Patent Description:
Laminated glass may be used as windows and glazings, for example, in architectural and transportation applications, comprising first and second glass sheets and a polymer interlayer therebetween. Vehicle windshields, for example, are typically a laminated glazing.

In the automotive industry, reduction of vehicle weight is sought to improve fuel efficiency and achieve a reduction of carbon dioxide emission and/or extend the cruising distance of a fully- or semi-electric vehicle. Due to the trend of weight reduction, light-weight laminated vehicle glazings (e.g., laminated windshield) are strongly desired.

One way to reduce the weight of a laminated glazing is to use thinner glass sheets. There is, however, a challenge to maintain mechanical robustness and strength of a light-weight laminate glazing compared with a conventional laminate glazing comprising relatively thicker glass sheets.

<CIT> generally discloses a light-weight laminated glazing comprising a non-chemically strengthened external glass sheet (first glass sheet) having a thickness ranging from about <NUM> to about <NUM> and a chemically strengthened internal alkali aluminosilicate glass sheet (second glass sheet) having a thickness equal to or less than <NUM>.

Although chemical strengthening may improve mechanical robustness of thinner glass sheets, it is challenging for economic performance and manufacturing productivity, because chemical strengthening after glass bending requires additional processes and reduces manufacturing yield due to potential changes to the bent shape of the glass sheets. Therefore, it is further desired to provide light-weight laminated glazing comprising non-chemically strengthened glass sheets by maintaining mechanical robustness and strength.

<CIT> discloses a laminated substrate with a partially reinforced intermediate layer. This intermediate layer has a first major region and a second reinforced peripheral region that is stiffer than the first major region to make the laminated substrate sufficient in both sound insulation property and stiffness.

<CIT> discloses a glass laminate structure with a partially reinforced intermediate layer. This intermediate layer has a first central region and a second peripheral region surrounding the first central region. The second peripheral region is stiffer than the first central region to make the glass laminate structure have an improved edge strength.

<CIT> describes a method of embedding rigid elements in a windshield. The windshield comprises an upper glass sheet, a lower glass sheet, one or more rigid elements between the two layers of glass, and a layer of interlayer material surrounding the rigid elements cured between the two layers of glass.

<CIT> discloses an interior rear view mirror mounting system for use on an automobile comprising: a laminated windshield; said windshield comprising a first bent glass panel having a front surface and a rear surface, and a second bent glass panel having a front surface and a rear surface; a sheet of polymeric interlayer laminating said first and second panel together; a mirror mounting button adhered to said rear surface of said second panel by a layer of substantially cured adhesive and an interior rear view mirror assembly supported by said button.

<CIT> discloses an intermediate layer in which the first major region is formed of a thermoplastic resin, and the second reinforced peripheral region is formed of a high shear modulus body without adhesiveness and an adhesive layer formed thereon. Forming this adhesive layer, however, requires additional processes to produce the laminated substrate.

<CIT> discloses thermosetting polymeric materials for the second peripheral region. These thermosetting polymeric materials may be inferior in adhesion to the glass substrates, due to their increased stiffness to have an elastic modulus that is greater than that of the first central region.

It is therefore at least one object of the present disclosure to provide a laminated vehicle glazing with an interlayer having a stiffer part that has a good balance between adhesion to the glass sheets and stiffness such that even a light-weight laminated vehicle glazing is maintained in mechanical robustness and strength.

According to the present invention there is provided a laminated vehicle glazing, comprising:.

According to the present disclosure, a laminated glazing interlayer has a stiff part which has a good balance between adhesion to glass and material stiffness, such that it is possible to maintain mechanical robustness and strength of the laminated vehicle glazing. The stiff part is positioned in an area corresponding to an attachment such that the stiff area may prevent breakage of the laminated vehicle glazing at the attachment.

In the following description, for purposes of explanation, specific details are set forth to promote a thorough understanding of one or more aspects of the disclosure. It may be evident in some or all instances, however, that many aspects described below can be practiced without adopting the specific design details described below.

