KR20140119295A - zero-surface anchoring alignment method for liquid crystal, contactless alignment method for liquid crystal, and liquid crystal display device using the same - Google Patents

Abstract

The present invention provides a method of realizing the zero plane anchoring state easily and stably and a liquid crystal display device using the zero plane anchoring state realized by this method.
To this end, in a liquid crystal cell in which a polymer brush is formed on a substrate subjected to a planarization treatment and liquid crystal is sandwiched between the substrates, it is possible to freely change the shape of the coexistence portion higher than the Tg of the coexistence portion of the polymer brush and the liquid crystal The liquid crystal alignment method comprising the steps of: Further, there is provided a liquid crystal display device comprising a liquid crystal cell manufactured by a zero plane anchoring liquid crystal alignment method.

Description

[0001] The present invention relates to a zero-surface anchoring liquid crystal alignment method, a non-contact liquid crystal alignment method using the same, and a liquid crystal display device using the same,

The present invention relates to a zero plane anchoring liquid crystal alignment method, a noncontact liquid crystal alignment method using the same, and a liquid crystal display device manufactured using these liquid crystal alignment methods.

Since liquid crystal display devices have characteristics such as thinness, light weight, and low power consumption, they are being used in a wide range of applications such as displays for mobile phones, computers and TVs.

Various display modes such as TN (Twisted Nematic), IPS (In-Plane Switching) and FLC (Ferroelectric Liquid Crystal) have been proposed as the display principle of a liquid crystal display. However, most of them require alignment directions of liquid crystal molecules . As a method of regulating the alignment direction of the liquid crystal molecules, an orientation film composed of polyimide or the like is formed on a substrate, and then a roller around which a fabric such as rayon or cotton is wound is kept in a state in which the rotation number and the distance between the roller and the substrate are kept constant (Rubbing method) of rubbing the surface of the alignment film in one direction by rotating the alignment film, or a method (photo alignment method) of generating anisotropy on the surface of the polyimide film by irradiating polarized ultraviolet rays. It is strongly bound to the surface and oriented in a certain direction. As a result, in the display mode other than the FLC, the memory property can not be found in principle, and the drive threshold value exists in other than the special display mode such as the V-Shape mode.

On the other hand, there is also proposed a new concept display (memory) in which the orientation direction of the liquid crystal molecules is oriented in an arbitrary direction by an external field (electric field, magnetic field, etc.) and the state is maintained (memorized). In order to realize such an operation, it is necessary to eliminate the alignment restraining force (anchoring) of the surface of the substrate. To realize this, a method of forming the liquid crystal device into a liquid-liquid crystal interface in a completely wet state has been reported (see Patent Document 1) . In this method, a liquid-liquid crystal phase separation is generated by mixing a substance insoluble in a liquid crystal substance (for example, polystyrene) into a liquid crystal substance, and this is caused to have strong affinity by a liquid phase phase-separated from the liquid crystal substance The liquid crystal material is sandwiched by the liquid layer so as to realize an anchoring state in which there is no alignment restraining force on the surface of the substrate, that is, a zero plane anchoring state. In this method, a method of stabilizing the liquid-liquid crystal interface is further carried out by adding a small amount of a block copolymer having a polystyrene molecule and a portion having affinity to both liquid crystal molecules in one molecule as a surfactant. In this specification, the term 'zero plane anchoring' refers to a state in which liquid crystal molecules in the in-plane direction are aligned in a horizontal direction or a diagonal direction, but the alignment regulating force of the liquid crystal molecules in the in-plane direction is zero, , And there is no alignment restraining force of the liquid crystal molecules in the horizontal plane.

Patent Document 1: Japanese Patent Publication No. 4053530

However, since the method of Patent Document 1 realizes the zero surface anchoring state by an exquisite balance between the surface treatment of the substrate and the liquid crystal and the substance insoluble in the liquid crystal substance added to the liquid crystal and the surfactant, if the balance is not properly maintained, And the liquid crystal is unstable, so that a desired state can not be realized. Further, depending on the processing method of the substrate, the state of the surface of the substrate changes with the elapse of time, so that the zero plane anchoring state can not be stably maintained. Therefore, in order to stably realize the zero plane anchoring state, it is necessary to optimize the type of surface insoluble substance and surfactant and the amount of addition of the insoluble substance in the liquid crystal substance and the liquid crystal substance added to the liquid crystal and liquid crystal, in need.

An object of the present invention is to provide a method of realizing a zero plane anchoring state simply and stably and a liquid crystal display device using the zero plane anchoring state realized by the method.

It is another object of the present invention to provide a liquid crystal display device realized by a simple and stable method of realizing noncontact liquid crystal alignment by applying the above technique and its method. In this specification, the term "non-contact liquid crystal alignment method" means a liquid crystal alignment method which does not require rubbing of the orientation film surface as in the conventional rubbing method. According to this method, the liquid crystal molecules are not only in a horizontal direction Direction.

