JPH0987388A - Perfluoroalkylated polyimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyimide which is excellent in liq.-crystal orientation properties, has a pretilt angle as high as 10 deg. or higher, and is useful as a liq.- crystal orientation film by selecting a (co)polyimide comprising specific structural units. SOLUTION: A polyimide comprising structural units represented by formula I (wherein (m) is 1-3; (n) is 1-12; and A is a tetravalent org. group) and a copolyimide comprising structural units represented by formula I and structural units represented by formula IV (wherein B is a divalent org. group; and C is a tetravalent org. group) are selected. The polyimide is obtd. by reacting a diamine represented by formula II with a tetracarboxylic dianhydride represented by formula III in a solvent and heating the resultant polyamic acid. The copolyimide is obtd. by reacting the diamine and a diamine represented by formula V with the dianhydride in a solvent and heating the resultant polyamic acid.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyimide having a perfluoroalkyl group.

[0002]

2. Description of the Related Art Polyimide resin has the highest heat resistance among commercially available plastics, has little change in characteristics due to temperature, and is excellent in impact resistance, dimensional stability, electrical properties and abrasion resistance. . Utilizing such characteristics, it is used as a material for aerospace and machinery, in addition to electric and electronic fields such as insulation, sealing materials and printed circuit boards. In recent years, it has also attracted attention as an alignment film material for liquid crystal display elements, and many polyimide alignment films have been developed.

In a liquid crystal display element used in a clock or a calculator, a twisted nematic (hereinafter abbreviated as TN) having a structure in which the arrangement direction of nematic liquid crystal molecules is twisted 90 degrees between a pair of upper and lower electrode substrates. ) Mode is mainly adopted. Also, a super twisted nematic (hereinafter abbreviated as STN) in which the twist angle of the liquid crystal is 180 to 270 degrees.
Modes are also now commonplace, and are being produced in large quantities for large displays such as word processors and personal computers. The alignment film used in such a liquid crystal display device is not enough to simply arrange the liquid crystal molecules, and in order to improve the responsiveness and ensure the bistability, a T film is formed between the substrate surface and the liquid crystal molecules.
It is preferable to have a pretilt angle of 1 to 4 degrees in the N mode and 4 to 8 degrees in the STN mode. Further, in recent years, a super-twist birefringence effect (hereinafter abbreviated as SBE) mode has been developed as a display element having more excellent contrast and viewing angle dependency. In this method, a high pretilt angle of 20 to 30 degrees is required. .

Japanese Unexamined Patent Publication No. 4-7333 and Japanese Unexamined Patent Publication No. 4-1
Japanese Patent Publication No. 02020 discloses a polyimide liquid crystal alignment film having an aliphatic side chain such as a linear alkyl group or a fluorinated alkyl group. However, the pretilt angle of these polyimide alignment films is not described. Japanese Patent Laid-Open No. 5-2
Japanese Patent No. 7244 discloses a liquid crystal alignment film using a diamine having an alkyl ester or the like in a side chain as a monomer. However, the pretilt angle of these polyimide alignment films was a low value of about 3 to 14 degrees.

[0005]

From the above problems, the object of the present invention is to provide a novel polyimide which is excellent in liquid crystal alignment and is useful as a liquid crystal alignment film having a high pretilt angle of 10 degrees or more. is there.

[0006]

Therefore, as a result of intensive investigations by the present inventors, the above formula obtained by a polycondensation reaction of a diamine component having a perfluoroalkyl group in its side chain and a tetracarboxylic dianhydride A polyimide comprising a structural unit of [1] and a polyimide alignment film comprising a copolymer of structural units of formula [1] and formula [4] are excellent in film forming property, adhesion to a glass substrate and thermal stability. In addition, they have found that they have good liquid crystal alignment and have a high pretilt angle of about 10 degrees or more, and completed the present invention.

That is, the constitution of the present invention is as follows. (1) A polyimide comprising a structural unit represented by the formula [1].

Embedded image (2) A diamino compound represented by the formula [2] and a formula [3]
A polyimide obtained by reacting a tetracarboxylic acid dianhydride represented by the following in a solvent to produce a polyamic acid, and heating the polyamic acid.

Embedded image

Embedded image (3) A polyimide comprising a structural unit represented by the formula [1] and a structural unit represented by the formula [4].

[Chemical 12]

Embedded image (4) The diamino compound represented by the formula [2], the diamino compound represented by the formula [5], and the tetracarboxylic dianhydride represented by the formula [3] are reacted in a solvent to form a polyamic acid. A polyimide obtained by generating and heating the polyamic acid.

Embedded image

[Chemical 15]

Embedded image (5) A liquid crystal alignment film using the polyimide described in any one of (1) to (4) above. (6) A liquid crystal display device comprising the liquid crystal alignment film described in (5) above.

