JP5513916B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element.

  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 point that the liquid crystal molecules are twisted in the second rotation direction) and the alignment treatment of the pair of transparent electrode substrates is performed so that the pretilt angles of the liquid crystal molecules in contact with the transparent electrode substrates are different from each other. It has the characteristics.

  In the liquid crystal display element described in Patent Document 1, the electro-optical characteristics are improved, and even when the turning angle in the first turning direction is set in the range of 91 to 100 °, the effect of the reverse twist arrangement is used. Electro-optical characteristics similar to those of a TN liquid crystal display element by a 90 ° rubbing method can be obtained. In addition, since the pretilt angles of the liquid crystal molecules in contact with the substrate are different from each other, the occurrence of disclination due to inadequate alignment of each liquid crystal molecule is prevented, and 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 material 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 material 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 defined by the combination of the alignment treatment direction and the pretilt angle is called a reverse twist (uniform twist) structure, and the alignment state of the liquid crystal molecules generated under the influence of the chiral material is called a spray 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. After the transition to the reverse twist structure, the reverse twist structure is stably maintained for several minutes to several tens of minutes after the voltage application is stopped. The liquid crystal element is used in a reverse twist structure and can be driven at a low voltage.

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

  The present invention relates 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 driven by a simple matrix. The invention is known (for example, see Patent Document 4). In the invention described in Patent Document 4, in order to cope with the problem of coloring due to birefringence, means for realizing monochrome display by laminating liquid crystal cells that compensate for coloring is disclosed.

  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, even if the retardation of the liquid crystal layer in the driving cell changes accordingly, the retardation of the optical compensation film hardly changes. However, there is a problem that coloring occurs 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 is highly dependent on display performance 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 pretilt angle differences. For this reason, the management of the manufacturing process is strict (the manufacturing margin is narrow), and the yield is low. The STN type liquid crystal display element requires a high pretilt angle of about 5 to 9 °, 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 when the viewing angle direction is slightly changed. 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.

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

  An object of the present invention is to provide a liquid crystal display element having excellent sharpness.

According to one aspect of the present invention, a first substrate including a first electrode and oriented in a first direction is disposed opposite to and parallel to the first substrate, and includes a second electrode. A second substrate aligned in a second direction; a liquid crystal layer that is disposed between the first substrate and the second substrate and includes a chiral material and twist-aligns; 2 direction, when viewed from the normal direction of the first substrate side, to the first direction is a direction having an axis which forms a 70 ° to 110 ° in a first direction around the liquid crystal The layer includes a uniform twist structure that twists in the first rotation direction by a voltage applied between the first electrode and the second electrode, and a second layer opposite to the first rotation direction. A spray twist structure that twists in the direction of the rotation is generated in a commutative manner, and the chiral material is formed on the liquid crystal molecules of the liquid crystal layer. The first when viewed from the normal direction of the substrate side, the first along the substrate in a direction toward the second substrate, with the second ability Ru swirled of the rotation direction, the The first substrate and the second substrate are aligned so that a pretilt angle θ greater than 0 ° and less than or equal to 5 ° is developed, the thickness of the liquid crystal layer is d, and the chiral pitch of the chiral material is p. Then, θ, d, and p are the following two formulas

A liquid crystal display element satisfying the above is provided.

  ADVANTAGE OF THE INVENTION According to this invention, a liquid crystal display element provided with the outstanding sharpness can be provided.

It is a flowchart which shows the manufacturing method of the liquid crystal display element by a 1st Example. 1 is a schematic cross-sectional view of a liquid crystal display element according to a first embodiment. It is a photograph which shows the spray twist structure state and reverse twist structure state of the liquid crystal display element by a 1st Example. (A) And (B) is a graph which shows the electro-optical characteristic of the liquid crystal display element by a 1st Example. It is a graph which shows the electro-optical characteristic in the reverse twist arrangement | sequence state of the liquid crystal display element by a 2nd Example. It is a graph which shows the electro-optical characteristic in the reverse twist arrangement | sequence state of the liquid crystal display element by a 3rd Example. It is a graph which shows the electro-optical characteristic in the reverse twist arrangement | sequence state of the liquid crystal display element which made the pretilt angle 21 degrees. It is a graph showing the relationship between the mixing ratio of two types of polyimide materials and the developed pretilt angle. It is a graph showing the relationship between the applied voltage and light transmittance in the reverse twist arrangement | sequence state of the liquid crystal display element by a 4th Example. (A)-(C) is a graph which shows the relationship between the applied voltage and the light transmittance in the reverse twist arrangement | sequence state of the liquid crystal display element by a 1st-3rd comparative example, respectively. It is the table | surface which put together the boundary voltage of the liquid crystal display element by a 1st-4th Example, and the physical-property value of the liquid crystal material used for each liquid crystal display element. It is a figure which shows an example of the waveform of the drive voltage applied by the power supply 20 between the upper ITO electrode 12a and the lower ITO electrode 12b. (A) And (B) is a graph which shows the example of the range of the pretilt angle (theta) and p / d in which the outstanding sharpness appears in a reverse TN liquid crystal display element.

  The twist direction of the liquid crystal material determined by the combination of the alignment treatment direction of the pair of alignment films and the pretilt angle and the twist direction of the liquid crystal material induced by the optically active substance (chiral material) are reversed. A liquid crystal display element described in Patent Document 3 having a liquid crystal layer and capable of commutatively realizing a reverse twist (uniform twist) structure and a spray twist structure by applying a voltage (electric field treatment) to the liquid crystal layer. Hereinafter, it is referred to as a reverse TN liquid crystal display element.

