JP2011081187A - Liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device and a method for manufacturing the device, which is excellent in alignment controllability of liquid crystal molecules and can be driven at a low voltage, while preventing various problems caused by a rubbing process. <P>SOLUTION: The liquid crystal display device uses a polymer brush as an alignment layer. The method for manufacturing the liquid crystal display device includes steps of: forming a polymer brush on a substrate; injecting a liquid crystal into a space between substrates where the polymer brush is formed; and aligning the liquid crystal by a non-contact aligning method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

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) liquid crystal molecules in a predetermined direction with respect to the substrate surface. As a conventional alignment technique, a polyimide is formed on the substrate. A method is known in which liquid crystal molecules are aligned by performing a rubbing treatment (rubbing method) after forming an alignment film composed of the above. 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 shifted due to a slight shift in the bonding position of the substrates when forming the liquid crystal cell (that is, the alignment axis is shifted), and the contrast of the liquid crystal display device is lowered.
(6) The rubbing process is difficult to quantify rubbing and difficult to manage.
(7) When the substrate size is increased, the influence of the deflection of the substrate and the roller is increased, so that uniform rubbing processing becomes difficult, and it is necessary to enlarge the apparatus for rubbing processing, 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 technique for controlling the alignment of liquid crystal molecules by containing a polymer (for example, Patent Document 3) has been proposed.

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

However, the conventional rubbingless alignment technique still has a problem that its effect is not sufficient.
In addition, the liquid crystal display device is required to be driven at a low voltage (reduction in power consumption) from the viewpoint of energy saving, but it is effective to reduce the thickness of the alignment film for driving at a low voltage. However, when a polyimide film is used as the alignment film, the polyimide film is a porous film, so that the polyimide film is generally about 100 nm from the viewpoint of preventing impurities from entering the liquid crystal layer from the base of the polyimide film. There is a problem that the thickness of the alignment film cannot be reduced. In addition, when the thickness of the polyimide film is reduced, there is a problem that the ability to control the alignment of liquid crystal molecules is lowered.

  The present invention has been made to solve the above-described problems, and is a liquid crystal that has excellent liquid crystal molecule alignment controllability and can be driven at a low voltage while preventing various problems caused by rubbing treatment. It is an object to provide a display device and a manufacturing method thereof.

As a result of intensive studies to solve the above problems, the present inventors have found that a polymer brush having a structure in which a large number of graft polymer chains extend in a direction perpendicular to the substrate surface has a high density of liquid crystal molecules. Based on the knowledge that the controllability is excellent and the effect of preventing the intrusion of impurities is high, it has been found that the above problems can be solved by using this polymer brush as an alignment film.
That is, the present invention is a liquid crystal display device using a polymer brush as an alignment film.
Further, the present invention includes a step of forming a polymer brush on a substrate, a step of injecting liquid crystal between the substrates on which the polymer brush is formed, and a step of aligning the liquid crystal by a non-contact alignment method. It is a manufacturing method of the liquid crystal display device characterized.
Furthermore, the present invention includes a step of forming a polymer brush on a substrate, a step of rubbing the polymer brush, and a step of injecting liquid crystal between the substrates on which the polymer brush is formed. It is a manufacturing method of a liquid crystal display device.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which is excellent in the orientation controllability of a liquid crystal molecule, and can be driven by a low voltage, while preventing the various problems resulting from a rubbing process, and its manufacturing method can be provided.

It is sectional drawing of the liquid crystal display device of this invention. It is a manufacturing flowchart of the liquid crystal display device of this invention. 6 is a graph showing the relationship between the rotation angle and the transmittance of the liquid crystal display device of Example 1. 6 is a graph showing the relationship between the rotation angle and the transmittance of the liquid crystal display device of Example 2. 6 is a graph showing VT curves of liquid crystal display devices of Examples 1 and 2 and Comparative Example 1. 6 is a graph showing luminance after voltage application in the liquid crystal display device of Example 1. 6 is a graph showing luminance after voltage application in the liquid crystal display device of Example 2.

