KR20190087819A - Liquid crystal alignment composition, method of preparing liquid crystal alignment film, and liquid crystal alignment film using the same - Google Patents

Abstract

The present invention relates to a liquid crystal aligning agent composition comprising a cross-linking agent compound in which a terminal functional group is substituted with a protecting group having a specific structure together with a polymer containing polyimide or a precursor repeating unit thereof. The liquid crystal aligning agent composition is capable of realizing improved aligning properties and electrical properties.

Description

TECHNICAL FIELD [0001] The present invention relates to a liquid crystal aligning composition, a method of manufacturing a liquid crystal alignment layer using the same, and a liquid crystal alignment layer using the same. BACKGROUND ART [0002] Liquid crystal alignment

The present invention relates to a liquid crystal aligning composition capable of improving dispersibility and having high reliability and capable of realizing improved orientation and electrical properties while having excellent film strength in synthesis of a liquid crystal alignment film, a method for producing a liquid crystal alignment film using the same, To a liquid crystal alignment film and a liquid crystal display device using the same.

In a liquid crystal display element, a liquid crystal alignment film plays a role of aligning the liquid crystal in a certain direction. Specifically, the liquid crystal alignment layer acts as a director for the arrangement of liquid crystal molecules, and when the liquid crystal moves due to the electric field to form an image, the liquid crystal alignment film makes a proper orientation. In order to obtain a uniform brightness and a high contrast ratio in a liquid crystal display device, it is essential to uniformly orient the liquid crystal.

Conventionally, as a method of orienting the liquid crystal, a rubbing method of applying a polymer film such as polyimide to a substrate such as glass and rubbing the surface with a fiber such as nylon or polyester in a predetermined direction has been used. However, the rubbing method may cause fine dust or electrical discharge (ESD) when the fiber and the polymer film are rubbed, which can cause serious problems in manufacturing the liquid crystal panel.

Recently, in order to solve the problems of the rubbing method, an optical alignment method for inducing anisotropy (anisotropy) in a polymer film by light irradiation instead of friction and arranging liquid crystals using the anisotropy has been studied.

Various materials have been introduced as materials that can be used for the above-mentioned photo alignment method. Among them, polyimide is mainly used for good performance of a liquid crystal alignment film. However, the polyimide is difficult to apply directly to a manufacturing process for forming an alignment film by coating in a solution state because the solvent solubility is poor.

Therefore, it is coated with a precursor such as polyamic acid or polyamic acid ester having excellent solubility, and then subjected to a heat treatment at a temperature of 200 to 230 ° C to form polyimide, followed by light irradiation to perform alignment treatment.

However, due to the enlargement of the panel, haze occurs on the surface of the liquid crystal alignment film due to the sweeping of the normal column space (CS) of the manufacturing process, resulting in a poor quality of the galaxy, there was.

Accordingly, although it has been proposed to add various cross-linking agents to the liquid crystal aligning agent composition in order to produce a liquid crystal alignment layer having a high film strength required in the display field, the solubility of the cross-linking agent compound is not sufficient and the stability and dispersibility of the cross- There is a limit in that the reliability is reduced as the alignment agent composition becomes difficult to have uniformity. In addition, due to the simple addition of the crosslinking compound, electric electrical properties at high temperature and low frequency are reduced, making it difficult to produce a liquid crystal alignment film applicable to a high performance / low power display.

Accordingly, there is a demand for development of a liquid crystal aligning agent composition capable of enhancing alignment properties and electrical characteristics of an alignment film while having an adequate level of film strength, and having a high dispersibility even in a composition.

The present invention relates to a liquid crystal aligning composition capable of improving dispersibility and having high reliability and capable of realizing improved orientation and electrical properties while having excellent film strength in synthesis of a liquid crystal alignment film.

The present invention also provides a process for producing a liquid crystal alignment film using the above liquid crystal aligning agent composition.

In addition, the present invention provides a liquid crystal alignment film and a liquid crystal display device including the same, which are manufactured by the above manufacturing method.

In order to solve the above problems, in the present specification, a polymer comprising at least one member selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit; And a crosslinking agent compound represented by the following formula (1).

[Chemical Formula 1]

In Formula 1, A is a functional group having a valence of 1 to 4, n is an integer of 1 to 4, and L ₁ and L ₂ is the same or different and each independently represents one of an aryl group having 1 to 10 carbon atoms or an alkylene group having 6 to 20 carbon atoms of each other, R ₁ and R ₂ are the same or different and are each independently a functional group represented by the following formula (2)

(2)

In Formula 2, R ₃ is an alkyl group having 1 to 20 carbon atoms, a silyl group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, or a halosilyl group having 1 to 20 carbon atoms.

The present invention also relates to a method of manufacturing a liquid crystal display device, comprising the steps of: applying the liquid crystal aligning composition to a substrate to form a coated film; Subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C; Irradiating or rubbing the heat-treated coating film with light to perform alignment treatment; And curing the coating film subjected to the orientation treatment by a second heat treatment at a temperature of 200 ° C to 300 ° C to cure the liquid crystal alignment film.

In this specification, there is also provided a liquid crystal alignment film and a liquid crystal display device including the same, which are produced according to the process for producing a liquid crystal alignment film.

Hereinafter, a liquid crystal aligning composition according to a specific embodiment of the present invention, a method for producing a liquid crystal alignment layer using the same, and a liquid crystal alignment layer using the same will be described in detail.

Ⅰ. Liquid crystal aligning agent composition

According to one embodiment of the present invention, a polymer comprising at least one member selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit; And a crosslinking agent compound represented by the formula (1) may be provided.

