid crystal molecules L have a positive dielectric anisotropy and are easily aligned parallel to the direction of the electric field. On the other hand, the alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side is substantially the same as the initial alignment direction even when the drive electrode layer 15 is driven at the first frequency. When the layer 15 is driven, as shown in FIG. 1, the displacement angle of the alignment direction of the liquid crystal molecules with respect to the initial alignment direction of the liquid crystal layer gradually increases from the strong anchoring alignment film 17 toward the weak anchoring alignment film 16. Become. FIG. 4 shows the alignment direction of the liquid crystal molecules L on the weak anchoring alignment film 16 side when the drive electrode layer 15 is driven at the first frequency.

  On the other hand, when an electric field is generated by applying a voltage at the second frequency (that is, when the drive electrode layer 15 is driven at the second frequency), as shown in FIGS. On the weak anchoring alignment film 16 side, the liquid crystal molecules L maintain a state of being aligned in the initial alignment direction (or in a state of being aligned in the initial alignment direction). This is because at the second frequency, the liquid crystal molecules L have negative dielectric anisotropy and are easily aligned perpendicular to the direction of the electric field. At this time, since the alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side is substantially the same as the initial alignment direction, all the liquid crystal molecules L are aligned in the initial alignment direction in the entire liquid crystal layer 18. It is.

  In this embodiment, in the IPS driving type liquid crystal display device 10 that moves the liquid crystal by applying a horizontal electric field, the responsiveness when stopping the image display even if the liquid crystal molecules easily move for bright display. Can be increased. That is, since the binding force to the liquid crystal molecules L by the weak anchoring alignment film 16 is weak, even if it is difficult to generate an electric field parallel to the substrates 13A and 13B immediately above the electrode line 20A, on the weak anchoring alignment film 16 side. Since the liquid crystal molecules L can move and the drive electrode layer 15 is driven at the first frequency, the liquid crystal molecules L have positive dielectric anisotropy and are easily aligned in parallel to the direction of the electric field. The panel 11 as a whole is easy to transmit light and can display brightly. On the other hand, since the strong anchoring alignment film 17 has a strong binding force on the liquid crystal molecules L, the strong anchoring alignment film 17 side is driven regardless of whether the drive electrode layer 15 is driven at the first frequency or the second frequency. Then, the state in which the liquid crystal molecules L are aligned in the initial alignment direction is maintained.

  When the drive electrode layer 15 is driven at the second frequency, the liquid crystal molecules L have negative dielectric anisotropy and are easily aligned perpendicular to the direction of the electric field. Then, the state in which the liquid crystal molecules L are aligned in the initial alignment direction is maintained (or is aligned in the initial alignment direction). Therefore, when the drive electrode layer 15 is driven at the second frequency in order to stop the image display, the responsiveness when the image display is stopped is high. Therefore, the liquid crystal display device 10 according to this embodiment can achieve a bright display and has high responsiveness when stopping image display.

  The liquid crystal layer 18 may include a chiral agent that imparts twist to the liquid crystal molecules L in an initial state (a state where no electric field is applied). However, in order to promote the above effect, it is preferable that no chiral agent is added to the liquid crystal layer 18.

  The strong anchoring alignment film 17 is formed as follows, for example. First, an alignment film made of polyimide or the like is formed on the substrate 13B. Thereafter, a roller wound with a cloth made of rayon, cotton, or the like is rotated with the rotation speed and the distance between the roller and the substrate 13B kept constant, and the surface of the alignment film is rubbed in a predetermined direction (rubbing method). Alternatively, anisotropy is generated on the surface of the alignment film made of polyimide by irradiating polarized ultraviolet rays (photo-alignment method). The strong anchoring alignment film 17 in which the alignment direction is set by a rubbing method, a photo alignment method, or the like gives a stronger alignment forcing force to the liquid crystal molecules L than the weak anchoring alignment film 16.

  As the weak anchoring alignment film 16, for example, a film formed with a polymer brush can be used. The polymer brush is formed of a graft polymer chain having one end fixed to the surface of the substrate 13A and the other end extending in a direction away from the surface of the substrate 13A. Such a graft polymer chain may be generated so as to extend from the substrate 13A side, or a polymer chain having a predetermined length may be attached to the substrate 13A in advance. The initial alignment direction of the weak anchoring alignment film 16 may be determined by a known method such as a rubbing method.

