Textured PVB Interlayers for Iceflower Defect Reduction
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Solution Overview
Problem
Existing lamination processes for safety glass using poly(vinyl butyral) (PVB) interlayers often result in defects known as 'iceflowers' due to trapped air, which are costly and only detected after installation, particularly in automotive applications.
Innovation Solution
A PVB interlayer with a textured surface having a controlled, collapsible roughness profile characterized by a higher number of peaks than valleys and specific surface roughness parameters, designed to enhance deairing during the lamination process, reducing trapped air and minimizing iceflower defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional smooth PVB interlayer is used in lamination process, then the manufacturing process is simple, but trapped air forms iceflower defects visible on the final product
Solution Approach 1:
The PVB interlayer surface is engineered with localized peaks and valleys of specific dimensions (peaks: 0.5-5 mils, valleys: 1-10 mils) to create deairing channels that actively remove trapped air during lamination, transforming a uniformly smooth surface into a functionally differentiated structure that prevents iceflower defects
Solution Approach 2:
The textured surface structure is pre-formed on the PVB interlayer before lamination, creating a ready-to-function deairing network that actively removes air during the lamination process, eliminating the need for post-lamination defect removal and preventing iceflower formation
2Reliability
If a textured surface with many peaks is used to improve deairing, then trapped air is reduced, but the surface roughness increases which may affect optical clarity
Solution Approach 1:
The surface texture parameters are precisely controlled within specific ranges: peak height of 0.5-5 mils, valley depth of 1-10 mils, and peak spacing of 0.01-0.5 inches. These parameter constraints ensure sufficient deairing capability while maintaining optical clarity by preventing excessive surface roughness that would scatter light
3Strength
If the PVB interlayer is heated to high temperature to improve adhesion, then bonding strength increases, but trapped air expands forming visible defects
Solution Approach 1:
The textured surface is pre-configured with deairing channels that actively remove air during the heating and pressing phases of lamination, creating a vacuum effect that prevents air expansion into visible defects even as temperature increases for adhesion bonding
Solution Approach 2:
The textured surface structure acts as an intermediary mechanism between the heating process and the air trapped in the laminate, providing a controlled pathway for air removal that mediates the conflict between thermal adhesion promotion and air expansion prevention
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 textured PVB interlayer provides superior deairing performance, reducing iceflower defects and allowing greater processing flexibility, with improved clarity and structural integrity in laminated glass products.
Implementation Method 1
a controlled, collapsible surface roughness profile (upon exposure to heat)
Implementation Method 2
provide very good initial contact and tack of PVB to a glass surface
Implementation Method 3
heating the assembly a second time to about 50° C. to about 120° C. to give the assembly enough temporary adhesion
Implementation Method 4
passing the assembly into a pressure nip roll for a first deairing
Data Source
AI summary
The invention provides a PVB interlayer sheet having a surface topography on at least one surface which is characterized as having a relatively low profile and a controlled, collapsible surface roughness profile (upon exposure to heat) having a population of significantly more surface peaks than negative peaks (valleys) in certain embodiments and slightly more distant peak spacing than is generally found in embossed PVB interlayers. The PVB interlayer sheets of the invention thus provide very good initial contact and tack of PVB to a glass surface, while leaving very little residual air behind after a first nip in a traditional glass lamination process when compared to other surface designs. The PVB interlayer sheets of the invention also exhibit a wide deairing window which affords greater tolerance of temperature and process variations.