KR101157946B1 - method for forming liquid crystal oriented film - Google Patents

Abstract

The present invention provides a method for forming a liquid crystal aligning film which selectively and simply forms a polymer brush only where necessary as a liquid crystal aligning film on a substrate, comprising the steps of: forming a mask in a portion where the formation of the polymer brush on the substrate is unnecessary; Depositing a substrate on which a mask is formed on a solution for forming an immobilization film to form an immobilization film on an exposed portion of the substrate; It is a method of forming the alignment film for liquid crystal containing the process of forming a polymer brush on the said fixation film by the living radical polymerization reaction of a polymerizable monomer, and the process of removing the said mask from the board | substrate with the said polymer brush.

Description

Method for forming liquid crystal oriented film

The present invention relates to a method of forming an alignment film for liquid crystal.

Recently, research on a technique called a polymer brush made by bonding a plurality of graft polymer chains to a substrate surface has been made, and has been applied in several fields. For example, Patent Document 1 describes a method of applying a polymer brush as an insulating film of an electronic device, and Patent Document 2 proposes hollow fine particles composed of a hollow portion and a polymer brush layer containing the same, and also Patent Document 3 An organic electronic device in which a semiconductor polymer brush is attached to at least one electrode surface has been proposed.

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-60540

Patent Document 2: International Publication No. 2006/087839

Patent Document 3: Japanese Patent Application Laid-Open No. 2007-527605

However, in Patent Documents 1 to 3, there is no description or suggestion of using a polymer brush as an alignment film for liquid crystal. Moreover, the said patent documents 1-3 do not describe the method of forming a polymer brush as an oriented film for liquid crystals on a board | substrate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a liquid crystal alignment film which selectively and simply forms a polymer brush only where necessary as a liquid crystal alignment film on a substrate.

The present invention for achieving the above object is a process for forming a mask on the portion of the polymer brush on the substrate is unnecessary, and the substrate formed with the mask is deposited in a solution for forming a fixed film to form a fixed film on the exposed portion of the substrate And depositing a substrate on which the immobilization film is formed in a solution for forming a polymer brush, and forming a polymer brush on the immobilization film by a living radical polymerization reaction of a radical polymerizable monomer included in the polymer brush formation solution. And a step of removing the mask from the substrate on which the polymer brush is formed.

The present invention is a process of depositing a substrate in a solution for forming an immobilization film to form an immobilization film on the substrate; Forming a polymer brush on the exposed portion of the fixed film by living radical polymerization reaction of a radically polymerizable monomer contained in the polymer brush-forming solution by immersing it in the forming solution, and removing a mask from the substrate on which the polymer brush is formed. It is a formation method of the alignment film for liquid crystals containing the process of removing.

According to the present invention, a process of forming an immobilization film on a substrate by depositing a substrate in a solution for forming an immobilization film; And a substrate on which the immobilized film is partially inactivated is deposited in a solution for forming a polymer brush, and the polymer brush is formed on an immobilized film activated by a living radical polymerization reaction of a radical polymerizable monomer contained in the polymer brush forming solution. It is a formation method of the oriented film for liquid crystals including the process of forming a form.

The present invention provides a process of forming an immobilization film on a substrate by applying a solution for forming an immobilization film to a portion requiring formation of a polymer brush on a substrate, and applying a solution for forming a polymer brush on the immobilization film by a printing method. To form a polymer brush on the immobilized film by a living radical polymerization reaction of a radically polymerizable monomer contained in the solution for forming a polymer brush.

According to the present invention, it is possible to provide a method of selectively forming a polymer brush only where necessary as a liquid crystal aligning film on a substrate and more easily forming it.

1A to 1D are schematic cross-sectional views showing an embodiment of an alignment film for liquid crystal formed by the method of the present invention.
2A to 2D are schematic cross-sectional views showing an embodiment of an alignment film for liquid crystal formed by the method of the present invention.
3A to 3D are schematic cross-sectional views showing embodiments of the alignment film for liquid crystal formed by the method of the present invention.
4A to 4D are schematic cross-sectional views showing embodiments of the alignment film for liquid crystal formed by the method of the present invention.
FIG. 5 is a graph showing a relationship between a rotation angle and a transmittance of a liquid crystal display device having a liquid crystal display film obtained in Example 1; FIG.
FIG. 6 is a graph showing a relationship between a rotation angle and a transmittance of a liquid crystal display device having a liquid crystal display film obtained in Example 2; FIG.

EMBODIMENT OF THE INVENTION Hereinafter, the formation method of the liquid crystal aligning film of this invention is demonstrated in detail, referring drawings.

1: A is a schematic cross section which shows embodiment of the alignment film for liquid crystals formed by the method of 1st invention. In FIG. 1D, an immobilization film 11 is formed on the surface of one side of the substrate 10, and a polymer brush 13 is formed on the immobilization film 11 as an alignment film for liquid crystal. Neither the immobilization film 11 nor the polymer brush 13 is formed in a portion 12 where the formation of the polymer brush 13 is unnecessary, that is, in a portion where an alignment film for liquid crystal, such as a seal portion or a terminal portion, is unnecessary in the liquid crystal display device. The substrate 10 is in an exposed state. The board | substrate 10 provided with the liquid crystal aligning film of such a structure can be used as an array board | substrate and an opposing board | substrate of a liquid crystal display device.

