Panel

Abstract

Panel for a vehicle with: a plate-like workpiece (3) including a central portion (13) and a peripheral portion (15) located outside the central portion (13), the central portion (13) and the peripheral portion (15) having an application surface (3S), the peripheral portion (15) having an edge surface (3E, 3F, 23E, 33E) extending in a thickness direction of the workpiece (3); and a layer (5) formed by applying a coating liquid (9) to the application surface (3S) of the workpiece (3) using a flooding method; wherein the application surface (3S) is continuous with the edge surface (3E, 3F, 23E, 33E), wherein when the workpiece (3) is viewed in a section perpendicular to the edge surface (3E, 3F, 23E, 33E) and extending in the direction of thickness, the application surface (3S) has a first curvature (C1) located in the central portion (13) and a second curvature (C3, C23, C33) located in the peripheral portion (15), wherein the first curvature (C1) has a first radius of curvature (R1), characterized by a specific curvature (C2, C32) located in the peripheral portion (15), wherein the specific curvature (C2, C32) has a specific radius of curvature (R2, R32) that is smaller than the first radius of curvature (R1), and the second curvature (C3, C23, C33) has a second radius of curvature (R3, R23, R33) that is smaller than the specific radius of curvature (R2, R32), wherein the edge surface (3E, 3F, 23E, 33E) has a curvature (C4), wherein the specific curvature (C2, C32) is continuous with the first curvature (C1) and is located outside thereof, and wherein the second curvature (C3, C23, C33) is continuous with the specific curvature (C2, C32) and is located outside thereof, and the curvature (C4) of the edge surface (3E, 3F, 23E, 33E) is continuous with the second curvature (C3, C23, C33) and is located outside thereof, and the first curvature (C1) and the determined curvature (C2, C32) have a common tangential line (L1, L31, L41), the determined curvature (C2, C32) and the second curvature (C3, C33, C43) have a common tangential line (L2, L22, L32), and the second curvature (C3, C33, C43) and the curvature (C4) of the edge surface (3E, 3F, 23E, 33E) have a common tangential line.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to a panel.JP 00 2007 137 748 A discloses a panel including a plate-like workpiece and a layer formed on an application surface of the workpiece by applying a coating liquid during flooding.The workpiece has a central portion and a peripheral portion placed so as to surround the central portion, and has an edge surface extending in the direction of thickness of the workpiece. The central portion has a curved surface forming a central portion of the application surface of the workpiece, and the peripheral portion has a curved surface forming the peripheral portion of the application surface. The curved surfaces of the central portion and the peripheral portion are formed continuously with each other and have substantially the same radius of curvature. In the aforementioned publication, the radius of curvature of the curved surfaces is determined by the weight of the workpiece.A layer is formed by applying a coating liquid to the application surface of the workpiece in the flooding process. The coating liquid uniformly covers the curved surface of the central portion, but tends to form a liquid pool in the area of the curved surface of the peripheral portion. It is considered that a liquid pool is formed because the coating liquid spreads easily on the curved surface of the middle portion by the weight of the coating liquid, whereas the peripheral portion has the edge surface adjacent to the curved surface, and it is difficult for the coating liquid to remain on the edge surface, so that the surface tension is generated only on the curved surface of the peripheral portion. This is even more likely to occur when the workpiece is placed in a substantially horizontal position during coating in the flow coating. When the coating liquid is dried in this state, the thickness of the layer varies between the curved surfaces of the central portion and the peripheral portion of the workpiece, so that the resulting panel does not meet the desired quality requirements of the panel.To address such a problem, the aforementioned publication proposes providing a suction nozzle at a location adjacent to the peripheral portion of the workpiece. The suction nozzle is movably ejected along the peripheral portion of the workpiece thereto while causing a suction air flow during the coating operation. Surplus coating liquid forming a collection on the peripheral portion is sucked with the air into the nozzle or allowed to flow down the edge surface of the peripheral portion by its own weight, with the result that a panel having a uniform thickness is produced