Fluorinated structured organic film photoreceptor layers
A method of forming an overcoat layer. The method comprises providing a substrate having an imaging structure formed thereon, the imaging structure comprising (i) a charge transport layer and a charge generating layer, or (ii) an imaging layer comprising both charge generating material and charge transport material. An overcoat composition is deposited on the imaging structure, the overcoat composition comprising a charge transport molecule, a fluorinated building block, a leveling agent, a liquid carrier and optionally a first catalyst. The fluorinated building block is a fluorinated alkyl monomer substituted at the α and ω positions with a hydroxyl, carboxyl, carbonyl or aldehyde functional group or the anhydrides of any of those functional groups. The overcoat composition is cured to form an overcoat layer that is a fluorinated structured organic film, the curing comprising treating an outer surface of the overcoat composition with at least one cross-linking process. The crosslinking process forms a cross-linking gradient in the overcoat layer. If the overcoat composition comprises the first catalyst, there is an insufficient amount of the first catalyst to fully cross-link the overcoat layer.
1. A method of forming an overcoat layer, comprising:
providing a substrate having an imaging structure formed thereon, the imaging structure comprising (i) a charge transport layer and a charge generating layer, or (ii) an imaging layer comprising both charge generating material and charge transport material;
depositing an overcoat composition on the imaging structure, the overcoat composition comprising a charge transport molecule, a fluorinated building block, a leveling agent, a liquid carrier and optionally a first catalyst, the fluorinated building block being a fluorinated alkyl monomer substituted at the α and ω positions with a hydroxyl, carboxyl, carbonyl or aldehyde functional group or the anhydrides of any of those functional groups; and
curing the overcoat composition to form an overcoat layer that is a fluorinated structured organic film, the curing comprising treating an outer surface of the overcoat composition with at least one cross-linking process, the cross-linking process forming a cross-linking gradient in the overcoat layer,
wherein if the overcoat composition comprises the first catalyst, there is an insufficient amount of the first catalyst to fully cross-link the overcoat layer, and
further wherein the at least one cross-linking process is selected from the group consisting of (i) applying a liquid catalyst to the surface and heating, the liquid catalyst comprising an acid solution, (ii) exposing the surface to plasma, and (iii) exposing the surface to hydrogen bombardment.
2. The method of claim 1 , wherein the overcoat layer comprises a first major surface distal from the imaging structure and a second major surface proximal the imaging structure, the cross-linking gradient comprising a cross-linking density at the first major surface that is greater than a cross-linking density at the second major surface.
3. The method of claim 1 , wherein the charge transport molecule is a triarylamine represented by the following general formula 1:
wherein Ar 1 , Ar 2 , Ar 3 , Ar 4 each independently represents a substituted or unsubstituted aryl group, Ar 5 is selected from the group consisting of a substituted or unsubstituted aryl group and a substituted or unsubstituted arylene group, and k represents 0 or 1,
wherein at least two of Ar 1 , Ar 2 , Ar 3 , Ar 4 and Ar 5 comprises a functional group selected from the group consisting of halogens, alcohols, ethers, ketones, carboxylic acids, esters, carbonates, amines, amides, imines, ureas, aldehydes, isocyanates, tosylates, alkenes, and alkynes.
4. The method of claim 3 , wherein the fluorinated building block is a linear fluorinated alkane terminated at the α and ω positions with hydroxyl groups, the linear alkane having from 4 to 12 carbon atoms.
5. The method of claim 3 , wherein the fluorinated building block is selected from the group consisting of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol, 2,2,3,3,4,4,5,5,6,6,7,7-dodecanfluoro-1 ,8-octanediol, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-perfluorodecane-1,10-diol, (2,3,5,6-tetrafluoro-4-hydroxymethyl-phenyl)-methanol, 2,2,3,3-tetrafluoro-1,4-butanediol, 2,2,3,3,4,4-hexafluoro-1,5-pentanediol, and2,2,3,3,4,4,5,5,6,6,7,7,8,8-tetradecafluoro-1,9-nonanediol.
6. The method of claim 1 , wherein the fluorinated diol is a linear fluorinated alkane terminated at the α and ω positions with hydroxyl groups, the linear alkane having from 4 to 12 carbon atoms.
7. The method of claim 1 , wherein the cross-linking process comprises applying the liquid catalyst following the depositing of the overcoat.
8. The method of claim 1 , wherein the heating is performed at a temperature ranging from about 70° C. to about 200° C.
9. The method of claim 1 , wherein the cross-linking process comprises exposing the surface to plasma.
10. The method of claim 1 , wherein if the cross-linking process includes exposing the surface to plasma or exposing the surface to hydrogen bombardment, then the cross-linking process further comprises exposing the surface to radiation.
11. The method of claim 1 , wherein the cross-linking process comprises exposing the surface to hydrogen bombardment.
12. The method of claim 1 , wherein the overcoat composition comprises the first catalyst in an amount of 0.05% by weight or less, relative to the total weight of the overcoat composition as deposited on the charge transfer layer.
13. The method of claim 1 , wherein the overcoat composition as deposited on the charge transfer layer is substantially free of catalyst.
14. The method of claim 1 , further comprising heating the overcoat composition prior to curing to remove 50% or more of the liquid carrier.
15. The method of claim 1 , wherein the overcoat composition comprises the first catalyst in an amount sufficient to provide a degree of cross-linking ranging from about 75% to about 20%.
16. The method of claim 15 , wherein the cross-linking process comprises applying the liquid catalyst following the depositing of the overcoat.