JP2014228820A - Liquid crystal element and driving method thereof, and liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving method for a liquid crystal element having excellent sharpness.SOLUTION: The driving method includes: (a) applying a voltage equal to or higher than a first threshold voltage between a first electrode and a second electrode to thereby transfer the alignment state of liquid crystal molecules from a spray twist alignment state where the liquid crystal molecules are twisted in a second turning direction by α° to a twist twisted nematic alignment state where the liquid crystal molecules are twisted in the second turning direction by (360-α)°; (b) applying, between the first electrode and the second electrode, a voltage equal to or higher than a second threshold voltage higher than the first threshold voltage to thereby transfer the alignment state of the liquid crystal molecules from the twisted nematic alignment state where the liquid crystal molecules are twisted in the second turning direction by (360-α)° to the twisted nematic alignment state where the liquid crystal molecules are twisted in a first turning direction by (180-α)°.

Description

  The present invention relates to a liquid crystal element including an optically active substance (chiral agent) in a liquid crystal layer, a driving method thereof, and a liquid crystal device.

  An invention of a twisted nematic (TN) type liquid crystal display element having a good display contrast and a wide effective viewing angle range is disclosed (for example, see Patent Document 1). The liquid crystal display element described in Patent Document 1 is in a direction opposite to the turning direction (first turning direction) of the liquid crystal molecules regulated by the combination of the orientation treatment directions applied to the pair of transparent electrode substrates that sandwich the liquid crystal layer ( The liquid crystal molecules are characterized in that the liquid crystal molecules are twisted in the second rotation direction) and the alignment treatment is performed so that the pretilt angles of the liquid crystal molecules in contact with the transparent electrode substrates are different from each other. Thereby, a good display contrast and a wide effective viewing angle range can be obtained.

  In the liquid crystal display element described in Patent Document 1, the electro-optical characteristics are improved, and the effect of reverse twist arrangement is achieved even when the twist angle (twist angle) in the first turning direction is set in the range of 91 to 100 °. As a result, the same electro-optical characteristics as those of the TN liquid crystal display element by the 90 ° rubbing method can be obtained. Further, since the pretilt angles are different from each other, the occurrence of disclination due to inadequate alignment of liquid crystal molecules is prevented, and a good display quality can be obtained.

  There is also a disclosure of an invention of a liquid crystal device in which a twist direction of 90 ° or less induced by an alignment film is opposite to a twist direction of a liquid crystal material in a nematic liquid crystal layer to which a chiral agent is added (see, for example, Patent Document 2) ). The liquid crystal device having this configuration can realize a reduction in driving voltage.

  An invention of a liquid crystal element that enables a significant reduction in drive voltage is known (see, for example, Patent Document 3). The liquid crystal element described in Patent Document 3, which is one of the results of the inventors' research, is a liquid crystal material induced by a chiral agent and a twist direction of a liquid crystal material determined by a combination of an alignment treatment direction and a pretilt angle of a set of alignment films. It is produced so that the twist direction of the material is opposite. The alignment state of the liquid crystal molecules generated under the influence of the chiral agent is a spray twist structure. The alignment state of the liquid crystal molecules defined by the combination of the alignment treatment direction and the pretilt angle is called a reverse twist structure.

  The spray twist structure is slightly stable when no voltage is applied, but the reverse twist structure is stable when the voltage is applied. For this reason, the spray twist structure can be changed to the reverse twist structure by applying a voltage.

  However, the liquid crystal element described in Patent Document 3 has a sharpness (steepness of change in light transmittance with respect to an applied voltage) that is equivalent to or slightly superior to that of a normal TN liquid crystal display element, and has a duty drive (simple matrix). When applied to driving), it is difficult to increase the display capacity.

  An invention relating to a super twisted nematic (STN) type liquid crystal display element in which the twist angle of liquid crystal molecules is made larger than that in a TN type liquid crystal display element, sharpness is improved, and large capacity display is possible while being duty-driven. Is known (see, for example, Patent Document 4). However, in the STN type liquid crystal display element, coloring occurs due to birefringence, and it is difficult to perform monochrome display. In order to cope with this problem, the invention described in Patent Document 4 discloses means for realizing monochrome display by stacking liquid crystal cells that compensate for coloring.

  However, when the compensation cell is used, the manufacturing cost of the liquid crystal cell and the thickness and weight of the liquid crystal display element are approximately doubled.

  Although an optical compensation film can be used instead of the compensation cell, the optical compensation film is not inexpensive. Furthermore, when the display environment temperature of the liquid crystal display element changes, the retardation of the liquid crystal layer in the driving cell changes accordingly, but the retardation of the optical compensation film hardly changes, so that optimal compensation is not performed. There are problems that coloring is not prevented and display contrast is lowered.

  The invention described in Patent Document 4 also has a problem common to STN type liquid crystal display elements. The STN type liquid crystal display element has a large display performance dependency with respect to changes in the gap and pretilt angle of the liquid crystal cell, and display unevenness is likely to occur due to slight cell thickness unevenness and a difference in pretilt angle. For this reason, the management of the manufacturing process is strict (the manufacturing margin is narrow), and the yield is low. In the STN type liquid crystal display element, a high pretilt angle of about 5 ° to 9 ° is required, and it is difficult to obtain a uniform pretilt angle, so management of the rubbing process is particularly important.

  Furthermore, the STN type liquid crystal display element has a large viewing angle dependency, and the display changes only by slightly changing the viewing angle direction. In particular, when the viewing angle is changed in the vertical direction, the display is inverted. In addition, the STN type liquid crystal display element requires a response time compared to the TN type liquid crystal display element. For example, the response time of a TN type liquid crystal display element at room temperature is about 30 msec, while that of an STN type liquid crystal display element is about 200 msec.

  The inventors of the present application have invented a liquid crystal display device having excellent sharpness (see, for example, Patent Document 5).

Japanese Patent No. 2510150 JP 2000-199903 A JP 2007-293278 A Japanese Patent Laid-Open No. 03-111812 JP 2011-164273 A

  The object of the present invention is, for example, (1) a spray twist arrangement state that twists in the second turning direction at a twist angle of 90 °, (2) a super twist nematic arrangement state that twists in the second turning direction at a twist angle of 270 °, and (3) To provide a liquid crystal element that has each of the reverse twist nematic alignment states twisted in the first turning direction at a twist angle of 90 °, has excellent sharpness, a driving method thereof, and a liquid crystal device.

  According to one aspect of the present invention, a first substrate including a first electrode and subjected to an alignment process is disposed opposite to and parallel to the first substrate, and includes a second electrode and includes a second electrode. Two substrates, a liquid crystal layer that is disposed between the first substrate and the second substrate, includes an optically active substance, and is twist-aligned. When the twist direction of the liquid crystal molecules when forming the uniform twist structure in combination is the first swivel direction, the optically active substance is in the liquid crystal molecules of the liquid crystal layer in the second swirl direction opposite to the first swirl direction. The first and second substrates are oriented so that a pretilt angle of 0.1 ° or more and 5 ° or less is expressed, and when 70 ° ≦ α ° ≦ 110 °, The liquid crystal molecules in the liquid crystal layer have a spray twist arrangement twisted by α ° in the second swivel direction. A liquid crystal element that can take three states: a row state, a twisted nematic arrangement state twisted by (360-α) ° in the second turning direction, and a twisted nematic arrangement state twisted by (180-α) ° in the first turning direction. Is provided.

