JP2006003789A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element provided with a monostable ferroelectric liquid crystal with uniform mono domain alignment in a fine and highly accurate cell gap. <P>SOLUTION: The liquid crystal display element consists of a liquid crystal layer comprising a liquid crystal substance injected between a pair of substrates at least one of which has an alignment layer, having chiral smectic C phase and showing a monostable state, and of an electrode for applying an electric field to the liquid crystal layer. A plurality of barriers extended in a fixed direction and spacers are provided between the substrates so that the direction of molecules of the liquid crystal substance in the monostable state is made nearly coincident with the extended direction of the barriers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element using monostable ferroelectric liquid crystal.

  Conventionally, a liquid crystal display element has been widely used as a display device. As this liquid crystal display element, a TFT-TN (Twisted Nematic) which is an active matrix driving method using a TFT (thin film transistor) substrate having a switching element for each pixel. ) Method has become mainstream. In recent years, IPS mode, MVA mode, etc. have been developed in order to improve the narrow viewing angle, which has been a drawback of liquid crystal display elements, as well as mobile device displays such as mobile phones and PDAs, and personal computer monitors. To the LCD TV monitor. However, as a problem when used as a TV monitor, for example, when displaying a moving image, the response speed of the liquid crystal is slow, which may cause a tail to be drawn when displaying a fast-moving image. It was an issue.

  On the other hand, the ferroelectric liquid crystal has spontaneous polarization and can respond at high speed. Ferroelectric liquid crystals have two stable states proposed by Clark and Lagerwol when no electric field is applied, and bistable ones with memory properties are widely known. By using this, a simple matrix drive is used. Liquid crystal display elements that display moving images have been developed. By using such a bistable ferroelectric liquid crystal, a pair of substrates are joined via a stripe-shaped partition structure, and the upper and lower substrates have a uniaxial alignment treatment direction and a partition direction substantially parallel to each other. A liquid crystal display or the like in which liquid crystal is confined in the formed minute space has been reported (Patent Documents 1 and 2). In addition, a liquid crystal panel body has been reported that prevents the liquid crystal cracking in the layer normal direction generated in the bistable ferroelectric liquid crystal by setting the angle formed by the partition wall direction and the layer normal direction to 50 ± 20 °. (Patent Document 3). However, since the bistable ferroelectric liquid crystal is difficult to display gradation and difficult to display a high-quality image, it has not attracted attention with the practical application of the TFT substrate described above.

On the other hand, monostable ferroelectric liquid crystal, which is stable in a single state when no voltage is applied, can display analog gradations by voltage change and is suitable for driving by TFT. Therefore, it has been attracting attention in recent years (Non-Patent Document 1). This monostable ferroelectric liquid crystal generally uses a liquid crystal substance that undergoes a phase transition directly from a cholesteric phase to a chiral smectic C phase (SmC *) without passing through a smectic A phase during a temperature drop process.
In general, a liquid crystal display element has a basic structure in which a transparent substrate provided with a transparent electrode and an alignment film is opposed to each other through a minute cell gap, and liquid crystal is sealed in the cell gap. The cell gap needs to have a desired size and high accuracy corresponding to the liquid crystal to be used. In the liquid crystal display element using the ferroelectric liquid crystal, the cell gap is 2 μm or less. In order to ensure such a small cell gap with high accuracy, spacers such as beads and columnar protrusions are provided between the substrates.

However, the above monostable ferroelectric liquid crystal is difficult to be uniformly aligned in a state of being enclosed in a cell gap, and a region (double domain) having a different layer normal direction is generated, resulting in a black and white reversal display during driving. There is a problem.
As a method of eliminating such a double domain to form a monodomain, an electric field applied slow cooling method in which liquid crystal is injected into the cell gap and then raised to a temperature higher than that of the cholesteric (Ch) phase and then lowered while applying a DC voltage (non-patented) Document 2) is known.
Further, as another method for obtaining a monodomain, there is known a method (Patent Document 4) in which an alignment film subjected to rubbing treatment is disposed on one of upper and lower alignment films and an alignment film subjected to photo-alignment treatment is disposed on the other. Yes.

