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Daylight fluorescent pigments ideal for safety applications

Daylight fluorescent pigments

Introducing a ground-breaking technology that enriches products and applications with vibrant, luminous colours.

Objects and surfaces compounded or treated with certain dyes and then captured within specially designed polymer systems have extraordinary luminous properties. Unlike conventional colourants, these materials can absorb shorter wavelengths of sunlight and then re-emit that light at longer wavelengths, producing a visual experience of colour intensity above and beyond anything we expect to see from light reflected from a “passive” coloured surface. Known as ‘daylight fluorescence,’ this phenomenon redefines our expectations of colour brilliance.

Daylight fluorescent pigments emit as much as four times the light reflected from surfaces coloured with conventional pigments and invariably attract more attention. The intense visibility fluorescent pigments make them ideal in safety applications such as traffic cones, barriers, safety vests, helmets, and signage in roadwork, construction, and marine applications. In addition to the intense visual appearance of daylight fluorescent objects and coatings, there’s an almost magical impression experienced because of the unexpected ‘glow’ given that adds a special attraction when used as an attention-capturing element in the colouring and design of sporting gear, textiles and clothing, children’s toys, product packaging, and even for adding a special extra “pop” to conventional paint colours. The applications of daylight fluorescent colourants are so diverse that an entire industry has developed to prepare and tailor these materials to be compatible with and to maximise their luminous performance across a range of product categories.

Consistent performance under diverse manufacturing conditions

Decades of research and development have gone into creating formulations that unlock the vibrant fluorescent properties of dyes like Rhodamine B (shown in Figure 1 in its powdered form), particularly in daylight fluorescent pigment applications. These colorants are specially designed for use in various materials such as inks, plastics, paints, textiles, and coatings. It’s crucial that the colorants are compatible with different liquid “vehicles” used in these applications to ensure optimal performance. Additionally, stability and longevity of the fluorescent pigment on different surfaces are key considerations, often requiring the incorporation of specific additives to enhance durability and maintain luminance over time.

Rhodamine B has inherent fluorescent capacities
Figure 1: Variations of Rhodamine B

Incorporation of daylight fluorescent pigments in plastics

Incorporation of daylight fluorescent pigments in plastics presents an entirely different range of application problems. Pigments designed for different methods of manufacture such as injection moulding, blow moulding and extrusion, must be able to “stand up” to elevated temperatures as high as 500°F for various lengths of time. They must also survive the extreme shearing forces applied to incorporate the pigment into the master batch prior to “let down” for subsequent stages of processing. Moreover, polymer-composed plastics have very different chemical entities with different physical and optical properties and require different methods of pigmentation and pigmenting entities. There is a world of difference in processing to achieve a luminous colour effect in crystal clarity of an acrylic sheet, depicted above, and the diffuse opacity of different polyethylene films and objects. Clearly, this is a case of “one size does not fit all”. For that reason, daylight fluorescent colourants for plastics are tailored for physical and chemical compatibility with the plastic and its follow-on processing. Similar to daylight fluorescent applications in liquid media, plastic pigment formulations are compounded with a variety of special additives to maximise product colour and luminance and minimise loss of fluorescent colour over time and under different conditions of exposure and use.

Dye molecules that create fluorescence can take on various molecular structures

Much chemical technology must be implemented to transform not one, but a multiplicity of dyes and other components into the brilliant spectrum of fluorescent colours. The dye molecules responsible for generating fluorescence can exist in several molecular forms, only one of which is fluorescent. The chemical structure of the polymer in which the dye is encapsulated must be capable of trapping and holding the dye in its fluorescing form, in a way that maximises the daylight fluorescent effect for the long term. The polymer must also provide a protective “cage” that shields the dye molecule from the various physical and chemical stresses to which it is exposed in the initial manufacturing process. It must form a stable colourant product that maintains target properties during subsequent stages of product formulation and use. In many of these coating systems, the dye-pigment particle is suspended, dispersed, or emulsified in a liquid carrier designed for the specific method of application. In fact, there are even product applications in which the dye-pigment systems are manufactured directly in the liquid vehicle, resulting in a “ready-to-use” daylight fluorescent emulsion system. These complex multi-component structures have a layered Russian-doll molecular design that must remain stable in storage and later formulation. That stability must not be disrupted by the addition of reactive components, often referred to as “driers”, designed to convert the liquid system into durable, solid polymer films once applied to surfaces in the form of prints and coatings.

