Refurbishment of LCD screens

Abstract

The screen 10 for a liquid crystal display is refurbished by applying a transparent laminate using a wet lamination technique. The laminate 14 comprises a viny film 16 and acrylic adhesive. The film i

Description

FIELD OF THE INVENTION The present invention relates to the refurbishment of LCD screens, such as those found on laptops. BACKGROUND ART The handling of so-called 'e-waste', i.e. used electronic devices, is an increasing problem, both in terms of the range of potentially-polluting materials that are included in electronic devices and also in the opportunity cost of disposal given the amount of scarce materials involved. These may include lithium-ion batteries, a plastic, composite, or aluminium outer casing, and a glass LCD screens. Electronic devices are also complex, high-value items requiring a high energy investment in their creation. For these reasons, refurbishment and re-use are attractive options in preference to disposal. In respect of laptop computing devices, one part requiring particular attention during the refurbishment process is the screen. As a part which is exposed to the environment in use, the screen often suffers damage to its outer surfaces. This includes scratches and also 'keyboard etching', damage caused to the outer lawyer of the screen while the laptop is closed, by oils and the like deposited on the key surfaces by the user's fingers. However, screen refurbishment is not easy. The usual approach is either to replace the entire screen, or to replace the outer polarising layer where the damage is concentrated. Wholesale replacement of the screen wastes its materials and energy investment, so it to be avoided. Replacement of the outer layer is challenging, however, with a number of problems. For instance, the polarising films vary in orientation; even among 100 nominally identicalmodel screens, up to four different orientations might be found, necessitating a systematic identification and application process. Further, screens are delicate, and are becoming increasingly slender and intricate. So simply extracting them is precarious, let alone removing the polarising film. In any case, a clean room environment is imperative; a standard warehouse will not suffice. SUMMARY OF THE INVENTION The present invention therefore provides a method of refurbishing an LCD screen, comprising the step of wet-applying to the screen surface a transparent laminate which comprises a vinyl film carrying an acrylic-based adhesive. We have found this to be particularly effective in resolving minor screen damage such as scratches and etching and returning the screen to an as-new or nearly new state. This allows the laptop to be refurbished easily and inexpensively. A high-quality result is achieved without having to replace the screen or remove a delicate polarising layer. The application process is straightforward and involves materials that are widely available at low cost. We have found that a calendered film is preferable for screens without a bezel, and cast films for screens with a bezel. The vinyl film is ideally less than 100 microns in thickness, more preferably between 25 and 85 microns in thickness. Calendered films for glass-fronted screens are ideally between 65 and 85 microns in thickness. Cast films for use on screens having a bezel are preferably between 25 and 45 microns thick. This ensures that the film is sufficiently thick to be easily handleable without stretching or being otherwise damaged, but is not so thick as to be visually obvious after application. We prefer that the laminate is wet-applied using an application fluid that includes water, detergent and (optionally) alcohol. Only a small amount of detergent is needed, around 1 drop per 100ml water. The alcohol content (when present) is preferably up to a maximum 30% by volume. We also prefer that the adhesive element of the laminate is applied to the vinyl layer with channels formed in the adhesive, i.e. a so-called "air-release" film. The channels may be defined between ridges or islands of adhesive, or the like. Generally, it is not recommended to wet-apply these films but we have found that the combination of an air-release-type film with wet application is particularly effective in dealing with scratches and similar damage to the underlying screen. The present invention also relates to a corresponding use, of a vinyl film carrying an acrylic-based adhesive in the refurbishment of an LCD screen under wet application, and to the thus-refurbished LCD screen and devices including such a refurbished screen. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described by way of example, with reference to figure 1 which illustrates the application process in schematic form. DETAILED DESCRIPTION OF THE EMBODIMENTS Most LCD screens have a polarising film as their top layer, producing a matte effect. Older touch-screens (such as iPhone) placed the polarising film beneath a glass layer. Glass-fronted touch screens are generally more robust. Nowadays, manufacturers are designing touch screens which resemble ordinary (non-touch) screens, with a layer of sensors immediately below the polarising film. This design makes removing the polarising film extremely delicate, requiring manual effort. We therefore tested numerous films which might be expected to yield good results due to their existing application in the field of protecting LCD screens. Thes included: • An additional layer of polarising film. Theoretically, aligning the polarising film at a right angle slightly darkens the screen, concealing marks present on the existing layer. However, this is only compatible with glass-fronted LCD screens, and requires precise hand placement to an orientation accuracy of approximately 3-5%. It is also too rigid, lacks breathability, and has issues with adherence due to plastic-on-plastic contact. • Clear Screen Protector film. This is available in glass and matte forms and is typically used for protective overlayers for mobile handset screens. We found this to be unsuitable because it only covers superficial marks, does not adhere well to the polarising film, displays any contamination beneath it, and is not breathable. It also looks very obviously like a removable screen protector. • Blue Light materials - i.e. screen covers which are intended to filter out light frequencies said to cause wakefulness and eye strain. These had problems similar to the screen protector films. • Motorbike Tint Material (in a lighter grade); This was the most successful material, but still had drawbacks in that it was not breathable, darkened the screen noticeably, and was difficult to apply. It is also only available with a backing paper, thus preventing machine cutting to the correct shape. • 3M IJ180 Clear Material is a printable wrap film for wrapping vehicles; as we