Further, as a method for bringing a ferroelectric liquid crystal into a monostable state, for example, a small amount of a polymerizable monomer and / or oligomer is added to the ferroelectric liquid crystal, and the polymer is stabilized while applying a DC electric field or an AC electric field. The chemical method (Patent Document 5) is known.
JP 7-318912 A Japanese Patent Laid-Open No. 7-159792 JP 2000-66176 A JP 2003-5223 A JP-A-9-21463 Liquoid Crystals, 1999, Vol. 26, No. 11,1599-1602 J. et al. Appl. Phys., 1986, Vol. 59, No. 7, 2355-2360

  However, the above-described electric field applied slow cooling method that eliminates double domains and makes them monodomains is complicated in the manufacturing process, and even if monodomains are obtained once, the orientation is disturbed when the temperature rises above the phase transition point, and again Since double domains appeared, there was a problem of lack of stability and impracticality. Further, the above-described polymer stabilization method has a problem that the process is complicated and the driving voltage becomes high. Further, the above-described method using a rubbing / photo-alignment film has a problem that it is difficult to obtain monodomain alignment uniformly throughout the entire display element when the area of the display element is increased.

In addition, it is difficult to obtain mono-domain alignment of a mono-stabilized ferroelectric liquid crystal simply by using the liquid crystal panel body using the above-described bistable ferroelectric liquid crystal.
The above problems become more prominent as the display area increases.
The present invention has been made in view of the above circumstances, and provides a liquid crystal display element including monostable ferroelectric liquid crystal with uniform monodomain alignment in a minute and highly accurate cell gap. For the purpose.

In order to achieve such an object, the present invention includes a pair of substrates provided with an alignment film on at least one substrate, and a liquid crystal substance exhibiting a monostable state having a chiral smectic C phase injected between the substrates. In a liquid crystal display device including a liquid crystal layer and an electrode for applying an electric field to the liquid crystal layer, a plurality of barriers extending in the same direction are provided between the substrates, and a spacer is provided. The molecular direction in the stable state was set to be substantially the same as the extending direction of the barrier.
As another aspect of the present invention, the pitch between the adjacent barriers is in the range of 0.5 to 3 mm.

As another aspect of the present invention, the spacer is a columnar convex portion.
As another aspect of the present invention, the barrier and the columnar protrusion are made of the same material.
As another aspect of the present invention, the barrier and the columnar protrusion are integrated.
As another aspect of the present invention, the barrier and the columnar protrusion are formed at the same time.
As another aspect of the present invention, the barrier is configured to occupy 50 to 100% of the distance between the substrates.
In addition, the difference between the molecular direction in the monostable state of the liquid crystal substance and the extending direction of the barrier is in the range of 0 to 5 °.

  According to the present invention, there are a plurality of barriers extending in the liquid crystal layer, and the extension direction of the barriers is substantially the same as the molecular direction of the liquid crystal substance in the monostable state, so that The injected liquid crystal material becomes a mono-domain oriented monostable ferroelectric liquid crystal layer with few alignment defects, which enables high-quality image display and aligns the barrier with the pixel electrode in the manufacturing stage. There is no need and process management is simple.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a field sequential type liquid crystal display element as an embodiment of the liquid crystal display element of the present invention, and FIG. 2 is a plan view for explaining the liquid crystal display element of the present invention shown in FIG. FIG. 1 and 2, a liquid crystal display element 1 includes a liquid crystal layer made of a liquid crystal material in which a pixel electrode substrate 2 and a common electrode substrate 3 are arranged to face each other and injected into a cell gap formed between the two substrates. 4 and a backlight 6 is disposed outside the pixel electrode substrate 2. Between the pixel electrode substrate 2 and the common electrode substrate 3, a plurality of barriers 5 having a width in the range of 1 to 3 μm and a plurality of columnar protrusions 7 serving as spacers are provided.

FIG. 2 is a plan view from the common electrode substrate 3 side, and shows a state in which the common electrode substrate 3 is removed leaving only the barrier 5 and the columnar protrusions 7. In FIG. 2, an alignment film 17 described later of the pixel electrode substrate 2 is not shown.
The pixel electrode substrate 2 includes a polarizing film 12 on one surface of a base material 11, a pixel electrode 13 on the other surface, a TFT (thin film transistor) 14 that is a switching element connected to the pixel electrode 13, and a TFT 14. The scanning line 15 and the signal line 16 are provided, and an alignment film 17 is provided so as to cover them.