  According to another aspect of the present invention, a first substrate including a first electrode and subjected to an alignment treatment is disposed opposite to and parallel to the first substrate, and includes a second electrode. A second liquid crystal substrate, a liquid crystal layer disposed between the first substrate and the second substrate, including an optically active material, and twist-aligned, and the first and second substrates. When the twist direction of the liquid crystal molecules when forming the uniform twist structure by the combination of the alignment treatments is the first rotation direction, the optically active substance is in the liquid crystal molecules of the liquid crystal layer, the first rotation direction opposite to the first rotation direction. The first and second substrates are oriented so that a pretilt angle of 0.1 ° or more and 5 ° or less is expressed, and 70 ° ≦ α ° ≦ 110 °. When the liquid crystal molecules of the liquid crystal layer are twisted α ° in the second swirl direction. Liquid crystal that can take three states: an twist arrangement state, a twist nematic arrangement state twisted by (360-α) ° in the second turning direction, and a twist nematic arrangement state twisted by (180-α) ° in the first turning direction. A method for driving an element, comprising: (a) applying a voltage equal to or higher than a first threshold voltage between the first electrode and the second electrode, and changing the alignment state of the liquid crystal molecules to the second rotation. A transition from a spray twist arrangement state twisted by α ° in the direction to a twist nematic arrangement state twisted by (360−α) ° in the second turning direction; and (b) the first electrode and the second electrode In the meantime, a voltage equal to or higher than the second threshold voltage higher than the first threshold voltage is applied, and the alignment state of the liquid crystal molecules is changed from the twisted nematic alignment state twisted by (360−α) ° in the second rotation direction. In the first turning direction (18 The driving method of the liquid crystal element and a step of transferring the-.alpha.) ° twisted twisted nematic alignment state is provided.

  Further, according to another aspect of the present invention, a first substrate including a first electrode and subjected to an alignment process is disposed opposite to and parallel to the first substrate, and includes a second electrode. A second liquid crystal substrate, a liquid crystal layer disposed between the first substrate and the second substrate, including an optically active material, and twist-aligned, and the first and second substrates. When the twist direction of the liquid crystal molecules when forming the uniform twist structure by the combination of the alignment treatments is the first rotation direction, the optically active substance is in the liquid crystal molecules of the liquid crystal layer, the first rotation direction opposite to the first rotation direction. The first and second substrates are oriented so that a pretilt angle of 0.1 ° or more and 5 ° or less is expressed, and 70 ° ≦ α ° ≦ 110 °. When the liquid crystal molecules of the liquid crystal layer are twisted α ° in the second swirl direction. Liquid crystal that can take three states: an twist arrangement state, a twist nematic arrangement state twisted by (360-α) ° in the second turning direction, and a twist nematic arrangement state twisted by (180-α) ° in the first turning direction. And a control device that controls driving of the liquid crystal element, wherein the control device (a) applies a voltage equal to or higher than a first threshold voltage between the first electrode and the second electrode. Applying and transferring the alignment state of the liquid crystal molecules from a spray twist alignment state twisted by α ° in the second turning direction to a twisted nematic alignment state twisted by (360−α) ° in the second turning direction; (B) A voltage equal to or higher than a second threshold voltage higher than the first threshold voltage is applied between the first electrode and the second electrode, and the alignment state of the liquid crystal molecules is changed to the second rotation. Twist twisted in the direction (360-α) ° A liquid crystal device for driving the liquid crystal element in a driving method having a step of transferring from matic arrangement state in twisted nematic alignment state twisted the in the first turning direction (180-α) ° is provided.

  According to the present invention, for example, (1) a spray twist arrangement state twisted in the second turning direction at a twist angle of 90 °, (2) a super twist nematic arrangement state twisted in the second turning direction at a twist angle of 270 °, and (3) It is possible to provide a liquid crystal element, a driving method thereof, and a liquid crystal device that have excellent sharpness by taking each arrangement state of a reverse twist nematic alignment state twisted in the first turning direction at a twist angle of 90 °.

FIG. 1 is a flowchart showing a method of manufacturing a liquid crystal display device according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the liquid crystal display device according to the first embodiment. FIG. 3 is a photograph showing a spray twist structure state and a reverse twist structure state of the liquid crystal display device according to the first embodiment. FIG. 4 is a schematic diagram showing the twist direction and angle of the liquid crystal molecules 14a viewed from the substrate normal direction on the upper substrate 10a side of the liquid crystal display device according to the first embodiment. FIG. 5 is a graph showing the electro-optical characteristics of the liquid crystal display element according to the first embodiment. 6A to 6D are graphs showing the electro-optical characteristics of the liquid crystal display elements according to the first to fourth embodiments, respectively. FIG. 7 shows the electro-optical characteristics of the liquid crystal display element according to the fifth embodiment in each of the 90 ° left-twisted spray twist arrangement state, the 270 ° left-twisted STN arrangement state, and the 90 ° right-twisted RTN arrangement state. It is a graph to show. FIG. 8A is a graph showing a twist angle of liquid crystal molecules in the liquid crystal display device according to the fifth embodiment, and FIG. 8B is a graph showing a twist angle of liquid crystal molecules in a 90 ° right twist RTN alignment state. 9A and 9B are graphs showing the free energy of the liquid crystal display element according to the fifth embodiment in each of the 90 ° spray twist arrangement state, the 270 ° STN arrangement state, and the 90 ° RTN arrangement state. 10A and 10B are examples of waveforms of drive voltages applied between the upper and lower electrodes. FIG. 11 is a flowchart illustrating a method of driving the liquid crystal display element according to the embodiment. FIG. 12 is a graph showing spectral characteristics of white display and black display in the liquid crystal display device according to the fifth embodiment.

  The twist direction of the liquid crystal molecules (first rotation direction) determined by the combination of the alignment treatment direction of the pair of alignment films and the pretilt angle is opposite to the twist direction of the liquid crystal molecules (second rotation direction) induced by the chiral agent. For example, the liquid crystal layer can be in a state where the liquid crystal molecules are twisted in each direction by applying a physical action to the liquid crystal layer, for example, by adding or removing a voltage higher than the saturation voltage of the electro-optical characteristics. The liquid crystal display element that is realized instead is called a reverse twisted nematic (RTN) type liquid crystal display element. The first turning direction is a turning direction in which liquid crystal molecules are twisted with a uniform twist structure when no chiral agent is added to the liquid crystal layer.

