JPH05320111A - Curable imide oligomer - Google Patents

Abstract

PURPOSE:To obtain a new curable imide oligomer industrially useful as laminate, heat-resistant coating compound, polymer material for electronic device, molding material, etc., having high heat resistance, excellent mechanical strength, dimensional stability, moisture resistance and processability. CONSTITUTION:A curable imide oligomer of formula I (Ar1 is tetrafunctional aromatic group; Ar2 is bifunctional aromatic group; X is group of formula II to formula IV; n is 0-15; R is substituent group having reactivity). A telechelic oligomer containing acid anhydride groups as both end groups among the oligomer is produced by dissolving compounds of formula V to formula VI (Y1 to Y4 are H or 1-5C alkyl; Ar is tetrafunctional aromatic group) in a polar organic solvent in a reactor in a sufficiently dried inert gas atmosphere such as argon or nitrogen and adding a compound of the formula H2N-Ar2-NH2 and/or a compound of formula VII (Ar3 is bifunctional organic group) as a solution dissolved in the same solvent or powder to the above-mentioned solution while taking care of heat generation or thickening.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel curable oligomer. More specifically, the present invention relates to an imide oligomer having excellent heat resistance, good solubility in an organic solvent, and a polyimide having reactivity suitable for lamination and molding.

[0002]

2. Description of the Related Art Thermosetting resins are used for various electrical insulating materials such as casting, impregnation, lamination, and molding materials.
It is used as a structural material. In recent years, the usage conditions of materials have become more and more severe in each of these uses, and in particular, the heat resistance of materials has become an important characteristic. Thermosetting polyimide resins and heat resistant epoxy resins have been conventionally used for applications requiring heat resistance. Among them, as the thermosetting polyimide resin, kelimide containing a combination of a bismaleimide compound and diaminodiphenylmethane as a main component is used [Matsuo Fujisawa, Plastics, Vol. 34, No. 7, p. 75, 1983].

Recently, for example, a thermosetting polyimide in which 3-aminophenylacetylene is used as a primary amine and the terminal is terminated is put on the market as thermid (Hughes Aircraft, JP-A-50-5348, etc.). Several methods for the synthesis of 3-aminophenylacetylene used herein (eg USP 4,125,563)
However, all of them have the problems that the synthetic route is long and the synthetic reagents are expensive. Also,
A thermosetting polyimide in which the end is terminated using propargylamine as a primary amine has also been proposed (Ube Industries, Ltd., JP-A-2-284923, JP-A-3-174).
427). However, it is known that the thermal reaction initiation temperature of the propargyl group is as high as 250 ° C., and the imide oligomer using this as a reactive group also has a high curing temperature and is inferior in terms of processability [“Polymer Engineering Science”]. (Polym. Eng. Sci.) ", 22 (1),
9-14 (1982)]. Further, generally, polyimide resins have poor moisture absorption resistance, and it has been pointed out that dimensional stability in the processing step is a problem.

[0004]

SUMMARY OF THE INVENTION The present inventors have arrived at the present invention as a result of intensive investigations in order to solve these technical problems in view of the above circumstances. That is, the present invention has the general formula (1)

[0005]

[Chemical 7]

(In the formula, Ar ₁ is a tetravalent aromatic group, Ar ₂
Represents a divalent aromatic group. Ar ₁ and Ar ₂ may be the same or different. Further, in the formula, X is a trivalent bond mode as shown below.

[0007]

[Chemical 8]

[0008] It is selected from among the same kind or different kinds. n is selected from 0 to 15. R is a reactive substituent. ) Is contained in the curable imide oligomer.

First, the method for producing the thermosetting oligomer of the present invention will be described. In an atmosphere of an inert gas such as argon or nitrogen in which the reaction tank is sufficiently dried, the general formula (2)

[0010]

[Chemical 9]

An acid dianhydride represented by the formula (wherein Ar ₁ is a tetravalent aromatic group) or a general formula (3)

[0012]

[Chemical 10]

An acid dianhydride derivative represented by the formula
Y ₁ , Y ₂ , Y ₃ , and Y ₄ are hydrogen, an alkyl group selected from C1 to 5, and Ar ₁ is a tetravalent aromatic group. ) Is dissolved in a polar organic solvent, and the organic diamine compound represented by the general formula (4) is dissolved in the solution.

