JP5650001B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

  The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a method for manufacturing a liquid crystal display device used for display panels of various devices.

Since the liquid crystal display device has characteristics such as a low driving voltage, low power consumption, and light weight, its use in a display panel for a watch, a mobile phone, a computer, a television display, and the like is expanding.
In such a liquid crystal display device, it is generally necessary to align (that is, align) the liquid crystal in a predetermined direction with respect to the substrate surface. As a conventional alignment technique, polyimide or the like is formed on the substrate. A method for aligning liquid crystals by performing a rubbing process after forming an alignment film made of (rubbing method) is known. The rubbing treatment is performed by rotating a roller wound with a cloth such as rayon or cotton while keeping the rotation speed and the distance between the roller and the substrate constant, and rubbing the surface of the alignment film in one direction.

However, the alignment technique by rubbing has various problems as listed below.
(1) The rubbing treatment may cause large scratches on the alignment film, and the scratches cause light leakage at the time of black display of the liquid crystal display device, thereby reducing the contrast of the liquid crystal display device.
(2) As a result of the rubbing treatment, the alignment film is peeled off, or the hair is detached from the cloth wound around the roller. As a result, the display quality and yield of the liquid crystal display device are lowered.
(3) A portion that is not rubbed occurs due to a step due to a TFT element or the like formed on the substrate, and the display quality and yield of the liquid crystal display device are lowered.
(4) The static electricity generated by the friction between the substrate and the roller destroys the TFT element formed on the substrate, and the yield decreases.

(5) The alignment direction of the upper and lower substrates is deviated (that is, the alignment axis is deviated) due to a slight misalignment in the rubbing direction and a slight misalignment of the substrates when forming the liquid crystal cell. The contrast of the image is reduced.
(6) In the rubbing treatment, it is difficult to quantify the characteristics of the rubbing cloth such as rayon or cotton, and management in manufacturing is difficult.
(7) When the substrate size is increased, uniform rubbing processing becomes difficult and an apparatus for rubbing processing needs to be enlarged, which increases the investment cost.

Therefore, as an alignment technique that does not require rubbing treatment (rubbing-less), an alignment technique using a magnetic field (for example, Patent Document 1), a technique using a liquid crystalline polymer as an alignment film (for example, Patent Document 2), a polymer in a liquid crystal There has been proposed a technique (for example, Patent Document 3) for controlling the alignment of the liquid crystal by containing.
However, these conventional rubbingless alignment techniques still have a problem that the effect is not sufficient.

In recent years, liquid crystal display devices are required to be driven at a low voltage (low power consumption) from the viewpoint of energy saving. Although it is effective to reduce the thickness of the alignment film for low-voltage driving, when using a polyimide film for the alignment film, the alignment film is used from the viewpoint of preventing impurities from entering the liquid crystal from the base of the polyimide film. There is a problem that the thickness of can not be reduced. In addition, when the thickness of the polyimide film is reduced, there is a problem that the alignment control ability of the liquid crystal is lowered.
In order to solve the above problems, the present inventors have proposed an alignment technique using a polymer brush as an alignment film in Japanese Patent Application No. 2009-233348.

Japanese Patent Laid-Open No. 7-13168 Japanese Patent Publication No. 7-54381 JP 2004-286984 A

However, the alignment technique using the polymer brush as an alignment film has a problem in that an investment for newly purchasing a magnetic field alignment apparatus is required because the liquid crystal is aligned by a magnetic field alignment method.
The present invention has been made to solve the above-described problems, and prevents various problems caused by the rubbing process, the polyimide alignment film, and the magnetic field alignment method. An object of the present invention is to provide a method capable of producing a liquid crystal display device excellent in liquid crystal alignment controllability at a low cost.

