KR20130026383A - Liquid crystal element, liquid crystal display - Google Patents

Abstract

PURPOSE: A liquid crystal element and a liquid crystal display device thereof are provided to omit basically required power besides power required for display conversion by using the bistability of two orientation states of the liquid crystal element. CONSTITUTION: A first and a second substrate(11,12) set an orientation processing direction for generating a first orientation state of liquid crystal molecules. A liquid crystal layer(24) contains a chiral agent for generating a second orientation state of the liquid crystal molecules. If a voltage is supplied to a gap between a second electrode and a common electrode(23), the second orientation state of the liquid crystal layer is transferred to the first orientation state. If the voltage is supplied to a gap between a first electrode and the second electrode, the first orientation state of the liquid crystal layer is transferred to the second orientation state. The orientation state is maintained after the voltage supply is released.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal device,

The present invention relates to a novel liquid crystal device and a liquid crystal display device using a transition between two alignment states.

Japanese Patent Publication No. 2510150 discloses a liquid crystal display device in which liquid crystal molecules are torsionally oriented in a turning direction opposite to the turning direction restricted by a combination of alignment treatment directions applied to each of a pair of substrates arranged opposite to each other, (Prior Art 1). Japanese Patent Laid-Open Publication No. 2007-293278 discloses a method of manufacturing a semiconductor device in which a pair of substrates arranged opposite to each other is rotated in a direction opposite to the turning direction (first turning direction) A liquid crystal element is disclosed in which a bit in the direction of tilt is oriented in the above first pivot direction while adding a chiral agent to increase the deformation in the liquid crystal layer thereby lowering the threshold voltage to enable low voltage driving (Prior Example 2).

In the liquid crystal display device of the above-described prior art example 1, although the orientation state of the reverse twist is unstable and it is possible to obtain an orientation state of reverse twist by applying a relatively high voltage to the liquid crystal layer, There is a problem of discarding the fabric in the oriented state. Although the liquid crystal device of the prior art example 2 has an advantage of lowering the threshold voltage as described above, when the voltage is turned off, the liquid crystal device transitions to a state of net torsion immediately (for example, several seconds), and conversely, there is a problem. It is not assumed in the prior art examples 1 and 2 that two orientation states of net torsion and reverse torsion are actively used as display or the like. That is, there are no disclosures or suggestions on the technical ideas such as the configuration and driving method necessary for positively utilizing bistability.

On the other hand, Japanese Laid-Open Patent Publication No. 2010-186045 discloses a technique relating to a reverse twisted nematic (TN) type liquid crystal device which is in a spray twist orientation in the initial state but is stabilized in a reverse twist orientation when a vertical electric field is applied once (Prior Example 3). However, the liquid crystal device of the preceding example 3 still has room for improvement in that a range in which a good contrast can be obtained is narrow.

Therefore, the inventors of the present invention are studying a novel reverse-type TN liquid crystal device capable of eliminating defects in the above-mentioned prior art examples 1-3. In addition, the inventors of the present invention have proposed a liquid crystal display device using the above-described novel reverse TN liquid crystal device, in which a plurality of liquid crystal devices are arranged and each liquid crystal device is individually The liquid crystal display device which is driven is also being studied. Here, an example of the structure of the switching element and the electrode for driving using the horizontal electric field is disclosed, for example, in Japanese Patent Publication No. 4238877 (Prior Example 4). However, the structure of the switching element and the electrode disclosed in the foregoing Example 4 is not suitable for driving the novel reverse TN type liquid crystal device by the inventors of the present invention.

It is a further object of the present invention to provide a novel liquid crystal device having a switching element and electrode structure suitable for generating transitions between two alignment states.

It is another object of the present invention to provide a liquid crystal display device capable of driving with low power consumption using a novel liquid crystal device.

A liquid crystal device according to an embodiment of the present invention includes: (a) a first substrate and a second substrate which are aligned on one side and are disposed to face each other; (b) (C) a second electrode provided on one surface of the first substrate and spaced apart from the first electrode, (d) a second electrode provided on one surface of the first substrate, (E) a common electrode provided on one surface side of the second substrate so that at least a part of the common electrode overlaps with the first electrode and the second electrode, and (f) And a liquid crystal layer provided between one surface of the first substrate and the second substrate, and (g) the first substrate and the second substrate are arranged such that liquid crystal molecules of the liquid crystal layer are twisted in a first direction (H) the liquid crystal layer is a liquid crystal molecule, (I) a voltage is applied between the second electrode and the common electrode to cause the liquid crystal layer to generate a second alignment state in a second direction opposite to the first direction, The liquid crystal layer transits from the first alignment state to the second alignment state by applying a voltage between the first electrode and the second electrode, .

According to the above configuration, a novel liquid crystal device having a structure of a switching element and an electrode suitable for generating a transition between two alignment states is obtained.

In the liquid crystal device, it is preferable that at least one of the first electrode and the second electrode has a plurality of rectilinear portions arranged in parallel and spaced apart from each other. It is also preferable that the first electrode and the second electrode are laminated via an insulating film.

Thus, it is possible to more effectively apply the electric field (horizontal electric field) in the direction parallel to the substrate surface necessary for generating the transition between the two alignment states to the liquid crystal layer.

