KR100801029B1 - Diamine Compound for LC Alignment Layer and LC Alignment Material - Google Patents

Abstract

The present invention relates to a diamine compound having a functional side chain designed to facilitate pretilt angle control and a liquid crystal aligning agent prepared using the same, and more particularly, to a functional diamine, an aromatic cyclic diamine, an aliphatic cyclic acid dianhydride, and an aromatic cyclic compound. The present invention relates to a polyamic acid obtained using an acid dianhydride and a polyimide obtained by imidating a polyamic acid. Polyamic acid as described above has the advantages of excellent electro-optic properties and easy pretilt angle, stable liquid crystal orientation, excellent chemical resistance, stable processability by the cleaning solvent used in the cleaning process in the LCD panel manufacturing process The liquid crystal aligning agent which has the liquid-crystal orientation which is not influenced and the orientation force which does not fall even after long-term voltage application can be provided.

Liquid crystal aligning film, polyamic acid, polyimide, pretilt angle, electro-optical characteristics, liquid crystal alignment, liquid crystal alignment

Description

Diamine compound and liquid crystal aligning agent using the same {Diamine Compound for LC Alignment Layer and LC Alignment Material}

1 is a 1 H-NMR spectrum of a diamine compound prepared by Preparation Example;

2 is a DSC of the diamine compound prepared in Preparation Example.

The present invention relates to a diamine compound having a functional side chain designed for the control of the pretilt angle and a liquid crystal aligning agent prepared using the same, and more particularly, to implement a pretilt angle that can be easily adjusted by introducing a side chain into the diamine compound. It is possible to increase the voltage preservation ratio, which is a basic and important characteristic among LCD driving characteristics, to improve other electro-optic characteristics, and to provide stable liquid crystal orientation, excellent liquid crystal alignment, excellent chemical resistance to cleaning process, stable processability, and the like. It is about the technology of providing the first.

Generally, the polyimide resin for liquid crystal aligning film currently used uses a pyromellitic dianhydride (PMDA), a non-phthalic dianhydride (BPDA) as an aromatic acid dianhydride, and paraphenylenediamine (p-) as an aromatic diamine component. PDA), metaphenylenediamine (m-PDA), 4,4-methylenedianiline (MDA), 2,2-bisamino phenylhexafluoropropane (HFDA), metabisaminophenoxydiphenylsulfone (m-BAPS ), Parabisaminophenoxydiphenylsulfone (p-BAPS), 4,4-bisaminophenoxyphenylpropane (BAPP), 4,4-bisaminophenoxyphenylhexafluoropropane (HF-BAPP) and the like are used. By condensation polymerization of these monomers.

However, when only aromatic acid dianhydride and diamine are used as described above, thermal stability, chemical resistance, mechanical properties, etc. are excellent, but transparency and solubility are degraded due to charge transfer complex, and electro-optic properties are deteriorated. There is this. In order to solve this problem, there have been attempts to improve the problem by introducing an aliphatic cyclic acid dianhydride monomer or an aliphatic cyclic diamine (Japanese Patent Laid-Open No. 11-84391), and a functional diamine having a side chain for increasing the pretilt angle and stability of the liquid crystal. Functional acid dianhydrides having side chains and the like have been introduced (Japanese Patent Laid-Open No. 06-136122). In addition, the development of a vertical alignment layer that can be applied in a vertical alignment mode (VA mode) constituting the LCD panel by aligning the liquid crystal perpendicular to the surface (US Patent No. 5,420,233).

However, with the recent growth of the liquid crystal display device market, the demand for high quality display devices continues to increase, and as liquid crystal display device manufacturers are rapidly becoming larger in area, the demand for highly productive alignment films is increasing. Therefore, there is a continuous demand for a high-performance liquid crystal alignment layer that satisfies the different requirements of the liquid crystal display device having low defect rate, excellent electro-optical characteristics, high reliability, and various developments in the LCD production process. .

The present invention is to solve the problems of the existing technology and to implement a liquid crystal aligning agent having better characteristics in many aspects, when using a polyamic acid prepared using a functional diamine with side chains as a liquid crystal aligning agent, It can be seen that a liquid crystal aligning agent capable of realizing a pretilt angle, providing excellent electro-optical properties, providing stable liquid crystal alignment force, excellent liquid crystal alignment property, and excellent chemical resistance and processability to the cleaning process. The present invention was completed.

Another aspect of the present invention relates to a polyamic acid prepared by copolymerizing the diamine compound, aliphatic cyclic acid dianhydride and aromatic cyclic acid dianhydride with an aromatic cyclic diamine and / or siloxane diamine.

