JP5386797B2 - Flexible polyimide film and manufacturing method thereof - Google Patents

Description

  More particularly, the present invention relates to a flexible polyimide film having an alicyclic structure and suitable for an electronic material and a method for producing the same.

In general, polyimide has high mechanical strength, heat resistance, insulation, and solvent resistance, and is therefore widely used as an electronic material for liquid crystal display elements and semiconductor protective materials, insulating materials, color filters, and the like. . Recently, applications as optical communication materials such as optical waveguide materials and substrates for mobile phones are also expected.
For this reason, in recent years, polyimides having many performances corresponding to applications such as transparency and flexibility in addition to heat resistance and solvent resistance have been desired.

Conventionally used, wholly aromatic polyimides obtained by polycondensation reaction of aromatic tetracarboxylic dianhydrides and aromatic diamines are colored with a dark amber color, and therefore require high transparency. Problems arise in.
In order to solve this coloring problem, a polyimide obtained by imidizing a polyimide precursor (polyamic acid) obtained by polycondensation of an alicyclic tetracarboxylic dianhydride and an aromatic diamine has been reported ( Patent Document 1).
Although this polyimide having an alicyclic skeleton is relatively less colored and excellent in transparency, it is fragile because it lacks flexibility, and it has been difficult to form a large-area film or thick film.

In recent years, a soluble polyimide obtained by chemically imidizing a polyamic acid synthesized from an alicyclic tetracarboxylic dianhydride and various diamines has been reported for the purpose of improving transparency and solubility in organic solvents ( (See Patent Documents 2 and 3).
However, a detailed study of film formation has not been performed for these polyimides.

JP 58-208322 A JP-A-2005-170818 JP 2005-105019 A

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a flexible polyimide film excellent in heat resistance and transparency, flexible and workable, and a method for producing the same.

  As a result of intensive studies in order to achieve the above object, the present inventors have found that the polyimide having a conventional alicyclic structure has a low imidation ratio and the flexibility of the polyimide having an alicyclic structure. Is found to be related to the imidization rate, and the polyamic acid of Patent Documents 2 and 3 described above is subjected to ring-closing imidization by heat, so that the imidization rate in the polymer is increased and the transparency is maintained. It discovered that the polyimide film excellent in the softness | flexibility was obtained, and completed this invention.

That is, the present invention
1. A flexible polyimide film comprising a repeating unit represented by the formula [1] or [2] and having an imidization ratio of 90% or more,
(In the formula, R ¹ represents an alkylene group having 1 to 10 carbon atoms or a haloalkylene group having 1 to 10 carbon atoms, and R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, carbon A C 1-10 alkyl group, a halogen atom, or a C 1-10 haloalkyl group, m represents an integer of 1-20, and n represents an integer of 2 or more.)
2. The flexible polyimide film of 1, wherein the repeating unit of the formula [1] is represented by the formula [3],
(Wherein R ¹ , R ² , R ³ , R ⁴ , m and n represent the same meaning as described above.)
3. 1 in the above formulas [1] and [2], m is 5;
4). 2 in the above formula [3], m is 5, a flexible polyimide film,
5. The flexible polyimide film according to any one of 1 to 4, wherein the imidization ratio is 95% or more,
6). The polyamic acid composed of the repeating unit represented by the formula [10] or [11] is heated from 25 ° C. to 160 to 300 ° C. over 2 to 10 hours, and then held at 160 to 300 ° C. for 1 to 10 hours. A method for producing a flexible polyimide film according to claim 1, wherein
(In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , m and n have the same meaning as described above.)
7). The process for producing a flexible polyimide film of 6, wherein the repeating unit of the formula [10] is represented by the formula [12],
(Wherein R ¹ , R ² , R ³ , R ⁴ , m and n represent the same meaning as described above.)
8). In the above formulas [10] and [11], a process for producing a flexible polyimide film of 6 wherein m is 5;
9. In the formula [12], a method for producing a flexible polyimide film of 7 in which m is 5 is provided.

The polyimide film of the present invention is not only good in workability because it is flexible, but also has light transmittance from the visible to the ultraviolet region (around 250 nm), as with conventional polyimides having an alicyclic skeleton, In addition, it has high heat resistance with a thermal decomposition temperature of 300 ° C. or higher.
The polyimide film of the present invention having such characteristics can be suitably used, for example, as a protective material for liquid crystal display elements and semiconductors, an electronic material such as an insulating material, and an optical communication material such as an optical waveguide.

