KR102100459B1 - Liquid crystal device and Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal element, in particular a liquid crystal element comprising an optically active substance (made of chiral) in a liquid crystal layer and a liquid crystal display device using the liquid crystal element.
In the present invention, the liquid crystal layer is provided between the first substrate and the second substrate, and the first substrate and the second substrate, which have been subjected to an alignment treatment on each one surface, and are disposed between the first substrate and one surface of the second substrate. Including, the first substrate and the second substrate, the liquid crystal molecules of the liquid crystal layer is set in the direction of the alignment treatment so as to cause a first alignment state twisted in the first direction, and further, each of The pretilt angle imparted to the liquid crystal molecules of the liquid crystal layer at an interface with the liquid crystal layer is 35 ° or more, and the liquid crystal layer is a product in which the liquid crystal molecules are twisted in a second direction opposite to the first direction. It contains a chiral agent having a property of causing a two-orientation state, and the chiral agent comprises a liquid crystal element added such that the ratio d / p of the chiral pitch to the layer thickness d of the liquid crystal layer is 0.25 or more and 0.75 or less. to provide. The liquid crystal element of the present invention performs good or various displays.

Description

Liquid crystal device and liquid crystal display device

The present invention relates to a liquid crystal element, in particular a liquid crystal element comprising an optically active substance (made of chiral) in a liquid crystal layer and a liquid crystal display device using the liquid crystal element.

The twist direction of the liquid crystal molecules (first turning direction) and the twist direction of the liquid crystal molecules caused by the chiral agent (second turning) determined by the combination of the alignment treatment direction and the pre-tilt angle of one set of alignment films The liquid crystal molecules are twisted in each direction (first turning direction) by having a liquid crystal layer made to be in the reverse direction, for example by applying a physical action to the liquid crystal layer, for example, a voltage higher than the saturation voltage of the electro-optical characteristic. The liquid crystal display device in which the reverse twist arrangement state and the spray twist arrangement state in the second turning direction are reversibly realized is referred to as a reverse twisted nematic (RTN) type liquid crystal display device. Call it. The first turning direction is a turning direction in which liquid crystal molecules are twisted when no chiral agent is added to the liquid crystal layer.

For example, a reverse twisted nematic liquid crystal display device is described in Patent Document 1. In the reverse twisted nematic liquid crystal display device described in Patent Document 1, the arrangement state in which the liquid crystal molecules are twisted in the first turning direction is unstable. It is possible to obtain an arrangement state twisted in the first turning direction by application of a high voltage, but with the passage of time, the liquid crystal molecules transition to an arrangement state twisted in the second turning direction.

While adding a chiral agent that rotates the liquid crystal molecules in the second turning direction, by arranging the liquid crystal molecules in the first turning direction by a combination of the orientation directions of the substrate, the twist in the liquid crystal layer is increased, and the driving voltage is significantly increased. Patent Document 2 discloses an invention of a reverse twisted nematic type liquid crystal device that enables a reduction in efficiency. However, in the invention described in Patent Literature 2, the application of the voltage for stopping the transition from the arrangement state twisted in the second turning direction to the arrangement state twisted in the first turning direction was stopped, and after a few seconds, the original arrangement state (first Since it re-transitions to the arrangement state twisted in the 2nd turning direction, when driving the liquid crystal element in the arrangement state twisted in the 2nd turning direction, there is a problem that a high driving voltage is required.

In the reverse twisted nematic type liquid crystal display device, in general, in the arrangement state in which the liquid crystal molecules are twisted in the first turning direction (reverse twist arrangement state) and in the arrangement state in which the liquid crystal molecules are twisted in the second rotation direction (spray twist arrangement state) High contrast ratio (transmittance of transmittance) even when there is no significant difference in the appearance of the appearance and a bistable property (reverse twist arrangement state and spray twist arrangement state are almost equal in energy and stable holding properties when no voltage is applied) There is a problem that it is difficult to obtain the difference.

Alignment is performed so that the angle formed by the rubbing direction between the upper and lower plates is greater than 90 degrees and less than 120 degrees, and a chiral agent having a twisting property is added to the liquid crystal layer so that it becomes the same direction as the angle formed by the rubbing direction. Patent Document 3 discloses an invention of a reverse twisted nematic liquid crystal display device, which is characterized by one. The reverse twisted nematic type liquid crystal display device described in Patent Document 3 is excellent in sharpness at any temperature as compared to a normal twisted nematic type liquid crystal display device. In addition, due to good sharpness, in particular, in a simple matrix driving liquid crystal display device, high-duty driving is possible or high contrast when driving at the same duty. In addition, the response to a low temperature is faster than a normal twisted nematic liquid crystal display device, and the transmittance is not reduced when off voltage is applied even in a high temperature environment, and a bright display can be realized. , It has the advantage of both liquid crystal display devices using TFT (thin film transistor; TFT).

The liquid crystal display device described in Patent Literature 3 has a very stable reverse twist arrangement, and the electro-optical characteristics in that state are superior to that of a normal twisted nematic liquid crystal display device. However, it is not an invention that actively utilizes the bi-stability of the reverse twist arrangement and the spray twist arrangement.

Patent Literature 4 discloses an invention of a liquid crystal element that performs display using a transition between a reverse twist arrangement state and a spray twist arrangement state. In the liquid crystal element of patent document 4, each arrangement state can be switched with each other. However, the display by each arrangement state is optional, and for example, the black display and the white display cannot be performed, but gray display (intermediate tone display) cannot be performed.

Patent Document 5 discloses an invention of a liquid crystal display panel in a FFS mode (fringe field switching mode) using TFT. According to the invention described in Patent Document 5, the actual aperture ratio of the liquid crystal display panel can be improved, the brightness and contrast of the display can be improved, and the display quality can be improved. The structure shown in Patent Document 5 is applicable to a liquid crystal device having a parallel alignment liquid crystal layer that does not contain a chiral agent, but for example, the display is performed by switching two stable arrangement states described in Patent Document 4 It is not suitable for reverse twisted nematic liquid crystal display devices. In addition, there is no description regarding the halftone display in Patent Document 5.

When driving in the FFS mode, it is common to set the liquid crystal layer in parallel orientation. In addition, many of the zell electrodes connected to the TFT are used as the pixel electrodes, and a beta electrode is generally provided below the zell electrodes as a common electrode. In this case, many electrodes are not formed on the opposing substrate.

Patent Literature 6 discloses an invention of a reverse twisted nematic liquid crystal display device having a relatively low pretilt angle of 20 ° or more and 45 ° or less, performed by the inventors of the present invention. When the chiral pitch is p and the thickness of the liquid crystal layer is d, relatively little chiral agent is added to this liquid crystal display device such that d / p is more than 0.04 and less than 0.25. The liquid crystal display device described in Patent Document 6 is a reverse twisted nematic liquid crystal display device capable of bistable display in a reverse twist arrangement state and a spray twist arrangement state, having high memory performance, a relatively high contrast ratio, and capable of electrical switching.

The liquid crystal display element described in Patent Document 6 is a liquid crystal display element having a high display quality with high contrast ratio. However, it cannot be said that the contrast at the time of front observation is high. This is relatively preferable when used as a reflective display, but is not desirable when used as a transmissive display.

In addition, although the memory performance at room temperature is high, for example, at a temperature different from room temperature, it is sometimes impossible to hold the display by the reverse twist arrangement, and it is difficult to keep it at a high temperature of 60 ° C or higher. . Therefore, depending on the application, for example, when used as a liquid crystal display device for vehicle mounting, aircraft use, or outdoor use, the memory performance of the display may be insufficient.

Japanese Patent No. 2510150 Japanese Patent Publication 2007-293278 Japanese Patent Publication 2010-186045 Japanese Patent Publication No. 2011-107376 Japanese Patent No. 4238877 Japanese Patent Publication No. 2011-203547

An object of the present invention is to provide a liquid crystal device capable of performing good or various displays, and a driving method thereof.

According to 1 aspect of this invention, it is arrange | positioned between the 1st board | substrate, the 2nd board | substrate arrange | positioned facing the electrical 1st board | substrate, and the electrical 1st board | substrate and the electrical 2nd board | substrate, and it is made of chiral. Provided is a liquid crystal device having a liquid crystal layer that realizes two different liquid crystal molecule arrangement states reversibly.

ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal element which can perform favorable or various display, and its driving method can be provided.

1 is a schematic cross-sectional view showing a liquid crystal display device according to a first embodiment.
2 is a schematic plan view showing a photomask used for etching an ITO film.
3A to 3E are schematic cross-sectional views showing an electric field direction when a voltage is applied.
4A to 4C are external photographs of the liquid crystal display device according to the first embodiment.
5A to 5C are graphs showing optical characteristics of the liquid crystal display device according to the first embodiment.
6A to 6C are photographs of a liquid crystal display device in which a vertical electric field is added to a part of the liquid crystal layer.
7 is a schematic cross-sectional view showing another example (modification example) of the formation mode of the first and second zell electrodes 12c and 12d.
8A is a schematic view showing a liquid crystal display device according to a second embodiment, and FIG. 8B is a schematic plan view showing the electrode structure of the pixel portion 34.
9A and 9B are schematic cross-sectional and plan views, respectively, showing a liquid crystal display device according to a third embodiment.
10A to 10G are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a third embodiment.
11A to 11D are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a third embodiment.
FIG. 12A is a photograph showing a pixel area after completion of the liquid crystal display device according to the third embodiment (initial state), and FIG. 12B shows a voltage between the common electrode 12a and the lower beta electrode 12b. It is a photograph showing a pixel area after application and a vertical field is added to the liquid crystal layer 15.
13A and 13B are schematic cross-sectional and plan views, respectively, showing a liquid crystal display device according to a fourth embodiment.
14A to 14G are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a fourth embodiment.
15A to 15E are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a fourth embodiment.
16 is a table showing the results of examining the retention of the display when the liquid crystal layer is in a reverse twist arrangement state with respect to a plurality of temperatures.
17 is a graph showing the temperature dependence of the pitch length of a chiral agent.
Fig. 18 is a table showing the results of examining the temperature dependence of the display holding (memory) according to the reverse twist arrangement state in more detail.
19A to 19D are photographs showing results of experiments on memory stability of a liquid crystal display device in which 2 wt% of an ultraviolet curable material is added.
FIG. 20 is a photomicrograph showing a liquid crystal display element (a liquid crystal display element after 30 minutes of heat treatment at 90 ° C.) showing an appearance photograph in FIG. 19C.
21A to 21D are photographs showing results of experiments on memory stability of a liquid crystal display device in which ultraviolet curable materials are added at different addition amounts (1 wt%, 2 wt%, 5 wt%).
Fig. 22 is a view showing typical manufacturing conditions and observed images of liquid crystal elements in a display state.
23 is a diagram showing evaluation results of contrast and display retention performance in a liquid crystal device having a pretilt angle of about 46 degrees and a twist angle of 70 degrees.
Fig. 24 shows the evaluation results of the temperature characteristics of the display retention performance in a liquid crystal device (d / p value of 0.444 to 0.500) with a pitch p of 8.0 μm to 9.0 μm among the conditions shown in Fig. 23. It is a drawing shown.
25 is a view showing an observation image of a liquid crystal element used for evaluation shown in FIG. 24.
Fig. 26 is a view showing an observation image of a liquid crystal element with pitch conditions of 9 μm (short pitch condition) and 12 μm (long pitch condition).
27 is a diagram showing optical characteristics of each liquid crystal element corresponding to the manufacturing conditions shown in FIG. 24.
28 is a view showing the optical characteristics of each liquid crystal element corresponding to the manufacturing conditions shown in FIG. 24.
29 is a view showing the optical characteristics of each liquid crystal element corresponding to the production conditions shown in FIG. 24.
30 is a view showing the optical characteristics of each liquid crystal element corresponding to the manufacturing conditions shown in FIG. 24.
FIG. 31 is a view showing the optical characteristics of each liquid crystal element corresponding to the manufacturing conditions shown in FIG. 24.
FIG. 32 is a diagram showing a state when switching is performed by applying a voltage to each electrode of the liquid crystal element according to the sixth embodiment.
33 is a flow chart showing a method of manufacturing a liquid crystal display device according to a seventh embodiment.
34A and 34B are photographs showing polarization microscope observation results in a display state for a plurality of manufactured liquid crystal display elements, and FIG. 34C is a diagram showing an outline of a liquid crystal molecule arrangement in a focal conic orientation. .
35A and 35B show a liquid crystal display device (a liquid crystal display device showing a display state in FIG. 34B) manufactured under conditions such that the pretilt angle is approximately 45 degrees and d / p is 0.8. A graph showing the transmittance visual dependence of the 180 ° orientation (left and right orientation), and a back contrast curve. It is a graph showing the characteristics.
36 is a graph showing a reverse twist arrangement state and a condition capable of realizing a bistable state of a focal conic arrangement state.
37 is a schematic plan view showing a pattern of an ITO film formed on the upper transparent substrate 11a.
38 is a schematic plan view showing a pattern of an ITO film formed on the lower transparent substrate 11b.
39 is a schematic plan view showing a photomask used for etching the ITO film.
40 is a schematic plan view showing a part of the formation region of the lower alignment layer 14b formed on the lower substrate 10b.
41 is a schematic plan view showing a structure of a liquid crystal display device according to a seventh embodiment.
42A to 42C are external photographs of the liquid crystal display device according to the seventh embodiment.

1 is a schematic cross-sectional view showing a liquid crystal display device according to a first embodiment.

First, a method of manufacturing the liquid crystal display device according to the first embodiment will be described.

A transparent conductive film, for example, a transparent substrate on which an ITO film was formed, for example, two glass substrates (upper transparent substrate 11a and lower transparent substrate 11b) was prepared, and these were washed.

The ITO film on the upper transparent substrate 11a was patterned using a Portiso process, and the upper beta electrode 12a was formed on the upper transparent substrate 11a. Patterning was performed so that the ITO film remained in the portion corresponding to the extraction electrode portion (terminal portion) and the display pixel. The ITO film was etched by wet etching using a second iron chloride. In addition, patterning may be performed by irradiating a laser beam to remove the ITO film at the irradiation position.

The ITO film on the lower transparent substrate 11b was patterned using a Portiso process, and the lower beta electrode 12b was formed on the lower transparent substrate 11b. The formation method is the same as the formation method of the upper beta electrode 12a of the upper transparent substrate 11a.

After formation of the lower beta electrode 12b, an insulating film 13 was formed on the lower transparent substrate 11b including the lower beta electrode 12b. The insulating film 13 is not formed, for example, on the extraction electrode portion of the lower beta electrode 12b. The insulating film 13 forms a resistor in the extraction electrode portion of the lower beta electrode 12b, a method of removing the resistor by lift-off after the insulating film 13 is formed, a sputter or the like with a metal mask covering the extraction electrode portion It can be formed by the method of forming by. The insulating film 13 can be an organic insulating film or an inorganic insulating film such as SiO ₂ or SiN _x . You may form it in combination of them. In the example, a laminated film of an acrylic organic insulating film and SiO ₂ was used as the insulating film 13.

In the example, a heat-resistant film (polyimide tape) was first attached to the extraction electrode portion of the lower beta electrode 12b, and the organic insulating film was spin coated in this state. Under the condition of spinning at 2000 rpm for 30 seconds, an organic insulating film having a film thickness of 1 μm was obtained.

Next, the lower transparent substrate 11b on which the organic insulating film was formed was fired at 220 ° C. for 1 hour in a clean oven, and then the lower transparent substrate 11 b was heated to 80 ° C. with a heat-resistant film attached thereto, and the SiO ₂ film was removed. The film was formed to a thickness of 1000 MPa by a factor method (AC discharge). The SiO ₂ film can also be formed using a vacuum deposition method, an ion beam method, or a chemical vapor deposition (CVD) method.

Here, when the heat-resistant film was peeled off, the organic insulating film and the SiO ₂ film could be removed with respect to the adhesion point of the heat-resistant film. Subsequently, in order to improve the insulation and transparency of the SiO ₂ film, the lower transparent substrate 11b was sued for 1 hour at 220 ° C. in a clean oven.

Although the formation of the SiO ₂ film is not essential, the insulating property of the insulating film 13 can be improved by forming the SiO ₂ film. Further, it is possible to improve the adhesion and patterning properties of the first and second zell electrodes 12c and 12d formed on the insulating film 13.

An organic insulating film may not be formed, and the insulating film 13 may be composed of only an SiO ₂ film. Since the SiO ₂ film tends to become porous, in this case, the thickness of the SiO ₂ film is preferably 4000 mm ₂ to 8000 mm ₂ . An inorganic insulating film 13 made of a laminated film of a SiO ₂ film and a SiN _x film can also be used.

An ITO film was formed on the insulating film 13. For the ITO film, the lower transparent substrate 11b was heated to 100 ° C, and was formed on the entire substrate by a sputtering method (AC discharge). The film thickness was about 1200 mm 2. This ITO film was patterned by the potoriso process, and the first zell electrode 12c, the second zl electrode 12d, and the extraction electrodes of the zl electrodes 12c and 12d were formed.

2 is a schematic plan view showing a photomask used for etching an ITO film. The photomask corresponds to a corresponding portion of the first zigzag electrode 12c, a corresponding portion of the second zigzag electrode 12d, a corresponding portion of the extraction electrode of the first zigzag electrode 12c, and an extraction electrode of the second zigzag electrode 12d Includes part. During etching, an electrode is formed of an ITO film covered with each corresponding portion. In addition, the inventors of the present invention have a plurality of electrode spacings of 20 µm, 30 µm, and the slit portions of two slit electrodes alternately arranged with an electrode spacing of 20 µm, 30 µm, 50 µm, 100 µm, and 200 µm. As the electrode pattern, the first zell electrode 12c and the second zl electrode 12d were produced.

Through the above process, the upper transparent substrate 11a on which the upper beta electrode 12a is formed, and the lower beta electrode 12b and the insulating film 13 thereon are interposed between the first and second zell electrodes 12c. , 12d) was prepared on the lower transparent substrate (11b). Then, the two transparent substrates 11a and 11b with electrodes were washed and dried. The washing is, for example, washing with water, pure water washing with or without detergent as an example. Brush cleaning, spray cleaning, etc. can be used. After dehydration, UV cleaning is performed and IR drying is performed.

