Rupa Roto Gravure Printing Inks

Rupa Inks and Coatings P Ltd

Roto Gravure Printing Inks

November 1st, 2009

RotoGravure Water Based Inks

NAME	DESCRIPTION	SUBSTRATE
Gr Aquapulp	Opaque Inks	Craft Paper and Board
Gr.Aqua sheen	Gloss Finish Inks	Process Inks
GrAquaGlo	Florescent Inks	Paper and Board
MetaRoto	Mettallic Finish inks	All Paper and board
GrAquaPlast	Process Inks	Paper and Plastic Surfaces

Roto Gravure Solvent Inks

NAME	DESCRIPTION	SUBSTRATE
Gr Lamester	Reverse Printing-Laminatable Inks	Polyester film
Gr RubyLam	Reverse Printing-Laminatable Inks	Polyester film
Gr Lam Pp	Reverse Printing-Laminatable Inks	Bopp and Polyester film
Gr Poly	Multi-Purpose Bag Inks	Pp, Ldpe, HM Hdpe
Gr Pulprint	Surface Printing Inks	All Papers and boards
Gr.PulpSheen	High Gloss Inks	Glassine and all Coated Papers
RotoPaque	Inks for Packaging carton	Craft Paper and Board
Gr Metocol	Transparent Ink	Blister foil & Metalized Polyester film
Gr.AnchorPlastl	Inks for Freezer Packaging	Pp,Ldpe,HM Hdpe,etc.,
Gr.Alkylfix	2pack ink for Alkali and Oil resist Packs	Pp, Ldpe, HM Hdpe

Buy Quality Gravure Inks from Rupa colour inks, Tamilnadu, India

Rotogravure (roto or gravure for short) is a type of intaglio printing process, in that it involves engraving the image onto an image carrier. In gravure printing, the image is engraved onto a copper cylinder because, like offset and flexography, it uses a rotary printing press. The vast majority of gravure presses print on reels of paper, rather than sheets of paper. (Sheetfed gravure is a small, specialty market.)Rotary gravure presses are the fastest and widest presses in operation, printing everything from narrow labels to 12 feet (4 m)-wide rolls of vinyl flooring.Additional operations may be in-line with a gravure press, such as saddle stitching facilities for magazine/brochure work. Once a staple of newspaper photo features, the rotogravure process is still used for commercial printing of magazines, postcards, and corrugated (cardboard) product packaging. Gravure is an industrial printing process mainly used for the high-speed production of large print magazines and runs at a constant and top quality, such as in the printing of large numbers of magazines and mail order catalogs.Other use for the gravure processes are in wallpapers and laminates for furniture where quality and consistency are desired. Gravure cylinders nowadays are typically engraved digitally by a diamond tipped or laser etching machine. On the gravure cylinder, the engraved image is composed of small recessed cells (or ‘dots’) that act as tiny wells. Their depth and size control the amount of ink that gets transferred to the substrate (paper or other material, such as plastic or foil) via a process of pressure, osmosis, and electrostatic pull. (A patented process called “Electrostatic Assist” is sometimes used to enhance ink transfer.)Gravure is capable of transferring more ink to the paper than other printing processes, gravure is noted for its remarkable density range (light to shadow) and hence is a process of choice for fine art and photography reproduction, though not typically as clean an image as that of sheet fed litho or web offset litho.Gravure is widely used for long-run magazine printing in excess of 1 million copies. Gravure’s major quality shortcoming is that all images, including type and “solids,” are actually printed as dots, and the screen pattern of these dots is readily visible to the naked eye. Examples of gravure work in the United States are typically long-run magazines, mail order catalogs, consumer packaging, and Sunday newspaper ad inserts.

Print Process Descriptions: Printing Industry Overview: Gravure

Gravure Printing Applications - Process Overview - Inks - Press Design and Equipment

Applications:

Typical gravure printed products include:Typical gravure printed products include:

• Food packaging

• Wall paper

• Wrapping paper

• Furniture laminates

• Paneling

• Greeting cards

• Magazines

  
  

  
  

  
  
  

Process Overview

• Diagram of Image Carriers Used in Printing Processes

Gravure printing is characteristically used for long run, high quality printing producing a sharp, fine image. The number of gravure printing plants in the U.S. is significantly lower than other printing processes. This is due, in part, to the cost of presses and components. While a lithographic press will cost in the range of $100,000 the cost of gravure press will be in the range of $1 million. Additionally a single gravure cylinder will cost around $5000 versus around $15 for a lithographic plate. Additionally, the gravure cylinder has a long service life and will yield a very large number of impressions without degradation. Gravure printing is an example of intaglio printing. It uses a depressed or sunken surface for the image. The image areas consist of honey comb shaped cells or wells that are etched or engraved into a copper cylinder. The unetched areas of the cylinder represent the non-image or unprinted areas. The cylinder rotates in a bath of ink called the ink pan.As the cylinder turns, the excess ink is wiped off the cylinder by a flexible steel doctor blade. The ink remaining in the recessed cells forms the image by direct transfer to the substrate (paper or other material) as it passes between the plate cylinder and the impression cylinder.

