Windshield

Abstract

The windshield according to the present invention is equipped with an outside glass plate, an inside glass plate arranged facing the outside glass plate, and an intermediate film arranged between the outside glass plate and the inside glass plate. In a region of at least part of the outside glass plate and the inside glass plate, the principal stress of compression of the vehicle-outer-side surface of the outside glass plate is greater than the principal stress of compression of the vehicle-inner-side surface of the inside glass plate.

Description

Technical Field

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

Background Art

[0002] An automotive laminated glass used for a windshield or the like is composed of an outer glass plate, an inner glass plate, and an intermediate film disposed between these glass plates. (For example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in order to improve the durability against collisions, conventional laminated glass has adopted an approach of making it difficult to crack by increasing the compressive stress on the surface. However, for example, when a person collides with the windshield from outside the vehicle in a collision accident or the like, if the windshield does not crack, the person who has collided may receive a large impact from the windshield.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a windshield that is easily cracked when a person collides from outside the vehicle and a method for manufacturing the same.

Means for Solving the Problems

[0006] Item 1. An outer glass plate, An inner glass plate disposed opposite to the outer glass plate, An intermediate film disposed between the outer glass plate and the inner glass plate, Comprising, A windshield in which, in at least a portion of the outer glass plate and the inner glass plate, the principal compressive stress on the outer surface of the outer glass plate is greater than the principal compressive stress on the inner surface of the inner glass plate.

[0007] Item 2. The windshield according to Item 1, wherein at least a portion of the area is a region below the vertical center of the outer glass plate and the inner glass plate.

[0008] Item 3. The windshield according to item 1 or 2, wherein in at least a portion of the area, the principal compressive stress on the outer surface of the outer glass plate is greater than the principal compressive stress on the inner surface of the outer glass plate.

[0009] Item 4. The windshield according to any one of items 1 to 3, wherein in at least a portion of the area, the principal compressive stress on the outer surface of the inner glass plate is less than the principal compressive stress on the inner surface of the inner glass plate.

[0010] Item 5. The windshield according to any one of items 1 to 3, wherein in at least a portion of the area, the principal compressive stress on the outer surface of the inner glass plate is greater than the principal compressive stress on the inner surface of the inner glass plate.

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

[0012] Item 7. The thickness of the outer glass plate is 0.7 mm or more and 5.0 mm or less. 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 area, the principal compressive stress on the outer 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 plate is t1, the thickness of the inner glass plate is t2, the principal compressive stress on the inner surface of the outer glass plate is S2, and the principal compressive stress on the inner surface of the inner glass plate is S4, S2 * S4 * (t1 , , , , , , , , ,

[0017] , , , , , [Figure 1] ,

[0018] , , , ,

[0016] , <( , , [Figure 3] , , , [Figure 2] + t1 * t2) 2 <1600, the windshield according to item 8 that satisfies the relational expression.

[0015] [[ID=X]]Item 10. A step of manufacturing an outer glass plate by a pressing method, A step of manufacturing an inner glass plate by a self-weight method, A step of disposing an intermediate film between the outer glass plate and the inner glass plate and fixing the outer glass plate and the inner glass plate through the intermediate film, A method for manufacturing a windshield, comprising:

[0016] Item 11. A step of manufacturing an outer glass plate by a pressing method, the step of performing rapid cooling on the outer glass plate after pressing, A step of manufacturing an outer glass plate by a pressing method, A step of manufacturing an inner glass plate by a pressing method, A step of disposing an intermediate film between the outer glass plate and the inner glass plate and fixing the outer glass plate and the inner glass plate through the intermediate film, A method for manufacturing a windshield, comprising:

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a windshield that is difficult to crack when impacted by flying stones or the like from outside the vehicle, but is easy to crack when a person collides from outside the vehicle.

