Polyimides as dielectric

1. A process for the preparation of an organic field-effect transistor (OFET) on a substrate, which organic field-effect transistor comprises a layer, which layer comprises polyimide B, and an additional layer comprising a semiconducting material, wherein the semiconducting material comprises units having a diketopyrrolopyrrole group (DPP polymer),

wherein the process comprises

i) forming a layer comprising photocurable polyimide A by applying photocurable polyimide A as a solution in an organic solvent A on the layer comprising the semiconducting material, wherein the organic solvent A is a mixture of butyl acetate and cyclopentanone in a weight ratio of butyl acetate/cyclopentanone is at least from 99/1 to 20/80,

ii) irradiating the layer comprising photocurable polyimide A with light of a wavelength of >=360 nm to form the layer comprising polyimide B.

2. The process of claim 1 , wherein the photocurable polyimide A is a polyimide which is obtainable by reacting a mixture of reactants, which mixture of reactants comprise at least one dianhydride A, and at least one diamine A, wherein the dianhydride A is a dianhydride carrying at least one photosensitive group and the diamine A is a diamine carrying at least one crosslinkable group.

3. The process of claim 2 , wherein the dianhydride A which is a dianhyride carrying at least one photosensitive group, is selected from the group consisting of

wherein

R 1 is C 1-10 -alkyl, C 1-10 -haloalkyl, halogen or phenyl

g is 0, 1, 2 or 3,

X is a direct bond, CH 2 , O, S or C(O).

4. The process of claim 2 , wherein the diamine A, which is a diamine carrying at least one crosslinkable group, is selected from the group consisting of (i) a diamine of formula

wherein

R 2 , R 3 are the same or different and are H, C 1-10 -alkyl or C 4-8 -cycloalkyl,

n is 1, 2, 3 or 4

m is 0, 1, 2 or 3

provided n+m<=4,

p is 0, 1, 2, 3 or 4,

L 1 is O, S, C 1-10 -alkylene, phenylene or C(O)

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S,

(ii) a diamine of formula

wherein

R 4 is H, C 1-10 -alkyl or C 4-8 -cycloalkyl

R 5 is O—C 1-10 -alkyl, O—C 1-10 -alkylene-O—C 1-10 -alkyl, O—C 1-10 -alkylene-N(C 1-10 -alkyl) 2 , N(C 1-10 -alkyl) 2 , O-phenyl, W, O—C 1-10 -alkylene-W, O-phenylene-W, N(R 6 )(C 1-10 -alkylene-W) or N(R 6 )(phenylene-W),

wherein

R 6 is H, C 1-10 -alkyl, C 4-10 -cycloalkyl or C 1-10 -alkylene-W,

W is O—C 2-10 -alkenyl, N(R 7 )(C 2-10 -alkenyl), O—C(O)—CR 8 ═CH 2 , N(R 7 )(C(O)—CR 8 ═CH 2 ),

or

wherein

R 7 is H, C 1-10 -alkyl, C 4-8 -cycloalkyl, C 2-10 -alkenyl or C(O)—CR 8 ═CH 2 ,

R 8 is H, C 1-10 -alkyl or C 4-8 -cycloalkyl,

R 9 is H, C 1-10 -alkyl or C 4-8 -cycloalkyl

q is 1, 2, 3 or 4

o is 0, 1, 2, 3

q+o<=4,

in case o is O, R 5 is W, O—C 1-10 -alkylene-W, O-phenylene-W, N(R 6 )(C 1-10 -alkylene-W) or N(R 6 )(phenylene-W),

wherein C 1-10 -alkylene, can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl, and/or C 4-8 -cycloalkyl, or interrupted by 0 or S,

and

(iii) a diamine of formula

wherein

R 10 and R 11 are the same or different and are H, C 1-10 -alkyl or C 4-8 -cycloalkyl

R 13 and R 14 are the same and different and are C 1-10 -alkyl, C 1-10 -haloalkyl, C 4-8 -cycloalkyl, C 2-10 -alkenyl, C 4-10 -cycloalkenyl or phenyl,

L 2 is C 1-10 -alkylene or phenylene

r is 0, 1, 2, 3 or 4

s is 0, 1, 2, 3 or 4

r+s<=4

in case both r and s are 0 then at least one of R 13 and R 14 is C 2-10 -alkenyl or

C 4-10 -cycloalkenyl,

t is 0 or an integer from 0 to 50,

u is 0 or 1

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S.

