Thermal ink jet

Fig. 19. Ink-jet system (a) piezoelectric ink-jet firing chamber and (b) bubble formation ia thermal ink-jet technology.

The principal physical properties influencing ink performance ate surface tension and viscosity. High surface tension is desired for good droplet formation and capillary refill in dtop-on-demand ink jet. Low viscosity is desired because less energy is required to pump and eject ink. Conductivity is also an important parameter. Continuous ink-jet inks must have some conductivity to allow for charging. Low conductivity is generally preferred for impulse, particularly thermal ink jet, because excess ions can cause corrosion of the printhead. 

Office. Various segments of the office market have the largest population of computers, and thus the greatest demand for computer printers. In 1994, however, more computers were purchased for home use than for the office. The fastest developing computer printer technology is thermal ink jet, whether measured by rates of performance increase, price decrease, or purchase. 

As seen in Figure 5.1, there are two main types of drop-on-demand technologies. The thermal ink jet or bubble jet has a heating element that causes a vapor bubble to eject an ink droplet from the nozzle. The piezo ink jet uses a piezoelectric transducer for ejecting ink droplets. The microjet technology is a further... 

Black Dyes. Water-soluble black ink jet dyes are selected from disazo, polyazo, metal complex, and sulfur dyes [7], For ink-jet systems using the piezo technology, C.I. Direct Black 19, 35255 [6428-31-5] and DirectBlack 154,303865 [54804-85-2 are used. Food Black 2, 27755 [.2118-39-0] was selected for thermal ink-jet printers due to its thermal stability, but this dye exhibits a poor waterfastness. Replacing the sulfo groups by carboxyl groups gave C.I. DirectBlack 195 (1), which has been introduced in commercial printers and shows much improved waterfastness due to pH-dependant differential solubility [3],... 

Meyer J, Bazilevsky AV, Rozhkov AN. (1997) Effect of polymeric additives on thermal ink jets. Proceeding of the International Conference on Digital Printing Technologies 675-680. 

Tsang JW, Moffatt JR. (1998) Preparation of microemulsion and Micellar color inks from modified water-soluble color chromaphores for thermal ink-jet printing, US5749952. 

In many commercially available demand-mode ink-jet systems today, a thin-film resistor is substituted for the piezoelectric transducer. When high current is passed through this resistor, the ink in contact with it is vaporized, forming a bubble over the resistor [17]. This vapor bubble serves the same function as the piezoelectric transducer. This t5rpe of printer is referred to as a thermal ink-jet printer. 

Thermal Ink-Jet or Bubble Jet Drop Generators Principle of Operation... 

R. R. Allen, J. D. Meyer, and W. R. Knight Thermodynamics and hydrodynamics of thermal ink jets, Hewlett-Packard Journal, 36, 21-27 (1985). 

W. Runge Nucleation in thermal ink-jet printers, IS T s Eighth International Congress on Advances in Non-Impacting Technologies, Springfield, 299-302 (1992). 

P. Chen, W. Chen and S. H. Chang Bubble growth and ink ejection process of a thermal ink jet print head. International Journal of Mechanical Sciences, 39 (6), 683-695 (1997). 

J.P. Baker, D.T. La, and R.A. Coverstone, Thermal ink jet pen body construction having improved ink storage and feed capability, US Patent 4 771295, assigned to Hewlett-Packard Company (Palo Alto, CA), September 13,1988. 

H. Liu and P. Bruinsma, Thermal ink-jet including polymer encapsulated pigment, US Patent 7997713, assigned to Hewlett-Packard Development Company, L.P. (Houston, TX), August 16,2011. 

Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets. The major components of this type of drop-on-de-mand system are an ink-filled channel having a nozzle on one end and a heat generating resistor near the nozzle. 

FIGURE 10 A thermal ink jet print head, showing the evolution of bubble formed from the ink heated by the resistive heating element. [From Le, H. P. (1998). J. Imaging Sci. Technol. 42,49-62 by permission of the copyright holder, the Society for Imaging Science and Technology.]... 

Devices employing the vaporization of superheated fluid are known concurrently as thermal ink jet or bubble jet printers, the choice of name depending on the manufacturer. Since drop on demand ink jets rely on capillary refiU, their operational frequencies are much lower than for continuous ink jet devices. This stresses the importance of the compactness of the actuating system so as to achieve reasonable printing speeds via multiple nozzle printheads. The nozzles must also be precisely registered with respect to each other if systematic print artifacts are to be avoided. 

FIGURE 19.68 Drop ejection sequence for thermal ink jet. Nominal time frames and values for various parameters are given to indicate the scale of the three processes of nucleation, bubble growth, and jet formation followed by drop ejection and refill. 

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