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that a polymer brush is formed on a substrate subjected to a planarization treatment, and a liquid crystal cell sandwiched between the substrates has a Tg Glass transition temperature), and at the same time, the zero plane anchoring state can be realized by heating to a temperature at which the shape of the coexistent portion can freely change.

That is, the present invention relates to a liquid crystal cell in which a polymer brush is formed on a substrate subjected to a planarization treatment and a liquid crystal is interposed between the substrates, wherein a Tg of the coexistence portion of the polymer brush and the liquid crystal is higher than that of the coexistence portion, The liquid crystal alignment method is a zero plane anchoring liquid crystal alignment method.

Further, the present invention is a liquid crystal display device comprising a liquid crystal cell manufactured by the zero plane anchoring liquid crystal alignment method.

Furthermore, the inventors of the present invention found that it is possible to regulate the orientation of liquid crystal molecules by non-contact means without rubbing the alignment film surface like the rubbing method by combining with the geometrical concave-convex structure formed on the substrate surface by applying the zero plane anchoring liquid crystal alignment method did.

That is, the present invention provides a liquid crystal cell in which a polymer brush is formed on a substrate having a geometrically concave-convex structure and a liquid crystal is sandwiched between the substrates, the liquid crystal cell having a higher Tg than a coexisting portion of the polymer brush and the liquid crystal, And the liquid is heated to a temperature at which the liquid crystal can be changed.

Further, the present invention is a liquid crystal display device comprising a liquid crystal cell manufactured by the non-contact liquid crystal alignment method.

According to the present invention, it is possible to provide a liquid crystal display device using a zero plane anchoring state realized by simple and stable realization of a zero plane anchoring state and a zero plane anchoring state realized by the method.

INDUSTRIAL APPLICABILITY The present invention can provide a liquid crystal display device realized by a simple and stable method of realizing a non-contact alignment method and its method.

1 is a cross-sectional view of a liquid crystal cell manufactured using the zero plane anchoring liquid crystal alignment method of the present invention.
2 is an enlarged cross-sectional view of a liquid crystal cell manufactured using the zero plane anchoring liquid crystal alignment method of the present invention.
3 (a) is a top view of a liquid crystal cell using a substrate on which a geometrically uneven structure is not formed, and FIG. 3 (b) is a top view of a liquid crystal cell using a substrate having a geometrically concave-convex structure.
4 is a graph showing the relationship between the time and the transmittance in the liquid crystal cell fabricated in the example (25 DEG C).
5 is a graph showing the relationship between the time and the transmittance in the liquid crystal cell fabricated in the example (45 DEG C).
Fig. 6 is a graph showing the relationship between the time and the transmittance in the liquid crystal cell fabricated in the example (65 deg. C).
7 is a graph showing the relationship between the time and the transmittance in the liquid crystal cell manufactured in the example (85 DEG C).
Fig. 8 is a microscope photograph of the liquid crystal cell produced in the example. Fig. 8 (a) is a photograph of the cross-Nicol polarizer polarized at 20 ° from the direction of the incidence polarizer, And the direction of the electrodes are made to coincide with each other.

≪ Embodiment 1 >

The zero plane anchoring liquid crystal alignment method of the present embodiment is a liquid crystal alignment method in which a polymer brush is formed on a substrate subjected to a planarization treatment and a liquid crystal cell is sandwiched between the substrates and has a higher Tg than a coexisting portion of the polymer brush and the liquid crystal, So that the shape is freely changed.

Hereinafter, the zero plane anchoring liquid crystal alignment method (hereinafter referred to as the zero plane alignment method) of the present embodiment will be described in detail with reference to the drawings.

Fig. 1 is a cross-sectional view of a liquid crystal cell manufactured by the zero plane alignment method of the present embodiment, and Fig. 2 is an enlarged cross-sectional view of this liquid crystal cell. 1 and 2, the liquid crystal cell has a structure in which the liquid crystal 5 is sandwiched between the substrates 1 on which the polymer brushes 2 are formed. The liquid crystal 5 penetrates the surface layer portion of the polymer brush 2 formed on the substrate 1 and the surface layer portion of the polymer brush 2 in contact with the liquid crystal 5 is swollen Not shown). The portion of the polymer brush 2 in which the liquid crystal 5 has penetrated is referred to as the coexisting portion 4 and the portion of the polymer brush 2 in which the liquid crystal 5 does not penetrate is referred to as the polymer brush layer 3 . In FIG. 1, the coexistence portion 4 and the polymer brush layer 3 are clearly distinguished from the viewpoint of facilitating the understanding of the present invention. However, as shown in FIG. 2, the coexistence portion 4 and the polymer brush layer 3, (3) is difficult to distinguish.