Moreover, for purposes of this disclosure, including with reference to the figures, a S1 surface of a first glass sheet ( "exterior glass") faces a vehicle exterior and a S4 surface of a second glass sheet ("interior glass") faces a vehicle interior. The first glass sheet has a S2 surface opposite the S1 surface, and the second glass sheet has a S3 surface opposite the S4 surface, such that in a laminated glazing, S2 and S3 surfaces face each other. An interlayer laminated between the first and second glass sheets may face the S2 and S3 surfaces.

This disclosure is directed to a laminated vehicle glazing having an improved interlayer where an area of the interlayer near an attachment is strengthened by an adhesive material stiffer than the portion of the interlayer that is not strengthened, or the major part of the interlayer. An attachment may, for example, be an accessory, such as a handle; an attachment which may be connected to an accessory, such as a mirror base or a bracket for a camera, sensor and the like; or a locating pin. As disclosed herein, the attachment component is attached to at least one main surface of the laminated vehicle glazing. It may be preferable that the attachment is attached to the S1 or S4 surface, depending on the attachment function.

An improved interlayer, as disclosed herein, may include an interlayer facing the S2 and S3 surfaces, wherein the interlayer includes a major part facing the S2 and S3 surfaces and, adjacent to the major part, a stiff part facing the S2 and S3 surfaces, wherein the major part is along at least one edge of the laminated glazing. In certain embodiments, the stiff part of the interlayer may be surrounded by the major part. The major part may include at least one layer made of a first polymer material, and the stiff part may include any suitable second adhesive material, wherein the second adhesive material has a higher Young's modulus than the first polymer interlayer material. As disclosed herein, the Young's modulus may be measured in accordance with ASTM D <NUM>-<NUM>, "Standard Practice for Plastic: Dynamic Mechanical Properties" or ASTM D638-<NUM> "Standard Test Method for Tensile Properties of Plastics". Values of Young's modulus measured at a <NUM> second load duration and <NUM> deg. C are employed herein.

An interlayer with a high Young's modulus may have less adhesion to the glass sheet compared to an interlayer with low Young's modulus. This phenomenon may be observed at temperatures as low as -<NUM> deg. C to -<NUM> deg. Less adhesion may increase the risk of interfacial peeling between the interlayer and the glass sheet(s), particularly in a peripheral portion of the glazing. As the major part may be along at least one edge of the laminated vehicle glazing in this disclosure, the risk of peeling may be reduced. Further, in some embodiments, the major part may extend at least partially along each edge of the laminated vehicle glazing, and in certain embodiments, the major part may surround a stiff part in the laminated glazing.

Further, an attachment on a glazing may provide stress to the glazing at the attachment. Thus, preferably, the attachment is be located at a stiff part of the glazing to improve mechanical robustness and strength of the glazing. In further embodiments, an area of the stiff part facing the attachment may be larger than surface area of an adhered surface of the attachment, wherein the adhered surface is adhered to the glazing.

<FIG> shows a conventional laminated vehicle glazing (i.e., a windshield) <NUM> from a S4 surface <NUM>, and <FIG> and <FIG> show a cross-sectional view of the glazing <NUM> along line AA'.

A conventional laminated glazing <NUM> may include a first glass sheet <NUM> with S1 <NUM> and S2 <NUM> surfaces and a second glass sheet <NUM> with S3 <NUM> and S4 <NUM> surfaces, which may be laminated with a conventional polymer interlayer <NUM>. A conventional polymer interlayer <NUM> may include a polymer sheet, which may be a conventional monolayer polymer sheet, a conventional tri-sublayer acoustic polymer sheet or a conventional wedge-shaped polymer sheet. The polymer interlayer <NUM> may include, for example, polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), polyvinyl acetate (PVA), ionomer, or polyethylene terephthalate (PET). Conventional first and second glass sheet thicknesses typically may be equal to or greater than <NUM>. Opaque printed regions <NUM> and/or <NUM> may be provided in a periphery of the laminated glazing (e.g. windshield) and/or in an area near a rear-view mirror base <NUM> or other attachments (not shown in <FIG>).

