GB2199285A - Anti-lacerative windscreen and method of making the same - Google Patents

Description

ANTI-LACERATIVE WINDSCREEN AND METHOD OF MAKING THE SAME

1. Field of the Invention

This invention relates to anti-lacerative laminates for use in motor vehicle window and windscreen constructions. 2. Descriptionof the Prior Art

Laminate type structures are used today in numerous structural applications to improve aesthetics, add strength, or to reflect visible or invisible radiation. Such structures include safety or anti-lacerative glass used in motor vehicle windscreens, heat mirrors for motor vehicles and buildings, damping devices, impact shields, etc. Plastic films are major components of such laminates and their ability to accept and retain adjacent structures is a major consideration in determining applications for such laminates.

Frequently., the plastic surface must be altered so that it will more readily accept and retain adjacent structures of like or dissimilar materials. The prior art discloses treating such surfaces by abrading, solvent cleaning, flame and corona treatment. The disadvantage of such methods are well known, as disclosed in Plastics Engineering, October 1985, pages 41 to 45. It is also disclosed in Plastics Engineering

2 199285) - 2 to treat plastic surfaces with a plasma. Plasma treatment enhances a substrate surface leading to greater bond strengths than other surface treatments and is generally cleaner and faster than the tre.atments discussed above. However, the present invention discloses an improved plasma system for treating plastic film surfaces. Plastic films treated with the plasma system of this invention have enhanced adherable surfaces which find use in many types of structural applications. The enhanced adherable plastic film of this invention is particularly useful as a component in inner structures of anti-lacerative windscreens where structural integrity is critical.

other critical design features of anti-lacerative windscreens include, of course, the ability to prevent or reduce facial, head and neck injuries to vehicle occupants during a collision and the ability to present and maintain a clear field of vision to the driver.

Today's motor vehicles though smaller than vehicles produced in the past are made with more glass. Typically, a car today comprises about 3.252 square metres (35 square feet) of glass and the motor industry envisions that the cars of the future will be produced with as much as 6.039 square metres (65 square feet) of glass.

In hot sunny weather, increases in a carfs glazed surface area can create very high interior car temperatures. In winter, on cloudy days or during the night the heat energy loss through such an increased glazed surface area can be quite substantial. of course, these effects can be countered by the industry by installing more powerful heating and cooling equipment in the motor vehicle. However, with the advent of lighter cars and equipment such a solution is counter-productive. The environmental changes may be more easily controlled by selectively positioning a metallic layer in the laminate structure of this invention.

Summary Of the Invention

The present invention relates to an anti-lacerative windscreen or window that meets all the above requirements by providing an anti-lacerative laminated windscreen having an inner construction comprising a polymeric film support layer having an enhanced adherablesurface on an outer surface of the layer and an excellent scratch-resistant coating on the inner side of the polymeric film support layer and an innermost lubricity layer of an organic polysiloxane over the scratch-resistant coating. Additionally, the laminate structure may include metalic layers selectively positioned within the laminate structure.

More specifically, the present invention relates to an inner laminated structure for an anti-lacerative laminate windscreen or window which comprises:

a polymeric film support layer having an inner and an outer surface, saidouter surface having an enhanced adherable surface created by subjecting said outer surface to plasma treatment, and a layer of a scratch-resistant radiation-cured coating having an inner and outer surface, comprising, a copolymer of a triacrylate or tetraacrylate monomer and acrylic acid, said outer surface of said coating adhered to said inner surface of said polymeric film support layer.

The enhanced adherable surface of the plastic layer is produced by exposing a surface of a plastic film to an A.C. plasma created by a symmetrical electrode system comprising:

a plasma housing having smooth interior surfaces; said housing supporting a plurality of parallel separated, elongated electrodes, each electrode having a hollow, elongated cooling channel running longitudinally through the centre of the electrodes, said channel being 1.

- 5 capable of communicating with the channel of a second electrode; means for connecting the electrodesIn electrical series; means for connecting said hollow channels in series; and means, connected to said means for connecting said electrodes in series, for supplying power to produce alternating current sufficient to sustain a plasma.

Brief Description of the Drawings

The features of the present invention will be de-scribed in connection with the accompanying drawings. The features described in the drawings relating to the present invention are illustrative and are not considered to limit the present invention. The drawings consist of 7 f gures. T e drawings are not to.scale.

