GB1580366A

GB1580366A - Laminated safety pane

Info

Publication number: GB1580366A
Application number: GB13987/77A
Authority: GB
Original assignee: BFG Glassgroup GIE
Current assignee: BFG Glassgroup GIE
Priority date: 1976-04-02
Filing date: 1977-04-01
Publication date: 1980-12-03
Also published as: LU74681A1; ES456644A1; FR2346301B1; JPS52121016A; SE423228B; IT1075374B; DE2703785C3; FR2346301A1; DE2703785A1; CA1090690A; NL7702339A; BE852676A; DE2703785B2; SE7701601L

Description

(54) LAMINATED SAFETY PANE (71) We, BFG GLASSGROUP, a French Body Corporate, of 43 Rue Caumartin, F-75009 Paris, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a laminated safety pane, for example for use as the windscreen of a motor vehicle, the pane being of the kind which comprises a first glass pane, a second glass pane, and a laminating material which glues the two panes together.

Laminated safety panes of the kind specified are becoming used to an ever-increasing extent as vehicle windscreens. In such laminated safety panes, as a rule, both the first and second panes are made of silicate glass and the laminating material, interconnecting the two silicate glass panes, is frequently a laminating foil of visco-elastic plastics, such as polyvinylbutyral (PVB), polyvinylalcohol (PVA), polyurethane (PU), polycarbonate (PC), polyvinylchloride (PVC) or the like. The safety of people travelling in vehicles has been shown to be considerably increased as a result of the use of such windscreens.Should a person travelling in a vehicle having a windscreen comprising a laminated safety pane of the kind specified, be thrown towards the windscreen in an accident, there is much less risk of the person penetrating the windscreen than with other kinds of windscreen even if the person is thrown quite voilently towards the windscreen. The risk is even lower if the person is secured by a safety belt in the vehicle. The resistance of such windscreens to penetration is achieved without making the windscreens so tough that the force of the blow required to cause damage to the windscreens is great enough, if applied by a human head, to cause serious skull or brain injuries. The risk of permanent brain damage brought about by impact of the head with a windscreen can thus be substantially eliminated.

However, with windscreens comprising laminated safety panes of the kind specifled, when, in an accident, the head of a person travelling in the vehicle comes into contact with the slightly fractured laminated safety pane, disfiguring cuts may occur to the passenger's head. A system of classifying such cuts according to seriousness and indicating the degree of seriousness by a number referred to as the laceration index (TLI) has been devised.

Clearly, of course, the danger of such lacerations occurring is considerably reduced if the inner pane of the laminated safety pane, presented to the interior of the vehicle, breaks into very fine fragments when struck. For this purpose, it has already been suggested that a toughened glass should be used for the inner pane.

Examples of the components used in laminated safety panes which break into fine fragments are the so-called Ten-Twenty and VHR glass. The use of a toughened glass of this kind as the inner pane increases the number of cracks which incur on impingement of as passenger's head on the laminated safety pane, the result being that the pane breaks up into finer fragments. The number of cracks depends on the energy absorbed by the laminated safety pane. The number of cracks increased by the use of a toughened inner pane has however not yet produced satisfactory results, since very fine fragments can be obtained only if the strength of the toughened inner pane is very high. As a result however, it becomes possible for serious skull or brain injuries to be caused when a persons's head strikes the pane since the pane will not give way unless the blow struck by the head is severe.The strength of the panes must be kept within very narrow limits, since both panes of the laminated safety pane must break slightly with an impingement velocity of 20 km/h otherwise there is a risk that the severe skull or brain injuries may be caused. Since it is difficult to control the strength of the toughened inner pane so accurately, in manufacture, that on the one hand the pane, when it breaks, breaks into fine fragments, while on the other hand the strength of the blow required to break the inner pane is low enough, panes of the kind specified, meeting the two conflicting requirements set out above, could not hitherto be produced reliably on an industrial scale.