On the transparent substrates 11a, 11b with electrodes, an alignment film material is applied to cover the electrodes 12a, 12c, 12d. The coating of the alignment film material was performed using a spin coat. It may be carried out by using Furekiso printing or inkjet printing. In the examples, the side chain density of the polyimide alignment film material, which is usually used for forming a vertical alignment film, was controlled and used as an alignment film material. The control of the side chain density is to enable the provision of an appropriate pretilt angle. The alignment film material was applied so that the thickness of the alignment film was 500 mm 2 to 800 mm 2.

The substrates 11a and 11b coated with the alignment film material were fired for 1 hour at a baking temperature of 200 ° C in a clean oven. In this way, the upper alignment layer 14a covering the upper beta electrode 12a and the lower alignment layer 14b covering the first and second zlatch electrodes 12c and 12d were formed.

Next, rubbing treatment (orientation treatment) was performed. The rubbing treatment was performed with an indentation amount of 0.8 mm (strong rubbing condition). In addition, the rubbing treatment was performed such that the twist angle of the liquid crystal display element was 70 degrees or 90 degrees.

In this way, the upper substrate 10a and the lower substrate 10b were produced. The upper substrate 10a includes an upper transparent substrate 11a, an upper beta electrode 12a formed on the upper transparent substrate 11a, and an upper alignment layer 14a formed to cover the upper beta electrode 12a. The lower substrate 10b is formed on the lower transparent substrate 11b, the lower beta electrode 12b formed on the lower transparent substrate 11b, the insulating film 13 and the insulating film 13 formed on the lower beta electrode 12b. It has a first alignment layer (12c, 12d), and a lower alignment layer (14b) formed so as to cover the first and second slant electrodes (12c, 12d), which are arranged on the interdigital part.

Subsequently, in order to keep the thickness of the liquid crystal cell constant, a gap control material was spread on one surface of the substrates 10a and 10b by, for example, a dry spreading method. A plastic ball having a particle diameter of 4 μm was used for the gap control material so that the thickness of the liquid crystal cell was 4 μm.

A seal material was printed on the other surfaces of the substrates 10a and 10b to form a main seal pattern. For example, a thermosetting sealant containing glass fibers having a particle diameter of 4 μm is printed by a screen printing method. The sealer may be applied using a dispenser. Moreover, it is not thermosetting property, and you may use the photocurable seal material and the hardening type seal material for light and fever.

The substrates 10a and 10b were superimposed. The substrates 10a and 10b were cellized by overlapping at a predetermined position, and heat treated in a pressed state to cure the seal material. For example, heat-hardening of a sealing material is performed using a hot press method. In this way, an empty cell is produced.

For example, a nematic liquid crystal material, for example, ZLI-2293 manufactured by Melk Co., Ltd. was injected into an empty cell by a vacuum injection method. A chiral agent was added to the liquid crystal material. As the chiral agent, CB15 manufactured by Melk Co., Ltd. was used. The chiral agent was added so that when the chiral pitch p and the thickness (cell thickness) d of the liquid crystal layer were set, d / p was, for example, 0.5 (d = 4 μm, p = 8 μm).

The liquid crystal injection port was sealed with, for example, an ultraviolet curing type end seal material, and the cell was heated above the phase transition temperature of the liquid crystal in order to align the liquid crystal molecules.

Thereafter, the scriber device was broken along the damage to the transparent substrates 11a and 11b, and divided into individual cells.

The small-segmented cells were chamfered and washed.

Lastly, polarizing plates 16a and 16b were attached to the surfaces of the two transparent substrates 11a and 11b opposite to the liquid crystal layer 15. The two polarizing plates 16a, 16b were arranged with cross nicol and parallel to the direction of the transmission axis and the rubbing direction. It can also be arranged to be orthogonal. A power source 20 was connected between the electrodes 12a, 12b, 12c, and 12d.

In this way, the liquid crystal display device according to the first embodiment was produced.

In the liquid crystal display device according to the first embodiment, the twisted nematic liquid crystal layer 15 sandwiched between the upper substrate 10a, the lower substrate 10b, and both substrates 10a and 10b are disposed to be parallel to each other. It is configured to include.

The upper substrate 10a includes an upper transparent substrate 11a, an upper beta electrode 12a formed on the upper transparent substrate 11a, and an upper alignment layer 14a formed on the upper beta electrode 12a. The lower substrate 10b is formed on the lower transparent substrate 11b, the lower beta electrode 12b formed on the lower transparent substrate 11b, the insulating film 13 and the insulating film 13 formed on the lower beta electrode 12b. The formed first and second slit electrodes 12c and 12d, and the lower alignment layer 14b formed on the insulating layer 13 to cover the first and second slit electrodes 12c and 12d.

The upper and lower transparent substrates 11a and 11b are made of glass, for example. The upper and lower beta electrodes 12a and 12b, and the first and second zell electrodes 12c and 12d are made of, for example, a transparent conductive material such as ITO. The first and second zell electrode 12c, 12d are comb-shaped electrodes each having a plurality of zell portion. The slit portions of the first and second slit electrodes 12c and 12d are staggered along the left and right directions of FIG. 1.

The liquid crystal layer 15 is disposed between the upper alignment layer 14a of the upper substrate 10a and the lower alignment layer 14b of the lower substrate 10b.

The upper and lower alignment films 14a and 14b are subjected to alignment treatment by rubbing. The alignment direction of the upper alignment layer 14a and the lower alignment layer 14b is, for example, an angle of 70 degrees or 90 degrees when viewed from the normal directions of the upper and lower substrates 10a and 10b. When the rubbing direction of the upper alignment layer 14a is the first direction and the rubbing direction of the lower alignment layer 14b is the second direction, the second direction is viewed from the normal direction of the upper substrate 10a, and is the first direction. With reference to, it is a direction forming a 70˚ or 90˚ in the right rotation direction. The arrangement state of the liquid crystal molecules of the liquid crystal layer 15 defined by the combination of the pre-tilt angle and the alignment treatment direction of the upper and lower substrates 10a and 10b is a reverse twist arrangement state twisted in the first turning direction.

A chiral agent is added to the liquid crystal material forming the liquid crystal layer 15. The arrangement state of the liquid crystal molecules generated under the influence of the chiral agent is a spray twist arrangement twisted in a second rotation direction opposite to the first rotation direction.

The power supply 20 is electrically connected to the upper and lower beta electrodes 12a and 12b, and the first and second zell electrodes 12c and 12d. By the power source 20, it is possible to apply a voltage (to give an electric potential difference) to the electrodes 12a to 12d.

3A to 3E are schematic cross-sectional views showing an electric field direction when a voltage is applied.

See FIG. 3A. For example, by applying an AC voltage between the upper and lower beta electrodes 12a and 12b, the entire liquid crystal layer 15 (pixel region) {a liquid crystal layer disposed between the upper and lower beta electrodes 12a and 12b ( 15)} can be added a longitudinal electric field (electric field in the thickness direction of the liquid crystal layer 15).

See FIG. 3B. For example, between the lower beta electrode 12b and the first and second zell electrodes 12c and 12d (between the lower beta electrode 12b and the first zell electrode 12c, and the lower beta electrode 12b and the By applying an alternating voltage between the two zell electrodes 12d, the entire liquid crystal layer 15 (pixel region) (the liquid crystal layer 15 above the lower beta electrode 12b, the first and second zl electrodes 12c) , 12d) Transverse electric field (electric field in a direction orthogonal to the thickness direction of the liquid crystal layer 15) to the liquid crystal layer 15 above the region between the first and second zest electrodes 12c and 12d. , An electric field in the in-plane direction of the substrates 10a and 10b}. Then, by applying a voltage between the electrodes 12b and the electrodes 12c and 12d, a lateral electric field is generated in the liquid crystal layer 15, and a driving mode for driving the liquid crystal display element is an FFS mode (fringe field switching mode). Is called. The lateral electric field generated in the liquid crystal layer 15 in the FFS mode of the sun shown in FIG. 3B is an electric field along the left-right direction in FIG. 1.

See FIG. 3C. By applying an alternating voltage between the upper beta electrode 12a and the first and second zell electrodes 12c and 12d, a part of the liquid crystal layer 15 (pixel region), for example, first and first A vertical electric field can be added to the liquid crystal layer 15 above the two-zell electrodes 12c and 12d.

See FIG. 3D. By applying an alternating voltage between the first zell electrode 12c and the second zell electrode 12d, a part of the liquid crystal layer 15 (pixel region), for example, the first zell electrode 12c and the A transverse electric field can be added to the liquid crystal layer 15 between the two zest electrodes 12d. In addition, a driving mode for driving a liquid crystal display device by driving a liquid crystal display element by generating a lateral electric field in a part of the liquid crystal layer (pixel region) by applying a voltage between the first and second zell electrodes 12c and 12d is an IPS mode (in- plane switching mode).

See FIG. 3E. By applying an alternating voltage between the lower beta electrode 12b and the first zell electrode 12c, a part of the liquid crystal layer 15 (pixel region), for example, the zl part of the first zell electrode 12c And a lateral electric field can be added to the liquid crystal layer 15 in the vicinity thereof. Likewise, by applying an alternating voltage between the lower beta electrode 12b and the second zell electrode 12d, the transverse electric field is applied to the zell portion of the second zell electrode 12d and the liquid crystal layer 15 near it. It is also possible to add.

4A to 4C are external photographs of the liquid crystal display device according to the first embodiment. 4A to 4C, the electrode widths of the slit portions of the first and second slit electrodes 12c and 12d are 20 μm, and the slit portions of both slit electrodes 12c and 12d are alternately arranged. It is a picture of the appearance of the region where the zlatch electrodes 12c and 12d are formed in the liquid crystal display device having a gap of 20 μm.

4A shows a photograph of the appearance of the liquid crystal display device according to the first embodiment (initial state). In the initial state, the liquid crystal molecules are in a spray twist arrangement state. A bright white mark is being obtained.

In this state, as shown in Fig. 3A, an AC voltage equal to or greater than a threshold voltage, that is, a minimum physical quantity voltage that causes a reaction, was applied between the upper beta electrode 12a and the lower beta electrode 12b. A vertical electric field is generated in the entire liquid crystal layer 15 (pixel region) by application of a voltage between both electrodes 12a and 12b.

4B is a photograph of the appearance after voltage is applied between the electrodes 12a and 12b. Also in front observation, a clear black display is obtained. It can be seen that the whole transitions from the spray twist arrangement to the reverse twist arrangement. Conversely, from this, it is confirmed that a vertical electric field is generated in the entire liquid crystal layer 15 (pixel region) by application of a voltage between both electrodes 12a and 12b.

5A to 5C are graphs showing optical characteristics of the liquid crystal display device according to the first embodiment. 5A to 5C show optical characteristics of the liquid crystal display device manufactured by setting the angle between the rubbing treatment directions of the upper substrate 10a and the lower substrate 10b to 70 degrees.

See FIG. 5A. 5A shows the orientation and polar angle dependence of the contrast ratio (transmittance in the spray twist arrangement / transmittance in the reverse twist arrangement). R _U in the figure indicates the direction of the rubbing process performed with respect to the upper substrate 10a, and R _L indicates it with respect to the lower substrate 10b. In the direction parallel to the arrow direction of A, the transmission axis direction of the upper polarizing plate 16a is shown, and in the direction parallel to the arrow direction of P, the transmission axis direction of the lower polarizing plate 16b is shown. The direction parallel to the thick arrow direction (90 ° -270 ° orientation) is in the center of the thickness direction of the liquid crystal layer 15 when the arrangement state of the liquid crystal molecules of the liquid crystal layer 15 is in a reverse twist arrangement state. It shows the alignment direction of the liquid crystal molecules located. Here, the 0 ° -180 ° orientation corresponds to the left-right direction in FIG. 1. That is, in the alignment direction of the liquid crystal molecules positioned in the center of the thickness direction of the liquid crystal layer 15 when the arrangement state of the liquid crystal molecules of the liquid crystal layer 15 is in a reverse twist arrangement state, and in the FFS mode of the sun shown in FIG. 3B. The direction of the generated lateral electric field is a direction orthogonal to each other. This point also applies to the liquid crystal display device manufactured by setting the angle between the rubbing treatment directions of the upper substrate 10a and the lower substrate 10b to 90 degrees.

5B shows the extreme angle dependence of the transmittance with respect to the 90 ° -270 ° orientation. The polar angle in the normal direction (frontal observation direction of the liquid crystal display element) of the substrates 10a and 10b is set to 0 degrees, the inclination angle inclined in the direction of 270 degrees is represented by a positive polar angle, and inclined to 90 degrees The inclination angle is expressed as the negative polar angle. The horizontal axis of the graph of Fig. 5B represents the polar angle in units "°", and the vertical axis represents the transmittance in units "%". The curve connecting the black rhombus (labeled “St”) represents the extreme dependence of the transmittance when the liquid crystal molecules are in a spray twist arrangement, and the curve connecting the black squares (labeled “Ut”) indicates that the liquid crystal molecules Represents it in reverse twist arrangement.

The transmittance in front observation in the spray twist arrangement is about 12.6%, and in the reverse twist arrangement it is about 0.02%.

In FIG. 5C, the polar angle dependence of the contrast ratio with respect to the 90 ° -270 ° orientation is shown. The horizontal axis of the graph in Fig. 5C is the same as that in Fig. 5B. The vertical axis represents the contrast ratio. In the liquid crystal display device according to the first embodiment, the contrast ratio is maximum (maximum value 566) when viewed from the front.

And, the same result was obtained for the liquid crystal display device manufactured by setting the angle between the rubbing treatment directions of the upper and lower substrates 10a and 10b to 90 degrees. As described above, the liquid crystal display device according to the first embodiment is a liquid crystal display device having excellent optical characteristics, which can be displayed with, for example, a bright white display or a clear black display.

See FIG. 4C. Next, the inventors of the present application apply an AC voltage of at least a minimum physical quantity voltage that causes a reaction between the lower beta electrode 12b and the first and second zell electrodes 12c and 12d, as shown in FIG. 3B. A transverse electric field (a direction in which the first and second zell electrodes 12c and 12d are alternately arranged, and an electric field along the left direction in FIGS. 1 and 3B) was generated over the entire liquid crystal layer 15 (pixel region).

Fig. 4C is a photograph of the appearance after adding the lateral electric field of the sun shown in Fig. 3B to the liquid crystal display device in the state shown in Fig. 4B. It can be seen that the front surface is retransferred to the spray twist arrangement state indicating the white display state as the initial state.

The liquid crystal molecules positioned at the center of the thickness direction of the liquid crystal layer 15 are tilted in the longitudinal direction (vertical direction) from the transverse direction (horizontal direction) to the reverse twist arrangement from the spray twist arrangement state by adding a vertical electric field. It can be thought of as switching to a state. In addition, the liquid crystal molecules located at the center of the thickness direction of the liquid crystal layer 15 are sprayed twisted from the vertical direction to the center of the liquid crystal molecules located at the center of the thickness direction of the liquid crystal layer 15 by adding a lateral electric field. By tilting in the direction of the director in the arrangement state, it can be considered that switching is performed from the reverse twist arrangement state to the spray twist arrangement state.

When the vertical electric field is added to the liquid crystal layer 15 in the reverse twist arrangement state, the reverse twist arrangement state is maintained, and when the lateral electric field is added to the liquid crystal layer 15 in the spray twist arrangement state, the spray twist arrangement is applied. State is maintained.

Subsequently, as shown in FIG. 3C, an alternating voltage of at least a minimum physical quantity voltage causing a reaction was applied between the upper beta electrode 12a and the first and second zell electrodes 12c and 12d. Effective application of the voltage between the electrodes 12a and 12c, 12d effectively terminates the liquid crystal layer 15 above a portion of the liquid crystal layer 15 (first and second zell electrodes 12c, 12d). An electric field is created. For this reason, the liquid crystal molecules above the first and second zell electrodes 12c and 12d transition from the spray twist arrangement state to the reverse twist arrangement state. Above the region between both zest electrodes 12c and 12d, the spray twist arrangement is maintained.

6A to 6C are photographs of a liquid crystal display device in which a vertical electric field is added to a part of the liquid crystal layer. Fig. 6A shows the whole picture, Fig. 6B shows the enlarged picture, and Fig. 6C shows the microscope picture. 6A to 6C, the electrode widths of the slit portions of the first and second slit electrodes 12c and 12d are 20 μm, and the slit portions of both slit electrodes 12c and 12d are alternately arranged. This is a picture of a liquid crystal display device manufactured with a spacing of 20 μm. For example, each character of "S", "T", "A", "N", "L", "E", "Y", "L", "C", "D", and "s" , 20 μm / 20 μm line {electrode width of the chisel parts of the first and second zell electrodes 12c, 12d} / space {distance between the chisel parts of the displaced first and second zell electrodes 12c, 12d } Is indicated by the patterned portion (arrangement area of the chisel portions of the first and second zell electrodes 12c and 12d).

6A and 6B, "S", "T", "A", "N", "L", "E", "Y", "L", "C", "D", " It can be seen that each character of s ”is displayed in an intermediate color tone (brightness) of white (displayed by a spray twist arrangement state) and black (display by a reverse twist arrangement state), that is, gray.

Fig. 6C is a photomicrograph of an area including a portion marked with gray (medium-tone display). On the gray display portion, microscopically, a black display portion (reverse twist arrangement state portion) and a white display portion (spray twist arrangement state portion) are arranged in a stripe shape. When a voltage is applied between the electrodes 12a and 12c and 12d, and the transition to the black display (reverse twist arrangement state) is seen from a plane, the first and second zlzzle electrodes 12c and 12d are It was the area where the chin section was arranged or slightly wider than the width of the chin section. In the other areas, a white display (spray twist arrangement state) was maintained. According to microscopic observation, the black display portion and the white display portion are arranged in a stripe shape, but visually, the black and white stripes are not observed, resulting in a natural gray display. It can be considered that this is because the stripe-shaped distribution of the black display portion and the white display portion has a finer detail than the resolution of the human eye.

In the example shown in the photographs of Figs. 6A to 6C, the line / space was 20 µm / 20 µm, but if it is about 50 µm to 100 µm / 50 µm to 100 µm or less, natural gray display is observed with the naked eye.