The liquid crystal display device having such an array substrate and an opposing substrate has the same structure as a known liquid crystal display device except that the polymer brush 13 is used as an alignment film for liquid crystal. For example, a pixel and a common electrode made of ITO may be used. The counter substrate can be arranged to face the array substrate thus disposed, and liquid crystal molecules can be injected between the array substrate and the counter substrate to form a liquid crystal layer.

In general, graft polymer chains once fixed to the substrate surface have a structure in which the thread bundle shape is contracted when the graft density is low. As a result, the structure is extended in the direction perpendicular to the substrate surface.

In the present invention, the "polymer brush 13" means that the latter structure, that is, a plurality of graft polymer chains have a high density extending in the vertical direction with respect to the substrate 10 surface.

As used herein, the term "high density" refers to the density of graft polymer chains that are so dense that three-dimensional repulsion occurs between adjacent graft polymer chains, and is generally 0.1 chains / nm ² or more, preferably 0.1 to 1.2 chains. Density of / nm ² . Here, the "density" of the graft polymer chain means the number of graft polymer chains formed on the substrate surface near the unit area (nm ² ).

The polymer brush 13 formed on the surface of the substrate 10 at a high density constitutes a layer of the polymer brush 13 (hereinafter referred to as a "polymer brush layer") on the substrate 10 surface. The thickness of this polymer brush layer is about several tens nm, specifically, it is 10 nm or more and less than 100 nm, Preferably it is 10 nm-80 nm. This thickness becomes thinner than the thickness (generally 100 nm) of the conventional polyimide oriented film, and the low voltage drive of a liquid crystal display device is attained.

In addition, the polymer brush layer has a size exclusion effect, and since a substance having a certain size cannot pass through the polymer brush layer, even if the thickness of the polymer brush layer is reduced, impurities can be prevented from entering the liquid crystal layer from the base. Moreover, this polymer brush layer has a good ability to control the orientation of liquid crystal molecules even if the thickness is relatively thin.

It is preferable that the polymer brush 13 exhibits UV curability from the viewpoint of increasing the orientation stability of the liquid crystal molecules. Specifically, the polymer brush 13 preferably has a functional group (for example, a (meth) acryl group) capable of UV curing.

In addition, it is preferable that the polymer brush 13 is a copolymer, especially a block copolymer from a viewpoint of providing various characteristics. If it is such a copolymer, the various effects which cannot be obtained with a single aggregate can be expected.

Moreover, it is preferable that the polymer brush 13 shows liquid crystal from a viewpoint of compatibility with a liquid crystal layer. Specifically, the polymer brush 13 preferably has a functional group (for example, a mesogen group) exhibiting liquid crystallinity.

To form the polymer brush 13 as the alignment film for liquid crystal shown in FIG. 1D, first, as shown in FIG. 1A, the mask 14 is formed in the portion 12 where the formation of the polymer brush on the substrate 10 is unnecessary. . The material to be used for the mask 14 may be one that can cover the substrate 10 so that the immobilization film 11 is not formed in subsequent steps. For example, a resin film, a photoresist, and a solder can be used. A resist, a dry film register, UV hardening resin etc. are mentioned.

Subsequently, as shown in FIG. 1B, the surface of the substrate 10 on the side where the mask 14 is formed is dipped in the solution for forming the immobilization film, and the immobilization film 11 is formed on the exposed portion of the substrate 10. On the other hand, when depositing the whole board | substrate 10 in the solution for immobilization film formation, you may form the mask 14 also in the back surface of the board | substrate 10 as needed.

After the immobilization film 11 is formed, the substrate 10 may be washed as necessary. As a material used for the immobilization film 11, what is necessary is just to be excellent in adhesiveness with an array board | substrate, an opposing board | substrate, an electrode, the polymer brush 13, etc. For example, a well-known general thing can be used for living radical polymerization. As an example of the immobilization film 11, the film formed from the alkoxysilane compound shown by following General formula (1) is mentioned.

In formula (1), R 1 is each independently an alkyl group of C 1 to C 3, preferably a methyl group or an ethyl group; R 2 is 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, it is an integer of 4-8.

Subsequently, as shown in FIG. 1C, the surface of the substrate 10 on the side where the immobilization film 11 is formed is immersed in a solution for forming a polymer brush containing a radical polymerizable monomer, a polymerization initiator, a copper halide, a ligand compound, and the like. The polymer brush 13 is formed on the immobilization film 11 by the living radical polymerization reaction of the radical polymerizable monomer.

On the other hand, in the case where the entire substrate 10 on which the immobilization film 11 is formed on both surfaces is immersed in the polymer brush forming solution, the mask ( 14) is preferred. In order to prevent inactivation of the polymer brush-forming solution, deposition and living radical polymerization reaction of the substrate with the polymer brush-forming solution is carried out under oxygen blocking conditions, for example, in a nitrogen (N ₂ ) atmosphere or an argon (Ar) atmosphere. It is preferable to carry out at.

After the polymer brush 13 is formed, the substrate 10 may be washed and dried as necessary. Here, the "living radical polymerization" refers to a polymerization reaction in which a chain transfer reaction and a stop reaction do not substantially occur in the radical polymerization reaction, and the chain growth terminal retains the activity even after the radical polymerizable monomer has completely reacted.

