JP5761180B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal alignment agent containing polysiloxane obtained by polycondensation of alkoxysilane, a liquid crystal alignment film obtained from the liquid crystal alignment agent, and a liquid crystal display device having the liquid crystal alignment film.

  In recent years, among liquid crystal display element display methods, vertical (VA) liquid crystal display elements are widely used for large-screen liquid crystal televisions and high-definition mobile applications (display units of digital cameras and mobile phones). . As the VA method, the MVA method (Multi Vertical Alignment) in which a projection for controlling the direction in which the liquid crystal falls is formed on the TFT substrate or the color filter substrate, or the direction in which the liquid crystal falls by the electric field by forming a slit in the ITO electrode of the substrate. A PVA (Paterned Vertical Alignment) system to be controlled is known.

  As another VA alignment method, there is a PSA (Polymer sustained Alignment) method. Among VA systems, the PSA system is a technology that has attracted attention in recent years. In this method, a photopolymerizable compound is usually added to a liquid crystal, and after producing a liquid crystal panel, an electric field is applied to irradiate the liquid crystal with ultraviolet rays (UV) while the liquid crystal is tilted. As a result, the polymerizable compound is photopolymerized to fix the alignment direction of the liquid crystal, causing a pretilt and improving the response speed. In the PSA method, a slit is formed in one electrode constituting the liquid crystal panel, and the electrode pattern on the opposite side can operate even in a structure in which no protrusion in the MVA method or a slit in the PVA method is provided. It has features that simplification of production and excellent panel transmittance can be obtained (see Patent Document 1).

On the other hand, inorganic liquid crystal alignment film materials are also known along with conventionally used organic liquid crystal alignment film materials such as polyimide. For example, a composition containing a reaction product of tetraalkoxysilane, trialkoxysilane, alcohol, and oxalic acid is used as a material for a coating-type inorganic alignment film, and is vertically aligned on an electrode substrate of a liquid crystal display element. It has been reported that a liquid crystal alignment film having excellent alignment properties, heat resistance and uniformity is formed (see Patent Document 2).
In addition, by using a liquid crystal aligning agent composition containing a tetraalkoxysilane, a specific trialkoxysilane and a reaction product with water, and a specific glycol ether solvent, display defects can be prevented and even after long-time driving. It has been reported that a liquid crystal alignment film is formed without leaving an afterimage, without reducing the ability to align liquid crystal, and with little reduction in voltage holding ratio against light and heat. (See Patent Document 3)

JP 2004-302061 A JP 09-281502 A JP 2005-250244 A

  Conventionally, in a PSA type liquid crystal display element, there is a problem that the polymerizable compound added to the liquid crystal has low solubility, and when the addition amount is increased, it is precipitated at a low temperature. On the other hand, when the addition amount of the polymerizable compound is reduced, a good alignment state cannot be obtained. Moreover, since the unreacted polymerizable compound remaining in the liquid crystal becomes an impurity (contamination) in the liquid crystal, there is a problem that the reliability of the liquid crystal display element is lowered.

  The object of the present invention is to improve the response speed and achieve good alignment even when the amount of the polymerizable compound added to the liquid crystal in the PSA method is small, and even when the liquid crystal without adding the polymerizable compound is used. An object of the present invention is to provide a liquid crystal aligning agent for a liquid crystal display element, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element having the liquid crystal aligning film capable of obtaining a state.

The gist of the present invention is as follows.
[1] A liquid crystal aligning agent for a device comprising polysiloxane obtained by polycondensation of an alkoxysilane represented by the formula (1) and an alkoxysilane containing the alkoxysilane represented by the formula (2) .
R ¹ Si (OR ² ) ₃ (1)
(R ¹ is a hydrocarbon group having 8 to 30 carbon atoms which may be substituted with a fluorine atom, and R ² represents an alkyl group having 1 to 5 carbon atoms.)

Ｒ^３は、炭素原子数１〜１８の炭化水素基であり、Ｒ^４は炭素数１〜５のアルキル基を表す。

R ³ is a hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents an alkyl group having 1 to 5 carbon atoms.

[2] The liquid crystal aligning agent according to the above [1], wherein R ^{3 in the} formula (2) is an alkylene group.
[3] The liquid crystal aligning agent according to the above [1], wherein R ^{3 in the} formula (2) is represented by the following formula (3) (where m and n are each an integer of 0 to 6).

[4] The polysiloxane according to any one of the above [1] to [3], wherein the polysiloxane is a polysiloxane obtained by polycondensation of an alkoxysilane containing an alkoxysilane represented by the following formula (4): Liquid crystal aligning agent.
(R ⁵ ) _n Si (OR ⁶ ) _4-n (4)
(R ⁵ is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms which may be substituted with a hetero atom, a halogen atom, an amino group, a glycidoxy group, a mercapto group, an isocyanate group or a ureido group; R ⁶ is an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 to 3.

[5] The liquid crystal aligning agent according to the above [4], wherein the alkoxysilane represented by the formula (4) is a tetraalkoxysilane in which n in the formula (4) is 0.
[6] The polysiloxane contains 0.1 to 30 mol% of the alkoxysilane represented by the formula (1) in all alkoxysilanes, and the alkoxysilane represented by the formula (2) in all alkoxysilanes. The liquid crystal aligning agent in any one of said [1]-[5] obtained by polycondensing the alkoxysilane containing 3 to 70 mol%.
[7] In the above [4] or [5] , the polysiloxane is obtained by polycondensation of an alkoxysilane represented by the formula (4) containing 10 to 96.9 mol% of the alkoxysilane in all alkoxysilanes . The liquid crystal aligning agent of description.

