JPWO2002006887A1 - Liquid crystal display element - Google Patents

Abstract

(57) [Abstract] A liquid crystal display element using nematic liquid crystal is provided, which has high definition, a wide viewing angle, and low power consumption, and which combines memory properties and wide viewing angle display characteristics. The liquid crystal display element using nematic liquid crystal comprises a pair of transparent substrates (SUB1, SUB2), a liquid crystal layer (LCL) disposed between the pair of substrates (SUB1, SUB2), a group of electrodes for applying an electric field having a component substantially parallel to the substrate surfaces to the liquid crystal layer (LCL), and an alignment layer disposed between the liquid crystal layer (LCL) and at least one of the pair of substrates (SUB1, SUB2), which is subjected to liquid crystal alignment regulation treatment in multiple directions, with all of the angles formed by the layers in the substrate plane being substantially equal and all of the rise angles from the substrate plane in each liquid crystal alignment regulation direction being substantially 0 degrees.

Description

Detailed Description of the Invention

The present invention relates to a liquid crystal display element, and more particularly to a low-power, high-resolution liquid crystal display element. Background Art: Conventionally, liquid crystal display elements using nematic liquid crystals have been used as display elements for portable information terminals such as mobile phones, taking advantage of their low driving voltage and low power consumption characteristics. With the rapid spread of portable information terminals in recent years, the production volume of such display elements has been expanding.
At the same time, demands for higher display performance, such as an increased number of display pixels (characters), are also growing. However, because portable devices must maintain or extend their battery-powered continuous operating time, technologies are needed that not only achieve the aforementioned high resolution and other advanced display functions but also achieve low power consumption. One such technology is the use of LCD elements with so-called display memory, which retains the display even when the voltage applied to the LCD element is turned off. By utilizing this memory characteristic, power consumption can be reduced in principle when the display content remains unchanged. Power consumption can also be reduced by applying voltage only to pixels whose display content has changed. Furthermore, when using conventional twisted nematic (TN) or super twisted nematic (STN) display elements with simple matrix drive, there is a well-known limit to the number of pixels that can be displayed due to the duty ratio. However, utilizing the memory characteristic eliminates this limit. A specific example of the prior art having such a display memory property is, for example, one using a ferroelectric liquid crystal [Applied Physics Letters, 36,899 (1999)].
80), JP-A-56-107216], and a combination of a nematic liquid crystal and a liquid crystal alignment layer subjected to a fine grating treatment (JP-A-11-51380
However, among the above-mentioned conventional technologies, the former one using ferroelectric (chiral smectic C) liquid crystal has a high speed response due to the ferroelectric effect, and is capable of wide viewing angle display by using switching between two homogeneous alignment states within the substrate plane, but compared to general liquid crystal display elements using nematic liquid crystal,
The layer structure unique to smectic liquid crystals makes alignment difficult to control, and once damaged by mechanical impact, this layer structure is difficult to recover, preventing widespread practical application. On the other hand, the latter, which uses nematic liquid crystals and a liquid crystal alignment layer with a fine grating, utilizes the flexoelectric effect to switch between homeotropic (vertical) and hybrid alignment states. However, this hybrid alignment results in poor viewing angle characteristics in certain directions. Furthermore, to reduce the driving voltage, a liquid crystal material with a sufficiently large flexoelectric coefficient is required. However, such liquid crystal materials are not commonly known, resulting in high driving voltage and power consumption. This technology has also not been widely adopted. As described above, with conventional technologies, it has been difficult to achieve both low power consumption due to memory properties and wide viewing angle display in liquid crystal display devices using nematic liquid crystals, which do not have a layer structure and are easy to align. In view of the above, an object of the present invention is to provide a high-resolution, wide-viewing-angle, low-power liquid crystal display device using nematic liquid crystals that combines memory properties and wide-viewing-angle display characteristics. The features of the present invention are described below. To achieve wide-viewing-angle display characteristics, switching between multiple liquid crystal alignment states must occur primarily within the plane of the substrates sandwiching the liquid crystal layer. At the same time, for these liquid crystal alignment states to have memory properties, these multiple alignment states must be energetically stable even after the applied voltage is turned off. The energy of the liquid crystal alignment state when no voltage