JP4699100B2 - Liquid crystal display element - Google Patents

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. However, when such a monostable ferroelectric liquid crystal is used, there is a problem that a region (double domain) having a different layer normal direction is generated, resulting in a black and white reversal display during driving.

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 Liquid Crystals, 1999, Vol. 26, No.11,1599-1602 J. 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 present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device including monostable ferroelectric liquid crystal with uniform monodomain alignment in a cell gap. .

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 element including a liquid crystal layer and an electrode for applying an electric field to the liquid crystal layer, the liquid crystal layer includes a plurality of barriers, and the liquid crystal substance has a molecular direction in a monostable state with an extension of the barriers. The configuration is substantially the same as the installation direction.
As another embodiment of the present invention, the liquid crystal substance is configured such that a difference between a molecular direction in a monostable state and a barrier extending direction is in a range of 0 to 5 °.
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 alignment film is configured to be a film imparted with anisotropy by rubbing treatment or photo-alignment treatment.
As another aspect of the present invention, the barrier is configured to occupy 50 to 100% of the distance between the substrates.

  According to the present invention, since the liquid crystal layer has a plurality of barriers and the molecular direction of the liquid crystal substance in the monostable state is substantially the same as the extending direction of the barriers, the liquid crystal layer has a monolith with few alignment defects. It becomes a domain-oriented monostable ferroelectric liquid crystal layer, which enables high-quality image display. Further, even if the pitch of the barriers is increased, the above-described effect can be obtained. Therefore, it is possible to reduce line-like defects in the display screen caused by the barriers, and it is possible to suppress deterioration in image quality. is there.

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. 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 described later. 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; An alignment film 24 is provided. In the illustrated example, the plurality of barriers 5 extend parallel to the signal line 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 said base material 11 and 21, flexibility, such as transparent rigid materials without flexibility, such as quartz glass, Pyrex (trademark) glass, a synthetic quartz board, or a transparent resin film, an optical resin board, etc. A transparent flexible material having these and these composite materials 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 can be performed by either photo-alignment treatment or rubbing treatment, but photo-alignment treatment is preferable. This is because the photo-alignment process is a non-contact alignment process and is useful in that there is no generation of static electricity or dust and quantitative control of the alignment process is possible.

  A film with anisotropy by photo-alignment treatment is a film obtained by irradiating a substrate coated with an alignment film material with light with controlled polarization to cause photoexcitation reaction (decomposition, isomerization, dimerization). By imparting anisotropy to the liquid crystal, the liquid crystal substance on the film is aligned. The alignment film subjected to the photo-alignment treatment is not particularly limited as long as it has an effect of aligning the liquid crystal substance by irradiating light and causing a photoexcitation reaction (photoaligning). As an alignment film, there are large photoreactive alignment films that impart anisotropy to alignment films by causing photoreactions, and photoisomerization that imparts anisotropy to alignment films by causing photoisomerization reactions. It can be divided into a mold alignment film.

The photoreactive alignment film imparts anisotropy to the alignment film by causing a photoreaction. The photoreactive alignment film is not particularly limited as long as it has such characteristics, but it imparts anisotropy to the alignment film by causing a photodimerization reaction or a photodecomposition reaction. It is preferable.
Here, the photodimerization reaction refers to a reaction in which reaction sites aligned in the polarization direction by light irradiation undergo radical polymerization and two molecules are polymerized. This reaction stabilizes the alignment in the polarization direction and is anisotropic to the alignment film. It is possible to impart sex. The photodegradation reaction is a reaction that decomposes molecular chains such as polyimide oriented in the polarization direction by light irradiation. This reaction leaves molecular chains oriented in the direction perpendicular to the polarization direction, and is anisotropic to the alignment film. It is possible to impart sex.
As the photoreactive alignment film, it is more preferable to use a photodimerization alignment film that imparts anisotropy to the alignment film by a photodimerization reaction because of high exposure sensitivity and wide selection of materials.

The photodimerization type alignment film is not particularly limited as long as it can impart anisotropy to the alignment film by a photodimerization reaction. However, the photodimerization alignment film has a radical polymerizable functional group and is polarized. It is preferable to use a photodimerization reactive compound having dichroism with different absorption depending on the direction. This is because by radical polymerization of the reaction site oriented in the polarization direction, the orientation of the photodimerization reactive compound is stabilized and anisotropy can be easily imparted to the orientation film.
Examples of the photodimerization reactive compound having such characteristics include a dimerization reactive polymer having at least one reactive site selected from cinnamate ester, coumarin, quinoline, chalcone group and cinnamoyl group as a side chain. Can do. Among these, the photodimerization reactive compound is preferably a dimerization reactive polymer containing cinnamate, coumarin or quinoline as a side chain. This is because anisotropy can be easily imparted to the alignment film by radical polymerization of α and β unsaturated ketone double bonds aligned in the polarization direction as reaction sites.

The main chain of the dimerization-reactive polymer is not particularly limited as long as it is generally known as a polymer main chain. However, mutual reaction between reaction sites of the side chain such as an aromatic hydrocarbon group is not limited. It is preferable that it does not have a substituent containing many π electrons that hinders the action.
The weight average molecular weight of the dimerization reactive polymer is not particularly limited, but is preferably in the range of 5,000 to 40,000, and is in the range of 10,000 to 20,000. It is more preferable. The weight average molecular weight can be measured by a gel permeation chromatography (GPC) method. If the weight average molecular weight of the dimerization reactive polymer is too small, it may not be possible to impart appropriate anisotropy to the alignment film. On the other hand, if it is too large, the viscosity of the coating liquid for alignment film becomes high, and it may be difficult to form a uniform coating film.
As the photodimerization type alignment film, for example, a dimerization reactive polymer represented by the following general formula (1) can be used.

