Surface cleaning and modification of glass, polymer, metal, ceramic, rubber by UV light.
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Surface cleaning and modification by UV light

Surfaces can be cleaned or modified by short wavelength, ultra violett UV light, so that following adhesion, deposition or sticking processes work more effective. It is possible to treat glass, polymer, metal, ceramic, rubber or other materials. For this application mainly high output low pressure mercury lamps are used. Such lamps are installed in many types of illumination equipment from SenLights.
One important application field is the surface cleaning of glasses and panels during LCD-Manufacturing.

The Technology

The sun emits UV light and the ozone in our atmosphere is generated by a chemical reaction triggered by this UV light. The same reaction can be used in UV illumination equipment for surface processing.

Sunlight ozone

The oxidation reaction to decompose organic compounds is proceeded first by cutting molecular bonding to draw out hydrogen atoms and then adding oxygen atoms. In this process the high energy UV radiation and radical oxygen atoms play an important role. The low pressure mercury lamp itself generates ozone and decomposes it to produce activated oxygen. It is an ideal light source for surface processing.

ozone generation by UV light

Cleaning Effects

There is a difference in mechanism between cleaning and modifying process, but both have common good effects for the purpose of enhancing the bonding force and adhesive properties. UV light or also plasma etching have a markedly higher cleaning capability than a wet type cleaning system. The contaminants that you can remove are organic compounds, mainly fat substances. However thick layers cannot be removed using UV light. Therefore, the most effective cleaning can be achieved by removing large amounts of contaminants first with a conventional wet cleaning system and then finish with the photo cleaning process. Rinse with ultra-pure water can proceed the light cleaning step in order to wash off fine dust that can be created under certain circumstances by UV cleaning. This is the latest cleaning technology.

Modification effects

Unlike the plasma processing, the photo modification has the advantage of excellent operability as it allows processing under normal atmosphere. In addition, you can irradiate UV uniformly to even geometrically complex objects by means of arranging lamp shapes or carrier units, so that it is suitable for molded products. It is remarkably effective to engineer plastics allowing a low temperature processing. However the effect depends also on the selected material and adhesive. Under clean conditions the modifying effect last for weeks, but if pollution resumes, the cleaning effect gets lost within shorter time.

Adhesive effects

After exposure to UV light, the surface of the substrate has been cleaned or modified and the bonding force of adhesives will rise. Also the wettability of the surface changes accordingly. In order to measure the quantitative effect of this surface improvement several methods are used:

contact angle Contact angle of a water drop. A method to measure the hydrophilic nature of a surface is to measure the contact angle of a water drop on the surface. Enhancement of wetting nature makes the surface energy larger and the contact angle of the water drop on the surface becomes smaller accordingly. This method is very accurate and can be automated.

wet surface Wettability reagent. A cheaper method is the usage of a wettability agent. You watch the extension of special liquid reagent on the test surface and compare it with the extension of reagent on a reference test substrate with a swab.The index is adjusted to the surface energy value. The results depends on the experience of the test person.

cross cut coating Usage of cross-cut coatings. An acrylic lacquer is deposited on a test substrate. Checkered kerfs are made on the coatings. Then a cellophane foil is attached to the surface and removed. The not exfoliated squares are counted.

Applications

The production of highly integrated state of the art products today requires a new technology applicable to its hyperfine processing. A short wavelength UV has an excellent modification or cleaning capability for solid surfaces. The photo surface processing using UV and ozone is nowadays an indispensable new technology to enhance the product yield of opto-electric products as well as semiconductor and liquid crystal display elements. Furthermore, the technology is contributing to the production of general industrial products such as plastic aquarium sealing as it is capable to improve the working environment and to promote mass production.
The method can be used as dry processing in normal atmosphere, shows excellent performance, has multi purpose and diversified applications, low damage rates and low running costs.

Adhesive force enhancement. This surface improvement is used for various materials like plastics, metals and inorganic compounds. It can be used for many applications  e.g before like aquarium tank sealing, sticking or mounting plastic parts or rubbers, before attachment of aluminium foils in micro condensers, mounting of magnetic heads, semiconductor lead frames, etc.

Adhesive property enhancement. Optimum fixing of HD lubricants, lens protecting films, liquid crystal back light diffusion panel, etc.

Coating property enhancement. This effect is used for mud guards, fender frames and air bags in cars, propulsion coils for super conductive linear motor cars, outdoor structures for power facilities, etc.

Cleaning. Cleaning of glasses and glass ceramics is an important application. It is used in LCD manufacturing, Plasma TV production, reticle plate cleaning, quartz oszillator manufaturing, cleaning of optical parts like lenses, prisms and mirrors, piezoelectric buzzers, ceramic LSI substrates and many more. Metal celaning is performed during the production of termnal tabs of flat TVs, IC wire bonding, micro motor shaft cleaning, laser printer mirror cleaning, semiconductor resin molding die cleaning, etc.

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Crystec Technology Trading GmbH will be pleased to further discuss details with you.
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