Windshield

Abstract

To provide a windshield which is easily broken when a person collides with the windshield from the outside of a vehicle, and a method for manufacturing the same.SOLUTION: A windshield according to the present invention includes an outer glass plate, an inner glass plate that is arranged so as to face the outer glass plate, and an interlayer film that is arranged between the outer glass plate and the inner glass plate, and in at least a partial region of the outer glass plate and the inner glass plate, a principal compressive stress on a surface of the outer glass plate on a vehicle exterior side is larger than a principal compressive stress on a surface of the inner glass plate on a vehicle interior side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a windshield and a method for manufacturing the same. [Background technology]

[0002] Laminated glass for automobiles used in windshields and the like is composed of an outer glass sheet, an inner glass sheet, and an interlayer film disposed between these glass sheets (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-64965 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional laminated glass has been designed to be shatter-resistant by increasing the compressive stress on the surface in order to improve its durability against impacts. However, if a person hits the windshield from outside the vehicle during a collision accident, for example, the person may receive a large impact from the windshield if the windshield does not shatter.

[0005] The present invention has been made to solve the above problems, and has as its object to provide a windshield that is easily broken when struck by a person from outside the vehicle, and a method for manufacturing the same. [Means for solving the problem]

[0006] Item 1. An outer glass plate; an inner glass plate disposed opposite the outer glass plate; an interlayer film disposed between the outer glass sheet and the inner glass sheet; Equipped with A windshield, wherein in at least a portion of the outer glass sheet and the inner glass sheet, the principal compressive stress of the vehicle exterior surface of the outer glass sheet is greater than the principal compressive stress of the vehicle interior surface of the inner glass sheet.

[0007] Item 2. The windshield according to item 1, wherein the at least some region is a region below the center of the outer glass sheet and the inner glass sheet in the up-down direction.

[0008] Item 3. The windshield according to Item 1 or 2, wherein in at least a portion of the region, the principal compressive stress on the vehicle exterior surface of the outer glass sheet is greater than the principal compressive stress on the vehicle interior surface of the outer glass sheet.

[0009] Item 4. The windshield according to any one of Items 1 to 3, wherein in at least a portion of the region, the principal compressive stress on the vehicle exterior surface of the inner glass sheet is smaller than the principal compressive stress on the vehicle interior surface of the inner glass sheet.

[0010] Item 5. The windshield according to any one of Items 1 to 3, wherein in at least a portion of the region, the principal compressive stress on the vehicle exterior surface of the inner glass sheet is greater than the principal compressive stress on the vehicle interior surface of the inner glass sheet.

[0011] Item 6. The windshield according to any one of Items 1 to 5, wherein the thickness of the outer glass sheet is greater than the thickness of the inner glass sheet.

[0012] Item 7. The thickness of the outer glass plate is 0.7 mm or more and 5.0 mm or less, Item 7. The windshield according to any one of items 1 to 6, wherein the thickness of the inner glass plate is 0.3 mm or more and 3.0 mm or less.

[0013] Item 8. The windshield according to any one of Items 1 to 7, wherein in at least a portion of the region, the principal compressive stress of the vehicle exterior surface of the outer glass plate is 5 MPa or more and 50 MPa or less.

[0014] Item 9. When the thickness of the outer glass sheet is t1, the thickness of the inner glass sheet is t2, the principal compressive stress of the inner surface of the outer glass sheet is S2, and the principal compressive stress of the inner surface of the inner glass sheet is S4, S2*S4*(t1 2 +t1*t2) 2 <1600.

[0015] Item 10. A step of producing an outer glass plate by a pressing method; preparing an inner glass sheet by gravity; disposing an interlayer film between the outer glass sheet and the inner glass sheet and fixing the outer glass sheet and the inner glass sheet via the interlayer film; A method for manufacturing a windshield, comprising:

