FR2526011A1 - METHOD FOR MANUFACTURING A CURVED GLASS PLASTIC SHEET PANEL - Google Patents

Abstract

THE INVENTION CONCERNS A PROCESS FOR MANUFACTURING A CURVED GLASS-PLASTIC SHEET PANEL OF WHICH AN EXTERNAL SHEET IS IN THE FORM OF A SHEET OF PLASTIC 2. LAMINATION PRESSURE EXERCISED ON THE OUTSIDE OF THE PLASTIC SHEET 2 BY MEANS OF A TEMPERED GLASS MOLDING PLATE 3 WHOSE THICKNESS DOES NOT EXCEED 75 THICKNESS OF THE GLASS SHEET (s) 1. L THE INVENTION IS PARTICULARLY USEFUL IN THE MANUFACTURE OF HIGH-QUALITY OPTICAL WINDSHIELDS.

Description

The present invention relates to a method for producing

  of a laminated, curved glass-plastic panel, one of which is

  outside is formed of a sheet of plastic material.

  This form of laminated panels can be used, for example, as a windshield or vehicle rear window. Windshields of this type, in which the said plastic sheet is secured to the concave curved face of a sheet of

  glass, may have a combination of very desirable properties.

  They constitute an important protection measure for the occupants of vehicles against the laceration by fragments of glass in the event of rupture of the windshield, for example during the impact of the head of an occupant against the windscreen. laminated panels of this type are also of interest in other uses, for example as interior or exterior windows of buildings

and other constructions.

  Laminated panels of the type concerned by the pre-

  The present invention comprises panels consisting of only two sheets (excluding any tie layer) and panels consisting of three or more sheets. In such a laminated panel having three or more sheets, there may be two or more sheets of paper. plastic material, and in this case, each of the outer sheets of the laminated panel may consist of a sheet of

plastic material.

  In order to simplify the description, the invention will be

  introduced by reference to the manufacture of a laminated

  taking, with the exception of the bonding layer, only two sheets,

  one made of glass and the other of plastic.

  The sheets of plastic and glass may be secured by activation of the plastic sheet or by means of an intermediate layer of bonding material which may be applied in the form of a composition or a preformed sheet, for example a thin sheet of polyvinylbuty ra I or other thermoplastic material An adhesive or an adhesion promoter can be used to promote the bonding between the sheets of

plastic and glass.

  In the process of manufacturing the laminated panel, the assembled leaflets and any bonding material must be

  subjected for a certain time to conditions of solidarity.

  These conditions include the exposure of collated slips to

  a lamination pressure that is normally exerted by a fluid.

  The lamination pressure should be exerted so as to be distributed substantially uniformly over the surface of the laminated panel so as to ensure that there is no interior

  laminated panel of areas or sheets of glass and plastics

  tick are not or are not properly secured to each other.

  it is also important to avoid wrinkling or other deformities.

  The tendency for deformation to occur may result, for example, from a difference between the coefficients of thermal expansion of the glass and plastic sheets in the range of temperatures at which the panel is heated in the room. This type of trend can be marked when using a thin and very flexible sheet of

plastic material.

  Achieving the joining step so as to obtain a very high quality laminated panel has proved very difficult The quality standards that are required are particularly difficult to achieve if the plastic sheet in the laminated panel is a sheet transparency which has and which must keep in the laminated panel of high optical qualities so that this sheet does not distort the visual images of objects viewed through the

  These qualities are obviously of fundamental importance.

  tale in the windshields of vehicles.

  The difficulties encountered in the operation of solidarity

  have even led to proposing the manufacture of a two-leaf windshield by molding the plastic film in situ between the glass sheet and a glass molding plate or another

  subject matter (see US Pat. No. 3,509,015) However,

  For other reasons, it is preferable to use a preformed sheet of plastic material for the plastic sheet of the laminated panel. For the distribution of the fastening pressure on the plastic sheet it has been proposed to use a suitably curved glass molding plate so that during

  that the submitted sheets are subject to the conditions of

  the plastic sheet of the panel is sandwiched between two sheets of glass, one being the glass sheet that will be part of the laminated panel and the other being the molding plate, which

  then is removed after completion of the securing operation.