  The common electrode substrate 3 includes a polarizing film 22 on one surface of the base material 21, a common electrode 23 on the other surface, and a plurality of barriers 5 extending at a pitch P on the common electrode 23; A plurality of columnar protrusions 7 as spacers and an alignment film 24 are provided. In the illustrated example, the plurality of barriers 5 extend in parallel with the signal lines 16 (in the direction of arrow a in FIG. 2), and this extending direction is substantially the same as the molecular direction of the liquid crystal substance in the monostable state.

As the above-mentioned base materials 11 and 21, a transparent rigid material having no flexibility such as quartz glass, pyrex glass and synthetic quartz plate, or a transparent transparent material having flexibility such as a transparent resin film and an optical resin plate, etc. Flexible materials and composite materials of these can be used. The thickness of the base materials 11 and 21 can be set in consideration of the material, the usage status of the liquid crystal display element, and the like, and can be set to about 0.1 to 1.0 mm, for example.
The pixel electrode 13 and the common electrode 23 are made of indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), or an alloy thereof, a sputtering method, a vacuum evaporation method, a CVD method, or the like. It can be formed by the general film forming method. The thickness of such an electrode can be appropriately set in the range of 0.05 to 0.2 μm.

The alignment films 17 and 24 are uniaxially aligned, and the pixel electrode substrate 2 and the common electrode substrate 3 face each other so that the alignment directions of the alignment films 17 and 24 are substantially parallel to each other. ing. The uniaxial alignment treatment of the alignment films 17 and 24 is preferably a photo-alignment treatment. In the rubbing treatment, the alignment treatment in the vicinity of the barrier 5 cannot be performed sufficiently, and alignment failure is likely to occur. Such an orientation failure is not preferable because it causes light leakage at the time of black display and causes a decrease in image contrast. In the liquid crystal display element of the present invention, the alignment films 17 and 24 may be the same alignment film, for example, an alignment film subjected to photo-alignment treatment, and the alignment films 17 and 24 may be different alignment films ( (Orientation films with different materials and / or orientation treatment methods) may be used. Further, an alignment film may be provided on one of the pixel electrode substrate 2 and the common electrode substrate 3.
As the alignment film subjected to the photo-alignment treatment, for example, a photodimerized alignment film represented by the following general formula (1) can be used.

In the general formula (1), R ¹ is a group represented by -A- (Z ¹ -B) _z -Z ^2- , and R ² is -A- (Z ¹ -B) _z -Z ^3-. It is group represented by these. Here, A and B are each independently a covalent single bond, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5- Diyl or 1,4-phenylene which may have a substituent is represented. Z ¹ and Z ² are each independently a covalent single bond, —CH ₂ —CH ₂ —, —CH ₂ O—, —OCH ₂ —, —CONR—, —RNCO—, —COO— or — Represents OOC-. R is a hydrogen atom or a lower alkyl group, and Z ³ is a hydrogen atom, an optionally substituted alkyl having 1 to 12 carbon atoms, alkoxy, cyano, nitro, or halogen. z is an integer of 0-4. C represents a photodimerization reaction site, and examples thereof include cinnamic acid ester, coumarin, quinoline, chalcone group, cinnamoyl group and the like. j and k are each independently 0 or 1.

  Among the photodimerized alignment films represented by the above general formula (1), more preferred are those represented by the following structural formulas 1 to 4.

In the above structural formulas 1 to 4, R ¹¹ represents —A ¹ — (Z ¹¹ —B ¹ ) _t —Z ¹² —, and A ¹ and B ¹ represent 1,4-phenylene, a covalent single bond, pyridine- It represents 2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, or 1,3-dioxane-2,5-diyl. Z ¹¹ and Z ¹² each independently represent a covalent single bond, —CH ₂ —CH ₂ —, —CH ₂ O—, —COO—, or —OOC—. t is an integer of 0-4. n is an integer of 4 to 30,000.

