Reverse Gravure Coating for Uniform Film Thickness

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Solution Overview

Problem

Existing gravure coating methods often result in non-uniform thickness and incomplete coating of a film's surface due to the pattern of recesses on the gravure roll, leading to exposed areas.

Innovation Solution

A reverse gravure coating method is employed, where the gravure roll rotates in the opposite direction to the film conveyance, with specific conditions (0 < a × c / b < 113) to ensure uniform coating, where a is the roll diameter, b is the rotation ratio, and c is the volume of recesses per unit area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a gravure roll with recesses is used for coating, then the coating solution can be applied to the film surface, but the coating thickness becomes non-uniform and the entire surface is not uniformly coated

Engineering Contradiction:

Improvecoating uniformityVSAvoidcoating completeness

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The invention inverts the conventional gravure coating approach by having the gravure roll rotate in the opposite direction to the film conveyance direction. This reverse rotation allows the coating solution to be uniformly distributed across the entire film surface, eliminating the non-uniform thickness and incomplete coating issues that occur with conventional forward rotation methods.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If the gravure roll rotates in the conventional direction, then the coating process is simple, but the coating solution forms a pattern corresponding to the recess shape rather than uniform coverage

Engineering Contradiction:

Improveprocess simplicityVSAvoidcoating uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

By reversing the rotation direction of the gravure roll relative to the film conveyance, the invention achieves uniform coating distribution while maintaining the simplicity of the gravure coating process. The reverse rotation causes the coating solution to be deposited in a manner that eliminates the pattern formation issue, providing both operational simplicity and coating uniformity.

Inventive Principle:

Principle #13The other way round (Inversion)

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

This method achieves uniform coating of the entire film surface, preventing exposure and ensuring consistent thickness, as demonstrated by improved appearance scores and weight per unit area uniformity in heat-resistant separators.

Implementation Method 1

The gravure coating method is carried out by (i) immersing, in a coating solution, a gravure roll having a surface on which unevenness is provided and (ii) causing the gravure roll to come into contact with a base material, so that the base material is coated with the coating solution collected in recesses.

Methodology Applied

Scientific EffectGravure coating:

Data Source

PatentUS10399111B2Coating method, coating device, and functional film production method

Publication Date: 2019.09.03 SUMITOMO CHEM CO LTD

AI summary

A film is uniformly coated with a coating solution. The following formula is satisfied:0<a×c/b<113where (i) a is a diameter (mm) of a gravure roll, (ii) b is a ratio of a circumferential velocity of the gravure roll to a conveyance speed at which the film is conveyed, and (iii) c is a volume (mL/m2) of recesses of the gravure roll, which volume is measured per unit area of a circumferential surface of the gravure roll.