As a result of diligent research to solve the above problems, the present inventors have used a polymer brush as an alignment film and formed a concavo-convex structure on at least one substrate so that the polymer brush and the liquid crystal are compatible with each other. After heating and holding at a temperature higher than the Tg (glass transition temperature) and lower than the NI point (phase transition temperature from N phase to I phase) of the liquid crystal, It was found that the liquid crystal can be easily uniformly aligned by cooling to a temperature lower than Tg.
That is, the present invention includes a step of forming a polymer brush on two substrates in which at least one substrate has a concavo-convex structure, and a step of producing a liquid crystal cell by injecting liquid crystal between the two substrates on which the polymer brush is formed. Heating and holding the liquid crystal cell at a temperature higher than the Tg of the portion where the polymer brush and the liquid crystal are compatible and lower than the NI point of the liquid crystal; and And a step of cooling to a temperature lower than the Tg of the portion where the brush and the liquid crystal are compatible with each other.

  According to the present invention, it is possible to prevent various problems caused by rubbing treatment, polyimide alignment film and magnetic field alignment method, and to effectively utilize existing devices to provide a liquid crystal display device excellent in liquid crystal alignment controllability at low cost. Methods that can be manufactured can be provided.

It is a figure (sectional drawing) for demonstrating the manufacturing method of the liquid crystal display device of this invention. It is a figure (top view) for demonstrating the manufacturing method of the liquid crystal display device of this invention. 4 is a graph showing the relationship between time and relative transmittance in the liquid crystal display device fabricated in Example 1. FIG.

  Hereinafter, preferred embodiments of a method for producing a liquid crystal display device of the present invention will be described with reference to the drawings. In the following, the present invention will be described by taking a method of manufacturing a horizontal electric field type liquid crystal display device as an example. It is.

FIG. 1 is a view (cross-sectional view) for explaining a method for manufacturing a liquid crystal display device of the present invention.
In the method for manufacturing a liquid crystal display device of the present invention, first, the concavo-convex structure 2 is formed on at least one substrate 1 (FIG. 1A). The concavo-convex structure 2 has a function of aligning the liquid crystal along the concavo-convex structure 2 after defining the alignment direction of the liquid crystal and performing the processing described below. The uneven structure 2 is not particularly limited, and examples thereof include a rib structure and an electrode structure. In particular, if the concavo-convex structure 2 is an electrode structure such as a comb-shaped electrode, it is not necessary to separately form the concavo-convex structure 2 for defining the alignment direction of the liquid crystal. Leads to reduction.

  It does not specifically limit as the board | substrate 1, A generally well-known thing can be used in a liquid crystal display device. Examples of the substrate 1 include an array substrate and a counter substrate. An example of the array substrate is an active matrix array substrate. In this active matrix array substrate, gate wirings and source wirings are generally arranged in a matrix on a glass substrate, and active elements such as thin layer transistors (TFTs) are formed at the intersections. A pixel electrode is connected to the element. An example of the counter substrate is a color filter substrate. In general, the color filter substrate is formed by forming a black matrix on a glass substrate to prevent unnecessary light leakage, and then adding R (red), G (green), and B (blue) colored layers. A pattern is formed, a protective film is formed if necessary, and a counter electrode facing the pixel electrode is formed.

  The method for forming the concavo-convex structure 2 on at least one substrate 1 is not particularly limited, and can be performed according to a known method. The substrate 1 may be cleaned before the formation of the concavo-convex structure 2 as necessary.

Next, the polymer brush 4 is formed on the two substrates 1 (FIG. 1B). Here, the “polymer brush 4” in the present specification means a structure in which a number of graft polymer chains have a high density and extend in a direction perpendicular to the surface of the substrate 1. In general, a graft polymer chain having one end fixed to the surface of the substrate 1 has a string-like contraction structure when the graft density is low. However, the polymer brush 4 has a high graft density, so that the adjacent graft polymer Due to the chain interaction (steric repulsion), the substrate 1 has a structure extending in the direction perpendicular to the surface. In the present specification, the term “high density” means the density of graft polymer chains that are so dense that steric repulsion occurs between adjacent graft polymer chains, and generally 0.1 chain / nm ² or more, The density is preferably 0.1 to 1.2 strands / nm ² . In the present specification, the “density of graft polymer chains” means the number of graft polymer chains formed on the surface of the substrate 1 per unit area (nm ² ).