Hereinafter, preferred embodiments of a liquid crystal display device and a manufacturing method thereof according to the present invention will be described with reference to the drawings. In the following, the present invention will be described by taking a horizontal electric field type liquid crystal display device as an example. However, the present invention is not limited to this, and the present invention can also be used for a vertical electric field type liquid crystal display device.
FIG. 1 is a cross-sectional view of the liquid crystal display device of the present invention. In FIG. 1, the liquid crystal display device includes an array substrate 1, a counter substrate 2 disposed so as to face the array substrate 1, and a liquid crystal layer 3 sandwiched between the array substrate 1 and the counter substrate 2. is doing. An electrode 4, an immobilizing film 5 and a polymer brush 6 are sequentially formed on the array substrate 1. In addition, an immobilization film 5 and a polymer brush 6 are sequentially formed on the counter substrate 2.
The liquid crystal display device of the present invention having such a configuration is basically the same as that of a known liquid crystal display device except that the polymer brush 6 is used as an alignment film. It is possible to manufacture according to the method.

  In general, a graft polymer chain having one end fixed to the surface of the substrate has a string-like, shrunken structure when the graft density is low. However, when the graft density is high, the interaction between adjacent graft polymer chains (three-dimensional) Due to the repulsion), the structure extends in the direction perpendicular to the substrate surface. In this specification, the “polymer brush 6” means the latter structure, that is, a structure in which a number of graft polymer chains have a high density and extend in a direction perpendicular to the substrate surface.

In the present specification, “high density” means the density of graft polymer chains that are so dense that steric repulsion occurs between adjacent graft polymer chains, and is generally 0.1 chain / nm ² or more, preferably The density is 0.1 to 1.2 strands / nm ² . Here, the “density” of the graft polymer chain means the number of graft polymer chains formed on the substrate surface per unit area (nm ² ).

  The polymer brush 6 formed on the substrate surface at a high density constitutes a layer of the polymer brush 6 (hereinafter referred to as “polymer brush layer”) on the substrate surface. The thickness of this polymer brush layer is several tens of nm, specifically 10 nm or more and less than 100 nm, preferably 10 nm to 80 nm. With such a thickness, the thickness of the conventional polyimide alignment film (generally 100 nm) is reduced, and the liquid crystal display device can be driven at a low voltage. Further, this polymer brush layer has a size exclusion effect, and a substance of a certain size cannot pass through the polymer brush layer. Therefore, even if the thickness of the polymer brush layer is reduced, the polymer brush layer is transferred from the base to the liquid crystal layer 3. Intrusion of impurities can be prevented. In addition, this polymer brush layer has good alignment control ability of the liquid crystal molecules 7 even though the thickness is relatively thin.

The polymer brush 6 preferably exhibits UV curability from the viewpoint of improving the alignment stability of the liquid crystal molecules 7. Specifically, the polymer brush 6 preferably has a functional group capable of UV curing (for example, a (meth) acryl group).
The polymer brush 6 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.
Further, the polymer brush 6 preferably exhibits liquid crystallinity from the viewpoint of compatibility with the liquid crystal layer 3. Specifically, the polymer brush 6 preferably has a functional group exhibiting liquid crystallinity (for example, a mesogenic group).

  The polymer brush 6 can be formed by living radical polymerization of a radical polymerizable monomer. Here, “living radical polymerization” is a polymerization reaction in which chain transfer reaction and termination reaction do not substantially occur in the radical polymerization reaction, and the chain growth terminal retains activity even after the radical polymerizable monomer is completely reacted. Say. 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-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl Methacrylate monomers such as tacrylate, 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- Hydroxyethyla Relate, 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, N Acrylate monomers such as N, dimethylacrylamide, N-methylolacrylamide and N-methylolmethacrylamide; styrene, styrene derivatives (o-, m-, p-methoxystyrene, o-, m-, pt-butoxystyrene) , O-, m-, p-chloromethylstyrene, etc.), vinyl esters (vinyl acetate, vinyl propionate, vinyl benzoate, vinyl acetate, etc.), vinyl ketones (vinyl Til ketone, vinyl hexyl ketone, methyl isopropenyl ketone, etc.), N-vinyl compounds (N-vinyl pyrrolidone, N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, etc.), (meth) acrylic acid derivatives (acrylonitrile, meta And vinyl monomers such as acrylonitrile, acrylamide, isopropylacrylamide, methacrylamide, etc.) and vinyl halides (vinyl chloride, vinylidene chloride, tetrachloroethylene, hexachloroprene, vinyl fluoride, etc.). The 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, 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.