The present inventors have found that when a crosslinking compound to be added together with a polyimide or a precursor polymer thereof such as the liquid crystal aligning agent composition of one embodiment has a structure in which the terminal of a hydroxyl group (-OH) which is a crosslinkable functional group is R ₁ or R ₂ It is confirmed through experiments that the physical properties of the liquid crystal alignment layer prepared from the crosslinking agent compound are uniformly dispersed in the liquid crystal aligning agent composition and that the reliability is improved. Completed.

When the functional group of R ₁ or R ₂ introduced into the crosslinkable functional group terminal of the crosslinking agent compound is heat-treated at a temperature of 90 ° C or higher, the hydroxyl group at the terminal of the crosslinkable functional group is recovered and the crosslinking reaction can proceed smoothly, Lt; 0 > C, it is possible to suppress the crosslinking reaction by the crosslinkable functional group to minimize the decrease in the solubility in the composition due to the formation of unnecessary crosslinked structure.

That is, in the liquid crystal aligning agent composition kept at a temperature lower than 90 캜, the structure of the crosslinking agent compound represented by the formula (1) is maintained, and the crosslinking reaction between the polyimide or the precursor polymer thereof and the crosslinking agent compound represented by the formula . In the crosslinking compound represented by the formula (1), the functional group of R ₁ or R ₂ is substituted with a hydrogen atom when the liquid crystal aligning composition is raised at a temperature of 90 ° C or higher, through a drying step, an exposure step, a curing step, While being substituted, the crosslinking reaction between the polyimide or its precursor polymer and the crosslinking compound represented by the above formula (1) may proceed.

Accordingly, the liquid crystal aligning composition of one embodiment can sufficiently improve the dispersibility of the crosslinking compound and the polyimide or its precursor polymer by inhibiting the crosslinking reactivity of the crosslinking compound added in the composition, and the liquid crystal alignment layer The strength of the alignment layer is improved through the cross-linking reaction between the cross-linking compound and the polyimide or its precursor polymer in the composition during the manufacturing process, and excellent alignment and electrical characteristics can be realized in the finally prepared liquid crystal alignment cell.

Hereinafter, the present invention will be described in more detail.

Unless defined otherwise herein, the following terms may be defined as follows.

In this specification, when a part is referred to as "including " an element, it is to be understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

In the present specification, examples of substituents are described below, but are not limited thereto.

In the present specification, the term "substituted" means that a functional group is substituted for a hydrogen atom in the compound, and the position to be substituted is not limited as far as the position where the hydrogen atom is substituted, , Two or more substituents may be the same as or different from each other.

As used herein, the term " substituted or unsubstituted " A halogen group; Cyano; A nitro group; A hydroxy group; Carbonyl group; An ester group; Imide; Amide group; An amino group; A carboxy group; Sulfonic acid group; A sulfonamide group; Phosphine oxide groups; An alkoxy group; An aryloxy group; An alkyloxy group; Arylthioxy group; An alkylsulfoxy group; Arylsulfoxy group; Silyl group; Boron group; An alkyl group; A cycloalkyl group; An alkenyl group; An aryl group; Aralkyl groups; An aralkenyl group; An alkylaryl group; Arylphosphine groups; Or a heterocyclic group containing at least one of N, O and S atoms, or a substituted or unsubstituted group in which at least two of the above-exemplified substituents are connected to each other . For example, "a substituent to which at least two substituents are connected" may be a biphenyl group. That is, the biphenyl group may be an aryl group, or may be interpreted as a substituent in which two phenyl groups are connected.

, 또는

는 다른 치환기에 연결되는 결합을 의미하고, 직접결합은 L 로 표시되는 부분에 별도의 원자가 존재하지 않은 경우를 의미한다. In the present specification,

, or

Means a bond connected to another substituent, and a direct bond means a case where no separate atom exists in a portion represented by L. [

In the present specification, the alkyl group is a monovalent functional group derived from an alkane, and may be linear or branched. The number of carbon atoms of the linear alkyl group is not particularly limited, but is preferably 1 to 20. The branched alkyl group has 3 to 20 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a tert-butyl group, But are not limited to, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, , n-heptyl, 1-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, Dimethylheptyl, 1-ethyl-propyl, 1,1-dimethylpropyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, 2,6- But are not limited thereto.

In the present specification, the aryl group is a monovalent functional group derived from arene, and is not particularly limited, but preferably has 6 to 20 carbon atoms, and may be a monocyclic aryl group or a polycyclic aryl group. The aryl group may be a phenyl group, a biphenyl group, a terphenyl group or the like as the monocyclic aryl group, but is not limited thereto. Examples of the polycyclic aryl group include, but are not limited to, a naphthyl group, an anthracenyl group, a phenanthryl group, a pyrenyl group, a perylenyl group, a klycenyl group and a fluorenyl group.

In the present specification, the alkoxy group may be linear, branched or cyclic. The number of carbon atoms of the alkoxy group is not particularly limited, but is preferably 1 to 30 carbon atoms. Specific examples include methoxy, ethoxy, n-propoxy, isopropoxy, i-propyloxy, n-butoxy, isobutoxy, tert-butoxy, sec-butoxy, n-pentyloxy, neopentyloxy, iso N-pentyloxy, n-hexyloxy, 3,3-dimethylbutyloxy, 2-ethylbutyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, benzyloxy, , But is not limited thereto.

In the present specification, the alkenyl group may be straight-chain or branched, and the number of carbon atoms is not particularly limited, but is preferably 2 to 40. According to one embodiment, the alkenyl group has 2 to 20 carbon atoms. According to another embodiment, the alkenyl group has 2 to 10 carbon atoms. According to another embodiment, the alkenyl group has 2 to 6 carbon atoms. Specific examples include vinyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, Butenyl, allyl, 1-phenylvinyl-1-yl, 2-phenylvinyl-1-yl, (Diphenyl-1-yl) vinyl-1-yl, stilbenyl, stilenyl, and the like.