Brief Description of the Drawings

[0018] [Figure 1] It is a plan view showing an embodiment of the windshield according to the present invention. [Figure 2] It is a sectional view taken along the line A-A of FIG. 1. [Figure 3]Figure 1 is a graph showing the stress distribution in the thickness direction of the windshield. [Figure 4] This graph shows the results of the drop test. [Figure 5] This graph shows another example of the stress distribution in the thickness direction of the windshield according to the present invention. [Figure 6] This graph shows another example of the stress distribution in the thickness direction of the windshield according to the present invention. [Figure 7] This graph shows another example of the stress distribution in the thickness direction of the windshield according to the present invention. [Figure 8] This is a plan view showing another example of a windshield according to the present invention. [Modes for carrying out 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 the sake of explanation, the vertical direction in Figure 1 will be referred to as "up and down," "vertical," or "vertical," and the left and right direction in Figure 1 will be referred to as "left and right."

[0020] As shown in Figure 1, this windshield comprises a horizontally elongated trapezoidal laminated glass 10 and a shielding layer 4 laminated on the laminated glass 10. The laminated glass 10 has an outer glass plate 11, an inner glass plate 12, and an interlayer 13 placed between them. Each component will be described in detail below.

[0021] <1. Glass plate> First, the outer glass plate 11 and the inner glass plate 12 will be explained. The outer glass plate 11 and the inner glass plate 12 can be made of known glass plates, and can be formed of heat-absorbing glass, general clear glass or green glass, or UV green glass. However, these glass plates 11 and 12 must achieve a visible light transmittance that complies with the safety standards of the country in which the automobile will be used. For example, the outer glass plate 11 can be used to ensure the required solar absorptance, and the inner glass plate 12 can be used to adjust the visible light transmittance to meet 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 R2O: 13-15% by mass (R is an alkali metal) Total iron oxide (T-Fe2O3) converted to Fe2O3: 0.08~0.14% by mass

[0023] (Heat-absorbing glass) The composition of heat-absorbing glass can be, for example, based on the composition of clear glass, with a ratio of total iron oxide (T-Fe2O3) converted to Fe2O3 of 0.4 to 1.3 mass%, a ratio of CeO2 of 0 to 2 mass%, a ratio of TiO2 of 0 to 0.5 mass%, and a reduction in the glass skeleton components (mainly SiO2 and Al2O3) by the amount of 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: 0.02~0.03% by mass

[0025] The thickness of the laminated glass 10 according to this embodiment is not particularly limited, but the sum of the thicknesses of the outer glass plate 11 and the inner glass plate 12 can be, for example, 2.1 to 6 mm. From the viewpoint of weight reduction, it is preferable that the sum of the thicknesses of the outer glass plate 11 and the inner glass plate 12 be 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 primarily needs to be durable and impact resistant against external damage, and as a car windshield, it needs to be impact resistant against flying objects such as pebbles. On the other hand, a larger thickness increases the weight, which is undesirable. From this viewpoint, 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 plate 12 can be the same as that of the outer glass plate 11, but for example, in order to reduce the weight of the laminated glass 10, the thickness can be made greater or less than that of the outer glass plate 11. Specifically, considering the strength of the glass, it is preferable that the thickness be 0.3 to 3.0 mm, preferably 0.7 to 2.3 mm, and particularly preferably 1.4 to 2.0 mm.

[0028] Furthermore, although the laminated glass 10 is curved so as to be convex on the outside of the vehicle, the thickness measurement positions in this case are two points, one above and one below the center line that extends vertically through the center of the laminated glass 10 in the left-right direction. The measuring instrument is not particularly limited, but for example, a thickness gauge such as the SM-112 manufactured by Teclock Co., Ltd. can be used. When measuring, the curved surface of the laminated glass 10 is placed on a flat surface, and the edge of the laminated glass 1 is clamped with the thickness gauge and measured.

[0029] The outer glass plate 11 and the inner glass plate 12 can be strengthened; for example, at least one of the glass plates can be strengthened by air cooling. Alternatively, neither glass plate can be chemically strengthened.

[0030] <2. Interlayer> The interlayer 13 is formed of multiple layers. For example, as shown in Figure 2, it can be composed of three layers, with a soft core layer 131 sandwiched between harder outer layers 132. However, it is not limited to this configuration; it can be formed of multiple layers having a 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 five or more odd-numbered layers with the core layer 131 at the center (one core layer and four outer layers), or even-numbered layers with the core layer 131 on the inside (one core layer and the other layers being outer layers). Alternatively, the interlayer 13 can be composed of a single layer.

