JPH0446750B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing curved glass-plastic laminates in which a sheet of plastic material forms the outer layer.

Laminated bodies of this type are used, for example, as windshields or rear lights of automobiles. Windshields of this type, in which the plastic layer is bonded to the concave curved side of the glass layer, have a very desirable combination of properties.
They provide an important means of protecting the occupant from being lacerated by glass fragments when the windshield is broken, for example when the occupant's head hits the glass window. Laminates of this type also have potential value for other purposes, such as interior or exterior windows in buildings or other structures.

Laminates according to the invention include laminates with only two layers (excluding the adhesive layer) and laminates with three or more such layers. It is also possible to have two or more plastic layers in a three or more layer laminate, with each outer layer of the laminate being formed from a plastic sheet.

To simplify the explanation, the adhesive layer is not included below.
The invention will be described with respect to the production of a laminate with only two layers, one of glass and one of plastic.

The plastic and glass layers of such a laminate may be joined by activating the plastic layer or an intermediate adhesive material applied as a prefabricated layer or composition, such as a thin sheet of polyvinyl butyral or other thermoplastic material. Integrated by layers. Adhesives or adhesion promoters can be used to promote bonding of the plastic and glass layers.

The method of forming the laminate requires that the assembled layers and adhesive material be exposed to bonding conditions for a certain period of time. These conditions include subjecting the assembled layers to lamination pressure, typically created by a liquid environment. This lamination pressure must be applied to be substantially uniformly distributed over the entire area of the laminate to ensure that there are no areas of the laminate where the glass and plastic layers are not bonded or are not properly bonded. It is also important to prevent wrinkles or other deformation of the plastic layer. The tendency for deformation may arise, for example, from differences in the coefficients of thermal expansion of the glass and plastic layers over the temperature range in which the assembly is heated during the bonding process. This tendency is most pronounced when using thin and highly flexible plastic layers.

It has proven extremely difficult to carry out the bonding process in such a way as to obtain a laminate of very high quality. The quality standards required for the plastic layers of the laminate to retain high optical properties so that objects do not appear distorted when viewed through the laminate are particularly difficult to achieve. These qualities are, of course, fundamentally important in the case of automobile windshields.

Because of the difficulties in this joining operation, it has been proposed to create a two-layer windshield by casting a plastic layer in-situ between the glass layer and a mold made of glass or other materials ( (See U.S. Pat. No. 3,509,015). However, for convenience and other reasons, it is preferred to use preformed sheets of plastic for the plastic layer of the laminate.

In order to spread the bonding pressure over the entire plastic layer, a suitably curved glass forming plate (hereinafter also referred to as glass forming plate) is used to ensure that the plastic layers of the laminate are It is proposed to be sandwiched between two glass layers, one of which forms part of the laminate and the other a molded plate of glass that is removed after the bonding operation is completed. There is. Such a method is described in US Pat. No. 3,808,077, which relates to the production of transparent laminated glazing. The patent emphasizes the importance of avoiding local distortion of the plastic layer during exposure to heat and pressure during bonding operations, and the glass forming plate is a smooth, hard surface whose shape is similar to that of the glass sheets to be laminated. This is emphasized by the requirement that they must match. The patent also states that the glass forming plates and the glass sheets to be laminated are approximately the same thickness, and that when the temperature and pressure applied to both sides of the plastic sheet through the group of glass sheets varies during the lamination cycle, the effect on the plastic sheet is It is recommended that it be approximately uniform throughout.
In the only example where dimensions are given for two glass sheets, each glass sheet is approximately 1/2
It is 8 inches (3.12mm). It is stated that a glass molded plate may be subjected to chemical strengthening treatment to strengthen it without distorting its shape.

The problem of producing glass/plastic laminates with high optical properties for use as automobile windshields is also described in French Patent No. 2,123,089. The patent also suggests using a curved glass forming plate to apply pressure to the plastic layer while bonding the plastic layer to the curved glass layer. The patent recognizes the importance of uniform distribution of pressure between the forming plate and the plastic layer. In the embodiment of the patent, the two glass sheets, the molded plate and the glass layer each have a thickness of 3 mm.
The preliminary bending of the formed plate was carried out in accordance with the general instructions given in that patent using the same bending press used for the bending operation of the glass sheets forming part of the laminate. There is. This method aims to produce a shaped plate with the same curvature as that of the glass layer of the laminate.