is applied and no electric field is applied to the liquid crystal layer is expressed as the sum of the elastic deformation energy of the liquid crystal layer itself and the interfacial interaction energy between the liquid crystal layer and the alignment layer on the substrate surface. Therefore, by using an interfacial interaction that ensures sufficient energy stability for all multiple alignment directions within the substrate plane, the multiple alignment states of the liquid crystal layer that switch within the substrate plane can be stabilized. Furthermore, to stably maintain these multiple alignment states and achieve stable switching between them, it is desirable that the energetic stabilities of the multiple alignment directions due to the interfacial interaction be equivalent. Specifically, a means for obtaining liquid crystal interface alignment in which multiple alignment directions within the substrate plane are energetically equivalent and stable is to use an alignment layer that has been subjected to liquid crystal alignment restriction (anchoring) treatment in multiple directions in the substrate plane, all of which form approximately equal angles with each other, and to make the rising (pretilt) angle of the liquid crystal molecules from the substrate plane in the alignment restriction direction approximately 0 degrees in all of these multiple liquid crystal alignment restrictions. This effect will be explained below using an example in which there are two alignment restriction directions within the substrate plane. Even in the case in which there are more alignment restriction directions, the rising (pretilt) angle described later can be adjusted.
The effect is the same except for the condition of the angle. As shown in Figure 1, an alignment layer having liquid crystal alignment constraints in two different directions, where the respective constraints are not extremely different, generally has a liquid crystal easy axis in the composite direction due to the competition between the alignment constraints in the two directions. If the angles between these two alignment constraint directions are not all 90 degrees, as in Figure 1(a), this symmetry is broken, and the easy axis in the direction that bisects the smaller relative angle becomes more energetically stable, and the equivalence between the two liquid crystal easy axes to achieve a bistable state is lost. Therefore, to make the alignment stability of the two easy axes equivalent, the angles between the two alignment constraint directions, which are the source of this, must all be equal, approximately 90 degrees, as in Figure 1(b). Furthermore, as mentioned above, when the angles between the two alignment constraint directions in the substrate plane are approximately 90 degrees,
Even in cases where the orientational force is 0.05°, when the orientational force is applied by a rubbing process, which is typically used to generate a liquid crystal orientational force, an angle of rise of the liquid crystal orientation from the substrate surface (pretilt angle; in typical rubbing processes, this angle is at least 1° and ranges from several degrees to several tens of degrees) inevitably occurs, and the resulting symmetry breakdown must also be considered. A liquid crystal orientational direction with a pretilt angle can be represented as a directed vector with an arrow pointing in the direction of rise of the liquid crystal molecules from the substrate surface, as shown in Figure 1(c). Therefore, considering the case of orientational directions with two mutually orthogonal pretilt angles as shown in Figure 1(c), the direction with the aligned arrows (indicated by the thick dotted line) among the two possible easy axes is more energetically stable. In this case, the equivalence between the two easy axes for achieving a bistable state is also lost. Considering the symmetry breakdown caused by this pretilt, it can be seen that equivalence between the two easy axes is achieved if at least one of the two orientational force directions has a pretilt angle of approximately 0°, as shown in Figure 1(d). On the other hand, when there are two or more alignment control directions, it is necessary to set the pretilt angle of all alignment control directions to approximately 0 degrees as shown in Figure 1(b) in order to obtain the equivalence between the resulting plurality of easy axes. As a method for providing the liquid crystal alignment control with the pretilt angle of approximately 0 degrees, which is necessary to ensure the equivalence of such a plurality of easy axes, for example, linearly polarized ultraviolet light is used to
The method may be a so-called photo-alignment method in which a surface previously coated with a photosensitive material having sensitivity to this light is irradiated, or a method in which a probe capable of applying stress to the substrate surface is scanned using an apparatus similar in basic structure to an apparatus known as an atomic force microscope (AFM), or a method in which a surface previously coated with a photosensitive material is scanned in an arbitrary pattern with a beam of light capable of inducing a chemical reaction, such as ultraviolet laser light. In addition, to obtain an alignment layer subjected to a liquid crystal alignment control treatment in multiple directions, for example, a photo-alignment treatment in which linearly polarized ultraviolet light is uniformly irradiated over the entire area to be treated is performed.
