Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1993-07-09
1997-09-02
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524524, 524563, 524594, 524376, 260DIG38, 106 3137, 106 3153, 106 3158, C09D 1110
Patent
active
056632177
DESCRIPTION:
BRIEF SUMMARY
This invention relates to ink compositions and more particularly to ink compositions for printing on plain paper using an ink jet printer, and a method of ink jet printing on paper. The invention is especially concerned with compositions suitable for use as inks in so-called "drop-on-demand" ink jet printers.
In ink jet printing, a fluid ink is forced under pressure, and sometimes at elevated temperature, through a very small nozzle in a printing head.
In one kind of printer, known as a "continuous" printer, ink droplets which are produced continuously are passed through a charging area where individual droplets receive an electrical charge in response to a signal and are directed towards a substrate to be printed. The droplets pass through an electrical field causing them to be deflected by an amount which is dependent on the intensity of the charge and the field. Droplets not required to form print on the substrate are directed to a by-pass gutter. Inks for use in such printers need to be conductive.
In another kind of printer, known as a "drop-on-demand" (DOD) printer, the ink droplets are expelled from the nozzle of a print head only when required during the printing process. Drop-on-demand printers can use an electrostatically accelerated ink jet or droplet sequences ejected by pressure impulse actuation. In the latter kind of DOD printer, each drop of ink is individually ejected from a nozzle by means of pressure pulses induced e.g. by use of a piezo-electric actuator acting on the ink in the channel supplying the nozzle or by generation of a vapour bubble in response to a thermal pulse. Inks for use in this kind of printer do not need to be electrically conductive and preferably are non-ionic and of very low conductivity, e.g. having a resistivity of at least 10.sup.6 ohm cm.
In ink jet printers which employ piezo-electric actuators having electrodes in direct contact with the ink it is important that the ink is free of components which would cause bubble generation or electrochemical removal of the electrodes.
EP-A-0386349 describes an ink specifically developed for use in DOD ink jet printers and comprising a solution of a dye in a solvent. However, while these inks are successful on certain coated papers they are not entirely appropriate for plain papers due to wicking of colorant along the fibres and through the paper thickness.
As the coated papers are expensive, it is now generally accepted that ink jet printer inks should be capable of producing well-defined print of good colour density on plain, i.e. uncoated, paper substrates.
Good print definition quality requires inter alia (a) rapid formation of a solid colored dot from the ink composition, (b) concentration of the ink colorants on the surface of the paper (c) control of the spread of the dot of colour formed on the surface of the paper substrate from the ink droplet, and (d) uniformity of colour and colour density over the area of the solid dot formed from the droplet. Preferably, also, the print should not deteriorate as a result of the action of water or light.
It is also important, especially when it is intended for use in a DOD ink jet printer, that the ink be stable on standing or storage; not become concentrated by loss of solvent or form aggregates in the nozzle or at the orifice of the nozzle because this could lead to clogging of the nozzle itself or of the channel supplying the nozzle; and not form deposits around the periphery of the nozzle orifice during drop ejection.
In the ink droplet, the colour-generating component, or dyestuff, is generally associated with a liquid carrier, alternatively referred to as a solvent. Thus, rapid formation of the solid dot requires either rapid solidification of the solvent or rapid removal of the solvent from the colour dot on the paper, e.g. by rapid sorption of the solvent into the paper.
One proposal for a suitable ink composition for a DOD ink jet printer has involved the use of dyestuffs which are precipitated from solution in the solvent on contacting the substrate surface as a resul
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Guarriello John J.
Michl Paul R.
XAAR Limited
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