H ₂ N--Ar ₂ --NH ₂ (4)

(Wherein Ar ₂ is a divalent organic group) and /
Or general formula (5)

[0016]

[Chemical 11]

(Wherein Ar ₃ is a divalent organic group) is dissolved in the same polar solvent as described above, or is added as a powder while paying attention to heat generation and thickening, and both ends are acid anhydrides. A base telechelic oligomer is obtained. The reaction temperature at this time is preferably in the range of -15 to 120 ° C, preferably -15 to 100 ° C, and more preferably -5 to 50 ° C. The reaction time is preferably about 1 to 5 hours. 1 having a thermosetting group represented by the general formula (6) in this reaction solution.
Class amine

[0018]

[Chemical 12]

(In the formula, R is a reactive substituent.) Is added to terminate the above oligomer terminal to obtain an oligoamic acid solution which is a precursor of a reactive imide oligomer. The reaction temperature at this time is preferably 0 to 120 ° C, preferably 0 to 100 ° C, and more preferably 40 to 100 ° C. The reaction time is preferably about 1 to 5 hours. After that, the polyamic acid solution is thermally closed.
After adding a non-solvent for dehydration, it is converted to polyimide under reflux and azeotropy. As the non-solvent used here, aromatic hydrocarbons such as xylene and toluene can be used, but toluene is preferably used. In the reaction, azeotropically distilled water is refluxed using a Dean-Stark reflux device until a theoretical amount of water is collected. The dehydration ring closure reaction to this imide structure can also use the chemical ring closure method together. After the reaction, the polyimide solution is poured into water or an alcohol solvent with vigorous stirring to precipitate the polyimide as a powder. The powder is collected by filtration and then dried at 80 ° C. under reduced pressure for 48 hours.

As the organic tetracarboxylic dianhydride used in the present invention, organic tetracarboxylic dianhydrides having any structure can be used, and the above-mentioned general formula (2),
Those represented by (3) are preferable, and the Ar ₁ group is a tetravalent organic group, and preferably an aromatic group. This Ar
Specific examples of _one group include the following.

[0021]

[Chemical 13]

[0022]

[Chemical 14]

Preferably, at least one of the following is selected.

[0024]

[Chemical 15]

The diamine represented by the general formula (5) used in the present invention can be synthesized, for example, by the following reaction.

[0026]

[Chemical 16]

That is, the general formula (7) corresponding to nitrobenzoic acid or derivative

HO-Ar ₃ --OH (7)

A diol represented by the formula (wherein Ar ₃ represents a divalent aromatic group) is obtained in the presence of a tertiary amine catalyst to obtain a dinitro compound, and then the nitro group is converted to an amino group by a reduction catalyst. It is obtained by doing. Ar ₃ of the diol of the general formula (7) used here is essentially any divalent organic group, but specifically,

[0030]

[Chemical 17]

[0031]

[Chemical 18]

Can be illustrated. An aromatic group is particularly desirable, and specifically,

[0033]

[Chemical 19]

It is preferable to use at least one of the above as a main component. Further, Ar _{2 of the} diamine compound represented by the general formula (4) can be essentially any divalent organic group, but specifically,

[0035]

[Chemical 20]

[0036]

[Chemical 21]

Can be illustrated. In particular, an aromatic group is desirable and specifically,

[0038]

[Chemical formula 22]

It is preferable that at least one of the above is used as a main component. As an example of the reactive functional group R represented by the general formula (6) used in the present invention for terminal termination,

[0040]

[Chemical formula 23]

From the viewpoint of cost and handling, it is preferable that

[0042]

[Chemical formula 24]

It is Examples of the organic solvent used in the reaction for producing a polyamic acid solution include, for example, dimethyl sulfoxide, sulfoxide-based solvents such as diethyl sulfoxide,
Examples thereof include formamide solvents such as N, N′-dimethylformamide and N, N′-diethylformamide, acetamide solvents such as N, N′-dimethylacetamide and N, N′-diethylacetamide. These may be used alone or as a mixed solvent of two or more kinds. Further, it can be used as a mixed solvent with a non-solvent of polyamic acid such as methanol, ethanol, isopropanol, benzenemethylcellosolve, etc. together with these polar solvents.