一般式（１）において、ＸはＨ又はＣＨ３であり、ｍは正の整数であって、ポリマーブラシのＴｇ（ガラス転移温度）が−５℃以下であるものである。Ｒは炭素原子数１〜２０のアルキル基が好ましく、炭素原子数４〜２０のアルキル基がさらに好ましく、炭素原子数６〜１８のアルキル基がさらに好ましい。また、分岐を有するアルキル基も好適に用いられる。 Below, a specific example of a polymer brush is shown.
A polymer brush is represented by the following general formula (1), for example.

In the general formula (1), X is H or CH3, m is a positive integer, and the Tg (glass transition temperature) of the polymer brush is −5 ° C. or lower. R is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 4 to 20 carbon atoms, and further preferably an alkyl group having 6 to 18 carbon atoms. A branched alkyl group is also preferably used.

  FIG. 6 is a cross-sectional view showing an example of a polymer brush formed on a substrate as a weak anchoring alignment film. As shown in FIG. 6, the liquid crystal molecules L penetrate the surface layer portion of the polymer brush 2 formed on the substrate 13A, and the surface layer portion of the polymer brush 2 in contact with the liquid crystal molecules L is swollen (FIG. 6). The swollen state is not shown in the figure).

  In the present specification, the portion of the polymer brush 2 into which the liquid crystal molecules L have permeated is represented as the coexisting portion 4, and the portion of the polymer brush 2 into which the liquid crystal molecules L have not penetrated is represented as the polymer brush layer 3. In FIG. 6, the coexistence part 4 and the polymer brush layer 3 are clearly distinguished from the viewpoint of facilitating understanding of the present invention, but actually, the boundary between the coexistence part 4 and the polymer brush layer 3 is shown. It is difficult to distinguish.

  By using the polymer brush 2 as described above, the Tg (glass transition temperature) of the coexistence part 4 is considerably lower than the normal temperature, so that the shape of the coexistence part 4 can be freely changed at normal temperature. . Therefore, the state of the coexistence part 4 changes at the interface between the coexistence part 4 and the liquid crystal molecules L, and the liquid crystal molecules L are forced to be aligned in the horizontal direction with respect to the substrate 13A, while the alignment forcing force is applied in any direction in the horizontal plane. It is possible to realize a state without zero (zero surface anchoring state).

  The Tg of the coexistence part 4 differs depending on the types of the polymer brush 2 and the liquid crystal molecules L to be used, and thus cannot be uniquely defined, but is generally lower than the Tg of the polymer brush 2 alone. Further, the Tg of the coexistence portion 4 also varies depending on the degree of penetration of the liquid crystal molecules L into the polymer brush 2 (that is, the ratio between the polymer brush 2 and the liquid crystal molecules L). Specifically, in the coexistence part 4, the coexistence part 4 on the liquid crystal molecule L side where the ratio of the liquid crystal molecules L is high has a low Tg, and the coexistence part 4 on the polymer brush layer 3 side where the ratio of the liquid crystal molecules L is low has a high Tg. Become.

  However, the polymer brush 2 is represented by the above general formula (1). In the general formula (1), X is H or CH3, m is a positive integer, and the Tg of the polymer brush is −5 ° C. or less. Since the Tg of the coexistence part 4 can be made sufficiently lower than room temperature, the liquid crystal molecules L are forced to align in a plane parallel to the surface of the substrate 13A at room temperature. On the other hand, it is possible to realize a state (zero-plane anchoring state) that does not have an alignment forcing force in any direction in the horizontal plane.

  The surface of the substrate 13A may be flattened as necessary. The planarization process is not particularly limited, and can be performed using a method known in the technical field. An example of the planarization process is a method of forming a planarization film on the surface of the substrate 13A. For example, a UV curable transparent resin or the like may be applied to the surface of the substrate 13A and UV cured.

  An example of the substrate 13A is an array substrate. An example of the array substrate is an active matrix array substrate. In this active matrix array substrate, gate wiring and source wiring are generally arranged in a matrix form on a glass substrate, and an active element such as a thin layer transistor (TFT) is formed at the intersection. A pixel electrode is connected to the active element.

