Patent Publication Number: US-2018039089-A1

Title: Decorative sheet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2016/056272 filed on Mar. 1, 2016, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2015-092621 filed on Apr. 30, 2015. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a decorative sheet that is bonded to an interior part or an exterior part of an automobile or the like. 
     2. Description of the Related Art 
     A technique of bonding a carbon fiber sheet to an interior part or an exterior part of an automobile or the like for decoration is disclosed (for example, refer to JP3847406B). However, a carbon fiber sheet is obtained by weaving carbon fibers by twill weaving in a sheet shape, and is extremely expensive. Therefore, a carbon texture sheet has been widely used instead of a carbon fiber sheet. This carbon texture sheet is obtained by printing a design similar to a carbon fiber pattern on one surface of a transparent resin sheet (for example, refer to JP2001-246664A). 
     On the other hand, as a sheet in which an image forming layer is provided on one surface of a transparent resin sheet, a lenticular lens sheet in which a plurality of cylindrical lenses are disposed in parallel is known. For example, in a sheet described in JP1999-212024A (H11-212024A), an image forming layer is formed by disposing a plurality of belt-shaped sub-divided regions in a unit region corresponding to each cylindrical lens. As a result, in a case where the user observes the image forming layer through the cylindrical lenses, images to be observed can switch between each other by changing an observation angle. 
     SUMMARY OF THE INVENTION 
     A carbon fiber sheet is obtained by weaving carbon fibers and has a fine three-dimensional structure. Therefore, the brightness of patterns changes by changing an observation direction, and thus a stereoscopic effect is produced. On the other hand, a carbon texture sheet is obtained by printing a design on a transparent resin sheet. Therefore, the brightness of patterns does not change even after changing an observation direction, and thus a stereoscopic effect is not produced. Therefore, in a carbon texture sheet, the quality of texture of carbon fibers cannot be obtained, and the decorativeness is poor. Thus, a carbon texture sheet is considered as a lower-cost alternative to a carbon fiber sheet. 
     Therefore, it is desired that a decorative sheet capable of obtaining a quality of texture equivalent to or higher than that of a carbon fiber sheet is prepared using a lenticular lens sheet. 
     An object of the present invention is to provide a decorative sheet capable of obtaining quality of a texture equivalent to or higher than that of a real carbon fiber sheet. 
     A decorative sheet according to the present invention includes a lenticular lens sheet and an image forming layer. In the lenticular lens sheet, a plurality of cylindrical lenses having a convex portion are disposed and a flat surface is provided on a side opposite to the convex portion. The image forming layer is provided on the flat surface and includes a first design and a second design having mutually inverted densities, in which the first design and the second design switch between each other by changing an observation direction in which the image forming layer is observed through the lenticular lens sheet. The image forming layer includes a first sub-divided region having the first design sub-divided in a belt shape, a second sub-divided region having the second design sub-divided in a belt shape, and a belt-shaped intermediate region being formed between the first sub-divided region and the second sub-divided region, in a unit region corresponding to each of the cylindrical lenses. 
     It is preferable that the image forming layer includes a gradation design that is formed in the intermediate region and in which a density changes in a direction in which the cylindrical lenses are disposed. 
     It is preferable that the first design, the second design, and the gradation design are formed of patterns obtained by combining a plurality of shapes. In addition, it is preferable that the shapes are quadrangles. It is preferable that the patterns are twill weaving patterns. 
     It is preferable that, in the direction in which the cylindrical lenses are disposed, a length of the intermediate region is shorter than a length of the first sub-divided region and a length of the second sub-divided region. 
     It is preferable that the lenticular lens sheet and the image forming layer are integrally bendable. It is preferable that the decorative sheet is bonded to an interior part of an automobile. 
     According to the present invention, the image to be observed switches between the first design and the second design by changing the observation direction in which the image forming layer is observed through the lenticular lens sheet. In addition, in the decorative sheet according to the present invention, the image forming layer includes a first sub-divided region having the first design sub-divided in a belt shape, a second sub-divided region having the second design sub-divided in a belt shape, and a belt-shaped intermediate region being formed between the first sub-divided region and the second sub-divided region, in a unit region corresponding to each of the cylindrical lenses. Therefore, quality of a texture equivalent to or higher than that of a real carbon fiber sheet can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a configuration of a decorative sheet according to the present invention. 