The oligomer of the present invention may be used in combination with so-called B-stage formation, if necessary. B-stage conversion is 100 ° C. or higher, preferably 15
0 ° C or higher, more preferably 200 ° C or higher, 1 minute or longer,
It is preferable that the heating is performed for 5 minutes or more under hot air circulation or under vacuum.

Although the mechanism for the highly heat-resistant polyimide having reactivity according to the present invention is not clear, formation of a benzene skeleton by thermosetting acetylene / acetylene or [3,3] sigmatropy of propargyl ether. It is said that the effect is due to the formation of a chromene skeleton by transition / polymerization by ring-opening thermosetting [eg, 3rd International Samppi Electric Conference (3rd. Int.SAMPE Elect. Conf.) 169, 1989. , Dow Chemical., JP-A-2-8527
5]. In addition, the number average degree of polymerization (Principles of Polymer Chemis
try) page 91, 1953], the degree of polymerization n is 0 to 30, preferably 0 to 20, and more preferably 1 to 15. When it is more than that, solubility in organic solvent is lowered, and when it is less than that, there arises a problem in mechanical strength.

When obtaining a thermosetting resin from the thermosetting oligomer of the present invention, if necessary, an epoxy resin or epoxy resin curing agent, a curing accelerator, a filler, a flame retardant, a reinforcing agent, a surface treatment agent, a pigment. The various elastomers can be used alone or in combination of two or more. These thermosetting resins are not limited in their usage and can be applied in various modes. Among them, electric laminates, so-called PWB
It can also be used as a matrix resin for (printed wiring board). When used for PWS applications, various fillers and reinforcing agents can be used. Examples of the filler include aluminum hydroxide, antimony trioxide, red phosphorus and the like. As the reinforcing material, carbon fiber, glass fiber, aramid fiber, liquid crystal polyester fiber such as Vectra, polybenzothiazole (PBT) fiber, woven fabric made of alumina fiber, etc., non-woven fabric, mat, paper (paper) or a combination thereof. Can be illustrated.

[0047]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples, and the present invention is within the scope of the invention. The present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

Reference Example 1 Synthesis of 4-nitrophenyl-1-propargyl ether A 500 ml three-necked flask was equipped with a 200 ml dropping funnel, a three-way cock, and a seal cap, dried under reduced pressure and replaced with argon, and then 8.0 g ( 0.2 mol) of sodium hydroxide was dissolved in 200 ml of water and charged into a reactor. After adding 27.82 g (0.2 mol) of 4-nitrophenol and 6.45 g (0.2 mol) of tetra-n-butylammonium bromide, 23.79 g (15.1 ml, 0.2 mol) of propargyl was added from the dropping funnel. Bromide was added over about 30 minutes, the mixture was reacted at 80 ° C. for 4 hours, and then stirred overnight at room temperature. The precipitated crystals were separated by filtration and recrystallized from toluene to obtain 30.0 g (yield: 92.0%) of 4-nitrophenyl-1-propargyl ether.

[Elemental analysis value] Calculated value: C; 61.02, H; 3.95, N; 7.9
1. Found: C; 59.82, H; 4.04, N; 7.7.
2. [Spectral data] IR (neat, cm ⁻¹ ) ν = 3600-3000, 30
00, 2950, 1620, 1600, 1580, 14
95, 1450, 1350, 1295, 1220, 11
60,990,905,860,780,735,69
0. ¹ H-NMR (chloroform-d, ppm) δ = 3.
6 (tr., 1H) 5.7 (d., J = 2.0 Hz, 2
H), 7.1 & 8.2 (dd., J = 6.0 Hz, 8
H)

Reference Example 2 Synthesis of 4-nitrophenyl-1-allyl ether The procedure of Reference Example 1 was repeated except that 23.79 g of propargyl bromide was changed to 24.79 g (17.1 ml, 0.2 mol) of allyl bromide. 30.9 g (yield: 9
(4.2%) of 4-nitrophenyl-1-allyl ether was obtained.

