Rotogravure
A little History
Rotogravure printing continues to be a significant printing technology, particularly for long print runs where high quality and consistency are crucial. Despite facing challenges, advancements in the process and its adaptation to changing industry needs have allowed it to maintain a presence in specific niche markets.
Invention and Early Development (Late 19th Century):
The roots of rotogravure can be traced back to the late 19th century. The process was initially developed as a means to reproduce photographs.
Karl Klic, a Czech inventor, is often credited with the invention of the rotogravure process in the 1870s.
Commercialisation in the Early 20th Century:
The early 20th century saw the commercialisation and refinement of rotogravure printing for mass production.
In 1912, the German engineer, Josef Rossner, patented a rotary gravure printing press. This marked a significant advancement in the technology.
Expansion and Adoption in the Printing Industry:
Rotogravure printing gained popularity for its ability to produce high-quality images with fine details and a wide range of tones.
The process became widely adopted for printing magazines, catalogs, packaging materials, and other high-quality printed materials.
Rotogravure in the Photomechanical Era:
In the mid-20th century, as photomechanical processes became more prevalent, rotogravure adapted to incorporate these technologies. Copper-plated cylinders engraved with photographic techniques became common, allowing for more precise and detailed image reproduction.
Challenges and Shifts in the Late 20th Century:
Despite its advantages, rotogravure faced challenges from other printing technologies, such as offset and flexography.
The late 20th century saw a decline in rotogravure's market share, particularly in certain print applications and geographical zones.
Modern Applications and Advancements:
While offset and digital printing have become more dominant in certain areas, rotogravure printing remains relevant, especially in the production of high-quality packaging materials, decorative printing, and publication printing.
Environmental Considerations:
The gravure process involves the use of solvent-based inks, which raised environmental concerns. As a result, there has been a shift towards water-based and electron beam (EB) curing inks in some applications.
Some Applications of Rotogravure Printing in Packaging
Rotogravure printing excels in these packaging applications due to its ability to produce high-resolution images, consistent print quality, and cost-effectiveness for large print runs. The process is particularly well-suited for packaging where visual appeal and brand representation are critical factors.
Flexible Packaging:
Flexible Pouches: Rotogravure is commonly used for printing on flexible pouches used in the packaging of snacks, confectionery, and various food products.
Stand-up Pouches: The process is suitable for printing detailed graphics on stand-up pouches, commonly used for packaging liquids, powders, and pet food.
Cigarette Packaging:
Cigarette Packs: Rotogravure printing is often employed for cigarette packaging, where intricate and high-quality graphics are essential for branding.
Cigarette Filter wraps: Rotogravure printing is often employed for cigarette filter wraps allowing a continuous pattern.
Labels:
Product Labels: Rotogravure is used for printing labels on a roll, offering high-resolution and detailed images for labeling products in various industries, including beverages, personal care, and pharmaceuticals.
Shrink Sleeves: Rotogravure is suitable for printing on shrink sleeves, providing 360-degree graphics for products like beverages and cosmetics.
Food Packaging:
Confectionery Wrappers: Rotogravure is used for printing vibrant and detailed graphics on wrappers for chocolates, candies, and other confectionery items.
Frozen Food Packaging: The process is applied to print on packaging materials for frozen foods, ensuring high-quality images.
Home and Personal Care Products:
Detergent Packaging: Rotogravure printing is employed for detergent packaging, where durable and visually appealing labels are important.
Toiletries Packaging: Products like shampoo bottles and personal care items often feature labels produced through rotogravure printing.
Pet Food Packaging:
Pet Food Bags: Rotogravure printing is used for printing on bags and packaging for pet food, providing sharp and colorful images.
Medical and Pharmaceutical Packaging:
Medical Pouches: Rotogravure is utilized for printing on pouches used for medical devices, diagnostic kits, and pharmaceutical products.
Blister Packs: The process is applied for printing on blister packaging used for tablets and capsules.
Dairy and Snack Packaging:
Cheese Packaging: Rotogravure printing is suitable for printing on packaging materials for cheese and other dairy products.
Snack Bags: The process is commonly used for printing on snack bags for chips, nuts, and other snack items.
Convenience Foods:
Instant Noodle Packaging: Rotogravure printing is employed for printing on packaging materials for instant noodles and other convenience food products.