The inventors of the present invention, the black display by the reverse twist arrangement state, the white display by the spray twist arrangement state, and the gray display (area in the reverse twist arrangement state and the area in the spray twist arrangement state coexist in one pixel, It was confirmed that the display by mixing) was retained (memory) in the same state unless a voltage was separately applied.

The liquid crystal display device according to the first embodiment is a liquid crystal display device having bistable stability in an array state in which the arrangement state of liquid crystal molecules is stable in both the reverse twist arrangement state and the spray twist arrangement state. It is a liquid crystal display device capable of various displays.

The inventors of the present invention produced the liquid crystal display device according to the reference example of 20 μm / 20 μm line / space and 10 μm cell thickness for an embodiment having a line / space of 20 μm / 20 μm and a cell thickness of 4 μm, and conducted the same experiment. did. A voltage was applied between the upper beta electrode and the first and second zell electrodes of the liquid crystal display device according to the reference example, but unlike the first embodiment, a gray display could not be obtained. When observed under a microscope, it was confirmed that not only the liquid crystal molecules above the first and second zlatched electrodes, but also the liquid crystal molecules above the region between both zlatched electrodes are transitioning in a reverse twist arrangement.

From the experiment on the reference example, it can be considered that gray display (medium tone display) is realized when the size of the line / space and the cell thickness satisfy certain conditions. As a result of the in-depth study, the inventors of the present invention do not substantially depend on the line size (electrode width of the chisel portion of the first and second chisel electrodes 12c and 12d) and the space size, as a result of in-depth study. It has been found that the relationship between the (distance between the jazz portions of the first and second jazz electrodes arranged alternately) and the cell thickness is important for realizing halftone display. When the cell thickness d was less than 10 μm, since the halftone display was obtained, the space size s of the zest-shaped electrode was expressed by the following equation (1).

s ＞ 2 × d ·· (1)

When satisfied, it may be said that halftone display is possible.

For the first embodiment, a voltage is applied between the upper beta electrodes 12a and the first and second slur electrodes 12c and 12d, and the liquid crystal above the first and second slur electrodes 12c and 12d is applied. A vertical electric field was added to the layer 15, and the liquid crystal molecules at that position were shifted to a reverse twisted arrangement, but only between the upper beta electrode 12a and the first zell electrode 12c, or the upper beta electrode 12a It is possible to realize halftone display even if an AC voltage equal to or greater than the minimum physical quantity voltage causing the reaction is applied only between the and the second zell electrode 12d.

When a voltage is applied between the upper beta electrode 12a and the first zell electrode 12c, a vertical electric field is added to the liquid crystal layer 15 above the first zell electrode 12c to spray the liquid crystal molecule at that position. Transition from the twist arrangement state to the reverse twist arrangement state. When a voltage is applied between the upper beta electrode 12a and the second slit electrode 12d, a vertical electric field is added to the liquid crystal layer 15 above the second slit electrode 12d, and the liquid crystal molecule at that position Transition from the spray twist arrangement to the reverse twist arrangement.

In the embodiment, the line / space is 20 µm / 20 µm (line: space = 1: 1), for example, 100% transmittance at the time of white display (all liquid crystal molecules in the pixel region are spray twisted). When the transmittance at the time of black display (all liquid crystal molecules in the pixel region is reverse twisted arrangement) is 0%, a gray display with a transmittance of about 50% can be obtained, but by adjusting the line / space ratio, It is also possible to change the hue (brightness) level of the halftone display. The size of the line and space can be arbitrarily selected under the condition of equation (1).

Fig. 7 shows another example (modification example) of the formation mode of the first and second zell electrodes 12c and 12d. In this figure, the line size (electrode width of the slit part) of the first zell electrode 12c is 20 µm, that of the second slit electrode 12d is 40 µm, and the space size of the positive electrodes 12c, 12d is 10 µm. The first and second zell electrodes 12c and 12d are shown. That is, the line size of the electrode 12c: The line size of the electrode 12d: The space size = 2: 4: 1.

When the first and second swell electrodes 12c and 12d are formed as described above, when a voltage equal to or greater than the minimum physical quantity voltage is applied between the upper beta electrode 12a and the first swell electrode 12c, the first swell electrode (12c) A vertical electric field is generated in the upper liquid crystal layer 15, and the liquid crystal molecules at the position transition from the spray twist arrangement state to the reverse twist arrangement state. For this reason, in this voltage application mode, halftone display with a transmittance of about 25% is realized.

In addition, when a voltage equal to or greater than the minimum physical quantity voltage causing a reaction is applied between the upper beta electrode 12a and the second zell electrode 12d, a vertical electric field is generated in the liquid crystal layer 15 above the second zell electrode 12d. Then, a halftone display with a transmittance of about 50% is realized for the liquid crystal molecules at that position to transition from the spray twist arrangement state to the reverse twist arrangement state.

In addition, when a voltage equal to or greater than the minimum physical quantity voltage causing a reaction is applied between the upper beta electrode 12a and the first and second zell electrodes 12c and 12d, the first and second zell electrodes 12c and 12d are upward. A vertical electric field is generated in the liquid crystal layer 15 of the liquid crystal, and the liquid crystal molecules at the position transition from the spray twist arrangement state to the reverse twist arrangement state, thereby achieving a halftone display with a transmittance of about 75%.

Such a halftone display, white display when the liquid crystal molecules of the entire liquid crystal layer 15 (pixel region) are in a spray twist arrangement state, and liquid crystal molecules of the entire liquid crystal layer 15 (pixel region) are in a reverse twist arrangement state. In addition to the black display at the time, in the liquid crystal display device according to the modification, it is possible to realize a display of five gradations in which the transmittance changes (proportionally) at an equal ratio.

The liquid crystal display device according to the modified example has a feature in that the line sizes of the first and second zell electrodes 12c and 12d are different. In addition, it has a feature in that the line size and space size of each electrode 12c, 12d are devised so that the transmittance can be changed at an equal ratio. According to the liquid crystal display element according to the modified example, it is possible to perform more various displays than the liquid crystal display element according to the first embodiment.

In the description so far, half-tone display was performed by generating a vertical electric field in a part of the liquid crystal layer 15 (pixel region) in a spray twist arrangement state, but, for example, liquid crystal according to the first embodiment and the modified example For the display element, it is also possible to cause a transverse electric field in a part of the liquid crystal layer 15 (pixel region) in the IPS mode described with reference to FIG. 3D, and to perform halftone display. For example, in the case where the liquid crystal molecules of the entire liquid crystal layer 15 (pixel region) are in a reverse twist arrangement state, when an AC voltage is applied between the first zell electrode 12c and the second zell electrode 12d, positive A transverse electric field is generated in the region between the chisel portions of the electrodes 12c and 12d and above, and the liquid crystal molecules of the liquid crystal layer 15 at the position transition to a spray twist arrangement state to display halftone.

For example, a lateral electric field is added in the IPS mode to the liquid crystal display device according to the first embodiment in which the liquid crystal molecules of the liquid crystal layer 15 are in a reverse twist arrangement state (between the first and second zell electrodes 12c and 12d). The color tone (brightness) of the halftone display obtained when AC voltage is applied is added to the partial electric field of the liquid crystal layer 15 (pixel region) in the spray twist arrangement state (upper beta electrode 12a), It is roughly the same as that of the halftone display performed by applying an AC voltage between the first and second zell electrodes 12c and 12d, the transmittance at the time of black display is 0%, and the transmittance at the time of white display is 100%. The transmittance at the time of is about 50%.

It is also possible to shift a part of the liquid crystal layer 15 (pixel region) in the reverse twist arrangement state to the spray twist arrangement state by adding the electric field of the sun described with reference to FIG. 3E, and to perform halftone display. In the case of the aspect shown in Fig. 3E, the region for forming the chisel portion of the first zell electrode 12c and the liquid crystal molecules of the liquid crystal layer 15 in the vicinity thereof are shifted to a spray twist arrangement to realize halftone display.

According to a method of generating a lateral electric field in a part of the liquid crystal layer 15 (pixel region) and shifting the liquid crystal molecules in the region from the reverse twist arrangement state to the spray twist arrangement state, the relationship of the electric expression (1) is not satisfied. Even if it is not, it is possible to obtain a halftone display. For this reason, the driving method for generating a transverse electric field in a part of the liquid crystal layer 15 (pixel region) and shifting the liquid crystal molecules in the region from the reverse twist arrangement state to the spray twist arrangement state is described in the liquid crystal layer 15 (pixels). It can also be said that the driving method (display conversion method) is more versatile than the driving method in which a longitudinal electric field is generated in a part of the region) and the liquid crystal molecules in the region are shifted from the spray twist arrangement state to the reverse twist arrangement state. However, in the case of an electric modification using a vertical electric field, it is possible to display 5 gradations, but when using a lateral electric field, only 3 gradations can be displayed, for example.

As described above, the liquid crystal display device according to the embodiment is a liquid crystal display device having a memory property in which the arrangement state of liquid crystal molecules is stable in both the reverse twist arrangement state and the spray twist arrangement state. It can be applied to a display using bi-stability, and in that case, it is possible to drive using memory. For example, in the case of dot matrices display, it is good to rewrite the display for each line, and a horizontal electric field is added to a pixel to display white, and a vertical electric field is added to a pixel to display black. do. In addition, a vertical electric field or a horizontal electric field is added to a part of the liquid crystal layer (pixel region) to the pixel for which halftone display is to be performed. Various driving methods can be considered. Hereinafter, a liquid crystal display device that performs matrix display using an XY electrode as a second embodiment will be described.

8A is a schematic view showing a liquid crystal display device according to a second embodiment, and FIG. 8B is a schematic plan view showing the electrode structure of the pixel portion 34.

The liquid crystal display device according to the second embodiment is a simple matrix type liquid crystal display device configured by arranging a plurality of pixel parts 34 in a matrix shape, and as each pixel part 34, according to the first embodiment The same pixel configuration as the liquid crystal display element is used. Specifically, in the liquid crystal display device according to the second embodiment, m control lines B1 to Bm extending in the X direction, drivers 31 that give control signals to these control lines B1 to Bm, and each are controlled. N control lines A1 to An extending in the Y direction crossing the lines B1 to Bm, a driver 32 that gives a control signal to these control lines A1 to An, and each Y crossing the control lines B1 to Bm N control lines C1 to Cn and D1 to Dn, and a driver 33 that gives a control signal to these control lines C1 to Cn and D1 to Dn, and each of the control lines B1 to Bm and the control lines A1 to An It comprises a pixel portion 34 defined in the intersection area.

Each of the control lines B1 to Bm, A1 to An, C1 to Cn, and D1 to Dn is made of, for example, a transparent conductive film such as ITO formed in a stripe shape. The intersection of the control lines B1 to Bm and A1 to An functions as the upper beta electrode 12a and the lower beta electrode 12b (see FIG. 8B). In addition, the control lines C1 to Cn are connected to a slit portion of the first slit electrode 12c, which is provided in an area corresponding to each pixel portion 34. Similarly, the control lines D1 to Dn are connected to the slit portions of the second slit electrodes 12d provided in regions corresponding to the respective pixel portions 34.

As an example of the driving method of the liquid crystal display device according to the second embodiment, a method of performing display switching for each control line B1, B2, B3, ... and lines (line sequential driving method) will be described. In this case, for example, a lateral electric field is applied to the pixel portion 34 that is desired to be a relatively bright display (display that approximates a white display), and a pixel portion that is desired to be a relatively dark display (display that is close to a black display). A vertical electric field is applied to (34).

As an example, in the case of performing black display or white display, a square wave voltage (for example, 150 Hz at about 1.5 V) is applied to the control line B1 to the extent that no oriented transition occurs, and the control lines A1 to An, C1 to For Cn and D1 to Dn, a square wave voltage (for example, 150 Hz at about 1.5 V) that is synchronous with it or shifted by a half period, that is, a threshold value, that is, a voltage of the minimum physical quantity causing the reaction. Is approved.

Specifically, among the control lines A1 to An, a square wave voltage shifted by a half-cycle from the square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 to be displayed in black. At this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. Thereby, a voltage of about 3.0 V is effectively applied to the pixel portion 34, and a vertical electric field is added. When the voltage is equal to or higher than the saturation voltage, the liquid crystal layer 15 causes an alignment state transition (a transition to a reverse twist arrangement state), thereby changing the light transmittance of the pixel portion 34.

On the other hand, of the control lines A1 to An, a 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 that does not need to change the display. Also at this time, no voltage is applied to the control lines C1 to Cn and D1 to Dn. Thereby, a voltage is not effectively applied to the pixel portion 34. Therefore, the alignment state transition does not occur in the liquid crystal layer 15, and the light transmittance does not change.

Further, among the control lines C1 to Cn and D1 to Dn, a square wave voltage shifted by a half-cycle from the square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 to be displayed in white. At this time, no voltage is applied to the control lines A1 to An. Thereby, a voltage of about 3.0 V is effectively applied to the pixel portion 34, and a lateral electric field is added. When the voltage is equal to or higher than the saturation voltage, the liquid crystal layer 15 causes an alignment state transition (transition to a spray twist arrangement state), whereby the light transmittance of the pixel portion 34 can be changed.

On the other hand, of the control lines C1 to Cn and D1 to Dn, a 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 that does not need to change the display. Even at this time, no voltage is applied to the control lines A1 to An. Thereby, a voltage is not effectively applied to the pixel portion 34. Therefore, the liquid crystal layer 15 does not have a transition in the alignment state, and the light transmittance does not change.

In the case where gray display (intermediate tone display) is performed, the degree to which the transition of the alignment state does not occur in the control line B1 with respect to the pixel portion 34 that performs black display (in the reverse twist arrangement state) as an example. A square wave voltage (for example, 150 Hz at about 1.5 V) is applied, and a square wave voltage (for example, 150 Hz at about 1.5 V) is applied to the control lines C1 to Cn in synchronization with it or causing a half-cycle shifted reaction. Approve.

Specifically, among the control lines C1 to Cn, a square wave voltage shifted by a half-cycle from the square wave voltage applied to the control line B1 is applied to the control line corresponding to the pixel portion 34 to be grayed out. At this time, no voltage is applied to the control lines A1 to An and D1 to Dn. Thereby, a voltage of about 3.0 V is effectively applied to the zest portion of the first zell electrode 12c and the liquid crystal molecules in the vicinity of the pixel portion 34, and a lateral electric field is added. If this voltage is equal to or higher than the saturation voltage, the liquid crystal molecules in the corresponding region cause an array state transition (a transition to a spray twist arrangement state) to change the light transmittance of the corresponding region (a region of about half of the pixel portion 34). You can.

On the other hand, of the control lines C1 to Cn, a 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 that does not need to change the display. Also at this time, no voltage is applied to the control lines A1 to An and D1 to Dn. Thereby, a voltage is not effectively applied to the pixel portion 34. Therefore, the liquid crystal layer 15 does not have a transition in the alignment state, and the light transmittance does not change.

In addition, although an example in which the voltage is synchronized with the control lines B1 and the control lines C1 to Cn, or a half-cycle shift is applied, it may be synchronized with the control lines B1 and the control lines D1 to Dn, or a voltage with a half-cycle shift may be applied.

The dot matrix display can be performed by performing the above-described driving sequentially with the control lines B2, B3, .... It is possible to hold the display state changed by such driving semi-permanently. In order to change this display, the above control can be performed again from the control line B1.

Further, by changing the electrode width of C1 to Cn or D1 to Dn or the period of the applied voltage, more detailed halftone display is possible.

In addition, although the case where the electrode width of the zlatch electrode is uniform is described here, it is okay to vary the electrode width depending on the place. When the electrode width is uniform, the moire pattern may be seen by the light-tone pattern of the halftone display that can be obtained, but it is possible to reduce it.

In addition, although an example of a so-called simple matrix type liquid crystal display device is shown here, an active matrix type liquid crystal display device using TFT or the like can be used. In the case of the active matrix type liquid crystal display device, it is not necessary to replace each line such as the control line B1, so that the replacement time can be shortened. Moreover, since it is also possible to apply a voltage of twice or more to the threshold, for example, it is possible to switch to a higher speed.

Hereinafter, a liquid crystal display device using a TFT as a third and fourth embodiment will be described.

9A and 9B are schematic cross-sectional and plan views, respectively, showing a liquid crystal display device according to a third embodiment. 9A is a cross-sectional view taken along line 9A-9A in FIG. 9B. 9B shows approximately one pixel, and a plurality of pixels are formed along the X direction and the Y direction.

In the liquid crystal display device according to the third embodiment, the twisted nematic liquid crystal layer 15 sandwiched between the upper substrate 10a, the lower substrate 10b, and both the substrates 10a and 10b are disposed opposite to each other in parallel. It is configured to include.

The upper substrate 10a includes an upper transparent substrate 11a, a common electrode (upper beta electrode) 12a formed on the upper transparent substrate 11a, and an upper alignment layer 14a formed on the common electrode 12a. do. The lower substrate 10b includes a lower transparent substrate 11b, a lower beta electrode 12b formed on the lower transparent substrate 11b, a common wire 22, a scanning line 23, and a lower transparent substrate 11b to cover them. ), The insulating film 13 formed on the insulating film 13, a slit electrode (pixel electrode) 21, a semiconductor film 24, a source electrode 25, a drain electrode 26, and so as to cover them And a lower alignment layer 14b formed on the insulating film 13.

The upper and lower transparent substrates 11a and 11b are, for example, transparent glass substrates disposed to face each other. It may be a transparent plastic substrate. Between the upper and lower alignment films 14a, 14b, for example, a plurality of spacers are dispersedly arranged (not shown), and the space between the two substrates 11a, 11b is spaced by such spacers. This is maintained.

The lower beta electrode 12b is provided on one side of the lower transparent substrate 11b. The lower beta electrode 12b is formed in a substantially spherical shape, for example, as shown in Fig. 9B, and a part thereof is electrically connected to a common line 22. The lower beta electrode 12b can be obtained by patterning a transparent conductive film such as ITO.

