Thermal Transfer Speed Control for Uniform Print Surfaces
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Solution Overview
Problem
Image forming apparatuses face issues with concave-convex portions on printed surfaces due to density differences during image formation, leading to nonuniform surface patterns and degraded print quality, especially when high-speed printing is employed, as it results in insufficient thermal energy application and pressure for the protection layer.
Innovation Solution
An image forming apparatus with a transport section that controls the speed of the print recording medium to vary the thickness variation amounts of the dye and protection layers, ensuring Dy ≥ Dx, where Dx and Dy represent the thickness variations before and after image formation, respectively, allowing for controlled thermal energy application to eliminate concave-convex differences and improve surface patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed printing is employed to increase productivity, then printing speed is improved, but concave-convex portions occur on the printed surface due to insufficient thermal energy application and pressure
Solution Approach 1:
The patent divides the thermal transfer process into two distinct stages: a first thermal transfer for the dye layer at high speed, and a second thermal transfer for the protection layer at low speed. This segmentation allows each stage to be optimized independently - the first stage maximizes productivity while the second stage ensures surface uniformity by applying sufficient thermal energy and pressure to eliminate concave-convex portions.
Solution Approach 2:
The patent dynamically adjusts the transport speed of the print recording medium between the two thermal transfer stages. The transport speed is set to a first (high) speed during the first thermal transfer and reduced to a second (low) speed during the second thermal transfer. This dynamic speed adjustment enables the system to achieve both high productivity and high surface quality by matching the transport speed to the thermal energy application requirements of each stage.
2Productivity
If transport speed is increased to highest possible level for high-speed printing, then productivity is improved, but the time period for application of pressure and thermal energy to the protection layer becomes shorter, causing unclear surface pattern
Solution Approach 1:
The patent segments the thermal transfer process into two stages with different speed requirements. The first stage uses high transport speed for dye layer transfer, while the second stage uses low transport speed for protection layer transfer. This segmentation resolves the contradiction by allowing the system to operate at high speed when productivity is the priority and switch to low speed when surface pattern clarity is the priority.
Solution Approach 2:
The patent implements dynamic transport speed control that adjusts the speed based on the specific thermal transfer stage. The controller reduces the transport speed during the second thermal transfer of the protection layer to ensure sufficient time for pressure and thermal energy application, thereby achieving clear surface patterns while maintaining overall high productivity through the first stage.
3Manufacturing precision
If thermal energy and pressure are applied to eliminate concave-convex portions, then surface uniformity is improved, but the process time increases, reducing productivity
Solution Approach 1:
The patent segments the thermal transfer process to apply intensive thermal energy and pressure only during the second stage for the protection layer, while maintaining high speed during the first stage for the dye layer. This segmentation allows the system to spend time on surface uniformity only when necessary, preserving overall productivity.
Solution Approach 2:
The patent dynamically adjusts the transport speed to match the thermal energy application requirements. During the first stage, high speed maintains productivity, while during the second stage, low speed enables sufficient thermal energy application for surface uniformity. This dynamic adjustment optimizes the trade-off between process time and productivity.
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 concave-convex portions caused by density differences during image formation and enhances the clarity and uniformity of the surface pattern by adjusting the transport speed to optimize thermal energy application, thereby improving print quality.
Implementation Method 1
a thermal head that applies thermal energy in a state where the receptive layer of the print recording medium opposes the dye layer and protection layer of the thermal transfer sheet and that sequentially thermally transfers the dye layer and protection layer of the thermal transfer sheet onto the print recording medium
Data Source
AI summary
An image is formed by thermally transferring dyes of a thermal transfer sheet onto a print recording medium, and then a protection layer is formed on the formed image. The transport speed of the print recording medium in the event of thermal transferring the dyes onto the print recording medium is set higher than that in the event of thermal transferring the protection layer onto the print recording medium. Thereby, the amount of thermal energy for application in the event of protection layer formation is increased to be greater than that in the event of image formation. Thereby, occurrence of concave-convex portions formed on the printed surface in association with a density difference in the event of image formation is prevented, and concurrently, the surface pattern in the event of image protection layer formation is improved.