In the general formula (1), M ¹ and M ² each independently represent a monomer unit of a homopolymer or a copolymer. Examples thereof include ethylene, acrylate, methacrylate, 2-chloroacrylate, acrylamide, methacrylamide, 2-chloroacrylamide, styrene derivatives, maleic acid derivatives, and siloxane. M ² may be acrylonitrile, methacrylonitrile, methacrylate, methyl methacrylate, hydroxyalkyl acrylate or hydroxyalkyl methacrylate. x and y represent the molar ratio of each monomer unit in the case of a copolymer, and are numbers satisfying 0 <x ≦ 1, 0 ≦ y <1 and satisfying x + y = 1, respectively. It is. n represents an integer of 4 to 30,000. D ¹ and D ² represent spacer units.
R ¹ is a group represented by —A— (Z ¹ —B) _z —Z ² —, and R ² is a group represented by —A— (Z ¹ —B) _z —Z ³ —. 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 dimerization reactive polymers represented by the 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.

As the photodimerization reactive compound, various photodimerization reaction sites and substituents can be selected from the above-described ones according to required characteristics. Moreover, the photodimerization reactive compound can also be used individually by 1 type or in combination of 2 or more types.
Examples of the material for the photodimerization type alignment film include “ROP102” and “ROP103” manufactured by Rolic technologies. Moreover, as a material of the photoreactive alignment film using photodecomposition reaction, for example, polyimide “RN1199” manufactured by Nissan Chemical Industries, Ltd. can be exemplified.

The photoisomerization type alignment film imparts anisotropy to the alignment film by causing a photoisomerization reaction. The photoisomerization type alignment film is not particularly limited as long as it has such characteristics, but photoisomerization reactivity that imparts anisotropy to the alignment film by causing a photoisomerization reaction. It is preferable to use a compound. By using such a photoisomerization-reactive compound, a stable isomer among a plurality of isomers is increased by light irradiation, whereby anisotropy can be easily imparted to the alignment film. is there.
The photoisomerization-reactive compound is not particularly limited as long as it has the above-mentioned characteristics, but has a dichroism that makes absorption different depending on the polarization direction and emits light by light irradiation. It is preferable that it causes an isomerization reaction. This is because anisotropy can be easily imparted to the alignment film by causing isomerization of the reaction site oriented in the polarization direction of the photoisomerization reactive compound having such characteristics.
Further, the photoisomerization reaction in which the photoisomerization reactive compound is generated is preferably a cis-trans isomerization reaction. This is because isomers of either the cis form or the trans form are increased by light irradiation, whereby anisotropy can be imparted to the alignment film.
Furthermore, examples of the photoisomerization reactive compound include a monomolecular compound or a polymerizable monomer that is polymerized by light or heat. These may be appropriately selected according to the type of liquid crystal material used, but the anisotropy can be stabilized by polymerizing after imparting anisotropy to the alignment film by light irradiation. It is preferable to use a polymerizable monomer. Among such polymerizable monomers, an acrylate monomer and a methacrylate monomer are preferable because anisotropy is imparted to the alignment film and the polymer can be easily polymerized while maintaining the anisotropy in a good state.
The polymerizable monomer may be a monofunctional monomer or a polyfunctional monomer, but is a bifunctional monomer because the anisotropy of the alignment film due to polymerization becomes more stable. It is preferable.

Specific examples of such a photoisomerization-reactive compound include compounds having a cis-trans isomerization-reactive skeleton such as an azobenzene skeleton or a stilbene skeleton. In this case, the number of cis-trans isomerization reactive skeletons contained in the molecule may be one or two or more. However, since the alignment control of the liquid crystal substance becomes easy, 2 It is preferable that
The cis-trans isomerization reactive skeleton may have a substituent in order to further enhance the interaction with the liquid crystal substance. The substituent is not particularly limited as long as it can enhance the interaction with the liquid crystal substance and does not interfere with the orientation of the cis-trans isomerization reactive skeleton, and examples thereof include a carboxyl group and a sulfonic acid. A sodium group, a hydroxyl group, etc. are mentioned. These structures can be appropriately selected depending on the type of liquid crystal substance used.
In addition to the cis-trans isomerization reactive skeleton, the photoisomerization reactive compound contains many π electrons such as aromatic hydrocarbon groups so that the interaction with the liquid crystal substance can be further enhanced. It may have an included group, and the cis-trans isomerization reactive skeleton and the aromatic hydrocarbon group may be bonded via a bonding group. The bonding group is not particularly limited as long as it can enhance the interaction with the liquid crystal substance. For example, —COO—, —OCO—, —O—, —C≡C—, —CH ₂ —CH _2- , —CH ₂ O—, —OCH ₂ — and the like can be mentioned.
In addition, when using a polymerizable monomer as a photoisomerization reactive compound, it is preferable to have the said cis-trans isomerization reactive skeleton as a side chain. By having the cis-trans isomerization reactive skeleton as a side chain, the effect of anisotropy imparted to the alignment film becomes larger, and it is particularly suitable for controlling the alignment of the liquid crystal substance. It is. In this case, the aromatic hydrocarbon group and bonding group contained in the molecule are contained in the side chain together with the cis-trans isomerization reactive skeleton so that the interaction with the liquid crystal substance is enhanced. It is preferable.
The side chain of the polymerizable monomer may have an aliphatic hydrocarbon group such as an alkylene group as a spacer so that the cis-trans isomerization reactive skeleton can be easily oriented.

Among the photoisomerization reactive compounds of the monomolecular compound or polymerizable monomer as described above, the photoisomerization reactive compound is preferably a compound having an azobenzene skeleton in the molecule. This is because the azobenzene skeleton contains a lot of π electrons and thus has a high interaction with the liquid crystal substance and is particularly suitable for controlling the alignment of the liquid crystal substance.
Hereinafter, the reason why the azobenzene skeleton can impart anisotropy to the alignment film by causing a photoisomerization reaction will be described. First, when the azobenzene skeleton is irradiated with linearly polarized ultraviolet light, the trans azobenzene skeleton having the molecular long axis oriented in the polarization direction is changed to a cis isomer as shown in the following formula.