  The polymer brush 4 forms a layer of the polymer brush 4 (hereinafter referred to as “polymer brush layer”) on the surface of the substrate 1 and the uneven structure 2. The thickness of the polymer brush layer needs to be adjusted according to the size of the step of the concavo-convex structure 2, but is generally several tens of nm, specifically 1 nm or more and less than 100 nm, preferably 10 nm to 80 nm. With such a thickness, the liquid crystal display device can be driven at a low voltage because the thickness is smaller than the thickness of the conventional polyimide alignment film (generally 100 nm). In addition, the polymer brush layer has a size exclusion effect, and a substance having a certain size cannot pass through the polymer brush layer. Therefore, even if the thickness of the polymer brush layer is reduced, it is possible to prevent impurities from entering the liquid crystal from the base. In addition, the polymer brush layer has good liquid crystal alignment control ability even if the thickness is relatively thin.

The polymer brush 4 preferably exhibits UV curability from the viewpoint of increasing the alignment stability of the liquid crystal. Specifically, the polymer brush 4 preferably has a functional group capable of UV curing.
The polymer brush 4 is preferably a copolymer, particularly a block copolymer, from the viewpoint of imparting various properties. With such a copolymer, various effects that cannot be obtained with a homopolymer can be expected.
Furthermore, the polymer brush 4 preferably exhibits liquid crystallinity from the viewpoint of compatibility with liquid crystal. Specifically, the polymer brush 4 preferably has liquid crystallinity.

  It does not specifically limit as a formation method of the polymer brush 4, It can carry out using a well-known method. Specifically, the polymer brush 4 can be formed by living radical polymerization of a radical polymerizable monomer. Here, in this specification, “living radical polymerization” means that the chain transfer reaction and termination reaction are not substantially caused in the radical polymerization reaction, and the chain growth terminal is active even after the radical polymerizable monomer is completely reacted. It means a polymerization reaction to be retained. In this polymerization reaction, the polymerization activity is retained at the end of the produced polymer even after the completion of the polymerization reaction, and when the radical polymerizable monomer is added, the polymerization reaction can be started again. Living radical polymerization allows the synthesis of a polymer having an arbitrary average molecular weight by adjusting the concentration ratio between the radical polymerizable monomer and the polymerization initiator, and the molecular weight distribution of the resulting polymer is extremely narrow. There are features.

  A typical example of the living radical polymerization used in the present invention is atom transfer radical polymerization (ATRP). For example, atom transfer living radical polymerization of a radical polymerizable monomer is performed using a copper halide / ligand complex in the presence of a polymerization initiator. A radical polymerizable monomer is added to a growing radical that reversibly grows by pulling out the terminal halogen of the polymer by a copper halide / ligand complex, and the molecular weight distribution is achieved by reversible activation / deactivation with sufficient frequency. Is regulated.

