Since its invention some 130 years ago, flexography has come a long way. This two-part series covers the origins of Flexo printing as well as its growth in popularity from the invention of the first rotary press using rubber plates to the commercialization of UV pigments in the 1990s.
Part One: The Birth of Flexographic Printing through the 1950s covered the history of flexographic printing from its inception to the 1960s. This is the second installment of Flexography. The 1960s, 1970s, 1980s, and 1990s will cover new products and applications developed during the 1960s, 1970s, 1980s, and 1990s, as well as the influence of the Flexographic Technical Association (FTA) on the flexo industry.
Flexo Chronicles: A Flexography History | Flexographic Printing from the 1960S to the Present
Printing Flexographic in the 1960S and 1970S
In the 1960s and 1970s, the flexographic printing industry focused heavily on press design and quality improvement. Throughout the early 1960s, press design was updated to include higher screen counts to allow press operators to achieve higher image resolution than was previously possible. Screen ruling continued to rise until it reached a plateau of around 120 lines per inch, a resolution that would allow printers to achieve better gray balance and correct halftones.
New inks were also developed for corrugated printing, a market where flexography demonstrated its ability to print with improved legibility, less deflection, and lower production costs due to less material waste. Acrylics, a synthetic resin, served as the foundation for these new inks. They dried faster, were harder, and had fewer viscosity variations than those based on shellac, which varied from batch to batch.
Ink technology underwent significant changes in the early 1970s as a result of the discovery and use of new solvents such as urethanes, acrylates, polyamides, and polyesters. The Flexographic Printing Institute (FTA) and Rochester Institute of Technology (RIT) collaborated to create the first college-level flexographic printing course in 1961.
This program began educating the innovators who would revolutionize the flexographic industry. The rubber roll that helped meter the ink was replaced by the doctor’s blade in 1964, forever changing the design of flexographic presses.
Flexography was thought to be primarily a letterpress process until the 1960s, with extremely fast-drying, low-viscosity inks that relied on solvent evaporation for effect. Flexographic, or aniline, inks were original “a solution of shellac in denatured alcohol to which [was] added alcohol-soluble basic dyes for coloring.” However, by the 1960s, three types of ink were available:
DuPont was the first company to introduce process-color printing in 1965, but it wasn’t until 1972 that the technology was realized. Water-based inks were appealing because they freed the industry from reliance on organic solvents. The first four-color narrow web presses were ready for production by the end of the 1960s.
When exposed to ultraviolet light, the photopolymer layer hardens and hardens, allowing it to be printed on a plate. To make printing plates, a high-contrast photographic negative is placed emulsion-side down on the plate. The exposed areas are exposed to UV light, and the unexposed areas are washed out with an alkaline solution.
In the 2000S, Flexographic Printing
Flexographic printing had become a dominant force in the packaging industry by the year 2000. Print houses were being purchased by key industry players, and larger investments in flexo operations were being made.
As the quality of flexographic printing improved, a shift within the printing industry led packaging printers away from gravure, the then-gold standard of printing, and toward flexography. Nowadays, the qualities of flexography and gravure printing are thought to be on par. According to the FTA, advancements in flexography have been impressive throughout the 2000s, ’10s, and now ’20s, and include improvements to:
- Aniloxes: The anilox line screenings are finer, and the cell structure is no longer hexagonal
- Inks: The inks dry much more slowly. Furthermore, the pigmentation and ink transfer has been significantly improved. Dot bridging due to ink drying issues is extremely rare in high-quality process printing
- Repro: Several new repro tools have been released to improve highlights and shadows, and Expanded Gamut (EG) has finally broken through
- Plate exposure: There are numerous new solutions, and LED technology introduces new opportunities for improvement
- Plates: Significant improvements have been made possible by plate exposure and improved ink transfer, as well as surface structures and dot solutions for highlights. The flat-top dot has had a significant impact on quality
- Tapes: Although this industry has not seen as many advancements and changes as others, the solution of replacing cushion foam tape is perhaps the most intriguing development for central impression (CI) drum machines
- Machines: Digitalization, speed, and press stability (the most difficult challenge) have all improved significantly, influencing quality and productivity
Major investments in packaging have occurred as flexographic printing continues to modernize throughout the twenty-first century, while eco-friendly and sustainable materials have grown in popularity. Keep an eye on this article for updates as the flexographic printing industry evolves.