Laminated glass for vehicles, automobile, and production method for laminated glass for vehicles

Abstract

To provide vehicle glass having high safety performance in a collision while having robustness.SOLUTION: In laminated glass for a vehicle, a percentage of a region having a breaking stress of 100 MPa or more and 600 MPa or less measured by a method described in ISO1288-5 (2016) is 90% or more of a see-through region.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated glass for vehicles, an automobile, and a method for manufacturing a laminated glass for vehicles. [Background technology]

[0002] High safety standards are required for vehicles such as automobiles. For example, windshields, as vehicle safety glass, are required to meet standards for preventing occupant ejection when an occupant is struck from the interior of the vehicle and absorbing impact from the perspective of occupant protection. Furthermore, in recent years, importance has been placed on safety performance in the event of a collision with a pedestrian. In particular, there is a strong demand for performance that can ensure the safety of a human body when a vehicle collides with the human body, i.e., performance that can protect the human body during a collision, and various configurations have been considered. For example, Patent Document 1 proposes a configuration that ensures the safety of a pedestrian by separating the connected cowl louvers and windshield when a downward impact from the front is applied to the periphery of the cowl louvers and windshield glass in a frontal collision of a vehicle with a pedestrian. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-213928 Summary of the Invention [Problem to be solved by the invention]

[0004] The high demand for safety as described above is also increasing for vehicle glass. While vehicle glass as a whole needs a certain degree of toughness, in consideration of protecting the human body in the event of a collision as described above, it is required to control the strength of the vehicle glass so that the vehicle glass is less likely to cause impact or damage to the human body when it collides with the human body.

[0005] However, it is known that glass formed into a plate shape inherently has a distribution of strength within its surface, and the strength of a glass plate is usually determined probabilistically based on factors such as safety factor and probability of breakage. Therefore, even if the strength of the vehicle glass as a whole is appropriate, there may be localized areas within the surface of the vehicle glass where the strength is excessively high, and if a human body collides with such an area where the strength is excessively high, there is a possibility that the human body may be injured.

[0006] Here, in order to reduce the strength in regions where the strength is excessively high locally within the plane, it is conceivable to reduce the strength of the vehicle glass as a whole by changing the glass composition or manufacturing method. However, in that case, the strength may also be reduced in regions where the strength is relatively low within the plane, which may impair the toughness required for the vehicle glass. Therefore, there is a demand for vehicle glass that has high safety performance in the event of a collision from the viewpoint of protecting the human body as described above, while ensuring the toughness of the vehicle glass by reducing or eliminating regions where the strength is excessively high and suppressing the strength distribution within the plane.

[0007] An object of one embodiment of the present invention is to provide a vehicle glass that has robustness and high safety performance in the event of a collision. [Means for solving the problem]

[0008] One aspect of the present invention is a laminated glass for vehicles, in which the proportion of the area in which the fracture stress, measured by the method described in ISO1288-5(2016), is 100 MPa or more and 600 MPa or less is 90% or more of the transparent area. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a vehicle glass that has robustness and high safety performance in the event of a collision. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view of a vehicle equipped with a laminated glass according to an embodiment of the present invention. [Figure 2]FIG. 2 is a cross-sectional view of the laminated glass shown in FIG. [Figure 3] 1 is a graph showing the results of Examples 1 and 2. [Figure 4] FIG. 10 shows the positions of samples cut out from windshields in Examples 3 and 4. [Figure 5] 1 is a graph showing the results of Examples 3 and 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Vehicle glass> One embodiment of the present invention is a vehicle glass, specifically a laminated glass for a vehicle. Fig. 1 shows an example in which a laminated glass for a vehicle 1 according to this embodiment is used as a window glass of an automobile 100. In the example of Fig. 1, the laminated glass for a vehicle 1 is the windshield of the automobile 100, but the laminated glass for a vehicle 1 can also be used as window glass other than the windshield, for example, a side glass, a rear glass, or a roof glass.

