KR100561565B1 - Polyimide resin and preparation method thereof - Google Patents

Abstract

The present invention relates to a polyimide resin prepared by polymerizing tetracarboxylic dianhydride, an aromatic diamine, and a functional diamine monomer, and a method for producing the polyimide resin, wherein the polyimide resin of the present invention has liquid crystal orientation, dissolution characteristics, light transmission characteristics, and the like. When used as a liquid crystal alignment film, it is useful as a liquid crystal alignment film material of a liquid crystal display device because it can significantly reduce the occurrence of alignment defects due to disclination after a rubbing process.

Polyimide, liquid crystal aligning film, tetracarboxylic dianhydride, aromatic diamine, functional diamine monomer

Description

POLYIMIDE RESIN AND PREPARATION METHOD THEREOF             

The present invention relates to a polyimide resin usable as a liquid crystal alignment film and a method for producing the same, and more particularly, to heat resistance, solubility, transparency, printability and liquid crystal obtained by polymerizing a functional diamine having tetracarboxylic dianhydride and an aliphatic side chain group. The present invention relates to a polyimide resin having excellent orientation ability and a method for producing the same.

Liquid crystal display (LCD) is leading the flat panel display market because it has the advantages of easy portability and low power consumption, and is expanding its application range from calculators and notebook computers to wall-mounted TVs and HDTVs. .

In general, the alignment of the liquid crystal in the liquid crystal display device is generally performed by a liquid crystal alignment film in which the alignment ability of the liquid crystal molecules is given by rubbing treatment, and resins such as polyimide, polyester, and polyamide are used as the material of the liquid crystal alignment film. . In particular, polyimide is used as an alignment layer material in most liquid crystal display devices because of its excellent heat resistance, chemical stability, and mechanical strength.

As mentioned above, the polyimide resin used as a raw material of the liquid crystal aligning film is generally produced by condensation of an aromatic tetracarboxylic dianhydride or its derivatives with an aromatic diamine or an aromatic diisocyanate, followed by imidization. Such polyimide resin may have various molecular structures and physical properties depending on the type of monomer used. In general, condensation polymerization of an aromatic tetracarboxylic dianhydride and an aromatic diamine yields a polyamic acid resin, which is a polyamide having a carboxyl group as shown in Scheme 1 below. Specifically, polyamic acid is prepared by reacting tetracarboxylic dianhydride with diamine in a suitable organic solvent to form a monoamic acid, followed by condensation reaction of the monoamic acid. Subsequently, when the obtained polyamic acid is imidated (dehydration reaction) at high temperature, a polyimide resin is produced.

Wherein A is a tetracarboxylic dianhydride monomer,

      B is at least one selected from aliphatic or aromatic diamine monomers.

The present inventors liquid crystal orientation and mixture of aliphatic cyclic acid dianhydride dioxotetrahydrofuryl 3-methylcyclohexane-1,2-dicarboxylic dianhydride (hereinafter referred to as "DOCDA") and aromatic tetracarboxylic dianhydride. There have been reports of novel soluble polyimide resins which have excellent heat resistance and permeability from mixtures of diamines and aromatic diamine compounds having dialkylamide substituents as functional monomers for and therefore applicable for liquid crystal alignment films.

However, when such a polymer is used as an alignment layer, the three-dimensional orientation of two alkyl groups in the dialkylamide group, which is a functional substituent, is slightly different, so that orientation defects due to disclination may occur after the rubbing process. This could be solved by introducing a functional substituent having an alkyl group of 8 or more carbon atoms, but in this case, a functional diamine composed of an alkyl group having a large pretilt angle and an 8 or more carbon atoms for the TN LCD cell has a poor yield in synthesis. There was.

An object of the present invention is to overcome the problems of the prior art described above, by introducing a functional diamine of the general formula (1), which is a monomer that is expected to have a high synthesis yield and excellent pretilt angle and orientation force, by synthesizing the polymer, printability The present invention provides a polyimide resin excellent in heat resistance, light transmittance and liquid crystal alignment, and a method for producing the same.

