Liquid crystal cells – elements and systems – Liquid crystal system – Liquid crystal writing tablet
Reexamination Certificate
1999-01-19
2003-01-07
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Liquid crystal writing tablet
C349S130000, C106S002000
Reexamination Certificate
active
06504583
ABSTRACT:
FIELD OF INVENTION
This invention relates to scratch resistant, anti-microbial surfaces, and more particularly to an anti-microbial, scratch resistant computer touch panel.
BACKGROUND OF INVENTION
Surface scratches affect product appearance and function in detrimental ways. This is especially true in the optics and display industry where the display surface is coated with a layer or layers intended to provide a specific function such as a filter or dielectric coating. In particular, computer touch screen panels are especially vulnerable. Touch panels have become more and more popular as input devices for computers. A touch is sensed by a touch panel when a finger or a stylus comes into contact with the outermost surface of the touch panel. The contact is translated into x and y coordinates of the finger or stylus on the panel. Some touch panels are transparent overlays placed over a display. Other touch panels are non-transparent devices typically used to control cursor movement for example on a portable computer, or as pen input devices for applications including writing or signature input to a computer. Since the data entry is based on contact, touch panels are inherently susceptible to scratches and to microbial contamination.
A scratch is made by a plastic deformation on a surface. The force that produces a scratch can be divided into two components: a component that is perpendicular to the surface and another component parallel to the surface. The component perpendicular to the surface produces a plastic deformation on the surface and the component parallel to the surface extends the damage by plowing material out of the way. The damage due to the perpendicular component is dependent upon the friction of the contact surfaces. The higher the friction coefficient, the larger the perpendicular component and thus the more damage which results.
Two of the most widely employed approaches for providing scratch resistance to a surface are the introduction of lubricants and solid/hard protective coatings applied to the outer most layer of the touch panel. The introduction of a lubricant reduces the energy dissipation along the surface attributable to the vertical component which would otherwise cause damage to the surface. Solid/hard coatings are intended to avoid the initial plastic deformation in the first place. Neither lubricants nor solid/hard protective coatings, however, provide sufficient scratch resistance to touch panels.
Non-homeotropic organosilanes have long been used as coupling agents which provide a stable bond between dissimilar surfaces. It is an important characteristic of coupling agents that they form a chemical bond to surface materials. Most of the anti-scratch surface treatments involve providing hard coatings although some use organosilanes to improve lubricity of glass surfaces.
Several other families of organosilanes have been tested. These include alkylsiloxanes, alkylaminosiloxanes, perfluoroalkylsiloxanes. None of these organosilanes, however, have been found to improve scratch resistance to the extent required for touch panels.
Touch panels can be found in applications from ATM's to casinos to point of sale terminals and portable computers. These environments are extremely harsh and susceptible to scratching from coins, bottles and glasses as well as being exposed to harsh outdoor elements where they are subject to airborne debris and even vandalism. Depending on the severity of the scratch, the function of the display may be greatly affected.
Moreover, these touch panels are subject to microbial colonization and damage. Forgetting for the moment the affects of scratches on the touch panel, these panels provide a suitable home for bacteria, fungi, algae, and other one celled organisms which thrive and propagate based on the availability of appropriate amounts of moisture, temperature, nutrients, and receptive surfaces. As these organisms metabolize, they produce chemical by-products. These chemicals are known to etch the touch of sensitive panels, producing odors. Further, the biomass of such colonies fog or obscure the optical properties of the panels, irreparably damaging the touch panel. Cleaning and disinfection with chemicals which leach and poison the organisms and environmental controls which minimize moisture have, to date, been the response to this problem. Although cleaning and disinfection is common practice, it is done with the knowledge of the risks of sub-lethal dose levels, ineffective doses, resistant organisms, environmental exposure, human exposure, and the limited duration of such cleaners after the initial treatment. Indeed, scratches which do not destroy the panel itself may provide a safe haven for the bacteria despite attempts to wipe the panel to remove such microorganisms.
Moreover, typical touch screen panels, e.g., capacitive touch screen panels, require direct contact with the skin of the user's finger. Thus, these panels are directly contacted by many different users. As these organisms thrive, the variety of chemicals that these organisms produce are also known affect the human user. Thus, these microorganisms, as well as their metabolic products can pose serious health risks to users ranging from minor skin irritation to more serious toxic response and disease. With the increased popularity of such touch panels, the public is becoming increasingly aware of and concerned with the presence of microorganisms on these panels and the potential consequences resulting from contact with such contaminated surfaces.
The foregoing concerns demonstrate growing detrimental affects of microorganisms to computer touch panels and a need for controlling microorganisms on such touch sensitive panels. The use of environmental controls has limited effectiveness on microorganism prevention in part because of the wide variety of environmental conditions under which various microorganisms can survive and in part because of the costs and difficulty of actually keeping moisture levels sufficiently low enough to minimize microbial growth.
SUMMARY OF INVENTION
It is therefore an object of this invention to provide a touch panel which is resistant to scratches and micro-organisms.
It is a further object of this invention to provide such an anti-microbial, scratch resistant touch panel which is durable and long lasting.
It is a further object of this invention to provide such an anti-microbial, scratch resistant touch panel which is simpler to produce and more durable than current methods.
It is a further object of this invention to provide an anti-microbial, scratch resistant coating which can be applied to most any touch panel surface.
The invention results from the realization that a truly durable and long lasting scratch resistant and anti-microbial touch panel can be obtained by applying a homeotropic organosilane to the outer most surface of the touch panel that chemically bonds to the surface and reduces energy dissipation of an object as the object is dragged transverse to the surface and inhibits the survivability of microorganisms which contact the touch panel.
This invention features an anti-microbial touch panel including a substrate, an active portion on one surface of the substrate and a homeotropic organosilane layer deposited on the active portion for reducing the survivability of microorganisms contacting the touch panel.
In a preferred embodiment the active portion may include a conductive layer. The active portion may include a protective layer. The protective layer may be an organosiloxane. The active portion may include a deformable conductive layer disposed on the conductive layer. The organosilane may be a liquid crystal silane. The substrate may be transparent. The transparent substrate may be glass and the touch panel may be a computer touch screen. The first conductive layer may be metal oxide. There may be a second conductive layer disposed on the substrate on a surface opposite the active portion. The first and second conductive layers may be tin oxide.
The invention also features an anti-microbial touch panel
Bottari Frank J.
Geaghan Bernard O.
Li Chia-Yen
3M Innovative Properties Company
Nguyen Dung
Pechman Robert J.
Sikes William L.
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