It is known that breakage into fine fragments can be obtained if the inner pane is made as thin as possible in panes of the kind specified. As a result the sagging of the whole pane when struck and broken by a person's head increases as compared with the case in which the inner pane is not made thin, so that the inner pane breaks up into fragments of relatively fine structure, and as a result the laceration index is reduce in other words there is less risk of disfiguring lacerations. Even with asymmetrical windscreens of this kind, in which the inner pane is substantially thinner than the outer pane, however, it has not yet been possible to reduce the laceration index to values low enough to be completely satisfactory.On the contrary, in both cases-i.e. both with the use of a toughened inner pane and a very thin inner pane-the result has been an improvement of the laceration index by only 1 to 2 units. Another disadvantage of the use of toughened panes is that it calls for extra operations in the manufacture of the laminated safety panes, so that such panes are more expensive than panes in which no toughened glass is used.

Starting from the knowledge that the laceration index of laminated safety panes of the kind specified can be further reduced only if the fragments into which the inner pane breaks are made even finer, it is an object of the invention to provide a laminated safety pane in which, when the safety pane is broken by impingement of an object on a selected one of the two panes the latter pane breaks up into individual pieces as small as possible which exclude lacerations to the maximum extent.

To this end, according to the invention, there is provided a laminated safety pane comprising a first silicate glass pane, a second, thinner silicate glass pane, and a laminating material which glues the two panes together, in which the adhesive strength of the connection between the second silicate glass pane and the laminating material is made substantially higher than that between the first silicate glass pane and the laminating material, the adhesive strength of the connection between the second silicate glass pane and the laminating material being 410 Pummel units and that of the connection between the first silicate glass pane and the laminating ma terial being 1-2 Pummel units; and at least the second silicate glass pane being made of non-prestressed silicate glass.

Preferably the second silicate glass pane is substantially thinner than the outer pane, being more particularly at most 2 mm in thickness.

The laminating material connecting the second and first silicate glass panes may be a layer of visco-elastic plastics, e.g. one of the number of such plastics previously mentioned. The layer of visco-elastic plastics is preferably in the form of a laminating foil.

It has been found that with a laminated safety pane according to the invention, the inner pane can break into particularly fine fragments which, when the pane is installed in a vehicle in the intended manner with said second, thinner pane facing inwardly, do not cause lacerations, with a considerable consequent reduction in the laceration index.The effect of a safety pane according to the invention, when installed in the intended manner in a vehicle with said second pane as the inner pane, particularly in those embodiments in which the strength of adhesion between the laminating foil and the inner pane is increased over the values of strength of adhesion normally achievable using laminating foils, is presumably due to the fact that as a result of the intimate connection to the laminating foil the inner pane is forced to share any bulging or bending deformation of the foil without becoming detached from the foil when some object, such as a human head, strikes the inner pane.The result is that a large number of closely spaced cracks or breakage lines are formed in the inner pane, i.e. the inner pane breaks into extremely fine fragments, since the inner pane is not able to bend to the same extent as the laminating material, particularly where, as is preferred, the laminating material is both resiliently and plastically deformable.

Embodiments of the invention are described below with reference to the accompanying drawings.

In the drawings: Fig. 1 is a diagrammatic cross-sectional view of a first form of laminated safety pane embodying the invention, and Fig. 2 is a diagrammatic cross-sectional view of a second form of laminated safety pane embodying the invention.

In the embodiment illustrated in Fig. 1 a laminated safety glass pane comprises a first silicate glass pane 10, a second silicate glass pane 12 and a laminating foil 14, for instance, of polyvinylbutyral, which glues the two silicate glass panes 10, 12 together.

The adhesion of the laminating foil 14 to the pane 12 is so adjusted that the adhesive strength is 6 Pummel units, while the adhesive strength of the connection between the pane 10 and the laminating foil 14 is 1-5 Pummel units.