In the liquid crystal device, it is preferable that the first substrate and the second substrate respectively give a pretilt angle of 20 DEG or more to the liquid crystal molecules of the liquid crystal layer at the interface with the liquid crystal layer. It is preferable that the chiral agent is added so that the ratio of the chiral pitch (d / p) to the layer thickness (d) of the liquid crystal layer is 0.04 or more and 0.6 or less.

As a result, the bistability of the two alignment states can be further enhanced.

A liquid crystal display device according to an embodiment of the present invention is a liquid crystal display device having a plurality of pixel portions, each of which is constituted by using the above-described liquid crystal device according to the present invention.

According to the above configuration, by using the bistability (memory property) of the two alignment states of the liquid crystal element, it is possible to obtain a low power consumption liquid crystal display device which basically requires no power other than the display conversion.

1 is a schematic diagram schematically showing the principle of a reverse-TN liquid crystal device.
2 is a conceptual diagram for explaining the relationship between the alignment state of the liquid crystal layer and the electric field direction when transitioning from the reverse twist state to the spray twist state.
3 is a cross-sectional view showing a configuration example of a reverse-TN liquid crystal device according to the first embodiment.
4 is a plan view of the reverse TN type liquid crystal device shown in Fig.
5 is a cross-sectional view showing a manufacturing method of a reverse TN type liquid crystal device according to the first embodiment.
6 is a cross-sectional view showing a manufacturing method of a reverse TN liquid crystal device according to the first embodiment.
7 is a diagram showing an example of display characteristics of a reverse-TN liquid crystal display device.
8 is a cross-sectional view showing a configuration example of a reverse-TN liquid crystal device according to the second embodiment.
Fig. 9 is a plan view of the reverse TN liquid crystal device shown in Fig. 8. Fig.
10 is a cross-sectional view showing a manufacturing method of a reverse TN liquid crystal device according to the second embodiment.
11 is a cross-sectional view showing a manufacturing method of a reverse TN liquid crystal device according to the second embodiment.
12 is a cross-sectional view schematically showing a configuration example of a reverse-TN liquid crystal device according to the third embodiment.
13 is a cross-sectional view showing a configuration example of a reverse TN liquid crystal device according to the third embodiment.
14 is a diagram showing an example of the reflectance characteristic of the reverse-TN liquid crystal device of the third embodiment.
15 is a diagram schematically showing a configuration example of a liquid crystal display device according to the fourth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a schematic diagram schematically showing the principle of a reverse-TN liquid crystal device. The reverse-type TN liquid crystal device has, as a basic configuration, an upper substrate 1 and a lower substrate 2 arranged opposite to each other, and a liquid crystal layer 3 provided therebetween. The surfaces of the upper substrate 1 and the lower substrate 2 are subjected to alignment treatment such as rubbing treatment. The upper substrate 1 and the lower substrate 2 are relatively arranged such that the alignment treatment directions (indicated by arrows in the drawing) cross each other at an angle of about 90 °. The liquid crystal layer 3 is formed by injecting a nematic liquid crystal material between the upper substrate 1 and the lower substrate 2. [ In the liquid crystal layer 3, a liquid crystal material to which a chiral agent is added is used, which causes the liquid crystal molecules to beat in a specific direction (rightward turning direction in the example of Fig. 1) in the azimuthal direction. (D / p) is about 0.04 to 0.6, for example, where d is the interval (cell thickness) between the upper substrate 1 and the lower substrate 2 and p is the chiral pitch of the chiral agent Respectively. In such a reverse TN type liquid crystal device, the liquid crystal layer 3 is spray-aligned in the initial state due to the action of the chiral agent, and the bit becomes a spray twist state (second alignment state). When a voltage exceeding the saturation voltage is applied to the liquid crystal layer 3 in the spray twist state in the layer thickness direction, a transition is made to a reverse twist state (uniform twist state: first alignment state) in which the liquid crystal molecules are twisted in the leftward turning direction do. In the liquid crystal layer 3 in the reverse twist state as described above, the liquid crystal molecules in the bulk are biased, so that the effect of reducing the driving voltage of the liquid crystal element appears.

2 is a conceptual diagram for explaining the relationship between the alignment state of the liquid crystal layer and the electric field direction when transitioning from the reverse twist state to the spray twist state. As shown in Fig. 2 (A), the electric field in the horizontal direction with respect to the substrate surface is divided into liquid crystal molecules at substantially the center in the thickness direction of the liquid crystal layer in the reverse twisted state The direction of the electric field is set so that the major axis direction of the liquid crystal molecules is not as parallel as possible, but orthogonally or nearly in parallel. As a result, since the liquid crystal molecules at substantially the center in the thickness direction of the liquid crystal layer are redirected along the electric field direction, the alignment state of the liquid crystal layer transitions from the reverse twist state to the spray twist state as shown in Fig. 2B . In the case where an electric field is applied to the liquid crystal layer in the reverse twisted state so as to be in parallel with or close to the long axis direction of the liquid crystal molecules at substantially the center in the layer thickness direction, Is difficult to occur. This is because almost no reorientation of the liquid crystal molecules due to the electric field occurs at the approximate center of the liquid crystal layer in the layer thickness direction. From the above, it is necessary to generate an electric field (longitudinal electric field) with respect to the layer thickness direction of the liquid crystal layer and an electric field (transverse electric field) in a direction orthogonal to the layer thickness direction in order to freely shift between the two alignment states in the reverse TN liquid crystal device And it is necessary for the transverse electric field to be in a direction substantially orthogonal to or close to the major axis direction of the liquid crystal molecules at substantially the center in the layer thickness direction of the liquid crystal layer in the reverse twisted state. The device structure for giving these vertical electric fields and lateral electric fields freely will be described below with specific examples.

