Polyurethane, curable composition, overcoat film, and flexible wiring board and production method therefor
Provided are a polyurethane and a curable composition capable of obtaining an overcoat film for a flexible wiring board that is excellent in low-warpage properties, flexibility, long-term insulation reliability, and wiring disconnection preventing properties. The polyurethane has: a structural unit of formula (1) (in formula (1), an n-number of R 1 each independently represents a 1,2-phenylene group or a 1,2-phenylene group having a substituent, an (n+1)-number of R 2 each independently represents a hydrocarbon group having 3-9 carbon atoms, and n represents an integer from 1 to 50); a structural unit of formula (2) (in formula (2). R 3 represents a divalent organic group having 6-14 carbon atoms); and a structural unit of formula (3) (in formula (3), R 3 represents a divalent organic group having 6-14 carbon atoms, and R 4 represents a methyl or ethyl group).
1. A curable composition, comprising:
(component (a)) a polyurethane having
a structural unit of formula (1)
wherein n R 1 s each independently represent a 1,2-phenylene group or a 1,2-phenylene group having a substituent; (n+1) R 2 s each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms; and n represents an integer of 1 to 50;
a structural unit of formula (2)
wherein R 3 represents a divalent organic group having 6 to 14 carbon atoms; and a structural unit of formula (3)
wherein R 3 represents a divalent organic group having 6 to 14 carbon atoms; and R 4 represents a methyl group or an ethyl group,
wherein the polyurethane has an aromatic ring concentration of 0.1 to 5.0 mmol/g, and
wherein the polyurethane does not contain a structural unit derived from a polyester polyol having a 1,3-phenylene group;
(component (b)) a solvent; and
(component (c)) a compound having two or more epoxy groups in one molecule.
2. A curable composition, comprising:
(component (a)) a polyurethane having
an aromatic ring concentration of 0.1 to 5.0 mmol/g and a number-average molecular weight of 10,000 to 50,000, which is composed of
a structural unit of formula (4)
wherein y R 3 s each independently represent a divalent organic group having 6 to 14 carbon atoms; and y represents an integer of not less than one;
a structural unit of formula (5)
wherein z R 3 s each independently represent a divalent organic group having 6 to 14 carbon atoms; z R 4 s each independently represent a methyl group or an ethyl group; and z represents an integer of not less than one; and
a structural unit of formula (6)
wherein (l× m) R 1 s each independently represent a phenylene group or a phenylene group having a substituent, provided that at least one of (l× m) R 1 s is a 1,2-phenylene group; [(l+1)×m] R 2 s each independently represent a hydrocarbon group having 3 to 9 carbon atoms; m R 3 s each independently represent a divalent organic group having 6 to 14 carbon atoms; m represents an integer of not less than one; and 1 independently represents an integer of 0 to 50, excluding a case where all of the m ls are 0;
wherein the polyurethane does not contain a structural unit derived from a polyester polyol having a 1,3-phenylene group;
(component (b)) a solvent and
(component (c)) a compound having two or more epoxy groups in one molecule.
3. The curable composition according to claim 1 , wherein component (a) has an acid value of 10 to 70 mg-KOH/g.
4. A curable composition comprising
(component (a)) a polyurethane having
a structural unit of formula (1′)
wherein n R 1′ s each independently represent a phenylene group or a phenylene group having a substituent, provided that at least one of n R 1′ s is a 1,2-phenylene group; (n+1) R 2 s each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms; and n represents an integer of 1 to 50;
a structural unit of formula (2)
wherein R 3 represents a divalent organic group having 6 to 14 carbon atoms; and
a structural unit of formula (3)
wherein R 3 represents a divalent organic group having 6 to 14 carbon atoms; and R 4 represents a methyl group or an ethyl group,
wherein the polyurethane has an aromatic ring concentration of 0.1 to 5.0 mmol/g, and
wherein the polyurethane does not contain a structural unit derived from a polyester polyol having a 1,3-phenylene group;
(component (b)) a solvent; and
(component (c)) a compound having two or more epoxy groups in one molecule.
5. The curable composition according to claim 4 , wherein
the amount of component (b) is 25 to 75% by mass based on the total amount of components (a), (b) and (c), and
the amount of component (a) is 40 to 99% by mass and the amount of component (c) is 1 to 60% by mass, based on the total amount of components (a) and (c).
6. The curable composition according to claim 4 , further comprising
(component (d)) at least one particulate selected from the group consisting of an inorganic particulate and organic particulate.
7. The curable composition according to claim 6 , wherein component (d) comprises a silica particulate.
8. The curable composition according to claim 6 , wherein component (d) comprises a hydrotalcite particulate.
9. The curable composition according to claim 6 , wherein
the amount of component (b) is 25 to 75% by mass and the amount of component (d) is 0.1 to 60% by mass, based on the total amount of components (a), (b), (c) and (d), and
the amount of component (a) is 40 to 99% by mass and the amount of component (c) is 1 to 60% by mass, based on the total amount of components (a) and (c).
10. A cured product of the curable composition according to claim 4 .
11. A flexible wiring board overcoat film comprising the cured product according to claim 10 .
12. A flexible wiring board comprising a flexible substrate and a wiring formed on the flexible substrate, wherein a part or all of a surface on which the wiring is formed is covered with the overcoat film according to claim 11 .
13. The flexible wiring board according to claim 12 , wherein the wiring is a tin-plated copper wiring.
14. A method of producing a flexible wiring board covered with an overcoat film, comprising
(step 1) the step of printing the curable composition according to claim 4 on at least a part of a wiring pattern section of a flexible wiring board to form a printed film on the pattern;
(step 2) the step of placing the printed film obtained in step 1 in an atmosphere of 40 to 100° C. to evaporate a part or all of the solvent contained in the printed film; and
(step 3) the step of heating and curing the printed film obtained in step 1 or the printed film obtained in step 2 at 100 to 170° C. to form an overcoat film.
15. The curable composition according to claim 2 , wherein component (a) has an acid value of 10 to 70 mg-KOH/g.
16. The curable composition according to claim 7 , wherein
the amount of component (b) is 25 to 75% by mass and the amount of component (d) is 0.1 to 60% by mass, based on the total amount of components (a), (b), (c) and (d), and
the amount of component (a) is 40 to 99% by mass and the amount of component (c) is 1 to 60% by mass, based on the total amount of components (a) and (c).
17. The curable composition according to claim 8 , wherein
the amount of component (b) is 25 to 75% by mass and the amount of component (d) is 0.1 to 60% by mass, based on the total amount of components (a), (b), (c) and (d), and
the amount of component (a) is 40 to 99% by mass and the amount of component (c) is 1 to 60% by mass, based on the total amount of components (a) and (c).
18. The curable composition according to claim 1 , further comprising
(component (d)) at least one particulate selected from the group consisting of an inorganic particulate and organic particulate.
19. The curable composition according to claim 2 , further comprising
(component (d)) at least one particulate selected from the group consisting of an inorganic particulate and organic particulate.