[0012] Fig. 2 shows a cross-sectional view of the laminated glass for vehicles 1 shown in Fig. 1. As shown in Fig. 2, the laminated glass for vehicles 1 is formed by joining a first glass plate 10 and a second glass plate 20 together via an interlayer film 30. In the example of Fig. 2, the first glass plate 10 is disposed on the exterior side of the vehicle, and the second glass plate 20 is disposed on the interior side of the vehicle. As shown in Fig. 2, the first glass plate 10 on the exterior side of the vehicle has a first surface 11 that faces the exterior side of the vehicle and a second surface 12 that faces the interior side of the vehicle, and the second glass plate 20 on the interior side of the vehicle has a third surface 21 that faces the exterior side of the vehicle and a fourth surface 22 that faces the interior side of the vehicle.

[0013] The material constituting the first glass plate 10 and the second glass plate 20 (hereinafter, sometimes collectively referred to as glass plates) is preferably inorganic glass. Examples of inorganic glass include soda lime silicate glass, aluminosilicate glass, borate glass, lithium aluminosilicate glass, and borosilicate glass. The method for forming glass plates made of inorganic glass is not particularly limited, but it is preferable that the glass plates are formed by a float method or the like.

[0014] The glass plate may be untempered glass. Untempered glass is glass obtained by forming molten glass into a plate shape and slowly cooling it, and has not been subjected to a tempering treatment such as air-cooling tempering or chemical tempering.

[0015] The first glass sheet 10 and the second glass sheet 20 may have the same thickness or different thicknesses. The thickness of the first glass sheet 10 may be 1.1 mm or more and 3.5 mm or less. When the first glass sheet 10 and the second glass sheet 20 have different thicknesses, the thickness of the second glass sheet 20 may be 0.5 mm or more and 2.3 mm or less. Furthermore, the configurations of the first glass sheet 10 and the second glass sheet 20 (such as the materials constituting the glass sheets and the manufacturing method of the glass sheets) may be the same or different from each other. Furthermore, the overall thickness of the laminated glass for vehicles 1 may be 2.3 mm or more and 8.0 mm or less.

[0016] The material of the interlayer film 30, which is disposed between the first glass sheet 10 and the second glass sheet 20 and bonds the first glass sheet 10 and the second glass sheet 20, is not particularly limited, but is preferably a thermoplastic resin. Examples of materials for the interlayer film 30 include conventionally used thermoplastic resins such as plasticized polyvinyl acetal resins, plasticized polyvinyl chloride resins, saturated polyester resins, plasticized saturated polyester resins, polyurethane resins, plasticized polyurethane resins, ethylene-vinyl acetate copolymer resins, ethylene-ethyl acrylate copolymer resins, cycloolefin polymer resins, and ionomer resins. Resin compositions containing modified hydrogenated block copolymers, as described in Japanese Patent No. 6065221, are also suitable. Among these, plasticized polyvinyl acetal resins are preferred because of their excellent balance of properties such as transparency, weather resistance, strength, adhesive strength, penetration resistance, impact energy absorption, moisture resistance, heat insulation, and sound insulation. The above thermoplastic resins may be used alone or in combination. The term "plasticized" in the plasticized polyvinyl acetal resin means that the resin has been plasticized by adding a plasticizer. The same applies to other plasticized resins.

[0017] The interlayer film 30 may be a resin that does not contain a plasticizer. It may also be a resin that does not contain a plasticizer, such as an ethylene-vinyl acetate copolymer resin. Examples of the polyvinyl acetal resin include polyvinyl formal resin obtained by reacting polyvinyl alcohol (PVA) with formaldehyde, polyvinyl acetal resin in the narrow sense obtained by reacting PVA with acetaldehyde, and polyvinyl butyral resin (PVB) obtained by reacting PVA with n-butylaldehyde. PVB is particularly preferred because of its excellent balance of properties such as transparency, weather resistance, strength, adhesive strength, penetration resistance, impact energy absorption, moisture resistance, heat insulation, and sound insulation. These polyvinyl acetal resins may be used alone or in combination.