3 is a cross-sectional view showing a configuration example of a reverse-TN liquid crystal device according to the first embodiment. 4 is a plan view of the reverse TN liquid crystal device shown in Fig. 3 shows a cross section taken along the line II-II in Fig. The reverse type TN liquid crystal device of the present embodiment shown in each figure has a first substrate (lower substrate) 11, a second substrate (upper substrate) 12, a first electrode 13, a common line 14, The second electrode (pixel electrode) 20, the first alignment film 21, the second alignment film 21, and the second alignment film 21 A liquid crystal layer 24, a signal line 25, a first polarizing plate (lower polarizing plate) 31, and a second polarizing plate (upper polarizing plate)

The first substrate 11 and the second substrate 12 are opposed to each other and are transparent substrates such as glass substrates and plastic substrates, for example. A plurality of spacers (grains) are dispersed (not shown) between the first substrate 11 and the second substrate 12, and the first substrate 11 and the second substrate 12 are separated by their spacers The mutual spacing of the substrates 12 is maintained.

The first electrode 13 is provided on one side of the first substrate 11. As shown in Fig. 4, the first electrode 13 is formed in a substantially rectangular shape, for example, and a part of the first electrode 13 is connected to the common line 14. [ The first electrode 13 is obtained, for example, by patterning a transparent conductive film such as indium tin oxide (ITO).

The common line 14 is provided on one surface of the first substrate 11 and extends in one direction (Y direction in Fig. 4). Through this common line 14, a predetermined potential is given to the first electrode 13 from voltage supply means (not shown). As the common line 14, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The scanning lines 15 are provided on one surface side of the first substrate 11 and extend in one direction (Y direction in FIG. 4). As shown in Fig. 4, the scanning line 15 of the present embodiment is disposed with the first electrode 13 sandwiched between the scanning line 15 and the common line 14. Fig. As the scanning line 15, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The insulating film 16 covers the first electrode 13, the common line 14 and the scanning line 15 on one surface of the first substrate 11. As the insulating film 16, for example, a silicon nitride film, a silicon oxide film, or a laminated film thereof is used.

The semiconductor film 17 is provided on the insulating film 16 at a predetermined position overlapping with the scanning line 15. [ Such a semiconductor film 17 is patterned into an island shape as shown in Fig. As the semiconductor film 17, for example, an amorphous silicon film is used. A portion of the scanning line 15 which overlaps with the semiconductor film 17 functions as a gate electrode of the thin film transistor. A portion of the insulating film 16 overlapping with the semiconductor 17 functions as a gate insulating film of the thin film transistor.

The source electrode 18 is provided at a predetermined position on the insulating film 16, and a part of the source electrode 18 is connected to the semiconductor film 17. The source electrode 18 of this embodiment is formed integrally with the signal line 25 as shown in Fig. As the source electrode 18 and the signal line 25, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The drain electrode 19 is provided at a predetermined position on the insulating film 16, and a part of the drain electrode 19 is connected to the semiconductor film 17. As the drain electrode 19, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The second electrode 20 is formed on the insulating film 16 and at least a part of the second electrode 20 is located at a predetermined position overlapping with the first electrode 13. The second electrode 20 has a plurality of openings (slits) 20a as shown in Fig. The second electrode 20 is obtained, for example, by patterning a transparent conductive film such as indium tin oxide (ITO). The size of the second electrode 20 is set to be about 20 占 퐉 and the width of each opening 20a (see Fig. 3 The length in the X direction) of about 20 mu m. A horizontal electric field can be applied to the liquid crystal layer 24 by applying a voltage between the second electrode 20 and the first electrode 13.

The first alignment film 21 covers the semiconductor film 17, the source electrode 18, the drain electrode 19 and the second electrode 20 on the insulating film 16 on one side of the first substrate 11 Is installed. Likewise, the second alignment film 22 is provided so as to cover the common electrode 23 on one surface of the second substrate 12. The first alignment film 21 and the second alignment film 22 are each subjected to uniaxial alignment treatment (for example, rubbing treatment, photo alignment treatment, etc.). The first alignment film 21 and the second alignment film 22 of the present embodiment are used to develop a relatively high pretilt angle (about 20 deg. Or more, more preferably about 35 deg. 10 deg.). The alignment treatment direction RL of the first alignment film 21 and the alignment treatment direction RL of the second alignment film 22 are aligned substantially at the center of the layer thickness direction when the alignment state of the liquid crystal layer 24 is in the reverse twist state The alignment direction D of the liquid crystal molecules of the first electrode 13 and the second electrode 20 is set to be substantially orthogonal to the electric field direction E generated by the first electrode 13 and the second electrode 20 (see Fig. 4).

The common electrode 23 is provided on one surface of the second substrate 12. At least a part of the common electrode 23 is formed so as to overlap with the first electrode 13 and the second electrode 20. The common electrode 23 is obtained, for example, by patterning a transparent conductive film such as indium tin oxide (ITO). A vertical electric field can be applied to the liquid crystal layer 24 by applying a voltage between the common electrode 23 and the first electrode 13 (or the second electrode 20).

