Adhesion enhancement of hard coatings deposited on flexible plastic substrates using an interfacial buffer layer

Abstract

An interfacial buffer layer has been developed to improve the silicon oxide (SiOx) hard coating adhered to a flexible plastic substrate through a consecutive plasma-enhanced chemical vapour deposition process, using the same organosilicon precursor. The adhesion of the hard coating structure, correlated with the buffer layer thickness, was rated by the standard tape-peeling test. An excellent adhesion (rank 5B) was available for the hard coating structure with an interfacial buffer layer deposited on polycarbonate and polymethylmethacrylate substrates. The degree of adhesion strength for the hard coating structures was measured by the standard scratch test. The increase in the critical loads determined from the scratch test was well correlated with the tape-peeling test results. The hard coating structure showed excellent adhesion and also corresponded to a minimum residual stress. The mechanisms responsible for the adhesion enhancement were linked to the specific chemical bonds of the hydrocarbon C–H bond, and cross-linking Si–C bond appeared in the interfacial buffer layer. The C–H bond was recognized as a hydrophobic group that was favourable for minimizing the adsorption of ambient contaminants potentially arising during deposition, while the cross-linking Si–C bond functioned to compensate the large tensile stress residing in the SiOx hard coating. As a consequence, a close contact and progressive morphology resulting in excellent adhesion were observed at the interface of the hard coating structure with an interfacial buffer layer.

Plasma and chromic acid treatments of polycarbonate surface to improve coating–substrate adhesion

“…[3,4] In coating deposition on PCs, two issues are particularly important: the deposition technology for protective coatings for large-scale application and the adhesion of coatings on the PC substrate because PC has bad surface wettability and poor interfacial adhesion. [5,6] Surface treatment or modification, such as oxidant etching, mechanical polishing, ultraviolet radiation, plasma activation, and primer layering, is a common approach to improve surface wetting and interfacial adhesion. [7][8][9][10][11] Among these techniques, plasma surface activation [12][13][14] and chromic acid etching [15][16][17] proved to be versatile in surface modification of polymer surface.…”

High Performance Multilayered Organosilicon/Silicon Oxynitride Water Barrier Structure Consecutively Deposited by Plasma-Enhanced Chemical Vapor Deposition at a Low-Temperature

“…The atomic ratio (O/Si) was gradually increased with the deposition temperature increasing and was saturated to about 1.98 as the substrate temperature reached 70 • C. Moreover, though the atomic concentration of the elemental nitrogen introduced into the films was limited in the range of 1.12 at.%-1.38 at.%, the atomic ratio of N/C for the samples deposited at a temperature of 70 • C was markedly increased from 0.77 to 1.84 as the SiO x N y film synthesized at 120 • C. This showed evidence of the deposition temperature being beneficial for the introduction of the nitrogen atoms and also for the decomposition of TMS precursor to cause a decrease in the carbon atoms in the synthesized films. Figure 4a-d highlights the narrow scan of Si 2p, O 1s, N 1s, and C 1s core levels for the SiO x N y films deposited at the substrate temperatures of 70 and 120 • C. In Figure 4a, the peak of the Si 2p core level for the SiO x N y films deposited at 70 • C was located at 103.8 eV, while that of the film deposited at 120 • C shifted to 103.5 eV, which corresponded well to the Si-O-Si chemical bond in the SiO x matrix [22,23]. The shift of the Si 2p peak toward a higher binding energy for the SiO x N y films deposited at 70 • C was attributed to the signal that emerged from the Si atoms, which was surrounded by the undissociated oxygen molecule (i.e., oxygen-rich condition) [24,25].…”

“…Figure 4a-d highlights the narrow scan of Si 2p, O 1s, N 1s, and C 1s core levels for the SiOxNy films deposited at the substrate temperatures of 70 and 120 °C . In Figure 4a, the peak of the Si 2p core level for the SiOxNy films deposited at 70 °C was located at 103.8 eV, while that of the film deposited at 120 °C shifted to 103.5 eV, which corresponded well to the Si-O-Si chemical bond in the SiOx matrix [22,23]. The shift The XPS survey spectra for the SiO x N y films deposited at the substrate temperatures of 70 and 120 • C are displayed in Figure 3a.…”

Impact on the Gas Barrier Property of Silicon Oxide Films Prepared by Tetramethylsilane-Based PECVD Incorporating with Ammonia

“…For the film synthesized from the TMS-O 2 gas mixture, the stretching and bending modes of the Si-O bonds could be determined at the peaks of 1066 and 817 cm −1 , respectively, while the signals related to the hydroxyl (O-H at around 2800-3700 cm −1 ) and silanol (Si-OH at 940 cm −1 ) were almost absent in the FTIR spectrum [27][28][29]. When the film was synthesized from the TMS-O 2 -NH 3 gas mixture at the gas flow ratios of 0.25 and 0.5, the Si-O bond was still the dominant signal over the FTIR spectra without the absorbance signal from the N-H bond at around 3200-3600 cm −1 [27,29].…”