The common wire 22 is provided on one side of the lower transparent substrate 11b and extends in one direction (Y direction in Fig. 9B). The common wire 22 is connected to the lower beta electrode 12b, and a predetermined potential is given to the lower beta electrode 12b from a voltage supply means (not shown) through the common wire 22. The common wire 22 is formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The scanning line 23 is provided on one side of the lower transparent substrate 11b and extends in one direction (Y direction in Fig. 9B). As shown in Fig. 9B, the scanning line 23 of this embodiment is disposed with the lower beta electrode 12b interposed between the common line 22. The scanning line 23 is formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The insulating film 13 is provided on one side of the lower transparent substrate 11b to cover the lower beta electrode 12b, the common wire 22, and the scanning line 23. As the insulating film 13, for example, a silicon nitride film, a silicon oxide film, or a laminated film of these is used.

The semiconductor film 24 is provided on the insulating film 13 at a predetermined position overlapping the scanning line 23. The semiconductor film 24 is patterned in an island shape, as shown in Fig. 9B. As the semiconductor film 24, an amorphous silicon film can be used, for example. The portion of the scanning line 23 overlapping with the semiconductor film 24 functions as a gate electrode of the TFT. The portion overlapping the semiconductor film 24 of the insulating film 13 functions as a gate insulating film of the TFT.

The source electrode 25 is provided at a predetermined position on the insulating film 13, and part of it is connected to the semiconductor film 24. The source electrode 25 of this embodiment is integrally formed with the signal line 27, as shown in Fig. 9B. The source electrode 25 and the signal line 27 are formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The drain electrode 26 is provided at a predetermined position on the insulating film 13, and part of it is connected to the semiconductor film 24. The drain electrode 26 is formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The slit electrode 21 is provided on the insulating film 13 at a predetermined position at least partially overlapping the lower beta electrode 12b. As shown in FIG. 9B, the slit electrode 21 has, for example, a plurality of spherical slits (openings) 21a. The slit electrode 21 can be obtained by patterning a transparent conductive film such as ITO. In the third embodiment, the size of the slit electrode 21 is 20 μm in width (electrode width, length in the X direction in FIG. 9B) of the straight portion between each slit 21a, and each slit 21a. Was set so that the width (length in the X direction in Fig. 9B) was 20 µm. And the size is not limited to this. For example, when the width of the slit 21a is set to s, it is possible to set so that the above expression (1) is satisfied. The slit electrode 21 is connected to the drain electrode 26. By applying a voltage between the slit electrode 21 and the lower beta electrode 12b, a lateral electric field can be applied to the liquid crystal layer 15.

The lower alignment film 14b is provided with a semiconductor film 24, a source electrode 25, a drain electrode 26, and a slit electrode 21 on the insulating film 13 on one side of the lower transparent substrate 11b. It is installed to cover.

Similarly, the upper alignment layer 14a is provided to cover the common electrode 12a on one side of the upper transparent substrate 11a. For each of the upper and lower alignment films 14a and 14b, uniaxial alignment processing is performed, for example, by rubbing. As the alignment films 14a and 14b, one that expresses a relatively high pretilt angle (20 degrees or more, preferably about 35 degrees ± 10 degrees) is used. The direction R _U of the alignment treatment of the upper alignment layer 14a and the direction R _L of the alignment processing of the lower alignment layer 14b are liquid crystal layers (when the arrangement state of the liquid crystal molecules of the liquid crystal layer 15 is in a reverse twist arrangement state. The direction D of the liquid crystal molecules located in the center of the thickness direction of 15) is generated when a voltage is applied between the lower beta electrode 12b and the slit electrode 21, the transverse electric field direction E (of the slit 21a) It is set to be substantially orthogonal to the direction parallel to the arrangement direction} (see Fig. 9B).

The common electrode 12a is provided on one side of the upper transparent substrate 11a. The common electrode 12a is formed such that at least a portion thereof overlaps the lower beta electrode 12b and the slit electrode 21. The common electrode 12a can be obtained by patterning a transparent conductive film such as ITO. By applying a voltage between the common electrode 12a and the lower beta electrode 12b, a vertical electric field can be applied to the liquid crystal layer 15 (pixel region). Further, by applying a voltage between the common electrode 12a and the slit electrode 21, a part of the liquid crystal layer 15 (pixel region) (except the upper portion of the slit 21a, except for the upper portion of the slit electrode 21) Liquid crystal layer 15} can be added with a vertical electric field.

The liquid crystal layer 15 is disposed between the upper substrate 10a and the lower substrate 10b, and is made of, for example, a nematic liquid crystal material having a dielectric constant anisotropy Δε. The thick line shown in the liquid crystal layer 15 in FIG. 9A schematically shows liquid crystal molecules in the liquid crystal layer 15. When no voltage is applied, the liquid crystal molecules are oriented with a predetermined pretilt angle with respect to each substrate surface of the upper substrate 10a and the lower substrate 10b. In addition, the angle formed by the directions R _U and R _L (see FIG. 9B) of each of the alignment treatments of the upper alignment layer 14a and the lower alignment layer 14b is set to, for example, about 90 degrees, when no voltage is applied. The liquid crystal molecules of the liquid crystal layer 15 are twisted and aligned in the azimuthal direction between the upper substrate 10a and the lower substrate 10b. In addition, a chiral agent is added to the liquid crystal layer 15.

The signal line 27 is provided on one side of the insulating film 13, and extends in one direction (X direction in FIG. 9B) substantially perpendicular to the direction in which the common line 22 and the scanning line 23 extend.

The upper polarizing plate 16a is disposed outside the upper substrate 10a. Moreover, the lower polarizing plate 16b is disposed outside the lower substrate 10b. The display of the liquid crystal display element according to the third embodiment is visually recognized by the user from the upper polarizing plate 16a side. The upper and lower polarizing plates 16a, 16b are arranged, for example, by cross nicol.

The liquid crystal display device according to the third embodiment is also a reverse twisted nematic liquid crystal display device. Also in the third embodiment, the arrangement state of the liquid crystal molecules of the liquid crystal layer 15, which is defined by the combination of the orientation processing direction of the upper and lower substrates 10a and 10b and the pretilt angle, is twisted in the first turning direction. It is a reverse twist arrangement. The arrangement state of the liquid crystal molecules generated under the influence of chiral agent is a spray twist arrangement twisted in a second rotation direction opposite to the first rotation direction. By adding a vertical electric field to the liquid crystal layer 15, the liquid crystal molecules of the liquid crystal layer 15 in the added region can be shifted from a spray twist arrangement state to a reverse twist arrangement state. Further, by adding a lateral electric field to the liquid crystal layer 15, the liquid crystal molecules of the liquid crystal layer 15 in the added region can be shifted from a reverse twist arrangement state to a spray twist arrangement state.

10A to 10G and FIGS. 11A to 11D are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a third embodiment.

The glass substrate used as the upper transparent substrate 11a and the lower transparent substrate 11b is prepared. For example, a glass substrate made of alkali-free glass having a thickness of 0.7 mm can be used.

See FIG. 10A. A common line 22 and a scanning line 23 are formed on one surface of the glass substrate for the lower transparent substrate 11b. For example, an aluminum film is formed on the lower transparent substrate 11b by a film forming method such as a sputtering method, and a molybdenum film is formed thereon. Then, a laminated film of an aluminum film and a molybdenum film is patterned by a dry etching method or the like.

See FIG. 10B. The lower beta electrode 12b is formed at a predetermined position on one side of the lower transparent substrate 11b. Specifically, an ITO film is formed on the lower transparent substrate 11b by a film forming method such as a sputtering method, and the ITO film is patterned by a wet etching method or the like.

See FIG. 10C. An insulating film 13 is formed on one side of the lower transparent substrate 11b by covering the lower beta electrode 12b, the common wire 22, and the scanning line 23. For example, a silicon nitride film is formed by a film forming method such as a sputtering method or a plasma CVD method.

See FIG. 10D. A semiconductor film 24 is formed at a predetermined position on the insulating film 13. An amorphous silicon film is formed on the insulating film 13 by a film-forming method such as plasma CVD, and the amorphous silicon film is patterned into an island shape by a dry etching method or the like.

See FIG. 10E. The source electrode 25, the drain electrode 26, and the signal line 27 are formed at predetermined positions on the insulating film 13. For example, a lamination film of a molybdenum film / aluminum film / molybdenum film is formed on the insulating film 13 and the semiconductor film 24 by a film forming method such as a sputtering method, and the laminated film is patterned by a dry etching method or the like. do.

See FIG. 10F. A slit electrode 21 is formed at a predetermined position on the insulating film 13. An ITO film is formed on the insulating film 13 by a film forming method such as a sputtering method, and the ITO film is patterned by a wet etching method or the like. Further, a passivation film may be additionally provided on the insulating film 13.

See FIG. 10G. On the other hand, a common electrode 12a is formed on the glass substrate for the upper transparent substrate 11a. Specifically, an ITO film is formed over the entire surface of the upper transparent substrate 11a by a film forming method such as a sputtering method. As for the actual manufacturing process, when the common electrode 12a is present on the entire surface of the substrate, there is a possibility of shorting by the main seal or film peeling at the time of scribing from the scribing. It is desirable to shield the outer periphery.

Hereinafter, the liquid crystal display device according to the third embodiment can be manufactured by the same method as the manufacturing method of the liquid crystal display device according to the first embodiment. However, it is preferable to use a material suitable for TFT driving as the liquid crystal material or the alignment film material.

See FIG. 11A. On the insulating film 13 on the lower transparent substrate 11b, a lower alignment film 14b is formed.

Moreover, as shown in Fig. 11B, an upper alignment layer 14a is formed on the common electrode 12a on the upper transparent substrate 11a.

The upper and lower transparent substrates 11a and 11b on which electrodes and the like are formed are cleaned. The washing is, for example, washing with water, and pure water washing as an example. It is preferable not to use detergent. Brush cleaning, spray cleaning, etc. can be used. After dehydration, UV cleaning is performed and IR drying is performed. Atmospheric pressure plasma cleaning may be performed.

In forming the alignment films 14a and 14b, an alignment film having a high voltage retention was selected, and specifically, a polyimide film having a low side chain density of a material used as a vertical alignment film was used. Appropriate methods such as fureciso printing, inkjet printing, spin coating, etc., here, spin coating methods are used to place the alignment film materials on the upper and lower transparent substrates 11a and 11b, respectively, to a suitable film thickness, for example, 500Å to 800Å. Coating was performed to a thickness and heat treatment (for example, in a clean oven, firing at 160 ° C to 180 ° C for 1 hour) was performed. Thereafter, for each of the upper and lower alignment layers 14a and 14b, rubbing treatment was performed with an alignment treatment, for example, a press-fitting amount of 0.8 mm. In the rubbing direction, for example, when the upper transparent substrate 11a and the lower transparent substrate 11b were polymerized, the twist angle of the liquid crystal molecules on the respective substrates 11a and 11b was set to an abbreviation of 90 degrees.

After the rubbing treatment, the substrates 11a and 11b may be cleaned, but this is not done here.

Thus, the upper substrate 10a and the lower substrate 10b were produced.

See FIG. 11C. Subsequently, in order to keep the thickness of the liquid crystal cell constant, a gap control material was spread on one surface of the substrates 10a and 10b, for example, by a dry spreading method. A plastic ball having a particle diameter of 4 μm was used as the gap control material, so that the thickness of the liquid crystal cell was 4 μm. The gap control may be such that the gap control material is scattered on the substrate surface, or a rib pattern may be formed on the upper substrate 10a, for example, to thereby maintain a predetermined cell thickness.

On one surface of the substrates 10a and 10b, a seal material was printed to form a main seal pattern. For example, a thermosetting sealant containing glass fibers having a particle diameter of 4 μm is printed by a screen printing method. The sealer may be applied using a dispenser. Moreover, it is not thermosetting property, and you may use the photocurable seal material and the hardening type seal material for light and fever.

The substrates 10a and 10b were overlapped. The substrates 10a and 10b were cellized by overlapping at a predetermined position, and heat-treated in a pressed state to cure the seal material. For example, heat-hardening of a sealing material is performed using a hot press method. Thus, an empty cell was produced.

See FIG. 11D. For example, a liquid crystal material is injected into a blank cell by a vacuum injection method. You can also use the ODF method. The vacuum injection method was used here. The liquid crystal material is a nematic type, and is preferably a material having high dielectric anisotropy and high voltage retention. For example, there is no particular restriction as long as it is a liquid crystal material used in a twisted nematic type liquid crystal display device generally driven by TFT.

A chiral agent was added to the liquid crystal material. As an example, R-811 of Melk Co., Ltd. was used as a chiral agent, and it was added so that d / p became 0.16.

After the liquid crystal injection, the end seal treatment was performed while pressing. The cell was heat-treated at a high temperature (a temperature equal to or higher than the phase transition temperature of the liquid crystal), and the alignment state of the liquid crystal molecules was summarized.

Finally, polarizing plates 16a and 16b were attached to the opposite sides of the liquid crystal layer 15 of the two transparent substrates 11a and 11b. The two polarizing plates 16a, 16b were arranged so that the cross nicol and the direction of the transmission axis and the direction of rubbing were parallel. It can also be arranged to be orthogonal.

In this way, the liquid crystal display device according to the third embodiment was produced.

The inventors of the present invention confirmed the display of the liquid crystal display device according to the third embodiment.

12A is a photograph showing a pixel area after completion of the liquid crystal display device according to the third embodiment (initial state). The entire surface is arranged in a spray twist, and a bright white mark is obtained.

12B is a photograph showing a pixel area after applying a voltage between the common electrode 12a and the lower beta electrode 12b and adding a vertical electric field to the liquid crystal layer 15. Here, an AC voltage (square wave) of 10 V and 100 Hz was applied for about 1 second. The entire surface transitions from the spray twist arrangement to the reverse twist arrangement, and a dark black display is obtained.

For example, for the configuration shown in Fig. 9B, since the voltage cannot be controlled to transition from the spray twist arrangement state to the reverse twist arrangement state for each pixel, the conversion from the white display to the black display is at least the scanning line 22. Performed line by line. Normally, a full line (overall surface) conversion would be desirable.

Next, a voltage was applied to each pixel TFT, and a lateral electric field was generated in the liquid crystal layer 15. Specifically, a voltage is applied to the scan line 23 (gate line) and the signal line 27 (source line), and a potential difference is provided between the lower beta electrode 12b, and the transverse electric field is applied to the liquid crystal layer 15. Added. A pulse wave of 10 V as the gate voltage and a voltage inverted by ± 10 V for each source voltage were added. As a result, it was confirmed that a white display like the photograph shown in Fig. 12A was obtained. By the addition of the lateral electric field, the liquid crystal molecules transition from the reverse twist arrangement state to the spray twist arrangement state. Switching from a black display to a white display, the voltage application time is sufficient for about 1 second. And immediately after stopping the application of the voltage, a black display state (reverse twist arrangement state) remained on the slit electrode 21 in a dot shape, but after 3 seconds to 4 seconds, all of the white on the slit electrode 21 is white. The display state (spray twist arrangement state) has been reached.

The conversion from black display to white display is by selecting the scan line 23 and signal line 27 to which voltage is applied, and can be controlled for each pixel, so that various displays can be realized by the waveform applied to the TFT.

Then, gray display (intermediate tone display) was performed. In the state in which the liquid crystal molecules of the liquid crystal layer 15 are in a spray twist arrangement, a voltage was applied between the drain electrode 26 and the common electrode 12a through the TFT. Here, an alternating voltage (square wave) of 10 V and 100 Hz was applied to the signal line 27 (source line) with pixels to be grayed out, and a gate voltage was applied in synchronization therewith. Thereby, a vertical electric field is added to a part of the liquid crystal layer 15 (the liquid crystal layer 15 above the slit electrode 21 except for the upper portion of the slit 21a), and the liquid crystal molecules at the position are reverse twisted. As transitioned. Thereafter, 0 V was applied to a signal line 27 (source line) of a pixel partially in a reverse twist arrangement state, and a gate voltage was applied in synchronization therewith. Thus, gray display was realized.

13A and 13B are schematic cross-sectional and plan views, respectively, showing a liquid crystal display device according to a fourth embodiment. 13A is a cross-sectional view taken along line 13A-13A in FIG. 13B. 13B shows approximately one pixel, and a plurality of pixels are formed along the X direction and the Y direction.

9A and 9B, the common wire 22a is formed on the insulating film 28 so that the common wire 22a is not the lower beta electrode 12b but is electrically connected to the slit electrode 21. The difference is that the drain electrode 26a is connected to the lower beta electrode 12b, not the slit electrode 21.

Hereinafter, the same reference numerals are used for components common to the third embodiment, and detailed descriptions thereof will be omitted.

In the liquid crystal display device according to the fourth embodiment, the twisted nematic liquid crystal layer 15 sandwiched between the upper substrate 10a, the lower substrate 10b, and both the substrates 10a and 10b are disposed opposite to each other in parallel. It is configured to include.

The upper substrate 10a includes an upper transparent substrate 11a, a common electrode (upper beta electrode) 12a formed on the upper transparent substrate 11a, and an upper alignment layer 14a formed on the common electrode 12a. do. The lower substrate 10b includes a lower transparent substrate 11b, a lower beta electrode 12b formed on the lower transparent substrate 11b, a scanning line 23, and an insulating film formed on the lower transparent substrate 11b so as to cover them. 13), the semiconductor film 24 formed on the insulating film 13, the source electrode 25, the drain electrode 26a, on the insulating film 28 and the insulating film 28 formed on the insulating film 13 to cover them The formed slit electrode (pixel electrode) 21, the common wire 22a, and the lower alignment film 14b formed on the insulating film 28 to cover them. Here, the drain electrode 26a is formed to penetrate the insulating film 13 and electrically connect to the lower beta electrode 12b.

The common wire 22a is provided on the insulating film 28 on one side of the lower transparent substrate 11b and extends in one direction (Y direction in Fig. 13B). The common wire 22a is connected to the slit electrode 21 as shown in Fig. 13B, and through the common wire 22a, a predetermined potential with respect to the slit electrode 21 from a voltage supply means (not shown) Is given. The common wire 22a is formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The drain electrode 26a is provided at a predetermined position on the insulating film 28, and a part of it passes through the insulating film 13 and is connected to the lower beta electrode 12b. The drain electrode 26a is formed of, for example, a metal film such as a laminated film of aluminum and molybdenum.