In the present specification, the silyl group is a monovalent functional group derived from silane, and may have, for example, a structure in which three alkyl groups or aryl groups are bonded to a silicon atom. The content of the alkyl group or the aryl group is as described above. Specific examples of the silyl group include trimethylsilyl, triethylsilyl, triisopropylsilyl, t-butyldimethylsilyl, vinyldimethylsilyl, propyldimethylsilyl, triphenylsilyl, diphenylsilyl , A phenylsilyl group, and the like.

In the present specification, the haloalkyl group or the halosilyl group or the haloalkoxy group means a functional group in which the above-mentioned alkyl group or silyl group or alkoxy group is substituted with a halogen group, and the content of the alkyl group or silyl group or alkoxy group is as described above, Examples of groups are fluorine, chlorine, bromine or iodine. The haloalkyl group has 1 to 20 carbon atoms, the halosilyl group has 1 to 20 carbon atoms, and the haloalkoxy group preferably has 1 to 20 carbon atoms.

In the present specification, the arylalkyl group means a functional group in which at least one hydrogen atom contained in the alkyl group is substituted with an aryl group, and the content of the alkyl group or the aryl group is as described above. The number of carbon atoms of the arylalkyl group may be 7 to 30, and the eryl of the arylalkyl group may include a phenylmethyl group.

In this specification, the alkylene group is a divalent functional group derived from an alkane, and the description of the alkyl group described above can be applied, except that they are bivalent functional groups. For example, it may be straight chain or branched and may be a methylene group, an ethylene group, a propylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group or a hexylene group.

In the present specification, the arylene group is a divalent functional group derived from arene, and the description of the aryl group described above can be applied, except that these are bivalent functional groups. For example, straight chain or branched, and may be a phenylene group, a biphenylene group, a terphenylene group or the like.

In the present specification, a multivalent organic group is a residue in which a plurality of hydrogen atoms bonded to an arbitrary compound are removed, for example, a divalent organic group, a trivalent organic group, and a tetravalent organic group . As an example, a tetravalent organic group derived from cyclobutane means a residue in which any four hydrogen atoms bonded to cyclobutane are removed.

In the present specification, a direct bond or a single bond means that no atom or atomic group exists at the corresponding position and is connected to the bond line. Specifically, it means a case where no additional atom exists in a part represented by L ₁ and L ₂ in the formula.

(1) Polymer

The polymer may include at least one member selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit. That is, the polymer may include one polyamic acid repeating unit, one polyamic acid ester repeating unit, one polyimide repeating unit, or a mixture of two or more thereof.

Specifically, the polyimide repeating unit may be represented by the following formula (4), the polyamic acid ester repeating unit may be represented by the following formula (5), and the polyamic acid repeating unit may be represented by the following formula (6).

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

In the formulas (4) to (6), X ₁ to X ₃ are the same or different and each independently a tetravalent organic group. X ₁ to X ₃ may be a functional group derived from a polyamic acid, a polyamic acid ester, or a tetracarboxylic dianhydride compound used in polyimide synthesis.

More specifically, each of X ₁ to X ₃ may independently be one of a tetravalent organic group represented by the following formula (7).

(7)

In Formula 7, R ₁₃ to R ₁₈ are each independently hydrogen or an alkyl group having 1 to 6 carbon atoms, L ₃ is a single bond, -O-, -CO-, -COO-, -S-, _{-SO 2 -, -CR 19 R 20} -, - (CH 2) Z -, -O (CH 2) Z O-, -COO (CH 2) Z OCO-, -CONH-, phenylene, or a combination thereof , Wherein R ₁₉ and R ₂₀ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms or a haloalkyl group, and Z is an integer of 1 to 10.

More preferably, X ₁₁ to X ₁₃ may each independently be an organic group of the following formula (7-1) derived from 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride.

[Formula 7-1]

In Formulas 4 to 6, Y ₁ to Y ₃ may be the same or different from each other, and each may independently be a divalent organic group. Y ₁ to Y ₃ may be a functional group derived from a polyamic acid, a polyamic acid ester, or a diamine compound used in polyimide synthesis.

As a specific example, Y ₁ to Y ₃ may be a divalent organic group represented by the following general formula (8).

[Chemical Formula 8]

Wherein R ₂₁ and R ₂₂ are each independently selected from the group consisting of hydrogen, halogen, cyano, nitrile, alkyl of 1 to 10 carbon atoms, alkenyl of 1 to 10 carbon atoms, alkoxy of 1 to 10 carbon atoms, Haloalkyl of 1 to 10 carbon atoms, p and q are each independently an integer of 0 to 4, L ₄ is a single bond, -O-, -CO-, -S-, -SO ₂ - _{, -C (CH 3) 2 -} , -C (CF 3) 2 -, -CONH-, -COO-, - (CH 2) y -, -O (CH 2) y O-, -O (CH 2 ) _y- , -NH-, -NH (CH ₂ ) _y -NH-, -NH (CH ₂ ) _y O-, -OCH ₂ -C (CH ₃ ) ₂ -CH ₂ O-, -COO- _{2) y} -OCO-, or -OCO- (CH _{2) y} -COO-, and, y is an integer from 1 to 10, and k and m are each independently an integer from 0 to 3, n is from 0 to 3 It is an integer.

In Formula 5, at least one of R ₁₁ and R ₁₂ may be alkyl having 1 to 10 carbon atoms, and the remainder may be hydrogen.

(2) Crosslinking compound

The liquid crystal aligning composition of one embodiment may contain, in addition to the polymer described above, a crosslinking compound, and the crosslinking compound may have a specific chemical structure represented by the general formula (1). The physical / chemical properties of the crosslinking compound appear to be due to the specific structure of formula (1) described above.

