h was deposited from an acetylene argon mixture at a pressure of 8 u00b7 10 4 torr and a discharge power of 10 watt with a deposition rate of 2 u00e5 s light blocking layer 4 of amorphous hydrogenated carbon u03b1 c h with a thickness of 1 u03bcm thus produced has an absorption coefficient u03b1 5 2 u00b7 10 4 cm u2212 1 and suppresses the optical transmission of the layer sequence glass or quartz glass substrate 1 transparent electrode ito 2 photoconducting layer 3 u03b1 si h light blocking layer 4 u03b1 c h by 180 fold at a wavelength of u03bb 632 nm the specific resistance of layers 2 3 and 4 was of the order of magnitude of 10 8 ohm cm as in example 1 light blocking layer 4 of amorphous hydrogenated carbon u03b1 c h was deposited from a c 2 h 2 argon mixture at a pressure of 2 u00b7 10 u2212 4 torr and a discharge power of 3 6 watt with a deposition rate of 1 7 u00e5 s at 0 6 u03bcm thickness this light blocking layer 4 had an absorption coefficient u03b1 5 4 u00b7 10 4 cm u2212 1 a 30 fold suppression of light was effected by the layer at a wavelength u03bb 632 nm the specific resistance of the layer sequence of transparent electrode ito 2 light blocking layer 4 of amorphous hydrogenated carbon u03b1 c h dielectric mirror 5 was of the order of magnitude of 10 8 ohm cm as in example 1 light blocking layer 4 of amorphous hydrogenated carbon u03b1 c h was deposited from a c 2.