In this polymerization reaction, even after the completion of the polymerization reaction, the end of the production aggregate maintains the polymerization activity, and when the radical polymerizable monomer is added, the polymerization reaction can be started again. The living radical polymerization is characterized in that the aggregate having an arbitrary average molecular weight can be synthesized by adjusting the concentration ratio between the radical polymerizable monomer and the polymerization initiator, and the molecular weight distribution of the aggregate to be produced is narrow.

Representative examples of living radical polymerization used in the present invention are atom transfer radical polymerization (ATRP). For example, in the presence of a polymerization initiator, atom transfer living radical polymerization of a radically polymerizable monomer is performed using a copper halide (CuX) / Ligand complex. The radically polymerizable monomer is added to the growth radicals that are reversibly grown by extracting the high molecular weight halogen from the copper halide / ligand complex, and the molecular weight distribution is regulated by reversible activation and inactivation in the repeated process. do.

The radically polymerizable monomer used for living radical polymerization has an unsaturated bond capable of radical polymerization in the presence of an organic radical, for example, methyl methacrylate, ethyl methacrylate, Propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, t-Butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate 2-ethyl hexyl methacrylate, nonyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, n- Octyl methacrylate, 2-methoxy ethyl methacrylate, butoxy ethyl methacrylate, methacrylate Methoxy tetra ethylene glycol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxy propyl methacrylate, 3-chloro- 2-hydroxypropyl methacrylate (3-chloro-2-hydrox propyl methacrylate), tetra hydro furfutyl methacrylate, 2-hydroxy-3-phenoxy propyl methacrylate (2- hydrox-3-phenoxy propyl methacrylate), Triethylene Glycol methacrylate, polyethylene glycol methacrylate, 2- (dimethyl amino) ethyl methacrylate (2- (Dimethyl amino) ethyl methacrylate monomers such as methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate n-butyl acrylate, t-butyl acrylate, hexyl acrylate, 2-ethyl hexyl acrylate, nonyl acrylate nonyl acrylate, benzyl acrylate, cyclohexyl acrylate, lauryl acrylate, n-octyl acrylate, 2-methoxy ethyl acrylate (2-methoxy acrylate), butoxy ethyl acrylate, methoxy tetra ethylene glycol acrylate, 2-hydroxyethyl acrylate, 2- 2-hydrox propyl acrylate, 3-chloro-2-hydrox propyl acrylate, tetra hydro furfutyl acrylate, 2 Hydroxy; -3-phenoxy propyl acrylate (2-hydrox-3-phenoxy propyl acrylate), diethylene glycol acrylate (Triethylene Glycol acrylate), polyethylene glycol acrylate, 2- (dimethyl amino) ethyl acrylate (2- (Dimethyl amino) ethyl acrylate), N, N-dimethyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide (N- acrylate-based monomers such as methylol metha crylamide; styrene (Stylene), styrene derivatives (o-, m-, p-methoxy styrene, o-, m-, p-t-Butkishi Styrene (butoxy stylene), o-, m-, p-chloro methyl styrene (such as chloro methyl stylene), vinyl esters (Vinyl acetate, propanoic vinyl, vinyl benzoate, Vinyl acetate), vinyl ketones (vinyl methyl ketone, vinyl hexyl ketone, Methyl isopropenyl (isopropyl ketone, etc.), N-vinyl compounds (N-vinyl pyrrolidone, N-vinyl pyrrole, N-vinyl carbazole) , N-vinyl indole (N-vinyl indole, etc.), (metha) acrylic acid derivatives (acrylonitrile, metha acrylonitrile, acrylamide, isopropyl Acrylamide (isopropyl Acrylamide, methacrylamide, etc.), halogenated vinyls (vinyl chloride, chloride vinylidene, tetra chloro ethylene, hexa chloroprene And vinyl monomers such as vinyl fluoride). These radically polymerizable monomers may be used independently or may be used together 2 or more types.

As a polymerization initiator, a well-known general thing can be used by living radical polymerization. Examples of the polymerization initiator include p-chloro methyl styrene, α-dichloro Xylene, α, α-dichloro Xylene, α, α-Dibro Mokisylene (α, α-dibromo Xylene), Hexakis (α-bromo methyl) (α-bromo Methyl) Benzene, benzalkonium chloride, benzal bromide, 1-Bromo-1-1 Benzyl halides such as phenylethane and 1-chloro-1 -phenyl ethane; propyl-2-bromopropionate, methyl-2-chloropropionate, ethyl-2-chloro Α-halogenated carboxylic acids such as propionate, methyl-2-bromopropionate and ethyl-2-bromo ISO butyrate (EBIB); tosyl such as p-toluenesulfonyl chloride (TsCl) ) Halides; alkyl halides such as tetrachloromethane, tribromo methane, 1-vinyl ethyl chloride, 1-vinylethyl bromide Cargoes; halogen derivatives of phosphate esters such as dimethyl phosphate chloride.

It does not specifically limit as copper halide which gives a copper halide / ligand complex, A well-known general thing can be used by living radical polymerization. Examples of copper halides include CuBr, CuCl, CuI, and the like.