can print on this, we considered adding a slight tint. However, the material is too thin, and the adhesive remains visible after application. Pairing it with a 3M matt or gloss laminate yielded mixed results, with strong adherence, ease of application and flexibility (thus reducing dimples), but an excessively matte finish combined with a silvering effect which took circa two weeks to dissipate and a washed-out look. We then tried a wet application of clear vehicle wrap films. Surprisingly, using just the laminate with a wet application almost made marks vanish, more so if the laminate is applied right to the edge of the bezel. These materials neither reduced the screen brightness nor caused a washed-out effect. They are also compatibility with plastic screen surfaces, have a clear adhesive and a close match to the original screen's satin finish. Vehicle wrap films also have a varying degree of flexibility to cope with curved vehicle panels, and this gives the covering a seamless look. We found that so-called "air-release" films produced a better result, concealing even deep scratches. In such films, the adhesive layer is applied to the vinyl later in elongate ridges or islands or another such pattern which defines small channels in the adhesive. Thus, under a dry application any air trapped beneath the film can escape via the channels, thus avoiding the formation of'bubbles' of film. However, wet application of air-release films is specifically taught against. This is partly because it is unnecessary; wet application methods for vehicle wraps are principally adopted so that there is a short period of time after application when the film can be lifted and moved if necessary, and air-release films are already able to be lifted and moved with relative ease. It is also because a wet application process for air-release film can trap excess fluid, preventing adhesion and causing the application to fail. If applied over uneven surfaces, moisture can also collect underneath the film and cause the vinyl to crack and its edges to lift. Our understanding is that by using a glue intended for dry application, but in a wet format, the glue mixes with and is diluted by the water, especially if it also contains some detergent and alcohol, thus forming a resin-like layer which is able to flow and fill scratches and other holes. What appears as visible etching on a screen is actually micro-scale ridges and divots; the resin fills these and makes the overall assembly optically clear. We have found that marks which show through after being covered with the same material applied dry are effectively concealed with a wet application. For this purpose, only a small amount of detergent is needed, typically 1 drop per 100ml of fluid. A drop is typically accepted as being 0.05mL and this therefore corresponds to a concentration of about 0.05%. Generally, a concentration of more than about .2% or .5% will be unnecessary and may cause contamination or adhesion issues. We therefore prefer a concentration of not more than these levels, ideally below about 0.1%. The amount of alcohol needed is dependent on the screen surface. Generally, one of a 30%, 20% or 10% concentration by volume will produce the best results, but there are some screen for which the alcohol is not needed. A suitable commercially-available film which we have found to be effective is the Avery Dennison® DOL range of films, especially the DOL 1400 and DOL 2000 Series films. The DOL 1400 Series film is a premium quality 30 micron clear cast vinyl film with a permanent acrylic based adhesive, whereas the DOL 2000 series is a 75-80 micron flexible transparent calendered vinyl with a permanent, clear, pressure sensitive, acrylic based adhesive. These films are designed to be used as protective overlaminate films for digitally printed images in order to protect the underlying printed image from environmental degradation. Thus, they are intended to be applied dry via a lamination machine on to another cast or calendered vinyl film. Both have an adhesive layer which is applied in elongate ridges with small channels between them, characteristic of an air-release film. This is illustrated schematically in figure 1. The outer surface of an LCD screen 10 which is being refurbished typically has a number of scratches 12 on its surface which have arisen during use. The clear transparent air-release laminate 14 being applied has a vinyl film 16 chosen to suit the screen in question, with a series of ridges 18 of an adhesive composition on its underside, separated by channels 20. An application fluid 22 has been applied to the surface 10 of the LCD screen; some of this is gradually expelled as the laminate 14 is applied to the LCD screen 10 in the usual manner, such as with a squeegee or other tool, and some dissolves or mixes with the glue 18 to leave the resin-like layer 24 beneath the vinyl layer 16. This serves to adhere the vinyl layer 16 to the LCD surface 10 and also fills the scratches 12. The reduced difference in refractive index between the outer layer of the LCD screen 10 and the resin layer 24 reduces the amount of scattering that takes place at the edges of the scratches 12 and thus renders the scratches 12 effectively invisible. Prior to application of the film, the LCD screen will of course have been thoroughly cleaned to remove grease and other deposits, using generally known techniques. Generally, cast films are recommended for their greater ability to conform to complex curves, but most LCD screens are flat and therefore at first sight this will not be required. However, we have found that the most appropriate film depends on the type of screen. Thus, on a screen such as the Lenovo T490 which has a bezel (i.e. a surrounding frame which conceals the edges of the screen, typically of a plastics material) we remove the bezel and then apply the film over the screen and wrap around its edges. For this, a cast film is superior as it is more flexible than a calendered film and has better adhesion. Cast films are also available in thinner forms which also assists in forming the film around the edges. The thinner material also fits under the bezel more easily. Meanwhile, the calendered film can be cut to shape to fit glass fronted laptops such as Apple Macbooks. This is much easier to lay down onto a flat surface and also adheres to glass better. The LCD screens to which this process can be applied will usually be part of (or intended for us with) a laptop computing device, but the process can be applied to other types of LCD screen such as those for monitors, tablet computing devices, mobile telephone handsets, or any other device with an LCD or similar type of screen. It will of course be understood that many variations may be made to the abovedescribed embodiment without departing from the scope of the present invention.