  An example of the substrate 13B facing the substrate 13A is a color filter substrate. Generally, a color filter substrate is formed by forming a black matrix on a glass substrate to prevent unnecessary light leakage, and then patterning colored layers of R (red), G (green), and B (blue). And a protective film is formed if necessary. When these substrates 13B are used, a transparent resin may be applied to the surface of the substrate 13B and cured to form a planarizing film.

  The polymer brush 2 formed on the substrate 13A preferably has a structure in which a number of graft polymer chains are dense and extend in a direction perpendicular to the surface of the substrate 13A.

  In general, a graft polymer chain having one end fixed to the surface of the substrate 13A has a string-like contraction structure when the graft density is low. However, since the polymer brush 2 has a high graft density, adjacent grafts Due to the interaction (steric repulsion) of the polymer chains, the structure extends in the direction perpendicular to the surface of the substrate 13A.

In the present specification, “high density” means the density of graft polymer chains that are so dense that steric repulsion occurs between adjacent graft polymer chains, and is generally 0.1 / nm ² or more, preferably 0. The density is from 1 to 1.2 lines / nm ² . Further, in this specification, the “density of graft polymer chains” means the number of graft polymer chains formed on the surface of the substrate 13A per unit area (nm ² ). However, the polymer brush 2 may have a number of graft polymer chains provided at a density lower than the “high density” shown above.

  The polymer brush 2 forms a layer of the polymer brush 2 on the surface of the substrate 13A. The layer thickness of the polymer brush 2 is not particularly limited, but is generally several tens of nm, specifically 1 nm or more and less than 100 nm, preferably 10 nm to 80 nm. Further, the layer of the polymer brush 2 has a size exclusion effect, and a substance having a certain size cannot pass through the layer of the polymer brush 2. Therefore, even if the thickness of the polymer brush 2 is reduced, it is possible to prevent impurities from entering the liquid crystal molecules L from the base.

  It does not specifically limit as a formation method of the polymer brush 2, It can carry out using a well-known method in the said technical field. Specifically, the polymer brush 2 can be formed by living radical polymerization of a radical polymerizable monomer. Here, in this specification, “living radical polymerization” means that the chain transfer reaction and termination reaction are not substantially caused in the radical polymerization reaction, and the chain growth terminal is active even after the radical polymerizable monomer is completely reacted. It means a polymerization reaction to be retained.

  In this polymerization reaction, the polymerization activity is retained at the end of the produced polymer even after the completion of the polymerization reaction, and when the radical polymerizable monomer is added, the polymerization reaction can be started again. Living radical polymerization allows the synthesis of a polymer having an arbitrary average molecular weight by adjusting the concentration ratio between the radical polymerizable monomer and the polymerization initiator, and the molecular weight distribution of the resulting polymer is extremely narrow. There are features.

  A typical example of living radical polymerization is atom transfer radical polymerization (ATRP). For example, atom transfer living radical polymerization of a radical polymerizable monomer is performed using a copper halide / ligand complex in the presence of a polymerization initiator. A radical polymerizable monomer is added to a growing radical that reversibly grows by pulling out the terminal halogen of the polymer by a copper halide / ligand complex, and the molecular weight distribution is achieved by reversible activation / deactivation with sufficient frequency. Is regulated.

  The radical polymerizable monomer used in the living radical polymerization has an unsaturated bond capable of performing radical polymerization in the presence of an organic radical, and examples thereof include t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, Methacrylate monomers such as nonyl methacrylate, lauryl methacrylate, n-octyl methacrylate; acrylate monomers such as t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, benzyl acrylate, lauryl acrylate, n-octyl acrylate; styrene, Styrene derivatives (for example, o-, m-, p-methoxystyrene, o-, m-, pt-butoxystyrene, o-, m-, p-chloromethyl Ethylene), vinyl esters (eg, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl acetate, etc.), vinyl ketones (eg, vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, etc.), N-vinyl compounds (For example, N-vinylpyrrolidone, N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, etc.), (meth) acrylic acid derivatives (for example, acrylonitrile, methacrylonitrile, acrylamide, isopropylacrylamide, methacrylamide, etc.), halogen And vinyl monomers such as vinyl chlorides (for example, vinyl chloride, vinylidene chloride, tetrachloroethylene, hexachloroprene, vinyl fluoride, etc.). These various radically polymerizable monomers may be used alone or in combination of two or more.

