Adhesive composition, and coverlay film, bonding sheet, copper-clad laminate and electromagnetic shielding material, each using said adhesive composition

Abstract

An adhesive composition containing (A) a modified polyolefin resin and (B) an epoxy compound, wherein the modified polyolefin resin (A) is a polyolefin resin graft modified with a modifying agent that contains an α,β-unsaturated carboxylic acid or a derivative thereof. The content of the epoxy compound (B) is 1-20 parts by mass relative to 100 parts by mass of the modified polyolefin resin (A); and the epoxy compound is composed of two or more types of epoxy compounds.

Claims

1. An adhesive composition, comprising: (A) a modified polyolefin-based resin; and (B) an epoxy resin, wherein the modified polyolefin-based resin (A) is a resin in which a polyolefin resin is graft-modified with a modifier comprising an α, β-unsaturated carboxylic acid or a derivative thereof, a content of the epoxy resin (B) is in a range of from 1 to 20 parts by mass based on 100 parts by mass of the modified polyolefin-based resin (A), and the epoxy resin (B) consists of two or more different epoxy resins selected from the group consisting of bisphenol epoxy resins, novolak epoxy resins, and epoxy resins having an alicyclic skeleton.

2. The adhesive composition of claim 1, wherein the epoxy resin (B) comprises a novolak epoxy resin.

3. The adhesive composition of claim 2, wherein the epoxy resin (B) comprises a bisphenol A novolak epoxy resin.

4. The adhesive composition of claim 1, wherein the epoxy resin (B) comprises an epoxy resin having an alicyclic skeleton.

5. The adhesive composition of claim 1, wherein the modified polyolefin-based resin (A) comprises a modified polypropylene resin.

6. The adhesive composition of claim 1, wherein the derivative of the α,β-unsaturated carboxylic acid is at least one compound selected from the group consisting of an itaconic anhydride, a maleic anhydride, an aconitic anhydride and a citraconic anhydride.

7. The adhesive composition of claim 1, wherein a content proportion of a graft portion derived from the α, β-unsaturated carboxylic acid or the derivative thereof is in a range of from 0.1% to 20% by mass based on 100% by mass of the modified polyolefin-based resin (A).

8. The adhesive composition of claim 1, further comprising (C) an imidazole-based compound comprising an alkoxysilyl group, wherein a content of the alkoxysilyl group-comprising imidazole-based compound (C) is in a range of from 0.3 to 5 parts by mass based on 100 parts by mass of a total content of the modified polyolefin-based resin (A) and the epoxy resin (B).

9. The adhesive composition of claim 1, further comprising (D) an antioxidant, wherein a content of the antioxidant (D) is in a range of from 0.1 to 10 parts by mass based on 100 parts by mass of a total content of the modified polyolefin-based resin (A) and the epoxy resin (B).

10. The adhesive composition of claim 1, further comprising (E) a phosphorus-containing compound (E), wherein a content of the phosphorus-containing compound (E) is in a range of from 0.5 to 50 parts by mass based on 100 parts by mass of a total content of the modified polyolefin-based resin (A) and the epoxy resin (B).

11. The adhesive composition of claim 1, further comprising (F) a conductive filler, wherein a content of the conductive filler (F) is in a range of from 10 to 350 parts by mass based on 100 parts by mass of a total content of the modified polyolefin-based resin (A) and the epoxy resin (B).

12. A coverlay film, comprising an adhesive layer formed using the adhesive composition of claim 1, the adhesive layer being formed on one side of a polyimide film.

13. A bonding sheet, comprising an adhesive layer formed using the adhesive composition of claim 1, the adhesive layer being formed on a surface of a releasable film.

14. A copper-clad laminated board, comprising an adhesive layer formed using the adhesive composition of claim 1, the adhesive layer being provided between a copper foil and at least one side of a polyimide film.

15. An electromagnetic shielding material, comprising an adhesive layer formed using the adhesive composition of claim 1 as an element.

Description

EXAMPLES

(1) The present invention is specifically described using Examples and Comparative Examples. The present invention is not limited to the following Examples.

(2) 1. Raw Materials

(3) 1-1. Modified Polyolefin-Based Resin (A)

(4) Modified polyolefin-based resins a1 to a4 obtained by the following method were used.