The use of shaped plates bent to a curvature that corresponds to the curvature of the glass sheets forming part of the laminate is also disclosed in British patent application no.
It is also described in No. 8037713 (Public Notice No. 2074090A). In the patent application, two glass sheets are bent as if they were one sheet in a single bending operation, following the method normally used for bending two glass sheets in conventional glass-plastic-glass windshields. It is proposed that.

Although it is desirable to avoid applying forces that could cause distortion of plastic sheets during the lamination process, attempts to accomplish this goal with previously proposed methods have not produced laminates with the desired standard of structural uniformity. Satisfactory results were not obtained for reliable manufacturing. In particular, it has not been possible to reliably produce a laminate with sufficiently high optical properties using these methods. It has been found that laminates often have optical defects, which are due to variations in the thickness of the plastic sheet and/or the conditions of its exposed surfaces. In a laminate having a high optical quality, the physical properties of the exposed surface of the plastic sheet are uniform or substantially uniform over its entire area, and such surface usually has a uniformly shiny or glossy appearance. There is.

The above-mentioned problems occur even when efforts are made to provide the glass forming plate with a curvature that substantially corresponds to the curvature of the glass sheets of the laminate. The surface curvature imparted to a single glass sheet by commercially available bending presses or by gravity bending methods in which the sheet is heated and allowed to sag under its own weight into contact with a curved die surface depends on many factors. The surface of the group is different from that of the group. In general, this discrepancy can be planned well enough to be approximately compensated for in selecting the die curvature, but it is not always possible to exactly match the planned curvature. Some description of the nature of the problem discussed here can be found in British Patent Application Publication No. 2074090A, which states that the reproducibility of curvature imparted by bending presses in industrial use is poor; It is stated that glass molded plates bent for use in the production of specific laminates are discarded after the first use. As mentioned above, this reproducibility problem also exists when using the gravity bending method.

One of the objects of the invention is to provide a method by which curved glass-plastic laminates of good structural uniformity can be produced on an industrial scale. In particular, it is an object of the present invention to provide a curved glass-plastic laminate, such as an automobile windshield, which has good optical properties due to the uniformity of the thickness and the condition of the outer surface of the plastic layer. Another object of the invention is to achieve this result in a manner compatible with the use of one and the same molded plate for the production of various laminates.

The basis of the present invention is that the relative flexibility of the laminated glass sheet and the forming plate made of glass is an important factor influencing the above-mentioned product quality, and that this relative flexibility is an important factor influencing the above-mentioned product quality. The discovery is that the flexibility should be different from that recommended in previous literature.

According to the invention, the plastic sheet on the one hand and the curved glass layer or layers on the other hand are subjected to bonding conditions including an external lamination pressure, provided that said pressure is dependent on the curvature of said curved glass layer or layers. A method of forming a curved glass-plastic laminate having an outer layer formed of a sheet of plastic material by distributing the entire outside of said plastic sheet with glass forming plates having substantially corresponding natural curvature, the method comprising: A method is provided, characterized in that the shaped plate is a tempered glass sheet having a thickness not exceeding 75% of the thickness of the curved glass layer or the total thickness of the curved glass layers.

When this method is carried out, a high quality product is produced with great reliability, which quality depends on the condition of the exposed surface of the plastic sheet and its curvature approximating that of the glass layer to which it is bonded. This latter factor indicates the uniformity of the thickness of the plastic sheet.

The disadvantages seen in the results of the conventional method described above appear to be due, in whole or in part, to the use of a formed glass plate having substantially the same thickness as the glass layer of the laminate sheet being manufactured. The use of thinner and therefore more flexible molded plates according to the invention facilitates the continuous production of laminates with very good optical properties. The use according to the invention of a molded plate that is substantially thinner than the glass layer or combination of glass layers is very compatible with sufficiently uniform heating of the plastic layer and avoids significant distortion thereof during the lamination process. .

If the laminate to be produced has more than one glass layer, these layers may be adhered to form a prelaminate, for example by means of a thermoplastic intermediate sheet, before being laminated to the plastic sheet constituting the outer layer of the final laminate. Can be done. Alternatively, the glass layers can be bonded in the same process step as is used to bond the plastic sheet to the adjacent glass layer to form the outer layer.

The method of the present invention is particularly suitable for manufacturing curved automobile windshields, and the present invention encompasses manufacturing such windshields by any such method.