[0016] Item 11. A step of producing an outer glass plate by a pressing method, wherein the outer glass plate after pressing is subjected to rapid cooling; preparing an outer glass sheet by pressing; preparing an inner glass plate by pressing; disposing an interlayer film between the outer glass sheet and the inner glass sheet and fixing the outer glass sheet and the inner glass sheet via the interlayer film; A method for manufacturing a windshield, comprising: [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a windshield that is resistant to cracking when struck by flying stones or the like from outside the vehicle, but is susceptible to cracking when struck by a person from outside the vehicle. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a plan view showing an embodiment of a windshield according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3]2 is a graph showing stress distribution in the thickness direction of the windshield of FIG. 1. [Figure 4] 10 is a graph showing the results of a drop test. [Figure 5] 10 is a graph showing another example of stress distribution in the thickness direction of the windshield according to the present invention. [Figure 6] 10 is a graph showing another example of stress distribution in the thickness direction of the windshield according to the present invention. [Figure 7] 10 is a graph showing another example of stress distribution in the thickness direction of the windshield according to the present invention. [Figure 8] FIG. 10 is a plan view showing another example of a windshield according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] First, the configuration of the windshield according to this embodiment will be described using Figures 1 and 2. Figure 1 is a plan view of the windshield according to this embodiment, and Figure 2 is a cross-sectional view taken along line AA in Figure 1. For ease of explanation, the up-down direction in Figure 1 will be referred to as "up-down," "vertical," and "length," and the left-right direction in Figure 1 will be referred to as "left-right."

[0020] As shown in Figure 1, this windshield includes a trapezoidal laminated glass 10 that is long in the horizontal direction, and a shielding layer 4 that is laminated on the laminated glass 10. The laminated glass 10 includes an outer glass sheet 11, an inner glass sheet 12, and an interlayer film 13 that is disposed between them. Each component will be described in detail below.

[0021] <1. Glass plate> First, the outer glass sheet 11 and the inner glass sheet 12 will be described. The outer glass sheet 11 and the inner glass sheet 12 can be made of known glass sheets, and can also be made of heat-absorbing glass, general clear glass, green glass, or UV-green glass. However, these glass sheets 11 and 12 must have a visible light transmittance that complies with the safety standards of the country in which the automobile is used. For example, the outer glass sheet 11 can ensure the required solar radiation absorption rate, and the inner glass sheet 12 can be adjusted to have a visible light transmittance that meets the safety standards. Examples of clear glass, heat-absorbing glass, and soda-lime glass are shown below.

[0022] (clear glass) SiO2:70~73% by mass Al2O3:0.6~2.4% by mass CaO: 7~12% by mass MgO: 1.0~4.5% by mass RO: 13 to 15 mass% (R is an alkali metal) Total iron oxide converted to Fe2O3 (T-Fe2O3): 0.08 to 0.14 mass%

[0023] (heat-absorbing glass) The composition of the heat ray absorbing glass can be, for example, based on the composition of clear glass, with the ratio of total iron oxide (T-Fe2O3) converted to Fe2O3 being 0.4 to 1.3 mass%, the ratio of CeO2 being 0 to 2 mass%, and the ratio of TiO2 being 0 to 0.5 mass%, and the amount of the glass framework components (mainly SiO2 and Al2O3) reduced by the amount of the increase in T-Fe2O3, CeO2, and TiO2.

[0024] (soda-lime glass) SiO2: 65~80% by mass Al2O3: 0~5% by mass CaO: 5~15% by mass MgO: 2% by mass or more NaO: 10~18% by mass K2O: 0~5% by mass MgO+CaO: 5~15% by mass Na2O+K2O: 10~20% by mass SO3:0.05~0.3% by mass B2O3: 0~5% by mass Total iron oxide (T-Fe2O3) converted to Fe2O3: 0.02 to 0.03 mass%

[0025] The thickness of the laminated glass 10 according to this embodiment is not particularly limited. However, the total thickness of the outer glass sheet 11 and the inner glass sheet 12 can be, for example, 2.1 to 6 mm. From the viewpoint of weight reduction, the total thickness of the outer glass sheet 11 and the inner glass sheet 12 is preferably 2.4 to 3.8 mm, more preferably 2.6 to 3.4 mm, and particularly preferably 2.7 to 3.2 mm.

[0026] The outer glass plate 11 is primarily required to be durable and impact resistant against external obstacles, and as an automobile windshield, it must be impact resistant against flying objects such as pebbles. On the other hand, the thicker the plate, the heavier it becomes, which is undesirable. From this perspective, the thickness of the outer glass plate 11 is preferably 0.7 to 5.0 mm, more preferably 1.5 to 3.0 mm, and particularly preferably 1.8 to 2.3 mm.

[0027] The thickness of the inner glass sheet 12 can be the same as that of the outer glass sheet 11, but can be made thicker or thinner than the outer glass sheet 11, for example, to reduce the weight of the laminated glass 10. Specifically, in consideration of the strength of the glass, the thickness is preferably 0.3 to 3.0 mm, more preferably 0.7 to 2.3 mm, and particularly preferably 1.4 to 2.0 mm.