That is, the present invention is to provide a polyimide resin characterized in that the repeating unit of formula (2) prepared by polymerizing a mixture of tetracarboxylic dianhydride, a functional diamine monomer of the formula (1) and an aromatic diamine.

In the above formula, R is an aliphatic or aromatic hydrocarbon having 1 to 18 carbon atoms,

             R 'is a C1-C3 aliphatic hydrocarbon.

Wherein A is a tetracarboxylic dianhydride monomer,

B is at least one selected from aromatic or functional diamine monomers.

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

One aspect of the invention is characterized by a polyimide resin comprising at least one of aromatic diamines and a functional diamine monomer of formula (1), wherein the repeating unit is of formula (2).

The diamines usable in the preparation of the polyimide resin of the present invention necessarily include the functional diamines of the general formula (1), in addition to paraphenylenediamine (p-PDA), bisaminophenylpropane, bisaminophenyl hexafluoropropane, oxydi And at least one diamine compound selected from aniline, methylenedianiline, metabisaminophenoxybenzene, parabisaminophenoxybenzene, metabisaminophenoxydiphenylsulfone and parabisaminophenoxydiphenylsulfone.

Examples of aromatic diamines usable in addition to the functional diamine in the present invention are shown in the following formula (3).

In the present invention, as the tetracarboxylic dianhydride, one or more aromatic tetracarboxylic dianhydrides represented by the following Formula 4 may be used together with an aliphatic cyclic dianhydride. For example, pyromellitic dianhydride ( PMDA), benzophenonetetracarboxylic acid (BTDA), oxydiphthalic dianhydride (ODPA), bisphthalic dianhydride (BPDA), hexafluoroisopropylidenediphthalic dianhydride (HFDA), dioxytetrahydrofuran- 3-methylcyclohexane-1,2-dicarboxylic dianhydride (DOCDA) and cyclo [2,2,2] oct-7-den-2,3,5,6-tetracarboxylic dianhydride (BODA) One or more kinds can be selected and used. Among them, DOCDA is particularly preferable because it allows to maintain the heat resistance, printability and transparency of the polyimide resin of the present invention.

In the method for preparing a polyimide resin according to the present invention, a polyamic acid is prepared by dissolving and polymerizing a diamine component and a tetracarboxylic dianhydride, followed by dehydration to prepare a polyimide resin. It is characterized by using a diamine monomer.

The organic solvent used in the polymerization of the polyamic acid in the present invention is N-methyl-2-pyrrolidinone (N-methyl-2-pyrrolidinone, NMP), dimethyl acetamide (dimethyl acetamide, DMAc), dimethyl formamide (dimethyl formamide, DMF), etc. These three solvents are preferable because they catalyze the polymerization reaction during the polymerization of the polyamic acid and promote imidization in the subsequent imidization process. In addition, tetrahydrofuran (THF), chloroform and the like can be used as a solvent.

 In the present invention, since the reaction ratio of dianhydride and diamine to be reacted at the time of polyamic acid polymerization is 1: 1, when the two monomers are reacted at the same molar ratio, the total amount of the dianhydride and diamine monomer in the total reaction solution is 2 to 30% by weight. 2-30% by weight of the polyamic acid solid content is dissolved in the resulting polyamic acid solution. Synthesis of the polyamic acid in the present invention is carried out by reacting for 2 to 48 hours at a reaction temperature of 0 to 30 ℃.

The polyimide resin of the present invention is produced by thermosetting the polyamic acid obtained by the above method. It is preferable to dry hardening conditions at 100-120 degreeC using a heating plate or oven, and to heat up in an oven under nitrogen atmosphere gradually, and to heat for 30 minutes-2 hours in the temperature range of 200-350 degreeC.

