Thin-Film Sheet with Cellulose Fine Fibers for Thermal Stability
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Solution Overview
Problem
Current technologies face challenges in producing a thin sheet with both high thermal stability and low thermal expansion, suitable for electronic materials and power storage devices, due to limitations in controlling fiber diameter and achieving stable resin impregnability and durability.
Innovation Solution
A composite prepreg sheet with a thin sheet composed of fine cellulose fibers, having a specific surface area equivalent fiber diameter of 0.20 µm to 2.0 µm, air impermeability of 1 s/100 ml to 100,000 s/100 ml, and a thickness of 2 µm to 22 µm, combined with a heat-curable or photo-curable resin, which enhances thermal stability and short-circuit resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If cellulose fine fibers with small fiber diameter (200 nm or less) are used to achieve thin sheet adaptability, then sheet thickness can be reduced to 25 μm or less, but resin impregnability deteriorates due to excessively small pore diameter
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fiber diameter of cellulose fine fibers within the range of 0.01 μm to 1.0 μm (with number average of 0.05 μm to 0.5 μm). This parameter optimization creates an optimal balance between achieving thin sheet thickness (2 μm to 22 μm) and maintaining sufficient pore diameter for resin impregnability, while also achieving the desired air impermeability (1 s/100 ml to 100,000 s/100 ml).
Solution Approach 2:
The patent employs composite materials by combining cellulose fine fibers with heat-curable resins and/or photo-curable resins to form a composite prepreg sheet. This composite structure allows the thin sheet to achieve both mechanical strength and thermal stability while maintaining porosity for resin impregnation, resolving the contradiction between thinness and manufacturability.
2Volume of moving object
If fiber diameter is reduced to achieve thin sheet adaptability, then sheet thickness decreases to several tens of micrometers, but thermal stability deteriorates due to insufficient fiber network structure
Solution Approach 1:
The patent uses composite materials by combining cellulose fine fibers with heat-curable resins and/or photo-curable resins. The resin matrix fills the spaces between fine fibers, creating a robust composite structure that provides thermal stability and mechanical strength even when the sheet thickness is reduced to 2 μm to 22 μm.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where cellulose fine fibers provide thermal stability and dimensional control, while the resin matrix provides mechanical strength and fills local gaps. This localized functional distribution allows the thin sheet to simultaneously achieve thinness and thermal stability.
3Volume of moving object
If sheet thickness is reduced to accommodate reduced size of electronic materials, then adaptability to electronic applications improves, but dimensional deformation and warping increase due to reduced rigidity
Solution Approach 1:
The patent employs composite materials where cellulose fine fibers form a stable network structure that resists dimensional deformation, while the resin matrix provides rigidity and structural support. This composite architecture enables the thin sheet (2 μm to 22 μm) to maintain dimensional stability during reflow soldering and other electronic manufacturing processes.
Solution Approach 2:
The patent applies parameter changes by optimizing the fiber diameter distribution and network structure of cellulose fine fibers. The specific surface area equivalent fiber diameter (0.01 μm to 1.0 μm) creates an optimal network density that provides dimensional stability even at reduced sheet thickness, preventing warping during electronic component assembly.
4Volume of moving object
If fine cellulose fibers with high porosity are used to achieve thin sheet adaptability, then sheet thickness decreases to 25 μm or less, but resin impregnability deteriorates due to low porosity and small pore size
Solution Approach 1:
The patent applies parameter changes by optimizing multiple parameters simultaneously: fiber diameter (0.01 μm to 1.0 μm), air impermeability (1 s/100 ml to 100,000 s/100 ml), and sheet thickness (2 μm to 22 μm). This multi-parameter optimization ensures sufficient total porosity for resin absorption while maintaining adequate individual pore size for resin penetration, resolving the contradiction between thinness and resin impregnability.
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 provides a thin sheet with superior thermal stability, elasticity, and short-circuit resistance, enabling its use as a core material for electronic components and separators in power storage devices with improved electrical characteristics and long-term stability.
Implementation Method 1
a cellulose nanofiber sheet that enables thickness to be controlled at the micron level with fine fibers and demonstrates extremely high thermal stability attributable to a hydrogen bond network
Implementation Method 2
a composite prepreg sheet containing: (A) a thin sheet composed of a single layer or multiple layers of three layers or less, which includes at least one layer of fine cellulose fibers
Data Source
AI summary
The present invention provides a thin-film sheet configured from a single layer or a plurality of layers less than or equal to three layers including at least a cellulose fine-fiber layer that includes regenerated cellulose fine fibers by 50 wt% or more, wherein the thin-film sheet achieves improvements in both thermal stability (thermal coefficient of linear expansion and retention of elasticity at high temperature) and sheet strength, and is characterized in that the requirements: (1) the specific surface area equivalent fiber diameter of fibers constituting the cellulose fine-fiber layer is 0.20-2.0 µm inclusive; (2) the air impermeability is 1-100,000 s/100 ml inclusive; and (3) the sheet thickness is 2-22 µm inclusive are satisfied. The present invention also provides a composite sheet, a composite prepreg sheet, a separator for power storage devices, etc., that include the thin-film sheet.