[0028] Furthermore, this laminated glass 10 is curved so as to be convex toward the exterior of the vehicle. In this case, the thickness is measured at two locations, one above and one below a center line extending vertically through the center of the laminated glass 10 in the left-right direction. The measuring device is not particularly limited, but a thickness gauge such as the SM-112 manufactured by Teclock Corporation can be used. During measurement, the curved surface of the laminated glass 10 is placed on a flat surface, and the edge of the laminated glass 10 is clamped between the thickness gauges to perform the measurement.

[0029] The outer glass sheet 11 and the inner glass sheet 12 can be tempered, but for example, at least one of the glass sheets can be air-cooled tempered. Alternatively, neither glass sheet can be chemically tempered.

[0030] <2. Interlayer film> The intermediate film 13 is formed of multiple layers. For example, as shown in FIG. 2, it can be configured as three layers, with a soft core layer 131 sandwiched between harder outer layers 132. However, the configuration is not limited to this, and it may be formed of multiple layers including the soft core layer 131. For example, it can be formed of two layers including the core layer 131 (one core layer and one outer layer), or an odd number of layers of five or more with the core layer 131 arranged in the center (one core layer and four outer layers), or an even number of layers including the core layer 131 inside (one core layer and the other layers are outer layers). Alternatively, the intermediate film 13 can be configured of a single layer.

[0031] The core layer 131 can be formed of a material softer than the outer layer 132, but is not limited to this. The materials constituting each layer 131, 132 are not particularly limited, and may be formed of, for example, a material that makes the core layer soft. For example, the outer layer 132 can be formed of polyvinyl butyral resin (PVB). Polyvinyl butyral resin is preferable because it has excellent adhesion to each glass plate and penetration resistance. On the other hand, the core layer 131 can be formed of ethylene vinyl acetate resin (EVA) or polyvinyl acetal resin, which is softer than the polyvinyl butyral resin constituting the outer layer 132. By sandwiching the soft core layer 131, sound insulation performance can be significantly improved while maintaining adhesion and penetration resistance equivalent to that of a single-layer resin interlayer film 3.

[0032] Furthermore, functional films having various functions can be used depending on the application as the core layer 131. For example, known heat-shielding films, heat-generating films, projection films, light-emitting films, antenna films, etc. can be used.

[0033] The total thickness of the intermediate film 13 is not particularly limited, but is preferably 0.3 to 6.0 mm, more preferably 0.5 to 4.0 mm, and particularly preferably 0.6 to 2.0 mm. On the other hand, the thickness of the core layer 131 is preferably 0.1 to 2.0 mm, and more preferably 0.1 to 0.6 mm. If the thickness is less than 0.1 mm, the soft core layer 131 will not have much of an effect, while if the thickness is greater than 2.0 mm or 0.6 mm, the total thickness will increase, resulting in increased costs. On the other hand, the thickness of the outer layer 132 is not particularly limited, but is preferably 0.1 to 2.0 mm, and more preferably 0.1 to 1.0 mm. Alternatively, the total thickness of the intermediate film 13 can be kept constant, and the thickness of the core layer 131 can be adjusted within this range.

[0034] The thickness of the interlayer film 13 does not need to be uniform over the entire surface, and it may be formed into a wedge shape for use in laminated glass for head-up displays, for example. In this case, the thickness of the interlayer film 13 is measured at the thinnest point, i.e., the bottom edge of the laminated glass.

[0035] The method for producing the interlayer film 13 is not particularly limited, and examples thereof include a method in which a resin component such as the polyvinyl acetal resin described above, a plasticizer, and other additives as necessary are blended and kneaded uniformly, and then each layer is extruded together, or a method in which two or more resin films produced by this method are laminated by a pressing method, a lamination method, etc. The resin films before lamination used in the lamination method by a pressing method, a lamination method, etc. may have a single-layer structure or a multi-layer structure.

[0036] <3. Shielding layer> As shown in Fig. 1, a shielding layer 4 is laminated on a dark colored ceramic such as black around the periphery of the laminated glass 10. This shielding layer 4 blocks visibility from inside and outside the vehicle, and is formed in a strip shape along the four sides of the laminated glass 10.