Since the cis isomer of the azobenzene skeleton is chemically unstable compared to the trans isomer, it thermally or absorbs visible light and returns to the trans isomer. Whether to become the right transformer body occurs with the same probability. Therefore, if the ultraviolet light is continuously absorbed, the ratio of the right-side trans isomer increases, and the average orientation direction of the azobenzene skeleton becomes perpendicular to the polarization direction of the ultraviolet light. By utilizing this phenomenon, the alignment direction of the azobenzene skeleton can be aligned, anisotropy can be imparted to the alignment film, and the alignment of the liquid crystal substance on the film can be controlled.
As the photoisomerizable alignment film, for example, a monomolecular compound having an azobenzene skeleton in the molecule represented by the following general formula (2) can be used.

In the general formula (2), each R ⁵¹ independently represents a hydroxy group. R ⁵² is _{^{- (A 51 -B 51 -A 51}} ) m - (D 51) n - represents a linking group represented ^{by, R 53} is _{^{(D 51) n - (A}} 51 -B 51 -A 51) _m represents a linking group represented by-. Here, A ⁵¹ represents a divalent hydrocarbon group, B ⁵¹ represents —O—, —COO—, —OCO—, —CONH—, —NHCO—, —NHCOO— or —OCONH—, and m represents Represents an integer of 0 to 3; D ⁵¹ represents a divalent hydrocarbon group when m is 0, and when m is an integer of 1 to 3, —O—, —COO—, —OCO—, —CONH—, —NHCO—, —NHCOO— Alternatively, -OCONH- is represented, and n represents 0 or 1. R ⁵⁴ each independently represents a halogen atom, a carboxy group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group or a methoxycarbonyl group. However, the carboxy group may form a salt with an alkali metal. R ⁵⁵ each independently represents a carboxy group, a sulfo group, a nitro group, an amino group or a hydroxy group. However, the carboxy group or the sulfo group may form a salt with the alkali metal.

  Examples of the monomolecular compound having an azobenzene skeleton in the molecule represented by the general formula (2) include those represented by the following structural formulas 5 to 8.

  As the photoisomerizable alignment film, for example, a polymerizable monomer having an azobenzene skeleton represented by the following general formula (3) as a side chain can be used.

In the general formula (3), each R ⁶¹ is independently (meth) acryloyloxy group, (meth) acrylamide group, vinyloxy group, vinyloxycarbonyl group, vinyliminocarbonyl group, vinyliminocarbonyloxy group, vinyl group. Represents an isopropenyloxy group, an isopropenyloxycarbonyl group, an isopropenyliminocarbonyl group, an isopropenyliminocarbonyloxy group, an isopropenyl group or an epoxy group. R ⁶² is _{^{- (A 61 -B 61 -A 61}} ) m - (D 61) n - represents a linking group represented ^{by, R 63} is _{^{(D 61) n - (A}} 61 -B 61 -A 61) _m represents a linking group represented by-. Here, A ⁶¹ represents a divalent hydrocarbon group, B ⁶¹ represents —O—, —COO—, —OCO—, —CONH—, —NHCO—, —NHCOO— or —OCONH—, and m represents Represents an integer of 0 to 3; D ⁶¹ represents a divalent hydrocarbon group when m is 0, and when m is an integer of 1 to 3, —O—, —COO—, —OCO—, —CONH—, —NHCO—, —NHCOO— Alternatively, -OCONH- is represented, and n represents 0 or 1. R ⁶⁴ each independently represents a halogen atom, a carboxy group, a halogenated methyl group, a halogenated methoxy group, a cyano group, a nitro group, a methoxy group or a methoxycarbonyl group. However, the carboxy group may form a salt with an alkali metal. R ⁶⁵ each independently represents a carboxy group, a sulfo group, a nitro group, an amino group or a hydroxy group. However, the carboxy group or the sulfo group may form a salt with the alkali metal.

  Examples of the polymerizable monomer having the azobenzene skeleton represented by the general formula (3) as a side chain include those represented by the following structural formulas 9 to 12.

  As the photoisomerization-reactive compound, various cis-trans isomerization-reactive skeletons and substituents can be selected from among the above-described compounds according to required characteristics. In addition, these photoisomerization reactive compounds can also be used individually by 1 type or in combination of 2 or more types.

  The alignment film subjected to the photo-alignment treatment may contain an additive within a range that does not hinder the optical alignment of the alignment film. Examples of the additive include a polymerization initiator and a polymerization inhibitor. The polymerization initiator or polymerization inhibitor may be appropriately selected from generally known compounds according to the type of photodimerization reactive compound or photoisomerization reactive compound. The addition amount of the polymerization initiator or polymerization inhibitor is preferably in the range of 0.001% by weight to 20% by weight with respect to the photodimerization reactive compound or the photoisomerization reactive compound, and is 0.1% by weight. More preferably, it is in the range of ˜5% by weight. This is because if the addition amount of the polymerization initiator or polymerization inhibitor is too small, the polymerization may not be started (prohibited), whereas if too much, the reaction may be inhibited.

For the alignment film provided with anisotropy by the photo-alignment treatment, for example, a coating solution for the alignment film obtained by diluting the above-described alignment film material with an organic solvent is applied and dried, and the resulting film is subjected to the photo-alignment treatment Can be formed.
In this case, the content of the photodimerization reactive compound in the alignment film coating solution is preferably in the range of 0.05 wt% to 10 wt%, and in the range of 0.2 wt% to 2 wt%. More preferably, it is within. In addition, the content of the photoisomerization reactive compound in the alignment film coating solution is preferably in the range of 0.05 wt% to 10 wt%, and in the range of 0.2 wt% to 5 wt%. It is more preferable that If the content is too small, it will be difficult to impart appropriate anisotropy to the alignment film. Conversely, if the content is too large, the viscosity of the coating solution will increase, making it difficult to form a uniform coating film. .
As the coating method, spin coating method, roll coating method, rod bar coating method, spray coating method, air knife coating method, slot die coating method, wire bar coating method and the like can be used.
The thickness of the film obtained by applying the alignment film material is preferably in the range of 1 nm to 200 nm, and more preferably in the range of 3 nm to 100 nm. If the thickness of the film is too thin, sufficient optical alignment may not be obtained. Conversely, if the thickness is too large, the liquid crystal substance may be disturbed in alignment, and it is not preferable in terms of cost.