Fig. 1 shows a cross-section of a conventional laminated windscreen; Fig. 2 shows a cross-section of a prior art construction of an anti- lacerative windscreen as disclosed in U.S. Patent-No. 4,242,403;

Fig. 3 shows a cross-section of the construction for an anti-lacerative windscreen or window of the present - 6 invention; Fig. 4 shows a cross-section of the construction for an anti-lacerative windscreen or window of the present invention including a metal and/or metallic compound layer and/or layers positioned between a soft cushioning layer and a plastic penetraton-resistant layer; Fig. 5 shows a cross-section of the construction for an anti-lacerative windscreen or window of the present invention including a metal and/or metallic compound layer and/or layers positioned between the penetration- resistant layer and the scratch-resistant layer; Fig. 6 is an elevated view part in section of the electrode system used to produce the enhanced adherable surface of the polymeric film support layer; and Fig. 7 is a side view in section along line a-a of Fig. 6.

Description of Preferred Embodiments

Fig. 1 illustrates a conventional laminated windscreen of 2.54 mm (0.1 inch) float glass sheets sandwiching a 0.762 mm, (0.030 inch) layer of polyvinyl butyral (PVB). This structure will be referred to throughout this specification as a conventional laminated windscreen, or as a substrate or a

7 - part of a substrate for this invention. The conventional structure is deemed a high penetration-resistant windscreen The layers typically are sealed to one another by autoclaving. The inner glass layer is primarily used to protect the PVB layer from atmospheric exposure, humidity and scratching. This conventional laminate structure has prevented orreduced serious head, neck and facial injuries resulting from car crashes. In the United States such a glass layer is required by federal law and the internal surface is usually required to be scratch-resistant.

A safety glass sold in Europe may consist of an outer layer of float glass, polyvinyl butyral, an inner layer of float glass and a layer of polyurethane adhered to the internal side of the second float glass layer. This structure too will be referred-to throughout this application as a conventional anti-lacerative windscreen or as a clear substrate for the structure of this invention. However, the polyurethane plastic layer is subject to abrasion. Effective November 16, 1983, the National Highway Traffic and Safety Administration amended its rules to that today such a windscreen may be used in the United States. The new rule may even allow a two-ply windscreen of float glass and polyurethane so long as the windscreen can meet the stringent test, "ANS Z2C, reported in 49 CFR section 571.205.

- 8 Figure 2 relates to a third prior art windscreen which includes all of the structures of Fig. 1. Additionally, on the inner side of the laminate is included an additional PVB layer of 0.38lmm (0.015 inches), a polyethylene terephthalate (PET) layer of 0.102mm (0.004 inches), and a final layer consisting of a scratch-resistant coating 2.8 x 10-6m thick of an organopolysiloxane layer with silica reinforcement. The additional PVB layer and PET layers are non-lacerative and the ultimate siloxane layer presents a surface adapted to resist wear and weathering without constituting a lacerative hazard. Another benefit derived from such additional structures is a structure resistant to penetration. Penetration resistance is provided by the PET layers. Another benefit is a structure having a better cushion to soften the impact for vehicle occupants or objects thrown onto the windscreen. Cushioning is provided by the pliable PVB layers. Such a structure has been described in U.S. Patent No. 4,242,403. That patent also discloses that the PET layer is surface-conditioned by electrical or chemical treatment but preferably by gas flame. Additionally, the patent discloses that the scratch-resistance of the fully cured, silica-reinforced organopolysiloxane compound of the innermost layer was found to exceed that of any material previously considered for the purpose. However, problems with the structure.disclosed in this patent include a weak bond between the PVB and PET layers. Industry requires or desires bonds of 68. 966-kPa (10lbs/inch). The bond between the PET and PVB layers in U.S. Patent No. 41242,403,-as demonstrated by a 900 pull test, is reported to be approximately 23.448 kPa (3.4lbs/inch). Additionally, although the scratch-resistant layer performs well under standard Taber abrasion tests, and although it meets current industry standards, it is not as scratch- resistant as could be desired. A Taber abrasion test is conducted by rubbing an abrasive wheel in a circular motion on a film's surface. The scratching test includes dragging 0000 steel wool approximatelystraight across the surface of a film.

Additionally, the scratch-resistant layer of U.S. Patent No. 4,242,403 is optically not the best. Specifically, the optical imperfection includes an "orange peel" effect. That is, the texture of the surface of the coating is similar to that found on the outside surface of an orange rind. By viewing or looking through this surface at a large angle relative to the normal the "orange peel" effect is seen which distorts transmitted light and observed images as does any uneven surface. Such a distortion could affect the vision of a driver looking through the windscreen in the direction of the front passenger side.

