| 摘要 |
PROBLEM TO BE SOLVED: To provide an image forming device with high fineness, high color purity and high reliability, and with sharply reduced discharge to damage it by setting a conductor on a face plate to a specified distance or more from the outermost peripheral part irradiated with electron beams toward the side wall part. SOLUTION: A conductor on a face plate is set to have a distance W or more shown by W>=2αH from the outermost peripheral part irradiated with electron beams toward the side wall (whereinαrepresents a parameter depending on the structure of an image forming member on the face plate withα=0.6-1, and H represents the distance between the face plate and a rear plate). The distance W takes the maximum value represented byθ=π/4 and is obtained from W=2αH. Since the backward scattered electron beam generated in the peripheral part is re-landed in the distance of 2αH at maximum from the peripheral part, it never collides when an insulating part such as glass or the side wall part is absent within this range. Accordingly, the charge and discharge accompanying the release of secondary electron or gas can be reduced to provide a reliable device.
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