An attachment is attached to the glass, including adherence thereto. Such attachments may include any suitable attachment known in the art, including rear view mirrors <NUM>; brackets for holding accessories, including sensors; holding mechanisms; handles; and placement pins <NUM>. Where the attachment is a rear-view mirror <NUM>, the attachment may be attached to the S4 surface <NUM> of an interior second glass sheet <NUM> via a mirror base <NUM> (also known as a button, mount, or knob).

In the automotive industry, mechanical robustness of laminated windshields may be regulated. For example, the Economic Commission for Europe Regulation <NUM> (ECE R43) presents standards for mechanical robustness and strength measured by a headform test (Annexes <NUM> and <NUM> in the ECE R43) and ball-impact test (Annexes <NUM> and <NUM> in the ECE R43), with which laminated windshields may be in compliance in the European Union. In addition to satisfaction of regulation ECE R43, laminated windshields may also satisfy an additional requirement for mechanical strength of an attachment, including an attachment of an accessory depending on a specification of vehicle manufacturers. For example, in-plane and out-of-plane torque tests (as described herein with reference to <FIG>) measuring mechanical robustness and strength may be required.

Present inventors investigated mechanical robustness and strength by performing headform tests, ball impact tests, in-plane toque tests and out-of-plane torque tests, for laminated glazings comprising at least one relatively thinner glass sheet (without chemical strengthening). Particularly, the thinner glass sheet was less than <NUM> in thickness, including <NUM>, <NUM>, and <NUM>. Surprisingly, the inventors found no relationship among the mechanical robustness measured by these four tests, and that the out-of-plane torque requirement for an attachment may be most challenging to pass with at least one thin glass sheet. An out-of-plane torque test for laminated glazings such as windshields, door windows, back window and sliding door window may be an important criterion and relevant to daily application. For example, forces may be applied to an attachment in the manual position adjustment of a rear-view mirror <NUM>, an accidental hit and/or high internal loads on bumpy roads.

For example, testing of laminated glazing constructions having a first glass sheet <NUM> in thickness, a second glass sheet <NUM> or <NUM> or <NUM> in thickness and a conventional polyvinyl butyral (PVB) polymer interlayer, resulted in passing only the headform test, ball impact test and in-plane torque test, and not passing the out-of-plane torque test for a mirror base. It has been also found that an origin of the failure mode (glass breakage) during out-of-plane torque testing for a mirror base <NUM> may be on or inside the thinner glass sheet. It can be understood that there is a need to improve out-of-plane torque mechanical robustness in light weight laminated glazings.

The present disclosure provides, among other features, a laminated vehicle glazing with an improved mechanical robustness for an attachment, which may include an accessory or other attachment, according to an exemplary aspect of the present disclosure. In some embodiments, it may be preferable that an attachment and glazing pass an out-of-plane torque test at at least <NUM> (Newton·meter), more preferably at least <NUM>.

<FIG> and <FIG> show a cross-sectional view of an exemplary embodiment of a laminated vehicle glazing <NUM> with an improved polymer interlayer <NUM> having at least one stiff part <NUM>. As illustrated, an attachment, such as a mirror base <NUM>, may be made over the stiff part <NUM> of the interlayer <NUM>.

Preparation of a laminated glazing may include fully or partially bending a first glass sheet <NUM> and a second glass sheet <NUM> to fit a vehicle window design. In some embodiments, soda-lime glass or aluminosilicate glasses manufactured by a float method or fusion method may be used. Any color, including clear, green, tinted or privacy, glass may be used. It may be preferable that the thickness of the second glass sheet <NUM> may be equal to or less than the thickness of the first glass sheet <NUM>. The thinner glass sheet as disclosed herein has a thickness of less than or equal to <NUM>, preferably less than or equal to <NUM>, more preferably less than or equal to <NUM>, and even more preferably less than or equal to <NUM>. In some further embodiments, the thin glass sheet may have a thickness equal to or less than <NUM>. In certain embodiments, the second glass sheet may be non-chemically strengthened glass. Optionally, a functional coating such as infrared ray reflecting (IRR) coating, which may include functional metallic silver layers, may be deposited on the S2 <NUM> or S3 <NUM> surface.