[8] The liquid crystal aligning agent according to any one of [1] to [7], wherein the polysiloxane content is 0.5 to 15% by mass in terms of SiO ₂ concentration.
[9] A liquid crystal alignment film obtained by applying the liquid crystal aligning agent according to any one of [1] to [8] to a substrate, drying and baking.
[10] A liquid crystal display device having the liquid crystal alignment film according to [9].
[11] The liquid crystal aligning agent according to any one of [1] to [8] is applied, and UV is irradiated in a state where a voltage is applied to a liquid crystal cell in which the liquid crystal is sandwiched between two baked substrates. Liquid crystal display element.
[12] A liquid crystal display element in which the liquid crystal aligning agent according to any one of [1] to [8] is applied, the liquid crystal is sandwiched between two baked substrates, and UV is irradiated in a state where a voltage is applied. Production method.

  According to the liquid crystal aligning agent of the present invention, even when the amount of the polymerizable compound added to the liquid crystal in the PSA method is small, or when using the liquid crystal without adding the polymerizable compound, the response speed is improved and good. A liquid crystal alignment film for a liquid crystal display element capable of obtaining an alignment state and a display element having the liquid crystal alignment film are obtained.

The present invention is described in detail below.
[Polysiloxane]
The present invention is a liquid crystal aligning agent for PSA system containing a polysiloxane obtained by polycondensation of an alkoxysilane represented by the formula (1) and an alkoxysilane containing the alkoxysilane represented by the formula (2).
R ¹ Si (OR ² ) ₃ (1)
R ¹ is a hydrocarbon group having 8 to 30 carbon atoms which may be substituted with a fluorine atom, and R ² represents an alkyl group having 1 to 5 carbon atoms. In the present specification, “may be substituted” means “substituted or not substituted”.

Ｒ^３は、炭素原子数１〜１８の炭化水素基であり、Ｒ^４は炭素数１〜５のアルキル基を表す。

R ³ is a hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents an alkyl group having 1 to 5 carbon atoms.

R ^{1 of the} alkoxysilane represented by the formula (1) (hereinafter also referred to as a specific organic group) is a hydrocarbon group having 8 to 30 carbon atoms, preferably 8 to 22 carbon atoms which may be substituted with fluorine. There is no particular limitation as long as it has the effect of vertically aligning the liquid crystal. Examples thereof include an alkyl group, a fluoroalkyl group, an alkenyl group, a phenethyl group, a styrylalkyl group, a naphthyl group, and a fluorophenylalkyl group. Among these, alkoxysilanes in which R ¹ is an alkyl group or a fluoroalkyl group are preferable because they are relatively inexpensive and easily available as commercial products. In particular, alkoxysilane in which R ¹ is an alkyl group is preferable. The polysiloxane used in the present invention may have a plurality of these specific organic groups.

R ² of the alkoxysilane represented by the formula (1) is an alkyl group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms. More preferably, R ² is a methyl group or an ethyl group.
Although the specific example of the alkoxysilane represented by this Formula (1) is given, it is not limited to this.

  For example, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, heptadecyltrimethoxysilane, Heptadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, nonadecyltrimethoxysilane, nonadecyltriethoxysilane, undecyltriethoxysilane, undecyltrimethoxysilane, 21-docosenyltriethoxysilane, trideca Fluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadecaful Lodecyltriethoxysilane, isooctyltriethoxysilane, phenethyltriethoxysilane, pentafluorophenylpropyltrimethoxysilane, m-styrylethyltrimethoxysilane, p-styrylethyltrimethoxysilane, (1-naphthyl) triethoxysilane, ( 1-naphthyl) trimethoxysilane and the like. Among them, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, heptadecyltrimethoxysilane Heptadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, nonadecyltrimethoxysilane, nonadecyltriethoxysilane, undecyltriethoxysilane, or undecyltrimethoxysilane is preferred.

  The alkoxysilane represented by the formula (1) having the specific organic group described above is preferably 0.1 mol% or more in order to obtain good liquid crystal alignment in all alkoxysilanes used for obtaining polysiloxane. More preferably, it is 0.5 mol% or more. More preferably, it is 1 mol% or more. Further, in order to obtain sufficient curing characteristics of the liquid crystal alignment film to be formed, 30 mol% or less is preferable. More preferably, it is 22 mol% or less.

R ^{3 of the} alkoxysilane represented by the formula (2) (hereinafter also referred to as a second specific organic group) is a hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 12 carbon atoms, Hydrogen; ring structures such as aliphatic ring, aromatic ring and hetero ring; and hetero atoms such as oxygen atom, nitrogen atom and sulfur atom may be contained. An alkylene group and a phenylene group are preferred. The number of carbon atoms of the alkylene group is 1-18, more preferably 1-12. The phenylene group is represented by the following formula (3), and m and n are each an integer of 0 to 6, preferably an integer of 0 to 2.

式（２）で表されるアルコキシシランのＲ^４は、上記した式（１）におけるＲ^２の定義と同じであり、また、Ｒ^４の好ましい基もＲ^２の場合と同じである。

R ⁴ of the alkoxysilane represented by the formula (2) is the same as the definition of R ^{2 in} the above formula (1), and a preferable group of R ⁴ is the same as that of R ² .

