POLYIMIDE COPOLYMER AND MOLDED ARTICLE USING SAME

Abstract

An object of the present invention is to provide a polyimide copolymer excelling in solder heat resistance and an adhesive property, and a molded article thereof. A polyimide copolymer is obtained by copolymerizing: (A) an acid dianhydride ingredient; (B) a diamine and/or diisocyanate ingredient represented by the following general formulas (1) to (3):

##STR00001##

where in the formulas, X is an amino group or an isocyanate group, each of R.sup.1 to R.sup.8 is independently a hydrogen atom, an alkyl group having a carbon number of 1 to 4, an alkenyl group having a carbon number of 2 to 4 or an alkoxy group having a carbon number of 1 to 4, at least one of R.sup.1 to R.sup.4 is not a hydrogen atom, and at least one of R.sup.5 to R.sup.8 is not a hydrogen atom; and (C) a diamine and/or diisocyanate ingredient having at least one kind selected from an ether group and a carboxyl group.

Claims

1. A polyimide copolymer obtained by copolymerizing: (A) an acid dianhydride ingredient; (B) a diamine and/or diisocyanate ingredient each represented by one of the following general formulas (1) to (3): ##STR00032## where, in the formulas, X is an amino group or an isocyanate group, each of R.sup.1 to R.sup.8 is independently a hydrogen atom, an alkyl group having a carbon number of 1 to 4, an alkenyl group having a carbon number of 2 to 4 or an alkoxy group having a carbon number of 1 to 4, at least one of R.sup.1 to R.sup.4 is not a hydrogen atom, and at least one of R.sup.5 to R.sup.8 is not a hydrogen atom; and (C) a diamine and/or diisocyanate ingredient having at least one kind selected from an ether group and a carboxyl group.

2. The polyimide copolymer according to claim 1, wherein the ingredient (A) is at least one kind selected from 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride, 4,4′-oxydiphthalic acid dianhydride, pyromellitic acid dianhydride, 4,4′-[propane-2,2-diyl bis(1,4-phenyleneoxy)]diphthalic acid dianhydride.

3. The polyimide copolymer according to claim 1, obtained by further copolymerizing a diamine and/or diisocyanate different from the ingredient (B) and the ingredient (C) as an ingredient (D).

4. A polyimide copolymer having a structural unit represented by the following general formula (101) and a structural unit represented by the following general formula (102): ##STR00033## where, in the formulas, W and Q are tetravalent organic groups derived from acid dianhydrides, and W and Q may be the same or different, in the formula (101), B is a divalent organic group derived from a diamine and/or diisocyanate compound each represented by one of the following general formulas (1) to (3): ##STR00034## in the formulas (1), (2) and (3), X is an amino group or an isocyanate group, each of R.sup.1 to R.sup.8 is independently a hydrogen atom, an alkyl group having a carbon number of 1 to 4, an alkenyl group having a carbon number of 2 to 4 or an alkoxy group having a carbon number of 1 to 4, at least one of R.sup.1 to R.sup.4 is not a hydrogen atom, and at least one of R.sup.1 to R.sup.8 is not a hydrogen atom, in the formula (102), C is a divalent organic group derived from a diamine and/or diisocyanate compound having at least one kind selected from an ether group and a carboxyl group.

5. The polyimide copolymer according to claim 4, further having a structural unit represented by the following general formula (103): ##STR00035## where, in the formula, T is a tetravalent organic group derived from an acid dianhydride, and T may be the same as or different from W and Q, and where, in the formula (103), D is a divalent organic group derived from a diamine and/or diisocyanate compound different from both B in the formula (101) and C in the formula (102).

6. A molded article comprising the polyimide copolymer according to claim 1.

7. The polyimide copolymer according to claim 2, obtained by further copolymerizing a diamine and/or diisocyanate different from the ingredient (B) and the ingredient (C) as an ingredient (D).