The pane 12 is much thinner than the pane 10. The laminating foil 14 can be of a material capable of very high adhesion to untreated glass, the surface of the pane 10 which is adjacent the laminating foil 14 having been given an alkaline treatment during manufacture of the laminated pane, prior to lamination, in order to ensure that the strength of adhesion of the foil 14 to the pane 10 is less than to the pane 12. The said alkaline treatment of said surface may consist in washing it down with a suitable soap solution.Alternatively, if laminating foils capable only of a lesser adhesion to untreated glass are used, such as, for instance, polyvinylbutyral foils, preferably that surface of the pane 12 which is adjacent the laminating foil 14 has been treated in manufacture of the laminated safety pane and prior to lamination, in such a way as to ensure that the respective surface layer of pane 12 is impoverished in alkali and alkaline earth atoms. In this case the treatment may consist, for instance, in boiling the pane 12 in acidified water. Of course, a primer, which is added to the washing water, can also be applied to that surface of the pane 12 which is adjacent the laminating foil 14.

An adhesion increasing coating, more particularly an adhesion increasing primer, may be applied to the surface of the pane 12 adjacent the foil 14 before lamination is performed.

Fig. 2 shows a variant embodiment in which the laminating foil 14 of the embodiment illustrated in Fig. 1 is replaced by a double foil consisting of first foil 15 and second foil 16. The principle underlying this use of the double foil is to provide, in effect, a foil of which one surface is capable of adhering to glass with a greater strength than the other surface. This might, of course, be achieved by means other than the use of a double foil, but a double foil is a convenient means of achieving the desired effect. In the embodiment of Figure 2, the foil surface capable of high adhesive strength is provided by the foil 16, whilst the foil surface capable only of lower adhesive strength is provided by the foil 15.

The foil 15 can be made, for instance, of soft PVC, while the foil 16 can be made of a copolymer of vinylchloride and glycidyl methacrylate with a content of about 40% by weight of a high-molecular, non-migrating plasticizer which does not absorb water. Such a combination of foils increases the adhesion between the laminating foil and the glass. Moreover, a composite laminating foil consisting of a first foil 15 and second foil 16 for use in the embodiment illustrated in Figure 2 can of course either be obtained from foil suppliers or alternatively the foils 15 and 16 can be pressed and bonded together only during the laminating process. The laminating layer 14 can of course also be produced by pouring the respective plastics material in a liquid form, for example molten or in solution, onto the pane 10 or 12.

The embodiments of Figures 1 and 2 are intended for use as vehicle windscreens, intended to be fitted with the pane 12 presented towards the inside of the vehicle.

The invention can of course be applied to multi-layer laminated safety glass systems ---e.g. systems in which more than two silicate glass panes are interconnected by suitable laminating foils. In such a case the strength of adhesion of the pane which is intended to be presented to the interior of the vehicle, to the adjoining laminating foil, should be made greater than that of the other panes to the respective laminating foils so that the pane intended to be presented to the vehicle interior, and herein referred to as the innermost pane, is forced to share exactly in the bulging movement of the laminating foil nearest to the interior of the vehicle, so that the innermost pane breaks into a large number of very small fragments.

If desired, in all the embodiments described, a further layer of tough, soft plastics, preferably a self-repairing layer is disposed on that side of the pane 12 which is remote from the laminating foil 14 or 15, 16. This further reduces the risk of injury to the head of a person striking the laminated pane from the side to which pane 12 is presented. Plastics layers of this kind are disclosed, for instance, in German Offenlegungsschrift No. 2,228,299 and German Auslegeschrift No. 2,220,753, to which reference can be made for further details.

In embodiments of the invention, such as those described with reference to Figs.

1 and 2, in which two glass panes are bonded together by an interposed laminating layer of plastics, the adhesive strength of the connection between the thinner pane and the laminating layer is between 4 and 10 Pummel units, and preferably between 4 and 6 Pummel units, while the adhesive strength of the connection between the thicker pane and the laminating layer is between 1 and 2 Pummel units.