  The polymerization initiator is not particularly limited, and those generally known in living radical polymerization can be used. Examples of the polymerization initiator include p-chloromethylstyrene, α-dichloroxylene, α, α-dichloroxylene, α, α-dibromoxylene, hexakis (α-bromomethyl) benzene, benzyl chloride, benzyl bromide, 1- Benzyl halides such as bromo-1-phenylethane, 1-chloro-1-phenylethane; propyl-2-bromopropionate, methyl-2-chloropropionate, ethyl-2-chloropropionate, methyl- Carboxylic acids in which the α-position is halogenated such as 2-bromopropionate and ethyl-2-bromoisobutyrate (EBIB); Tosyl halides such as p-toluenesulfonyl chloride (TsCl); Tetrachloromethane, Tribromo Alkanes such as methane, 1-vinylethyl chloride, 1-vinylethyl bromide Ruharogen products; halogenated derivatives of phosphoric acid esters such as dimethyl phosphoric acid chloride and the like. These various polymerization initiators may be used alone or in combination of two or more.

  The copper halide that gives the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of the copper halide include CuBr, CuCl, and CuI. These various copper halides may be used alone or in combination of two or more.

  The ligand compound that gives the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of ligand compounds include triphenylphosphane, 4,4′-dinonyl-2,2′-dipyridine (dNbipy), N, N, N ′, N′N ″ -pentamethyldiethylenetriamine, 1,1,4 , 7,10,10-hexamethyltriethylenetetraamine, etc. These various ligand compounds may be used alone or in combination of two or more.

  The amount of the radically polymerizable monomer, polymerization initiator, copper halide and ligand compound may be appropriately adjusted according to the type of raw material used. In general, the amount of the radically polymerizable monomer is 1 mol of the polymerization initiator. Is 5 to 10,000 mol, preferably 50 to 5,000 mol, copper halide is 0.1 to 100 mol, preferably 0.5 to 100 mol, and the ligand compound is 0.2 to 200 mol, preferably 1.0 to 200 mol. is there.

  Living radical polymerization is usually performed without a solvent, but a solvent generally used in living radical polymerization may be used. Examples of usable solvents include benzene, toluene, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene, and the like. And organic solvents such as water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol and the like. These various solvents may be used alone or in combination of two or more. The amount of the solvent may be appropriately adjusted according to the type of raw material to be used. Generally, the solvent is 0.01 to 100 mL, preferably 0.05 to 10 mL with respect to 1 g of the radical polymerizable monomer. is there.

  Living radical polymerization can be carried out by immersing the substrate 13A in a polymer brush forming solution containing the above raw materials, or applying a polymer brush forming solution containing the above raw materials to the substrate 13A and heating. The heating conditions are not particularly limited, and may be appropriately adjusted according to the raw materials used. In general, the heating temperature is 60 to 150 ° C., and the heating time is 0.1 to 10 hours. This polymerization reaction is generally carried out at normal pressure, but it may be pressurized or reduced. The substrate 13A may be cleaned before the formation of the polymer brush 2 as necessary.

  The molecular weight of the polymer brush 2 formed by living radical polymerization can be adjusted depending on the reaction temperature, reaction time, and the type and amount of the raw material used, but generally the number average molecular weight is 500 to 1,000,000, preferably Can form a polymer brush 2 of 1,000 to 500,000. Further, the molecular weight distribution (Mw / Mn) of the polymer brush 2 can be controlled between 1.05 and 1.60.

  The polymer brush 2 may be formed on the surface of the substrate 13A through an immobilization film as necessary from the viewpoint of improving the adhesion between the substrate 13A and the polymer brush 2. The immobilization film is not particularly limited as long as it has excellent adhesion to the substrate 13A and the polymer brush 2, and a generally known film can be used for living radical polymerization. Examples of the immobilization film include a film formed from an alkoxysilane compound represented by the following general formula (2).

