KR20110055431A - Liquid crystal device - Google Patents

Abstract

PURPOSE: A liquid crystal display device of high display quality and supplies a TN type liquid crystal device is provided to supply a liquid crystal display device of low power consumption by using new TN type liquid crystal display device. CONSTITUTION: A first substrate(11) faces with a second substrate(15). A liquid crystal layer(14) is installed between one side of a first substrate and one side of a second substrate. An electric field applying unit applies electric field on the liquid crystal layer. The first substrate and the second substrate are relatively arranged so that a first orientation state is arranged about the liquid crystal molecule of the liquid crystal layer. The liquid crystal layer adds chiral agent generating a second orientation state.

Description

Liquid Crystal Device

The present invention relates to a liquid crystal device and a liquid crystal display device having the same.

Japanese Patent No. 2510150 discloses a liquid crystal display device in which electro-optical characteristics are improved by twisting and aligning liquid crystal molecules in a turning direction opposite to a turning direction regulated by a combination of alignment treatment directions performed on a pair of opposed substrates, respectively. Is disclosed.

In addition, Japanese Patent Application Laid-Open No. 2007-293278 discloses a turning direction (second turning direction) opposite to a turning direction (first turning direction) regulated by a combination of alignment treatment directions applied to a pair of opposingly disposed substrates, respectively. The bit is a liquid crystal which adds a chiral agent and increases the distortion in the liquid crystal layer by twisting and orienting the liquid crystal molecules in the above-described first turning direction, thereby lowering the threshold value voltage to enable low voltage driving. A device is disclosed.

By the way, in the liquid crystal display device of Japanese Patent No. 2510150, the alignment state of reverse twist is unstable, and the reverse state of twisting can be obtained by applying a relatively high voltage to the liquid crystal layer. There is a problem of transition to a torsional alignment state. In addition, although the liquid crystal element of Japanese Patent Laid-Open No. 2007-293278 has the advantage of lowering the threshold voltage as described above, when the voltage is turned off (for example, several seconds), the liquid crystal element immediately transitions to an orientation state of forward twisting. Conversely, there is a problem of raising the threshold value. In addition, neither of these assumes active use of two alignment states, forward twist and reverse twist, for use in display and the like. In other words, there is no disclosure or suggestion of technical thoughts such as a configuration, a driving method, and the like necessary for actively utilizing bistable stability. Furthermore, in reverse twisted nematic (RTN) type liquid crystal elements as described in the above invention, the liquid crystal molecules are generally twisted in the first turning direction (reverse twisted arrangement state) and the second turning. In the arrangement state twisted in the direction (spray twist arrangement state), there is no significant difference in the apparent display state (light transmittance), and high contrast ratio is hardly obtained even if bistable stability is given.

A specific aspect according to the present invention is to provide a novel TN type liquid crystal device using a transition between two alignment states.

Another object of the present invention is to provide a liquid crystal display device capable of driving low power consumption by using a novel TN type liquid crystal device.

Another object of the present invention is to provide a liquid crystal device having a high display quality.

In one embodiment of the liquid crystal device according to the present invention, (a) each surface is subjected to an alignment treatment, and the first substrate and the second substrate are disposed to face each other, and (b) one surface and the second substrate of the first substrate. A liquid crystal layer provided between one surface of the substrate, and (c) an electric field applying means for applying an electric field to the liquid crystal layer, and (d) the first substrate and the second substrate with respect to the liquid crystal molecules of the liquid crystal layer. (E) the liquid crystal layer is twisted in a second turning direction opposite to the first turning direction with respect to the liquid crystal molecules, and is disposed relatively so that a first alignment state twisted in a first turning direction is likely to occur. A chiral agent having a property of generating an alignment state is added, and (f) the liquid crystal layer is applied with an electric field in a direction substantially perpendicular to each one surface of the first substrate and the second substrate by the electric field applying means. Thereby to the first alignment state It is a liquid crystal element that transitions.

Preferably, the electric field applying means has at least a first electrode provided on one side of the first substrate and a second electrode provided on one side of the second substrate.

Preferably, the liquid crystal layer transitions to the second alignment state by applying an electric field in a direction substantially parallel to each one surface of the first substrate and the second substrate.

Preferably, the electric field applying means further has a third electrode and a fourth electrode which are provided on the upper side of the second electrode of the second substrate via an insulating layer and are spaced apart from each other.

Preferably, the first substrate and the second substrate are oriented so as to express a pretilt angle of 20 ° or more and 45 ° or less, respectively.

More preferably, the first substrate and the second substrate are oriented so as to express a pretilt angle of 31 ° or more and 37 ° or less, respectively.

In these cases, the addition amount of the chiral agent to the liquid crystal layer is preferably adjusted so that d / p is greater than 0.04 and less than 0.25 when the chiral pitch is p and the thickness of the liquid crystal layer is d. .

It is also preferable that the first substrate is oriented so as to express a pretilt angle of 40 ° or more and 65 ° or less, and the second substrate is oriented so as to express a pretilt angle of 1 ° or more and 15 ° or less.

In this case, it is also preferable that the addition amount of the chiral agent to the liquid crystal layer is adjusted so that d / p is 0.125 or more and 0.5 or less when p is the chiral pitch and d is the thickness of the liquid crystal layer.

More preferably, the angle formed between the orientation processing direction of the first substrate and the orientation processing direction of the second substrate is 90 ° or more and 100 ° or less as viewed from the normal direction of each of the first and second substrates. .

According to the present invention, it is possible to provide a novel TN type liquid crystal device using a transition between two alignment states, to provide a liquid crystal display device capable of driving low power consumption by using the same, and to provide a liquid crystal device having high display quality.

1 is a schematic cross-sectional view showing a structure of a liquid crystal device according to an embodiment.
2 is a plan view schematically showing the structure of each electrode.
FIG. 3: is a schematic cross section explaining the electric field which can be provided using each electrode with respect to a liquid crystal layer.
4 is a schematic perspective view for explaining an alignment state of liquid crystal molecules of a liquid crystal layer when no voltage is applied.
5 is a schematic perspective view for explaining an alignment state of liquid crystal molecules of a liquid crystal layer when no voltage is applied.
6 is a view for explaining in detail the conditions for obtaining bi-stable.
FIG. 7 is a diagram (micrograph) of observing a state when an electric field is applied to the liquid crystal layer and switched using the respective electrodes with respect to the liquid crystal element.
8 is a view showing a measurement result of electro-optical characteristics (voltage-transmittance characteristics) of the liquid crystal device according to the embodiment.
9 is a view showing a measurement result of electro-optical characteristics (voltage-transmittance characteristics) of the liquid crystal device according to the embodiment.
10 is a view showing a measurement result of electro-optical characteristics (voltage-transmittance characteristics) of the liquid crystal device according to the embodiment.
FIG. 11 is a diagram showing results obtained by theoretical calculation of the relationship between the stability of orientation and the cell conditions for Cases I and II.
FIG. 12 is a diagram showing results obtained by theoretical calculation of the relationship between the stability of orientation and cell conditions in Case III. FIG.
It is a figure for demonstrating the result examined by experiment about the relationship of the rubbing direction and the direction of a lateral electric field.
14 is a diagram illustrating a measurement example of transmittance characteristics of the liquid crystal device according to the embodiment.
It is a figure which shows the characteristic table which put together the measurement result of the transmittance characteristic.
It is a figure which shows the characteristic table which put together the measurement result of the transmittance characteristic.
It is a figure which shows the characteristic table which put together the measurement result of the transmittance characteristic.
18 is a diagram schematically illustrating a configuration example of a liquid crystal display device.
19 is a flowchart illustrating a method of manufacturing a liquid crystal device according to an embodiment.
20 is a table showing a combination of the firing temperature at the time of forming the alignment film and the amount of indentation at the time of rubbing treatment.
21 (a) to 21 (c) are photographs showing the appearance of a plurality of produced liquid crystal elements.
22A to 22F are tables showing manufacturing conditions of the liquid crystal element, tables and photographs showing the observation results.
23 is a schematic cross-sectional view in one pixel of the liquid crystal element according to the embodiment.
24 is a schematic plan view showing a pattern of an ITO film formed on the upper transparent substrate 111a.
25 is a schematic plan view showing a pattern of an ITO film formed on the lower transparent substrate 111b.
Fig. 26 is a schematic plan view showing a photomask used for etching an ITO film.
FIG. 27 is a schematic plan view showing a part of the formation region of the lower alignment layer 114b formed on the lower substrate 110b.
28 is a schematic plan view showing the structure of a liquid crystal element according to the embodiment.
29 (a) to 29 (c) are external photographs of the liquid crystal device according to the embodiment, and (d) to (f) are schematic cross-sectional views showing electric field directions when voltage is applied.
30A to 30D are graphs showing voltage-transmittance characteristics of the liquid crystal device according to the embodiment and the liquid crystal device manufactured under other preferable conditions.
31A and 31B are graphs showing visual-contrast characteristics of the liquid crystal device according to the embodiment.
32 is a schematic cross-sectional view in one pixel of the liquid crystal device 200 according to the embodiment.
33 is a schematic plan view and a cross-sectional view illustrating an alignment state of liquid crystal molecules in the liquid crystal layer 203 according to the embodiment.
34 is a flowchart illustrating a method of manufacturing a liquid crystal device according to an embodiment.
35 is a table showing a result of visual observation of a display state of cell fabrication conditions of a liquid crystal element.
36 is a graph showing the voltage-light transmittance characteristics of the liquid crystal device according to the embodiment prepared under the cell fabrication conditions No. 1 to 3;
Fig. 37 is a table showing the results of visually observing the retention time in the black display state by changing the addition amount of the chiral agent in the liquid crystal element according to the cell production condition No. 3;

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings.

1 is a schematic cross-sectional view showing the structure of a liquid crystal element of an embodiment. The liquid crystal element of the present embodiment shown in FIG. 1 includes, as a basic configuration, a first substrate 11 and a second substrate 15 that are disposed opposite each other, and a liquid crystal layer 14 disposed between the two substrates. The first polarizing plate 21 is disposed outside the first substrate 11, and the second polarizing plate 22 is disposed outside the second substrate 15. Hereinafter, the structure of the liquid crystal element will be described in more detail. In addition, illustration and description are abbreviate | omitted about members, such as the sealing material which seals the circumference | surroundings of the liquid crystal layer 14, and the like.

The first substrate 11 is, for example, a transparent substrate such as a glass substrate or a plastic substrate. Like the first substrate 11, the second substrate 15 is, for example, a transparent substrate such as a glass substrate or a plastic substrate. For example, a plurality of spacers (particle-like members) are dispersed and disposed between the first substrate 11 and the second substrate 15, and the first substrate 11 and the second substrate are arranged by these spacers. (15) The distance from each other is maintained.

The first electrode 12 is provided on one surface side of the first substrate 11. Similarly, the second electrode 16 is provided on one surface side of the second substrate 15. In addition, the third electrode 18 and the fourth electrode 19 are provided on the upper side of the second electrode 16 of the second substrate 15 via an insulating layer 17 (for example, a silicon oxide film or the like). They are separated from each other. The first electrode 12, the second electrode 16, the third electrode 18 and the fourth electrode 19 are each configured by appropriately patterning a transparent conductive film such as indium tin oxide (ITO), for example. .

The alignment film 13 is provided to cover the first electrode 12 on one side of the first substrate 11. Similarly, the alignment film 20 is provided to cover the second electrode 16 on one surface side of the second substrate 15. In the present embodiment, as the alignment film 13 and the alignment film 20, an alignment state of the initial state (when no voltage is applied) of the liquid crystal layer 14 is regulated to a horizontal alignment state (horizontal alignment film). The rubbing treatment is typically performed on the alignment films 13 and 20 to generate an alignment control force with respect to the liquid crystal layer 14 and to provide a pretilt angle. In other words, an alignment process is performed on one surface of each of the first substrate 11 and the second substrate 15.

The liquid crystal layer 14 is provided between the first electrode 12 of the first substrate 11 and the second electrode 16 of the second substrate 15. In this embodiment, the liquid crystal layer 14 is constituted by using a liquid crystal material (nematic liquid crystal material) whose dielectric anisotropy Δε is positive (Δε> 0). The ellipses shown in the liquid crystal layer 14 schematically show liquid crystal molecules in the liquid crystal layer 14. When no voltage is applied, the liquid crystal molecules are aligned almost horizontally with a predetermined pretilt angle with respect to the respective substrate surfaces of the first substrate 11 and the second substrate 15. In this embodiment, the orientation orientations of the liquid crystal molecules in the liquid crystal layer 14 are aligned with the first substrate 11 by crossing the directions in which the alignment regulating forces of the first substrate 11 and the second substrate 15 are generated. It is in a twisted nematic alignment state which is gradually twisted between the second substrates 15. This will be described in more detail later.

2 is a plan view schematically showing the structure of each electrode. As shown in FIG. 2, the 3rd electrode 18 and the 4th electrode 19 have a comb-tooth shape, respectively, and these electrode branches are arrange | positioned differently. The first electrode 12 and the second electrode 16 are disposed so as to overlap each of the electrode branches of the third electrode 18 and the fourth electrode 19, respectively. The first electrode 12 and the second electrode 16 are arranged so that at least some of them overlap each other. Each of these electrodes functions as an electric field application means for imparting an electric field to the liquid crystal layer 14.

FIG. 3: is a schematic cross section explaining the electric field which can be provided using each electrode with respect to a liquid crystal layer. In FIG. 3, only each electrode is typically shown for convenience of explanation. As shown in FIG. 3A, an electric field can be generated between the two electrodes by applying a voltage between the first electrode 12 and the second electrode 16. The electric field in this case becomes an electric field along the thickness direction (cell thickness direction) of the 1st electrode 11 and the 2nd electrode 15 as shown. This field is sometimes referred to as the "vertical field."

In addition, as shown in FIG. 3B, an electric field can be generated between the two electrodes by applying a voltage between the third electrode 18 and the fourth electrode 19. The electric field in this case becomes an electric field along the direction substantially parallel to each one surface of the 1st board | substrate 11 and the 2nd board | substrate 15 as shown in figure. This field is sometimes referred to as a `` horizontal field. '' Thereafter, a mode using such an electric field may be referred to as an 'IPS mode'.

As shown in FIG. 3C, an electric field can be generated between the two electrodes by applying a voltage between the third electrode 18 and the fourth electrode 19 and the second electrode 16. . The electric field in this case becomes an electric field along the direction substantially parallel to each one surface of the 1st board | substrate 11 and the 2nd board | substrate 15 as shown in figure. This field is sometimes referred to as a `` horizontal field. '' Thereafter, a mode using such an electric field may be referred to as a 'FFS mode'.