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

[0032] Furthermore, the core layer 131 can be a functional film having various functions depending on the application. 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 interlayer 13 is not particularly defined, but is preferably 0.3 to 6.0 mm, more preferably 0.5 to 4.0 mm, and most 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 it is less than 0.1 mm, the influence of the soft core layer 131 becomes less significant, and if it is greater than 2.0 mm or 0.6 mm, the total thickness increases, leading to increased costs. On the other hand, the thickness of the outer layer 132 is not particularly limited, but is preferably, for example, 0.1 to 2.0 mm, and more preferably 0.1 to 1.0 mm. Alternatively, the total thickness of the interlayer 13 can be kept constant, and the thickness of the core layer 131 can be adjusted within that limit.

[0034] Furthermore, the thickness of the interlayer 13 does not need to be uniform across the entire surface; for example, it can be wedge-shaped for laminated glass used in head-up displays. In this case, the thickness of the interlayer 13 is measured at the point with the smallest thickness, i.e., the bottom edge of the laminated glass.

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

[0036] <3. Shielding layer> As shown in Figure 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 the view from both inside and outside the vehicle and is formed in a band shape along the four sides of the laminated glass 10.

[0037] The shielding layer 4 can be laminated only on the inner surface of the inner glass plate 12, or in various other configurations, such as only on the inner surface of the outer glass plate 11, or on the inner surfaces of both the outer glass plate 11 and the inner glass plate 12. It can also be formed from ceramics or various other materials, but for example, it can have the following composition.

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

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

[0040] In addition to laminating ceramics, the shielding layer 4 can also be formed by attaching a dark-colored resin shielding film.

[0041] <4. Stress distribution of laminated glass> Figure 3 is a graph showing the principal stress distribution of laminated glass according to this embodiment. In the graph of Figure 3, the horizontal axis represents the thickness direction of the laminated glass 10, and the vertical axis represents the stress. However, stress is shown with compression as negative and tension as positive. As shown in Figure 3, in this laminated glass 10, the principal stress on the outer surface of the outer glass plate 11 is compressive, and as you move inward in the thickness direction of the outer glass plate 11, the principal stress changes to tension. Then, after the tensile principal stress reaches a peak near the center in the thickness direction, the principal stress decreases as you move inward towards the interior surface and changes to compression. The interior surface is formed to show approximately the same compressive principal stress as the outer surface. For the sake of explanation, below, the compressive principal stress on the outer surface of the outer glass plate 11 will be referred to as S1, and the compressive principal stress on the interior surface will be referred to as S2. In the example of Figure 3, S1 and S2 are approximately the same. The principal stress at the tensile peak will be referred to as S10.

[0042] The inner glass plate 12 exhibits a stress distribution similar to that of the outer glass plate 11. Specifically, the principal stress on the outer surface of the inner glass plate 12 is compressive, and as you move towards the interior of the inner glass plate 12 in the thickness direction, the principal stress changes to tensile. After the tensile principal stress reaches a peak near the center in the thickness direction, the principal stress decreases as you move towards the inner surface, and then changes to compressive. The inner surface is formed to exhibit almost the same compressive principal stress as the outer surface. For the sake of explanation, in the following, the compressive principal stress on the outer surface of the inner glass plate 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 in Figure 3, S3 and S4 are almost 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 between 5 MPa and 50 MPa, and more preferably between 5 MPa and 40 MPa. For example, if the principal stress S1 is 5 MPa or higher, damage due to flying stones can be suppressed. On the other hand, if the principal stress S1 is 40 MPa or higher, optical distortion will worsen. 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 later 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. Also, 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-sectional stress meter (for example, SCALP-04 from Orihara Seisakusho Co., Ltd.) can be used to measure principal stresses. First, the glass cross-sectional stress meter is placed in the center of the surface to be measured, and the meter is rotated within the surface to take measurements at three angles (0, 45, and 90 degrees). Then, a rosette analysis is performed on the measured 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 have found that, for example, when an object collides with the outer glass plate 11 from outside the laminated glass, the inner glass plate 12 breaks first, followed by the outer glass plate 11. The inventors have found this through the following experiment. First, six laminated glass pieces were prepared, each with a thickness of 2 mm, a principal stress S1 of S4 + 5 MPa, and a principal stress S3 = S4, with different principal stresses S4. Furthermore, a spherical weight of 10 ± 0.2 kg with a radius of approximately 95 ± 1 mm was prepared and dropped from a predetermined height onto each of the above laminated glass pieces with the outer glass plate 11 facing upwards. As a result, it was confirmed that in all laminated glass pieces, the inner glass plate 12 broke before the outer glass plate 11. Figure 4 shows the relationship between the principal stress S4 and when the inner glass plate 12 broke in this test. These results suggest that the smaller the principal stress S4, the more likely the inner glass plate 12 is to crack.

