Thermal Transfer Sheet Back Face Layer Slippage and Heat Resistance
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Solution Overview
Problem
Thermal transfer sheets suffer damage to the dye receiving layer under high temperature and high humidity conditions, leading to reduced gloss and the generation of printing wrinkles, especially due to low slippage between the sheet and the thermal head, and exhibit issues with heat resistance and slipping property under varying environmental conditions.
Innovation Solution
A thermal transfer sheet with a dyestuff layer or transcriptive protective layer on one surface and a back face layer on the other, where the back face layer comprises a resin with a weight-average molecular weight greater than 15,000, a polyester resin with a weight-average molecular weight not exceeding 15,000, and a lubricant ingredient, optimized within specific weight percentage ranges to enhance heat resistance and slipping property.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a back face layer is added to improve slippage between the thermal transfer sheet and thermal head, then slippage is improved, but the layer suffers damages under high temperature and high humidity conditions leading to reduced gloss
Solution Approach 1:
The back face layer uses a composite resin system combining polyester resin (low molecular weight ≤15,000) and polyvinyl acetal resin (high molecular weight >15,000). The polyester resin provides initial slippage properties, while the polyvinyl acetal resin forms a heat-resistant crosslinked network that prevents damage under high temperature and high humidity conditions, resolving the contradiction between slippage and durability.
Solution Approach 2:
The patent specifies precise molecular weight parameters: polyester resin with Mw ≤15,000 for slippage and polyvinyl acetal resin with Mw >15,000 for heat resistance. This parameter differentiation allows each component to perform its specific function optimally, achieving both good slippage and damage resistance simultaneously.
2Ease of operation
If lubricant ingredient is increased to improve slippage property, then slippage is improved, but printing wrinkles are generated under low temperature and low humidity conditions
Solution Approach 1:
The patent optimizes lubricant content to 1-30 parts by weight per 100 parts of total resin, preventing excessive lubrication that causes wrinkles. Combined with the specific resin molecular weights, this controlled lubricant level provides sufficient slippage without causing printing defects under low temperature and low humidity conditions.
Solution Approach 2:
The composite resin system balances slippage and wrinkle prevention: polyester resin contributes to slippage with controlled lubricant, while polyvinyl acetal resin provides structural integrity that prevents wrinkle formation, achieving both goals simultaneously.
3Ease of operation
If resin with low molecular weight is used to improve slippage, then slippage is improved, but heat resistance is insufficient under high temperature conditions
Solution Approach 1:
The back face layer combines polyester resin (Mw ≤15,000) for slippage with polyvinyl acetal resin (Mw >15,000) for heat resistance. The high molecular weight polyvinyl acetal resin forms a stable crosslinked network that maintains structural integrity at high temperatures, while the low molecular weight polyester resin ensures adequate slippage properties.
Solution Approach 2:
The patent uses molecular weight as a key differentiating parameter: polyester resin with Mw ≤15,000 optimizes slippage, while polyvinyl acetal resin with Mw >15,000 ensures heat resistance. This parameter-based material selection resolves the contradiction between slippage and thermal stability.
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 results in a glossy image with minimal or no printing wrinkles, even under high temperature and high humidity conditions, and improves the thermal transfer sheet's performance by maintaining image quality and preventing defects across different environmental conditions.
Implementation Method 1
the back face layer comprises (A) a resin of which weight-average molecular weight (Mw) is more than 15,000; (B) a polyester resin of which weight-average molecular weight (Mw) is not more than 15,000; and (C) a lubricant ingredient
Implementation Method 2
a back face layer having a cross-linking structure is formed on the substrate by using concurrently a binder resin which has a reacting group such as hydroxyl group with a polyisocyanate
Data Source
Figure 1
AI summary
Provided is a thermal transfer sheet capable of forming an image having excellent glossiness, and having no printing wrinkle or having a lesser possibility of generating winkles. A thermal transfer sheet in which a dyestuff layer or a transcriptive protective layer is formed on one surface of a substrate and a back face layer is formed on another surface of the substrate, wherein the back face layer contains (A) a resin of which weight-average molecular weight (Mw) is more than 15, 000; (B) a polyester resin of which weight-average molecular weight (Mw) is not more than 15, 000; and (C) a lubricant ingredient; and wherein the (B) polyester resin is contained at an amount range of 3 % by weight to 40 % by weight on the basis of the total solid content weight of the back face layer.