In the general formula (2), R ¹ is each independently a C1-C3 alkyl group or a C1-C3 alkoxy group, preferably a methyl group, an ethyl group, a methoxy group, or an ethoxy group, and R ² is Each independently represents a methyl group or an ethyl group, X is a halogen atom, preferably Br, and n is an integer of 3 to 10, more preferably an integer of 4 to 8.

  The polymer brush 2 is preferably covalently bonded to the immobilization film. If the immobilization film and the polymer brush 2 are connected by a covalent bond having a strong binding force, the polymer brush 2 can be sufficiently prevented from peeling off. As a result, the possibility of deterioration of the characteristics of the liquid crystal panel 11 is reduced, and the reliability of the liquid crystal panel 11 is improved.

  The method for forming the immobilization film is not particularly limited, and may be appropriately set depending on the material to be used. For example, the immobilization film can be formed by immersing the substrate 13A in the immobilization film forming solution, or by applying the immobilization film formation solution to the substrate 13A and then drying. Here, in order to form an immobilization film in a predetermined portion, masking may be performed on a portion where the immobilization film is not formed. The substrate 13A may be cleaned before the formation of the immobilization film as necessary.

  A method for injecting a liquid crystal material containing liquid crystal molecules L between the substrate 13B and the substrate 13A on which the polymer brush 2 is formed is not particularly limited, and a vacuum injection method using a capillary phenomenon, a liquid crystal dropping injection method ( A known method such as ODF (One Drop Filling) can be used. For example, when using a vacuum injection method utilizing capillary action, the following may be performed.

  First, the electrode layer 15 is formed on one substrate 13A by a known method. A spacer is formed on the other substrate 13B by a known method such as photolithography, and then an immobilization film (if necessary) and a polymer brush 2 are formed. Here, if necessary, it may be flattened by forming a flattening film or the like on the substrate 13A (other than the spacer portion), and an immobilization film (if necessary) and the polymer brush 2 may be formed thereon. .

  Next, after cleaning and drying one substrate 13B, a sealing material is applied, superimposed on the other substrate 13A, and the sealing material is cured and bonded by heating or UV irradiation. Here, it is necessary to open an injection port for injecting a liquid crystal material including the liquid crystal molecules L and the chiral agent in a part of the sealing material. Next, after injecting a liquid crystal material containing liquid crystal molecules L between the substrates 13A and 13B from the injection port by a vacuum injection method, the injection port is sealed.

[Example]
A substrate 13A provided with a weak anchoring alignment film 16 having a polymer brush 2 in a zero-plane anchoring state and a substrate 13B provided with a strong anchoring alignment film 17 made of rubbed polyimide are interposed via a sealing material. Pasted together. The cell gap was 3 μm.

  The liquid crystal display device 10 according to the first embodiment was manufactured by injecting the dual-frequency driving liquid crystal having the above-described two components into this structure at 100 ° C. and causing the liquid crystal molecules L to be homogeneously aligned. The display start response time Ton when a voltage of 10 V was applied to the liquid crystal layer 18 at 100 Hz (first frequency) from a state in which the liquid crystal display device 10 was maintained at 50 ° C. and no electric field was applied to the liquid crystal layer 18 was obtained. Further, for this liquid crystal display device 10, the display stop response time Toff when a voltage of 15 V was applied to the liquid crystal layer 18 at 1000 kHz (second frequency) was determined from the display state.

  Further, as a comparative example, a liquid crystal display device having normal liquid crystal instead of dual frequency driving liquid crystal was manufactured. When an electric field is applied, the liquid crystal molecules are twisted on the weak anchoring alignment film 16 side to display an image, and when no electric field is applied, the liquid crystal molecules are in an initial alignment state on the weak anchoring alignment film 16 side. Go back and stop displaying images. Also for the liquid crystal display device of the comparative example, the display start response time Ton is obtained when a voltage of 10 V is applied to the liquid crystal layer at 100 Hz (first frequency) from a state where the electric field is not applied to the liquid crystal layer while maintaining the temperature at 50 ° C. It was. Further, for the liquid crystal display device of this comparative example, the display stop response time Toff when the voltage applied to the liquid crystal layer was cut off was determined from the display state.

  The results of the above experiment are shown in FIG. As is clear from FIG. 7, the display stop response time Toff of the comparative example was shortened by 50% or more compared to the comparative example.

