JPS6257421A - Colorless, transparent polyimide molded article and production thereof - Google Patents

Abstract

PURPOSE:The titled colorless, transparent molded article suitable for liquid crystal orientation membrane, etc., obtained by reacting a specific aromatic diamine with a specified tetracarboxylic acid compound to give a precursor, dissolving the precursor in a proper solvent, forming and imidating it. CONSTITUTION:Firstly, (A) a diamino compound comprising mainly a diamine shown by the formula I (X1-X4 are H, CH3, etc.,), II (X5 is -O-, -SO2-, etc.,) or III [X6 is -SO2-, -C(CH3)2, etc.,] is reacted with (B) a tetracarboxylic acid compound comprising mainly a tetracarboxylic acid dianhydride shown by the formula IV, to give a polyimide precursor. Then, the precursor is dissolved in an organic solvent selected from dimethylacetamide, DMF, bis-(2- methoxyethyl) ether, cresol and a halophenol. Then, a molded article of the polyimide precursor is formed from a solution of the polyimide precursor in an organic polar solvent and imidated to give the aimed molded article consisting of a repeating unit shown by the formula V, VI or VII.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a colorless and transparent polyimide molded body used for liquid crystal alignment films and the like.

[Prior Art] Liquid crystal alignment films are required to have high transparency and excellent electrical and mechanical properties, and polyimide films having such properties have been used as the above-mentioned liquid crystal alignment films. There is. However, although polyimide films have excellent electrical and mechanical properties and are highly transparent, their transparency is colored, so there is a need to remove this color. For this purpose, various polyimides have been proposed, but among them, a repeating unit represented by the general formula (■) is disclosed in JP-A-58-91430 as a polyimide alignment film with a low degree of coloration and high transparency. Those made of aromatic polyimide polymers having the following properties are excellent.

However, although the above-mentioned polyimide alignment film has excellent transparency, it is still colored yellow, so it is not completely satisfactory as a liquid crystal alignment film.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a colorless and transparent polyimide molded product and a method for producing the same, rather than having the colored transparency described above.

[Means for solving problems]

In order to achieve the above object, the present invention provides the following general formula (
A colorless and transparent polyimide molded body containing at least one of the repeating units represented by I), the repeating units represented by the general formula (■), and the repeating units represented by the general formula CI[I] is used as a first component. The summary of 1. (margin) includes the steps of preparing an organic polar solvent solution of a polyimide precursor in which the following component (A) is dissolved in component (B), and preparing polyimide from the organic polar solvent solution of the polyimide precursor. The second gist is a method for producing a colorless and transparent polyimide molded article, which is characterized by comprising a step of forming a molded article of a precursor and a step of imidizing the molded article of the polyimide precursor. .

(A) Diamine represented by general formula (IV), general formula (V
) and a diamino compound whose main components are at least one of the diamines represented by the general formula (VT) and a tetracarboxylic dianhydride represented by the general formula (■). A polyimide precursor obtained by reacting a tetracarboxylic acid compound.

HtN f Xs-◎=NHz ・(V)
At least one organic polar solvent selected from the group consisting of dimethylacetamide, dimethylformamide, bis(2-methoxyethyl)ether, cresol and halogenated phenol.

As a result of a series of studies on the causes of coloration of polyimide films, the present inventors discovered that the combination of aromatic tetracarboxylic dianhydride and diamino compound, which are the starting materials of polyimide, greatly affects coloration. Especially as aromatic tetracarboxylic dianhydride, 3.3', 4.4°
- By using diphenylsulfone tetracarboxylic dianhydride, colorless transparency is greatly improved compared to conventional polyimide membranes, and when this is combined with an aromatic diamine having an amino group at the meta position, it becomes almost completely transparent. They discovered that scales can be formed into a colorless and transparent polyimide molded body, and arrived at the present invention.

The polyimide molded product of the present invention is completely different from conventional polyimide molded products in that it is completely colorless and transparent, and also has the excellent electrical and mechanical properties inherent to polyimide, making it an extremely excellent liquid crystal alignment film. In addition, it can be applied to various applications such as solar systems and aerospace fields, and can be expected to have revolutionary effects.