  Such a method is described in US Pat. No. 3,808,077, which relates to the manufacture of transparent laminated windows. In this patent, the importance of avoiding localized deformation of the sheet

  of plastic material during its exposure to heat and

  in the joining operation is underlined by the requirement that the glass molding plate must have a rigid polished surface whose shape matches that of the sheet of glass to be flipped. Furthermore, it is recommended in the patent that the plate the glass mold and the glass sheet to be approximately the same thickness so that since the temperature and pressure applied through the glass sheets on opposite sides of the plastic sheet vary during the lamination cycle ,

  the effect on the plastic sheet is approximately

  In the only example where the dimensions of the two glass sheets are given, each of them at approximately one-eighth of an inch (= 3.12 mm) As a variant, the glass molding plate can be subjected to a thermal tempering treatment that reinforces the plate without distortion or

deformation.

  The problem posed by the production of laminated glassplastic panels of high optical quality for use as a vehicle windshield is also described in French Patent No. 2,123,089. This patent also proposes the use of a curved glass molding plate for applying the pressure against the plastic sheet during the joining of this sheet to a curved glass sheet This patent recognizes the importance of a uniform distribution of pressure between the molding plate and the plastic sheet In the only example of implementation given in this patent, each of the two sheets of glass, that is to say the molding plate and said glass sheet, has a thickness of

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  3 mm and according to the general instructions given in the patent prebending of the molding plate is carried out by means of the same bending press that is used for bending the glass sheet which will be part of the laminated panel. is intended for the production of a molding plate whose curvature is the same

  to that of the glass sheet of the laminated panel.

  The use of a molding plate which has been curved according to a curvature corresponding to that of the glass sheet which will be part of the laminated panel is also described in the application

  British Patent No 80 37 713 filed on 25 November 1980 (published in

  No 2 074 090 (A) This request proposes simul-

  the two sheets of glass in one and the same bending operation, following the practice usually used to cover the two glass sheets of a glass-plastic-glass windshield.

traditional.

  Although it is desirable to avoid application on the

  sheet of plastic material of forces likely to cause its defor-

  In the process of laminating, the pursuit of this objective by measures previously proposed has not been satisfactory for the efficient production of laminated panels of structural uniformity required. In particular, these measures do not effectively guarantee the production of laminated panels having optical properties of sufficiently high level The laminated panels often have optical defects that have been found to be due to variations in the thickness of the plastic sheet and / or

  the state of its exposed face In the high quality laminated panels

  optical nature, the physical nature of the exposed face of the

  plastic material is uniform and substantially such on the whole

  its surface and this face usually has a shiny appearance.

lant or iced.

  The above problem occurs even if we take

  care to give the glass molding plate a corresponding curvature

  substantially to that of the glass sheet of the laminated panel The surface curvature given to a single sheet of glass by means of commercially available bending presses, or by means of a gravity bending process in which the sheet and is allowed to bend under its own weight until it comes into contact with a curved mold face, may differ more or less, depending on many factors, from the surface or forming surfaces of the mold (s) ( s) In general, this disparity can be sufficiently predetermined to allow it to be roughly compensated by choosing the curvature of the mold, but precise conformity to a predetermined curvature can not be obtained systematically. An indication of the nature of the problem discussed here is given in British Patent Application 2,074,090 A, already cited, which mentions that due to the poor reproducibility of the curved As obtained by commercially used bending presses, the curved glass molding plate intended for the manufacture of a given laminated panel must be rejected after its first use. As indicated above, this reproducibility problem exists. also when using a process

gravity bending.

  One of the objects of the present invention is to provide a method of manufacturing panels on an industrial scale.

  laminated glass-plastic laminated with good structural uniformity.

  In particular, one of the objects of the present invention is to provide curved glass-plastic laminated panels, for example

  vehicle windshields that are of high optical quality thanks to the uni-

  shape of the thickness and condition of the outer face of the plastic sheet Another object is to obtain this result in a way that is consistent with the use of one and the same

  molding plate in the production of different laminated panels.

  The basis of the invention is the discovery that flexibilities

  The relative strengths of the glass sheet of the laminated panel and the glass molding plate are an important factor influencing the qualities of the product mentioned above and this relative flexibility should be different from that recommended in the publications.

previous ones cited above.