  The reverse TN 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 inventor of the present application has studied reverse TN type liquid crystal display devices manufactured under various conditions for the purpose of reducing the threshold of the drive voltage, and disclosed the results in Patent Document 3. As a result of research by the present inventors, the reverse twist structure state is more stable as the pretilt angle is higher, and the threshold of the drive voltage is lower as the chiral material has a shorter chiral pitch, but the reverse twist structure state is 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 performed for low pretilt angle conditions, but the reverse twist structure state was originally an unstable array state, so the short pitch condition that makes the reverse twist structure state more unstable (chiral pitch less than 20 μm) was examined. Did not go.

  The present invention is the result of research related to a reverse twist structure state in a very unstable state, which is normally excluded from research, such as a low pretilt angle and a short pitch condition. Under these unique conditions, the present inventors have discovered an unexpected phenomenon in which the sharpness of the liquid crystal display element becomes extremely steep. It is not clear at this time why such a phenomenon occurs. The occurrence of such a phenomenon was also unpredictable by simulation.

  The present invention will be described below based on examples.

  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). The rubbing process is a process of rotating a cylindrical roll wound with a cloth at a high speed and rubbing the alignment film, whereby liquid crystal molecules in contact with the substrate can be aligned (aligned) in one direction.

  In order to keep the thickness (distance between substrates) of the liquid crystal cell constant, a gap control material is sprayed on one glass substrate surface by a dry spraying method (step S107). As the gap control material, 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, ES-7500 manufactured by Mitsui Chemicals, Inc., which is a thermosetting sealing material, is printed by a screen printing method. ES-7500 contains several percent of glass fibers with a particle size of 5 μm. Note that a sealing material can be applied using a dispenser. Further, instead of thermosetting, a photo-curing sealing material or a light / heat combined curing type sealing material may be used.

  On the surface of the substrate on which the main seal pattern is formed, a conductive material including a gold-plated plastic ball (Au ball) or the like is printed at a predetermined position to form a conductive material pattern. For example, ES-7500 containing a few percent of Au balls having a particle size of about 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 sealing material. Here, the two liquid crystal substrates were combined such that the alignment of liquid crystal molecules was twisted by 90 ° in the right direction when viewed from the normal direction of the upper substrate. For example, the sealing material is thermally cured by baking at 150 ° C. using 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 is used. A chiral material was added to the liquid crystal. The amount of addition 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 seal material (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 alignment 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 was 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. .

  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. The thickness of the liquid crystal layer 14 is, for example, 5 μm.

  The upper and lower alignment films 13a and 13b are subjected to alignment treatment by rubbing. The alignment treatment directions of the upper alignment film 13a and the lower alignment film 13b are orthogonal to each other. When the rubbing direction of the upper alignment film 13a is the first direction and the rubbing direction of the lower alignment film 13b is the second direction, the second direction is the first direction when viewed from the normal direction of the upper substrate 10a. The direction is 90 ° with respect to the reference. The combination of the direction in which the pretilt angle is formed (the direction in which the liquid crystal molecules rise with respect to the substrate) and the direction of the pretilt angle in the lower substrate, as determined by the direction of the rubbing process on the upper substrate, is a liquid crystal material with a spray structure. More specifically, for example, when a liquid crystal material not including a chiral material is disposed between the alignment films, a combination that results in a uniform twist structure that is twisted by 90 ° in the right direction is formed. . The pretilt angle given to the upper and lower alignment films 13a and 13b was 1 °.

  A chiral material is added to the liquid crystal layer 14. The amount added is adjusted so that the chiral pitch is 15 μm. The alignment of the liquid crystal molecules 14a generated under the influence of the chiral material is a splay that twists in the left-twist direction along the direction from the upper substrate 10a to the lower substrate 10b when viewed from the normal direction of the upper substrate 10a. It becomes a twist structure.

  The twist direction of the liquid crystal molecules 14a in the liquid crystal cell completed state was left twist (spray twist structure) in the same direction as the twist direction by the chiral material.

  A power source 20 is connected between the upper ITO electrode 12a and the lower ITO electrode 12b. By applying an alternating voltage equal to or higher than the threshold voltage between the electrodes 12a and 12b by the power source 20, the arrangement of the liquid crystal molecules 14a can be changed (transferred) from the spray twist structure to the uniform twist (reverse twist) structure. it can. Further, the liquid crystal display element can be driven using the power source 20.

  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. For this reason, the liquid crystal display element by an Example becomes a normally white type liquid crystal display element.

  FIG. 3 is a photograph showing a spray twist structure state and a reverse twist structure state of the liquid crystal display element 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.

  As described above, the liquid crystal display element according to the first embodiment applies an alternating voltage equal to or higher than the threshold voltage between the upper ITO electrode 12a and the lower ITO electrode 12b to change the alignment state of the liquid crystal molecules 14a. It is possible to transfer from a twist structure to a reverse twist structure. The transition occurs more rapidly as the frequency of the applied voltage is higher.