in the curved surfaces of the central portion and the peripheral portion.However, manufacturing the panel according to the aforementioned publication requires the use of a suction nozzle that makes the layer uniform in the curved surfaces of the central portion and the peripheral portion, thereby not only increasing the initial equipment cost and requiring additional operations, but also increasing the production cost of the panel.The present invention, which has been made in view of the aforementioned problems, is directed to producing a panel having a desired quality while reducing the production cost.SUMMARY OF THE INVENTIONIn accordance with one aspect of the present invention, there is provided a panel comprising a plate-like workpiece having a central portion and a peripheral portion placed outside the central portion. The central portion and the peripheral portion have an application surface, and the peripheral portion has an edge surface extending in a direction of thickness of the workpiece. The panel further has a layer formed by applying a coating liquid to the application surface of the workpiece using a flow coating method. The application surface is continuous with the edge surface. When the workpiece is viewed in a cross section that is perpendicular to the edge surface and extends in the direction of thickness, the application surface has a first curvature located in the central portion, a certain curvature located in the peripheral portion, and a second curvature located in the peripheral portion. The first curvature has a first radius of curvature. The determined curvature has a determined radius of curvature and is continuous with the first curvature and is outside the first curvature. The second curvature has a second radius of curvature that is less than the determined radius of curvature. The second curvature is continuous with the determined curvature and is outside the determined curvature.Other aspects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.BRIEF DESCRIPTION OF THE DRAWINGSThe invention may best be understood, together with objects and advantages thereof, by reference to the following description of the presently preferred embodiments, taken in conjunction with the accompanying drawings, in which: FIG. 1 is a front view of a panel according to a first embodiment of the present invention, showing a state in which a coating liquid is applied to an application surface of a workpiece in a flooding process; FIG. 2 is a side view of the panel of FIG. 1 ; FIG. 3 is a partial perspective view of the workpiece of FIG. 1 ; FIG. 4 is a partially enlarged sectional view of the workpiece with a layer taken along line A-A of FIG. 3 ; FIG. 5 is a partially enlarged sectional view of the workpiece taken along line A-A of FIG. 3 with a layer; FIG. 6 is a partially enlarged sectional view of a workpiece according to a second embodiment of the present invention; FIG. 7 is a partially enlarged sectional view of a workpiece according to a third embodiment of the present invention; FIG. 8 is a graph showing the relationship between the length of the workpiece and the thickness of the layers of panels according to the first to third embodiments of the present invention and a comparative example; FIG. 9 is a partially enlarged sectional view of a workpiece having a layer according to a first comparative example; and FIG. 10 is a graph showing the relationship between the length of the workpiece and the thickness of layers of a panel of a first comparative example whose workpiece was placed in a horizontal position and coated with the layer and a panel of a second comparative example whose workpiece was placed in a vertical position and coated with the layer.DETAILED DESCRIPTION OF THE EMBODIMENTS(First Embodiment)Referring to FIGS. 1 and 2, a workpiece 3 is shown placed substantially in a horizontal position on a base 1. The workpiece 3 has a plate-like shape, and the workpiece 3 is transparent and made of a polycarbonate resin (PC). The workpiece 3 has, on its upper surface, an application surface 3S on which a layer 5 is formed.As shown in FIG. 3, the workpiece 3 has a central portion 13 and a peripheral portion 15 surrounding the central portion 13. The central portion 13 located at the center of the workpiece 3 has a first curved surface S 1 forming a central region of the application surface 3S. The peripheral portion 15 is located outside the central portion 13 and has edge surfaces 3E, 3F extending in the thickness direction of the workpiece 3. The application surface 3S is continuous with the edge surfaces 3E, 3F.As seen in the sectional view of the workpiece 3 which is perpendicular to the edge surface and extends in the thickness direction in FIG. 4, the first curved surface S 1 has a first curvature C 1 having a circular arc with a first radius of