Polyimide resin according to the present invention has a weight average molecular weight (Mw) of about 2,000 ~ 500,000g / mol, maintains the intrinsic viscosity in the range of 0.5 ~ 1.5dL / g, and has a glass transition temperature of 250 ~ 350 ℃ . Moreover, the polyimide resin of this invention is suitable for using as a liquid crystal aligning film for liquid crystal display elements in the pretilt angle of 1-15 degrees.

In addition, the polyimide resin of the present invention exhibits high solubility of 10% by weight or more even at polar temperatures, organic solvents, and low hygroscopic solvents. Specifically, dimethylacetimide, dimethylformamide, N-methyl-2-pyrroli High solubility at room temperature in a single solvent or two or more mixed solvents selected from the group consisting of don, tetrahydrofuran, chloroform, acetone, ethyl acetate, butyrolactone, butoxyethanol, ethoxyethanol, and butoxypropanol Indicates.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the protection scope of the present invention.

Preparation Example 1; Preparation of 3,5-dinitrobenzoyl-N-methyldodecylamine (DNM-112)

Dissolve 3,5-dinitrobenzoyl chloride (108.29 g, 0.5 mole) in 150 ml of methylene chloride as a reaction solvent while slowly passing nitrogen gas through a 1,000 ml reactor equipped with a stirrer and a nitrogen injection device, and then pass nitrogen gas. N-methyldodecylamine (110 g, 0.55 mole) dissolved in 150 ml of methylene chloride was added dropwise over 30 minutes to proceed with the reaction for 10 hours at room temperature. After the reaction was completed, the acid in the reaction mixture was washed 2-3 times with distilled water, and the solvent methylene chloride was completely removed using an aspirator, and then recrystallized from ethanol (DNM-112). At this time, the reaction yield was 89%.

Preparation Example 2; Preparation of 3,5-diaminobenzoyl-N-methyldodecylamine (DAM-112)

10.0 g of DNM-112 obtained in Preparation Example 1 was dissolved in 200 ml of ethanol and placed in a hydrogen reactor with 2.0 g of Pd / C (5%), followed by reduction for 5 hours at 40 ° C. After completion of the reaction, the reaction mixture was filtered using Celite, and the reaction solvent was distilled under reduced pressure. Recrystallization in ethyl acetate / hexane (1/1) cosolvent gave DAM-112 in a yield of about 70%.

Preparation Example 3; Preparation of 3,5-dinitrobenzoyl-N-methyloctylamine (DNM-108)

Except for using methyl octylamine instead of methyl dodecylamine was carried out in the same manner as in Preparation Example 1 to obtain DNM-108 in a yield of 92%.

Preparation Example 4; Preparation of 3,5-diaminobenzoyl-N-methyloctylamine (DAM-108)

Except for using DNM-108 obtained in Preparation Example 3 instead of DNM-112 in Preparation Example 2 was carried out in the same manner as in Preparation Example 2 to obtain DAM-108 in a yield of 80%.

Preparation Example 5; Preparation of 3,5-dinitrobenzoyl-N-methylbutylamine (DNM-104)

Except for using methylbutylamine instead of methyldodecylamine was carried out in the same manner as in Preparation Example 1 to obtain DNM-108 in a yield of 79%.

Preparation Example 6; Preparation of 5-diaminobenzoyl-N-methylbutylamine (DAM-104)

Except for using DNM-104 obtained in Preparation Example 5 instead of DNM-112 in Preparation Example 2 was carried out in the same manner as Preparation Example 2 to obtain a DAM-104 in a yield of 85%.

As shown in Table 1, DAM, which is a functional monomer having two alkyl groups having different carbon atoms, may be prepared in a relatively high yield of 70% or more. The structure of the prepared monomer was confirmed using NMR and IR spectroscopy. The yields and molecular weights of the monomers prepared in Preparation Examples 2, 4 and 6 are shown in Table 1 below.