This can be achieved by repeating the process multiple times, changing the linear polarization direction. For the multiple liquid crystal easy axes obtained as described above to be sufficiently stable, precise control of the relative strength of the alignment constraint forces of the multiple competing alignment constraint directions, which are the source of the conflict, is required. This is evident from the fact that the above-mentioned competition does not occur when the relative strengths are extremely different. In the case of alignment constraint forces in two directions, for example, precise control of the ratio of the relative alignment constraint forces can be achieved particularly easily by dividing and arranging multiple regions with two different alignment constraint directions within the substrate plane while controlling the total area ratio of the two regions, such as in a checkerboard pattern. Next, to achieve the in-plane switching of nematic liquid crystals to obtain the wide viewing angle characteristics described above, a group of electrodes can be used to apply an electric field with a component approximately parallel to the substrate plane to the liquid crystal layer. As a form of in-plane switching, alignment layers that make the above-mentioned multiple alignment directions energetically stable may be disposed on both substrates, thereby generating in-plane switching at both substrate interfaces. Alternatively, such an alignment layer may be disposed on only one substrate, and the other substrate may be imparted with alignment ability by a conventional rubbing method, thereby generating in-plane switching only at the interface of one substrate. In either case, wide viewing angle characteristics can be achieved by in-plane switching of the substrates. As display methods, for example, in the former case, a birefringence optical mode display between homogeneous states with different in-plane orientations can be used, and in the latter case, an optical rotation mode display between a homogeneous and twisted planar state can be used. When using the latter bistable switching between the homogeneous and twisted planar states, twist deformation of the liquid crystal layer can cause a large energy difference between these bistable switching states, which can result in undesirable driving characteristics such as a large asymmetry in the switching threshold voltage. To reduce this, a liquid crystal composition containing an appropriate amount of an asymmetric molecular component as a chiral dopant can be used to stabilize the twisted planar state. The liquid crystal material for the liquid crystal display device of the present invention can be a material with a positive or negative dielectric anisotropy (Δε). Furthermore, by using a liquid crystal material whose Δε sign can be either positive or negative depending on the frequency of the applied AC electric field, and by using an AC electric field frequency that makes Δε positive for one-way switching between bistable states and an AC electric field frequency that makes Δε negative for reverse switching, bidirectional switching between the two states is possible with just a pair of comb-tooth electrodes, thereby simplifying the electrode structure and manufacturing process. Furthermore, in addition to the comb-tooth electrode group, a pair of planar electrodes provided on both substrate surfaces can be used to apply an electric field to the liquid crystal layer approximately perpendicular to the substrate surfaces, as in a conventional twisted nematic (TN) system, to transition the twisted planar state to a homeotropic (vertical alignment) state. When the electric field is turned off from this state, the liquid crystal transitions to a homogeneous state. Therefore, applying such a vertical electric field can also enable switching between states, which is particularly effective for simultaneous refreshing of all pixel displays. BEST MODE FOR CARRYING OUT THE INVENTION The following describes in detail embodiments of the present invention. Fig. 2 is a diagram showing the configuration of a liquid crystal display element showing a first embodiment of the present invention. In this figure, two transparent glass substrates with a thickness of 1.1 mm and polished surfaces were used as substrates SUB1 and SUB2. A pair of comb-tooth electrodes EL2A and EL2B were formed on substrate SUB1 by patterning a transparent conductive layer made of the same ITO (indium tin oxide) formed on the substrate, and an insulating protective film IL1 made of silicon nitride and having a thickness of 600 nm was further formed thereon. Similarly, another pair of comb-tooth electrodes EL1A and EL1B was formed on the above comb-tooth electrode EL
A transparent conductive layer made of the same ITO as that formed on the insulating film IL1 is patterned in a direction substantially perpendicular to the insulating film IL2, and a 200 mm thick film made of silicon nitride is further formed on the transparent conductive layer.