  Moreover, as an alignment film which performs a photo-alignment treatment, for example, a photoisomerization type alignment film represented by the following structural formulas 5 to 7 can also be used.

  The barrier 5 extended on the common electrode 23 of the common electrode substrate 3 is a monodomain having a small number of alignment defects. The liquid crystal material injected into the cell gap formed between the pixel electrode substrate 2 and the common electrode substrate 3 This is a member for forming an alignment monostable ferroelectric liquid crystal layer. The width W of the barrier 5 can be in the range of 1 to 3 μm, preferably 1.5 to 2.5 μm. If the width W of the barrier 5 is less than 1 μm, the strength of the barrier 5 becomes insufficient. If it exceeds 3 μm, line-shaped defects on the display screen caused by the barrier 5 become prominent and image quality is deteriorated. By setting the width W of the barrier 5 within the above range, even if the barrier 5 is present in the pixel, it is difficult to be recognized as a defect, and high-quality image display is possible.

  The pitch P of the adjacent barriers 5 can be in the range of 0.5 to 3 mm, preferably 0.8 to 2.5 mm. If the pitch P of the barriers 5 is less than 0.5 mm, the barrier 5 is the cause. The number of line-shaped defects on the display screen increases, resulting in a decrease in image quality. When the thickness exceeds 3 mm, uniform alignment of the injected liquid crystal material becomes difficult.

  The height of the barrier 5 can be set in accordance with the set value of the cell gap (inter-substrate distance) between the pixel electrode substrate 2 and the common electrode substrate 3 and is 50 to 100% of the cell gap. Can be set as follows. If the height of the barrier 5 is less than 50% of the cell gap, alignment defects are likely to occur, and the liquid crystal layer 4 cannot be made a uniform monodomain aligned ferroelectric liquid crystal layer. In the liquid crystal display element 1 of the present invention, in order to ensure the cell gap between the pixel electrode substrate 2 and the common electrode substrate 3 with high accuracy, spacers such as beads and columnar protrusions can be disposed between the substrates, Further, the height of the barrier 5 can be set to 100% of the cell gap to also serve as a spacer.

  In the illustrated example, for ease of explanation, the relationship between the positions and dimensions of the pixel electrode 13 and the barrier 5 is shown for convenience. In the illustrated example, one barrier 5 is extended in the direction of arrow a for every four arrangements of the pixel electrodes 13. For example, the arrangement pitch of the pixel electrodes 13 is 128 μm, and the pitch P of the barriers 5 is 1. In the case of 5 mm, one barrier 5 exists for every about 12 arrayed pixel electrodes 13.

  Said barrier 5 can be formed by well-known methods, such as 2P (Photo Polymerization) method and the photolithographic method, for example. In the 2P method, for example, ethylene glycol (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) ) Acrylate, hexane glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin tridi (meth) acrylate, trimethylolpropane di (meth) acrylate, 1,4-butanediol di Acrylate, pentaerythritol (meth) acrylate, dipentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate , Monomers such as dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, urethane acrylate, epoxy acrylate, polyester acrylate, epoxy, vinyl ether, polyene / thiol-based oligomers, polyvinyl cinnamon that causes photodimerization reaction Barrier 5 is formed by applying a photocrosslinkable polymer such as an acid-based resin on the base material 21, irradiating and curing ultraviolet rays in a state where the original plate for barrier formation is pressure-bonded to the coating film, and then peeling the original plate. Form. In the photolithography method, a material as exemplified in the above-described 2P method is applied onto the base material 21, the coating film is exposed through a desired photomask for forming a barrier, and then developed to develop a barrier. 5 is formed. In particular, the 2P method is suitable for forming an extremely thin barrier having a width of 2 μm or less. In addition, said (meth) acrylate means an acrylate or a methacrylate.

  Further, the columnar convex portions 7 constituting the liquid crystal display element 1 are for forming a predetermined cell gap with high accuracy between the pixel electrode substrate 2 and the common electrode substrate 3 and have a height of 1.2. It can set suitably in the range of -3 micrometers. The shape of the columnar convex portions 7 is not particularly limited, such as a columnar shape, a truncated cone shape, a prismatic shape, a truncated prismatic shape, and the arrangement density can be about 1 to 20 per 1 mm square. This columnar convex portion 7 can also be formed by a known method such as 2P method or photolithography method, and may be made of the same material as that of the barrier 5 described above. It is preferable to use the same material for the barrier 5 and the columnar convex portion 7 because both have the same thermal behavior, and stress concentration in the liquid crystal display element is suppressed. Moreover, a process can be made simpler by forming the above-mentioned barrier 5 and the columnar convex part 7 simultaneously by the same formation method.