As a ligand compound which gives a copper halide / ligand complex, it does not specifically limit, A well-known general thing can be used by living radical polymerization. Examples of the ligand compound include triphenylphosphane, 4,4'-dinonyl 2 (4,4'-dinonyl-2), 2'-dipyridine (dNbipy), N, N , N ', N'N "-pentamethyl diethylene triamine (N, N, N', N'N" -Penta Methyl Diethylene Triamine), 1, 1, 4, 7, 10, 10-hexamethyl triethylene Tetraamine (1,1,4,7,10,10-Hexamethyl Triethylene tetramine) and the like.

Although the quantity of a radically polymerizable monomer, a polymerization initiator, a copper halide, and a ligand compound may be adjusted according to the kind of raw material to be used, Generally, 1-1 mol of radically polymerizable monomers are preferable with respect to 1 mol of polymerization initiators, Preferably it is 50 ~ 5,000 mol, copper halide is 0.1-100 mol, Preferably it is 0.5-100 mol, The ligand compound is 0.2-200 mol, Preferably it is 1.0-200 mol.

In addition, although living radical polymerization is normally performed without a solvent, you may use the solvent generally used for living radical polymerization. As a solvent which can be used, for example, benzene, toluene, N, N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), acetone Organic solvents such as Acetone, Chloroform, Carbon tetrachloride, Tetrahydrofurane (THF), Ethyl acetate, and Trifluoromethylbenzene; Water, Methanol , Ethanol, ISO propanol, n-Butanol, Ethyl Cellosolve, Butyl Cellosolve, 1-methoxy-2-propanol (1 aqueous solvents such as -methoxy-2-propanol). The amount of the solvent may be appropriately adjusted depending on the kind of the raw material to be used, but in general, the solvent is 0.01 to 100 ml, and preferably 0.05 to 10 ml with respect to 1 g of the radically polymerizable monomer.

Although the molecular weight of the polymer brush 13 formed by living radical polymerization can be adjusted by reaction temperature, reaction time, and the kind and quantity of raw materials to be used, the number average molecular weight is generally 500 to 1,000,000, preferably 1,000 to 500,000. A polymer brush 6 can be obtained. In addition, the molecular weight distribution (Mw / Mn) of the polymer brush 13 can be controlled between 1.05 and 1.60. The polymer brush 13 having this feature can orientate liquid crystal molecules in the liquid crystal layer in parallel with respect to the array substrate and the opposing substrate.

In addition, since the polymer brush 13 is sufficiently prevented from peeling off, and the characteristics of the liquid crystal display device are reduced, thereby improving the reliability of the liquid crystal display device, the polymer brush 13 and the immobilization film 11 have a bonding force. It is preferable to select materials of the polymer brush 13 and the immobilization film 11 so as to be connected by this strong covalent bond.

Finally, by removing the mask 14 from the substrate 10 on which the polymer brush 13 is formed, the substrate 10 on which the polymer brush 13 is formed can be obtained as the alignment film for liquid crystal shown in FIG. 1D. In addition, you may remove the mask 14 before forming the polymer brush 13.

2A to 2D are schematic cross-sectional views showing an embodiment of an alignment film for liquid crystal formed by the method of the second invention. In FIG. 2D, the immobilization film 11 is formed on the surface of one side of the substrate 10, and the polymer brush 13 as the alignment film for liquid crystal is formed on the immobilization film 11. The polymer brush 13 is not formed on the portion 12 where the formation of the polymer brush 13 is unnecessary, that is, the portion where the liquid crystal alignment film such as the seal portion or the terminal portion is unnecessary in the liquid crystal display device, and the immobilization film 11 is exposed. It is in a state. The board | substrate 10 provided with the liquid crystal aligning film of such a structure can be used as an array substrate and an opposing board | substrate of a liquid crystal display device.

The liquid crystal display device provided with such an array substrate and an opposing substrate has the same structure as a known liquid crystal display device except that the polymer brush 13 is used as an alignment film for liquid crystal. For example, a pixel and a common electrode made of ITO may be used. The counter substrate can be arranged to face the array substrate thus disposed, and liquid crystal molecules can be injected between the array substrate and the counter substrate to form a liquid crystal layer.

In general, graft polymer chains once fixed to the substrate surface have a structure in which the thread bundle shape is contracted when the graft density is low. As a result, the structure is extended in the direction perpendicular to the substrate surface.

In the present invention, the "polymer brush 13" means that the latter structure, that is, a plurality of graft polymer chains have a high density extending in the vertical direction with respect to the substrate 10 surface. In the present invention, the term "high density" means the density of the graft polymer chains that are so dense that three-dimensional repulsion occurs between adjacent graft polymer chains, and is usually 0.1 chain or more per 1 nm ^{2 of the} substrate 10 surface, and is preferable. For example, the density is 0.1 to 1.2 chains.

The polymer brush 13 formed on the surface of the substrate 10 at a high density constitutes a layer of the polymer brush 13 (hereinafter referred to as a "polymer brush layer") on the substrate 10 surface. The thickness of this polymer brush layer is about several tens nm, specifically, it is 10 nm or more and less than 100 nm, Preferably it is 10 nm-80 nm. If it is such a thickness, it becomes thinner than the thickness (generally 100 nm) of the conventional polyimide aligning film, and the low-voltage drive of a liquid crystal display device is attained.