The liquid crystal layer 24 is provided between one surface of the first substrate 11 and one surface of the second substrate 12. In this embodiment, the liquid crystal layer 24 is formed by using a nematic liquid crystal material having a positive dielectric anisotropy (DELTA epsilon) (DELTA epsilon > 0). A thick line in the liquid crystal layer 24 schematically shows liquid crystal molecules in the liquid crystal layer 24. The liquid crystal molecules when no voltage is applied have a predetermined pretilt angle with respect to the respective substrate surfaces of the first substrate 11 and the second substrate 12 and align. The angle formed by the directions RU and RL (refer to FIG. 4) of the alignment treatment of the first alignment film 21 and the second alignment film 22 is set to, for example, about 90 degrees, The liquid crystal molecules of the liquid crystal layer 24 are twisted in the azimuthal direction between the first substrate 11 and the second substrate 12 and aligned.

The signal line 25 is provided on one side of the insulating film 16 and extends in one direction (X direction shown in Fig. 4) which is substantially perpendicular to the common line 14 and the scanning line 15. [ As shown in Fig. 4, the signal line 25 of this embodiment is formed integrally with the source electrode 18. As shown in Fig. As the signal line 25, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The first polarizing plate 31 is disposed outside the first substrate 11. The second polarizing plate 32 is disposed outside the second substrate 12. In this embodiment, it is observed by the user on the second polarizing plate 32 side. The first polarizing plate 31 and the second polarizing plate 32 are disposed, for example, substantially orthogonal to each other with respect to the transmission axis (cross-Nicol arrangement).

Next, an example of a method of manufacturing a reverse TN liquid crystal device according to the first embodiment will be described with reference to Figs. 5 and 6. Fig.

First, a glass substrate for use as the first substrate 11 and the second substrate 12 is prepared. For example, a glass substrate made of a non-alkali glass having a thickness of 0.7 mm is used.

Next, a common line 14 and a scanning line 15 are formed on one surface of the first substrate 11 (Fig. 5 (A)). Specifically, an aluminum film is formed over the entire one surface of the first substrate 11 by a film forming method such as a sputtering method, and a molybdenum film is formed thereon. Thereafter, a laminated film of an aluminum film and a molybdenum film is patterned by a dry etching method or the like.

Then, the first electrode 13 is formed at a predetermined position on one side of the first substrate 11 (Fig. 5 (B)). Specifically, an indium tin oxide film (ITO film) is formed over one entire surface of the first substrate 11 by a film forming method such as a sputtering method. Thereafter, this ITO film is patterned by a wet etching method or the like.

Next, an insulating film 16 is formed on one surface of the first substrate 11 so as to cover the first electrode 13, the common line 14, and the scanning line 15 (FIG. 5C) . Specifically, a silicon nitride film is formed by a film formation method such as a sputtering method or a plasma CVD (Chemical Vapor Deposition) method.

Then, the semiconductor film 17 is formed at a predetermined position on the insulating film 16 of the first substrate 11 (FIG. 5 (D)). Specifically, an amorphous silicon film is formed over the entire surface of the first substrate 11 by a film formation method such as a plasma CVD method. Thereafter, the amorphous silicon film is patterned into an island shape by a dry etching method or the like.

Next, a source electrode 18, a drain electrode 19, and a signal line 25 are formed at predetermined positions on the insulating film 16 of the first substrate 11 (Fig. 5 (E)). Specifically, a laminated film of a molybdenum film / aluminum film / molybdenum film is formed over the entire one surface of the first substrate 11 by a film forming method such as a sputtering method. Thereafter, this laminated film is patterned by a dry etching method or the like.

Then, the second electrode 20 is formed at a predetermined position on the insulating film 16 of the first substrate 11 (FIG. 5 (F)). Specifically, an ITO film is formed over the entire one surface of the first substrate 11 by a film forming method such as a sputtering method. Thereafter, this ITO film is patterned by a wet etching method or the like. Further, a passivation film may be further formed on the insulating film 16 (not shown).

On the other hand, a common electrode 23 is formed on one surface of the second substrate 12 (FIG. 5 (G)). Specifically, an ITO film is formed over the entire one surface of the second substrate 12 by a film forming method such as a sputtering method. In the actual manufacturing process, when the common electrode 23 is present on the entire surface of the substrate, there is a possibility of causing a short circuit by the main sealing portion and peeling of the film during braking in scribing. Therefore, It is preferable to shield (regulate) the outer periphery.

Next, a first alignment film 21 is formed over the entire surface of the insulating film 16 of the first substrate 11 (FIG. 6A), and a second alignment film 21 is formed on the common electrode 23 of the second substrate 12 The second alignment film 22 is formed over the whole of the first alignment film 22 (Fig. 6 (B)). Here, for example, each alignment film is formed by using a polyimide film having a lowered side chain density of a material generally used as a vertical alignment film. The alignment film material is formed on the first substrate 11 and the second substrate 12 by suitable methods such as a flexo printing method, an inkjet method, a spin coat method, a slit coat method, a slit method and a spin coat method, (For example, about 500 to 800 ANGSTROM) and heat-treated (for example, baked at 160 to 180 DEG C for 1 hour). Thereafter, alignment treatment is performed on each of the first alignment film 21 and the second alignment film 22. Here, for example, the rubbing treatment is performed, and the amount of the rubbing under the condition is set to 0.8 mm (Strong rubbing condition). Here, when the first substrate 11 and the second substrate 12 are overlapped with each other, the rubbing direction is set so that the twist angle of the liquid crystal molecules on each substrate becomes approximately 90 degrees.

