1. Field of the Invention
The present invention relates to an apparatus for producing an electrophotographic photosensitive member wherein the apparatus has stretching hoods which can cover members to be coated individually when forming coating films on each surface of the plural members to be coated by dip coating, and a process for producing an electrophotographic photosensitive member by employing the apparatus.
2. Description of the Related Art
Electrophotographic photosensitive members for use in copiers and laser beam printers are produced by forming a photosensitive layer on the surface of the members to be coated containing a support. Dip coating method, which can form a photosensitive layer at the same time on each surface of the plural members to be coated, is often adopted in the production process for the reason that the method is space-saving and of low cost.
The dip coating method is a method containing steps of dipping a member to be coated in a coating liquid for photosensitive layer or the like placed in a coating bath, lifting up the coated member from the coating liquid, and then drying the coating film formed on the surface of the member to be coated. The dip coating method is thus easy to perform and facilitates mass production (simultaneous coating of plural members). However, the state of the solvent vapor present around the member to be coated may vary affected by airflow from the outside when the coated member is lifted up from the coating bath. On this account, the dip coating method has a problem that irregularities may occur in the coating film formed on the surface of the member to be coated.
Japanese Patent Application Laid-Open No. 2007-086176, Japanese Patent No. 3797532 and Japanese Patent Application Laid-Open No. H07-104488 disclose a technique of providing a hood around a member to be coated for overcoming this problem. In addition, Japanese Patent Application Laid-Open No. 2007-206151 discloses a technique of providing a hood covering up the whole of the plural members to be coated. These techniques intend to control the airflow from the outside with a hood and to suppress the occurrence of the irregularities of the coating film. In addition, these hoods are constructed as stretching hoods so that the hoods can extend in association with the movement of the member to be coated when the member to be coated is lifted up.
However, when such a stretching hood for covering the whole of the plural members to be coated as disclosed in Japanese Patent Application Laid-Open No. 2007-206151 is used, difference will be caused between the state of the solvent vapor present around the members to be coated disposed on the outer side and the state of the solvent vapor present around the members to be coated disposed on the inner side in the case where the apparatus is configured so that dip coating of plural members to be coated can be performed at the same time as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 2007-206151. As a result, drying may proceed differently and the condition of the formed coating film may be different between the coating film formed on the surface of the members on the outer side and the coating film formed on the surface of the members on the inner side.
Accordingly, in the case where plural members to be coated are dip coated at the same time, it is necessary to provide plural stretching hoods so as to enable to cover each side of the plural members to be coated individually.
However, in the case where plural stretching hoods for covering each side of the plural members to be coated individually are provided as disclosed in Japanese Patent Application Laid-Open No. 2007-086176, Japanese Patent No. 3797532 and Japanese Patent Application Laid-Open No. H07-104488, plural stretching hoods are disposed in a limited space and inconvenient situation that adjacent stretching hoods touch with each other may occur. When dip coating of plural members to be coated is performed in such a condition, the stretching hoods may interfere with each other, resulting in difference in the individual extension and contraction movement among of the stretching hoods, and the state of the solvent vapor around the plural members to be coated will become different. In addition, when the extension and contraction operation of the plural stretching hoods is repeated, difference among the stretching hoods may be resulted in the way of the extension and contraction even if there is no interference among the stretching hoods as mentioned above. As a result, even if the airflow from the outside can be suppressed by using the stretching hoods, the difference in the state of the solvent vapor around the members to be coated will result in the difference in the irregularities of the coating film among the produced plural electrophotographic photosensitive members, thus causing individual difference in the electrophotographic characteristics.