  The threshold voltage value causing the transition depends on the kind of liquid crystal material, the amount of chiral material added, etc. In the liquid crystal display element according to the first embodiment, by applying a voltage of 7 V or more for about 3 seconds, The alignment state of a part of the liquid crystal molecules 14a on the electrodes 12a and 12b was transferred to a reverse twist structure. When a voltage of 10 V and 200 Hz was applied for 3 minutes, the structure of all the liquid crystal molecules 14a on the electrodes 12a and 12b was completely transferred to the reverse twist structure. The experiment described later was conducted after the structure was completely transferred to the reverse twist structure.

  As shown in FIG. 3, there is no visual difference between the spray twist arrangement state and the reverse twist arrangement state. Moreover, the same favorable white display was performed in any arrangement state. Both alignment states are twisted nematic alignments, although the twist directions of the liquid crystal molecules are different, and are almost indistinguishable when the cell is observed from the normal direction of the substrate. Both arrangement states can be easily distinguished when, for example, the liquid crystal cell is observed from an oblique direction and a voltage slightly higher than a threshold voltage that causes transition is applied. This is because the directions in which the liquid crystal molecules in the vicinity of the center in the thickness direction of the liquid crystal cell rise (the best viewing direction) differ from each other by 90 °.

  When a voltage of about the saturation voltage is applied between the electrodes 12a and 12b of the liquid crystal display element according to the first embodiment, the liquid crystal molecules 14a become the substrates 10a and 10b in both the spray twist arrangement state and the reverse twist arrangement state. Standing up in the vertical direction, good black display was obtained. Further, in each of the two structures, white display and black display were observed with different viewing angles, and it was confirmed that both had relatively wide viewing angle characteristics with almost no display inversion. Compared with the spray twist structure, the viewing angle of the reverse twist structure was slightly narrow, but no significant difference was observed.

  From the above, it has been found that the liquid crystal display element according to the first example can obtain a good black and white display without any special optical compensation in either the spray twist structure or the reverse twist structure. This point is not limited to the first embodiment, but is the same for other embodiments.

  When the liquid crystal display element according to the first embodiment, which had transitioned to the reverse twist arrangement state, was left in a state where no voltage was applied, it was observed that the reverse twist arrangement gradually returned to the spray twist arrangement. From this, it can be seen that the liquid crystal display element according to the first embodiment is more stable in the spray twist arrangement state than in the reverse twist arrangement state when no voltage is applied. In the liquid crystal display device according to the first example, when the voltage-free state lasted for about 2 minutes, the reverse transition from the reverse twist arrangement to the spray twist arrangement occurred. However, when the voltage is applied to some extent, the reverse twist arrangement state can be maintained for a long time.

  The inventors of the present application measured the electro-optical characteristics of the liquid crystal display element according to the first example. The results are shown in FIGS. 4 (A) and 4 (B). FIG. 4A shows the relationship between applied voltage and light transmittance in the spray twist arrangement state, and FIG. 4B shows that in the reverse twist arrangement state. In both figures, 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 "%". Light transmission means that light incident from one side of the polarizing plates 15a and 15b passes to the other side.

  The sharpness (steepness of change in light transmittance with respect to the applied voltage) is clearly different between the spray twist arrangement state and the reverse twist arrangement state. As shown in FIG. 4B, in the reverse twist arrangement state, the applied voltage It can be seen that the steepness of the change in light transmittance with respect to is large (sharpness is excellent).

  V10 / V90 and V5 / V90 were calculated as sharpness values for each of the spray twist arrangement state and the reverse twist arrangement state. Here, V5, V10, and V90 are voltage values that give 5% light transmittance, 10% light transmittance, and 90% light transmittance, respectively, where the brightest light transmittance is 100%. . As a result of the calculation, V10 / V90 = 1.746 and V5 / V90 = 1.987 in the spray twist arrangement state, and V10 / V90 = 1.037 and V5 / V90 = 1.041 in the reverse twist arrangement state. Sharpness values were determined.

  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 in the reverse twist arrangement state. That is, the liquid crystal display element according to the first embodiment can be driven at a high duty of 1/480 duty driving using the reverse twist arrangement state.

  On the other hand, the sharpness value required to drive the liquid crystal display element by 1/8 duty is 1.447 or less. The liquid crystal display element according to the first embodiment cannot realize this necessary value for both V10 / V90 and V5 / V90 in the spray twist arrangement state. That is, using the spray twist arrangement state, it can be seen that bright display cannot be performed even in the case of 1/8 duty driving.

In duty driving (simple matrix driving), 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 (1).

(1)

A liquid crystal display device according to the second embodiment will be described. The second embodiment differs from the first embodiment in the liquid crystal material used. In the second embodiment, a liquid crystal layer was formed using RDP-83107 manufactured by DIC Corporation, which is a nematic liquid crystal material. The kind and amount of chiral material added to the liquid crystal are the same as in the first embodiment. That is, the chiral pitch is 15 μm in the left twist direction along the direction from the upper substrate to the lower substrate.

  FIG. 5 is a graph showing electro-optical characteristics of the liquid crystal display device according to the second embodiment in a reverse twist 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 light transmittance of the liquid crystal display element in the unit “%”. Two liquid crystal display elements according to the second embodiment were produced, and the relationship between the applied voltage and the light transmittance was examined for both.

  It can be seen that the liquid crystal display element according to the second example is also excellent in sharpness, as in the case of the first example shown in FIG. It can also be seen that the individual difference in applied voltage-light transmittance characteristics is small, and the margin for the cell conditions is relatively wide.

