Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-03-18
1999-12-07
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C09D 500
Patent
active
05998502&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to inks for ink jet printers and especially those which operate continuously. It will be described with reference to such printers but it will be appreciated that the inks described herein may also find uses in a far wider range of less demanding applications, such as drop on demand.
An ink jet printer projects from a printer head a stream of ink droplets to impact on the substrate to be marked as the substrate is conveyed, typically at high speed, past the head. The droplets are controlled, typically electrically, so that they are deposited in a controlled array and the substrate is thereby printed with a desired indicia. Typically such indicia are code numbers and letters, dates such as "sell by" dates and other alphanumeric data,such as mail addressing. Precision is clearly essential as well as high speed.
In addition whilst the jet will be continuously operating during a printing run, the ink must also be stable physically and chemically during periods between runs.
Ink which is not deposited on the substrate is collected automatically and recycled to a return tank. To enable the ink to be applied in this way it has to have a viscosity held to close limits. In addition in order for the ink to dry or set on the substrate it is necessary for components of the ink to evaporate off from the image on the substrate. Accordingly to maintain sufficient fluidity a make up fluid has to be added to the return tank to replace lost fluids.
Typically an ink jet ink contains a colouring agent, a liquid vehicle, and a polymer. The adhesion of the polymer to the substrate and thus the adhesion of the image may be increased by adhesion promoters, such as agents effective to cross link the polymer, to form bonds between the polymer and the substrate or to do both.
In addition, where droplet formation and control is achieved electrically, it is necessary for the ink to be electrically conductive. Conductivity may be imparted by the colouring agent when this includes a charged species. If it does not impart sufficient or any conductivity this may be provided by a conductivity controller, e.g. a species ionizable in the ink, e.g. in the liquid vehicle, such as an inorganic salt or an organic salt.
The art is constantly striving to achieve deposits of sufficient durability on an increasing range of substrates. Some have concerned themselves with printing on glass or glazed ceramics (e.g. GB 1541937 and 1524881). Others have concerned themselves with polymer substrates such as acrylonitrile butadiene styrene polymers (ABS); polyolefins, such as polyethylene; polystyrene; polyvinyl chloride (PVC), plasticized or unplasticized; polyesters; and cellulose. Metal surfaces such as aluminium and stainless steel are also important substrates as are papers.
With regard to the colouring agent this has usually been related to the liquid vehicle. The colouring agents may be soluble in organic solvents e.g. methyl ethyl ketone, or C.sub.1-5 alcohols e.g. methanol or ethanol (for example as industrial methylated spirits) or they may be soluble in alcohols mixed with water, or soluble in both alcohol and water.
Examples of colouring agents which have been advocated for use in ink jet inks are dyestuffs soluble in alcohol alone such as Basic Blue 81, Solvent Orange 7 and Solvent Blue 58. Examples which are soluble lr alcohol and water are Basic Violet 10, Acid Red 52, Acid Black 1, Acid Blue 59, Acid Red 73 and Acid Blue 9.
Triarylmethane dyes have also been advocated. Examples of these are Crystal Violet Fn (available from BASF) and Victoria Blue B base (available from Hilton Davis).
The colouring agents are employed in amounts appropriate to give the desired colour intensity in the deposit. Typically the ink contains 0.1 to 10% of the colouring agent e.g. 3 to 7% preferably 4 to 6%.
The liquid vehicle has to be such as to impart the desired fluidity (or low viscosity) to the ink but must evaporate at a high enough rate to leave the deposited image resistant to smudging soon after it is deposited. It must also
REFERENCES:
patent: 3253940 (1966-05-01), Floyd
patent: 3597376 (1971-08-01), Tashiro
Bowles Jenny Marie
Burr Raymond David
Hazlewood Shaun Christopher
Hudd Alan Lionel
Reza Naser
Cain Edward J.
Conte Robert FaI
Domino UK Limited
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