In the zero plane orientation method of the present embodiment, the liquid crystal cell is heated to a temperature higher than the Tg (glass transition temperature) of the coexistence section 4 and at the same time the shape of the coexistence section 4 can be freely varied. The state of the coexisting portion 4 is changed at the interface between the coexistence portion 4 and the liquid crystal 5 and the liquid crystal molecules 6 are aligned in the horizontal direction with respect to the substrate 1, It is possible to give the coexistence section 4 a state in which the orientation regulating force is not provided in any direction (zero plane anchoring state).

If the heating temperature is lower than the Tg of the coexistence portion 4, the shape of the coexistence portion 4 can not be freely changed, and therefore the state of the coexistence portion 4 is not sufficiently changed and the zero plane anchoring state can not be obtained.

The Tg of the coexisting portion 4 can not be uniquely defined because it depends on the type of the polymer brush 2 and the liquid crystal 5 to be used. Generally, the Tg of the polymer brush 2 alone Respectively. For example, in the case of the polymer brush 2 formed by using methyl methacrylate as a raw material (polymerizable monomer) of the polymer brush 2, the Tg of the coexistent portion 4 is generally Lt; RTI ID = 0.0 > 60 C. < / RTI > The Tg of the coexisting portion 4 also changes depending on the degree of penetration of the liquid crystal 5 into the polymer brush 2 (that is, the ratio between the polymer brush 2 and the liquid crystal 5). Concretely, in the coexisting portion 4, the coexisting portion 4 on the side of the liquid crystal 5 in which the ratio of the liquid crystal 5 is large has a low Tg and a low ratio of the liquid crystal 5 to the polymer brush layer 3 side The Tg of the coexistence portion 4 of the first embodiment increases.

The heating temperature of the coexisting portion 4 is preferably at least 60 ° C lower than the Tg of the polymer brush 2, more preferably at least 25 ° C lower than the Tg of the polymer brush 2, more preferably at least 25 ° C lower than the Tg of the polymer brush 2 from the viewpoint of stably obtaining the zero plane anchoring state Is above 10 ° C lower.

The upper limit of the heating temperature is not particularly limited, but is preferably lower than the NI point (phase transition temperature from N phase to I phase) of the liquid crystal 5. If the heating temperature is equal to or higher than the NI point, the liquid crystal 5 becomes I-phase (isotropic liquid phase), and a desired state may not be obtained.

The heating device for performing the heating process is not particularly limited as long as the temperature can be adjusted, and a known heating device can be used.

Next, the liquid crystal cell used in the zero plane orientation method of the present embodiment and its manufacturing method will be described in detail.

The liquid crystal cell used in the zero plane orientation method of the present embodiment can be manufactured by injecting the liquid crystal 5 between the substrates 1 on which the polymer brushes 2 are formed.

The substrate 1 is not particularly limited as long as it is planarized, and those generally known in the art can be used. In the case where the substrate surface has a concavo-convex structure, since the liquid crystal molecules are oriented along the concavo-convex structure, the zero plane anchoring state can not be substantially realized.

The planarization treatment is not particularly limited and can be carried out by using methods known in the art. As an example of the planarization treatment, a method of forming a planarizing film on the surface of the substrate 1 can be mentioned. For example, a UV curable transparent resin or the like may be coated on the surface of the substrate 1 and UV cured.

Examples of the substrate 1 include an array substrate and an opposite substrate. An example of the array substrate is an active matrix array substrate. The active matrix array substrate generally has a gate wiring and a source wiring arranged in a matrix on a glass substrate, an active element such as a thin film transistor (TFT) is formed at an intersection portion, and a pixel electrode is connected to the active element. An example of the counter substrate is a color filter substrate. In general, a color filter substrate is formed by forming a black matrix on a glass substrate to prevent unnecessary light spots, forming a colored layer of R (red), G (green), and B (blue) And a counter electrode facing the pixel electrode is formed. In the case of using these substrates 1, a transparent resin may be applied to the surface of the substrate 1 and cured to form a planarized film.

The polymer brush 2 to be formed on the substrate 1 is not particularly limited and those generally known in the art can be used. In the present specification, the term 'polymer brush (2)' means that a plurality of graft polymer chains are elongated in a direction perpendicular to the surface of the substrate 1 at a high density. Generally, a graft polymer chain having one end fixed to the surface of a substrate 1 has an entangled structure of a coil shape when the graft density is low. However, since the polymer brush 2 has a high graft density, interaction between adjacent graft polymer chains ) Extending in a direction perpendicular to the surface of the substrate 1. The substrate 1 has a structure shown in Fig. Also it means the density is called "high-density" compact the graft polymer so result in steric repulsion between the graft polymer chain to the adjacent chain in this specification and generally in the range of 0.1 strands / nm ² or more, preferably 0.1 to 1.2 strands / nm < / ^RTI > In this specification, the term "density of the graft polymer chain" means the number of strands of the graft polymer chain formed on the surface of the substrate 1 per unit area (nm ² ).

