Pressure-Sensitive Adhesive Sheet with Dynamic Glass Transition
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Solution Overview
Problem
Traditional pressure-sensitive adhesive sheets face challenges in achieving reworkability, gradual increase in adhesiveness over time, and low contamination properties, especially when adherends are sensitive to heating or ultraviolet irradiation, leading to contamination and poor reusability.
Innovation Solution
A pressure-sensitive adhesive composition comprising a polymer (A) with a glass transition temperature lower than 0°C and a polymer (B) containing monomers with a polyorganosiloxane skeleton, which provides a balance between initial peelability and increased adhesiveness over time, while minimizing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heating or ultraviolet irradiation is used to change pressure-sensitive adhesive force, then adhesiveness can be increased over time, but adherends may be adversely affected by these treatments
Solution Approach 1:
The patent changes the chemical composition parameters of the pressure-sensitive adhesive by incorporating specific polymers with defined glass transition temperatures and functional group equivalents. This allows the adhesive to achieve temperature-dependent adhesion changes without external heating, and to bond to heat-sensitive adherends without causing damage.
Solution Approach 2:
The patent introduces a polymer component with specific molecular characteristics as an intermediary substance that enables adhesion control through molecular mobility changes rather than external energy input. This mediator allows the adhesive to reflow and reattach without subjecting the adherend to harmful heating or UV irradiation.
2Ease of operation
If pressure-sensitive adhesive force is reduced for reworkability, then reattachment becomes possible, but adherend contamination by adhesive deposit or additives occurs
Solution Approach 1:
The patent uses polymers with specific glass transition temperatures to control the adhesive's molecular mobility. At room temperature, the adhesive maintains low initial adhesion for easy reworkability. When heated above the glass transition temperature, the polymer chains become mobile, allowing the adhesive to flow and reattach cleanly without leaving contamination, thus resolving the contradiction between reworkability and contamination.
Solution Approach 2:
The patent creates a dynamic adhesive system where the polymer's physical state changes with temperature. The adhesive transitions from a rigid state at room temperature (enabling clean peeling and reworkability) to a mobile state when heated (enabling clean reattachment without contamination). This dynamic behavior allows the adhesive to provide both reworkability and low contamination property at different stages of use.
3Strength
If pressure-sensitive adhesive force is large from the beginning, then strong fixing is achieved, but reattachment becomes difficult
Solution Approach 1:
The patent employs polymers with glass transition temperatures between -50°C and 0°C, creating a dynamic adhesive system where molecular mobility increases with temperature. At room temperature, the adhesive exhibits low initial adhesion allowing easy reattachment. When heated above the glass transition temperature, the polymer chains gain mobility, enabling the adhesive to flow and form strong bonds, thus providing both easy reworkability and strong fixing capability at different stages.
Solution Approach 2:
The patent changes the physical state parameters of the adhesive polymer through temperature control. By selecting polymers with specific glass transition temperatures, the adhesive transitions from a glassy, rigid state at room temperature (low adhesion, easy reworkability) to a rubbery, mobile state when heated (high adhesion, strong fixing). This parameter change enables the adhesive to provide both weak initial bonding for reworkability and strong final bonding for secure fixing.
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 composition ensures low initial adhesiveness for easy rework, gradual increase in adhesiveness over time for secure fixing, and reduced contamination upon peeling, suitable for various adherends including metal surfaces and optical applications.
Implementation Method 1
100 parts by mass of a polymer (A) having a glass transition temperature lower than 0° C.
Implementation Method 2
0.1 to 20 parts by mass of a polymer (B) that contains, as monomer units, both a monomer having a functional group equivalent (Fge) of 1000 g/mol≤Fge<5000 g/mol and a monomer having a polyorganosiloxane skeleton
Data Source
AI summary
A pressure-sensitive adhesive composition according to an embodiment includes: 100 parts by mass of a polymer (A) having a glass transition temperature lower than 0° C.; and 0.1 to 20 parts by mass of a polymer (B) that contains, as monomer units, both a monomer having a functional group equivalent (Fge) of 1000 g/mol≤Fge<15000 g/mol and having a polyorganosiloxane skeleton and a monomer whose homopolymer has a glass transition temperature of 40° C. or higher, and that has a weight average molecular weight (MwB) of 10000≤MwB≤100000.