[Second Embodiment]
8 and 9 are cross-sectional views showing a schematic configuration of an IPS drive type liquid crystal display device 10 according to the second embodiment of the present invention. FIG. 8 shows liquid crystal molecules at the time of displaying an image on the liquid crystal layer. FIG. 9 shows a distribution in the alignment direction of liquid crystal molecules when an image is not displayed on the liquid crystal layer. In the second embodiment of the present invention, an electric field is applied to the liquid crystal layer by using a dual-frequency driving liquid crystal different from that of the first embodiment, both when an image is displayed and when not displayed. 1 and 2, the dotted line represents the electric field. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals in the drawing, and the description thereof is omitted.

  The liquid crystal display device 10 of this embodiment is substantially the same as the liquid crystal display device 10 of the first embodiment, except for the type of dual frequency drive liquid crystal that forms the liquid crystal layer 18. However, the strong anchoring alignment film 17 causes the liquid crystal molecules L of the liquid crystal layer 18 to have a major axis direction substantially in a predetermined alignment direction (direction X in FIG. 8) in a plane parallel to the surfaces of the substrates 13A and 13B. The orientation direction is set so as to match.

  Similarly to the first embodiment, each electrode line 20A of the drive electrode layer 15 is formed in a straight line such that the long axis direction extends along the direction Y in a plane parallel to the surface of the substrate 13A, for example. . In the drive electrode layer 15, such electrode lines 20A are arranged at regular intervals along a direction X orthogonal to the direction Y in a plane parallel to the surface of the substrate 13A.

  The drive circuit 24 drives the drive electrode layer 15 at a first frequency when an image is displayed on the liquid crystal layer 18, and the drive electrode at a second frequency different from the first frequency when an image is not displayed on the liquid crystal layer 18. Drive layer 15. Therefore, in this embodiment, an electric field is applied to the liquid crystal layer 18 both when an image is displayed and when it is not displayed. However, when the drive circuit 24 does not drive the drive electrode layer 15 and does not apply an electric field to the liquid crystal layer 18, no image is displayed on the liquid crystal layer 18.

  The liquid crystal layer 18 is composed of a two-frequency drive liquid crystal, and the liquid crystal molecules L have dielectric anisotropy Δε having different positive and negative when the drive electrode layer 15 is driven at the first frequency and the second frequency. More specifically, as shown in FIG. 10, the liquid crystal molecules L have a negative dielectric anisotropy at a low frequency and a positive dielectric anisotropy at a high frequency. This is the opposite of the first embodiment.

  In this embodiment, the first frequency for displaying an image is, for example, 100 kHz to 2000 kHz, and the second frequency for stopping the display of an image is, for example, 50 Hz to 100 Hz.

  FIG. 8 shows the distribution in the orientation direction of the liquid crystal molecules when the drive electrode layer 15 is driven at the first frequency (that is, when an image is displayed on the liquid crystal layer 18), and FIG. 9 shows the second frequency. Shows the distribution of the alignment direction of the liquid crystal molecules when the drive electrode layer 15 is driven (that is, when no image is displayed on the liquid crystal layer 18). The initial alignment direction of the liquid crystal molecules when no electric field is applied to the liquid crystal layer 18 is the same as the direction shown in FIG. The initial alignment direction of the liquid crystal molecules is the same on the weak anchoring alignment film 16 side and the strong anchoring alignment film 17 side (that is, the liquid crystal molecules are homogeneous alignment).

  The strong anchoring alignment film 17 has a strong binding force for maintaining the initial alignment direction with respect to the liquid crystal molecules when an electric field is applied. Therefore, even if an electric field is generated by applying a voltage, the liquid crystal molecules L on the strong anchoring alignment film 17 side in the liquid crystal layer 18 have their major axis directions in a plane along the surfaces of the substrates 13A and 13B. The initial alignment state substantially matched with the alignment processing direction (direction X) of the strong anchoring alignment film 17 is maintained. The alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side is always the direction shown in FIG. As is clear from the comparison between FIG. 8 and FIG. 9, the alignment of the liquid crystal molecules L on the strong anchoring alignment film 17 side regardless of whether the drive electrode layer 15 is driven at the first frequency or the second frequency. The direction hardly changes from the initial alignment direction.