Understanding how to formulate and compound daylight fluorescent products for specific applications is crucial to maintain their unique optical characteristics and performance. Manufacturers need extensive technical expertise and familiarity with these materials to effectively design and deploy them due to the diverse formulation requirements and conditions.

Protecting and extending daylight fluorescence lifetimes

Sunlight and oxygen in the environment can cause daylight fluorescent materials to lose their brightness over time. This is because UV light and oxygen convert the dye molecules into non-fluorescent substances, resulting in a gradual decrease in brightness and colour fading (Figure 2). This loss of brilliance and purity affects the luminous lifespan of these materials and is seen as a significant challenge in maintaining their vibrant appearance.

Xenon arc-simulated 8-hr daylight exposure of two pigment samples in different polymer resin systems
Figure 2: Xenon arc-simulated 8-hr daylight exposure of two pigment samples in different polymer resin systems. Note that sample colours differ before (left) and after exposure (right). Xenon arc devices are employed to expose pigmented surfaces to accelerated equivalents of sunlight exposure.

Accordingly, and depending on the application, daylight fluorescent colourants are formulated with a variety of additives specifically designed to scavenge reactive environmental agents and shield fluorescent surfaces from energetic light-activated decomposition. Further protection can be accomplished by applying a clear barrier coating containing UV-screening agents over the daylight fluorescent film, print or coating. This further isolates the finished products from corrosive environmental contaminants and reduces exposure to the negative influence of UV. Pigment applications are also field tested under extended conditions of use to provide real-world guidance in the selection of incorporated protective agents best suited to extend the daylight fluorescent lifetime.

8-Hour fading profile for four representative daylight fluorescent pigment samples in three shades

Differential fading results from a combination of effects including relative dye concentrations, intrinsic susceptibility to loss of fluorescence, post-faded residual colour, nature of the pigment matrix and any protective additives or overlay coatings. Notice in Figure 3 that differential colour change over time is highly dependent on dye formulation and pigment-polymer matrix. Technical guidance by the supplier becomes essential in gauging colourant detection and conditions of usage.

8-Hour fading profile for four representative daylight fluorescent pigment samples in three shades
Figure 3: 8 hour fade test

Daylight fluorescent products are superior to non-fluorescent ones and are made for functional printing. In Figure 4, inked letterpress rollers show how fluorescent ink flows evenly, creating strong printed images. This leads to clear and accurate prints during printing, making the process smoother and easier to clean afterward. Printed colour samples next to it demonstrate the pure, bright and strong colours produced.

Daylight fluorescent products in functional printing applications
Figure 4: Daylight fluorescent products in functional printing applications

The importance of quality control

Daylight fluorescent colorants, with their intense brightness and clarity, are more prone to colour contamination than regular pigments. Therefore, strict quality control measures are followed during manufacturing and formulation to ensure consistent colour and processing properties from batch to batch. This rigorous process ensures the vibrant colours maintain their fidelity and performance throughout production (Figure 5).

Batch-to-batch quality control of pigments
Figure 5: Batch-to-batch quality control of colour consistency and processing properties are important

The science behind light, colour and fluorescence

Light, a small part of the electromagnetic spectrum from the sun and space, reaches the earth. Most energetic radiation is blocked by the earth’s magnetic field or absorbed by the ozone layer. The UV region, invisible but essential for life, comes first, followed by the visible spectrum, which is our focus. Below are lower energy waves like infrared, microwaves, and radio waves. Our senses help us navigate the world, but it’s our ability to detect visible light, from about 450 to 750 nanometres (Figure 6), that organises our environment and enables us to function.