[0018] A shielding layer may be provided around the periphery of the laminated vehicle glass 1 to protect the sealant or the like that adheres and holds the vehicle glass 1 to the vehicle body when the glass is installed in an opening in the vehicle. The shielding layer can be formed, for example, by applying and firing a ceramic color paste that includes a fusible glass frit containing a black pigment. The shielding layer can be provided on one or more of the second surface 12, the third surface 21, and the fourth surface 22 of the laminated vehicle glass 1.

[0019] The laminated glass for vehicles 1 may be curved entirely or partially. In this case, the glass sheets (the first glass sheet 10 and the second glass sheet 20) may each be curved to a predetermined curvature. The radius of curvature of the glass sheets may be 1,000 to 100,000 mm. When the laminated glass for vehicles 1 is curved, the glass sheets may be curved so that the first surface 11 of the first glass sheet 10 and the third surface 21 of the second glass sheet 20, i.e., the vehicle exterior side, are convex. When the glass sheets are curved inorganic glass, the glass sheets can be bent by gravity forming, press forming, or the like after being formed by a float process. Bending is performed by heating the glass to soften it. The heating temperature of the glass during bending is approximately 550°C or higher and 700°C or lower. The laminated glass for vehicles 1 may have a single-bend shape, for example, bent in only one direction, for example, only in the longitudinal or vertical direction of the automobile 100 when installed in an opening of the automobile 100. The laminated glass for vehicles 1 may also have a complex curved shape that is bent in the front-rear direction and the up-down direction. The radii of curvature of the first glass plate 10 and the second glass plate 20 in the laminated glass for vehicles 1 may be the same or different.

[0020] Laminated glass for vehicles is required to have various safety-related properties and functions, and these requirements are becoming increasingly greater. In particular, when laminated glass for vehicles is used as window glass for a vehicle, it is required to have appropriate robustness as window glass, and also to provide safety performance for the human body in the event of an impact from the viewpoints of occupant protection, pedestrian protection, etc. In particular, in recent years, importance has been placed on pedestrian protection, and vehicle glass is also required to satisfy specific standards such as the Head Injury Criterion (HIC).

[0021] In contrast, in the laminated glass for vehicles according to this embodiment, the proportion of the area in which the fracture stress is 100 MPa or more and 600 MPa or less, as measured by the method using R30 described in ISO1288-5 (2016), is 90% or more of the transparent area. The proportion may be preferably 95% or more, and more preferably 98% or more.

[0022] In this specification, the see-through region refers to a portion of a laminated glass for a vehicle excluding the shielding layer formed on the laminated glass for a vehicle.

[0023] In the present invention, the breaking stress or bending strength can be measured in each of multiple regions included in the laminated glass for vehicles. In this case, the measurement can be performed on the laminated glass for vehicles as is, or the laminated glass for vehicles can be divided by cutting and the breaking stress can be measured for each divided region. In this case, the size of the divided glass may be 100 mm × 100 mm, but is not limited to this size. The size of the divided glass may be 60 mm to 300 mm × 60 mm to 300 mm. When cutting out the laminated glass for vehicles, the measurement can be performed using the cut laminated glass as is, or the interlayer film can be removed from the laminated glass and each individual glass sheet can be measured. Alternatively, the measurement can be performed on each individual glass sheet before it is made into a laminated glass. Therefore, in the first glass sheet 10 and / or the second glass sheet 20 included in the laminated glass, the proportion of the region in which the breaking stress is 100 MPa or more and 600 MPa or less, as measured by the method using R30 described in ISO1288-5 (2016), may be 90% or more of the viewing region. The breaking stress is preferably measured before the laminated glass for vehicles is mounted on a vehicle.