Secondly, on autoclaving the product disclosed in U.S. Patent No. 4,242, 403, the scratch-resistant layer is reported to have a tendency towards cracking when exposed to high temperatures. Such material has to be disposed of as scrap which increases production costs.

Similarly, when structures of the 4,242,403 patent are subjected to accelerated weather conditioning, the scratch-resistant layer is subject to cracking. This can be demonstrated by placing the structure having the scratch-resistant coating in an ultra-violet/condensation screening device sold by Atlas under the name WCON. Such a device is a standard weathering device used by the film industry today, and exposes samples to alternating periods of eight hours of U.V. light at 600C (140OF), and four hours of 100% relative humidity at 400C (1040F).

The scratch-resistant layer of this invention is not subject to cracking during autoclaving or when subjected to accelerated weather conditioning.

Fig. 3 shows the novel anti-lacerative structure for a motor vehicle windscreen or window of the present invention. This structure solves all of the problems mentioned above. The structure of this invention has an improved bond strength between the PVB and the PET layers. This bond strength is - 11 reported to be between 103.448 to 206.896 kPa (15 to 30lbs/inch) per a 900 pull test. The bond strength-between polyurethane and PET may also be of this order. No visible distortion can be seen with the, structure of this invention. Finally, the scratch-resistant layer passes government standards for Taber abrasion testing, exhibits excellent scratch resistance, and excellent weatherability.

The laminate of Fig. 3 is composed of about a 0.102mm (0.004 inch) clear polymeric support such as PET. The PET has an enhanced adherable surface on one side. To the enhanced surface a 0.381mm (0.015 inch) thick layerof PVB or polyurethane is applied. A conventional windscreen, as shown in Fig. 1 or any federally acceptable substrate or glass substrate, may be applied to the free PVB or polyurethane layer. To the opposing side of the PET surface is applied about a 2 to 4 X 10-6M thick coating of a scratch-resistant material disclosed and claimed in U.S. Patent No. 4,557, 980 to Hodnett which is hereby incorporated herein by reference. The use of this coating results in a scratch-resistant surface having good weathering characteristics and excellent optical clarity, which meets government requirements under Taber abrasion tests and is scratchresistant.

The scratch-resistant coating is obtained by radiation-induced polymerization of an acrylic coating according to U.S. Patent No. 4,557,980. The innermost layer is a thin layer of a thermally cured dimethyl polysiloxane compound obtained from General Electric as product SS4191, which is a toluene solution of curable dimethyl polysiloxane. The solids content of this material is 30%; at 25'C (770F), it has a density of 0.904 g/CM3 and it has a Pensky Martin flash point of 14.CC (58OF). This coating is typically used as a release coating for pressure-sensitive adhesives. However, in the present invention it serves two purposes; firs'tly, it functions as a successful antiblocking agent allowing for easy release of the product from the mould of the autoclave, and the easy release of stacked products from one another. Secondly, the silicone layer functions as a lubricity layer. That is, the lubricity layer helps withstand abrasion by acting as a lubricant preventing grinding.

In assembling the structure of this invention, a surface 15a of PET layer 15 is subjected to a plasma treatment created by a symmetrical electrode system more fully disclosed below. Generally, the enhanced surface 15a is produced by moving the PET layer 15 through an A.C. plasma which cleans and activates the surface 15a of the film. Essentially ionized argon gas cleans the surface while ionized oxygen activates the surface.

-- 13 To the opposite surface 15b of the PET layer 15 i applied the scratch.- resistant coating 16 of U.S. Patent No. 4,557,980. This coating mixture possesses desirable rheological characteristics, high optical clarity, and superior adhesion, abrasion and scratch resistance and good weathering properties. This layer is applied to the PET surface by conventional techniques disclosed in U.S. Patent No. 4,557,980. Preferably.the coating is applied by using conventional roll coating techniques which permit a thin coating. After application of coating 16, the layer is polymerized in situ by ultraviolet radiation., electron beam radiation, or any source of ionizing radiation capable of producing free radicals.

