Light-Converting Effect
functional structure:Molecules of ethylene bond,exazole and thiophene have different energy states.under normal conditions,these molecules are in the lowest ground state level;when illuminated,they would absorb the loght energy which is consistent with their characteristic frequency.They lifting from ground state to the higher excitable vibration level,by internal inverison,they relaxation to the excitable vibration level at lowest (equilibrium excited state)within a very short of time(10-8seconds),then returns to the higher level of the ground state,sending out light at the same time ,such light is called fluorescence.Generally, the energy sending out light at the same time,such light is called fluorescence.Generally,the energy sending out fluorescence is always less than the energy it absords(as final ground state is higher than the former one).
According to the formula E=h V=hc/入(h:stands for planck constant,c:light speed,入:wave),the greater the energy is ,the shorter the wave is;the less the energy,the longer the wave.Generally,fluorescence with wave rang 335-365nm can send out 450nm fluorescence after conversion.lf the wave shorter than 355nm,the fluorescence sent out is slightly red;while longer than 365nm,the fluorescence slightly green.lt is in this way that fluorescent brightener converts invisible ultraviolet light into visible white light.
Brightning Principle
Actually,natural light can be divided into single corresponding light wave of red,orange,yellow,green,blue,black and violet whthin 380-760nm.But it is not necessary to have so many kinds of lingt with different waves to synthetize white light.On TV screen,only three colours of loght are needed to synthetize white light ln fact,only two kinds of proper light waves which are intercomplementary colors can also synthetize white light suchas blue and yellow,red and blue grenn.When illuminated,materials(fabric,plastics,etc)can absorb blue light,reflect yellow light,and therefore we see yellow not white light.Fluorescent brightener can absorb ultraviolet light and send out white and blue light ,and so blue light and original yellow light are complementary colors conse-quently,we see white light.This is the brightening pringciple of fluorescent brightenenr.