In a preferred method of the invention, the glass shaped plate has a thickness not exceeding 50% of the thickness of the glass layer or the total thickness of the group of glass layers. This condition is particularly favorable for the production of laminates with high optical properties.

Preferably, the glass shaped plate (hereinafter simply referred to as shaped plate) has a thickness of not more than 1.5 mm. The advantage of using such a very thin formed sheet is that very little force is required to flex and conform it to the exact surface profile of the plastic sheet, thus compensating for small discrepancies in curvature. . Since the resistance to the deflection adjustment of the forming plate is very low, it is necessary to prevent the plastic sheet from being damaged by localized or at least non-uniform pressures temporarily exerted by the forming plate during this deflection adjustment. There is no need for the sheet to have a high degree of deflection resistance.
Most preferably, the thickness of the molded plate is not more than 1.2 mm. In general, molded plates with thicknesses well below the specified values can be used.
However, it is clearly desirable that the shaped plate be sufficiently resistant to breakage under easy handling conditions and that it be free of defects that would cause distortion of the plastic sheet pressed against it during the lamination process. It is generally recommended to use molded plates with a thickness not less than 0.7 mm.

The best way to give the glass sheets from which the shaped sheet is to have a curvature that substantially corresponds to the curvature of the glass layer or layers is to bend the glass sheets as one, ie, together in face-to-face relationship. This effectively means employing the methods commonly used to pre-bend the glass sheets prior to their incorporation into curved glass-plastic-glass laminated windshields. A preferred method of the invention using this method for making shaped glass sheets is claimed in claim 6.

After being used to produce a first laminate, this molded plate can be used to produce other laminates having glass sheets of the same curvature as those incorporated in the first laminate. The glass sheets of these other laminates may be bent, for example, by the same bending method and with the same bending press as the glass sheets of the first laminate. As already mentioned, the bending methods used in industry cannot perfectly reproduce a fixed glass sheet curvature, so slight adjustments in deflection must be made with the glass forming plate during repeated use. I can hardly avoid it.

Use a thin glass sheet as a molding plate, e.g. 3mm thick.
When using the following sheets, this sheet must be chemically strengthened. Chemical strengthening, known per se, in which the sodium ions in the surface layer of the glass are replaced by potassium ions resulting from contact with a chemical strengthening medium at temperatures too low to cause complete stress relaxation in the glass within a useful time. Preferably, the method is used.

The plastic laminate sheet that comes next to the forming plate in the bonding operation is (due to its thickness) an inherently flat sheet which is bent under the bonding pressure to follow the curved glass layer to be bonded.
It can be an inherently curved sheet, such as a sheet with an inherent curvature that substantially corresponds to the glass layer, or a thin, relatively brittle sheet that is the same as the curvature of the supporting surface on which it rests.

The plastic laminate sheet can be comprised of a plastic composition used as a plastic sheet in any known glass-plastic laminate. Various plastics are made by the applicant.
UK Patent Application No. 25 November 1980
No. 8037713, and these are preferably used.

The formed plate must of course be non-adhesive under bonding conditions to the plastic laminate sheet located adjacent to the formed plate in the bonding operation. To prevent adhesion, the side of the molded plate facing the plastic sheet can be coated with an anti-adhesion agent, such as a silicone-functional silane. Removal of the molded plate from the laminate is facilitated if the molded plate is somewhat larger than the laminate, for example 1 to 2 mm larger in at least one direction than the dimensions of the laminate.

The actual bonding operation is carried out using any suitable method known in the art for manufacturing curved glass-plastic laminates, as long as the use of thin flexible glass forming plates is possible.

The bonding operation preferably includes the steps of bonding the assembled laminate layer sheet group and the molded plate and exposing them to external pressure, and also includes a step before bonding or complete bonding of each of these layers to remove gases that may interfere with bonding. It involves exposing the interlayer space or spaces to a pressure below atmospheric pressure. This type of lamination method itself is well known, and an actual example is British Patent No. 1368785,
Described in UK Patent Application No. 8037713.

In some known lamination methods, the combination of laminate layers to be bonded is surrounded by a deformable cavity through which external pressure is transmitted as lamination pressure to the layer assembly. This enclosure forms part of or surrounds the sealing ring, and this ring surrounds the assembly;
At the same time, a certain space is defined, through which gas is exhausted by a pump and gas from between the layers is suctioned and removed.