Production Example Monomer Yield (%) Molecular Weight Preparation Example 2 DAM-112 70 362 Preparation Example 4 DAM-108 79 306 Preparation Example 6 DAM-104 85 250

Example 1

Methyl dodecylamine (15.86 g, 0.08 mole; MDA), p-PDA (1.08 g, 0.01 mole) while slowly passing nitrogen gas through a 500 mL reactor equipped with a stirrer, temperature controller, nitrogen injector, dropping funnel and cooler. ;) And the functional diamine DAM-112 (3.62 g, 0.01 mole) obtained in Preparation Example 2 were dissolved in the reaction solvent NMP and passed through nitrogen gas to DOCDA (13.2 g, 0.05 mole) and PMDA (10.91 g, 0.05 mole) was added slowly. At this time, the solid content (solid content) was fixed at 20wt% and the reaction temperature was carried out at 25 ℃ for 10 hours. After the reaction was completed, a solvent was added to a desired composition to obtain a polyamic acid resin solution, followed by imidization, to synthesize the polyimide resin of the present invention, and to evaluate the overall physical properties thereof.

Example 2

A polyimide resin was prepared in the same manner as in Example 1, except that the functional diamine DAM-108 (3.06 g, 0.01 mole) obtained in Preparation Example 4 was used instead of the diamine DAM-112 in Example 1. It synthesized and evaluated the overall physical properties and the results are shown in Table 2 together.

Example 3

A polyimide resin was prepared in the same manner as in Example 1, except that the functional diamine DAM-104 (2.50 g, 0.01 mole) obtained in Preparation Example 6 was used instead of the diamine DAM-112 in Example 1. It synthesized and evaluated the overall physical properties and the results are shown in Table 2 together.

Comparative Example 1

A polyimide resin was synthesized in the same manner as in Example 1, except that 3,5-diaminobenzoyl dibutylamine (2.63 g, 0.01 mole) was used instead of the diamine DAM-112 in Example 1. And the physical properties were evaluated and the results are shown in Table 2 together.

Comparative Example 2

A polyimide resin was synthesized in the same manner as in Example 1, except that 3,5-diaminobenzoyl dioctyl amine (3.75 g, 0.01 mole) was used instead of the diamine DAM-112 in Example 1. And the physical properties were evaluated and the results are shown in Table 2 together.

Comparative Example 3

A polyimide resin was synthesized in the same manner as in Example 1, except that 3,5-diaminobenzoyl didodecylamine (4.87 g, 0.01 mole) was used instead of the diamine DAM-112 in Example 1. And the physical properties were evaluated and the results are shown in Table 2 together.

Intrinsic viscosity Glass transition temperature (℃) Film properties Curing rate (%) Dismissal occurrence Pretilt angle (°) Example 1 0.73 275 Chewy 81% 0 6.1 Example 2 0.78 280 Chewy 90% 0 3.5 Example 3 0.69 311 Chewy 82% One 2.4 Comparative Example 1 0.71 290 Chewy 87% 4 2.7 Comparative Example 2 0.67 278 Chewy 87% 3 4.1 Comparative Example 3 0.59 267 Tenderness 91% 2 6.0

[Property evaluation method]

(1) intrinsic viscosity

The intrinsic viscosity of the polymer was measured at 30 ° C. at a concentration of 0.5 g / dL using NMP as a solvent.

(2) Measurement of glass transition temperature

In order to evaluate the thermal properties of the polyimide resins of Examples and Comparative Examples, the glass transition temperature was measured by using a differential scanning calorimeter (DSC). As confirmed through the results of Table 2, the novel polyimide resins of the present invention showed a slight difference depending on the length of the alkyl substituent of the functional diamine used, but generally showed a glass transition temperature (Tg) between 270 ° C and 320 ° C. It is shown.