[0037] The shielding layer 4 may be laminated only on the vehicle interior surface of the inner glass sheet 12, or may be laminated in various other ways, such as only on the inner surface of the outer glass sheet 11, or on the inner surfaces of the outer glass sheet 11 and the inner glass sheet 12. The shielding layer 4 may be formed from ceramic or various other materials, such as the following composition:

[0038] [Table 1] *1, Main components: copper oxide, chromium oxide, iron oxide and manganese oxide *2, Main ingredients: bismuth borosilicate, zinc borosilicate

[0039] The ceramic can be formed by screen printing, but it can also be produced by transferring a firing transfer film to a glass plate and firing it. When using screen printing, for example, the following settings can be used: polyester screen: 355 mesh, coating thickness: 20 μm, tension: 20 Nm, squeegee hardness: 80 degrees, mounting angle: 75°, printing speed: 300 mm / s, and the ceramic can be formed by drying in a drying oven at 150°C for 10 minutes.

[0040] The shielding layer 4 can be formed by laminating ceramics or by attaching a dark-colored resin shielding film.

[0041] <4. Stress distribution in laminated glass> FIG. 3 is a graph showing the principal stress distribution of the laminated glass according to this embodiment. The horizontal axis of the graph in FIG. 3 represents the thickness direction of the laminated glass 10, and the vertical axis represents stress. Note that stress is expressed as negative for compression and positive for tension. As shown in FIG. 3 , in this laminated glass 10, the principal stress on the vehicle exterior side of the outer glass sheet 11 is compressive, and changes to tensile as the principal stress moves toward the interior of the outer glass sheet 11 in the thickness direction. After the tensile principal stress peaks near the center in the thickness direction, the principal stress decreases and changes to compressive as the vehicle interior side moves toward the interior side. The vehicle interior side is formed to exhibit substantially the same compressive principal stress as the vehicle exterior side. Hereinafter, for ease of explanation, the compressive principal stress on the vehicle exterior side of the outer glass sheet 11 will be referred to as S1, and the compressive principal stress on the vehicle interior side will be referred to as S2. In the example of FIG. 3 , S1 and S2 are substantially the same. The peak tensile principal stress will be referred to as S10.

[0042] The inner glass sheet 12 also exhibits a stress distribution similar to that of the outer glass sheet 11. That is, the principal stress on the outer surface of the inner glass sheet 12 is compressive, and the principal stress changes to tensile as it moves toward the interior of the inner glass sheet 12 in the thickness direction. After the tensile principal stress reaches a peak near the center in the thickness direction, the principal stress decreases and changes to compressive as it moves toward the inner surface. The inner surface is formed to exhibit substantially the same compressive principal stress as the outer surface. Hereinafter, for ease of explanation, the compressive principal stress on the outer surface of the inner glass sheet 12 will be referred to as S3, and the compressive principal stress on the inner surface will be referred to as S4. In the example of FIG. 3, S3 and S4 are substantially the same. The peak tensile principal stress will be referred to as S20.

[0043] Specifically, the principal compressive stresses S1 and S2 of the outer glass plate 11 are preferably 5 MPa or more and 50 MPa or less, and more preferably 5 MPa or more and 40 MPa or less. For example, if the principal stress S1 is 5 MPa or more, breakage due to flying stones can be suppressed. On the other hand, if the principal stress S1 is 40 MPa or more, optical distortion deteriorates. Furthermore, the principal compressive stresses S3 and S4 of the inner glass plate 12 are preferably 10 MPa or less, and more preferably 5 MPa or less. In particular, if S4 is 10 MPa or less, the drop height of the weight described below can be reduced.

[0044] Furthermore, the principal tensile stress S10 of the outer glass plate 11 is preferably 2.5 MPa or more and 25 MPa or less, and more preferably 2.5 MPa or more and 20 MPa or less. The principal tensile stress S20 of the inner glass plate 12 is preferably 5 MPa or less, and more preferably 2.5 MPa or less.

[0045] A glass cross-section stress meter (for example, SCALP-04 from Orihara Manufacturing Co., Ltd.) can be used to measure principal stresses. First, the glass cross-section stress meter is set in the center of the surface to be measured, and the stress meter is rotated within the surface to measure at three angles (0, 45, and 90 degrees). Rosette analysis is then performed on the measurement results to calculate the direction and magnitude of the principal stresses.