In addition, the polymer brush layer has a size exclusion effect, and since a substance of a certain size cannot pass through the polymer brush layer, even if the thickness of the polymer brush layer is thinned, intrusion of impurities from the base to the liquid crystal layer can be prevented. have. Moreover, this polymer brush layer has good alignment control ability of liquid crystal molecules even if the thickness is relatively thin.

It is preferable that the polymer brush 13 exhibits UV curability from the viewpoint of increasing the orientation stability of the liquid crystal molecules. Specifically, the polymer brush 13 preferably has a functional group (for example, a (meth) acrylic group) capable of UV curing.

In addition, it is preferable that the polymer brush 13 is a copolymer, especially a block copolymer from a viewpoint of providing various characteristics. If it is such a copolymer, the various effects which cannot be obtained with a single aggregate can be expected.

Moreover, it is preferable that the polymer brush 13 exhibit liquid crystal from the viewpoint of compatibility with the liquid crystal layer. Specifically, the polymer brush 13 preferably has a functional group (for example, a mesogen group) exhibiting liquid crystallinity.

To form the polymer brush 13 as the liquid crystal alignment film shown in FIG. 2D, first, as shown in FIG. 2A, the surface of one side of the substrate 10 is dipped into a solution for forming an immobilization film, and the surface of one side of the substrate 10 is formed. The immobilization film 11 is formed on it. On the other hand, when depositing the whole board | substrate 10 in the solution for immobilization film formation, you may form the mask 14 on the back surface of the board | substrate 10 as needed. After the immobilization film 11 is formed, the substrate 10 may be washed as necessary. Since the material and the formation method of the immobilization film 11 are the same as that of 1st invention, the description is abbreviate | omitted.

Subsequently, as shown in FIG. 2B, the mask 14 is formed in the part 12 in which the formation of the polymer brush on the immobilization film 11 is unnecessary. On the other hand, when the immobilization film 11 is formed on both surfaces of the substrate 10 by depositing the entire substrate 10 in a solution for forming the immobilization film in the previous step, the mask 14 is formed on the rear surface of the substrate 10. It is preferable.

The material to be used for the mask 14 may be one that can cover the substrate 10 so that the immobilization film 11 is not formed in subsequent steps. For example, a resin film, a photoresist, and a solder can be used. A resist, a dry film register, UV hardening resin etc. are mentioned.

Subsequently, as shown in FIG. 2C, the surface of the substrate 10 on the side where the mask 14 is formed is immersed in a solution for forming a polymer brush containing a radical polymerizable monomer, a polymerization initiator, a copper halide, a ligand compound, and the like. The polymer brush 13 is formed in the exposed part of the fixed film 11 by the living radical polymerization reaction of the polymerizable monomer. After the polymer brush 13 is formed, the substrate 10 may be washed and dried as necessary. Since the material and the formation method of the polymer brush 13 are the same as that of 1st invention, the description is abbreviate | omitted.

By removing the mask 14 from the substrate 10 on which the polymer brush 13 is finally formed, the substrate 10 on which the polymer brush 13 is formed can be obtained as the alignment film for liquid crystal shown in FIG. 2D.

3A to 3D are schematic cross-sectional views showing an embodiment of an alignment film for liquid crystal formed by the method of the third invention. In FIG. 3D, the immobilization film 11 is formed on the surface of one side of the substrate 10, and the polymer brush 13 as the alignment film for liquid crystal is formed on the immobilization film 11. In the portion 12 where the formation of the polymer brush 13 is unnecessary, that is, the portion where the liquid crystal alignment layer such as the seal portion or the terminal portion is unnecessary in the liquid crystal display device, the polymer brush 13 is not formed and the immobilized film 11 is inactivated. This is in an exposed state. The board | substrate 10 provided with the liquid crystal aligning film of such a structure can be used as an array substrate and an opposing board | substrate of a liquid crystal display device.

The liquid crystal display device provided with such an array substrate and an opposing substrate has the same structure as a known liquid crystal display device except that the polymer brush 13 is used as an alignment film for liquid crystal. For example, a pixel and a common electrode made of ITO may be used. The counter substrate can be arranged to face the array substrate thus disposed, and liquid crystal molecules can be injected between the array substrate and the counter substrate to form a liquid crystal layer.

In general, graft polymer chains once fixed to the substrate surface have a structure in which the thread bundle shape is contracted when the graft density is low. As a result, the structure is extended in the direction perpendicular to the substrate surface.

In the present invention, the "polymer brush 13" means that the latter structure, that is, a plurality of graft polymer chains have a high density extending in the vertical direction with respect to the substrate 10 surface. In the present invention, the term "high density" means the density of the graft polymer chains that are so dense that three-dimensional repulsion occurs between adjacent graft polymer chains, and is usually 0.1 chain or more per 1 nm ^{2 of the} substrate 10 surface, and is preferable. For example, the density is 0.1 to 1.2 chains.

The polymer brush 13 formed on the surface of the substrate 10 at a high density constitutes a layer of the polymer brush 13 (hereinafter referred to as a "polymer brush layer") on the substrate 10 surface. The thickness of this polymer brush layer is about several tens nm, specifically, it is 10 nm or more and less than 100 nm, Preferably it is 10 nm-80 nm. If it is such a thickness, it becomes thinner than the thickness (generally 100 nm) of the conventional polyimide aligning film, and the low-voltage drive of a liquid crystal display device is attained.

