GB2387381A

GB2387381A - Repairing scratches in transparent surfaces

Info

Publication number: GB2387381A
Application number: GB0207256A
Authority: GB
Inventors: David Charles Croxson
Original assignee: CROXSON DAVID; RITEC INTERNAT Ltd
Current assignee: CROXSON DAVID; RITEC INTERNAT Ltd
Priority date: 2002-03-27
Filing date: 2002-03-27
Publication date: 2003-10-15
Anticipated expiration: 2022-03-27
Also published as: GB0207256D0; GB2387381B

Abstract

A method of repairing a scratch on a surface of a substrate eg glass comprises the steps of: applying an anaerobically curable resin 3 over a scratched surface 1; locating a release surface 5 onto the resin to sandwich the resin between the release surface and the scratched surface; curing the resin eg by UV lights 7; and removing the release surface from the resin to leave the cured resin masking the scratched surface.

Description

"A METHOD OF MASKING SCRATCHES IN TRANSPARENT

SURFACES"

This invention relates to a method of masking scratches in transparent surfaces, particularly in panes of glass.

Glass has a surface that is readily prone to marking. Where a high degree of clarity or surface precision is required marks caused by impact or abrasion from hard implements are typically polished from the surface. This process is well-

established but is labour intensive and slow, particularly where scratches are deep and frequent. In some cases, the polishing can bevel the surface and can affect the optical properties and performance of certain surfaces particularly coated pre-treated glass.

Glass is increasingly prone to deliberate attack from vandalism that is known as "Dutch graffiti" or "Scratchfitti". Vandalism often occurs on public vehicles including trains and buses and can affect both internal and external surfaces.

Where the graffiti is offensive or unsightly, the glass panel is covered and, at an early stage, inevitably withdrawn from service. If the damaged glass remains on view, further graffiti attacks are more likely. The glass panel must eventually be withdrawn from service when the graffiti obstructs vision affecting use, safety or ambience to a significant detrimental level.

On being withdrawn, typically the glass is either replaced (usually a minimum 24 hour process requiring removal of surrounding items, frames, fittings and resealing of frames etc.) or scratches are laboriously polished out by grinding on site - again a lengthy process. In all cases, on being repaired or replaced and returning to service the glass can suffer further and immediate vandalism.

One method of masking scratches involves pre-treating a scratch by lightly sanding the glass scratch and surface to provide a surface roughness and break away any impacted or loose glass particles. The entire surface is then de-

greased and all surface contaminants removed to provide a chemically clean glass surface susceptible to physical bonding by a polyurethane coating. A low viscosity polyurethane resin is used to in-fill deep scratches by hand.

Subsequently, the whole affected surface is flow-coated with the resin which flows freely across the glass and any pre-treated deep scratches to form a uniform glazed surface. The resin produces a largely ripple and run-free surface because of its low viscosity with an optical clarity and colour that is not significantly different from the underlying glass. A suitable low viscosity polyurethane resin is Ritecoat Scratchmask manufactured by Ritec International Ltd. Whilst this process has proved popular in trials, it has been found that the bond between the glass and the resin is susceptible to de-lamination from moisture ingress. Further, once a small area of the resin has been affected by de-

lamination, further de-lamination swiftly follows and the affected area becomes more susceptible to peeling and picking, thereby providing an unsightly finish.

Another disadvantage is that the curing time for a polyurethane resin is a function of ambient temperature, humidity and air flow and can take several hours. As a consequence, the uncured material itself must be protected whilst curing from moisture and the elements. Whilst curing the resin is sticky to the

touch and any airborne particles, debris, insects or the like, readily adhere to the partly cured resin spoiling the glazed finish.

It is an object of the present invention to seek to provide a method of masking scratches which does not suffer from the aforementioned problems.

Accordingly, one aspect of the present invention provides a method of masking a scratch on a surface of a substrate comprising the steps of: applying an anaerobically curable resin over a scratched surface; locating a release surface onto the resin to sandwich the resin between the release surface and the scratched surface; curing the resin sandwiched between the release surface and the scratched surface; and removing the release surface from the resin to leave the cured resin masking the scratched surface.

Preferably, the step of locating the release surface comprises pressing the release surface against the scratched surface.

Conveniently, the step of expelling air from between the release surface and the scratched surface.

Advantageously, the step of expelling air comprises squeegeeing the release surface against the scratched surface.

Preferably, the release surface is a surface of a film, sheet or block.

Conveniently, the resin is cured by or polymerization is catalysed by W light.

Advantageously, W light is applied through the transparent substrate to cure the resin.

1'' Preferably, the resin sandwiched between the scratched surface and the release surface infills scratches in the scratched surface.

Conveniently, the release surface is held against the scratched surface, sandwiching the resin, by suction.

Advantageously, the resin sandwiched between the scratched surface and the release surface infills scratches in the scratched surface.