Another aspect of the invention relates to a soluble polyimide prepared by partially or wholly imidating the polyamic acid.

Another aspect of the invention relates to a mixture of said polyamic acid and soluble polyimide.

Another aspect of the present invention relates to a liquid crystal aligning film obtained by dissolving the polyamic acid, soluble polyimide or a mixture thereof in a solvent and coating it, in whole or in part, by imidization thereof.

Another aspect of the present invention relates to a liquid crystal display device comprising the liquid crystal alignment film.

Therefore, the present invention provides a diamine compound represented by the following formula (1).

[Formula 1]

(A is a single bond, -O-, -COO-, -CONH-, -OCO-, aromatic ring, alicyclic ring or heterocycle, B, C, D is -H, -CH3 or halogen atom, E Is a single bond, -O-, -COO-, -CONH-, -OCO-, an aromatic ring, an alicyclic ring or a heterocyclic ring, each F is independently a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms , One or more halogen atoms may be substituted.)

The diamine compound is characterized in that the material represented by the formula (2).

[Formula 2]

The present invention also provides a polyamic acid, which is produced by reacting the diamine compound with an acid dianhydride.

In addition, the polyamic acid is characterized in that the acid dianhydride is any one or a mixture of aliphatic cyclic acid dianhydride and aromatic cyclic acid dianhydride.

The polyamic acid is copolymerized by adding any one or a mixture of aromatic cyclic diamines and siloxane diamines.

The present invention also provides a soluble polyimide obtained by imidating the polyamic acid in part or in whole.

The present invention also provides a liquid crystal aligning film, which is produced using any one or a mixture of the polyamic acid and the soluble polyimide.

Moreover, in this invention, the liquid crystal display element containing the said liquid crystal aligning film is provided.

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

Functional diamine newly provided in the present invention is represented by the following formula (1).

[Formula 1]

(A is a single bond, -O-, -COO-, -CONH-, -OCO-, aromatic ring, alicyclic ring or heterocycle, B, C, D is -H, -CH3 or halogen atom, E Is a single bond, -O-, -COO-, -CONH-, -OCO-, an aromatic ring, an alicyclic ring or a heterocyclic ring, each F is independently a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms , One or more halogen atoms may be substituted.)

Specific examples of the functional diamine compound are shown in the following Chemical Formula 2, but this is merely for illustrative purposes, and the structure of the functional diamine of the present invention is not limited to the following chemical formula.

[Formula 2]

In the case of the functional diamine monomer according to the present invention, the orientation of the liquid crystal in the side chain direction is induced, and the processability and chemical resistance are improved, thereby obtaining a stable effect on the printing / rubbing process and the cleaning process. The liquid crystal orientation induced in the side chain direction can easily provide for ease of pretilt adjustment with varying content of functional diamines. This is an advantage that can easily respond to the needs of the liquid crystal display device producer. In addition, since a large number of alkyl groups can be simultaneously introduced into the side chain in the dendron structure, a small amount can bring about a great effect on the vertical alignment of the liquid crystal. This property is also suitable for VA mode in which the liquid crystal is oriented in the vertical direction, and has a good influence on the stability of the vertical alignment force.

The polyamic acid according to the present invention essentially includes functional diamines, aliphatic cyclic acid dianhydrides and aromatic cyclic acid dianhydrides having a specific structure having the functional side chains set forth above, wherein any of aromatic cyclic diamines and siloxane-based diamines Or mixtures thereof. That is, the polyamic acid may be obtained by reacting a diamine compound with an acid dianhydride. The polyamic acid may be copolymerized by adding any one or a mixture of aromatic cyclic diamines and siloxane diamines.

The method for preparing a polyamic acid by copolymerizing an acid dianhydride and a diamine compound can be applied without limitation to the method known to be capable of copolymerizing a conventional polyamic acid.

By containing the said functional diamine in the polyamic acid of this invention, adjustment of a pretilt angle becomes easy and it shows the outstanding orientation. Since the pretilt angle is adjusted according to the content of the functional diamine, it is also possible to prepare a polyamic acid using only the functional diamine and use it as a liquid crystal alignment layer, depending on the mode of the liquid crystal display, without containing any aromatic cyclic diamine or siloxane-based diamine. . The use of aromatic diamines or siloxane-based diamines is optional. Therefore, the content of the functional diamine represented by the formula (1) in the polyamic acid occupies 0.1 to 100 mol%, preferably 0.5 to 30 mol%, more preferably 1 to 20 mol% of the total diamine monomers.

