Dry tinting technology

Based on 20 years of experience, a world-renowned Japanese manufacturer has completed a fully automated dry tinting system. The digital tinting method works completely differently compared to traditional dipping and is said to have a number of advantages in terms of productivity, environmental impact, and material versatility as a result.

Before the particular technology and its advantages are explained, the challenges of the traditional dipping method should first be explained in more detail in order to clarify the differences.

Challenges with conventional tinting

The traditional dipping method is immersing lenses in a dye solution. This is a very well-known, simple, and proven process in mass production, but it also brings with it a few challenges. One of them is the unstable color. Variations in lens materials, lot numbers, lens power, and dye solution life lead to inconsistent colors.

The process is also based heavily on the experience and specialized skills of employees. Color adjustment by the operator is frequently required, as the colors are not stable using conventional methods. To obtain the skills to make color adjustments, long-term training is required. When an operator leaves the company, this can become a major challenge for managers.But there are other challenges too, and one of them relates to the environment. There are many dyeing pots based on base material types and colors, and this results in a large amount of liquid waste. This is expensive and not sustainable. Also, the environment for operators is not comfortable. The water bath is constantly heated to around 100°C, which means that operators have to work in a hot and humid environment.

And finally, there are material limitations. High-index lenses such as 1.74 and polycarbonate cannot be tinted using this method, potentially leading to missed business opportunities. These challenges are to be tackled with the help of digital tinting technology.

Technical details of dry tinting technology

Dry tinting technology was developed to address these issues. Unlike the dipping method, this technology operates in a dry environment. It uses exclusive inks and special paper or foil, with the dye being transferred to the lens surface under vacuum conditions without contact. Non-contact transferring creates beautiful gradation patterns and natural color combinations. Nidek offers two systems for dry tinting technology called TTM-2000 and AutoTint. The process of dry tinting follows three steps:

1. Printing process: Exclusive inks are printed on special foil or paper using an inkjet printer. The printing software developed by Nidek controls each ink amount digitally and creates the precise printing patterns.

2. Transfer process (sublimation): The printed paper or foil is placed opposite the lens without contact and then put into a vacuum chamber. Under vacuum conditions, the printed paper is heated by a halogen lamp, causing the dye to sublimate and transfer to the lens surface without contact.

3. Heating process: After the dye transfer, lenses are heated to over 100°C, allowing the dye to penetrate and fix into the lens material. This high-temperature process ensures that the lenses can be tinted uniformly, even for materials such as 1.74 and polycarbonate that are difficult to tint using traditional methods.

Advantages of dry tinting technology

Stable color: The ink amount is precisely controlled by a computer and inkjet printer, ensuring consistent color without specialized skills.

No need for special skills: No special skills are required, as the same color can be produced by anyone with the machine. Training time is also significantly reduced compared to conventional tinting, and operators need to learn only how to operate the equipment.

Environmental benefits: The process generates minimal liquid waste, significantly reducing environmental impact and associated costs. The estimated volume of liquid waste to tint four hundred thousand lenses per year is approximately 12,000 liters with dip tinting and only 10 liters with dry tinting (based on Nidek’s research in 2021).

Versatility: This technology can tint a wide range of materials, including high-index lenses such as 1.74 or polycarbonate. Dry tinting can tint up to Class4 (more than 85% tinting density).

UV resistance: The dyes of dry tinting have excellent UV resistance and are enhanced more by the tinting on the concave side of the lens. The standard is concave tinting, but convex tinting is also applicable.

Clean working environment: Dry tinting does not use the dye solution, resulting in a cleaner and more comfortable working environment.

A few color fading: As it penetrates well into the substrate, it is adaptable to any hard coat and does not suffer from color fading caused by cleaning or hard coat liquids. It can contribute to improved yields after hard coating.

Design flexibility: The technology creates new designs, such as center tinting, multicolor gradations, and rainbow patterns, expanding the range of color and design variations.

Conclusion

Nidek´s labs already have 20 years of experience with this process. It is well established and shows successful results.

And finally, the recently launched AutoTint system automates the entire tinting process, from printing to sublimation and heating. It connects with job management systems, receives lens information, and automatically tints the lenses. The use of laser heating in the automated system significantly reduces processing time and ensures consistent quality with machine-based color judgment.

By transitioning from analog to digital and incorporating environmentally friendly methods, it makes a huge difference to labs around the world. The technology offers stable color, versatility, and automation. Nidek believes the technology and products promise to make the tinting process more efficient, sustainable, and innovative compared to the conventional way that relied on human skills by enabling anyone to tint to the same color in a short time.