The method for producing the polyimide of the present invention is represented by the formula [2]
A compound represented by, for example, 1H, 1H, 7H-dodecafluoro-1-heptyl = 3,5-diaminobenza-
Or 1H, 1H, 11H-eicosafluoro-1
Undecyl = 3,5-diaminobenzoate was used as the amine component.

Here, 1H, 1 represented by the above formula [2]
The method for producing H, 7H-dodecafluoro-1-heptyl = 3,5-diaminobenzoate and 1H, 1H, 11H-eicosafluoro-1-undecyl = 3,5-diaminobenzoate was initially Was condensed with 3,5-dinitrobenzoyl chloride in the presence of triethylamine to give perfluoroalkyl = 3,5-
Dinitrobenzoate was obtained. Then, these compounds were produced by catalytic reduction in the presence of a palladium-carbon catalyst.

This can be expressed by the following equation.

Embedded image

Tetracarboxylic acid dianhydride is any compound represented by the formula [3]. Specifically, pyromellitic dianhydride (PMDA), 3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic dianhydride (ODPA), 3,3 '4
4'-benzophenone tetracarboxylic dianhydride (BT
DA), 4,4′-sulfonyldiphthalic dianhydride (SDPA) and other aromatic tetracarboxylic dianhydrides, and cyclobutane tetracarboxylic dianhydride and other aliphatic tetracarboxylic dianhydrides. .

The diamine component used in producing the copolymer is all compounds represented by the formula [5]. Specific examples include aromatic diamine compounds such as phenylenediamines and substituted benzidines, and aliphatic diamine compounds such as alkylenediamines and cycloalkylenediamines.

The length of the perfluoroalkyl moiety in the polyimide molecule consisting of the structural unit represented by the formula [1] is preferably 1 to 12, but in order to stably obtain a large pretilt angle, n = 3 or more. It is preferable that n be 10 or less in order to improve the coating property on the glass substrate.

The molar ratio of each structural unit in the copolymer of the structural units represented by the formulas [1] and [4] is represented by the formula [1]
The structural unit represented by formula (4) is preferably 5 to 95 mol%, the structural unit represented by formula [4] is preferably 95 to 5%, and more preferably the structural unit represented by formula [1] is 20%. ~ 95
Mol%, the constitutional unit represented by the formula [4] is 80 to 5 mol%
It is. When the ratio of the constitutional units represented by the formula [1] or the formula [4] is 5 mol% or less, the effect of copolymerization is lost. Further, if the ratio of the constitutional unit represented by the formula [1] is 20 mol% or less, the pretilt angle may decrease.

To produce the polyimide of the present invention, the polyimide precursor polyamic acid obtained by the condensation reaction of diamine and tetracarboxylic dianhydride is coated on a substrate, heat-treated and dehydrated to react with the polyimide. The method of forming the film on the substrate is preferred. Specifically, the polyamic acid obtained by the condensation reaction of diamine and tetracarboxylic dianhydride is treated with N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide. It is dissolved in a solvent such as (DMSO), butyl cellosolve, or ethyl carbitol to prepare a 0.1 to 30 wt% solution, and this solution is applied onto a substrate to form a thin film. After coating, heat treatment is performed at 100 to 450 ° C., preferably 180 to 220 ° C., and dehydration ring closure reaction is performed to form a polyimide film.

In order to form the liquid crystal alignment film of the present invention on a substrate, a polyimide precursor polyamic acid obtained by a condensation reaction of a diamine and a tetracarboxylic dianhydride is coated on the substrate and heat-treated. A method of forming a polyimide-based polymer film on a substrate by a dehydration reaction is preferable. Specifically, the polyamic acid obtained by the condensation reaction of a diamine and a tetracarboxylic dianhydride is referred to as NM
P, DMAc, DMF, DMSO, butyl cellosolve,
Dissolve in a solvent such as ethyl carbitol, 0.1 to 30
Adjust to a weight% solution, and use this solution with a brush coating method, a dipping method,
A spin coating method, a spray method, a printing method or the like is applied on the substrate to form a thin film. After coating, heat treatment is performed at 100 to 450 ° C., preferably 180 to 220 ° C., and a dehydration ring-closing reaction is performed to provide a polyimide polymer film. If the surface of the substrate is treated with a silane coupling agent before coating, and a polymer film is formed thereon, the adhesiveness between the film and the substrate can be improved. Thereafter, the coated surface is rubbed in one direction with a cloth or the like to obtain a liquid crystal alignment film.

The above polyamic acid is obtained by the condensation reaction of diamine and tetracarboxylic dianhydride. These reactions are performed under anhydrous conditions under the conditions of DMAc, NMP, DM
In a solvent such as F, DMSO, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, dioxane or tetrahydrofuran,
It is preferably carried out in a NMP solvent at a temperature of -10 to 30 ° C.