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.
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 and the like.

  The amount of radically polymerizable monomer, polymerization initiator, copper halide, and ligand compound may be adjusted as appropriate according to the type of raw material used. Generally, the amount of 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.

  In addition, although living radical polymerization is normally performed without a solvent, you may use the solvent generally used by living radical polymerization. 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. The amount of the solvent may be appropriately adjusted according to the type of raw material to be used, but 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.

The molecular weight of the polymer brush 6 formed by living radical polymerization can be adjusted depending on the reaction temperature, reaction time, and the type and amount of the raw material used, but generally the number average molecular weight is 500 to 1,000,000, preferably Can obtain a polymer brush 6 of 1,000 to 500,000. Further, the molecular weight distribution (Mw / Mn) of the polymer brush 6 can be controlled between 1.05 and 1.60.
The polymer brush 6 having such characteristics can align the liquid crystal molecules 7 in the liquid crystal layer 3 in parallel with the array substrate 1 and the counter substrate 2.

The polymer brush 6 is formed on the array substrate 1 or the counter substrate 2 provided with the electrodes 4 with an immobilization film 5 as necessary.
The immobilization film 5 is not particularly limited as long as it has excellent adhesion to the array substrate 1, the counter substrate 2, the electrode 4, and the polymer brush 6, and is generally known in living radical polymerization. Things can be used. Examples of the immobilizing film 5 include a film formed from an alkoxysilane compound represented by the following general formula (1).

  In general formula (1), each R1 is independently a C1-C3 alkyl group, preferably a methyl group or an ethyl group; each R2 is independently a methyl group or an ethyl group; X is a halogen atom, preferably Is Br; n is an integer from 3 to 10, more preferably an integer from 4 to 8.

  A polymer brush 6 is preferably covalently bonded to the immobilization film 5. If the immobilization film 5 and the polymer brush 6 are connected by a covalent bond having a strong binding force, the polymer brush 6 can be sufficiently prevented from being peeled off, and the possibility that the characteristics of the liquid crystal display device are deteriorated is reduced. The reliability of the liquid crystal display device is improved.

  The array substrate 1 on which the fixing film 5 is formed is not particularly limited, and a generally known liquid crystal display device can be used. An example of the array substrate 1 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.

  The counter substrate 2 on which the fixing film 5 is formed is also not particularly limited, and a generally known liquid crystal display device can be used. An example of the counter substrate 2 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 electrode 4 on which the fixing film 5 is formed is not particularly limited, and a generally known liquid crystal display device can be used. An example of the electrode 4 is a comb electrode made of ITO (indium tin oxide).
The liquid crystal used for the liquid crystal layer 3 is not particularly limited, and generally known liquid crystal display devices can be used.

Next, the manufacturing method of the liquid crystal display device of this invention is demonstrated. FIG. 2 is a manufacturing flow diagram of the liquid crystal display device of the present invention. In the following, the present invention will be described by taking a method of performing liquid crystal injection utilizing the capillary phenomenon as an example, but the present invention is not limited to this, and a method using liquid crystal dropping injection (ODF) can also be used.
First, the electrode 4 is formed on the array substrate 1. The formation method of the electrode 4 is not particularly limited, and can be formed according to a known method. The array substrate 1 may be cleaned before the formation of the electrodes 4 as necessary.
Next, an immobilization film 5 is formed on the array substrate 1 on which the electrodes 4 are formed and the counter substrate 2. However, if the adhesion between the array substrate 1 on which the electrodes 4 are formed and the counter substrate 2 and the polymer brush 6 is good, the immobilization film 5 need not be formed. The method for forming the immobilization film 5 is not particularly limited, and may be appropriately set according to the material to be used. For example, the immobilization film 5 can be formed by immersing the array substrate 1 and the counter substrate 2 provided with the electrodes 4 in the immobilization film forming solution, and then drying. Here, in order to form the immobilization film 5 at a predetermined portion, masking may be performed on a portion where the immobilization film 5 is not formed. Further, the counter substrate 2 may be cleaned before the formation of the immobilization film 5 as necessary.