curvature R 1 of 3000 mm with the point O 1 as the center. Further, as shown in FIG. 3, the surface of the workpiece 3 is slightly curved above the line A-A. Thus, a line from the point O1 to the application surface 3S is slightly curved as shown in FIG. 4. The sectional view of the workpiece 3 shown in FIG. 4 is also applicable to the section of the workpiece along the line B-B of FIG. 3.The peripheral portion 15 has a certain surface S 2 and a second curved surface S 3. Referring to FIG. 4, the specific surface S2 has a specific curvature C2 which is a circular arc having a specific radius of curvature R2 of 10.00 mm with the point O2 as the center. The determined radius of curvature R2 is considerably smaller, although not infinite, than the first radius of curvature R1.The specific surface S 2 is formed continuously with the first curved surface S 1 of the application surface 3S. In FIG. 4, reference character B 1 denotes a boundary between the first curvature C 1 and the specified curvature C 2, and L 1 denotes a line tangent to both the first curvature C 1 and the specified curvature C 2.The second curved surface S 3 has, as seen in FIG. 4, a second curvature C 3 that is an arc having a second radius of curvature R 3 of 3.0 mm that is smaller than the specified radius of curvature R 2 with the point O 3 as the center. More specifically, the determined radius of curvature R 2 approximates the second radius of curvature R 3, and the determined radius of curvature is about 3.3 times as large as the second radius of curvature R 3.The second curvature C 3 is formed continuously with the determined curvature C 2. In FIG. 4, B 2 denotes a boundary between the specific curvature C 2 and the second curvature C 3, and L 2 denotes a line tangential to both the specific curvature C 2 and the second curvature C 3.The second curvature C 3 is formed continuously with a curvature C 4 of the edge surfaces 3E, 3F, respectively. The second curvature C 3 has boundaries B 3 with both curvatures C 4 of the end surfaces 3E, 3F, and the tangential line L 3 extends in a thickness direction of the workpiece 3 along the edge surfaces 3E, 3F.In coating the workpiece 3 using the flooding method, a nozzle 11 is provided to face the upper surface of the workpiece 3, as shown in FIGS. 1 and 2. While the nozzle 11 is ejected from the upper surface of the workpiece 3 in the partial direction shown in FIG. 2, coating liquid 9 flows out through a slit of the nozzle 11 and is applied to the application surface 3S of the workpiece 3. The coating liquid 9 applied to the surface is dried to form a transparent hard coating. Thus, the panel of the first embodiment is formed. The panel thus manufactured has the workpiece 3 and the layer 5 formed by applying the coating liquid 9 to the application surface 3S of the workpiece 3 using the flooding method.Referring to the graph of FIG. 8, the curve line (A) shows a relationship between the dimension of the workpiece 3 measured in the longitudinal direction and the thickness of the layer 5 with respect to the boundary B 1 between the first curvature C 1 and the determined curvature C 2. As shown by the line (A), the coating liquid 9 tends to reduce liquid accumulation in the area of the specific area S 2 of the peripheral portion 15 in the workpiece 3 of the first embodiment. Since the specific radius of curvature R 2 does not include the value infinity, the specific surface S 2 is not flat, so that the coating liquid 9 hardly forms liquid accumulation in the area of the specific surface S 2.When the coating liquid 9 is dried in this state, the layer 5 is formed in the region of the first curved surface S 1 of the central portion 13 and the specific surface S 2 and the second curved surface S 3 of the peripheral portion 15 with a substantially uniform thickness. T1 to T4 in Fig. 8 indicate various levels of film thicknesses, where T1 represents the most severe level. As can be seen from the curve (A) in FIG. 8, the thickness of the layer 5 of the panel according to the present embodiment is in the range between the most severe level T 1 and the next level T 2. Thus, a desired panel is produced with the workpiece 3.Generally, in a panel, when the panel has a first curved surface having a first radius of curvature formed in a central portion and a peripheral portion, the panel must have a second curved surface having a second radius of curvature considerably smaller than the first radius of curvature and continuous with the edge surface of the peripheral portion. The second curved surface may be referred to as chamfer and is formed continuously with and outside the first curved surface such that the periphery of a workpiece is free of cracks. When the workpiece is made of resin, the second radius of curvature may be set relatively large. When a coating liquid is