Desigen,Preparation And Properites Sduty Of Disulfide-bond Containing Photoresists For UV Nanoimprinting Lithography Technology And Photoinitiators

UV nano imprinting lithography technology(UV-NIL)as the most effective toll for pattern transfer,has been widely applied in the fabrication of the advanced functional materials with high accuracy.However,as the most essential materials,the photoresists used in UV nano imprinting process still maintain many problems such as high volume shrinkage,poor demolding ability as well as complex formulations.These issues lead to the distortion of the transferred patterns and the increase of the cost,greatly limiting the further development and application of UV nanoimprinting lithography technology.Therefore,it is of great theoretical and practical significance to design and prepare novel photoresists with low volume shrinkage,good demold ability and simple formulations for UV-NIL.Moreover,UV-LED photopolymerization has becoming the development direction of photopolymerization technology currently,because it has advantages of low energy consumption and high luminous efficiency,no ozone in the curing process,and the lamp which can be switched on and off in an instant.Accordingly,the development of novel efficient photopoinitiators for UV-LED photopolymerization is very urgent.To begin with,based on the unique characteristics of the reversible reaction of "cleavage-recombination" of the disulfide bond under the UV light irradiation and reductivity of the disulfide bond in the presence of reducing agent,we have prepared a series of disulfide bond-containing photoresists with low volume shrinkage and excellent degradation ability by introducing a photopolymerizable aliphatic organic disulfide so as to solve the problem of high volume shrinkage and poor demold ability of traditional photoresists for UV-NIL.Furthermore,we have designed and prepared a series of novel photoresists with low volume shrinkage and no photoinitiators by the introducing of a photopolymerizable aromatic organic disulfide with initiating photopolymerization ability.The introduction of aromatic organic disulfides could not only reduce the volume shrinkage of the photoresists but also simplify the formulation of the photoresists.In addition,we designed and prepared a series of dinaphthyl disulfides cleavable photoinitiators for UV-LED photopolymerization based on the good initiating ability of aromatic organic disulfides under UV light.The main research contents and results are as follows:(1)A series of nanoimprinting photoresists containing a aliphatic photopolymerizable disulfide monomer,disulfanediylbis(propane-3,1-diyl)diacrylate(DTDA),was prepared.It was found that the introduction of DTDA could improve the double bond conversion and polymerization rate of the photoresist,and significantly reduce the volume shrinkage of the photoresist.For DTDA/methylmethacrylate(MMA)/isobornyl acrylate(IBOA)system,the minimum volume shrinkage was 0.93%.The addition of DTDA also influenced the physical and mechanical properties as well as thermal property of the photoresist.With the increase of DTDA content,the viscosity of photoresist was increased,and the indentation hardness and Young's modulus were decreased,while the glass transition temperature,T5%and Tmax increased first and then followed by decrease.The prepared DTDA-containing photoresist had excellent nanoimprinting and pattern transfer capabilities and could achieve the duplication of the pattern of 210 nm linewidth.Besides,the photoresist containing DTDA could degrade in the presence of the reducing agent,tributyl phosphine(TBP),which resulted in its good demolding performance.(2)A series of nanoimprinting photoresists containing disulfanediyl bis(4,1-phenylene)diacrylate(ADSDA)was prepared.It was found that ADSDA not only had an excellent initiating photopolymerization ability,but also could reduce the volume shrinkage of the photoresist.For ADSDA/benzyl methacrylate(BMA)system,the minimum volume shrinkage was 0.56%.The introduction of ADSDA affected the physical and thermal properties of the photoresist.With the increase of ADSDA content,the indentation hardness,Young's modulus and glass transition temperature of the photoresist increased first and then decreased,while the T5%and Tmax of the photoresist decreased with the increase of ADSDA content.The photoresist with ADSDA had excellent nanoimprinting and pattern transfer ability as well as realized the full transfer of patterns with 208 nm linewidth.(3)Three kinds of naphthyl organic disulfide photoinitiators(DNDS,DNDS-OH and DNDS-Ac)which are suitable for LED photopolymerization were designed and synthesized.Their light absorption,photodegradation property and photolysis mechanism were studied by ultraviolet absorption spectroscopy and electron spin resonance(ESR)and theoretical calculation,and their photopolymerization properties were also investigated.It was found that the geometry of three photoinitiators are all nonplanar,as a result,their molar extinction coefficients were both lower than 300 M-1 cm-1 at the commonly used LED wavelength.However,they could still generate corresponding naphthalene sulfur radicals through the breaking of the disulfide bond under the irradiation of 405 nm LED light source to initiate photopolymerization reaction.Among them,DNDS-OH with strong electron-donor group,hydroxyl group,had the fastest initiation speed,and the polymer film initiated by DNDS-OH was colorless and transparent,thus DNDS-OH has a good application potential in the field of LED photopolymerization.