8. A molded article comprising the polyimide copolymer according to claim 2.

9. A molded article comprising the polyimide copolymer according to claim 3.

10. A molded article comprising the polyimide copolymer according to claim 4.

11. A molded article comprising the polyimide copolymer according to claim 5.

Description

EXAMPLES

[0090] The polyimide copolymer and the molded article thereof of the present invention are explained with reference to Examples, but the polyimide copolymer and the molded article thereof of the present invention are not limited to these Examples.

Example 1

[0091] In a 500 mL-four neck separable flask equipped with an anchor-type stirrer made of stainless, a nitrogen introduction pipe, and Dean-Stark equipment, 37.23 g (0.12 moles) of 4,4′-oxydiphthalic dianhydride (ODPA), 7.13 g (0.04 moles) of DETDA, 23.76 g (0.08 moles) of 3,3′-(m-phenylenedioxy)dianiline (APB-N), 148.85 g of N-methyl-2-pyrolidone (NMP), 1.90 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under nitrogen flow. Water generated by the reaction was removed from the reaction system by azeotropic distillation with toluene.

[0092] A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 1. In the tables, “Ex.” stands for “Example”, “Com. Ex.” stands for “Comparative example”, and “n/a” stands for “not available” or “unmeasurable.”

[0093] After completion of the reaction, the reaction system was cooled to 120° C., and then 42.53 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (23). Here, two kinds of divalent organic groups represented by the following X are present in one molecule of the polyimide copolymer represented by the following structural formula. That is, the obtained polyimide copolymer comprises a unit represented by a general formula (30) which is shown in Comparative Example 1 and a unit represented by a general formula (31) which is shown in Comparative Example 2, each mentioned below.

##STR00019##

[0094] where, in the formula, R is a methyl group or an ethyl group.

Example 2

[0095] In an apparatus as used in Example 1, 35.31 g (0.12 moles) of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA), 10.70 g (0.06 moles) of DETDA, 81.42 g of NMP, 2.85 g of pyridine, and 50 g of toluene were put into. After having purged the reaction system with nitrogen, the reactants were heated and stirred for 2 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed from the reaction system by azeotropic distillation with toluene.

[0096] Next, 17.65 g (0.06 moles) of BPDA, 35.62 g (0.12 moles) of APB-N, and 135.10 g of NMP were added to the reaction system, and then reacted by heating at 180° C. for five and half hours while stirring. Water generated by the reaction was removed from the reaction system by azeotropic distillation with toluene and pyridine. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 1.

[0097] After completion of the reaction, the reaction system was cooled to 120° C., and then 61.68 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (24).

##STR00020##

[0098] where, in the formula, R is a methyl group or an ethyl group.

Example 3

[0099] In an apparatus as used in Example 1, 35.31 g (0.12 moles) of BPDA, 7.13 g (0.04 moles) of DETDA, 23.75 g of APB-N, 144.34 g of NMP, 1.90 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed from the reaction system by azeotropic distillation with toluene. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 1.

[0100] After completion of the reaction, the reaction system was cooled to 120° C., and then 41.24 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (25). Here, two kinds of divalent organic groups represented by the following X are present in one molecule of the polyimide copolymer represented by the following structural formula. That is, the obtained polyimide copolymer comprises a unit represented by a general formula (32) which is shown in Comparative Example 3 and a unit represented by a general formula (33) which is shown in Comparative Example 4, each mentioned below.

##STR00021##

[0101] where, in the formula, R is a methyl group or an ethyl group.

Example 4

[0102] In an apparatus as used in Example 1, 44.13 g (0.15 moles) of BPDA, 31.05 g (0.1 moles) of 4,4′-methylene bis(2,6-diethyl aniline) (M-DEA), 15.12 g (0.05 moles) of APB-N, 157.65 g of NMP, 2.37 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed from the reaction system by azeotropic distillation with the toluene. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 2.

[0103] After completion of the reaction, the reaction system was cooled to 120° C., and then 97.02 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (26). Here, two kinds of divalent

##STR00022##

organic groups represented by the following X are present in one molecule of the polyimide copolymer represented by the following structural formula.