  A liquid crystal display device according to a third embodiment will be described. In the third embodiment, the liquid crystal material used is different from those in the first and second embodiments. In the third embodiment, a liquid crystal layer is formed using RDP-83108 manufactured by DIC Corporation, which is a nematic liquid crystal material. The type and amount of chiral material added to the liquid crystal are the same as in the first and second embodiments. The chiral pitch is 15 μm in the left twist direction along the direction from the upper substrate to the lower substrate.

  FIG. 6 is a graph showing electro-optical characteristics of the liquid crystal display element according to the third embodiment in a reverse twist 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 light transmittance of the liquid crystal display element in the unit “%”. The inventors of the present application manufactured four liquid crystal display elements according to the third embodiment, and examined the relationship between the applied voltage and the light transmittance for each element.

  It can be seen that the liquid crystal display element according to the third embodiment is also excellent in sharpness, as in the case of the first embodiment shown in FIG. 4B and the second embodiment shown in FIG. Also in the third embodiment, it can be seen that the individual difference in applied voltage-light transmittance characteristics is small, and the margin for the cell condition is relatively wide.

  In the liquid crystal display elements according to the first to third embodiments, the thickness (cell thickness) d of the liquid crystal layer 14 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 material added to the liquid crystal.

In the case of a TN type liquid crystal display element, in order to obtain a bright display, in the Gucci Terry formula indicating the light transmittance T _NB at the time of normally black of the TN type liquid crystal cell, the condition of the first minimum or the second minimum is set. It is necessary to satisfy. The Gucci Terry equation is expressed by the following equation (2).

(2)

Here, u is a value calculated by the following equation (3).

(3)

In equation (3), 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 as described above.

  In order to satisfy the condition of the first minimum or the second minimum of the Gucci Terry equation, it is desirable to select a liquid crystal material (refractive index anisotropy Δn of liquid crystal) according to the cell thickness d. 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.

  As the cell thickness d is smaller, the alignment state of the liquid crystal molecules is considered to be strongly defined by the combination of the alignment treatment direction and the pretilt angle. Therefore, the liquid crystal display element having the smaller cell thickness d is in the reverse twist alignment state. Is presumably stable.

  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, the influence of the chiral material appears strongly, and the spray twist arrangement state tends to exist stably. As a result, the threshold voltage required for transition from the spray twist arrangement state to the reverse twist arrangement state increases, and the time during which the reverse twist 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, the distortion in the liquid crystal layer given by the chiral material also becomes smaller and the sharpness tends to deteriorate. It is preferable that the amount of chiral material added is large, that is, the chiral pitch p is small. It would be desirable for the value of d / p to be approximately greater than 1/4.

  In the liquid crystal display elements according to the first to third embodiments, an alignment film was formed using an alignment film material that exhibits a low pretilt angle. For comparison, the inventors of the present invention produced liquid crystal display elements by changing only the alignment film material used in the first embodiment and the pretilt angle applied to the alignment film. A material showing a relatively high pretilt angle was used as the alignment film material, and a pretilt angle of 21 ° was given to the formed alignment film.

  FIG. 7 is a graph showing electro-optical characteristics in a reverse twist arrangement state of the liquid crystal display element with a pretilt angle of 21 °. 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 “%”. Four liquid crystal display elements having a pretilt angle of 21 ° were produced, and the relationship between applied voltage and light transmittance was examined for each.

  The four liquid crystal display elements with a pretilt angle of 21 ° have individual differences, but all have low drive voltage thresholds. However, the excellent sharpness as shown in FIG. From the results shown in FIG. 7, in order to achieve excellent sharpness, an alignment film is formed using an alignment film material that exhibits a low pretilt angle, and an alignment treatment is applied to the formed alignment film to provide a low pretilt angle. Is considered desirable.

  The inventor of the present application has studied the relationship between the sharpness and the pretilt angle of the reverse TN liquid crystal display element. First, the controllability of the pretilt angle will be described. The inventors of the present invention applied a polyimide material exhibiting a high pretilt angle (PIA-768-01X manufactured by Chisso Petrochemical Co., Ltd.) to a polyimide material exhibiting a low pretilt angle (PIA-359-01X manufactured by Chisso Petrochemical Co., Ltd.). It was confirmed that an alignment film formed of two kinds of mixed polyimide materials to which the above was added can continuously exhibit a pretilt angle.

  FIG. 8 is a graph showing the relationship between the mixing ratio of two types of polyimide materials and the developed pretilt angle. The horizontal axis of the graph indicates the content ratio (concentration) of PIA-768-01X in the mixed polyimide material in the unit “%”, and the vertical axis indicates the magnitude of the developed pretilt angle in the unit “°”. In measuring the pretilt angle, a liquid crystal material ZLI4792 manufactured by Merck & Co., Inc. was used. From this figure, it can be seen that the pretilt angle increases in proportion to the content ratio of the polyimide material PIA-768-01X. Therefore, the pretilt angle to be expressed can be continuously controlled by adjusting the mixing ratio of the polyimide materials PIA-768-01X and PIA-359-01X.

  Hereinafter, liquid crystal display elements according to the fourth embodiment and the first to third comparative examples will be described. The fourth embodiment is a liquid crystal display element in which an alignment film is formed of a mixed polyimide material in which the mixing ratio of polyimide alignment film materials PIA-768-01X and PIA-359-01X is 20:80, first to third The comparative examples are liquid crystal display elements having alignment films formed in this order at a mixing ratio of 45:55, 40:60, and 30:70.