(5) (1) Modified Polyolefin-Based Resin a1

(6) There were dissolved, in a toluene solvent, 100 parts by mass of a propylene-butene random copolymer manufactured using a metallocene catalyst as a polymerization catalyst and composed of 75 mol % of propylene unit and 25 mol % of butene unit, 22 parts by mass of a maleic anhydride and 6 parts by mass of di-t-butyl peroxide, and then the solution was warmed to 140° C. in a 1-L autoclave and stirred at this temperature for 3 hours. After that, the obtained reaction solution was cooled, and the reaction solution was poured into a container containing a large amount of methylethylketone to precipitate a resin. The remaining unreacted material or the like was separated and purified by centrifugation. Then, the collected resin was dried at 70° C. under reduced pressure for 5 hours to manufacture a modified polyolefin-based resin a1. The modified polyolefin-based resin a1 had a weight average molecular weight of 55,000 and an acid value of 30 mg KOH/g. Moreover, the content proportion of a graft portion constituting this modified polyolefin-based resin a1 was 5.2% by mass.

(7) (2) Modified Polyolefin-Based Resin a2

(8) There were dissolved, in a toluene solvent, 100 parts by mass of a propylene-butene random copolymer manufactured using a metallocene catalyst as a polymerization catalyst and composed of 75 mol % of propylene unit and 25 mol % of butene unit, 18 parts by mass of a maleic anhydride and 6 parts by mass of di-t-butyl peroxide, and then the solution was warmed to 140° C. in a 1-L autoclave and stirred at this temperature for 3 hours. After that, the obtained reaction solution was cooled, and the reaction solution was poured into a container containing a large amount of methylethylketone to precipitate a resin. The remaining unreacted material or the like was separated and purified by centrifugation. Then, the collected resin was dried at 70° C. under reduced pressure for 5 hours to manufacture a modified polyolefin-based resin a2. The modified polyolefin-based resin a2 had a weight average molecular weight of 65,000 and an acid value of 20 mg KOH/g. Moreover, the content proportion of a graft portion constituting this modified polyolefin-based resin a2 was 3.5% by mass.

(9) (3) Modified Polyolefin-Based Resin a3

(10) Kneaded and reacted were 100 parts by mass of a propylene-ethylene random copolymer manufactured using a metallocene catalyst as a polymerization catalyst and composed of 97 mol % of propylene unit and 3 mol % of ethylene unit, 1.5 parts by mass of a maleic anhydride, 0.8 part by mass of lauryl methacrylate and 1.2 parts by mass of di-t-butyl peroxide using a twin-screw extruder in which the maximum temperature of the cylinder part was set to 170° C. Thereafter, degassing was performed under reduced pressure in the extruder to remove the remaining unreacted material, thereby manufacturing a modified polyolefin-based resin a3. The modified polyolefin-based resin a3 had a weight average molecular weight of 130,000 and an acid value of 15 mg KOH/g. Moreover, the content proportion of a graft portion constituting this modified polyolefin-based resin a3 was 2.6% by mass.

(11) (4) Modified Polyolefin-Based Resin a4

(12) Kneaded and reacted were 100 parts by mass of a hydrogenated styrene butadiene block copolymer “TUFTEC H1052” (trade name) manufactured by Asahi Kasei Corporation, 1.5 parts by mass of a maleic anhydride, 0.8 part by mass of lauryl methacrylate, and 1.2 parts by mass of di-t-butyl peroxide using a twin-screw extruder in which the maximum temperature of the cylinder part was set to 170° C. Thereafter, degassing was performed under reduced pressure in the extruder to remove the remaining unreacted material, thereby manufacturing a modified polyolefin-based resin a4. The modified polyolefin-based resin a4 had a weight average molecular weight of 60,000 and an acid value of 15 mg KOH/g. Moreover, the content proportion of a graft portion constituting this modified polyolefin-based resin a4 was 2.6% by mass.

(13) 1-2. Epoxy Resin (B)

(14) (1) Epoxy Resin b1

(15) Bisphenol A novolak type epoxy resin “EPICLON N-865” (trade name) manufactured by DIC Corporation

(16) (2) Epoxy Resin b2

(17) Dicyclopentadiene skeleton-containing epoxy resin “EPICLON HP-7200” (trade name) manufactured by DIC Corporation

(18) (3) Epoxy Resin b3

(19) Cresol novolak type epoxy resin “EOCN-102S” (trade name) manufactured by Nippon Kayaku Co., Ltd.