In Formula 1, A is a functional group having a valence of 1 to 4, and n is an integer of 1 to 4. The A is a functional group located at the center of the crosslinking compound, and the functional groups represented by the brackets "[]" in formula (1) can be bonded to the terminal functional group contained in A by n number of functional groups.

That is, in the above formula (1), when n is 1, A is a monovalent functional group. When n is 2, A is a divalent functional group. Also, when n is 3, A is a trivalent functional group. When n is 4, A is a tetravalent functional group. Preferably, in Formula 1, n is 2, and A is an alkylene group having 1 to 10 carbon atoms, specifically, a butylene group.

In the above formula (1), L ₁ and L ₂ is the same or different and each independently represents one of an aryl group having 1 to 10 carbon atoms or an alkylene group having 6 to 20 carbon atoms of each other, preferably L ₁ and L _{2 may} be the same alkylene group having 1 to 5 carbon atoms, for example, an ethylene group.

In the above formula (1), R ₁ and R ₂ is a functional group substituted for a hydrogen atom at the end of a hydroxyl group (-OH), which is a crosslinkable functional group of the crosslinking compound, and inhibits the crosslinking reaction between the polyimide or a precursor polymer thereof and the crosslinking compound represented by the formula .

As described later, the R < ₁ > and R & R ₂ may be desorbed while being displaced by hydrogen atoms upon rising to a temperature of 90 ° C or higher through a drying process, an exposure process, a curing process, or the like for producing a liquid crystal alignment film from a liquid crystal aligning composition.

The R < ₁ & R ₂ are the same as or different from each other, and each independently can be a functional group represented by the above-described formula (2).

In the general formula (2), R ₃ is an alkyl group having 1 to 20 carbon atoms, a silyl group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, or a halosilyl group having 1 to 20 carbon atoms.

More specifically, in Formula 2, R ₃ is an alkyl group having 3 to 10 carbon atoms, a silyl group having 5 to 10 carbon atoms, a haloalkyl group having 10 to 15 carbon atoms, or a halosilyl group having 15 to 20 carbon atoms .

Preferably, R ₃ in Formula 2 may be one of n-butyl, tert-butyl and 2,6-dimethylheptan-4-yl.

Specifically, in Formula 1, A is an alkylene group having 1 to 10 carbon atoms, and n may be 2. That is, the crosslinking compound represented by Formula 1 may include a compound represented by Formula 1-1.

[Formula 1-1]

In Formula 1-1, A 'is an alkylene group having 1 to 10 carbon atoms, and L ₁ ' To L ₄ 'each independently represents an alkylene group having 1 to 5 carbon atoms, and R ₁ ' To And R ₄ 'each independently can be a functional group represented by the above-described formula (2).

More specifically, examples of the crosslinking compound represented by the formula (1-1) include A 'is a butylene group having 4 carbon atoms, and L ₁ ' To L ₄ 'is an ethylene group having 2 carbon atoms, and R ₁ ' To And R ₄ 'are compounds represented by the following general formula (1-2) in which all of the functional groups represented by the general formula (2) (R ₃ is tert-butyl group) are exemplified.

[Formula 1-2]

The crosslinking agent compound represented by Formula 1 may be used in an amount of 1 to 30 wt%, or 2 to 25 wt%, or 10 to 25 wt%, or 10 wt%, based on the total weight of the liquid crystal aligning agent composition, By weight to 25% by weight or less. If the content of the crosslinking compound is excessively large, the flexibility of the polymer may be decreased as the crosslinking degree of the polymer for liquid crystal aligning agent is excessively increased, and the storage stability due to viscosity increase of the composition may be decreased and the dispersibility of the crosslinking agent in the composition may be decreased The gelation reaction in the composition may reduce the applicability to the substrate.

On the other hand, if the content of the crosslinking agent is too small, it may be difficult to sufficiently realize the mechanical strength and electrical property improving effect due to the increase of the crosslinking degree of the polymer for the liquid crystal aligning agent.

The crosslinking compound represented by Formula 1 may have a transmittance change of 10% or less, or 0% to 10%, or 5% or less, or 0% to 5%, measured at a wavelength of 400 nm, have.

&Quot; (2) "

Percent change in permeability (%) = permeability of solvent - permeability of mixed solution

In the formula (2), the mixed solution is a mixture of the crosslinking compound represented by the formula (1) and a solvent. Examples of the solvent include, but are not limited to, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl- But are not limited to, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, 3-ethoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide, 1,3-dimethyl- imidazolidinone, Methyl ethyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, 4-hydroxy- Ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethyl Ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether and ethylene glycol monobutyl ether acetate. have. These may be used alone or in combination.

In the mixed solution of Formula 2, the crosslinking compound represented by Formula 1 may be used in an amount of 1 wt% to 30 wt%, or 2 wt% to 25 wt%, or 10 wt% to 25 wt% %, Or more than 10% by weight and not more than 25% by weight.

When the rate of change of the transmittance measured at a wavelength of 400 nm is excessively increased to more than 10% by the following formula (2) of the crosslinking compound represented by the formula (1), the solubility of the crosslinking compound in the liquid crystal aligning composition is very poor, The reliability may be reduced such that the cross-linking agent remains on the thin film in the form of particles in the produced liquid crystal alignment film, resulting in poor quality of the alignment film.

Ⅱ. Method of manufacturing liquid crystal alignment film

The present invention also provides a method of manufacturing a liquid crystal display device, comprising the steps of: (1) forming a coating film by applying a liquid crystal aligning agent composition of one embodiment to a substrate; Subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C (step 2); Irradiating or rubbing the heat-treated coating film with light to perform alignment treatment (step 3); And a step (step 4) of curing the coating film subjected to the orientation treatment by a second heat treatment at a temperature of 200 ° C to 300 ° C.