         FIG. 2  is a cross-sectional view showing major parts of the decorative sheet taken along a direction in which cylindrical lenses are disposed. 
         FIGS. 3A to 3C  are diagrams showing images which are observed in a case where the decorative sheet is observed through the cylindrical lenses. 
         FIG. 4  is a plan view showing an image formed on an image forming layer. 
         FIG. 5  is an enlarged plan view showing a V-V range of  FIG. 4 . 
         FIG. 6  is a graph showing gradations of unit regions U 1  to U 5  shown in  FIG. 5 . 
         FIGS. 7A to 7C  are diagrams showing images which are observed in a case where the decorative sheet to which plain weaving patterns are applied is observed through the cylindrical lenses. 
         FIG. 8  is a perspective view showing an example in which the decorative sheet is bonded to an interior part of an automobile. 
         FIG. 9  is a cross-sectional view showing a state where the decorative sheet is bent. 
         FIG. 10  is a perspective view showing an example in which the decorative sheet is applied to a lighting device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     As shown in  FIG. 1 , a decorative sheet  10  includes: a lenticular lens sheet  11 ; and an image forming medium  12  in which an image forming layer  13  is formed. The image forming medium  12  is a transparent resin sheet. 
     The lenticular lens sheet  11  includes a plurality of cylindrical lenses  15 . Each of the cylindrical lenses  15  includes a convex portion  15 A having a partially cylindrical shape, and a surface of the cylindrical lens  15  opposite to the convex portion  15 A is flat. Each of the cylindrical lenses  15  extends in a Y direction and is disposed parallel to an adjacent cylindrical lens  15 . That is, the cylindrical lenses  15  are disposed at a regular pitch in an X direction perpendicular to the Y direction. The lenticular lens sheet  11  includes a flat surface  11 A opposite to the convex portion  15 A. 
     As shown in  FIG. 2 , in the decorative sheet  10 , the image forming layer  13  is observed from the side including the convex portion  15 A of the lenticular lens sheet  11 . A curvature of the convex portion  15 A of the cylindrical lens  15  is set such that a focal point thereof is positioned in the image forming layer  13 . 
     As a material of the lenticular lens sheet  11 , for example, a transparent resin material such as polyethylene terephthalate (PET), polypropylene (PP), glycol-modified polyethylene terephthalate (PETG), polycarbonate, acryl, or an acrylate resin is used. 
     The image forming layer  13  is provided on the flat surface  11 A side of the lenticular lens sheet  11 . The image forming layer  13  is formed by printing or transferring an image on the image forming medium  12  as the transparent resin sheet. A material of the image forming layer  13  is not particularly limited as long as it is a material that can be closely attached to the image forming medium  12 . For example, a well-known paint or the like is capable of being used. 
     In addition, the lenticular lens sheet  11  and the image forming medium  12  are joined to each other using a method such as adhesion or pressure sensitive adhesion. As a joining agent (adhesive or pressure sensitive adhesive) for joining the lenticular lens sheet  11  and the image forming medium  12 , a transparent material that is capable of allowing the image forming layer  13  to be observed through the lenticular lens sheet  11  is used. In addition, it is preferable that the decorative sheet in which the lenticular lens sheet  11  and the image forming medium  12  are integrated is flexible. 
     The image forming layer  13  includes a first sub-divided region S 1 , a second sub-divided region S 2 , and an intermediate region SM. One set of the first sub-divided region S 1 , the second sub-divided region S 2 , and the intermediate region SM are provided in a unit region U ( FIGS. 4 and 5 ) corresponding to each of the cylindrical lenses  15 , and extend in the Y direction. The first sub-divided region S 1  is disposed on a side region (for example, a left-side region) in the unit region U. The second sub-divided region S 2  is disposed on the other side region (for example, a right-side region) in the unit region U. The intermediate region SM is disposed in the center region between the first sub-divided region S 1  and the second sub-divided region S 2 . The first sub-divided region S 1  and the second sub-divided region S 2  are formed at positions that are symmetrical to each other with respect to an optical axis of the cylindrical lens  15 . 