(20) (4) Epoxy Resin b4

(21) Bisphenol A type epoxy resin “JER 828” (trade name) manufactured by Mitsubishi Chemical Corporation

(22) 1-3. Imidazole-Based Compound Having Alkoxysilyl Group (C)

(23) (1) Imidazole-Based Compound c1

(24) 1-(2-Hydroxy-3-trimethoxysilylpropoxypropyl)-imidazole

(25) (2) Imidazole-Based Compound c2

(26) Acetic acid adduct of imidazole-based compound c1

(27) 1-4. Antioxidant (D)

(28) Phenolic antioxidant “ADEKASTAB A330” (trade name) manufactured by Adeka Corporation

(29) 1-5. Phosphorus-Containing Compound (E)

(30) Aluminum dimethylphosphinate “Exolit OP935” (trade name) manufactured by CLARIANT

(31) 1-6. Conductive Filler (F)

(32) Copper powder “FCC-115A” (trade name) manufactured by Fukuda Metal Foil & Powder Co., Ltd.

(33) 1-7. Curing Accelerator

(34) Imidazole-based curing accelerator “CUREZOL C11-Z” (trade name) manufactured by Shikoku Chemicals Corporation

(35) 1-8. Other Fillers

(36) Fumed Silica “AEROSIL R974” (trade name) (average particle size: 12 nm) manufactured by Nippon Aerosil Co., Ltd.

(37) 1-9. Solvent

(38) Mixed solvent composed of methylcyclohexane, toluene, methylethylketone and methanol (mass ratio=270:180:5:2)

Examples 1 to 14 and Comparative Examples 1 to 4

(39) The raw materials were added to a flask equipped with a stirrer in the proportions indicated in Table 1 and stirred for 6 hours under warming at 60° C. to dissolve component (A), component (B), component (C), component (D) and a curing accelerator in a solvent and to disperse component (E), component (F) and the other fillers therein, thereby manufacturing liquid adhesive compositions of Examples 1 to 14 and Comparative Examples 1 to 4.

(40) Using all these liquid adhesive compositions, coverlay films, bonding sheets, and adhesive test pieces A and B were prepared to make evaluation for the following items (i) to (v). Moreover, liquid adhesive compositions (without a conductive filler) were manufactured using the components, except component (F), of the liquid adhesive compositions of Examples 1 to 14 and Comparative Examples 1 to 4, and evaluation was made for the following item (vi).

(41) (1) Preparation of Coverlay Film

(42) The respective liquid adhesive compositions were roll-coated onto a surface of a polyimide film having a thickness of 25 μm so that the thickness after drying reached 40 μm, and dried at 140° C. for 2 minutes, thereby producing a coverlay film having an adhesive layer.

(43) (2) Preparation of Adhesive Test Piece A

(44) A gold-plated copper foil having a thickness of 35 μm was prepared. Then, the copper foil was overlaid so that the gold-plated surface was in contact with the adhesive layer surface of the respective coverlay films, and lamination was performed under conditions of 150° C., 0.3 MPa and 1 m/min. The resulting laminates (polyimide film/adhesive layer/gold-plated copper foil) were pressure-bonded by heating under the conditions of 150° C. and 3 MPa for 5 minutes, and then further subjected to after-curing at 160° C. for 2 hours in an oven, thereby producing adhesive test pieces A.

(45) (3) Preparation of Bonding Sheet

(46) A releasable PET film having a thickness of 35 μm was prepared. Then, the respective liquid adhesive compositions were roll-coated onto a surface of the releasable PET film so that the thickness after drying reached 25 μm, and dried at 140° C. for 2 minutes, thereby producing bonding sheets having an adhesive layer.

(47) (4) Preparation of Adhesive Test Piece B

(48) A nickel-plated SUS304 plate having a thickness of 300 μm was prepared, and overlaid so that the nickel-plated surface was in contact with the adhesive layer of the respective bonding sheets, and lamination was performed under conditions of 150° C., 0.3 MPa and 1 m/min., thereby producing laminates X (SUS304 plate/bonding sheet).

(49) On the other hand, prepared was a flexible printed wiring board provided with a polyimide film having a thickness of 25 μm, a copper circuit pattern formed on a surface on one side of the polyimide film, and a coverlay film part (polyimide layer having a thickness of 25 μm) covering the circuit pattern by bringing the adhesive layer into contact with the circuit pattern. A through hole having a diameter of 1 mm is formed in the coverlay film part covering the circuit pattern, and the copper circuit pattern is exposed through the through hole.

