Structure of Antireflective Films with Si-O-P Bonds and Impact Factors on Its Performance

doi:10.3724/SP.J.1077.2014.13416

Abstract

Abstract:

An antireflective (AR) film was successfully prepared by dip-coating on silica glass substrate. During the preparation, aqueous colloidal silica (ACS) was used as silica source, orthophosphoric acid as adhesion promoting agent and hydrogen peroxide as activating agent. The structure, formation mechanism and performance of the film were investigated by FTIR, XRD, FESEM, TEM and AFM. The hydrogen peroxide in silica sol repairs the surface Si-O^- bonds of colloidal silica particles greatly. As a result, their stabilities and reaction activities are improved. During the heat-treatment of the film, the orthophosphoric acid is firstly transformed into the chain of metaphosphoric acid and subsequently reacted with surface Si-OH from colloidal silica particles and the substrate, resulting in the formation of the numerous Si-O-P cross-linkings and the stable silicophosphate gel structure. When molar ratio of H₃PO₄: H₂O₂: EtOH: SiO₂ is 0.49: 0.52: 30: 1, the average transmittance of the film in the visible light is 98%, and the pencil hardness grade reaches 6H.

Key words: aqueous colloidal silica, orthophosphoric acid, hydrogen peroxide, Si-O-P bonds, antireflective films

CLC Number:

TB34

WANG Yan, WANG Hong-Ning, CHEN Ruo-Yu. Structure of Antireflective Films with Si-O-P Bonds and Impact Factors on Its Performance[J]. Journal of Inorganic Materials, 2014, 29(6): 639-644.

Figures/Tables 8

Fig. 1 FTIR spectra (A) and XRD patterns (B) of the SiO2 gels with different n(H3PO4/SiO2)(A) a-0, b-0.49, c-0.98; (B) a-0.49, b-0.98

Fig. 2 Schematic illustration of the formation mechanism for SiO2 antireflective film

Table 1 SBET and the Si-OH content of the SiO2 gels with different n(H3PO4)﹕n(H2O2)﹕n(EtOH)﹕n(SiO2)= 0.52﹕30﹕1) and pencil hardness grades of the corresponding SiO2 films

n(H₃PO₄/SiO₂)	0	0.16	0.33	0.49	0.65	0.82	0.98
S_BET/(m²•g^-1)	230.5	76.3	59.6	38.7	21.6	2.1	/
Si-OH content/(bonds•nm^-2)	10.2	7.8	5.6	4.3	3.1	2.3	/
Pencil hardness grade	5B	F	3H	6H	4H	3H	H

Fig. 3 Average transmittance in the visible light of the SiO2 films with different n(H3PO4/SiO2) (n(H2O2/EtOH/SiO2)= 0.52: 30: 1)

Fig. 4 Si-OH content of the SiO2 particles in modified ACS with different n(H2O2/SiO2)

Table 2 Pencil hardness grades and the average transmittance in the visible light of the SiO2 films with different n(H2O2/SiO2) (n(H3PO4/EtOH/SiO2)= 0.49: 30: 1)

n(H₂O₂/SiO₂)	0	0.26	0.39	0.52	0.64	0.77	0.90	1.03
Pencil hardness grade	F	3H	3H	6H	6H	5H	5H	5H
Average transmittance/%	98.0	97.7	98.0	98.0	97.6	97.9	97.8	98.0

Fig. 5 Surface FESEM (a), cross-sectional FESEM (b), TEM (c) and AFM (d) images of the SiO2 film

Fig. 6 Variations of average transmittance in the visible light of SiO2 films with exposure time

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