     In the decorative sheet  10 , in a case where the image forming layer  13  is observed in a right-side inclined direction (DA in  FIG. 2 ), only the first sub-divided region S 1  is observed, where the right-side inclined direction is inclined to the right side from a vertical direction (DV in  FIG. 2 ) perpendicular to the image forming layer  13 . In addition, in the decorative sheet  10 , in a case where the image forming layer  13  is observed from a left-side inclined direction (DB in  FIG. 2 ), only the second sub-divided region S 2  is observed, where the left-side inclined direction is inclined to the left side from the vertical direction DV In the decorative sheet  10 , in a case where the image forming layer  13  is observed from the vertical direction DV, only the intermediate region SM is observed. 
     In the first sub-divided region S 1 , a first design P 1  shown in  FIG. 3A  is sub-divided in a belt shape to form an image. In the second sub-divided region S 2 , a second design P 2  shown in  FIG. 3C  is sub-divided in a belt shape to form an image. In the intermediate region SM, a gradation design PG shown in  FIG. 3B  is sub-divided in a belt shape to form an image. Specifically, as shown in  FIG. 4 , the images of the first design P 1 , the second design P 2 , and the gradation design PG are formed in the first sub-divided region S 1 , the second sub-divided region S 2 , and the intermediate region SM, respectively, in a state where they are sub-divided in a belt shape. 
     Accordingly, in the decorative sheet  10 , the first design P 1 , the gradation design PG and the second design P 2  are sequentially observed by sequentially changing an observation direction, in which the image forming layer is observed through the lenticular lens sheet  11 , from the right-side inclined direction DA, the vertical direction DV, to the left-side inclined direction DB in the X direction. 
     The first design P 1  and the second design P 2  are formed of patterns obtained by combining a plurality of different shapes. Here, shapes that match each other look different by rotating the direction. 
     In the embodiment, the first design P 1  and the second design P 2  are similar to twill weaving patterns formed in a case where carbon fibers are twill-woven. Twill weaving is a weaving method in which rows in a vertical direction of carbon fibers and rows in a horizontal direction of the carbon fibers cross each other in alternating rows of two. In the twill weaving pattern, as shown in  FIGS. 3A to 3C , a first pattern and a second pattern are alternately repeated, in which the first pattern has a structure in which first rectangles R 1  having a long length in the vertical direction (having a long length of a side in the Y direction) are disposed obliquely at an angle of 45° with respect to the X direction or the Y direction, and the second pattern has a structure in which second rectangles R 2  having a long length in the horizontal direction (having a long length of a side in the X direction) are disposed obliquely at an angle of 45° with respect to the X direction or the Y direction. That is, the first design P 1  and the second design P 2  are formed of a combination of the first pattern and the second pattern including the first rectangles R 1  and the second rectangles R 2 , respectively. 
     In the gradation design PG, likewise, the first pattern and the second pattern are alternately repeated, in which the first pattern has a structure in which the first rectangles R 1  are disposed obliquely at an angle of 45° , and the second pattern has a structure in which the second rectangles R 2  are disposed obliquely at an angle of 45° . 
     On the image forming layer  13 , an image is formed at a density (also referred to as “gradation value”) in a predetermined gradation range. In the embodiment, an image formed on the image forming layer  13  is achromatic and is expressed in so-called gray scale. The first design P 1  and the second design P 2  are drawn using a minimum gradation value (minimum density) and a maximum gradation value (maximum density). Specifically, in the first design P 1 , the first rectangles R 1  are drawn uniformly at the minimum density, and the second rectangles R 2  are drawn uniformly at the maximum density. On the other hand, in the second design P 2 , the first rectangles R 1  are drawn uniformly at the maximum density, and the second rectangles R 2  are drawn uniformly at the minimum density. 
     In each of the first design P 1  and the second design P 2 , the first rectangle R 1  and the second rectangle R 2  have mutually inverted densities. The reason for this is as follows. In a twill weaving pattern of real carbon fibers, light reflection components vary between carbon fibers (corresponding to the first rectangles R 1 ) in the vertical direction (Y direction) and carbon fibers (corresponding to the second rectangles R 2 ) in the horizontal direction (X direction), and the densities also vary therebetween when the twill weaving pattern is observed. The configuration of the first design P 1  and the second design P 2  is set to be similar to that of the twill weaving pattern of real carbon fibers. 