The glass forming plates used in the method of the invention may form part of the enclosure applied to the combination of laminate sheets prior to the bonding operation. For example, the edges of such a plate may be secured to one of the two endless lips of the sealing ring, the other endless lip being brought into airtight sealing contact with the opposite side of the assembly.

In order to obtain high optical properties, it is advantageous to carry out the process according to the invention according to the following process steps. The processing steps include exposing the combination of glass and plastic layers to a sub-atmospheric edge pressure to promote degassing of the interlayer spaces, heating the combination while exposing the main surfaces of the combination to at least extra-atmospheric pressure, and then While laminating the combined body and exposing it to external pressure,
It consists of the step of increasing the edge pressure until the combination reaches its maximum temperature to reduce or eliminate the difference between the edge pressure and the external bonding pressure. Thereafter, the combined body is continued to be heated, and the bonding external pressure is maintained to complete the bonding of each layer of the laminate. These processing steps have been found to counteract the tendency for the outer surfaces of the laminate to become non-parallel at its edges as a result of plastic flow.
The use of such a process in combination with relatively thin molded plates is extremely advantageous for producing laminates of good quality.

Specific examples of the present invention will be described below with reference to the drawings.

The figure shows an autoclave in which a combination consisting of a curved vitreous sheet 1, a thermoplastic sheet 2 and a curved glass molded plate 3 is positioned. Sheets 1, 2 and 3 are shown separated to show that they are not joined. In fact, they are placed in contact with each other before the joining operation. A flexible enclosure 4 partially encloses the sheet combination. This enclosure has an endless flexible peripheral lip 5 extending over the forming plate 3, around the edges of the composite sheet, and touching the exposed surface of the vitreous sheet 1.

This enclosure defines, with the sheet assembly, a space 6 surrounding the edges of the assembly. A tube 7 is hermetically inserted into the peripheral wall of the enclosure, through which gas is exhausted from the space 6 and from between the sheets 1 and 2. When the autoclave is closed, this tube extends out through the wall of the autoclave and is seated in a gas-tight manner against said wall. The tube is connected to a pump (not shown) outside the autoclave. The interior 8 of the autoclave is connected by a conduit 9 to a pump (not shown). The autoclave is equipped with heating means (not shown).

To bond glass sheet 1 and thermoplastic sheet 2 to form a two-layer laminate, these sheets are exposed to a predetermined heating and lamination pressure schedule for a certain period of time. Gas is drawn from space 6 to remove gas from between sheets 1 and 2, and the assembly is then held for a period of time under temperature and autoclave pressure conditions in which sheets 1 and 2 are firmly joined.
If desired, the contact pressure between sheets 1 and 2 is removed or reduced by drawing gas from the interior 8 of the autoclave prior to heating the assembly to a temperature at which thermoplastic sheet 2 joins glass sheet 1. gas can be easily sucked between the sheets.

The function of the forming plate 3 is to ensure that the thermoplastic sheet 2 is pressed and held under uniform pressure against the glass sheet 1 over its entire area during the bonding process. Forming plate 3 is sheet 1 or 2
This prevents local wrinkling or distortion of the thermoplastic sheet due to differences in thermal expansion.

According to the invention, the molded plate 3 has a thickness of 75
%, preferably not more than 50% thick. If the curvature of the formed plate 3 does not perfectly match the curvature of the glass sheet 1, under the external bonding pressure applied in the autoclave, the formed plate 3 will sag with respect to the sheet 1 until the curvature mismatch disappears. Become. Sheet 1 retains its natural curvature during the lamination process.

Preferably, the thickness of the molded plate 3 is 0.7 to 1.5 mm, most preferably 0.7 to 1.2 mm. Chemically strengthened glass sheets with a thickness of 1.5 mm or less exhibit negligible resistance to slight deflections. During the adjustment of deflection under lamination pressure as described above, even if the plastic sheet does not have much resistance to cold flow, it will not deform under the unevenly distributed pressure applied thereon.

The glass sheets making up the glass sheet 1 and the shaped plate 3 are bent to the desired curvature by conventional bending methods.
For example, by combining two sheets face-to-face and supporting them by the two exposed edges of the combination, the sheets are allowed to move under their own weight until the bottom sheet is flush with the concave surface of the underlying die. It is heated to a temperature sufficient to cause it to sag and then cooled to freeze its curvature.

Following the bending operation, the group of glass sheets is removed from the bending station and the tensile curved glass sheet 3 is then subjected to a chemical strengthening treatment.