Aromatic cyclic diamines used in the preparation of the polyamic acid of the present invention include paraphenylenediamine (p-PDA), 4,4-methylenedianiline (MDA), 4,4-oxydianiline (ODA), metabisamino Phenoxydiphenylsulfone (m-BAPS), parabisaminophenoxydiphenylsulfone (p-BAPS), 2,2-bisaminophenoxyphenylpropane (BAPP), 2,2-bisaminophenoxyphenylhexafluoropropane (HF-BAPP) and the like, but is not limited thereto.

The siloxane-based diamine used in preparing the polyamic acid of the present invention has a structure as shown in the following formula (3).

[Formula 3]

(Where n is an integer of 1 to 10)

The amount of the aromatic cyclic diamine and / or siloxane diamine is 0 to 99.9 mol%, preferably 70 to 99.5 mol%, more preferably 80 to 99 mol% based on the total diamine content.

The aromatic cyclic acid dianhydride used in the production of the polyamic acid of the present invention can withstand the rubbing process in which the alignment film coated at about 0.1 μm is applied to induce the unidirectional alignment of the liquid crystal, and the heat resistance to the high temperature processing process of 200 ° C. or higher. It is maintained, and excellent chemical resistance can be expressed.

Such aromatic cyclic acid dianhydrides include pyromellitic dianhydride (PMDA), nonphthalic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA), benzophenone tetracarboxylic dianhydride (BTDA), and hexafluoroisopropylidenedidie Phthalic dianhydride (6-FDA), but is not limited thereto.

The content of the aromatic cyclic acid dianhydride is 10 to 95 mol%, more preferably 50 to 90 mol% relative to the total content of the acid dianhydride used. If the aromatic cyclic acid dianhydride is less than 10 mol%, mechanical properties and heat resistance of the alignment layer are lowered, and if it is more than 80 mol%, electrical properties such as voltage retention are lowered.

The aliphatic cyclic acid dianhydride used in the preparation of the polyamic acid of the present invention is insoluble in a general organic solvent, low permeability in the visible light region by a charge transfer complex, and electro-optical properties due to its molecular structurally high polarity. The problem of degradation is compensated for.

As the aliphatic cyclic acid dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methylcyclohexene-1,2-dicarboxylic acid anhydride (DOCDA), bicyclooctene-2,3,5 , 6-tetracarboxylic dianhydride (BODA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) and the like, but is not limited thereto.

The content is 5 to 90 mol%, preferably 10 to 50 mol% relative to the total acid dianhydride content used.

Polyamic acid according to the present invention is generally used N-methyl-2-pyrrolidone (NMP), gamma-butyrolactone (GBL) dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran ( Very good solubility in aprotic polar solvents such as THF). Such excellent solubility is thought to be great in the effect of the functional diamine in which three benzene rings exist in three dimensions with large three-dimensional repulsion in the introduction of aliphatic cyclic acid dianhydride and molecular structure. In the situation where the printability of the alignment agent is very important in recent years due to the large size, high resolution and high quality of the liquid crystal display device, such excellent solubility in solvents has a good effect on the printability to the substrate when applied to the liquid crystal alignment layer. Go crazy.

The polyamic acid of the present invention has a number average molecular weight in the range of 10,000 to 500,000 g / mol, and when the imidation is performed, the glass transition temperature is in the range of 200 to 350 ° C. according to the imidization ratio or structure.

In the present invention, the polyamic acid is dissolved in a solvent and coated on a substrate, and then imidated in whole or in part to provide a liquid crystal alignment layer.

In the present invention, the polyamic acid may be partially or wholly imidized to prepare a soluble polyimide, and then used alone to use a liquid crystal alignment film, or a mixture of the polyamic acid and the soluble polyimide may be used to prepare a liquid crystal alignment film. Can be. The liquid crystal alignment layer may be used in a liquid crystal display device.

The alignment film exhibits a high transmittance of 90% or more in the visible light region in light transmittance, is excellent in the alignment of the liquid crystal, and can be easily adjusted within the range of 1 to 90 °. In addition, since the functional diamine is included, the refractive index of the polymer may be lowered and the dielectric constant may also be lowered.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are for the purpose of explanation and are not intended to limit the present invention.