In some embodiments, opaque printing regions <NUM> and/or <NUM> may be provided on S2 <NUM>, S3 <NUM>, or S4 <NUM> surfaces or combinations thereof, at the periphery of the windshield <NUM> and/or in an area near an attachment, including an accessory attachment. For example, an opaque printing region <NUM> may be provided at and around the attachment of a rear-view mirror base <NUM>. A peripheral opaque printed region <NUM> is not shown in <FIG>. In some embodiments, a shade band may be provided in a major part of a polymer interlayer.

In certain embodiments, the attachment may be a mirror base <NUM> for attaching a rear-view mirror <NUM> to a windshield <NUM>. Particularly, a rear-view mirror <NUM> may be attached to the S4 surface <NUM> via a mirror base <NUM>. The attachment may be attached via any suitable adhesive source, in any suitable form. For example, the adhesive source may include structural bonding tapes formulated for bonding plastic or metal materials to inorganic glasses, such as those made by <NUM>: <NUM>, <NUM> or <NUM>. The preferable adhesive source may depend on the attachment to be adhered. The attachment may include various materials such as metals and/or polymers which may be better suited to a particular adhesive. Further, the area of the adhesive may depend on the size and/or configuration of the attachment. The size of the adherence may affect the force required in an out-of-plane torque test as a broader area of adherence may disperse stress over a larger area in the glass, which may increase the force required to break the glass. Thus, the necessary Young's modulus of the stiff part <NUM> may be higher where an attachment is small and force is dispersed over the smaller attachment.

A polymer interlayer <NUM> with a strengthened part may include a major part <NUM> and a stiff part <NUM>. The major part <NUM> may be a conventional polymer interlayer material known in the art, such as PVB, ethylene vinyl acetate (EVA), polyvinyl acetate (PVA), ionomer, or polyethylene terephthalate (PET). In some embodiments, the major part <NUM> may be monolayer, multilayer (such as for acoustic applications), or have a wedge angle(s). Optionally colored pigments/dyes or other functional particles such as infrared absorbing particles or ultraviolet absorbing particles may be dispersed in the polymer interlayer <NUM>. The thickness of the polymer interlayer <NUM> may be properly chosen. For example, without limitation, a typical interlayer thickness may be in the range of about <NUM> to about <NUM> such as <NUM>, <NUM> and <NUM>. Preferably the stiff part <NUM> has a thickness substantially matching that of adjacent major part <NUM> interlayer.

The stiff part <NUM> is a stiffer (i.e., having higher Young's Modulus) material than the major part <NUM>, and provide enough adhesion between the stiff part <NUM> and the glass sheets <NUM>, <NUM> and the major part <NUM>. It may also be preferable that the stiff part <NUM> material is mechanically and chemically stable and robust during lamination and in practical application. Further, it is preferable that the stiff part <NUM> material is compatible with the major part <NUM>, including having adhesion between the materials. The increased stiffness of the stiff part <NUM> may depend on various factors, thus the difference in stiffness between the major part <NUM> and the stiff part <NUM> may vary. The desired stiffness of the stiff part <NUM> may, for example, depend on the shape and size of adhesion between the glass and the attachment. Further, the shape and size of an attachment or accessory may affect the type of force applied thereto and the necessary increased stiffness.

The stiff part <NUM> may be any suitable material, particularly any suitable adhesive. For example, the stiff part <NUM> may be an adhesive sheet, a paste, or a resin. Such suitable stiff part <NUM> material may include, for example, carbon fiber reinforced plastic (CFRP). Further embodiments may include a stiff part <NUM> which is more or less stiff than the CFRP, including high stiffness PVB or polycarbonate (PC). Further embodiments of a stiff part <NUM> may include reinforcement other than carbon fibers, including, for example, polymer or glass fibers. The stiff part <NUM> may be formed by any suitable adhesive having a higher stiffness than a major part <NUM>. The major part <NUM> may be formed of a conventional interlayer as disclosed herein, including an interlayer having a wedged angle or a tri-layer acoustic damping interlayer. Preferably the major part <NUM> is formed by an interlayer having a Young's modulus of about <NUM> - <NUM> GPa. Where the major part <NUM> comprises multiple layers (such as two skin layers and one soft core layer), the Young's modulus of the multilayered major part <NUM> may be used, rather than a Young's modulus of an individual layer. In some embodiments, the stiff part <NUM> is formed of a material having a Young's modulus of at least about <NUM> GPa, preferably at least about <NUM> GPa, more preferably at least about <NUM> GPa, and even more preferably at least about <NUM> GPa. A glazing may preferably have at least one stiff part <NUM> but may include additional stiff parts for additional attachments. Further, the stiff part <NUM> material may be clear or colored. In some embodiments, sensors may collect information through an area of the stiff part <NUM>, and it may be preferable in such embodiments to provide a clear stiff part <NUM>.