The polymer brush 2 forms a layer of the polymer brush 2 on the surface of the substrate 1. The thickness of the polymer brush (2) layer is not particularly limited, but is generally several tens nm, specifically 1 nm or more and less than 100 nm, preferably 10 nm to 80 nm. In addition, the size of the polymer brush (2) has a size excluding effect, so that a certain size of material can not pass through the polymer brush (2) layer. Therefore, even if the thickness of the polymer brush 2 layer is reduced, it is possible to prevent impurities from entering the liquid crystal 5 from the substrate.

The method of forming the polymer brush 2 is not particularly limited and can be carried out by using a method known in the art. Specifically, the polymer brush 2 can be formed by living radical polymerization of a radically polymerizable monomer. The term "living radical polymerization" as used herein means a polymerization reaction in which the chain transfer reaction and the termination reaction do not substantially occur in the radical polymerization reaction and the chain growth terminal remains active even after all the radical polymerizable monomers are reacted do. In this polymerization reaction, the polymerization activity is maintained at the end of the produced polymer even after completion of the polymerization reaction, and the polymerization reaction can be started again by adding the radical polymerizable monomer. The living radical polymerization is characterized in that it is possible to synthesize a polymer having an arbitrary average molecular weight by controlling the concentration ratio of the radical polymerizable monomer and the polymerization initiator, and the molecular weight distribution of the produced polymer is very narrow.

A representative example of living radical polymerization is atom transfer radical polymerization (ATRP). For example, atom transfer living radical polymerization of a radically polymerizable monomer is carried out using a halogenated copper / ligand complex in the presence of a polymerization initiator. Radical polymerizable monomers are added to the growth radicals reversibly grown by extraction of the polymer terminal halogen with the copper halide / ligand complex, and the molecular weight distribution is regulated by a sufficient frequency of reversible activation and inactivation.

The radical polymerizable monomer used for the living radical polymerization is a polymer having an unsaturated bond capable of performing radical polymerization in the presence of an organic radical, and examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate Acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, ethyl acrylate, butyl acrylate, ethyl acrylate, butyl acrylate, Methoxyethyl methacrylate, methoxy tetraethylene glycol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2 -Hydroxypropyl methacrylate, tetrahydroperfuryl methacrylate, 2-hydroxy-3-phenoxy Methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate, 2- (dimethylamino) methacrylate-based monomers such as methacrylate; Acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, benzyl acrylate, cyclohexyl acrylate, Acrylate, n-octyl acrylate, 2-methoxyethyl acrylate, butoxy ethyl acrylate, methoxytetraethylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, 2- (diethylamino) ethyl acrylate, diethylene glycol acrylate, , N, N-dimethyl acrylamide, N-methylol acrylamide, N-methylol Acrylate monomers such as acrylamide and acrylamide; M-, p-methoxystyrene, o-, m-, pt-butoxystyrene, o-, m-, p-chloromethylstyrene, and the like) , Vinyl esters (such as vinyl acetate, vinyl propionate and vinyl benzoate), vinyl ketones (such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone), N-vinyl compounds (Meth) acrylic acid derivatives (for example, acrylonitrile, methacrylonitrile, acrylamide, isopropylacrylamide, and the like), vinyl pyrrolidone Vinyl monomers such as vinyl chloride, vinylidene chloride, tetrachlorethylene, hexachloroprene, and vinyl fluoride), and the like can be given. These various radical polymerizable monomers may be used alone or in combination of two or more.

The polymerization initiator is not particularly limited and those generally known in living radical polymerization can be used. Examples of the polymerization initiator include p-chloromethylstyrene, alpha -dichloro xylene, alpha, alpha -dichloro xylene, alpha, alpha -dibromo xylene, hexakis (alpha -bromomethyl) benzene, Benzyl bromide, benzyl halide such as benzyl bromide, 1-bromo-1-phenylethane and 1-chloro-1-phenylethane; Methyl-2-chloropropionate, methyl-2-bromopropionate, ethyl-2-bromoisobutyrate (EBIB) A halogenated carboxylic acid such as? tosyl halides such as p-toluenesulfonyl chloride (TsCl); Alkyl halides such as tetrachloromethane, tribromomethane, 1-vinylethyl chloride and 1-vinylethyl bromide; And halogen derivatives of phosphoric acid esters such as dimethylphosphoric chloride. These various polymerization initiators may be used alone or in combination of two or more.

The halogenated copper that provides the copper halide / ligand complex is not particularly limited and those generally known in living radical polymerization can be used. Examples of the halogenated copper include CuBr, CuCl, CuI and the like. These various types of halogenated copper may be used alone or in combination of two or more.