Production Example

Preparation of 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) chroman-6-yl ester

Tocopherol (1) is added to a reactor filled with nitrogen, and THF is dissolved. Put it in to dissolve. Triethylamine was added to the dissolved solution and stirred for 10 minutes. 3,5-Dinitrobenzoyl chloride (2) was added thereto, followed by reaction at room temperature for 3 hours, and then the temperature was raised to 50 ° C. for 3 hours. After completion of the reaction, the temperature of the reactor is cooled to room temperature and the resulting solid is filtered. Finally the remaining solution is vacuum distilled to solidify and recrystallize to obtain pure 3. The 3,5-dinitrobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) chroman-6-yl ester (3) thus obtained was hydrogenated. Put it in a high pressure reactor that can react and add ethanol. 5 wt% Pd / C was added and the temperature was raised to 60 ° C. and stirred. After the completion of the temperature increase of 60 ℃, the reaction proceeds by applying a hydrogen pressure of 60 psi for 6 hours.

After completion of the reaction, the reaction solution was filtered and the remaining solution was vacuum distilled to obtain a solid. The solid thus obtained was recrystallized with ethanol and finally pure 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tri Decyl) chroman-6-yl ester (4) was obtained with a yield of 25%. The structure was confirmed by ¹ H-NMR spectrum. DSC measurement results showing its thermal behavior is shown in FIG.

Example 1

0.99 mol of 4,4-methylenedianiline and 3,5-diaminobenzoic acid-2,5,7,8 while passing nitrogen through a four-necked flask equipped with a stirrer, a thermostat, a nitrogen gas injector and a cooler 0.01 mol of tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) chroman-6-yl ester (4) was added, followed by dissolving with N-methyl-2-pyrrolidone (NMP). . Add 0.50 mol of 5- (2,5-dioxotetrahydrofuryl) -3-methylcyclohexane-1,2-dicarboxylic acid anhydride (DOCDA) and 0.50 mol of pyromellitic dianhydride (PMDA) in the solid state Stir vigorously. The solid content at this time is 15% by weight in mass ratio, the reaction was carried out for 24 hours while maintaining the temperature below 25 ℃ to prepare a polyamic acid solution.

The alignment film solution prepared by the above method was applied on the ITO surface of 10 cm × 10 cm sized ITO glass, spin-coated under certain conditions to make it uniformly 0.1 탆 thick, and then desolvated at 70 ° C. on a hot plate. Sampled through curing process at 210 ℃. The printability of the alignment film solution was evaluated by observing spreading and curling characteristics of the prepared sample through visual and optical microscopy. The printability evaluation results are shown in Table 1 below.

In order to evaluate the liquid crystal alignment, chemical resistance, pretilt angle and electrical and optical properties of the alignment film solution, a liquid crystal cell different from the above sample was prepared and used. The manufacture of the liquid crystal cell is as follows. It was patterned using a photolithography process to remove the other portions of ITO, leaving only 1.5 cm × 1.5 cm square ITO shapes and electrode ITO shapes for voltage application on standardized sized ITO glass substrates. The alignment layer solution was applied to the patterned ITO surface substrate and spin-coated to make a thickness of 0.1 μm, followed by curing at 70 ° C. and 210 ° C. After rubbing the two substrates rubbed at a certain depth and at a constant speed so that the rubbing directions are opposite to each other (for VA mode), the square ITO shape coincides up and down while maintaining a cell gap of 4.75 μm. Splicing. After filling the liquid crystal in the cell made in this way, the liquid crystal alignment was observed using an orthogonally polarized optical microscope, and the results are summarized in Table 1 below. The liquid crystal cell for pretilt angle evaluation was manufactured separately from the above method so as to maintain the cell gap at 50 μm.

In order to evaluate the chemical resistance of the alignment film solution manufactured by the said method, the washing | cleaning process was added after the rubbing process among the liquid crystal cell manufacturing methods. After cleaning the surface of the alignment layer subjected to the rubbing process using a rubbing machine using isopropyl alcohol and pure water, the liquid crystal cell was fabricated by bonding. The AC cell was operated by applying an AC voltage of 60 kV to 1 to 2 V. While producing the liquid crystal aligning stain by the cleaning solvent while observing the results are shown in Table 1 below.

In order to measure the pretilt angle of the liquid crystal by the alignment film solution, a liquid crystal cell having a 50 μm cell gap was prepared, and a crystal rotation method was used. The measurement results are shown in Table 1 below.