4 and 5 are schematic perspective views for explaining the alignment state of the liquid crystal molecules of the liquid crystal layer when no voltage is applied. The liquid crystal element of this embodiment is a so-called bistable liquid crystal element having two stable alignment states as the alignment state when no voltage is applied. Then, by applying an electric field to the liquid crystal layer 14 using each of the electrodes described above, it is possible to transition from one alignment state to the other alignment state.

Specifically, the liquid crystal element shown in FIG. 4 is in an alignment state (first alignment state) in which liquid crystal molecules of the liquid crystal layer 14 are twisted in the first turning direction. When the liquid crystal molecules of the liquid crystal layer 14 are viewed from the plane of the first substrate 11 side, distortion occurs in the counterclockwise direction. Such a first alignment state is a direction easily twisted in accordance with the relative relationship between the pretilt angles generated by the alignment treatment performed on each surface of the first substrate 11 and the second substrate 15 (direction of superiority). This is achieved by twisting liquid crystal molecules. This first alignment state is stably maintained even when no voltage is applied. On the other hand, in the liquid crystal element shown in FIG. 5, the liquid crystal molecules of the liquid crystal layer 14 are in an alignment state (second alignment state) in which the liquid crystal molecules are twisted in the second turning direction opposite to the first turning direction. When the liquid crystal molecules of the liquid crystal layer 14 are viewed in a plane from the first substrate 11 side, distortion occurs in the clockwise direction. Such a second alignment state is opposite to the direction in which it is easy to twist according to the relative positional relationship of the pretilt angles generated by the alignment process performed on each surface of the first substrate 11 and the second substrate 15. This is realized by adding a chiral agent having a property of generating torsion to the liquid crystal layer 14. This second alignment state is also kept stable when no voltage is applied.

By appropriately applying the transverse electric field or the longitudinal electric field to the liquid crystal layer 14 using each of the electrodes described above, it is possible to generate the transition of the alignment state from the first alignment state to the second alignment state or vice versa. Specifically, using the first electrode 12 and the second electrode 16 (see FIG. 3A), the first electrode 11 and the second substrate 15 are substantially perpendicular to each one surface of the first substrate 11 and the second substrate 15. By applying an electric field (vertical electric field) in the direction, the alignment state of the liquid crystal layer 14 transitions to the first alignment state (see FIG. 4). In addition, the third electrode 18 and the fourth electrode 19 are used (see FIG. 3B), or the third electrode 18, the fourth electrode 19, and the second electrode 16 are formed. In combination (see FIG. 3C), an electric field (horizontal electric field) is applied to almost one surface of each of the first substrate 11 and the second substrate 15 in a substantially horizontal direction, whereby the liquid crystal layer 14 Orientation state transitions to the second orientation state (see FIG. 5). In any case, the first alignment state or the second alignment state is maintained even if no electric field is applied after applying the electric field. That is, bistable stability is shown.

The conditions for obtaining bistable stability will be described in more detail. As described above, bistable stability is related to the relationship between the pre-tilt angle on each surface of the first substrate 11 and the second substrate 15 or the twist angle (twist angle) of the liquid crystal molecules of the liquid crystal layer 14 and the liquid crystal layer. It is obtained by using a special state obtained when the chirality of the chiral agent added to (14) is set in a specific range. This "special state" is demonstrated using the table of FIG. The special state refers to a state in which both the first alignment state and the second alignment state are very stable when classified into cases I to III as shown. Specifically, in case I, the angle formed by the rubbing direction with respect to each of the alignment films 13 and 20 is set to 100 °, and the cell thickness (layer thickness of the liquid crystal layer 14) d and the chiral pitch made of chiral are made. The condition which made ratio (d / p) of (p) 0.04. Case II refers to the condition that the angle formed by the rubbing direction is 87 ° and d / p is 0. The case III refers to a condition in which the angle formed by the rubbing direction is 75 ° and the d / p is 0.04.

Hereinafter, the present invention will be described in more detail with reference to more specific examples.

First, the specific example of the manufacturing method of a liquid crystal element is demonstrated.

As the first substrate 11 and the second substrate 15, a glass substrate in which an ITO (indium tin oxide) film, which is one of the transparent conductive films, was formed in advance was used. About the 1st board | substrate 11, the ITO film | membrane of the glass substrate with this ITO film | membrane was patterned by the method of photolithography etc., and the 1st electrode 12 was formed. As the etching method, wet etching with a second iron chloride solution was used. In the patterning here, the extraction electrode portion and the portion corresponding to the first electrode 12 are left. The second electrode 16 was formed by similarly patterning the second substrate 15.

Next, the insulating layer 17 was formed above the second electrode 16 of the second substrate 15. At this time, it is necessary to prevent the insulating layer 17 from being formed in the extraction electrode portion. For example, the insulating layer is formed by forming a resist in the extraction electrode portion in advance and forming the insulating layer 17 and then lifting it off, or by using a film forming method such as sputtering with the extraction electrode portion hidden by a metal mask or the like. The method of forming (17), etc. are mentioned. Examples of the insulating layer 17 include organic insulating films, inorganic insulating films such as silicon oxide films and silicon nitride films, and combinations thereof (laminated films). In this embodiment, a laminated film of an acrylic organic insulating film and a silicon oxide film was used as the insulating layer 17. On the other hand, as a film formation method, the printing method which does not use plates, such as a spin coat method, the slit coat method, the inkjet method, etc. other than the sputtering method, and the printing method using the board represented by flexographic printing can be employ | adopted. Moreover, various film formation methods, such as a vacuum deposition method, an ion beam method, and a chemical vapor deposition method (CVD method), can be employ | adopted (it is the same below).

A heat resistant film (polyimide tape) was attached to the extraction electrode portion (terminal portion) on the glass substrate, and the organic insulating film material was spin-coated on the glass substrate in that state. A film having a thickness of 1 μm was obtained under the condition of spinning at 2000 rpm for 30 seconds. This was baked in the clean oven on 220 degreeC and the conditions of 1 hour. Subsequently, the silicon oxide film was formed by the sputtering method (alternative discharge) with the heat resistant film stuck. The glass substrate was heated to 80 ° C., and a silicon oxide film of 1000 kPa was formed. Here, when the heat resistant film was peeled off, both the organic insulating film and the silicon oxide film could be peeled off cleanly. This glass substrate was further baked in the clean oven on 220 degreeC and the conditions of 1 hour. This is a treatment for increasing the insulation and transparency of the silicon oxide film.

On the other hand, although the silicon oxide film does not necessarily need to be formed, the effect of improving the adhesiveness and pattern precision of a transparent conductive film, such as an ITO film formed after that by forming a silicon oxide film, can be obtained. Moreover, the insulation as the whole insulating layer 17 is also improved. On the other hand, it is also conceivable to form the insulating layer 17 only with the silicon oxide film without forming the organic insulating film. In this case, since the silicon oxide film is likely to be porous, it is preferable to make the film thickness sufficiently thick (for example, about 4000 to 8000 Pa). Moreover, you may use as a laminated film of a silicon nitride film and a silicon oxide film. In this case, these may be formed alternately by, for example, sputtering or the like.

Next, an ITO film was formed on the insulating layer 17 of the glass substrate as the second substrate 15 by the sputtering method (alternative discharge). Specifically, the substrate was heated at 100 ° C., and an ITO film of about 1200 kPa was formed on the entire surface of the substrate. This ITO film was patterned by photolithography or the like. As a photomask, what has the comb-tooth shaped mask pattern corresponding to the shape (refer FIG. 2) of the 3rd electrode 18 and the 4th electrode 19 to be finally obtained was used. Each of the third electrode 18 and the fourth electrode 19 has a width of each electrode branch formed in the shape of a comb teeth in one of two types, 20 µm and 30 µm, and the interval between each electrode branch is 20 µm, 30, respectively. It was set to any one of five kinds of micrometer, 50 micrometer, 100 micrometer, and 200 micrometer. On the other hand, if there is no pattern in the extraction electrode portion, the lower ITO film is removed by etching, and thus a photomask in which the pattern is formed in the extraction electrode portion is used. As mentioned above, the 2nd board | substrate 15 which has the 2nd electrode 16, the 3rd electrode 18, and the 4th electrode 19 was completed.

Next, the liquid crystal element (liquid crystal cell) was produced using the 1st board | substrate 11 and the 2nd board | substrate 15 produced as mentioned above. Specifically, the first substrate 11 and the second substrate 15 were first subjected to water washing (brush washing or spray washing, pure water washing, etc.), draining, ultraviolet washing, and drying.

Thereafter, an alignment film material was applied to one surface of each of the first substrate 11 and the second substrate 15. As the alignment film, a polyimide film exhibiting a relatively high pretilt angle, which is generally used as an alignment film for STN type liquid crystal elements, was used. An oriented film material was apply | coated to each surface of the 1st board | substrate 11 and the 2nd board | substrate 15, and they were baked at 180 degreeC by the clean oven for 1 hour. As a coating method of an alignment film material, various methods, such as flexographic printing, inkjet printing, or a spin coat method, can be employ | adopted. In this example, the spin coat method was used. The conditions of the spin coat were adjusted so that the film thickness of an oriented film might be 500-800 GPa. Thereafter, rubbing treatment, which is one of the alignment treatments, was performed on each of the alignment film 13 of the first substrate 11 and the alignment film 20 of the second substrate 15. The amount of indentation at the time of rubbing was 0.4 mm, and there is no particular difference as long as it is a condition generally called strong anchoring condition. At this time, the pretilt angle given to liquid crystal molecules by each alignment film was about 6-12 degrees.

Next, the 1st board | substrate 11 and the 2nd board | substrate 15 were attached so that one surface of each other may face. The twist angle (twist angle) was set to 100 °, the angle formed by the rubbing direction in Case I, 87 ° in Case II, and 75 ° in Case III. The gap between the first substrate 11 and the second substrate 15, that is, the layer thickness (cell thickness) of the liquid crystal layer 14 was set to 4 μm. Thereafter, the liquid crystal layer 14 was formed by injecting a liquid crystal material into the gap between the first substrate 11 and the second substrate 15. Chiral agent was added to the liquid crystal material. As described above, the amount of the chiral agent was adjusted so that d / p was 0.04 in Case I, d / p was 0 in Case II, and d / p was 0.04 in Case III.

Thereafter, the first polarizing plate 21 was attached to the outside of the first substrate 11, and the second polarizing plate 22 was attached to the outside of the second substrate 15. The absorption axis of each polarizing plate parallels the rubbing direction and the absorption axis with respect to one side (for example, the first polarizing plate 21), and the rubbing direction and absorption with respect to the other side (for example, the second polarizing plate 22). The axis was shifted by 45 °. In general, the rubbing direction and the absorption axis of the polarizing plate are often arranged in parallel or perpendicular to each other. However, in this embodiment, such a disposition makes it difficult to obtain a difference in transmittance between the first alignment state and the second alignment state. Therefore, the arrangement of the absorption shaft was deliberately shifted from both parallel or perpendicular to the rubbing direction.

The micrograph which observed the state at the time of switching and applying the electric field to the liquid crystal layer 14 using each electrode about the liquid crystal element produced as mentioned above is shown in FIG. The micrograph shown in FIG. 7 is the liquid crystal element of the case II (refer FIG. 6) mentioned above, 20 micrometers of the width | variety of each electrode branch of the 3rd electrode 18 and the 4th electrode 19, and the space | interval of an electrode branch mutually. It relates to a liquid crystal element having a thickness of 20 µm and an angle formed by the rubbing direction of 87 degrees. On the other hand, although not shown, the same result was also the case of Case I and Case III.

The alignment state of the liquid crystal layer 14 in the state where the liquid crystal element was completed was the above-described second alignment state (spray twist state). The photomicrograph is (a) of FIG. And the micrograph when the vertical electric field is applied to the liquid crystal layer 14 using the 1st electrode 12 and the 2nd electrode 16 is (b) of FIG. As shown in FIG.7 (b), the orientation state of the liquid crystal layer 14 is transitioned to the 1st orientation state (reverse twist state) mentioned above by application of a longitudinal electric field. From this, even if the third electrode 18 and the fourth electrode 19 exist while sandwiching the insulating layer 17 between the first electrode 12 and the second electrode 16, the vertical electric field is applied. It is confirmed.

After the liquid crystal layer 14 is transitioned to the first alignment state, the first electrode 11 and the second substrate 15 are substantially parallel to each surface of the first substrate 11 and the second substrate 15 using the third electrode 18 and the fourth electrode 19. The photomicrograph of FIG. 7C when one electric field is applied (IPS mode) is shown. In this case, it turns out that it transitioned to the 2nd orientation state which is an initial state.

After the liquid crystal layer 14 is transitioned to the first alignment state, the first substrate 11 and the second substrate are formed using the second electrode 16, the third electrode 18, and the fourth electrode 19. The micrograph of FIG. 7D when the electric field almost parallel to each surface of (15) is applied (FFS mode) is shown. Also in this case, it turns out that it transitioned to the 2nd orientation state which is an initial state.

Here, the difference between the IPS mode and the FFS mode will be discussed. In the IPS mode, since the transverse electric field is generated only between the third electrode 18 and the fourth electrode 19 basically (see FIG. 3B), the alignment state is preferentially performed in the region where the transverse electric field is generated. It is thought that the transition is occurring. For this reason, as shown to Fig.7 (c), it is thought that the part from which an orientation state differs is generated in a line shape. On the other hand, in the FFS mode, since the transverse electric field is generated on the upper side of the third electrode 18 and the fourth electrode 19 (see FIG. 3 (c)), it is considered that the transition of the alignment state occurs constantly. do. Therefore, when the liquid crystal element of the present embodiment is evaluated in terms of aperture ratio (transmittance ratio and contrast ratio), it can be said that the FFS mode is superior to the IPS mode.

The reason why the transition (switching) of the alignment state is enabled is considered. In the second alignment state (spray twist state), the liquid crystal molecules in the center in the cell thickness direction of the liquid crystal layer 14 are almost horizontal. When the first alignment state (reverse twist state) is caused by the longitudinal electric field, Liquid crystal molecules are slightly inclined. Thereafter, the transverse electric field is loaded on the liquid crystal molecules at the center of the cell thickness in the first alignment state by the transverse electric field (IPS mode or FFS mode), so that the liquid crystal molecules at the center of the cell thickness in the second alignment state should be in the direction of the director. Since it is inclined, it is thought that it transitioned to the 2nd orientation state which is an initial state again.

Next, the measurement result of the electro-optical characteristics (voltage-transmittance characteristics) of the liquid crystal element according to the embodiment will be described. 8 is an electro-optical characteristic of the liquid crystal element of case I described above, FIG. 9 is an electro-optical characteristic of the liquid crystal element of case II described above, and FIG. 10 is an electro-optical characteristic of the liquid crystal element of case III described above. 8 to 10, the transmission axis of the first polarizing plate 21 is parallel to the rubbing direction of the first substrate 11, and the transmission axis of the second polarizing plate 22 is the rubbing direction of the second substrate 15. The liquid crystal layer of the first alignment state (reverse twist state: denoted 'R-TN' in the drawing) or the second alignment state (spray twist state: denoted 'S-TN' in the figure). 14 shows electro-optic characteristics when a longitudinal electric field is applied using the first electrode 12 and the second electrode 16. In each figure, the dotted line shows the characteristic in a 1st orientation state, and the solid line shows the characteristic in a 2nd orientation state.

