Information About Printers, Ink & Ink Cartridges

In general

In the personal and small business computer market, inkjet printers currently predominate. Inkjets are usually inexpensive, quiet, and reasonably fast; and many models can produce high-quality output. Like most modern technologies, the present-day inkjet has built on the progress made by many earlier versions. Among many contributors, Epson, Hewlett-Packard and Canon can claim a substantial share of credit for the development of the modern inkjet. In the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales: Canon, Hewlett-Packard, Epson, and Lexmark.

Ink jet printers use one of three main technologies: thermal, piezoelectric, and continuous.

Thermal Ink Jet

Most consumer ink jet printers (Lexmark, Hewlett-Packard, Canon) work by having a print cartridge with a series of tiny electrically heated chambers constructed by photolithography. To produce an image, the printer runs a pulse of current through the heating elements. A steam explosion in the chamber forms a bubble, which propels a droplet of ink onto the paper (hence Canon's tradename for its inkjets, Bubblejet). The ink's surface tension as well as the condensing and thus contraction of the vapour-bubble, pulls another charge of ink into the chamber through a narrow channel attached to an ink reservoir.

The ink used is usually water-soluble pigment or dye-based but the print head is produced usually at less cost than other ink jet technologies. The technology principle was discovered by Canon engineer Ichiro Endo in August 1977.

Note that this is not the same thing as a thermal printer, which produce images by heating thermal paper, as seen on some fax machines, cash register and ATM receipts, and lottery ticket printers.

Piezoelectric Ink Jet

All Epson printers and most commercial and industrial ink jet printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the crystal changes shape or size, which generates a pressure pulse in the fluid forcing a droplet of ink from the nozzle. This is essentially the same mechanism as the thermal inkjet but generates the pressure pulse using a different physical principle. Piezoelectric ink jet allows a wider variety of inks than thermal or continuous ink jet but is more expensive.

Continuous Ink Jet

The continuous ink jet method is used commercially for marking and coding of products and packages. The first patent on the idea is from 1867, by William Thomson. The first commercial model was introduced in 1951 by Siemens. In continuous ink jet technology, a high-pressure pump directs liquid ink from a reservoir through a gun body and a microscopic nozzle, creating a continuous stream of ink droplets. A piezoelectric crystal effects an acoustic wave as it vibrates within the gun body and causes the stream of liquid to break into droplets at regular intervals - 64000 to 165000 drops per second may be achieved. The ink droplets are subjected to an electrostatic field created by a charging electrode as they form. The field is varied according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet. Charged droplets are separated by one or more uncharged “guard droplets” to minimize electrostatic repulsion between neighboring droplets.

The charged droplets pass through an electrostatic field and are directed (deflected) to the receptor material (substrate) to be printed by electrostatic deflection plates, or are allowed to continue on undeflected to a collection gutter for re-use. The more highly charged droplets are deflected to a greater degree.

Continuous ink jet is one of the oldest ink jet technologies in use and is fairly mature. One of its advantages is the very high velocity (~50 m/s) of the ink droplets, which allows the ink drops to be thrown a long distance to the target. Another advantage is freedom from nozzle clogging as the jet is always in use. Volatile solvents (ketones and alcohols) can therefore be used, giving the ability of the ink to "bite" into the substrate and dry quickly. The fluid handling systems can be quite complex. Droplets are generated at ~ 64 to 165 kHz; only a few percent of the droplets are used to print; the rest are recycled.

The ink system requires active solvent regulation in order to accommodate for solvent evaporation during the time of flight (time between nozzle ejection to gutter reclamation) and from the venting process whereby air that is drawn into the gutter along with the unused drops is vented out from the reservoir. Viscosity is monitored and a solvent (or solvent blend) is added in order to counteract the described solvent loss.

Inkjet Inks

The basic problem with inkjet inks is the conflicting requirement for a colouring agent that will stay on the surface and rapid dispersement of the carrier.