Ready-to-Eat Meals: Packages for ready-to-eat meals often feature rotogravure-printed labels.
Other applications of rotogravure printing
Publication and Commercial Printing:
Magazines and Catalogs: Gravure printing is used for high-volume printing of magazines and catalogs, where image quality and consistency are critical.
Decorative Printing: Gravure is employed for decorative printing on products such as gift wraps, calendars, and other promotional materials.
Textiles:
Wallpapers and Fabrics: Gravure printing is used in the textile industry for printing patterns on wallpapers, plastics and fabrics. It allows for intricate designs and vibrant colors.
Security Printing:
Banknotes: Gravure is utilised in the printing of banknotes and security documents due to its ability to reproduce intricate details and provide a level of security against counterfeiting.
Decorative Printing:
Gift Wrapping Paper: Gravure is commonly used for printing decorative patterns and designs on gift wrapping paper.
Laminate Flooring: Gravure printing is applied to create realistic wood or tile patterns on laminate flooring or other items.
Wide-Web Printing:
Gravure printing is well-suited for wide-web applications, such as printing large rolls of materials used in packaging, labels, and publications.
Electronics:
Printed Electronics: Gravure is utilised in the field of printed electronics for applications like printing conductive inks and patterns on substrates for electronic components.
Automotive Industry:
Gravure printing is used for printing decorative elements on automotive interior components, including dashboards and panels.
Industrial Applications:
Gravure printing is applied in various industrial settings for printing patterns on materials used in construction, laminates, and other industrial products.
Main Substrates used in Rotogravure Printing for Packaging
The choice of substrate in rotogravure printing depends on factors such as the desired packaging properties, printing speed, and environmental considerations. Manufacturers often select specific combinations to achieve the best results for their packaging requirements.
Flexible Packaging Films:
Polyethylene (PE): Used for a variety of flexible packaging applications, including food packaging, pouches, and bags.
Polypropylene (PP): Commonly used for packaging snacks, confectionery, and other consumer goods.
Polyester (PET): Used for flexible packaging, labels, and shrink sleeves.
Biaxially Oriented Polypropylene (BOPP): Commonly used in packaging for snacks, confectionery, and more.
Oriented Polypropylene (OPP): Commonly used in packaging for snacks, confectionery, shrink sleeves, and more.
Paper and Paperboard:
Coated and Uncoated Papers: Suitable for various packaging applications, including labels, folding cartons, and more.
Carton Board: Used for packaging boxes, cartons, and other paperboard applications.
Metal Foils:
Aluminum Foil: Commonly used in pharmaceutical packaging, food packaging, and other applications requiring barrier properties.
Metalised Films: Films with a metallic appearance are used in flexible packaging for visual appeal.
Labels and Tags:
Pressure-Sensitive Labels (PSL): Gravure printing is used for producing high-quality labels for various products.
In-Mold Labels (IML): Used for packaging containers, especially in the food and beverage industry.
Plastic Packaging:
Polyvinyl Chloride (PVC): Used in various packaging applications, including shrink sleeves and labels.
Polystyrene (PS): Commonly used in packaging for consumer goods, electronics, and more.
Acrylonitrile Butadiene Styrene (ABS): Used in packaging for products like toys and consumer electronics.
Flexible Packaging Substrates:
Laminated Films: Suitable for gravure printing in flexible packaging for food, snacks, and personal care products.
High-Barrier Films: Films designed to provide enhanced barrier properties for packaging sensitive products.
Inks, Coatings and Lacquers
In rotogravure printing for packaging, various primers, lacquers, varnishes, inks, and special coatings are employed to achieve specific visual effects, enhance durability, and provide protection to the printed material. The selection of these components depends on factors such as the substrate material, printing technology, and the desired characteristics of the packaging.
These coatings and inks contribute to the overall appearance, functionality, and durability of rotogravure-printed packaging materials. The choice of each component depends on the specific requirements of the packaging application, the characteristics of the substrate, and the desired visual effects. Rotogravure printing is particularly well-suited for high-volume printing on various flexible packaging materials.
Primers:
Purpose: Primers are applied as a pre-treatment to enhance adhesion, ink absorption, and durability on the substrate.