In the liquid crystal element of the case I shown in FIG. 8, it can be seen that the electro-optical characteristics in the first alignment state and the electro-optical characteristics in the second alignment state almost overlap in the polarizing plate arrangement described above. On the other hand, in the liquid crystal elements of the case II shown in FIG. 9 and the case III shown in FIG. 10, it turns out that the electro-optical characteristic in a 1st orientation state and a 2nd orientation state is seen to differ. Note that the characteristic in the vicinity of the applied voltage of 2 V, a relatively bright (i.e., high transmittance) state is obtained in the case of the second alignment state by the difference in the threshold voltage in the electro-optical characteristic due to the difference in the alignment state. In the case of the first alignment state, it can be seen that a relatively dark state (that is, low transmittance) is obtained. Therefore, a plurality of liquid crystal elements as in the present embodiment are provided, and the two alignment states are arbitrarily switched in each liquid crystal element by applying an electric field, and then the first electrode 12 and the second electrode 16 are used. By applying a voltage of about 2V (called a holding voltage) to the liquid crystal layer 14, a liquid crystal display device capable of displaying a two-value image (still image) called contrast more clearly can be configured.

By the way, in the above description, three cases are illustrated as stable conditions in the first alignment state, but the stable conditions are not limited thereto. Hereinafter, the theoretical verification results for the stable conditions will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram showing the results obtained by theoretical calculation of the relationship between the stability of orientation and cell conditions for Cases I and II. Similarly, FIG. 12 is a diagram showing the results obtained by theoretical calculation of the relationship between the stability of orientation and cell conditions for Case III.

11 and 12 show the conditions (stable conditions in the first alignment state) in the embodiment in circles. Thus, it is shown that the said embodiment is only an example of the conditions which are stable in a 1st orientation state to the last, and theoretically, the orientation stability of a 1st orientation state can be obtained in a wider range. Examining the position of the circles in detail, it can be seen that the position is slightly below the theoretical curve when the pretilt angle is 8 °. Since the upper part of the theoretical curve becomes a region that cannot be stably maintained in the first alignment state, the lower part of the lower part of the theoretical curve is preferably at least lower than the position. Further, if the area is lower than the theoretical curve, it is difficult to return to the second alignment state or the second alignment state is not. Therefore, the area slightly lower than the circle is preferable, and the rubbing direction at any theoretical curve of d / p is When the angle to be made is Φx, it is considered that bistable switching is possible if it is approximately Φx-10 °.

Therefore, in case I and case II, bistable switching is possible when the relationship between the angle? I (°) formed in the rubbing direction and d / p is in the relation as in Equation 1 below.

80≤ΦI-((d / p) x 360) ≤90 (where pretilt angle is 8 ° or less). (One)

On the other hand, in the case III, bistable switching is possible when the relationship between the angle ΦI (°) formed in the rubbing direction and d / p is in the relation as in Equation 2 below.

80≤ΦI + ((d / p) x 360) ≤90 (where pretilt angle is 8 ° or less) (2)

On the other hand, Expression 1 and Expression 2 are established when the pretilt angle is approximately 8 ° or less. For example, Expression 1 is corrected as follows when the pretilt angle is 15 °.

75≤ΦI-((d / p) x 360) ≤85... (One)'

For example, when the pretilt angle is 25 degrees, equation 1 is corrected as follows.

68?? I-((d / p) x 360)? (One)''

In addition, also in Formula 2, an upper limit and a lower limit change with a pretilt angle.

Next, the result examined by experiment about the relationship between a rubbing direction and a transverse electric field direction is demonstrated. It is a schematic diagram for demonstrating a examination result. In the left side of the figure, the direction of the electric field generated by combining the third electrode 18 and the fourth electrode 19 of the liquid crystal element, or these and the second electrode 16, and the first substrate 11 and the second The correspondence relationship of the rubbing direction in each board | substrate 15 is shown. In addition, in the figure, the state which looked at the orientation state of the liquid crystal molecule of the liquid crystal layer 14 from upper side is typically shown. As shown, depending on the relationship between the electric field direction and the rubbing direction of the transverse electric field, it was seen that the transition of the alignment state occurred and did not occur.

Specifically, near the interface between the electric field direction of the transverse electric field and the center of the liquid crystal layer 14 or the lower substrate (for example, the second substrate 15) in the second alignment state (right torsional S-TN alignment). When the directions of the liquid crystal molecules in parallel are parallel, it can be seen that it is easy to transition from the first alignment state (left torsional R-TN alignment) to the second alignment state (Figs. 13 (a) and 13 (b). ) Reference). On the other hand, when the direction of the electric field of the transverse electric field and the direction of the liquid crystal molecules near the center of the liquid crystal layer 14 in the second alignment state or near the interface of the lower substrate are orthogonal, it is difficult to transition to the second alignment state. (See FIG. 13C and FIG. 13D).

In the case where the transition of the alignment state is likely to occur, the transverse electric field 7V is the threshold value, and when 10V is applied, it is returned to the original alignment state after about 1 minute. When the transverse electric field is generated by combining the second electrode 16, the third electrode 18 and the fourth electrode 19 (FFS mode), the electric field is more strongly carried out, so that the transition of the alignment state tends to occur. This looked. However, when each electrode branch of the 3rd electrode 18 and the 4th electrode 19 has a large space | interval, when a lateral electric field is produced combining the 3rd electrode 18 and the 4th electrode 19 ( IPS mode) tends to occur in the transition of the alignment state.

Next, the relationship between the angle formed by the optical axes of the first polarizing plate 21 and the second polarizing plate 22, the transmittance, and the contrast will be described. Standard light source (C) (color temperature 6740K) was used for the transmittance measurement. Representative measurement examples are shown in FIG. 14. This measurement example is for the liquid crystal element of case II. This liquid crystal device had low contrast (2 or less), but was able to recognize the difference with the naked eye. This is due to the difference in color tone. Specifically, two types of red color tone and blue color tone that are close to pink were recognized. The characteristic table which summarized the measurement result is shown to FIG.

In FIG. 15, the angle (unit: °) of the upper polarizing plate (for example, 1st polarizing plate 21) and the lower polarizing plate (for example, 2nd polarizing plate 22) with respect to the liquid crystal element of case II, The difference (unit:%) of the transmittance | permeability of a 1st orientation state and a 2nd orientation state in wavelength is shown, contrast ratio (Cr), and a transmittance | permeability. Good results are shown on the left side of the table at wavelengths near blue (440 to 480 nm) or red (610 to 650 nm), respectively, and characteristics at opposite wavelengths under the same conditions are shown on the right side of the table, respectively. When comparing with a limited wavelength, it turns out that the contrast ratio of about 2-3 is obtained by transmission. This result indicates that when the backlight is a blue or red monochromatic light source, a display having a relatively high contrast can be obtained. It can also be seen that the contrast can be obtained even when the light source is switched between blue and red. In this case, negative / positive reverse display can be performed. Considering the angles formed between the polarizing plates, it can be seen that any of 30 °, 45 °, and 60 ° is not obtained when the angle is 0 ° or 90 °. From this, in order to make the difference of a hue more clear in the liquid crystal element of this embodiment and an Example, it can be said that it is preferable to set the angle which a polarizing plate makes in the range of 30-60 degrees.

16 shows results of the liquid crystal device of case I, and FIG. 17 shows results of the liquid crystal device of case III. It can be seen that the liquid crystal device of case I exhibits a tendency similar to that of the liquid crystal device of case II described above. Moreover, although the liquid crystal element of case III differs slightly from the liquid crystal element of case II mentioned above, it turns out that the contrast by color tone is acquired to some extent.

As described above, according to the present embodiment and the example, a novel TN type liquid crystal element using a transition between two alignment states is provided. In addition, it has been confirmed that this liquid crystal device obtains stable threshold value characteristics and sharpness characteristics in a wide temperature range (for example, -20 ° C to 80 ° C). That is, according to the present embodiment and the example, the state of the transmitted light can be controlled to two different states by using the transition between the two alignment states. Since the application of an electric field is basically unnecessary except when transitioning to either of the two alignment states, the liquid crystal element can be driven with very low power consumption. In particular, when the reflection type liquid crystal device is used, the advantage of low power consumption is great. In addition, this liquid crystal device has a comparatively excellent visual characteristic like a general TN type liquid crystal device. When performing visual compensation, a low cost optical compensation film similar to that used for a general TN type liquid crystal device can be utilized. Since the manufacturing process is basically the same as that of the general TN type liquid crystal device, the liquid crystal device according to the present invention can be manufactured at low cost.

Next, an example of the configuration of a liquid crystal display device capable of driving low power consumption using the memory characteristics of the liquid crystal element will be described.

18 is a diagram schematically illustrating a configuration example of a liquid crystal display device. The liquid crystal display device shown in FIG. 18 is a simple matrix liquid crystal display device configured by arranging a plurality of pixel portions 34 in a matrix form, and the liquid crystal elements according to the above-described embodiments and the like are used as the pixel portions 34. . Specifically, the liquid crystal display device includes m control lines B1 to Bm extending in the X direction, a driver 31 for supplying control signals to the control lines B1 to Bm, and each of the control lines. N control lines A1 to An extending in the Y direction crossing (B1 to Bm), a driver 32 for supplying a control signal to the control lines A1 to An, and each of the control lines ( Driver 33 for supplying control signals to the n control lines C1 to Cn and D1 to Dn extending in the Y direction crossing B1 to Bm, and to the control lines C1 to Cn and D1 to Dn. And the pixel portion 34 provided at the intersections of the control lines B1 to Bm and the control lines A1 to An.

Each control line B1-Bm, A1-An, C1-Cn, and D1-Dn consists of a transparent conductive film, such as ITO formed in stripe shape, for example. The portion where the control lines B1 to Bm and the control lines A1 to An intersect serves as the above-described first electrode 12 and second electrode 16 (see FIG. 2). The control lines C1 to Cn are provided in regions corresponding to the pixel portions 34 and are connected to the comb-shaped electrode branches (not shown in FIG. 18) as the third electrodes 18. Similarly, the control lines D1 to Dn are provided in regions corresponding to the pixel portions 34, and are connected to comb-shaped electrode branches (not shown in FIG. 18) as the third electrodes 18.

Various methods can be considered as a driving method of the liquid crystal display device of the structure shown in FIG. For example, the method (line sequential driving method) which performs display update for every control line B1, B2, B3, ... and lines is demonstrated. In this case, a vertical electric field may be applied to the pixel portion 34 for the relatively bright display, and a horizontal electric field may be applied to the pixel portion 34 for the relatively dark display.

For example, a square wave voltage (for example, 150 Hz at about 1.5V) is applied to the control line B1, and control lines A1 to An and C1 to Cn and D1 to Dn) are applied with a square wave voltage (for example, about 1.5V to 150Hz) in synchronization with it or about a threshold voltage shifted by half period.

Specifically, a square wave voltage shifted by a half cycle from a square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 for bright display among the control lines A1 to An. At this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. As a result, a voltage (vertical electric field) of about 3.0 V is effectively applied to the liquid crystal element of the pixel portion 34. If the voltage is equal to or higher than the saturation voltage, the liquid crystal layer 14 can cause the transition of the alignment state to change the light transmittance of the pixel portion 34. On the other hand, the square wave voltage synchronized with the square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 in which the display does not need to be changed among the control lines A1 to An. At this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. As a result, the pixel portion 34 is in a state in which no voltage is effectively applied. Therefore, the transition of the alignment state does not occur in the liquid crystal layer 14, and the light transmittance does not change.

Further, a square wave voltage shifted by a half cycle from a square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 for bright display among the control lines C1 to Cn and D1 to Dn. At this time, no voltage is applied to the control lines A1 to An. As a result, a voltage (horizontal electric field) of about 3.0 V is effectively applied to the liquid crystal element of the pixel portion 34. If the voltage is equal to or higher than the saturation voltage, the liquid crystal layer 14 can cause the transition of the alignment state to change the light transmittance of the pixel portion 34. On the other hand, a square wave voltage synchronized with a square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 in which the display does not need to be changed among the control lines C1 to Cn and D1 to Dn. do. At this time, no voltage is applied to the control lines A1 to An. As a result, the pixel portion 34 is in a state in which no voltage is effectively applied. Therefore, the transition of the alignment state does not occur in the liquid crystal layer 14, and the light transmittance does not change.

By performing the above-described driving in sequence with the control lines B2, B3, ..., dot matrix display becomes possible. The display state updated by such driving can be maintained semipermanently. In order to update this display, the control may be executed again from the control line B1. On the other hand, an example in which the present invention is applied to a so-called simple matrix liquid crystal display device is shown here, but the present invention can also be applied to an active matrix liquid crystal display device using a thin film transistor or the like. In the case of the active matrix liquid crystal display device, since it is not necessary to update every line such as the control line B1, the update time can be shortened. In addition, since the voltage can be applied twice or more with respect to the threshold value, it can be updated at a higher speed. However, since there is an electrode for a transverse electric field and a longitudinal electric field on one substrate, two thin film transistors per pixel are required.

Hereinafter, another embodiment according to the present invention will be described with reference to the drawings.

The twist direction (first turning direction) of the liquid crystal molecules determined by the combination of the alignment treatment direction and the pretilt angle of one set of alignment films and the twist direction of the liquid crystal molecules induced by the optically active material (chiral agent) (second The liquid crystal layer manufactured so that the turning direction is reversed, and, for example, the liquid crystal molecules are twisted in each direction by imparting a physical action to the liquid crystal layer (reverse twist (uniform twist) with respect to the first turning direction). The liquid crystal element which can realize the spray twist arrangement state with respect to the 2nd turning direction in a flexible manner is called a reverse twist nematic (RTN) type liquid crystal element. The first turning direction is a turning direction in which liquid crystal molecules are twisted when no optically active substance (chiral agent) is added to the liquid crystal layer.

19 is a flowchart showing a method of manufacturing a liquid crystal element (liquid crystal display element) according to the embodiment. The present inventors first prepared a plurality of liquid crystal elements according to the flowchart shown in the drawings, and preliminarily considered a range of pretilt angles for achieving good display.

For example, two transparent substrates on which an indium tin oxide (ITO) electrode is formed are prepared (step S101). Here, a test cell having a parallel plate electrode was used, and two transparent substrates were washed and dried (step S102).