(3) curing rate measurement

In order to evaluate the curing characteristics of the polyimide resins, a polyimide resin was applied to a thickness of 2 μm, cured on a heating plate for 180 ° C./10 minutes, and the curing rate was measured using an infrared spectroscopy (IR).

(4) Whether or not to generate disclination

Of the 10 cells fabricated, the number of cells in which the disclination occurred was evaluated.

(5) pretilt angle

The polyimide resins were diluted with r-butyrolactone, roll coated to a thickness of 2 μm, and then cured and rubbed to evaluate characteristics of the liquid crystal cell. The alignment state of the liquid crystal was observed using a polarizing microscope, and the pretilt angle of the liquid crystal cell was measured using a crystal rotation method.

As shown in Table 2, all of the polyimide resins prepared by Examples according to the present invention are amorphous transparent resins, the molecular weight measured by a viscometer was in the range of about 0.69 ~ 0.78 dL / g, of the present invention Polyimide-based liquid crystal alignment films showed very good liquid crystal alignment and time stability. In addition, the pretilt angle was about 2 ° to 6 °, which showed characteristics suitable for use as a liquid crystal alignment film for TFT-LCD.

The novel polyimide resin of the present invention is not only excellent in liquid crystal orientation, but also useful as a liquid crystal alignment film material for liquid crystal display devices due to its excellent dissolution characteristics and light transmission characteristics. Furthermore, when the polyimide resin of the present invention is applied as a liquid crystal alignment film, it is possible to obtain an effect that the occurrence of orientation defects due to disclination after the rubbing process is significantly reduced.

Claims (9)

A polyimide resin prepared by polymerizing a mixture of tetracarboxylic dianhydride, a functional diamine monomer of the general formula (1) and an aromatic diamine, and having the following general formula (2) as a repeating unit. [Formula 1]

In the above formula, R is an aliphatic or aromatic hydrocarbon having 1 to 18 carbon atoms,              R 'is a C1-C3 aliphatic hydrocarbon. [Formula 2]

Wherein A is a tetracarboxylic dianhydride monomer,           B is at least one selected from aliphatic or aromatic diamine monomers. The polyimide resin according to claim 1, wherein the aromatic diamine is one selected from the group consisting of aromatic diamines of the following general formula (3). [Formula 3]

The polyimide resin according to claim 1, wherein the tetracarboxylic dianhydride is one selected from the group represented by the following general formula (4). [Formula 4]

The method of claim 1, wherein the tetracarboxylic dianhydride is dioxytetrahydrofuran-3-methylcyclohexane-1,2-dicarboxylic dianhydride (DOCDA) or cyclo [2,2,2] oct-7- It is a den-2,3,5,6- tetracarboxylic dianhydride (BODA), The polyimide resin characterized by the above-mentioned. The polyimide resin according to claim 1, wherein the intrinsic viscosity of the polyimide resin is in the range of 0.5 to 1.5 dL / g. The polyimide resin according to claim 1, wherein the polyimide resin has a glass transition temperature of 250 to 350 ° C. The polyimide resin according to claim 1, wherein the pretilt angle of the polyimide resin is 1 ° to 15 °. The method of claim 1, wherein the polyimide resin is dimethylacetimide, dimethylformamide, N-methyl-2-pyrrolidone, tetrahydrofuran, chloroform, acetone, ethyl acetate, butyrolactone, butoxyethanol, ethoxy A polyimide resin characterized by dissolving at room temperature in a single solvent or two or more mixed solvents selected from the group consisting of ethanol and butoxypropanol. In preparing a polyamic acid by polymerizing a diamine component and tetracarboxylic dianhydride, and then imidizing the diamine component, an aromatic diamine and a functional diamine represented by the following Chemical Formula 1 are used as a diamine component. Method for producing a resin. [Formula 1]

In the above formula, R is an aliphatic or aromatic hydrocarbon having 1 to 18 carbon atoms,              R 'is a C1-C3 aliphatic hydrocarbon.