[0104] where, in the formula, R is a methyl group or an ethyl group.

Example 5

[0105] In an apparatus as used in Example 1, 22.07 g (0.075 moles) of BPDA, 4.46 g (0.025 moles) of DETDA, 11.18 g (0.038 moles) of APB-N, 2.84 g (0.013 moles) of 4-amino-N-(3-aminophenyl) benzamide (3,4′-DABAN), 88.32 g of NMP, 1.18 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed from the reaction system by azeotropic distillation with toluene. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B), the ingredient (C) and the ingredient (D) used for the reaction is shown in Table 2.

[0106] After completion of the reaction, the reaction system was cooled to 120° C., and then 126.15 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 15 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (27). Here, the polyimide copolymer has a molecule having three kinds of divalent organic groups represented by the following X.

##STR00023##

[0107] where, in the formula, R is a methyl group or an ethyl group.

Example 6

[0108] In an apparatus as used in Example 1, 26.17 g (0.12 moles) of pyromellitic dianhydride (PMDA), 7.13 g (0.04 moles) of DETDA, 23.70 g (0.08 moles) of APB-N, 122.91 g of NMP, 1.90 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system by azeotropic distillation with the toluene. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 2.

[0109] After completion of the reaction, the reaction system was cooled to 120° C., and then 35.12 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (28). Here, two kinds of divalent organic groups represented by the following X are contained in one molecule of the polyimide copolymer represented by the following structural formula. That is, the obtained polyimide copolymer contains a unit represented by a general formula (34) which is shown in Comparative Example 5 and a unit represented by a general formula (35) which is shown in Comparative Example 6, each mentioned below.

##STR00024##

[0110] where, in the formula, R is a methyl group or an ethyl group.

Example 7

[0111] In an apparatus as used in Example 1, 62.46 g (0.12 moles) of 4,4′-[propane-2,2-diyl bis(1,4-phenyleneoxy)]diphthalic acid dianhydride (BisDA), 10.70 g (0.06 moles) of DETDA, 9.59 g (0.06 moles) of 3,5-diaminobenzoic acid (3,5-DABA), 182.98 g of NMP, 1.90 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen,a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system by azeotropic distillation with the toluene. A composition ratio (parts by mass) of the ingredient (A), the ingredient (B) and the ingredient (C) used for the reaction is shown in Table 2.

[0112] After completion of the reaction, the reaction system was cooled at 120° C., and then 52.28 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25 mass %. A structure of the obtained polyimide copolymer is represented by the following formula (29). Here, two kinds of divalent organic groups represented by the following X are contained in one molecule of the polyimide copolymer represented by the following structural formula.

##STR00025##

[0113] where in the formula, R is a methyl group or an ethyl group.

Comparative Example 1

[0114] In an apparatus as used in Example 1, 40.33 g (0.13 moles) of ODPA, 38.44 g (0.13 moles) of APB-N, 137.58 g of NMP, 2.06 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system as an azeotropic mixture with the toluene and the pyridine. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (C) used for the reaction is shown in Table 1.

[0115] After completion of the reaction, the reaction system was cooled at 120° C., and then 84.66 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25%. A structure of the obtained polyimide copolymer is represented by the following formula (30).

##STR00026##

Comparative Example 2

[0116] In an apparatus as used in Example 1, 55.84 g (0.18 moles) of ODPA, 32.33 g (0.18 moles) of DETDA, 151.70 g of NMP, 2.85 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, a reaction was carried out for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system as an azeotropic mixture with the toluene and the pyridine. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (B) used for the reaction is shown in Table 1.

[0117] After completion of the reaction, the reaction system was cooled at 120° C., and then 93.35 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25%. A structure of the obtained polyimide copolymer is represented by the following formula (31).

##STR00027##

[0118] where in the formula, R is a methyl group or an ethyl group.

Comparative Example 3

[0119] In an apparatus as used in Example 1, 44.13 g (0.15 moles) of BDPA, 44.34 g (0.15 moles) of APB-N, 154.26 g of NMP, 2.37 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, the reactants were heated and stirred for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system as an azeotropic mixture with the toluene and the pyridine. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (C) used for the reaction is shown in Table 1.