  The present invention provides a method of manufacture

  a curved glass-plastic laminated panel including an outer sheet

  is formed of a sheet of plastic material, during which the said sheet of plastic material is subjected on the one hand, and one or

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  several curved glass sheets on the other hand, under certain conditions

  for fastening comprising an external laminating pressure

  part on the outside of such a sheet of plastic material by means of a glass molding plate which has a natural curvature corresponding substantially to that of said curved glass sheet (s) ( s), characterized in that said molding plate consists of a toughened glass sheet having a thickness equal to or less than 75% of the thickness or sum of the thicknesses of said sheet (s) ( s) glass

curved (s).

  When this method is used, products of a given high quality can be produced more reliably, this quality being estimated in terms of the state of the exposed face of the plastics sheet and the adjustment of that face to the curvature of the plastics material. the glass sheet to which such a sheet is secured, the last factor being indicative of the uniformity of thickness of the plastic sheet. It may appear that the disadvantage, in terms of result, of the prior methods as described above is caused wholly or partly by the use of a glass molding plate of thickness substantially equal to that of the glass sheet. of the laminated panel which is manufactured When using according to the invention a thinner and therefore more flexible molding plate, the mass production of laminated panels of very

  good optical quality is facilitated The use of a plate of mold

  lage which is substantially thinner than the glass sheet of the laminated panel or the set of glass sheets of the panel

  laminated according to the invention, is entirely compatible with a heater

  sufficiently uniform foliage of the plastic sheet to

  avoid any significant deformation of this sheet during the

e-court 7 e.

  In the case where the laminated panel to be manufactured comprises more than one sheet of glass, these sheets can be secured to one another, for example by means of an intermediate sheet of thermoplastic material, to form a subassembly. laminated prior to laminating these sheets to a plastic sheet forming an outer sheet of the laminated panel

  As a variant, said glass sheets can be solidari-

  to the other during the same step of the process as that o the plastic sheet for forming said outer sheet is secured to the neighboring glass sheet. Processes according to the invention are particularly suitable for the manufacture of curved windshields for vehicles and the invention comprises the manufacture of such a windshield by means of

of such a method.

  In preferred processes according to the invention, the molding plate has a thickness which does not exceed 50% of the thickness or the sum of the thicknesses of the said curved glass sheet (s). These conditions contribute especially to the production

  laminated panels of high optical quality.

  Preferably, the molding plate has a thickness which does not exceed 1.5 mm. The advantage of using such a very thin molding plate is that it requires very little force to make it conform, by bending to the profile. correct surface of the

  sheet of plastic material, compensating in this way

  Bending disparities Since the resistance to such an adjustment bending of the molding plate is very low, the plastic sheet must not possess a high resistance to deformation for

  avoid deterioration by localized or at least non-uniform pressure

  form which is temporarily exerted on it by the plate of mold

  During this adjustment bending, the molding plate preferably has a thickness of not more than 1.2 mm.

  In general, it is possible to use a casting plate

  is considerably lower than the values quoted.

  it is obviously desirable for the molding plate to be sufficiently

  resistant to breakage under suitable conditions of

  the plate is free of defects which could

  void the deformation of the plastic sheet against which the plate is pressed during the lamination process It will be

  generally desirable to use a molding plate whose thickness

  be not less than 0.7 mm.

  The best way to give the glass sheet that

  will form the molding plate a corresponding substantial curvature

  the glass sheet (s) is to bend these sheets of glass in one operation, that is, to bead them together, in face-to-face relation. a method which is common practice for bending glass sheets before incorporation into a laminated windshield

  glass-plastic-curved glass The best processes according to the in-

  in which this method of preparing the

  glass molding plate are claimed in claim 6.

  After its use in the manufacture of a first laminated panel, the molding plate can then be used in the manufacture of other laminated panels comprising glass sheets having a curvature similar to the glass sheet incorporated in said first laminated panel For example, the glass sheets of these other laminated panels may have been bowed by the same bending process, in the same bending press as the glass sheet of the first laminated panel Because, as has already been established, the bending processes used commercially do not allow the perfect reproduction of a given curvature of glass sheet, it is almost inevitable that, during its repetitive use, the glass molding plate has to undergo small

adjustment bends.