Small inkjet printers as being used in offices or at home, all use aqueous inks based on a mixture of water, glycol and some dyes or pigments. These inks are inexpensive to manufacture, but are difficult to control on the surface of media and therefore often require specially coated media. Aqueous inks are mainly being used in printers with disposable, so-called thermal, inkjet heads, as these heads require water in order to perform.

In professional wide format printers, a much wider range of inks is in use currently. Most of these inks require piezo inkjet heads:

In solvent inks, VOCs are the main ingredient. Advantage of these inks is that they are very inexpensive and enable printing on uncoated vinyl substrates, which are used a lot in advertising for billboards and fleet graphics.

UV-curable inks consist mainly of acrylic monomers with an initiator package. After printing, the ink has to be cured by exposure to strong UV-light. The advantage of UV-curable inks is that they "dry" as soon as they are cured, they can be printed on a wide range of uncoated substrates and make a very robust image. Disadvantages is that they are more expensive, require expensive curing modules in the printer and the cured ink has a significant volume and so gives a slight relief on the surface.

Dye sublimation inks contain special sublimation dyes and are used to print directly or indirectly on fabrics that consist of a high percentage of polyester fibres. In a heating step the dyes sublimate into the fibers and create an image with strong color and good durability.

Inkjet head design

Two main design philosophies operate in inkjet head design. Each has strengths and weaknesses.

The fixed-head philosophy provides an inbuilt print head (often referred to as a 'Gaither Head') that is designed to last for the whole life of the printer. The idea is that because the head need not be replaced every time the ink runs out, consumable costs are typically lower and the head itself can be more precise than a cheap disposable one. On the other hand, if the head is damaged, it is usually necessary to replace the entire printer. Epson have traditionally used fixed print heads featuring micropiezo technology. These print heads are available in consumer products and are traditionally more accurate in dot placement than comparable thermal printers.

Other fixed head designs are more likely to be found on industrial high-end printers and large format plotters.

Fixed-head designs normally use piezo inkjet heads. Because development of these heads requires a large investment in research and development, there are only a few companies offering them: Kodak VersamarkTrident, Xaar, Spectra (Dimatix), Hitachi / Ricoh, HP Scitex, Brother, Konica Minolta, Seiko Epson, and ToshibaTec (a licensee of Xaar). Hewlett-Packard has come up with fixed-head printer based on Thermal Inkjet with its newer printer model such as HP Photosmart 3310.

The disposable head philosophy uses a print head which is part of the replaceable ink cartridge. Every time the printer runs out of ink, the entire cartridge is replaced with a new one. This adds to the cost of consumables and makes it more difficult to manufacture a high-precision head at a reasonable cost, but also means that a damaged print head is only a minor problem: the user can simply buy a new cartridge. Hewlett-Packard has traditionally favoured the disposable print head, as did Canon in its early models.

An intermediate method does exist: a disposable ink tank connected to a disposable head, which is replaced infrequently (perhaps every tenth ink tank or so). Most high-volume Hewlett-Packard inkjet printers use this setup, with the disposable print heads used on lower volume models.

Canon now uses (in most models) replaceable print heads which are designed to last the life of the printer, but can be replaced by the user if they should become clogged. For models with "Think Tank" technology, the ink tanks are separate for each ink color.

Cleaning mechanisms

The primary cause of inkjet printing problems is due to moisture evaporating from the nozzles on the printhead, causing the pigments and dyes to dry out and form a solid block of hardened mass that plugs the microscopic ink passageways. Most printers attempt to prevent this drying from occurring by covering the printhead nozzles with a rubber cap when the printer is not in use. However this seal is not perfect, and over a period of several weeks the moisture can still seep out, causing the ink to dry and harden.

To combat this drying, nearly all inkjet printers include a mechanism to reapply moisture to the printhead. Typically there is no separate supply of pure ink-free solvent available to do this job, and so instead the ink itself is used to remoisten the printhead. The printer attempts to fire all nozzles at once, and as the ink sprays out, some of it will wick across the printhead to the dry channels and partially softens the hardened ink. After spraying, a rubber wiper blade is swept across the printhead to spread the moisture evenly across the printhead, and the jets are again all fired to dislodge any ink clumps blocking the channels.