The ligand compound providing the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of the ligand compound include triphenylphosphane, 4,4'-dynonyl-2.2'-dipyridine (dNbipy), N, N, N'N'N'-pentamethyldiethylenetriamine, 1,1,4 , 7,10,10-hexamethyltetraethylenetetramine, and the like. These ligand compounds may be used alone or in combination of two or more.

The amount of the radical polymerizable monomer, the polymerization initiator, the halogenated copper and the ligand compound may be appropriately controlled depending on the kind of the raw material to be used. Generally, the radical polymerizable monomer is used in an amount of 5 to 10,000 mol, Preferably from 0.5 to 100 mol, and the ligand compound is from 0.2 to 200 mol, preferably from 1.0 to 200 mol.

The living radical polymerization is usually carried out in a solventless state, but a solvent generally used in living radical polymerization may be used. Examples of usable solvents include benzene, toluene, N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF) An organic solvent such as benzene, toluene or xylene; Water-soluble solvents such as water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve and 1-methoxy-2-propanol. These various solvents may be used alone or in combination of two or more. The amount of the solvent may be appropriately adjusted depending on the kind of the raw material to be used, but the solvent is generally 0.01 to 100 ml, preferably 0.05 to 10 ml per 1 g of the radical polymerizable monomer.

The living radical polymerization can be carried out by immersing and heating the substrate 1 in a solution for forming a polymer brush containing the raw material. The heating conditions are not particularly limited and may be appropriately adjusted depending on the raw materials to be used. In general, the heating temperature is 60 to 150 占 폚 and the heating time is 0.1 to 10 hours. This polymerization reaction is generally carried out at atmospheric pressure, but may be pressurized or reduced. The substrate 1 may be cleaned before the formation of the polymer brush 2, if necessary.

The molecular weight of the polymer brush 2 formed by the living radical polymerization can be controlled by the reaction temperature, the reaction time and the kind and amount of the raw materials used, but the number average molecular weight is generally 500 to 1,000,000, preferably 1,000 to 500,000 The polymer brush 2 can be formed. The molecular weight distribution (Mw / Mn) of the polymer brush 2 can be controlled to be between 1.05 and 1.60.

The polymer brush 2 may be formed on the surface of the substrate 1 with the immobilizing film interposed therebetween as needed from the standpoint of enhancing the fixability between the substrate 1 and the polymer brush 2.

The immobilizing film is not particularly limited as long as the immobilizing film is excellent in fixation property to the substrate 1 and the polymer brush 2, and those generally known in living radical polymerization can be used. An example of the immobilized film is a film formed from an alkoxysilane compound represented by the following general formula (1).

Formula 1

In the general formula (1), R ¹ is each independently an alkyl group having ¹ to 3 carbon atoms, preferably a methyl group or an ethyl group; R ² are each independently a methyl group or an ethyl group; X is a halogen atom, preferably Br; n is an integer of 3 to 10, more preferably an integer of 4 to 8.

It is preferable that the polymer brush 2 is covalently bonded to the immobilization film. If the immobilizing film and the polymer brush 2 are bonded by a covalent bond having strong bonding force, peeling of the polymer brush 2 can be sufficiently prevented. As a result, the possibility of degradation of the liquid crystal cell characteristics is lowered and the reliability of the liquid crystal cell is improved.

The method of forming the immobilized film is not particularly limited, and may be set appropriately according to the material to be used. For example, the immobilization film can be formed by immersing the substrate 1 in a solution for immobilizing a film and then drying it. Here, in order to form a fixed film on a predetermined portion, a masking process may be performed on a portion where the immobilization film is not formed. Further, the substrate 1 may be cleaned before formation of the immobilized film, if necessary.

The method of injecting the liquid crystal 5 between the two substrates 1 on which the polymer brush 2 is formed is not particularly limited and known methods such as a vacuum injection method using a capillary phenomenon and a liquid drop injection method (ODF) .

For example, in the case of using the vacuum injection method using the capillary phenomenon, the following procedure is performed.

A spacer, a fixed film (if necessary) and a polymer brush 2 are formed on a one-sided substrate 1 by a known method such as photolithography. On the other substrate 1, an electrode, a fixing film (if necessary) and a polymer brush 2 are formed. Here, in order to make the zero plane anchoring state free from the alignment restraining force in the plane, an electrode is formed on the substrate 1, and then a flattening film or the like is formed thereon to planarize, and a polymerized film (if necessary) .

Next, the one-sided substrate 1 is cleaned and dried, and then a sealing material is applied, and the sealing material is superimposed on the other substrate 1 and cured by heating, UV irradiation, or the like. Here, it is necessary to open an injection port for injecting the liquid crystal 5 into a part of the sealing material.

Subsequently, the liquid crystal 5 is injected between the substrates 1 from the injection port by a vacuum injection method, and then the injection port is sealed.