An alignment film material is applied onto the transparent substrate so as to cover the ITO electrode (step S103). Application of the alignment film material was carried out using spin coat. Flexo printing or inkjet printing may also be used. Usually, the side chain density of the polyimide oriented film material used for formation of a vertical alignment film was lowered, and it used as an oriented film material. The alignment film material was applied so that the thickness of the alignment film became 500 to 800 Pa. Temporary firing (step S104) and main firing (step S105) are performed on the transparent substrate coated with the alignment film material. This firing was carried out under four conditions of 160 ° C, 180 ° C, 200 ° C and 220 ° C. In this way, an alignment film covering the ITO electrode was formed (steps S103 to S105).

Next, a rubbing process (orientation process) is performed (step S106). For example, the rubbing process is a step of rotating the rolled cylindrical roll at high speed to rub on the alignment film, whereby the liquid crystal molecules in contact with the substrate can be aligned (orientated) in one direction. The rubbing treatment was carried out under three conditions in which the indentation amount was 0.4 mm, 0.8 mm, and 1.2 mm. In addition, the rubbing process was performed so that the twist angle of the liquid crystal element might be 90 degrees.

20 is a table showing a combination of an alignment film firing temperature and an indentation amount during rubbing treatment. The present inventors produced the liquid crystal element under nine conditions of No. 1 to No. 9 shown in FIG.

Reference is again made to FIG. 19. In order to keep the thickness (distance between substrates) of the liquid crystal cell constant, the gap adjusting material is sprayed onto the surface of one transparent substrate by, for example, a dry spraying method (step S107). As the gap adjusting material, a plastic ball having a particle diameter of 4 μm was used.

On the other transparent substrate surface, a seal material is printed to form a main seal pattern (step S108). For example, a thermosetting sealing material including a glass fiber having a particle diameter of 4 µm is printed by screen printing. The sealing material may also be applied using a dispenser. Moreover, you may use the photocurable sealing material which is not thermosetting, or the curable sealing material for light and heat bottles.

The transparent substrates are stacked (step S109). Two transparent substrates are superimposed on a predetermined position and cellized and heat-treated in a pressed state to cure the sealing material. For example, the sealing material is thermosetted using a hot press method. In this way, an empty cell is produced.

For example, the nematic liquid crystal is injected into the empty cell by the vacuum injection method (step S110). As liquid crystal material, ZLI2293 manufactured by Merck Co., Ltd. was used. Chiral agent was added to the liquid crystal. As chiral agent, Merck CB15 by the company was used. The addition amount of the chiral agent was adjusted so that d / p was 0.16 or 0.25 when the chiral pitch was p and the thickness (cell thickness) of the liquid crystal layer was d.

The liquid crystal inlet is sealed with, for example, an ultraviolet (UV) curable end seal material (step S111), and the cell is heated above the phase transition temperature of the liquid crystal to adjust the orientation of the liquid crystal molecules (step S112). Thereafter, the scriber device breaks according to the marks on the transparent substrate and divides the cells into small cells.

A chamfer (step S113) and a cleaning (step S114) are performed for the cells divided into small sections.

Finally, the polarizing plate is attached to the surface opposite to the liquid crystal layer in the two transparent substrates (step S115). Two polarizing plates were cross nicol, and were arrange | positioned so that the direction of a transmission axis and a rubbing direction might become parallel. It may be arranged to be orthogonal. A power source was connected between the ITO electrodes of the two transparent substrates.

21 (a) to 21 (c) are photographs showing the appearance of a plurality of produced liquid crystal elements. The fabricated liquid crystal device is in a spray twist arrangement from the initial state. When a voltage equal to or higher than the saturation voltage value is applied between the ITO electrodes of the two transparent substrates, the state transitions to the reverse twist arrangement.

See FIG. 21A. Table No. shown in FIG. Liquid crystal element produced under the conditions of 1 (firing temperature of 160 ° C., indentation amount of 0.8 mm at the time of rubbing treatment), and No. The liquid crystal element manufactured under the condition of 3 (firing temperature of 180 ° C. and indentation amount of 0.8 mm at the time of rubbing treatment) can be used even when no voltage is applied in the reverse twisted arrangement state even when d / p is set to 0.16 or 0.25. The appearance as shown in 21 (a), that is, a relatively dark black display was shown. The light transmittance was about 4%. In addition, very dark black marks were observed upon application of voltage in a reverse twisted arrangement. The light transmittance could be lowered to almost 0%. Furthermore, when the light transmittance in the spray twist arrangement was measured, it was about 18% when no voltage was applied. It can be seen that the liquid crystal element manufactured under the conditions of Nos. 1 and 3 can display a greatly different appearance in the reverse twisted arrangement state and the spray twisted arrangement state. In other words, black can be displayed in the reverse twist arrangement and white can be displayed in the spray twist arrangement. As a result of measurement by the spectroscopic ellipso method, it was found that the liquid crystal elements exhibited a pretilt angle of 23 to 35 degrees.

See FIG. 21B. The liquid crystal element produced under the condition of No. 2 in the table shown in Fig. 20 (firing temperature of 180 deg. C, 0.4 mm of indentation during rubbing treatment) was dark from the initial state even when d / p was set to 0.25. Indication was shown. Since the indentation amount at the time of rubbing process was small and the pretilt angle became high, it is thought that the liquid crystal molecule arrangement | positioning state near vertical alignment was brought. The brightness of the display did not change significantly with the application of voltage, and the light transmittance was about 1% or less regardless of the applied voltage and the applied voltage value.

See FIG. 21C. The liquid crystal elements produced under conditions other than the conditions of Nos. 1 to 3 in the table shown in FIG. 20 have a light transmittance in the spray twist arrangement state and the reverse twist arrangement state, regardless of whether the d / p value is 0.16 or 0.25. No big difference was observed and almost the same display appearance was shown. The light transmittance in the absence of voltage was about 25% in both arrangements, and the light transmittance was reduced to about 1% or less in both arrangements by voltage application. Fig. 21C shows the appearance of the display (color display) when no voltage is applied in the reverse twisted arrangement. When the pretilt angle of the liquid crystal element manufactured on conditions other than the conditions of No.1-No.3 of the table shown in FIG. 20 was measured by the spectroscopic eryphso method, it turns out that the pretilt angle of 8-15 degrees is expressing. Could.

When the present inventors measured the pretilt angle with respect to many liquid crystal elements, the range of the pretilt angle which can be displayed black preferably when the voltage of a reverse twist arrangement state is not applied was 31.5-36.2 degrees. Also, the maximum pretilt angle at which black display was not possible when no voltage was applied in the reverse twisted arrangement state was 17.1 °. Moreover, the minimum value of the pretilt angle displayed black was 48 degrees even when the voltage in the spray twist arrangement state was not applied.

From this, an RTN type liquid crystal device is produced with the pretilt angle applied to the upper and lower substrates of 20 ° or more and 45 ° or less, more preferably 31 ° or more and 37 ° or less, thereby producing black display when no voltage is applied in the reverse twisted array state. It is thought that white display can be realized when no voltage is applied in the spray twist arrangement state (when no vertical electric field is added).

In the RTN type liquid crystal device having the range of the pretilt angle described above, the principle of the relatively dark black display when the voltage in the reverse twisted arrangement state is not applied is not fully explained. However, when the RTN type liquid crystal device is dropped (reverse twist) Since the threshold value of the array state is lower than the threshold value at the time of rise (spray twist arrangement state), and the threshold value is lower than 0 V under special conditions, it is assumed that such display is realized.

In general, in the reverse twisted arrangement state, a large twist occurs inside the liquid crystal layer due to the pretilt angle given by the substrate alignment process and the torsion force imparted by the chiral agent. The liquid crystal molecules near the center in the thickness direction of the layer are considered to be inclined with respect to the substrate plane. In the RTN type liquid crystal device having a high pretilt angle of 20 ° or more, the inclination angle of the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer is very large, and is assumed to rise almost perpendicularly to the substrate. Therefore, it is considered that a relatively dark black display is obtained even when no voltage is applied. On the other hand, in the reverse twist arrangement, the inclination angle in bulk is higher than the pretilt angle at the interface with the substrate. This has also been confirmed by liquid crystal molecular orientation simulation based on continuum theory.

Next, the present inventors fabricate a plurality of liquid crystal elements according to the flowchart shown in FIG. 19 under the condition of No. 1 or No. 3 in the table shown in FIG. 20, and are relatively dark when the voltage is not applied in the reverse twisted arrangement state. The preliminary consideration was given to the firing temperature, twist angle, and cell thickness (thickness of the liquid crystal layer) in which the holding time of the black marks is increased. 22A to 22F show manufacturing conditions and observation results of the liquid crystal device.

Fig. 22A is a table showing the manufacturing conditions of the liquid crystal element. First, two transparent substrates on which ITO electrodes were formed were prepared. Here, a test cell having a parallel plate electrode was used, and two transparent substrates were washed and dried.

An alignment film material was applied on the transparent substrate to cover the ITO electrode. Application of the alignment film material was carried out using spin coat. Usually, the side chain density of the polyimide oriented film material used for formation of a vertical alignment film was lowered, and it used as an oriented film material. The alignment film material was applied so that the thickness of the alignment film became 500 to 800 Pa. Plasticity and main plasticity were performed on the transparent substrate coated with the alignment film material. As shown to Fig.22 (a), main baking was implemented at 160 degreeC or 180 degreeC. In this way, an alignment film covering the ITO electrode was formed.

Subsequently, the rubbing treatment was performed with an indentation amount of 0.8 mm. As shown in Fig. 22A, the rubbing treatment was performed under three conditions in which the twist angles between the upper and lower substrates were set to 80 °, 90 °, and 100 °.

The gap adjusting material was sprayed on one transparent substrate surface. As the gap adjusting material, plastic balls having particle diameters of 3 μm, 4 μm, and 5 μm are used, and as shown in FIG. 22A, a plurality of liquid crystal elements having cell thicknesses of 3 μm, 4 μm, and 5 μm are used. Produced. On the other transparent substrate surface, a thermosetting sealing material including glass fibers was printed by screen printing to form a main seal pattern. Two transparent substrates were overlapped at predetermined positions, heat treated, and the sealing material was cured to produce empty cells.

The nematic liquid crystal was injected into the empty cell by the vacuum injection method. As liquid crystal material, ZLI2293 manufactured by Merck Co., Ltd. was used. Chiral agent was added to the liquid crystal. As chiral agent, Merck CB15 by the company was used. The addition amount of a chiral agent was adjusted so that d / p might be 0.04, 0.08, 0.125, 0.16, 0.20, 0.25, 0.33.

The liquid crystal inlet was sealed with an ultraviolet curable end seal material, and the cell was heated above the phase transition temperature of the liquid crystal. With a scriber device, break according to the marks on the transparent substrate and divide into small cells.

The small divided cells were chamfered and washed, and a polarizing plate was attached to the surface on the side opposite to the liquid crystal layer in the two transparent substrates. The two polarizing plates were cross nicol, and were arrange | positioned so that the direction of a transmission axis and a rubbing direction might become parallel. A power source was connected between the ITO electrodes of the two transparent substrates. By applying an AC voltage of 5 V between the ITO electrodes of the thus produced liquid crystal element, it was possible to transition from the spray twist arrangement state to the reverse twist arrangement state (relative dark black display).

FIG.22 (b) is a table which shows the result of having measured the retention time of the comparatively dark black display (reverse twist arrangement state) when the addition amount of a chiral agent to a liquid crystal material is changed.

The liquid crystal element produced under condition A shown in FIG. 22A and the liquid crystal element produced under condition B are compared. In the liquid crystal element manufactured under the condition A, the reverse twist arrangement after the transition from the spray twist arrangement state to the reverse twist arrangement state (relative black display) in four cases where d / p = 0.08, 0.125, 0.16, 0.20 It remained there for more than a few weeks (marked as '∞' in the table). In the case of d / p = 0.04, the desired operation is partially performed, but the parts which become blacker than the initial state are mixed. From this, it is considered that d / p = 0.04 is a boundary condition for obtaining uniformity for use as a display element.

On the other hand, in the liquid crystal element produced under condition B, the reverse twist arrangement was maintained for several weeks or more when d / p = 0.08 and 0.125. In the condition B, similarly to the condition A, when the d / p = 0.04, the parts which become blacker than the initial state were mixed.

From this, the fabrication temperature is set to 160 ° C rather than the liquid crystal element at 180 ° C to stabilize the reverse twist arrangement, that is, to obtain the bistable stability of the reverse twist arrangement and the spray twist arrangement. It can be seen that the / p margin is wide. On the other hand, Fig. 22C shows the appearance of the display in the reverse twisted arrangement state held in the liquid crystal element manufactured under the condition A, d / p = 0.125. By manufacturing a liquid crystal element at a firing temperature of at least 160 ° C or more and 180 ° C or less, it is possible to maintain a black display when no voltage is applied in a reverse twist arrangement for a long time.

Next, the liquid crystal elements produced under conditions A, C, and D are compared. In the liquid crystal device manufactured under the condition C, the reverse twist arrangement was not maintained for a long time at all d / p. When a liquid crystal device is manufactured with a twist angle of 80 °, it can be seen that bistable stability of two array states is difficult to obtain.

On the other hand, the liquid crystal element produced under the condition A and the liquid crystal element produced under the condition D did not show a large difference in the holding time. However, in the case of condition D, as shown in the example shown in FIG. 21B in the liquid crystal device manufactured at d / p = 0.125, dark display was shown from the initial state. In addition, the holding time at d / p = 0.25 and 0.33 was slightly shorter than that in the condition A. From this, a liquid crystal device is manufactured with a twist angle of at least 90 ° and 100 ° or less, so that a black display can be maintained for a long time when no voltage is applied in a reverse twist arrangement state, and the liquid crystal device has a twist angle of 100 °. It can be seen that the bi-stability between the reverse twisted arrangement and the spray twisted arrangement is slightly easier to produce at 90 ° than the fabrication.

Next, comparison is made based on the cell thickness. When the cell thickness was as thin as 3 µm (Condition E), there was no clear difference in retainability by the value of d / p, and the reverse twist arrangement was maintained for several weeks or more at all d / p. 22D shows the display appearance of the liquid crystal element manufactured under condition E and d / p = 0.125. However, under condition E, when the value of d / p was 0.20, 0.25, the phenomenon that the reverse twist arrangement gradually spreaded out to the region outside the electrode despite the fact that no voltage was applied. Its state is shown in Fig. 22E. If the reverse twist arrangement spreads to an area outside the electrode, it is difficult to control the portion, so attention is required.