Most Epson printers also use a supplemental air-suction pump, utilizing the rubber capping station to suck ink through a severely clogged cartridge. Due to the built-in head design, the suction pump is also needed to prime the ink channels inside a new Epson printer, and to reprime the channels between ink tank changes.

The ink consumed in the cleaning process needs to be collected somewhere to prevent ink from leaking all over the surface under the printer. The collection area is known as the spittoon, and in Hewlett Packard printers this is an open plastic tray underneath the cartridge storage and cleaning/wiping station. In Epson printers, there is typically a large fibrous absorption pad in a pan underneath the paper feed platen. For printers several years old, it is common for the dried ink in the spittoon to form a pile that can stack up and touch the printheads.

The type of ink used in the printer can affect how quickly the printhead nozzles become clogged. While the official brand of ink is highly engineered to match the printer mechanism, generic inks cannot exactly match the composition of the official brand since the actual ink composition is a trade secret. Generic ink brands may alternately be too volatile to keep the printhead moist during storage, or may be too thick and jellied leading to frequent printhead channel clogging.

There is a second type of ink drying that most printers are unable to prevent. In order for ink to spray out of the cartridge, air needs to enter somewhere to displace the removed ink. The air enters via an extremely long, thin labyrinth tube, up to 10 cm long, wrapping back and forth across the ink tank. The channel is long and narrow to slow down moisture from evaporating out through the vent tube, but some evaporation still occurs and eventually the ink cartridge dries up from the inside out.

Advantages

Compared to earlier consumer-oriented printers, inkjets have a number of advantages. They are quieter in operation than impact dot matrix or daisywheel printers. They can print finer, smoother details through higher printhead resolution, and many inkjets with photorealistic-quality color printing are widely available.

In comparison to more expensive technologies like thermal wax, dye sublimations, and laser printers, inkjets have the advantage of practically no warm up time and lower cost per page (except when compared to laser printers).

Present-day inkjet printers use stochastic or FM screening, which gives better-quality results than low-cost laser printers when printing photographic images. Some inkjet printers print dots of more than one size, so that the screening is not purely "FM".

For some inkjet printers, monochrome ink sets are available either from the printer manufacturer or third-party suppliers. These allow the inkjet printer to compete with the silver-based photographic papers traditionally used in black-and-white photography, and provide the same range of tones – neutral, "warm" or "cold". When switching between full-color and monochrome ink sets, it is necessary to flush out the old ink from the print head with a special cleaning cartridge.

As opposed to most other types of printers, inkjet cartridges can be refilled. Most cartridges can be easily refilled by drilling a hole in and filling the tank portion of the cartridge. This method is more cost effective as opposed to buying a new cartridge each time one runs dry.

Disadvantages

Inkjet printers may have a number of disadvantages:

1. The print heads may clog when ink dries up in them during a prolonged period of disuse
2. The ink is often very expensive (for a typical OEM cartridge priced at £15, containing 5 ml of ink, the ink effectively costs $3000 per liter)
3. Many "intelligent" ink cartridges contain a microchip that communicates the estimated ink level to the printer; this may cause the printer to display an error message, or incorrectly inform the user that the ink cartridge is empty. In some cases, these messages can be ignored, but many inkjet printers will refuse to print with a cartridge that declares itself empty, in order to prevent consumers from refilling cartridges.
4. The color gamut of inkjet printers is limited
5. The capacity of ink cartridges is limited; a typical black ink cartridge will print 100-300 pages of text, while a toner cartridge for a laser printer may last 2,500-10,000 pages.
6. The lifetime of inkjet prints is limited; they may eventually fade and the color balance may change
7. Some inkjets use multiple-ink cartridges which combine C, M and Y ink tanks; these must be replaced as a unit when only one color runs outs.
8. For best results, inkjet printers require more expensive paper than laser printers.
9. Double-sided printing is not usually practical with inkjet printers.
10. Because the ink used in most inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of water, which can cause severe "blurring" or "running." Similarly, water-based highlighter markers can blur inkjet-printed documents.