Types:
Corona Treatment: A surface treatment method that increases the surface energy of substrates, improving adhesion for inks and coatings.
Solvent-Based Primers: Improve adhesion on various substrates, preparing the surface for ink application.
Water-Based Primers: Enhance adhesion on paper and cardboard substrates, providing a base for subsequent inks.
Lacquers and Varnishes:
Purpose: Lacquers and varnishes provide protective coatings over the printed surface, enhancing visual appeal and offering additional functionalities.
Types:
Gloss and Matte Varnishes: Applied over the printed surface for gloss or matte finishes, providing protection and improving aesthetics.
Water-Based Varnishes: Suitable for paper-based substrates, providing protection and a clear finish.
UV-Curable Clear Coats: Offer added protection, gloss, and durability, especially for UV-curable inks.
Specialty Varnishes: Include formulations for specific effects like textures, textures, or scratch resistance.
Inks:
Purpose: Inks are the actual printing materials that create the images on the packaging substrate.
Types:
Solvent-Based Inks: Traditional inks commonly used in rotogravure printing for their fast-drying and high-quality properties.
Water-Based Inks: Environmentally friendly inks suitable for paper-based substrates, providing vibrant colors.
UV-Curable Inks: Cure instantly under UV light, offering high color vibrancy and durability on various substrates.
Specialty Inks: Include metallic inks, fluorescent inks, and other specialty formulations for unique visual effects.
Special Coatings:
Purpose: Special coatings add unique visual effects or provide specific functionalities to the printed material.
Types:
Soft Touch Coatings: Add a tactile and soft feel to the packaging surface.
Scratch-Resistant Coatings: Enhance durability by protecting against scratches and abrasions.
Glow-in-the-Dark Coatings: Create phosphorescent effects for attention-grabbing packaging.
Thermochromic Coatings: Change color with temperature variations, adding an interactive element to the packaging.
Textured Coatings: Add texture and dimension to the printed surface for a unique look and feel.
Anti-Microbial Coatings: Provide protection against microbial growth on the packaging surface.
Anti-Counterfeiting Coatings: Include features such as holographic effects or invisible inks to deter counterfeiting.
Print Process
Rotogravure printing, often referred to as gravure printing or simply "roto printing," is a high-quality and high-speed printing process. It is commonly used for long print runs, especially in applications like packaging, magazines, and decorative materials. Here's an overview of the rotogravure printing process:
Preparation of the Cylinder:
The key component in rotogravure printing is the printing cylinder. The cylinder is typically made of steel or copper and is coated with a layer of a photosensitive material for etching, and dry copper for electronic engraving.
Engraving Process:
The cylinder is engraved with tiny cells or wells using an engraving machine. Each cell corresponds to a specific dot in the final printed image.
The engraving can be done using various methods, with the most common technique being electronic engraving (carbon stylus vibrating at high frequency), followed by laser engraving and chemical etching.
The depth, shape and size of the cells vary, and this controls the amount of ink that the cells can hold.
Ink Application:
The engraved cylinder is then immersed in ink, and excess ink is wiped off the surface, leaving ink only in the engraved cells.
The rotogravure printing press typically uses a closed ink-tray system to ensure precise ink application and control.
Doctor Blade System:
A doctor blade, typically made of steel or plastic, skims off excess ink from the non-engraved areas of the cylinder, leaving ink only in the engraved cells.
The doctor blade is set at a specific angle and pressure to control the thickness of the ink layer.
Substrate Contact:
The substrate (material to be printed), often a continuous web of paper, plastic, or metal, is brought into contact with the rotating inked cylinder.
The substrate conforms to the engraved pattern on the cylinder, picking up ink from the cells.
Drying and Curing:
After the ink is transferred to the substrate, the printed material passes through a drying or curing system. This can involve the use of heat, air, or ultraviolet (UV) light, depending on the type of ink used.
Repeat Process for Multiple Colours:
For multicolour printing, each colour requires a separate engraved cylinder. The substrate passes through each color unit in sequence, applying different colours layer by layer.
The registration between colours is crucial to ensure the accurate alignment of different ink layers.
Final Drying and Finishing:
Once all colours have been applied, the printed material goes through a final drying or curing process to set the inks.
Additional finishing processes, such as coating or laminating, may be applied depending on the desired characteristics of the final product.
