also the conditions of the accelerated light resistance test include a power density of about 40 times that of a high brightness projector real machine and a substrate surface temperature of the sample of 70 u00b0 c that is the test was performed at an acceleration of 40 times the real machine the graph shown in fig3 shows that an adhesive layer of the sample using a uv adhesive a manufactured by kyoritsu chemical co ltd xlv90 is turned yellow after a real machine equivalent time of about 5 000 hours has passed also the sample was broken after a real machine equivalent time of about 6 000 hours has passed therefore when a polarization conversion element using the uv adhesive a is used for a projector the brightness of the projector is decreased after about 6 000 hours and thus it is necessary to change the polarization conversion element to a new one at intervals of 5 000 hours in addition an adhesive layer of the sample using a uv adhesive b manufactured by adell co ltd ut20 is turned yellow and broken after a real machine equivalent time of about 18 000 hours has passed therefore also when a polarization conversion element using the uv adhesive b is used for a projector it is necessary to change the polarization conversion element to a new one at intervals of 18 000 hours on the other hand the sample using a silicone based adhesive c dimethyl silicone showed no decrease in transmittance even after a real machine equivalent time of about 55 000 hours has passed therefore by using the silicone based adhesive heat resistance and light resistance are improved and the polarization conversion element can be used for.