  Although the specific example of the alkoxysilane represented by Formula (2) is given, it is not limited to these. For example, allyltrimethoxysilane, allyltriethoxysilane, butenyltrimethoxysilane, butenyltriethoxysilane, pentenyltrimethoxysilane, pentenyltriethoxysilane, hexynyltrimethoxysilane, hexynyltriethoxysilane, heptenyltrimethoxy Silane, heptenyltriethoxysilane, octenyltrimethoxysilane, octenyltriethoxysilane, undecynyltrimethoxysilane, undecynyltriethoxysilane, allyloxyundecyltrimethoxysilane, allyloxyundecyltriethoxysilane, vinylphenyl Examples include trimethoxysilane, vinylphenyltriethoxysilane, vinylphenylethyltrimethoxysilane, and vinylphenylethyltriethoxysilane.

In order to improve the response speed of the liquid crystal display element even when the amount of the polymerizable compound added to the liquid crystal in the PSA method is small and when the liquid crystal to which no polymerizable compound is added is used, The alkoxysilane represented by the formula (2) having two specific organic groups is preferably 3 mol% or more in all alkoxysilanes used for obtaining the polysiloxane. More preferably, it is 5 mol% or more. More preferably, it is 10 mol% or more. Moreover, in order to fully harden the liquid crystal aligning film formed, 70 mol% or less is preferable.
In the present invention, the alkoxysilane represented by the formula (1) is preferably contained in an amount of 0.1 to 30 mol%, particularly preferably 2 to 20 mol% in the total alkoxysilane used, and the formula (2). It is preferable that 3-70 mol%, especially preferably 5-30 mol% is contained in the total alkoxysilane used.

In this invention, when obtaining polysiloxane, the alkoxysilane represented by following formula (4) can also be used besides the alkoxysilane represented by Formula (1) and Formula (2). Since the alkoxysilane represented by the formula (4) can impart various properties to the polysiloxane, one or more types can be selected and used according to the required properties.
(R ⁵ ) _n Si (OR ⁶ ) _4-n (4)
R ⁵ is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms which may be substituted with a hetero atom, a halogen atom, an amino group, a glycidoxy group, a mercapto group, an isocyanate group or a ureido group. R ⁶ is an alkyl group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, and n represents an integer of 0 to 3, preferably 0 to 2.

R ⁵ of the alkoxysilane represented by the formula (4) is a hydrogen atom or an organic group having 1 to 6 carbon atoms (hereinafter also referred to as a third organic group). Examples of third organic groups include aliphatic hydrocarbons; ring structures such as aliphatic rings, aromatic rings, and heterocycles; unsaturated bonds; heteroatoms such as oxygen, nitrogen, and sulfur atoms Or an organic group having 1 to 6 carbon atoms, which may have a branched structure. This organic group may be substituted with a halogen atom, amino group, glycidoxy group, mercapto group, isocyanate group, ureido group or the like.

Although the specific example of the alkoxysilane represented by Formula (4) is given, it is not limited to this.
In the alkoxysilane of formula (4), specific examples of alkoxysilane when R ⁵ is a hydrogen atom include trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane and the like.

Further, in the alkoxysilane of the formula (4), specific examples of the alkoxysilane when R ⁵ is a third organic group include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane. , Propyltrimethoxysilane, propyltriethoxysilane, methyltripropoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, N-2 (Aminoethyl) 3-aminopropyltrimethoxysilane, 3- (2-aminoethylaminopropyl) trimethoxysilane, 3- (2-aminoethylaminopropyl) triethoxysilane, 2-aminoethylaminomethyltrimethoxysilane, 2- (2-A Minoethylthioethyl) triethoxysilane, 3-mercaptopropyltriethoxysilane, mercaptomethyltrimethoxysilane, vinyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, trifluoropropyltrimethoxysilane, chloropropyltriethoxysilane, bromo Propyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3-aminopropylmethyldiethoxysilane, 3 -Aminopropyldimethylethoxysilane, trimethylethoxysilane, trimethylmethoxysilane, γ-ureidopropyltriethoxy Silane, .gamma.-ureidopropyltrimethoxysilane and .gamma.-ureidopropyl tripropoxysilane, and the like.

The polysiloxane used in the present invention is a kind of the alkoxysilane represented by the above formula (4) as long as the effects of the present invention are not impaired for the purpose of improving the adhesion with the substrate and the affinity with the liquid crystal molecules. Or you may have multiple types.
In the alkoxysilane represented by the formula (4), the alkoxysilane in which n is 0 is tetraalkoxysilane. Tetraalkoxysilane is preferable for obtaining the polysiloxane of the present invention because it easily condenses with the alkoxysilane represented by the formulas (1) and (2).
As such alkoxysilane in which n is 0 in the formula (4), tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane or tetrabutoxysilane is more preferable, and tetramethoxysilane or tetraethoxysilane is particularly preferable.

  When using together the alkoxysilane represented by Formula (4), the usage-amount of the alkoxysilane represented by Formula (4) is 10-96.9 mol% in all the alkoxysilanes used in order to obtain polysiloxane. It is preferable that More preferably, it is 35-99.8 mol%.