When the cell thickness is 5 占 퐉 thick (Condition F), the range of d / p having a longer holding time compared to Condition A or E is narrow, and only the liquid crystal element manufactured with d / p = 0.16 has a reverse twist arrangement. It lasted more than a few weeks. Fig. 22 (f) shows a display appearance of the liquid crystal element. As a result of the observations of the present inventors, even when the cell thickness is thick (condition F) or thin (condition E), similarly to the liquid crystal element fabricated in condition A, a relatively dark black display was obtained when no voltage was applied in the reverse twisted arrangement state. . This shows that even if the cell thickness of the liquid crystal element is somewhat uneven, for example, bistable display having a high contrast ratio is possible. From the observations showing the results in the table of Fig. 22B, by producing a liquid crystal element with a cell thickness of at least 3 μm or more and 5 μm or less, it is possible to maintain a black display in the absence of voltage in a reverse twist arrangement for a long time. It was confirmed.

Although d / p may be correlated with other conditions, for example, it may be considered that it is preferable to set it to more than 0.04 and less than 0.25 from the black display holding time of the liquid crystal elements produced under conditions A, D and E. .

The present inventors produced the liquid crystal element which concerns on an Example based on the above preliminary consideration.

23 is a schematic cross-sectional view in one pixel of the liquid crystal element according to the embodiment.

The liquid crystal device according to the embodiment includes an upper substrate 110a, a lower substrate 110b, and a twisted nematic liquid crystal layer 115 sandwiched between the two substrates 110a and 110b, which are disposed to face each other in parallel. .

The upper substrate 110a includes an upper transparent substrate 111a, an upper electrode 112a formed on the upper transparent substrate 111a, and an upper alignment layer 114a formed on the upper electrode 112a. The lower substrate 110b includes the lower transparent substrate 111b, the lower electrode 112b formed on the lower transparent substrate 111b, the insulating film 113 formed on the lower electrode 112b, and the first and second insulating films 113 formed on the lower substrate 112b. And the lower alignment film 114b formed on the insulating film 113 to cover the second comb electrodes 112c and 112d and the first and second comb electrodes 112c and 112d. Meanwhile, the upper electrode 112a is the first electrode, the lower electrode 112b is the second electrode, the first comb electrode 112c is the third electrode, and the second comb electrode 112d is the first electrode. It corresponds to four electrodes'.

The upper and lower transparent substrates 111a and 111b are formed of glass, for example. The upper and lower electrodes 112a and 112b and the first and second comb electrodes 112c and 112d are formed of, for example, a transparent conductive material such as ITO. The first and second comb electrodes 112c and 112d are comb electrodes each having a plurality of comb portions. Comb portions of the first and second comb electrodes 112c and 112d are arranged differently along the left and right directions of FIG. 23.

The liquid crystal layer 115 is disposed between the upper alignment layer 114a of the upper substrate 110a and the lower alignment layer 114b of the lower substrate 110b.

The upper alignment film 114a and the lower alignment film 114b are subjected to an alignment process by rubbing. The orientation processing directions of the upper alignment film 114a and the lower alignment film 114b are orthogonal to each other when viewed from the normal direction of the upper substrate 110a and the lower substrate 110b. If the rubbing direction of the upper alignment layer 114a is referred to as the first direction and the rubbing direction of the lower alignment layer 114b is referred to as the second direction, the second direction is counterclockwise with respect to the first direction as viewed from the normal direction of the upper substrate 110a. 90 degrees in the direction. The arrangement state of the liquid crystal molecules of the liquid crystal layer 115, which is defined by the combination of the orientation processing direction of the upper substrate 110a and the lower substrate 110b and the pretilt angle, is viewed from the normal direction of the upper substrate 110a to the right. A 90 ° twisted uniform twist (reverse twist) arrangement.

The chiral agent is added to the liquid crystal material forming the liquid crystal layer 115. The arrangement state of the liquid crystal molecules generated based on the influence of the chiral agent is distorted in the left torsion direction according to the direction from the upper substrate 110a to the lower substrate 110b as seen from the normal direction of the upper substrate 110a. It becomes a spray twist arrangement.

The twist direction of the liquid crystal molecules in the liquid crystal cell completion state was the left twist (spray twist arrangement) which is the same direction as the twist direction by the chiral agent.

The power supply 120 is electrically connected to the upper and lower electrodes 112a and 112b and the first and second comb electrodes 112c and 112d. A voltage may be applied to the electrodes 112a to 112d by the power supply 120. For example, by applying an alternating voltage of at least a threshold voltage between the two electrodes 112a and 112b, the arrangement state of the liquid crystal molecules can be transferred from the spray twist arrangement to the uniform twist (reverse twist) arrangement.

The upper polarizing plate 116a and the lower polarizing plate 116b are disposed on the surface opposite to the liquid crystal layer 115 on the upper substrate 110a and the lower substrate 110b, respectively. The two polarizing plates 116a and 116b are cross nicol so that the light transmission axis is parallel to the rubbing direction of the upper substrate 110a and the lower substrate 110b. The liquid crystal device according to the embodiment is a normally white liquid crystal device.

24 to 28, a configuration and a manufacturing method of the liquid crystal device according to the embodiment will be described in detail.

24 is a schematic plan view showing a pattern of an ITO film formed on the upper transparent substrate 111a. As the ITO film shown in FIG. 24, for example, a pixel electrode (an electrode forming the upper electrode 112a in each pixel) and an extraction electrode of the pixel electrode are formed.

For example, the ITO film pattern is formed such that the ITO film extends in a stripe shape in the left and right directions in FIG. 24. In FIG. 24, reference numerals 112A ₁ to 112A ₁₀ are used for the ITO film constituting the pixel electrode.

Patterning of the ITO film | membrane was performed using the photolithographic process after washing the glass substrate with ITO. ITO was etched by wet etching with ferric chloride. You may pattern by irradiating a laser beam and removing an ITO film | membrane.

25 is a schematic plan view showing a pattern of an ITO film formed on the lower transparent substrate 111b. As the ITO film shown in FIG. 25, for example, a pixel electrode (an electrode forming the lower electrode 112b in each pixel) and an extraction electrode of the pixel electrode are formed.

For example, the ITO film pattern is formed such that the ITO film extends in a stripe shape in the vertical direction in FIG. 25. In Figure 25 is shown with a sign of a part 112B ₁ ~ 112B ₉ ITO film constituting the pixel electrode. In addition, the up-down direction of FIG. 25 and the left-right direction of FIG. 24 are directions orthogonal to each other.

The patterning of the ITO film can be performed by the same method as the method for forming the ITO film pattern described with reference to FIG. 24.

After the ITO film is patterned, the insulating film 113 is formed on the lower transparent substrate 111b including the ITO film. The insulating film 113 is not formed in, for example, a portion (terminal portion) of the extraction electrodes 112BT ₁ to 112BT ₉ . In FIG. 25, regions where the insulating film 113 is not formed are shown by diagonal lines. The insulating film 113 can be formed by forming a resist on a portion of the extraction electrode or the like, removing the resist by lift-off after the formation of the insulating film, or by forming a sputter with a metal mask covering the portion of the extraction electrode. . The insulating film 113 may be an organic insulating film or an inorganic insulating film such as SiO ₂ or SiN _x . It may be formed by combinations thereof. In the embodiment, an acrylic organic insulating film and a laminated film of SiO ₂ were used as the insulating film 113.

In the embodiment, first, a heat resistant film (polyimide tape) was attached to the extraction electrode portion, and the organic insulating film was spin-coated (spinned at 2000 rpm for 30 seconds) with a film thickness of 1 m. Subsequently, the lower transparent substrate 111b spin-coated with the organic insulating film was baked at 220 ° C. for 1 hour with a clean oven, and then the lower transparent substrate 111b was heated to 80 ° C. with the heat resistant film attached thereto, and the SiO ₂ film was sputtered. It formed by thickness (1000 micrometers) by the method (AC discharge). The SiO ₂ film may be formed using a vacuum deposition method, an ion beam method, a CVD method, or the like.

Here, when the heat resistant film was peeled off, the organic insulating film and the SiO ₂ film could be removed from the attachment portion of the heat resistant film. Subsequently, in order to improve the insulation and transparency of the SiO ₂ film, the lower transparent substrate 111b was baked in a clean oven at 220 ° C. for 1 hour.

Although the formation of the SiO ₂ film is not essential, the insulating property of the insulating film 113 can be improved by forming the SiO ₂ film. In addition, the adhesion and patterning properties of the first and second comb electrodes 112c and 112d formed on the insulating film 113 can be improved.

The insulating film 113 may be composed of only SiO ₂ film without forming an organic insulating film. Since the SiO ₂ film tends to be porous, in this case, the thickness of the SiO ₂ film is preferably 4000 to 8000 Pa. The inorganic insulating film 113 formed of a stack of a SiO ₂ film and a SiN _X film may be used.

An ITO film was formed over the insulating film 113. The ITO film was formed on the entire substrate by heating the lower transparent substrate 111b to 100 ° C. by sputtering (alternative discharge). The film thickness was about 1200 kPa. The ITO film may be formed using a vacuum deposition method, an ion beam method, a CVD method, or the like. The ITO film was patterned by a photolithography process to form a first comb electrode 112c, a second comb electrode 112d and extraction electrodes of the electrodes 112c and 112d.

Fig. 26 is a schematic plan view showing a photomask used for etching an ITO film. The photomask includes a portion corresponding to the first comb electrode 112c, a portion corresponding to the second comb electrode 112d, a portion corresponding to the extraction electrode of the first comb electrode 112c, a portion corresponding to the extraction electrode of the second comb electrode 112d, and a lower side. And an extracting electrode corresponding portion of the electrode 112b. At the time of etching, an electrode is formed of an ITO film covered with each corresponding portion. On the other hand, the present inventors set the electrode width of the comb portion of the comb electrode to 20 µm and 30 µm, and the electrode spacing when alternating the comb portions of the two comb electrodes were 20 µm, 30 µm, 50 µm, 100 µm. The first comb electrode 112c and the second comb electrode 112d were produced using a plurality of electrode patterns having a thickness of 200 µm.

Two board | substrates with electrode were prepared through the above process (step S101 of FIG. 19). Two substrates with electrodes are washed and dried (step S102). In the case of water washing, pure cleaning should be performed. You may carry out using a detergent. Any of brush cleaning and spray cleaning can be cleaned. The water is then drained and dried. As a method other than water washing, UV washing and IR drying can be performed.

An alignment film material was applied onto the two electrode substrates to cover the ITO electrode (step S103). Application of the alignment film material was carried out using spin coat. You may implement using flexographic printing or inkjet printing. Usually, the side chain density of the polyimide oriented film material used for formation of a vertical alignment film was lowered, and it used as an oriented film material. The alignment film material was applied so that the thickness of the alignment film became 500 to 800 Pa. The plasticity (step S104) and the main baking (step S105) were performed with respect to the substrate with an electrode coated with the alignment film material. This firing was carried out at 160 ° C. for 1 hour. You may carry out at the temperature of 160 degreeC or more and 180 degrees C or less. In this way, an alignment film covering the ITO electrode was formed (steps S103 to S105).

FIG. 27 is a schematic plan view showing a part of the formation region of the lower alignment layer 114b formed on the lower substrate 110b. For example, the lower alignment layer 114b includes first and second comb electrodes 112c and 112d and is formed in a region where pixels are divided. In FIG. 27, only the upper left portion is shown as the formation region of the lower alignment film 114b. The same applies to the other comb electrodes 112c and 112d arrangement areas.

Next, a rubbing process (orientation process) was performed (step S106). The rubbing treatment was carried out with an indentation amount of 0.8 mm. Moreover, it implemented so that the twist angle of a liquid crystal element might be 90 degrees.

In order to make the cell thickness 4 micrometers, the gap regulator of 4 micrometers of particle diameters was spread | dispersed on one board | substrate surface (step S107). In order to make the cell thickness into 3 micrometers or more and 5 micrometers or less, it is also possible to spread | disperse a gap control material with a particle diameter of 3 micrometers or more and 5 micrometers or less. On the other substrate surface, a sealing material was printed to form a main seal pattern (step S108). Two board | substrates were overlapped at the predetermined position (step S109), and the sealing material was hardened.

The two substrates are stacked in a rubbing direction of the upper alignment layer 114a in the first direction and the lower alignment layer so that the alignment of the liquid crystal molecules becomes a uniform twist (reverse twist) array twisted 90 degrees to the right as viewed from the upper substrate normal direction. When the rubbing direction of 114b) was referred to as the second direction, the second direction was set to be 90 ° counterclockwise with respect to the first direction as viewed from the normal direction of the upper substrate 110a. In addition, a twist angle can be 90 degrees or more and 100 degrees or less.

The nematic liquid crystal was injected by vacuum injection (step S110). As liquid crystal material, ZLI2293 manufactured by Merck Co., Ltd. was used. Chiral agent was added to the liquid crystal. As chiral agent, Merck CB15 by the company was used. The addition amount of the chiral agent was adjusted so that d / p was 0.16 when p was the chiral pitch and the thickness of the liquid crystal layer was d. It may be more than 0.04 and less than 0.25.

The liquid crystal inlet was sealed with an ultraviolet curable end seal material (step S111), and the cell was heated above the phase transition temperature of the liquid crystal to adjust the orientation of the liquid crystal molecules (step S112). Thereafter, the scriber device breaks according to the marks on the transparent substrate and divides the cells into small cells. Chamfering (step S113) and washing | cleaning (step S114) were performed about the cell divided | segmented small.

Finally, the polarizing plate was affixed on the surface opposite to the liquid crystal layer in two board | substrates (step S115). The two polarizing plates were cross nicol, and were arrange | positioned so that the direction of a transmission axis and a rubbing direction might become parallel. It may be arranged to be orthogonal. A power source was connected between the ITO electrodes (upper and lower electrodes 112a and 112b) and the first and second comb electrodes 112c and 112d of the two substrates.

28 is a schematic plan view showing the structure of a liquid crystal element according to the embodiment. In FIG. 28, all the structures shown in FIGS. 24 to 27 are superimposed. One pixel is divided into a horizontal electrode extending in the left and right directions and a vertical electrode extending in the vertical direction. In FIG. 28, reference numerals 112A ₁ to 112A ₁₀ are used for the horizontal electrodes, and reference numerals 112B ₁ to 112B ₉ are used for some of the vertical electrodes. Indicated by the arrows, the horizontal electrodes 112A ₉ and the vertical electrodes 112B ₈ are pixels which are divided in regions where the horizontal electrodes 112A ₉ overlap in the substrate normal direction. The horizontal electrode 112A ₉ in this pixel corresponds to the upper electrode 112a in FIG. 23, and the vertical electrode 112B ₈ corresponds to the lower electrode 112b.

29A to 29C are external photographs of the liquid crystal device according to the exemplary embodiment, and FIGS. 29D to 29F are schematic cross-sectional views showing electric field directions when voltage is applied. 29A to 29C, the electrode width of the comb portions of the first and second comb electrodes 112c and 112d is 20 µm, and the comb teeth of the two comb electrodes 112c and 112d are shown. It is an external photograph of the comb electrode 112c, 112d formation area | region of the liquid crystal element produced by making the electrode space | interval 20 micrometers when a part alternately arrange | positions.