(50) The releasable PET film was peeled off from the respective laminates X so that the adhesive layer adhered to the SUS304 plate was brought into full contact with the surface of the flexible printed wiring board on the side of the coverlay film part for pressure-bonding under conditions of 150° C. and 3 MPa for 5 minutes. Then, after-curing was further performed at 160° C. for 2 hours in an oven, thereby preparing adhesive test pieces B (SUS 304 plate/adhesive layer/flexible printed wiring board).

(51) (i) Peel Adhesion Strength

(52) In order to evaluate the adhesiveness, a 180° peel adhesion strength (N/mm) when the gold-plated copper foil of each of the adhesive test piece A was peeled off from the polyimide film was measured in accordance with JIS C 6481 “Test method for copper-clad laminated board for printed wiring board” under conditions: a temperature of 23° C. and a tensile speed of 50 mm/min. The width of each of the adhesive test pieces at the time of measurement was set to 10 mm.

(53) (ii) Solder Heat Resistance

(54) Test was conducted under the following conditions in accordance with JIS C 6481.

(55) The respective adhesive test pieces A were floated in a solder bath at 260° C. for 60 seconds, with the surface of the polyimide film facing up, to visually evaluate the presence or absence of an appearance abnormality such as swelling or peeling of the adhesive layer. As a result, those in which an appearance abnormality such as swelling or peeling was not confirmed were shown as “o”, and those in which an appearance abnormality such as swelling or peeling was confirmed were shown as “x”.

(56) Furthermore, the test pieces taken out of the solder bath were subjected to 180° peel adhesion strength (N/cm) measurement when the polyimide film was peeled off from the gold-plated copper foil at 23° C. according to JIS C 6481. The width of the respective adhesive test pieces at the time of measurement was set to 10 mm, and the tensile speed was set to 50 mm/min.

(57) (iii) Flame Retardancy

(58) The coverlay film was cured at 160° C. for 2 hours to evaluate the flame retardancy according to UL-94. Those that passed the test (VTM-0 class) were shown as “∘”, and those that failed the test were shown as “x”.

(59) (iv) Conductivity (Connection Resistance)

(60) A connection resistance value between the SUS plate of the respective adhesive test pieces B (SUS plate/adhesive layer/flexible printed wiring board) and the copper portion of the circuit pattern of the flexible printed wiring board was measured by a resistance value measuring device. As a result, those having a connection resistance value of less than 1Ω were shown as “o”, those having a connection resistance value of 1Ω to 3Ω were shown as “A”, and those having a connection resistance value of more than 3Ω were shown as “x”.

(61) (v) Conductivity after Soldering (Connection Resistance)

(62) The respective adhesive test piece B was floated in a solder bath at 260° C. for 60 seconds. Thereafter, a connection resistance value between the SUS plate of the respective adhesive test pieces B taken out of the solder bath and the copper portion of the circuit pattern of the flexible printed wiring board was measured by a resistance value measuring device. As a result, those having a connection resistance value of less than 1Ω were shown as “o”, those having a connection resistance value of 1 to 3Ω were shown as “Δ”, and those having a connection resistance value of more than 3Ω were shown as “x”.

(63) (vi) Dielectric Properties (Dielectric Constant and Dielectric Loss Tangent)

(64) The respective liquid adhesive compositions (without a conductive filler) were roll-coated onto a surface of a releasable polyethylene terephthalate film having a thickness of 38 μm. Subsequently, the coated film was allowed to stand in an oven, and the coating film was dried at 120° C. for 3 minutes to form a coating (adhesive layer), thereby producing a bonding sheet. After that, the bonding sheets were allowed to stand in an oven and heated at 180° C. for 30 minutes. The releasable film was then peeled off to prepare cured test pieces for evaluation of the dielectric properties.

(65) The dielectric constant (ε) and the dielectric loss tangent (tan δ) of a cured test piece having a size of 15 mm×80 mm×50 μm were measured by a split post dielectric resonator method (SPDR method) using “Network Analyzer 85071 E-300” manufactured by Agilent Technologies at a temperature of 23° C. and a frequency of 1 GHz.