The obtained film can impart anisotropy by causing a photoexcitation reaction by irradiating light with polarization controlled. The wavelength region of the light to be irradiated may be appropriately selected according to the material of the alignment film to be used, but is preferably in the ultraviolet light range, that is, in the range of 100 nm to 400 nm, more preferably 250 nm to 380 nm. Is within the range.
The polarization direction is not particularly limited as long as it can cause a photoexcitation reaction. However, since the alignment state of the liquid crystal substance can be improved, it is substantially perpendicular to the substrate surface. It is preferable. In the case of a photoisomerizable alignment film, the photo-alignment treatment can also be performed by irradiating non-polarized ultraviolet rays. The light irradiation direction is not particularly limited as long as it can cause a photoexcitation reaction. However, since the alignment state of the liquid crystal material can be improved, the light irradiation direction is 10 ° oblique to the substrate surface. It is preferable to be within the range of ° to 45 °, more preferably within the range of 30 ° to 45 °, and most preferably 45 °.
Furthermore, when the polymerizable monomer as described above is used as the photoisomerization-reactive compound, it is polymerized by heating after the photo-alignment treatment, and the anisotropy imparted to the alignment film is stabilized. Can be

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 having different materials and / or orientation treatment methods) may be used. Among them, the orientation films 17 and 24 are preferably different orientation films. This is because the occurrence of alignment defects such as double domains can be effectively suppressed, and monodomain alignment can be obtained. The reason why a good alignment state can be obtained by using different alignment films is not clear, but is considered to be due to the difference in interaction between the alignment films and the liquid crystal substance. In addition, the liquid crystal material is aligned by the alignment regulating force of the alignment film, regardless of the electric field applied slow cooling method, so that alignment disorder due to temperature rise above the phase transition point hardly occurs, and liquid crystal display with excellent alignment stability It can be set as an element.
In the case where the alignment films 17 and 24 are different alignment films, for example, as described above, an alignment film having different materials and alignment treatment methods can be used. For example, one of the alignment films is subjected to photo-alignment treatment and the other is used. A rubbing-treated alignment film can be used, or one can be a photodimerization alignment film and the other can be a photoisomerization alignment film.
Further, when the alignment film is a photodimerization type alignment film, for example, by selecting various photodimerization reactive polymers as described above, it is possible to obtain alignment films with different materials to be used. At this time, the composition of the material can be changed by changing the addition amount of the additive. Further, when the alignment film is a photoisomerization type alignment film, by selecting various cis-trans isomerization reactive skeletons and substituents from the above-mentioned photoisomerization reactive compounds according to the required characteristics. , The alignment film can be made of different materials. At this time, the composition of the material can be changed by changing the addition amount of the additive.
Furthermore, the liquid crystal display element of the present invention may be provided with an alignment film on either the pixel electrode substrate 2 or the common electrode substrate 3.

  The barrier 5 extending on the common electrode 23 of the common electrode substrate 3 makes the alignment of the liquid crystal material injected into the cell gap formed between the pixel electrode substrate 2 and the common electrode substrate 3 uniform. It is a member for. The difference between the extending direction of the barrier 5 and the molecular direction in the monostable state of the liquid crystal substance is preferably in the range of 0 to 5 °. Moreover, 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. The width W of the barrier 5 is preferably narrow considering the aperture ratio. However, when the barrier 5 is also used as a spacer, if the barrier 5 is too narrow, it does not function in strength. Therefore, the width W of the barrier 5 can be appropriately set within a range of 5 to 30 μm, for example, in consideration of the function of the barrier 5. If the pitch P of the barriers 5 is less than 0.5 mm, the line-shaped defects on the display screen caused by the barriers 5 increase, resulting in a decrease in image quality. If the pitch P exceeds 3 mm, the injected liquid crystal substance It becomes difficult to achieve uniform orientation.

  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 and irradiating it with 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 addition, said (meth) acrylate means an acrylate or a methacrylate.

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, for example, the phase transition from the cholesteric phase directly to the chiral smectic C phase (SmC *) without passing through the smectic A phase. It has been done. The phase sequence of the liquid crystal is not particularly limited as long as it exhibits a chiral smectic C phase (SmC *), but the liquid crystal substance may be a nematic phase-cholesteric phase-chiral smectic C phase (SmC *), Alternatively, it is preferable that the phase change between the nematic phase and the chiral smectic C phase (SmC *) and not via the smectic A phase. By using a liquid crystal substance that exhibits monostability and does not pass through the smectic A phase, it becomes possible to drive by an active matrix method using TFTs, and to control gradation by voltage modulation, thereby achieving high definition and high performance. This is because display of quality can be realized.
In addition, when the liquid crystal display element of the present invention is driven by a field sequential method, the liquid crystal substance operates in a molecular direction of the liquid crystal substance only when a positive or negative voltage is applied, and half-V shaped switching (hereinafter referred to as half-V shaped switching). , Referred to as HV-shaped switching). When a liquid crystal material exhibiting such HV-shaped switching characteristics is used, the opening time as a black and white shutter can be made sufficiently long, whereby each color that can be temporally switched can be displayed brighter, and bright colors This is because a liquid crystal display element for display can be realized. Here, the “HV-shaped switching characteristic” refers to an electro-optical characteristic in which the light transmittance with respect to the applied voltage is asymmetric.
Among the above, 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 is suitable as a material that exhibits HV-shaped switching characteristics. Specific examples of such a liquid crystal substance include “R2301” and “FELIX-3206” sold by AZ Electronic Materials.

  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 thickness of the liquid crystal layer is preferably in the range of 1.2 μm to 3.0 μm, more preferably in the range of 1.3 μm to 2.5 μm, and still more preferably in the range of 1.4 μm to 2.0 μm. Is within. This is because if the thickness of the liquid crystal layer is thinner than the above range, the contrast may be lowered, and conversely if the thickness of the liquid crystal layer is thicker than the above range, the liquid crystal substance may be difficult to align.

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 above-described embodiment, the barrier 5 is provided on the common electrode 23 of the common electrode substrate 3, but may be provided on the pixel electrode 13 of the pixel electrode substrate 2. 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.