[0046] In the laminated glass according to this embodiment, the principal stress S1 is greater than the principal stress S4 (S1 > S4). The inventors discovered that, for example, when an object strikes the outer glass sheet 11 from outside the laminated glass, the inner glass sheet 12 breaks first, followed by the outer glass sheet 11. The inventors discovered this through the following experiment. First, six laminated glasses were prepared, each with a thickness of 2 mm for both glass sheets 11 and 12, a principal stress S1 of S4 + 5 MPa, a principal stress S3 = S4, and different principal stresses S4. Furthermore, a spherical weight with a radius of approximately 95 ± 1 mm and a weight of 10 ± 0.2 kg was prepared and dropped from a predetermined height onto each of the laminated glasses with the outer glass sheet 11 facing upward. As a result, it was confirmed that, in all of the laminated glasses, the inner glass sheet 12 broke before the outer glass sheet 11 broke. Figure 4 shows the relationship between the principal stress S4 in this test and the time when the inner glass sheet 12 broke. This result shows that the smaller the principal stress S4, the more likely the inner glass plate 12 is to break.

[0047] In addition to the relationship of principal stress S1>S4 as described above, it is preferable that the principal stress S2, the principal stress S4, the thickness t1 of the outer glass sheet 11, and the thickness t2 of the inner glass sheet 12 satisfy the following formula (1): Hereinafter, the left side of formula (1) will be referred to as the impact index. S2*S4*(t1 2 +t1*t2) 2 <1600 (1)

[0048] Equation (1) shows that head injuries can be reduced when a pedestrian collides with a windshield. Here, the head injury criterion (HIC) introduced by the National Highway Traffic Safety Administration (NHTSA) of the United States Department of Transportation is used. This HIC uses a standard value of 1000, and it is stipulated that if an impact with an HIC of 1000 is applied to the head, there is a 50% chance that serious head injuries will occur.

[0049] The following considerations were made in calculating formula (1). First, the present inventors discovered that a laminated glass in which both glass plates 11 and 12 have a thickness of 2 mm and principal stresses S2 and S4 of less than 5 MPa has an HIC of 1000 or less. Furthermore, for a laminated glass having glass plates of this thickness and principal stresses, a simulation was performed in which a weight was dropped from a predetermined height onto the laminated glass under the same conditions as in the above-mentioned experiment. First, an approximation curve for the graph shown in FIG. 4 was calculated, and the relationship between the principal stress S4 and the height (h1) of the weight was found to be as shown in formula (2) below (correlation coefficient R=0.9977). h1=59.923*S4+261.11 (2)

[0050] Based on this formula (2), if we expand the case where the thickness of each glass plate 11, 12 is other than 2 mm, and if the thickness of the outer glass plate 11 is t1 and the thickness of the inner glass plate 12 is t2, the relationship between the generated stress and the plate thickness gives the following relationship between the principal stress S4 when the inner glass plate 12 breaks and the height of the weight (h1). h1=(59.923*S4+261.11)*((t1+t2) / (2+2)) 2 (3)

[0051] Next, we calculated the drop height when the outer glass sheet 11 breaks after the inner glass sheet 12 breaks. Since the rigidity of the laminated glass is maintained only by the outer glass sheet 11, it is considered that only the outer glass sheet 11 breaks. Therefore, from the relationship in equation (2), the relationship between the principal stress S2 at which the outer glass sheet 11 breaks and the height of the weight (h2) is expressed as follows: h2=(59.923*S2+261.11)*(t1 / 2) 2 (4)

[0052] Therefore, the drop height (h) of the weight at which both the inner glass sheet 12 and the outer glass sheet 11 of the laminated glass break is h=h1+h2.

[0053] In this simulation, the height of the weight when the inner glass plate 12 and the outer glass plate 11 broke was 634 mm. Therefore, if the weight is dropped from a height lower than this, the HIC will be less than 1000. This is because energy is consumed as the glass breaks, and the impact is smaller because the glass breaks at a lower height.

[0054] Because the stress values ​​S2 and S4 are related to the drop height, if both glass sheets 11 and 12 are 2 mm thick, the drop height will be 634 mm or less if S2 * S4 < 25. Taking into account that laminated glass breaks due to bending fracture, that the inner glass sheet 12 breaks first, and the relationship between sheet thickness and generated stress, the formula (1) above was expanded to include cases where the thickness of each glass sheet 11 and 12 is other than 2 mm. Therefore, by specifying S2, S4, t1, and t2 to satisfy formula (1), the HIC can be reduced to 1000 or less, reducing the possibility of injury when a head strikes the windshield.

