Disclosed herein are various embodiments that relate to a light-emitting part for a vehicle, and particularly, to a light-emitting part for a vehicle that includes a curved plate-shaped light-emitting portion that uniformly emits light.
Hitherto, light-emitting parts for vehicles have been used. Some known light-emitting parts for a vehicle include a plurality of prism portions disposed in a planar shape on a light guiding plate in order to provide surface light-emission without using a plurality of dot-shaped light sources. Light incident from the dot-shaped light sources to the light guiding plate is reflected in a planar shape by the plurality of prism portions toward a plate-shaped transmissive body. Further, some examples of a method of uniformly emitting light from the planar plate-shaped transmissive body include a method of changing the height of the prism portion or the gap between the prism portions in response to the distance between the light source and the prism portion in consideration of the light attenuation effect, for example, as described in Japanese Patent Document No. 2006-222030 A (“the '030 Document”) and Japanese Patent Document No. 2008-15448 A (“the '448 Document”).
Japanese Patent Document No. 11-321478 A (“the '478 Document”) discloses a light-emitting part using a decorative sheet. A decorative sheet is used to allow light from metal to be transmitted therethrough so that a metallic effect is visually obtained. Specifically, an adhesive layer, an anchor layer, a metal deposition layer exhibiting a metallic effect, an anchor layer, a colored layer, a hard coat layer, and a base film having a surface subjected to hairline pattern processing are laminated from a surface of a resin layer used as a base and formed as a lamination film serving as a transfer foil. Then, a sheet is subjected to in-mold molding to transfer a pattern to the surface of the resin layer as the base, and the base film is peeled off after the in-mold molding to finish a surface of a molded product with a metallic effect.
Further, Japanese Patent Document No. 2004-90897 A (“the '897 Document”) discloses another example of a light-emitting part for vehicles. In the light-emitting part disclosed in the '897 Document, a vehicle interior panel is formed by an optically transparent panel having a design portion laminated thereon and has a desired design at a vehicle interior side surface so that a light shielding region, shielding the light from the opposite side to the vehicle interior side, and a light transmitting region, transmitting the light from the opposite side to the vehicle interior side, are alternately arranged, and a light source is disposed inside the optically transparent panel. Then, when the light source is lit at night, the light is incident from the rear surface of the optically transparent panel. Subsequently, when incident light enters the light transmitting region and is transmitted through the front surface of the optically transparent panel, the light illuminates the dark vehicle interior. Thus, the light-emitting part serves as a decorative illumination unit.
When the height or the pitch of the prism portion is changed in response to the distance from the light source in order to uniformly emit the light from the planar plate-shaped transmissive body, the uniformity of the light emitted from the light guiding plate is maintained even when the light is emitted from the transmissive body if the gap between the light guiding plate and the transmissive body is constant. However, when there is a difference in gap between the light guiding plate and the transmissive body due to the combination of the planar plate-shaped light guiding plate and the curved plate-shaped transmissive body, an attenuation degree of the light is changed due to a difference in gap therebetween. Accordingly, even when the light emitted from the light guiding plate is uniform, the uniformity of the light is not kept when the light is emitted through the transmissive body.
For this reason, in the techniques disclosed in the above-cited references, the light can be uniformly emitted from the transmissive body when the gap between the light guiding plate and the transmissive body is constant. However, when the gap between the light guiding plate and the transmissive body is not constant, the light cannot be uniformly emitted from the transmissive body.
Further, there is a tendency to increase the complexity of the shape of vehicle interior parts in order to improve the design thereof. Particularly, there are many members of vehicle interior parts that use a curve or a curved surface to achieve an improved design. Such a member having such a curve or curved surface may give a psychologically calming impression to a passenger of the vehicle. However, when the sheet is disposed on the curve and the curved surface by using the decorative sheet (the film) of the '478 Document, a problem arises in that a tension difference occurs in the case of a complex shape. Particularly, this problem noticeably occurs due to a tension difference between the flat surface portion and the curved surface portion. In this way, when the tension difference occurs, a crack may occur in the high-tension portion, that is, the curved surface portion. Thus, there is a possibility that cracks or visual imperfections may occur on the design. The light-emitting part for the vehicle is obtained by using the decorative sheet (the film) as described above so that the light is emitted from the light source to the decorative sheet (the film). However, in the decorative sheet (the film) of the '478 Document, the decorative appearance is simplified since the layers are uniformly laminated as multiple layers. For this reason, there has been a demand for a technique of improving durability while ensuring a better design of the decorative film.
Further, in the light-emitting part for the vehicle of the '897 Document, a decorative lamination structure is described in which a light shielding layer, including a transmissive portion transmitting the light transmitted through the optical transparent panel, and a light shielding portion, shielding the light, and a design layer, disposed at the vehicle interior side in relation to the light shielding layer and formed to match the surface shape of the optical transparent panel, are laminated on the vehicle interior side surface of the optical transparent panel. According to the light-emitting part with such a configuration, a design such as a metallic effect or a grain effect of the design layer is visually recognized at daytime, and the light emitted from the light source is visually recognized from the design layer through the transmissive portion at nighttime. Accordingly, the design layer is visually recognized while the light is transmitted therethrough at nighttime in a manner differently from the daytime. Here, in order to improve the transmissivity of the light emitted from the light source toward the vehicle interior side for the decorative illumination function, it is desirable to form the design layer as thin as possible. However, when the film thickness of the design layer is thin, a boundary line between the light shielding portion and the transmissive portion forming the light shielding layer is visually recognized at the vehicle interior side when the light is not emitted therefrom. Accordingly, a passenger feels uncomfortable when the vehicle interior is bright, and hence a good design is not obtained. For this reason, there has been a demand for a light-emitting part for a vehicle which improves the functionality as decorative illumination and the texture of a decorative illumination region to obtain a good design.