Thermal Transfer Labels Guide

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Ink is normally in a liquid form, however, there are several printing technology, which utilizes solid ink. The first method is sublimation transfer, which is a dry image printing process that uses dye crystals. When these dye crystals are subjected to heat and pressure, they are convert from a solid into a gas form without becoming a liquid. This technology differs from all other printing procedures in that the transferred image is adhered to the substrate molecules instead of on the print media’s surface, as is the case with inkjet printing.

The solid ink is melted, converted into a liquid, then sprayed or piezoelectrically driven onto the media. One major advantage of solid ink is that the ink does not have to dry. Instead, it solidifies almost immediately on the printing media surface. In addition, the solid ink does not dry out, nor does it require a wick as liquid ink does. Solid ink bounds to the paper surface producing colors that are more vivid and sharper images.

Solid Ink Printing

In 1995, Tektronix development indirect printing and revolutionized solid ink printing. Tektronix used an ink-jet printhead that spray-painted a complete image on a spinning drum. Once the image was applied to the drum surface, it was transferred from the drum onto paper. This concept made it possible to use a very simple paper path, with the paper being feed straight through the printer similar to that of an offset printing process. However, this indirect printing process places severe restrictions on the ink. The ink had to be hard at room temperature, have a low melt point and had to be able to easily jet through the tiny apertures of the printhead. In addition, the ink had to solidifies almost immediately on the drum surface and stay in place on a rapidly spinning drum. Lastly, the ink had to transfer from the drum to paper during the offset printing step. This led to the development of the solid inks used today.

The solid ink resembled that of crayon-like cartridges. The color quality of solid ink printing is stunning. In addition, its print speeds exceeded most equivalent-priced laser printer, due to the fact that it prints colors in a single pass instead of having to make four passes. The Tektronix-developed technology applies all four-color solid ink mirror images onto the drum in a single pass.

Thermochromic ink is ink that is designed to change color with the change of temperature. The printed image will vanish as the temperature increases above the response temperature of the thermochromic ink. When the temperature lowers below the response temperature the image will revert back to its original color.

Thermochromic ink has various applications including high quality promotional items, advertising, labels, packaging, security documents, textiles, toys, novelties, and anti-counterfeiting for such items as event tickets, lottery tickets. Thermochromic ink can also be used for safety as temperature indicators and warnings for such items as hot drinks and food.

It contains microencapsulated thermochromic pigment that changes from color to colorless as the temperature rises, when the temperature decreased the pigment returns to normal. In aqueous conditions, the pigment is encapsulated, resulting in a slurry mixture, resembling that of plaster-of-paris.

The microcapsule wall of the pigment can endure most standard mixing and application procedures. However, if too much force is used during the mixing or application procedure, the microcapsule will be crushed, and the ability of the ink to change color will be destroyed

There are three types of thermal transfer printer ribbons: wax, wax-resin, and pure resin. These are usually monochrome, (usually black) however there are also three-colored CMY and four-color CMYK ribbons available. The different types of printer ribbons are specially formulated for use on different label materials and to extend the life of the thermal transfer label or to protect the thermal transfer label from harsh environments.

Wax ribbons-these are the least expensive ribbon and are used for printing onto thermal transfer paper labels. The life of these labels can extend for several years when kept dry and not subjected to certain chemicals or oils that could melt the wax image.

Wax-resin-these ribbons are used on thermal transfer paper as well as synthetic labels used for pharmaceutical labels, drum and pallet labels, inventory control, and labels for mattress and pillows. Wax-resin ribbons produce a finer image on very smooth paper or coated paper labels and are more durable than wax. However, they are not waterproof and can only withstand slight contact with water.

Pure resin-these ribbons are specially formulated to print on thermal transfer synthetics labels such as polyester, polypropylene, and vinyl. The resin ink is extremely durable to abrasion, oils, solvents, and extreme temperatures. The ink dissolves or melts slightly into the plastic surface of the label, which gives it its durability. These synthetic labels are often used for outdoor labeling, UL/CSA applications, pharmaceutical labels, drums, pallets, dry-cleaning labels, automotive and aircraft, as well as manufactured parts.

The main component for thermal transfer printing is the thermal print head. This mechanism provides the heat energy required to create the image on the print media. Thermal print heads are fixed in position and the media moving past the print head to create the image. For this reason the print head and he print ribbon are as wide as the media on which they are printing.

The print head is a very simple mechanism and does not require a scanning mechanism. The print accuracy on thermal transfer printers is superior because the print element position is fixed to the web motion direction. The spacing of the print elements on the linear array print head can be held to a tolerance of 0.0001 inch, making thermal transfer printers an accurate method of printing. This is especially significant for machine-readable bar codes.

When bar code labels are printed vertical to the print head motion, the print accuracy is dependent on the accuracy of the print head motion. In addition, the print quality of the image edge is affected by the time needed to heat the printing elements for the thermal ink to melt, as well as the time needed to cool the elements so that they will not melt the ink.

The association between the print head and the platen located behind the print media is significant for the proper operation of the printer. It is important that the thermal printing elements are located vertical to the center-point of the cylindrical platen. Also critical to the printing process is the pressure between the print head, ribbon, and print media. When the print elements are not positioned on the centerline of the cylindrical platen, the printing elements will not produce the exact size dot on the printed media, thus the printed image will be smudged or poor quality.

