Characters on computer keyboards are typically printed using one of the two different processes, namely tampographic printing and laser marking. Tampographic printing is time consuming (app. 3-5 mins.), requires skilled workers and employs difficult-to-handle chemicals. On the other hand, the laser marking process is rapid «1 min.), relatively cheap, avoids the need for chemicals and can be carried out with fewer, less skilled operatives than required fortampographic printing. Data from a keyboard production company indicated that there has been a sudden decline in the percentage (from 60% in 2001 to less than 10% in 2003) of laser marked keyboard users over recent years due to a lack of initial contrast of white characters on a dark plastic and poor durability. Under usual office conditions, characters that are used more regularly e.g. 'e' or 's', can be erased in less than 3-6 months. Further, generating a durable high contrast laser mark on dark coloured polymers has also long been an issue. The thesis initially reports on an investigation into the reasons for lack of initial contrast and subsequent discolouration of laser marked and tampo printed characters. This is followed by the development of a range of plastics compounds based on ABS and containing a series of different additives. Criteria for selecting additives that would respond appropriately to a laser are also proposed. The compounds were laser marked under a 1064nm Nd:YAG laser at different power, frequency and speed settings. Plaques of the material were manufactured and laser marked in a grid-like pattern to study both the effect of frequency and speed of marking. The mechanisms associated with the laser-material interaction during the marking process were also investigated using light microscopy and scanning electron microscopy. Microscopy was also employed toobserve the morphology of the marks left by the laser. Finally a unique test regime was designed to characterise the durability of the laser markings under conditions that attempt to simulate those experienced in practice. Results show that aluminium trihydroxide generated superior contrast and exhibited enhanced durability characteristics when compared with nine other micro-additives. Nano-additives, such as nano titanium dioxide portrayed better contrast and durability performance when compared to their micro-size additive equivalents. Analysis of the test plaque results clearly demonstrated that for a specific material compound, it is possible to optimise the laser settings to achieve the best combination of character contrast and durability. Finally, this work is believed to have made a significant contribution to the rather sparse laser markable polymers research field. It will assist in the development of a more fundamental understanding of laser/material interactions and provide a basis for future work in optimising materials formulations for successful laser marking.

In the last several years, there has been an interest in graphical user interfaces as compared with character user interfaces. The "mouse" is the device most closely associated with graphical user interfaces. Key strokes are more closely associated with character user interfaces. Given these associations, is there a preference for the keyboard or for the mouse as an input device? The determination of user preference was reduced to the determination of preference of key strokes or mouse clicks for selection of main menu items. The subjects, university students working with Microsoft Works by Microsoft Corporation, copyright 1987-1989, were learning how to use application software. While Microsoft Works was running, tracking software recorded every user key stroke and mouse click, together with data about these key strokes and mouse clicks. From the analysis of these data, common preference for the means of menu item selection was determined.