A method of multi-tone printing employs a drop-on-demand printing apparatus for depositing ink droplets on printing element areas of a substrate which is movable relatively to the apparatus. The droplets are deposited from an array of channels on the substrate which is movable relatively to the channels. The channels length and nozzle location and dimensions afford each channel with a high longitudinal resonant frequency and energy pulses are supplied to selected channels at or near the resonant frequency of the channels to deposit from each selected channel in the corresponding printing element area of the substrate a number of drops equal to the number of pulses applied thereto, the number of pulses applied being dependent on the tone of printing required. Single channel and color versions of the invention are also disclosed.

A recording transparency and method of preparing the same from water solution are disclosed. The transparency is receptive to a wide variety of inks and other indicia, exhibits rapid ink drying times, excellent dot size and shape retention, and excellent water resistance and stability. The transparency comprises a transparent substrate coated from an aqueous solution of a polymeric sorbent selected from synthetic transparent cellulosic polymers, especially one or a mixture of hydroxyethyl cellulose polymers, and a surfactant composition comprising nonionic detergent, anionic detergent and complexing agent.

A method of manufacturing one or more nozzles for an ink jet printhead initially comprises bonding a nozzle plate to the ink ejection end of the printhead. A mask is then secured in contact with the nozzle plate, the mask having a plurality of apertures each defining a respective nozzle exit. Laser radiation applied to the mask exposes the areas defined by the apertures to ablate the plate material between the nozzle exits on the external surface of the plate and corresponding nozzle inlets on the opposite surface of the plate. The assembly comprising the printhead, plate and mask is rocked during the exposure step to increase the area of the nozzle inlet relative to its outlet. Also, prior to the nozzle formation step, one or more ink troughs may be provided for supplying an external source of ink for each nozzle. The ink troughs, which may be formed using laser ablation techniques similar to those used in the formation of the nozzles, facilitate a continuous, positive flow of ink through the nozzles.

A method of providing the surface area of a substrate with a first zone which is solvent-wettable and a second zone which is solvent-non-wettable, and which is particularly suitable for application to the printheads and nozzle plates of drop-on-demand ink jet printers or like products where the spacing between zones of the same kind can be as little as just tens of microns, and wherein the solvent-non-wettable zone displays excellent abrasion resistance and resistance to solvents, is virtually non-wettable by a wide range of solvents and bonds well even to plastics substrates, comprises: (i) providing a surface having good solvent wettability at least over that part of the area of the substrate which is to form said first zone; (ii) providing said area with a first layer which comprises siloxic material which bonds to the substrate and which is in contact with the substrate over at least that part of the area which is to form said second zone; (iii) providing said area with an overlayer comprising organic fluorocompound which bonds to said first layer and provides a surface of poor solvent wettability, said overlayer being in contact with said first layer over at least that part of the area which is to form said second zone; and (iv) by etching or washing, removing overlying material from said surface having good solvent wettability over that part of the area which is to form said first zone whereby to expose said surface.

An ink jet ink composition and method of printing on plain paper are provided wherein the composition comprises a mixture of a nonaqueous solvent (e.g. selected glycol ethers), a resin (e.g. an ethylene-vinyl acetate copolymer) which is substantially completely soluble in the solvent at elevated operation temperatures but substantially insoluble in the solvent at room temperature and a dyestuff which is soluble in the resin at room temperature and above but substantially insoluble in the solvent at room temperature. The ink composition is fluid at room temperature, and has very low viscosity at elevated operating temperatures.