The substrate used as a liquid crystal display element is usually one on which an electrode, specifically, a transparent electrode of ITO (indium oxide-tin oxide) or tin oxide is formed.
Further, an insulating film for preventing alkali elution from the substrate, an undercoat film such as a color filter or a color filter overcoat may be provided between the electrode and the substrate, and the insulating film, the color filter film or the like may be provided on the electrode. You may provide the overcoat film of. TFT on the electrode
(Thin-Film-Transistor) element,
MIM (Metal-Insulator-Meta)
l) An active element such as an element may be formed. For these electrodes, undercoat, and other internal structure of the liquid crystal cell, the structure of a conventional liquid crystal display element can be used.

Using the substrate thus formed, cells are formed, liquid crystal is injected, and the injection port is sealed to form a liquid crystal display element. As the liquid crystal to be enclosed, various liquid crystals such as a normal nematic liquid crystal and a liquid crystal added with a dichroic dye can be used. The liquid crystal alignment film of the present invention has good liquid crystal alignment and has a high pretilt angle of about 10 degrees or more.

The liquid crystal display device of the present invention is characterized by having a liquid crystal alignment film having a good liquid crystal alignment property and a high pretilt angle of about 10 degrees or more, that is, the liquid crystal alignment film of the present invention. It is composed of a substrate, a voltage applying means, a liquid crystal alignment film, a liquid crystal layer and the like.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

Next, the physical properties of the polyimide or polyamic acid obtained in the examples were measured by the following methods. Decomposition temperature (Td): A differential thermogravimetric simultaneous measurement device (TG / DTA-220 manufactured by Seiko Denshi Kogyo Co., Ltd.) was used to measure the temperature at a temperature rising rate of 10 ° C./min. Logarithmic viscosity: 3 in NMP solvent using Ubbelohde viscometer
It was measured at a concentration of 0.5 g / dl at 0 ° C. Pretilt angle: Measured using a magnetic field capacitance method.

[0023]

【Example】

Example 1 Production of Polyimide Comprising Structural Unit Shown in Formula [1]: 1) 1H, 1H, 7H-dodecafluoro-1-heptyl = 3,5-diaminobenzoate (shown in Formula [2] Production of m = 1, n = 6). 100 ml of tetrahydrofuran (THF) was placed in a 300 ml three-necked flask equipped with a stirrer, and 1H,
1H, 7H-dodecafluoro-1-heptanol 10.
0 g (0.030 mol), triethylamine 5.0 ml
Was added and stirred at 0 ° C. To this, 6.91 g (0.030 mol) of 3,5-dinitrobenzoyl chloride was added to THF5.
The solution dissolved in 0 ml was added dropwise over 30 minutes, and the reaction was carried out for 6 hours. After completion of the reaction, this liquid was added to 1 L of water and extracted with 1.5 L of ethyl acetate. Then 3 organic layers
It was washed 3 times with N hydrochloric acid, 3 times with saturated aqueous sodium hydrogen carbonate, and further washed with water. The obtained ethyl acetate layer was dried over anhydrous sodium sulfate, the solvent was distilled off under reduced pressure, and the obtained crystal was recrystallized twice with n-heptane / ethyl acetate to give 1H, 1H, 7H-dodecafluoro-. 12.6 g (0.024 mol) of 1-heptyl = 3,5-dinitrobenzoate was obtained. Melting point is 1
It was 07.7-108.8 degreeC. The structure of this compound was confirmed by IR and NMR, and then catalytic reduction was performed.

That is, 1H, 1H-heptafluoro-
1-Butyl = 3,5-dinitrobenzoate 12.6 g
(0.024 mol) was dissolved in 200 ml of ethyl acetate, 1.20 g of 5% palladium-carbon was added, and catalytic reduction was performed at room temperature and atmospheric pressure. After completion of the reaction, the catalyst was filtered off, the solvent was distilled off under reduced pressure, and the obtained crystals were recrystallized twice from n-heptane / ethyl acetate to give 1H, 1H, 7H-dodecafluoro-1-heptyl = 3. , 5-diaminobenzoate 9.
79 g (0.021 mol) was obtained. The melting point of this compound was 114.6 to 115.9 ° C.