[0120] After completion of the reaction, the reaction system was cooled at 120° C., and then 94.93 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25%. A structure of the obtained polyimide copolymer is represented by the following formula (32).

##STR00028##

Comparative Example 4

[0121] In an apparatus as used in Example 1, 52.96 g (0.18 moles) of BDPA, 32.32 g (0.18 moles) of DETDA, 146.33 g of NMP, 2.85 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, the reactants were heated and stirred for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system as an azeotropic mixture with the toluene and the pyridine. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (B) used for the reaction is shown in Table 1.

[0122] After completion of the reaction, the reaction system was cooled at 120° C., and then 90.05 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25%. A structure of the obtained polyimide copolymer is represented by the following formula (33).

##STR00029##

[0123] where in the formula, R is a methyl group or an ethyl group.

Comparative Example 5

[0124] In an apparatus as used in Example 1, 32.72 g (0.15 moles) of PMDA, 44.27 g (0.15 moles) of APB-N, 132.94 g of NMP, 2.37 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, the reactants were heated at 180° C. under the nitrogen flow to start a reaction. However, a resin ingredient was precipitated after one and half hours from the start of the reaction. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (C) used for the reaction is shown in Table 2. A structure of the obtained resin ingredient is represented by the following formula (34).

##STR00030##

Comparative Example 6

[0125] In an apparatus as used in Example 1, 52.35 g (0.24 moles) of PMDA, 43.04 g (0.24 moles) of DETDA, 161.09 g of NMP, 3.80 g of pyridine, and 50 g of toluene were put into. After having purged with nitrogen, the inside of the reaction system was substituted with nitrogen the reactants were heated and stirred for 6 hours at 180° C. under the nitrogen flow. Water generated by the reaction was removed outside the reaction system as an azeotropic mixture with the toluene and the pyridine. A composition ratio (parts by mass) of the ingredient (A) and the ingredient (B) used for the reaction is shown in Table 2.

[0126] After completion of the reaction, the reaction system was cooled at 120° C., and then 99.13 g of NMP was added thereto to obtain a polyimide copolymer solution having a concentration of 25%. A structure of the obtained polyimide copolymer is represented by the following formula (35).

##STR00031##

[0127] where in the formula, R is a methyl group or an ethyl group.

[0128] A Solubility in solvent and a glass transition temperature of the polyimide copolymer of each of Examples and Comparative Examples were evaluated. As to molded article, samples for evaluation were molded by vacuum press into two kinds of forms of RCC and a bonding film, and then an adhesive strength and solder heat resistance thereof were measured.

[0129] (Manufacturing of RCC)

[0130] The polyimide copolymer solution obtained in each of Examples and Comparative Examples was applied onto an electrolysis copper foil having a thickness of 18 μm and a surface roughness (Rz) of 2.0 μm so that a dry film thickness thereof became 10 μm using a spin coating method. Thereafter, it was fixed on a stainless frame, and temporarily dried for 5 minutes at 120° C. After the temporarily drying, it was dried for 30 minutes at 180° C. and for 1 hour at 250° C. under the nitrogen atmosphere to manufacture the RCC.

[0131] (Manufacturing of Bonding Film)

[0132] The polyimide copolymer solution obtained in each of Examples and Comparative Examples was applied by spin coating onto a PET film having a thickness of 125 μm in such an amount that a dried film thickness thereof became 20 μm. Thereafter, it was fixed on a stainless frame, and temporarily dried for 5 minutes at 120° C. After the temporarily drying, the PET film was peeled, and then the obtained polyimide copolymer in the form of film was fixed on the stainless frame, and then dried for 30 minutes at 180° C. and for 1 hour at 250° C. under the nitrogen atmosphere to manufacture the bonding film.

