Wide Casting Belt Segmentation for LCD Film Weld Mark Elimination
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Solution Overview
Problem
Current methods for manufacturing wide cellulose acylate films for liquid crystal displays and optical compensation films face challenges in achieving high-quality films due to limitations in belt casting, including visible marks from central welding joints and restricted maximum widths, which hinder the production of films that meet increasing size demands.
Innovation Solution
A wide casting belt configuration with a central belt and two side belts, where all welding joints are aligned on the same straight line, allowing for continuous welding and minimizing the visibility of weld marks, along with a method involving casting, stretching, trimming, and drying processes to produce films with desired widths and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a belt is used for casting, then the surface can be minutely processed through grinding and abrasion, but a joint must be formed to link both ends, creating visible weld marks that reduce optical quality
Solution Approach 1:
The casting belt is divided into multiple segments (first belt, second belt, third belt) that are joined together. This segmentation allows the belt to achieve greater width while distributing the welding joints to positions where they do not create visible marks on the final product, thus resolving the contradiction between surface quality and weld mark visibility.
Solution Approach 2:
The welding joints are positioned in the width direction rather than the length direction of the belt. By changing the orientation and distribution of joints from longitudinal to transverse arrangement, the weld marks fall on areas that are trimmed or positioned at edges of the final product, eliminating their visual impact while maintaining belt continuity.
2Productivity
If the belt width is increased to manufacture wider films, then product yield increases, but the belt must be formed by welding multiple belts together, creating central joints that produce visible marks
Solution Approach 1:
The wide casting belt is constructed by segmenting and joining multiple narrower belts (first, second, and third belts) in the width direction. This allows the system to achieve the necessary width for high-yield production of wide films while strategically positioning the welding joints so they do not interfere with the optical quality of the central product area.
Solution Approach 2:
Different regions of the casting belt are assigned different functions: the central region (second belt) is optimized for producing high-quality product areas, while the side regions (first and third belts) accommodate the welding joints. This local differentiation ensures that weld marks appear only in non-critical areas, maintaining overall optical quality while enabling wide film production.
3Productivity
If drum casting is used for high speed casting, then mass production is enabled, but the drum requires nickel plating and hard chromium plating followed by abrasion, increasing manufacturing complexity
Solution Approach 1:
The complex multi-step surface processing procedure (nickel plating, hard chromium plating, and abrasion) is extracted and replaced with a simpler grinding and abrasion process applied directly to the stainless steel belt. This maintains the high-speed casting capability while significantly reducing manufacturing complexity and the number of processing steps required.
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
Enables the production of wide films without central weld marks, maintaining optical quality and satisfying requirements for intrafacial retardation, facial retardation, and thickness without increasing stretching rates, facilitating the manufacturing of films with widths up to 1500 mm or more.
Implementation Method 1
a dope is casted on a belt, a some amount of solvent is dried and stripped off (detached)
Implementation Method 2
a gel type film stripped off from the wide casting belt; stretching the gel type film stripped off from the wide casting belt, using a tenter
Implementation Method 3
drying the film obtained from the first trimming process, using a dryer
Data Source
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AI summary
The present invention relates to a wide casting belt, and more particularly, to a wide casting belt used for manufacturing a film in a gel state by casting dope used during the manufacture of a polarizing plate for a liquid crystal display, and an optical compensation film, etc. The present invention also relates to a method for manufacturing a wide film using the wide casting belt, and to a wide film manufactured with said wide casting belt.