2) Polymerization reaction In a 50 ml three-necked flask, 1H, 1H, 7H-dodecafluoro-1-heptyl = 3,5-diaminobenzoa-
0.6992 g (1.50 mmol), 3.0 ml NMP
Was added, and the mixture was dissolved with stirring under a nitrogen stream at room temperature. Next, this liquid was kept at 10 ° C., and 0.4413 g (1.50 g) of BPDA was added.
mmol) was added. The vessel wall was rinsed with 3.0 ml of NMP, and the reaction was continued for 3 hours. The obtained reaction solution is N
After diluting to 4.0 wt% with MP / butyl cellosolve = 1/1 solvent, it was applied on the ITO glass substrate by spin coating method (spinner method). After coating, bake at 200 ° C for 30 minutes,
A polyimide film having a film thickness of 600Å was obtained. This polyimide had a decomposition temperature of 370.1 ° C. The remaining reaction solution was poured into 300 ml of methanol and the deposited precipitate was filtered. The filtered material was dried under reduced pressure at room temperature to obtain a polyamic acid. The intrinsic viscosity of this polyamic acid is 0.
28 (30 ° C., 0.5 g / dl, NMP solution).

3) Preparation of Cell and Measurement of Pretilt Angle Subsequently, the film surfaces of the two substrates were each rubbed, and a liquid crystal cell having a cell thickness of 20 μm was assembled so that the rubbing directions were anti-parallel, and manufactured by Chisso Corporation. Liquid crystal L
IXON-5048 was enclosed. After that, the liquid crystal is 120 ℃
Was heat-treated for 30 minutes. After the heat treatment, it was allowed to cool and the pretilt angle was calculated to be 24.1 degrees.

Example 2 Production of Polyimide Comprising Structural Units Shown in Formulas [1] and [4]: Diamine component was used as 1H, 1H, 7H-dodecafluoro-1-heptyl = 3,5-diaminobenzoa-
The procedure was carried out in accordance with 2) and 3) of Example 1 except that a mixture of 0.5593 g (1.20 mmol) and 1,3-phenylenediamine 0.0324 g (0.30 mmol) was used. Table 1 shows the physical properties of the obtained polyimide.

Examples 3 to 4 1H, 1H, 7H-dodecafluoro-1-heptyl =
The procedure of Example 2 was repeated, except that the mixing ratio of 3,5-diaminobenzoate and 1,3-phenylenediamine was changed. Table 1 shows the physical properties of the obtained polyimide.

Example 5 Production of Polyimide Comprising Structural Units Represented by Formula [1] and Formula [4]: 1) 1H, 1H, 11H-Eicosafluoro-1-undecyl = 3 Represented by Formula [2] Preparation of 5-diaminobenzoate (where m = 1 and n = 10). 1H, 1H, 7H-dodecafluoro-1-heptanol was added to 1H, 1H, 11H-eicosafluoroundecano-
Was manufactured according to 1) of Example 1 except that The melting point of the obtained 1H, 1H, 11H-eicosafluoro-1-undecyl = 3,5-diaminobenzoate was 138.5-141.4 ° C.

2) Polymerization reaction and pretilt angle measurement 1H, 1H, 11H-eicosafluoro-1-undecyl = 3,5-diaminobenzoate 0.4989 g (0.40 g)
75 mmol), 1,3-phenylenediamine 0.08
The same procedure as in Example 2 was performed except that 11 g (0.75 mmol) was used as the diamine component. Table 1 shows the physical properties of the obtained polyimide.

Example 6 Example 3 was repeated except that the mixing ratio of 1H, 1H, 11H-dodecafluoro-1-undecyl = 3,5-diaminobenzoate and 1,3-phenylenediamine was changed. It was Table 1 shows the physical properties of the obtained polyimide.

[0032]

[Table 1]

[0033]

The polyimide obtained by the present invention has a high decomposition temperature of 360 ° C. or higher and can be used at high temperatures.
Further, a liquid crystal alignment film using the present polyimide is excellent in adhesion to a glass substrate and liquid crystal alignment property, and is useful as an alignment film for a liquid crystal cell. Further, since it has a high pretilt angle of about 11.5 degrees or more, it is useful as a material for an alignment film of a liquid crystal cell for STN and SBE, and particularly useful as a material for an alignment film of a liquid crystal cell for SBE.

[Brief description of drawings]

1 is the IR of the polyimide film obtained in Example 1.
It is a spectrum figure.

Claims (6)

[Claims] 1. A polyimide comprising a structural unit represented by the formula [1]. Embedded image 2. A diamino compound represented by the formula [2],
A polyimide obtained by reacting a tetracarboxylic dianhydride represented by the formula [3] in a solvent to produce a polyamic acid, and heating the polyamic acid. Embedded image Embedded image 3. A structural unit represented by formula [1] and formula [4]
A polyimide comprising a structural unit represented by. Embedded image Embedded image 4. A polyamic acid obtained by reacting a diamino compound represented by the formula [2], a diamino compound represented by the formula [5], and a tetracarboxylic dianhydride represented by the formula [3] in a solvent. A polyimide obtained by generating an acid and heating the polyamic acid. [Chemical 6] [Chemical 7] Embedded image 5. A liquid crystal alignment film comprising the polyimide according to any one of claims 1 to 4. 6. A liquid crystal display device comprising the liquid crystal alignment film according to claim 5.