  The RTN liquid crystal display element has a feature that low power consumption driving is realized because the threshold of the driving voltage can be lowered. The inventors of the present application have studied RTN type liquid crystal display devices manufactured under various conditions for the purpose of reducing the threshold of the driving voltage, and disclosed the results in Patent Document 3. As a result of the present inventors' study, the reverse twist structure state becomes more stable as the pretilt angle is higher, and the threshold of the drive voltage is lowered as the chiral agent pitch is shorter, but the reverse twist structure state becomes unstable. It was found.

  Patent Document 3 describes the results of research centered on high pretilt angle conditions in which the reverse twist structure state is stable. Experiments were also conducted for low pretilt angle conditions. However, since the reverse twist structure state is originally an unstable liquid crystal molecular arrangement state, the short pitch condition (for example, the chiral pitch is 20 μm or less) that makes the reverse twist structure state more unstable. Was not considered.

  The present invention is a result of research on a reverse twist structure state in a very unstable condition such as a low pretilt angle and a short pitch condition, which is normally excluded from research. Under these unique conditions, the present inventors have discovered an unexpected phenomenon in which the threshold voltage of the driving voltage of the liquid crystal display element is relatively high and the sharpness is extremely steep, and disclosed in Patent Document 5. However, the reason why such a phenomenon occurs has not been clarified so far.

  As a result of diligent research, the inventors of the present application have found a mechanism for causing this phenomenon, and have invented a liquid crystal element, a driving method thereof, and a liquid crystal device according to the present application.

  FIG. 1 is a flowchart showing a method of manufacturing a liquid crystal display device according to the first embodiment.

  Two transparent substrates on which a transparent conductive film, for example, an ITO (indium tin oxide) film is formed are prepared. The transparent substrate is made of, for example, soda lime glass having a thickness of 0.7 mm. The thickness of the ITO film is, for example, 1500 mm. These transparent substrates are washed and dried (step S101), and the ITO film is patterned using a photolithography process to form a transparent electrode (ITO electrode) on the transparent substrate (glass substrate) (step S102). Etching of the ITO electrode pattern is performed, for example, by wet etching using an etchant containing ferric chloride as a main component.

  On the glass substrate, an alignment film material is applied so as to cover the ITO electrode (step S103). The alignment film material is applied using, for example, flexographic printing. Inkjet printing may be used. For example, SE-130 manufactured by Nissan Chemical Co., Ltd. is used as the alignment film material. SE-130 is a horizontal alignment film material for a TN liquid crystal display element that exhibits a low pretilt angle. The alignment film material is not limited to this.

  The glass substrate coated with the alignment film material is placed on a hot plate and pre-baked (pre-baked) at 100 ° C. for 3 minutes (step S104). Then, main baking is performed in a clean oven at 200 ° C. for 1 hour (step S105). Thus, an alignment film covering the ITO electrode is formed (steps S103 to S105).

  Next, a rubbing process (orientation process) is performed (step S106). In order to align (orient) the liquid crystal molecules in contact with the substrate in one direction, a cylindrical roll wound with a cloth is rotated at high speed to rub on the alignment film.

  In order to keep the thickness of the liquid crystal layer (inter-substrate distance) constant, a gap control agent is sprayed on one glass substrate surface by a dry spraying method (step S107). As the gap control agent, a silica-based material having a particle size of 5 μm (High Presica UF manufactured by Ube Nitto Kasei Co., Ltd.) was used. Plastic balls can also be used.

  A sealant is printed on the other glass substrate surface to form a main seal pattern (step S108). For example, a glass fiber having a particle size of 5 μm is added to ES-7500 manufactured by Mitsui Chemicals, which is a thermosetting sealant, and printing is performed by a screen printing method. A sealant can also be applied using a dispenser. A photo-curing sealant or a light / heat combination curable sealant may be used.

  A conductive material including a plastic ball (Au ball) plated with gold is printed at a predetermined position on the substrate surface on which the main seal pattern is formed to form a conductive material pattern. For example, ES-7500 to which glass fiber having a particle diameter of 5 μm is added and further containing several percent of Au balls having a particle diameter of approximately 6 μm is screen-printed as a conductive material. The conductive material pattern may be printed on a substrate different from the substrate on which the main seal pattern is printed.

  A glass substrate is bonded together (step S109). Two glass substrates are superposed at predetermined positions to form a cell, and heat treatment is performed in a pressed state to cure the sealant. Here, two glass substrates are overlapped so that the liquid crystal molecules when forming a uniform twist structure by a combination of alignment treatments are twisted 90 ° to the right along the direction from the upper substrate to the lower substrate. It was. The thermosetting of the sealant is performed by baking at 150 ° C. using, for example, a hot press method. Thereafter, the glass substrate is scratched with a scriber device, broken along a part of the scratch, and divided into strips.

  A nematic liquid crystal is injected into the empty cell, for example, by a vacuum injection method using the divided strip-shaped empty cell as a unit (step S110). As the liquid crystal material, for example, RDP-84910 manufactured by DIC Corporation was used. A chiral agent was added to the liquid crystal. The addition amount was adjusted so that the chiral pitch was 15 μm in the left twist direction along the direction from the upper substrate to the lower substrate.

  The liquid crystal inlet is sealed with, for example, an ultraviolet (UV) curable end sealant (step S111), and the cell is heated to a temperature higher than the phase transition temperature of the liquid crystal in order to adjust the orientation of the liquid crystal molecules (step S112). For example, heat treatment is performed in an oven at 120 ° C. for 30 minutes. Then, it breaks along the remainder of the damage | wound attached to the glass substrate with the scriber apparatus, and divides it into an individual cell.

  Chamfering (step S113) and cleaning (step S114) are performed on the subdivided cells. In the washing process, the cell is washed with a detergent, an organic solvent, etc., and the liquid crystal adhering to the cell and the powder during chamfering are washed away.

  Finally, a polarizing plate cut to a predetermined size is attached to the surface of the two glass substrates opposite to the liquid crystal layer (step S115). The two polarizing plates were arranged in crossed Nicols to realize a normally white TN liquid crystal display element.

  A power source and a control device capable of driving a liquid crystal display element by a driving method described later, for example, were connected between the ITO electrodes of both substrates.

  FIG. 2 is a schematic cross-sectional view of the liquid crystal display device according to the first embodiment.

  The liquid crystal display device according to the first embodiment includes an upper substrate 10a, a lower substrate 10b, and a twisted nematic liquid crystal layer 14 sandwiched between the substrates 10a and 10b. Is done.

  The upper substrate 10a includes an upper glass substrate 11a, an upper ITO electrode 12a formed on the upper glass substrate 11a, and an upper alignment film 13a formed on the upper ITO electrode 12a. Similarly, the lower substrate 10b includes a lower glass substrate 11b, a lower ITO electrode 12b formed on the lower glass substrate 11b, and a lower alignment film 13b formed on the lower ITO electrode 12b.

  The liquid crystal layer 14 is disposed between the upper alignment film 13a of the upper substrate 10a and the lower alignment film 13b of the lower substrate 10b, and has a thickness of 5 μm, for example.