(66) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 Raw material (A) Modified a1 100 100 100 100 100 100 100 (parts by mass) polyolefin- a2 100 based resin a3 100 a4 100 (B) Epoxy resin b1 5 5 5 5 5 5 5 5 b2 10 10 10 10 10 10 10 10 10 b3 5 b4 5 10 (C) Alkoxysilyl group- c1 1 1 1 1 1 1 1 containing imidazole- c2 1 based compound (D) Antioxidant 1 1 1 1 1 1 1 1 1 1 (E) Phosphorus-containing 10 10 10 10 10 10 10 10 10 compound (F) Conductive filler 30 30 30 30 30 30 30 30 30 30 Curing accelerator 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Other fillers (silica) 10 10 10 10 10 10 10 10 10 10 Solvent 300 300 300 300 300 300 300 300 300 300 Example Comparative Example 11 12 13 14 1 2 3 4 Raw material (A) Modified a1 100 100 100 100 100 100 100 100 (parts by mass) polyolefin- a2 based resin a3 a4 (B) Epoxy resin b1 5 5 5 5 15 b2 10 10 10 10 15 b3 15 b4 (C) Alkoxysilyl group- c1 1 1 1 1 1 1 1 containing imidazole- c2 based compound (D) Antioxidant 1 1 1 1 1 1 1 (E) Phosphorus-containing 10 10 10 10 10 10 10 10 compound (F) Conductive filler 150 350 30 30 30 30 30 Curing accelerator 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Other fillers (silica) 10 10 10 10 10 10 10 10 Solvent 300 300 300 300 300 300 300 300
The evaluation results are indicated in Table 2.

(67) TABLE-US-00002 TABLE 2 Example 1 2 3 4 5 6 7 8 9 10 Adhesiveness Initial Peel 9 9 8 9 9 9 6 9 7 9 strength (N/cm) After Peel 10 7 5 6 9 7 5 10 5 10 soldering strength (N/cm) Appearance ∘ ∘ Δ Δ ∘ Δ ∘ ∘ Δ ∘ Flame retardancy ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ x Conductivity Initial ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ After soldering ∘ ∘ Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ Dielectric Dielectric constant (s) 2.4 2.4 2.4 2.5 2.4 2.4 2.5 2.4 2.4 2.4 properties Dielectric loss tangent 0.004 0.003 0.005 0.004 0.004 0.004 0.004 0.004 0.004 0.004 (tan δ) Example Comparative Example 11 12 13 14 1 2 3 4 Adhesiveness Initial Peel 8 6 10 9 9 8 8 5 strength (N/cm) After Peel 8 5 9 7 10 2 5 1 soldering strength (N/cm) Appearance ∘ ∘ ∘ Δ ∘ x Δ x Flame retardancy ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Conductivity Initial ∘ ∘ x ∘ ∘ ∘ ∘ Δ After soldering ∘ ∘ x Δ ∘ x x x Dielectric Dielectric constant (s) 2.4 2.4 2.4 2.5 2.7 2.3 2.6 2.3 properties Dielectric loss tangent 0.004 0.004 0.004 0.005 0.008 0.003 0.007 0.003 (tan δ)

(68) From the results indicated in Table 2, the following matter is clarified.

(69) The adhesive compositions of Examples 1 to 14 were all excellent in adhesiveness to a gold-plated copper foil. Among these, Examples 1 and 8 are examples of an adhesive composition containing an imidazole-based compound having an alkoxysilyl group (C), and were excellent in adhesiveness to a gold-plated copper foil and reflow resistance as compared with Example 9 not containing this.

(70) On the other hand, Comparative Examples 1 to 3 are compositions containing only one kind of epoxy resin, and thus were inferior in either or both of reflow resistance and dielectric properties, and Comparative Example 4 containing no epoxy resin was insufficient in reflow resistance.

(71) In addition, the adhesive compositions (without a conductive filler) of Examples 1 to 14 were all excellent in dielectric properties of the cured product.

INDUSTRIAL APPLICABILITY

(72) The adhesive composition of the present invention is excellent in adhesiveness to an adherend such as a resin film or a gold-plated copper foil and dielectric properties of a cured product, and also excellent in solder heat resistance. Furthermore, the cured product obtained using the adhesive composition containing a conductive filler is excellent also in conductivity. Therefore, the adhesive composition of the present invention is suitable for the manufacture of a coverlay film, a flexible copper-clad laminated board, a bonding sheet, a conductive bonding sheet, an electromagnetic shielding material and the like.