FIG. 29A shows an external photograph of a state in which a liquid crystal element is completed (initial state). In the initial state, the liquid crystal molecules are in a spray twist arrangement.

In this state, as shown in Fig. 29D, a voltage was applied between the upper electrode 112a and the lower electrode 112b. By applying voltage to the two electrodes 112a and 112b, a vertical electric field (an electric field in the thickness direction of the liquid crystal layer) is generated in the liquid crystal layer.

FIG. 29B is a photograph of appearance after voltage is applied to the electrodes 112a and 112b. It can be seen that the whole has transitioned from the spray twist arrangement to the reverse twist arrangement. On the contrary, it is confirmed that a vertical electric field is generated in the liquid crystal layer by applying voltages to the two electrodes 112a and 112b.

Next, as shown in FIG. 29E, a voltage was applied between the first comb electrode 112c and the second comb electrode 112d. By applying voltages to the two electrodes 112c and 112d, a transverse electric field (an electric field in a direction orthogonal to the thickness direction of the liquid crystal layer and an electric field in the substrate plane direction) is generated in the liquid crystal layer. On the other hand, the driving mode for driving the liquid crystal element by generating a transverse electric field in the liquid crystal layer by applying the voltage to the first and second comb electrodes 112c and 112d is called an in-plane switching mode.

When the liquid crystal element in the state shown in FIG. 29B was driven in the IPS mode, it was confirmed that the liquid crystal element was transitioned to the same state as the initial state (spray twist arrangement).

Furthermore, as shown in FIG. 29 (f), a voltage was applied to the lower electrode 11b, the first comb electrode 112c, and the second comb electrode 112d. The transverse electric field is also generated in the liquid crystal layer by applying the voltage to the electrodes 112b, 112c, and 112d. On the other hand, the driving mode for driving the liquid crystal element by generating a transverse electric field in the liquid crystal layer by applying voltage to the electrodes 112b, 112c, and 112d is called a fringe field switching mode.

FIG. 29C is a photograph of appearance after driving the liquid crystal element in the state shown in FIG. 29B in the FFS mode. It can be seen that the front surface has transitioned to the same state as the initial state (spray twist arrangement).

As a result of observation by the present inventors, when driving in the IPS mode, the entire surface did not transition to the spray twist arrangement, but instead of the front surface, the transition was made to the spray twist arrangement in a stripe shape corresponding to the pattern of the comb electrode. It is considered that in the IPS mode, the transverse electric field is generated only between the comb electrodes 112c and 112d. On the other hand, when driving in the FFS mode, it is considered that the front side transitions to the spray twist arrangement state because the transverse electric field is also generated on the comb electrodes 112c and 112d in the FFS mode. The liquid crystal element according to the embodiment is a liquid crystal element capable of switching the spray twist arrangement state and the reverse twist arrangement state. The former can be transferred to the latter by the application of a longitudinal electric field. In addition, the latter can be transferred to the former by the application of the transverse electric field. On the other hand, in the application of the transverse electric field, driving in the FFS mode is preferable to the IPS mode in terms of aperture ratio, light transmittance, contrast ratio, and the like.

It is considered that the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer are inclined from the transverse direction to the longitudinal direction by the addition of the longitudinal electric field, so that switching from the spray twist arrangement to the reverse twist arrangement is achieved. In addition, it is considered that the liquid crystal molecules in the vicinity of the center of the thickness direction of the liquid crystal layer are inclined from the longitudinal direction to the horizontal direction by the addition of the transverse electric field, thereby switching from the reverse twist arrangement to the spray twist arrangement.

The liquid crystal element according to the embodiment is a liquid crystal element in which the spray twist arrangement state and the reverse twist arrangement state transition from each other by the direction of the added electric field, and each state is stably maintained. In the liquid crystal device according to the embodiment, for example, display using memory characteristics is possible.

The pixels to be displayed in white are in the spray twist arrangement, and the pixels to be in black are in the reverse twist arrangement. At least a vertical electric field is applied to the pixel to change from white display to black display. A vertical electric field may also be applied to the pixel for which the black display is to be maintained. Conversely, a horizontal electric field is applied to at least the pixel to change from black display to white display. A horizontal electric field may also be applied to the pixel for which the white display is to be maintained.

The display update can be performed for each line, for example. For example, in FIG. 28, a square wave (for example, about 150 Hz and 5V) that does not occur in one of the vertical electrodes 112B ₁ to 112B ₉ , for example, the vertical electrodes 112B ₁ . Apply. In addition, a square wave (for example, about 150 Hz or 5V) is applied to the horizontal electrodes 112A ₆ to 112A ₁₀ or to the first and second comb electrodes in synchronism with the voltage applied to the vertical electrodes 112B ₁ . do.

Vertically in the electrode (112B ₁₎ waveform, and adding the synchronized waveform pixel added to, effectively as without the display change since the state voltage is not applied, the longitudinal electrodes (112B ₁₎ was added to the waveform and the half-period shifted waveform added to the In the pixel, since a voltage of about 10 V is effectively applied, the pixel becomes a voltage higher than the saturation voltage, so that the white display and the black display can be changed to each other.

For example, a square wave having a half cycle shifted to the first and second comb electrodes is applied to the pixel for white display, and no voltage is applied to the horizontal electrodes 112A ₆ to 112A ₁₀ . Square pixels shifted by half a period from the horizontal electrodes 112A ₆ to 112A ₁₀ are applied to the pixels to be displayed in black, and no voltage is applied to the first and second comb electrodes.

A matrix wave is also applied to the vertical electrodes 112B ₂ to 112B ₉ after the vertical electrodes 112B ₁ and driven in a similar manner. The updated display can be maintained semipermanently.

The liquid crystal element according to the embodiment can be driven by, for example, a driving method using memory characteristics such as the above-described line sequential update method (line sequential drive). Ultra-low power consumption without power consumption is possible except when updating the display. In particular, the advantage is large when applied to a reflective display. In addition, a large-capacity dot matrix display can be performed by simple matrix display without using expensive TFT or the like. That is, a large capacity display can be performed at low cost. Furthermore, the liquid crystal device according to the embodiment can be manufactured at low cost by, for example, the manufacturing method described with reference to FIGS. 19 and 24 to 28.

30A to 30D are graphs showing voltage-transmittance characteristics of the liquid crystal device according to the embodiment and the liquid crystal device manufactured under other preferable conditions. The horizontal axis of each graph represents the applied voltage in units of 'V', and the vertical axis represents the light transmittance in units of '%'. The solid curve shows the voltage-transmittance characteristics in the reverse twisted arrangement (indicated as 'after transition' in the drawing), and the curve in broken lines indicates the 'before transition' in the spray twist arrangement. The voltage-light transmittance characteristics are shown. It is the electro-optical characteristic at the time of applying a voltage between the upper and lower electrodes 112a and 112b in each arrangement state, and generating a vertical electric field. On the other hand, the numbers before the "before transition" and "after the transition" represent d / p values in FIGS. 30A to 30C and cell thicknesses in FIG.

FIG. 30A shows the electro-optical characteristics of the liquid crystal device (liquid crystal device according to the embodiment) manufactured under condition A of FIG. 22A. It can be seen that the light transmittances of the two arrays in the absence of voltage are significantly different, and that a high contrast ratio can be displayed. The liquid crystal device according to the embodiment has a high contrast ratio and is a liquid crystal device that can easily realize high quality display in which both the white display state and the black display state are stable. The black marks are dark and easy to see clearly.

30B shows electro-optical characteristics of the liquid crystal element produced under condition B of FIG. 22A. Although slightly different from the example shown in Fig. 30A, the light transmittances of the two arrays at the time of voltage application differ greatly, and high contrast ratio and high quality display are possible. On the other hand, in the electro-optical characteristics shown in FIG. 30A and the electro-optical characteristics shown in FIG. 30B, the dependency tendency of d / p of light transmittance is reversed. Although the detailed cause is not clear, it turns out that the tendency of d / p to obtain the optimal electro-optical characteristic differs according to manufacturing conditions.

FIG. 30C is an electro-optical characteristic of the liquid crystal device manufactured under condition D of FIG. 22A. It does not differ significantly from the example shown in FIG. 30A, and high contrast ratio and high quality display are possible. In addition, in the example shown in (c) of FIG. 30, it turns out that dependency of light transmittance on d / p is small and it is stable about d / p.

The difference in the electro-optical characteristics of the cell thickness is shown in FIG. Even if the cell thickness is any of 3 µm, 4 µm and 5 µm, it can be seen that a relatively dark black display is obtained when no voltage is applied in the reverse twisted array state. By optimizing the liquid crystal material, it is considered that a relatively bright light transmittance and a high contrast ratio can be achieved at any cell thickness.

31A and 31B are graphs showing visual-contrast characteristics of the liquid crystal device according to the embodiment. In both graphs, the horizontal axis represents the time in the best viewing direction (polar angle, tilt angle from the substrate normal direction) in units of '°'. The direction in which the liquid crystal molecules in the center of the liquid crystal layer thickness direction rise in the reverse twist arrangement state becomes the best viewing direction. In addition, the vertical axis shows contrast ratio. The contrast ratio is a value obtained by dividing the light transmittance in the spray twist arrangement (white display) by the light transmittance in the reverse twist arrangement (black display).

As shown in FIG. 31A, a contrast ratio of 16 or more is obtained at a time (polar angle) of about 40 ° in the liquid crystal element according to the embodiment.

31 (b) shows the visual-contrast characteristic (solid line) of the liquid crystal element according to the embodiment, for example, the visual-contrast characteristic (dashed line) of the conventional liquid crystal element showing the display appearance in FIG. 21 (c). ). As shown, in the conventional liquid crystal element, the contrast ratio is around 1 regardless of time (polar angle). In addition, the maximum value of the contrast ratio of the conventional liquid crystal element was 1.09. It can be seen that the liquid crystal device according to the embodiment is a liquid crystal device having high display quality in which high contrast is realized in a wide viewing range.

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

For example, in the embodiment, the polarizing plate is arranged in cross nicol and used as a liquid crystal element of normally white display. The polarizing plate may be arranged in parallel nicol and may be a liquid crystal element of normally black display. However, it would be easier to display normally at a higher contrast ratio. In the case of normally white display, in order to obtain a good black display, it is preferable that the angle formed by the transmission axis directions of the upper and lower polarizing plates 116a and 116b is around 90 °.

On the other hand, in the embodiment, since the upper and lower polarizing plates 116a and 116b use a type having a relatively low light transmittance, for example, as shown in FIG. 30 (a), a white display (spray twist arrangement) is shown. Although the light transmittance is about 15 to 20%, when using a form with a relatively high light transmittance, it may be possible to set the light transmittance of a white display to, for example, about 25 to 30%.

In addition, although the twist angle was 90 degrees in the Example, it can also be set as another angle. In this case, it is necessary to adjust a retardation valve in the liquid crystal layer in order to brighten the brightness in the white display.

Further, in the embodiment, the electrode for generating the transverse electric field is formed only on the lower substrate 110b, but may be formed on the upper substrate 110a as well as the lower substrate 110b. The electrode for generating the transverse electric field may be formed on at least one of the upper substrate 110a and the lower substrate 110b.

Hereinafter, another embodiment according to the present invention will be described with reference to the drawings.

32 is a schematic cross-sectional view in one pixel of the liquid crystal device 200 according to the embodiment. In the liquid crystal device 200 according to the embodiment, the upper substrate 201, the lower substrate 202, and the twisted nematic liquid crystal layer 203 sandwiched between the two substrates 201 and 202 are arranged in parallel to each other. It is configured to include.

The upper substrate 201 includes an upper transparent substrate 212, a transparent electrode 213 formed on the upper transparent substrate 212, and an upper alignment layer 214 formed on the transparent electrode 213. The lower substrate 220 includes a lower transparent substrate 222, a transparent electrode 223 formed on the lower transparent substrate 222, and a lower alignment layer 224 formed on the transparent electrode 223.

The upper and lower transparent substrates 212 and 222 are formed of, for example, glass. The transparent electrodes 213 and 223 are formed of, for example, a transparent conductive material such as ITO.

The liquid crystal layer 203 is disposed between the upper alignment layer 214 of the upper substrate 201 and the lower alignment layer 224 of the lower substrate 202.

The upper and lower alignment films 214 and 224 are subjected to an alignment treatment by rubbing. The orientation processing directions of the upper alignment film 214 and the lower alignment film 224 are perpendicular to each other when viewed from the viewing directions of the upper and lower substrates 201 and 202.

A chiral agent is added to the liquid crystal material which forms the liquid crystal layer 203. The alignment state of the liquid crystal molecules generated based on the influence of the chiral agent is spray twist twisted in the left torsion direction according to the direction from the upper substrate 201 to the lower substrate 202 in the normal direction of the upper substrate 201. Orientation.

FIG. 33A is a schematic plan view showing the alignment state of the liquid crystal molecules 203a in the liquid crystal layer 203 in the spray twist arrangement state. The state seen from the viewing direction of the upper substrate 201 is shown.

33B illustrates the liquid crystal layer 203 as viewed from the front (A1 direction in FIG. 33A) when the liquid crystal molecules 203a in the liquid crystal layer 203 according to the embodiment are in a spray twist alignment state. A schematic cross section of the time.

FIG. 33C shows the liquid crystal layer 203 horizontally (A2 direction in FIG. 33A) when the liquid crystal molecules 203a in the liquid crystal layer 203 according to the embodiment are in a spray twist alignment state. A schematic cross section of the time.

FIG. 33D is a schematic plan view showing the alignment state of the liquid crystal molecules 203a in the liquid crystal layer 203 in the uniform twist (reverse twist) alignment state. The state seen from the viewing direction of the upper substrate 201 is shown.

FIG. 33E shows the liquid crystal layer 203 in front of the liquid crystal layer 203 when the liquid crystal molecules 203a in the liquid crystal layer 203 according to the embodiment are in a uniform twist (reverse twist) alignment state (A1 in FIG. 33 (d)). Is a schematic cross-sectional view as seen from (direction).

FIG. 33 (f) crosses the liquid crystal layer 203 when the liquid crystal molecules 203a in the liquid crystal layer 203 according to the embodiment are in a uniform twist (reverse twist) alignment state (A2 in FIG. 33 (d)). Is a schematic cross-sectional view as seen from (direction).

The twist direction of the liquid crystal molecules 203a in the liquid crystal cell completion state is the spray twist which becomes the left twist RD1 which is the same direction as the twist direction by the chiral agent as shown in Figs. 33A to 33C. It was an orientation state.