  The upper and lower alignment films 13a and 13b are subjected to alignment treatment by rubbing. The direction in which the pretilt angle is formed in each of the upper and lower substrates 10a and 10b (the direction in which the liquid crystal molecules 14a rise with respect to the substrates 10a and 10b) is determined by the direction of the rubbing process. In the embodiment, the direction of the pretilt angle in the upper and lower substrates 10a and 10b is more specifically, for example, when the liquid crystal material forms a uniform twist structure that does not include a spray structure, for example, a liquid crystal material that does not include a chiral agent. Is twisted 90 ° rightward along the direction from the upper substrate 10a toward the lower substrate 10b when viewed from the substrate normal direction on the upper substrate 10a side. It became the combination which becomes. The pretilt angle given to the upper and lower alignment films 13a and 13b was 1 °.

  A chiral agent is added to the liquid crystal layer 14 in an amount that makes the chiral pitch 15 μm. The alignment of the liquid crystal molecules 14a generated under the influence of the chiral agent is twisted in the left-twist direction along the direction from the upper substrate 10a to the lower substrate 10b when viewed from the substrate normal direction on the upper substrate 10a side. It is a structure.

  An upper polarizing plate 15a and a lower polarizing plate 15b are disposed on the surfaces of the upper substrate 10a and the lower substrate 10b opposite to the liquid crystal layer 14, respectively. Both polarizing plates 15a and 15b are arranged in a crossed Nicol manner so that the light transmission axis is parallel to the rubbing direction of the upper and lower substrates 10a and 10b.

  A control device 20 including a power source is connected between the upper ITO electrode 12a and the lower ITO electrode 12b. For example, the arrangement of the liquid crystal molecules 14a can be transferred from the spray twist structure to the uniform twist (reverse twist) structure by applying an AC voltage equal to or higher than the threshold voltage between the electrodes 12a and 12b by a power source.

  FIG. 3 is a photograph showing a spray twist structure state and a reverse twist structure state of the liquid crystal display device according to the first embodiment. The photograph was taken from the normal direction of the upper substrate 10a of the liquid crystal display device according to the first embodiment.

  The inventors of the present invention twist the liquid crystal display element according to the first embodiment from the normal direction of the substrate on the side of the upper substrate 10a (1) in the left direction (second turning direction) with a twist angle of 90 °. Spray twist arrangement state, (2) STN (super twist nematic) arrangement state twisted leftward with a twist angle of 270 °, and (3) RTN twisted rightward (first turning direction) with a twist angle of 90 ° ( It was discovered that each twisted state can be taken.

  FIG. 4 is a schematic diagram showing the twist direction and angle of the liquid crystal molecules 14a viewed from the substrate normal direction on the upper substrate 10a side of the liquid crystal display device according to the first embodiment.

  The twist direction of the liquid crystal molecules 14a immediately after completion of the liquid crystal display element is a left twist in the same direction as the twist direction (second turning direction) by the chiral agent, and the array state is a spray twist array state in which the twist angle is 90 °. In this state, for example, when a voltage within a predetermined range is applied between the electrodes 12 a and 12 b and a vertical electric field is applied to the liquid crystal layer 14, the state transitions to the STN alignment state with a twist angle of 270 °. The twist direction of the liquid crystal molecules in the 90 ° spray twist alignment state and the 270 ° STN alignment state is the same direction. If this voltage application state is maintained, the alignment state (270 ° STN alignment state) of the liquid crystal molecules 14a is also maintained. When the applied voltage is gradually increased and a strong vertical electric field is applied to the liquid crystal layer 14 in the 270 ° STN alignment state, the state changes to the RTN alignment state in which the twist angle is 90 °. This phase transition is performed very rapidly without the occurrence of a disclination line when a voltage equal to or higher than the threshold voltage is applied between the electrodes 12a and 12b. The twist direction of the liquid crystal molecules 14a in the 90 ° RTN alignment state is the opposite direction (first turning direction) to that in the 90 ° spray twist alignment state and the 270 ° STN alignment state. In the photograph of FIG. 3, the 270 ° STN arrangement state that appears when the spray twist arrangement state shifts to the 90 ° RTN arrangement state is omitted.

  By simply erasing the vertical electric field from the liquid crystal layer 14 in the 90 ° RTN alignment state (turning off the voltage applied between the electrodes 12a and 12b for a moment), the liquid crystal molecules 14a transition to the 270 ° STN alignment state. When the voltage applied between the electrodes 12a and 12b is left off, the liquid crystal molecules 14a gradually change the alignment state from the 270 ° STN alignment state, and after a few minutes, transition to the 90 ° spray twist alignment state.

  Note that when the applied voltage is instantaneously turned off in the 270 ° STN alignment state, the liquid crystal molecules maintain the 270 ° STN alignment state.

  The 270 ° STN alignment state appears in the liquid crystal display element according to the first embodiment, for example, in the process in which the liquid crystal molecules 14a transition from the spray twist alignment state to the RTN alignment state, and is stable when a voltage value in a certain range is applied. , An arrangement state of the liquid crystal molecules 14a which can be called “metastable”.

  FIG. 5 is a graph showing the electro-optical characteristics of the liquid crystal display element according to the first embodiment. The horizontal axis of the graph indicates the voltage applied between the electrodes 12a and 12b in the unit "V", and the vertical axis indicates the light transmittance of the liquid crystal display element in the unit "%".

  It can be seen that the liquid crystal display element according to the first example has a large steepness of change in light transmittance with respect to the applied voltage (excellent sharpness).

  When V10 / V90 and V5 / V90 were calculated, sharpness values of 1.037 and 1.041 were obtained, respectively. Here, V5, V10, and V90 are voltage values at which 5% light transmittance, 10% light transmittance, and 90% light transmittance are obtained when the highest light transmittance is 100%. The sharpness value required to drive the liquid crystal display element at 1/480 duty is 1.0465 or less. The liquid crystal display element according to the first embodiment achieves this necessary value for both V10 / V90 and V5 / V90.

  The liquid crystal display element according to the first embodiment is a liquid crystal display element that exhibits excellent sharpness characteristics and can be driven at a high duty of 1/480 duty driving. As a result of intensive studies by the inventors of the present application, it has been found that such excellent sharpness characteristics appear when the pretilt angle is not less than 0.1 ° and not more than 5 °.

  The inventors of the present application fabricated liquid crystal display elements according to second to fourth examples that differ from the liquid crystal display element according to the first example only in the liquid crystal material, and examined the electro-optical characteristics. In the second, third, and fourth examples, RDP-83107, RDP-83108, and RDP-83409 manufactured by DIC Corporation were used as liquid crystal materials, respectively. The liquid crystal display elements according to the second to fourth embodiments also have a spray twist arrangement state in which the twist angle is 90 ° in the left direction and the twist angle 270 ° in the left direction when viewed from the substrate normal direction on the upper substrate side. A twisted STN array state and an RTN array state twisted in the right direction at a twist angle of 90 ° can be taken.

