| 摘要 |
PURPOSE:To eliminate a possibility of increasing a cost at the time of production by surely forming partial plating only in the part where plating is necessary. CONSTITUTION:A mark plate 2 is composed of a mark plate body 3 made of a resin and a plating layer 4. A line groove 5 having an approximately V shape in section is annularly formed on the peripheral surface of a mark 1 and a plating layer 4 consisting of an electroless plating layer 6 and electroplating layer 7 is formed on the peripheral side outer than this line groove 5. A relation between the radius r1 of curvature of the curved part in the section of the base 5a of the line groove 5 and the ratio (D/W) of the depth D to the width W of the line groove 5 is D/W>6, 7*r1+1.0 and satisfies D/W>180*r1-15.7. An electroless plating liquid does not, therefore, arrive at the bottom 5a of the line groove 5 and there is no possibility that the electroless plating layer 6 is formed in this part. There is no possibility either that the electroless plating layer 6 is formed like a bridge across the line groove 5. The electroplating layer 7 and eventually the plating layer 4 are thus formed only the part where the plating is necessary.
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