Thermal Transfer Sheet Peel Layer Stability
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Solution Overview
Problem
Thermal transfer sheets used for printing minute texts and figures suffer from smudges and blurs, especially when stored in high-temperature environments, due to the instability of release layers containing polyvinyl alcohol and water-dispersible urethane, which are prone to moisture and heat-related issues.
Innovation Solution
A thermal transfer sheet with a peel layer comprising a binder resin, epoxy-modified silicone oil, and polyethylene wax, where the total content of silicone oil and wax is between 0.1% and 15% of the solid content of the binder resin, improving the peeling process and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a release layer comprising acrylic-styrene-based resin is used, then the thermal transfer sheet can be used for heat-fusion type printing, but the release layer softens due to heat from thermal head causing high peel force, transfer failure, image whitening, and abnormal noise
Solution Approach 1:
The invention changes the chemical composition parameters of the release layer by specifying particular resin combinations (polyester resin with specific glass transition temperature range of 40-100°C, and polyurethane resin with specific softening point range of 50-120°C) and their content ratios (polyester resin 30-70 mass%, polyurethane resin 30-70 mass%). This parameter optimization ensures the release layer maintains appropriate softening characteristics that prevent both excessive softening (causing high peel force) and excessive rigidity (causing poor release), thereby resolving the contradiction between heat-fusion adaptability and peeling stability.
2Ease of operation
If a water-based release layer comprising polyvinyl alcohol and water-dispersible urethane is used, then the peeling process is improved, but the release layer is unstable under high moisture environment causing image whitening and abnormal noise
Solution Approach 1:
The invention creates a composite release layer material combining polyester resin and polyurethane resin in specific proportions. This composite structure integrates the advantages of both resin types: polyester resin provides moisture resistance and dimensional stability, while polyurethane resin contributes to peeling ease and flexibility. The synergistic combination resolves the contradiction by achieving both peeling ease and moisture stability that neither material could provide alone.
3Object-affected harmful factors
If polyamide-based resins are used in the release layer, then heat applied to thermal head is reduced and moisture environment effect is minimized, but smudges and blurs appear in minute texts and figures after storage under high temperatures
Solution Approach 1:
The invention optimizes the glass transition temperature parameter of the polyester resin component to a specific range (40-100°C) and the softening point parameter of the polyurethane resin to (50-120°C). These parameter specifications ensure the release layer has sufficient thermal stability to prevent smudging during high-temperature storage and printing, while maintaining appropriate release characteristics. The controlled parameter ranges prevent the excessive heat resistance that would cause smudging, while still providing adequate protection against heat and moisture harmful factors.
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 proposed thermal transfer sheet significantly reduces smudges and blurs, ensuring excellent storage stability and print quality even after storage under high-temperature conditions, as demonstrated by improved reproducibility of white and black lines in printed materials.
Implementation Method 1
the peel layer contains a binder resin, a silicone oil and a wax component... the total content of the silicone oil and the wax component in the peel layer is 0.1 mass % or more and 15 mass % or less, based on the solid content of mass of the binder resin
Implementation Method 2
the silicone oil is an epoxy-modified silicone oil... improvement in smudges and blurs (excellent in storage stability) of the transfer layer when printed matters are prepared even after storing the transfer layer under environment of high temperatures
Implementation Method 3
the wax component is a polyethylene wax... a water-based release layer is unstable to moisture and especially under high moisture environment; problems may occur such as whitening of an image due to roughening of a peel interface
Data Source
Figure 1~2
AI summary
There is provided a transfer sheet with improvement in smudges and blurs of a transfer layer when printed matters are produced even after storing the transfer sheet under high temperatures. The transfer sheet according to the present invention comprises a substrate, and in the order a peel layer and a transfer layer on the substrate, wherein the peel layer contains a binder resin, a silicone oil and/or a wax component and the total contents of the silicone oil and the wax component in the peel layer is 0.1 mass % or more and 15 mass % or less, based on the solid content of mass of the binder resin.