Then, a main sealant containing an appropriate amount of gap control agent (for example, 2 to 5 wt%) is formed on one of the substrates (for example, the first substrate 11). The main sealant is formed, for example, by screen printing or a dispenser. In addition, the diameter of the gap control agent is set so that the thickness of the liquid crystal layer 24 is about 4 mu m. Then, a gap control agent is dispersed on the other substrate (for example, the second substrate 12). For example, in this embodiment, a plastic ball having a particle diameter of 4 탆 is dispersed by a dry gap acid aerator. Thereafter, the first substrate 11 and the second substrate 12 are superimposed on each other, and the main sealant is cured by performing heat treatment in a state where the pressure is constantly applied by a press machine or the like. Here, for example, a heat treatment is performed at 150 占 폚 for 3 hours (Fig. 6 (C)).

Next, the liquid crystal layer 24 is formed by filling the gap between the first substrate 11 and the second substrate 12 with a liquid crystal material (Fig. 6 (D)). The liquid crystal material is filled, for example, by a vacuum injection method. In this embodiment, a liquid crystal material to which a chiral agent is added while having a positive dielectric anisotropy (DELTA epsilon) is used. The addition amount of the chiral agent is preferably set so that d / p is 0.04 or more and 0.6 or less, for example, d / p is set to 0.16. After the liquid crystal material is injected, an end sealing agent is applied to the injection port and sealed. Then, the alignment state of the liquid crystal molecules in the liquid crystal layer 24 is adjusted by appropriately performing a heat treatment (for example, at 120 DEG C for one hour) at a temperature equal to or higher than the phase transition temperature of the liquid crystal material.

The first polarizing plate 31 is attached to the outside of the first substrate 11 and the second polarizing plate 32 is attached to the outside of the second substrate 12. The transmission axes of the first polarizing plate 31 and the second polarizing plate 32 are substantially orthogonal to each other (cross-Nicol arrangement). Thus, the reverse TN type liquid crystal device of the first embodiment is completed (see Fig. 3).

The voltage applied to the liquid crystal layer using each electrode for the reversed TN type liquid crystal device which has been completed through the above-described steps is shown as follows when the spray twist state and the reverse twist state are transited to each other.

In the reverse-type TN liquid crystal device of the present embodiment, in the initial state, the liquid crystal molecules of the liquid crystal layer 24 are aligned in a spray twisted state. In such a spray twist state, a white display (bright display) in a relatively bright state in appearance is obtained. On the other hand, a vertical electric field is generated by applying a voltage to each of the first electrode 13 and the common electrode 23 by a voltage applying means (not shown). For example, an alternating voltage (rectangular wave) of 10 V and 100 Hz is applied for about 0.01 to 0.5 seconds, and the application of the voltage is stopped immediately thereafter. Thereby, the alignment state of the liquid crystal layer 24 transits to the reverse twist state. In such a reverse twist state, a black display (dark display) in an apparently dark state is obtained. Fig. 7 shows an example of the display characteristics of the reverse-TN liquid crystal display element. For example, if the liquid crystal display device is constituted by arranging these reverse TN liquid crystal elements in a matrix, it is difficult to control each pixel (for each element) at the transition from the spray twist state to the reverse twist state , The state transition is controlled for all the pixels simultaneously or for each line of the plurality of first electrodes 13 sharing the common line 14. [

Next, a predetermined voltage is applied to the scanning line 15 in the voltage applying means to make the thin film transistor conductive, and a predetermined voltage is applied to the signal line 25 from the voltage applying means to form the second electrode 20 ). Accordingly, a potential difference is generated between the first electrode 13 and the second electrode 20, so that a horizontal electric field is applied to the liquid crystal layer 24, so that the alignment state of the liquid crystal layer 24 is a twisted state State. The voltage (gate voltage) to be applied to the scanning line 15 is, for example, 10 V, and the voltage applied to the signal line 25 is a voltage obtained by inverting, for example, ± 10 V for each frame. The time for applying the horizontal electric field is, for example, about 0.01 to 0.5 seconds.

Since the alignment state is maintained even after the voltage application is canceled in both the spray twist state and the reverse twist state, the voltage is basically not required to be applied after the display is changed, and the power consumption can be suppressed to be extremely low. For example, if the liquid crystal display device is constituted by arranging these reverse TN type liquid crystal devices in a matrix, if it is desired to change the display again, a plurality of first electrodes 13 ), And then a vertical electric field is applied to the second electrode 20 to control the application / non-application of voltage to the second electrode 20 by using a thin film transistor, whereby a desired image can be displayed by selectively applying a horizontal electric field to each pixel . In the method of changing the display for each line, when reading a sentence such as a novel, it is possible to change the line to be read in order, so that the stress of the reader can be alleviated even if a certain time is required for switching.

Next, another example of the configuration of the reverse TN type liquid crystal device will be described.