WHAT WE CLAIM IS: - 1. A laminated safety pane comprising a first silicate glass pane, a second, thinner silicate glass pane, and a laminating material which glues the two panes together, in which the adhesive strength of the connection between the second silicate glass pane and the laminating material is made substantially higher than that between the first silicate glass pane and the laminating material, the adhesive strength of the connection between the second silicate glass pane and the laminating material being 4-10

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. pane 10. The laminating foil 14 can be of a material capable of very high adhesion to untreated glass, the surface of the pane 10 which is adjacent the laminating foil 14 having been given an alkaline treatment during manufacture of the laminated pane, prior to lamination, in order to ensure that the strength of adhesion of the foil 14 to the pane 10 is less than to the pane 12. The said alkaline treatment of said surface may consist in washing it down with a suitable soap solution.Alternatively, if laminating foils capable only of a lesser adhesion to untreated glass are used, such as, for instance, polyvinylbutyral foils, preferably that surface of the pane 12 which is adjacent the laminating foil 14 has been treated in manufacture of the laminated safety pane and prior to lamination, in such a way as to ensure that the respective surface layer of pane 12 is impoverished in alkali and alkaline earth atoms. In this case the treatment may consist, for instance, in boiling the pane 12 in acidified water. Of course, a primer, which is added to the washing water, can also be applied to that surface of the pane 12 which is adjacent the laminating foil 14. An adhesion increasing coating, more particularly an adhesion increasing primer, may be applied to the surface of the pane 12 adjacent the foil 14 before lamination is performed. Fig. 2 shows a variant embodiment in which the laminating foil 14 of the embodiment illustrated in Fig. 1 is replaced by a double foil consisting of first foil 15 and second foil 16. The principle underlying this use of the double foil is to provide, in effect, a foil of which one surface is capable of adhering to glass with a greater strength than the other surface. This might, of course, be achieved by means other than the use of a double foil, but a double foil is a convenient means of achieving the desired effect. In the embodiment of Figure 2, the foil surface capable of high adhesive strength is provided by the foil 16, whilst the foil surface capable only of lower adhesive strength is provided by the foil 15. The foil 15 can be made, for instance, of soft PVC, while the foil 16 can be made of a copolymer of vinylchloride and glycidyl methacrylate with a content of about 40% by weight of a high-molecular, non-migrating plasticizer which does not absorb water. Such a combination of foils increases the adhesion between the laminating foil and the glass. Moreover, a composite laminating foil consisting of a first foil 15 and second foil 16 for use in the embodiment illustrated in Figure 2 can of course either be obtained from foil suppliers or alternatively the foils 15 and 16 can be pressed and bonded together only during the laminating process. The laminating layer 14 can of course also be produced by pouring the respective plastics material in a liquid form, for example molten or in solution, onto the pane 10 or 12. The embodiments of Figures 1 and 2 are intended for use as vehicle windscreens, intended to be fitted with the pane 12 presented towards the inside of the vehicle. The invention can of course be applied to multi-layer laminated safety glass systems ---e.g. systems in which more than two silicate glass panes are interconnected by suitable laminating foils. In such a case the strength of adhesion of the pane which is intended to be presented to the interior of the vehicle, to the adjoining laminating foil, should be made greater than that of the other panes to the respective laminating foils so that the pane intended to be presented to the vehicle interior, and herein referred to as the innermost pane, is forced to share exactly in the bulging movement of the laminating foil nearest to the interior of the vehicle, so that the innermost pane breaks into a large number of very small fragments. If desired, in all the embodiments described, a further layer of tough, soft plastics, preferably a self-repairing layer is disposed on that side of the pane 12 which is remote from the laminating foil 14 or 15, 16. This further reduces the risk of injury to the head of a person striking the laminated pane from the side to which pane 12 is presented. Plastics layers of this kind are disclosed, for instance, in German Offenlegungsschrift No. 2,228,299 and German Auslegeschrift No. 2,220,753, to which reference can be made for further details. In embodiments of the invention, such as those described with reference to Figs.