  In the liquid crystal display element of the present invention, a reactive liquid crystal layer formed by fixing a reactive liquid crystal may be formed between the alignment film and the liquid crystal layer. Such a reactive liquid crystal is aligned by an alignment film. For example, the reactive liquid crystal layer is formed by irradiating ultraviolet rays to polymerize the reactive liquid crystal and fixing the alignment state. Since the reactive liquid crystal layer is fixed on the alignment film in this way and the anisotropy is imparted to the reactive liquid crystal layer by the alignment film, the reactive liquid crystal layer is used as an alignment film for aligning the liquid crystal substance. Can function. Further, since the reactive liquid crystal layer is fixed on the alignment film, alignment disorder hardly occurs even when the temperature of the liquid crystal material is raised to a temperature higher than the phase transition point, and the alignment stability is excellent. Further, the reactive liquid crystal is relatively similar in structure to the liquid crystal material and has a strong interaction with the liquid crystal material, and thus has an advantage that the alignment of the liquid crystal material can be effectively controlled.

  The reactive liquid crystal layer may be formed on any one of the alignment films, or may be formed on both alignment films. When the reactive liquid crystal layer is formed on one of the alignment films, the liquid crystal substance is sandwiched between different layers (alignment film and reactive liquid crystal layer), so that alignment defects such as double domains Generation can be effectively suppressed, and a monodomain orientation can be obtained. Moreover, when the reactive liquid crystal layer is formed on both alignment films, it is preferable that the materials used for the respective reactive liquid crystal layers are different in order to obtain monodomain alignment.

  The reactive liquid crystal is preferably one that exhibits a nematic phase. This is because the nematic phase is relatively easy to control the alignment among the liquid crystal phases.

The reactive liquid crystal preferably contains a polymerizable liquid crystal material. This is because the alignment state of the reactive liquid crystal can be fixed.
As the polymerizable liquid crystal material contained in the reactive liquid crystal, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used, and a polymerizable liquid crystal monomer is preferably used. This is because the polymerizable liquid crystal monomer can be aligned at a lower temperature than the polymerizable liquid crystal oligomer and the polymerizable liquid crystal polymer, has high sensitivity in alignment, and can be easily aligned.
The polymerizable liquid crystal monomer is not particularly limited as long as it is a liquid crystal monomer having a polymerizable functional group, and examples thereof include a monoacrylate monomer and a diacrylate monomer. These polymerizable liquid crystal monomers may be used alone or in combination of two or more.

  Examples of the monoacrylate monomer include those represented by the following general formulas (4) and (5).

In the above general formulas (4) and (5), A ²¹ , B ²¹ , D ²¹ , E ²¹ and F ²¹ represent benzene, cyclohexane or pyrimidine, and these may have a substituent such as halogen. . A ²¹ and B ²¹ , or D ²¹ and E ²¹ may be bonded via a bonding group such as an acetylene group, a methylene group, or an ester group. M ²¹ and M ²² may be any of a hydrogen atom, an alkyl group having 3 to 9 carbon atoms, an alkoxycarbonyl group having 3 to 9 carbon atoms, or a cyano group. Furthermore, the acryloyloxy group at the molecular chain end and A ²¹ or D ²¹ may be bonded via a spacer such as an alkylene group having 3 to 6 carbon atoms.

  Moreover, as a diacrylate monomer, what is shown to following Structural formula 13,14 can be mentioned, for example.

In Structural Formulas 13 and 14, X and Y are hydrogen, alkyl having 1 to 20 carbons, alkenyl having 1 to 20 carbons, alkyloxy having 1 to 20 carbons, or alkyloxycarbonyl having 1 to 20 carbons. , Formyl, alkylcarbonyl having 1 to 20 carbons, alkylcarbonyloxy having 1 to 20 carbons, halogen, cyano or nitro. M represents an integer in the range of 2-20. X is preferably an alkyloxycarbonyl having 1 to 20 carbon atoms, methyl or chlorine, and among them, an alkyloxycarbonyl having 1 to 20 carbon atoms, particularly CH ₃ (CH ₂ ) ₄ OCO is preferable.

  Furthermore, as a diacrylate monomer, what is shown to the following Structural formula 15 can be mentioned, for example.

In the above structural formula 15, Z ³¹ and Z ³² are each independently independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C. Represents ≡C—, —OCH ₂ —, —CH ₂ O—, —CH ₂ CH ₂ COO—, —OCOCH ₂ CH ₂ —, and R ³¹ represents hydrogen or alkyl having 1 to 5 carbon atoms. K and m represent 0 or 1, and n represents an integer in the range of 2 to 8.

  Specific examples of the diacrylate monomer represented by Structural Formula 15 include those represented by Structural Formula 16 below.

In the above structural formula 16, Z ²¹ and Z ²² are each independently independently directly bonded —COO—, —OCO—, —O—, —CH ₂ CH ₂ —, —CH═CH—, —C. Represents ≡C—, —OCH ₂ —, —CH ₂ O—, —CH ₂ CH ₂ COO—, —OCOCH ₂ CH ₂ —. M represents 0 or 1, and n represents an integer in the range of 2-8.

  In the present invention, among those described above, those represented by structural formulas 13 and 15 are preferably used. Examples of the reactive liquid crystal containing the diacrylate monomer represented by the structural formula 15 include “Adeka Kiracol PLC-7183” and “Adeka Kiracol PLC-7209” manufactured by Asahi Denka Kogyo Co., Ltd. . Examples of the reactive liquid crystal containing an acrylate monomer include “ROF-5101” and “ROF-5102” manufactured by Rolic technologies.

  In the present invention, among the polymerizable liquid crystal monomers, diacrylate monomers are preferred. This is because the diacrylate monomer can be easily polymerized while maintaining the orientation state in a good state.

  The polymerizable liquid crystal monomer described above does not have to exhibit a nematic phase. These polymerizable liquid crystal monomers may be used as a mixture of two or more as described above, and any composition in which these are mixed, that is, a reactive liquid crystal, can exhibit a nematic phase.

