Thermal Head Energy Control for Multi-Color Print Quality
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Solution Overview
Problem
Printers using thermal heads often experience deterioration in print quality due to the formation of white lines when resuming print medium conveyance after a halt, especially when using multi-color print media, as parts of the media are redundantly heated, leading to uneven thermal energy application and color development.
Innovation Solution
A printer with a thermal head having multiple heating elements, where the thermal energy application is controlled to apply specific quantities per unit area to different areas of the print medium, ensuring that overlapping areas receive a combined thermal energy within a defined range to prevent excessive heating and maintain consistent color development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the printer conveys the print medium in forward and backward directions to prevent white line formation, then white line formation is prevented, but thermal energy is redundantly applied to certain areas causing uneven color development
Solution Approach 1:
The patent applies different thermal energy quantities to different areas of the print medium based on their conveyance history. Areas that were heated during forward conveyance receive reduced thermal energy during backward conveyance, while areas heated during backward conveyance receive full thermal energy during forward conveyance. This local differentiation prevents redundant heating and ensures uniform color development across the print medium.
2Productivity
If the thermal head applies thermal energy to the print medium during conveyance resumption, then printing can continue, but uneven thermal energy application causes different colors to develop in different areas
Solution Approach 1:
The controller determines the conveyance direction and history before applying thermal energy. Based on whether the medium was previously conveyed forward or backward, the controller pre-calculates the appropriate thermal energy quantity to apply. This preliminary assessment prevents uneven heating by anticipating which areas need full heating and which areas received prior heating during the halt period.
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 solution effectively prevents the formation of white lines and ensures consistent color development across the print medium, maintaining high print quality by adjusting thermal energy application to specific areas, thereby addressing the issue of uneven heating and color variation.
Implementation Method 1
a thermal head 31 having a plurality of heating elements 32 arranged in an arrangement direction, the thermal head 31 being configured to selectively energize the plurality of heating elements 32, thereby applying thermal energy to a print medium 3A
Implementation Method 2
the print medium 3A being configured to develop a first color when supplied with a quantity of thermal energy per unit area that is equal to or more than a first quantity and equal to or less than a second quantity and to develop a second color when supplied with a quantity of thermal energy per unit area that is equal to or more than a third quantity more than the second quantity
Data Source
AI summary
A printer includes a controller configured to, while conveying a print medium, apply a fourth quantity of thermal energy per unit area to a first area of the print medium and apply a fifth quantity of thermal energy per unit area to a second area that at least partially overlaps the first area in a conveyance direction, the print medium developing a color when supplied with a quantity of thermal energy per unit area equal to or more than a first quantity and equal to or less than a second quantity and developing another color when supplied with a quantity of thermal energy per unit area equal to or more than a third quantity more than the second quantity, the fourth and fifth quantities being more than the first quantity and less than the second quantity, a sum of the fourth and fifth quantities being less than the third quantity.