5. The process of claim 2 , wherein the diamine A, which is a diamine carrying at least one crosslinkable group, is a diamine of formula

wherein

R 2 , R 3 are the same or different and are H, C 1-10 -alkyl or C 4-8 -cycloalkyl,

n is 1, 2, 3 or 4

m is 0, 1, 2 or 3

provided n+m<=4,

p is 0, 1, 2, 3 or 4,

L 1 is O, S, C 1-10 -alkylene, phenylene or C(O)

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S.

6. The process of claim 2 , wherein the mixture of reactants comprises at least one dianhydride B and/or at least one diamine B, wherein the dianhydride B is a dianhydride carrying no photosensitive group, and the diamine B is a diamine carrying no crosslinkable group.

7. The process of claim 6 , wherein dianhydride B, which is a dianhydride carrying no photosensitive group, is selected from the group consisting of

wherein

R 12 is C 1-10 -alkyl, C 1-10 -haloalkyl, halogen or phenyl

h is 0, 1, 2 or 3,

Y is a C 1-10 -alkylene, O or S.

8. The process of claim 6 , wherein the diamine B, which is a diamine carrying no crosslinkable group, is selected from the group consisting of (i) a diamine of formula

wherein

R 15 is halogen or O—C 1-10 -alkyl,

d is 0, 1, 2, 3 or 4

v is 0, 1, 2, 3 or 4,

L 3 is a direct bond, O, S, C 1-10 -alkylene or CO,

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by 0 or S,

(ii) a diamine of formula

wherein

R 16 is halogen or O- C1-10 -alkyl

R 17 is O—C 1-10 -alkyl, O—C 1-10 -alkylene-O—C 1-10 -alkyl, O-phenyl, O—C 1-10 -alkylene-N(C 1-10 -alkyl) 2 or N(C 1-10 -alkyl) 2

w is 0, 1, 2 or 3

x is 1, 2, 3, 4

w+x<=4,

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S,

(iii) a diamine of formula

wherein

R 18 is halogen or O—C 1-10 -alkyl,

R 19 and R 20 are the same and different and are C 1-10 -alkyl, C 1-10 -haloalkyl or C 4-8 -cycloalkyl or phenyl,

L 3 is C 1-10 -alkylene or phenylene

y is 0, 1, 2, 3 or 4

z is 0 or 1

a is 0 or an integer from 1 to 50,

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S,

and

(iv) a diamine of formula

wherein

R 21 and R 22 are the same and different and are C 1-10 -alkyl, C 1-10 -haloalkyl or C 4-8 -cycloalkyl,

L 4 is C 1-10 -alkylene, C 4-8 -cycloalkylene or C 4-8 -cycloalkylene-Z—C 4-8 -cycloalkylene,

wherein Z is C 1-10 -alkylene, S, O or CO

b is 0 or 1

c is 0 or an integer from 1 to 50,

e is 0 or 1

wherein C 1-10 -alkylene can be optionally substituted with one or more C 1-10 -alkyl, C 1-10 -haloalkyl and/or C 4-8 -cycloalkyl, or interrupted by O or S.

9. The process of claim 1 , wherein the DPP polymer comprises a unit selected from the group consisting of

a polymer unit of formula

a copolymer unit of formula

a copolymer unit of formula

and

A copolymer unit of formula

wherein

n′ is 4 to 1000

x′ is 0.995 to 0.005,

y′ is 0.005 to 0.995, and

x′+y′=1;

r′ is 0.985 to 0.005,

s′ is 0.005 to 0.985,

t′ is 0.005 to 0.985,

u′ is 0.005 to 0.985, and

r′+s′+t′+u′=1;

A is a group of formula

wherein

a″ is 1, 2, or 3,

a′″ is 0, 1, 2, or 3,

b′ is 0, 1, 2, or 3,

b″ is 0, 1, 2, or 3,

c′ is 0, 1, 2, or 3,

c″ is 0, 1, 2, or 3,

d′ is 0, 1, 2, or 3,

d″ is 0, 1, 2, or 3,

with the proviso that b″ is not 0, if a′″ is 0;