The major unit operations in a gravure printing operation are:

• Image preparation

• Cylinder preparation

• Printing

• Finishing

Web Gravure Inks - Solvent Based, Water Based

Gravure inks are fluid inks with a very low viscosity that allows them to be drawn into the engraved cells in the cylinder then transferred onto the substrate. In order to dry the ink and drive off the solvents or water, which essentially replaces most of the solvent, the paper is run through Gas fired or electric fired driers. The ink will dry before the paper reaches the next printing station on the press. This is necessary because wet inks cannot be overprinted without smearing and smudging. Therefore, high volume air dryers are placed after each printing station.The solvent-laden air from the dryers is passed through either a solvent recovery system or solvent vapor incinerator. A typical recovery system uses beds of activated carbon to absorb the solvent. Saturated beds are regenerated by steam. The solvent laden steam is then condensed and the water and solvent separate by gravity. Greater than 95 percent of the ink solvents can be recovered using this process (Buonicore). The solvents can either be reused or destroyed by incineration.Water based inks, especially used for packaging and product gravure, require a higher temperature and longer drier exposure time in order to drive off the water and lower vapor pressure constituents. As mentioned subsequent sections, Flexo and Gravure inks are very similar and the constituents are essentially the same. Again, a pollution control device may be needed.

Gravure Press Design and Equipment

Web-fed gravure presses account for almost all publication, packaging, and product gravure printing. These presses are generally custom manufactured machines designed for a specific range of products. The typical press is highly automated and consists of multiple print units. The printing mechanism in a rotogravure press consists of a gravure cylinder and a smaller, rubber clad impression cylinder.Other types of gravure presses in commercial use today are sheet-fed, intaglio plate, and offset gravure. These types of presses are used primarily for special printing applications.

Web Fed Gravure

There are several types of web presses used in gravure printing, including publication presses, packaging presses, product presses, label presses, and folding carton presses. The printing process is basically the same regardless of which press is used.

Publication Gravure

Publication gravure is used primarily for very long press runs required to print mass-circulation periodicals, directories, inserts, and catalogs. Publication gravure maintains a competitive edge in the printing of mass-circulation magazines because the process offers high speed, high quality four color illustrations on less expensive paper, variable cut-off lengths, and flexible folding equipment. These presses can have as many as ten printing stations - four for color and one for monochrome text and illustration in each direction so that both sides of the web can be printed in one non-stop operation. They can handle web widths of up to 125 inches and are equipped to print most large format publications in circulation today. Publication gravure presses can also be fitted with cylinders of differing diameters to accommodate varying page sizes.The major types of chemicals used in publication gravure include adhesives, metal plating solutions, inks, and cleaning solvents. In terms of chemicals, publication gravure differs from packaging and product gravure primarily in its heavy reliance on toluene-based ink (GATF 1992b). The publication gravure industry has had little success with water-based inks (Buonicore). The industry has found that in publication gravure where the substrate is always paper stock, water-based inks have not been capable of printing commercially acceptable quality productions runs of 2,000 to 3,000 feet per minute.

Packaging Gravure

Packaging rotogravure presses are used for printing folding cartons as well as a variety of other flexible packaging materials. In addition to printing, packaging gravure presses are equipped to fold, cut, and crease paper boxes in a continuous process. Packages are usually printed on only one side, so the number of print stations is usually about half that required for publication gravure presses. However, in addition to printing stations for the four basic colors, packaging gravure presses may employ printing stations for the application of metallic inks and varnishes as well as laminating stations designed to apply foils to the paper substrate prior to printing.Packaging gravure presses are designed with the accurate cutting and creasing needs of the packaging material in mind. However, image quality is generally less important in packaging printing than in most other types of printing and, subsequently, receives less emphasis.The chemicals used in packaging gravure are similar to those used in publication gravure. However, the inks used in packaging gravure are largely alcohol- and not toluene-based (GATF 1992b). Water-based inks are being successfully used for lower quality, non-process printing on paper and paperboard packaging and for printing on non-absorbent packaging substrates such as plastics, aluminum, and laminates (Tyszka 1993). Use of water-based inks is expected to increase; however, problems still limit their use at press speeds above 1,000 feet per minute (Buonicore).