  On the other hand, the weak anchoring alignment film 16 has a weak restraining force for maintaining the initial orientation direction with respect to the liquid crystal molecules when an electric field is applied, and preferably has a restraining force of zero. When an electric field is generated by applying a voltage at the first frequency (that is, when the drive electrode layer 15 is driven at the first frequency), when the applied voltage exceeds a threshold, FIG. As shown, on the weak anchoring alignment film 16 side, the alignment direction of the liquid crystal molecules L changes from the initial alignment direction according to the magnitude of the electric field in a plane parallel to the substrates 13A and 13B. This is because at the first frequency, the liquid crystal molecules L have negative dielectric anisotropy and are easily aligned perpendicular to the direction of the electric field. On the other hand, the alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side is substantially the same as the initial alignment direction even when the drive electrode layer 15 is driven at the first frequency. When the layer 15 is driven, as shown in FIG. 8, the displacement angle of the alignment direction of the liquid crystal molecules with respect to the initial alignment direction of the liquid crystal layer gradually increases from the strong anchoring alignment film 17 toward the weak anchoring alignment film 16. Become. The alignment direction of the liquid crystal molecules L on the weak anchoring alignment film 16 side when the drive electrode layer 15 is driven at the first frequency is the direction shown in FIG.

  On the other hand, when an electric field is generated by applying a voltage at the second frequency (that is, when the drive electrode layer 15 is driven at the second frequency), as shown in FIGS. On the weak anchoring alignment film 16 side, the liquid crystal molecules L maintain a state of being aligned in the initial alignment direction (or in a state of being aligned in the initial alignment direction). This is because at the second frequency, the liquid crystal molecules L have a positive dielectric anisotropy and are easily aligned parallel to the direction of the electric field. At this time, since the alignment direction of the liquid crystal molecules L on the strong anchoring alignment film 17 side is substantially the same as the initial alignment direction, all the liquid crystal molecules L are aligned in the initial alignment direction in the entire liquid crystal layer 18. It is.

  In this embodiment, in the IPS driving type liquid crystal display device 10 that moves the liquid crystal by applying a horizontal electric field, the responsiveness when stopping the image display even if the liquid crystal molecules easily move for bright display. Can be increased. That is, since the binding force to the liquid crystal molecules L by the weak anchoring alignment film 16 is weak, even if it is difficult to generate an electric field parallel to the substrates 13A and 13B immediately above the electrode line 20A, on the weak anchoring alignment film 16 side. Since the liquid crystal molecules L can move and the drive electrode layer 15 is driven at the first frequency, the liquid crystal molecules L have negative dielectric anisotropy and are easily aligned perpendicular to the direction of the electric field. The panel 11 as a whole is easy to transmit light and can display brightly. On the other hand, since the strong anchoring alignment film 17 has a strong binding force on the liquid crystal molecules L, the strong anchoring alignment film 17 side is driven regardless of whether the drive electrode layer 15 is driven at the first frequency or the second frequency. Then, the state in which the liquid crystal molecules L are aligned in the initial alignment direction is maintained.

  When the drive electrode layer 15 is driven at the second frequency, the liquid crystal molecules L have a positive dielectric anisotropy and are easily aligned in parallel to the direction of the electric field. Then, the state in which the liquid crystal molecules L are aligned in the initial alignment direction is maintained (or is aligned in the initial alignment direction). Therefore, when the drive electrode layer 15 is driven at the second frequency in order to stop the image display, the responsiveness when the image display is stopped is high. Therefore, the liquid crystal display device 10 according to this embodiment can achieve a bright display and has high responsiveness when stopping image display.

  The liquid crystal layer 18 may include a chiral agent that imparts twist to the liquid crystal molecules L in an initial state (a state where no electric field is applied). However, in order to promote the above effect, it is preferable that no chiral agent is added to the liquid crystal layer 18.

The preferred embodiments of the present invention have been described in detail above, but various modifications and equivalent embodiments are possible from those having ordinary knowledge in the technical field.
Therefore, the scope of right of the present invention is not limited to this, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the claims are also included in the present invention.