In further embodiments, a stiff part <NUM> material may a material or a combination of materials which may be curable. For example, the stiff part <NUM> material may be cured by ultraviolet light, heat, or photochemical reaction. The stiffness of the stiff part <NUM> material may increase upon curing and may be more pliable or less stiff prior to curing.

Further, according to another aspect of the present disclosure, a suitable material for a stiff part <NUM> having high stiffness may be selected based on the thickness of a glass sheet to which an attachment is to be made. Particularly the material for a stiff part <NUM> may be selected to provide sufficient stiffness of the laminated glazing at the stiff part <NUM>. Particularly, a ring-on-ring deflection test, as described herein, may be used to determine the possible deflection of a glazing and inform the lamination stiffness. The stiffness of the interlayer material used for a stiff part <NUM> may depend on a glass thickness. For example, in some embodiments, a thinner glass sheet may be laminated having a stiff part <NUM> interlayer which is stiffer than a stiff part <NUM> interlayer in a laminate having a thicker glass sheet.

A ring-on-ring deflection test is basically based on ISO <NUM>-<NUM>:<NUM>, "Glass in Building - Determination of the bending strength of glass, Part <NUM>: Coaxial double ring test on flat specimens with small test surface areas", except as to the experimental conditions specifically described herein. A schematic cross-sectional image of the test is shown in <FIG>. A supporting ring <NUM> and a loading ring <NUM> may be concentric cylindrical shaped jigs having different diameters. A specimen <NUM> is sandwiched between the supporting ring <NUM> and the loading ring <NUM> and a load is applied by a load cell above the loading ring <NUM>, bending the specimen <NUM>. The contact parts of the rings <NUM>, <NUM> which come into contact with the specimen <NUM> may be round with predetermined radiuses of curvature.

A ring-on-ring deflection test may include:.

Moreover, the area of the stiff part <NUM> may be preferably larger than that of the attachment, such as a mirror base <NUM>, to prevent deformation of the laminated windshields under out-of-plane torque forces such that the external load may be distributed across a larger area or distributed from the relatively thinner second glass sheet <NUM> to the relatively thicker first glass sheet <NUM>. The area of the stiff part <NUM> may depend on the strength of the material used in the stiff part <NUM>, as a smaller area may be needed where a stiffer stiff part <NUM> is used and the force distribution may be effective in a small area. In certain embodiments, it may be preferable that the attachment is made closer to the center of the stiff part <NUM> than to an edge of the stiff part <NUM> to distribute the forces around the stiff part <NUM> and limit the necessary size of the stiff part <NUM>. For example, it may be preferable that the center of an adhered surface of the attachment is closer to the center of the stiff part <NUM> than to an edge of the stiff part <NUM>. In some embodiments, a stiff part <NUM> may include more than one attachment, such that the stiff part <NUM> is large enough that multiple attachments may be attached over the stiff part <NUM>. The shape of the stiff part <NUM> may be the same or different from an attachment, and may include any shape, such as a circle, rectangle, ring, etc..

Attachments to a glazing may include any suitable attachment. This may include accessories or attachments for accessories. For example, a mirror base is an attachment which an accessory (a rear-view mirror) may be attached to. Further attachments or accessories may include placement pins, sensor brackets, or handles.

The location of a stiff part <NUM> in the glazing <NUM> may depend on the type of attachment to be adhered to a glazing. For example, where the attachment is a mirror base or other attachments to be placed near an edge of the glazing, the stiff part <NUM> may be closer to a first peripheral edge of the interlayer than to a second peripheral edge, within a central region connecting the first and second opposing peripheral edges.