Product Gravure

The continuous printing surface found on gravure press cylinders provides the “repeat” required to print the continuous patterns found on textiles and a variety of other products. In the textile industry, a gravure heat transfer process using subliming dyes is used to print images on paper. These images are then transferred from the paper to a fabric (usually polyester) through a combination of heat and pressure. The gravure process is also used to print continuous patterns on wallboard, wallpaper, floor coverings, and plastics.The chemicals used in product gravure are similar to those used in both publication and packaging gravure. However, product gravure uses both water- and solvent-based inks (GATF 1992b). The industry has used water-based inks successfully on medium-weight papers and on nonabsorbent substrates such as plastics, aluminum, and laminates (Tyszka 1993). However, problems such as paper distortion and curl persist with lightweight papers (Buonicore).

Image Preparation

Image preparation begins with camera-ready (mechanical) art/copy or electronically produced art supplied by the customer. Images are captured for printing by camera, scanner, or computer. Components of the image are manually assembled and positioned in a printing flat when a camera is used. This process is called stripping. When art/copy is scanned or digitally captured, the image is assembled by the computer with special software. A proof is prepared to check for position and accuracy. When color is involved, a color proof is submitted to the customer for approval.

Cylinder Preparation

The gravure cylinder is composed of a steel or aluminum base, is copper plated and then polished to a predetermined diameter. Precise diameter of gravure cylinders in a set is critical. Any variances in diameter, as little as 2 thousandths of an inch can significantly affect the print registration. These cylinders are extremely sensitive to scratches and abrasions. Extreme care is taken when handling and storing the cylinders.Because copper is so soft the image areas quickly wear. Cylinders that are used for press runs of a million impressions or more are chromium plated. Some gravure printers “Double Chrome” cylinders in order to run them even longer. When the chromium begins to wear or the image is no lit is stripped off and the cylinder is re-chromed. This is much cheaper (and environmentally responsible) than etching a new cylinder. Once the cylinder has degraded or the image is no longer needed the image can be stripped off and the base cylinder can be reused for other printing jobs unlike other printing processes.

Gravure Cylinder Imaging:

• Chemical Etching

• Electromechanically Engraved

• Direct Digital Engraving.

There are three processes used for making gravure cylinders. The first is for conventional gravure using chemical etching that produces cells of the same size or area with varying depths. The second is Electromechanically engraved cylinders.In electromechanically engraved cylinder making, the image or copy is wrapped around a scanning cylinder. The scanning head moves across the scanning cylinder which sends impulses to a computer. The computer signals a pneumatic head, which contains a diamond stylus, when and where to make a cell in the copper cylinder. The diamond stylus cuts an inverted pyramid shaped cell into the copper cylinder. Engraved cells may be up to 200 microns wide and up to 50 microns deep.Chemical etching is hardly used now, but the process involves applying iron chloride solution of varying strengths over carbon tissue that has been sensitized to light by submerging it in a bath of potassium bichromate and water. The carbon tissue is a water-sensitive, fibrous paper that has been coated with a smooth gelatin resist.In summary the gelatin resist is made to adhere to the cylinder. The cylinder is then exposed to UV light to harden the gelatin resist and then rinsed with plain water. Finally the etching technician applies the ferric chloride etchant which creates the printing cells on the cylinder.Electromechanically engraved cells hold a lot less ink, yet print quality is equal to or better than chemically etched cylinders. In fact, an Electromechanically engraved cell holds approximately 30% less ink than a chemically engraved cell.Recently direct digital engraving has become widespread. With this process the image can be created and manipulated using an image handling computer. Therefore, the steps of creating, copying, and rescanning film, and the loss of quality inherent in these steps, can be avoided (GAA 1991).

Web Gravure Printing

The Doctor Blade and Impression Cylinder

The doctor blade is a simple device used to shear the ink from the surface of the plate cylinder. Pressure is applied to the doctor blade to assure uniform contact along the length of the cylinder. The blades must be angled to cut the surface of the ink, but pressure and angle must be carefully adjusted to prevent premature wear on the cylinder. The doctor blade also oscillates back and forth to prevent a flat surface being worn into the cylinder.The rubber coated impression roll brings the substrate in contact with the engraved cylinder resulting in proper ink transfer. The impression roll also acts to adjust the tension between print units and helps move the substrate through the press.The impression roll is made of a tubular sleeve coated with a rubber compound. The cover material is determined by the press conditions. Typically the coating is made of natural rubber, neoprene, nitrile or polyurethane. These impression rolls are typically purchased from an outside vendor rather than made on site.

Tags: brochure work, Flexo Inks, flexography, flexoink, gravure,Gravure Inks, India, intaglio, ISO 9001 certified ink manufacturing company, Offset Inks, Pad Printing Inks, Printing Inks, rotogravure,Rupa colour inks, Screen Inks, Silk Screen Ink, Speciality Inks,Tamilnadu, UV Inks, Water Based Inks