An insulating protective film IL2 having a thickness of nm was formed. LCL is a liquid crystal layer. The longitudinal directions of the comb-tooth electrodes EL1 and EL2 are the y-axis and x-axis directions, respectively, in the coordinate system shown in the figure. The comb-tooth electrodes have a width of 6 μm and an electrode spacing of 4 μm. The number of inter-comb gaps in the figure is shown as three for ease of explanation, but the actual device has eight. Next, a solution of SE7210, a solvent-soluble polyimide precursor manufactured by Nissan Chemical Industries, Ltd., was applied to the insulating film IL2, heated to 200°C, and left for 30 minutes to remove the solvent, yielding a dense polyimide film. The surface of the polyimide film thus obtained was then subjected to a tensile test using a device with the same structure as the AFM device. The Si3
A probe made of N4 or Si with an atomically sharpened tip was used to scan to form a linear stress application pattern. This probe scanning pattern is explained using Figure 3. The scanning was controlled to perform linear scans in approximately orthogonal directions, represented by SCN1A and SCN1B, in each of the small areas divided into square checkerboard patterns in Figure 3. Each of the small square areas measured approximately 1 μm square, and the probe scanned linearly within the area at a density of 35 lines/μm to form multiple linear stress application patterns. These scans were performed in a single stroke, with adjacent scan directions in opposite directions to each other, so that the pretilt angle of the liquid crystal alignment was approximately 0 degrees. Note that these pattern shapes and pattern densities are merely examples and should be adjusted according to the characteristics of the liquid crystal material used. The grid direction and linear scan directions SCN1A and SCN1B are set to form approximately 45-degree angles with the x-axis and y-axis, respectively, in the coordinate system shown in Figure 2. The alignment layer AL1 thus formed, in which a plurality of regions having a plurality of liquid crystal easy axis directions are arranged in the substrate plane, is formed as follows:
This resulted in an alignment layer with two easy alignment axes, LD1A and ALD1B. On the other substrate, SUB2, a dense polyimide film was obtained in the same manner as above, and then the surface of the alignment film was rubbed with a buff cloth attached to a rubbing roller to impart liquid crystal alignment ability with a single easy alignment axis represented by ALD2 in the x-axis direction of the coordinate axes in the figure. Next, these two substrates were placed with their surfaces having liquid crystal alignment ability facing each other, and a cell was assembled with spacers made of dispersed spherical polymer beads and a peripheral sealant interposed therebetween. Next, a nematic liquid crystal composition ZLI manufactured by Merck was placed between the substrates of this liquid crystal cell.
-4535 (dielectric anisotropy Δε is positive and its value is 14.8, refractive index anisotropy Δn
The liquid crystal panel was obtained by vacuum-injecting a liquid crystal layer having a refractive index of 0.0865 and sealing it with a sealing material made of ultraviolet-curable resin. The thickness of the liquid crystal layer was adjusted to 6.4 μm with the spacer. Therefore, the retardation (Δn
Next, this panel was attached to two polarizing plates POL1 and POL2 (G122 manufactured by Nitto Denko Corporation).
0DU), and the polarization transmission axis POL1 of one of the polarizing plates is aligned with the rubbing direction AL
The first electrode POL1 was arranged parallel to the first comb-tooth electrodes EL1A, EL1B, and the second electrode POL2 was arranged perpendicular to the first comb-tooth electrodes EL1A, EL1B. After that, a driving circuit, a backlight, etc. were connected to obtain a liquid crystal display element. The switching characteristics of the liquid crystal display element of this first embodiment will be explained with reference to Figure 4. In the figure, V1 and V2 represent the voltages of the first comb-tooth electrodes EL1A, EL1B and the second comb-tooth electrodes EL1C, EL1D, and the second comb-tooth electrodes EL1E, EL1F, and the second comb-tooth electrodes EL1G, EL1H ...
