| 摘要 |
PURPOSE:To raise the pressure of contact of a thermal head and a platen roller, uniformize pressure distribution and enable recording with high image quality, by providing a back-up roller rotated in contact with a platen roller on the movable direction side of the platen roller. CONSTITUTION:When a pressure is exerted on the platen roller 3 by the thermal head 1, the roller 3 with a small diameter may undergo a bending deformation with the result of a lowering in the pressure of contact thereof with the thermal head 1 at a central part, leading to a lowering in the image quality on a recording paper. The avoid this, the back-up roller 4 is provided with a crowning part 4a at a central part of the span thereof to cover the bending deformation of the platen roller 3. Accordingly, the back-up roller 4 and the platen roller 3 can be brought into smooth contact with each other for rotation, the pressure of contact of the head 1 and the roller 3 can be prevented from being lowered, the pressure of contact can be enhanced, and a uniform pressure distribution can be obtained. |