  Next, a polymer brush 6 is formed on the array substrate 1 and the counter substrate 2 on which the fixing film 5 is formed. The polymer brush 6 is formed by living radical polymerization (for example, ATRP). For example, the array substrate 1 and the counter substrate 2 on which the immobilization film 5 is formed are immersed in a polymer brush forming solution containing a radical polymerizable polymer, a polymerization initiator, and a copper halide / ligand complex, and heated. Thus, the polymer brush 6 can be formed. The heating conditions are not particularly limited, and may be appropriately adjusted according to the raw materials to be used. In general, the heating temperature is 60 to 150 ° C., and the heating time is 0.5 to 10 hours. At this time, the pressure is generally a normal pressure, but may be increased or decreased. Note that the array substrate 1 and the counter substrate 2 on which the immobilization film 5 is formed may be cleaned before the formation of the polymer brush 6 as necessary.

Next, the array substrate 1 on which the polymer brush 6 is formed and the counter substrate 2 are bonded together. For example, the array substrate 1 and the counter substrate 2 can be bonded to each other by applying the sealant and spraying the spacers, then overlapping the array substrate 1 and the counter substrate 2 and curing the sealant.
Next, liquid crystal is injected between the array substrate 1 and the counter substrate 2 by utilizing capillary action, and when the injection is completed, the injection port is closed and sealed.

  Next, liquid crystal molecules are uniaxially aligned by a non-contact alignment method such as a magnetic field alignment method or a template alignment method. When using the magnetic field alignment method, for example, while heating at a temperature equal to or higher than the glass transition temperature Tg of the polymer brush 6, while applying a magnetic field using a permanent magnet or a superconducting magnet in the direction in which the liquid crystal molecules 7 are to be aligned, Remove until cool. By performing such heating and magnetic field alignment treatment, non-contact uniaxial alignment becomes possible. The heating conditions may be appropriately adjusted according to the glass transition temperature of the formed polymer brush 6 and are not particularly limited, but the heating temperature is generally 60 to 150 ° C. and the heating time is 10 minutes to 1 hour. Similarly, the application condition of the magnetic field may be appropriately adjusted according to the type of liquid crystal used, and is not particularly limited, but the magnetic flux density is generally 0.5T to 5T. Moreover, it is preferable that the temperature-fall rate to normal temperature is 1 degree-C / min-20 degree-C / min. When the temperature lowering rate is less than 1 ° C./min, the process time becomes long and may not be practical. On the other hand, when the temperature lowering rate exceeds 20 ° C./min, the alignment control of the liquid crystal molecules 7 may not be sufficient.

Next, by irradiating UV (ultraviolet rays) as necessary, the orientation of the polymer brush 6 is fixed and the orientation stability of the liquid crystal molecules 7 is improved. The intensity of UV may be appropriately adjusted according to the type of polymer brush 6 formed, and is not particularly limited, but is generally several hundred to several tens of thousands mJ. UV irradiation may be performed without applying a magnetic field, but may be performed with a magnetic field applied.
The template orientation method is described in Japanese Patent Application No. 2009-166497 filed on Jul. 15, 2009 by the present applicant, and is incorporated herein by reference.
The liquid crystal display device of the present invention thus manufactured prevents various problems caused by the rubbing treatment and is excellent in alignment controllability of liquid crystal molecules. In addition, since the orientation is performed by the magnetic field, the orientation control can be quantified by adjusting the application condition of the magnetic field, and the management becomes easy. Further, since the alignment process is performed after the liquid crystal is injected, 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 can be improved.

