Process of surface modification of dielectric structures in organic electronic devices to increase surface energy
The invention relates to a process of modifying the surface energy of dielectric structures, like for example dielectric layers or bank structures, in organic electronic (OE) devices, more specifically in organic field effect transistors (OFETs).
1. A process of surface treatment of a dielectric structure in an organic electronic (OE) device, comprising the step of exposing the surface of the dielectric structure, or specific parts of said surface, to a solvent blend comprising
a first solvent selected from the group consisting of aliphatic or aromatic alcohols, and
a second solvent selected from the group consisting of aliphatic esters and aliphatic ketones.
2. The process according to claim 1 , wherein the first solvent is selected from the group consisting of methanol, cyclohexanol, isopropanol, benzyl alcohol.
3. The process according to claim 1 , wherein the second solvent is selected from the group consisting of methyl acetate, ethyl acetate, methyl n-amyl ketone.
4. The process according to claim 1 , wherein the dielectric structure comprises a crosslinked organic polymer.
5. The process according to claim 1 , wherein the dielectric structure comprises a crosslinked and fluorinated organic polymer comprising one or more crosslinkable groups.
6. The process according to claim 1 , wherein the dielectric structure comprises a polycycloolefinic polymer.
7. The process according to claim 6 , wherein the polycycloolefinic polymer is a norbornene-type polymer.
8. The process according to claim 6 , wherein the polycycloolefinic polymer comprises two or more distinct types of repeating units.
9. The process according to claim 6 , wherein the polycycloolefinic polymer comprises a first type of repeating unit having a pendant fluorinated group.
10. The process according to claim 9 , wherein the polycycloolefinic polymer comprises a first type of repeating unit having a pendant alkyl, aryl or aralkyl group that is fluorinated or perfluorinated.
11. The process according to claim 6 , wherein the polycycloolefinic polymer comprises a second type of repeating unit having a pendant crosslinkable group.
12. The process according to claim 11 , wherein the polycycloolefinic polymer comprises a second type of repeating unit having a substituted or unsubstituted maleimide portion, an epoxide portion, a vinyl portion, an acetylene portion, an indenyl portion, a cinnamate portion or a coumarin portion.
13. The process according to claim 6 , wherein the polycycloolefinic polymer comprises one or more distinct types of repeating units of Formula I
wherein Z is selected from —CH 2 —, —CH 2 —CH 2 — or —O—, m is an integer from 0 to 5, each of R 1 , R 2 , R 3 and R 4 are independently selected from H, a C 1 to C 25 hydrocarbyl, a C 1 to C 25 halohydrocarbyl or a C 1 to C 25 perhalocarbyl group, wherein at least one of R 1 , R 2 , R 3 and R 4 comprises a fluorinated group.
14. The process according to claim 13 , wherein the polycycloolefinic polymer comprises one or more repeating units of Formula I that are formed by one or more norbornene-type monomers selected from the group consisting of the following formulae:
where “C 6 F 5 ” means pentafluorophenyl, in sub-formula 11 “PFAc” means —OC(O)—C 7 F 15 , and for each of the above subformulae having a methylene bridging group (a CH 2 covalently bonded to both the norbornene ring and a functional group) it will be understood that the methylene bridging group can be replaced by a covalent bond or a group —(CH 2 ) b — as in formula 6, and b is an integer from 1 to 6.
15. The process according to claim 6 , wherein the polycycloolefinic polymer comprises one or more repeating units of Formula I that are formed during polymerization from norbornene-type monomers selected from the group consisting of the following formulae:
where n is an integer from 1 to 8, Q 1 and Q 2 are each independently from one another —H or —CH 3 , and R′ is —H or —OCH 3 .
16. The process according to claim 6 , wherein the polycycloolefinic polymer comprises one or more repeating units of Formula I that are formed during polymerization from norbornene-type monomers selected from the group consisting of the following formulae:
where “Me” means methyl, “Et” means ethyl, “OMe-p” means para-methoxy, “Ph” and “C 6 H 5 ” mean phenyl, “C 6 H 4 ” means phenylene, and for each of the above subformulae having a methylene bridging group (a CH 2 covalently bonded to both the norbornene ring and a functional group), it will be understood that the methylene bridging group can be replaced by a covalent bond or a group —(CH 2 ) b —, and b is an integer from 1 to 6.
17. The process according to claim 1 , wherein the dielectric structure is a gate dielectric layer, passivation layer, planarization layer, insulating structure or bank structure, or a part of one of the aforementioned layers or structures.
18. The process according to claim 1 , wherein the OE device further comprises a gate electrode and an organic semiconductor (OSC) layer, and the dielectric structure is a gate dielectric layer that comprises a first dielectric layer that contacts the OSC layer and a second dielectric layer that contacts the gate electrode, wherein both the first and the second dielectric layer comprise a fluorinated polymer.
19. The process according to claim 18 , wherein the first layer comprises an organic fluoropolymer having a permittivity ∈ of 3.0 or less, which is not a polycycloolefinic polymer, and the second dielectric layer comprises a crosslinked fluorinated polycycloolefinic polymer.
20. The process according to claim 19 , wherein the organic fluoropolymer of the first layer is a perfluoropolymer having a permittivity ∈ of 3.0 or less.
21. A process for treating selected parts of insulating structures or bank structures with a solvent blend, comprising the steps of
a) forming insulating structures or bank structures ( 21 , 22 ) by depositing a dielectric material on a substrate ( 20 ) and optionally curing the dielectric material, to define a pixel area ( 24 ),
b) depositing a solvent blend ( 23 ) as defined in claim 1 , into the pixel area ( 24 ), so that the level of the solvent is at the same height as the height of the insulating structures or bank structures ( 21 , 22 ), and not wetting over the top of the insulating structures or bank structures ( 21 , 22 ),
c) allowing the solvents to evaporate, and optionally subjecting the insulating structures or bank structures ( 21 , 22 ) to a further curing step.