Preferably, the cured resin has optical characteristics similar to the transparent substrate. In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, in which: Figure 1 is a plan view of a scratched transparent surface; Figure 2 shows the scratched surface of Figure 1, with a resin applied according to one embodiment of the present invention; Figure 3 shows a film overlaid on the scratched surface; Figure 4 shows the resin sandwiched between the plastics film and the glass surface, excess resin being squeezed out from between the two surfaces; and Figure 5 shows the resultant masked scratch with the film removed; and

' - - Figure 6 is a schematic cross-section through the scratched surface, resin and film of Figure 4.

Referring to Figure 1, a surface 1 of a pane of glass has been graffitied by scratching the letter "A" on the glass surface. The unsightly scratch 2 is to be masked or hidden by a process embodying the present invention to make it difficult, if not impossible, to detect the underlying graffiti 2 scratched into the glass surface 1.

Firstly, the surface to be treated is prepared by light abrasive sanding to remove any loose glass particles or surface contaminants and break away any impacted glass particles. The glass surface is then de-greased thereby providing a chemically clean glass surface. Techniques and materials for abrasive surface preparation and chemical cleaning of glass surfaces are well known and preferred materials comprise either Triple Zero steel wool or 600-800 grade wet or dry abrasive paper for surface preparation; and Ritec Pre-Cleaner, Ritec SR5, Ritec SR10 and Rites SR20 Stain Removers manufactured by Ritec International Ltd for de-greasing and chemically cleaning the exposed glass surface. With the glass surface in situ, usually in a vertical orientation, an anaerobic curing W catalysed low viscosity flowable resin 3 is applied to the prepared glass surface 1 as shown in Figure 2. The resin 3 is spread uniformly across the glass surface 1 using a wide flexible spatula with particular attention being paid to in-filling any deep scratches 2. Preferably, the anaerobic W curing resin has, when cured, optical characteristics which are substantially identical to the glass which is being treated. An example of an appropriate resin 3 material is Acrylic 665 resin manufactured by Bohle AG although other resins are equally suitable as described below.

The next step is the application of a resin resistant clear film or sheet 4 over the scratched surface 2 and more particularly the application of a smooth release surface 5 to the uncured resin 3 as shown in Figure 3.. The resin 3 over the scratched surface is sandwiched between the resin resistant clear film 4 and the scratched surface 1 and the film 4 pressed down on to the scratched surface 1.

In order to spread the resin 3 uniformly between the film 4 and the glass surface 1, the film is pressed onto the glass surface 1 squeezing the resin between the film and the glass surface, surplus resin being forced to the edges of the film as shown in Figure 4. The film 4 can then be squeeged by applying pressure from the centre of the film 4 towards the periphery in a sweeping action thereby removing any air from between the glass surface and the film as well as any I excess resin 3A, the excess 3A being expressed from the edges of the film 4.

The surface of the resin resistant clear film 4 presented to the scratched glass surface 1 is smooth and flat so that the surface of the thin film of resin sandwiched between the resin resistant clear film 4 and the glass surface 1 is I also smooth.

With the clear film 4 still in place, as shown in Figure 4, the resin 3 is now cured. Since the resin 3 is an anaerobic W curing resin, only resin which is not exposed to air but which is exposed to W light is cured. The next step is, therefore, to expose the resin to a W light source. Preferably, the W light source comprises a light box 6 housing one or more W light sources 7 which is sized to cover the glass and at least the resin 3 and which is usually held in place (as shown in Figure 7) or fixed into place by temporary fittings. The light box can be applied to either side of the glass pane so as to radiate the resin I either through the glass pane or through the clear film 4. It should be noted that the clear film 4 is transparent to both visible and W light. During curing, the

film 4 remains over the resin 3 protecting the resin surface. Preferably, the film 4 is held against the resin 4 by suction but may also be positively mechanically pressed against the glass surface 1. Because the film 4 is preferably held to the resin 3 by suction, this technique is extremely well suited to being performed with the glass surface in situ, usually with the glass surface in a vertical orientation. Typically, the curing process takes some 3 to 4 minutes. Once the resin has been fully cured or polymerised, the resin resistant clear film 4 is peeled away from the cured resin surface 3B leaving a smooth glazed transparent surface coating of resin 3 that is fully bonded to the glass surface 1 as shown in Figure 5. The film 4 is peeled away from the cured resin 3 in much the same way as a release paper is peeled off from an adhesive.

It is important that the resin resistant clear film is selected or formulated to ensure that it bonds neither mechanically nor chemically to the cured resin 2 and can be de-laminated therefrom easily. Examples of appropriate resin resistant clear films 4 are polypropylene or polyethylene sheet transparent to both visible and W light. These materials are readily available and can be formulated with various additives to enhance transparency and/or rigidity as required. Importantly, both these materials are resistant to bonding with the acrylic resin which is the anaerobic curing W catalysed low viscosity Plowable material. Because the resin 3 has very low viscosity and optical characteristics which are substantially identical or similar to the glass either by selection or formulation of the resin, the scratches 2 in the glass surface 1 which are filled with the resin 3 are substantially undetectable by the naked eye - the effect is similar to

e immersing a scratched glass surface in water, whereupon because of the similar refractive Indexes of the water and the glass, the scratches appear to disappear It is important that the film 4 when applied over the resin 3 creates an anaerobic environment for the resin coating and that all voids or scratches are filled by the resin. The resin is selected to cure as a hard, water impermeable surface and the polymerization thereof is triggered by W light. It is, however, possible for the curing process to take place other than by W light, but it is essential that no air is allowed to remain between the glass surface 1 and the film 4 so that only resin 3 which is not in contact with air is cured.