Hereinafter, the present invention will be described in more detail.
In the above formulas [1] to [3] and [10] to [12], specific examples of the alkylene group having 1 to 10 carbon atoms include —CH ₂ —, — (CH ₂ ) ₂ —, — (CH ₂ ) ₃ -,-(CH ₂ ) ₄ -,-(CH ₂ ) ₅ -,-(CH ₂ ) ₆ -,-(CH ₂ ) ₇ -,-(CH ₂ ) ₈ -,-(CH ₂ ) ₉ -,-(CH ₂ ) _10- , -C (CH ₃ ) _2- , -CH ₂ C (CH ₃ ) ₂ CH ₂ -,-(CH ₂ ) ₂ C (CH ₃ ) ₂ (CH ₂ ) ₂ -Etc. are mentioned.
Examples of the haloalkylene group having 1 to 10 carbon atoms include those obtained by substituting at least one hydrogen atom of the alkylene group with a halogen atom, specifically, —CF ₂ —, — (CF ₂ ) ₂ —, _{- (CF 2) 3 -,} - (CF 2) 4 -, - (CF 2) 5 -, - (CF 2) 6 -, - (CF 2) 7 -, - (CF 2) 8 -, - ( _{CF 2) 9 -, - (} CF 2) 10 -, - C (CF 3) 2 -, - CF 2 C (CF 3) 2 CF 2 -, - (CF 2) 2 C (CF 3) 2 (CF ₂ ) _2- and the like.
Although m which shows the repeating number of an alkylene chain represents the integer of 1-20, the integer of 2-10 is preferable from the point of availability.

The alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, Examples include t-butyl, n-pentyl, i-amyl, t-amyl, neo-pentyl, n-hexyl, heptyl, octyl, nonyl, decyl group and the like.
Examples of the haloalkyl group having 1 to 10 carbon atoms include those obtained by substituting at least one hydrogen atom of the alkyl group with a halogen atom, specifically, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group. And nonafluorobutyl group.
Examples of the halogen atom include fluorine, chlorine, bromine and iodine atoms.
In the above, n represents normal, i represents iso, s represents secondary, and t represents tertiary.

In the present invention, the number average molecular weight of polyimide (polyamic acid) is preferably at least 5000, more preferably 6000 to 100,000, considering the flexibility when it is made into a film.
For this reason, n in each of the above formulas is an integer of 2 or more, but an integer having a number average molecular weight of polyimide (polyamic acid) of 5000 or more is preferable, specifically, 8 to 180, particularly 10 to 100 is preferable. It is.

  Polyimides having repeating units represented by the formulas [1], [2] and [3] described above are alicyclic tetracarboxylic acid dicarboxylic acids represented by the following formulas [7], [8] and [16], respectively. It can be produced by polycondensation reaction of an anhydride compound (including tetracarboxylic acid compound) and a diamine compound (including diamine compound) represented by the following formula [9].

(In the formula, R ⁴ and R ⁵ are the same as above.)

(Wherein R ^{1 to} R ³ and m are the same as above)

In particular, as the alicyclic tetracarboxylic dianhydride compound, tricyclo [4.2.1.0 ^2,5 ] nonane-3-end, 4-end in which R ⁴ is a hydrogen atom in the formula [16] , 7-endo, 8-endo-tetracarboxylic acid-3,4: 7,8-dianhydride (hereinafter abbreviated as TCNDA), 4-oxatetra wherein R ⁵ is a hydrogen atom in formula [8] Cyclo [5.4.0.0 ^2,6 . 1 ^8,11 ] dodecane-3,5-dione-9-spiro-3 ′-(tetrahydrofuran-2 ′, 5′-dione) (hereinafter abbreviated as ODSF) is preferred.

