The glass surface is smooth and inert, with a large difference in thermal expansion coefficient compared to organic coatings. The volume shrinkage caused by UV curing instant polymerization will directly accumulate residual stress at the interface, affecting the performance of UV glass coatings. Taige Additive provides UV glass coating additive matching solutions to meet the composite needs of high hardness, yellowing resistance, and high transparency UV glass in consumer electronics, smart homes, and other fields.

1. The application difficulties of UV glass coating

①  The influence of pigment dispersion on light exposure

The absorption spectrum of the photoinitiator must match the wavelength of the light source in order to be excited. In real color UV coatings, light needs to penetrate the pigment obstruction in order for the photoinitiator to absorb photons for outer electron transitions and generate active species. The triangle matching of coating type, light source, and initiator is crucial, as shown in the table below :

The uniformity of pigment dispersion by dispersants can to some extent affect the uniformity of light exposure, especially for high coverage powders such as titanium dioxide and talcum powder. Uniform light exposure can avoid the formation of weak boundaries, ensuring the stability of coating performance and continuous production.

②  Compatibility of multiple resins and additives

A typical example of a glass UV white background has a dual challenge of “high pigment light blocking+inert substrate”, such as high Tg and high hardness UV coatings and rigid substrates, which will result in no release of shrinkage stress and seriously affect adhesion. Therefore, the selection of resin is very important, and common resin differences are shown in the following table :

The solution of using EA hardness resistance, PEA adjustment flexibility, and adhesion resin is compatible with coating flexibility, shrinkage stress, hardness, and other properties, which also greatly tests the compatibility and performance of additives in multi resin systems.

③  Low rank officials and surface active dryness

The glass substrate is mainly composed of low molecular weight monomers (to reduce shrinkage) and a small amount of medium molecular weight monomers (to enhance cross-linking). The system mainly composed of low molecular weight monomers has certain requirements for the dryness of surfactants, such as dispersants, leveling agents, wetting agents, etc. Inappropriate surfactants can affect the cross-linking density and may reduce the adhesion and mechanical strength of the low molecular weight system.

2. UV Glass Coating Additive Solution

①  UV white primer

In practical application testing, the UV glass white primer auxiliary solution has the following performance advantages :

●  Strong adhesion and excellent stability

As a UV glass primer, adhesion is the primary performance. Tech-7145 is a specially modified phosphate ester compound. Compared with general organic silicon adhesion promoters, Tech-7145 has better storage stability. The viscosity of UV slurry is more stable when stored for a long time, which meets the actual production process of reciprocating machine spraying and recycling old oil. The key to improving adhesion and water resistance mainly comes from anchoring the two interfaces, which plays an intermolecular role at the microscopic level, specifically :

Glass surface:

Room temperature Si-OH+R-O-P (=O) (OH) 2 → P=O ···· HO-Si and P-OH ···· O-Si

UV resin end:

Tech-7145 (R-CH=CH2)+UV resin → covalently cross-linked network and not prone to yellowing

In this supporting scheme, 1.5% Tech-7145 forms bidirectional anchoring on the glass surface and participates in the light curing reaction. The measured UV white adhesion reaches level 0

●   Rapid wetting and bubble control in high-speed processes

In the consideration of wetting leveling agents on glass surfaces, traditional organosilicon has the risk of foam stabilization and re coating obstacles, while traditional acrylic esters have average fast wetting properties and cannot meet the needs of high-speed production lines. Tech-1068, as a special polyester copolymer, does not affect the recoating properties and is crucial in UV white base coatings. Compared to traditional acrylic esters, it has faster wetting properties and comes with a certain defoaming effect, which brings favorable advantages to high-speed processes and provides a prerequisite for adhesion of UV base coatings.

Tech-4855 defoamer does not contain aromatic hydrocarbons, and its 0.1% addition effectively promotes the elimination of microbubbles in UV slurry. Compared with organic silicon defoamers, it has no risk of fogging and shrinkage, and is not easily absorbed by resin. The defoaming effect lasts throughout the entire construction period. Mainly eliminate the three main sources of bubbles in UV white primer:

① Mechanical aeration: Air is entrained during high-speed dispersion and sanding processes

② Substrate release of gas: Gas in the micro pores of the glass surface is released after coating

③ Reactive gas release: Trace gases (such as nitrogen) produced by the decomposition of photoinitiators

The UV white primer has no obvious defects on the surface after coating, with excellent wetting effect and no pinholes or exposed substrate.

●  Uniform coverage → Better curing effect

Whether the dispersant disperses the pigment evenly will to some extent affect the uniformity of light exposure. Uniform light exposure can avoid the formation of weak boundaries. Tech-598 dispersant-  The functional groups can strongly adsorb onto the surface of talc powder, while the solvation chains extend into the UV resin matrix, forming a spatially stable layer.

UV curing has a fast drying rate, complete curing of the bottom surface without cracks, good interlayer adhesion, good adhesion to the substrate, and easy polishing.

3. UV coated high gloss oil

The requirement for surface tension in spray coating construction is very high – the coating needs to form a uniform curtain like flow on the vertical plane, and any uneven surface tension will lead to “orange peel” or “edge shrinkage”.

In this additive scheme, 0.1% Tech-2033 organic silicon leveling agent can quickly reduce surface tension, improve flowability and spreadability, while 0.2% non silicon leveling agent Tech-1061 provides long wave leveling, thereby achieving a mirror effect. 0.1% Tech-4855 does not affect the high transparency of UV coated high gloss oil, eliminates microbubbles, and avoids the occurrence of fine pinholes.

UV coating smooth paste – high transparency

Practical application of UV coating smooth surface – Part

4. Summary

In the UV glass additive matching solution provided this time, the UV white primer additive matching solution can effectively solve the problem of “difficult adhesion” of glass, provide a high coverage white background, and make a “flat printing layer”; The matching scheme of UV coating varnish additive reflects better flatness and excellent glossiness, with a smooth and flawless surface.