Examples and experimental results are explained herein. In the following description, for the purposes of explanation and not limitation, examples with specific details are set forth to provide a thorough understanding of the present disclosure.

Examples A-<NUM>, A-<NUM>, and A-<NUM> in Table <NUM> show exemplary (flat) laminated glass specimens having <NUM> x <NUM> dimension for an out-of-plane torque test which measures mechanical robustness and strength of a mirror base attached to the second (interior) glass sheet. The laminated glass specimens were prepared by a known lamination process for a laminated vehicle glazing: de-airing using bag in a temperature range from <NUM> to <NUM> deg. and autoclaving in a temperature range from <NUM> to <NUM> deg. with a pressure of <NUM> to <NUM> bar.

Soda-lime glass sheets, defined by ISO <NUM>-<NUM>:<NUM>, made from a float process were used for the first and second flat glass sheets. The first (exterior) glass sheet had <NUM> thickness, and the second (interior) glass sheet had <NUM>, <NUM>, or <NUM> thickness. A known conventional automotive PVB polymer interlayer having <NUM> thickness was used for the major part <NUM>. Carbon fiber reinforced plastic (CFRP) interlayers with Young's modulus of about <NUM> GPa were used for the stiff part <NUM> near a mirror base. Particularly, the CFRP interlayer used in these examples included epoxy prepreg reinforced by carbon fibers with <NUM> - <NUM> % carbon fiber by volume, which may be available as CE <NUM>-<NUM>-<NUM>, CE <NUM>-<NUM>-<NUM> and CE <NUM>-<NUM>-<NUM> of Carbon-Werke Weiβgerber GmbH. The PVB polymer interlayer was replaced by the CFRP interlayer in a patched area larger than that of a mirror base, and the mirror base adhered to a center of the second glass sheet over the patched area.

Further examples Y-<NUM>, Y-<NUM> and Y-<NUM> in Table <NUM> were prepared in the same way as examples A-<NUM>, A-<NUM> and A-<NUM>, except that a higher stiffness PVB polymer interlayer (particularly, DG <NUM> from Eastman Chemical) was used for the stiff part rather than CFRP interlayer.

Comparative examples X-<NUM>, X-<NUM> and X-<NUM> in Table <NUM> were prepared in the same way for Examples A-<NUM>, A-<NUM> and A-<NUM>, except that no stiff part in the major PVB polymer was provided.

<FIG> illustrates an experimental set-up of a laminated glass specimen <NUM> for a torque measurement in a mirror base breakage test. The test specimens <NUM> were formed of an exterior glass sheet <NUM>, an interlayer <NUM>, and an interior glass sheet <NUM>. The test specimens <NUM> were fixed with clamps to immobilize the specimens <NUM> during testing (the clamps are not shown in <FIG>). A torque wrench <NUM> was attached to the mirror base <NUM> via a universal joint <NUM> (called Cardan joint). Out-of-plane torque force to a direction <NUM> shown in <FIG> was applied by moving the torque wrench <NUM> in the out-of-plane <NUM> direction. Out-of-plane torque values were recorded when the test specimens <NUM> were broken during the test. Averaged breakage torque values over <NUM> - <NUM> specimens, depending on the specimen construction, were calculated.

The results are shown in Table <NUM>. The average breakage (out-of-plane) torque values of examples A-<NUM>, A-<NUM>, and A-<NUM> were significantly improved compared to those of the comparative example X series. Thus, examples A-<NUM>, A-<NUM>, and A-<NUM> may pass the mechanical robustness requirement of the out-of-plane torque test. Good adhesion of the stiff part to the glass sheet and a high Young's modulus may allow distribution of the applied out-of-plane torque to a larger area and may provide enough support against breakage during torque testing.