Pummel units and that of the connection between the first silicate glass pane and the laminating material being 1-2 Pummel units; and at least the second silicate glass pane being made of non-prestressed silicate glass.

2. A laminated safety pane as claimed in claim 1, in which said second silicate glass pane is at most 2 mm in thickness.

3. A laminated safety pane according to claim 2, in which the thickness of the second silicate glass pane is at most 1 mm and the thickness of the first silicate glass pane is at least 2 mm.

4. A laminated safety pane as claimed in any preceding claim, in which said laminating material is a layer of visco-elastic plastics selected from the group comprising polyvinylbutyral (PVB), polyvinylalcohol (PVA), polyurethane (PU), polycarbonate (PC) and polyvinylchloride (PVC).

5. A laminated safety pane as claimed in claim 4 in which the laminating material is a laminating foil.

6. A laminated safety pane as claimed in any preceding claim, in which the adhesive strength of the connection between said second silicate glass pane and said laminating material is 4-6 Pummel units.

7. A laminated safety pane as claimed in any preceding claim, in which the surface layer of said second silicate glass pane adjacent the laminating material is impoverished in alkali and alkaline earth atoms, to increase adhesive strength.

8. A laminated safety pane as claimed in claim 7, in which the surface layer of said second silicate glass pane adjacent said laminating material has been de-alkalized by treatment with hot acidified water.

9. A laminated safety pane as claimed in claim 5, or any of claims 6 to 8 when dependent thereon, which has been formed by a method including the step of applying adhesion-increasing primer to the surface of the second silicate glass pane destined to be adjacent said laminating foil, before the lamination is performed.

10. A laminated safety pane as claimed in claim 9, in which said second silicate glass pane has been treated with primercontaining washing solution, before the iamination has been performed.

11. A laminated safety pane as claimed in claim 5 or claim 6, in which said lamiting foil has one surface which is more strongly adhesive than its other surface, the surface of high adhesion being adjacent said second silicate glass pane.

12. A laminated safety pane as claimed in claim 11, in which said laminating foil comprises a first foil layer, adjacent said first silicate glass pane, and a second foil layer adjacent said second silicate glass pane, and a second foil layer being more strongly adhesive to glass than the first foil layer.

13. A laminated safety pane as claimed in claim 12, in which said first foil layer consists of soft PVC and said second foil layer consists of a copolymer of vinylchloride and glycidyl methacrylate with a content of about 40% by wt. of a high-molecular, non-migrating and non-water-absofb- ing plasticizer.

14. A laminated safety pane as claimed in claim 5 or claim 6 in which said laminanating foil is very strongly adhesive to untreated glass and wherein the surface of said first silicate glass pane adjacent the laminating foil has been treated to reduce its capability of being adhered to by plastics.

15. A laminated safety pane as claimed in claim 14, in which the surface of said first silicate glass pane adjacent the laminating foil has been treated with alkali, before the lamination is performed, to reduce its capability of being adhered to by plastics.

16. A laminated safety pane as claimed in claim 15, in which the surface of said first silicate glass pane adjacent said laminating woil has been pretreated with soap solution before the lamination is performed.

17. A laminated safety pane as claimed in any preceding claim including a tough, soft plastics layer disposed on the side of said second pane remote from said laminating foil.

18. A laminated safety pane as claimed in claim 17, in which said plastics layer is self-repairing.

19. A laminated safety pane substantially as hereinbefore described with reference to and as shown in Figure 1 of the accompanying drawings.

20. A laminated safety pane substantially as hereinbefore described with reference to and as shown in Figure 2 of the accompanying drawings.