4 shows the waveform of the voltage applied between the comb-tooth electrodes EL2A and EL2B, and Tr shows the accompanying change in transmittance of the liquid crystal element. As shown in Fig. 4, the liquid crystal element shown in this embodiment can be switched between two memory states, bright and dark, by selectively applying an AC voltage as V1 or V2. In this embodiment, the switching AC voltage (frequency 1 kHz) is 8 V as V1.
Vpp and V2 were 6 Vpp, and some drive voltage asymmetry was observed. Figure 5 shows schematic diagrams of the liquid crystal alignment states in the liquid crystal layer corresponding to the dark state (see Figure 5(a)) and the bright state (see Figure 5(b)). As shown in this figure, switching between these two states is achieved by liquid crystal molecular alignment switching approximately within the substrate plane. Next, the viewing angle characteristics of the liquid crystal display element of this example were measured using a Minolta liquid crystal viewing angle measuring device CV-1000. Wide viewing angle characteristics were obtained, with a contrast ratio of 10:1 or greater across the entire viewing angle range of 140 degrees vertically and horizontally, and no grayscale inversion. Visual image quality inspection also revealed no significant change in display color, even when viewed from an oblique angle, and a highly uniform display was obtained. Next, a second example of the present invention will be described. In the first embodiment, a photosensitive material film was formed on the surface of one of the substrates as the alignment layer, and the surface was scanned with ultraviolet light. In addition, CB-15 manufactured by Merck was used as the chiral dopant for the liquid crystal material, and the helical pitch length of the composition was adjusted to about 15 μm. In particular, a mixture of [Chemical Formula 1] containing a diazobenzene group and 4,4'-diaminodiphenylmethane in an equimolar ratio was used as the diamine compound, and a polyamic acid was synthesized with the acid anhydride of pyromellitic dianhydride and/or 1,2,3,4-cyclobutanetetracarboxylic dianhydride. After coating the surface of the substrate, the liquid crystal display element was dried for 200 minutes.
The film was baked at 400°C for 30 minutes, imidized, and then a GaN laser beam with a wavelength of 420 nm was used as a scanning beam to arrange the same pattern as in Example 1 on the surface to form an alignment layer.
Alternatively, a laser may be used. Also, as the photosensitive material, [Chemical Formula 2] or [Chemical Formula 3] may be used instead of [Chemical Formula 1]. 6 is a diagram showing the electro-optical characteristics of this embodiment corresponding to FIG. 4. In this embodiment, the switching AC voltages are 5 Vpp as V1 and 4.8 Vpp as V2.
p, and the energy stabilization effect of the twisted planar state due to the addition of a chiral dopant almost completely eliminated the asymmetry in the drive voltages V1 and V2. In the same viewing angle measurement as in Example 1, a highly uniform display with wide viewing angle characteristics almost identical to Example 1 was obtained. Next, Example 3 of the present invention will be described. Example 3 was prepared by fabricating a liquid crystal display element in the same manner as Example 1, except that, as shown in Figure 7, Merck TX2A was used as the liquid crystal material and a dual-frequency drive circuit was used, with only one set of comb-tooth electrodes. The liquid crystal composition TX2A is a nematic composition for dual-frequency drive, with its dielectric anisotropy (Δε) being positive at low frequencies and negative at high frequencies, and its crossover frequency is 6 kHz. The drive waveform and electro-optical characteristics of this Example are shown in Figure 8. As shown in this figure,
In this example, switching from a dark (homogeneous) state to a bright (twisted planar) state was achieved using a 4 kHz, 8 Vpp AC voltage, which makes TX2A's Δε positive, as V1, and an 8 kHz, 10 Vpp AC voltage, which makes Δε negative, as V2, for reverse switching. This enabled switching between these two states with a single set of comb-shaped electrodes. In this example, viewing angle measurements similar to those in the first example demonstrated a highly uniform display with wide viewing angle characteristics similar to those in the first example. Next, a fourth example of the present invention will be described. A liquid crystal display element was fabricated in the same manner as in the third example, except that, as shown in Figure 9, a pair of parallel plate electrodes was added to each of the substrates SUB1 and SUB2. The pair of parallel plate electrodes was composed of ITO transparent electrodes and connected to a drive circuit to which an AC voltage V2 was applied. The electro-optical characteristics and viewing angle characteristics of this example were similar to those of the third example, but:
By applying a 4 kHz, 20 Vpp AC voltage between the added parallel plate electrodes, it was possible to refresh the display of multiple pixels from a bright state to a dark state at once. Next, a fifth embodiment of the present invention will be described. In the third embodiment described above, as shown in Figure 10, a light reflector REF and a λ/4 plate QP were added on top of the substrate SUB1, and the cell gap was reduced to half, 3.