[0024] In the method described in ISO 1288-5 (2016), a plate glass to be tested is placed on a support ring with a specified diameter, and a load is gradually increased from above using a loading ring with a smaller diameter than the support ring. The load at break is measured, and the breaking stress value is calculated based on the specified formula described in ISO 1288-5 (2016). If the laminated glass for a vehicle, such as a windshield, is curved, the breaking stress of the cut-out curved area is measured. In such cases, the specified formula described in the ISO is not used, but an approximate formula is derived from stress measurements, and the breaking stress value can be calculated by substituting the measured values ​​into the approximate formula.

[0025] In the configuration according to this embodiment, the region having a predetermined fracture stress value accounts for a predetermined percentage or more of the see-through region, and the proportion of the region having a strength within an appropriate range that can maintain the robustness of the vehicle glass and ensure safety performance for humans in the event of an impact is increased. In other words, the in-plane strength is homogenized or leveled so that the strength measured in multiple regions of the vehicle glass falls within a more appropriate range. In other words, the in-plane strength distribution or strength variation is reduced. Therefore, according to this embodiment, it is possible to provide a vehicle glass that, overall, has the robustness required for a vehicle glass and has improved safety performance for humans or other living organisms in the event of an impact.

[0026] The breaking stress is measured by applying a load from one side of the laminated glass for vehicles, and the side to which the load is applied may be the vehicle interior side or the vehicle exterior side. That is, in the laminated glass for vehicles according to this embodiment, when a load is applied from the vehicle interior side, the proportion of the region where the breaking stress is 100 MPa or more and 600 MPa or less as measured by the method described in ISO 1288-5 (2016) may be 90% or more of the see-through region, and / or when a load is applied from the vehicle exterior side, the proportion of the region where the breaking stress is 100 MPa or more and 600 MPa or less as measured by the method described in ISO 1288-5 (2016) may be 90% or more of the see-through region. When the above proportion is satisfied in the measurement when a load is applied from the vehicle interior side, safety performance when an impact is received from the vehicle interior side can be improved, which is preferable from the perspective of occupant protection. Conversely, when the above proportion is satisfied in the measurement when a load is applied from the vehicle exterior side, safety performance when an impact is received from the vehicle exterior side can be improved, which is preferable from the perspective of pedestrian protection.

[0027] In one embodiment of the laminated glass for vehicles, the proportion of the area where the fracture stress exceeds 600 MPa as measured by the method described in ISO 1288-5 (2016) is preferably 5% or less of the visible area. This proportion is preferably 3% or less, and more preferably 1% or less. This configuration makes it possible to reduce or eliminate areas in the laminated glass where the strength is excessively high. Therefore, even if an occupant or pedestrian collides with the laminated glass for vehicles during an impact, the possibility of the occupant or pedestrian striking their head or the like against an area with excessive strength and sustaining injury can be reduced, thereby improving safety performance for the human body.

[0028] In the above embodiment, the side on which the load is applied when measuring the breaking stress may be either the exterior side or the interior side of the vehicle. That is, when a load is applied from the exterior side of the vehicle, the proportion of the region where the breaking stress measured by the method described in ISO1288-5(2016) exceeds 600 MPa may be 5% or less of the see-through region, and / or when a load is applied from the interior side of the vehicle, the proportion of the region where the breaking stress measured by the method described in ISO1288-5(2016) exceeds 600 MPa may be 5% or less of the see-through region. Here, it is particularly preferable from the perspective of pedestrian protection if the breaking stress is measured by applying a load from the exterior side of the vehicle.

[0029] In one embodiment of the laminated glass for vehicles, the proportion of the area where the fracture stress is less than 100 MPa as measured by the method described in ISO1288-5(2016) is preferably 5% or less of the visible area. This proportion is preferably 3% or less, more preferably 1% or less. This configuration ensures that the robustness of the laminated glass for vehicles is maintained.