applied to the application surface of the workpiece using the flow coating method, the coating liquid tends to form a liquid pool around a boundary between the first curved surface and the second curved surface.The workpiece 3 of the present invention has the specific surface S 2 between the first curved surface S 1 in the central portion 13 and the second curved surface S 3 in the peripheral portion 15. The specific surface S 2 is continuous with and outside the first curved surface S 1 in the application surface, and the second curved surface S 3 is continuous with and outside the specific surface S 2. When the coating liquid 9 is applied to the application surface 3S of the workpiece 3 using the flow coating method, the coating liquid 9 tends to less form liquid accumulation in the area of the specific surface S 2 because the surface tension of the coating liquid 9 can be relaxed by the specific surface S 2 between the first curved surface S 1 and the second curved surface S 3.According to the present embodiment, the manufacture of the panel does not require equipment such as a suction nozzle and an operation for sucking the coating liquid 9 through the nozzle.Therefore, the workpiece 3 of the present embodiment allows to produce a panel having the desired quality while reducing the production cost.Moreover, since the workpiece 3 and the layer 5 according to the first embodiment are transparent, a disturbed view caused by the thickness variation of the layer 5 can be minimized. The panel of the present invention provides a clear view when used as a sunroof or window of a vehicle.(Second Embodiment)A workpiece of a panel according to a second embodiment of the present invention will be described below with reference to FIG. 6. Reference numeral 23 denotes the workpiece of a panel of the second embodiment of the present invention. The workpiece 23 has a peripheral portion 25 including the specific surface S 2 and a second curved surface S 23. As seen in the cross section of FIG. 6, the specific surface S 2 has the specific curvature C 2 having a circular arc with the specific radius of curvature R 2 with the point O 2 as the center. The second curved surface S 23 has a second curvature C 23 having an arc with the second radius of curvature R 23 of 1.5 mm with the point O 23 as the center. The determined radius of curvature R 2 approximates the second radius of curvature R 23, and the determined radius of curvature is set to be about 6.7 times as large as the second radius of curvature R 23.In FIG. 5, B 22 denotes a boundary between the specific curvature C 2 of the specific surface S 2 and the second curve C 23 of the second curved surface S 23, and L 22 denotes a line tangential to the specific curvature C 2 and the second curvature C 23. B 23 denotes a boundary between the second curvature C 23 of the second curved surface 23 and a curvature C 24 of the edge surface 23E of the workpiece 23, and L 23 denotes a line tangential to the second curvature C 23 at the boundary B 23. Conditions of room temperature and humidity in applying the coating liquid 9 to the application surface 3S and the rest of the configurations are substantially the same as in the first embodiment.Referring to FIG. 8, the curved line (B) shows a relationship between the dimension of the workpiece 23 measured in the longitudinal direction and the thickness of the layer 5 with respect to the boundary B 1 between the first curved surface S 1 and the specific surface S 2. As with the workpiece 23 of the panel of the second embodiment, the coating liquid 9 is less apt to form liquid accumulation in the area of the specified area S 2 of the peripheral portion 25 of the workpiece 23. The thickness of the film 5 is in the range between T1 and T3. Thus, a desired panel is also manufactured using the workpiece 23. The second embodiment also enables the other effects of the first embodiment.(Third Embodiment)Next, a workpiece of a panel according to a third embodiment of the present invention will be described with reference to FIG. 7. Reference numeral 33 denotes a workpiece according to the third embodiment, and the workpiece 33 has a specific surface S 32 and a second curved surface S 33. The specific surface S 32 has a specific curvature C 32 having an arc with a specific radius of curvature R 32 of 20.0 mm with the point O 32 as the center. The second curved surface S 33 has a second curvature C 33 that is an arc having a second radius of curvature R 33 of 3.0 mm with the point O 33 as the center. The determined radius of curvature R 32 approximates the second radius of curvature R 33, and the determined radius of curvature R 32 is set to be about 6.7 times as large as the second radius of curvature R 33.B 31 is the boundary between the first curvature C 1 and the specific curvature C 32, and L 31 is a line