  6A to 6D are graphs showing the electro-optical characteristics of the liquid crystal display elements according to the first to fourth embodiments, respectively. The horizontal axis of the graph indicates the voltage applied between the electrodes in the unit “V”, and the vertical axis indicates the light transmittance of the liquid crystal display element in the unit “%”. The graphs of FIGS. 6A to 6D show the light transmittance when the highest light transmittance is 100%. In each graph, the actual measurement value and the simulation value are indicated by a solid line and a dotted line, respectively. The liquid crystal display elements according to the first to fourth examples are found to be liquid crystal display elements having excellent sharpness from both actual measurement and simulation.

  Next, the inventors performed simulation on the liquid crystal display element according to the fifth example to reproduce the electro-optical characteristics. The liquid crystal display element according to the fifth embodiment is the first embodiment in that ZLI-4792 which is a nematic liquid crystal material manufactured by Merck Co., Ltd. is used as the liquid crystal material, and the pretilt angle is set to 3 °. And different. Also in the liquid crystal display device according to the fifth embodiment, the liquid crystal molecules in the liquid crystal layer are 90 ° spray twisted in the left direction and 270 ° STN in the left direction when viewed from the substrate normal direction on the upper substrate side. There can be three states: an array state and a 90 ° RTN array state with rightward twist.

  FIG. 7 shows the electro-optical characteristics of the liquid crystal display element according to the fifth embodiment in each of the 90 ° left-twisted spray twist arrangement state, the 270 ° left-twisted STN arrangement state, and the 90 ° right-twisted RTN arrangement state. It is a graph to show. The meanings of both axes of the graph are the same as those in the graph of FIG. Curve a represents the 90 ° spray twist arrangement state, curve b represents the 270 ° STN arrangement state, and curve c represents the electro-optical characteristic of the 90 ° RTN arrangement state.

  In the 270 ° STN arrangement state (curve b), the light transmittance changes sharply between 2.6V and 2.7V (about 2.68V), which can be seen in FIGS. 5 and 6A to 6D. It is very similar to the electro-optical characteristic showing the steepness (excellent sharpness) of the change in light transmittance with respect to the applied voltage. The electro-optical characteristic of the 270 ° STN arrangement state after the light transmittance sharply decreases (the voltage value exceeds about 2.68 V) is equal to that of the 90 ° RTN arrangement state.

  FIG. 8A is a graph showing a liquid crystal molecule twist angle (director twist angle) in the liquid crystal display device according to the fifth embodiment. The horizontal axis of the graph shows the normalized position of the liquid crystal layer in the thickness direction. The position where the liquid crystal layer (liquid crystal molecule) was in contact with the upper substrate was 0, and the position where the liquid crystal layer was in contact with the lower substrate was 1. The vertical axis represents the twist angle in the unit “°”. The positive direction indicates the right twist direction (first turning direction) when viewed from the normal direction on the upper substrate side, and the negative direction indicates the left twist direction (second turning direction). The curves a to d show the liquid crystal molecule twist angles when the applied voltage between the upper and lower substrates is 2 V to 5 V, respectively.

  When the applied voltage is 2 V (curve a), the liquid crystal molecules are twisted 270 ° leftward between the upper and lower substrates. The amount of change in the twist angle is constant regardless of the position in the liquid crystal layer thickness direction.

  A reversal of the twist direction occurs between 2V and 3V (curve a and curve b). The voltage causing the reversal of the twist direction was equal to the voltage (about 2.68 V) at which the light transmittance changes sharply (see FIG. 7).

  When the applied voltage is in the range of 3V to 5V (curve b to curve d), the liquid crystal molecules are twisted 90 ° rightward between the upper and lower substrates. The twist of the liquid crystal molecules occurs mainly near the center of the liquid crystal layer in the thickness direction (positions of about 0.4 to 0.6).

  FIG. 8B is a graph showing the twist angle of the liquid crystal molecules in the 90 ° right twist RTN alignment state. The meanings of both axes of the graph are the same as those in the graph of FIG. 8A. Curves a to f indicate the twist angles of liquid crystal molecules when the voltage applied between the upper and lower substrates is 0 V to 5 V, respectively.

  When the applied voltage is in the range of 3 V to 5 V (curve d to curve f), the liquid crystal molecules are twisted 90 ° rightward between the upper and lower substrates, and the twist is mainly near the center in the thickness direction of the liquid crystal layer (approximately 0.4 to 0. 0. At position 6). 8A and 8B, the liquid crystal molecules of the liquid crystal display device according to the fifth embodiment are liquid crystal molecules in a 90 ° right-twisted RTN alignment state at an applied voltage of 3V to 5V. It can be seen that the same behavior is exhibited.

  From the simulation of the liquid crystal display element according to the fifth embodiment (see FIGS. 7, 8A and 8B), in the liquid crystal display element according to the embodiment, the twist direction reversal (270 °) generated by applying a voltage of about 2.68V. It is considered that a steep change in the light transmittance occurs due to the transition from the STN arrangement state to the 90 ° RTN arrangement state.

  9A and 9B are graphs showing the free energy of the liquid crystal display element according to the fifth embodiment in each of the 90 ° spray twist arrangement state, the 270 ° STN arrangement state, and the 90 ° RTN arrangement state.

The horizontal axis of the graph indicates the voltage applied between the electrodes in the unit “V”, and the vertical axis indicates the Gibbs free energy in the unit “μJ / m ² ”. Curve a represents the free energy when the liquid crystal molecules are in the 90 ° spray twist alignment state, curve b represents the 270 ° STN alignment state, and curve c represents the free energy when in the 90 ° RTN alignment state. For reference, the free energy in the liquid crystal molecular alignment state (90 ° right-twisted TN alignment state) when no chiral agent is added to the liquid crystal layer of the liquid crystal display element according to the fifth embodiment is added as a curve d. did. FIG. 9B is an enlarged graph of a part of FIG. 9A (applied voltage range of 2V to 3V).

  In the range where the applied voltage is a little over 2.2V, the 270 ° STN arrangement state among the three states (curve a to curve c) of 90 ° spray twist arrangement state, 270 ° STN arrangement state, and 90 ° RTN arrangement state (Curve b) has the lowest free energy and is stable. However, at a voltage value of slightly over 2.4 V, the free energy of the 270 ° STN arrangement state (curve b) is the highest and unstable, while the free energy of the 90 ° RTN arrangement state (curve c) is the lowest, It is stable. As a result, a torsional reversal (transition from the 270 ° STN arrangement state to the 90 ° RTN arrangement state) occurs between 2.683V and 2.684V.

  For example, the 90 ° RTN arrangement state (curve c) and the 90 ° TN arrangement state (curve d) are common in that they are twisted by 90 ° to the right, but in the 90 ° RTN arrangement state (curve c), the left Since a chiral agent that gives a turning property in the direction is added, the free energy is higher than that of the 90 ° TN arrangement state (curve d), and is unstable.