[0030] In the above embodiment, the side to which a load is applied when measuring the breaking stress may be either the exterior side or the interior side of the vehicle. That is, when a load is applied from the interior side of the vehicle, the proportion of the region where the breaking stress measured by the method described in ISO1288-5(2016) is less than 100 MPa may be 5% or less of the see-through region, and / or when a load is applied from the exterior side of the vehicle, the proportion of the region where the breaking stress measured by the method described in ISO1288-5(2016) is less than 100 MPa may be 5% or less of the see-through region.

[0031] Furthermore, when a load is applied from the inside or outside of the vehicle, it is more preferable that the proportion of the region where the fracture stress exceeds 600 MPa as measured by the method described in ISO1288-5 (2016) is 5% or less of the see-through region, and the proportion of the region where the fracture stress is less than 100 MPa as measured by the same method is 5% or less of the see-through region. This makes it possible to further reduce or eliminate regions with excessively high strength, thereby suppressing the strength distribution. Therefore, while maintaining the robustness required for laminated glass for vehicles, the effect of reducing or eliminating injury to the human body even when the human body collides with the laminated glass is further demonstrated. Furthermore, from the perspective of pedestrian protection, it is particularly preferable if the fracture stress is measured when a load is applied from the outside of the vehicle.

[0032] <Method of manufacturing vehicle glass> The above-mentioned vehicle glass can be manufactured by a manufacturing method according to one embodiment of the present invention, which will be described below. That is, the manufacturing method for laminated vehicle glass according to one embodiment of the present invention is a method for manufacturing laminated vehicle glass, in which the laminated vehicle glass is formed by laminating a first glass plate disposed on the vehicle exterior side and a second glass plate disposed on the vehicle interior side with an interlayer film interposed therebetween, the first glass plate having a first surface on the vehicle exterior side and a second surface on the vehicle interior side, and the second glass plate having a third surface on the vehicle exterior side and a fourth surface on the vehicle interior side, and at least one of the first to fourth surfaces is subjected to a strength leveling treatment. The strength leveling treatment may be performed on each glass plate before the laminated vehicle glass is formed, or may be performed after the laminated vehicle glass is formed.

[0033] Strength leveling treatment is a treatment for reducing the distribution or variation in strength within the surface of a laminated glass for vehicles. In other words, it is a treatment for adjusting the distribution of strength values ​​(breaking stress or bending strength) measured in multiple regions within the laminated glass for vehicles so that it narrows. The strength leveling treatment can be applied to at least one of the first surface 11, second surface 12, third surface 21, and fourth surface 22 (FIG. 2) of the laminated glass for vehicles 1. It is particularly preferable to apply the strength leveling treatment to one or more of the second surface 12, third surface 21, and fourth surface 22 of the laminated glass for vehicles.

[0034] The strength leveling treatment (also called strength homogenization treatment or strength control treatment) can be carried out by bringing a substance into contact with the surface of the laminated glass for vehicles or the surface of the glass plate that constitutes the laminated glass for vehicles.

[0035] In one example of a strength leveling treatment, a tool can be brought into contact with the surface of the glass plate. The shape of the tool is not particularly limited and may be a film, sheet, roll, brush, or paintbrush, etc., and may or may not be flexible or elastic. It may also be disk-shaped or blade-shaped. The material of the tool may be ceramic, metal, resin, etc. It may also be molded from a foam, such as a foamed resin molded body or foamed resin sheet, or molded from fibers, such as a fiber structure formed by assembling fibers three-dimensionally or two-dimensionally, particularly cloth, nonwoven fabric, paper, etc. When the tool is made of resin or contains resin, specific examples of the resin include ultra-low density polyethylene, linear low-density polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyurethane, silicone resin, EVA, and olefin-based elastomers. The tool may be made of any of the above materials alone or in combination.

