Coating Liquid Supplying Roll with Fine Concaves for Photoreceptor Uniformity
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Solution Overview
Problem
Existing methods for applying a coating liquid to cylindrical substrates, such as electrophotographic photoreceptors, face challenges in achieving uniform thickness, seamless coatings, and high production efficiency due to issues like solvent vaporization, uneven coating, and physical properties affecting the lifting rate in dip coating, and residence of coating material in roll coating.
Innovation Solution
An apparatus and method utilizing an applicator roll and a coating liquid supplying roll with fine concaves, where the loss tangent of the coating liquid is between 1 and 10, and the concave portion's design ensures uniform coating by controlling the coating liquid amount and transferring it seamlessly onto the substrate, preventing unevenness and sagging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solvent having a low boiling point is used in the coating material, then the coating material can be applied to the substrate, but the solvent is vaporized during coating, causing the concentration of solids to increase and the coating film surface to become irregular
Solution Approach 1:
The patent changes the physical-chemical parameters of the coating liquid by controlling the loss tangent (tan δ) within 1-10 and adjusting viscosity to 10-1000 cP. This parameter optimization prevents solvent vaporization issues while maintaining coating uniformity, resolving the contradiction between coating applicability and film uniformity.
2Manufacturing precision
If a solvent having a high boiling point is used, then the coating film leveling is improved, but the solvent vaporization is slow causing delayed fixing and coating material sagging
Solution Approach 1:
The patent optimizes the loss tangent parameter to 1-10 and viscosity to 10-1000 cP, which balances the solvent evaporation rate. This ensures adequate leveling time while preventing sagging and maintaining production efficiency, resolving the contradiction between film smoothness and fixing speed.
3Manufacturing precision
If the dip coating method is used, then the coating film surface smoothness is improved, but the coating film is formed in the interior and end face of the substrate requiring additional peeling steps
Solution Approach 1:
The patent extracts the coating application to only the peripheral surface of the substrate using a cylindrical applicator roll, preventing coating on the interior and end faces. This eliminates the need for peeling steps while maintaining surface smoothness, resolving the contradiction between film quality and process complexity.
4Manufacturing precision
If the lifting rate after dipping is made slow to achieve uniform thickness, then the coating film uniformity is improved, but the production efficiency is reduced
Solution Approach 1:
The patent replaces the mechanical dip-coating process with a roll-to-roll contact transfer system. The coating is applied through controlled contact between rolls at adjustable speeds, achieving uniform thickness without slow lifting rates, thus maintaining high production efficiency.
5Productivity
If the blade coating method is used to achieve high producibility, then the production efficiency is improved, but the coating film thickness becomes non-uniform due to surface tension effects
Solution Approach 1:
The patent introduces an intermediary applicator roll that transfers coating material to the substrate. This intermediary mechanism controls coating thickness through roll contact pressure and speed, eliminating surface tension effects while maintaining high production efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the formation of a coating film with uniform thickness and excellent uniformity on cylindrical substrates, enhancing production efficiency and image quality in electrophotographic photoreceptors.
Implementation Method 1
a coating liquid supplying roll (5) having a fine concave portion (8) having a plurality of fine concaves (8a) formed therein
Implementation Method 2
a phenomenon wherein a part of the coating film coated on the substrate swells occurs due to a surface tension of the substrate
Implementation Method 3
a loss tangent tan δ (=G''/G'), which is a ratio of loss modulus (G'') to a storage modulus (G') of the coating liquid at a frequency of 6.28 radians/sec, is 1 or more and not more than 10
Implementation Method 4
supplying the coating liquid to an applicator roll (4) from the coating liquid supplying roll (5); and applying the coating liquid from the applicator roll (4) in such a manner that it is contact-transferred onto the cylindrical substrate (2)
Data Source
AI summary
A coating liquid to be used for coating has a loss tangent tan δ of from 1 to 10 at a frequency of 6.28 radians/sec. A coating liquid supplying roll has a fine concave portion in at least a part of the circumferential length thereof, and in the vicinities of the both circumferential ends of the fine concave portion, the fine concave portion 8 has concave depth decreasing portions formed in such a manner that the depth of a fine concave decreases. The fine concave portion is constructed in such a manner that the sum L (=L1+L2) of a circumferential length L1 of a portion in which the fine concaves are formed in substantially the same depth and a circumferential length L2 of one concave depth decreasing portion becomes an integral multiple (1 or more) of a circumference Lc of the cylindrical substrate.