These disadvantages have been addressed in a variety of ways:

1. Clogging appears to be an inherent limitation of the design of inkjet print heads, because the ink must travel through very fine channels in order to precisely control the drop size.
2. Third-party ink suppliers sell ink cartridges at significantly reduced costs (often 10%-30% of OEM cartridge prices) and also sell kits to refill cartridges, and bulk ink, at even lower prices.
3. Many vendors' "intelligent" ink cartridges have been reverse-engineered. It is now possible to buy inexpensive devices to reliably reset such cartridges to report themselves as full, so that they may be refilled many times.
4. Color gamut is also addressed by some third-party ink suppliers. The gamut for CMYK inkjet printers is broadly similar to that of CMYK offset litho printing, and it is not possible to improve much on the printer manufacturers' ink set. Printers using six or more ink colors can give a substantially improved color gamut, approximating the Adobe RGB color space. Six-color printers are based on the CcMmYK color model. When more than six colors are used, the additional inks may include a light black, a second full black (allowing the ink to be chosen to match the type of paper, and addressing metamerism issues), and additional colors such as red, green and blue.
5. Ink capacity is inherently limited because the ink cartridges must fit inside the printer, usually directly attached to a moving print head. (but see continous ink systems, below)
6. Print lifetime is highly dependent on the quality and formulation of the ink, as well as the paper chosen. The earliest inkjet printers, intended for home and small office applications, used dye-based inks. Even the best dye-based inks are not as durable as pigment-based inks, which are now available for many inkjet printers.

Third-party ink and cartridges

The high cost of OEM ink cartridges, and the intentional obstacles to refilling them (disadvantages 2 and 3 above) have been addressed by third-party ink suppliers.

Many printer manufacturers discourage customers from using third-party inks, claiming that they may damage the print heads, leak, and produce inferior-quality output. However, some OEM cartridges can be refilled, and the "intelligent" cartridge microchips may be circumvented as explained above. Some cartridges lose ink capacity upon refilling due to air growth in the internal foam.

The quality of third-party ink and cartridges is widely debated. Consumer Reports has noted that third-party cartridges may contain less ink than OEM cartridges, and thus yield no cost savings. Wilhelm Imaging Research claims that with third-party inks the lifetime of prints may be considerably reduced. However, an April 2007 review showed that, in a double-blind test, reviewers generally preferred the output produced using third-party ink over OEM ink. They plan next to compare the longevity of prints using OEM and third-party ink. OEM inks generally have undergone significant system reliability testing with the cartridge and print-head materials, whereas R&D efforts on 3rd party inks material compatibility is likely to be significantly less.

Continuous ink system

Many of the disadvantages of inkjet printers (items 2-7 above) are addressed by third-party continuous ink systems (not to be confused with continuous ink jet printers, described above). These conversion kits connect the ink cartridges to reservoirs outside the printer: they can therefore hold much more ink, and may be replaced or filled individually. Continuous ink systems typically hold pigment inks, and some have been produced for printers that were only designed to use dye-based inks. The suppliers often provide color profiles for their ink systems when used with specific papers.

Overall expense

Even with many available options for cost-reduction, inkjet printing remains expensive. Unless photo-realistic reproduction is necessary, value-minded consumers often prefer laser printers for medium- to high-volume printing applications.

Underlying business model

A common business model for inkjet printers involves selling the actual printer at or below production cost, while dramatically marking up the price of the (proprietary) ink cartridges.

Alternatives for consumers are cheaper copies of cartridges, produced by other companies, and refilling cartridges, for which refill kits are available. Owing to the large differences in pricing due to OEM markups, there are many companies specializing in these alternative ink cartridges. Most printer manufacturers discourage refilling disposable cartridges. Aside from the obvious economic reasons, the heating elements in thermal cartridges often burn out when the ink supply is depleted, permanently damaging the print head.

Some inkjet printers enforce this product tying using microchips in the cartridges to prevent the use of third-party or refilled ink cartridges. In Lexmark Int'l v. Static Control Components, the United States Court of Appeals for the Sixth Circuit ruled that circumvention of this technique does not violate the Digital Millennium Copyright Act. In fact, the European Commission ruled this practice anticompetitive: it will disappear in newer models sold in the European Union.