  The radical polymerizable monomer used in the living radical polymerization has an unsaturated bond capable of performing radical polymerization in the presence of an organic radical. For example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate , T-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, n-octyl methacrylate, 2-methoxyethyl methacrylate, butoxyethyl methacrylate, methoxytetraethylene glycol methacrylate, 2-hydroxy Ethyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2-hydroxy Methacrylate monomers such as propyl methacrylate, tetrahydrofurfuryl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, diethylene glycol methacrylate, polyethylene glycol methacrylate, 2- (dimethylamino) ethyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate, n -Butyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, benzyl acrylate, cyclohexyl acrylate, lauryl acrylate, n-octyl acrylate, 2-methoxyethyl acrylate, butoxyethyl acrylate, methoxytetraethylene glycol acrylate, 2-hydroxy Til acrylate, 2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, diethylene glycol acrylate, polyethylene glycol acrylate, 2- (dimethylamino) ethyl acrylate, Acrylate monomers such as N, N-dimethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide; styrene, styrene derivatives (for example, o-, m-, p-methoxystyrene, o-, m-, pt) -Butoxystyrene, o-, m-, p-chloromethylstyrene, etc.), vinyl esters (for example, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl acetate, etc.), Vinyl ketones (for example, vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, etc.), N-vinyl compounds (for example, N-vinyl pyrrolidone, N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, etc.), Vinyl monomers such as (meth) acrylic acid derivatives (for example, acrylonitrile, methacrylonitrile, acrylamide, isopropylacrylamide, methacrylamide), vinyl halides (for example, vinyl chloride, vinylidene chloride, tetrachloroethylene, hexachloroprene, vinyl fluoride, etc.) Is mentioned. These various radically 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, α-dichloroxylene, α, α-dichloroxylene, α, α-dibromoxylene, hexakis (α-bromomethyl) benzene, benzyl chloride, benzyl bromide, 1- Benzyl halides such as bromo-1-phenylethane, 1-chloro-1-phenylethane; propyl-2-bromopropionate, methyl-2-chloropropionate, ethyl-2-chloropropionate, methyl- Carboxylic acids in which the α-position is halogenated such as 2-bromopropionate and ethyl-2-bromoisobutyrate (EBIB); Tosyl halides such as p-toluenesulfonyl chloride (TsCl); Tetrachloromethane, Tribromo Alkanes such as methane, 1-vinylethyl chloride, 1-vinylethyl bromide Ruharogen products; halogenated derivatives of phosphoric acid esters such as dimethyl phosphoric acid chloride and the like. These various polymerization initiators may be used alone or in combination of two or more.

The copper halide that gives the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of the copper halide include CuBr, CuCl, and CuI. These various copper halides may be used alone or in combination of two or more.
The ligand compound that gives the copper halide / ligand complex is not particularly limited, and those generally known in living radical polymerization can be used. Examples of ligand compounds include triphenylphosphane, 4,4′-dinonyl-2,2′-dipyridine (dNbipy), N, N, N ′, N′N ″ -pentamethyldiethylenetriamine, 1,1,4 , 7,10,10-hexamethyltriethylenetetraamine, etc. These various ligand compounds may be used alone or in combination of two or more.

  The amount of the radically polymerizable monomer, polymerization initiator, copper halide and ligand compound may be appropriately adjusted according to the type of raw material used. In general, the amount of the radically polymerizable monomer is 1 mol of the polymerization initiator. 5 to 10,000 mol, preferably 50 to 5,000 mol, copper halide 0.1 to 100 mol, preferably 0.5 to 100 mol, ligand compound 0.2 to 200 mol, preferably 1.0 to 200 mol. is there.

  Living radical polymerization is usually performed without a solvent, but a solvent generally used in living radical polymerization may be used. Usable solvents include, for example, benzene, toluene, N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, chloroform, carbon tetrachloride, tetrahydrofuran (THF), ethyl acetate, trifluoromethylbenzene and the like. And organic solvents such as water, methanol, ethanol, isopropanol, n-butanol, ethyl cellosolve, butyl cellosolve, 1-methoxy-2-propanol and the like. These various solvents may be used alone or in combination of two or more. The amount of the solvent may be appropriately adjusted according to the type of raw material to be used. Generally, the solvent is 0.01 to 100 mL, preferably 0.05 to 10 mL with respect to 1 g of the radical polymerizable monomer. is there.

  Living radical polymerization can be performed by immersing the substrate 1 in a polymer brush-forming solution containing the above raw materials and heating. The heating conditions are not particularly limited, and may be appropriately adjusted according to the raw materials used. In general, the heating temperature is 60 to 150 ° C., and the heating time is 0.1 to 10 hours. This polymerization reaction is generally carried out at normal pressure, but it may be pressurized or reduced. In addition, you may wash | clean the board | substrate 1 before formation of the polymer brush 4 as needed.

The molecular weight of the polymer brush 4 formed by living radical polymerization can be adjusted depending on the reaction temperature, reaction time, and type and amount of the raw material used, but generally the number average molecular weight is 500 to 1,000,000, preferably Can form 1,000 to 500,000 polymer brushes 4. Moreover, the molecular weight distribution (Mw / Mn) of the polymer brush 4 can be controlled between 1.05 and 1.60.
The polymer brush 4 thus formed can align the liquid crystal parallel to the substrate 1.