In the polyimide film of the present invention, as long as the physical properties of the polyimide film are not affected, the tetracarboxylic acid compound used for the synthesis of normal polyimide other than the alicyclic tetracarboxylic dianhydride compound described above and its Derivatives may be used simultaneously.
Specific examples thereof include 1,2,3,4-tetracarboxylic acid, 2,3,4,5-tetrahydrofuran tetracarboxylic acid, 1,2,4,5-cyclohexane acid, 3,4-dicarboxy-1 -Cyclohexyl succinic acid, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid, bicyclo [3.3.0] octane-2,4,6,8-tetracarboxylic acid, etc. And alicyclic tetracarboxylic acids and acid dianhydrides thereof, and dicarboxylic acid diacid halides thereof.
Also, pyromellitic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,3,6 , 7-anthracenetetracarboxylic acid, 1,2,5,6-anthracenetetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3,3 ′, 4-biphenyltetracarboxylic acid, Bis (3,4-dicarboxyphenyl) ether, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, bis (3,4-dicarboxyphenyl) methane, 2,2-bis (3,4-di Carboxyphenyl) propane, 1,1,1,3,3,3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) dimethyl Aromatic tetracarboxylic acids such as silane, bis (3,4-dicarboxyphenyl) diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid, 2,6-bis (3,4-dicarboxyphenyl) pyridine And acid dianhydrides thereof, and dicarboxylic acid diacid halides thereof. In addition, these tetracarboxylic acid compounds may be used individually by 1 type, or may be used in mixture of 2 or more types.

  On the other hand, the alicyclic diamine compound represented by the formula [9] is a bis (substituted aminophenoxy) alkylene compound (abbreviated as a BAPA compound), but considering the availability, the formula [13] A 1,5-bis (4-aminophenoxy) pentane (hereinafter abbreviated as DA5MG) compound which is an alicyclic diamine compound represented by the formula:

(In the formula, R ² and R ³ are the same as above.)

  Specific examples of the alicyclic diamine that can be used for the synthesis of the polyimide of the present invention include, but are not limited to, compounds represented by the following formulae.

As for the diamine compound, other diamine compounds may be used as long as the physical properties of the obtained polyimide film are not affected.
Specific examples thereof include p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-. Diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, diaminodiphenylmethane, diaminodiphenyl ether, 2,2′-diaminodiphenylpropane, bis (3,5-diethyl-4-aminophenyl) methane, diaminodiphenyl Sulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, 9,10-bis (4-aminophenyl) anthracene, 1,3 -Bis (4-aminophenoxy) benzene, 4,4'-bis (4- Minophenoxy) diphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, aromatic diamines such as 2,2′-trifluoromethyl-4,4′-diaminobiphenyl, bis (4- Alicyclic diamine compounds such as aminocyclohexyl) methane, bis (4-amino-3-methylcyclohexyl) methane, 4,4′-methylenebis (2-methylcyclohexylamine) and aliphatics such as tetramethylenediamine and hexamethylenediamine A diamine compound etc. are mentioned, These diamine compounds can be used individually by 1 type or in mixture of 2 or more types.

The ratio of the number of moles of all tetracarboxylic dianhydride compounds to the number of moles of all diamine compounds when synthesizing the polyimide of the present invention is preferably 0.8 to 1.2. Similar to the normal polycondensation reaction, the closer the molar ratio is to 1, the higher the degree of polymerization of the polymer produced. If the degree of polymerization is too small, the strength of the polyimide coating film becomes insufficient, and if the degree of polymerization is too large, workability at the time of forming the polyimide coating film may be deteriorated.
Therefore, the degree of polymerization of the product in this reaction is 0.05 to 5.0 dl / g in terms of reduced viscosity of the polyamic acid solution (concentration 0.5 g / g in hexamethylphosphoramide (HMPA) at a temperature of 30 ° C.). dl) is preferred.

Examples of the solvent used in the polyimide synthesis of the present invention include m-cresol, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, N, N-dimethylacetamide (DMAc), and N-methylcapto. Examples include lactam, dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethylphosphoramide (HMPA), and γ-butyrolactone.
Among these, DMAc and NMP are preferable from the viewpoints of polymerizability and colorability. In addition, the said solvent may be used individually by 1 type, or may be used in mixture of 2 or more types.
The temperature of the polycondensation reaction can be selected from -20 to 150 ° C, preferably -5 to 100 ° C.

The flexible polyimide film of the present invention is a polyamic acid (polyimide precursor) solution obtained by polycondensation of tetracarboxylic dianhydride and diamine in a solvent as described above. It can be obtained by dehydration ring closure while evaporating the solvent.
In this case, a polyimide film having a high imidization rate is obtained by using a heating method in which the temperature is increased from 25 ° C. (room temperature) to 160 to 300 ° C. over 2 to 10 hours and then held at 160 to 300 ° C. for 1 to 10 hours. Can be formed. In particular, a heating method in which the temperature is raised from 25 ° C. (room temperature) to 250 ° C. over 2 to 5 hours and then held at about 250 ° C. for 1 to 5 hours is optimal. With this method, the imidization rate is higher, A flexible polyimide film without foaming can be obtained.
The imidation ratio of the polyimide constituting the polyimide film of the present invention is preferably 90% or more, more preferably 95% or more for exhibiting sufficient flexibility, and C = O amide absorption (1650 cm) in the infrared absorption spectrum. It is optimal that it has been imidized to the extent that ^-1 is not confirmed.