Furthermore, you may add a photoinitiator and a polymerization inhibitor to the said reactive liquid crystal as needed.
Examples of the photopolymerization initiator that can be used in the present invention include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, benzoylmethyl benzoate, 4-benzoyl-4'-methyldiphenyl. Sulfide, benzyl methyl ketal, dimethylaminomethyl benzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoyl formate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropyl Phenyl) -2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4- And propoxythioxanthone. In addition to the photopolymerization initiator, it is also possible to add a sensitizer as long as the object of the present invention is not impaired.
The amount of the photopolymerization initiator added is generally 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. It can be added to the liquid crystal.

  The thickness of the reactive liquid crystal layer is appropriately adjusted according to the target anisotropy, and can be set, for example, within a range of 1 nm to 1000 nm, and preferably within a range of 3 nm to 100 nm. This is because if the reactive liquid crystal layer is too thick, anisotropy more than necessary occurs, and if the reactive liquid crystal layer is too thin, the predetermined anisotropy may not be obtained.

  Such a reactive liquid crystal layer is formed by applying a coating liquid for a reactive liquid crystal layer containing a reactive liquid crystal on an alignment film, performing an alignment treatment, and fixing the alignment state of the reactive liquid crystal. Can do. Alternatively, the reactive liquid crystal layer may be formed by forming a dry film or the like in advance and laminating it on the alignment film instead of applying the coating liquid for the reactive liquid crystal layer. From the viewpoint of simplicity of the production process, it is preferable to use a method in which a reactive liquid crystal is dissolved in a solvent to prepare a coating liquid for a reactive liquid crystal layer, which is applied onto an alignment film, and the solvent is removed.

The solvent used in the coating liquid for the reactive liquid crystal layer is not particularly limited as long as it can dissolve the reactive liquid crystal and the like and does not inhibit the alignment ability of the alignment film. For example, hydrocarbons such as benzene, toluene, xylene, n-butylbenzene, diethylbenzene and tetralin; ethers such as methoxybenzene, 1,2-dimethoxybenzene and diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2 Ketones such as 1,4-pentanedione; esters such as ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone; 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl Amide solvents such as acetamide; t-butyl alcohol, diacetone alcohol, glycerin, monoacetin, ethylene glycol, triethyleneglycol 1 or more types of alcohols such as hexylene glycol, phenols, phenols such as phenol and parachlorophenol, and cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and ethylene glycol monomethyl ether acetate can be used. is there.
Further, if only a single kind of solvent is used, the solubility of the reactive liquid crystal or the like may be insufficient or the alignment film may be eroded. In this case, this inconvenience can be avoided by using a mixture of two or more solvents. Among the above-mentioned solvents, hydrocarbons and glycol monoether acetate solvents are preferable as the sole solvent, and a mixed system of ethers or ketones and glycol solvent is preferable as the mixed solvent. It is.
Although the concentration of the coating liquid for the reactive liquid crystal layer depends on the solubility of the reactive liquid crystal and the thickness of the reactive liquid crystal layer, it cannot be defined unconditionally, but is usually 0.1 to 40% by weight, preferably 1 to It is adjusted in the range of 20% by weight. If the concentration is lower than the above range, the reactive liquid crystal may be difficult to align. Conversely, if the concentration is higher than the above range, the viscosity of the coating liquid for the reactive liquid crystal layer is increased, so that a uniform coating film is formed. This is because it may be difficult.

Furthermore, the following compounds can be added to the reactive liquid crystal layer coating solution as long as the object of the present invention is not impaired. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amine epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meth) Acry Photopolymerizable compound in epoxy (meth) acrylate obtained by reacting an acid; photopolymerizable liquid crystal compound having an acryl group and a methacryl group; and the like.
The amount of these compounds added to the reactive liquid crystal is selected within a range that does not impair the object of the present invention. Addition of these compounds improves the curability of the reactive liquid crystal, increases the mechanical strength of the resulting reactive liquid crystal layer, and improves its stability.

Examples of the coating method of the reactive liquid crystal layer coating liquid include spin coating, roll coating, printing, dip coating, die coating, casting, bar coating, blade coating, spray coating, Examples include a gravure coating method, a reverse coating method, and an extrusion coating method.
Further, after the reactive liquid crystal layer coating liquid is applied, the solvent is removed. The solvent is removed by, for example, removal under reduced pressure or removal by heating, or a combination thereof.

In the present invention, the reactive liquid crystal applied as described above is aligned by the alignment film so as to have liquid crystal regularity. That is, a nematic phase is developed in the reactive liquid crystal. This is usually performed by a method such as a method of performing a heat treatment below the NI transition point. Here, the NI transition point indicates the temperature at which the liquid crystal phase transitions to the isotropic phase.
The reactive liquid crystal contains a polymerizable liquid crystal material, and in order to fix the alignment state of the polymerizable liquid crystal material, a method of irradiating actinic radiation that activates polymerization is used. As used herein, active radiation refers to radiation that has the ability to cause polymerization of a polymerizable liquid crystal material.
The actinic radiation is not particularly limited as long as it is a radiation capable of polymerizing the polymerizable liquid crystal material, but usually ultraviolet light or visible light is used from the viewpoint of the ease of the apparatus. Irradiation light having a wavelength of 150 to 500 nm, preferably 250 to 450 nm, and more preferably 300 to 400 nm is used.
In the present invention, a method of irradiating ultraviolet rays with active radiation to a polymerizable liquid crystal material in which the photopolymerization initiator generates radicals with ultraviolet rays and the polymerizable liquid crystal material undergoes radical polymerization is a preferable method. . This is because the method using ultraviolet rays as actinic radiation is an already established technique, and therefore it can be easily applied to the present invention including the photopolymerization initiator to be used.
As a light source of this irradiation light, a low pressure mercury lamp (sterilization lamp, fluorescent chemical lamp, black light), a high pressure discharge lamp (high pressure mercury lamp, metal halide lamp), a short arc discharge lamp (super high pressure mercury lamp, xenon lamp, mercury xenon). Lamp). In particular, the use of metal halide lamps, xenon lamps, high-pressure mercury lamps, etc. is recommended. The irradiation intensity is appropriately adjusted according to the composition of the reactive liquid crystal and the amount of photopolymerization initiator.
Such irradiation with active radiation may be performed under a temperature condition in which the polymerizable liquid crystal material becomes a liquid crystal phase, or may be performed at a temperature lower than the temperature at which the liquid crystal phase is formed. This is because the alignment state of the polymerizable liquid crystal material once in the liquid crystal phase is not disturbed suddenly even if the temperature is lowered thereafter.
Further, as a method for fixing the alignment state of the polymerizable liquid crystal material, in addition to the method of irradiating the active radiation, a method of polymerizing the polymerizable liquid crystal material by heating can be used. As the reactive liquid crystal used in this case, it is preferable that the polymerizable liquid crystal monomer contained in the reactive liquid crystal is thermally polymerized below the NI transition point of the reactive liquid crystal.