     In addition, the first design P 1  and the second design P 2  have mutually inverted densities. Specifically, the first rectangle R 1  having the minimum density in the first design P 1  has the maximum density in the second design P 2 , and the second rectangle R 2  having the maximum density in the first design P 1  has the minimum density in the second design P 2 . The reason for this is as follows. In a twill weaving pattern of real carbon fibers, the densities vary depending on an observation direction, and different designs are observed. The configuration of the first design P 1  and the second design P 2  is set to be similar to that of the twill weaving pattern of real carbon fibers. 
     In addition, the gradation design PG is drawn at a gradation value (intermediate density) between the minimum gradation value and the maximum gradation value. Specifically, in the gradation design PG, the density in each of the first rectangle R 1  and the second rectangle R 2  gradually changes in the X direction. In a case where the first rectangles R 1  and the second rectangles R 2  are drawn at one density, the density is uniform in the entire area, and thus a twill weaving pattern does not appear. By gradually changing the density in each of the first rectangle R 1  and the second rectangle R 2  in the X direction, the gradation design PG has the intermediate density between the minimum density and the maximum density, and thus the twill weaving pattern can be drawn. 
       FIG. 5  shows a partial region of the first rectangle R 1  of the image forming layer  13 . As in the relationship between the first design P 1  and the second design P 2 , the first sub-divided region S 1  and the second sub-divided region S 2  have mutually inverted densities. Symbols U 1  to U 5  represent five unit regions U disposed in the X direction. 
     The length of the first sub-divided region, the intermediate region, and the second sub-divided region, and relationships therebetween are not particularly limited. In the embodiment, in a case where the length of the first sub-divided region S 1 , the length of the intermediate region SM, and the length of the second sub-divided region S 2  in the X direction are represented by W 1 , WM, and W 2 , respectively, relationships of WM&lt;W 1 , WM&lt;W 2 , and W 1 =W 2  are satisfied. Specifically, in the embodiment, a relationship of “W 1 :WM:W 2 =5:2:5” is satisfied. 
       FIG. 6  is a graph showing gradation values (densities) of the unit regions U 1  to U 5 . In the same drawing, the maximum gradation value (maximum density) is represented by GH, and the minimum gradation value (minimum density) is represented by GL. A density GM of the intermediate region SM ranges between the maximum density GH and the minimum density GL, and gradually changes in the direction (X direction) in which the cylindrical lenses  15  are disposed. 
     With the above-described configuration, in a case where the direction in which the decorative sheet  10  is observed changes to the X direction, when the image to be observed switches from the first design P 1  to the second design P 2  or switches from the second design P 2  to the first design P 1 , the gradation design PG, in which the twill weaving pattern is drawn at the intermediate density between the density of the first design P 1  and the density of the second design P 2 , is observed. 
     As described above, in the decorative sheet  10  according to the present invention, in a case where the observation direction changes, the image to be observed switches between the first design P 1  and the second design P 2  having mutually inverted densities, and the brightness of the patterns appears to be changing. Therefore, a stereoscopic effect is produced. As a result, with the decorative sheet  10 , quality of a texture equivalent to or higher than that of a real carbon fiber sheet is capable of being obtained. 
     In particular, in a real carbon fiber sheet, in a case where the observation direction changes, light reflection components reflected by carbon fibers change, and thus the brightness of patterns changes. Therefore, in an environment where the light amount is small, the brightness is not likely to change. However, in the decorative sheet  10  according to the present invention, even in a case where the light amount is small, the first design P 1  and the second design P 2  switch between each other due to the function of the lenticular lens sheet  11 , and a change in brightness clearly appears. 
     In addition, in the decorative sheet  10  according to the present invention, by adjusting the length WM of the intermediate region SM, even a small amount of gaze movement, (change in the observation direction) which is half or less than that in a real carbon fiber sheet, is capable of allowing the first design P 1  and the second design P 2  to switch between each other. 