The polymer brush 4 may be formed on the surface of the substrate 1 and the concavo-convex structure 2 through the immobilization film 3 as necessary from the viewpoint of enhancing the adhesion between the substrate 1 and the concavo-convex structure 2 and the polymer brush 4. Good.
The immobilization film 3 is not particularly limited as long as it has excellent adhesion to the substrate 1, the concavo-convex structure 2, and the polymer brush 4, and those generally known in living radical polymerization should be used. Can do. An example of the immobilization film 3 is a film formed from an alkoxysilane compound represented by the following general formula (1).

In the general formula (1), each R ¹ is independently a C1-C3 alkyl group, preferably a methyl group or an ethyl group; each R ² is independently a methyl group or an ethyl group; X is a halogen atom , Preferably Br; n is an integer of 3-10, more preferably an integer of 4-8.

  It is preferable that the polymer brush 4 is covalently bonded to the immobilizing film 3. If the immobilization film 3 and the polymer brush 4 are connected by a covalent bond having a strong binding force, the polymer brush 4 can be sufficiently prevented from peeling off. As a result, the possibility of deterioration of the characteristics of the liquid crystal display device is reduced, and the reliability of the liquid crystal display device is improved.

  The formation method of the immobilization film 3 is not particularly limited, and may be set as appropriate according to the material to be used. For example, the immobilization film 3 can be formed by immersing the substrate 1 in the immobilization film forming solution and then drying it. Here, in order to form the immobilization film 3 in a predetermined portion, masking may be applied to a portion where the immobilization film 3 is not formed. Further, the substrate 1 may be cleaned before the formation of the immobilization film 3 as necessary.

Next, a liquid crystal 5 is injected between the two substrates 1 on which the polymer brush 4 is formed (FIG. 1C). The method for injecting the liquid crystal 5 is not particularly limited, and a known method such as a vacuum injection method using a capillary phenomenon or a liquid crystal dropping injection method (ODF) can be used.
For example, when using a vacuum injection method utilizing capillary action, the following may be performed.
First, a spacer, an immobilizing film 3 (if necessary), and a polymer brush 4 are formed on one substrate 1 by a known method such as photolithography. On the other substrate 1, an electrode, an immobilizing film 3 (if necessary) and a polymer brush 4 are formed. When an electrode is not used as the concavo-convex structure 2 that defines the alignment direction of the liquid crystal 5, after forming various wirings on one substrate 1, it is flattened with a UV curable flattening film or the like, and an immobilization film thereon 3 (if necessary) and the polymer brush 4 are formed, and the spacer, the rib for defining the alignment direction of the liquid crystal 5, the immobilizing film 3 (if necessary) and the polymer brush 4 are formed on the other substrate 1. .
Next, after cleaning and drying one of the substrates 1, a sealing material is applied, superimposed on the other substrate 1, and the sealing material is cured and bonded by heating or UV irradiation. Here, it is necessary to open an injection port for injecting the liquid crystal 5 in a part of the sealing material.
Next, after the liquid crystal 5 is injected between the substrates 1 from the injection port by a vacuum injection method, the injection port is sealed.

The liquid crystal 5 used in the present invention is not particularly limited as long as the NI point of the liquid crystal 5 is higher than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible, and a known liquid crystal can be used.
Moreover, you may mix | blend a photopolymerizable monomer with the liquid crystal 5 from a viewpoint of improving the alignment stability of the liquid crystal 5. FIG.
The photopolymerizable monomer is not particularly limited, and generally known monomers can be used. Commercially available photopolymerizable monomers such as Actilane 421, Actilane 441, Actilane 450 sold by Nippon Sebel Hegner Co., Ltd., and ULC-000-K1 sold by DIC Corporation may be used.