The example Y series showed failure between the glass and the interlayer, indicating a problem during the lamination process. As there was a failure of adhesion between the glass and the interlayer due to the lamination process, the stiff interlayer is considered in the example B series discussed herein. In view of the example B series, it may be understood that a higher stiffness PVB polymer for the stiff part <NUM> may improve a mechanical robustness and a strength of the laminated vehicle glazing. Thus, in some embodiments, the higher stiffness PVB polymer may provide enough additional strength over a conventional PVB. Particularly, the size of the attachment, such as a mirror base, and the size of the stiff part <NUM> of higher stiffness PVB may determine whether the higher stiffness PVB has sufficient stiffness to provide additional strength to a glazing for an attachment thereto as shown in the example B series.

Contrary to the example A and Y series, comparative examples X-<NUM>, X-<NUM> and X-<NUM> show that a relatively thinner second (interior) glass sheet may reduce stiffness of the laminated glass construction having a conventional PVB polymer interlayer. As a result, when the out-of-plane torque is applied, these comparative examples may experience a relatively large deformation. The conventional PVB interlayer without a stiff part <NUM> may not provide enough support to the thinner glass sheet to resist the out-of-plane torque, resulting in a lower breakage torque, compared to the example A and Y series.

Examples B-<NUM> and B2, as provided in Table <NUM>, were formed by laminating flat glass substrates with a higher stiffness PVB (particularly, DG41 available from Eastman Chemical) having a Young's modulus of about <NUM> to about <NUM> GPa. Example B-<NUM> was formed having a <NUM> thick first soda-lime glass sheet and a <NUM> second soda-lime glass sheet and was a laminated construction <NUM> (<NUM> inches) square. Example B-<NUM> was formed as a <NUM> (<NUM> inches) square laminate having a <NUM> first soda-lime glass sheet and a <NUM> second soda-lime glass sheet. The lamination processes for preparing example B series were the same as those used for the example A, Y, and X series. The higher stiffness PVB was used over the entire laminate area, and a mirror base was applied to the center of the laminate. The out-of-plane torques testing was performed by the same method as in the example A, Y, and X series. The area of a stiff part <NUM> may affect results of an out-of-plane torque test. The example B series included samples having an entire area of higher stiffness PVB, which may pass mechanical robustness tests, including the out-of-plane torque test. A larger stiff area may distribute forces applied thereto, increasing the force required to cause breakage. A larger adhesive attachment area may further improve force distribution.

Comparative examples Z-<NUM> and Z-<NUM> were formed in the same manner as examples B-<NUM> and B-<NUM>, respectively, except that a conventional PVB interlayer was used across the entire laminates. The conventional PVB used had a Young's modulus of about <NUM> to about <NUM> GPa. The comparative examples Z-<NUM> and Z-<NUM> showed lower force necessary to cause breakage in the out-of-plane torque test than the example B series, and the higher stiffness interlayer provided additional strength to the laminate.

Table <NUM> provides examples for bending deflection measurements by the ring-on-ring test. In the specimen P-series, the laminated flat glass specimens, <NUM> x <NUM>, were formed having a fixed <NUM> thickness for the first glass sheet and various thicknesses of the second glass sheet. Referential specimen P-ref and comparative example specimens P-<NUM> and P-<NUM> comprised the conventional PVB interlayer having a Young's modulus of about <NUM> to about <NUM> GPa. The example specimens P-<NUM> and P-<NUM> comprised a higher stiffness PVB (particularly, DG41 available from Eastman Chemical) having a Young's modulus of about <NUM> to about <NUM> GPa. The lamination processes were the same as those used for the example A, Y, and X series. A Universal Strength Testing Machine (Model <NUM>, INSTRON) was used for the ring-on-ring bending test. As described herein, a supporting ring with a diameter of <NUM> and a contact point radius of curvature of <NUM> and a loading ring with a diameter of <NUM> and a contact point radius of curvature of <NUM> were used. Values of "referential deflection" and "measured deflection" at an external load of <NUM> N (which was applied to the S1 (exterior) surface of the first glass sheet) were measured with a loading rate of <NUM>/min at <NUM> deg. C and at the relative humidity level of <NUM> %. "Normalized deflection" was calculated based on the referential and measured deflections. As shown in Table <NUM>, the comparative examples P-<NUM> and P-<NUM> showed larger deflection (i.e., more easily deformable) than the reference P-ref. Such laminated glazing constructions may not be sufficiently stiff to pass the out-of-plane torque requirements (see Comparative example X-series in Table <NUM>). However, example constructions P-<NUM> and P-<NUM> showed much smaller measured and normalized deflection values (deflected less under pressure). As shown in the example B-series in Table <NUM>, these example constructions using the higher stiffness polymer for the stiff part <NUM> may provide enough rigid support for the out-of-plane torque.