8 is a cross-sectional view showing a configuration example of a reverse-TN liquid crystal device according to the second embodiment. 9 is a plan view of the reverse TN type liquid crystal device shown in Fig. 8 shows a cross section taken along line VIII-VIII of FIG. The reverse type TN liquid crystal device 5 of the present embodiment shown in each drawing has a first substrate (lower substrate) 11, a second substrate (upper substrate) 12, a first electrode 13, a common line 14a The scanning line 15, the insulating film 16, the semiconductor film 17, the source electrode 18, the drain electrode 19a, the second electrode 20, the first alignment film 21, the second alignment film 22, A common electrode 23, a liquid crystal layer 24, a signal line 25, an insulating film 26, a first polarizing plate (lower polarizing plate) 31 and a second polarizing plate (upper polarizing plate) 32 . The same reference numerals are used for components common to those of the first embodiment, and a detailed description thereof will be omitted.

The common line 14a is provided on the insulating film 26 on one surface of the first substrate 11 and extends in one direction (Y direction in FIG. 8). This common line 14a is connected to the second electrode 20 as shown in Fig. 9 and is connected to the second electrode 20 via a common line 14a by a not shown voltage supply means. Is obtained.

The drain electrode 19a is provided at a predetermined position on the insulating film 16 and a part thereof is connected to the first electrode 13 through the insulating film 16. [ As the drain electrode 19a, for example, a metal film such as a laminated film of aluminum and molybdenum is used.

The insulating film 26 is provided so as to cover the semiconductor film 17, the source electrode 18 and the drain electrode 19a on the insulating film 16 on one side of the first substrate 11. As the insulating film 26, for example, a silicon nitride film, a silicon oxide film, or a laminated film thereof is used.

The second electrode 20 is provided on a predetermined position on the insulating film 26 and at least a part of which overlaps with the first electrode 13. The second electrode 20 is connected to the common line 14a as shown in Fig. In this embodiment, the second electrode 20 and the common line 14 are integrally formed. The second electrode 20 is obtained, for example, by patterning a transparent conductive film such as indium tin oxide (ITO). By applying a voltage between the second electrode 20 and the first electrode 13, a horizontal electric field can be applied to the liquid crystal layer 24.

The first alignment film 21 is provided on the insulating film 26 on one side of the first substrate 11 so as to cover the common line 14a and the second electrode 20.

Next, an example of a method of manufacturing a reverse TN type liquid crystal device according to the second embodiment will be described with reference to Figs. 10 and 11. Fig. In addition, descriptions common to those in the first embodiment are omitted as appropriate.

A scanning line 15 made of a predetermined metal film is formed on one surface of the first substrate 11 (Fig. 10 (A)). Next, a first electrode 13 made of an ITO film or the like is formed at a predetermined position on one side of the first substrate 11 (Fig. 10 (B)). Then, the insulating film 16 is formed so as to cover the first electrode 13 and the scanning line 15 on one side of the first substrate 11 (FIG. 10 (C)).

Next, a semiconductor film 17 is formed at a predetermined position on the insulating film 16 of the first substrate 11 (Fig. 10D), and the source electrode 18, the drain electrode 19a, 25) are further formed (Fig. 10 (E)). The drain electrode 19a can be formed by previously providing an opening for exposing a part of the first electrode 13 at a predetermined position of the insulating film 16 and then forming a metal film by a sputtering method or the like and patterning .

The insulating film 26 covering the semiconductor film 17, the source electrode 18, the drain electrode 19a and the signal line 25 is formed on the insulating film 16 of the first substrate 11 F)). Next, the common line 14a and the second electrode 20 are formed at predetermined positions on the insulating film 26 of the first substrate 11 (FIG. 10 (G)). Further, a passivation film may be further provided on the insulating film 26 (not shown). On the other hand, a common electrode 23 is formed on one surface of the second substrate 12 (Fig. 11 (A)).

Next, a first alignment film 21 is formed over the entire surface of the insulating film 16 of the first substrate 11 (FIG. 11B), and a second alignment film 21 is formed on the common electrode 23 of the second substrate 12 The second alignment film 22 is formed over the entire surface of the substrate 10 (Fig. 11 (C)).

After the main sealant is formed on one of the substrates and the gap control agent is dispersed on the other substrate, the first substrate 11 and the second substrate 12 are overlapped with each other, and the pressure is constantly applied by a press machine or the like The main sealant is cured by heat treatment (Fig. 11 (D)). Next, the liquid crystal layer 24 is formed by filling the gap between the first substrate 11 and the second substrate 12 with a liquid crystal material (Fig. 11 (E)).

Thereafter, the first polarizing plate 31 is attached to the outside of the first substrate 11 and the second polarizing plate 32 is attached to the outside of the second substrate 12. The transmission axes of the first polarizing plate 31 and the second polarizing plate 32 are arranged substantially orthogonally (cross-Nicol arrangement). Thus, the reverse TN type liquid crystal device of the second embodiment is completed (see Fig. 8).

A voltage was applied to the liquid crystal layer using each of the electrodes for the reversed TN type liquid crystal device completed through the above-described processes, and the states when the spray twist state and the reverse twist state were transited to each other were confirmed as follows.