  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.
First, as a material for the photodimerization type alignment film, four types of alignment film coating liquids were prepared by dissolving the compounds A to D represented by the following structural formulas A to D in cyclopentanone (2 wt%), respectively. .

[Example 1]
Two glass substrates (10.16 mm × 10.16 mm) 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. Thereafter, it was patterned into a stripe shape having a width of 10 μm and a pitch of 1.5 mm by photolithography, and baked at 270 ° C. for 30 minutes. Thus, a barrier having a height of 1.5 μm was formed on the ITO thin film of the glass substrate.

  Next, an alignment film coating solution in which the compound A represented by the structural formula A is dissolved on both the ITO thin films of the glass substrate on which the barrier is formed as described above and the glass substrate on which the barrier is not formed is spin-coated. (4000 rpm, 30 seconds) and dried in an oven at 180 ° C. for 10 minutes. Then, 100 mJ exposure was carried out with polarized ultraviolet light, 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.
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 material (R2301 manufactured by AZ Electronic Materials) is attached to the upper part of the inlet. Then, it was injected into the cell gap at a temperature 10 to 20 ° C. higher than the nematic phase-isotropic transition temperature using a vacuum oven. After the injection, the liquid crystal material was gradually cooled to room temperature.

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%.

  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).

[Example 2]
Two glass substrates (10.16 mm × 10.16 mm) having an indium tin oxide (ITO) thin film formed on the surface were prepared.
Next, a barrier was formed in the same manner as in Example 1 on one ITO thin film on the glass substrate. However, the height of the barrier was set to four types of 0.4 μm, 0.8 μm, 1.2 μm, and 1.5 μm by controlling the coating amount of the photosensitive resin material.

Next, an alignment film was formed in the same manner as in Example 1 on the ITO thin films of both the four types of glass substrates on which the barriers were formed as described above and the glass substrate on which the barriers were not formed. This 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 °.
Next, in the same manner as in Example 1, a liquid crystal layer was formed in the cell gap of both glass substrates.
As a result, four types of samples having different barrier heights were produced. As a result of observing the alignment state of the liquid crystal layer for each sample in the same manner as in Example 1, the sample has a barrier height in the range of 50 to 100% of the gap (distance between substrates (1.5 μm)) (barrier height). : 0.8 μm, 1.2 μm, 1.5 μm), it was confirmed that the liquid crystal layer is a monostable ferroelectric liquid crystal with uniform monodomain alignment. In particular, in the samples having a barrier height of 1.2 μm and 1.5 μm, the monodomain orientation was extremely uniform (occupation area of the region having the same layer normal direction was 98%).

  However, in the sample (barrier height: 0.4 μm) in which the height of the barrier is less than 50% of the gap (distance between substrates (1.5 μm)), the liquid crystal layer has a double domain orientation (the region where the normal direction of the layers is the same). Occupied area of 60%).

[Example 3]
In the same manner as in Example 1, except that the alignment film coating solution dissolving the compound B represented by the structural formula B was used instead of the alignment film coating solution dissolving the compound A represented by the structural formula A, The liquid crystal layer was formed in the cell gap. 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 °.
It was confirmed that the liquid crystal layer formed in the cell gap was a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of 98% in the region having the same layer normal direction).

[Example 4]
In the same manner as in Example 1, except that the alignment film coating solution in which the compound C represented by the structural formula C was dissolved instead of the alignment film coating solution in which the compound A represented by the structural formula A was dissolved, The liquid crystal layer was formed in the cell gap. 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 was confirmed to be a monostable ferroelectric liquid crystal having uniform monodomain alignment (occupied area of 97% in the region having the same layer normal direction).

[Example 5]
In the same manner as in Example 1, except that the alignment film coating solution in which the compound D represented by the structural formula D was used instead of the alignment film coating solution in which the compound A represented by the structural formula A was dissolved, The liquid crystal layer was formed in the cell gap. 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 was confirmed to be a monostable ferroelectric liquid crystal having uniform monodomain alignment (occupied area of 97% in the region having the same layer normal direction).

[Example 6]
A glass substrate similar to that in Example 1 was prepared, and a barrier was formed on the ITO thin film of one glass substrate in the same manner as in Example 1.
Next, an alignment film coating solution in which the compound A represented by the structural formula A is dissolved is applied to the glass substrate on which the barrier is formed as described above by a spin coating method (4000 rpm, 30 seconds), and 180 ° in an oven. After drying at 10 ° C. for 10 minutes, the photo-alignment treatment was performed by exposing to 100 mJ with polarized ultraviolet light. Further, an alignment film coating solution in which compound B represented by structural formula B is dissolved is applied onto an ITO thin film of a glass substrate on which no barrier is formed by spin coating (4000 rpm, 30 seconds), After drying at 180 ° C. for 10 minutes, the photo-alignment treatment was performed by exposing to 100 mJ with polarized ultraviolet light. 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 °.

Next, using the glass substrate on which the barrier was formed and the glass substrate on which the barrier was not formed, the liquid crystal layer was formed in the cell gap in the same manner as in Example 1.
It was confirmed that the liquid crystal layer formed in the cell gap was a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of the region having the same layer normal direction was 98%).