[Production method of polysiloxane]
The method for obtaining the polysiloxane used in the present invention is not particularly limited. In the present invention, it is obtained by condensing an alkoxysilane having the above-mentioned formulas (1) and (2) as essential components in an organic solvent. Usually, polysiloxane is obtained as a solution obtained by polycondensation of such alkoxysilanes and uniformly dissolved in an organic solvent.
As a method for polycondensation of polysiloxane, for example, a method of hydrolyzing and condensing alkoxysilane in a solvent such as alcohol or glycol can be mentioned. At that time, the hydrolysis / condensation reaction may be either partial hydrolysis or complete hydrolysis. In the case of complete hydrolysis, theoretically, it is sufficient to add 0.5 times mole of water of all alkoxy groups in the alkoxysilane, but it is usually preferable to add an excess amount of water more than 0.5 times mole.
In the present invention, the amount of water used in the above reaction can be appropriately selected as desired, but it is usually preferably 0.5 to 2.5 moles of all alkoxy groups in the alkoxysilane.

  Usually, for the purpose of promoting hydrolysis / condensation reaction, acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, succinic acid, maleic acid, fumaric acid; alkalis such as ammonia, methylamine, ethylamine, ethanolamine, triethylamine A metal salt such as hydrochloric acid, sulfuric acid or nitric acid; In addition, it is also common to further promote the hydrolysis / condensation reaction by heating the solution in which the alkoxysilane is dissolved. At that time, the heating temperature and the heating time can be appropriately selected as desired. For example, heating / stirring at 50 ° C. for 24 hours, heating / stirring under reflux for 1 hour, and the like can be mentioned.

  As another method, for example, a method of heating and polycondensing a mixture of alkoxysilane, a solvent and oxalic acid can be mentioned. Specifically, after adding oxalic acid to alcohol in advance to obtain an alcohol solution of oxalic acid, the alkoxysilane is mixed while the solution is heated. In that case, it is preferable that the quantity of the oxalic acid to be used shall be 0.2-2 mol with respect to 1 mol of all the alkoxy groups which alkoxysilane has. Heating in this method can be performed at a liquid temperature of 50 to 180 ° C. Preferably, it is a method of heating for several tens of minutes to several tens of hours under reflux so that evaporation or volatilization of the liquid does not occur.

When using multiple types of alkoxysilane when obtaining polysiloxane, you may use as a mixture which mixed alkoxysilane beforehand, and may mix multiple types of alkoxysilane sequentially.
The solvent used for polycondensation of alkoxysilane (hereinafter also referred to as polymerization solvent) is not particularly limited as long as it can dissolve alkoxysilane. Moreover, even when alkoxysilane does not melt | dissolve, what is melt | dissolved should just melt | dissolve with the progress of the polycondensation reaction of alkoxysilane. In general, since an alcohol is generated by a polycondensation reaction of alkoxysilane, an alcohol, a glycol, a glycol ether, or an organic solvent having good compatibility with the alcohol is used.

  Specific examples of such a polymerization solvent include alcohols such as methanol, ethanol, propanol, butanol and diacetone alcohol: ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1 , 5-pentanediol, 2,4-pentanediol, 2,3-pentanediol, 1,6-hexanediol and the like glycols: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether , Ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether , Diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, Glycol ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, propylene glycol dibutyl ether, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone , Dimethyl sulfoxide, tetramethylurea, hexamethylphosphotriamide, m-cresol and the like.

In the present invention, a plurality of the above polymerization solvents may be mixed and used.
The polysiloxane polymerization solution (hereinafter also referred to as polymerization solution) obtained by the above method has a concentration obtained by converting silicon atoms of all alkoxysilanes charged as raw materials into SiO ₂ (hereinafter referred to as SiO ₂ conversion concentration). .) Is preferably 20% by mass or less, and more preferably 5 to 15% by mass. By selecting an arbitrary concentration within this concentration range, gel formation can be suppressed and a homogeneous solution can be obtained.

[Polysiloxane solution]
In the present invention, the polymerization solution obtained by the above method may be used as a polysiloxane solution as it is, or if necessary, the solution obtained by the above method may be concentrated or diluted by adding a solvent. Or may be substituted with another solvent to form a polysiloxane solution.
In that case, the solvent to be used (hereinafter also referred to as additive solvent) may be the same as the polymerization solvent, or may be another solvent. The additive solvent is not particularly limited as long as the polysiloxane is uniformly dissolved, and one kind or plural kinds can be arbitrarily selected and used.

Specific examples of such an additive solvent include, in addition to the solvents mentioned as examples of the polymerization solvent described above, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as methyl acetate, ethyl acetate, and ethyl lactate. Can be mentioned.
These solvents can improve the applicability when the liquid crystal aligning agent is applied onto the substrate by adjusting the viscosity of the liquid crystal aligning agent, or by spin coating, flexographic printing, ink jetting or the like.

[Other ingredients]
In the present invention, other components other than polysiloxane, such as inorganic fine particles, metalloxane oligomers, metalloxane polymers, leveling agents, and surfactants are included as long as the effects of the present invention are not impaired. May be.
As the inorganic fine particles, fine particles such as silica fine particles, alumina fine particles, titania fine particles, and magnesium fluoride fine particles are preferable, and those in the state of a colloidal solution are particularly preferable. This colloidal solution may be a dispersion of inorganic fine particles in a dispersion medium, or a commercially available colloidal solution. In the present invention, by containing inorganic fine particles, the surface shape of the formed cured film can be changed or other functions can be imparted. The inorganic fine particles preferably have an average particle size of 0.001 to 0.2 μm, more preferably 0.001 to 0.1 μm. When the average particle diameter of the inorganic fine particles exceeds 0.2 μm, the transparency of the cured film formed using the prepared coating liquid may be lowered.
Examples of the dispersion medium for the inorganic fine particles include water and organic solvents. As a colloidal solution, it is preferable that pH or pKa is adjusted to 1-10 from the viewpoint of the stability of the coating liquid for forming a film. More preferably, it is 2-7.