[0133] The above mentioned RCC and bonding film were used and bonded to an electrolysis copper foil having a surface roughness (Rz) of 2.0 μm using a vacuum press machine to produce multilayer substrates. The pressing was carried out by increasing a surface pressure to 5 MPa, which was kept for 5 minutes at 110° C., followed by increasing the temperature to 300° C., which was kept for 30 minutes.

[0134] (Solubility in Solvent)

[0135] When the polyimide copolymer solution was prepared in each of Examples and Comparative Examples, a polyimide copolymer which was soluble in the solvent used for polymerizing was rated as “A”, while those precipitated from the solvent during the polymerization process to exhibit the insolubility was rated as “B”. The results are shown in Table 1 and Table 2.

[0136] (Glass Transition Temperature)

[0137] By using the above mentioned bonding film, a glass transition temperature thereof was measured. For the measurement, DSC6200 (produced by Seiko Instruments Inc.) was used. Here, the film was heated up to 500° C. at a temperature increasing rate of 10° C./min, and a midpoint glass transition temperature was defined as the glass transition temperature. The obtained results are shown in Table 1 and Table 2.

[0138] (Adhesive Strength)

[0139] The above mentioned multilayer substrate was processed into a test piece having a width of 10 mm, and then the bonding strength at 180° thereof was measured by using a creep meter (“RE2-33005B” produced by Yamaden co., ltd.). The measurement was carried out twice at a pulling rate of 1 mm/sec, and a maximum stress was defined as the adhesive strength. The results are shown in Table 1 and Table 2. It should be noted that the same results were obtained for both the multilayer substrate in which the RCC was used and the multilayer substrate in which the bonding film was used.

[0140] (Solder Heat Resistance)

[0141] The above mentioned multilayer substrate was processed into a test piece having a size of 25 mm×25 mm. The test piece was floated on a solder bath at a predetermined temperature (260° C., 280° C., 300° C., or 320° C.) for 60 seconds, and then appearance degradation such as peeling or blistering was observed and rated according to the following criteria. The results are shown in Table 1 and Table 2. It should be noted that the same results were obtained in both the laminated board in which the RCC was used and the laminated board in which the bonding film was used.

[0142] A: No degradation in appearance was observed.

[0143] B: Peeling or blistering having a diameter of less than 1 mm was observed.

[0144] C: Peeling or blistering having a diameter of 1 mm or more was observed.

TABLE-US-00001 TABLE 1 Com. Com. Com. Ex. 1 Ex. 1 Ex. 2 Ex. 2 Ex. 3 Ex. 3 Com. Ex. 4 Acid di- (A) (A1) ODPA 100 100 100 — — — — anhydride (A2) BPDA — — — 100 100 100 100 (A3) PMDA — — — — — — — (A4) BisDA — — — — — — — Diamine (B) (B1) 33 — 100 33 33 — 100 DETDA (B2) M- — — — — — — — DEA (C) (C1) APB-N 67 100 — 67 67 100 — (C2) 3,5- — — — — — — — DABA (D) (D1) 3,4- — — — — — — — DABAN Solubility in solvent A A A A A A A Glass transition temperature 197 167 340 227 226 192 >500 (° C.) adhesive strength (kgf/cm) 1.7 1.7 0 1.5 1.7 1.7 0 Solder heat 260° C. 60 s A B C A A A C resistance 280° C. 60 s A C C A A A C 300° C. 60 s A C C A A C C 320° C. 60 s B C C A A C C

TABLE-US-00002 TABLE 2 Com. Com. Ex. 4 Ex. 5 Ex. 6 Ex. 5 Ex. 6 Ex. 7 Acid di- (A) (A1) ODPA — — — — — — anhydride (A2) BPDA 100 100 — — — — (A3) PMDA — — 100 100 100 — (A4) BisDA — — — — — 100 Diamine (B) (B1) — 33 33 — 100 50 DETDA (B2) M- 67 — — — — — DEA (C) (C1) APB-N 33 51 67 100 — — (C2) 3,5- — — — — — 50 DABA (D) (D1) 3,4- — 17 — — — — DABAN Solubility in solvent A A A B A A Glass transition temperature 240 249 243 n/a >500 248 (° C.) adhesive strength (kgf/cm) 1.2 1.6 1.5 n/a 0 1.4 Solder heat 260° C. 60 s A A A n/a C A resistance 280° C. 60 s A A A n/a C A 300° C. 60 s A A A n/a C A 320° C. 60 s A A B n/a C A

