What are Surfactants/Surface Modifiers?

Fluorosurfactants demonstrate an excellent surfactant effect with an additive amount of 0.05 to 0.5 wt% (in solid content) based on the ease of surface segregation of fluorine-containing groups. In particular, remarkable results can be anticipated in thin film coatings (highly volatile content, low viscosity solutions) and coatings associated with high speeds and high shearing forces.

Compared to hydrocarbon-based or silicone-based surfactants, fluorosurfactants achieve even lower surface tension. Solutions with fluorosurfactants added to them achieve excellent wettability from low surface tension (γL).

Fluorosurfactants easily exist in large amounts near the surface which has an effect that controls the evaporation speed of solvents and achieves excellent uniform coating properties (leveling). This effect becomes even more prominent in oligomer-based surfactants and it changes by molecular weight, compatibility with matrix resins, and the amount of additive.

[Differences of leveling performance in low-speed spin coating]
A thin film that contains a large amount of solvent was formed by spin coating at low speed. A flat and smooth coating was formed by the fluorosurfactants effect in the drying processing.

[Coating conditions]
1. Prepared a propylene glycol monomethyl ether acetate (PGMEA) solution with Phenolite KA-105L (DIC, phenolic resin) at 25 wt%.
2. Spin-coated the solution on a 10 x 10 cm Cr substrate at 500 rpm.
3. Dried on a hot plate at 110°C for 1 minute (film thickness: approx. 2.5 μm).

The photographs show the surface state under a sodium lamp. These patterns are like the contour lines on a map. Sections with narrow line widths have extreme unevenness. Sections with wide line widths have flat, smooth surfaces.

In coating methods accompanied with high-shearing forces like spin coating, dynamic surface tension may have a greater affect on coating properties than static surface tension. Low dynamic surface tension means a small change in surface tension in dynamic processes such as coating.

The surface state of the coating on a silicon water after spin coating at 3000 rpm (film thickness: approx. 2 μm), as viewed by a microscope

MEGAFACE work efficiently as dispersants by the following mechanisms to achive good dispersability of fluoropolymers such as PTFE (polytetrafluoroethylene).

The fluoro moieties of MEGAFACE can adhere to the fluoropolymer surface, while the "non-fluoro" compatible groups are designed for affinity to dispersing media. Steric hindrance of the compatible groups prevents aggregation of the fluoropolymers and improves the dispersion stability.

[Recommended additive amount]
0.5 to 5 wt% (in fluoropolymer particles)

[Examples of application]
■ Solid lubricant coatings, automotive window frame rubber, automotive parts (sliding members), home electronics (movable parts), movable part coatings for optical equipment/precision equipment
■ Fluorine-based heat-resistant coatings
■ Engine oil additives

Fluorosurfactants realize excellent leveling properties also for new and promising leading-edge insulating materials, such as polyimide and polysiloxane resins.

[Coating conditions]

Mapped thicknesses of 400 points – Less gap between color tones means less gap between film thicknesses

Measured 100 points along the diagonal line of the substrate to visualize asperities more finely

DIC have realized commercial production of fluorosurfactants by “ living polymerization ”. Precisely controlled molecular design can be of great advantage for the development of targeted performance. Especially, block-polymerized surfactants can control surface properties effectively with the integration of functional groups within molecules.

For the processes requiring trace metal control, such as front end process for semiconductor device production, DIC have established the production process and quality assurance system of metal impurity control below 100 ppb. Additionally, DIC is working toward improvement aiming for further metal reductions of single ppb.

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