  Examples of the organic solvent used for the dispersion medium of the colloidal solution include alcohols such as methanol, propanol, butanol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexylene glycol, diethylene glycol, dipropylene glycol, and ethylene glycol monopropyl ether; Ketones such as methyl ethyl ketone and methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene; amides such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone; esters such as ethyl acetate, butyl acetate and γ-butyrolactone; Examples include ethers such as tetrahydrofuran and 1,4-dioxane. Of these, alcohols or ketones are preferred. These organic solvents can be used alone or in admixture of two or more as a dispersion medium.

As the metalloxane oligomer and metalloxane polymer, single or composite oxide precursors such as silicon, titanium, aluminum, tantalum, antimony, bismuth, tin, indium, and zinc are used. The metalloxane oligomer or metalloxane polymer may be a commercially available product or may be obtained from a monomer such as a metal alkoxide, nitrate, hydrochloride, or carboxylate by a conventional method such as hydrolysis.
Specific examples of commercially available metalloxane oligomers and metalloxane polymers include siloxane oligomers or siloxanes such as methyl silicate 51, methyl silicate 53A, ethyl silicate 40, ethyl silicate 48, EMS-485, and SS-101 manufactured by Colcoat. Examples thereof include titanoxane oligomers such as a polymer and titanium-n-butoxide tetramer manufactured by Kanto Chemical Co., Inc. You may use these individually or in mixture of 2 or more types.

Moreover, a leveling agent, surfactant, etc. can use a well-known thing, and since a commercial item is easy to acquire especially, it is preferable.
Moreover, the method of mixing the above-mentioned other components with polysiloxane may be simultaneous with or after polysiloxane, and is not particularly limited.

[Liquid crystal aligning agent]
The liquid crystal aligning agent of this invention is the solution containing the polysiloxane mentioned above and other components as needed. In this case, as the solvent, a solvent selected from the group consisting of the above-mentioned polysiloxane polymerization solvent and additive solvent is used. The content of polysiloxane in the liquid crystal aligning agent is preferably 0.5 to 15% by mass, more preferably 1 to 6% by mass in terms of SiO ₂ equivalent concentration. Be in the range of such terms of SiO ₂ concentration, easy to obtain a desired film thickness by a single coating, easy pot life sufficient solution is obtained.

The method for preparing the liquid crystal aligning agent of the present invention is not particularly limited. The polysiloxane used in the present invention may be in a state where other components added as necessary are uniformly mixed. Since polysiloxane is usually polycondensed in a solvent, it is convenient to use the polysiloxane solution as it is or to add other components to the polysiloxane solution as necessary. Furthermore, the most convenient method is to use the polysiloxane polymerization solution as it is.
Moreover, when adjusting content of polysiloxane in a liquid crystal aligning agent, the solvent chosen from the group which consists of the polymerization solvent and addition solvent of the polysiloxane mentioned above can be used.

[Liquid crystal alignment film]
The liquid crystal aligning film of this invention is obtained using the liquid crystal aligning agent of this invention. For example, after applying the liquid crystal aligning agent of this invention to a board | substrate, the cured film obtained by drying and baking can also be used as a liquid crystal aligning film as it is. In addition, the cured film is rubbed, irradiated with polarized light or light of a specific wavelength, processed with an ion beam, etc., or irradiated with UV in a state where a voltage is applied to the liquid crystal display element after filling the liquid crystal. It is also possible. The liquid crystal aligning agent of the present invention is useful both in the case of the PSA system in which a polymerizable compound is added to the liquid crystal and in the case where no polymerizable compound is added to the liquid crystal.
The substrate on which the liquid crystal aligning agent is applied is not particularly limited as long as it is a highly transparent substrate, but a substrate in which a transparent electrode for driving liquid crystal is formed on the substrate is preferable.

Specific examples of the substrate include glass plate, polycarbonate, poly (meth) acrylate, polyethersulfone, polyarylate, polyurethane, polysulfone, polyether, polyetherketone, trimethylpentene, polyolefin, polyethylene terephthalate, (meth) acrylonitrile. And a substrate in which a transparent electrode is formed on a plastic plate such as triacetyl cellulose, diacetyl cellulose, and acetate butyrate cellulose.
Examples of the method for applying the liquid crystal aligning agent include spin coating, printing, ink jet, spraying, roll coating, and the like.In terms of productivity, the transfer printing method is widely used industrially. The present invention is also preferably used.

The drying process after applying the liquid crystal aligning agent is not necessarily required, but if the time from application to baking is not constant for each substrate, or if baking is not performed immediately after application, a drying process is included. Is preferred. The drying is not particularly limited as long as the solvent is removed to such an extent that the shape of the coating film is not deformed by transporting the substrate or the like. For example, a method of drying on a hot plate at a temperature of 40 ° C. to 150 ° C., preferably 60 ° C. to 100 ° C. for 0.5 to 30 minutes, preferably 1 to 5 minutes can be mentioned.
The coating film formed by applying the liquid crystal aligning agent by the above method can be baked to obtain a cured film. At that time, the firing temperature can be carried out at an arbitrary temperature of 100 ° C. to 350 ° C., preferably 140 ° C. to 300 ° C., more preferably 150 ° C. to 230 ° C., further preferably 160 ° C. to 220 ° C. It is. Firing can be performed at an arbitrary time of 5 minutes to 240 minutes. Preferably it is 10 to 90 minutes, More preferably, it is 20 to 90 minutes. For the heating, a generally known method such as a hot plate, a hot air circulation oven, an IR (infrared) oven, a belt furnace or the like can be used.

