Curved Display Resin Lamination Shrinkage Control
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Solution Overview
Problem
The manufacturing of image display devices with curved light transmissive cover members using photocurable resin compositions often results in curing shrinkage issues, leading to voids and color unevenness due to non-uniform coating thickness and residual stress in the cured resin layer.
Innovation Solution
The method involves integrating an image display member with a curved light transmissive cover member to form a hollow body with openings, filling the hollow portion with a photocurable resin composition, and photocuring it from one side to the other, concentrating curing shrinkage space on the opposite side, thereby preventing voids and reducing residual stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If photocurable resin composition is applied to the concave surface of the curved light transmissive cover member, then the coating thickness becomes non-uniform (0-500 μm at sides, several mm at center), but this leads to remarkable curing shrinkage in the central portion, forming concave portions and voids
Solution Approach 1:
The patent inverts the conventional lamination approach by integrating the image display member and curved cover member with their concave surfaces facing each other to form a hollow body, then filling the hollow portion with photocurable resin. This inversion transforms the harmful non-uniform thick coating into a controlled filling process where the resin is supplied from the opening side, allowing curing shrinkage to concentrate away from the display surface.
Solution Approach 2:
The patent transitions from a conventional planar lamination approach to a three-dimensional hollow body filling approach. By creating a hollow body structure and filling it from one end, the process accommodates the curved geometry while controlling resin distribution and shrinkage in a dimensional space that prevents display surface defects.
2Quantity of substance
If the coating thickness of photocurable resin composition is increased to several mm in the central portion, then the curing shrinkage becomes remarkably large, but this causes color unevenness in the display due to residual stress
Solution Approach 1:
The patent extracts the harmful effect of curing shrinkage from the display surface region by concentrating it on the opening side of the hollow body. The photocurable resin is filled and cured in such a way that the shrinkage space is generated and concentrated away from the display surface, thereby preventing color unevenness while still providing sufficient resin quantity for proper bonding.
3Manufacturing precision
If a flat image display member is laminated on a flat light transmissive cover member with uniform coating thickness of about 150 μm, then voids are hardly generated and residual stress influence can be ignored, but this cannot achieve the desired curved shape for improved design and touch feeling
Solution Approach 1:
The patent changes the geometric parameters of the system by integrating the image display member and curved cover member with their concave surfaces facing each other, creating a hollow body structure. This parameter change allows the use of photocurable resin filling and curing processes that accommodate curved geometries while controlling shrinkage to prevent display surface defects.
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 approach effectively prevents voids on the display surface and reduces color unevenness by concentrating curing shrinkage space, ensuring a uniform and stress-reduced cured resin layer for improved image display quality.
Implementation Method 1
irradiating the photocurable resin composition filled in the liquid accommodating portion with ultraviolet rays from the side of the cured light transmissive cover member to form a cured resin layer
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A
AI summary
An image display device in which an image display member and a curved light transmissive cover member are laminated with a cured resin layer interposed therebetween is manufactured by integrating the image display member and the curved light transmissive cover member with each other with a concave surface of the light transmissive cover member facing the image display member to form a hollow body having a hollow portion with an opening as a liquid accommodating portion, filling the liquid accommodating portion with a photocurable resin composition from the opening, and photocuring the photocurable resin composition to concentrate a space generated by curing shrinkage on the opening side.