R 40 and R 41 are the same or different and are selected from the group consisting of hydrogen, C 1-100 alkyl, —COOR 106″ , C 1-100 alkyl which is substituted with one or more halogen, hydroxyl, nitro, —CN, or C 6 -C 18 aryl and/or interrupted by —O—, —COO—, —OCO—, or —S—; C 7 -C 100 arylalkyl, carbamoyl, C 5 -C 12 cycloalkyl, which can be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy, C 6 -C 24 aryl, which can be substituted one to three times with C 1 -C 8 alkyl, C 1 -C 25 thioalkoxy, and/or C 1 -C 25 alkoxy, or pentafluorophenyl, wherein

R 106″ is C 1 -C 50 alkyl,

Ar 1 , Ar 1′ , Ar 2 , Ar 2′ , Ar 3 , Ar 3′ , Ar 4 and Ar 4′ are independently of each other heteroaromatic, or aromatic rings, which optionally can be condensed and/or substituted

wherein

one of X 3 and X 4 is N and the other is CR 99 ,

wherein R 99 is hydrogen, halogen, or C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl, or C 1 -C 25 alkoxy,

R 104 , R 104′ , R 123 and R 123′ are independently of each other hydrogen, halogen, or C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl, or C 1 -C 25 alkoxy,

R 105 , R 105′ , R 106 and R 106′ are independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 7 -C 25 arylalkyl, or C 1 -C 18 alkoxy,

R 107 is C 7 -C 25 arylalkyl, C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 18 alkyl, C 1 -C 18 perfluoroalkyl, or C 1-18 alkoxy; C 1 -C 18 alkyl; C 1 -C 18 alkyl which is interrupted by —O—, or —S—; or —COOR 124 ;

R 124 is C 1 -C 25 alkyl which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl,

R 108 and R 109 are independently of each other H, C 1 -C 25 alkyl, C 1 -C 25 alkyl which is substituted by E′ and/or interrupted by D′, C 7 -C 25 arylalkyl, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by G, C 2 -C 20 heteroaryl, C 2 -C 20 heteroaryl which is substituted by G, C 2 -C 18 alkenyl, C 2 -C 18 alkynyl, C 1-18 alkoxy, C 1 -C 18 alkoxy which is substituted by E′ and/or interrupted by D′, or C 7 -C 25 aralkyl,

or

R 108 and R 109 together form a group of formula ═CR 110 R 111 , wherein

R 110 and R 111 are independently of each other H, C 1 -C 18 alkyl, C 1 -C 18 alkyl which is substituted by E′ and/or interrupted by D′, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by G, or C 2 -C 20 heteroaryl, or C 2 -C 20 heteroaryl which is substituted by G,

or

R 108 and R 109 together form a five or six membered ring, which optionally can be substituted by C 1 -C 18 alkyl, C 1 -C 18 alkyl which is substituted by E′ and/or interrupted by D′, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by G, C 2 -C 20 heteroaryl, C 2 -C 20 heteroaryl which is substituted by G, C 2 -C 18 alkenyl, C 2 -C 18 alkynyl, C 1 -C 18 alkoxy, C 1 -C 18 alkoxy which is substituted by E′ and/or interrupted by D′, or C 7 -C 25 aralkyl, wherein

D′ is —CO—, —COO—, —S—, —O—, or —NR 112 —,

E′ is C 1 -C 8 thioalkoxy, C 1 -C 8 alkoxy, CN, —NR 112 R 113 , —CONR 112 R 113 , or halogen,

G is E′, or C 1 -C 18 alkyl, and

R 112 and R 113 are independently of each other H; C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 18 alkyl, or C 1 -C 18 alkoxy; C 1 -C 18 alkyl; or C 1 -C 18 alkyl which is interrupted by —O— and

B, D and E are independently of each other a group of formula

or a group of formula (24),

with the proviso that in case B, D and E are a group of formula (24), they are different from A, wherein

k′ is 1,

l′ is 0, or 1,

r′ is 0, or 1,

z′ is 0, or 1, and

Ar 5 , Ar 6 , Ar 7 and Ar 8 are independently of each other a group of formula

wherein one of X 5 and X 6 is N and the other is CR 140 ,

R 140 , R 140′ , R 170 and R 170′ are independently of each other H, or a C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen atoms.

10. An organic field-effect transistor on a substrate obtainable by the process of claim 1 .