Step 1 is a step of coating the substrate with the above-mentioned liquid crystal aligning agent composition to form a coating film. The content of the liquid crystal aligning agent composition includes all of the above-mentioned contents in one embodiment.

The method of applying the liquid crystal aligning composition to a substrate is not particularly limited, and for example, screen printing, offset printing, flexographic printing, ink jet, or the like may be used.

The liquid crystal aligning composition may be dissolved or dispersed in an organic solvent. Specific examples of the organic solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2- Dimethyl sulfoxide, dimethyl sulfoxide, dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide,? -Butyrolactone, 3-methoxy-N, N-dimethylacetamide, N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide, 1,3-dimethyl- imidazolidinone, ethylamylketone, methylnonylketone, , Methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, Ether, ethylene glycol monoethyl ether acetate, ethylene glycol moiety And the like propyl ether, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate. These may be used alone or in combination.

In addition, the liquid crystal aligning composition may further include other components in addition to the organic solvent. As a non-limiting example, when the liquid crystal aligning agent composition is applied, it is possible to improve the uniformity of the film thickness or the surface smoothness, or to improve the adhesion of the liquid crystal alignment film to the substrate or to change the dielectric constant or conductivity of the liquid crystal alignment film Or an additive capable of increasing the denseness of the liquid crystal alignment film may be further included. Examples of such additives include various solvents, surfactants, silane compounds, dielectrics, and crosslinking compounds.

The step 2 is a step of subjecting the coating film formed by applying the liquid crystal aligning composition to a substrate to a primary heat treatment at a temperature of 50 to 250 캜.

In the first heat treatment step of the coating film, the heat treatment may be performed by a heating means such as a hot plate, a hot air circulation path, and an infrared ray furnace, and is preferably performed at 50 to 250 ° C. In the cross-linking compound represented by the general formula (1) contained in the liquid crystal aligning composition of the embodiment by heat treatment in the step of primary heat treatment of the coating film, R ₁ and The crosslinking reaction between the crosslinking agent and the polymer including the polyamic acid repeating unit, the polyamic acid ester repeating unit, the polyimide repeating unit, or a mixture of two or more of them may be proceeded while the R ₂ functional group is substituted with a hydrogen atom have.

On the other hand, in the step of subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C, the imidization reaction of the polyamic acid or the polyamic acid ester polymer proceeds and polyimide can be synthesized. In the excessive heat treatment for the synthesized polyimide It is preferable that the primary heat treatment step is performed for 1 minute to 20 minutes.

Specifically, in the first heat treatment step, a crosslinking agent compound represented by the following formula (3) may be contained in the liquid crystal aligning agent composition.

(3)

In Formula 3, A, n, L _1, and L < ₂ > is the same as defined in Formula 1 of the embodiment.

When the crosslinking compound represented by Formula 3 is included in the liquid crystal aligning composition of one embodiment, the crosslinking compound is hardly uniformly dispersed in the composition as the crosslinking reaction progresses from the inside of the composition, and the storage stability is also decreased.

On the other hand, in the liquid crystal aligning composition of the present invention, the cross-linking compound represented by the formula (1) is added to inhibit the cross-linking reaction in the composition, and in the first heat treatment step of producing the liquid crystal alignment layer, Can be induced to be converted into the crosslinking compound represented by the general formula (3). Accordingly, the dispersibility and stability of the crosslinking compound can be enhanced in the composition, and the effect of improving the film strength can be realized by forming the crosslinking structure in the alignment layer.

More specifically, the step of subjecting the coating film to a primary heat treatment at a temperature of 50 ° C to 250 ° C includes: drying the coating film at a temperature of 50 ° C to 90 ° C; And drying the coated film at a temperature of 90 ° C to 250 ° C. In the step of drying the coated film at a temperature of 50 ° C to 90 ° C, the crosslinking agent compound represented by the formula (1) is contained in the liquid crystal aligning agent composition And the crosslinking compound represented by Formula 1 may be converted into the crosslinking compound represented by Formula 3 in the step of heat-treating the dried coating at a temperature of 90 ° C to 250 ° C.

The step 3 is a step of irradiating or rubbing light to the primary heat-treated coating film to carry out orientation treatment.

The light irradiation in the alignment treatment step may be to irradiate polarized ultraviolet light having a wavelength of 150 nm to 450 nm. At this time, the intensity of the exposure differs depending on the kind of the polymer for a liquid crystal aligning agent, and it is possible to irradiate energy of 10 mJ / cm 2 to 10 J / cm 2, preferably 30 mJ / cm 2 to 2 J / cm 2.

Examples of the ultraviolet ray include a polarizing device using a substrate coated with a dielectric anisotropic material on the surface of a transparent substrate such as quartz glass, soda lime glass, and soda lime free glass, a polarizer on which minute aluminum or metal wires are deposited, The polarizing ultraviolet ray is subjected to alignment treatment by irradiating a polarized ultraviolet ray selected from a polarized ultraviolet ray by a method of passing or reflecting the light through a Brewster's polarizing device or the like by reflection. At this time, the polarized ultraviolet ray may be irradiated perpendicularly to the substrate surface, or may be irradiated at an angle of incidence at a specific angle. By this method, the alignment ability of the liquid crystal molecules is imparted to the coating film.

Further, in the step of performing the alignment treatment, a rubbing cloth may be used. More specifically, the rubbing treatment can rub the surface of the coating film after the heat treatment step in one direction while rotating the rubbing roller having the cloth of the rubbing cloth attached to the metal roller.