[Elemental analysis value] Calculated value: C; 60.34, H; 5.03, N; 7.8
2. Found: C; 59.75, H; 5.08, N; 8.0.
2. [Spectral data] IR (neat, cm ⁻¹ ) ν = 3600-3000, 30
00, 2950, 1620, 1600, 1580, 14
95, 1450, 1350, 1295, 1220, 11
60,990,905,860,780,735,69
0. ¹ H-NMR (chloroform-d, ppm) δ = 3.
8 (d., J = 2.0 Hz, 2H), 5.1 (m., 2)
H), 5.9 (m, 1H), 7.9 (m.4H)

Reference Example 3 Synthesis of 4-aminophenyl-1-propargyl ether: A 500 ml three-necked flask was equipped with a 200 ml dropping funnel, a three-way cock and a seal gap, dried under reduced pressure and replaced with argon, and then 26.91 g ( 0.16 mol of 4-nitrophenyl-1-propargyl ether synthesized in Reference Example 1 and 270 ml of dioxane were charged into a reaction vessel. 260.49 g (1.16 mol) of tin chloride and 2
70 ml of concentrated hydrochloric acid was added dropwise over 2 hours under ice cooling. The reaction solution was stirred under ice cooling for 1 hour and then added dropwise to 1 liter of a 10 wt% sodium hydroxide aqueous solution. After filtering out the precipitated tin hydroxide, the filtrate was extracted from methylene chloride. After dehydration and filtration, the solvent was distilled off and the precipitated crystals were separated by filtration and recrystallized from toluene. 20.12g
(Yield; 89.2%) of 4-aminophenyl-1-propargyl ether was obtained.

[Elemental analysis value] Calculated value: C; 73.46, H; 6.12, N; 9.5
2. Found: C; 73.85, H; 5.98, N; 9.8.
6. [Spectral data] IR (neat, cm ⁻¹ ) ν = 3600-3000, 30
00, 2950, 1620, 1600, 1580, 14
95, 1450, 1350, 1295, 1220, 11
60,990,905,860,780,735,69
0. ¹ H-NMR (chloroform-d, ppm) δ = 2.
5 (tr., 1H), 3.5 (br.s., 2H),
4.75 (d., J = 1.2 Hz, 1H), 6.7
(M., 4H)

Reference Example 4 Synthesis of 4-aminophenyl-1-allyl ether 4-nitrophenyl-1-propargyl ether 26.
91 g (0.16 mol) to 23.67 g (0.14 mol)
l) was replaced with 4-nitrophenyl-1-allyl ether synthesized in Reference Example 2 and the same procedure as Reference Example 3 was performed to obtain 21.62 g (yield; 93.2%) of 4-aminophenyl 1-allyl ether was obtained.

[Elemental analysis value] Calculated value: C; 80.74, H; 5.81, N; 13.4
5. Found: C; 80.53, H; 5.98, N; 13.8.
1. [Spectral data] IR (neat, cm ⁻¹ ) ν = 3600-3000, 30
00, 2950, 1620, 1600, 1580, 14
95, 1450, 1350, 1295, 1220, 11
60,990,905,860,780,735,69
0. ¹ H-NMR (chloroform-d, ppm) δ = 3.
5 (tr., 1H), 4.2 (br.s., 2H),
5.15 (d., J = 1.2 Hz, 1H), 6.7
(M., 4H)

Reference Example 5 2,2-bis (4-nitrobenzoyloxyphenyl)
Propane reflux condenser, thermometer, stirrer, dropping funnel attached 1
In a 4-liter 4-neck flask, 360 ml of dry pyridine, 3
71 g (2 mol) of p-nitrobenzoyl chloride and 457 g (2 mol) of bisphenol A were charged, and the atmosphere was replaced with nitrogen. The mixture was reacted under heating under reflux for 3 hours. The reaction solution was poured into 2 liters of ice water, and the precipitated solid was filtered and dried. Recrystallized from toluene to give 697 g (89.6).
%) 2,2-bis (4-nitrobenzoyloxyphenyl) propane was obtained. [Elemental analysis value] Calculated value: C; 65.37, H; 4.28, N; 5.4
5. Found: C; 65.05, H; 4.38, N; 5.6.
5.