The polysiloxane in the liquid crystal alignment film undergoes polycondensation in the firing step. However, in the present invention, it is not necessary to completely polycondense unless the effects of the present invention are impaired. However, firing is preferably performed at a temperature higher by 10 ° C. or more than the heat treatment temperature required for the liquid crystal cell production process, such as curing of the sealant.
The thickness of the cured film can be selected as necessary, but is preferably 5 nm or more, more preferably 10 nm or more, because the reliability of the liquid crystal display element can be easily obtained. Moreover, when the thickness of the cured film is preferably 300 nm or less, more preferably 150 nm or less, the power consumption of the liquid crystal display element does not become extremely large, which is suitable.

<Liquid crystal display element>
The liquid crystal display element of the present invention can be obtained by forming a liquid crystal alignment film on a substrate by the above method and then preparing a liquid crystal cell by a known method. As an example of manufacturing a liquid crystal cell, a method is generally employed in which a pair of substrates on which a liquid crystal alignment film is formed are fixed with a sealant with a spacer interposed therebetween, and liquid crystal is injected and sealed. In this case, the size of the spacer used is 1 to 30 μm, preferably 2 to 10 μm.
The method for injecting the liquid crystal is not particularly limited, and examples thereof include a vacuum method for injecting liquid crystal after the inside of the manufactured liquid crystal cell is decompressed, and a dropping method for sealing after dropping the liquid crystal.

  In the PSA liquid crystal display element, a liquid crystal to which a photopolymerizable compound is preferably added in a small amount (typically 0.2 to 1% by weight) can be used as the liquid crystal to be used. A polymerizable compound by irradiating ultraviolet rays (UV) having a wavelength of 230 to 400 nm, more preferably 300 to 380 nm in a state where a voltage is applied between electrodes on both sides of a liquid crystal cell into which liquid crystal is introduced Is polymerized and cross-linked in situ, thereby increasing the response speed of the liquid crystal display. Here, the applied voltage is 5 to 30 Vp-p, preferably 5 to 20 Vp-p. The UV irradiation amount to be irradiated is 1 to 60 J, preferably 40 J or less, and the smaller the UV irradiation amount, the lowering of reliability due to the destruction of the members constituting the liquid crystal display can be suppressed, and the UV irradiation time. It is preferable because the manufacturing tact can be increased by reducing. The liquid crystal aligning agent of this invention is used also with the liquid crystal display element to which a polymeric compound is not added.

  The substrate used for the liquid crystal display element is not particularly limited as long as it is a highly transparent substrate, but is usually a substrate in which a transparent electrode for driving liquid crystal is formed on the substrate. A specific example is the same as the substrate described in [Liquid crystal alignment film]. In the case of a PSA type liquid crystal cell, a standard electrode pattern such as PVA or MVA or a protrusion pattern can be used for the substrate. However, the PSA type liquid crystal display can operate even in a structure in which a line / slit electrode pattern of 1 to 10 μm is formed on one side substrate and no slit pattern or projection pattern is formed on the opposite substrate. The liquid crystal display can simplify the manufacturing process and obtain high transmittance.

As a high-performance element such as a TFT type element, an element in which an element such as a transistor is formed between an electrode for driving a liquid crystal and a substrate is used.
In the case of a transmissive liquid crystal element, it is common to use a substrate as described above. However, in a reflective liquid crystal display element, an opaque substrate such as a silicon wafer can be used if only one substrate is used. It is. At that time, a material such as aluminum that reflects light may be used for the electrode formed on the substrate.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention should not be construed as being limited thereto.
Abbreviations in the compounds used in the examples are as follows.
TEOS: tetraethoxysilane C18: octadecyltriethoxysilane VTES: vinyltriethoxysilane ARMS: allyltrimethoxysilane OTMS: octenyltrimethoxysilane STMS: styryltrimethoxysilane HG: 2-methyl-2,4-pentanediol : Hexylene glycol)
BCS: 2-butoxyethanol UPS: 3-ureidopropylethoxysilane

<Synthesis Example 1>
In a 200 mL four-necked reaction flask equipped with a thermometer and a reflux tube, HG 24.0 g, BCS 8.0 g, TEOS 27.9 g, C18 1.7 g, and ARMS 9.7 g were mixed to obtain a solution of an alkoxysilane monomer. Was prepared. To this solution, a solution in which 12.0 g of HG, 4.0 g of BCS, 10.8 g of water, and 0.9 g of oxalic acid as a catalyst were mixed dropwise at room temperature over 30 minutes. The solution was stirred for 30 minutes and then refluxed for 1 hour, and a mixed solution of 0.6 g of a methanol solution having a UPS content of 92% by mass, 0.3 g of HG and 0.1 g of BCS was added in advance. The mixture was further refluxed for 30 minutes and then allowed to cool to obtain a polysiloxane solution having a SiO ₂ equivalent concentration of 12% by weight.
The obtained polysiloxane solution 10.0 g, were mixed BCS20.0G, give in terms of SiO ₂ concentration of 4 wt% of the liquid crystal alignment agent (K1).