The liquid crystal 5 used in the present invention is not particularly limited, but those known in the art can be used. It is preferable that the NI point of the liquid crystal 5 is higher than the Tg of the coexistence portion 4.

According to the zero plane alignment method of the present embodiment, which is performed as described above, the liquid crystal molecules 6 can be easily and zero-surface-anchored in the state that they have alignment regulating force in the horizontal direction with respect to the substrate 1, It can be stably realized.

The liquid crystal cell fabricated using the zero plane alignment method has the above-described characteristics and thus can be used for a liquid crystal display device. The configuration of the liquid crystal display device other than the liquid crystal cell is not particularly limited, and a configuration known in the art can be employed.

The liquid crystal display device of the present embodiment can perform liquid crystal switching by the liquid crystal alignment rotation means by the change of the external field. The external field is not particularly limited, and an electric field, a magnetic field, a light irradiation, or a combination thereof can be used.

For example, in the case of using an electric field in the outer field, a method of arranging the comb electrodes in line symmetry on the two opposing substrates 1 and selecting the substrate 1 to which the electric field is applied according to the direction to be rotated, There is a method of arranging four electrodes every 90 degrees and applying a different voltage (generally a low-frequency alternating current whose phase agrees with each other) between two opposing electrodes. In the latter method, the direction of the electric field synthesized by changing the two orthogonal electric field ratios can be directed to an arbitrary angle. When light irradiation is used for the external field, the alignment rotation torque can be imparted by mixing liquid crystal molecules having an azo group.

≪ Embodiment 2 >

The non-contact liquid crystal alignment method (hereinafter referred to as the "non-contact alignment method") of the present embodiment is applied to the zero plane alignment method described above. By combining the zero plane alignment method with the geometrical concave- convex structure formed on the substrate surface, It can be utilized as an orientation technique. That is, the non-contact alignment method of the present embodiment is a liquid crystal cell in which a polymer brush is formed on a substrate having a geometrically concave-convex structure and a liquid crystal is sandwiched between the substrate and the polymer brush and the Tg of the coexisting portion of the polymer brush and the liquid crystal And the shape of the coexistence portion is heated to a temperature capable of freely varying.

The non-contact orientation method of the present embodiment is based on the application of the zero plane orientation method described above and is basically the same as that of the zero plane orientation method.

In the non-contact alignment method of the present embodiment, a geometric concavo-convex structure is formed on the substrate surface. The geometric concavo-convex structure has a function of defining the alignment direction of the liquid crystal 5 and aligning the liquid crystal 5 along this structure. Fig. 3 shows a top view (a) of the liquid crystal cell using the substrate 1 on which the geometrically uneven structure is not formed, and a top view (b) of the liquid crystal cell using the substrate 1 on which the geometrically uneven structure is formed. 3, it is possible to control the alignment of the liquid crystal molecules 6 in the horizontal direction with respect to the substrate 1 in the liquid crystal cell using the substrate 1 on which the geometric concavo-convex structure 7 is not formed, It is impossible to control the alignment direction in the substrate. On the contrary, in the liquid crystal cell using the substrate 1 having the geometrical concavo-convex structure 7 formed thereon, not only the orientation of the liquid crystal molecules 6 in the horizontal direction with respect to the substrate 1 but also the orientation of the liquid crystal molecules 6 in the horizontal plane The orientation direction can be oriented along the geometric concave-convex structure 7.

In the non-contact alignment method of the present embodiment, the liquid crystal cell fabricated using the substrate having the geometric concavo-convex structure 7 is heated at a temperature higher than the Tg of the coexistence section 4 and capable of freely changing the shape of the coexistence section 4 The liquid crystal molecules 6 can be oriented along the geometric concavo-convex structure 7 while being horizontal to the substrate. The alignment of the liquid crystal molecules in the coexisting portion 4 can be fixed and aligned in the uniaxial direction by cooling the coexisting portion 4 to a temperature lower than the Tg of the coexistence portion 4 after the heat treatment, Can be realized.

The geometric concavo-convex structure 7 is not particularly limited, and examples thereof include a rib structure and an electrode structure. Particularly, if the geometrical concavo-convex structure 7 has an electrode structure such as a comb-like electrode, it is not necessary to separately form a structure for regulating the alignment direction of the liquid crystal 5, which leads to improvement of manufacturing efficiency and production cost reduction of the liquid crystal cell. The method for forming the geometric concavo-convex structure 7 is not particularly limited and can be carried out according to a known method.

The liquid crystal cell manufactured using the non-contact alignment method of the present embodiment has the above-described characteristics and can be used in a liquid crystal display device. The configuration of the liquid crystal display device other than the liquid crystal cell is not particularly limited, and a known configuration in the art can be employed.

