NEW GLASS INK TECHNOLOGY FOR GLASS DECORATION

For many years, screen-printing technology has been used for glass decoration.
Typically, this was split by two base chemistries – organic and inorganic. Organic inks are based on organic pigments. These are most commonly used in graphic-arts printing, but have some limitations in thermal stability. Inorganic inks – using inorganic ceramic frit pigments – are inherently less vibrant in colour, but have other beneficial properties. 

“Many organic glass inks are formulated using epoxy resin technology”

While both have established positions in the market, their performance characteristics have traditionally meant they serve different applications rather than compete directly. Today, however, advances in organic ink chemistry are beginning to blur those long-standing boundaries. Traditionally, inks fit into application areas based on the final product requirements as outlined in the table (below).

“Sun Chemical has introduced the SunVetro SGF series – a new generation of non-epoxy, two-component, screen-printing inks”

Inorganic glass ink technology usually consists of finely ground glass (ceramic frit) fused with colouring metallic oxide pigments in a bulk carrier such as solvents and hot-melt waxes. Once printed to a surface, they are then fired at very high temperature – typically above 600°C – in a lehr or furnace. This firing process burns off the carrier materials and the pigmented glass frit fuses them into the glass itself, rendering it permanent. 

This fusion process delivers exceptional durability. Ceramic decorations can withstand prolonged UV exposure, harsh weather conditions, chemical attack, abrasion and elevated temperatures. As a result, they become the preferred choice for demanding applications, such as architectural glass, appliance glass and long-term outdoor signage.

“It is likely that ceramic frit-based inks will remain the benchmark”

Organic inks are managed differently. These systems typically use organic pigments dispersed within polymer-based binders and often dissolved in organic solvents. The binder can be chemically reactive and therefore be cross-linked (hardened) by a chemical hardener or exposure to UV light. 

After this curing process, the ink forms a strongly adhered layer on the surface. The resulting physical resistance of the ink layer, whilst very durable in many instances, can be susceptible to chemical, physical and environmental attack. This process cannot match that of a fused ceramic frit image (see table below).

Despite some limitations, there are still many advantages of organic ink systems. Consequently, they remain a popular option for many glass printers. Organic pigments provide bright, vibrant colours and an extensive colour gamut. In addition, they enable high-opacity whites that can be difficult or costly to achieve with ceramic frit-based inks. Colour matching and mixing are also considerably simpler. Additionally, organic pigments are typically free of heavy metals, whereas many inorganic pigments, able to achieve more vibrant colours, either contain heavy metals or use expensive precious metals. Processing requirements further strengthen the appeal of organic technologies. Unlike ceramic systems, which require high-temperature firing. Organic 
inks cure at relatively low temperatures, reducing energy consumption and simplifying production. They can also be printed using conventional screen-printing equipment without specialised screens, screen-heating systems or process controls often associated with frit-based alternatives.

These advantages have made organic inks a practical choice for promotional glassware, furniture and interior decorative panels. Organic inks are also a realistic option for various industrial applications where extreme durability is not the primary requirement.

Many organic glass inks are formulated using epoxy resin technology. Whilst successfully applied in some applications, it can limit their use in markets where extended outdoor durability is required. Epoxy-based formulations can suffer from yellowing, chalking and cracking over time when exposed to long-term outdoor conditions. There are additional regulatory concerns over the use of bisphenol A which can be found in residual amounts in epoxy-based systems.

The industry has also seen significant growth in UV-curable glass inks which can address many of the challenges outlined. In the case of UV technology, ink is cross-linked via a UV light-activated chemical reaction. This provides instant cure and a high durability print. These technologies have enabled faster processing and provided access to applications previously served by ceramic systems. However, even the most advanced UV-curable products have generally struggled to match the long-term outdoor performance of inorganic decoration without application of a post-print varnish to increase light stability.

Recent innovation in this area has focused on organic ink chemistries that meet market requirements for strong adhesion to glass, long-term outdoor durability and lightfastness, while also providing a hard, scratch- and abrasion-resistant surface 
with high water and chemical resistance. 

An ink with this combination of properties could significantly broaden the range of applications suitable for organic glass decoration.

In response to these market needs, Sun Chemical worked closely with customers to develop the SunVetro SGF series, a new generation of non-epoxy, two-component screen-printing inks for glass and other hard substrates.

Key attributes include:

• Low-temperature curing without major equipment changes
• High colour strength and broad colour gamut
• Excellent weather resistance and lightfastness
• Strong chemical and abrasion resistance
• Good screen stability and press performance
• Durable gloss finish
• BPA-free formulation

SunVetro SGF inks also offer the potential to expand the field of use beyond glass printing. This opens other markets, including printing metals, chrome-plated surfaces, coated substrates, thermoplastics – such 
as PMMA and ABS – and duroplastics.

Highly durable organic glass ink presents an opportunity to rethink how certain glass decoration projects are realised. Applications that previously required ceramic inks – solely to meet durability requirements – may now be candidates for lower-energy organic solutions. Potentially, this could simplify manufacturing and reduce energy costs while expanding design possibilities with a wider colour gamut.

Markets such as decorative architectural glass, premium signage, drinkware, cosmetic packaging and indirect food-contact applications could benefit from a combination of brighter colour, regulatory compliance and enhanced durability.

It is likely that ceramic frit-based inks will remain the benchmark for the most demanding environments. However, the potential to grow the market for organic inks in glass decoration with products, 
such as SunVetro SGF, is clear. For glass manufacturers and decorators, this could mean greater flexibility in choosing the right balance of performance, sustainability, processing efficiency and visual impact.