In the reverse-type TN liquid crystal device of the present embodiment, in the initial state, the liquid crystal molecules of the liquid crystal layer 24 are aligned in a spray twisted state. In such a spray twist state, a white display (bright display) in a relatively bright state in appearance is obtained. On the other hand, a vertical electric field is generated by using the first electrode 13 and the common electrode 23 as described above. For example, an AC voltage (short waveform) of 10 V and 100 Hz is applied for about 0.01 to 0.5 seconds, and the application of the voltage is stopped immediately thereafter. Thus, the alignment state of the liquid crystal layer 24 transitions to the reverse twist state. In such a reverse twist state, a black display (dark display) in an apparently dark state is obtained. For example, if such a liquid crystal display device is constituted by arranging such reverse TN liquid crystal devices in a matrix form, it is possible to control each pixel (for each device) at the time of transition from the spray twist state to the reverse twist state. At this time, the first electrode 13 needs to be electrically free.

Next, a predetermined voltage is applied from the voltage applying means to the signal line 25 while applying the predetermined voltage to the scanning line 15 from the voltage application means to bring the thin film transistor into a conduction state, thereby applying a voltage to the second electrode 20 . Accordingly, a relative potential difference is generated between the first electrode 13 and the second electrode 20, so that a horizontal electric field is applied to the liquid crystal layer 24 so that the liquid crystal layer 24 is oriented in the reverse twist state, Transition to the twist state. The voltage (gate voltage) to be applied to the scanning line 15 is, for example, 10 V, and the voltage applied to the signal line 25 is a voltage obtained by inverting, for example, ± 10 V for each frame. The time for applying the horizontal electric field is, for example, about 01 to about 0.5 seconds.

Since the alignment state is maintained even after the voltage application is canceled in either the spray twist state or the reverse twist state described above, it is not necessary to apply the voltage at all after the display is changed, and the power consumption can be suppressed to a very low level. For example, if such a liquid crystal display device is constituted by arranging such reverse TN liquid crystal devices in a matrix, in the present embodiment, the transition from the spray twist state to the reverse twist state and the transition from the reverse twist state to the spray twist state It is possible to control each pixel. Therefore, the degree of freedom of display change is higher than in the first embodiment. For example, in the electrophoretic electronic paper display currently proposed, it is necessary to reset the entire screen to the white display or the black display once, otherwise, it becomes impossible to move all the electrophoretic particles to the desired position, In the case where the repeated display switching is performed, the electrophoretic particles may be displaced. However, according to the present embodiment, such defects do not occur.

Next, another example of the configuration of the reverse TN type liquid crystal device will be described.

12 is a cross-sectional view schematically showing a configuration example of a reverse-TN liquid crystal device according to the third embodiment. 12 (A) is a reflection type liquid crystal device for performing display using light from the outside. The liquid crystal panel 50 includes a liquid crystal panel 50, A scattering plate 52 disposed on the upper surface side of the liquid crystal panel 50, a lambda / 4 wave plate 53 placed over the scattering plate 52, And a polarizing plate 54 placed on the four-wave plate 53 in a superimposed manner. As the reflection plate 51, for example, a silver film can be used. As the scattering plate 52, for example, a plurality of sheets having a haze value of 43 to 45% can be used. As the? / 4 wave plate 53, for example, a phase difference of about 137 nm can be used. The scattering plate 52 may be disposed on the lower surface side of the liquid crystal panel 50. In this case, a scattering plate 52 is disposed between the reflection plate 51 and the liquid crystal panel 50.

12B, the angle formed by the rubbing direction RL of the lower substrate and the rubbing direction RU of the upper substrate in the liquid crystal panel 50 is, for example, 70 deg. An example of an appropriate value). In the liquid crystal material of the liquid crystal layer, for example, a chiral agent is added so that d / p = 0.143. The value of? N of the liquid crystal material of the liquid crystal layer is, for example, about 0.065 to 0.15. The transmission axis P of the polarizing plate 54 is set parallel to the rubbing direction RU of the upper substrate and the retardation axis P 'of the? / 4 wave plate 53 is set to be substantially parallel to the transmission axis of the polarizing plate 54 Lt; RTI ID = 0.0 > 45. The internal structure of the liquid crystal panel 50 is the same as that of the liquid crystal device of the first embodiment or the second embodiment described above (all except for the polarizer).

13 is a cross-sectional view showing a configuration example of a reverse TN liquid crystal device according to the third embodiment. Here, as an example, the case where the liquid crystal element of the first embodiment is employed as the liquid crystal panel 50 is shown, but the same applies to the case of employing the liquid crystal element of the second embodiment. The first electrode 13b in the liquid crystal panel 50 is made of a metal film, and furthermore, irregularities are formed on the surface. Accordingly, the first electrode 13b can also function as both the reflection plate 51 and the scattering plate 52. The manufacturing method of the reverse-TN liquid crystal device of the third embodiment is the same as that of the first embodiment or the second embodiment described above. For example, the forming process of the first electrode 13b is performed in the process of forming the scanning line 15 A common process can be adopted. In addition, the first electrode 13b serves only as a function of the reflection plate 51, and the scattering plate 52 may be externally mounted as described above.

14 is a diagram showing an example of the reflectance characteristic of the reverse-TN liquid crystal device of the third embodiment. 14 shows the reflectance characteristic of? N dependence when the twist angle of the liquid crystal layer is set at 70 占 and the light is incident in the direction of 30 占 with respect to the substrate plane normal of the liquid crystal element and the reflectance is measured in the normal direction. In this case, it can be seen that the reflectance and the contrast ratio are particularly excellent when? N of the liquid crystal material is 0.08. In this case, the retardation axis of the? / 4 wave plate 53 is set to be orthogonal to the major axis direction of the liquid crystal molecules at the substantially center of the liquid crystal layer in the layer thickness direction, and the transmission axis of the polarizing plate 54 is set at But the setting is not limited to this. The reflection type eliminates the need for a backlight, and it is possible to suppress power consumption in particular.

