Information Recording Property Of The Optical-thermal Sensitive Microcapsule Material

The optical-thermal sensitive microcapsule can be applied as high-resolution planar information recording medium based on its optical and thermal response produced in microcapsule cells, with the advantages of environment-protection and energy-saving properties. Since the key factor for practical application is the optical-thermal information recording efficiency, in this thesis the thermal color-forming reaction and the optical crosslinking mechanism in microcapsule cells, which are synthesized with interfacial polymerization technique, are emphasized, after proper thermal and optical response system are designed used as microcapsule core functional compounds. The main conclusions are presented as follows.1,According to the different requirement for recording resolution, the optical-thermal sensitive microcapsule with 1,10,20 micrometer diameter are synthesized respectively in accordance with the preferred parameters obtained from the analysis of oil/water phase viscosity, shearing time, reacting temperature as well as the reacting environment during the interfacial polymerization process. Shell to core thickness ratio is adjusted to 1:16. The microcapsule shell formation process of the optical-thermal sensitive microcapsules is detected in the first time. The polyurea-structured condensation polymerization reaction is accelerated at higher temperature. The obtained microcapsules can be acted as basic cells applied in optical or thermal information recording regions to achieve different resolution.2,The color-forming mechanism between thermal dye-precursor ODB-2 or CK-16 and the developer D-8 are clarified. Then the information recording microcapsule material is designed in the form that the D-8 aggregations of micrometre size, which with lower melting point, are dispersed outer the microcapsule, while the dye-precursors of higher melting point are encapsulated in the microcapsules. The ODB-2 dye-precursor microcapsule has faster thermal responding velocity and more practical image color as well as image contrast than that of the CK-16 microcapsule.3,For thermal information recording, the proper color-forming temperature of the thermal sensitive microcapsule is in the range from 130 to 180℃detected by thermal phase change technique. The accelerating point for thermal image formation is 130℃analyzed based on the relationship between image density and thermal developing temperature. The optimized parameters for thermal image recording are obtained. With temperature-controllable FT-IR technique, the color-forming reaction process in thermal sensitive coatings is detected. After the D-8 dye-aggregations are melted, the melting animalcular D-8 dyes diffuse with higher activity to contact with ODB-2 precursor and form colore image. Furthermore, microscopy analysis verifies that the color-forming reaction is taken place in microcapsule cells.4,According to photopolymerization mechanism, the photoinitiators of ITX and TPO are selected as the composite initiating system in microcapsules to heighten the UV irradiation absorbing efficiency. The optical reaction in the microcapsules is detected in the first time. It presents that the C=C bonds are cleavaged and the macromolecule polymer network are formed in microcapsule cells initiated by the photoinitiator radicals during UV exposure. The influence of microcapsule shell, thermal sensitive dye-precursor as well as photoinitiators on the photopolymerization degree is investigated. The competitive absorption to the irradiation is the main factor to decrease the quantum yields of photoinitiator radicals.5,For image density property of the optical-thermal sensitive microcapsule material, the thermal stability status of the photocrosslinked core latent image center is verified with 195 as the initial decomposing temperature, which is higher than the optimal color-forming temperature ranged from 130 to 180℃. The polymer network affects and constrains the color-forming efficiency of the dye-precursors, which results image grads according to different UV-exposing conditions. The image-density contrast of 0.25 is obtained after exposed for 20s, which can satisfy the rapidness requirement for optical information recording.As for the practical usage of the information recording microcapsule system, the color-forming tone is adjusted and the image density properties of microcapsule with different diameter are obtained. Then, with developer D-8 microencapsulated, the preservation stability of the microcapsule material is heightened by decreasing the fog image formation.In conclusion, the optical and thermal responses have been detected in the microcapsule cells. Results obtained in this thesis can be used to propel the investigation of the novel optical-thermal sensitive microcapsule material in order to achieve higher resolution and multiple colors-forming characteristic for potential applications in digital information recording-reproducing regions.