In addition, the polymer brush layer has a size exclusion effect, and since a substance of a certain size cannot pass through the polymer brush layer, even if the thickness of the polymer brush layer is thinned, intrusion of impurities from the base to the liquid crystal layer can be prevented. have. Moreover, this polymer brush layer has good alignment control ability of liquid crystal molecules even if the thickness is relatively thin.

It is preferable that the polymer brush 13 exhibits UV curability from the viewpoint of increasing the orientation stability of the liquid crystal molecules. Specifically, the polymer brush 13 preferably has a functional group (for example, a (meth) acrylic group) capable of UV curing.

In addition, it is preferable that the polymer brush 13 is a copolymer, especially a block copolymer from a viewpoint of providing various characteristics. If it is such a copolymer, the various effects which cannot be obtained with a single aggregate can be expected.

Moreover, it is preferable that the polymer brush 13 exhibit liquid crystal from the viewpoint of compatibility with the liquid crystal layer. Specifically, the polymer brush 13 preferably has a functional group (for example, a mesogen group) exhibiting liquid crystallinity.

To form the polymer brush 13 as the alignment film for liquid crystal shown in FIG. 3D, first, as shown in FIG. 3A, the surface of one side of the substrate 10 is dipped into a solution for forming an immobilization film, and the surface of one side of the substrate 10 is formed. The immobilization film 11 is formed on it. On the other hand, when depositing the whole board | substrate 10 in the solution for immobilization film formation, you may form the mask 14 on the back surface of the board | substrate 10 as needed. After the immobilization film 11 is formed, the substrate 10 may be washed as necessary. Since the material and the formation method of the immobilization film 11 are the same as that of 1st invention, the description is abbreviate | omitted.

Subsequently, as shown in FIG. 3B, the UV blocking mask 15 is disposed in the portion 12 where the formation of the polymer brush on the immobilization film 11 is unnecessary, and the formation of the polymer brush on the immobilization film 11 is unnecessary. Ultraviolet rays are irradiated to (12) to deactivate the immobilized film 11 of the portion to which the ultraviolet rays are irradiated. On the other hand, in the previous step, when the entirety of the substrate 10 is deposited on the solution for forming the immobilization film to form the immobilization film 11 on both sides of the substrate 10, the back surface of the substrate 10 is irradiated with ultraviolet rays to fix the immobilization film ( It is preferable to inactivate 11). In this way, the immobilized film 16 is not formed with the polymer brush 13 in a subsequent process. Irradiation of ultraviolet light can be suitably adjusted according to the kind of material used, and is usually several hundreds to tens of thousands of mJ / cm 2.

Finally, as shown in FIG. 3C, the surface of the substrate 10 on the side where the immobilization film 11 and the inactivated immobilization film 16 are formed contains a radical polymerizable monomer, a polymerization initiator, a copper halide, a ligand compound, and the like. The polymer brush 13 is formed on the exposed portion of the immobilization film 11 by the living radical polymerization reaction of the radical polymerizable monomer by dipping in a solution for forming a polymer brush. The board | substrate 10 in which 13 was formed can be obtained. After the polymer brush 13 is formed, the substrate 10 may be washed and dried as necessary. Since the material and the formation method of the polymer brush 13 are the same as that of 1st invention, the description is abbreviate | omitted.

4A to 4D are schematic cross-sectional views showing an embodiment of an alignment film for liquid crystal formed by the method of the fourth invention. In FIG. 4D, the immobilization film 11 is formed on the surface of one side of the substrate 10, and the polymer brush 13 as the alignment film for liquid crystal is formed on the immobilization film 11. The polymer brush 13 is not formed on the portion 12 where the formation of the polymer brush 13 is unnecessary, that is, the portion where the liquid crystal alignment film such as the seal portion or the terminal portion is unnecessary in the liquid crystal display device, and the immobilization film 11 is exposed. It is in a state. The board | substrate 10 provided with the liquid crystal aligning film of such a structure can be used as an array substrate and an opposing board | substrate of a liquid crystal display device.

The liquid crystal display device provided with such an array substrate and an opposing substrate has the same structure as a known liquid crystal display device except that the polymer brush 13 is used as an alignment film for liquid crystal. For example, a pixel and a common electrode made of ITO may be used. The counter substrate can be arranged to face the array substrate thus disposed, and liquid crystal molecules can be injected between the array substrate and the counter substrate to form a liquid crystal layer.

In general, graft polymer chains once fixed to the substrate surface have a structure in which the thread bundle shape is contracted when the graft density is low. As a result, the structure is extended in the direction perpendicular to the substrate surface.

In the present invention, the "polymer brush 13" means that the latter structure, that is, a plurality of graft polymer chains have a high density extending in the vertical direction with respect to the substrate 10 surface. In the present invention, the term "high density" means the density of the graft polymer chains that are so dense that three-dimensional repulsion occurs between adjacent graft polymer chains, and is usually 0.1 chain or more per 1 nm ^{2 of the} substrate 10 surface, and is preferable. For example, the density is 0.1 to 1.2 chains.