  When using a thin glass sheet for the molding plate, for example a sheet whose thickness does not exceed

  not 3 mm, the leaf must be chemically tren-

  The use of a well known chemical quenching process in which sodium ions from the surface layers of the glass are replaced at a temperature which is too low to allow the complete relaxation of the stresses in the glass to occur in the available time, by potassium ions from a medium of

  chemical quenching in contact with glass.

  The plastic sheet of the laminated panel,

  which is arranged against the molding plate in the soil operation -

  depending on its thickness) may be a flat sheet which is flexed under the lamination pressure in accordance with the curved glass sheet to which it is to be joined, a curved sheet, for example a sheet which has a corresponding natural curvature substantially to this glass sheet, or a relatively inconsistent thin sheet that adopts the curvature of

  any bearing surface on which it is deposited.

  The plastic sheet of the laminated panel may for example be composed of a material used for the sheet

  of plastic material of any known glass-plastic laminated panel.

  Various suitable plastics are mentioned in the

  Description of the British Patent Application No. 80 37 713 filed

  by the plaintiff on 25 November 1980 (Publication No. 0274 090 A)

  which description is incorporated herein by reference.

  The molding plate should obviously, under the conditions of joining, not to adhere to the plastic sheet of the laminated panel which is placed against the molding plate in the joining operation To avoid adhesion, the face of the plate molding that will face the sheet of material

  plastic laminate can be coated with an adhesion inhibitor

  The detachment of the molding plate from the laminated panel is facilitated if the molding plate is slightly larger than the laminated parcel, for example if the dimension of the plate is 1 or 2 mm larger than the laminated panel. of

  laminated panel in at least one direction.

  The actual joining operation may be carried out by any suitable method known per se in the art of making curved glass-plastic laminates, provided that it is compatible with the use of the thin-casting plate,

flexible, glass.

  Preferably, the joining operation comprises a step of application to the assembly formed by the sheets of the panel

  laminate and molding plate, an external sheet pressure

  and the application to the space or spaces between the sheets of a pressure lower than the atmospheric pressure during a step preparatory to the securing or the final solidarization of the sheets, in order to remove gases which could otherwise impair the Such lamination methods are known per se and examples are described in British Patent 1,368,785 and British Patent Application 80,337,713.

  In some known methods of lamination, the assem-

  The sheets of the panel to be joined are wrapped in a flexible envelope by means of which the external pressure can be transmitted as a laminating pressure to the assembly of the sheets. The envelope may partly form, or may comprise, a ring. seal which encloses the periphery of the assembly of the sheets so as to delimit with them a space in which gas can be evacuated by means of a pump so as to extract

  space gases / spaces between the sheets.

  The glass molding plate used in a method according to the invention can be part of the said envelope applied to

  the assembly of the sheets of the panel before the solidarisa-

  For example, the edge of such a plate may be attached to one of the two endless lips of a sealing ring, the other endless lip being able to make airtight contact with the opposite face.

assembly.

  In order to obtain high optical qualities, it is

  tageux to realize the method according to the invention by observing the process steps described and claimed in the patent application filed by the applicant on the same date as the present application and

  entitled "Method of manufacturing a laminated panel" and

  priority of British patent application No. 82 12 669

  of 30 04 1982 The description of this application is incorporated here

  As a reference Essentially, the steps of this method include exposing the assembly of the glass and plastic sheets to a lower edge pressure at atmospheric pressure to promote outgassing of spaces between them.

  sheets and heating the assembly while the main faces

  blades of the assembly are subjected to an external pressure at least equal to the atmospheric pressure and then, while

  the assembly is subjected to the external laminating pressure, the element

  providing said edge pressure to reduce or eliminate any difference between said edge pressure and said external pressure

  before the assembly reaches its maximum temperature.

  The heating of the assembly is then continued and the outer lamination pressure is maintained to complete the joining of the sheets of the panel. It has been found that the steps of the method avoid any tendency of the outer faces of the panel to be presented.

  a non-parallelism resulting from a creep of plastic material.

  The use of such process steps in combination with the relatively thin casting plate greatly favors the production of

  high quality laminated panels.

  Certain embodiments of the invention, chosen by way of example, will now be described with reference to the attached schematic drawing showing an assembly of sheets in progress.

  fastening to form a laminated panel.