The colorless and transparent polyimide molded article of the present invention has the general formula (■)
3,3′,4.4”-diphenylsulfonetetracarboxylic dianhydride represented by and general formula (IV) to (■)
It can be obtained by reaction with an aromatic diamine having an amino group at the meta position represented by:

X.

11J-◎-XS-◎-ML (V) Representative examples of the aromatic diamine having an amino group at the above meta position include the following.

HzNtNHt Metaphenylenediamine 2.4-) Luenediamine 4.6-dimethyl-Metaphenylenediamine 2.4-Diaminomesitylene 4-Chlor-Metaphenylenediamine 4-Fluoro-Metaphenylenediamine 3.5-Diaminobenzoic acid 5-nitro - Metaphenylene diamine 3.3' - Diaminodiphenyl ether 3.3' -
Diaminodiphenylsulfone 3.3' -Diaminodiphenylthioether 3.3' -Diaminodiphenylmethane 3.3' -Diaminobenzophenone, 4-bis(3-aminophenoxy)benzene H,N-
◎-0-◎-0-◎-NHz l, 3-bis(3-aminophenoxy)benzene (blank below) The above aromatic diamines having an amino group at the meta position may be used alone, or may be used as appropriate. May be used in combination.

The tetracarboxylic dianhydride to be reacted with the aromatic diamine having an amino group at the meta position has the general formula (IV
3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride represented by ), and its esters, amides, and halides.

- Derivatives such as anhydrides can also be used, and these, including the above-mentioned dianhydrides, are collectively referred to as tetracarboxylic acid compounds. However, among the above compounds, the use of dianhydrides gives good results.

Then, by reacting the 3,3", 4.4'-diphenyltetracarboxylic dianhydride as described above in combination with an aromatic diamine having an amino group at the meta position, the general formula (■) can be obtained for the first time. A colorless and transparent polyimide molded product containing one or more of the repeating units represented by (III) as a main component can be obtained.The term "main component" here may also mean that the entire body consists only of the main component. This is the purpose of including it.

In this case, the greater the content of the repeating units represented by the above general formulas (1) to (III), which are the main components of the colorless and transparent polyimide molded product, the higher the colorless transparency of the resulting polyimide molded product. However, the above general formula (1
) to (III) is contained in an amount of 70 mol % or more, at least the colorless transparency required in the present invention is ensured. Aromatic tetracarboxylic dianhydrides other than anhydrides and diamino compounds other than aromatic diamines having an amino group at the meta position can be used. but,
The content of repeating units represented by the above general formulas (1) to (III) is preferably 70 mol% or more, and the most preferable range is 95 mol% or more.

Examples of the other aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride and 3.3'.

4.4'-biphenyltetracarboxylic dianhydride,
2.3', 3.4'-biphenyltetracarboxylic dianhydride, 3.3', 4.4'-benzophenonetetracarboxylic dianhydride, 3.3', 4,4'-diphenyl ether tetracarboxylic acid dianhydride, 2.2-
Bis(3,4-dicarboxyphenyl)hexafluoropropanihydride, 2.3,6.7-naphthalenetetracarboxylic dianhydride, 1.2.5.6-naphthalenetetracarboxylic dianhydride, Examples include derivatives such as 1.4.5.8-naphthalenetetracarboxylic dianhydride or its ester, and these can be used alone or in combination.

In addition, other diamino compounds include 4°4°-diaminodiphenyl ether, 3.4'-diaminodiphenyl ether, 4,4''-diaminodiphenylsulfone, 4,4'-diaminodiphenylmethane, 4.
．． 4'-diaminobenzopheno7.4.4'-
Diaminodiphenylpropane, paraphenylenediamine, benzidine, 3.3°-dimethylbenzidine, 4.
4°-diaminodiphenylthioether, 3.3′
-dimethoxy-4°4°-diaminodiphenylmethane,
3.3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)-hexafluoropropane Akerale can be used alone or in combination.

The colorless and transparent polyimide molded article of the present invention can be produced by polymerizing the above-mentioned aromatic tetracarboxylic dianhydride and diamino compound in an organic polar solvent at a temperature of 80°C or lower to prepare a polyamic acid solution. A molded body of a desired shape is formed using a solution, and this molded body is placed in air or an inert gas at a temperature of 50 to 3.
It can be obtained by evaporating and removing the organic polar solvent under conditions of 50° C. and normal pressure or reduced pressure, and simultaneously dehydrating and ring-closing the polyamic acid to form a polyimide.