The polymer brush 13 formed on the surface of the substrate 10 at a high density constitutes a layer of the polymer brush 13 (hereinafter referred to as a "polymer brush layer") on the substrate 10 surface. The thickness of this polymer brush layer is about several tens nm, specifically, it is 10 nm or more and less than 100 nm, Preferably it is 10 nm-80 nm. If it is such a thickness, it becomes thinner than the thickness (generally 100 nm) of the conventional polyimide aligning film, and the low voltage drive of a liquid crystal display device is attained.

In addition, the polymer brush layer has a size exclusion effect, and since a substance of a certain size cannot pass through the polymer brush layer, even if the thickness of the polymer brush layer is thinned, intrusion of impurities from the base to the liquid crystal layer can be prevented. have. Moreover, this polymer brush layer has good alignment control ability of liquid crystal molecules even if the thickness is relatively thin.

It is preferable that the polymer brush 13 exhibits UV curability from the viewpoint of increasing the orientation stability of the liquid crystal molecules. Specifically, the polymer brush 13 preferably has a functional group (for example, a (meth) acrylic group) capable of UV curing.

In addition, it is preferable that the polymer brush 13 is a copolymer, especially a block copolymer from a viewpoint of providing various characteristics. If it is such a copolymer, the various effects which cannot be obtained with a single aggregate can be expected.

Moreover, it is preferable that the polymer brush 13 exhibit liquid crystal from the viewpoint of compatibility with the liquid crystal layer. Specifically, the polymer brush 13 preferably has a functional group (for example, a mesogen group) exhibiting liquid crystallinity.

Forming the polymer brush 13 as the alignment film for liquid crystal shown in FIG. 4D is, first, as shown in FIG. 4A, the solution for forming the immobilized film is formed on a portion where the polymer brush needs to be formed on the surface of one side of the substrate 10. 17) is applied by a printing method, and then dried as necessary to form the immobilized film 11 on the substrate 10. As a printing method for apply | coating the solution 17 for immobilization film formation, press printing method, the inkjet method, etc. are mentioned. Although the material similar to 1st invention can be used for the material of the fixed film 11, it is necessary to use the thing of the form suitable for the printing method.

Subsequently, as shown in FIG. 4B, the solution 18 for polymer brush formation containing a radically polymerizable monomer, a polymerization initiator, a copper halide, a ligand compound, etc. is apply | coated by the printing method on the immobilization film 11, and necessary To form a polymer brush 13 on the immobilized film 11 by a living radical polymerization reaction of a radical polymerizable monomer, wherein the polymer brush 13 is formed as the alignment film for liquid crystal shown in FIG. ) Can be obtained.

As a printing method for apply | coating the polymer brush formation solution 18, a press printing method, the inkjet method, etc. are mentioned. In view of preventing the deactivation of the polymer brush-forming solution 18, the application of the polymer brush-forming solution 18 to the substrate and the living radical polymerization reaction are carried out under oxygen blocking conditions, for example, nitrogen (N ₂ ). It is preferable to perform in atmosphere and argon (Ar) atmosphere.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1

A glass substrate made of ITO and a common electrode and a counter substrate on which a photo spacer having a height of about 3 μm were formed were prepared, and a mask was formed on a portion where a polymer brush was not required to be formed. Next, two glass substrates which masked the solution for immobilization film formation containing 38 g of ethanol, 2 g of ammonia water (28%), and 0.4 g of 2-bromo- 2-methylpropionylhexyl triethkisilane (BHE) Was deposited at room temperature (25 ° C.) for about one day, and then dried to form an immobilized film.

Subsequently, the two glass substrates on which the immobilization film was formed were washed and dried, and then styrene (radically polymerizable monomer), ethyl-2-bromo ISO butylate (polymerization initiator), CuBr (copper halide), and 4, 4'- Dioryl 2,2'-bipyridine (ligand compound) is immersed in the solution for polymer brush formation at a molar ratio of 1900: 1: 19: 38, heated to 110 ° C for 3 hours, and subjected to living radical polymerization, brush (hereinafter, referred to as PS brush) was formed. Next, the two glass substrates on which the PS brush was formed were washed and dried, and then the mask was removed from the glass substrate.

The molecular weight of the formed PS brush was evaluated using a GPC measuring device (manufactured by Nippon Spectroscopy Co., Ltd.). Polystyrene was used as a standard sample and UV detector was used as a 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 (Panaritical (X'Pert-Pro-MAD manufactured by PANalytical). As a result, the thickness of the PS brush layer was evaluated. 50.6 nm.

Moreover, as a result of evaluating the graft density of PS brush, it was 0.23 chains / nm <^2> per 1 nm <^{2> of} glass surfaces.

Subsequently, after actually apply | coating to the one surface of the glass substrate in which PS brush was formed, two glass substrates were bonded and it hardened | cured by heating at 120 degreeC for 2 hours in nitrogen atmosphere. The P-type liquid crystal was injected between the two glass substrates by a capillary phenomenon, and when the liquid crystal injection was completed, the injection hole was closed and sealed. The liquid crystal display device was obtained by heating at a temperature of 80 ° C. for 20 minutes while applying a magnetic field of 1T in a predetermined direction, and then cooling the temperature to a room temperature of 10 ° C./min while applying a magnetic field.