After layer 16 is cured, lubricity layer 17 is applied over layer 16 b y conventional techniques. Layer 17 may be cured thermally. Thermally-cured silicone release coatings as well-as radiation curable coatings of this type are per se well known. Additionally, the lubricity layer 17 may be cured by catalyst systems comprising tin or platinum. The dimethyl polysiloxane may be modified as is known by those skilled in the art to adjust the degree of lubricity required. Layer 17, although subject to being-worn away or rem oved after installation of the windscreen or window, is important in that the final product is easily removed from the laminating device S - 14 when layer 17 is present. Additionally, layer 17 when remaining on the windscreen after installation improves the durability and long term acceptability and scratch-resistant properties of the windscreen.

After formation of structure including layers 15, 16, and 17, PVB layer 14 is applied to the enhanced adherable surface 15a of PET layer 15. Thereafter, a conventional windscreen such as that shown in Fig. 1 may be applied to the unoc cupied surface of the PVB layer. Alternatively, any federally acceptable clear substrate functioning as a windscreen may be applied to the PVB layer 14. A polyurethane layer may be substituted for the M layer 14. The free polyurethane surface may then be topped off with the glass windscreen of Fig. 1. When polyurethane is substituted for PVB, the polyurethane layer acts as a soft cushioning layer and the PET layer remains as a penetration-resistant layer.

on assembling the structure as described above the product is subjected to heat and pressure to form an anti-lacerative windscreen or window. The laminated product of this invention has superior optical qualities, is of a greater bond strength, improved scratch-resistance and abrasionresistance, and possesses better durability than existing products.

- is - The enhanced surface of the P ET layer is produced by moving the surface 15a of PET layer 15 past a plasma such as that created by the symmetrical electrode system 30 of Figs. 6 and 7. The term symmetrical refers to an A. C. electrode system which is electrically floating relative to ground.

The symmetrical electrode system 30 includes-a curved metal housing 31 having smooth interior surfaces. The rear of the housing is closed while the front is exposed as shown in Figs. 6 and 7. Supported by the housing in the interior of the unit are a plurality of circular elongated electrodes 32a, b, c and d. The electrodes supported by the housing pass through the housing. The electrodes however do not touch the housing but are insulated therefrom by glass-filled polytetrafluoroethylene insulating material 40 as shown in Fig. 6. The electrodes are electrically connected alternately in series by conductors 33 and are positioned in a parallel separated relationship as shown in Figs. 6 and 7. Electrodes 32a and c are anodes while electrodes b and d are cathodes. Although the distance of separation between the layers is not critical, the separation must be sufficient to produce a plasma on supplying current to the electrodes.

The distance where a plasma cannot be generated is less than the Debye length.

16 - The electrodes 32a-d are made of aluminium, but their exterior is provided with a dielectric oxide coating 34 by anodizing the electrode. oxide coating 34 is aluminium oxide.

The electrodes system is of aluminium in view of aluminium's low sputtering rate in a plasma. The oxide coating 34 has an even lower sputtering rate. The integrity of the electrode is important in that the surface 15a of PET layer 15 is to be cleaned. A sputtering electrode may, deposit aluminium compounds on the substrate surface which may inhibit desired surface-adhesion characteristics of the PET surface 15a.

The thickness of the aluminium oxide layer 34 is not essentially critical. The range of thickness may be between about 0.0254mm (0.001 inches) and 0.127 mm (0.005 inches), and preferably, about 0.0508mm (0.002 inches). The thickness is critical in regard to the efficiency of the apparatus. That is, by insulating the electrodes with a dielectric 34, a capacitor is formed at each electrode with the electrode being one conducting element and the plasma being the other conducting element. Thus, an A.C. current may flow from one electrode through the capacitance of the electrode, through the c'onducting plasma, through the capacitance of another electrode and to the other electrode itself. Associated with each of these elements is a resistance or impedance to current flow which determines how much power is dissipated in each element.

In order to maximize the power dissipated in the plasma, the capacitive impedance of the electrodes should be small compared to the plasma impedance. The capacitative impedance Z is given by:

2 rr f c Thus, the capacitance C should be made large. A standard electrical text will demonstrate that the thickness of the dielectric should be small to accomplish this. The actual thickness which can be tolerated depends on factors which affect the individual element impedances. Electrode dimensions, number of electrodes, operating pressure, supply frequency, and gas types and ratios are factors which have the major influence. Although four electrodes are shown the number may be increased or decreased so long as the electrodes are evenly paired. Although both Figs. 6 and 7 show room for additional electrodes, the housing 31 may be made smaller so that ports 37 and 38 are closer to the electrodes 32a-d.