A reflective liquid crystal display element was fabricated in the same manner as in Example 3, except that the thickness of the alignment layer AL1 was set to 2 μm, and the stress value applied by the probe when scanning the alignment layer AL1 in two scanning directions SCN1A and SCN1B was adjusted to provide two liquid crystal alignment easy axes ALD1A and ALD2A that form a 45-degree angle with each other. This was used as Example 5. In this example, the retardation axis direction of the λ/4 plate QP was set to an angle of approximately 45 degrees with the transmission axis of the polarizer POL2, and the alignment easy axis ALD1A of the alignment layer AL1 was in the same direction as ALD2, while ALD1B was rotated 45 degrees relative to ALD2. Due to the above-mentioned configuration of the alignment layer AL1, the alignment state of the two stable liquid crystal layers in this example was a 45-degree twisted structure similar to that shown in Figure 5(b), and the alignment state of the two stable liquid crystal layers in this example was a 45-degree twisted structure similar to that shown in Figure 5(b).
As with the transmissive configuration shown in the figure, the liquid crystal is dark in the uniform alignment state and bright in the (45°) twisted planar state. The electro-optical characteristics and viewing angle characteristics of this embodiment are almost the same as those of the third embodiment, but
The difference is that the optical characteristic is obtained as reflectance instead of transmittance. Next, a sixth embodiment of the present invention will be described. In the above-mentioned first embodiment, the surface of the polyimide film formed on the substrate SUB1 side was once rubbed in the direction of 45 degrees to the x-axis of the coordinate axes in Figure 1 with a buff cloth attached to a rubbing roller, just like the substrate SUB2 side, to impart liquid crystal alignment ability with a single easy axis of alignment. Thereafter, using an apparatus with the same structure as the AFM apparatus in the same way as in the first embodiment, a probe made of _Si3N4 or _Si and having a sharpened tip at the atomic level, adjusted to apply a stress of 20 to 30 nN to the film surface, was used to perform a rubbing treatment in the direction of 45 degrees to the y-axis of the coordinate axes in Figure 1.
The entire surface of the previously rubbed region was uniformly scanned in a 90-degree direction to form a linear stress application pattern. The alignment layer AL1 thus formed was subjected to rubbing and AFM scanning, with the rubbing direction and scanning direction alternately rotated by 90 degrees from each other, resulting in an alignment layer with easy alignment axes in two directions, the ALD1A and ALD1B directions corresponding to the x- and y-axes of the coordinate system in Figure 1, as in Example 1. The electro-optical characteristics and viewing angle characteristics of this example were substantially the same as those of Example 1. Next, a seventh example of the present invention will be described. A liquid crystal display element was fabricated in the same manner as Example 2, except that, instead of scanning the surface of a photosensitive material film formed on the surface of one substrate as the alignment layer on one substrate side with ultraviolet light, light from an ultraviolet light source was converted into linearly polarized ultraviolet light using a polarization element utilizing a Brewster angle, and the light was irradiated twice through two photomasks with the same square checkerboard pattern as in Examples 1 and 2. This was designated Example 7. Specifically, as in Example 2, a diamine compound containing a diazobenzene group, [Chemical Formula 1], and 4,4'-diaminodiphenylmethane were mixed in an equimolar ratio. The polyamic acid was synthesized with pyromellitic dianhydride and/or 1,2,3,4-cyclobutanetetracarboxylic dianhydride. The resulting solution was applied to the substrate surface and baked at 200°C for 30 minutes for imidization. The resulting solution was then irradiated twice with polarized UV light, the linear polarization directions of which were rotated 90 degrees relative to each other. The first irradiation was performed on the black areas of the photomask checkerboard pattern, and the second irradiation was performed on the white areas. The polarized UV light was irradiated perpendicular to the substrate surface so that the pretilt angle of the resulting liquid crystal alignment was approximately 0 degrees. Instead of [Chemical Formula 1], [Chemical Formula 2] or [Chemical Formula 3] may also be used as the photosensitive material. The electro-optical and viewing angle characteristics of this example were essentially the same as those of Example 2. Next, an eighth example of the present invention will be described. In the seventh embodiment, two photomasks with the same checkerboard pattern as in the seventh embodiment were used as alignment layers on both sides of the two substrates sandwiching the liquid crystal layer.