  Next, a method for driving the liquid crystal display element according to the embodiment will be described. Here, a case where the fifth liquid crystal display element is duty-driven will be described.

  10A and 10B show examples of waveforms of drive voltages applied between the upper and lower electrodes. In both figures, the horizontal axis represents time, and the vertical axis represents voltage. For example, the selection waveform Vs in FIG. 10A is a drive voltage waveform applied to the selected pixel, and the non-selection waveform Vus in FIG. 10B is a drive voltage waveform applied to the non-selected pixel. The effective voltage of the selection waveform Vs is set to, for example, a voltage higher than a threshold voltage capable of shifting the alignment state of liquid crystal molecules from the 270 ° STN alignment state to the 90 ° RTN alignment state, for example, a voltage equivalent to 2.7 V of static drive. The effective value voltage of the non-selected waveform Vus is set to, for example, a voltage lower than the threshold voltage, for example, a voltage equivalent to 2.6 V of static drive.

  FIG. 11 is a flowchart illustrating a method of driving the liquid crystal display element according to the embodiment.

  First, a voltage within a predetermined range, for example, an AC voltage (reset pulse) of 2.2 V is applied between the upper and lower electrodes of all the pixels, and a vertical electric field is applied to the liquid crystal layer so that it is in a 90 ° spray twist arrangement state. The liquid crystal molecules are transferred to the 270 ° STN alignment state (step S201). Here, the voltage within the predetermined range is, for example, a threshold voltage that can transfer the alignment state of the liquid crystal molecules from the 90 ° spray twist alignment state to the 270 ° STN alignment state, and from the 270 ° STN alignment state to the 90 ° RTN alignment state. The voltage is lower than the threshold voltage that can be transferred. It should be noted that the non-selection waveform Vus may be applied to all the pixels so that the alignment state of the liquid crystal molecules may be changed from the 90 ° spray twist alignment state to the 270 ° STN alignment state. White display is performed by the pixels in the 270 ° STN arrangement state.

  The non-selection waveform Vus is continuously applied to the pixels that perform white display, for example, at a constant cycle (step S202). The continuous application of the non-selected waveform Vus maintains the 270 ° STN arrangement state.

  The selection waveform Vs is applied to at least some of the pixels (step S203). The liquid crystal molecules of the pixel to which the selection waveform Vs is applied shift from the 270 ° STN alignment state to the 90 ° RTN alignment state. This phase transition is performed promptly and is completed in about 100 msec to 500 msec. The display state of the pixel to which the selection waveform Vs is applied is changed from white display to black display. An image is displayed by pixels that perform white display and pixels that perform black display.

  A pixel that is once displayed in black by adding the selection waveform Vs can maintain black display (90 ° RTN arrangement state) by continuously applying the non-selection waveform Vus thereafter (step S202). That is, for example, an image can be held by continuously applying the non-selection waveform Vus to all the pixels, for example, at a constant period (step S202). Note that, for example, the selection waveform Vs may be continuously applied to the pixel performing black display.

  When the image is changed by adding a black display portion, the selection waveform Vs is applied to the pixels that are additionally displayed black (step S203). In this way, the image (display content) can be additionally changed.

  When rewriting to a completely different image, the drive voltage (drive waveform) of all the pixels is turned off once, for example, instantaneously (step S204). Since the transition from the 90 ° RTN arrangement state to the 270 ° STN arrangement state occurs when the driving voltage is instantaneously turned off, all the pixels are displayed in white (270 ° STN arrangement state), and the display state can be reset. The transition from the 90 ° RTN arrangement state to the 270 ° STN arrangement state is completed in 1 s to 2 s or less. The display state can be changed from a black display to a white display by reducing the voltage to a voltage at which the 90 ° RTN arrangement state is not maintained, for example, the voltage transitions to the 270 ° STN arrangement state. .

  From this state, for example, the selection waveform Vs is applied to the pixel that performs black display (step S203), and the non-selection waveform Vus is continuously applied to all the pixels (step S202), thereby rewriting and rewriting the new image. Can be held.

  Note that when a state in which no drive voltage is applied continues for several minutes, the liquid crystal molecules transition to a spray twist alignment state. In this case, a reset pulse is applied again (step S201).

  In the driving method of the liquid crystal display element according to the embodiment, display is performed with the arrangement state of the liquid crystal molecules in the pixel unit as the 270 ° STN arrangement state or the 90 ° RTN arrangement state. When the alignment state of the liquid crystal molecules transitions from the 270 ° STN alignment state to the 90 ° RTN alignment state, the light transmittance changes sharply. Since the sharpness is excellent, display can be performed with a large display capacity. The driving method of the liquid crystal display element according to the embodiment can be particularly preferably used when a large capacity display is performed with relatively little rewriting.

  Note that the non-selected waveform Vus (step S202) applied to maintain white display (270 ° STN arrangement state) or black display (90 ° RTN arrangement state) can be considered as an image holding waveform. Therefore, for example, the effective value voltage of the non-selected waveform Vus can be made lower than a voltage equivalent to 2.6 V of static drive. The driving waveform may be a simple waveform such as a square wave. By reducing the effective value voltage or simplifying the waveform, the power consumption during driving can be reduced.

In duty driving, effective value driving is performed, and a relatively high voltage having a waveform as shown in FIGS. 10A and 10B is instantaneously applied, for example, at a constant period. In the embodiment, a voltage higher than the threshold voltage is applied between the upper and lower electrodes to change the alignment state of the liquid crystal molecules from the 90 ° spray twist alignment state to the 270 ° STN alignment state, and then to perform duty driving. It is also possible to perform display for a long time with an effective value voltage smaller than the transition voltage (effective value voltage necessary for transition from the 90 ° spray twist arrangement state to the 270 ° STN arrangement state). In this case, the higher the duty display, the higher the peak voltage value of the drive waveform, and the liquid crystal molecules are considered to be more stable in the 270 ° STN alignment state. From this point of view, the liquid crystal display element according to the embodiment preferably has a duty driving condition higher than 1/120 duty. Further, the lower the stable voltage V _c is relative to the transition voltage, the more stable the 270 ° STN arrangement state is. Therefore, in comparison with the transition voltage, it is desirable to employ a liquid crystal material and the cell structure to reduce the stable voltage V _c.

  Liquid crystal display elements according to other embodiments can be similarly driven. For example, in the case of the first embodiment, the effective value voltage of the selected waveform Vs is set to a voltage equivalent to 1.3 V of static drive as an example, and the effective value voltage of the non-selected waveform Vus is set to 1. What is necessary is just to set to the voltage equivalent to 2V (refer FIG. 6A). As a result of examining the response characteristics, it was found that the liquid crystal display element according to the example can be switched at a relatively high speed in several tens of milliseconds, for example.