Reference Example 6 2,2-bis (4-aminobenzoyloxyphenyl)
Propane reflux condenser, thermometer, stirrer, dropping funnel attached 1
To a liter 4-necked flask, 500 ml of ethanol was added, 148.4 (0.25 mol) of the dinitro compound obtained in Reference Example 5 was dispersed, and 10% by weight of supported palladium-activated carbon (2.5 g) was added. 66g from dropping funnel
(1.05 mol) of hydrazine was added over 30 minutes while paying attention to rapid reflux, and then reflux was continued for 3 hours. After the reaction, the precipitate was removed by filtration, the filtrate was concentrated with an evaporator, and recrystallized from ethanol. 111.5 g (yield 86.7%) of 2,2-bis (4-aminobenzoyloxyphenyl) propane was obtained. [Elemental analysis value] Calculated value: C; 74.01, H; 5.73, N; 6.1
7. Found: C; 73.84, H; 5.83, N; 6.5.
1.

[0058]

Example 1 A 500-ml three-necked flask was equipped with a 200-ml dropping funnel, a three-way cock and a seam cap, and dried under reduced pressure.
The atmosphere was replaced with argon. After charging 6.44 g (0.022 mol) of benzophenonetetracarboxylic dianhydride into the reactor, 150 ml of dimethylformamide (DMF) was added. 1.47 g (0.005 mol) of 1,3-bis (3-aminophenoxy) benzene and 2.23 g
(0.005 mol) of 2,2-bis (4) obtained in Reference Example 6
30 ml of -aminobenzoyloxyphenyl) propane
After being dissolved in DMF, the solution was introduced into the reactor through the dropping funnel. After stirring at 80 ° C. for 2 hours, 2.75 g (0.
02 mol) of 4-aminophenyl-1-obtained in Reference Example 4
Allyl ether was dissolved in 20 ml of DMF and added. After the reaction temperature of the obtained oligoamic acid was returned to room temperature, 11 ml of acetic anhydride and 10 ml of pyridine were added, and the mixture was chemically dehydrated and cyclized to obtain an imide oligomer having the following structure.

[0060]

[Chemical 25]

After the reaction, the reaction solution was poured into 1 liter of methanol to precipitate the produced imide oligomer. Filter under reduced pressure with an aspirator, in vacuum at 80 ° C
When dried for 48 hours at 11.9 g (yield; 97.
The oligomer was obtained as a pale yellow powder (5%).

[Spectral Data] IR (neat, cm ⁻¹ ) ν = 3000, 2950, 17
80, 1750, 1700, 1620, 1600, 15
80, 1495, 1450, 1350, 1295, 12
20, 1160, 990, 905, 860, 780, 7
35,690.

When the oligomer was B-staged by melting and defoaming in a vacuum oven at 220 ° C., it became a reddish brown powder. Using 8.3 g of B-staged imide oligomer, 220 ° C. for 20 minutes, 250 ° C. for 30 minutes
Min., 270 ° C., 1 hour, pressed under contact pressure, having a density of 1.39 g / cm ³ 12 mm (width) × 12 cm (length)
A cast plate of × 3.4 mm (thickness) was obtained. This casting plate is 5
A flexural strength of 8.8 kg / mm ^2, and the flexural modulus of 315 kg / mm ^2, and impact strength of 35Kg · cm / cm ^2, was a resin having a glass transition temperature of 253 ℃ (Tg). The moisture absorption rate was 0.27% (C-96 / 20/65).

Example 2 Instead of 1.47 g (0.005 mol) of 1,3-bis (3-aminophenoxy) benzene, 0.54 g (0.
005 mol) of metaphenylenediamine and 2.75 g (0.02 mol) of 4-aminophenyl-1.
-In the same manner as in Example 1 except that 4-aminophenyl-1-propargyl ether obtained in Reference Example 3 was used instead of the allyl ether, an imide oligomer having the following structure was obtained.

[0065]

[Chemical formula 26]

[Spectral Data] IR (neat, cm ⁻¹ ) ν = 3000, 2950, 17
80, 1750, 1700, 1620, 1600, 15
80, 1495, 1450, 1350, 1295, 12
20, 1160, 990, 905, 860, 780, 7
35,690.