The step 4 is a step of performing a secondary heat treatment at a temperature of 200 ° C to 300 ° C to cure the coating film subjected to the orientation treatment. At this time, the heat treatment may be performed by a heating means such as a hot plate, a hot air circulation path, and an infrared ray furnace.

Ⅲ. Liquid crystal alignment film

The present invention also provides a liquid crystal alignment film produced by the above-described method for producing a liquid crystal alignment film.

As described above, a polymer comprising at least one member selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit; And a crosslinking agent compound represented by the above formula (1), the liquid crystal alignment layer having excellent orientation properties and electrical characteristics can be manufactured while durability according to the improvement of film strength is enhanced.

Specifically, the liquid crystal alignment layer may have a film strength of 1.0% or less, or 0.01% to 0.33%, or 0.10% to 0.33% calculated by the following formula (1).

[Equation 1]

Film strength = haze of liquid crystal alignment film after rubbing treatment - haze of liquid crystal alignment film before rubbing treatment.

The rubbing treatment for the liquid crystal alignment layer may be performed by rubbing the surface of the alignment layer while rotating the surface of the alignment layer at 850 rpm using a rubbing machine manufactured by sindo engineering. The haze value may be measured using a hazemeter.

IV. Liquid crystal display element

The present invention also provides a liquid crystal display element comprising the above-described liquid crystal alignment film.

The liquid crystal alignment layer may be introduced into the liquid crystal cell by a known method, and the liquid crystal cell may be introduced into the liquid crystal display element by a known method. The liquid crystal alignment layer can be manufactured from the liquid crystal aligning agent composition of one embodiment to achieve excellent stability and excellent physical properties. Thereby, a liquid crystal display element capable of exhibiting high reliability can be provided.

On the other hand, the liquid crystal alignment display device may have a voltage holding ratio (VHR) of 99% or more, or 99% to 100%, measured by using 6254C equipment manufactured by TOYO Corporation at a temperature of 1 Hz and 60 degrees.

According to the present invention, there is provided a liquid crystal aligning composition capable of improving dispersibility and having high reliability, and having excellent film strength when synthesizing a liquid crystal alignment film, and capable of realizing improved orientation and electrical characteristics, a process for producing a liquid crystal alignment film using the same, And a liquid crystal alignment film and a liquid crystal display device using the same.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

≪ Preparation Examples and Comparative Preparations: Preparation of Crosslinking Compound >

Production Example 1

Compound 1 [0121] 3.204 g (10 mmol) of [N, N, N ', N'-Tetrakis (2-hydroxyethyl) adipamide] and 7.4008 g (44 mmol) of 2- [tert-butoxycarbonyl] imidazole were dissolved in toluene Toluene, 90 ml), 6.081 g (44 mmol) of potassium hydroxide [KOH] was added, and the mixture was stirred at 60 ° C for 16 hours. When the reaction was completed, the reaction product was slowly added to a container containing 500 mL of water and stirred for 1 hour. The solid obtained by filtration was washed with 200 mL of ultrapure water to prepare 6.2 g (yield: 86%) of compound 3 [(tert-butoxycarbonyl) -N, N, N ', N'-tetrakisethyladipamide]. The compound 3 was used as a crosslinking agent in Production Example 1.

Comparative Preparation Example 1

In Production Example 1 Compound 1 [N, N, N ', N'-Tetrakis (2-hydroxyethyl) adipamide] was used as a crosslinking agent in Comparative Preparation Example 1.

≪ Example: Production of liquid crystal aligning agent composition and liquid crystal alignment layer >

Example 1

(1) Preparation of liquid crystal aligning agent composition

1.22 g (5 mmol) of 4,4 '- (tetramethylenedioxy) dianiline was dissolved in 14.67 g of anhydrous N-methylpyrrolidone (NMP) 1.37 g (1.65 mmol) of 3 ', 4,4'-biphenyltetracarboxylic acid dianhydride [3,3', 4,4'-biphenyltetracarboxylic acid dianhydride] was added thereto at 25 ° C. and the mixture was stirred for 24 hours, .

To the polyamic acid solution was added the compound 3 [(tert-butoxycarbonyl) -N, N ', N'-tetrakisethyladipamide] obtained in Preparation Example 1 as a crosslinking agent in an amount of 3 wt% Followed by stirring for a time period to prepare a liquid crystal aligning agent composition.

(2) Production of liquid crystal alignment film

An ITO electrode having a thickness of 60 nm and an area of 1 cm x 1 cm was patterned, and the liquid crystal aligning agent composition obtained in (1) of Example 1 was spin-coated on a rectangular glass substrate having a size of 2.5 cm x 2.7 cm Respectively. Subsequently, the substrate coated with the liquid crystal aligning agent composition was placed on a hot plate at 80 DEG C for 2 minutes to dry, and then dried at 230 DEG C for 15 minutes. Thereafter, an ultraviolet ray of 254 nm was irradiated at an exposure amount of 0.25 J / cm 2 using an exposure device equipped with a line polarizer, and the film was subjected to orientation treatment and fired (cured) in an oven at 230 캜 for 15 minutes to prepare a liquid crystal alignment film having a thickness of 0.1 탆 .

Example 2

The same procedure as in Example 1 was carried out except that the compound 3 [(tert-butoxycarbonyl) -N, N ', N'-tetrakisethyladipamide] obtained in Preparation Example 1 was used as a crosslinking agent in an amount of 20% A liquid crystal aligning agent composition and a liquid crystal alignment layer were prepared.

≪ Comparative Example: Preparation of liquid crystal aligning agent composition and liquid crystal alignment layer >

Comparative Example 1

Except that the compound 3 [(tert-butoxycarbonyl) -N, N, N ', N'-tetrakisethyladipamide] obtained in Preparation Example 1 was not added as a crosslinking agent to the liquid crystal aligning composition and Thereby preparing a liquid crystal alignment film.