As shown in (a)-(c) of FIG. 33, the spray twist orientation state has the same direction of the pretilt angle in the interface with the two alignment films 214 and 224 which sandwich the liquid crystal layer 203, When the pretilt angles of the two interfaces are the same, the polar angle of the liquid crystal molecules 203a is changed to 0 in the region near the middle of the liquid crystal layer, so that the alignment direction of the liquid crystal molecules crosses the liquid crystal layer 203 (in the A2 direction in the drawing). As shown in Fig. 33 (c), it is an orientation in which a spray orientation distributed in a fan shape and a twist orientation in which the liquid crystal molecules are twisted 90 degrees in the horizontal direction between the upper and lower substrates are combined.

The reverse twist (uniform twist) alignment state is twisted in the opposite direction RD2 to the spray twist alignment state shown in Figs. 33A to 33C as shown in Figs. 33D to 33F. It is an orientation state.

When the rubbing direction of the upper alignment layer 214 is the first direction OD1 and the rubbing direction of the lower alignment layer 224 is the second direction OD2, the second direction OD2 is the viewing direction of the upper substrate 201. It is a direction which makes 90 degrees counterclockwise with respect to 1st direction OD1. The orientation state of the liquid crystal molecules of the liquid crystal layer 203, which is defined by the combination of the orientation processing directions of the upper and lower substrates 201 and 202 and the pretilt angle, is shown in FIG. 33D, the upper substrate 201. ), It is a uniform twist (reverse twist) orientation twisted 90 ° to the right (second turning direction) RD2 from the normal direction.

Returning to FIG. 32, the drive power supply 220 is electrically connected to the vertically transparent electrodes 213 and 223. As shown in FIG. The voltage may be applied to the electrodes 213 and 223 by the driving power source 220. For example, by applying an alternating voltage equal to or greater than the threshold voltage between the two electrodes 213 and 223, the alignment state of the liquid crystal molecules can be transferred from the spray twist orientation to the uniform twist (reverse twist) orientation.

The upper polarizing plate 211 and the lower polarizing plate 221 are disposed on the surface opposite to the liquid crystal layer 203 in each of the upper substrate 201 and the lower substrate 202. The two polarizing plates 211 and 221 are cross nicol and are arranged such that the light transmission axis is parallel to the rubbing directions of the upper and lower substrates 201 and 202. The liquid crystal device 200 according to the embodiment is a normally white liquid crystal device.

34 is a flowchart illustrating a method of manufacturing the liquid crystal device 200 according to the embodiment. The present inventors first manufacture the liquid crystal device 200 according to the embodiment shown in FIG. 32 according to the flowchart shown in FIG. 34 under various conditions, and consider the firing conditions and the amount of indentation in the rubbing treatment of the alignment film for achieving good display. It was. Hereinafter, a method of manufacturing the liquid crystal device 200 according to the embodiment will be described with reference to FIGS. 32 and 34.

A transparent electrode 213, for example, prepares a transparent substrate 212 on which an indium tin oxide (ITO) electrode 213 is formed, and at the same time, a transparent substrate on which a transparent electrode 223, for example, an ITO electrode 223 is formed ( 222 is prepared (step S201). Here, two transparent substrates 212 and 222 were cleaned and dried using a test cell having a parallel plate type electrode (step S202).

An alignment film material is applied onto the transparent substrates 212 and 222 so as to cover the ITO electrodes 213 and 223 (step S203). Application of the alignment film material was carried out using spin coat. You may implement using flexographic printing or inkjet printing.

With respect to one of the pair of transparent substrates 212 and 222, the side chain density of the polyimide alignment layer material used for forming the vertical alignment layer is usually lowered and used as the material of the alignment layer (ultra high pretilt side alignment layer) 214. Used. For the other substrate 222, a polyimide film exhibiting a relatively high pretilt angle, which is usually used as an alignment film for super twisted nematic (STN), is made of the material of the alignment film (high pretilt side alignment film) 224. Used as. The alignment film material was applied such that the thicknesses of the alignment films 214 and 224 were 500 to 800 GPa. Plasticity (step S204) and main baking (step S205) are performed on the transparent substrates 212 and 222 coated with the alignment film material. Main firing was carried out under two conditions of 180 ° C and 220 ° C. In this way, alignment layers 214 and 224 covering the ITO electrodes 213 and 223 were formed (steps S203 to S205).

 Next, rubbing treatment (orientation treatment) is performed on each of the alignment films 214 and 224 (step S206). The rubbing treatment is, for example, a step of rotating the rolled cylindrical rolls at high speed to rub on the alignment film, whereby the liquid crystal molecules in contact with the substrate can be aligned (orientated) in one direction. The rubbing treatment was carried out by changing the conditions to 0 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm. In addition, the rubbing treatment was performed such that the twist angle of the liquid crystal element 200 was 90 degrees.

Subsequently, in order to keep the thickness (distance between substrates) of the liquid crystal cell constant, the gap adjusting material is sprayed on the one transparent substrate surface by, for example, a dry spray method (step S207). As the gap adjusting material, a plastic ball having a particle diameter of 4 μm was used.

On the other transparent substrate surface, a sealing material is printed and a main seal pattern is formed (step S208). For example, a thermosetting sealing material including a glass fiber having a particle diameter of 4 µm is printed by screen printing. The sealing material may also be applied using a dispenser. Moreover, you may use the photocurable sealing material which is not thermosetting, or the hardening type sealing material for light and heat diseases.

The transparent substrates 212 and 222 are overlapped (step S209). Two transparent substrates are superimposed on a predetermined position and cellized and heat-treated in a pressed state to cure the sealing material. For example, the sealing material is thermosetted by using a hot press method. In this way, an empty cell is produced.

For example, the nematic liquid crystal is injected into the empty cell by vacuum injection (step S210). Chiral agent was added to the liquid crystal. As chiral agent, Merck CB15 by the company was used. The amount of chiral addition was adjusted so that d / p was 0.4 when the chiral pitch was p and the thickness (cell thickness) of the liquid crystal layer was d. In addition, as mentioned later, about the liquid crystal cell preparation conditions with favorable visual observation, the amount of addition of a chiral agent was experimented by changing conditions to d / p = 0.04-1.0.

Subsequently, the liquid crystal inlet is sealed with, for example, an ultraviolet (UV) curable end seal material (step S211), and the cell is heated above the phase transition temperature of the liquid crystal to adjust the orientation of the liquid crystal molecules (step S212). Thereafter, the scriber device breaks according to the marks on the transparent substrate and divides the cells into small cells. Chamfering (step S213) and washing (step S214) are performed for the cells divided into small sections.

Finally, the polarizing plates 211 and 221 are attached to the surface opposite to the liquid crystal layer 203 of the two transparent substrates 212 and 222 (step S215). The two polarizing plates 211 and 221 were cross nicol and were arrange | positioned so that the direction of a transmission axis and a rubbing direction might become parallel. The two polarizing plates 211 and 221 can also be arrange | positioned so that the direction of a transmission axis and a rubbing direction may orthogonally cross. The driving power source 220 is connected between the ITO electrodes 213 and 223 of the two transparent substrates 212 and 222.

FIG. 35 is a representative example (No. 1 to No. 8) and display of cell fabrication conditions (combination of firing temperature at the time of alignment film formation and indentation amount at the rubbing treatment) of the liquid crystal element produced by the manufacturing method shown in FIG. 34; It is a table which shows the result of having observed the state visually. On the other hand, the present inventors produced liquid crystal elements even under cell production conditions other than those shown in Fig. 35, but as a result, no black display was obtained.

In the state where the liquid crystal element is completed, it is an alignment state (spray twist alignment state) twisted in the second turning direction, and in this case, since it becomes twist nematic (TN) -LCD of cross nicol arrangement, it is No.1-No.8. Bright white marks were obtained in the liquid crystal elements produced under any cell fabrication conditions. By applying a voltage equal to or higher than the saturation voltage to the liquid crystal element (an alternating voltage equal to or greater than the threshold voltage between the electrodes 213 and 223 in Fig. 32), the alignment state of the liquid crystal molecules is shifted from the spray twist orientation to the reverse twist orientation.

Conditions of No. 1 in the table (180 ° C firing temperature of the ultra-high tilt side alignment film 214, 0.8 mm of indentation during rubbing treatment, 220 ° C of firing temperature of high pretilt-side alignment membrane 224, and indentation during rubbing treatment In the liquid crystal element produced at 0.8 mm), it was observed that a light black display remained for about 5 minutes in the OFF state after the transition to the reverse twist orientation.

The condition of No. 2 in the table (180 ° C firing temperature of the ultra-high tilt side alignment film 214, 0.6 mm of indentation amount during the rubbing treatment, 220 ° C of firing temperature of the high pretilt side alignment layer 224, and indentation amount during the rubbing treatment 0.8 mm) and the conditions of No. 3 (the firing temperature of the ultra-high tilt side alignment film 214 is 180 ° C., the indentation amount at the time of rubbing treatment 0.4 mm, and the high pre-tilt side are the same as No. 2). Conditions of the liquid crystal element No. 7 (firing temperature of 180 deg. C of the ultra-high tilt side alignment film 214, 0.4 mm of indentation amount during rubbing treatment, firing temperature of 220 deg. The liquid crystal element fabricated with the indentation amount of 0.4 mm) exhibited a dark display in which the transmission state was relatively dark even though no voltage was applied (OFF state) after the transition to the reverse twist orientation. That is, when the firing condition of the ultra-high pretilt side alignment film 214 was set to 180 ° and the amount of indentation in the rubbing treatment was 0.4 mm or 0.6 mm, the transmission state of the produced liquid crystal element was relatively dark. .

On the other hand, the liquid crystal element of No. 3 in which the indentation amount during the rubbing treatment of the high pretilt side alignment film 224 was 0.8 mm, and the indentation amount during rubbing treatment of the high pretilt side alignment film 224 was 0.4 mm In the liquid crystal element of No. 7, there is no change in the observation result (the visual observation state and the time for which the black display is maintained (15 minutes in these conditions)), and thus, the manufacturing conditions of the high pretilt side alignment film 224 are not so high. It seems to have no dependencies.

Further, in the liquid crystal element of No. 2 in which the indentation amount during the rubbing treatment of the ultra-high pretilt side alignment film 214 was 0.6 mm, the black display was maintained for 5 minutes, and thus the ultra high pretilt-side alignment film 214 was used. When the amount of indentation in the rubbing process of 늘어나 increases, it is considered that the time for holding the black display decreases.

When the pretilt angle of the ultra-high pretilt-side alignment film 214 under the condition No. 2 in which the relatively dark black display was obtained was measured by the spectroscopy ellipsis method, it was found that the pretilt angle was about 45 °. . Moreover, when the pretilt angle of the ultra-high pretilt side oriented film 214 in No.3 and No.7 was measured by the spectroscopic ellipsis method, it turned out that the pretilt angle of about 61 degrees is shown.

The conditions of Nos. 4 to 6 in the table (the firing temperature of the ultra high pretilt-side alignment film 214 at 220 ° C., the indentation amounts at the time of rubbing 0.2 mm, 0.0mm, 0.2 mm, and the high pretilt-side alignment film 224 are all at the firing temperatures). Liquid crystal element produced at 220 ° C., 0.4 mm of indentation during rubbing, and No. 8 conditions (firing temperature of 220 ° C. of ultra-high pretilt side alignment film 214, 0.4 mm of rubbing during rubbing), and high free The tilt side is the same as Nos. 4 to 6), and in the OFF state after the transition to the reverse twist orientation, relatively dark black displays such as the above conditions No. 2, No. 3 and No. 7 do not reach. I only kept the search mark for five minutes.

The pretilt angle of the ultra-high pretilt-side alignment film 214 under the conditions Nos. 4 to 6 and No. 8 indicating the search display was measured by the spectroscopic ellipsis method and showed a pretilt angle of about 35 °. I could see that.

As described above, in order to obtain a liquid crystal device exhibiting a relatively dark black display in the OFF state after the transition to the reverse twist orientation, the pretilt angle of the ultra-high pretilt side alignment film 214 needs to be in the range of generally 40 ° or more and 65 ° or less. I think there is. On the other hand, when the pretilt angle of the high pretilt side oriented film 224 was measured, it turned out that the pretilt angle of about 8-12 degrees is shown. Therefore, the pretilt angle of the high pretilt side alignment film 224 should be 20 degrees or less, it is preferable that it is 1-15 degrees, and it is thought that it is more preferable to be around 10 degrees.

Fig. 36 shows conditions No. 1 to 3 of the table shown in Fig. 35 (the firing temperature of the ultra high pretilt side alignment film 214 at 180 ° C, and the amount of indentations during the rubbing treatment are 0.4 mm, 0.6 mm, 0.8 mm, and high pretilt side, respectively). The alignment films 224 are graphs showing the voltage-light transmittance characteristics of the liquid crystal element according to the embodiment, all made by the firing temperature of 220 ° C. and common to the indentation amount of 0.8 mm at the time of rubbing. The horizontal axis of each graph represents the applied voltage in units of 'V', and the vertical axis represents the light transmittance in units of '%'. The curve shown by the solid line shows the voltage-light transmittance characteristic in the reverse twist orientation, and the curve shown by the broken line shows the voltage-light transmittance characteristic in the spray twist orientation. Shown are electro-optical characteristics when a vertical electric field is generated by applying a voltage between the upper and lower electrodes 213 and 223 in each alignment state.

In the liquid crystal element according to condition No. 1 of the table shown in FIG. 4 in which the indentation amount during the rubbing treatment of the ultra-high tilt side alignment film 214 is 0.8 mm, a relatively high threshold value is exhibited at the time of spray twist orientation (rising), and the reverse twist is performed. In the orientation (falling), the threshold value is lowered, but it can be seen that the transmittance is about 20% at the OFF voltage (0V). These results are the same as those seen in the RTN type liquid crystal device according to the prior art.

In the liquid crystal element according to condition No. 2 of the table | surface shown in FIG. 4 which is 0.6 mm, and the indentation amount at the time of the rubbing process of the ultrahigh tilt side oriented film 214 in 0.4 mm, spray twist orientation ( In the case of rise, the same characteristics as that of the liquid crystal element (the same characteristics as the conventional RTN type liquid crystal element) under the condition of No. 1 are exhibited. However, it can be seen that in the reverse twist orientation (falling), the transmittance is very low at the OFF voltage (0V). Specifically, in the liquid crystal element according to condition No. 2 of the table shown in FIG. 35 having a press-fit amount of 0.6 mm, the transmittance at the OFF voltage (0 V) was 1.2%, the ON transmittance was 20%, and the contrast ratio was 17. In the liquid crystal element according to condition No. 3 in the table shown in FIG. 35 having a press-fit amount of 0.4 mm, the transmittance at OFF voltage (0 V) was 2.4%, the ON transmittance was 17.8%, and the contrast ratio was 7.4. From this result, it turns out that the liquid crystal element by condition No. 2 of the table shown in FIG. 35 whose intrusion amount is 0.6 mm as display performance is more excellent.