Example 8 was produced as in Example 7, using an alignment layer irradiated twice with linearly polarized ultraviolet light, and further varying the relative intensity of these two UV light irradiations to make the angle between the two easy axes of the resulting alignment layer 45 degrees, as in Example 5, and without adding a chiral dopant. The switching mode in this example is that alignment layers in which two alignment directions are energetically stable are disposed on both substrates, resulting in in-plane switching (a switching angle of 45 degrees) at the interfaces of both substrates. This, combined with two polarizers arranged in a crossed Nicol configuration, results in a display using a birefringence optical mode between homogeneous states with different in-plane orientations. The electro-optical characteristics and viewing angle characteristics of this example are almost the same as those of Example 7, but
As mentioned above, the difference is that the optical characteristic is obtained as the transmittance in the birefringence mode. Next, an eighth embodiment of the present invention will be described. In the seventh embodiment, when the surface of the photosensitive material film formed on the surface of one of the substrates as the alignment layer is irradiated with linearly polarized ultraviolet light, three photomasks with a honeycomb pattern as shown in Figure 11 are used as photomasks, and the polarized ultraviolet light is irradiated three times while the linear polarization direction of each photomask is rotated by 60 degrees. Furthermore, the electrodes on the substrate SUB1 are arranged in three directions, crossing each other at an angle of 60 degrees.
A liquid crystal display element was fabricated in the same manner as in Example 7, except that a drive circuit was provided for each pair of comb-tooth electrodes, and a phase plate with appropriately adjusted optical characteristics was added immediately before the polarizer on the output side, to form Example 9. The three honeycomb pattern photomasks and the corresponding polarization directions of linearly polarized ultraviolet light irradiation are shown in Figures 11(b), 11(c), and 11(d). The switching mode in this example is such that an alignment layer in which three alignment directions, each differing by 60 degrees, are energetically stable, is disposed on one of the substrates,
By applying an appropriate driving voltage to the three pairs of comb electrodes, in-plane switching (switching angles of 60 degrees and 120 degrees) occurs at the substrate interface. Therefore, the liquid crystal cell as a whole is in a homogeneous state (twist angle 0 degrees),
It is possible to take three memory states: a 60-degree twist, a 120-degree twist, and a 60-degree twist. Furthermore, by adjusting the optical characteristics of the phase plate so that black is displayed in the homogeneous state and white is displayed in the 120-degree twist state, optical characteristics of three gradations, including a half-tone display in the 60-degree twist state, are obtained. Note that the present invention is not limited to the above examples, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. As explained in detail above, according to the present invention, a liquid crystal display element using nematic liquid crystal can achieve both low power consumption due to memory characteristics and wide viewing angle display. Industrial Applicability The liquid crystal display element of the present invention can be applied to electronic devices having display devices,
In particular, it is suitable for portable information terminals because it can achieve both low power consumption due to its memory characteristics and wide viewing angle display.