A preferred photopolymerizable monomer is a compound represented by the following general formula (2).
P ¹ -A ^1- (Z ¹ -A ² ) _n -P ² (2)
In the general formula (2), P ¹ and P ² are functional groups, each independently an acrylate, methacrylate, vinyl, vinyloxy or epoxy group; A ¹ and A ² have a ring structure and are each independent 1, 4-phenylene or naphthalene-2,6-diyl group; Z ¹ is a —COO— or —OCO— group or a single bond; n is 0, 1 or 2;

In the general formula (2), P ¹ and P ² are preferably acrylate groups, Z ¹ is preferably a single bond, and n is preferably 0 or 1.
More preferable photopolymerizability is a compound represented by the following formulas (2a) to (2c).

In the above formula, P ¹ and P ² are as defined in the general formula (2).
The photopolymerizable monomer is preferably blended so as to be 0.1 to 5% by mass in the liquid crystal 5. When the blending amount of the photopolymerizable monomer is less than 0.1% by mass, the alignment stability of the liquid crystal 5 may not be sufficiently obtained. On the other hand, when the compounding quantity of a photopolymerizable monomer exceeds 5 mass%, an unreacted photopolymerizable monomer remains and liquid crystal characteristics may deteriorate.

  When the liquid crystal 5 is injected between the two substrates 1, the liquid crystal 5 is aligned parallel to the surface of the substrate 1. Here, FIG. 2A shows a top view of the liquid crystal cell corresponding to the cross-sectional view of the liquid crystal cell of FIG. As shown in FIG. 1C and FIG. 2A, the liquid crystal 5 is horizontally aligned with respect to the substrate 1, but the alignment direction in the horizontal plane does not match.

  Therefore, next, the liquid crystal cell is heated and held at a temperature higher than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible and lower than the NI point of the liquid crystal 5. The liquid crystal 5 is cooled to a temperature lower than the Tg of the part where it is compatible (FIG. 1 (d)). Here, FIG. 2B shows a top view of the liquid crystal cell corresponding to the cross-sectional view of the liquid crystal cell in FIG. As shown in FIG. 1D and FIG. 2B, by performing this process, the alignment direction of the liquid crystal 5 in the horizontal plane can be matched along the concavo-convex structure 2.

Specifically, first, the concavo-convex structure 2 is obtained by heating and holding the liquid crystal cell at a temperature higher than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible and lower than the NI point of the liquid crystal 5. The alignment direction of the liquid crystal 5 in the horizontal plane is made to coincide with the concavo-convex structure 2.
Here, it is considered that the liquid crystal 5 is slightly swollen at the tip of the polymer brush 4 in the vicinity of the interface between the polymer brush 4 and the liquid crystal 5. Therefore, in this specification, the “part where the polymer brush 4 and the liquid crystal 5 are compatible” means the tip of the polymer brush 4 where the liquid crystal 5 is slightly swollen. The Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible is lower than the Tg of the polymer brush 4 alone. The Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible varies depending on the types of the polymer brush 4 and the liquid crystal 5 to be used, and thus cannot be uniquely defined. However, methyl methacrylate is used as a radical polymerizable monomer. In the case of the formed polymer brush 4, it is considered that the temperature is about 60 ° C. lower than the Tg of the polymer brush 4 alone.

If the heating temperature is equal to or lower than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible, the fluidity of the liquid crystal 5 cannot be obtained, so that the alignment direction of the liquid crystal 5 in the horizontal plane is matched along the concavo-convex structure 2. I can't. Therefore, the lower limit of the heating temperature is preferably equal to or higher than the Tg of the liquid crystal 5.
On the other hand, when the heating temperature is equal to or higher than the NI point, the liquid crystal 5 becomes an I phase (isotropic liquid phase), and the alignment direction of the liquid crystal 5 in the horizontal plane cannot be matched along the concavo-convex structure 2.