Laminates with layers other than sheets 1 and 2 are made in a similar manner. For example, a prelaminate consisting of two glass sheets and an intermediate adhesive layer consisting of a prefabricated thermoplastic sheet or film can be used instead of the glass sheet 1.

To make a laminate, such as a plastic-glass-plastic laminate, in which each exposed layer is a plastic sheet, molded plates of thin sheets of tempered glass according to the invention are utilized on both sides of the assembled laminate.

The present invention will be explained below with reference to Examples.

Example 1 A flat sheet of float glass 3 mm thick and polyurethane 0.6 mm thick (commercially available from Bayer)
made laminated car windshields from the sheets. The float glass sheet was bent to the desired curvature using conventional weight bending techniques. The bending direction was such that the air side of the float glass (that is, the side exposed to the atmosphere in the float tank) was concave. For use in the lamination process, 1.2 mm thick mechanically drawn glass with rounded edges is bent in the same manner and with the same bending equipment used to bend float glass sheets to form curved sheets.
It was chemically strengthened by soaking it in KNO ₃ bath at 465℃ for 24 hours to make a glass molded plate. The mechanically drawn glass sheets used to make the shaped sheets were of the same length and width dimensions as the glass and plastic sheets to be laminated.

When comparing 3mm and 1.2mm curved glass sheets, the curvatures did not match. There was a 3 mm gap at the lateral centerline between the sheets when they were held in an overlapping relationship with their opposing ends concave side down.

Dimethyl-dichlorosilane was applied to the convex side of the resulting molded plate to prevent adhesion to polyurethane, and an isopropyl alcohol solution of aminosilane (primer solution) was sprayed on the concave side of the 3 mm glass sheet. The glass and plastic sheets to be laminated were combined in such a way that the polyurethane sheet was sandwiched between the two glass sheets, and the combination was prepared in a similar manner to that used in Example 2 of GB 2074090A. It was subjected to a lamination heating and environmental hydraulic schedule.

After completion of lamination, the molded plates were removed and the laminated windshield was tested.

Once the laminate was obtained, the molded plate was removed and the windshield was examined. It has been found that the exposed surface of the plastic sheet corresponds almost exactly to the theoretical curvature determined by the curvature of the glass sheet and the thickness of the plastic sheet. The exposed surface of the plastic sheet was found to be uniformly smooth and shiny throughout the laminate. From these points, this laminate was of high optical quality.

Example 2 In this example the same components and methods as used in Example 1 were used except that the shaped plate was made from a 0.8 mm machine drawn glass sheet instead of 1.2 mm thick. When comparing the float glass sheet and the molded plate after bending, there was a difference in their final curvature. The difference in curvature when measured before the lamination process using the same method as in Example 1 was 5 mm. After the lamination process, the laminate was examined. It was found that the optical quality was comparable to that of Example 1.

Example 3 A 2 mm thick mechanically drawn glass sheet is made into a 1 mm thick sheet.
An automobile windshield was made by laminating it on a sheet of Astra Glass (registered trademark, plasticized polyvinyl chloride, manufactured by Dynamite Nobel). The glass sheet was bent to a predetermined curvature using the gravity bending method described above. Since it is used for lamination, the thickness
A shaped plate was made by bending a mechanically drawn glass sheet with a 1.5 mm round edge. In this example, the two glass sheets were bent together in a face-to-face relationship.
Following the bending operation, the 1.5 mm forming glass plate was strengthened using the same chemical strengthening method used in Example 1.

Comparing the curved glass sheets of 2 mm and 1.5 mm, the curvatures were measured in the same manner as in Example 1 and their curvatures were 1.
A difference of mm was observed.

A curved 2mm glass sheet is attached to a PVC sheet under heat and pressure, and at this time the pressure is applied by a glass forming plate.
Transmitted to PVC sheet.

After lamination, the exposed surface of the PVC sheet is uniformly smooth or shiny, with uniform thickness, and the geometric profile of the exposed surface is theoretically determined by the thickness before lamination and the curvature of the glass sheet. It was observed that the curvature was in very good agreement.

Comparative Example 1 Example 3 was repeated. However, instead of the 1.5 mm thick glass sheet, a 2 mm thick mechanically drawn glass sheet was used to make the molded plate. After chemically strengthening a 2 mm glass sheet to be used as a forming plate, the curvatures of the two glass sheets were compared. Measurements were made in the same manner as in Example 1, and the difference therebetween was 1 mm, as in Example 3.