It can also be obtained by a chemical imidization method, such as by removing the solvent and imidizing the polyamic acid with a benzene solution of pyridine and acetic anhydride to form a polyimide.

The above organic polar solvents include dimethylformamide,
Organic polar solvents such as dimethylacetamide, diglyme [bis(2-methoxyethyl)ether], talesol, and halogenated phenol are suitable. Particularly preferred is dimethylacetamide. These organic polar solvents may be used alone or in combination of two or more without any problem. However, it is not preferable to use N-methyl-2-pyrrolidone as the organic polar solvent. N-methyl-2
- pyrrolidone is heated to excipients of polyamic acid solution;
This is because it is partially decomposed by heating during dehydration ring closure and imidization, and the decomposed product remains and becomes blackish brown, which causes the resulting polyimide molded product to be colored yellowish brown.

In this regard, the suitable solvents exemplified above are evaporated before being decomposed by the heating described above, and do not cause coloring of the polyimide molding, such as N-methyl-2-pyrrolidone. That is, by using the above-mentioned organic polar solvent, it is possible to obtain a polyimide molded article that is almost completely colorless and transparent, and this is a major feature of the present invention.

In addition, if N-methyl-2-pyrrolidone is used as a polymerization solvent and the resulting polyamic acid is dissolved in a suitable solvent as exemplified above by solvent substitution after polyimide acid synthesis, N-methyl-2-pyrrolidone can be dissolved. The above-mentioned disadvantages can be eliminated, and a polyimide molded product that is almost completely colorless and transparent can be obtained in this manner as well. in this case,
The suitable solvents exemplified above serve as diluting solvents. In producing the above polyamic acid, the polymerization solvent and the diluent solvent may be of different types, and the produced polyamic acid may be dissolved in the diluent solvent by solvent substitution.

In addition, when using the suitable organic polar solvents exemplified above, some of the above solvents may be replaced with poor solvents or good solvents that do not impair transparency, such as ethanol, toluene, benzene, xylene, dioxane, tetrahydrofuran, and nitrobenzene. It may be used in place of . In that case, the amount of substitution is
It goes without saying that the amount should be within a range that does not impair solubility, and generally there will be no problem if it is within a range of 40% by weight.

As described above, when producing a colorless and transparent polyimide molded article, the logarithmic viscosity (N-methyl-2
- measured at 30 DEG C. at a concentration of 0.5 g/100 ml in pyrrolidone) is preferably in the range 0.3 to 5.0.

More preferred is 0.4 to 2.0. If the logarithmic viscosity is too low, the resulting polyimide molded article will have low mechanical strength, which is not preferable. On the other hand, if the logarithmic viscosity is too high, it is not preferable because it makes it difficult to cast the polyamic acid solution into an appropriate shape. In addition, the concentration of the polyamic acid solution is also from 5 to 30 from the viewpoint of workability.
It is preferable to set the amount to 15 to 25% by weight.

The above logarithmic viscosity is calculated by the following formula, and the viscosity in the formula is measured by a capillary viscometer.

The shaping method using a polyamic acid solution varies depending on the shape of the desired molded product, but for example, when obtaining a polyimide film, the polyamic acid solution is applied to a mirror surface of a glass plate, stainless steel plate, etc. to a certain thickness. spread to become
The polyamic acid is imidized by gradually heating at a temperature of 100 to 350°C to cause dehydration and ring closure. In forming a film from a polyamic acid solution, the removal of the polar solvent and the heating for imidization of the polyamic acid may be performed continuously, or these steps may be performed under reduced pressure or in an inert gas atmosphere. Good too. Furthermore, the properties of the resulting polyimide film can be improved by finally heating it to around 400° C. for a short time. Another method for forming a polyimide film is to cast the above polyamic acid solution onto a glass plate, etc.
A film is formed by heating and drying at 50°C for 30 to 120 minutes, and this film is immersed in a benzene solution of pyridine and acetic anhydride to remove the solvent and undergo an imidization reaction, thereby converting the film into a polyimide film. , a polyimide film can also be obtained by this method.

The polyimide film obtained in this way is completely colorless and transparent and is not colored yellow or yellowish brown unlike conventional films, so it has extremely good transparency even if it is a thick film.