[0145] (Discussion)

[0146] As shown in Table 1, it was found that Comparative Example 1, which was obtained from the ingredient (A) and the ingredient (C) to have only the structural unit represented by the above mentioned general formula (102), had a good adhesive strength, but had a low glass transition temperature, resulting in insufficient solder heat resistance. On the other hand, it was found that Comparative Example 2, which was obtained from the ingredient (A) and the ingredient (B) to have only the structural unit represented by the above mentioned general formula (101), had a high glass transition temperature, but had a low adhesive strength to be unable to follow a dimensional change of the material thereof due to the heat of the solder bath. In contrast, it was confirmed that Example 1, which was obtained from the ingredient (A), the ingredient (B) and the ingredient (C) to have the structural unit represented by above mentioned general formula (101) and the structural unit represented by the general formula (102), had an excellent adhesive strength and superior solder heat resistance.

[0147] From the above results, the effects of the polyimide copolymer of the present invention, which had the structural unit represented by the general formula (101) and the structural unit represented by the general formula (102) in one molecule thereof, were confirmed.

[0148] Further, from the results of Comparative Example 3 in Table 1, of which ingredient (A) was BPDA, it was confirmed that the copolymer, which was obtained from the ingredient (A) and the ingredient (C) only, did not have enough solder heat resistance. On the other hand, from the results of Comparative Example 4 in Table 1, of which ingredient (A) was BPDA, it was confirmed that the copolymer, which was obtained from the ingredient (A) and the ingredient (B) only, had a low bonding strength and could not follow the dimension change of the material thereof due to the heat of the solder bath. In contrast, it was confirmed that Example 2 and Example 3, which were obtained from the ingredient (A), the ingredient (B) and the ingredient (C), had excellent adhesive strength and superior solder heat resistance.

[0149] In this regard, the manufacturing methods of Example 2 and Example 3 are different from each other, and thus the structures of the obtained polyimide copolymers are also different from each other. That is, in Example 2, the structural units represented by the general formula (101) and the structural units represented by the general formula (102) are block-copolymerized, while in Example 3, the structural units represented by the general formula (101) and the structural units represented by the general formula (102) are random-copolymerized. However, it was confirmed that both Example 2 and Example 3 had excellent adhesive strength and superior solder heat resistance.

[0150] From Table 2, it was found that Example 4, in which the kind of the ingredient (C) was changed from Example 3, also had an excellent adhesive strength and superior solder heat resistance. Further, Example 5, in which the ingredient (D) was added to the composition of Example 3, also exhibited excellent adhesive strength and superior solder heat resistance.

[0151] Furthermore, from the results of Comparative Example 5 in Table 2, where the ingredient (A) was PMDA, it was found that the copolymer, which was obtained from only the ingredient (A) and the ingredient (C), did not exhibit enough solvent solubility. From the results of Comparative Example 6, where the ingredient (A) was PMDA, it was found that the copolymer, which was obtained from only the ingredient (A) and the ingredient (B), had low adhesive strength and did not exhibit enough solder heat resistance. In contrast, it was confirmed that Example 6, which was obtained from the ingredient (A), the ingredient (B) and the ingredient (C), had high solvent solubility, excellent adhesive strength and superior solder heat resistance.

[0152] It was found that Example 7, in which used was BisDA as the ingredient (A), DETDA as the ingredient (B) and 3,5-DABA as the ingredient (C), also had excellent bonding strength and superior solder heat resistance.

[0153] From the above results, it was confirmed that the polyimide copolymer of the present invention makes a good adhesive having solder heat resistance applicable to a process using lead-free solder, and a adhesive strength of 1.0 kgf/cm or more.