  The liquid crystal material of the liquid crystal layer 4 constituting the liquid crystal display element 1 is injected into the cell gap in the liquid phase, and is directly phase-shifted from the cholesteric phase to the chiral smectic C phase (SmC *) without passing through the smectic A phase. It is a thing. By making the molecular direction in the monostable state of the liquid crystal substance substantially parallel to the extending direction of the barrier 5 described above, preferably by setting the difference between the molecular direction and the extending direction of the barrier 5 to a range of 0 to 5 °. By the action of the barrier 5, the liquid crystal substance takes a monostable state in which the molecular axes are uniformly monodomain aligned in the absence of an electric field. In the present invention, a case where the ratio of the area of the region having the same layer normal direction to the total area is 95% or more is defined as “monostable state with uniform monodomain orientation”. Thus, in order to make the molecular direction of the liquid crystal material in the monostable state substantially parallel to the extending direction of the barrier 5, the direction of the uniaxial alignment of the alignment films 17 and 24 is appropriately set according to the liquid crystal material used. do it.

  The backlight 6 constituting the liquid crystal display element 1 includes, for example, a plurality of LEDs that emit red (R), green (G), and blue (B) light so as to face the pixel electrode substrate 2. And a pixel electrode substrate 2 may be provided with a light diffusion plate. Alternatively, only the light diffusing plate may be disposed so as to face the pixel electrode substrate 2, and R, G, and B LEDs may be disposed on the side end portion of the light diffusing plate via a light guide plate.

In the liquid crystal display element 1 of the present invention, columnar convex portions are disposed as spacers between the substrates, but other spacers such as beads may be disposed, and two or more kinds of spacers are disposed in combination. May be.
Moreover, in this invention, as shown in FIG. 3, it is good also as that in which the columnar convex part 7 was integrally provided along the extension direction of the barrier 5. As shown in FIG. By integrating the barrier 5 and the columnar protrusion 7 in this way, the strength of the barrier 5 can be ensured even if the width of the barrier 5 is extremely small. The material and the formation method of the barrier 5 integrated with the columnar protrusion 7 are the same as those described above for the barrier 5. In this case as well, columnar protrusions or beads that are not integrated with the barrier 5 may be disposed between the substrates as spacers.

In the above-described embodiment, the barrier 5 and the columnar protrusion 7 are provided on the common electrode 23 of the common electrode substrate 3, but both may be provided on the pixel electrode 13 of the pixel electrode substrate 2. May be provided on the pixel electrode substrate 2 and the other may be provided on the common electrode substrate 3. Further, the extending direction of the barrier 5 (the direction of the arrow a in FIG. 2) is parallel to the signal line 16, but the barrier 5 may be extended so as to cross the signal line 16 at a desired angle.
In addition to injecting the liquid crystal material into the cell gap in the liquid phase, the liquid crystal layer 4 drops a predetermined amount of the liquid crystal material in the liquid phase on the common electrode substrate 3 on which the barrier 5 is formed, and then in vacuum Alternatively, the pixel electrode substrate 2 may be formed by bonding. In this case, by setting the height of the barrier 5 to be less than 100% of the cell gap and 50% or more, it is only necessary to control the total amount of liquid crystal substance to be dropped, and within the individual regions partitioned by each barrier. Control of the amount of liquid crystal substance to be dropped is unnecessary, and process management becomes easy.

  In the above-described embodiment, R, G, and B are used as individual light sources (LEDs) as a backlight. However, a light source that can emit light by continuously switching R, G, and B is used as a backlight. May be. The method of the liquid crystal display element of the present invention is not limited to the field sequential method, and may be a liquid crystal display element that performs color display using a color filter.