The insulating film 28 is provided over the insulating film 13 on one side of the lower transparent substrate 11b by covering the semiconductor film 24, the source electrode 25, and the drain electrode 26a. As the insulating film 28, for example, a silicon nitride film, a silicon oxide film, or a laminated film of these is used.

The slit electrode 21 is provided on the insulating film 28 at a predetermined position at least partially overlapping the lower beta electrode 12b. As shown in Fig. 13B, the slit electrode 21 has a plurality of slits (openings) 21a, and is connected to the common wire 22a. In the fourth embodiment, the slit electrode 21 and the common wire 22a are integrally formed. The slit electrode 21 can be obtained by patterning a transparent conductive film such as ITO. By applying a voltage between the slit electrode 21 and the lower beta electrode 12b, a lateral electric field can be applied to the liquid crystal layer 15.

The lower alignment layer 14b is provided on the insulating layer 28 on one side of the lower transparent substrate 11b so as to cover the common wire 22a and the slit electrode 21.

The liquid crystal display device according to the fourth embodiment is also a reverse twisted nematic liquid crystal display device. Also in the fourth embodiment, the arrangement state of the liquid crystal molecules of the liquid crystal layer 15 defined by the combination of the pre-tilt angle and the alignment treatment direction of the upper and lower substrates 10a and 10b is twisted in the first turning direction. It is a reverse twist arrangement, and the arrangement state of the liquid crystal molecules generated under the influence of chiral agent is a spray twist arrangement twisted in a second rotation direction opposite to the first rotation direction. By adding a vertical electric field to the liquid crystal layer 15, the liquid crystal molecules of the liquid crystal layer 15 in the added region can be shifted from a spray twist arrangement state to a reverse twist arrangement state. Further, by adding a lateral electric field to the liquid crystal layer 15, the liquid crystal molecules of the liquid crystal layer 15 in the added region can be shifted from a reverse twist arrangement state to a spray twist arrangement state.

14A to 14G and FIGS. 15A to 15E are schematic cross-sectional views showing a method of manufacturing a liquid crystal display device according to a fourth embodiment. Hereinafter, in the description of the manufacturing method, detailed descriptions of the contents common to the third embodiment will be omitted.

As shown in Fig. 14A, a scan line 23 made of a predetermined metal film is formed on one surface of the lower transparent substrate 11b.

As shown in Fig. 14B, a lower beta electrode 12b made of, for example, ITO is formed at a predetermined position on one side of the lower transparent substrate 11b.

As shown in FIG. 14C, an insulating film 13 is formed by covering the lower beta electrode 12b and the scanning line 23 on one side of the lower transparent substrate 11b.

As shown in Fig. 14D, a semiconductor film 24 is formed at a predetermined position on the insulating film 13.

14E, the source electrode 25, the drain electrode 26a, and the signal line 27 are formed. For the drain electrode 26a, an opening for exposing a portion of the lower beta electrode 12b at a predetermined position in the insulating film 13 is provided in advance, and then formed by forming a metal film and patterning it by a sputtering method or the like. This is possible.

As shown in FIG. 14F, an insulating film 28 covering the semiconductor film 24, the source electrode 25, the drain electrode 26a, and the signal line 27 is formed on the insulating film 13.

As shown in Fig. 14G, the common wire 22a and the slit electrode 21 are formed at predetermined positions on the insulating film 28. Further, a passivation film may be provided on the insulating film 28.

On the other hand, as shown in Fig. 15A, a common electrode 12a is formed on one surface of the upper transparent substrate 11a.

Further, as shown in Fig. 15B, a lower alignment layer 14b is formed on the insulating film 28 above the lower transparent substrate 11b.

Further, as shown in Fig. 15C, an upper alignment layer 14a is formed on the common electrode 12a on the upper transparent substrate 11a.

The alignment treatment is performed on the upper and lower alignment layers 14a and 14b, and through the same steps as in the third embodiment, such as the substrate polymerization process and the liquid crystal layer 15 formation process shown in FIGS. 15D and 15E, the fourth A liquid crystal display device according to an embodiment is produced.

In the liquid crystal display device according to the fourth embodiment, an effective longitudinal electric field is added to a part of the liquid crystal layer 15 (pixel region), and, like other embodiments, coexistence and mixing of reverse twist arrangement and spray twist arrangement It is a liquid crystal display element that can form a halftone and can perform halftone display.

In the liquid crystal display device according to the third and fourth embodiments, one TFT is formed in each pixel, but a plurality of TFTs may be formed. In this case, for example, by dividing the pixel electrode, it is possible to further realize multi-gradation display. It is also possible to display images such as photographs. Here, the pixel electrodes need not be divided into the same area.

Although the third and fourth embodiments are transmissive liquid crystal display elements, for example, the lower beta electrode 12b may be a reflective electrode, and a reflective liquid crystal display element. In that case, it is preferable to set the twist angle to approximately 70 degrees.

The liquid crystal display elements according to the first to fourth embodiments and modifications are liquid crystal display elements capable of easily realizing stable display of a high contrast white display state, a black display state, and a halftone display state. As an electrode constituting the pixel, a zlatz electrode or a slit electrode is used. According to the liquid crystal display elements according to the first to fourth embodiments, a longitudinal electric field or a transverse electric field is partially generated in the liquid crystal layer of the pixel region, and a distribution of transmittance is attached within the pixels (areas having different transmittances in the pixels, That is, when viewed from the substrate normal direction, for example, liquid crystal molecules of the liquid crystal layer form an area in a reverse twist arrangement state and an area in a spray twist arrangement state), and various displays can be performed. As shown in the modification of the first embodiment, the electrode size (width, area, etc.) is considered, and multi-level gradation display in five steps, for example, is also possible. In addition, a portion of the liquid crystal layer in the pixel region may be in a reverse twist arrangement, and another portion may be in a spray twist arrangement, and for example, it is not necessary to have the same arrangement when viewed along the normal direction of the substrate. In the liquid crystal display device according to the first to fourth embodiments and modifications, an electrode capable of generating an electric field in which a part of the liquid crystal layer in the pixel area is in a reverse twist arrangement state and another part is in a spray twist arrangement state is formed. Equipped.

Further, the liquid crystal display elements according to the first to fourth embodiments can be manufactured at low cost. The manufacturing method is substantially the same as that of a general twisted nematic liquid crystal display device, except for the alignment film material, rubbing conditions (control of the press-in amount), and the firing conditions of the alignment film, and thus is similar to a general twisted nematic liquid crystal display device. In comparison, the factor of cost increase is small.

In the liquid crystal display elements according to the first to fourth embodiments, the reverse twist arrangement state of the liquid crystal layer 15, the spray twist arrangement state, and their mixed state are stably maintained. For this reason, in any of the white display, black display, and gray display, after changing the display, the display state is maintained while the voltage is not applied. No power is consumed except when the display is changed. For this reason, it is possible to drive ultra-low power consumption with extremely low power consumption. Especially when applied to a reflective display, the merit is great. The display can be held semi-permanently and is compatible with a high contrast ratio.

As shown in the second embodiment, as a driving method, a driving method using memory characteristics, such as a line sequential driving method, can be applied. Therefore, in this case, a large-capacity dot matrix display can be performed by simple matrix display without using an expensive TFT or the like. That is, it is possible to display a large capacity at a low cost.

When a switching element such as a TFT is used, large-capacity display switching can be performed at high speed. In the case of using a TFT as a liquid crystal display device, it is also possible to use, for example, a TFT substrate widely used as an IPS liquid crystal. Although it is necessary to form a transparent electrode on the counter substrate, for example, since it can be easily formed using a mask sputter or the like, the cost increase factor is small. There is a merit that the counter substrate is equipped with an electrode, and it is difficult to be adversely affected by static electricity during rubbing.

Further, according to the liquid crystal display elements according to the first to fourth embodiments and modifications, it is possible to realize a display that is highly suitable in any case of a transmissive display, a specular display, or a reflective display.

Next, the liquid crystal display device according to the fifth embodiment will be described in comparison with the comparative example.

The inventors of the present invention first produced a plurality of reverse twisted nematic liquid crystal display elements according to comparative examples, and investigated the display characteristics thereof.

Two transparent substrates on which a transparent electrode, for example, an indium tin oxide (ITO) electrode, are formed are prepared. Here, a test cell having a parallel plate type electrode was used, and two transparent substrates were cleaned and dried.

On the transparent substrate, an alignment film material is applied to cover the ITO electrode. Coating of the alignment film material was performed using a spin coat. It may be carried out by using Furekiso printing or inkjet printing. In this example, the side chain density of the polyimide alignment layer material having a low side chain density was controlled as a vertical alignment layer material, which is usually used for forming a vertical alignment layer, and used as an alignment layer material. This is because the control of the side chain density makes it possible to provide an appropriate pretilt angle. The alignment film material was applied so that the thickness of the alignment film was 500 mm 2 to 800 mm 2.

The plastic substrate coated with the alignment film material is subjected to plastic firing and main firing. The main firing was performed at different firing temperatures between 160 ° C and 260 ° C. Thus, an alignment film covering the ITO electrode was formed.

Next, rubbing processing (orientation processing) is performed. The rubbing treatment is, for example, a process of rotating a roll of a cylindrical shape wound with cloth at a high speed to rub an alignment film, whereby liquid crystal molecules in contact with the substrate are aligned (orientated) in one direction. The rubbing treatment was performed under three conditions in which the indentation amounts were 0.4 mm, 0.8 mm, and 1.2 mm. In addition, the rubbing treatment was performed such that the twist angle of the liquid crystal display element was 70 degrees or 90 degrees.

Subsequently, in order to keep the thickness (distance between the substrates) of the liquid crystal cell constant, a gap control material was spread on the other transparent substrate surface, for example, by a dry spreading method. A plastic ball having a particle diameter of 4 μm was used for the gap control material, and the thickness of the liquid crystal cell was set to 4 μm.

On the other hand, a seal material was printed on the transparent substrate surface to form a main seal pattern. For example, a thermosetting sealant containing glass fibers having a particle diameter of 4 μm is printed by a screen printing method. The sealer may be applied using a dispenser. Moreover, it is not thermosetting property, and you may use the photocurable seal material and the hardening type seal material for light and fever.

The transparent substrate was put on top. The two transparent substrates were polymerized at a predetermined position to be cellized, and heat treated in a pressed state to cure the seal material. For example, heat-hardening of a sealing material is performed using a hot press method. In this way, an empty cell is produced.

For example, a nematic liquid crystal is injected into a blank cell by a vacuum injection method. A chiral agent was added to the liquid crystal. As the chiral agent, CB15 or R-811 manufactured by Melk Co., Ltd. was used. The chiral agent was added under conditions of a plurality of addition amounts such that when the chiral pitch p and the cell thickness d were set, d / p was, for example, 0.33 to 0.53.

The liquid crystal injection port was sealed with, for example, an ultraviolet curing type end seal material, and the cells were heated above the phase transition temperature of the liquid crystal in order to arrange the alignment of the liquid crystal molecules. And for a reverse twisted nematic liquid crystal display device, for example, after injection of a liquid crystal material, or when heated above the phase transition temperature of the liquid crystal, the spray twist arrangement is distorted in a direction in which a torsional force according to the chiral agent is generated. .

Thereafter, the scriber device was broken along the damage to the transparent substrate, and divided into small cells.

The small-segmented cells were chamfered and washed.

Finally, a polarizing plate was pasted to the surfaces of the two transparent substrates opposite to the liquid crystal layer. The two polarizing plates were arranged so that the cross nicol and the direction of the transmission axis and the direction of rubbing were parallel. It can also be arranged orthogonally. A power supply was connected between the ITO electrodes of both transparent substrates.

Thus, a liquid crystal display device according to a comparative example was produced. In the liquid crystal display device according to the comparative example, the liquid crystal molecules of the liquid crystal layer show the spray twist arrangement state with respect to the initial state, and by applying the vertical electric field, the spray twist arrangement state can be shifted to the reverse twist arrangement state, and the horizontal A reverse twisted nematic type liquid crystal display device capable of transitioning from a reverse twist arrangement state to a spray twist arrangement state by application of an electric field.

The inventors of the present invention conducted various investigations on the display of the reverse twisted nematic liquid crystal display device according to the comparative example.

First, visual observation of the display was conducted. The liquid crystal display device according to the comparative example was displayed at a high contrast ratio even when viewed from the front. Moreover, even if it was left for 3 months at room temperature, the display was retained.

Next, the holdability of the display when the liquid crystal layer was in a reverse twist arrangement was examined for a plurality of temperatures.

16 is a table showing the investigation results. In Fig. 16, after each type of chiral agent added and one liquid crystal display element (comparative example) for each addition amount (chiral pitch) was left at each temperature of -40 ° C, 40 ° C, 50 ° C for 24 hours, The result of observing and judging whether or not the display by the reverse twist arrangement state is held is shown. The O mark indicates that it was well maintained (the reverse twist arrangement was almost maintained in the liquid crystal layer), and the X mark indicates that it was not observed (almost shifted to the spray twist arrangement), and the triangular display indicates the intermediate state. (Some of the reverse twist arrangement is maintained, and some transition to the spray twist arrangement).

When CB15 was used as a chiral agent and the addition amount was adjusted so that the chiral pitch was 8.0 µm, the display by the reverse twist arrangement was maintained satisfactorily at any temperature of -40 ° C, 40 ° C, or 50 ° C. It can be seen that it is. In this way, also for the comparative example, it is possible to make a liquid crystal display device having high memory performance over a wide temperature range by selecting a material or an additive amount of a chiral agent. However, in the liquid crystal display device in which R-811 is added so that the chiral pitch is 8.0 μm, 8.5 μm, and 9.0 μm, and in the liquid crystal display device in which CB15 is added so that the chiral pitch is 9.0 μm, the reverse twist is performed. It can be seen that the temperature range in which the display by the arrangement state is stably held cannot be said to be wide. It can be considered that this is due to the pitch length of the chiral agent changing with temperature.

17 is a graph showing the temperature dependence of the pitch length of a chiral agent. The horizontal axis of the graph represents the temperature in units "° C", and the vertical axis represents the pitch length in units "μm". The broken line a shows the temperature dependence of the pitch length with respect to CB15, and the broken line b shows it with respect to R-811. The amount of pitch change with respect to the temperature varies depending on the material of the chiral material, but it can be seen that even if the material is selected, it varies considerably.

The inventors of the present invention have investigated in more detail the temperature dependence of the display holding (memory property) according to the reverse twist arrangement state.

18 is a table showing the results of the investigation. In Fig. 18, four kinds of liquid crystal display elements (comparative examples) are added for each type of chiral agent added and its amount (chiral pitch p) at 40 ° C, 50 ° C, 60 ° C, 70 ° C, 80 ° C and 90 ° C. After heat treatment at each temperature for 30 minutes, the result of observing and judging whether or not the indication by the reverse twist arrangement state is held is shown. The numbers in the table indicate the number of liquid crystal display elements whose display was held satisfactorily. For example, the notation "3/4" shows that 3 out of 4 liquid crystal display elements favorably hold the display. The X display means that there was no liquid crystal display element that was favorably holding the display.

When the heat treatment temperature is 50 ° C. or less, the display according to the reverse twist arrangement state is maintained in a relatively large number of liquid crystal display elements, but when it is 60 ° C. or higher, memory performance is lost and it can be seen that the transition is to the spray twist arrangement state.

In this way, the reverse twisted nematic type liquid crystal display device according to the comparative example, for example, has high memory at room temperature, but may not be able to hold the display according to the reverse twist orientation at a temperature different from room temperature. It is difficult to hold in the above high temperature state.

Next, a liquid crystal display device according to a fifth embodiment will be described. 1 is a schematic cross-sectional view of a liquid crystal display device according to a fifth embodiment. The manufacturing method of the liquid crystal display device according to the fifth embodiment is almost the same as that of the first embodiment. In the fifth embodiment, the main firing was performed at different firing temperatures between 160 ° C and 260 ° C. In addition, the rubbing treatment was performed under three conditions with the indentation amounts being 0.4 mm, 0.8 mm, and 1.2 mm. In addition, the rubbing treatment was performed such that the twist angle of the liquid crystal display device was 70 ° or 90 °.

Next, CB15 or R-811 made by Melk Co., Ltd. was used as a chiral agent to be added to the liquid crystal material. The chiral agent was added in conditions of a plurality of addition amounts such that when the chiral pitch p and the thickness d of the liquid crystal layer were d / p, for example, 0.33 to 0.53.

Among the liquid crystal materials, for example, a material that can be polymerized by light or heat, for example, UV curable liquid crystal (UV curable material having liquid crystallinity), UCL-001, manufactured by Dainippon Ink Co., Ltd. in the fifth embodiment. Was added. The material is not limited to this. From the viewpoint of memory stability, which will be described later, it is preferable that the material is UV curable. Although materials having no liquid crystallinity can exhibit the same effects as those described later, it is preferable to use an ultraviolet curable material having liquid crystallinity in consideration of orientation.

The inventors of the present invention, based on the total mass of the material (liquid crystal material, chiral agent, and monomer material having ultraviolet curability) that injects the amount of the ultraviolet curable monomer material into the liquid crystal layer 15, 1 wt%, A plurality of liquid crystal display devices were manufactured under three conditions of 2 wt% and 5 wt%.

In the fifth embodiment, after injecting a liquid crystal material containing a chiral agent and a UV curable liquid crystal, ultraviolet rays are irradiated to cause a polymerization reaction of the UV curable liquid crystal, and a polymer (polymer) in the liquid crystal layer 15 ) Was synthesized (polymerization treatment). For the experiment, ultraviolet irradiation was performed for both liquid crystal molecules in the liquid crystal layer 15 in a reverse twist arrangement state and in a spray twist arrangement state. The ultraviolet ray was irradiated under conditions such that the irradiation amount was 18 mW / cm ² and the accumulated exposure amount was 1 J / cm ² , but the ultraviolet irradiation condition was not limited to this.

