Timeline

1919

• Mototaro Eguchi discovers thermoelectret with carnauba wax and rosin mixture - On Dielectric Polarisation

1928

• Paul Selenyi researches charge injection into dielectrics charging by cathode ray on tube glass - Über die durch Kathodenstrahlen bewirkte elektrische Aufladung des Glases und deren praktische Verwendung

1935

• Paul Selenyi applies for patent on charge injection with ion beam - US2143214A - Production of images

1937

• Nadjakov discovers photoelectret with sulfur - On a new kind of permanent polarization of dielectrics

1938

• Paul Selenyi develops electrographic oscillograph - On the Electrographic Recording of Fast Electrical Phenomena

1939

• Chester Carlson applies for patent US2297691A - Electrophotography

1954

• Robert Gerson and J. H. Roghbaugh postulate trapping as mechanism of electret formation