[0047] As described above, in addition to the relationship between principal stress S1 > S4, it is also preferable that principal stresses S2, S4, the thickness t1 of the outer glass plate 11, and the thickness t2 of the inner glass plate 12 satisfy the following equation (1). Hereafter, the left side of equation (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 U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA) is used. The HIC is set at 1000, and it is stipulated that an impact with an HIC of 1000 to the head has a 50% probability of causing serious head injury.

[0049] In calculating equation (1), the following considerations were made. First, the inventors found that in laminated glass where the thickness of both glass plates 11 and 12 is 2 mm each, and the principal stresses S2 and S4 are less than 5 MPa, the HIC will be 1000 or less. Furthermore, simulations were performed on glass plates of this thickness and laminated glass with principal stresses, under the same conditions as the experiment described above, in which a weight was dropped onto the laminated glass from a predetermined height. First, when the approximate curve of the graph shown in Figure 4 was calculated, the relationship between the principal stress S4 and the height of the weight (h1) was as shown in equation (2) below (correlation coefficient R = 0.9977). h1 = 59.923 * S4 + 261.11 (2)

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

[0051] Next, we calculated the drop height when the outer glass plate 11 breaks after the inner glass plate 12 has broken. Since the laminated glass maintains its rigidity only with the outer glass plate 11, we can consider only the outer glass plate 11 to be the case, and from the relationship in equation (2), the relationship between the principal stress S2 at which the outer glass plate 11 breaks and the height of the weight (h2) is given by the following equation. h2 = (59.923 * S2 + 261.11) * (t1 / 2) 2 (4)

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

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

[0054] Since the stress values ​​S2 and S4 of laminated glass are related to the drop height, if the thickness of both glass plates 11 and 12 is 2 mm each, then if S2*S4 < 25, the drop height will be 634 mm or less. Taking into account that the breakage of laminated glass occurs due to bending fracture, that the inner glass plate 12 breaks first, and the relationship between plate thickness and generated stress, the above equation (1) was defined by extending it to cases where the thickness of each glass plate 11 and 12 is other than 2 mm. Therefore, by defining S2, S4, t1, and t2 to satisfy equation (1), the HIC can be made 1000 or less, and the possibility of damage when the head collides with the windshield can be reduced.

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

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

[0057] However, in order to form the stress distribution shown in Figure 3, it is preferable to form the outer glass plate 11 by pressing and the inner glass plate 12 by gravity. Forming the glass plates by pressing results in larger principal stresses in compression and tension compared to the gravity method. Alternatively, both glass plates 11 and 12 can be formed by pressing. However, in this case, it is necessary to include a quenching step after pressing the outer glass plate 11, while the inner glass plate 12 is not quenched after pressing but is allowed to cool slowly. By applying quenching after pressing in this way, the principal stresses in compression and tension increase.

[0058] Once the outer glass plate 11 and the inner glass plate 12 are formed into a curved shape, the interlayer film 13 is then sandwiched between the outer glass plate 11 and the inner glass plate 12, placed in a rubber bag, and pre-bonded at approximately 70-110°C under reduced pressure suction. Other pre-bonding methods are also possible. For example, the interlayer film 13 is sandwiched between the outer glass plate 11 and the inner glass plate 12 and heated in an oven at 45-65°C. Subsequently, this laminated glass is pressed with a roller at 0.45-0.55 MPa. Next, this laminated glass is heated again in an oven at 80-105°C, and then pressed again with a roller at 0.45-0.55 MPa. In this way, pre-bonding is completed.

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

[0060] <6. Features> As described above, the principal compressive stress S1 on the outer surface of the outer glass plate 11 is large. Therefore, even if the windshield is struck by something outside the vehicle, such as the outer glass plate 11, the deformation is small. With such small deformation, the large principal compressive stress S1 can suppress cracking.