When the oligomer was B-staged by melting and defoaming in a vacuum oven at 220 ° C., it became a reddish brown powder. Using 8.9 g of B-staged imide oligomer, 220 ° C. for 20 minutes, 250 ° C. for 30 minutes
Min., 270 ° C., 1 hour, pressed under contact pressure, having a density of 1.36 g / cm ³ 12 mm (width) × 12 cm (length)
A cast plate of × 3.8 mm (thickness) was obtained. This casting plate is 3
A flexural strength of 8.8 kg / mm ^2, and the flexural modulus of 425 kg / mm ^2, and impact strength of 30Kg · cm / cm ^2, was a resin having a glass transition temperature of 239 ℃ (Tg). The moisture absorption rate was 0.18% (C-96 / 20/65).

Example 3 Instead of 1.47 g (0.005 mol) of 1,3-bis (3-aminophenoxy) benzene, 1.06 g (0.
005 mol) of diaminobenzophenone,
An imide oligomer having the following structure was obtained in the same manner as in Example 1 except that 4-aminophenyl-1-propargyl ether obtained in Reference Example 3 was used instead of -aminophenyl-1-allyl ether.

[0069]

[Chemical 27]

[Spectral Data] IR (neat, cm ⁻¹ ) ν = 3000, 2950, 17
80, 1750, 1700, 1620, 1600, 15
80, 1495, 1450, 1350, 1295, 12
20, 1160, 990, 905, 860, 780, 7
35,690.

When the oligomer was B-staged by melting and defoaming in a vacuum oven at 220 ° C., it became a reddish brown powder. Using 7.5 g of B-staged imide oligomer, 220 ° C. for 20 minutes, 250 ° C. for 30 minutes
Min., 270 ° C, 1 hour, pressed under contact pressure, having a density of 1.37 g / cm ³ 12 mm (width) x 12 cm (length)
A cast plate of x 3.2 mm (thickness) was obtained. This casting plate has 4
A flexural strength of 6.8 kg / mm ^2, and the flexural modulus of 315 kg / mm ^2, and impact strength of 22Kg · cm / cm ^2, was a resin having a glass transition temperature of 248 ℃ (Tg). The moisture absorption rate was 0.23% (C-96 / 20/65).

Comparative Example Using 9.2 g of a commercially available imide type thermosetting oligomer, 220 ° C. for 20 minutes, 250 ° C. for 30 minutes, 270 ° C.
Pressed under contact pressure for 1 hour, density 1.35g / cm ³
12mm (width) × 12cm (length) × 3.5mm (thickness)
To obtain a casting plate. The cast plate has a flexural strength of 38.2Kg / mm ^2, and a flexural modulus 261Kg / mm ^2, 18Kg · cm
/ Cm ² impact strength and glass transition temperature (T
g)). Moisture absorption rate is 0.75% (C-
96/20/65).

[0073]

INDUSTRIAL APPLICABILITY The thermosetting oligomer having reactivity according to the present invention can provide a cured product having excellent processing characteristics and extremely high heat resistance which has never been obtained. Furthermore, the thermosetting oligomer having reactivity according to the present invention has excellent mechanical strength, dimensional stability, electrical properties, etc., and in particular, it is possible to provide a polyimide in which voids and cracks are less likely to occur in molded articles. it can. As described above, since the reactive oligomer of the present invention has many characteristics, it has a very high industrial value in a wide range of applications such as laminates, heat resistant coatings, polymer materials for electronic devices and molding materials. Can be provided, and its usefulness is extremely large.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 7, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Delete

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0065

[Correction method] Delete

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Delete

Claims (5)

[Claims] 1. A compound represented by the general formula (1): (In the formula, Ar ₁ represents a tetravalent aromatic group and Ar ₂ represents a divalent aromatic group. Ar ₁ and Ar ₂ may be the same kind or different kinds. , X is a trivalent bond, and is shown below. And may be the same or different. n is selected from 0 to 15. R is a reactive substituent. ) The curable imide oligomer represented by. _{2. At} least 2 mol% or more of Ar ₂ has the following structure: The imide oligomer according to claim 1, having Ar ₃ (wherein Ar ₃ represents a divalent aromatic group). 3. The imide oligomer according to claim 1, wherein Ar ₁ is at least one selected from the following. [Chemical 4] 4. The imide oligomer according to claim 2, wherein Ar ₃ is at least one selected from the following. [Chemical 5] 5. The imide oligomer according to claim 1, wherein R is at least one selected from the following. [Chemical 6]