The power is supplied to the electrode system and hence, to the plasma from an A.C. power supply operating at a 18 - frequency of about 35 KHz. The output from the supply must be matched to the electrode and plasma impedance by means of a matching step- up transformer. Such a transformer is adjustable in ratio to allow for matching under a range of different operating conditions.

The electrode surface area is deliberately made as large as possible consistent with all other factors which affect the efficient operation of the plasma process, to allow as low a power density as possible to be used. This further minimizes contamination of the PET surface with sputtered electrode material. The outer diameter of the electrodes including the oxide layer is between about 1.270cm (0.5 inch) and 3.810cm (1.5 inch). The -electrode can have a length of between 0.127 to 2.438m (5 inches to 8 feet).

Additionally, the electrodes 32a-d have a hollow elongated channel 35 that runs longitudinally through the centre of the electrode. The inner diameter of the channel is between about 0.635 and 3.175 cm (0.25 and 1. 25 inches). Cooling water is passed through channels 35 during the plasma treatment to prevent overheating and structural failure of the equipment. The cooling channel of one electrode communicates with the cooling channel of a second electrode by insulating conduits 36 which are located outside the housing to maintain a smooth interior surface. These cooling channels 35 are connected in series by conduits 36 located outside of the housing in accordance with the electrical ser'ies connections so that the electrodes are-not shorted by current flowing through the cooling water. Additionally, the metal housing 31 which contains the plasma may be cooled by water flowing through additional conduits (not shown) mounted to the rear or.back of the housing.

The curved metal housing 31 fits closely to-a water Cooled backup roller over which the substrate film 15 is passed so that the plasma may act on the film surface. This allows the plasma region to be maintained at a relatively high pressure compared to the surrounding vacuum environment. This avoids overloading the.vacuum pumps and reduces the quantity of gas required. The housing 31 includes ports 37 and 38 for receiving injection gases and for sensing the pressure-inside the housing. The ports are flush with the inside surface of the housing to avoid protrusions into the plasma region which would otherwise give rise to instabilities in operation, and to avoid sputtering and hence contamination of the substrate surface with the materials making up the ports. Alternatively channels may be substituted for ports. Channels may be positioned flush with the housing and run longitudinally in a direction parallel to the electrodes at the top and bottom of the system where port 38 is designated as being at the top of the system and port 37 the bottom. Channels provide an even distribution of ionizing gas when electrode lengths approach dimensions of about 60. 96cm (2 feet) or greater.

The entire apparatus housing the electrode system includes vacuum pumps, a power supply, a matching transformer, control panels, gas supplies, a supply roll for the polymeric support film, a take-up roll, a watercooled drum and a vacuum-tight enclosure enclosing the electrode system and roll of film. This equipment is per se known and available to those skilied in the art.

The plasma system is operated at about 3.325 Pa (25 millitorr) of pressure and the plasma voltage is maintained at least about 1,800 volts. The power supplied to the electrode system is at least 3.281 kW/m (lkW/ft) of electrode length and at a frequency of about 35 kHz. This frequency is well below the radio frequency of 13.56 MHz normally employed, to avoid the buildup of bias voltages on the insulating substrate surface which would inhibit the fullest possible treatment of the surface.

In operation, the metal housing 31 is mounted to a flange of equipment which allows the film 15 with surface 15a to pass in front of the electrodes and hence, the generated plasma 39. A vacuum-tight cover is placed over the electrode - 21 system and the atmosphere in front of the.electrodes is evacuated and argon gas and oxygen-containing gas such as nitrous oxide are directed into the chamber. A potential is applied across the electrodes creating an electric field. A discharge is initiated when an electron is released by photoionization or field emission. The electron is accelerated to the anode by the ele,Ctric field, gains kinetic energy and collides with the argon and oxygen-containing gases, generating argon and oxygen ions and releasing additional electrons. This process rapidly continues'until a self-sustained steady state plasma 39 is created. By alternating the current in this manner, electrons and positive ions are constantly being directed and pulled in opposite directions. The rapid change in polarity prevents a net positive charge from building on the film which could repel ions preventing the surface from being further treated. It is believed that the argon gas ions clean the surface of the film and the oxygen-containing gas oxidizes the surface of the film. Such a plasma treatment is believed to activate the surface. However, the exact mechanism of the d isclosed plasma treatment is not fully known in producing the enhanced adherable surface of the PET layer 15.