[0061] On the other hand, the principal compressive stress S4 on the inner surface of the inner glass plate 12 is smaller than the principal stress S1, making the laminated glass 10 more prone to breaking when a person collides with it from outside the vehicle. Because a person is heavy, the deformation of the glass plate is large when a collision occurs. When a person collides with the windshield from outside the vehicle, both glass plates 11 and 12 deform similarly, becoming convex inwards. At this time, tensile stress acts on the inner surface of the inner glass plate 12 due to the deformation, but because the principal compressive stress S4 on the inner surface of the inner glass plate 12 is small, when it deforms as described above, the inner glass plate 12 breaks first. As a result, the rigidity of the laminated glass 10 decreases, and the outer glass plate 11 also breaks subsequently. Therefore, the laminated glass 10 is more prone to breaking when a person collides with it from outside the vehicle. This reduces the impact that the colliding person receives from the laminated glass 10.

[0062] In particular, defining S2, S4, t1, and t2 in such a way as to satisfy equation (1) above can reduce the likelihood of head injury when the head collides with the windshield.

[0063] <7. Variation> 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 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 plate 11 are approximately the same, but for example, as shown in Figure 5, S1 > S2 can be made. This makes the principal stress S2 on the inner surface smaller, so when the inner glass plate 12 cracks, the outer glass plate 11 is more likely to crack afterward. Specifically, for example, S2 can be made 10 MPa smaller than S1. To create such a difference in principal stresses S1 and S2, for example, the outer surface of the outer glass plate 11 can be cooled more strongly than the inner surface after pressing.

[0065] <7-2> In the above 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 between 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 between 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 a part thereof. When forming it in a 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 often collides with the lower part of the windshield.

[0068] <7-4> The configuration of the shielding layer 4 is not particularly limited. As described above, it can be arranged along the periphery of each glass plate, and as shown in Figure 7, an extended portion 42 for an in-vehicle camera can also be provided. A camera viewing window 421 is formed in this extended portion 42, allowing for photography of the area outside the vehicle. Furthermore, this extended portion 42 can also conceal the bracket supporting the camera from view outside the vehicle. In addition to providing such an extended portion, the shielding layer 4 according to the present invention can have various shapes. Note that the shielding layer 4 is not essential and may not be provided. [Examples]

[0069] The following describes embodiments of the present invention. However, the present invention is not limited to the following embodiments.

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

[0071] <2. Ball Drop Test> Next, a drop test was conducted using simulation. In this test, a spherical weight with a radius of approximately 95 ± 1 mm and a weight of 10 ± 0.2 kg was assumed and dropped onto the windshields according to the above 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 easily the glass plate breaks from the impact of 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 another in which it was dropped from inside the vehicle (from the inner glass plate side). The results were as follows. [Table 3]

[0072] The judgments in Table 3 are based on the following criteria: A: Both glass plates will break if the weight is less than 634mm tall. B: Both glass plates will break if the weight is 634mm or higher. As mentioned above, 634mm is the height at which the HIC is approximately 1000.

[0073] In Examples 1-11, the height of the weight dropped from outside the vehicle caused both glass plates to break, and this was observed in the lower examples. This is because, as mentioned above, the principal stress S1 is greater than the principal stress S4, so when a weight is dropped from outside the vehicle, the inner glass plate breaks first, followed by the outer glass plate. In Examples 1-11, the height of the weight at which both glass plates break is less than 634 mm, so the HIC is considered to be less than 1000.

[0074] Comparing Example 7 and Example 9, in Example 9, S2 is smaller than S1, as shown in Figure 5. Therefore, in the case of dropping the weight from outside the vehicle, the weight height in Example 9 is lower than in Example 7.

[0075] Comparing Example 2 and Example 7, in Example 2, S4 is smaller than S3, as shown in Figure 6. Therefore, in the case of dropping the weight from outside the vehicle, the weight height is lower in Example 2 than in Example 7.

[0076] Comparing Example 8 with Example 7, in Example 8, S3 is smaller than S4, as shown in Figure 6. Therefore, in the dropping of the weight from inside the vehicle, the weight height is lower in Example 8 than in Example 7.