[0036] It is preferable that the surface of the tool has fine irregularities formed at least on the portion that comes into contact with the glass plate. Such fine irregularities on the surface of the tool can be formed by roughening the surface of at least the portion that comes into contact with the glass plate, by adhering and fixing fine powder, or by kneading powder into the surface during molding of a material such as a resin.

[0037] When the tool is brought into contact with the glass plate, the tool may be moved relative to the glass plate while in contact with the glass plate, or the tool may be brought into contact with the glass plate with a predetermined pressing force, or with no pressing force, or substantially no pressing force.

[0038] The tool may be configured, for example, by passing a soft roll of foaming agent covered with a cover having fine irregularities through an elastic core and contacting the glass. Alternatively, a sheet-like object having an irregular surface may be brought into contact with the surface of the glass plate. This allows for efficient strength leveling on the production line.

[0039] Furthermore, in the strength leveling process, the tool may be brought into contact with the glass plate in the presence of a liquid. The liquid may be water, an aqueous solution, or an organic solvent, as long as it does not alter the glass or the tool. The liquid may be volatile or non-volatile.

[0040] In another example of the strength leveling treatment, a powder may be brought into contact with the surface of the laminated glass or glass sheet. For example, the powder may be spread on the surface of the glass sheet, and then the surface of the glass sheet may be wiped or swept with the tool, followed by washing to remove the powder. When wiping or sweeping the surface of the glass sheet with the tool, the powder may be wiped or swept directly over the powder, or a liquid such as water may be added before wiping or sweeping. Alternatively, the powder may be brought into contact with the glass sheet, and the tool may be placed on top of the powder, and the tool may be moved relative to the glass sheet along the surface of the glass sheet, with or without applying a pressing force. The tool used in the strength leveling treatment using the powder may be the same as the tool used in the above example of the strength leveling treatment in which the tool is brought into contact with the surface of the glass sheet.

[0041] The powder used in the strength leveling treatment using powder may contain inorganic or organic materials, or both. However, inorganic powders are preferred. Examples of inorganic powders include cerium oxide, glass beads, titanium oxide, diamond, calcium carbonate, anhydrous silicic acid, sodium hydrogen phosphate, silicon nitride, silicon carbide, and aluminum oxide. These powders can be used alone or in combination. The powder used may have an average particle size of 10 nm to 100 μm as measured by the sedimentation method. The powder may be used in a dry state, wetted with a liquid, or in a slurry form. The liquid used with the powder is not particularly limited as long as it does not denature the glass and powder. The liquid, which may be water, an aqueous solution, or an organic solvent, may be volatile or nonvolatile.

[0042] Although the details of the mechanism by which the strength of vehicle glass is leveled by the strength leveling treatment are not entirely clear, it is believed that fine cracks (also called microcracks, which are invisible fine cracks on the order of nanometers or less) on the surface of the glass sheet are involved. That is, fine cracks are originally present on the surface of the glass sheet after manufacture, and the uneven distribution of these fine cracks is a cause of variations in the strength of vehicle glass. However, the strength leveling treatment can introduce new cracks into the surface of the glass sheet, and these introduced cracks are thought to be able to reduce the strength of areas with excessively high strength. However, since the strength leveling treatment does not further reduce or barely reduce the strength of areas that originally have relatively low strength, it is possible to level the strength within the plane as a result.

[0043] When a laminated glass for vehicles is subjected to an impact, the impact can be absorbed by breakage or cracking of the glass. However, if the surface opposite the impact side is made more susceptible to breakage or cracking, the impact is particularly easily absorbed. Therefore, by performing a strength leveling treatment on the surface opposite the impact side to reduce or eliminate areas with excessively high strength, the impact can be more easily absorbed. Therefore, from the perspective of reducing or eliminating injury to a pedestrian when a pedestrian is hit from the outside of the laminated glass for vehicles, it is preferable that the strength leveling treatment be applied to one or more of the second surface 12 and the fourth surface 22, and more preferably that it be applied to at least the second surface 12, which is more susceptible to the impact. On the other hand, for the same reason, from the perspective of reducing or eliminating injury to an occupant when a occupant is hit from the inside of the laminated glass for vehicles, it is preferable that the strength leveling treatment be applied to one or more of the third surface 21 and the first surface 11, and more preferably that it be applied to at least the third surface 21, which is more susceptible to the impact. [Example]

[0044] In this example, strength tests were carried out on a glass plate that had been subjected to strength leveling treatment and an untreated glass plate, and the two were compared.

