Coating processes – Immersion or partial immersion
Reexamination Certificate
1995-08-21
2001-04-24
Beck, Shrive (Department: 1762)
Coating processes
Immersion or partial immersion
C427S299000, C134S003000, C134S026000, C430S056000
Reexamination Certificate
active
06221436
ABSTRACT:
This invention relates generally to a method for coating a substrate with layered material to fabricate for example a photoreceptor for use in an electrostatographic printing apparatus. In particular, the present invention pertains to a coating method involving a substrate cleaning operation and at least one dip coating step.
Dip coating is a coating method involving dipping a substrate in a coating solution and taking up the substrate. In dip coating, the coating thickness depends on the concentration of the coating material and the take-up speed, i.e., the speed of the substrate being lifted from the surface of the coating solution. It is known that the coating thickness generally increases with the coating material concentration and with the take-up speed.
The substrate is generally cleaned prior to dip coating since the substrate may have surface contaminants such as dust, fingerprints, and residual cutting fluids which can cause coating defects. There is a need, which the present invention addresses, for substrate cleaning solvents which are preferably environmentally friendly (e.g., avoiding if possible the use of halogenated solvents), and wherein the substrate cleaning operation can be readily added to the substrate coating line.
The following documents disclose conventional dip coating methods, dip coating apparatus, and photosensitive members: Miyake, U.S. Pat. No. 5,213,937; Dossel et al., U.S. Pat. No. 4,652,507; and Pietrzykowski, Jr. et al., U.S. Pat. No. 5,334,246, the disclosures of which are totally incorporated by reference. In particular, Miyake, U.S. Pat. No. 5,213,937, discloses washing the substrate with a solvent such as dichloroethylene, trichloroethylene, and chloroform (col. 3, lines 17-22).
SUMMARY OF THE INVENTION
The present invention is accomplished in embodiments by providing a method for depositing layered material onto a substrate including a layer formed from a coating solution, wherein the method comprises:
(a) cleaning the substrate by dipping the substrate into and raising the substrate from a cleaning solvent selected from the group consisting of (i) a mixture comprising an alcohol and an alkane; and (ii) a liquid compatible with the coating solution; and
(b) dipping the substrate subsequent to (a) into and raising the substrate from the coating solution, thereby depositing the layer on the substrate, wherein when the cleaning solvent is the liquid compatible with the coating solution, any cleaning solvent present on the substrate upon the dipping of the substrate into the coating solution fails to detrimentally affect the layer.
There is also provided in embodiments a method for depositing layered material onto a substrate including a layer formed from a coating solution, wherein the method comprises:
(a) cleaning the substrate by dipping the substrate into and raising the substrate from a cleaning solvent comprising an alcohol and an alkane; and
(b) dipping the substrate subsequent to (a) into and raising the substrate from the coating solution, thereby depositing the layer on the substrate, wherein the layer is a charge blocking layer or a photosensitive layer of a photoreceptor.
There is further provided in embodiments a method for depositing layered material onto a substrate including a layer formed from a coating solution having a coating solvent, wherein the method comprises:
(a) cleaning the substrate by dipping the substrate into and raising the substrate from a cleaning solvent compatible with the coating solution; and
(b) dipping the substrate subsequent to (a) into and raising the substrate from the coating solution, thereby depositing the layer on the substrate, wherein the layer is a charge blocking layer or a photosensitive layer of a photoreceptor, wherein any cleaning solvent present on the substrate upon the dipping of the substrate into the coating solution fails to detrimentally affect the layer.
DETAILED DESCRIPTION
In embodiments of the present invention, the substrate is cleaned prior to dip coating by dipping the substrate into and raising the substrate from a cleaning solvent consisting only of an alcohol and an alkane. The alcohol and alkane are present in the following amounts (by weight based on the total weight of the two components): alcohol, from about 50% to about 90%, and preferably from about 60% to about 80%, and especially about 70%; and alkane, from about 10% to about 50%, from about 20% to about 40%, and especially about 30%.
Suitable alcohols include compounds having one, two, or more —OH groups. Preferred alcohols include for example: aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol, ally alcohol; alicyclic alcohols such as cyclohexanol; aromatic alcohols such as as phenol and benzyl alcohol; and heterocyclic alcohols such as furfuryl alcohol. Especially preferred alcohols contain a single —OH group and have one to six carbon atoms such as the paraffinic alcohols.
Suitable alkanes are those having boiling points between about 25 to about 100 degrees Centigrade which include for example isopentane, n-pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, isohexane, 3-methylpentane, n-hexane and n-heptane.
The combination of alcohol and alkane is effective for removing a wide spectrum of contaminants from the substrate. Since the lower molecular weight alcohols are good polar solvents, they are generally better at dissolving ionic contaminants such as inorganic salts, fingerprints, and the like. Alkanes, being non-polar, provide good solvency for covalently bonded materials such as paraffinic and naphthenic oils or greases and particularly silicone oils which are often the source for coating resist spots. Thus, the combination of two different types of solvents, the alcohol and the alkane, can remove a broader spectrum of contaminants than the use of a single solvent type. The alcohol and alkane mixture, particularly isopropanol and hexane, is effective at removing silicone contaminants such as polydimethylsiloxane from the substrate. In contrast, the conventional mild acid and alkaline aqueous cleaners are not effective at removing the silicone contaminants which are a major contributor to the dip coating defect known as resist spots. Although the efficacy of alkaline cleaners to remove silicones improves with increasing pH, the resulting level of surface destruction via etching is unacceptable for aluminum photoreceptor substrates.
The mixture of the alcohol and the alkane may be an azeotropic solution to facilitate purification of the mixture via distillation to remove contaminants. After purification, the alcohol and alkane mixture may be recycled for further use as a cleaning solvent. An example of an azeotropic mixture is isopropanol and hexane.
In embodiments of the present invention, the substrate is cleaned prior to dip coating by dipping the substrate into and raising the substrate from a cleaning solvent compatible with the coating solution of the first coating station. The term “compatible” means that the cleaning solvent, if present on the substrate during dipping of the substrate into the coating solution, will not detrimentally affect the coated layer, either its physical properties such as uniformity and thickness, or its performance such as electrical characteristics in the resulting photoreceptor. The term “compatible” is intended to refer to the residual amount of the cleaning solvent that may be present on the substrate upon its withdrawal from the cleaning solvent. It is recognized that the exact amount of residual cleaning solvent depends for example on the take-up speed of the substrate from the cleaning solvent, the evaporation rate of the specific cleaning solvent, and the use of a drying step. However, to determine the effect of the cleaning solvent on the resulting coated layer, the amount of the cleaning solvent in question is a smaller amount such as that found in a bead at the bottom edge of the substrate and perhaps elsewhere on substrate surface, rather than a larger amount such as by mixing copious amounts of the cleaning solvent with the coating solution
Herbert William G.
O'Dell Gene W.
Perry Philip G.
Beck Shrive
Chen Bret B.
Soong Zosan S.
Xerox Corporation
LandOfFree
Coating method involving substrate cleaning does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coating method involving substrate cleaning, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coating method involving substrate cleaning will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2528069