In the above description, the alignment process using a magnetic field has been described. However, when the polymer brush 6 is used as an alignment film, the alignment process using a rubbing process can be performed. Even if the polymer brush 6 is oriented by rubbing treatment, it is less likely to be scratched than a conventional orientation film such as a polyimide film, so that conventional problems due to the rubbing treatment can be largely prevented.
In the case of performing the alignment treatment by rubbing treatment, after the polymer brush 6 is formed, it may be rubbed and cured by UV irradiation.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the following Example.
Example 1
In Example 1, a liquid crystal display device having an alignment film formed using styrene as a radical polymerizable monomer was produced.
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 (25 ° C.) overnight and then dried to form an immobilized film. Next, after washing and drying the two glass substrates on which the fixed film was formed, styrene (radical polymerizable monomer), ethyl-2-bromoisobutyrate (polymerization initiator), CuBr (copper halide) And 4,4′-dionyl-2,2′-bipyridine (ligand compound) at a molar ratio of 1900: 1: 19: 38 and immersed in a solution for forming a polymer brush and heated at 110 ° C. for 3 hours to form a living radical By polymerizing, a polymer brush (hereinafter referred to as PS brush) was formed. 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 (manufactured by JASCO Corporation). Polystyrene was used as the standard sample, and a UV detector was used as the detector. As a result, the number average molecular weight (Mn) of the PS brush was 1.34 × 10 ⁵ and the molecular weight distribution (Mw / Mn) was 1.51.
In addition, the thickness of the PS brush layer (PS brush layer) was evaluated using an X-ray reflectivity measuring apparatus (Panalytic (X'Pert-Pro-MAD manufactured by PANalytical)). The thickness was 50.6 nm.
Furthermore, as a result of evaluating the graft density of the PS brush, it was 0.23 strands / 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, P-type liquid crystal was injected between the two glass substrates by capillary action, and when the injection was completed, the injection port was closed and sealed. Next, after heating for 20 minutes at a temperature of 80 ° C. while applying a magnetic field of 1T in a predetermined direction, the liquid crystal display device is obtained by cooling to room temperature at a rate of temperature decrease of 10 ° C./min while applying the magnetic field. It was.

(Example 2)
In Example 2, a liquid crystal display device having an alignment film formed using methyl methacrylate as a radical polymerizable monomer was produced.
Here, methyl methacrylate (radical polymerizable monomer), ethyl-2-bromoisobutyrate (polymerization initiator), CuBr (copper halide) and 4,4'-dionyl-2,2'-bipyridine (ligand compound) In the same manner as in Example 1 except that it was immersed in a solution for forming a polymer brush containing 2000: 1: 20: 40 in a molar ratio and heated at 90 ° C. for 1.5 hours for living radical polymerization. Hereinafter, a liquid crystal display device was obtained.

The molecular weight of the formed PMMA brush was evaluated using a GPC measuring apparatus (manufactured by JASCO Corporation). Polymethylmethacrylate was used as the standard sample, and RI (refractive index) detector was used as the detector. As a result, the number average molecular weight (Mn) of the PMMA brush was 1.67 × 10 ⁵ and the molecular weight distribution (Mw / Mn) was 1.43.
In addition, the thickness of the PMMA brush layer (PMMA brush layer) was evaluated using an X-ray reflectivity measuring apparatus (Panalytic (X'Pert-Pro-MAD manufactured by PANalytical)). The thickness was 50.2 nm.
Furthermore, as a result of evaluating the graft density of the PMMA brush, it was 0.21 strand / nm ² .

(Comparative Example 1)
In Comparative Example 1, a conventional liquid crystal display device having a rubbing alignment film was produced.
Here, a polyimide film is formed on the glass substrate on which the comb-teeth electrode made of ITO is formed and the counter substrate on which the photo spacer having a height of about 3 μm is formed, and then a rubbing treatment is performed to form a rubbing alignment film. Obtained a liquid crystal display device in the same manner as in Example 1. The thickness of the rubbing alignment film was about 100 nm.