  Further, in the liquid crystal display element of the present invention, in order to obtain flatness of the surface in contact with the liquid crystal substance, an overcoat layer is provided on the TFT 14, the scanning line 15, and the signal line 16, and the alignment film is interposed through this overcoat layer. Is preferably formed. As a material for the overcoat layer, a transparent (visible light transmittance of 50% or more) material can be used. Specifically, a photocurable resin having a reactive vinyl group of acrylate type or methacrylate type, a thermosetting resin, or a transparent oxide such as polysiloxane can be used. Moreover, as transparent resin, polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl chloride resin, melamine resin, phenol resin, alkyd resin, epoxy resin, polyurethane resin, polyester resin, A maleic acid resin, a polyamide resin, etc. can be used.

  When the above resin material is liquid, the overcoat is formed by applying a film by spin coating, roll coating, cast coating, or the like, and the photocurable resin is thermally cured as necessary after ultraviolet irradiation. The thermosetting resin is cured as it is after film formation. Moreover, when the material used is shape | molded in the film form, it can stick directly or via an adhesive. The thickness of such an overcoat layer is preferably set to 0.1 μm or less, for example.

Next, the present invention will be described in more detail by showing more specific examples.
[Example 1]
Two glass substrates having an indium tin oxide (ITO) thin film formed on the surface were prepared. A photosensitive resin material (NN780 manufactured by JSR Co., Ltd.) was applied on one ITO thin film of the glass substrate by spin coating (2000 rpm, 10 seconds), vacuum-dried, and heated on a hot plate. Drying was performed at 3 ° C. for 3 minutes. Then, after patterning into a stripe shape having a width of 1.5 μm and a pitch of 1 mm by a photolithography method, columnar convex portions having a 10 μm square were patterned at an arrangement density of 4 (pieces / mm square) and baked at 270 ° C. for 30 minutes. As a result, a barrier having a height of 1.5 μm and columnar protrusions were formed on the ITO thin film of the glass substrate. Next, a coating solution prepared by diluting a photosensitive resin material (NN780 manufactured by JSR Corporation) 10 times with trimethoxybutyl acetate (solvent) on an ITO thin film on which barriers and columnar protrusions are formed is spin-coated. Apply by coating method (2000 rpm, 10 seconds), vacuum dry, dry on hot plate at 90 ° C. for 3 minutes, irradiate with ultraviolet light, baked at 230 ° C. for 30 minutes, 150 nm thick overcoat layer To obtain a common electrode substrate.

  Further, on another glass substrate, an x electrode (line width 8 μm) as a scanning line and a y electrode (line width 8 μm) as a signal line in a direction orthogonal to the scanning line were formed at a pitch of 102 μm. In addition, a pixel electrode made of an indium tin oxide (ITO) thin film and a TFT switching element were formed in a pixel region surrounded by the x electrode and the y electrode. The width of the pixel electrode was 55 μm. Next, a coating solution prepared by diluting a photosensitive resin material (NN780 manufactured by JSR Corporation) 10 times with trimethoxybutyl acetate (solvent) over the entire surface of the glass substrate so as to cover the pixel electrode is spin-coated ( 2000 rpm, 10 seconds), vacuum drying, drying at 90 ° C. for 3 minutes on a hot plate, irradiation with ultraviolet rays and baking at 230 ° C. for 30 minutes to form a 150 nm thick overcoat layer Thus, a pixel electrode substrate was obtained.

  Next, on the overcoat layers of both substrates prepared as described above, an alignment film coating solution in which compound A represented by the following structural formula A is dissolved in cyclopentanone (2 wt%) is spin-coated (4000 r). .pm for 30 seconds) and dried in an oven at 180 ° C. for 10 minutes.

Then, 100 mJ exposure was carried out with polarized ultraviolet light, and the photo-alignment process was performed, and the alignment film was formed. This photo-alignment treatment includes six types of treatments with different orientation directions (six types of irradiation from directions where the glass substrate is −5 °, 0 °, 5 °, 15 °, 25 °, 40 ° with respect to polarized light). Was set.
Next, a sealing material is applied to the periphery of the glass substrate on which the barrier is not formed, and both are set so that the relationship with the glass substrate on which the barrier is formed is parallel and antiparallel to the polarized ultraviolet irradiation direction. The substrates were opposed and thermocompression bonded. As a result, the barrier and columnar protrusions of the common electrode are present on the pixel electrode.