[0045] [Experiment 1] (Example 1) Eight glass plates, each measuring 66 mm x 66 mm and 2 mm thick, manufactured under the same conditions were prepared, and one side of each glass plate was subjected to a strength leveling treatment. A cotton cloth was spread over the glass plate, and approximately 10 g of eight types of powder (Kanto loam) listed in JIS Z8901 "Test Powders and Test Particles" was applied to an area of ​​200 cm. 2 The powder was spread to a uniform thickness over an area of ​​approximately 100 mL, and 100 mL of water was sprinkled evenly over the area where the powder was placed. Next, the powder-containing side of the cloth was placed on the surface of a glass plate, and while applying a pressing force of approximately 3 kg, the cloth was rubbed back and forth three times with a stroke of 6 cm in approximately 2 seconds while in contact with the surface of the glass plate. A strength test was conducted on the glass plate after this strength leveling treatment.

[0046] (Example 2) Eight glass plates similar to the untreated glass plates prepared in Example 1 were prepared and subjected to a strength test.

[0047] <Strength test> The strength of the glass plates in Examples 1 and 2 was measured as breaking stress (MPa) as follows. The breaking stress was measured using R30 in accordance with ISO1288-5 (2016). More specifically, a support ring with a diameter of 60 mm and a loading ring with a diameter of 12 mm were used, and a load was applied from the side that had not been subjected to the leveling treatment, i.e., the untreated side, at a loading rate of 0.3 mm per minute using the loading ring, and the breaking load was measured. The breaking stress was calculated using the formula described in ISO1288-5 (2016).

[0048] The results are shown in Figure 3. As shown in Figure 3, the average breaking stress was 455 MPa without leveling (Example 2), but decreased to 352 MPa after leveling (Example 1). Furthermore, the maximum breaking stress significantly decreased from 752 MPa without leveling (Example 2) to 552 MPa after leveling (Example 1). This indicates that regions with excessively high breaking stress (strength) were eliminated. Meanwhile, the minimum breaking stress was 148 MPa without leveling (Example 2), but decreased to 156 MPa after leveling (Example 1), showing very little change. This indicates that the strength leveling process suppresses the distribution of strength within the plane.

[0049] [Experiment 2] (Example 3) A set of 2 mm-thick glass sheets, an outer panel (reference numeral 10 in Figure 2) and an inner panel (reference numeral 20 in Figure 2), were prepared using the same process as mass-produced windshields. The third surface (the surface indicated by reference numeral 21 on the inner panel 20 in Figure 2) was subjected to a leveling treatment similar to that performed in Experiment 1 using eight types of powder and cotton cloth. After the treatment, the glass sheets were washed and returned to the mass-production process. The outer and inner panels were laminated to produce windshields. The resulting windshields were composed of a 2 mm-thick glass sheet, a 0.76 mm-thick PVB interlayer film, and another 2 mm-thick glass sheet. As shown in Figure 4 (a view of the fabricated windshield from the vehicle exterior), 12 100 mm x 100 mm samples (numbered S1 to S12) were cut from the center of the windshield.

[0050] (Example 4) A windshield was produced in the same manner as in Example 3 except that the leveling treatment was not carried out, and 12 samples of 100 mm x 100 mm were cut out from the center of the windshield, as shown in Figure 4.

