Semiconductor device manufacturing: process – Radiation or energy treatment modifying properties of...
Reexamination Certificate
1999-08-23
2001-07-10
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Radiation or energy treatment modifying properties of...
C422S022000, C422S024000, C426S236000, C426S237000
Reexamination Certificate
active
06258736
ABSTRACT:
The invention relates to a device having at least one surface layer with a disinfectable and/or oxidizing outer side. The invention furthermore relates to a method for disinfection and/or oxidation on the outer side of a surface layer.
Hygiene plays an important role in many areas of modern life. These include in particular the field of health. For example, in hospitals or doctor's surgeries, certain areas or pieces of equipment, such as operating tables, have to be kept as free from germs as possible, or even completely germ-free. It is also necessary to pay considerable attention to hygiene when handling foodstuffs which are intended for human consumption. This applies, for example, to sale counters for foodstuffs, work surfaces in companies which process foodstuffs, such as butcher's shops or restaurants, but also dairies, including their beverage lines. Research, diagnostics and administration in the fields of microbiology and biotechnology should also be mentioned, in addition to a considerable number of further applications.
In all these fields, it is desirable or even necessary for certain surfaces to be kept free from germs as far as possible or even completely. The same applies to internal surfaces of containers, pipelines and valves.
To do this, it is known for open surfaces to be kept clean by mechanical cleaning with bactericidal agents. If appropriate, equipment can be sterilized using elevated temperatures. In certain cases, irradiation with UV light is also employed. However, this is not always fully effective and, in addition, often causes considerable problems with regard to the danger or strain imposed on people, and therefore large-scale UV disinfection operations are only carried out at times when no work is being done, e.g. overnight.
The drawback of the known cleaning methods is that germs begin to build up again immediately after the cleaning operation has taken place. The bactericidal action is dependent on the care taken by the cleaning staff and on the cleaning intervals. A highly sterilized state can therefore only be maintained with great difficulty and a high level of outlay. A further difficulty is that some bacteria build up a certain resistance to the bactericidal agents, so that in fact sterilization is impossible, or not sufficiently possible, even despite strenuous efforts. Under certain circumstances, this problem will often not be noticed.
An even more difficult problem is the cleaning of internal surfaces which can only be rinsed or sterilized with the aid of steam. Rinsing constantly produces dead spaces and “cold” areas which are not affected by the cleaning work. This may result in the formation of colonies of bacteria, promoting subsequent germ formation. Moreover, operations have to be suspended for cleaning. The same also applies to external surfaces. For toxicological reasons, large-scale disinfecting measures using formaldehyde or ethylene oxide present considerable problems, since these gases penetrate into the material and are released over relatively long periods (e.g. quarantine stations). As a result, it is necessary to keep a larger stock of instruments or rooms ready, since availability is limited as a result of these times when gases are being released.
The invention is based on the object of providing a device having at least one surface layer, with an outer side which can be disinfected relatively easily and with a relatively high reliability and/or has an oxidizing action.
A further object of the invention is to provide a device which makes it possible to disinfect internal surfaces which cannot be reached by direct irradiation with UV light. Another object of the invention is to provide a method for disinfection and/or cleaning on the outer side of a surface layer.
The invention is based on a device with at least one surface layer made from a semiconductor material having an inner side, which rests on a support, and a disinfectable and/or oxidizing outer side, and with a UV radiation source.
The device is then characterized in that the support conducts light, and in that UV radiation from the UV radiation source is input directly on to the inner side of the semiconductor material via the light-conducting support.
Light guides are arrangements of optical components for guiding light onwards by means of total reflection, the reduction in the refractive index inside the light guide from the inside outwards playing a particularly significant role. For a good light guide, it is desirable for the light losses brought about by absorption, scattering and radiation to be kept as low as possible. It has now surprisingly been found that the low, hitherto undesirable outwards emission of radiation along an optical waveguide is sufficient to activate the inner side of a semiconductor which has been applied thereto and thus to bring about disinfection and/or oxidation.
It is therefore possible for the objects or work surfaces which it is desired to clean or disinfect to be provided with the light-conducting support and the surface layer made from a semiconductor material. However, it is also possible for the objects which are to be disinfected or cleaned themselves to be designed as light-conducting supports and for the surface layer made from the semiconductor material to be applied thereto.
In order to simplify the following explanation, the following text always refers to “disinfection”, even if only a reduction in the number of germs on the surface takes place. Although in many cases complete sterilization is possible, it is not always necessary or desired.
To disinfect the surface layer, the UV light source is started up so that it emits UV radiation. However, this UV radiation is directed towards the inner side or rear side, which is not visible from the outside, of the semiconductor material. It is therefore entirely possible for the surface to be covered with tools or other equipment which could lead to shadows in the event of the outer side being irradiated. The UV radiation no longer has to emerge on the outside in order to bring about the desired disinfection. Although the biological, physical and chemical processes involved have not yet been fully explained, it is assumed that the UV radiation excites the semiconductor material, i.e. photoactivates the material. Photoactivation means that the light absorption in the semiconductor, e.g. n-TiO
2
, causes electrons to be lifted from the valence band into the conduction band. The result is a redox potential which kills germs via the formation of radical species or mechanisms. Since these processes are unspecific, oxidative degradation reactions also occur in addition. Since the semiconductor is not changed, it is called a catalyst. Thus the surface which is irradiated from the inside is disinfected in a simple manner. Disinfection of this nature may even take place during normal use, so that complete or at least substantial sterilization can be maintained even during operation.
A light-conducting support is arranged between the UV light source and the inner side. This makes it possible to select the arrangement of the UV light source in relation to the surface layer more freely. In certain cases, it is not possible to arrange the light source on the rear side or inner side of the surface layer, since there is no space available there. If a light-conducting support is now used, the UV radiation can also be guided on to the inner side of the semiconductor material from other locations.
The light-conducting support may preferably be configured as a panel, for example as the table top of an operating table. In this case, the panel-like support is preferably coated on one side, but if necessary on both sides, with semiconductor material.
However, it is also possible to design the light-conducting support in the form of a tube, so that pipelines can be made available as cut-to-length stock, including the connection fittings. In the case of supports which are designed in the form of a tube, it is preferable for the inner surface of the tube to be coated with the semicondu
Foley & Lardner
Rocchegiani Renzo N.
Smith Matthew
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