[0055] <5. Windshield manufacturing method> Next, an example of a method for manufacturing the windshield configured as above will be described. First, a method for manufacturing the laminated glass 1 will be described.

[0056] First, the above-described shielding layer 4 is laminated on at least one of the flat outer glass plate 11 and the flat inner glass plate 12. Next, these glass plates 11, 12 are formed so as to be curved. The forming method is not particularly limited, and any known method can be used. For example, a flat glass plate can be formed into a curved shape by passing it through a heating furnace and then pressing it with an upper mold and a lower mold (pressing method). Alternatively, the flat glass plate can be placed on a frame-shaped forming mold and passed through a heating furnace. This softens the glass plate, and it is formed into a curved shape by its own weight (gravity method).

[0057] However, in order to form the stress distribution shown in FIG. 3, it is preferable to form the outer glass sheet 11 by pressing and the inner glass sheet 12 by gravity. Forming the glass sheets by pressing increases the principal compressive and tensile stresses compared to gravity. Alternatively, both glass sheets 11, 12 can be formed by pressing. In this case, however, a step of rapidly cooling (quenching) the outer glass sheet 11 after pressing is provided, while the inner glass sheet 12 must be slowly cooled after pressing without being rapidly cooled. In this way, rapid cooling after pressing increases the principal compressive and tensile stresses.

[0058] After the outer glass sheet 11 and the inner glass sheet 12 are formed into a curved shape, the interlayer film 13 is sandwiched between the outer glass sheet 11 and the inner glass sheet 12, placed in a rubber bag, and pre-bonded at approximately 70 to 110°C while suctioning under reduced pressure. Other pre-bonding methods are also possible. For example, the interlayer film 13 is sandwiched between the outer glass sheet 11 and the inner glass sheet 12 and heated in an oven at 45 to 65°C. The laminated glass is then pressed with a roll at 0.45 to 0.55 MPa. The laminated glass is then heated again in an oven at 80 to 105°C, and pressed again with a roll at 0.45 to 0.55 MPa. This completes the pre-bonding process.

[0059] Next, the pre-bonded laminated glass is subjected to the main bonding in an autoclave, for example, at 8 to 15 atmospheres and 100 to 150°C. Specifically, the main bonding can be performed under conditions of, for example, 14 atmospheres and 145°C. In this way, the laminated glass 1 according to this embodiment is produced.

[0060] <6. Features> In the windshield described above, the principal compressive stress S1 on the surface of the outer glass sheet 11 facing the vehicle exterior is large, so that, for example, even if the windshield is struck by something outside the vehicle, the deformation is small. With such small deformation, the large principal compressive stress S1 can prevent cracks.

[0061] On the other hand, the compressive principal stress S4 on the interior surface of the inner glass sheet 12 is smaller than the principal stress S1, making the laminated glass 10 more susceptible to breakage when a person collides with it from outside. Because a person is heavy, the glass sheets are significantly deformed when they collide. When a person collides with the windshield from outside, both glass sheets 11 and 12 deform similarly, forming a convex shape toward the interior of the vehicle. At this time, tensile stress acts on the interior surface of the inner glass sheet 12 due to the deformation. However, because the compressive principal stress S4 on the interior surface of the inner glass sheet 12 is smaller, the inner glass sheet 12 breaks first when it deforms as described above. This reduces the rigidity of the laminated glass 10, which then causes the outer glass sheet 11 to break. Therefore, the laminated glass 10 is more susceptible to breakage when a person collides with it from outside. This reduces the impact that the colliding person receives from the laminated glass 10.

[0062] In particular, if S2, S4, t1, and t2 are defined so as to satisfy the above formula (1), it is possible to reduce the possibility of injury when the head strikes the windshield.

[0063] <7. Variations> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible without departing from the spirit of the present invention. The following modifications can be combined as appropriate.

[0064] <7-1> In the above embodiment, the principal stresses S1 and S2 of the outer glass sheet 11 are approximately the same. However, as shown in FIG. 5, for example, S1 may be greater than S2. This reduces the principal stress S2 on the inner surface of the vehicle, making it more likely that the outer glass sheet 11 will subsequently break if the inner glass sheet 12 breaks. Specifically, for example, S2 may be set to be 10 MPa smaller than S1. Note that such a difference between the principal stresses S1 and S2 can be achieved by, for example, cooling the outer surface of the outer glass sheet 11 on the vehicle interior side more strongly than the inner surface after pressing.