Comparative Example 2

The compound 1 [N, N, N ', N'-tetraisopropylethylamine] obtained in Comparative Preparation Example 1 was used as a crosslinking agent in place of the compound 3 [(tert-butoxycarbonyl) -N, N' Tetrakis (2-hydroxyethyl) adipamide] was added to prepare a liquid crystal aligning composition and a liquid crystal alignment layer.

Comparative Example 3

The compound 1 [N, N, N ', N'-tetraisopropylethylamine] obtained in Comparative Preparation Example 1 was used as a crosslinking agent in place of the compound 3 [(tert-butoxycarbonyl) -N, N' Tetrakis (2-hydroxyethyl) adipamide] was added to prepare a liquid crystal aligning composition and a liquid crystal alignment layer.

≪ Experimental Example: Measurement of physical properties of liquid crystal aligning composition and liquid crystal alignment layer obtained in Examples and Comparative Examples >

Examples and the liquid crystal aligning agent composition obtained in Comparative Example, or the liquid crystal alignment film, and the physical properties were measured by the following method from this liquid crystal alignment cell is manufactured by using the results are shown in Table 1.

A specific method of producing a liquid crystal alignment cell is as follows. The liquid crystal alignment layers formed on the two glass substrates used as the upper and lower substrates were aligned so that their alignment directions were aligned with each other, and then the upper and lower plates were bonded together and cured by using a sealing agent. Liquid crystal was injected into the empty cell, and the injection port was sealed with a sealing agent to prepare a liquid crystal alignment cell.

1. AC afterimage

A polarizing plate was attached to the upper and lower plates of the liquid crystal alignment cell. The liquid crystal cell with the polarizer was attached on a backlight of 7,000 cd / m < 2 > and the luminance in a black state was measured using a PR-880 instrument for measuring luminance brightness. Then, the liquid crystal cell was driven at room temperature with an AC voltage of 5 V for 24 hours. Thereafter, in a state where the voltage of the liquid crystal cell was turned off, the brightness in the black state was measured in the same manner as described above. The difference between the initial luminance (L0) measured before the driving of the liquid crystal cell and the measured latter luminance (L1) was divided by the initial luminance (L0) and multiplied by 100 to calculate the luminance variation. The calculated luminance variation ratio is closer to 0%, which means that the alignment stability is excellent. Based on the measurement results of the luminance change rate, the afterimage level was evaluated under the following criteria.

Excellent: Less than 10% luminance variation

Normal: The luminance variation is 10% to 20%.

2. Thickness

For the liquid crystal alignment layers obtained in the Examples and Comparative Examples, the surface of the liquid crystal alignment layer was rubbed while rotating at 850 rpm using a rubbing machine manufactured by sindo engineering, haze values were measured using a hazemeter, The film strength was evaluated by calculating the difference from the haze value before the rubbing treatment as shown in Equation (1). When the haze change value is less than 1, the film strength is excellent.

[Equation 1]

Film strength = haze of liquid crystal alignment film after rubbing treatment - haze of liquid crystal alignment film before rubbing treatment.

3. Voltage holding ratio (VHR)

For the liquid crystal alignment cell, the voltage holding ratio was measured at 1 Hz and 60 ° C using 6254C equipment of TOYO corporation as a measuring instrument.

4. Solubility

The cross-linking agents used in the liquid crystal aligning agent compositions of Examples and Comparative Examples were added to a solvent (? -Butyrolactone) so as to satisfy the addition amount of the cross-linking agent shown in Table 1 below and mixed for 10 seconds. The permeability change rate before and after the addition of the mixed solution was calculated using the following equation (2) using a JASCO Asia Portal V-770 UV-VIS-NIR Spectrophotometer at room temperature (25 ° C) and 400 nm wavelength using a cell.

&Quot; (2) "

Transmittance change rate (%) = permeability of solvent - permeability of mixed solution.

5. Storage stability

With respect to the liquid crystal aligning compositions of the examples and comparative examples, the initial viscosity and the viscosity after storage for 30 days at room temperature were respectively measured, and the rate of change in viscosity was measured by the following formula.

The viscosity of the liquid crystal aligning composition may be measured at 25 ° C, a rotation speed of 0.5 rpm, and a torque of a Brookfield viscometer on an RV-7 spindle.

[Mathematical Expression]

Viscosity change rate (%) = (viscosity of the liquid crystal aligning agent composition after storage for 30 days at room temperature-viscosity of the first liquid crystal aligning agent composition) / viscosity of the first liquid crystal aligning composition * 100.

Then, the storage stability level was evaluated under the following criteria.

Excellent: Less than 8% change in viscosity over 30 days

Bad: Viscosity change over 30 days is over 8%

Experimental Examples of Examples and Comparative Examples Measurement results division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Diamine BPDA BPDA BPDA BPDA BPDA Type of cross-linking agent Production Example 1 Production Example 1 - Comparative Preparation Example 1 Comparative Preparation Example 1 Amount of crosslinking agent
(weight%) 3 20 - 3 20 AC afterimage Great usually Great Great Not measurable Hardness (%) 0.32 0.15 9.37 0.35 Not measurable VHR (%) 99 99 75 98 Not measurable Transmittance change rate (%) 0 0.1 - 70 80 Viscosity change rate (%) Great Great Great Great Bad

* BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride [3,3', 4,4'-Biphenyltetracarboxylic acid dianhydride]

As shown in Table 1, the liquid crystal aligning composition of the Example containing the crosslinking agent of Production Example 1 together with the polyimide-based polymer in the composition exhibited a viscosity change rate of less than 8% for 30 days and exhibited excellent storage stability , And the obtained orientation film exhibited excellent electrical properties with a high voltage holding ratio (VHR) of 99% or more. The haze change value before and after the rubbing treatment was as low as 0.15% to 0.32%, indicating excellent film strength.