I inspected this windshield after laminating it. The outer surface of the plastic sheet was not uniformly shiny and glossy. In this area, a matte or nearly matte area was observed, similar to the surface of the plastic sheet before the lamination process.

Example 4 A windshield was fabricated by bonding the concave surface of a prefabricated curved glass-plastic-glass laminate to a polyurethane sheet. The preformed laminate is made of a 2.6 mm thick curved float glass sheet with a 0.6 mm thick polyurethane intermediate layer interposed on the concave side.
It was made by joining the convex sides of 1.5 mm mechanically drawn glass curved sheets. A polyurethane sheet having a thickness of 0.6 mm was laminated to the concave side of this preformed laminate using the method of the present invention. In this lamination process, the thickness
A molded plate made of a 2.0 mm mechanically drawn glass curved sheet and chemically strengthened by the method of Example 1 was used.
Prior to this lamination step, the curvature of the formed plate was compared to the curvature of the inner (1.5 mm) glass sheet of the preformed laminate. Measured as in Example 1, the difference in curvature is approximately 1 mm.
It was hot.

After the windshield was constructed by laminating the preformed laminate to a polyurethane sheet, the windshield was inspected. The geometric profile of the exposed surface of the polyurethane sheet is parallel (within small tolerances) at every point to the concave surface of the adjacent mechanically drawn glass sheet, in that the laminate is undistorted when viewed through it. It was confirmed that the optical quality was high.

[Brief explanation of drawings]

The attached FIG. 1 is an enlarged sectional view of an apparatus for carrying out the method of the present invention and a laminate obtained by the method of the present invention. DESCRIPTION OF SYMBOLS 1... Curved glass sheet, 2... Thermoplastic sheet, 3... Glass molded plate, 4... Flexible enclosure, 5
...Rip.

Claims (1)

[Scope of Claims] 1. One plastic sheet and one or more curved glass layers on the other hand are formed into plastic sheets by forming a glass plate having a characteristic curvature that substantially corresponds to the curvature of the curved glass layer or layer group. A method of forming a curved glass-plastic laminate having an outer layer formed of a sheet of plastic material by subjecting the shaped plate to bonding conditions including an external bonding pressure distributed over the entire exterior of the curved glass layer. A method characterized in that the sheet is a sheet of tempered glass with a thickness not exceeding 75% of the total thickness of the glass layers. 2. The method according to claim 1, wherein the formed plate has a thickness not exceeding 50% of the thickness of the curved glass layer or the total thickness of the group of glass layers. 3. The method according to claim 1 or 2, wherein the formed plate has a thickness not exceeding 1.5 mm. 4. The method according to claim 3, wherein the formed plate has a thickness not exceeding 1.2 mm. 5 heating the assembly of the glass layer or layers and the plastic layer while subjecting the assembly to a subatmospheric edge pressure to promote degassing of the interlayer spaces and exposing major surfaces of the assembly to at least extraatmospheric pressure; During lamination and exposure of the assembly to external pressure, and until the assembly reaches its maximum temperature, the edge pressure is increased to reduce or eliminate the difference between the edge pressure and the lamination external pressure, and then heating of the assembly is continued and lamination is performed. 5. The method according to claim 1, wherein the external bonding pressure is maintained until each layer of the body is completely bonded. 6. Prepare one or more glass sheets forming a curved glass layer or layer group of a glass-plastic laminate, and measure the thickness of the glass laminated layer or the total thickness of the glass laminated layer group for the purpose of making a molded plate. prepare another glass sheet with a thickness not exceeding 75% of the thickness, and subject the said glass layer sheet and said other glass sheet together in a face-to-face relationship to a bending operation,
This gives the glass layer sheet(s) a permanent curvature corresponding to the curvature required for the glass layer or layer group of the laminate, and at the same time gives the separate sheet a permanent curvature that matches it, thereby reinforcing the curved separate sheet. One plastic sheet and the other curved glass layer sheet or sheet group are bonded together and subjected to bonding conditions including external pressure, and at this time the other curved sheet is positioned next to the plastic sheet,
A method of forming a curved glass-plastic laminate having an outer layer formed of a sheet of plastic material such that this separate glass sheet serves as a forming plate that distributes external pressure when laminated over the outside of the plastic sheet. 7. A number of sheets forming the glass layers of the laminate to be manufactured are bent together in said bending operation and the layers are glued together to form a prelaminate before being bonded to the plastic sheet. The method described in Section 6.