  FIG. 12 is a graph showing spectral characteristics of white display and black display in the liquid crystal display device according to the fifth embodiment. The horizontal axis of the graph indicates the wavelength in the unit “nm”, and the vertical axis indicates the light transmittance in the unit “%”. Curve a represents the spectral characteristics of white display (270 ° STN arrangement state), and curve b represents the spectral characteristics of black display (90 ° RTN arrangement state).

  A substantially flat white display (natural white display) and a black display with good light shielding properties (natural black display) are obtained regardless of the wavelength. The liquid crystal display element by an Example is a liquid crystal display element which only stuck the polarizing plate to the liquid crystal cell, and the optical compensation film etc. are not used. That is, a natural white display can be obtained by using an inexpensive liquid crystal material or alignment film used for the TN liquid crystal display element. On the other hand, for example, when duty driving is performed, large-capacity display that is difficult to obtain with a TN liquid crystal display element can be performed. Response characteristics are not bad.

  The reason why a natural white display can be obtained in the 270 ° STN arrangement state is unknown at this time. However, it is known from the simulation that a natural white display can be obtained in the 270 ° STN arrangement state where the pretilt angle is low.

  In the liquid crystal display elements according to the first to fifth embodiments, the thickness (cell thickness) d of the liquid crystal layer was 5 μm, and the chiral pitch p was 15 μm. The value of d / p is 1/3. The cell thickness d is not limited to 5 μm. The value of d / p is desirably adjusted by the amount of chiral agent added to the liquid crystal.

  In the case of a TN liquid crystal display element, in order to obtain a bright display, it is necessary to satisfy the conditions of the first minimum or the second minimum in the Gucci Terry equation. The Gucci Terry equation is expressed by the following equation (1).

Here, _TNB is the light transmittance at the time of normally black of the TN type liquid crystal cell, and u is a value calculated by the following equation (2).

  In equation (2), Δn is the refractive index anisotropy of the liquid crystal, λ is the wavelength of light incident on the liquid crystal cell, and d is the cell thickness.

  Also in the liquid crystal display element (RTN type liquid crystal display element) according to the embodiment, in order to satisfy the condition of the first minimum or the second minimum of the Gucci-Terry formula, the liquid crystal material (the refractive index anisotropic of the liquid crystal) depends on the cell thickness d. It is desirable to select the property Δn). For example, when the cell thickness d is reduced, the value of the refractive index anisotropy Δn is increased. Conversely, when the cell thickness d is increased, the liquid crystal material is reduced so as to decrease the value of the refractive index anisotropy Δn. select.

  Note that the smaller the cell thickness d, the stronger the alignment state of the liquid crystal molecules is considered to be affected by the substrate interface. Therefore, the liquid crystal display element with the smaller cell thickness d stably maintains the 270 ° STN alignment state. It is speculated that it is possible.

  It may be desirable to set the value of d / p to 1/3 or a value close thereto as in the embodiment. However, even if the value changes slightly, it is considered that the same effect is produced. As the value of d / p increases in the range exceeding 1/3, the influence of the chiral agent appears strongly, and the spray twist arrangement state tends to exist stably. As a result, the voltage required for transition from the spray twist arrangement state to the 270 ° STN arrangement state is increased, and the time during which the 270 ° STN arrangement state is stably maintained tends to be shortened. For this reason, it is desirable that the value of d / p is approximately ½ or less. On the other hand, it is considered that as the value of d / p becomes smaller in the range of less than 1/3, the distortion in the liquid crystal layer given by the chiral agent becomes smaller, and the sharpness tends to deteriorate. It would be desirable for the value of d / p to be approximately greater than 1/4. Since the value of d / p is also related to the cell thickness d itself, the desirable range cannot be fully stated.

In addition, in the liquid crystal display element according to the example, it was found that the stability of the 270 ° STN alignment state is higher as the value of the elastic constant K ₁₁ of the spread of the liquid crystal material is larger and the value of the elastic constant K ₂₂ of the twist is smaller. . From the viewpoint of the stability of the 270 ° STN alignment state, a liquid crystal layer may be formed using a liquid crystal material having a ratio K ₁₁ / K ₂₂ of, for example, two or more, the expansion elastic constant K ₁₁ and the torsion elastic constant K _22. Would be preferred.

  The liquid crystal display element and the liquid crystal display device according to the embodiment have excellent sharpness characteristics, and are manufactured at the same cost as a normal TN liquid crystal display element by using a material and a cell structure used for the TN liquid crystal display element. Is possible. In addition, since a low pretilt angle is a preferable condition, it can be manufactured using a highly reliable alignment film material for a TN type liquid crystal display element widely used in industry, and thus has high reliability. . Furthermore, a natural black and white display can be obtained without an optical compensation film. In addition, large capacity display is possible, and high duty driving of at least 1/480 duty or more can be performed. Response characteristics are also good. Due to the excellent sharpness characteristics, for example, the number of upper and lower electrodes (the number of scanning lines) when performing dot display by duty driving is set to 100 or more, and display can be performed with high display performance. Furthermore, power consumption during driving can be reduced.

  Further, according to the driving method of the liquid crystal display element according to the embodiment, it is possible to perform a large capacity display with low power consumption.

In the duty drive, when the number of scanning lines is N, the ON voltage is V _on , and the OFF voltage is V _off , the relationship is expressed by the following equation (3). For example, in the example of driving the liquid crystal display element according to the fifth embodiment, V _on is a voltage equivalent to 2.7 V of static drive, and V _off is a voltage equivalent to 2.6 V.

According to equation (3), when N ≧ _100, as _{1 <V} on _/ V _off ≦ about 1.1 next, N is _{increased, V} on _/ V _off are closer to 1. Since the liquid crystal display element according to the embodiment has excellent sharpness characteristics, the number of scanning lines can be increased to display precisely.

    As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these.

  For example, in the embodiment, the twist angle α ° of the liquid crystal molecules in the RTN alignment state is set to 90 °, but may be changed within a range of about ± 20 ° (70 ° to 110 °). However, considering the brightness of the white display, it is desirable to set the twist angle at 90 ° or in the vicinity thereof. When 70 ° ≦ α ° ≦ 110 °, the liquid crystal molecules of the liquid crystal display element according to the embodiment are viewed in the normal direction of the substrate on the upper substrate side. (360-α) ° STN arrangement state and right-twisting (180-α) ° RTN arrangement state.

  In the examples, the angle formed by the transmission axes of the upper polarizing plate and the lower polarizing plate is 90 ° (crossed Nicols arrangement), but the angle formed by the transmission axes of both polarizing plates is within a range of about ± 5 °. Can be changed. However, from the viewpoint of preventing light leakage, it is preferably disposed at an angle of 90 ° or in the vicinity thereof. Note that a normally black liquid crystal display element can be formed by arranging polarizing plates in parallel Nicols. In that case, both polarizing plates can be arranged with the angle formed by the transmission axis being, for example, 20 ° or less. The desirable arrangement of the polarizing plate is also related to the twist angle of the liquid crystal molecules.

  Further, the transition from the 90 ° spray twist arrangement state to the 270 ° STN arrangement state occurs more rapidly as the frequency of the applied voltage is higher. For this reason, the reset pulse is preferably a high-frequency AC voltage.