Next, an inlet for injecting liquid crystal into the cell gap of both glass substrates is provided at one end in the barrier extending direction, and a liquid crystal substance (Clariant R2301) is attached to the upper part of the inlet, and vacuum is applied. Using an oven, it was injected into the cell gap at a temperature 20 ° C. higher than the nematic phase-isotropic transition temperature. After the injection, the liquid crystal material was gradually cooled to room temperature to obtain a liquid crystal display element.
This produced six types of samples. As a result of measuring the molecular direction of the liquid crystal for each of these samples (disposing the sample between two polarizing plates arranged in crossed Nicols, rotating the sample, the darkest direction indicates the molecular orientation direction), The difference between the extending direction of the barrier and the molecular direction of the liquid crystal substance was 0 °, 5 °, 10 °, 20 °, 30 °, and 45 ° in each sample.

Moreover, as a result of observing the alignment state of the liquid crystal layer of each sample with a polarizing microscope, the liquid crystal layer has a uniform monodomain alignment in the sample where the difference between the barrier extension direction and the molecular direction of the liquid crystal substance is 0 ° and 5 °. This was confirmed to be a monostable ferroelectric liquid crystal. In addition, the case where the ratio of the area of the region having the same layer normal direction to the total area is 95% or more is referred to as “monostable ferroelectric liquid crystal with uniform monodomain alignment”. The area occupied by the same layer normal direction was 98%.
In addition, in order to drive the TFT switching element, the scanning line and the signal line of the pixel electrode substrate of the above two types of samples (samples in which the difference between the barrier extension direction and the molecular direction of the liquid crystal substance is 0 °, 5 °) The voltage was applied. That is, when a rectangular voltage of +5 V and −5 V was applied to the pixel electrode at a frequency of 180 Hz, a uniform display was obtained over the entire surface. Similarly, even when a rectangular voltage of +3 V or -3 V was applied to the pixel electrode at a frequency of 180 Hz, a uniform display was obtained over the entire surface.

  However, in the sample in which the difference between the barrier extension direction and the molecular direction of the liquid crystal material is 10 °, double domain alignment is partially observed (occupation area of the region having the same layer normal direction is 85%), and 20 °. In each of the 30 ° and 45 ° samples, the liquid crystal layer was in a double domain orientation (occupied area of the region having the same layer normal direction was 70% or less). In addition, when + 5V and -5V rectangular voltages were applied to the pixel electrodes of these samples at a frequency of 180 Hz, no abnormal display was observed, but +3 V and -3 V rectangular voltages were applied at a frequency of 180 Hz. As a result, many white streak-like defects were observed at the boundary of the double domain.

[Example 2]
A liquid crystal display device was produced in the same manner as in Example 1 except that the barriers and the columnar protrusions were formed as follows. However, the photo-alignment treatment was set to a condition where the difference between the barrier extension direction and the molecular direction of the liquid crystal substance was 0 °.
In order to form the barriers and the columnar protrusions, first, a photosensitive resin material (NN780 manufactured by JSR Corporation) is applied onto the ITO thin film of the glass substrate by spin coating (2000 rpm, 10 seconds), and then vacuum drying is performed. And dried on a hot plate at 90 ° C. for 3 minutes. Thereafter, stripes having a width of 1.5 μm and a pitch of 1 mm and columnar convex portions having 10 μm square (arrangement density of 4 (pieces / mm square)) were patterned by photolithography and baked at 230 ° C. for 30 minutes. As a result, a barrier having a height of 1.5 μm and columnar protrusions were formed on the ITO thin film of the glass substrate.

The liquid crystal layer formed in the cell gap of the liquid crystal display device manufactured as described above is a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of the same layer normal direction is 98%). It was confirmed that.
Further, when a rectangular voltage of +5 V and −5 V was applied to the pixel electrode of the sample at a frequency of 180 Hz, a uniform display was obtained over the entire surface. Similarly, even when + 3V and -3V rectangular voltages were applied to the pixel electrodes at a frequency of 180 Hz, uniform display was obtained over the entire surface.