  The drawing shows an autoclave in which is placed an assembly comprising a curved sheet 1 of vitreous material, a sheet of thermoplastic material 2, and a curved molding plate 3 The sheets 1, 2 and 3 are shown spaced apart from one another. other to indicate that they are not secured to each other They are actually arranged in contact with each other before

the solidarity operation.

  A flexible envelope 4 partially encloses the assembly.

  The envelope extends over the molding plate 3 and surrounds the edges of the assembled sheets and is provided with flexible peripheral endless lips such as those which rest against the

  exposed face of the vitreous sheet 1.

  This envelope delimits with the assembly of the sheets a space 6 surrounding the edges of the assembly A tube 7 is sealed to the peripheral wall of the envelope so that gas can be extracted from the space 6 and the space between sheets 1 and 2, via

  When the autoclave is closed, this tube extends out-

  The tube is connected to a pump (not shown) disposed outside the autoclave inside the autoclave through a wall of the autoclave, into which the tube is hermetically sealed.

  the autoclave is connected via a conduit 9 to a pump (not shown).

  The autoclave is provided with heating means (not shown).

  sented). To secure the glass sheet 1 and the sheet of thermoplastic material 2 to one another to form a two-layer laminated panel, these sheets are exposed for some time

  to a predetermined laminating heating and pressure program

  The gas is drawn from the space 6 to remove gas from the space between the sheets 1 and 2 and the assembly is then maintained for a certain time under conditions of autoclave temperature and pressure which cause the final joining of the sheets 1 and 2 to one another If desired, before heating the assembly to a temperature at which the sheet of thermoplastic material 2 will become solid with the glass sheet 1, one can suck gas of the interior of the autoclave so as to suppress or reduce the contact pressure between the sheets 1 and 2 and to facilitate the suction

of gas from between these leaves.

  The function of the molding plate 3 is to ensure that the thermoplastic sheet 2 is held over its entire surface under uniform pressure against the glass sheet 1 while the bonding occurs. The molding plate prevents wrinkling or locally localized sheet of thermoplastic material caused by thermal expansion variations of the sheets 1 or 2 or by other reasons According to the present invention, the molding plate 3 is formed of a tempered glass sheet having a thickness which born

  not exceed 75% c, and preferably not more than 50c, thick

  If the curvature of this plate 3 does not correspond perfectly to that of the glass sheet 1, the plate undergoes

  flexion with respect to sheet 1, under the external sheet pressure

  applied in the autoclave, until the difference in curvature disappears Leaf 1 retains its natural curvature during

laminating process.

  Preferably, the sheet 3 has a thickness of between 0.7 and 1.5 μm and preferably between 0.7 and 1.2 mm. A sheet of chemically tempered glass 1.5 mm thick or less offers little resistance to slight bending During the lamination pressure adjustment bends described above, the sheet 2 of thermoplastic material will not be deformed by non-uniformly distributed pressure applied to it, even if the thermoplastic material of this sheet is not very resistant to

25260 1 1

cold creep.

  The glass sheet 1 and the glass sheet intended to form the molding plate 3 can be curved to the desired curvature by a conventional bending process. For example, the two sheets, face-to-face assembled, can be heated, while are supported on two opposite edges of the assembly, at a temperature sufficient to bend the sheets under their own weight until the bottom sheet conforms in surface conformity with the convex surface of an underlying mold, and then

  cooled to freeze the imparted curvature.

  After the bending operation, the glass sheets are removed from the bending station and separated and the glass sheet

  curved 3 can then be subjected to a chemical quenching treatment.

  It will be noted that a laminated panel comprising additional sheets to the sheets 1 and 2 may be similarly formed. By way of example, a laminated panel may be formed in which a laminated subassembly comprising two glass sheets and an intermediate bonding layer , the latter being formed by a preformed sheet or film of material

  thermoplastic, is used in place of the single sheet of glass 1.

  To form a laminated panel in which each of the exposed leaflets is a plastic sheet, for example to form a laminated plastic-glass-plastic panel, a molding plate comprising a thin sheet of glass may be used

  quenched according to the present invention, on both sides of the

appearance of the sheets of the panel.

  Examples of methods according to the invention follow

Example 1

  A laminated vehicle windshield is formed from a 3mm thick float glass sheet and a sheet

  polyurethane (marketed by Bayer) 0.6 mm thick.