The film is generally moved past the plasma at a rate of between 3.048 and 6.096 m/min (10 and 20ft/min) and is supported on a water-cooled drum. However, although this is - 22 the range of film speed currently used, 5.486m/min (18ft/min) is preferred. It is believed that film speed may be increased along with increases in power to produce an enhanced adherable surface having characteristics similar to those produced when the film is travelling at about 5.486 m/min (18ft/min) at a power of 3.281 kW/m (lkW/ft) of electrode length.

The film is advantageously moved passed the plasma 39 in a direction perpendicular to the longitudinal axis of the electrodes. I The laminate structure of the present invention may include a thin layer of metal and/or a metallic deposit or deposits on either surface of the PET layer 15 used in this invention. Such deposit or deposits will be conveniently referred to as a metallic layer. Such metallic layers include those disclosed in U.S.patents Nos. 4,248,687 and 4,337,990 to Fan and Fan et al, respectively. These patents are hereby incorporated herein by reference.

The metallic layers may be included into a laminate structure of the present invention such as shown in Figs. 4 and 5. The metallic deposit of U.S. Patent No. 4,248,687 is tin-doped indium oxide and the metallic deposit of U.S. Patent No. 4,337,990 includes a silver layer sandwiched between two oxide layers. These metallic layers may be applied to either surface 15a or 15b of PET layer 15. Advantageously, the metallic layers are applied by sputtering them onto the PET layer. Generally, when ametallic layer is sputtered onto PET layer 15a as metallic layer 18, as shown in Fig. 4, the metallic layer aids in reflecting-heat-producing electromagnetic radiation such as radiation having wavelengths falling in the near-infrared spectrum. The metallic layer prevents heat from entering the motor vehicle. When positioned on surface 15a the metallic layer functions only as solar heat control layer.

When the metallic layer 19 is sputtered onto surface 15b so that only a thin scratch-resistant layer contacts the opposite surface of the metallic layer the layer functions as a low emissivity layer. That is, the metallic layer 19 reflects heat energy of wavelengths in the far- infrared preventing heat from radiating from structures in the interior of the car.

Solar control and low emissivity (hereinafter referred to as low E) are more fully explained below.

The visible band of the electromagnetic spectrum of solar energy covers a wavelength from about 400 to 700 nanometres. At shorter wavelengths, 300400 nanometres, is the ultra violet band and at wavelengths longer than the visible region is the near-in-frared band at about 700 to 2,500 nm. The near-infrared can be considered as sun heat and thedesirability of admitting this region into a motor vehicle depends on the need.

Generally, these wavelengths when encountering a glazed surface wil be reflected, transmitted or absorbed. only small percentages of the visible and near-infrared wavelengths are reflected by a glass surface. A PVB surface having nearly the same index of refraction as glass will reflect the same percentage of radiation. Some of this radiation is absorbed, however most of the radiation is transmitted. The transmission of the near infrared as mentioned above causes a heat buildup. Materials which reflect a greater percentage of the near-infrared radiation but transmit visible light are useful to control the heating effects inside a car.

Including such metallic materials as layers in the improved antilacerative windscreen of this invention produces a highly marketable product.

An oxide/silver/oxide layer 18 when disposed on layer 15a as shown in Fig. 4 produces a solar heat control device by reflecting much of the solar radiation which produces heat back to the atmosphere and away from the car's interior.

By switching the position of the metallic layer, i.e., sputtering it onto surface 15b of PET layer 15, a low E window or windscreen is produced. That is, just as the sun radiates energy and heat, so do objects such as the materials present in a room or vehicle at about 200 to 250C. As an object 1 heats up, its peak emission of energy'is shifted to shorter wavelengths in the radiation spectrum,. For instance, the sun is a very hot body and its peak emission falls within the visible spectrum of radiation about 500 nm. However, the cooler structures present ina motor vehicle have a peak emission of radiation of approximately 10,000 nm which is radiation of a wavelength falling within the far-infrared region of the spectrum. The loss of this radiated energy to the windows of a car and then to the atmosphere by conduction on a cold cloudy day is disadvantageous to the comfort of occupants. Retaining the energy radiated by occupants and the car"s interior structure on such a day is advantageous. As disclosed above, positIoning structures within a 1. aminate that will reflect this radiation back into the car resolves this problem.

The structure shown in Fig. 5 of this invention wherein the metallic layer 19 of an oxide/silver/oxide or of tin-doped indium oxide is sputtered onto PET surface 15b solves this problem. This metallic layer positioned on layer 15b reflects the far-infrared radiation back into the car's interior.