[0065] <7-2> In the above-described embodiment, the principal stresses S3 and S4 of the inner glass plate 12 are substantially the same. However, for example, as shown in FIG. 6, S4 < S3 can also be set. As a result, since the principal compressive stress S4 on the inner surface of the vehicle is small, when a tensile stress acts on the outer surface of the vehicle due to a collision of a person from outside the vehicle, it becomes more likely to crack. Specifically, for example, S4 can be made 10 MPa smaller than S3. In order to provide such a difference in the principal stresses S3 and S4, for example, after pressing, the outer surface of the inner glass plate 12 may be cooled more strongly than the inner surface.

[0066] Alternatively, as shown in FIG. 7, S4 > S3 can also be set. As a result, since the principal compressive stress S3 on the outer surface of the vehicle is small, for example, when a person collides with the windshield from the inside of the vehicle, a tensile stress due to deformation acts on the outer surface, making it more likely to crack. Specifically, for example, S3 can be made 3 MPa smaller than S4. In order to provide such a difference in the principal stresses S3 and S4, for example, in the self-weight method, the inner surface of the inner glass plate 12 may be cooled at a lower temperature than the outer surface.

[0067] <7-3> The distribution of the principal stresses as described above does not have to be formed over the entire laminated glass, and may be formed only in part. When forming it in part, for example, it is preferable to form such a distribution at least below the center in the vertical direction of the laminated glass. This is because when a person collides with the windshield from outside the vehicle, it is often the case that the lower part of the windshield is collided with.

[0068] <7-4> The configuration of the shielding layer 4 is not particularly limited, and as described above, it may be disposed along the peripheral edge of each glass plate, or, as shown in FIG. 7, an extension 42 for an on-board camera may be provided. This extension 42 has a photographing window 421 for the camera, allowing the camera to photograph the outside of the vehicle. This extension 42 can also hide the bracket supporting the camera from outside the vehicle. In addition to being provided with such an extension, the shielding layer 4 according to the present invention can be formed in various shapes. Note that the shielding layer 4 is not essential and may not be provided. [Example]

[0069] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0070] <1. Examples and Comparative Examples> Windshields according to Examples 1 to 11 and Comparative Examples 1 and 2 were produced by simulation. The principal stresses S1 to S4 shown in Table 2 below are the same as those shown in the above embodiment. In Examples 1 to 11, S1 is larger than S4, but in Comparative Examples 1 and 2, S1 and S4 are the same. [Table 2]

[0071] <2. Drop ball test> Next, a ball drop test was conducted by simulation. In this test, a spherical weight of 10±0.2 kg with a radius of approximately 95±1 mm was assumed and dropped onto the windshields of the above-mentioned Examples and Comparative Examples, and the height at which the glass plate broke (hereinafter referred to as the weight height) was calculated. Therefore, it is considered that the lower the weight height, the more likely the glass plate is to break upon impact with an object the size of a human head, such as a weight. Two types of tests were also conducted: one in which the weight was dropped from outside the vehicle (from the outer glass plate side) and one in which it was dropped from inside the vehicle (from the inner glass plate side). The results are as follows: [Table 3]

[0072] The judgments in Table 3 are as follows: A: Both glass plates break when the weight is less than 634 mm high. B: If the weight is 634 mm or higher, both glass plates will break. As mentioned above, 634 mm is the height at which the HIC is approximately 1000.

[0073] In Examples 1 to 11, the weight height at which both glass sheets break when a weight is dropped from outside the vehicle is low. This is because, as described above, the principal stress S1 is greater than the principal stress S4, and therefore, when a weight is dropped from outside the vehicle, it is believed that the inner glass sheet breaks first, followed by the outer glass sheet. In Examples 1 to 11, the weight height at which both glass sheets break is less than 634 mm, and therefore it is believed that the HIC is less than 1,000.

[0074] Comparing Example 7 and Example 9, in Example 9, S2 is smaller than S1 as shown in Fig. 5. Therefore, when a weight is dropped from outside the vehicle, Example 9 has a lower weight height than Example 7.

[0075] Comparing Example 2 and Example 7, in Example 2, S4 is smaller than S3 as shown in Fig. 6. Therefore, when a weight is dropped from outside the vehicle, Example 2 has a lower weight height than Example 7.