tangent to the first curvature C 1 and the specific curvature C 32. B 32 is the boundary between the specific curvature C 32 and the second curvature C 33, and L 32 is a line tangent to the specific curvature C 32 and the second curvature C 33. B 33 is the boundary between the second curvature C 33 and a curvature C 34 of an edge surface 33E of the workpiece 33, and L 33 is a line tangential to the second curvature C 33 at the boundary B 33. The rest of the configuration is substantially the same as the first embodiment.Referring to FIG. 8, the curve line (C) shows a relationship between the dimension of the workpiece 33 measured in the longitudinal direction and the thickness of the layer 5 with respect to the boundary B 31 between the first curvature C 1 and the determined curvature C 32. In the workpiece 33, the coating liquid 9 is less likely to form liquid accumulation in the area of the specified area S 32 of the peripheral portion 35. The thickness of the layer 5 is in the range between T1 and T4. Therefore, a desired panel is manufactured with the workpiece 33. The rest of the effects of the workpiece 23 is substantially the same as in the first embodiment.As is apparent from the above description with reference to the first, second, and third embodiments, the coating liquid 9 is unlikely to form liquid accumulation in the area of the specific surface of the peripheral portion of the workpiece when the specific radius of curvature is 3.3 to 6.7 times larger than the second radius of curvature.(First Comparative Example)Referring to FIG. 9, reference numeral 43 denotes a workpiece of a first comparative example. Unlike the first, second and third embodiments, the workpiece 43 has a peripheral portion 45 having a second curved surface S 43 but not having a specific surface. The second curved surface S 43 has a second curvature C 43 that is a circular arc having a second radius of curvature R 43 of 3.0 mm with the point O 43 as a center.The second curvature C 43 is formed continuously with the first curvature C 1. More specifically, the first curvature C 1 and the second curvature C 43 share a boundary B 43 therebetween, and L 41 is a line tangential to the first curvature C 1 and the second curvature C 43. The second curvature C 43 is formed continuously with a curvature C 44 of the edge surface 43E. L 43 is a line tangential to the second curvature C 43 at the boundary B 43. The rest of the configuration is substantially the same as the first embodiment.Referring to FIG. 8, the curve line (D) shows a relationship between the dimension of the workpiece 43 measured in the longitudinal direction and the thickness of the layer 5 with respect to the boundary B 41 between the first curvature C 1 and the second curvature C 43. As shown by the line (D), the coating liquid 9 may form liquid accumulation in the area adjacent to the boundary B 41. As a result, the thickness of the layer 25 becomes irregular, has a thickened layer between the first curved surface S1 of the central portion 13 and the second curved surface S43 of the peripheral portion 45.(Second Comparative Example)Referring to the graph in FIG. 10, the curves (E) and (F) show the relationship between the dimension of the workpiece measured in the longitudinal direction and the thickness of the layer of the panel according to the first and second comparative examples, respectively. U1 and U2 in the graph indicate the standard of the coating thickness. In the second comparative example of the panel, the workpiece is placed in a substantially vertical position and coated with the coating liquid. The rest of the configuration is substantially the same as in the first embodiment.As shown in FIG. 10, the thickness of the layer of the panel of the first comparative example is in the range of U1 and U2, whereas the thickness of the layer of the panel of the second comparative example does not fall in the range between U1 and U2. If the workpiece is placed in a generally vertical manner during coating, then the coating liquid flows downward by its own weight, so that a thickness variation occurs in the layer.As can be seen from a comparison between the curved lines (E) and (F) in the graph of FIG. 10, it is desirable that the workpiece be placed in a substantially horizontal position rather than a vertical position during coating of the workpiece in flooding in order to make the thickness of the layer uniform.The present invention described in the context of the embodiments and in comparison with the comparative examples is not limited to the above-described embodiments, but may be modified in various ways within the scope of the invention as exemplified below.The first radius of curvature may be changed as appropriate. For example, the first radius of curvature may be greater than 3000 mm or infinite. The edge surface