BRIEF DESCRIPTION OF THE DRAWINGS [0023] Fig. 1 is a diagram showing the configuration of a liquid crystal display element according to a first embodiment of the present invention. Fig. 2 is a diagram showing the configuration of a liquid crystal display element according to a first embodiment of the present invention. Fig. 3 is a perspective view showing a scanning pattern of a probe of a liquid crystal display element according to a first embodiment of the present invention. Fig. 4 is a diagram showing the switching characteristics of a liquid crystal display element according to a first embodiment of the present invention. Fig. 5 is a diagram showing a schematic diagram of the orientation state in liquid crystal corresponding to the dark state and the light state according to a first embodiment of the present invention. Fig. 6 is a diagram showing the electro-optical characteristics of a second embodiment corresponding to Fig. 4. Fig. 7 is a diagram showing the configuration of a liquid crystal display element according to a third embodiment of the present invention. Fig. 8 is a diagram showing the drive waveform and electro-optical characteristics of a liquid crystal display element according to a third embodiment of the present invention. Fig. 9 is a diagram showing the configuration of a liquid crystal display element according to a fourth embodiment of the present invention. Fig. 10 is a diagram showing the configuration of a liquid crystal display element according to a fifth embodiment of the present invention. Fig. 11 is a diagram showing the configuration of a mask pattern according to a ninth embodiment of the present invention.

───────────────────────────────────────────────────── (Note) This publication is based on the publication published internationally by the International Bureau of Patents (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (11)

[Claims] [Claim 1] A liquid crystal display element having a pair of substrates, at least one of which is transparent, a group of electrodes formed on at least one of the pair of substrates for applying an electric field having a component approximately parallel to the substrate plane to the liquid crystal layer, a liquid crystal layer disposed between the pair of substrates, and an alignment layer disposed between the liquid crystal layer and at least one of the pair of substrates and treated to regulate liquid crystal alignment in multiple directions, characterized in that the angles that the multiple liquid crystal alignment regulation directions of the alignment layer make with each other within the substrate plane are all approximately equal, and the rise angles from the substrate plane in each liquid crystal alignment regulation direction are all approximately 0 degrees. [Claim 2] A liquid crystal display element having a pair of substrates, at least one of which is transparent, a group of electrodes formed on at least one of the pair of substrates for applying an electric field having a component approximately parallel to the substrate plane to the liquid crystal layer, a liquid crystal layer disposed between the pair of substrates, and an alignment layer disposed between the liquid crystal layer and at least one of the pair of substrates and subjected to liquid crystal alignment regulation in two directions, wherein the two liquid crystal alignment regulation directions of the alignment layer form an angle of approximately 90 degrees with each other within the substrate plane,
The liquid crystal display element is characterized in that one of the liquid crystal alignment regulation directions has a rising angle of approximately 0 degrees from the substrate surface, and the other direction is not approximately 0 degrees. [Claim 3] A liquid crystal display element as described in claim 1 or 2, characterized in that at least one of the liquid crystal alignment control treatments in different directions is a treatment that is applied uniformly to the entire area to be treated, but is performed in multiple steps for each direction. [Claim 4] A liquid crystal display element as described in claim 1 or 2, characterized in that at least one of the liquid crystal alignment control processes in different directions is a process in which the entire area to be processed is divided into multiple sub-areas for each direction and performed. [Claim 5] A liquid crystal display element as described in claim 1, 2, 3 or 4, characterized in that at least one of the liquid crystal alignment control treatments in different directions is a treatment of irradiating light capable of inducing a chemical reaction on the substrate surface as linearly polarized light. 6. A liquid crystal display element according to claim 1, wherein at least one of the liquid crystal alignment control processes in a plurality of different directions is a process of scanning the substrate surface with a probe capable of applying stress to the substrate surface. [Claim 7] A liquid crystal display element as described in claim 1, 2, 3 or 4, characterized in that at least one of the liquid crystal alignment control treatments in different directions is a treatment of scanning with light capable of inducing a chemical reaction on the substrate surface. 8. A liquid crystal display element according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the liquid crystal layer is made of a liquid crystal material containing asymmetric molecules as a compositional component. [Claim 9] A liquid crystal display element as described in claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that the liquid crystal layer is made of a liquid crystal material whose sign of dielectric anisotropy can be either positive or negative depending on the frequency of the applied AC electric field. [Claim 10] A liquid crystal display element as described in claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that it has a pair of electrodes arranged on each of the pair of substrates, separate from a group of electrodes that apply an electric field having a component approximately parallel to the substrates to the liquid crystal layer. 11. A liquid crystal display element according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein a light reflector is disposed on one of said pair of substrates.