Patent ID: 7212771

Claim:
A grid electrode which is disposed along a corotron wire with a predetermined interval between the grid electrode and the corotron wire, comprising: a planar, plate-shaped member having a plurality of openings in each of which a longitudinal direction and a short side direction are formed, the longitudinal directions of the respective plurality of openings being lined up so as to be in a same direction, the plate shaped member also having connecting portions connecting openings which are adjacent to each other in the opening longitudinal direction and connecting portions connecting openings which are adjacent to each other in the opening short side direction, wherein, at each opening, a shortest distance from a center point to an opening edge is S, and S is less than 1.5 mm, a grid opening ratio is greater than or equal to 82%, and a length of the longitudinal direction of the opening is at least 1.3 times a length of the short side direction of the opening, and wherein the connecting portions connecting openings which are adjacent to each other in the opening longitudinal direction are not disposed on a same line which is orthogonal to the corotron wire.