Further, the pressure may be reduced during heating. In this case, the degree of reduced pressure is not particularly limited, but is preferably 0.1 MPa to 1 Pa (gauge pressure, the same applies hereinafter), more preferably 1000 to 1 Pa.
After the polyimide film formed on the substrate by the above method is peeled off in warm water or the like, it is dried at 50 to 100 ° C. under normal pressure or reduced pressure to obtain a flexible polyimide film.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to the following Example. The measuring device for each physical property in the examples is as follows.
[1] IR
Apparatus: JASCO FT / IR-460plus manufactured by JASCO Corporation
[2] UV-Vis
Equipment: V-570 type UV-visible spectrophotometer [3] TGA manufactured by JASCO Corporation
Apparatus: Seiko Electronics Co., Ltd. TG / DTA (differential calorific value simultaneous measurement apparatus) 220U
[4] Viscosity device: ELD-50 (E-type viscometer) manufactured by Tokyo Keiki Co., Ltd.
[5] Film thickness meter Apparatus: OZAKI MFG CO. LTD, PEACOCK, DIAL THIKNESS GAUGE

[Example 1] Preparation of TCNDA-DA5MG polyimide film

A dry 30 ml three-necked flask was charged with 0.5300 g (1.851 mmol) of DA5MG and 4.0670 g of dehydrated N, N-dimethylacetamide (hereinafter abbreviated as DMAc) under a nitrogen stream, The mixture was stirred and dissolved with a mechanical stirrer. Subsequently, 0.4818 g (1.837 mmol) of TCNDA was added under a nitrogen stream, and the mixture was stirred at 25 ° C. for 23 hours.
The obtained polymerization solution (polyamic acid) was cast on a glass plate dried with a heat gun for 15 minutes, and heated under reduced pressure (degree of vacuum 100 to 500 Pa) at 250 ° C. for 3 hours (from 25 ° C. (room temperature) to 2 hours of temperature increase). The glass film was immersed in hot water and the polyimide film was peeled off.
The film was sandwiched between filter papers and dried in an oven at 60 ° C. for 3 hours to obtain a colorless and transparent polyimide film. The thickness of the film was 15 μm.

From the infrared absorption spectrum of the film (see FIG. 1), C═O stretching vibration of imide carbonyl was observed at 1773 cm ⁻¹ and 1705 cm ^−1, and C—N stretching vibration of an imide structure was confirmed at 1387 cm ⁻¹ .
Further, since no C═O amide absorption was observed in the vicinity of 1650 cm ⁻¹ , it was judged that imidization proceeded almost completely.
The UV-Vis spectrum of the obtained film showed a light transmittance of 80% at 350 nm (see FIG. 5).

The thermal characteristics (under a nitrogen atmosphere) and the viscosity were as follows.
5% weight loss temperature (T ₅ ): 408.5 ° C
10% weight loss temperature (T ₁₀ ): 438.1 ° C
Decomposition temperature ( _Td ): 441.1 ° C
Glass transition temperature (T _g): 258.5 ℃
Polyamic acid intrinsic viscosity (25 ° C.): 0.59 (dL / g) (solvent HMPA)