Further, in Table <NUM>, similar experiments were performed with samples having various thicknesses of the first glass, for specimen Q-series (first glass thickness <NUM>), R-series (first glass thickness <NUM>), S-series (first glass thickness <NUM>). Normalized deflections for all examples (Q-<NUM>, Q-<NUM>, R-<NUM> and S-<NUM>) were less than <NUM> and the examples had higher stiffness compared with each respective reference specimen (Q-ref, R-red and S-ref).

According another aspect of the present disclosure, referring to <FIG>, a process <NUM> for manufacturing a laminated vehicle glazing having an improved interlayer where a partial area near a mirror base is stiffer to improve mechanical robustness and strength may comprise the following steps.

Step <NUM> may include preparing a major polymer interlayer with a pre-defined cutout shape which may be replaced by a stiff part. The area of the pre-defined cutout shape may be larger than that of an attachment. Mechanical die-cuts or any other cutter including a laser cutter may be used to form the cutout. The major polymer interlayer may be placed on a first glass sheet.

Step <NUM> may include preparing a stiff interlayer to match the pre-defined shape of the cutout described in the step <NUM>.

Step <NUM> may include preparing an interlayer with a stiff part by combining the major polymer interlayer (prepared in the step <NUM>) and the stiff interlayer (prepared in the step <NUM>). In particular embodiments, the major polymer interlayer may not overlap with the stiff interlayer. In further methods embodied herein, the stiff interlayer may be a non-sheet adhesive which may be applied within the cutout shape of the major polymer interlayer. In certain embodiments, the stiff interlayer may increase in stiffness upon curing, wherein the curing may include any suitable means, including ultraviolet radiation.

Step <NUM> may include sandwiching the interlayer (prepared in the step <NUM>) between first and second glass sheets, and a generally-known de-airing process may be applied thereto. The first and second glass sheets may be prepared in advance in a preferred bent shape using a conventional bending process, such as gravity sag bending or press-bending. Optional opaque regions such as black or silver enamel printing may be provided on either of the S2, S3 or S4 surface(s) or combinations thereof, in a periphery of the laminated vehicle glazing or in the area near an attachment.

Step <NUM> may include application of an attachment on a pre-defined position of the second glass sheet over the stiff interlayer. In further embodiments, the attachment may be applied to the first glass sheet over the stiff interlayer.

Claim 1:
A laminated vehicle glazing, comprising:
a first glass sheet (<NUM>) having an S1 surface (<NUM>) facing a vehicle exterior and an S2 surface (<NUM>) opposite to the S1 surface;
a second glass sheet (<NUM>) having an S4 surface (<NUM>) facing a vehicle interior and an S3 surface (<NUM>) opposite to the S4 surface; and
an interlayer (<NUM>) positioned between the first and second glass sheets (<NUM>,<NUM>), facing the S2 and S3 surfaces,
wherein the interlayer (<NUM>) comprises a major part (<NUM>) and a stiff part (<NUM>) adjacent to the major part, the major part being along at least one edge of the laminated vehicle glazing;
wherein the major part (<NUM>) comprises at least one layer of a first interlayer material, and the stiff part (<NUM>) comprises at least one layer of a second interlayer material,
wherein the stiff part (<NUM>) is adhered to the first and second glass sheets (<NUM>,<NUM>) and to the major part (<NUM>), and the second interlayer material has a higher Young's modulus than the first interlayer material; and
wherein at least one of the first and second glass sheets (<NUM>,<NUM>) has a thickness equal to or less than <NUM>;
the laminated vehicle glazing further comprising at least one attachment (<NUM>) attached to the laminated vehicle glazing, wherein the attachment is attached over the stiff part (<NUM>) of the interlayer.