The liquid crystal display device manufactured by the non-contact orientation technique of the present embodiment can prevent various problems caused by the conventional rubbing treatment and the magnetic field alignment method. In particular, since alignment control of the liquid crystal molecules 6 can be performed by heat treatment, it is not necessary to newly introduce a magnetic field aligning device or the like, and the manufacturing cost can also be reduced. In addition, since the alignment treatment is performed in the cell state, there is no alignment axis mismatch (mismatch in the direction of rubbing, overlapping mismatch) occurring in the rubbing process, and the contrast is also increased.

<Examples>

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples.

A glass substrate on which a comb electrode formed of ITO was formed and an opposing glass substrate on which a photo spacer with a height of about 3 mu m were formed was prepared and a portion not required to form a polymer brush was masked. Subsequently, to the immobilization film forming solution containing 38 g of ethanol, 2 g of ammonia water (28%) and 0.4 g of 2-bromo-2-methylpropionyloxyhexyltriethoxysilane (BHE) Was immersed overnight at room temperature and then dried to form a fixed film.

Subsequently, the two glass substrates on which the immobilized film was formed were washed and dried. Thereafter, styrene (radical polymerizable monomer, 45.0 g), ethyl-2-bromoisobutyrate (polymerization initiator, 0.081 g), CuBr 0.619 g) and 4,4'-dioyl-2,2'-bipyridine (ligand compound, 3.54 g) in a molar ratio of 1000: 1: 12: 24, For 3 hours to form a polymer brush (hereinafter, referred to as "PS brush"). Next, the two glass substrates on which the PS brush was formed were cleaned and dried.

The molecular weight of the formed PS brush was evaluated using a GPC measuring device (LC-2000 plus, manufactured by Nippon Bunko K.K.). Polystyrene was used as a standard sample and a UV detector was used as a detector. As a result, the PS brush had a number average molecular weight (Mn) of 70,600, a weight average molecular weight (Mw) of 85,400 and a molecular weight distribution (Mw / Mn) of 1.21.

The thickness of the layer of the PS brush (PS brush layer) was evaluated using an X-ray reflectance measuring bin (Ultima IV, Rigaku Co., Ltd.). As a result, the thickness of the PS brush layer was 48.2 nm.

Further, evaluation was made on the graft density of the PS brush to find that it was 0.43 strands / nm ² . Further, it is not easy to determine the Tg of the polymer brush, but the Tg of the bulk PS is about 100 DEG C, and therefore, it can be considered to be a value close to this value.

Subsequently, a sealing agent was applied to one side of the glass substrate on which the PS brush was formed, and then the two glass substrates were attached, and the sealing agent was cured by heating at 120 DEG C for 2 hours under a nitrogen atmosphere. Then, a liquid crystal (JC-5051XX manufactured by Chisso Co., Ltd., NI point: 112 ° C) was injected between the two glass substrates by a vacuum injection method. When the injection was completed, the injection port was closed to seal the liquid crystal cell. Thereafter, while applying a magnetic field of 1 T (Tesla), the liquid crystal cell was cooled from 120 ° C to room temperature at 3 ° C / min to achieve uniaxial alignment. The direction of application of the magnetic field is a direction inclined by 20 ° from the comb electrode.

Next, a voltage of 8.0 V (frequency 60 Hz) was applied to the liquid crystal cell obtained above under the temperature conditions of 25 DEG C, 45 DEG C, 65 DEG C and 85 DEG C using an LCD evaluation device (LCD-5200 manufactured by Otsuka Electronics Co., Ltd.) After the application of 10000 seconds, the relationship between the time when the voltage was turned off and the transmittance was examined. A graph showing this relationship is shown in Figs.

As shown in the graph of FIG. 4, at a temperature of 25 캜, there was no change in the transmittance at the time of voltage application, and when the voltage was turned OFF, the transmittance immediately became 0%. This result shows that the polymer brush interface functions as an anchoring interface having a stronger strength at 25 ° C.

On the other hand, as shown in the graphs of FIGS. 5 to 7, the transmittance was changed at both the voltage application and the OFF at a temperature of 45 ° C. or higher. When the voltage is applied at a temperature of 45 占 폚 or more, the change of the transmittance at OFF is due to the change of the alignment direction of the liquid crystal molecules near the polymer brush interface. That is, when voltage is applied, the liquid crystal in the vicinity of the center of the liquid crystal cell is aligned parallel to the electric field direction, and a twisted alignment state is formed from the vicinity of the polymer brush interface toward the central portion of the liquid crystal cell. This torsional elastic force causes the liquid crystal molecules in the vicinity of the polymer brush interface to gradually rotate in the electric field direction, thereby causing a change in the transmittance. On the other hand, when the voltage is turned OFF, the liquid crystal molecules near the polymer brush interface gradually return to the initial alignment direction, so that a change in the transmittance is observed. At a temperature of 65 ° C and 85 ° C, when the voltage is turned off, the transmittance tends to rise once after the transmittance reaches 0%. However, this tends to rise to the torsional elasticity of the bulk liquid crystal aligned along the comb- Is a phenomenon observed because the alignment direction of the liquid crystal molecules at the polymer brush interface gradually changes in a direction parallel to the comb electrodes. These phenomena indicate that the polymer brush interface is in a &quot; soft &quot; state at a temperature of 45 캜 or higher, so that it is rotated by the torsional elastic force of the bulk liquid crystal. However, since a considerable time is required until the equilibrium state is reached after the voltage is turned off in the range of 45 ° C to 85 ° C, it is judged that the zero plane anchoring state is not realized at 85 ° C or less.

