Page 152 - Handbook of Adhesion Promoters

8.5 Glass 145

Figure 8.4. Adhesion mechanism of silver nanoparticles on substrate with 3-glycidoxypropyltrimethoxysilane
prepolymer at the interface of the film. [Adapted, by permission, from Hong, JU; Kumar, ABVK; Han, HS;
Koo, YH; Kim, HW; Park, JH; Kang, HS; Lee, BC; Piao, L; Kim, S-H, Bull. Korean Chem. Soc., 34, 8, 2539-42,
2013.]

8.5 GLASS
Noble metal nanoparticles, especially silver nanoparticles possess high electrical conduc-
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tivity on the order of 10 S cm and high operational stability. These nanoparticles can be
used for the direct printing on various substrates, including glass, using screen printing,
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flexography, gravure offset lithography, and ink-jet printing. The major issue is the poor
adhesion of the conducting lines on substrates which tend to crack after sintering, both on
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the glass and flexible polymer substrates. The 3-glycidoxypropyltrimethoxysilane pre-
polymer can provide crucial molecular interactions between the silver nanoparticles and
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the substrate (glass or PET) to improve the adhesion (Figure 8.4).
UV-curable silane-coupling agent was synthesized by the reaction between the
hydroxyl group of bisphenol A epoxy diacrylate and the isocyanate group of 3-isocyanato-
propyltriethoxysilane to be used in color filter industry to correct decrease of adhesion
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after ITO sputtering process. The acrylate double bond copolymerized with resins to form
covalent bonds and the alkoxy group reacted with glass substrate to produce a strong
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Si–O–Si bond and improve adhesion.
This primer (GE SS4120) containing 5-10 wt% ethyl silicate 40, 30-60 wt% metha-
nol, and 30-60 wt% ethanol increased adhesion of silicone sealant to glass, silicone wafer,
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and brushed aluminum.
The silicone sealant is composed of ethoxy-terminated polydimethylsiloxane and a
mixture of substances (silanes and titanates) which are crosslinkers and adhesion promot-
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ers to aluminum and glass. The silane hydrolysis produces Si–OH groups which are poly-
functional and thus cause crosslinking and reaction with hydroxyl groups on the surface of
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aluminium or glass. When sealant is exposed to humidity it begins to cure. Silanes dif-
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fuse to meet the advancing cure front, where they react with water. At the same time, they
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slow the rate of cure of polymer matrix (ethoxy-terminated polydimethylsiloxane). The
diffusion of silanes to advanced cure front depletes their concentration at the interface