The metallic layer oxide/silver/oxide 19 may be applied in thicknesses of about 10 to 100 nanometres which yield an emissivity Of 0.06 to 0.2. Metallic layer 19 of the - 26 type tin-doped indium oxide may be applied in thicknesses of about 50 to 500 nanometres which yield an emissivity of 0.1 to 0.3.

In this position the oxide/silver/oxide layer 19 also functions as a good solar heat control device. The structure shown in Fig. 5 wherein layer 19 is the oxide/silver/oxide metallic layer is preferably used. Such a structure has enhanced structural integrity, great anti-lacerative properties, excellent scratch-resistance, and acts not only as a solar control device, but also as a low emissivity structure. Where a metallic layer is positioned on PET layer 15 at surface 15b, the scratch resistant layer 16 may be applied over the metallic layer to protect it. When the scratch-resistant layer is disposed over the metallic layer, the emissivity of the product when metallic layer 19 is oxide/silver/oxide is 0.16 to 0.57 and the emissivity of the product containing tin-doped indium oxide as metallic layer 19 is 0.2 to 0.67.

Additionally, metallic layers having low emissivity generally have a resistivity of 15 ohms per sq. or less. An electric current may be supplied to such a layer thus creating a built-in demister or antifogging device. Electrical contacts may be applied to the metal layer which receive the electric current.

The structure shown in Fig. 4 has less of an enhanced structural integrity than that of Fig. 3 in view of the fact that a metallic layer is deposited onto the treated layer 15a Of PET layer 15. The PET layer is usually about 0.10.2 millimetres (0.004 inches) thick. Layer 15 may consist of two PET layers each being about 0.051 millimetres (0.002 inches) thick. Metallic layer 18 may then be sputtered on the outer surface of the 0.051 milimetres (0.002 inches) layer positioned. next to scratch-resistant boating 16 or on the inner surface of the 0.051 millimetres (0.002 inches) PET layer next to the PVB or polyurethane layer 14. The outer surface of the 0.051 millimetres (0.002 inches) layer next to the PVB or polyurethane layer may of course be treated by subjecting it to a plasma generated by the electrode system disclosed above. In sandwiching metallic layer 18 between two PET layers-,-having a combined desired thickness, the structural integrity between a PET layer and a PVB or polyurethane layer may be maintained.

The scratch-resistant layer of this inventLon when applied over either layer 15b or metallic layer 19 is resistant against both scratching and abrasion. Currently, federal standards require that the inside surface of a windscreen have absolute haze values of less than 4% after testing as per A.S.T.M. D-1044. Average results obtained with the scratch-resistant coating layer 16 of this invention are between 3.7 and 3.8% absolute haze. By introducing an - 28 innermost lubricity layer onto the inner surface 16, a reduction in the average abrasion resistance to less than about 3.0% may be obtained.

As disclosed above, the Taber haze test consists of applying rubber wheels containing abrasive particles to the inside surface of a sample of the window material and rotating the wheels. Fortunately, conditions simulated by this test are rarely encountered in the normal use of a car windscreen or window. More accurately, an owner or service attendant will clean selected aread of the interior of a windscreen by wiping a soiled area with a cloth. The cloth may be dirty itself or contain abrasive particles on it. These particles are likely to scratch the glass. A test which more accurately simulates real life conditions would be to wipe a surface with a very fine steel wool pad, grade 0000 to determine the scratch resistance. Wiping layer 16 comprising the acrylic coating defined above with a steel wool pad results in only minor scratching. The scratch-resistant coating of U.S. Patent No. 4,242,403 when subjected to this same test exhibits a marked increase in scratching as compared to that of layer 16 of the present invention.

Layer 16 in combination with the other structures disclosed above, especially in view of the enhanced adherable surface of the PET layer created by the process and apparatus disclosed herein, produces an excellent anti-lacerative windscreen meeting or exceeding the standards of existing structures. In important characteristics such as structural integrity and scratch-resistance the disclosed product out-performs the prior art devices.

of course, the disclosure of the above invention is not intended to limit the present invention to the specific embodiments set forth herein. It is recognized that other changes may be made in the product, apparatus, and process of forming the product without departing from the scope of the teachings recited herein. For instance, a'n enhanced adherable layer may be created on any surface of any structure disclosed herein where such surface forms a part of a bonding interface.