[Example 3]
A liquid crystal display device was produced in the same manner as in Example 1 except that the barriers and the columnar protrusions were formed as follows. However, the photo-alignment treatment was set to a condition where the difference between the barrier extension direction and the molecular direction of the liquid crystal substance was 0 °.
In order to form the barriers and the columnar protrusions, first, a photosensitive resin material (NN780 manufactured by JSR Corporation) is applied onto the ITO thin film of the glass substrate by spin coating (2000 rpm, 10 seconds), and then vacuum drying is performed. And dried on a hot plate at 90 ° C. for 3 minutes. Thereafter, as shown in FIG. 3, columnar convex portions (arrangement density 4 (pieces / mm square)) having a radius of 5 μm are simultaneously patterned by photolithography on a stripe having a width of 1.5 μm and a pitch of 1 mm. Baked at 30 ° C. for 30 minutes. As a result, a barrier having a height of 1.5 μm integrated with the columnar protrusion was formed on the ITO thin film of the glass substrate.

The liquid crystal layer formed in the cell gap of the liquid crystal display device manufactured as described above is a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of the same layer normal direction is 98%). It was confirmed that.
Further, when a rectangular voltage of +5 V and −5 V was applied to the pixel electrode of the sample at a frequency of 180 Hz, a uniform display was obtained over the entire surface. Similarly, even when + 3V and -3V rectangular voltages were applied to the pixel electrodes at a frequency of 180 Hz, uniform display was obtained over the entire surface.

[Comparative example]
A liquid crystal display device was produced in the same manner as in Example 1 except that the thickness of the barrier was 4 μm. However, the photo-alignment treatment was set to a condition where the difference between the barrier extension direction and the molecular direction of the liquid crystal substance was 0 °.
The liquid crystal layer formed in the cell gap of the liquid crystal display device manufactured as described above is a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of the same layer normal direction is 98%). It was confirmed that.
However, when a rectangular voltage of +5 V and −5 V was applied to the pixel electrode of the above sample at a frequency of 180 Hz, stripe-like unevenness was observed.

  The present invention can be applied to a liquid crystal display element having a monostable ferroelectric liquid crystal.

It is a schematic sectional drawing which shows the liquid crystal display element of the field sequential system which is one Embodiment of the liquid crystal display element of this invention. It is a top view for demonstrating the liquid crystal display element of this invention shown by FIG. It is a fragmentary perspective view which shows the other example of the barrier which comprises the liquid crystal display element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2 ... Pixel electrode board | substrate 3 ... Common electrode board | substrate 4 ... Liquid crystal layer 5 ... Barrier 6 ... Backlight 7 ... Columnar convex part 11, 21 ... Base material 12, 22 ... Polarizing film 13 ... Pixel electrode 14 ... TFT
DESCRIPTION OF SYMBOLS 15 ... Scanning line 16 ... Signal line 17, 24 ... Alignment film 23 ... Common electrode

Claims (8)

A pair of substrates each provided with an alignment film on at least one substrate; a liquid crystal layer made of a liquid crystal material having a monostable state having a chiral smectic C phase injected between the substrates; and an electric field for applying an electric field to the liquid crystal layer In a liquid crystal display element comprising an electrode,
A liquid crystal display comprising a plurality of barriers extending in the same direction between substrates and a spacer, wherein the liquid crystal substance has a molecular direction in a monostable state substantially the same as the extension direction of the barriers. element.   The liquid crystal display element according to claim 1, wherein a pitch of the adjacent barriers is in a range of 0.5 to 3 mm.   The liquid crystal display element according to claim 1, wherein the spacer is a columnar protrusion.   The liquid crystal display element according to claim 3, wherein the barrier and the columnar protrusion are made of the same material.   The liquid crystal display element according to claim 4, wherein the barrier and the columnar protrusion are integrated.   The liquid crystal display element according to claim 4, wherein the barrier and the columnar protrusion are formed simultaneously.   The liquid crystal display element according to claim 1, wherein the barrier occupies 50 to 100% of a distance between substrates.   8. The liquid crystal display according to claim 1, wherein a difference between a molecular direction of the liquid crystal substance in a monostable state and an extending direction of the barrier is in a range of 0 to 5 °. element.

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