The holding time at the above heating temperature varies depending on the heating temperature and cannot be uniquely defined, but is generally several seconds to several tens of hours. For example, when heating at a temperature sufficiently higher than the portion where the polymer brush 4 and the liquid crystal 5 are compatible (temperature near the NI point), the orientation direction of the liquid crystal 5 in the horizontal plane is matched along the concavo-convex structure 2 instantly. Can be made. On the other hand, when heating at a temperature in the vicinity of Tg where the polymer brush 4 and the liquid crystal 5 are compatible, it takes a certain time to align the alignment direction of the liquid crystal 5 in the horizontal plane along the concavo-convex structure 2.
The heating device for performing the heat treatment 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 subjected to the heat treatment is cooled to a temperature lower than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible, preferably to room temperature, so that the alignment of the liquid crystal 5 matched in the horizontal plane is achieved. Keep the direction. That is, by cooling to the above temperature, the portion where the polymer brush 4 and the liquid crystal 5 are compatible can be vitrified while being uniaxially oriented, so that the anchoring ability can be exhibited. If the temperature is equal to or higher than the Tg of the portion where the polymer brush 4 and the liquid crystal 5 are compatible, the alignment direction of the liquid crystal 5 aligned along the concavo-convex structure 2 on the horizontal plane cannot be sufficiently maintained.
The method for the cooling treatment is not particularly limited, and may be naturally cooled by stopping the heat treatment or may be forcibly cooled using a known cooling device.

In addition, as an optional step, when the polymer brush 4 is UV curable and / or when a photopolymerizable monomer is mixed with the liquid crystal 5, UV (ultraviolet light) is applied to the liquid crystal cell when uniform alignment is obtained or after cooling treatment. ). As a result, it is possible to further enhance the alignment stability of the liquid crystal and expand the temperature range in which the anchoring ability is exhibited.
Specifically, when the polymer brush 4 is UV curable, the surface layer of the polymer brush layer can be cured and fixed by UV irradiation, so that it is possible to increase the orientation holding power of the liquid crystal. Further, when a photopolymerizable monomer is mixed in the liquid crystal 5, the photopolymerizable monomer is polymerized on the surface of the polymer brush layer by UV irradiation and is fixed as a polymer, so that the alignment holding power of the liquid crystal 5 is further enhanced. It becomes possible.

The UV irradiation conditions may be appropriately adjusted according to the type of polymer brush 4 and photopolymerizable monomer used, the wavelength of UV, and the like, and are not particularly limited, but the UV intensity is generally several hundred to several tens of thousands mJ. It is. For example, when irradiating UV having a wavelength of 300 to 400 nm, the exposure amount is preferably 0.1 to 10 J / cm ² .

  According to the method for producing a liquid crystal display device of the present invention thus performed, various problems caused by the rubbing treatment, the polyimide alignment film, and the magnetic field alignment method can be prevented, and the liquid crystal alignment controllability is excellent. A liquid crystal display device can be obtained. In particular, since the alignment control of the liquid crystal is performed by heating and cooling treatment, it is not necessary to newly introduce a magnetic field alignment device, and the manufacturing cost can be reduced. Further, since the alignment process is performed in the cell state, there is no alignment axis shift (rubbing direction shift or overlap shift) caused by the rubbing process, and the contrast of the liquid crystal display device is increased.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the following Example.
Example 1
A glass substrate on which a comb-like electrode made of ITO was formed and a counter substrate on which a photospacer having a height of about 3 μm was formed were prepared, and a portion where it was not necessary to form a polymer brush was masked. Next, two films subjected to masking were applied to an immobilized film forming solution containing 38 g of ethanol, 2 g of aqueous ammonia (28%), and 0.4 g of 2-bromo-2-methylpropionyloxyhexyltriethoxysilane (BHE). The glass substrate was immersed at room temperature overnight and then dried to form an immobilized film.
Next, the two glass substrates on which the fixed film was formed were washed and dried, and then styrene (radical polymerizable monomer, 45.0 g), ethyl-2-bromoisobutyrate (polymerization initiator, 0.081 g). ), CuBr (copper halide, 0.619 g) and 4,4′-dionyl-2,2′-bipyridine (ligand compound, 3.54 g) in a molar ratio of 1000: 1: 12: 24 A polymer brush (hereinafter referred to as a PS brush) was formed by immersing in an aqueous solution and heating at 110 ° C. for 3 hours for living radical polymerization. Next, the two glass substrates on which the PS brushes were formed were washed and dried.