USB cable markup

Another common business model for selling newer inkjet printers involves selling them at very low prices—sometimes below cost—but without the USB 2.0 cable necessary to connect the printer to a computer. Vendors recover the costs by charging very high prices for separate USB cables. This allows retailers to advertise extremely low prices for inkjet printers.

Large electronics retailers that sell inkjet printers, such as Best Buy and Circuit City, sell a variety of USB cables, but all have very high markup. If a customer buys both a cheap inkjet printer and a USB cable, the high profit margin on the cable will allow the retailer recover the losses from selling the printer below cost. However, similar USB cables can be purchased for much lower prices from retailers that do not also sell inkjet printers. Compare these prices on equivalent products:

Professional inkjet printers

Besides the well known small inkjet printers for home and office, there is a market for professional inkjet printers; some being for page-width format printing, and most being for wide format printing. "Page-width format" means that the print width ranges from about 8.5" to 37" (about 20 cm to 100 cm). "Wide format" means that these are printers ranging in print width from 24" up to 15' (about 75 cm to 5 m). The application of the page-width printers is for printing high-volume business communications that have a lesser need for flashy layout and color. Particularly with the addition of variable data technologies, the page-width printers are important in billing, tagging, and individualized catalogs and newspapers. The application of most of the wide format printers is for printing advertising graphics; a minor application is printing of designs by architects or engineers.

Another specialty application for inkjets is producing prepress color proofs for printing jobs created in the digital realm. Such printers are designed to give accurate color rendition of how the final image will look (a "proof") when the job is finally produced on a large volume press such as a four offset lithography press. A well-known example of an inkjet designed for proof work is an Iris printer, and outputs from them are commonly "iris proofs" or just "irises".

In terms of units, the major supplier is Hewlett-Packard, which supply over 90 percent of the market for printers for printing technical drawings. The major products in their DesignJet series are the DesignJet 500/800, the DesignJet 1050 and the DesignJet 4000/4500. Besides this they also have the HP Designjet 5500, a six-color printer that is used especially for printing graphics. The constantly growing niche of page-format printing has been filled by Kodak, with the Kodak Versamark(tm) VJ1000, VT3000, and VX5000 printing systems. Scitex also made a short-lived entry into high-speed, variable-data, inkjet printing, but sold its profitable assets associated with the technology to Kodak in 2005.

A few other suppliers of low volume wide format printers are Epson, Kodak and Canon. Epson has a group of 3 Japanese companies around it that all use predominantly heads and inks coming from Epson: Mimaki, Roland and Mutoh.

More professional high-volume inkjet printers are made by a range of companies. These printers can range in price from 25,000€ to as high as 1.5 million €. Carriage widths on these units can range from 54" to 192" (about 1.4 to 5 m) and ink technologies tend toward solvent, eco-solvent and UV-curing as opposed to water-based (aqueous) ink sets. Major applications where these printers are used are for outdoor settings for billboards, truck sides and truck curtains, building graphics and banners, while indoor displays include point-of-sales displays, backlit displays, exhibition graphics and museum graphics.

The major suppliers for professional wide- and grand-format printers include: LexJet, Inca, Durst, Océ, NUR, Lüscher, VUTEk, Zünd, Scitex Vision, Gandinnovations, Mutoh, Mimaki, Roland DGA, Seiko I Infotech, Leggett and Platt, Agfa, Raster Printers and MacDermid ColorSpan.

Inkjet Printing of Functional Materials

Three-dimensional printing constructs a prototype by printing cross-sections on top of one another.

High-end inkjet printers can be used to produce fine-art prints called giclées.

U.S. Patent 6,319,530 teaches a "Method of photocopying an image onto an edible web for decorating iced baked goods". In plain English, this invention enables one to inkjet print a food-grade color photograph on a birthday cake's surface. Many bakeries now carry Edible Image brand printers.

Inkjet printers and similar technologies are to be used in the production of many microscopic items.