In the fifth embodiment, the liquid crystal layer 15 contains a polymerizable polymer (polymer) synthesized by irradiating ultraviolet light to a UV curable liquid crystal in a polymerizable material and in the embodiment. The polymerizable material is added in a range of 5% or less with respect to the mass of the liquid crystal layer 15 (the total mass of the liquid crystal material, the chiral agent, and the polymerizable material).

The inventors of the present invention conducted various investigations on the display of the liquid crystal display device according to the fifth embodiment.

19A to 19D are photographs showing results of experiments on memory stability of a liquid crystal display device in which 2 wt% of an ultraviolet curable material is added.

19A is an external photograph showing a liquid crystal display device after irradiating 1J / cm ² with ultraviolet rays to cause a polymerization reaction and synthesizing a polymer (polymer) in the liquid crystal layer 15. The photo on the left shows the appearance of the liquid crystal display element irradiated with ultraviolet light in the spray twist arrangement state, and the photo on the right shows the appearance of the liquid crystal display element irradiated with ultraviolet light in the reverse twist arrangement condition. This point is common to all of FIGS. 19A to 19D.

The liquid crystal display device according to the fifth embodiment displays white color in the spray twist arrangement state and black display in the reverse twist arrangement state. The liquid crystal display element which was in the spray twist arrangement state at the time of ultraviolet irradiation is maintained in the spray twist arrangement state even after ultraviolet irradiation, and the liquid crystal display element in the reverse twist arrangement state at the time of ultraviolet irradiation is maintained in the reverse twist arrangement state after the ultraviolet irradiation. .

19B is an external photograph showing a liquid crystal display device after applying a voltage equal to or greater than a threshold voltage to the upper beta electrode 12a and the lower beta electrode 12b and adding a vertical electric field to the liquid crystal layer 15.

It can be seen that the liquid crystal display element shown in the picture on the left transitions from the spray twist arrangement state to the reverse twist arrangement state. In the liquid crystal display element shown in the photo on the right, the reverse twist arrangement is maintained.

Fig. 19C is a photograph of the appearance of the liquid crystal display device after heat treatment at 90 ° C for 30 minutes. It can be seen that the reverse twist arrangement is maintained stably even after heat treatment at a high temperature of 90 ° C.

19D shows a liquid crystal display after applying a voltage equal to or greater than a threshold voltage causing a reaction to the lower beta electrode 12b and the first and second zell electrodes 12c and 12d, and adding a lateral electric field to the liquid crystal layer 15. It is a picture of the appearance of the device.

In the photo on the left (liquid crystal display element irradiated with ultraviolet light in the spray twist arrangement state) and in the photo on the right (liquid crystal display element irradiated with ultraviolet light in the reverse twist arrangement condition), spray twist arrangement is performed by adding a lateral electric field. It can be seen that the state is transitioning.

From the results shown in Figs. 19A to 19D, the liquid crystal display device according to the fifth embodiment has the switching properties (switching between the reverse twist arrangement state and the spray twist arrangement state) and high memory performance by adding an electric field. It can be seen that it is a liquid crystal display device having (thermal stability) together.

Fig. 20 is a photomicrograph showing a liquid crystal display element (a liquid crystal display element after heat treatment at 90 ° C. for 30 minutes) shown in Fig. 19C. The left side shows a micrograph of the liquid crystal display element irradiated with ultraviolet light in the reverse twist arrangement state, and the right side shows a micrograph of the liquid crystal display element irradiated with ultraviolet rays in the reverse twist arrangement state. In both left and right, a picture taken at the corner of the display area is shown above, and a picture taken at the edge of the display area is shown below. Microscopic observation shows that there is a tens of micrometers of shaking at the boundary between the display area (reverse twist arrangement state) and the non-display area (spray twist arrangement state), but the display area is stable and the reverse twist arrangement state is maintained. have. In addition, a significant difference is not recognized between the liquid crystal display element irradiated with ultraviolet rays in the reverse twist arrangement state (photo on the left) and the liquid crystal display element irradiated with ultraviolet rays in the spray twist arrangement condition (the photo on the right). It can be seen that the reverse twist arrangement is stably held.

Next, the inventors of the present invention experimented on the relationship between the addition concentration of the UV-curable material and the memory properties.

21A to 21D are photographs showing results of experiments on memory stability of a liquid crystal display device in which ultraviolet curable materials are added at different addition amounts (1 wt%, 2 wt%, 5 wt%). Similar to the photographs shown in Figs. 19A to 19D, in Figs. 21A to 21D, the photographs in the left column show the appearance of the liquid crystal display element irradiated with ultraviolet light in the spray twist arrangement state, and the photographs in the right column are in the reverse twist arrangement state. The appearance of the liquid crystal display element irradiated with ultraviolet rays is shown. In addition, in common with FIGS. 21A to 21D, the upper part is an external photograph of a liquid crystal display device manufactured by adding 1% by weight of an ultraviolet-curable material, and a middle part of the liquid crystal display device produced by adding 2% by weight of an ultraviolet-curable material. The external photograph and the lower part show the external photograph of the liquid crystal display device manufactured by adding 5% by weight of the ultraviolet curable material. In addition, cell thickness unevenness was observed in the liquid crystal display device manufactured by adding 1 wt% and 5 wt%.

21A is a photograph showing the appearance of a liquid crystal display device after irradiating 1J / cm ² ultraviolet rays to cause a polymerization reaction and synthesizing a polymer (polymer) in the liquid crystal layer 15.

In any case where the amount of addition was 1 wt%, 2 wt%, or 5 wt%, the liquid crystal display device which was in the spray twist arrangement state during UV irradiation, the spray twist arrangement was maintained even after UV irradiation, and the liquid crystal in the reverse twist arrangement state during UV irradiation It can be said that the reverse twist arrangement is maintained in the display element even after irradiation with ultraviolet rays.

FIG. 21B is an external photograph showing a liquid crystal display device after applying a voltage equal to or greater than a threshold voltage to the upper beta electrode 12a and the lower beta electrode 12b and adding a vertical electric field to the liquid crystal layer 15.

It can be seen that the liquid crystal display element shown in the photograph on the left column transitions from the spray twist arrangement state to the reverse twist arrangement state. In the liquid crystal display element shown in the right column, the reverse twist arrangement is maintained.

Fig. 21C is a photograph of the appearance of the liquid crystal display device after heat treatment at 90 ° C for 30 minutes. It can be seen that even after heat treatment at a high temperature of 90 ° C., the reverse twist arrangement is maintained stably regardless of the amount of ultraviolet curable material added (1 wt%, 2 wt%, 5 wt%).

21D also shows a liquid crystal display after applying a voltage equal to or greater than a minimum physical quantity voltage to the lower beta electrodes 12b and the first and second zell electrodes 12c and 12d and adding a lateral electric field to the liquid crystal layer 15. This is a picture showing the appearance of the device.

In the photo of the left column (liquid crystal display element irradiated with ultraviolet light in the state of spray twist arrangement), in any case of 1 wt%, 2 wt%, or 5 wt% of the addition amount of the ultraviolet-curable material, the spray twist is caused by the addition of a lateral electric field. It is transitioning in an array.

Referring to the photo of the superior column (liquid crystal display element irradiated with ultraviolet rays in the reverse twist arrangement state), for the liquid crystal display element having an amount of ultraviolet curable material of 1 wt% and 2 wt%, spray twist arrangement by addition of a transverse electric field Although it transitions to the state, it can be seen that, for a 5 wt% liquid crystal display device, even when a lateral electric field is added, the reverse twist arrangement state remains the same (does not transition to the spray twist arrangement state).

From the results shown in Figs. 21A to 21D, a liquid crystal display device according to an embodiment in which a polymerizable material is added to a liquid crystal layer, polymerized therein, and a polymer (polymer) is synthesized in the liquid crystal layer, It can be said to be a liquid crystal display device having both switchability (switching between reverse twisted and spray twisted) and high memory (thermal stability). However, when the amount of addition is 5 wt%, in the liquid crystal display element irradiated with ultraviolet rays in the reverse twist arrangement state, polymerization is possible because the transverse electric field after heat treatment was unable to transition from the reverse twist arrangement state to the spray twist arrangement state. It is desirable that the amount of the material added is 5 wt% or less.

In addition, the liquid crystal display element according to the fifth example was displayed at a high contrast ratio even when viewed from the front, like the liquid crystal display element according to the comparative example.

The liquid crystal display device according to the fifth embodiment has high display memory performance (thermal stability) and can hold the display semi-permanently regardless of temperature, even in a high-temperature environment of, for example, about 90 ° C. The display in each arrangement state (reverse twist arrangement state, or spray twist arrangement state) can be stably held. For this reason, it can be used for a liquid crystal display device requiring high reliability, such as for vehicle mounting, aircraft, and outdoor use. In addition, it is compatible with the display at a high contrast ratio. In this way, the liquid crystal display device according to the fifth embodiment is a liquid crystal display device having high display quality.

In addition, it is not necessary to perform ultraviolet irradiation in a state in which a voltage is applied to the liquid crystal display element. It is good to irradiate ultraviolet light in either of two stable arrangement states (reverse twist arrangement state or spray twist arrangement state).

The liquid crystal display device according to the fifth embodiment can be driven by a driving method using a memory property, and is capable of ultra-low power consumption. Especially, when applied to a reflective display, the merits are large, and large-capacity displays at low cost. It is possible to carry out, and in the production, the same effect as in the first embodiment can be exhibited in that the cost increase factor is small compared to a general twisted nematic liquid crystal display device.

Subsequently, the liquid crystal element according to the sixth embodiment will be described.

1 is a schematic cross-sectional view of a liquid crystal device according to a sixth embodiment. The manufacturing method of the liquid crystal element according to the sixth embodiment is substantially the same as that of the first embodiment. In the sixth example, the indentation amount during rubbing was set to 0.4 mm to 1.2 mm. Thereby, the upper and lower alignment films 14a and 14b can express a pretilt angle of about 35 ° to 60 ° with respect to the liquid crystal molecules. Moreover, the chiral agent was added on condition that d / p became 0.25-0.75.

The inventors of the present invention produced several liquid crystal elements having different manufacturing conditions in order to find suitable alignment conditions of the liquid crystal elements. As the alignment film material, a polyimide material having a low side chain density of a material usually used as a vertical alignment film was used, and the firing temperature at the time of forming the alignment film and the amount of indentation during rubbing were set as variable parameters. Specifically, some temperatures were set in the range of 160 ° C to 260 ° C for the firing temperature. Moreover, the indentation amount at the time of rubbing was set to 0.4 mm, 0.8 mm, and 1.2 mm. The film thickness of the alignment film was set to 500 mm 2 to 800 mm 2. The twist angle of the liquid crystal molecules of the liquid crystal layer was set to 90 degrees or 70 degrees. The term "twist angle" as used herein refers to an conceivable angle in the spray twist state, and the actual twist angle in the reverse twist state is (180 ° -φ). This is the same for other examples. The liquid crystal layer thickness was 4 μm. A chiral agent is added to the liquid crystal material constituting the liquid crystal layer, and the added amount is set so that the value of d / p is 0.167 to 0.800. The upper polarizing plate 16a and the lower polarizing plate 16b are arranged so that each transmission axis is substantially parallel to the rubbing direction when the twist angle φ is 90 °, and both are arranged in a cross-Nicol arrangement, and the twist angle φ In the case of 70 °, each transmission axis was positioned 10 ° away from the rubbing direction, and both were arranged in a cross nicol arrangement.

22 is a view showing typical manufacturing conditions and observed images of liquid crystal elements in a display state. Specifically, FIG. 22A is an observation image of a liquid crystal device immediately after transition of the liquid crystal layer from a spray twist alignment state to a reverse twist alignment state partially by application of a voltage, and FIG. 22B is a liquid crystal device after 3 months have elapsed. It is an observation. As shown in Fig. 22A, it can be seen that the liquid crystal element of this example shows a high contrast ratio even when viewed from the front. Moreover, as shown in FIG. 22B, it can be seen that even after 3 months, most of the display is retained.

Fig. 23 is a diagram showing evaluation results of contrast and display retention performance in a liquid crystal device having a pretilt angle of about 46 degrees and a twist angle of 70 degrees. In FIG. 23, the result of evaluating the amount of front contrast and the state retention time for each liquid crystal device produced by setting the d / p value of the liquid crystal layer under a plurality of conditions between 0.167 to 0.800 is shown. have. In addition, the firing temperature of the alignment film of each liquid crystal element was set to 200 ° C, CB15 was used as a chiral agent, and a relatively small value of refractive index anisotropy Δn was used as the liquid crystal material. In addition, with respect to the front contrast, the liquid crystal layer was changed from a spray twist alignment state to a reverse twist alignment state by applying a voltage, and a change over time of the retention performance in the reverse twist alignment state was observed. As a result, for the front contrast, the value of d / p was good between 0.333 and 0.500, and particularly high contrast was obtained at 0.385 or more. When the value of d / p is between 0.167 and 0.286, the transmitted light becomes dark (dark display), and when the d / p is between 0.615 and 0.800, the transmitted light becomes bright (bright display), and both have low contrast. In addition, for the state retention time, d / p = 0.333 or more for 1 hour, d / p = 0.385, d / p = 0.421 for each liquid crystal element or more, d / p = 0.444, d / p In each liquid crystal device of = 0.500, it was possible to obtain a state holding time for more than one week.

Fig. 24 shows the evaluation results of the temperature characteristics of the display holding performance in the liquid crystal element with a pitch p of 8.0 µm to 9.0 µm (a liquid crystal element with a d / p value of 0.444 to 0.500) among the conditions shown in Fig. 23. It is a drawing shown. Here, two types (R-8111, CB15) are also used for the chiral agent. The evaluation here is to observe whether the display in the reverse twist alignment state is maintained after the liquid crystal element is left under each temperature condition for 24 hours. In the case of a temperature condition of 40 ° C, all of the liquid crystal elements other than the liquid crystal elements having a chiral agent of CB15 and a pitch of 9.0 µm exhibited high display retention performance. However, in the case of a temperature condition of 50 ° C, the display holding performance of some liquid crystal elements was lowered. Moreover, in the case of a temperature condition of -40 ° C, the display holding performance was deteriorated in a liquid crystal device having a chiral agent of R-811 and a pitch of 8.0 µm. It can be considered that this result is due to the change in the pitch of the chiral agent depending on the temperature condition, but it can be seen that high display retention performance can be obtained over a wide temperature range by selecting the type of chiral agent or its addition amount. have.

25 is a view showing an observation image of a liquid crystal element used for evaluation shown in FIG. 24. Specifically, FIG. 25A is an observation image of a liquid crystal element made of chiral R-811, pitch 8.0 μm, and FIG. 25B is an observation image of a liquid crystal element made of chiral R-811, pitch 8.5 μm, FIG. 25C Is an observation image of a liquid crystal element made of chiral R-811, a pitch of 9.0 μm, FIG. 25D is an observation image of a liquid crystal element made of chiral CB15, a pitch of 8.0 μm, and FIG. 25E is a chiral substance CB15, pitch 9.0 It is an observation image of a liquid crystal element set to μm. The pretilt angle of each liquid crystal element is about 46 degrees. It can be seen that any liquid crystal element has high front contrast and excellent display retention performance.

Fig. 26 is a view showing an observation image of a liquid crystal element with pitch conditions of 9 μm (short pitch condition) and 12 μm (long pitch condition). Specifically, FIG. 26A is an observation image before the voltage is applied to the liquid crystal element in the short pitch condition, FIG. 26B is an observation image immediately after the voltage is applied to the liquid crystal element in the short pitch condition, and FIG. 26C is the liquid crystal in the long pitch condition It is an observation image before voltage application of an element, and FIG. 26D is an observation image immediately after voltage application of a liquid crystal element in a long pitch condition. 26E shows the relationship between the rubbing direction and the alignment state in each liquid crystal element. In addition, the pretilt angle of each liquid crystal element is about 46 degrees, and the production conditions are as described above. As shown in Figs. 26A and 26B, the liquid crystal element in the short pitch condition has a high front contrast, and the boundary of the electrode is clearly shown. On the other hand, as shown in Fig. 26c and Fig. 26d, it can be seen that the liquid crystal element of the long pitch condition has a slightly low front contrast, and the boundary of the electrode is indistinct even after the voltage is applied, and the rubbing curve is remarkable. have. It can be seen that the long pitch condition (d / p = 0.333) shown here is a very undesirable condition when the pretilt angle is high (about 46 °). From these results, it can be said that in order to obtain stable display holding performance, it is necessary to satisfy both conditions of a relatively high pretilt angle and a short pitch.

27 to 31 are views showing the optical characteristics of each liquid crystal element corresponding to the production conditions shown in FIG. 24. Specifically, FIGS. 27A, 28A, 29A, 30A, and 31A respectively show visual characteristics, and FIGS. 27B, 28B, 29B, 30B, and 31B respectively show the rubbing direction and the arrangement of the transmission axis of the polarizing plate. 27C, 28C, 29C, 30C, and 31C show contrast characteristics, respectively, and FIGS. 27D, 28D, 29D, 30D, and 31D show transmittance characteristics (T _St ) in a spray twist state, respectively. It shows the transmittance characteristic (T _Ut ) in the reverse twisted state. In addition, the optical characteristics shown in FIG. 27 are those of chiral R-811 and a liquid crystal element having a pitch of 8.0 μm, and the optical characteristics shown in FIG. 28 are those of chiral R-811 and a liquid crystal element having a pitch of 8.5 μm, The optical properties shown in FIG. 29 are those of a chiral R-811 and a liquid crystal device having a pitch of 9.0 μm, and the optical properties shown in FIG. 30 are those of a chiral CB15 and a liquid crystal device having a pitch of 8.0 μm, shown in FIG. The optical properties are those of the chiral CB15 and a liquid crystal device with a pitch of 9.0 μm. The firing temperature of the alignment film is 200 ° C (a pretilt angle of about 35 ° to 60 °) and a twist angle of 70 ° in any liquid crystal element. In the case of any liquid crystal element, the contrast ratio at the front is high (CR = 141 to 677). In particular, the liquid crystal element made of CB15 made by Chiral and 8.0 μm in pitch does not show display inversion at any time and can obtain high visibility. It can be seen that there is (see Fig. 30). And when the pre-tilt angle under this condition was measured, it was found that the pre-tilt angle of about 35 degrees to 60 degrees (deviation in measurement result by measurement method) was shown.