[0077] Next, the impact index calculated using equation (1) is as follows. Examples 1 to 11 all show 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 in the event of a head collision. [Table 4]

[0078] <3. Stone-throwing test> The following experiment was conducted. First, the stone projectile launching device was positioned at a distance of 1 m from the windshields of the above-described examples and comparative examples. Next, stones weighing 2.0 ± 0.2 mm were projected towards the windshields of the examples and comparative examples at a speed of 64 km / h (40 MPa). In each test, five projectiles were launched at different locations in the same area to check for the occurrence of cone cracks. Then, the same test was performed at 15 different locations to check for the occurrence of cone cracks. Finally, the occurrence rate was calculated from the presence or absence of cone cracks at all locations.

[0079] The judgments in Table 5 below are based on the following reasoning. A: Incidence rate less than 1% B: Incidence rate greater than 1% and less than or equal to 2% [Table 5]

[0080] Based on these results, it is considered that cracking due to flying stones depends on S1. In particular, Examples 1 to 11 obtained good results in both the ball drop test and the flying stone test described above. [Explanation of Symbols]

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

Claims

1. It is a windshield, An outer glass panel made of soda-lime glass, positioned on the outside of the vehicle, An inner glass plate, made of soda-lime glass, is positioned opposite the outer glass plate and on the inside of the vehicle, An interlayer is disposed between the outer glass plate and the inner glass plate, Equipped with, The thickness of the outer glass plate is 0.7 mm or more and 5.0 mm or less. The thickness of the inner glass plate is 0.3 mm or more and 3.0 mm or less. In at least a portion of the outer and inner glass plates, the principal compressive stress on the outer surface of the outer glass plate is greater than the principal compressive stress on the inner surface of the inner glass plate, so that the inner glass plate breaks before the outer glass plate, thereby reducing the impact received by a person colliding with the windshield from outside the vehicle. A windshield in which, in at least a portion of the aforementioned region, the principal compressive stress on the outer surface of the outer glass plate is 5 MPa or more and 50 MPa or less.

2. The windshield according to claim 1, wherein at least a portion of the region is a region below the vertical center of the outer glass plate and the inner glass plate.

3. The windshield according to claim 1 or 2, wherein in at least a portion of the region, the principal compressive stress on the outer surface of the outer glass plate is greater than the principal compressive stress on the inner surface of the outer glass plate.

4. The windshield according to any one of claims 1 to 3, wherein in at least a portion of the region, the principal compressive stress on the outer surface of the inner glass plate is smaller than the principal compressive stress on the inner surface of the inner glass plate.

5. The windshield according to any one of claims 1 to 3, wherein in at least a portion of the region, the principal compressive stress on the outer surface of the inner glass plate is greater than the principal compressive stress on the inner surface of the inner glass plate.

6. The windshield according to any one of claims 1 to 5, wherein the thickness of the outer glass plate is greater than the thickness of the inner glass plate.

7. When the thickness of the outer glass plate is t1 (mm), the thickness of the inner glass plate is t2 (mm), the principal compressive stress on the inner surface of the outer glass plate is S2 (MPa), and the principal compressive stress on the inner surface of the inner glass plate is S4 (MPa), S2*S4*(t1 2 (+t1*t2) 2 A windshield according to any one of claims 1 to 6 that satisfies the relationship <1600.

8. A method for manufacturing a windshield according to claim 1, The process involves a step of manufacturing the outer glass plate using a pressing method, The process involves creating an inner glass plate using the self-weight method, The steps include: placing an interlayer between the outer glass plate and the inner glass plate, and fixing the outer glass plate and the inner glass plate via the interlayer; A method for manufacturing a windshield, which includes [a specific feature / feature].

9. A method for manufacturing a windshield according to claim 1, A step of manufacturing an outer glass plate by a pressing method, comprising the step of rapidly cooling the outer glass plate after pressing, The process involves a step of manufacturing the outer glass plate using a pressing method, The process involves a step of manufacturing the inner glass plate using a pressing method, The steps include: placing an interlayer between the outer glass plate and the inner glass plate, and fixing the outer glass plate and the inner glass plate via the interlayer; A method for manufacturing a windshield, which includes [a specific feature / feature].

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