[0051] <Strength test> Similar to Experiment 1, measurements were conducted in accordance with ISO 1288-5 (2016) and R30, except that the sample size was 100 mm x 100 mm and the loading rate was 1 mm per minute. More specifically, a support ring with a diameter of 60 mm and a loading ring with a diameter of 12 mm were used, and a load was applied from the inner plate (the surface of inner plate 20 indicated by reference numeral 22 in Figure 2) using the loading ring to measure the breaking load. To calculate the breaking stress, strain gauges (Kyowa Electric KFGS-5-120-D17-11) were used on two samples to determine the relationship between load and stress, and the breaking stress was calculated.

[0052] The results are shown in Figure 5. As shown in Figure 5, the average breaking stress was 397 MPa without leveling (Example 4), but decreased to 350 MPa after leveling (Example 3). Furthermore, the maximum breaking stress significantly decreased from 684 MPa without leveling (Example 4) to 499 MPa after leveling (Example 3). This indicates that regions with excessively high breaking stress (strength) were eliminated. Meanwhile, the minimum breaking stress was 147 MPa without leveling (Example 4), but decreased to 160 MPa after leveling (Example 3), showing very little change. This indicates that the strength leveling process suppresses the distribution of strength within the plane. Note that the results do not include the results for samples with strain gauges.

[0053] This application claims priority based on Japanese Patent Application No. 2020-015447, filed with the Japan Patent Office on January 31, 2020, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0054] 1. Laminated glass 10 First glass plate 11 1st surface 12 Second surface 20 Second glass plate 21 Third surface 22 4th surface 30 Interlayer 100 Automobiles

Claims

1. A laminated glass for vehicles, in which the proportion of an area in which the fracture stress, measured by the method described in ISO1288-5 (2016), is 100 MPa or more and 600 MPa or less is 90% or more of the see-through area.

2. 2. The laminated glass for vehicles according to claim 1, wherein the proportion of an area in which the fracture stress measured by the method described in ISO 1288-5 (2016) exceeds 600 MPa is 5% or less of the transparent area.

3. 3. The laminated glass for vehicles according to claim 1, wherein the proportion of an area in which the fracture stress measured by the method described in ISO 1288-5 (2016) is less than 100 MPa is 5% or less of the transparent area.

4. The laminated glass for vehicles according to claim 1 , wherein the breaking stress is a value measured by applying a load from the inside of the vehicle.

5. 5. The laminated glass for vehicles according to claim 4, wherein the breaking stress is a value measured by applying a load from the outside of the vehicle.

6. The laminated glass for vehicles according to claim 1 , wherein the breaking stress is a value measured before the laminated glass for vehicles is assembled to a vehicle.

7. The laminated glass for a vehicle according to claim 1 , which is a windshield.

8. An automobile comprising the laminated glass for vehicles according to any one of claims 1 to 7.

9. A method for manufacturing laminated glass for vehicles, comprising: the vehicle laminated glass is formed by laminating a first glass plate disposed on an exterior side of the vehicle and a second glass plate disposed on an interior side of the vehicle with an interlayer film interposed therebetween, the first glass sheet has a first surface facing the vehicle exterior and a second surface facing the vehicle interior, the second glass plate has a third surface on the vehicle exterior side and a fourth surface on the vehicle interior side, a strength leveling treatment being performed on at least one of the first surface to the fourth surface.

10. The method for manufacturing a laminated glass for a vehicle according to claim 9, wherein a strength leveling treatment is performed on at least one of the second surface, the third surface, and the fourth surface.

11. The method for producing a laminated glass for a vehicle according to claim 9 or 10, wherein the strength leveling treatment is carried out using a powder.

12. The method for producing a laminated glass for vehicles according to claim 9 or 10, wherein the strength leveling treatment is carried out by contacting the laminated glass with a tool having fine irregularities on its surface.

13. The method for producing a laminated glass for a vehicle according to claim 11 or 12, wherein the strength leveling treatment is carried out in the presence of a liquid.

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