[Example 2] Production of ODSF-DA5MG polyimide film

DA5MG 0.4785 g (1.671 mmol) and dehydrated DMAc 3.765 g (solid content 20% by mass) were charged in a dry 30 ml three-necked flask under a nitrogen stream and dissolved by stirring with a mechanical stirrer. Subsequently, 0.4624 g (1.673 mmol) of ODSF was added under a nitrogen stream, and the mixture was stirred at 25 ° C. for 24 hours.
The obtained polymerization solution (polyamic acid) was brown because unpurified DA5MG was used. The obtained polymerization solution was cast on a glass plate dried for 15 minutes with a heat gun, and heated under reduced pressure (degree of vacuum 100 to 500 Pa) at 250 ° C. for 3 hours (from 25 ° C. (room temperature) to 2 hours, 250 ° C. heat retention 1 Time), the polyimide film was peeled off by immersing the glass plate in hot water.
The film was sandwiched between filter papers and dried in an oven at 60 ° C. for 3 hours to obtain a colorless and transparent polyimide film. The film thickness was 18 μm.
Infrared absorption spectrum (see FIG. 2) from 1775 cm ^-1 and 1700 cm ^-1 and the C = O stretching vibration of an imide carbonyl of the film, C-N stretching vibration of an imide structure to 1390 cm ^-1 was confirmed.
Further, since no C═O amide absorption was observed in the vicinity of 1650 cm ⁻¹ , it was judged that imidization proceeded almost completely.
The UV-Vis spectrum of the obtained film showed a light transmittance of 85% at 350 nm (see FIG. 6).

The thermal characteristics (under a nitrogen atmosphere) and the viscosity were as follows.
5% weight loss temperature (T ₅ ): 403.5 ° C
10% weight loss temperature (T ₁₀ ): 432.0 ° C
Decomposition temperature ( _Td ): 437.5 ° C
Polyamic acid intrinsic viscosity (25 ° C.): 0.81 (dL / g) (solvent HMPA)

Table 1 shows the results of a tensile test performed on the polyimide films obtained in Examples 1 and 2 by the following method.
[Tensile test method]
As shown in FIG. 7, the test piece B was adhered to the mount (printing paper) D using the adhesive C (Aron Alpha (registered trademark) jelly, manufactured by Toagosei Co., Ltd.) (filled portion in FIG. 7), Both ends of the photographic paper B in the longitudinal direction are attached to the test chuck with cellophane tape A (Cello Tape (registered trademark), manufactured by Nichiban Co., Ltd.) (the hatched portion in FIG. 7) and pulled outward in the longitudinal direction at a pulling speed of 1 mm / min. It was.

2 is an infrared absorption spectrum of TCNDA-DA5MG polyimide obtained in Example 1. 2 is an infrared absorption spectrum of ODSF-DA5MG polyimide obtained in Example 2. 2 is a photograph of a TCNDA-DA5MG polyimide film obtained in Example 1. 2 is a photograph of an ODSF-DA5MG polyimide film obtained in Example 2. 2 is a UV-Vis spectrum of TCNDA-DA5MG polyimide obtained in Example 1. FIG. 2 is a UV-Vis spectrum of ODSF-DA5MG polyimide obtained in Example 2. FIG. It is the schematic which shows the tensile test method of a polyimide film.

Explanation of symbols

A Cellophane tape B Test piece C Adhesive D Mount (Printing paper)

Claims (9)

A flexible polyimide film comprising a repeating unit represented by the formula [1] or [2] and having an imidization ratio of 90% or more.
(In the formula, R ¹ represents an alkylene group having 1 to 10 carbon atoms or a haloalkylene group having 1 to 10 carbon atoms, and R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, carbon A C 1-10 alkyl group, a halogen atom, or a C 1-10 haloalkyl group, m represents an integer of 1-20, and n represents an integer of 2 or more.) The flexible polyimide film according to claim 1, wherein the repeating unit of the formula [1] is represented by the formula [3].
(Wherein R ¹ , R ² , R ³ , R ⁴ , m and n represent the same meaning as described above.)   The flexible polyimide film according to claim 1, wherein m is 5 in the formulas [1] and [2].   The flexible polyimide film according to claim 2, wherein m is 5 in the formula [3].   The flexible polyimide film according to claim 1, wherein the imidization ratio is 95% or more. The polyamic acid composed of the repeating unit represented by the formula [10] or [11] is heated from 25 ° C. to 160 to 300 ° C. over 2 to 10 hours, and then held at 160 to 300 ° C. for 1 to 10 hours. The method for producing a flexible polyimide film according to claim 1, wherein ring-immobilization is performed.
(In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , m and n have the same meaning as described above.) The method for producing a flexible polyimide film according to claim 6, wherein the repeating unit of the formula [10] is represented by the formula [12].
(Wherein R ¹ , R ² , R ³ , R ⁴ , m and n represent the same meaning as described above.)   In the said Formula [10] and [11], m is 5, The manufacturing method of the flexible polyimide film of Claim 6.   In the said Formula [12], m is 5, The manufacturing method of the flexible polyimide film of Claim 7.