This is considered to be due to the crosslinking agent of Production Example 1 used in the liquid crystal aligning agent composition of the above Example, specifically, in order to determine the solubility of the crosslinking agent of Preparation Example 1 in the? -Butyrolactone solvent, As a result of measuring the rate of change, a very low transmittance change was shown from 0% to 0.1%.

Thus, the crosslinking agent of Preparation Example 1 is excellent in solubility in solvents commonly used in the liquid crystal aligning agent composition, and the performance of the liquid crystal alignment layer can be improved with a relatively small amount of a crosslinking agent at a high efficiency, It is confirmed that the reliability of the liquid crystal alignment layer can be improved.

On the other hand, the alignment film obtained from the liquid crystal aligning agent composition of Comparative Example 1 containing no crosslinking agent of Production Example 1 had a low voltage holding ratio (VHR) of 75%, and the electrical characteristic was decreased. The haze change value before and after the rubbing treatment increased sharply to 9.37% And the film strength was very poor.

On the other hand, in the case of the crosslinking agent of Comparative Preparation Example 1 used in the liquid crystal aligning agent compositions of Comparative Examples 2 and 3, in order to determine the solubility in the? -Butyrolactone solvent, the rate of change of the transparency before and after the addition of the crosslinking agent was measured. To 80%. Thus, the cross-linking agent of Comparative Preparation Example 1 has a very poor solubility in a solvent compatible with the liquid crystal aligning agent composition, so that the dispersibility in the liquid crystal aligning agent composition is reduced and the reliability of the finally prepared liquid crystal alignment layer is decreased Respectively.

In particular, when the cross-linking agent of Comparative Production Example 1 was added in an excessive amount as in Comparative Example 3, the solubility of the composition in the composition was very poor, and the cross-linking agent remained on the thin film in the form of particles in the finally prepared liquid crystal alignment film, It was confirmed that the quality was so bad that the measurement was impossible.

Claims (13)

A polymer comprising at least one member selected from the group consisting of a polyamic acid repeating unit, a polyamic acid ester repeating unit, and a polyimide repeating unit; And
1. A liquid crystal aligning composition comprising a crosslinking compound represented by the following formula
[Chemical Formula 1]

In Formula 1,
A is a functional group of 1 to 4,
n is an integer of 1 to 4,
L ₁ and L < ₂ > are the same or different from each other and each independently represents an alkylene group having 1 to 10 carbon atoms or an arylene group having 6 to 20 carbon atoms,
R ₁ and R ₂ are the same or different and are each independently a functional group represented by the following formula (2)
(2)

In Formula 2, R ₃ is an alkyl group having 1 to 20 carbon atoms, a silyl group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, or a halosilyl group having 1 to 20 carbon atoms.
The method according to claim 1,
In Formula 2, R ₃ is an alkyl group having 3 to 10 carbon atoms, a silyl group having 5 to 10 carbon atoms, a haloalkyl group having 10 to 15 carbon atoms, or a halosilyl group having 15 to 20 carbon atoms.
The method according to claim 1,
Wherein R ₃ in Formula 2 is one of normal butyl, tert-butyl, or 2,6-dimethylheptan-4-yl.
The method according to claim 1,
In Formula 1, A is an alkylene group having 1 to 10 carbon atoms, and n is 2.
The method according to claim 1,
The content of the crosslinking agent compound represented by Formula 1 is 1 to 30% by weight based on the total weight of the liquid crystal aligning agent composition.
The method according to claim 1,
Wherein the crosslinking compound represented by Formula 1 comprises a compound represented by Formula 1-1:
[Formula 1-1]

.
In Formula 1-1, A 'is an alkylene group having 1 to 10 carbon atoms, and L ₁ ' To L ₄ 'each independently represents an alkylene group having 1 to 5 carbon atoms, and R ₁ ' To R ₄ 'each independently represents a functional group represented by the following formula (2)
(2)

In Formula 2, R ₃ is an alkyl group having 1 to 20 carbon atoms, a silyl group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, or a halosilyl group having 1 to 20 carbon atoms.
The method according to claim 1,
Wherein the crosslinking compound represented by the formula (1) has a transmittance change rate of 10% or less as measured at a wavelength of 400 nm according to the following formula (2)
&Quot; (2) "
Percent change in permeability (%) = permeability of solvent - permeability of mixed solution
In the formula (2), the mixed solution is a mixture of the crosslinking compound represented by the formula (1) and a solvent.
A method for manufacturing a liquid crystal display device, comprising: applying a liquid crystal aligning agent composition according to any one of claims 1 to 7 to a substrate to form a coating film;
Subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C;
Irradiating or rubbing the heat-treated coating film with light to perform alignment treatment; And
Curing the coating film subjected to the orientation treatment by a second heat treatment at a temperature of 200 to 300 占 폚 and curing the liquid crystal alignment film.
9. The method of claim 8,
The step of subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C
Drying the coating film at a temperature of 50 ° C to 90 ° C; And
And heat-treating the dried coating film at a temperature of 90 ° C to 250 ° C.
9. The method of claim 8,
Wherein the liquid crystal aligning agent composition contains a crosslinking compound represented by the following formula (3) in the first heat treatment step:
(3)

In Formula 3,
A, n, L _1, and L < ₂ > is as defined in claim 1.
9. The method of claim 8,
Wherein the step of subjecting the coating film to a first heat treatment at a temperature of 50 ° C to 250 ° C is performed for 1 minute to 20 minutes.
A liquid crystal alignment film produced by the method for producing a liquid crystal alignment film according to claim 8.
14. A liquid crystal display element comprising the liquid crystal alignment film of claim 12.