Note that shaping using the above polyamic acid solution is not limited to the formation of a polyimide film as described above;
It can also be applied to the formation of molded objects such as plastic lenses, and in that case, the imidization of polyamic acid can be appropriately selected from either the above-mentioned thermal imidization or chemical imidization. .

In the case where a polyamic acid solution is imidized to form a polyimide as described above, the resulting polyimide has a logarithmic viscosity (0.5 a/g 0 in 97% sulfuric acid) from the viewpoint of properties.
) is preferably set within the range of 0.3 to 4.0. Most preferable is 0
．． It is 4 or more.

The polyimide molded product thus obtained is completely different from conventional molded products, and is completely colorless and transparent, and has extremely high transparency. In the present invention, completely colorless and transparent means that the visible light (500 nm) transmittance for a polyimide film with a thickness of 50 ± 5 μm is 85%.
or more, and the degree of yellowness (yellowness index) is 2
It refers to something less than 0.

〔Effect of the invention〕

As described above, the polyimide molded article of the present invention is obtained by combining diphenyltetracarboxylic dianhydride and a special aromatic diamine having an amino group at the meta position, and unlike the conventional ones, The chairs, which are colored yellow to tan, are completely colorless and transparent, so they have extremely high transparency. Therefore, it is possible to form a thick liquid crystal alignment film, and in addition, its colorless transparency can be used to make base film materials for solar cells, polarization film materials, and special aerospace materials such as solar cells and thermal control systems. It can be suitably used as a coating material for industrial components, optical applications requiring heat resistance, and coating materials for those applications. Moreover, the refractive index is 1.
Since it is the largest of all polymers at 7 or more, it is also useful as a coating material for plastic lenses or lenses.

Next, examples will be described together with comparative examples.

In addition, in the table below, DPSA is 3.3゛, 4.4
″-diphenylsulfone tetracarboxylic dianhydride,
5-BPDA is 3. 3', 4. 4'-biphenyltetracarboxylic dianhydride, m-PDA is metaphenylenediamine, 2.4-TDA is 2.4-)luenediamine, 4,6-dimethyl-metaphenylenediamine, 2.4-diaminomesitylene , 4-CMPA is 4-chloro-meta-phenylenediamine, 4-FMPA is 4-fluoro-meta-phenylenediamine, 3.5-DABA is 3.5-diaminobenzoic acid, 3.3'-DDE is 3
．． 3゛-diaminodiphenyl ether, 3,3゜-DD
S is 3.3°-diaminodiphenylsulfone, 3.3
'-DPE is 3.3°-diaminodiphenylthioether, 3.3'-DDM is 3,3°-diaminodiphenylmethane, 3.3'-DBP is 3,3'-diaminobenzophenone, 1,4.3-BAPB is 1,4. -bis(3-aminophenoxy)benzene, 1,3.3-B
APB is 1.3. -bis(3-aminophenoxy)benzene, 3.3'-BAPS is 4,4''-di(3-aminophenoxy)diphenylsulfone, 3.3'-B
APP is 4,4'-di(3-aminophenoxy)diphenylpropane, 3.3'-BAPF is 4.4'-di(3-aminophenoxy)diphenylhexafluoropropane, 4.4'-DDE is 4 .4°-diaminodiphenyl ether, 4.4°-BAPP is 4.4°-di(4-aminophenoxy)diphenylpropane, DMA
c is dimethylacetamide, diglyme is bis(2
-methoxyethyl)ether, NMP is N-methyl-2
- indicates pyrrolidone.

[Examples 1-24. Comparative Examples 1 to 3] The solvents shown in the table below and the diamino compound were placed in a No. 11 separable flask and mixed well at room temperature until the diamino compound was completely dissolved. In this case, the amount of the solvent used is such that the monomer concentration of the diamino compound and the aromatic tetracarboxylic dianhydride shown in Table 1 below is 20%.
It was set to be % by weight.

Next, the aromatic tetracarboxylic dianhydride shown in the same table was gradually added to the flask while suppressing the temperature rise due to heat generation. The reaction mixture was then stirred at room temperature for 4 hours to obtain a polyamic acid solution having a logarithmic viscosity shown in the table below.