  In the embodiments, the upper and lower substrates are both transparent substrates, but at least one of them may be a transparent substrate.

    It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like are possible.

  It can be used for all products that display using liquid crystal. In particular, it is suitable for applications requiring little rewriting and requiring a large capacity display. For example, it can be suitably used for advertisement displays, children's toys, and alternative displays for paper and printed matter such as newspapers and magazines.

  Further, it can be preferably used for a liquid crystal display element driven by a duty, particularly a liquid crystal display element which requires a relatively large capacity display.

  Furthermore, you may combine with an active element. Moreover, it can also be used as a liquid crystal optical element such as an element for a surface writing light source.

10a upper substrate 10b lower substrate 11a upper glass substrate 11b lower glass substrate 12a upper ITO electrode 12b lower ITO electrode 13a upper alignment film 13b lower alignment film 14 liquid crystal layer 14a liquid crystal molecule 15a upper polarizer 15b lower polarizer 20 Control device

Claims (8)

A first substrate comprising a first electrode and subjected to orientation treatment;
A second substrate disposed in parallel and opposite to the first substrate, provided with a second electrode, and subjected to an orientation treatment;
A liquid crystal layer that is disposed between the first substrate and the second substrate, includes an optically active material, and is twist-aligned;
When the twist direction of the liquid crystal molecules when the uniform twist structure is formed by a combination of the alignment treatments of the first and second substrates is the first turning direction, the optically active substance is added to the liquid crystal molecules of the liquid crystal layer. Giving a turnability in the second turning direction opposite to the first turning direction,
The first and second substrates are aligned so that a pretilt angle of 0.1 ° or more and 5 ° or less is developed,
When 70 ° ≦ α ° ≦ 110 °, the liquid crystal molecules of the liquid crystal layer are in a spray twist arrangement state in which the liquid crystal layer is twisted by α ° in the second turning direction, and twisted in the second turning direction by (360−α) °. A liquid crystal element capable of taking three states of a nematic alignment state and a twisted nematic alignment state twisted by (180−α) ° in the first turning direction. A first substrate having a first electrode and subjected to an alignment treatment; a second substrate having a second electrode and being subjected to an alignment treatment; disposed opposite to and parallel to the first substrate; and the first substrate When a uniform twist structure is formed by a combination of alignment treatments of the first and second substrates, which is disposed between the substrate and the second substrate, includes an optically active substance, and has a liquid crystal layer that is twist-aligned. When the twist direction of the liquid crystal molecules is the first turning direction, the optically active substance gives the liquid crystal molecules of the liquid crystal layer a turning property in the second turning direction opposite to the first turning direction. The first and second substrates are aligned so that a pretilt angle of 0.1 ° to 5 ° is expressed. When 70 ° ≦ α ° ≦ 110 °, the liquid crystal molecules of the liquid crystal layer are Spray twist array state twisted by α ° in two turning directions, the second turning direction A twisted nematic alignment state twisted by (360-α) ° and a twisted nematic alignment state twisted by (180-α) ° in the first turning direction.
(A) A spray twist in which a voltage higher than a first threshold voltage is applied between the first electrode and the second electrode, and the alignment state of the liquid crystal molecules is twisted by α ° in the second turning direction. Transition from an array state to a twisted nematic array state twisted by (360-α) ° in the second turning direction;
(B) A voltage equal to or higher than a second threshold voltage higher than the first threshold voltage is applied between the first electrode and the second electrode, and the alignment state of the liquid crystal molecules is changed to the second rotation. Transition from a twisted nematic alignment state twisted in the direction (360-α) ° to a twisted nematic alignment state twisted in the first turning direction (180-α) °. Furthermore,
(C) A twisted nematic arrangement in which the voltage applied between the first electrode and the second electrode is lowered and the arrangement state of the liquid crystal molecules is twisted by (180−α) ° in the first turning direction. The method for driving a liquid crystal element according to claim 2, further comprising a step of changing from a state to a twisted nematic alignment state twisted by (360−α) ° in the second turning direction. Furthermore,
(D) Continue the voltage for maintaining the twisted nematic arrangement state twisted by (360-α) ° in the second turning direction or the twisted nematic arrangement state twisted by (180-α) ° in the first turning direction. The method for driving a liquid crystal element according to claim 2, further comprising a step of applying the same. A first substrate having a first electrode and subjected to an alignment treatment; a second substrate having a second electrode and being subjected to an alignment treatment; disposed opposite to and parallel to the first substrate; and the first substrate When a uniform twist structure is formed by a combination of alignment treatments of the first and second substrates, which is disposed between the substrate and the second substrate, includes an optically active substance, and has a liquid crystal layer that is twist-aligned. When the twist direction of the liquid crystal molecules is the first turning direction, the optically active substance gives the liquid crystal molecules of the liquid crystal layer a turning property in the second turning direction opposite to the first turning direction. The first and second substrates are aligned so that a pretilt angle of 0.1 ° to 5 ° is expressed. When 70 ° ≦ α ° ≦ 110 °, the liquid crystal molecules of the liquid crystal layer are Spray twist array state twisted by α ° in two turning directions, the second turning direction A twisted nematic alignment state twisted by (360-α) ° and a twisted nematic alignment state twisted by (180-α) ° in the first turning direction;
A control device for controlling the driving of the liquid crystal element,
The controller is
(A) A spray twist in which a voltage higher than a first threshold voltage is applied between the first electrode and the second electrode, and the alignment state of the liquid crystal molecules is twisted by α ° in the second turning direction. Transition from an array state to a twisted nematic array state twisted by (360-α) ° in the second turning direction;
(B) A voltage equal to or higher than a second threshold voltage higher than the first threshold voltage is applied between the first electrode and the second electrode, and the alignment state of the liquid crystal molecules is changed to the second rotation. Liquid crystal for driving the liquid crystal element by a driving method including a step of changing from a twisted nematic alignment state twisted in the direction (360-α) ° to a twisted nematic alignment state twisted in the first turning direction (180-α) ° apparatus. Furthermore, the control device comprises:
(C) A twisted nematic arrangement in which the voltage applied between the first electrode and the second electrode is lowered and the arrangement state of the liquid crystal molecules is twisted by (180−α) ° in the first turning direction. The liquid crystal device according to claim 5, wherein the liquid crystal element is driven by a driving method including a step of changing from a state to a twisted nematic alignment state twisted by (360−α) ° in the second turning direction. Furthermore, the control device comprises:
(D) Continue the voltage for maintaining the twisted nematic arrangement state twisted by (360-α) ° in the second turning direction or the twisted nematic arrangement state twisted by (180-α) ° in the first turning direction. The liquid crystal device according to claim 5, wherein the liquid crystal element is driven by a driving method including a step of applying the light. The liquid crystal element performs dot display with duty drive,
The liquid crystal device according to claim 5, wherein the number of the first and second electrodes is 100 or more.