  The float glass sheet is curved to the desired curvature by a conventional gravity bending method as described above, the bending direction being such that the air side face of the float glass (i.e. face exposed to the atmosphere in the float tank) becomes concave To perform the process of

252601 1

  laminating, a glass molding plate is prepared by bending a stretched glass sheet 1.2 mm thick, having edges

  rounded, by the same method and with the same installation of

  bage than that used to bend the float glass sheet, and by quenching the curved sheet for 24 hours in a bath of KNO 3 at a temperature of 465 ° C The stretched glass sheet used to make the casting plate is of the same dimensions

  in length and width than the sheets of glass and plastic material

tick to be assembled by lamination.

  Comparison of 3 mm curved glass sheets

  and 1, 2 mm shows that they have a difference in curvature.

  When the sheets are supported at their opposite ends in superposition, their convex faces facing down, there is a

  gap of 3 mm between the leaves at their central transverse axis.

  The prepared molding plate is coated on its convex side with dimethyldichlorosilane to prevent its adhesion to the polyurethane and the concave face of the 3 mm glass sheet is spray-coated with an aminosilane bonding solution in isopropyl alcohol. The sheets of glass and plastic material to be assembled by laminating are then assembled with the polyurethane sheet sandwiched between the two glass sheets and the assembly is subjected to a program of heat and external pressure of fluid as used. in example 2 of British Patent Application 2,074,090 A. At the end of the lamination operation, the molding plate is removed and the laminated windshield is examined. It is found that the exposed face of the foil is plastic material corresponds to

  very precisely to the theoretical curvature determined by the court

  of the glass sheet and the thickness of the sheet of plastic

  It is found that the exposed face of the plastic sheet is uniformly smooth and shiny over the entire surface of the laminated panel. Therefore, the laminated panel is of high

optical quality.

Example 2

  In this example, components and processes identical to those used in Example 1 are used, except that the molding plate is formed from a drawn glass sheet having a thickness of 0.8 mm instead of 1, 2 mm Comparison of the float glass sheet and the molding plate after bending

  shows that there is a difference between their final curvatures.

  of curvature, measured before the lamination step of the same

  as in Example 1, is 5 mm.

  we look at the panel We find that it has an optical quality

  comparable to that of the laminated panel produced according to Example 1.

Example 3

  A vehicle windshield is laminated with a 2 mm thick drawn glass sheet and a 1 mm thick sheet of ASTRAGLAS (Trade Mark) which is a plasticized polyvinyl chloride supplied by Dynamit Nobel The glass sheet is curved to the desired curvature by a method of gravity bending as described above For use in the lamination process, a bending molding plate is prepared

  a stretched glass sheet 1, 5 mm thick, with rounded edges.

  The <Ipi'x fevilles of glass are, in this example, curved together,

  in one operation, that is, in a face-to-face relationship.

  bending ration, the 1.5 mm thick glass molding plate

  is chemically quenched by the same chemical quenching process

  than that used in Example 1.

  The comparison of the curved glass sheets of 2 mm and 1.5 mm shows that there is a difference of 1 mm between their

  curvatures, the difference being measured as in Example 1.

  The 2 mm thick curved sheet is laminated to the PVC sheet by applying heat and pressure, the pressure being transmitted to the PVC sheet by the plate

glass molding.

  At the end of the lamination operation, it is found that the exposed face of the PVC sheet is uniformly smooth and glossy and the sheet has a uniform thickness, the geometric profile of its exposed face being in good compliance with the theoretical curvature determined by its thickness before lamination and by the curvature of the

glass sheet.

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  Example 4 (Comparative) Example 3 was repeated except that a 2 mm thick stretched glass sheet was used instead of a 1.5 mm thick glass sheet to make the molding plate. After the chemical quenching of the glass sheet to be used as a

  molding, we compare the curvatures of the two sheets of glass.

  between them, measured as in Example 1, is 1 mm,

than in Example 3.

  After the foliation operation, we examine the

  The outside of the plastic sheet is not uniform

  glossy and glossy memento In the surface of this face are areas where the face is more or less dull, as the surface of the face

  plastic sheet before the lamination step.