The polyamic acid solution obtained as described above was cast onto a glass plate to form a film, and this film was dried in a hot air dryer at 120°C for 60 minutes, and then at 180°C for 60 minutes.
The mixture was then heated at 250° C. for 6 hours to imidize it, thereby producing a polyimide film having a thickness of 50±5 μm. Furthermore, when the infrared absorption spectrum of the above film was measured, no absorption peculiar to amic acid was observed.
A characteristic absorption of the imide group was observed near 78Qcm-'.

Next, the yellowness index of the polyimide film obtained as described above was measured, and the transmittance in visible light (500 nm) was measured.
It is also shown in the table below.

(Left space below) In the table, Examples 1 to 17 show examples using aromatic diamines having an amino group at the meta position, and Example 1
8.19 is 3. 3', 4. Example 20 shows an example in which 4°-diphenylsulfone tetracarboxylic dianhydride (DPSA) and other tetracarboxylic dianhydrides were used in combination, and Example 20 shows a diamine having an amino group at the meta position (3,3°-DD
An example is shown in which E) and another diamine (4,4'-DDE) are used together. In addition, Example 21 shows an example in which both the tetracarboxylic dianhydride and the diamine are used in combination with other tetracarboxylic dianhydrides and other diamines, and Examples 22 to 24 change the solvent from dimethylacetamide to diglyme. An example is shown in which it is changed to .

As is clear from the table, the polyimide films of Examples 1 to 24 all have a yellowness index of 20 or less, a transmittance of 85% or more, and are almost completely colorless and transparent. On the other hand, comparative example 1
(Japanese Patent Application Laid-Open No. 58-91430) uses a diamino compound having an amino group at the para position rather than one having an amino group at the meta position, so the yellowness index and transmittance were not measured. It can be seen that it is inferior to the example, and in particular the yellowness index value is poor and it is colored yellow. Further, in Comparative Example 2, a diamino compound having an amino group at the para-position W was used as in Comparative Example 1, and since an acid other than the above-mentioned DPSA was used, the yellowness index was even worse. Furthermore, since Comparative Example 3 uses N-methyl-2-pyrrolidone as a solvent, the yellowness index and transmittance are worse than Comparative Example 1.2, and the film is colored yellowish brown. I know that there is.

Claims (1)

[Claims] (1) Colorless and transparent whose main component is at least one of the following repeating unit represented by general formula (I), the repeating unit represented by general formula (II), and the repeating unit represented by general formula (III). Polyimide molded body. ▲There are mathematical formulas, chemical formulas, tables, etc.▼…(I) [In formula (I), X_1 to X_4 are -H, -CH
_3, -C_2H_5, -NO_2, -F, -COOH
Or -Cl. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) [In formula (II), X_5 is -O-, -SO_2-,
-CH_2-, -S-, -CO- or ▲There are mathematical formulas, chemical formulas, tables, etc.▼. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(III) [In formula (III), X_6 is -SO_2-, -C(
CH_3)_1 or -C(CF_3)_2-. ] (2) A step of preparing an organic polar solvent solution of a polyimide precursor in which the following component (A) is dissolved in component (B), and a molded product of the polyimide precursor from the organic polar solvent solution of the polyimide precursor. 1. A method for producing a colorless and transparent polyimide molded article, comprising the steps of: forming a polyimide precursor; and imidizing a molded article of this polyimide precursor. (A) Diamine represented by general formula (IV), general formula (V)
A diamino compound whose main component is at least one of the diamine represented by the formula (VI) and the diamine represented by the general formula (VI), and a tetracarboxylic dianhydride represented by the general formula (VII). A polyimide precursor obtained by reacting a carboxylic acid compound. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(VI) [In formula (IV), X_1 to X_4 are -H, -CH_
3, -C_2H_5, -NO_2, -F, -COOH or -Cl. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(V) [In formula (V), X_5 is -O-, -SO_2-,
-CH_2-, -S-, -CO- or ▲There are mathematical formulas, chemical formulas, tables, etc.▼. ] ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(VI) [In formula (VI), X_6 is -SO_2-, -C(C
H_3)_2- or -C(CF_3)_2. ]
▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(VII
I) (B) dimethylacetamide, dimethylformamide,
At least one organic polar solvent selected from the group consisting of bis(2-methoxyethyl)ether, cresol and halogenated phenol.