Laminated Glass Interlayer Birefringence Control to Prevent Edge Protrusion
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Solution Overview
Problem
Conventional interlayer films for laminated glass often protrude from the ends during the production process, especially when passing through heated rolls, leading to inefficiencies and potential safety issues.
Innovation Solution
An interlayer film comprising a thermoplastic resin and a plasticizer, with specific birefringence index values in both machine direction (MD) and transverse direction (TD), is used to minimize protrusion by controlling tensile force and strain, ensuring the film remains securely positioned between glass plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the laminate is made to pass through a gap between heated rolls during production, then the laminated glass can be heated and pressurized to achieve bonding, but the interlayer film portion protrudes from the end part
Solution Approach 1:
The patent applies parameter changes by controlling the birefringence index (Δn) of the interlayer film to be 0.005 or less in both MD and TD directions. This optical parameter control reflects and ensures uniform molecular orientation and dimensional stability of the film during heating and pressing, preventing protrusion while maintaining bonding quality.
Solution Approach 2:
The patent implements preliminary action by pre-controlling the birefringence characteristics of the interlayer film before the lamination process. By ensuring the film has appropriate optical properties beforehand, the film is prepared to resist deformation during subsequent heating and pressing operations, preventing end protrusion.
2Productivity
If conventional interlayer films are used, then the production process can proceed, but the interlayer film protrudes from end parts reducing efficiency and safety
Solution Approach 1:
The patent changes the optical parameter (birefringence index Δn ≤ 0.005) of the interlayer film to achieve dimensional stability during processing. This parameter control prevents protrusion that would cause production delays and safety issues, thereby improving both productivity and reliability simultaneously.
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 interlayer film effectively suppresses protrusion from the ends, enhancing production efficiency and safety by maintaining the film's position during the laminating process, with a total ΔnMAX value of less than 0.070 × 10^-3 in both MD and TD directions.
Implementation Method 1
a birefringence index in a machine flow direction of the first surface part A, a birefringence index in a machine flow direction of the second surface part B, and a birefringence index in a machine flow direction of the center part C
Data Source
Figure 1~3
Figure 4~5(c)
Figure 6(a)~6(c)
AI summary
There is provided an interlayer film for laminated glass with which an interlayer film portion is less liable to protrude at the time of producing laminated glass. In the interlayer film for laminated glass according to the present invention, when, in the MD direction of the interlayer film, a birefringence index of the first surface part, a birefringence index of the second surface part, and a birefringence index of the center part are defined as ΔnMDA, ΔnMDB, and ΔnMDC, respectively, in the TD direction of the interlayer film, a birefringence index of the first surface part, a birefringence index of the second surface part, and a birefringence index of the center part are defined as ΔnTDA, ΔnTDB, and ΔnTDC, respectively, a higher absolute value among the absolute value of the difference between ΔnMDA and ΔnMDC and the absolute value of the difference between ΔnMDB and ΔnMDC is defined as ΔnMDMAX, and a higher absolute value among the absolute value of the difference between ΔnTDA and ΔnTDC and the absolute value of the difference between ΔnTDB and ΔnTDC is defined as ΔnTDMAX, the total of ΔnMDMAX and ΔnTDMAX is 0.070 × 10-3 or less.