  For example, in the above-described embodiment, specific formation methods are exemplified for the strong anchoring alignment film 17 and the weak anchoring alignment film 16, but the present invention is not limited thereto. That is, if the strong anchoring alignment film 17 and the weak anchoring alignment film 16 have different alignment forcing forces to correct the alignment direction of the liquid crystal molecules L when an electric field is applied, the strong anchoring alignment film 17 is different. The weak anchoring alignment film 16 may be formed by any other method and material.

  In the above embodiment, the substrate 13A provided with the drive electrode layer 15 is provided on the backlight unit 12 side, and the substrate 13B facing the substrate 13A is provided on the light emission side. However, as shown in FIG. 11, the substrate 13A on which the drive electrode layer 15 is provided may be provided on the light emission side, and the substrate 13B facing the substrate 13A may be provided on the backlight unit 12 side. In this case, the color filter is provided on the substrate 13A.

  In the above embodiment, the liquid crystal display device 10 is an IPS driving method. However, the present invention is not limited to the IPS driving method, and an FFS driving method, which applies an electric field in a direction parallel to the substrate (lateral direction) to liquid crystal molecules, AFFS. It can also be used in a liquid crystal display device of (Advanced Friedel Field Switching) driving method.

2 Polymer brush 3 Polymer brush layer 4 Coexistence part 10 Liquid crystal display device 11 Liquid crystal panel 11f Front surface 11r Back surface 12 Backlight unit 13A Substrate (first substrate)
13B substrate (second substrate)
14A Polarizing plate (first polarizing plate)
14B Polarizing plate (second polarizing plate)
15 Drive electrode layer 16 Weak anchoring alignment film (first alignment film)
17 Strong anchoring alignment film (second alignment film)
18 Liquid crystal layer 20A Electrode line L Liquid crystal molecule

Claims (6)

A first substrate on which a first alignment film is formed;
A second substrate on which a second alignment film is formed so as to be opposed to the first alignment film with a space therebetween;
A liquid crystal layer disposed between the first alignment film and the second alignment film and transmitting or blocking light by driving liquid crystal molecules;
A driving electrode layer provided on the first substrate and applying an electric field to the liquid crystal molecules in a direction parallel to the first substrate and the second substrate;
The drive electrode layer is driven at a first frequency when an image is displayed on the liquid crystal layer, and the drive electrode layer is driven at a second frequency different from the first frequency when an image is not displayed on the liquid crystal layer. Drive circuit
The liquid crystal molecules have dielectric anisotropy with different positive and negative when the drive electrode layer is driven at the first frequency and the second frequency,
The second alignment film has a stronger binding force to maintain the initial alignment direction with respect to the liquid crystal molecules when the electric field is applied, compared to the first alignment film.
When the drive electrode layer is driven at the first frequency, on the first alignment film side, the alignment direction of the liquid crystal molecules is in a plane parallel to the first substrate and the second substrate, It changes according to the magnitude of the electric field from the initial orientation direction,
A liquid crystal display device in which liquid crystal molecules are aligned in the initial alignment direction on the first alignment film side when the drive electrode layer is driven at the second frequency. The first frequency is lower than the second frequency;
The liquid crystal molecules have a positive dielectric anisotropy when the drive electrode layer is driven at the first frequency, and a negative dielectric constant when the drive electrode layer is driven at the second frequency. The liquid crystal display device according to claim 1, which has anisotropy. The first frequency is higher than the second frequency;
The liquid crystal molecules have a negative dielectric anisotropy when the driving electrode layer is driven at the first frequency, and a positive dielectric constant when the driving electrode layer is driven at the second frequency. The liquid crystal display device according to claim 1, which has anisotropy.   The initial alignment direction is an alignment direction of liquid crystal molecules when the electric field is not applied, and is the same direction on the first alignment film side and the second alignment film side. The liquid crystal display device according to any one of the above.   When the drive electrode layer is driven at the first frequency, the displacement of the alignment direction of the liquid crystal molecules with respect to the initial alignment direction of the liquid crystal layer from the second alignment film toward the first alignment film The liquid crystal display device according to claim 1, wherein the angle gradually increases.   The liquid crystal display device according to claim 1, wherein no chiral agent is added to the liquid crystal layer.

Images