A New Thermal Crystal Transformation Method To Fabricate Phthalocyanines With High Crystallinity And The Research Of Their Photoconductive Properties

In this paper, the research of thermal induction crystal phase transformation method to fabricate phthalocyanines in different polymorphs was proceeded according to thermodynamic principle. The H2 Pc was fabricated by condensation of 1,3-diiminoisoindoline in alkaline conditions and TiOPc was fabricated by 1,3-diiminoisoindoline and tetrabutyl titanate. Purification by concentrated sulfuric acid could lead to low crystallinity of them. We systematically surveyed the holding temperature, heating rates, holding time, type of cooling, gases and other possiable factors for therml phase transformation by tube furnace which could adjust conditions. Besides, the degree of crystallinity was used to carry through quantitative analysis of its transformation and to get different phthalocyanines with high crystallinity. The result shows that this method is much more environmental friendly and simple, as well as stronger feasibility.The TiOPc after acid paste purification presents an amorphous structure. TiOPc could be transformed to β-TiOPc with crystallinity higher than 97% when annealed at 300 °C for 2 hours with 5 °C/min heating rate, and its morphology showed nano-scale stacked lamellar structure. Additionally, magnification experiments were operated under the optimized conditions. The results prove the stability and feasibility of its application. Using it as charge generation materials in OPC devices, excellent photosensitivity data was shown(V0=752 V, Vr=4.88 V, Rd=26.0 V/s, E1/2=0.203 μJ /cm2). On the other hand, the H2 Pc after purification presents an incomplete α polymorph. According to the behavior of its thermal crystal phase transformation, 100% α-H2 Pc could be got when it was annealed at 190 °C for 2 hours and β-H2 Pc with high conversion(95%) could be obtained at temperatures higher than 280°C for 2 hours. The study of its surface chemical character and surface profile found that H2 Pc tranformed in insert gases could obtain more uniform morphologies, and appropriate holding time ensured the nano scale of H2 Pc. The OPC devices using high-precision H2 Pc got by thermal transformation as charge generation materials were proved that they had good photosensitivity, the α-H2 Pc device: V0=691 V, Vr=26.85 V, Rd=22 V/s, E1/2=0.577 μJ/cm2, the β-H2 Pc device: V0=686 V, Vr=26.68 V, Rd=43.0 V/s, E1/2=0.421 μJ/cm2. The result shows that β-TiOPc、α-H2 Pc and β-H2 Pc fabricated bt thermal crystal phase transformation method are suitable to be used as charge generation materials in high power laser printers.