Development Of Long-lived Easy-cleaning UV Coating

Surface contamination of material is a common phenomenon in daily life.The strength of interaction between contaminant and the surface of material determines the adhesion strength of contaminant on the surface.Most researches revealed that the strength of interaction between contaminant and the coating surface is closely related to the surface energy of the coating surface.Thus,an easy-cleaning resin with a low surface energy coated on the material surface is the common method to improve the surface antifouling properties of materials.Easy-cleaning resin is widely applied to anti-fouling functional products,such as self-cleaning windows,anti-fouling automotive interiors,anti-graffiti architectural coatings,and anti-fingerprint mobile phone screen.With the development of technology,electronic products such as mobile phones,tablet computers,and laptops have become the necessities in daily life.Consumers pay an increasing attention to the quality of electronic products.Therefore,the surface of electronic touch screen not only possesses long-lived easy-cleaning performance,but also exhibits a high light transmission and a comfortable sense of touch.Fingerprints are different from general contaminants due to their complex chemical composition.The main component of fingerprints is the oleic acid,which is inclined to residue on the surface with high surface energy.Thereby,the fingerprints are easier to residue on the surface of the electronic touch screen.The average thickness of fingerprint depositions on the surface is 1 μm,which is greater than the wavelength of visible light(550 nm).The residual fingerprint is easier to cause light scattering and result in the decreased transmittance on the surface.Accordingly,reducing the interaction between the coating surface and fingerprint grease with the easy-cleaning resin is practical significance for inhibiting the adhesion of fingerprints.In this case,a long-lived easy-cleaning UV coating was required to develop by the coating company in Zhejiang Province.In this paper,the functional resins with various structures were prepared and added to the photocurable coatings,which gave the UV coating surface long-lived easy-cleaning performance.Meanwhile,the effects of different structures of functional resins on the long-lived easy-cleaning properties of UV coatings were investigated.The conclusions are as follows:(1)The functional resins with different structures were synthesized by free radical polymerization.(i)Fluorinated functional resin.The contents of the fluorinated monomer tridecafluorooctyl methacrylate in the resins were 3.24 mol%,5.47 mol%,8.34 mol%,12.95 mol%and 20.74 mol%,respectively.The double bond(C=C)content was 11±3 mol%.(ii)Silicone functional resin.The contents of the silicon-containing monomer silicon methacrylate in the resins were 0.07 mol%,0.15 mol%,0.32 mol%,0.62 mol%,1.70 mol%,4.30 mol%and 6.92 mol%,respectively.The double bond(C=C)content was 11±3 mol%.For the high double bond(C=C)content silicone functional resin,the double bond contents in the resins were 11.99 mol%,16.81 mol%,24.39 mol%and 27.86 mol%,respectively.The content of the silicon-containing monomer silicon methacrylate was 2.5±0.5 mol%.(iii)Fluorosilicon functional resin.The contents of the fluorinated monomer tridecafluorooctyl methacrylate were 4.61 mol%5 6.06 mol%,9.07 mol%and 23.42 mol%,respectively.The content of the silicon-containing monomer silicon methacrylate was 1.4±0.3 mol%,and the double bond(C=C)content in the resin was 11±2 mol%.The chemical composition and structures of the functional resins were characterized by gel permeation chromatography,fourier transform infrared spectrometer and nuclear magnetic resonance.(2)The functional resins with different structures were added to the photocurable coatings to evaluate the performance of the UV coatings.It was found that the silicone functional resin exhibited the best performance than others.Contrast to the fluorinated functional resin,the phase separation phenomenon of nano-micropores was not observed between the silicone functional resin and the photocurable coating.Meanwhile,the siloxane chains generated the wriggling motion effect on the surface,including distorting,stretching,retracting.These minimized the contact area between the ink and the coating,and exhibited the long-lived cleaning surface.(3)The effect of silicone functional resins with different structures on UV coatings was investigated.It was found that increasing the double bond(C=C)content of the silicone functional resin could effectively improve the oil-resistant pen wiping performance of the UV coating surface.When the content of the high double bond silicone functional resin in the photocurable coating(2.26 mol%of silicon-containing monomer silicon methacrylate,and 27.86 mol%of double bond)is 1 wt%,the UV coating surface can be resistant to oil pen wipe up to 93 times.The high double bond content in the resin enables the siloxane chains to be more stably fixed to the surface of UV coating,giving the coating surface excellent long-lived easy-cleaning performance.(4)The effects of silicon functional resins on the high light transmission,smoothness and anti-fingerprint properties of UV coatings were also investigated.It was found that the UV coating prepared by adding silicon functional resin exhibited a high light transmittance(T>95%)at a wavelength of 500 nm.Because there was no macroscopic phase separation between the silicon functional resin and the photocurable coating.Therefore,there was no light scattering phenomenon on the coating surface of the coating.In addition,the surface friction coefficient of the UV coating prepared after adding the silicon functional resin was reduced to a minimum of 0.0048,which made the coating have a comfortable and smooth touch feeling and had considerable market prospects.The anti-fingerprint effect of obtained coating surface reached the grade of B(the adhesive fingerprint was very light and easy to be wiped off).Such performances of our product are comparable to that of Daikin’s modified perfluoropolyether anti-fingerprint resin(DAC-HP).