The reason why such a characteristic is exhibited is not fully explained, but generally, in a reverse twist alignment state, it is considered that a large distortion occurs due to the relationship between the pretilt angle of the interface inside the liquid crystal layer and the twist force due to the chiral agent. You can. Due to this distortion, the liquid crystal molecules in the vicinity of the center in the layer thickness direction of the liquid crystal layer are inclined with respect to the substrate plane even in the voltage off state. In general, in a reverse twist orientation, the inclination angle in the bulk is higher than the pretilt angle of the interface. This has also been confirmed in liquid crystal molecule alignment simulations based on continuum theory. Each liquid crystal element of the embodiment makes the pretilt angle very high, so that the inclination angle of the liquid crystal molecules in the vicinity of the center of the layer thickness direction of the liquid crystal layer can be made very high, and the liquid crystal molecules stand up to a state close to the vertical orientation. I guess it is. This makes it possible to obtain a relatively dark black display even in the front direction even in the voltage off state.

Next, the manufacturing conditions and the state of switching of the display state will be described with respect to the liquid crystal element (the liquid crystal element according to the sixth embodiment) manufactured under conditions that can be considered suitable within the above-described verification range. As for the specific production conditions, the alignment film had a firing condition of 200 ° C for 1 hour, and a film thickness of 500 mm to 800 mm. In addition, the indentation amount at the time of the rubbing treatment was 0.8 mm. The twist angle φ of the liquid crystal layer was 90 ° or 70 °, and the layer thickness was 4 μm. ZLI-2293 (manufactured by Melk Co.) was used as the liquid crystal material, and CB15 was used as a chiral agent. The amount of the chiral agent added was such that d / p = 0.5 (pitch 8 μm). The polarizing plates were arranged such that their transmission axes were parallel or orthogonal to the rubbing direction, and the transmission axes of each other were approximately orthogonal to each other. Here, the polarizing plates were arranged so that each transmission axis was parallel to the rubbing direction of the alignment film of the adjacent substrates, respectively.

32 is a diagram showing a state when a voltage is applied to each electrode and switched when the liquid crystal element according to the sixth embodiment is applied. Specifically, FIG. 32A is a view showing the electrode pattern, rubbing direction, and arrangement of polarizing plates, FIG. 32B is an observation image of a liquid crystal element in an initial state, and FIG. 32C is an observation of a liquid crystal element after application of a vertical electric field. Fig. 32D is an observation image of a liquid crystal element after application of a lateral electric field. In the liquid crystal element here, the electrode width of the comb-shaped electrode (first zell electrode 12c and second zl electrode 12d) is 20 μm, and the electrode spacing is 20 μm. In addition, "Ru" shown in FIG. 32A indicates the rubbing direction of the upper substrate, "Rb" indicates the rubbing direction of the lower substrate, and "P" and "A" indicate the transmission axis direction of each polarizing plate.

As shown in FIG. 32B, in the state after completion of the liquid crystal element, the liquid crystal layer is in a spray twist alignment state, and the transmitted light is in a bright state (ie, white display). Then, as shown in Fig. 32C, after a vertical electric field is applied to the liquid crystal layer, the liquid crystal layer transitions to a reverse twist alignment state, and the transmitted light is in a dark state (that is, black display). Then, as shown in FIG. 32D, after applying the transverse electric field to the liquid crystal layer using the zest electrodes 12c and 12d, the liquid crystal layer transitions back to the spray twist state, and the transmitted light is bright as in the initial state. It is (white display). It can be considered as follows that such switching is possible. In the spray-twisted alignment state, the liquid crystal molecules in the center of the layer thickness direction of the liquid crystal layer are oriented in the horizontal direction, but in the reverse twisted alignment state by application of a vertical electric field, in the center of the layer thickness direction of the liquid crystal layer. The liquid crystal molecules are aligned in the vertical direction. Thereafter, the lateral electric field is applied to the liquid crystal molecules at approximately the center of the layer thickness direction of the reverse twisted liquid crystal layer by application of the lateral electric field, and the liquid crystal molecules are aligned again in the horizontal direction. Since this alignment direction is an alignment direction in which liquid crystal molecules should be present at approximately the center of the layer thickness direction of the liquid crystal layer in the spray twist alignment state, it can be considered that the liquid crystal layer transitions to the spray twist state.

Also, as a comparative example, a case where the addition amount of the chiral agent of the liquid crystal element was reduced (d / p <0.25) was confirmed. In the initial state (spray twist alignment state), the bulk of the liquid crystal layer was approximately vertically aligned. It turned out, and it turned out that switching of the contrast state is difficult. In addition, when the pretilt angle is set to approximately 70 ° or higher, it has been found that even if the chiral agent is adjusted in response to this, it is difficult to obtain a contrast state between the spray twist state and the reverse twist state. From this, it can be said that it is necessary to set the relationship between the addition amount of the chiral agent and the pretilt angle as the above conditions in order to achieve bistableness with a relatively black display. Here, the pre-tilt angle was set to 46 degrees, but as is generally known, the pre-tilt angle in this region is very difficult to measure, and the numerical value has an error width. There may be a deviation of ± 15˚ to 30˚ due to differences in measurement methods or measurement accuracy.

According to the liquid crystal element according to the sixth embodiment, bistable display in a bright (bright) display state and a dark (dark) display state with high contrast can be easily realized. In particular, the transmittance of the dark display is low, and a reliable display can be realized even when viewed from the front.

The liquid crystal display device according to the sixth embodiment is capable of driving with a low-power consumption that can be driven by a driving method using memory characteristics, and has a large merit and a large capacity at a low cost, especially when applied to a reflective display. It is possible to conduct. In the production, the cost increase factor is small compared with the general twisted nematic liquid crystal display device, and the same effect as in the first embodiment can be exhibited.

33 is a flow chart showing a method of manufacturing a liquid crystal display device according to a seventh embodiment. The inventors of the present invention prepared a plurality of liquid crystal display elements in accordance with the flow chart shown in this drawing, and considered conditions for achieving good display.

Two transparent substrates on which a transparent electrode, for example, an ITO electrode is formed, are prepared (step S101). Here, a test cell having a parallel plate type electrode was used, and two transparent substrates were cleaned and dried (step S102).

On the transparent substrate, an alignment film material is applied to cover the ITO electrode (step S103). The coating of the alignment film material was performed using a spin coat. It may be carried out by using Furekiso printing or inkjet printing. In this example, the side chain density of the polyimide alignment film material usually used for forming a vertical alignment film is made low and used as an alignment film material. The control of the side chain density is to enable the provision of an appropriate pretilt angle. The alignment film material was applied so that the thickness of the alignment film was 500 mm 2 to 800 mm 2.

Temporary firing (step S104) and main firing (step S105) of the transparent substrate coated with the alignment film material are performed. The main firing was performed by changing the firing temperature between 160 ° C and 200 ° C. In this way, alignment films covering the ITO electrode were formed (steps S103 to S105).

Next, rubbing processing (orientation processing) is performed (step S106). The rubbing treatment is, for example, a process of rotating a roll of a cylindrical roll wound on a cloth at a high speed to rub an alignment film, whereby liquid crystal molecules in contact with the substrate are aligned (orientated) in one direction. The rubbing treatment was performed under three conditions in which the indentation amounts were 0.4 mm, 0.8 mm, and 1.2 mm. In addition, the rubbing treatment was performed such that the twist angle of the liquid crystal display element was 70 degrees or 90 degrees.

Subsequently, in order to keep the thickness of the liquid crystal cell constant, a gap control material is scattered on one of the transparent substrate surfaces by, for example, a dry dispersion method (step S107). A plastic ball having a particle diameter of 4 μm is used as the gap control material. Then, the thickness of the liquid crystal cell was set to 4 μm.

A seal material is printed on the other transparent substrate surface to form a main seal pattern (step S108). For example, a thermosetting sealant containing glass fibers having a particle diameter of 4 μm is printed by a screen printing method. A sealer can also be applied using a dispenser. Moreover, it is not thermosetting property, and you may use the photocurable seal material and the hardening type seal material for light and fever.

The transparent substrate is polymerized (step S109). The two transparent substrates are polymerized at a predetermined position to be cellized, and heat treated in a pressed state to cure the sealant. For example, heat-hardening of a sealing material is performed using a hot press method. In this way, a blank cell is produced.

For example, a nematic liquid crystal is injected into a blank cell by a vacuum injection method (step S110). A chiral agent was added to the liquid crystal. As the chiral agent, CB15 or S-811 manufactured by Melk Co., Ltd. was used. The addition amount of the chiral agent was adjusted so that, when the chiral pitch p and the cell thickness d were set, d / p was, for example, 0.5 to 1.2.

The liquid crystal injection port is sealed with, for example, an ultraviolet curing type end seal material (step S111), and the cells are heated above the phase transition temperature of the liquid crystals to clean up the alignment of the liquid crystal molecules (step S112). Then, it breaks along the damage inscribed on the transparent substrate with a scriber device, and is divided into small cells.

Chamfering (step S113) and washing (step S114) are performed on the cells divided into small portions.

Finally, a polarizing plate is pasted to the surfaces opposite to the liquid crystal layer of the two transparent substrates (step S115). The two polarizing plates were arranged so that the cross nicol and the direction of the transmission axis and the direction of rubbing were parallel. It can also be arranged orthogonally. A power supply was connected between the ITO electrodes of both transparent substrates.

34A and 34B are photographs showing the results of polarization microscopic observation in a display state for a plurality of manufactured liquid crystal display elements. The photograph in FIG. 34A shows the display state when the front view of the liquid crystal display device manufactured under the condition that the pretilt angle is about 35 degrees and d / p is 0.57, and the photo in FIG. 34B shows the pretilt angle of about 45 degrees. It shows that of the liquid crystal display element manufactured on condition of (degree) and d / p being 0.8.

In Fig. 34A, the part that is shown in black (black display) is an area where voltage is applied between the electrodes of both transparent substrates, and the part that is shown in white (white display) is an area where no voltage is applied. The same applies to FIG. 34B. In FIG. 34B, an enlarged photograph of a portion that appears white is also shown.

The white part is visible to the naked eye as a uniform white mark, but when viewed under a microscope, a finely oriented pattern is recognized. This can be thought of as a focal-conic orientation.

34C schematically shows the arrangement of the liquid crystal molecules in the focal-conic alignment. The focal-conic orientation refers to an arrangement in which liquid crystal molecules take a spiral structure in the liquid crystal layer so that the axis of the spiral is parallel to the substrate (upper and lower substrate) surfaces.

On the other hand, in the part shown in black in the photographs of Figs. 34A and 34B, the liquid crystal molecules repel the torsional force imparted by the chiral agent, and the reverse twisting in the direction to be easily twisted from the relationship of the pretilt angle of the upper and lower substrates. It can be considered that the twist arrangement state is indicated. Since the liquid crystal molecules located at the center of the thickness direction of the liquid crystal layer stand in a certain vertical direction, a black display will be obtained. In the manufacturing conditions of the liquid crystal cell shown in the photograph in Fig. 34A and in the production conditions of the liquid crystal cell shown in the photograph in Fig. 34B, since the amount of the chiral agent added is relatively large, distortion (distortion) inside the liquid crystal layer is large, and the liquid crystal It is presumed that the central molecules in the thickness direction of the layer stand up close to the vertical.

The produced liquid crystal display device is in a focal-conic arrangement state in an initial state. When a voltage equal to or higher than the saturation voltage value of the electro-optical characteristic is applied between the ITO electrodes of both transparent substrates (it causes a vertical electric field having a strength equal to or higher than the threshold voltage), the state transitions to the reverse twist arrangement state. From the photographs shown in Figs. 34A and 34B, it can be seen that the produced liquid crystal display device displays at a high contrast ratio even when viewed from the front.

In addition, the memory characteristics of the white display (pochalconic arrangement) and the black display (reverse twist arrangement) are very stable, and microscopic changes in the liquid crystal molecules are observed under a microscope, but are stable over a long period of time, at least over half a year. did.

FIG. 35A shows a 0 ° to 180 ° orientation (left and right orientation) for a liquid crystal display device (a liquid crystal display device showing a display state in FIG. 34B) manufactured under conditions such that the pretilt angle is about 45 ° and d / p is 0.8. ) Is a graph showing transmissivity and time dependence. The horizontal axis of the graph represents the observation angle when the front direction (substrate normal direction) is set to 0 degrees in units of "degrees". The observation angle inclined upward to the right is represented by a positive angle, and the observation angle inclined upward to the left is represented by a negative angle. The vertical axis of the graph represents the transmittance in units of “%”. The curve following the rhombus (indicated by S-t) represents the time dependence of the transmittance in the focal-conic array. The curve connecting the square (indicated by U-t) represents it in a reverse twist arrangement.

In addition, Fig. 35B shows the isocontrast curve of a liquid crystal display device (a liquid crystal display device showing the display state in Fig. 34B) produced under conditions where the pretilt angle is about 45 degrees and d / p is 0.8.

As can be seen from Fig. 35B, a substantially symmetrical isocontrast curve is obtained for the produced liquid crystal display device in all directions. In addition, as shown in Fig. 35A, the liquid crystal display device produced from the fact that almost horizontally symmetrical transmittance and time dependence is obtained even in the focal-conic array (white display) and in the reverse twisted arrangement (black display). It can be clearly seen that is equipped with a contrast characteristic that is symmetrical to the left and right. Thus, the produced liquid crystal display element is a liquid crystal display element excellent in visual characteristics.

For comparison, visual contrast characteristics of the liquid crystal display device according to the embodiment of the invention described in Patent Document 6 are shown in FIG. 35C. This figure is the same drawing as that described in the drawing (Fig. 13 (A)) of Patent Document 6. As can be seen from Fig. 35C, in the liquid crystal display element described in Patent Document 6, the contrast ratio is asymmetric. The liquid crystal display device preliminarily produced according to a flow chart (FIG. 33) showing the manufacturing method of the liquid crystal display device according to the seventh embodiment, compared with the previous invention, realizes the contrast ratio left and right symmetry. Because it is being used, it has excellent visual characteristics. 35C, in the embodiment of the invention described in Patent Document 6, the contrast ratio at the time of front observation is slightly larger than 3, and in the graph shown in FIG. 35A, according to the flow chart shown in FIG. When observing the front side of the manufactured liquid crystal display device, the contrast ratio is calculated to a degree slightly less than 4. As described above, even when viewed from the front, it is possible to display at a high contrast ratio. And these features (height of display quality) are also equipped with the liquid crystal display element (to be described later) according to the seventh embodiment.

The present inventor has studied the condition that the reverse twist arrangement state and the focal-conic arrangement state are realized reversibly by giving a physical action to the liquid crystal layer, for example, so that each arrangement state of the liquid crystal molecules is stabilized together.

Fig. 36 is a graph showing the conditions for enabling the reverse twist arrangement state and the bistable state of the focal-conic arrangement state to be realized. The horizontal axis of the graph represents the pretilt angle in units of degrees, and the vertical axis represents the amount of chiral agent added using d / p.

In this figure, in the combination of the pretilt angle and d / p in the range below the curve following the rhombus, the focal-conic arrangement state is not expressed. That is, if the addition amount of the chiral agent is too small, the spray twist arrangement state appears, not the pocalconic arrangement state.

In addition, in the combination of the pretilt angle and d / p in the range above the squared curve, it is always in a focal-conic arrangement. That is, if the amount of the chiral agent added is too large, the phase transition from the pocalconic arrangement to the reverse twist arrangement cannot be performed.

The curve moves slightly up and down depending on the anchoring strength of the interface or the elastic constant of the liquid crystal, but in the combination of the pretilt angle and d / p in the range between both curves, the reverse twist arrangement state and the focal conic arrangement state Bistable state is realized. The bistable state of the reverse twist arrangement state and the focal-conic arrangement state is a special state that appears when the chirality of chiral agent is controlled within a certain range.

The circle display indicates the display state in FIG. 34B, and indicates the pretilt angle (about 45 °) and d / p (0.8) of the liquid crystal display device showing visual characteristics in FIGS. 35A and 35B.

From the results shown in the figure, it can be seen that the closer the pretilt angle is to the vertical, the easier it is to form a focal-conic arrangement even if the value of d / p is low. According to experiments repeatedly conducted by the inventors of the present invention, even if the pretilt angle is low, if the liquid crystal molecule orientation is brought close to vertical by voltage, the focal-conic arrangement state is observed. If the value was not relatively high, the focal-conic sequence was not expressed.

The reverse twist arrangement state and the bistable state of the focal-conic arrangement state are realized in both of the upper and lower substrates sandwiching the liquid crystal layer, and an alignment treatment in which a pretilt angle of 20 degrees or more and 85 degrees or less is expressed, It can be said that a chiral agent is added to the liquid crystal layer in a range where d / p is 0.5 or more and 2 or less. In addition, when the orientation treatment is performed so that a pretilt angle of 35 degrees or more and 55 degrees or less is expressed in both of the upper and lower plates, when a chiral agent is added in a range where d / p is 0.5 or more and 1.2 or less, It can be said that the bistable state of the reverse twisted state and the focal-conic state is feasible.

The inventors of the present invention produced the liquid crystal display device according to the seventh example based on the above preliminary considerations.

A schematic cross-sectional view within one pixel of the liquid crystal display according to the seventh embodiment is the same as in FIG. 1.

A chiral agent is added to the liquid crystal material forming the liquid crystal layer 15. The arrangement state of the liquid crystal molecules in the liquid crystal cell completion state (initial state) was a focal-conic arrangement. For example, by applying an AC voltage equal to or greater than a threshold voltage between the two beta electrodes 12a and 12b by the power source 20, the arrangement state of the liquid crystal molecules can be transferred from a focal-conic arrangement to a reverse twist arrangement. .

37 to 41, the configuration and manufacturing method of the liquid crystal display device according to the seventh embodiment will be described in detail.

37 is a schematic plan view showing a pattern of an ITO film formed on the upper transparent substrate 11a. In the ITO film shown in this figure, for example, a pixel electrode (electrode forming the upper beta electrode 12a for each pixel) and a taking electrode of the pixel electrode are formed.