  The liquid crystal display device according to the fourth example was manufactured by a method similar to the manufacturing method described with reference to FIG. The differences and additional details are as follows.

  On a pair of square glass substrates (thickness 1.1 mm) each having a side of 2 cm, a square ITO electrode having a side of 1 cm and a peripheral electrode for taking out the conduction to the outside were formed. In forming the alignment film, a polyimide material for alignment film in which PIA-768-01X manufactured by Chisso Petrochemical Co., Ltd. was mixed at a ratio of 20% and PIA-359-01X at a ratio of 80% was formed with a thickness of about 0.1 μm. It apply | coated on the glass substrate. A cotton velvet cloth was used for the rubbing treatment. The rubbing direction was a direction orthogonal to each other when a pair of glass substrates were bonded together. Specifically, when the rubbing direction of the upper alignment film is the first direction and the rubbing direction of the lower alignment film is the second direction, the second direction is the first direction as viewed from the normal direction of the upper substrate. It was set as the direction which makes 90 degrees on the basis of this direction. The combination of the direction in which the pretilt angle is formed (the direction in which the liquid crystal molecules stand up with respect to the substrate) and the direction of the pretilt angle in the lower substrate, as determined by the rubbing direction of the upper substrate, More specifically, for example, when a liquid crystal material that does not include a chiral material is disposed between the alignment films, the combination has a uniform structure that is twisted by 90 ° in the right direction.

  On the alignment film of one glass substrate, a 5 μm diameter silica gap control material (Ube Nitto Kasei Co., Ltd., High Plesica UF) was sprayed, and then an epoxy sealant was applied to the periphery of the glass substrate at 150 ° C. Was cured by heating at a temperature of 1 hour. In the seal portion, an inlet and an outlet for injecting a liquid crystal material were prepared.

  The empty cell thus prepared was placed on a hot plate, and the liquid crystal composition was injected from the inlet into the space surrounded by the sealing material using the capillary phenomenon. As the liquid crystal material, RDP-83409 manufactured by DIC Corporation was used. A chiral material was added to the liquid crystal. The addition amount was adjusted so that the chiral pitch was 15 μm in the right twist direction along the direction from the upper substrate to the lower substrate. After the injection of the liquid crystal composition, an epoxy adhesive was placed at the injection port and the exhaust port and allowed to stand for one day to be cured and sealed. When the alignment state of the liquid crystal was observed with a polarizing microscope, a uniform alignment state on the entire surface was confirmed. The pretilt angle imparted to the alignment film was about 5 ° as a result of measurement with a liquid crystal element pretilt angle measuring device PAS-001 manufactured by Toyo Corporation.

  When the applied voltage-light transmittance characteristics in this state were confirmed, it was found that a threshold value of a driving voltage higher than that of a normal TN liquid crystal display element was observed, and a liquid crystal element having a spray twist structure was formed. Further, when a rectangular wave voltage of 10 V was applied between the electrodes of the liquid crystal element to maintain a state in which the liquid crystal molecules were arranged substantially perpendicular to the substrate, a change was observed in the color tone of the liquid crystal element. The change in color occurred partially, and the part where the color changed changed gradually and spread over the whole surface in a few minutes. It is considered that the transition from the spray twist arrangement state to the reverse twist arrangement state occurred in the region where the color tone changed. The reverse twist arrangement state existed for several tens of seconds after the application of voltage was stopped, but after that, the reverse twist arrangement state re-transferred to the spray twist arrangement state.

  FIG. 9 is a graph showing the relationship between the applied voltage and the light transmittance in the reverse twist arrangement state of the liquid crystal display element according to the fourth embodiment. 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 inventors of the present application produced four liquid crystal display elements according to the fourth embodiment, and examined the relationship between the applied voltage and the light transmittance for each element. LCD5200 which is a liquid crystal element electro-optical characteristic measuring apparatus made from Otsuka Electronics Co., Ltd. was used for the measurement.

  One of the four produced has excellent sharpness similar to that of the first to third embodiments shown in FIGS. 4 (B), 5 and 6, but the remaining three. Is not allowed. Therefore, in the reverse TN type liquid crystal display element, the superiority of sharpness does not continuously change depending on the pretilt angle, but the pretilt angle given to the upper and lower substrates is both 0 ° at the pretilt angle of 5 °. It is considered that excellent sharpness appears under the condition of 5 ° or less.

  FIGS. 10A to 10C show the relationship between the applied voltage and the light transmittance in the reverse twist arrangement state of the liquid crystal display elements according to the first to third comparative examples, respectively. As described above, in the first to third comparative examples, the mixing ratio of the polyimide alignment film materials PIA-768-01X and PIA-359-01X is 45:55, 40:60, and 30:70. A liquid crystal display element in which an alignment film is formed of a polyimide material. The liquid crystal display elements according to the first to third comparative examples were manufactured by the same method as that of the fourth example except that the mixing ratio of the alignment film materials was changed. A plurality of liquid crystal cells were prepared for each comparative example. 10A to 10C, the horizontal axis represents the voltage applied between the electrodes in the unit “V”, and the vertical axis represents the light transmittance of the liquid crystal display element in the unit “%”.