Additionally, metallic layers 18 and 19 may include oxide instead of those layers disclosed above, an antimony-doped tin oxide layer. However, any doping species which provides free charge carriers gan be employed. For example, where indium oxide is used, dopants may include Sn, Ge, Si, or Sb. The oxide layers of the oxide/silver/oxide structure may comprise those oxides disclosed in U.S. Patent No. 4,337,990.

Claims (18)

1. 4 1. A laminate structure for an anti-lacerative laminate windscreen or window which comprises: a polymeric film support layer, the outer surface of which possesses enhanced adherability as a consequence of plasma treatment, and, on the inner surface of the said polymeric film support layer,. a layer of scratch-resistant radiation-cured coating comprised of a copolymer of a triacrylate or tetraacrylate monomer and acrylic acid.
2. 2. A laminate structure according to Claim 1, wherein said polymeric film support layer is polyethylene terephthalate.
3. 3. A laminate structure according to Claim 1 or 2, further comprising an innermost lubricity layer in contact with the inner surface of the said scratch-resistant coating.
4. 4. A laminate structure according to any one of Claims 1 to 3, which further includes a solar control layer positioned on the enhanced adherable layer of the said polymeric film support.
5. 5. A laminate structure according to any one of Claims 1 to 3, which further includes a metal layer between said polymeric film support layer and said scratch-resistant coating.
6. 6. A laminate structure according to Claim 5, wherein said metal layer consists of a three layer structure of oxide/silVer/oxide or an alloy of tin-doped indium oxide.
7. 7._ A laminate structure according to Claim 5 or 6, further comprising electrical contacts connected to a power source at one end and at an opposing end connected to said metal layer.
8. 8. A laminate structure according to any one of Claims 1 to 7 which further comprises a layer of soft cushioning polymer, the inner surface of which is attached to the enhanced adherable surface of the said polymeric film support layer.
9. 9. A laminate structure according to Claim 8, wherein said soft cushioning polymer is either a polyurethane or polyvinyl butryral.
10. 10. A laminate structure according to any one of Claims 1 to 9 which is firmly adhered to the inner surface of a motor vehicle windscreen or window so that the outer surface of the PET layer lies closest to the inner windscreen/window surface.
11. 11. A laminate structure according to Claim 1 substantially as hereinbefore described with reference to any one of Figures 3 to 5.
12. 12. A symmetrical electrode system for exposing a surface of a polymeric film support to an A.C. plasma comprising: a plasma housing having smooth interior surfaces; said housing supporting a plurality of parallel separated elongated electrodes, each electrode having a hollow elongated cooling channel running longitudinally through the centre of the electrodes capable of communicating with the channels of a second electrode; means for connecting the electrodes in electrical series; series; and means for connecting said hollow channels in means, connected to said means for connecting said electrodes in series, for supplying power to produce an alternating current sufficient to sustain a plasma.
13. 13. The symmetrical electrode system according to Claim 12, wherein said electrodes are aluminium electrodes.
14. 14. The symmetrical electrode system according to Claim 13, wherein said aluminium electrodes are anodized producing a surface coating of aluminium oxide.
15. 15. The symmetrical electrode system according to any one of Claims 12 to 14, further comprising means for monitoring gas pressure and injecting ion creating gases to produce a plasma, said means being flush with said interior of said housing.
16. 16. The apparatus according to Claim 15, wherein said means formonitoring gas pressure and injecting ion creating gases is a port.
17. 17. A symmetrical eflectrode system for exposing a surface of a polymeric film support layer to an A.C. plasma substantially as hereinbefore described with reference to Figures 6 and 7.

    1 surface on a moving said generated by described in 19 frequency of produce said 20 surface on a hereinbefore
18. 18. A process of producing an enhanced adherable polymeric film support surface, which comprises polymeric film support layer past a plasma any one of the symmetrical electrode systems Claims 12 to 17.

    The process according to Claim 18, wherein the the cur-rent supplied to the electrodes which plasma is at least about 35 kilohertz.

    A process of producing an enhanced adherable polymeric film support layer substantially as described.

    Published 1986 at Trie Patent Oflice. State Ho._se. 66 71 Fligh Holborn, London WC1R 4TP PuTILlier copies may be obtained trorr. The Pat-nt SaJe5 B:&r.ch. S,. 1Aa-_v Cray. Orping-,cr.. Kent BR5 3RD Printed by MWuplex techniques lid S. Ma--y Cray, Kent Cc.. 1187