Thermal Head Covering Layer Surface Roughness
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Solution Overview
Problem
Existing thermal heads face issues with the recording medium not peeling off smoothly from the lateral surface of the covering layer due to uniform contact, leading to increased contact area and difficulty in transportation.
Innovation Solution
The thermal head design features a covering layer with a higher arithmetic-average surface roughness on its lateral surface compared to its upper surface, allowing uniform resin application and stabilization, reducing contact area, and enabling easy peeling and smooth transportation of the recording medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the arithmetic-average surface roughness Ra of the lateral surface of the covering layer is made low (uniform with upper surface), then the resin for covering member can be spread uniformly and curing stabilizes the shape, but the contact area between the lateral surface and recording medium increases causing the recording medium to stick and not peel off smoothly
Solution Approach 1:
The patent applies different surface roughness characteristics to different regions of the covering layer: the upper surface maintains low Ra (0.01-0.1 μm) for uniform resin spreading, while the lateral surface has higher Ra (0.05-2.0 μm) to reduce contact area and prevent sticking. This local differentiation resolves the contradiction between resin uniformity and peeling smoothness.
2Stability of the object's composition
If the contact area between the lateral surface of the covering layer and the recording medium is increased, then the resin for covering member can be stabilized during curing, but the recording medium cannot be readily peeled off from the lateral surface
Solution Approach 1:
The patent creates local quality differences in surface roughness between the upper surface and lateral surface of the covering layer. The lateral surface's higher roughness (Ra 0.05-2.0 μm) reduces the actual contact area with the recording medium, enabling easy peeling while the resin still achieves adequate stabilization through the upper surface's low roughness characteristic.
3Ease of operation
If the arithmetic-average surface roughness Ra of the lateral surface is made higher than that of the upper surface, then the recording medium can easily peel off from the lateral surface, but the resin for covering member may not spread uniformly on the upper surface
Solution Approach 1:
The patent carefully controls the surface roughness parameters within specific ranges: upper surface Ra of 0.01-0.1 μm ensures uniform resin spreading, while lateral surface Ra of 0.05-2.0 μm enables easy peeling. The local quality differentiation is precisely quantified to avoid the trade-off between these two requirements.
Data Source
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AI summary
[Abstract] A thermal head of the present disclosure includes a substrate 7, a heat generating unit 9, an electrode, a covering layer 27, and a covering member 29. The heat generating unit 9 is positioned above the substrate 7. The electrode is positioned above the substrate and connected to the heat generating unit 9. The covering layer 27 covers at least a part of the electrode when viewed in plan. The covering member 29 is positioned on the covering layer 27. The covering layer 27 has an upper surface 27a and a lateral surface 27b that is positioned on a side of the heat generating unit 9. An arithmetic-average surface roughness Ra of the lateral surface 27b is higher than an arithmetic-average surface roughness Ra of the upper surface 27a.