  The pre-tilt angle of the first comparative example (mixing ratio 45:55) showing the electro-optical characteristics shown in FIG. 10A is considered to be slightly over 15 ° as judged from the graph of FIG. 10B and 10C, the pre-tilt angles of the second comparative example (mixing ratio 40:60) and the third comparative example (mixing ratio 30:70) showing the electro-optical characteristics are 15 °, respectively. It is considered weak and 7-8 °.

  From the results shown in FIGS. 10A to 10C, it can be seen that in the first to third comparative examples, the sharpness superiority in the reverse twist arrangement state is not observed. It is also reconfirmed that the sharpness excellence does not continuously change depending on the pretilt angle.

  As described above, excellent sharpness characteristics appear under the condition that the pretilt angle is greater than 0 ° and less than or equal to 5 °. As already described, the ratio d / p between the thickness d of the liquid crystal layer and the chiral pitch p of the chiral material is preferably greater than ¼ and ½ or less.

  The inventors of the present application provide a reverse TN liquid crystal display element having a liquid crystal layer thickness d = 5 μm, a chiral pitch p = 20 μm, d / p = 1/4, and a pretilt angle θ = 1 °, and a thickness of the liquid crystal layer A reverse TN liquid crystal display device having d = 5 μm, chiral pitch p = 20 μm, d / p = 1/4, and pretilt angle θ = 5 ° was fabricated, and the electro-optical characteristics in the reverse twist arrangement state were examined. As a result, excellent sharpness as seen in the examples was not recognized. Accordingly, when the pretilt angle θ is 1 ° or more and 5 ° or less, it is considered that d / p is larger than ¼ as a necessary condition for obtaining excellent sharpness characteristics.

  The reverse TN liquid crystal display element according to the embodiment can obtain a black and white display without an optical compensator, is inexpensive and easy to manufacture, has a relatively wide viewing angle, and has a high response speed. This is a liquid crystal display element that can realize excellent sharpness while maintaining the above advantages. Since sharpness is excellent, for example, when simple matrix driving is performed, display can be performed with a large display capacity.

  Further, since it is a liquid crystal display element having a low pretilt angle, it can be manufactured using a highly reliable alignment film material for TN liquid crystal display elements widely used in industry, and thus has high reliability. It is a liquid crystal display element provided with.

  Further, the liquid crystal display element according to the embodiment can be driven by 1/480 duty. In simple matrix driving, 1/480 duty driving is driving with the highest number of duties. For this reason, the application range is wide, and for example, it can be used for almost all liquid crystal display elements driven by a simple matrix.

  In addition, because of excellent sharpness characteristics, the number of common electrodes (either the upper ITO electrode 12a or the lower ITO electrode 12b) is large, for example, 100 or more, and display can be performed with high display performance.

FIG. 11 is a table summarizing the boundary voltages of the liquid crystal display elements according to the first to fourth embodiments and the physical property values of the liquid crystal materials used in the liquid crystal display elements. V _c in the table indicates the measured value of the boundary voltage of the liquid crystal display element in the unit “V”. The boundary voltage is a voltage that returns to the spray twist alignment state when the applied voltage of the liquid crystal display element in the reverse twist alignment state is gradually lowered. Δε represents the dielectric anisotropy of the liquid crystal material. K ₁₁ , K ₂₂ , and K ₃₃ respectively represent the elastic constant of the spread of the liquid crystal material, the elastic constant of the twist, and the elastic constant of the bending in the unit “pN”. Further, γ1 represents the rotational viscosity of the liquid crystal material in the unit “mPa · s”.

It will be said to be stable in the reverse twist alignment state as the boundary voltage V _c is less liquid crystal display device. Therefore, in the preparation of a reverse TN-type liquid crystal display device, it is desirable to select a liquid crystal material and the cell structure to reduce the boundary voltage V _c.

As a result of the present inventors' study, in a reverse TN-type liquid crystal display device according to an embodiment, it was found that a higher stability value is large reverse twist alignment state smaller value of K ₂₂ of K _11. From the viewpoint of the stability of the reverse twist arrangement state, it is possible to form a liquid crystal layer using a liquid crystal material in which the ratio “K ₁₁ / K ₂₂ ” of the elastic constant K _{11 of} spread and the elastic constant K ₂₂ of twist is 2 or more. Would be preferred.

The characteristics of the liquid crystal display element according to the example will be described using the physical property values in the table shown in FIG. The following expression (4) is an expression for calculating the threshold voltage _Vth of the drive voltage in the reverse twist arrangement state of a general reverse TN liquid crystal display element having a pretilt angle of 0 °.

(4)

In the equation (4), ε ₀ represents a vacuum dielectric constant (8.84541882 × 10 ⁻¹² F / m). In the case of a reverse TN liquid crystal display element with a twist angle of 90 °, K is a value calculated by the following equation (5).

(5)

In general, when the pretilt angle is 0 °, the threshold value of the drive voltage becomes maximum. That is, the drive voltage threshold value of the reverse TN liquid crystal display element whose pretilt angle is not 0 ° is smaller than the voltage value _Vth obtained by the equations (4) and (5). Therefore, for example, the driving voltage threshold value of the liquid crystal display elements according to the first to fourth embodiments should be smaller than _Vth .

Referring to the table of FIG. 11, when the physical property values of the liquid crystal materials constituting the liquid crystal layers of the liquid crystal display elements according to the first to fourth embodiments are substituted into formulas (4) and (5), V _th is as follows: Is calculated.

In the case of RDP84910 (first embodiment), V _th ≈0.62V.