The electromagnetic spectrum showing the region of visible light
Figure 6: The electromagnetic spectrum showing the region of visible light


How does colour emerge from daylight, which we experience as “white” light? Where does the colour come from? The answer – it’s there all the time! And this can be easily proved by allowing sunlight to pass through a glass prism. What comes out the far side is a rainbow if colour (Figure 7). When we experience daylight or “white” light, all three of the eye’s red, blue, and green photoreceptors are being stimulated.

The rainbow colours seen as sunlight passes through a glass prism
Figure 7: The rainbow colours seen as sunlight passes through a glass prism


Conventional colours are produced by subtraction

When daylight or “white” light from any source interacts with a pigmented surface or passes through a pigmented medium, the resulting visible colour of the light, reflected or transmitted, is the residual components of that light that has not been absorbed. That means when you see a red flower or a green leaf, it is because (in the case of the red flower) more of the blue and green components of sunlight have been absorbed, leaving light primarily in the red region of the spectrum reflected to reach the viewer. In the case of the green leaf, more of the red region of the spectrum is absorbed, and the reflected or transmitted light is seen primarily as green (Figure 8). In both cases, the colours of the light that emerges are the wavelengths of light that have not been absorbed. With conventional pigments, the energy of the absorbed light is typically dissipated as invisible heat through enhanced molecular vibrations.

Daylight interacting with a pigmented surface
Figure 8: When daylight or “white” light from any source interacts with a pigmented surface, the colours of the light that emerge are the wavelengths of light that have not been absorbed

Source: Image constructed by Alan Schein

The phenomenon of daylight fluorescence

The two super-imposed curves in Figure 9 are the absorption (blue) and emission (red) spectra of a daylight fluorescent colourant. Like a conventional pigment, the daylight fluorescent colourant absorbs and reflects light, but unlike its conventional counterpart, some of the absorbed light energises the contained fluorescent dye in a way that enables it to re-emit some of that absorbed radiant energy at a longer wavelength (colour). The additional emitted light is what gives daylight fluorescent materials their extra luminous appearance.

The absorption (blue) and emission (red) spectra of a daylight fluorescent colourant
Figure 9: The absorption (blue) and emission (red) spectra of a daylight fluorescent colourant


More and brighter light

Comparison of light output from conventional and daylight fluorescent pigments shows daylight fluorescence emits up to four times more light intensity, making it visually striking and attention-grabbing! (Figure 10)

Comparison spectra of the light output of conventional and daylight fluorescent pigments
Figure 10: Comparison spectra of the light output of comparably coloured conventional and daylight fluorescent pigments


More on Brilliant Group

Brilliant Group is focused on making it easy for customers to implement daylight fluorescent colours. Each product in the broad portfolio of pigments, toners, dispersions and ink concentrates is available in the same, easy-to-order, formulation anywhere in the world.

Independently-owned, founded and run by chemists, they involve their R&D team
directly in supporting customers to ensure success. The intense luminosity of daylight fluorescence – as much as four times greater than conventional colour – captures
attention like nothing else. This visual “magic” is routinely deployed to save lives and prevent accidents in a wide range of transportation, marine and sports applications. Its sales-generating visual appeal has no equal in areas as diverse as product packaging, toys, clothing, plastics, household furnishings and surface coatings. At Brilliant, they
continue to be amazed by the “magic” of daylight fluorescence and are dedicated to support and expand its limitless possibilities.

As long-term specialists in fluorescent colour, the team brings decades of experience in how to best employ these unique products for maximum and lasting effect – they utilise this experience and know-how in helping customers meet their coloration needs and explore new opportunities. They maintain constant dialogue with customers as well as the necessary market intelligence to keep abreast of evolving industry standards and to explore new challenges in colour and visual appearance.

Brilliant Group headquarters, R&D lab, quality control and U.S.-based manufacturing are located in California’s San Francisco Bay Area. They maintain inventory in multiple locations in North America, Europe and Asia, and also employ a global network of distribution partners to meet the increasing demand for their products in numerous international

With an extensive range of colours and product types, Carst & Walker UK & Carst & Walker Ireland can provide solutions to many applications and markets using Brilliant daylight fluorescent pigments. Get in touch with us to find out more.