As described above, in the liquid crystal elements according to conditions No. 2 and No. 3 in the table shown in FIG. 35, it is understood that the light transmittances of the two alignment states in the absence of voltage are greatly different, and that the display of high contrast ratio is possible. The liquid crystal device according to the embodiment is a liquid crystal device having a high contrast ratio and capable of easily realizing a high quality display in which both a white display state and a black display state are stable. The black marks are dark and easy to see clearly.

On the other hand, for the liquid crystal element according to condition No. 7 of the table shown in FIG. 35, voltage-transmittance characteristics were not measured, but as described above, it is considered that there is little dependence on the manufacturing conditions of the high pretilt-side alignment film 224. Therefore, it is assumed that the liquid crystal element according to condition No. 7 also exhibits the same voltage-light transmittance characteristics as the liquid crystal element according to conditions No. 2 and No. 3.

Although the detailed cause of the characteristics in which the liquid crystal elements according to conditions No. 2 and No. 3 in the table shown in FIG. 35 have a relatively dark black display in the OFF state (the transmittance at the OFF voltage is very low) is not clear, an RTN type liquid crystal element is unknown. It has a property that the threshold value at the time of falling (reverse twist arrangement) is lower than the threshold value at the time of rising (spray twist arrangement), and this indication is realized because the threshold value is lower than 0V under special conditions. I guess.

In general, in the reverse twisted arrangement state, a large distortion occurs inside the liquid crystal layer due to the pretilt angle given by the substrate alignment process and the torsion force imparted by the chiral agent. It is thought that the liquid crystal molecules near the center in the thickness direction will be inclined with respect to the substrate plane. In the RTN type liquid crystal device having a high pretilt angle of 20 ° or more, the inclination angle of the liquid crystal molecules in the vicinity of the center in the thickness direction of the liquid crystal layer is very large, and is assumed to stand almost perpendicular to the substrate. Therefore, it is thought that a relatively dark black display is obtained even when no voltage is applied. On the other hand, in the reverse twist arrangement, the inclination angle in bulk becomes higher than the pretilt angle at the interface with the substrate. This has also been confirmed by liquid crystal molecular orientation simulation based on continuum theory.

Focusing on the characteristic at the time of spray twist orientation (rising) of FIG. 36, it turns out that the threshold value becomes low, as the amount of indentation at the time of the rubbing process of the ultrahigh-tilt side oriented film 214 becomes small.

In the spray twist orientation, when the pretilt angles of the two interfaces are the same, the inclination angle of the liquid crystal molecules near the center of the liquid crystal layer becomes parallel to the substrate plane. In contrast, in the present embodiment, different pretilt angles are provided at the interface between the alignment film 214 and the liquid crystal layer 203 and at the interface between the alignment film 224 and the liquid crystal layer 203. As the difference in the pretilt angle increases, it is considered that the inclination angle of the liquid crystal molecules near the center of the liquid crystal layer 203 increases and the threshold value tends to decrease.

Since the alignment processing conditions of the high pretilt side alignment film 224 of the liquid crystal element shown in FIG. 36 are all common, the ultra high pretilt side alignment film 214 as the indentation amount during the rubbing treatment of the ultra high pretilt side alignment film 214 decreases. ) And the pretilt angle at the interface between the liquid crystal layer 203 increases, and as a result, the threshold value is predicted to be low.

In addition, as is clear from the table shown in FIG. 35, the indentation amount during the rubbing treatment of the ultra high pretilt-side alignment film 214 during the rubbing treatment of the ultra-high tilt side alignment film 214 was about 5 minutes at 0.4 mm, and the indentation amount was 0.4 mm. In the case of increased to about 15 minutes. From this, it is understood that a high pretilt angle at the interface between the ultra-high pretilt side alignment film 214 and the liquid crystal layer 203 is advantageous in terms of holding time.

FIG. 37 shows the cell fabrication condition No. 3 in which the visual observation results shown in the table of FIG. 35 were good (firing temperature of 180 ° C. of the ultra high pretilt side alignment film 214, 0.4 mm of indentation during rubbing treatment, and high pretilt side alignment film). Table 22 shows the results of visually observing the holding time of the black display state by varying the addition amount of the chiral agent with respect to the liquid crystal element with a firing temperature of 220 ° C. (224 mm and an indentation amount of 0.8 mm at the time of rubbing treatment). When the chiral pitch was p and the thickness (cell thickness) of the liquid crystal layer was d, the addition amount of the chiral agent was changed so that d / p was 0.040 to 1.000.

In the range of d / p of 0.125-0.5, when the liquid crystal element was completed, it became a spray twist orientation state, and when the voltage more than saturation voltage was applied, the comparatively dark black display in reverse twist orientation was observed.

When d / p was less than 0.125, the comparatively dark black display state in the reverse twist orientation was already at the time when the liquid crystal element was completed, and thus it was not possible to transition to the spray twist alignment state.

Moreover, even if d / p is 0.125 or more, it was mixed in the range of 0.125-0.54 that the comparatively dark black display state in reverse twist orientation was already at the time of completion of a liquid crystal element. Therefore, it is considered that the range of 0.125 to 0.154 is the lower limit for bistable display.

On the other hand, when d / p was larger than 0.5, it became another twist state (perhaps 270 degree twist), and was not able to transition to a reverse twist orientation state.

In addition, there was a variation in the holding time of the reverse twist alignment state, but the longer the d / p was, the longer the trend was. Therefore, it is considered that d / p as small as possible in the range of bistable display (d / p above 0.154 and 0.5 or less in the table of FIG. 37) is preferable. Therefore, from the table of Fig. 37, it is considered that d / p is about 0.167 to 0.182, which is the best, and in this case, the reverse twist orientation is maintained for about 20 minutes. On the other hand, as d / p is changed from 0.2 to 0.5, since the holding time is gradually shortened from 15 minutes to 5 minutes, it can be seen that the holding time can be controlled to some extent by changing the d / p.

When the liquid crystal device according to the present embodiment is applied to a display, driving using memory characteristics is possible. For example, when a dot matrix display is assumed, a display update may be performed for each line, and a voltage higher than a saturation voltage may be applied to a pixel for black display, without applying a voltage to a pixel for white display.

For driving, various methods can be considered. As an example, in the case of the XY electrode matrix display, a square wave (for example, about 1.5V at about 150V at about 1.5V) is applied to one line (for example, X1 line) of the X electrode. ) Is applied to the Y electrodes Y1 to Yn orthogonal thereto, and a square wave (for example, 1.5 Hz to about 150 Hz) is applied to the Y electrodes Y1 to Yn orthogonal to the square wave applied to the X electrode or about a threshold voltage shifted by half the period. In a pixel in which a waveform synchronized with the waveform applied to the X1 line is applied to the Y line, the display is effectively unchanged since the voltage is effectively not applied. In the pixel to which the waveform applied to the X1 line and the waveform shifted by half the period is applied to the Y line, a voltage of about 3 V is effectively applied. Therefore, from a spray twist orientation state to a reverse twist orientation state by a voltage higher than the saturation voltage The white mark changes to a black mark. A square wave (for example, about 1.5V to 150 Hz) about the threshold voltage is applied to the pixel of the line shape other than the unselected X1 line, but the orientation state does not change because the voltage is not enough to change the orientation state. The matrix display can be performed by sequentially driving the X1 line to the other lines.

The display updated by the driving method as described above can be maintained without applying a voltage for about 5 to 20 minutes. In the case of updating this display, all the pixels can be reset to the spray twist alignment state by waiting for the holding time (about 5 to 20 minutes) or by applying heat above the phase transition temperature of the liquid crystal to the liquid crystal element. After that, it can be updated one after another.

Furthermore, in the case of actively returning from the reverse twist alignment state to the spray twist alignment state, it is effective to form an electrode carrying a transverse electric field. For example, when a line-shaped electrode which is displaced in a planar position on the upper substrate side and the lower substrate side is disposed, an oblique electric field can be applied to the liquid crystal layer by applying a voltage between the electrodes. This simple electrode arrangement also allows the transition from spray twist orientation to reverse twist orientation by dropping the voltage by dropping the voltage (or stepwise), and spray twist orientation from reverse twist orientation by steeply dropping the voltage (pulse shape). It was confirmed by the inventors that the present inventors actively return.

In addition, as another example of the structure and manufacturing method of the liquid crystal element which has the electrode mounted in the above-mentioned transverse electric field, description of Paragraph <0119>-<0152> of this specification is referred. In addition, the description of Paragraph <0153>-<0169> of this specification is referred for the driving method.

As described above, according to the embodiment of the present invention, bistable display in a high contrast white display state and a black display state can be easily realized. At the same time, it has a comparatively excellent visual characteristic as in general TN-LCD. In addition, when performing visual compensation, a low-cost optical compensation film can be utilized as in a general TN-LCD.

Further, according to the embodiment of the present invention, since no power is required except when updating the display, ultra-low power consumption can be driven. In particular, when applied to a reflective display, it is considered that the advantage of ultra-low power consumption is great. In addition, when the holding time is short, regular voltage application is required. In the present embodiment, since it is often necessary, the present embodiment only needs to apply it once every few minutes (5 to 20 minutes), thereby dramatically reducing power consumption. Can be.

In addition, since it is possible to apply a driving method (line sequential update method or the like) using the memory property, a large-capacity dot matrix display can be performed by simple matrix display without using expensive TFT or the like.

In addition, the manufacturing process by the above-mentioned Example is basically the same as that of the general TN-LCD manufacturing process. The difference is that the use of different alignment film materials on the upper and lower substrates differs from the rubbing conditions (control of indentation amount) and the firing conditions of the alignment film on the upper and lower substrates. Within the range used in the LCD manufacturing process). Therefore, there is little cause of cost increase in a manufacturing process, and it can manufacture at low cost like general TN-LCD.

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

For example, in the embodiment, the polarizing plate is arranged in cross nicol and used as a liquid crystal element of normally white display. The polarizing plate may be arranged in parallel nicol and may be a liquid crystal element of normally black display. However, it is easier to realize display with a higher contrast ratio if it is normally white. In the case of normally white display, in order to obtain good black display, it is preferable that the angle which the transmission axis direction of the upper and lower polarizing plates 211 and 221 make is 90 degree vicinity.

On the other hand, in the embodiment, since the upper and lower polarizing plates 211 and 221 use a form with a relatively low light transmittance, for example, as shown in FIG. 36, the light transmittance of the white display (spray twist arrangement) is 20 to 20. FIG. Although it is about 25%, when using a form with a relatively high light transmittance, it will be possible to set the light transmittance of a white display to about 30 to 35%, for example.

In addition, although the twist angle was 90 degrees in the Example, it can also be set as another angle. In this case, it will be necessary to adjust the delay value in the liquid crystal layer in order to brighten the brightness in the white display.

In addition, this invention is not limited to the content of the above-mentioned Example, It can variously deform and implement within the range of the summary of this invention. Although the rubbing process was mentioned as a specific example of an orientation process in embodiment and Example mentioned above, other orientation processing (for example, a photo-alignment method, a diagonal deposition method, etc.) can also be used. In addition, numerical conditions etc. which were shown in description are only a preferable example, and are not limited to them.

Overall liquid crystal element For example, it can use for the whole liquid crystal element which performs a simple matrix drive. Also, the present invention can be used for liquid crystal devices requiring low power consumption, wide visual characteristics, low cost, and the like.

In terms of memory characteristics, the present invention can be suitably applied to reflective, transmissive, and projection displays such as display surfaces of information devices (PCs, portable information terminals, etc.) that save power and do not require frequent updates. . It can also be used for the information display surface of magnetically recorded or electrically recorded cards, children's toys, electronic paper and the like.

11: first substrate 12: first electrode
13, 20: alignment layer 14, 115, 203: liquid crystal layer
15: second substrate 16: second electrode
17: insulating layer 18: third electrode
19: fourth electrode 21: first polarizing plate
22: second polarizer 31, 32, 33: driver
34: pixel portion 110a, 201: upper substrate
110b, 202: lower substrate 111a, 212: upper transparent substrate
111b and 222: lower transparent substrate 112a: upper electrode
112b: lower electrode 112c: first comb electrode
112d: second comb electrode 113: insulating film
114a, 214: upper alignment layer 114b, 224: lower alignment layer
116a and 211: upper polarizing plate 116b and 221: lower polarizing plate
120: power supply 213: upper ITO electrode
223: lower ITO electrode 220: driving power source

Claims (10)

The first substrate and the second substrate which is subjected to an orientation treatment on each surface, and disposed to face each other,
A liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate;
An electric field applying means for applying an electric field to the liquid crystal layer,
The first substrate and the second substrate are relatively arranged to generate a first alignment state twisted in the first pivot direction with respect to the liquid crystal molecules of the liquid crystal layer,
The liquid crystal layer includes a chiral agent having a property of generating a second alignment state twisted in a second turning direction opposite to the first turning direction with respect to the liquid crystal molecules,
And the liquid crystal layer transitions to the first alignment state by applying an electric field in a direction substantially perpendicular to each one surface of the first substrate and the second substrate by the electric field applying means. The method of claim 1,
And said electric field applying means has at least a first electrode provided on one side of said first substrate and a second electrode provided on one side of said second substrate. The method according to claim 1 or 2,
And the liquid crystal layer transitions to the second alignment state by applying an electric field in a direction substantially parallel to one surface of each of the first substrate and the second substrate. The method of claim 3, wherein
The electric field applying means further includes a third electrode and a fourth electrode which are provided on an upper side of the second electrode of the second substrate through an insulating layer and are spaced apart from each other. The method according to claim 1 or 2,
And the first substrate and the second substrate are oriented so as to exhibit a pretilt angle of 20 ° or more and 45 ° or less, respectively. The method of claim 5, wherein
And the first substrate and the second substrate are oriented so as to exhibit a pretilt angle of 31 ° or more and 37 ° or less, respectively. The method according to claim 1 or 2,
The amount of the chiral agent added to the liquid crystal layer is adjusted so that d / p is greater than 0.04 and less than 0.25 when the chiral pitch is p and the thickness of the liquid crystal layer is d. The method according to claim 1 or 2,
The first substrate is oriented to express a pretilt angle of 40 ° or more and 65 ° or less,
And the second substrate is oriented so that a pretilt angle of 1 ° or more and 15 ° or less is expressed. The method of claim 8,
The amount of the chiral agent added to the liquid crystal layer is adjusted so that d / p is 0.125 or more and 0.5 or less when p is the chiral pitch and d is the thickness of the liquid crystal layer. The method according to claim 1 or 2,
An angle formed between an orientation processing direction of the first substrate and an orientation processing direction of the second substrate is 90 ° or more and 100 ° or less as viewed from the normal direction of each of the first and second substrates.

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