of the workpiece can be either planar or curved.The first curved surface may be provided with a plurality of radii of curvature. The first curved surface may have an infinite radius, such that the first curved surface may be planar or partially planar. According to the present invention, the planar surface is a specific concept of the curved surface. The particular surface may be provided with a plurality of radii of curvature that may have an infinite radius such that the particular surface may be partially planar. However, it is preferable that the second curved surface is formed only by the second radius of curvature, which makes it possible to make the workpiece simpler.The determined radius of curvature approximates the second radius of curvature rather than the first radius of curvature because the coating liquid is less likely to form a liquid pool in the peripheral portion of the panel as compared to the case where the determined radius of curvature approximates the first radius of curvature.The panel of the present invention is applicable to a vehicle sunroof or window.A panel has a plate-like workpiece including a central portion and a peripheral portion having an application surface. The panel further has a layer formed by applying a coating liquid to the application surface using a flooding method. When the workpiece is viewed in a section that is perpendicular to the edge surface and extends in the direction of thickness, the application surface has a first curvature, a certain curvature, and a second curvature. The first curvature has a first radius of curvature. The determined curvature has a determined radius of curvature and is continuous with and external to the first curvature. The second curvature has a second radius of curvature that is less than the determined radius of curvature. The second curvature is continuous with and external to the determined curvature.

Claims

A panel for a vehicle, comprising: a plate-like workpiece (3) including a central portion (13) and a peripheral portion (15) placed outside the central portion (13), the central portion (13) and the peripheral portion (15) having an application surface (3S), the peripheral portion (15) having an edge surface (3E, 3F, 23E, 33E) extending in a thickness direction of the workpiece (3); and a layer (5) formed by applying a coating liquid (9) to the application surface (3S) of the workpiece (3) using a flooding method; wherein the application surface (3S) is continuous with the edge surface (3E, 3F, 23E, 33E), wherein when the workpiece (3) is viewed in a section, which extends perpendicularly to the edge surface (3E, 3F, 23E, 33E) and extends in the direction of thickness, the application surface (3S) has a first curvature (C1) located in the central portion (13) and a second curvature (C3, C23, C33) located in the peripheral portion (15), the first curvature (C1) having a first radius of curvature (R1), characterized by a specific curvature (C2, C32) located in the peripheral portion (15), the specific curvature (C2, C32) having a specific radius of curvature (R2, R32) which is smaller than the first radius of curvature (R1), and the second curvature (C3, C23, C33) has a second radius of curvature (R3, R23, R33) that is smaller than the determined radius of curvature (R2, R32), wherein the edge surface (3E, 3F, 23E, 33E) has a curvature (C4), wherein the determined curvature (C2, C32) is continuous with the first curvature (C1) and is located outside thereof, and wherein the second curvature (C3, C23, C33) is continuous with the determined curvature (C2, C32) and is located outside thereof, and the curvature (C4) of the edge surface (3E, 3F, 23E, 33E) is continuous with the second curvature (C3, C23, C33) is located outside thereof, and the first curvature (C1) and the determined curvature (C2, C32) have a common tangential line (L1, L31, L41), the determined curvature (C2, C32) and the second curvature (C3, C33, C43) have a common tangential line (L2, L22, L32), and the second curvature (C3, C33, C43) and the curvature (C4) of the edge surface (3E, 3F, 23E, 33E) have a common tangential line.Panel according to claim 1, characterized in that the determined radius of curvature (R2, R32) approximates the second radius of curvature (R3, R23, R33) rather than the first radius of curvature (R1).Panel according to claim 2, characterized in that the determined radius of curvature (R2, R32) is 3.3 to 6.7 times as large as the second radius of curvature (R3, R23, R33).Panel according to any one of claims 1 to 3, characterized in that the determined radius of curvature (R2, R32) does not comprise an infinite radius of curvature.Panel according to any one of claims 1 to 4, characterised in that the workpiece (3) and the layer (5) are transparent.

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