In the case of RDP83107 (second embodiment), V _th ≈0.89V.

In the case of RDP83108 (third embodiment), V _th ≈0.89V.

In the case of RDP83409 (fourth embodiment), V _th ≈0.98V.

However, referring to FIG. 4B, the threshold voltage (switching voltage: the voltage value at which the light transmittance starts changing when a voltage is applied) of the liquid crystal display element according to the first embodiment is 1.2 to 1. .3V, which is approximately twice V _th ≈0.62V. Referring to FIG. 5, the threshold voltage of the driving voltage of the liquid crystal display device according to the second embodiment is about 1.8V, which is about twice V _th ≈0.89V. Further, referring to FIG. 6, the threshold voltage of the driving voltage of the liquid crystal display device according to the third embodiment is 1.5 to 1.7 V, which exceeds 1.5 times V _th ≈0.89 V. Yes. Referring to FIG. 9, the driving voltage threshold value of the liquid crystal display device according to the fourth embodiment is 1.3 to 1.5V. This is 1.3 times or more of V _th ≈0.98V. As described above, the liquid crystal display element according to the example has a threshold of the driving voltage that is 1.3 times or more larger than the threshold voltage _Vth obtained by the equations (4) and (5).

  FIG. 12 shows an example of a waveform of a drive voltage applied by the power source 20 between the upper ITO electrode 12a and the lower ITO electrode 12b. In the figure, the horizontal axis represents time, and the vertical axis represents voltage value. “Selected waveform Vs” represents a drive voltage waveform applied to the selected pixel, and “non-selected waveform Vus” represents a drive voltage waveform applied to the non-selected pixel.

  When the liquid crystal display element according to the embodiment is driven, a relatively high voltage having a waveform as shown in the drawing is instantaneously applied not only to the selected pixel but also to the non-selected pixel, for example, at a constant cycle. Therefore, in the liquid crystal display element according to the embodiment, first, a voltage equal to or higher than the threshold voltage is applied between the electrodes 12a and 12b, and the arrangement state of the liquid crystal molecules 14a is changed from the spray twist arrangement to the reverse twist arrangement. If duty driving is performed, it is possible to continue display without applying a transition voltage for a long time. At this time, the higher the duty drive display, the higher the peak voltage value, and it is considered that the reverse twist arrangement state is more stable. From this point of view, the liquid crystal display element according to the embodiment is preferably driven by setting the driving condition of the simple matrix driving to a duty higher than 1/120 duty.

  Finally, the hypothetical view of the present inventors regarding the reason why excellent sharpness appears in the reverse twist arrangement state of the reverse TN liquid crystal display element will be described.

  For example, with respect to the reverse TN type liquid crystal display element described in Patent Document 3 which is the previous application of the present inventors, the liquid crystal in the reverse twist arrangement state can be obtained even when the voltage is off, from the simulation and the light transmittance when the voltage is off. It has been found that the liquid crystal molecules near the center in the thickness direction of the layer are slightly raised due to internal strain. The reason why the threshold value of the drive voltage of the reverse TN liquid crystal display element is low is considered to be that, from this state, the voltage required for raising the liquid crystal molecules substantially perpendicular to the substrate can be reduced. Further, in the reverse TN liquid crystal display element (normally white type) described in Patent Document 3, the light transmittance at the time of voltage OFF in the reverse twist arrangement state is slightly lower than that in the spray twist arrangement state. However, this is also considered to be because the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are in a slightly raised state when the voltage is turned off.

  However, for example, referring to FIGS. 4A and 4B showing the electro-optical characteristics of the liquid crystal display element according to the first embodiment, the light transmittance at the time of voltage OFF in the reverse twist arrangement state is in the spray twist arrangement state. Rather big of that. In addition, the reverse twist arrangement state is also greater with respect to the drive voltage threshold (applied voltage when the light transmittance starts to decrease).

  From these facts, in the liquid crystal display element according to the example, when the voltage in the reverse twist alignment state is turned off, the liquid crystal molecules near the center in the liquid crystal layer thickness direction should be large even though there should be a large distortion inside the liquid crystal layer. There is almost no rise, and it is presumed that they are oriented almost parallel to the substrate surface. When a voltage is applied to the liquid crystal display element according to the embodiment, the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are hardly raised, so that the liquid crystal molecules do not tilt in the electric field direction unless a high voltage is applied to some extent. As soon as it begins to tilt, the suppressed internal strain and relatively large electric field cause a steep change in the direction of the liquid crystal director, and almost no liquid crystal molecules near the center of the liquid crystal layer thickness direction with a slight voltage difference. Standing vertically, it is thought that excellent sharpness is realized.

  However, it is unclear why there is almost no rise of liquid crystal molecules near the center in the thickness direction of the liquid crystal layer, although there should be a large strain inside the liquid crystal layer. The existence of a large strain in the liquid crystal layer due to the addition of the chiral material, the small pretilt angle imparted to the alignment film, the value of the elastic constant of the liquid crystal material forming the liquid crystal layer, etc. are considered to be related.