When the polarizing plate was comprised on both sides of this liquid crystal display device, and a liquid crystal display device was rotated between the polarizing plates, the relationship between the rotation angle and the transmittance | permeability of the liquid crystal display device was investigated. The results are shown in FIG. On the other hand, the panel was set and measured so that the transmission axis of the incident light side polarizing plate might correspond to the alignment direction (the application direction of the magnetic field) of the liquid crystal.

As can be seen from FIG. 5, in this liquid crystal display, periodic extinction can be seen every 90 degrees, so that the liquid crystal is uniaxially oriented in the horizontal direction with respect to the glass substrate, and the PS brush layer functions as an alignment film for liquid crystal. It was confirmed that there is.

Example 2

The side on which the immobilization film is formed on the two glass substrates has a surface of methyl methacrylate (radically polymerizable monomer), ethyl-2-bromo ISO butylate (polymerization initiator), CuBr (copper halide), and 4, 4'-dionyl. 2,2'- bipyridine (ligand compound) was immersed in the solution for polymer brush formation in the molar ratio of 2000: 1: 20: 40, and it heated similarly to Example 1 except heating at 90 degreeC for 1.5 hours, and living radical polymerization. The polymer brush (hereinafter referred to as PMMA brush) was formed to obtain two glass substrates.

The molecular weight of the formed PMMA brush was evaluated using a GPC measuring device (manufactured by Nippon Spectroscopy Co., Ltd.). Polymethyl methacrylate was used as a standard sample and RI (refractive index) detector was used as a detector. As a result, the 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 (Panaritical (X'Pert-Pro-MAD manufactured by PANalytical). As a result, the thickness of the PMMA brush layer Was 50.2 nm.

Moreover, as a result of evaluating the graft density of PMMA brush, it was 0.21 chains / nm <^2> per 1 nm <^{2> of} glass surfaces.

Next, using the glass substrate in which the PMMA brush was formed, it carried out similarly to Example 1, and produced the liquid crystal display device. When the polarizing plate was comprised on both sides of this liquid crystal display device, and the liquid crystal display device was rotated between the polarizing plates, the relationship between the rotation angle and the transmittance | permeability of the liquid crystal display device was investigated. The results are shown in FIG. On the other hand, the panel was set and measured so that the transmission axis of the incident light side polarizing plate might correspond to the alignment direction (the application direction of the magnetic field) of the liquid crystal.

As can be seen in FIG. 5, in this liquid crystal display, periodic extinction can be seen every 90 °, so that the liquid crystal is uniaxially oriented in the horizontal direction with respect to the glass substrate, and the PMMA brush layer functions as an alignment film for liquid crystal. It was confirmed that there is.

10 array substrate 11: immobilization film
12: portion where the polymer brush is unnecessary to form 13: polymer brush
14 mask 15 UV protection mask
16: Inactivated Immobilized Film 17: Solution for Immobilized Film Formation
18: solution for forming polymer brush

Claims (6)

Forming a mask in a portion where the formation of the polymer brush on the substrate is unnecessary;
Depositing a substrate on which the mask is formed in a solution for forming an immobilization film to form an immobilization film on an exposed portion of the substrate;
Depositing a substrate on which the immobilization film is formed in a solution for forming a polymer brush to form a polymer brush on the immobilization film by living radical polymerization of a radical polymerizable monomer included in the polymer brush formation solution;
And removing the mask from the substrate on which the polymer brush is formed. Forming a fixed film on the substrate by immersing the substrate in a solution for forming a fixed film;
Forming a mask in a portion where formation of the polymer brush on the immobilization film is unnecessary;
Depositing the substrate on which the mask is formed in a solution for forming a polymer brush, and forming a polymer brush in an exposed portion of the immobilization film by living radical polymerization of a radically polymerizable monomer included in the polymer brush forming solution;
And removing the mask from the substrate on which the polymer brush is formed. Forming a fixed film on the substrate by immersing the substrate in a solution for forming a fixed film;
Irradiating an ultraviolet ray to a portion where the formation of the polymer brush on the immobilization film is unnecessary, and inactivating the immobilization film of the portion to which the ultraviolet ray is irradiated;
Depositing a substrate on which the immobilization film is partially inactivated in a solution for forming a polymer brush, and forming a polymer brush on the immobilization film activated by a living radical polymerization reaction of a radical polymerizable monomer included in the polymer brush formation solution Forming method of the alignment film for liquid crystals characterized by including the. 4. The method of forming an alignment film for liquid crystal according to any one of claims 1 to 3, wherein the deposition into the solution for forming the polymer brush and the living radical polymerization reaction are performed under oxygen blocking conditions. A process of forming an immobilization film on the substrate by applying the immobilization film formation solution to a portion requiring formation of the polymer brush on the substrate by a printing method;
And applying a polymer brush forming solution on the immobilization film by a printing method to form a polymer brush on the immobilization film by living radical polymerization of a radically polymerizable monomer included in the polymer brush forming solution. Method of forming an alignment film for liquid crystal. 6. The method for forming an alignment film for liquid crystal according to claim 5, wherein the application to the solution for forming a polymer brush and the living radical polymerization reaction are performed under oxygen blocking conditions.

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