Smart Window Film Laminate Gap Layer to Prevent Liquid Crystal Mura
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Solution Overview
Problem
Conventional transmittance variable optical laminates face issues with uneven distribution of liquid crystals during glass bonding, leading to liquid crystal mura, especially when a polarizing plate and conductive layer are in direct contact without a substrate, and there is a need for a structure that minimizes pressure on the liquid crystal layer to prevent such defects.
Innovation Solution
Incorporating a gap layer at the ends of the optical laminate, made of polyvinyl butyral (PVB) film, with specific storage modulus ranges, and a two-step bonding process to reduce pressure on the liquid crystal layer, thereby preventing liquid crystal mura.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass bonding is performed on a conventional optical laminate without a gap layer, then bonding strength is achieved, but pressure causes uneven liquid crystal distribution and liquid crystal mura
Solution Approach 1:
A gap layer made of polyvinyl butyral (PVB) film is introduced as an intermediary element between the glass and the optical laminate. This gap layer has a thickness of 0.3 to 0.8 mm, which is greater than the thickness of the optical laminate (0.1 to 0.3 mm), and serves to distribute the bonding pressure uniformly, preventing direct pressure transmission to the liquid crystal layer while maintaining bonding strength.
Solution Approach 2:
The gap layer acts as a cushioning element that is pre-installed before the bonding process. It absorbs and distributes the pressure applied during glass bonding, preventing the pressure from directly affecting the liquid crystal layer. This beforehand cushioning ensures that the liquid crystal remains evenly distributed throughout the bonding process.
2Length of moving object
If the optical laminate thickness is reduced for thinner design, then device thickness is minimized, but liquid crystal mura becomes more likely to occur due to increased pressure sensitivity
Solution Approach 1:
The gap layer serves as a protective intermediary that decouples the pressure application from the thin optical laminate. Even though the optical laminate thickness is reduced to 0.1-0.3 mm for a thinner design, the gap layer (0.3-0.8 mm) provides sufficient cushioning to protect the thin laminate and its liquid crystal layer from pressure-induced mura during bonding.
3Ease of manufacture
If a separate substrate is used to form the conductive layer, then manufacturing stability is improved, but laminate thickness increases significantly
Solution Approach 1:
The conductive layer is merged directly with the optical laminate structure, eliminating the need for a separate substrate. The optical laminate itself serves as the base for the conductive layer, integrating multiple functions into a single component and reducing the overall laminate thickness while maintaining manufacturing stability through the gap layer protection.
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 effectively minimizes pressure on the liquid crystal layer, preventing uneven distribution and liquid crystal mura, while allowing for a significantly reduced thickness of the laminate compared to conventional methods.
Implementation Method 1
a transmittance variable optical laminate capable of changing the transmittance of light when a voltage is applied has been developed. The transmittance variable optical laminate is driven to change transmittance by driving liquid crystals in response to application of a voltage.
Implementation Method 2
a gap layer formed at ends of the optical laminate and including a polyvinyl butyral (PVB) film, wherein the thickness of the gap layer is larger than the thickness of the optical laminate
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~4c
AI summary
Disclosed is a film laminate including: an optical laminate; and a gap layer formed at ends of the optical laminate and including a polyvinyl butyral (PVB) film, wherein the thickness of the gap layer is larger than the thickness of the optical laminate. By providing a structure in which the gap layer thicker than the optical laminate is formed in a pillar shape at ends of the optical laminate so as to minimize the pressure applied to a liquid crystal layer during glass bonding, the uneven distribution of liquid crystals due to the fluidity thereof does not occur, and thus the occurrence of liquid crystal mura may be prevented.