[0076] Comparing Example 8 with Example 7, S3 is smaller than S4 in Example 8 as shown in Fig. 6. Therefore, when a weight is dropped from inside the vehicle, the weight height in Example 8 is lower than that in Example 7.

[0077] Next, the impact index of formula (1) was calculated as follows: Examples 1 to 11 all exhibited lower impact indices than Comparative Examples 1 and 2. In particular, Examples 1, 2, 5, and 11 are considered to have a lower probability of injury even if the head hits the ground. [Table 4]

[0078] <3. Stepping stone test> The following experiment was conducted. First, a stone projecting device was placed 1 m away from the windshields of the above-mentioned Examples and Comparative Examples. Next, stones weighing 2.0 ± 0.2 mm were projected at 64 km / h (40 mph) toward the windshields of the Examples and Comparative Examples. Five stones were projected at different locations in the same area in one test to confirm whether cone cracks occurred. Then, the same test was conducted on 15 areas to confirm whether cone cracks occurred. Finally, the occurrence rate was calculated based on the presence or absence of cone cracks in all locations.

[0079] The judgments in Table 5 below are determined as follows: A: Incidence rate less than 1% B: Incidence rate is greater than 1% and less than 2% [Table 5]

[0080] From the above results, it is believed that cracking due to flying stones depends on S 1. In particular, Examples 1 to 11 obtained good results in both the above-mentioned ball drop test and flying stone test. [Explanation of symbols]

[0081] 10. Laminated glass 11 Outer glass plate 12 Inner glass plate 13 Interlayer 4 Shielding layer

Claims

1. An outer glass plate; an inner glass plate disposed opposite the outer glass plate; an interlayer film disposed between the outer glass sheet and the inner glass sheet; Equipped with A windshield, wherein in at least a portion of the outer glass sheet and the inner glass sheet, the principal compressive stress of the vehicle exterior surface of the outer glass sheet is greater than the principal compressive stress of the vehicle interior surface of the inner glass sheet.

2. The windshield according to claim 1 , wherein the at least some region is a region below the center of the outer glass sheet and the inner glass sheet in the up-down direction.

3. 3. The windshield according to claim 1, wherein in at least the partial region, a principal compressive stress on the vehicle exterior surface of the outer glass sheet is greater than a principal compressive stress on the vehicle interior surface of the outer glass sheet.

4. 4. The windshield according to claim 1, wherein in at least the partial region, a principal compressive stress on the vehicle exterior surface of the inner glass sheet is smaller than a principal compressive stress on the vehicle interior surface of the inner glass sheet.

5. 4. The windshield according to claim 1, wherein in at least the partial region, a principal compressive stress on the vehicle exterior surface of the inner glass sheet is greater than a principal compressive stress on the vehicle interior surface of the inner glass sheet.

6. 6. The windshield according to claim 1, wherein the thickness of the outer glass sheet is greater than the thickness of the inner glass sheet.

7. The thickness of the outer glass plate is 0.7 mm or more and 5.0 mm or less, 7. The windshield according to claim 1, wherein the inner glass sheet has a thickness of 0.3 mm or more and 3.0 mm or less.

8. 8. The windshield according to claim 1, wherein a principal compressive stress of the vehicle exterior surface of the outer glass sheet in at least the partial region is 5 MPa or more and 50 MPa or less.

9. When the thickness of the outer glass sheet is t1, the thickness of the inner glass sheet is t2, the principal compressive stress of the inner surface of the outer glass sheet is S2, and the principal compressive stress of the inner surface of the inner glass sheet is S4, S2 * S4 * (t1 2 + t1 * t2) 2 The windshield according to claim 8, wherein the windshield satisfies the relationship: <1600.

10. preparing an outer glass sheet by pressing; preparing an inner glass sheet by gravity; disposing an interlayer film between the outer glass sheet and the inner glass sheet and fixing the outer glass sheet and the inner glass sheet via the interlayer film; A method for manufacturing a windshield, comprising:

11. a step of preparing an outer glass sheet by a pressing method, and subjecting the pressed outer glass sheet to quenching; preparing an outer glass sheet by pressing; preparing an inner glass plate by pressing; disposing an interlayer film between the outer glass sheet and the inner glass sheet and fixing the outer glass sheet and the inner glass sheet via the interlayer film; A method for manufacturing a windshield, comprising:

Images