Electron Transport Undercoat Layer for Electrophotographic Photoreceptors
Publication Date: 2005-Nov-08
The IP.com Prior Art Database
AbstractSubstrates for organic photoconductors (OPC) are usually coated with an undercoat layer (UCL). The UCL functions as an electron transporting, hole blocking layer. The UCL must also be capable of preventing low humidity cycle-down and help control charge deficient spots (CDS). Additional functions of the UCL include improved print quality, ensuring environmental insensitivity, and cyclic stability, as well as masking of substrate defects.
Substrates for organic photoconductors (OPC) are usually coated with an undercoat layer (UCL). The UCL functions as an electron transporting, hole blocking layer. The UCL must also be capable of preventing low humidity cycle-down and help control charge deficient spots (CDS). Additional functions of the UCL include improved print quality, ensuring environmental insensitivity, and cyclic stability, as well as masking of substrate defects. Current OPC are manufactured with UCL produced by dispersing a metal oxide (eg. TiO2) in a polymeric binder. Costly processing as well as dispersion quality control & stability disadvantage dispersed systems. For example, non-homogeneity of the dispersed the oxide particles within the binder matrix may give rise to electrical non-uniformity in the device.
Poor dispersion quality may also result in incomplete coverage of the substrate, leading to pin holes, which produce CDS. There are efforts currently underway to develop non-dispersed UCLs such as those based on poly(vinylbenzoyl alcohol) (PVBA) and titanium isopropoxide (TIP). However, some of the major problems associated with these non-dispersed UCLs being developed include the fact that they exhibit poor electrical stability, including high VL , a rise in residual voltage during cycling, as well as print defects such as high background. Thus, the challenge is to develop a benchmark, single-phase, non-particulate UCL that meets the physical and electrical requirements for electrophotographic printing.
This invention disclosure describes the use of electron transport co-polymers as a unique single-phase, non-particulate UCL.
The concept has been reduced to practice, first by the synthesis of Vinylbenzoyl 9-Dicyanomethylene Fluorene-4-Carboxylate (VDFC) and subsequent preparation of a copolymer with n-Butyl methacrylate (BMA) and a terpolymer with BMA and vinylbenzoyl alcohol (VBA), respectively. The resulting polymers were used as undercoat layers (UCL), respectively, for the fabrication of photoreceptor devices. Adhesion between the respective UCL and both the aluminum substrate and the charge generation layer (CGL) respectively, is excellent. The UCLs exhibit very efficient charge transport.
Synthesis of Vinylbenzoyl acetate (1)
In a 1L 3-neck flask equipped with a condenser, mechanical stirrer and thermometer, 108g (0.708 mol) of vinylbenzoyl chloride
(60/40 m-/p-) and 80.8 (0.824 mol) of potassium acetate were added, followed by 250 mL of DMSO. The mixture was stirred at 40 0C for 48 hours. After being allowed to cool to room temperature, the mixture was diluted with water and poured into a separatory funnel. The organic layer was separated, followed by extraction of the aqueous layer with chloroform. The combined organic layer was then washed with water, dried over magnesium sulfate and placed on the rotary evaporator to remove...