(Evaluation of orientation controllability)
When the polarizing plates are provided in crossed Nicols on both sides of the liquid crystal display devices obtained in Examples 1 and 2, and the liquid crystal display device is rotated between the polarizing plates, the rotation angle and transmittance of the liquid crystal display device I investigated the relationship. The measurement was started by setting the panel on a measuring instrument so that the transmission axis of the incident light side polarizing plate coincided with the alignment direction of the liquid crystal (magnetic field application direction). The result of the liquid crystal display device in Example 1 is shown in FIG. 3, and the result of the liquid crystal display device in Example 2 is shown in FIG.
As can be seen from these figures, in the liquid crystal display devices of Examples 1 and 2, periodic quenching was observed every 90 °, and the liquid crystal was uniaxially aligned in the horizontal direction with respect to the glass substrate, and the alignment state was good. I found out that

(Evaluation of VT curve)
Polarizers were provided in crossed Nicols on both sides of the liquid crystal display devices obtained in Examples 1 and 2 and Comparative Example 1, applied to the liquid crystal display device while changing the voltage, and the transmittance was measured. In addition, it arrange | positioned so that the transmission axis of the incident light side polarizing plate may correspond to the orientation direction of a liquid crystal (the application direction of a magnetic field in Examples 1 and 2 and the rubbing direction in Comparative Example 1). The results are shown in FIG.
As can be seen from the figure, in the liquid crystal display devices of Examples 1 and 2, the VT curve is shifted to the low voltage side as compared with the liquid crystal display device of Comparative Example 1, and the drive voltage can be lowered. I found it possible.

(Evaluation of anchoring ability)
Polarizers were provided in crossed Nicols on both sides of the liquid crystal display devices obtained in Examples 1 and 2, and a voltage showing maximum luminance was applied for 15 seconds (normal temperature, 60 Hz AC drive). In addition, it arrange | positioned so that the transmission axis of the incident light side polarizing plate may correspond with the orientation direction (application direction of a magnetic field) of a liquid crystal. Here, a voltage of 6.5 V was applied to the liquid crystal display device of Example 1, and a voltage of 7.5 V was applied to the liquid crystal display device of Example 2. Thereafter, the voltage was turned off, and the luminance was measured at 5 second intervals. Here, the luminance was measured using a luminance meter (BM5 manufactured by Topcon Corporation). The result of the liquid crystal display device in Example 1 is shown in FIG. 6, and the result of the liquid crystal display device in Example 2 is shown in FIG.
As can be seen from these figures, the liquid crystal display devices of Examples 1 and 2 returned to the luminance before voltage application immediately after the voltage was turned off, and it was found that the anchoring ability was high.

  As can be seen from the above results, according to the present invention, a liquid crystal display device having excellent liquid crystal molecule alignment controllability and capable of being driven at a low voltage while preventing various problems due to rubbing treatment, and a method for manufacturing the same Can be provided.

  1 array substrate, 2 counter substrate, 3 liquid crystal layer, 4 electrode, 5 immobilization film, 6 polymer brush, 7 liquid crystal molecule.

Claims (10)

  A liquid crystal display device using a polymer brush as an alignment film.   The liquid crystal display device according to claim 1, wherein an immobilization film is formed as an underlayer of the polymer brush, and the polymer brush is covalently bonded to the immobilization film.   The liquid crystal display device according to claim 1, wherein the polymer brush is UV curable.   The liquid crystal display device according to claim 1, wherein the polymer brush is a copolymer.   The liquid crystal display device according to claim 1, wherein the polymer brush is a block copolymer.   The liquid crystal display device according to claim 1, wherein the polymer brush exhibits liquid crystallinity. The liquid crystal display device according to claim 1, wherein a polymer chain density of the polymer brush is 0.1 / nm ² or more. Forming a polymer brush on the substrate;
Injecting liquid crystal between the substrates on which the polymer brush is formed;
And a step of aligning the liquid crystal by a non-contact alignment method.   The method for manufacturing a liquid crystal display device according to claim 8, wherein the non-contact alignment method is a magnetic field alignment method or a template alignment method. Forming a polymer brush on the substrate;
Rubbing the polymer brush;
And a step of injecting liquid crystal between the substrates having the polymer brush subjected to the rubbing treatment.

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