* Example 5

  A windshield is formed by joining the concave surface to a laminated, curved, preformed glass-plastic-glass panel to a polyurethane sheet. The preformed panel comprises a curved float glass sheet 2, 6 mm thick secured by its concave face to the convex face of a 1.5 mm thick stretched glass sheet by means of a 0.6 mm thick polyurethane layer. The concave face of this preformed panel is assembled by lamination, by a process according to the invention, to a polyurethane sheet 0.6 mm thick In this lamination step a molding plate formed by a sheet is used

  curved glass 2 mm thick, which has been tempered

  By this method, the curvature of the molding plate is compared with that of the inner glass sheet (1.5 mm thick) of the preformed panel. Curvature -measured as

in Example 1, is about 1 mm.

  After the lamination operation of the preformed panel

  to the polyurethane sheet, we examine the windshield thus formed.

  It is found that the geometric profile of the exposed face of the

  polyurethane is in all parallel regions (within tolerances of

  rance very low; to that of the concave face of the neighboring stretched glass sheet and the laminated panel has a high optical quality in terms of absence of distortion effect on objects viewed

through the laminated panel.

Claims (8)

  A method of manufacturing a curved glass-plastic laminated panel, an outer sheet of which is formed of a sheet (2) of plastic material, during which the said sheet (2) of plastic material is subjected, on the one hand, and one or more curved glass sheets (1) on the other hand, at conditions of solidification comprising an external laminating pressure distributed on the outer face of such a sheet (2) of plastics material by means of a glass molding plate (3) which has a natural curvature corresponding substantially to that of said curved glass sheet (s), characterized in that said molding plate (3) consists of a toughened glass sheet having a thickness equal to or less than 75% of the thickness or the sum   thicknesses of the said curved glass sheet (s) (1).   2 Process according to claim 1 characterized in that the molding plate (3) has a thickness that does not exceed% of the thickness or the sum of the thicknesses of the said (s)   curved glass sheet (s) (1).   Process according to Claim 1 or 2, characterized in that the molding plate (3) has a thickness which does not exceed 1.5 mm.   4 Process according to claim 3, characterized in that the molding plate (3) has a thickness which does not exceed 1.2 mm.   Method according to one of claims 1 to 4,   characterized in that the assembly comprising the glass sheet (s) (1) and the plastic sheet (2) is subjected to a pressure lower than the atmospheric pressure on its edges to promote the degassing of the space (s) intermediate between the leaves and   the assembly is heated while its main faces are   at an external pressure at least equal to atmospheric pressure   and while the assembly is subjected to the outer lamination pressure, the edge pressure is high, to reduce or eliminate any difference between said edge pressure and said outer lamination pressure before the assembly reaches its maximum temperature, the heating of the assembly being then continued and the outer pressure of lamination being maintained   to complete the solidarization of the sheets.   6 Process for the production of a curved glass-plastic laminated panel, an outer sheet of which is formed from a sheet (2) of plastics material, characterized in that one or more glass sheets (1) are used to form curved glass sheet (s) of the laminated glass-plastic panel,   takes as a molding plate (3), an additional glass sheet   with a thickness not exceeding 75; of the thickness or sum of the thicknesses of the glass sheet or sheets, the said sheet (s) of glass and the said additional sheet of glass arranged face-to-face are subjected to one operation. of bending which gives to this or these sheet (s) of glass a permanent curvature corresponding to that desired for the sheet (s) of glass of the laminated panel and which simultaneously gives a curvature   permanent like the extra glass sheet, soak -   said additional sheet and subjecting the plastic sheet (2) on the one hand and said one or more curved glass sheet (s) on the other hand to conditions of joining comprising an external pressure of lamination, while the said additional glass sheet curved   is placed against the said plastic sheet so as to serve as   molding material (3) which distributes the laminating pressure on the outer face.   wall of said plastic sheet (2).   7 Process according to claim 6, characterized in that several sheets intended to form sheets of the laminated panel are curved together during the bending operation and these sheets are joined together in the form of a laminated sub-assembly before their solidarity with the so-called plastic sheet.   8 Process for the production of glass-plastic laminated panels, each of which is curved beforehand with an outer sheet formed of a sheet of plastics material (2), characterized in that a first laminated panel is produced according to a process according to a method   Claims 1 to 7 and the molding plate (3) used in this   process is then used to manufacture, by a similar process,   a second curved glass-plastic laminated panel.   Process according to one of claims 1 to 8,   characterized in that the curved glass-plastic laminated panel formed is a vehicle windshield.