Thermal transfer printer heads have a longer life than direct thermal printers do because they use approximately 33% less energy to produce the same quality image. In addition, the coating, and base layer of the thermal transfer ribbon prevents the ink from adhering to the print head.

As the thermal transfer ribbon and the ink receiving media is moved past the print head a microprocessor selectively heat individual resistive print head elements to create the image. By alternating the movement of the print media, and selectively heating the wax residue, a matrix of individual dots is created and an image is produced.

Direct to plate printing is a form of printing which has become extremely popular due to its cost-effectiveness. This innovating technology is also environmentally friendly and has a higher productivity rate.

Because this process eliminates film in the printing process, the technology has had to completely expand in order to provide the print quality that consumers demand. To ensure that there was no loss of print quality, several manufacturers have development their own techniques. One such company was Kodak, who developed Direct Thermal Printing Plate. This process uses thermal imaging techniques instead of silver halide or photopolymer technologies. This technology uses focused heat from a laser diode to the surface coating onto a plate until the required temperature has been reached. Once the correct temperature has been achieved, an image is formed. The addition of more heat will not have an effect on the image. The image will exactly match the platesetter image.

Traditional film and plate printing processing require the use of harmful chemical substances, though direct to plate printing will not completely eliminate all harmful chemicals, it is more environmentally friendly. Other benefits include less expensive operating cost as the majority of the process is produced through a computer and the print media is also less expensive.

However, noticeable disadvantage of direct to plate printing is that there isn?t an opportunity for proofing of prints, which is a vital step at every stage of the printing process. By proofing film, the developer has an opportunity to notice any errors and correct them if possible. However, with direct to plate printing, there isn?t any way to accurately proof an image before printing and this drawback has been noted as a flaw in the technology.

Hot Stamping is a printing process that uses heated dies that are stamped onto a sheet of colored or metallic foil resins which causes the foil to be printed onto paper, vinyl, textiles, wood, hard plastic, leather, or whatever media is being printed. Heated dies, which can be made out of silicone rubber or metal, contain raised graphic images, which press the foil resins onto the print media surface.

The foil for hot stamping is available every possible color and pattern from standard gold and silver to marbleized colors in addition, leaf is also available in matte, pearlescent, holographic, opalescent, and glossy finishes. Semi-transparent layers permit underlying colors and designs to show through, creating unique vibrant images with depth. Hot stamping can be applied to more medias than ink.

Items such as leather photograph albums, cloth bookmarks, can be imprinted with hot stamping. Other uses include wedding invitations, business cards, folders, signs, and magnets.

Hindsight is always 20/20. In 2000, marketing research predicted that thermal wax transfer technology would decline in popularity. This prediction was wrong. In fact, several companies were then and still are developing technologies to improve the process.

One such development is variable thermal wax transfer printing, which reduces dithering artifacts and can print in 64 shades/color.

This system uses the same printing mechanism as a dye sublimation printer. However, instead of laying down a transparent die, thermal wax transfer printers melts dots of wax-based ink, which adhere to nearly any type of media, from regular print paper to metals, synthetics, and film.

Thermal transfer printers produce images by placing color dots side by side. This process is known as dithering, which simulates more colors and shades than what is actually in a palette, which is how halftones can be created in a monochrome printer. The process of dithering cannot produce the precise same results as the actual colors, but dithering can produce images, which appear more realistic.

Variable thermal wax transfer printing produces image quality far better than ink jet technology. One reason for this is the fact that thermal wax transfer uses pigments similar to printing inks. In addition, the pigment base is also lighter, and more rub fast.

As with any printing system, the more colors used the sharper the image.

Thermal dye transfer is also known as dye sublimation. Sublimation is a chemical process where a substance is changed directly from a solid to a gas without that substance, becoming a liquid. Thermal dye transfer printing is a process that uses sublimation in order to print full-color images on a variety of mediums, including paper. Heat is used to vaporize the dye material, which immediately solidifies once it comes in contact with the print medium. This type of printer makes it possible to obtain an excellent quality picture with a relatively low printer resolution. One of the first printers to use thermal dye transfer was Tektronix’ “Phaser” computer printers.

Thermal dye transfer can also be used as an indirect printing process. An example of this would be standard black and white laser printers, which use special transfer toner that contains sublimation dyes that can later be permanently heat transferred to T-shirts, hats, tote bags, mugs, puzzles and other surfaces.

The dye ribbon for the thermal dye transfer printer has four separate panels, three of which contain dyes for the primary colors, cyan, magenta, and yellow, and the fourth panel contains a clear coating. This clear coating improves the image’s stability and permanence. In fact, with proper care and storage thermal prints can last for generations.

This process is so revolutionary that Kodak uses thermal printers for its picture maker stations and also in their EasyShare printer docks. Thermal printing dyes penetrate the paper, which means they don?t require drying time, and are fade resist. In addition, the produces images produced have finer density gradations, and a more photographic.

Thermal dye transfer printers are also used in high-precision applications, such as with medical imaging, and in the graphics/printing industry. More advanced thermal printers use a laser to heat the dye ribbon, which more accurately transfers the dye particles to the print media.