Considering these results, although there is a Tg of the coexisting portion between 25 ° C and 45 ° C, the temperature at which the shape of the coexisted portion can freely change even at a temperature of 85 ° C, that is, a temperature at which the zero plane anchoring state can be realized I think you did not.

Therefore, when the liquid crystal cell obtained above was heated to about 115 ° C, which is an isotropic phase, and cooled at a rate of 1 ° C / minute, the instant at which the liquid crystal cell was below the NI point (112 ° C) Were uniformly oriented parallel to the direction of the comb electrodes. A micrograph showing the result is shown in Fig. 8 (a) is a micrograph taken at an angle of 20 占 from the direction of the incidence-side flat plate of the Cross-Nicol polarizer, Fig. 8 (b) is a photograph taken with the direction of the incidence-side polarizer of the Cross- It's a picture. As apparent from these microscope photographs, it was confirmed that the liquid crystal molecules were instantly uniformly oriented in the direction parallel to the comb electrodes when heated to the above temperature.

Therefore, in the liquid crystal cell fabricated in the embodiment, it can be considered that there exists a temperature capable of freely changing the shape of the coexistence portion, that is, a temperature capable of realizing the zero plane anchoring state, in the temperature range from 85 ° C to 112 ° C.

As can be seen from the above-mentioned results, according to the present invention, although the alignment regulating force of the liquid crystal molecules in the horizontal or diagonal direction exists, the zero plane anchoring state in which there is no alignment regulating force in the in-plane direction can be realized easily and stably, The liquid crystal display device using the zero plane anchoring state can be provided. Further, according to the present invention, it is possible to provide a method of realizing a non-contact alignment method easily and stably and a liquid crystal display device realized by this method.

1: substrate
2: Polymer brush
3: polymer brush layer
4: Coexistence Department
5: liquid crystal
6: liquid crystal molecule
7: Geometrical concave and convex structure

Claims (14)

A liquid crystal cell in which a polymer brush is formed on a substrate subjected to a planarization treatment and liquid crystal is sandwiched between the substrates is heated to a temperature higher than a Tg of the coexistence portion of the polymer brush and the liquid crystal and capable of freely changing the shape of the coexistence portion Wherein the liquid crystal alignment is performed by heating the zero plane anchoring liquid crystal.
The method of claim 1, wherein
Wherein the heating temperature is not lower than the Tg of the polymer brush by 60 占 폚.
The method of claim 1, wherein
Wherein the heating temperature is at least 25 占 폚 lower than the Tg of the polymer brush.
The method of claim 1, wherein
Wherein the polymer brush has a graft density of 0.1 strands / nm ² .
A liquid crystal display device comprising a liquid crystal cell manufactured by the zero plane anchoring liquid crystal alignment method according to any one of claims 1 to 4.
The method of claim 5, wherein
Wherein the switching of the liquid crystal is performed by the liquid crystal orientation rotating means by the change of the external field.
The method of claim 6, wherein
Wherein the external field is an electric field, a magnetic field, a light irradiation, or a combination thereof.
A liquid crystal cell in which a polymer brush is formed on a substrate having a geometrically concave-convex structure and a liquid crystal is sandwiched between the substrates. The liquid crystal cell has a temperature higher than the Tg of the coexistence portion of the polymer brush and the liquid crystal and capable of freely changing the shape of the coexistence portion In the liquid crystal alignment layer.
The method of claim 8, wherein
Wherein the heating temperature is at least 60 deg. C lower than the Tg of the polymer brush.
The method of claim 8, wherein
Wherein the heating temperature is at least 25 占 폚 lower than the Tg of the polymer brush.
The method of claim 8, wherein
Wherein the polymer brush has a graft density of 0.1 strand / nm ² .
A liquid crystal display device comprising a liquid crystal cell manufactured by the non-contact liquid crystal alignment method according to any one of claims 8 to 11.
The method of claim 12, wherein
Wherein the switching of the liquid crystal is performed by the liquid crystal orientation rotating means by the change of the external field.
The method of claim 13, wherein
Wherein the external field is an electric field, a magnetic field, a light irradiation, or a combination thereof.

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