The electrical and optical characteristics of the alignment layer mentioned above were measured and compared by measuring the voltage holding ratio, contrast ratio, response speed, and residual DC voltage using a liquid crystal cell having a 4.75 μm cell gap. Brief description of each electrical and optical characteristics is as follows. The voltage holding ratio refers to the degree to which the liquid crystal layer in the state of floating with the external power source maintains the charged voltage during the non-selection period in the active driving type TFT-LCD, and a value close to 100% is ideal. The contrast ratio is expressed as the ratio of the transmittance when no voltage is applied and when the driving voltage is applied, and is calculated by dividing the high transmittance by the low transmittance. The higher this is, the better. The response speed refers to a time at which the liquid crystal cell transitions between a dark state and a bright state depending on whether a voltage is applied, and is calculated from a transmittance change curve measured by alternately applying a voltage showing the lowest transmittance and the highest transmittance. The residual DC voltage refers to a voltage applied to the liquid crystal layer even when no impurities are applied from the ionized liquid crystal layer to the alignment layer. As a measuring method, a method using flicker and a method using a capacitance change curve (C-V) of the liquid crystal layer according to DC voltage are common. The results of the electrical and optical characteristics of the alignment layer using the liquid crystal cell are shown in Table 2 below.

Example 2

Using 0.95 mol of 4,4-methylenedianiline, 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) A polyamic acid solution was obtained in the same manner as in Example 1, except that 0.05 mol of mann-6-yl ester (4) was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Example 3

Using 0.90 mol of 4,4-methylenedianiline, 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) A polyamic acid solution was obtained in the same manner as in Example 1, except that 0.10 mol of mann-6-yl ester (4) was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, and the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Example 4

Using 0.85 mol of 4,4-methylenedianiline, 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) A polyamic acid solution was obtained in the same manner as in Example 1, except that 0.15 mol of mann-6-yl ester (4) was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Example 5

Using 0.80 mol of 4,4-methylenedianiline, 3,5-diaminobenzoic acid-2,5,7,8-tetramethyl-2-yl (4,8,12-trimethyl-tridecyl) A polyamic acid solution was obtained in the same manner as in Example 1, except that 0.20 mol of mann-6-yl ester (4) was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Comparative Example 1

A polyamic acid solution was obtained in the same manner as in Example 1, except that 0.90 mol of 4,4-methylenedianiline was used and 0.10 mol of 2,4-diaminophenoxyhexadecane was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Comparative Example 2

A polyamic acid solution was obtained in the same manner as in Example 1 except that 0.80 mol of 4,4-methylenedianiline was used and 0.20 mol of 2,4-diaminophenoxyhexadecane was used. In addition, printability, liquid crystal alignment, and chemical resistance were observed in the same manner as in Example 1, the pretilt angles were measured, and these are shown in Table 1 below. The results of the electrical and optical properties are summarized in Table 2 below.

Advantageous Effects of Invention The present invention can provide a liquid crystal aligning material which is excellent in liquid crystal alignment property and vertical alignment force and stable in processability and washing process.

Claims (8)

delete delete Diamine compound represented by the following formula (1), 5- (2,5-dioxotetrahydrofuryl) -3-methylcyclohexene-1,2-dicarboxylic acid anhydride (DOCDA), bicyclooctene-2,3, 5,6-tetracarboxylic dianhydride (BODA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) And aliphatic ring acid dianhydrides selected from 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA), pyromellitic dianhydride (PMDA), nonphthalic dianhydride (BPDA), and oxydiphthalic acid A polyamic acid produced by reacting an aromatic acid dianhydride selected from anhydride (ODPA), benzophenone tetracarboxylic dianhydride (BTDA) and hexafluoroisopropylidenediphthalic dianhydride (6-FDA). [Formula 1]

(A is -COO-, B, C, D is -H, or -CH ₃ , E is a single bond, F is a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, at least one halogen atom is substituted) Can be.) delete The method of claim 3, wherein the polyamic acid is paraphenylenediamine (p-PDA), 4,4-methylenedianiline (MDA), 4,4-oxydianiline (ODA), metabisaminophenoxydiphenylsulfone ( m-BAPS), parabisaminophenoxydiphenylsulfone (p-BAPS), 2,2-bisaminophenoxyphenylpropane (BAPP) and 2,2-bisaminophenoxyphenylhexafluoropropane (HF-BAPP) A polyamic acid copolymerized by adding any one or a mixture of aromatic cyclic diamines selected from siloxanes, and siloxane diamines represented by the following general formula (3). [Formula 3]

(Where n is an integer of 1 to 10) The soluble polyimide obtained by imidating the polyamic acid of Claim 3 partially or entirely. The liquid crystal aligning film manufactured using the polyamic acid of Claim 3, and the soluble polyimide of Claim 6, or its mixture. delete

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