<Synthesis Example 2>
In a 200 mL four-necked reaction flask equipped with a thermometer and a reflux tube, 21.6 g of HG, 7.2 g of BCS, 27.5 g of TEOS, 1.7 g of C18, and 13.9 g of OTMS were mixed to obtain a solution of an alkoxysilane monomer. Was prepared. To this solution, a solution in which 10.8 g of HG, 3.6 g of BCS, 10.8 g of water, and 0.9 g of oxalic acid as a catalyst were mixed dropwise at room temperature over 30 minutes. The solution was stirred for 30 minutes and then refluxed for 1 hour, and a mixed solution of 1.2 g of a methanol solution having a UPS content of 92% by mass, 0.6 g of HG and 0.2 g of BCS was added in advance. The mixture was further refluxed for 30 minutes and then allowed to cool to obtain a polysiloxane solution having a SiO ₂ equivalent concentration of 12% by weight.
The obtained polysiloxane solution 10.0 g, were mixed BCS20.0G, give in terms of SiO ₂ concentration of 4 wt% of the liquid crystal alignment agent (K2).

<Synthesis Example 3>
A solution of alkoxysilane monomer by mixing 21.8 g of HG, 7.3 g of BCS, 27.5 g of TEOS, 1.7 g of C18, and 13.5 g of STMS in a 200 mL four-necked reaction flask equipped with a thermometer and a reflux tube. Was prepared. To this solution, a solution prepared by previously mixing 10.9 g of HG, 3.6 g of BCS, 10.8 g of water, and 0.9 g of oxalic acid as a catalyst was added dropwise over 30 minutes at room temperature. The solution was stirred for 30 minutes and then refluxed for 1 hour, and a mixed solution of 1.2 g of a methanol solution having a UPS content of 92% by mass, 0.6 g of HG and 0.2 g of BCS was added in advance. The mixture was further refluxed for 30 minutes and then allowed to cool to obtain a polysiloxane solution having a SiO ₂ equivalent concentration of 12% by weight.
The obtained polysiloxane solution 10.0 g, were mixed BCS20.0G, give in terms of SiO ₂ concentration of 4 wt% of the liquid crystal alignment agent (K3).

<Comparative Synthesis Example 1>
In a 200 mL four-neck reaction flask equipped with a thermometer and a reflux tube, 23.3 g of HG, 7.7 g of BCS, 40.8 g of TEOS, and 1.7 g of C18 were mixed to prepare an alkoxysilane monomer solution. To this solution, a solution prepared by previously mixing 11.6 g of HG, 3.9 g of BCS, 10.8 g of water and 0.2 g of oxalic acid as a catalyst was added dropwise over 30 minutes at room temperature. The solution was stirred for 30 minutes and then refluxed for 1 hour, and then allowed to cool to obtain a polysiloxane solution having a solid content concentration of 12% by weight as SiO ₂ .
The obtained polysiloxane solution 10.0 g, were mixed BCS20.0G, give in terms of SiO ₂ concentration of 4 wt% of the liquid crystal alignment agent (L1).

<Comparative Synthesis Example 2>
In a 200 mL four-necked reaction flask equipped with a thermometer and a reflux tube, 21.8 g of HG, 7.3 g of BCS, 27.5 g of TEOS, 1.7 g of C18 and 13.5 g of VTES were mixed to prepare a solution of the alkoxysilane monomer. Prepared. To this solution, a solution prepared by previously mixing 10.9 g of HG, 3.6 g of BCS, 10.8 g of water, and 0.9 g of oxalic acid as a catalyst was added dropwise over 30 minutes at room temperature. The solution was stirred for 30 minutes and then refluxed for 1 hour, and a mixed solution of 1.2 g of a methanol solution having a UPS content of 92% by mass, 0.6 g of HG and 0.2 g of BCS was added in advance. The mixture was further refluxed for 30 minutes and then allowed to cool to obtain a polysiloxane solution having a SiO ₂ equivalent concentration of 12% by weight.
The obtained polysiloxane solution 10.0 g, were mixed BCS20.0G, give in terms of SiO ₂ concentration of 4 wt% of the liquid crystal alignment agent (L2).

<Example 1>
The liquid crystal aligning agent [K1] obtained in Synthesis Example 1 was spin-coated on the ITO surface of an ITO electrode substrate on which an ITO electrode pattern having a pixel size of 100 μm × 300 μm and a line / space of 5 μm was formed. After drying on an 80 ° C. hot plate for 5 minutes, baking was performed in a hot air circulation oven at 180 ° C. for 30 minutes to form a liquid crystal alignment film having a thickness of 100 nm.
The liquid crystal aligning agent [K1] obtained in Synthesis Example 1 is spin-coated on the ITO surface on which no electrode pattern is formed, dried on an 80 ° C. hot plate for 5 minutes, and then heated in a 180 ° C. hot air circulation oven. Baking was performed for 30 minutes to form a liquid crystal alignment film having a thickness of 100 nm. These two substrates were prepared, and a 6 μm bead spacer was sprayed on the liquid crystal alignment film surface of one of the substrates, and a sealant was printed thereon. The other substrate was bonded with the liquid crystal alignment film surface inside, and then the sealing agent was cured to produce an empty cell. A liquid crystal cell was prepared by injecting liquid crystal MLC-6608 (trade name, manufactured by Merck & Co., Inc.) into the empty cell by vacuum injection.