[Example 7]
Two glass substrates similar to Example 1 were prepared, and a barrier having a height of 1.5 μm was formed on the ITO thin film of one glass substrate in the same manner as Example 1.
Next, an alignment film coating solution in which the compound A represented by the structural formula A is dissolved is applied on the ITO thin film of the glass substrate on which the barrier is formed by spin coating (4000 rpm, 30 seconds), and 180 ° in an oven. After drying at 10 ° C. for 10 minutes, the photo-alignment treatment was performed by exposing to 100 mJ with polarized ultraviolet light. Further, an alignment film coating solution in which compound B represented by structural formula B is dissolved is applied onto an ITO thin film of a glass substrate on which no barrier is formed by spin coating (4000 rpm, 30 seconds), After drying at 180 ° C. for 10 minutes, the photo-alignment treatment was performed by exposing to 100 mJ with polarized ultraviolet light. 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 °.

  Next, in the same manner as in Example 1, the liquid crystal layer was formed in the cell gap. It was confirmed that the liquid crystal layer formed in the cell gap was a monostable ferroelectric liquid crystal with uniform monodomain alignment (occupied area of 98% in the region having the same layer normal direction).

[Comparative Example 1]
Two glass substrates similar to those in Example 1 were prepared. On the ITO thin film of each glass substrate, an alignment film coating solution in which compound A represented by structural formula A is dissolved is applied by spin coating (4000 rpm, 30 seconds) and dried in an oven at 180 ° C. for 10 minutes. Was done. Then, 100 mJ exposure was carried out with polarized ultraviolet light, the photo-alignment process was performed, and the alignment film was formed.

Next, granular spacers having an average particle diameter of 1.5 μm were sprayed on the alignment film of one glass substrate, and a sealing material was applied to the peripheral portion of the other glass substrate. And it was made to oppose, and thermocompression-bonded so that the relationship between both glass substrates might be parallel and anti-parallel to said polarized ultraviolet irradiation direction.
Next, a liquid crystal material (R2301 manufactured by AZ Electronic Materials Co., Ltd.) is attached to the upper part of the injection port for injecting liquid crystal into the cell gap of both glass substrates, and nematic phase-isotropic transition temperature using a vacuum oven. Injection into the cell gap was performed at a temperature higher by 10 to 20 ° C., followed by slow cooling to return to room temperature. However, it was confirmed that a double domain was generated in the liquid crystal layer in the cell gap (the occupied area of the region having the same layer normal direction was 55%), and an alignment defect was generated.

[Comparative Example 2]
Instead of the alignment film coating solution in which the compound A represented by the structural formula A was dissolved, the alignment film coating solution in which the compound B represented by the structural formula B was dissolved was used in the same manner as in Comparative Example 1, The liquid crystal layer was formed in the cell gap. However, it was confirmed that a double domain was generated in the liquid crystal layer in the cell gap (the occupied area of the region having the same layer normal direction was 50%), and alignment defects were generated.

[Comparative Example 3]
Instead of the alignment film coating solution in which the compound A represented by the structural formula A was dissolved, the alignment film coating solution in which the compound C represented by the structural formula C was dissolved was used in the same manner as in Comparative Example 1, The liquid crystal layer was formed in the cell gap. However, it was confirmed that a double domain was generated in the liquid crystal layer in the cell gap (the occupied area of the region having the same layer normal direction was 50%), and alignment defects were generated.

[Comparative Example 4]
Instead of the alignment film coating solution in which the compound A represented by the structural formula A was dissolved, the alignment film coating solution in which the compound D represented by the structural formula D was dissolved was used in the same manner as in Comparative Example 1, The liquid crystal layer was formed in the cell gap. However, it was confirmed that a double domain was generated in the liquid crystal layer in the cell gap (the occupied area of the region having the same layer normal direction was 50%), and alignment defects were generated.

[Example 8]
Two glass substrates (10.16 mm × 10.16 mm) having an indium tin oxide (ITO) thin film formed on the surface were prepared.
Next, a barrier was formed in the same manner as in Example 1 on one ITO thin film on the glass substrate. However, by changing the exposure pattern of the photosensitive resin material, the barrier pitch was set to five types of 3.5 mm, 3 mm, 1.5 mm, 0.5 mm, and 0.4 mm.

Next, an alignment film was formed in the same manner as in Example 1 on the ITO thin films of both the five types of glass substrates on which the barriers were formed as described above and the glass substrate on which the barriers were not formed. This 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 °.
Next, in the same manner as in Example 1, a liquid crystal layer was formed in the cell gap of both glass substrates.
This produced five types of samples with different barrier pitches. For each sample, the alignment state of the liquid crystal layer was observed in the same manner as in Example 1. As a result, a sample having a barrier pitch of 3.5 mm could not maintain a uniform gap in the cell. In the samples with the barrier pitches of 3 mm, 1.5 mm, and 0.5 mm, it was confirmed that the liquid crystal layer was a monostable ferroelectric liquid crystal with uniform monodomain alignment. In particular, in the sample having a barrier pitch of 1.5 mm, the monodomain orientation was extremely uniform (occupation area of the region having the same layer normal direction was 98%).

  However, in the sample having a barrier pitch of 0.4 mm, the liquid crystal layer had double domain orientation (occupied area of the region having the same layer normal direction was 90%).

  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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element 2 ... Pixel electrode substrate 3 ... Common electrode substrate 4 ... Liquid crystal layer 5 ... Barrier 6 ... Backlight 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 (5)

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,
Comprising a plurality of barriers in the liquid crystal layer, the liquid crystal material is Ri extension direction substantially the same der molecular direction the barrier at the monostable state,
The liquid crystal material is characterized in that the liquid crystal phase series does not pass through the smectic A phase and is uniformly monodomain aligned .   2. The liquid crystal display device according to claim 1, wherein a difference between a molecular direction of the liquid crystal substance in a monostable state and a barrier extending direction is in a range of 0 to 5 °.   The liquid crystal display element according to claim 1, wherein a pitch between the adjacent barriers is in a range of 0.5 to 3 mm.   4. The liquid crystal display element according to claim 1, wherein the alignment film is a film provided with anisotropy by a rubbing process or a photo-alignment process.   The liquid crystal display element according to claim 1, wherein the barrier occupies 50 to 100% of a distance between substrates.

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