The thickness of the resin resistant clear film 4 can be anywhere from a thin film sheet of 200p thickness to a self-supporting sheet having a thickness in the order of 5mm. Whilst the film 4 is preferably thin to promote ready peeling or de-lamination from the resin, it is also envisaged that a solid block or more substantial structure can be used instead of a film or sheet. The essential functions of the film, sheet or block is to present a smooth flat surface to the scratched surface for sandwiching the anaerobically curable resin therebetween so that the film, sheet or blocks protects the resin surface during curing and when the film, sheet or block is removed from the cured resin, a smooth cured resin surface remains. Thus, a protective release surface is provided by the film, sheet or block.

Preferably, the film 4 can be re-used on similar sized glass panes or could also be cut down to size or pre-cut to pre-defined sizes for use on specific glass surfaces. Resin adhesives used to adhere glass to glass are particularly well suited for use in the above method and are available, for example, from Bohle AG.

-- - By using the above method, the smooth surface of the film 4 defines the surface of the cured resin thus providing a smooth cured resin surface.

If the treated surface is further scratched or graffitied, then it can be repaired in situ simply by repeating the above described process.

Although the process does not provide a truly optically clear glass pane, it does, nevertheless, provide significant advantages over existing repair techniques: the process embodying the present invention masks scratches making it difficult, if not impossible, for them to be read or viewed and makes the presence of graffiti difficult to detect. This will deter further or more frequent attacks or scratching of glass and also allows someone looking through the glass not to be distracted or have their view obscured by scratch marks, thereby improving safety, convenience and general ambience, since one is able to see clearly through what would otherwise be a damaged surface.

The process embodying the present invention can be completed quickly and in situ and does not suffer from the problem of exposing a tacky or sticky surface of partly cured resin to ambient conditions, airborne particles, insects or the like since, during the curing process, the resin resistant film 4 protects what will form the external glazed surface of the resin.

Any uncured resin material 8 extruded from the edges of the plastics film 4 can easily and quickly be wiped away from the surface 1 and will not be cured, since curing only takes place when the resin is not exposed to air - i.e. anaerobically - even if the resin is inadvertently exposed to W light in the case of a W cured resin.

-: The use of the present invention is not limited to glass panes but can also be used with other transparent or semi-transparent panes such as perspex sheeting, PVC sheeting and the like.

The viscosity of the resin can be adjusted so as to flow more readily into thin scratches although the squeegeeing or pressure action between the resin resistance film 4 and the glass surface 1 readily promote infilling of scratches 2. The viscosity of the resin 3 can be increased so that the resin 3 can be used in a vertical orientation and spread onto a vertical glass surface so that this process can readily be applied to in situ glass panels, for example in railway carriages. The hardness of the resin can also be varied so as to achieve a desired hardness which is less susceptible to scratching.

An example of an anaerobic curing W catalysed plowable resin suitable for use with the present invention is Acrylic 665 resin manufactured by Bohle AG but as previously described, other resins, particularly resin adhesives used to adhere glass to glass are particularly well suited for use in the above method.

The thickness of the resin resistant clear plastics film can be anywhere from a thin film sheet of 200p thickness to a self-supporting sheet having a thickness I in the order of Smm.

In the present specification "comprises" means "includes or consists of" and

"comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or

the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for

attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A method of masking a scratch on a surface of a substrate comprising the steps of: applying an anaerobically curable resin over a scratched surface; locating a release surface onto the resin to sandwich the resin between the release surface and the scratched surface; curing the resin sandwiched between the release surface and the scratched surface; removing the release surface from the resin to leave the cured resin masking the scratched surface.

2. A method according to Claim 1, wherein the step of locating the release

surface comprises pressing the release surface against the scratched surface.

3. A method according to Claim 1 or 2 comprising the step of expelling air from between the release surface and the scratched surface.

4. A method according to Claim 3, wherein the step of expelling air comprises squeegeeing the release surface against the scratched surface.

5. A method according to any preceding claim, wherein the release surface is a surface of a film, sheet or block.

e

6. A method according to any preceding claim, wherein the resin is cured by or polymerization is catalysed by W light.

7. A method according to Claim 6, wherein W light is applied through the transparent substrate to cure the resin.

8. A method according to any preceding claim, wherein the resin sandwiched between the scratched surface and the release surface infills scratches in the scratched surface.

9. A method according to any preceding claim, wherein the release surface is held against the scratched surface, sandwiching the resin, by suction.

10. A method according to any preceding claim, wherein the resin sandwiched between the scratched surface and the release surface infills scratches in the scratched surface.

11. A method according to any preceding claim, wherein the cured resin has optical characteristics similar to the transparent substrate.

12. A method substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

13. Any novel feature or combination of features described herein.