  According to observation, in the reverse twist arrangement state of the reverse TN liquid crystal display element, the ratio “θ / (p / d)” between the pretilt angle θ and p / d (p: chiral pitch, d: cell thickness). Is larger than a certain value, a phenomenon occurs in which liquid crystal molecules near the center in the thickness direction of the liquid crystal layer rise in the absence of applied voltage. According to the study by the inventors of the present application, when θ / (p / d) is larger than 2 °, rising of liquid crystal molecules near the center in the thickness direction of the liquid crystal layer is observed. Therefore, in the graph showing the relationship between the applied voltage and the light transmittance of the reverse TN liquid crystal display element that satisfies this condition, the threshold characteristic is not seen, and the light transmittance starts to change from 0V.

On the other hand, when θ / (p / d) is 2 ° or less, the phenomenon in which the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer rise up is not observed when no voltage is applied, and the applied voltage, light transmittance, A steep threshold characteristic is recognized in the graph showing the relationship. That is, excellent sharpness appears under the condition of the following expression (6).

(6)

here,

(7)

(8)

It is.

  FIGS. 13A and 13B are graphs showing examples of pretilt angles θ and p / d ranges in which excellent sharpness appears in a reverse TN liquid crystal display element. In both graphs, the horizontal axis represents p / d, and the vertical axis represents the pretilt angle θ in the unit “°”. A hatched region (the boundary region includes a solid line part, does not include a broken line part, and does not include a point with a white circle) satisfies Expressions (6) to (8).

Linear _{l A} of FIG. 13 (A), the straight line _{l B} shown in FIG. 13 (B) are both inclination of the two lines. That is, the straight lines l _A and l _B are included in the straight line group represented by the following expression (9).

(9)

In equation (9), β is a constant that depends on the liquid crystal material. In the straight line l _A in FIG. 13A, β = −1, and in the straight line l _B in FIG. 13B, β = 1. FIGS. 13A and 13B show the case of β = ± 1, but β takes other values depending on the liquid crystal material used in the reverse TN type liquid crystal display element. The straight line with the slope 2 that demarcates the region (combination of θ and p / d) where excellent sharpness appears rises and falls. Therefore, the range of the combination of θ and p / d that realizes excellent sharpness varies depending on the liquid crystal material.

    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 in the reverse twist arrangement state is 90 °, but may be changed in a range of about ± 20 ° (70 ° to 110 °). However, in consideration of the brightness of white display, it is desirable that the twist angle be 90 ° or the vicinity thereof.

  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 °. It can also 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.

    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 liquid crystal display elements in general, for example, in-vehicle liquid crystal display elements that perform various displays such as audio display and heat control display, and liquid crystal display elements for office automation equipment such as copiers. Further, it can be suitably used for a liquid crystal display element driven by a simple matrix, particularly when a large display capacity is required.

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 Power supply

Claims (7)

A first substrate comprising a first electrode and oriented in a first direction;
A second substrate disposed opposite to and parallel to the first substrate, provided with a second electrode, and oriented in a second direction;
A liquid crystal layer that is disposed between the first substrate and the second substrate, includes a chiral material, and has a twist alignment;
The second direction is a direction having an axis that forms an angle of 70 ° to 110 ° in the first rotation direction with respect to the first direction when viewed from the normal direction on the first substrate side;
The liquid crystal layer has a uniform twist structure that is twisted in the first rotation direction by a voltage applied between the first electrode and the second electrode, and is opposite to the first rotation direction. A spray twist structure twisting in the second direction of rotation is produced commutatively,
The chiral material is formed on the liquid crystal molecules of the liquid crystal layer along the second direction along the direction from the first substrate toward the second substrate when viewed from the normal direction on the first substrate side. with the capability of Ru swirled of to,
The first substrate and the second substrate are aligned so that a pretilt angle θ greater than 0 ° and less than or equal to 5 ° is expressed,
When the thickness of the liquid crystal layer is d and the chiral pitch of the chiral material is p, the θ, the d, and the p are the following formulas (1) and (2)
(1)
(2)
A liquid crystal display element that satisfies the requirements. When the elastic constant of the spread of the liquid crystal material constituting the liquid crystal layer is K ₁₁ and the elastic constant of torsion is K ₂₂ , K ₁₁ and K ₂₂ are expressed by the following formula (3)
(3)
The liquid crystal display element according to claim 1, wherein: The second direction is a direction having an axis that forms an angle of 90 ° in the first rotation direction with respect to the first direction when viewed from the normal direction on the first substrate side. Or the liquid crystal display element of 2.   The liquid crystal display element according to claim 1, wherein the first substrate and the second substrate are subjected to an alignment treatment so that a pretilt angle θ of 1 ° or more and 5 ° or less is developed.   5. The liquid crystal display element according to claim 1, wherein the second electrode is a common electrode, and the number of electrodes of the common electrode is 100 or more. Furthermore,
A first polarizing plate disposed on the opposite side of the first substrate from the liquid crystal layer;
A second polarizing plate disposed on the opposite side of the second substrate from the liquid crystal layer;
Including
In the uniform twist structure, when a voltage is applied between the first electrode and the second electrode, light is incident from one side of the first polarizing plate and the second polarizing plate. However, the voltage value at which the amount passing to the other side starts to change is K ₃₃ as the bending elastic constant of the liquid crystal material constituting the liquid crystal layer, Δε as the dielectric anisotropy, and ε ₀ as the vacuum dielectric constant. When doing the following formula (4) and (5)
(4)
(5)
The liquid crystal display element according to claim 1, wherein the liquid crystal display element is 1.3 times or more of the voltage value _Vth obtained by the following equation. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is driven with a driving condition of simple matrix driving set to a duty higher than 1/120 duty.