  The response speed characteristics of these liquid crystal cells were measured by the method described later. Then, 20 J of UV (wavelength: 280 to 330 nm) was irradiated from the outside of the liquid crystal cell in a state where a voltage of 20 Vp-p was applied to the liquid crystal cell. Thereafter, the response speed characteristic was measured again, and the response speed before and after UV irradiation was compared. The results are shown in Table 1.

<Example 2>
A liquid crystal cell was prepared in the same manner as in Example 1 except that the liquid crystal alignment treatment agent [K1] was changed to the liquid crystal alignment treatment agent [K2] obtained in Synthesis Example 2, and the response speed was measured. The results are shown in Table 1.

<Example 3>
A liquid crystal cell was produced in the same manner as in Example 4 except that the liquid crystal alignment treatment agent [K1] was changed to the liquid crystal alignment treatment agent [K3] obtained in Synthesis Example 3, and the response speed was measured. The results are shown in Table 1.

<Comparative Example 1>
A liquid crystal cell was prepared in the same manner as in Examples 1 to 3 except that the liquid crystal alignment treatment agent [K1] was changed to the liquid crystal alignment treatment agent [L1] obtained in Comparative Synthesis Example 1, and the response speed was measured. did. The results are shown in Table 1.

<Comparative Example 2>
A liquid crystal cell was prepared and the response speed was measured in the same manner as in Examples 1 to 3, except that the liquid crystal alignment treatment agent [K1] was changed to the liquid crystal alignment treatment agent [L2] obtained in Comparative Synthesis Example 2. did. The results are shown in Table 1.

[Response speed characteristics]
The time variation of the brightness of the liquid crystal panel when a square wave with a voltage of ± 4 V and a frequency of 1 kHz was applied to a liquid crystal cell to which no voltage was applied was captured with an oscilloscope. When the voltage is not applied, the luminance is 0%, a voltage of ± 4 V is applied, the saturated luminance value is 100%, and the time when the luminance changes from 10% to 90% is the response speed of the rise (unit: Millisecond).

  As can be seen from Table 1, in the liquid crystal cell of the example, the response speed was improved after UV irradiation even when a liquid crystal to which no polymerizable compound was added was used. On the other hand, in the comparative example, the response speed did not improve before and after UV irradiation.

  The liquid crystal aligning agent of the present invention can improve the response speed and obtain a good alignment state even in the case of a PSA system in which a polymerizable compound is added to the liquid crystal or a liquid crystal in which no polymerizable compound is added. The liquid crystal display element produced using the liquid crystal aligning agent of this invention is useful as a TFT liquid crystal display element, a TN liquid crystal display element, a VA liquid crystal display element, etc.

Claims (12)

A liquid crystal aligning agent comprising a polysiloxane obtained by polycondensation of an alkoxysilane represented by formula (1) and an alkoxysilane containing an alkoxysilane represented by formula (2).
R ¹ Si (OR ² ) ₃ (1)
(R ¹ is a hydrocarbon group having 8 to 30 carbon atoms which may be substituted with a fluorine atom, and R ² represents an alkyl group having 1 to 5 carbon atoms.)

R ³ is a hydrocarbon group having 1 to 18 carbon atoms, and R ⁴ represents an alkyl group having 1 to 5 carbon atoms. The liquid crystal aligning agent according to claim 1, wherein R ^{3 in the} formula (2) is an alkylene group. The liquid crystal aligning agent of claim 1 ^{R 3} is represented by the following formula (3) (where, m, n is the independently an integer of 0-6) represented by the formula (2).

The liquid crystal aligning agent in any one of Claims 1-3 whose polysiloxane is polysiloxane obtained by further polycondensing the alkoxysilane containing the alkoxysilane represented by following formula (4).
(R ⁵ ) _n Si (OR ⁶ ) _4-n (4)
(R ⁵ is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms which may be substituted with a hetero atom, a halogen atom, an amino group, a glycidoxy group, a mercapto group, an isocyanate group or a ureido group; R ⁶ is an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 to 3.   The liquid crystal aligning agent of Claim 4 whose alkoxysilane represented by said Formula (4) is tetraalkoxysilane whose n in Formula (4) is 0.   The polysiloxane contains 0.1 to 30 mol% of the alkoxysilane represented by the formula (1) in all alkoxysilanes, and the alkoxysilane represented by the formula (2) in 3 to 3 The liquid crystal aligning agent in any one of Claims 1-5 obtained by polycondensing the alkoxysilane containing 70 mol%. The polysiloxane in the total alkoxysilane alkoxysilane represented by the formula (4), the liquid crystal aligning agent of claim 4 or 5 obtained by polycondensation of an alkoxysilane containing 10 to 96.9 mol%. The content of polysiloxane, in terms of SiO ₂ concentration, the liquid crystal alignment agent according to any one of claims 1 to 6 contained 0.5 to 15 mass%.   The liquid crystal aligning film obtained by apply | coating the liquid crystal aligning agent in any one of Claims 1-8 to a board | substrate, drying and baking.   The liquid crystal display element which has a liquid crystal aligning film of Claim 9.   The liquid crystal display element which apply | coated the liquid crystal aligning agent in any one of Claims 1-8, and irradiated UV in the state which applied the voltage to the liquid crystal cell with which the liquid crystal was pinched | interposed with the board | substrate baked.   A method for producing a liquid crystal display element, wherein the liquid crystal aligning agent according to claim 1 is applied, the liquid crystal is sandwiched between two baked substrates, and UV is irradiated in a state where a voltage is applied.