PRODUCTION OF HALOGRAM DIFFRACTION GRATING

PURPOSE:To improve the strength and particularly moisture resistance of a pattern by providing an underlying layer consisting of a plastic or curable resin which is not attacked by the photoresist in the coating stage on a substrate and coating the photoresist thereon. CONSTITUTION:An underlying layer 33 consisting of a plastic resin or curable resin which is not attacked by photoresist in the coating stage is formed on a substrate 31 and the photoresist is coated thereon. For example, PVAL, epoxy resin, etc. are used for such layer 33 and the photoresist coating layer is subjected to hologram recording by the conventional method. The strength and particularly moisture resistance of a diffraction grating pattern 39 can be improved by forming the layer 33 by using the resin which is not attacked by the photoresist in the coating stage thereof in the above-mentioned way. The cracking of the diffraction grating pattern 39 occuring in high temp. and high humidity, dew condensation, etc. is thus prevented and the deterioration in diffraction efficiency is prevented. The diffraction grating is used for a laser printer, bar code reader for POS, etc.