Claims

1. A method of refurbishing an LCD screen, comprising the step of wet-applying to the screen surface a transparent laminate which comprises a vinyl film carrying an acrylicbased adhesive.

2. A method according to claim 1 in which the vinyl film is less than 100 microns in thickness.

3. A method according to claim 1 in which the vinyl film is between 25 and 85 microns in thickness.

4. A method according to any one of the preceding claims in which the LCD screen does not have a bezel and the vinyl film is a calendered film.

5. A method according to claim 4 in which the vinyl film is between 65 and 85 microns in thickness.

6. A method according to any one of claims 1 to 3 in which the LCD screen has a bezel and the vinyl film is a cast film.

7. A method according to claim 6 in which the vinyl film is between 25 and 45 microns in thickness.

8. A method according to any one of the preceding claims in which the laminate is wet-applied using an application fluid that includes water, detergent and alcohol.

9. A method according to claim 8 in which the detergent concentration in the application fluid is less than about 0.2% by volume.

10. A method according to claim 8 or claim 9 in which the alcohol concentration in the application fluid is less than about 30% by volume.

11. A method according to any one of the preceding claims in which the adhesive element of the laminate is applied to the vinyl layer with channels between them.

12. A method according to claim 11 in which the channels are defined between ridges or islands of adhesive.

13. The use of a vinyl film carrying an acrylic-based adhesive in the refurbishment of an LCD screen under wet application.

14. An LCD screen refurbished according to the method of any one of claims 1 to 12.

15. A computing device including a screen according to claim 14.

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