Next, in the fourth embodiment, a configuration example of a liquid crystal display device capable of driving with low power consumption using the memory property of any one of the liquid crystal devices of the first to third embodiments will be described.

15 is a diagram schematically showing a configuration example of a liquid crystal display device according to the fourth embodiment. The liquid crystal display device shown in Fig. 15 is an active matrix liquid crystal display device in which a plurality of pixel portions 100 are arranged in a matrix, and each of the pixel portions 100 is provided with a liquid crystal element of any of the above- . More specifically, the liquid crystal display device includes a plurality of scanning lines 101 extending in a first direction, a driver 104 for supplying a voltage to each scanning line 101, A driver 105 for supplying a voltage to each signal line 102 and a driver 105 for supplying a voltage to each common line 103. The signal line 102 and the common line 103 extend in two directions, And a pixel portion 100 provided at an intersection of each scanning line 101 and each signal line 102. [ In each pixel portion 100, one of the first electrode and the second electrode is connected to the common line 103, and the other is connected to the thin film transistor. Further, common electrodes are provided in common to the pixel units 100.

According to each of the embodiments described above, a novel liquid crystal device having a switching element and an electrode structure suitable for generating a transition between two alignment states is obtained. Further, by using the bistability (memory property) of the two alignment states of the liquid crystal element, a liquid crystal display device with essentially no power consumption is obtained except for the display switching.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention.

For example, in each of the above embodiments, the twist angle of the liquid crystal layer is 70 ° (reflection type) or 90 ° (transmission type), but the twist angle is not limited thereto. In this case, in order to further secure the brightness in the white display, the retardation value in the liquid crystal layer may be adjusted.

In addition, the liquid crystal device in the normally white state in which the angle formed by the transmission axes of the first polarizing plate and the second polarizing plate is about 90 degrees is exemplified. However, the liquid crystal device is in the normally black state . The orientation treatment method is not limited to the rubbing method.

The structure of the thin film transistor as an example of the switching element is not limited to the bottom gate type shown in the drawings, and may be a top gate type.

The second electrode is not limited to having a plurality of slits as described above, and may be a comb-like electrode having a plurality of electrode branches (linear portions), for example. Furthermore, the first electrode may be a comb-shaped electrode, and the respective electrode branches of the second electrode and the first electrode may be arranged differently from each other. In such a case, the first electrode and the second electrode can be disposed on the same surface.

1: upper substrate 2: lower substrate
3: liquid crystal layer 11: first substrate (lower substrate)
12: second substrate (upper substrate) 13, 13b: first electrode
14, 14a: common line 15: scanning line
16: insulating film 17: semiconductor film
18: source electrode 19, 19a: drain electrode
20: second electrode 21: first alignment layer
22: second alignment film 23: common electrode
24: liquid crystal layer 25: signal line
26: insulating film 31: first polarizing plate (lower polarizing plate)
32: second polarizer (upper polarizer) 50: liquid crystal panel
51: reflection plate 52: scatter plate
54:? / 4 wave plate 54: polarizer
100: pixel portion 101: scanning line
102: Signal line 103: Common line
104, 105, and 106: driver

Claims (6)

A first substrate and a second substrate which are subjected to an alignment treatment on their respective surfaces,
A first electrode provided on one side of the first substrate,
A second electrode provided on one side of the first substrate and spaced apart from the first electrode;
A switching element provided on one side of the first substrate and connected to the first electrode or the second electrode;
A common electrode provided on one surface of the second substrate so that at least a part of the common electrode overlaps with the first electrode and the second electrode,
And a liquid crystal layer provided between one surface of the first substrate and one surface of the second substrate,
Wherein the first substrate and the second substrate set the alignment treatment direction so as to generate a first alignment state in which liquid crystal molecules of the liquid crystal layer are bit-
Wherein the liquid crystal layer contains a chiral agent capable of generating a second alignment state which bit the liquid crystal molecules in a second direction opposite to the first direction,
A voltage is applied between the second electrode and the common electrode to cause the liquid crystal layer to transition from the second alignment state to the first alignment state and a voltage is applied between the first electrode and the second electrode, Layer shifts from the first alignment state to the second alignment state. The method according to claim 1,
Wherein at least one of the first electrode and the second electrode has a plurality of rectilinear sections arranged in parallel to each other. The method according to claim 1,
Wherein the first electrode and the second electrode are laminated via an insulating film. The method according to claim 1,
Wherein the first substrate and the second substrate each give a pretilt angle of 20 DEG or more to the liquid crystal molecules of the liquid crystal layer at the interface with the liquid crystal layer. The method according to claim 1,
Wherein the chiral agent is added so that the ratio of the chiral pitch (d / p) to the layer thickness (d) of the liquid crystal layer is 0.04 or more and 0.6 or less. A liquid crystal display device comprising a plurality of pixel portions, each of the plurality of pixel portions comprising the liquid crystal device according to any one of Claims 1 to 5.

Images