The ITO film pattern is formed, for example, by extending the ITO film in a stripe shape in the left and right directions of the drawing. In this drawing, the ITO film constituting the pixel electrode is denoted by 12A ₁ to 12A ₁₀ .

The patterning of the ITO film was performed using a photolitho process after washing the ITO glass substrate. The etching of ITO was performed by wet etching using iron chloride. Patterning may be performed by irradiating a laser beam and removing the ITO film.

38 is a schematic plan view showing a pattern of an ITO film formed on the lower transparent substrate 11b. In the ITO film shown in this figure, for example, a pixel electrode (electrode forming the lower beta electrode 12b for each pixel) and a taking electrode of the pixel electrode are formed.

The ITO film pattern is formed, for example, by extending the ITO film in a stripe shape in the vertical direction of the drawing. In this drawing, parts of the ITO film constituting the pixel electrode are denoted by 12B ₁ to 12B ₉ . The vertical direction of this drawing and the horizontal direction of FIG. 37 are directions perpendicular to each other.

Patterning of the ITO film can be performed by the same method as the method of forming the ITO film pattern described with reference to FIG. 37.

After patterning the ITO film, an insulating film 13 is formed on the lower transparent substrate 11b including the ITO film. The insulating film 13 is not formed, for example, in the extraction electrodes 12BT ₁ to 12BT ₉ (terminal portions). In this drawing, diagonal lines are indicated in regions where the insulating film 13 is not formed. The insulating film 13 can be formed by forming a resistor on the extraction electrode portion or the like, and removing the resistor by lift-off after forming the insulating film, or by using a metal mask to form the resistor with a sputter. Do. In addition, the insulating film 13 may be an inorganic insulating film such as an organic insulating film or SiO₂, SiN _x. You may form it in combination of these. Here, a laminated film of an acrylic organic insulating film and SiO2 was used as the insulating film 13.

For the seventh example, first, a heat-resistant film (polyimide tape) was applied to the extraction electrode portion, etc., and an organic insulating film was spin-coated (spinned at 2000 rpm for 30 seconds) at a film thickness of 1 µm. Next, the lower transparent substrate 11b on which the organic insulating film has been spin-coated is baked at a high temperature at 220 ° C for 1 hour in a clean oven, and then the lower transparent substrate 11b is heated to 80 ° C with a heat-resistant film attached thereto. The SiO₂ film was formed to a thickness of 1000 mm 2 by sputtering (AC discharge). The SiO2 film can also be formed using a vacuum deposition method, an ion beam method, or a CVD method.

Here, if the heat resistant film was peeled off, the organic insulating film and the SiO2 film could be removed with respect to the adhesion point of the heat resistant film. Subsequently, in order to improve the insulation and transparency of the SiO2 film, the lower transparent substrate 11b was baked in a clean oven at 220 ° C for 1 hour at a high temperature.

Although the formation of the SiO2 film is not essential, the insulating property of the insulating film 13 can be improved by forming the SiO2 film. Further, it is possible to improve the adhesion and patterning properties of the first and second zell electrodes 12c and 12d formed on the insulating film 13.

An organic insulating film 13 may not be formed, and the insulating film 13 may be composed of only an SiO ₂ film. Since the SiO ₂ film tends to become porous, in this case, the thickness of the SiO ₂ film is preferably 4000 mm ₂ to 8000 mm ₂ . An inorganic insulating film 13 made of a stack of SiO ₂ film and SiN _x film can also be used.

An ITO film was formed on the insulating film 13. In the ITO film, the lower transparent substrate 11b was heated to 100 ° C, and was formed on the entire substrate by sputtering (alternating discharge). The film thickness was about 1200 mm 2. The ITO film can also be formed using a vacuum deposition method, an ion beam method, a CVD method or the like. This ITO film was patterned by the potoriso process, and the first zell electrode 12c, the second zl electrode 12d, and the extraction electrodes of these electrodes 12c, 12d were formed.

39 is a schematic plan view showing a photomask used for etching an ITO film. The photomask includes a corresponding portion of the first slit electrode 12c, a corresponding portion of the second slit electrode 12d, a corresponding portion of the extraction electrode of the first slit electrode 12c, and a corresponding portion of the extraction electrode of the second slit electrode 12d, And a corresponding portion of the extraction electrode of the lower beta electrode 12b. During etching, an electrode is formed with an ITO film covered at each corresponding portion. The inventors of the present invention have a plurality of electrode widths of 20 µm, 30 µm, and the electrode spacing when the lattice portions of two comb-shaped electrodes are alternately arranged to be 20 µm, 30 µm, 50 µm, 100 µm, and 200 µm. As the electrode pattern of the first, the first zell electrode 12c and the second zl electrode 12d were produced.

Through the above steps, two electrode-attached substrates were prepared (step S101 in FIG. 33). The substrate with two electrodes is washed and dried (step S102). In the case of water washing, pure water is washed. You can also use detergent. It can also be cleaned with either brush cleaning or spray cleaning. After that, it is dehydrated and dried. As a method other than washing with water, it is possible to perform UV cleaning and IR drying.

On the substrate with two electrodes, an alignment film material was applied so as to cover the ITO electrode (step S103). The coating of the alignment film material was performed using a spin coat. It may be carried out by using Furekiso printing or inkjet printing. Usually, the side chain density of the polyimide alignment film material used for forming a vertical alignment film is made low and used as an alignment film material. This is the same material as the alignment film material used in the liquid crystal display device produced for preliminary consideration. The alignment film material was applied so that the thickness of the alignment film was 500 mm 2 to 800 mm 2. Preliminary firing (step S104) and main firing (step S105) of the substrate with an electrode coated with an alignment film material were performed. The main firing was performed at 180 ° C for 1 hour in a clean oven. It may be performed at a temperature of 160 ° C or higher and 180 ° C or lower. Thus, an alignment film covering the ITO electrode was formed (steps S103 to S105).

40 is a schematic plan view showing a part of the formation region of the lower alignment layer 14b formed on the lower substrate 10b. The lower alignment layer 14b is formed in a region where, for example, the first and second zell electrodes 12c and 12d are disposed, and pixels are determined. In this drawing, only the upper left portion is shown as the formation region of the lower alignment layer 14b, but the same is true for other arrangement regions of the plunge electrodes 12c and 12d.

Next, rubbing processing (orientation processing) was performed (step S106). In the rubbing treatment, the indentation amount is 0.8 mm, and the upper alignment layer 14a and the lower alignment layer 14b are both 20 degrees or more and 85 degrees or less, for example, 35 degrees or more and 55 degrees or less, for example, 45 degrees pre-tilt. Each was made to express. Moreover, it implemented so that the twist angle of a liquid crystal display element might be 90 degrees.

In addition, the pretilt angle of this region is very difficult to measure, and the numerical value of 45 ° may contain a small number of errors. Due to differences in measurement methods or measurement accuracy, there may be a deviation of ± 15˚ to ± 30˚.

In order to set the cell thickness to 4 µm, a gap control material having a particle diameter of 4 µm was dispersed on one substrate surface (step S107). In order to make the cell thickness 3 μm or more and 5 μm or less, it is also possible to distribute a gap control material having a particle size of 3 μm or more and 5 μm or less. A seal material was printed on one substrate surface to form a main seal pattern (step S108). Two substrates were polymerized at a predetermined position (step S109), and the seal material was cured.

In the polymerization of the two substrates, when the rubbing direction of the upper alignment layer 14a is the first direction and the rubbing direction of the lower alignment layer 14b is the second direction, the second direction is the upper substrate 10a. Viewed from the normal direction (upper side), based on the first direction, it was performed so as to be 90 ° in the right rotation direction.

Nematic liquid crystals were injected by a vacuum injection method (step S110). As the liquid crystal material, a low refractive index anisotropic material having a refractive index anisotropy Δn of 0.067 was used. A chiral agent was added to the liquid crystal. As the chiral agent, CB15 manufactured by Melk Co., Ltd. was used. The addition amount of the chiral agent was adjusted so that when the chiral pitch was p and the cell thickness was d, d / p was 0.8 (p = 5 μm). d / p is, for example, 0.5 or more and 2 or less and 35 degrees or more when the orientation treatment is performed such that the pretilt angle of 20 degrees or more and 85 degrees or less is expressed in the upper and lower alignment layers 14a and 14b according to the pretilt angle. When the orientation treatment is performed so that a pretilt angle of 55 ° or less is expressed, it may be 0.5 or more and 1.2 or less.

The liquid crystal injection port was sealed with an ultraviolet curing type end seal material (step S111), and the cells were heated above the phase transition temperature of the liquid crystals in order to arrange the alignment of the liquid crystal molecules (step S112). Thereafter, the scriber device was broken along the damage to the transparent substrate, and divided into individual cells. The small divided cells were chamfered (step S113) and washed (step S114).

Lastly, a polarizing plate was pasted to the surface opposite to the liquid crystal layer of the two substrates (step S115). The two polarizing plates were arranged so that the cross nicol and the direction of the transmission axis and the direction of rubbing were parallel. It can also be arranged orthogonally. A power supply was connected to the ITO electrodes of both substrates (the upper and lower beta electrodes 12a, 12b, and the first and second zell electrodes 12c, 12d).

41 is a schematic plan view showing the structure of a liquid crystal display device according to a seventh embodiment. In FIG. 41, all the structures shown in FIGS. 37 to 40 are polymerized. One pixel is defined as a horizontal electrode extending in the left-right direction and a vertical electrode extending in the vertical direction. In this drawing, the cross electrodes are denoted by 12A ₁ to 12A ₁₀ , and a part of the longitudinal electrodes are denoted by 12B ₁ to 12B ₉ . What is shown by the arrow is a pixel defined in a region where the horizontal electrode 12A ₉ and the vertical electrode 12B ₈ overlap when viewed in the direction of the substrate normal. The lateral electrode 12A ₉ in this pixel corresponds to the upper beta electrode 12a in FIG. 1, and the vertical electrode 12B ₈ corresponds to the lower beta electrode 12b.

42A to 42C are external photographs of the liquid crystal display device according to the seventh embodiment. 42A to 42C show the electrode widths of the slit portions of the first and second slit electrodes 12c and 12d are 20 µm, and the slit portions of both slit electrodes 12c and 12d are alternately arranged. This is a front observation photograph of the regions where the zlatch electrodes 12c and 12d are formed in the liquid crystal display device manufactured with a spacing of 20 μm.

42A shows a photograph of the appearance of the liquid crystal display device in a completed state (initial state). As for the initial state, the liquid crystal molecules are in a focal-conic arrangement state. Visually, a uniform white mark was obtained.

In this state, a voltage was applied between the upper beta electrode 12a and the lower beta electrode 12b. A vertical electric field is generated in the liquid crystal layer 15 by application of a voltage to both electrodes 12a and 12b.

42B is a photograph of the appearance after voltage is applied to the electrodes 12a and 12b. It can be seen that the whole transitioned from the pocalconic arrangement to the reverse twist arrangement. Moreover, it can be seen from the front that a black display is obtained. In addition, on the contrary, it is confirmed that a vertical electric field is generated in the liquid crystal layer 15 by application of a voltage from this to both electrodes 12a and 12b.

Next, in the FFS mode, a lateral electric field was generated in the liquid crystal layer 15.

Fig. 42C is an external photograph after driving the liquid crystal display device in the state shown in Fig. 42B in the FFS mode. It can be seen that the front surface is retranslated to the same state as the initial state (the focal-conic array state).

The liquid crystal display element according to the seventh embodiment is a liquid crystal display element capable of switching between a focal-conic arrangement state and a reverse twist arrangement state. The former can be transferred to the latter by application of a vertical electric field. Moreover, the latter can be shifted to the former by application of a lateral electric field. In addition to driving in the FFS mode, driving in the IPS mode can be employed as a method of transitioning the reverse twist arrangement state to the focal-conic arrangement state.

When a vertical electric field is added to a liquid crystal layer in a focal-conic arrangement in which liquid crystal molecules are spirally drawn in an in-plane direction, the orientation of the liquid crystal layer in the center of the thickness direction of the liquid crystal layer is vertically shifted by 90 degrees due to the influence of the interface. Tilts. In this way, it can be considered to switch from the focal-conic arrangement state to the reverse twist arrangement state. In addition, it can be considered that the switching from the reverse twist arrangement state to the focal-conic arrangement state is made by dispersing the alignment of the liquid crystal molecules at the interface of the reverse twist arrangement state by the addition of the lateral electric field.

The liquid crystal display device according to the seventh embodiment is a liquid crystal display device in which the focal-conic arrangement state and the reverse twist arrangement state transition to each other and the states are stably held depending on the direction of the electric field to be added. A bistable display in a high contrast white display state or a black display state can be easily realized. In particular, the black display is dark, and it is possible to realize a clear display even when viewed from the front. For this reason, it can be suitably applied to any of a transmissive display, a tuban display, and a reflective display. Further, the liquid crystal display element according to the seventh embodiment is a liquid crystal display element having a contrast ratio that is symmetrical to the left and right.

In the liquid crystal display device according to the seventh embodiment, for example, display using memory characteristics is possible. Pixels that want to display white are in a focal-conic arrangement, and pixels that want to display black are in a reverse twist arrangement. At least, a vertical electric field is applied to a pixel to be changed from a white display to a black display. A vertical electric field may be applied to the pixels that want to maintain the black display. Conversely, a horizontal electric field is added to at least a pixel that is to be changed from a black display to a white display. A horizontal electric field may be applied to pixels that want to maintain white display.

The liquid crystal display device according to the seventh embodiment can be driven like the second embodiment. The display can be held semi-permanently and is compatible with a high contrast ratio.

The liquid crystal display device according to the seventh embodiment can be driven by a driving method using a memory property, and is capable of ultra-low power consumption. In particular, when applied to a reflective display, the merits are large, and large-capacity displays at low cost. It is possible to carry out, and in the production, the same effect as that of the first embodiment can be exhibited in that the cost increase factor is small compared to a general twisted nematic liquid crystal display device.

In the above, the present invention has been described in accordance with examples and the like, but the present invention is not limited to these.

For example, in the first embodiment and the like, the polarizing plate is arranged in cross nicol to form a liquid crystal display device with no-marley white display, but the polarizing plate may be arranged in parallel nicol to form a liquid crystal display device with no-marley black display. It would be easy to realize the display with high contrast ratio just by making it white. In the case of a no-marley white display, in order to obtain a good black display, the angle formed by the transmission axis directions of the upper and lower polarizing plates 16a and 16b is preferably around 90 degrees.

Moreover, although the orientation process was performed by rubbing about the Example, the orientation process can be performed using other orientation processing methods, such as a photo-alignment method and a gradient direction vapor deposition method, for example.

In addition, in the embodiment, only electrodes on the lower substrate 10b, electrodes for causing a lateral electric field were formed in all and part of the liquid crystal layer 15 (pixel region), but not only on the lower substrate 10b, but also on the upper substrate 10a. It can also be formed. The electrode causing the lateral electric field may be formed on at least one of the upper substrate 10a and the lower substrate 10b.

In addition, in the fifth embodiment, a polymerizable material was added under the conditions of 1 wt%, 2 wt%, and 5 wt% with respect to the mass of the liquid crystal layer 15. It is not limited to the range of 1 wt% or more and 5 wt% or less, and even if the amount of the polymerizable material added is in the range of 0.5 wt% or more and 5 wt% or less, the same effect can be obtained.

In addition, it will be apparent to those skilled in the art that various changes, improvements, and combinations are possible.

It can be used for the entire liquid crystal device, for example, for the entire liquid crystal display device that performs simple matrix driving. In addition, it can be used for liquid crystal display devices that require low power consumption, wide visual characteristics, and low price.

In terms of memory characteristics, it can be suitably applied to reflective, transmissive, and projection displays, such as display surfaces of information devices (personal computers, portable information terminals, etc.) that do not require frequent replacement due to power saving. Do. In addition, it can be used for information display surfaces of magnetically or electrically recorded cards, children's toys, electronic paper, and the like.

In addition, it can be used for a display to maintain the display even in the event of a power failure due to a disaster.

10a upper substrate
10b lower substrate
11a Upper transparent substrate
11b Lower transparent substrate
12a upper beta electrode
12b lower beta electrode
12c first zell electrode
12d second zell electrode
13 insulating film
14a upper alignment layer
14b lower alignment layer
15 liquid crystal layer
16a upper polarizer
16b lower polarizer
20 power
21 slit electrode
21a slit
22, 22a common ship
23 scan lines
24 semiconductor film
25 source electrode
26, 26a drain electrode
27 signal lines
28 insulating film
31 ~ 33 driver
34 pixels

Claims (5)

Alignment processing is performed on each one surface, and the first substrate and the second substrate disposed opposite to each other,
A liquid crystal layer is provided between one surface of the first substrate and one surface of the second substrate, and is composed of a liquid crystal material having a dielectric constant anisotropy.
The first substrate and the second substrate set the orientation of the alignment treatment so that the liquid crystal molecules of the liquid crystal layer are distorted in the first direction, and further, each of the liquid crystal molecules is in contact with the liquid crystal layer. The pretilt angle applied to the liquid crystal molecules of the liquid crystal layer at the interface is 35 degrees or more,
The liquid crystal layer contains a chiral agent having a property that causes the liquid crystal molecules to be twisted in a second direction opposite to the first direction.
The chiral agent is a liquid crystal element added so that the ratio d / p of the chiral pitch to the layer thickness d of the liquid crystal layer is 0.385 or more and 0.5 or less. The liquid crystal layer according to claim 1, wherein the twist angle in the second alignment state is 70 ° or more and 90 ° or less. Further comprising an electric field applying means for applying an electric field to the liquid crystal layer,
The liquid crystal layer transitions to the first alignment state by applying an electric field in a direction substantially perpendicular to each surface of the first substrate and the second substrate by the electric field applying means, and the first The liquid crystal device according to claim 1 or 2, wherein the liquid crystal layer transitions to the second alignment state by applying an electric field in a direction substantially parallel to each surface of the substrate and the second substrate. The liquid crystal device according to claim 1, wherein the pre-tilt angle is smaller than 70 °. A liquid crystal display device comprising a plurality of pixel portions, each of the plurality of pixel portions being constituted by using the liquid crystal element according to claim 1.

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