The molecular weight of the formed PS brush was evaluated using a GPC measurement device (LC-2000plus manufactured by JASCO Corporation). Polystyrene was used as the standard sample, and a UV detector was used as the detector. As a result, this PS brush had a number average molecular weight (Mn) of 64,323, a weight average molecular weight (Mw) of 77,830, and a molecular weight distribution (Mw / Mn) of 1.21.
Moreover, about the thickness of the layer (PS brush layer) of PS brush, it evaluated using the X-ray-reflectance measuring apparatus (Rigaku Corporation Ultimate IV). As a result, the thickness of the PS brush layer was 36.5 nm.
Furthermore, as a result of evaluating the graft density of the PS brush, it was 0.41 strand / nm ² .

Next, after applying the sealing agent to one of the glass substrates on which the PS brush was formed, the two glass substrates were bonded together, and the sealing agent was cured by heating at 120 ° C. for 2 hours in a nitrogen atmosphere. Then, liquid crystal (JC-5051xx manufactured by Chisso Corporation, NI point: 112 ° C.) is injected between two glass substrates by a vacuum injection method, and after the injection is completed, the injection port is closed and sealed. A cell was produced.
Next, after heating the liquid crystal cell obtained above to 110 ° C. using a heating device and holding it for 10 seconds, the heating device is stopped and cooled to room temperature, so that the liquid crystal is aligned along the comb electrodes. A uniformly aligned liquid crystal display device was obtained.

(Evaluation of anchoring ability)
First, using a LCD evaluation apparatus (LCD-5200 manufactured by Otsuka Electronics Co., Ltd.), the relationship between the voltage and the relative transmittance in the liquid crystal display device produced in Example 1 was examined under a condition of a frequency of 60 Hz and 20 ° C. As a result, it was found that the voltage at which the relative transmittance was 100% was 7.3V. Next, using the same LCD evaluation apparatus, the relationship between time and relative transmittance in a liquid crystal display device was examined. In this evaluation, a voltage of 7.3 V was applied for 200 × 10 ⁻³ seconds (20 ° C., 60 Hz), and then the voltage was turned off. The result is shown in FIG.
As can be seen from the results of FIG. 3, the liquid crystal display device of Example 1 had a relative transmittance of 100% as soon as voltage was applied. Also, it was found that the relative transmittance was 0% immediately after the voltage was turned off, and the anchoring ability was high.

  As can be seen from the above results, according to the present invention, various problems caused by the rubbing process, the polyimide alignment film and the magnetic field alignment method can be prevented, and the existing apparatus can be effectively used to control the alignment of the liquid crystal at a low cost. It is possible to provide a method capable of manufacturing a liquid crystal display device having excellent properties.

  1 substrate, 2 uneven structure, 3 fixing film, 4 polymer brush, 5 liquid crystal.

Claims (4)

Forming a polymer brush on two substrates, wherein at least one substrate has a concavo-convex structure;
Injecting liquid crystal between two substrates on which the polymer brush is formed to produce a liquid crystal cell;
Heating and holding the liquid crystal cell at a temperature higher than the Tg of the portion where the polymer brush and the liquid crystal are compatible and lower than the NI point of the liquid crystal;
And a step of cooling the liquid crystal cell to a temperature lower than a Tg of a portion where the polymer brush and the liquid crystal are compatible with each other.   The method for manufacturing a liquid crystal display device according to claim 1, wherein the uneven structure is an electrode structure and / or a rib structure.   The liquid crystal according to claim 1, wherein the polymer brush is UV curable, and / or further includes a step of mixing a photopolymerizable monomer with the liquid crystal and performing UV irradiation after the cooling step. Manufacturing method of display device.   The method for manufacturing a liquid crystal display device according to claim 1, further comprising a step of forming an immobilization film on the two substrates before the step of forming the polymer brush. .

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