     In addition, in the decorative sheet  10 , the intermediate region SM is formed between the first sub-divided region S 1  and the second sub-divided region S 2  corresponding to the first design P 1  and the second design P 2  that are sub-divided in a belt shape. Therefore, when the observation direction of the observer continuously changes, the first design P 1  and the second design P 2  can be prevented from being simultaneously observed, and separation between the images can be reliably performed. In a case where the separation between the images is not sufficient, when the images switch between each other, a low-density image may be observed as a ghost. In the decorative sheet  10  according to the present invention, the observation of the ghost is prevented. 
     In addition, in the decorative sheet  10 , the density of the intermediate region SM is set to the intermediate density between the maximum density and the minimum density which are used in the first sub-divided region S 1  and the second sub-divided region S 2 . When the image to be observed switches from the first design P 1  to the second design P 2 , the image having intermediate density is observed, and thus the images switches between each other smoothly. As a result, with the decorative sheet  10 , a similar quality of texture to that of a carbon fiber sheet is obtained. 
     In addition, in each of the first rectangle R 1  and the second rectangle R 2  of the gradation design PG, the density of the intermediate region SM gradually changes in the X direction. Therefore, the twill weaving pattern is drawn at the intermediate density. As a result, even while the image to be observed switches between the first design P 1  and the second design P 2 , the twill weaving pattern drawn at the intermediate density is observed. Therefore, in the decorative sheet  10 , a natural texture which is more similar to that of a carbon fiber sheet can be obtained. 
     Further, the length WM of the intermediate region SM in the X direction is shorter than the length W 1  of the first sub-divided region S 1  and the length W 2  of the second sub-divided region S 2 . Therefore, an angle range in which the gradation design PG is observed is only the vicinity of the vertical direction DV. Therefore, when the observation direction of the observer continuously changes, the period of time in which the gradation design PG is observed is short. Therefore, the first design P 1  and the second design P 2  can switch between each other naturally within a short period of time. 
     In the first embodiment, the first design P 1 , the second design P 2 , and the gradation design PG are twill weaving patterns, but the present invention is not limited thereto. For example, plain weaving patterns may be adopted as shown in a modification example of  FIGS. 7A to 7C . Plain weaving is a weaving method in which rows in a vertical direction of carbon fibers and rows in a horizontal direction of the carbon fibers alternately cross each other. That is, the plain weaving pattern corresponds to a pattern in which the first rectangles R 1  and the second rectangles R 2  ( FIG. 3 ) formed in the twill weaving patterns of the first embodiment are substantially squares. 
     Accordingly, in the first design P 1 , the second design P 2 , and the gradation design PG of the modification example shown in  FIGS. 7A to 7C , first squares T 1  and second squares T 2  are disposed in a zigzag manner. The densities of the first square T 1  and the second square T 2  are the same as those of the first rectangle R 1  and the second rectangle R 2  of the first embodiment, respectively. 
     The first design P 1 , the second design P 2 , and the gradation design PG are not limited to combinations of the first rectangles R 1  and the second rectangles R 2  in the first embodiment or combinations of the first squares T 1  and the second squares T 2  in the modification example. The first design P 1 , the second design P 2 , and the gradation design PG are not particularly limited as long as they are patterns obtained by combining quadrangles. In addition, in the first embodiment and the modification example, the first design P 1 , the second design P 2 , and the gradation design PG are achromatic images but may be chromatic images. 
     In the first embodiment and the modification example, the image forming medium  12  is bonded to the flat surface  11 A of the lenticular lens sheet  11  after forming the image forming layer  13  on the image forming medium  12 . However, the image forming layer  13  may be directly formed on the flat surface  11 A of the lenticular lens sheet  11  without using the image forming medium  12 . 
     Hereinafter, the form of use of the decorative sheet according to the present invention will be described.  FIG. 8  shows an example in which the decorative sheet  10  according to the first embodiment is bonded to an interior part of an automobile  21 . The decorative sheet  10  is bonded such that the image forming medium  12  side is in contact with the interior part. 
     The decorative sheet  10  is bonded to, for example, a steering wheel  22 , a door panel  23 , or a dashboard  24  of the automobile  21 . The decorative sheet  10  is flexible and thus is bonded in a state where it is bent to conform to a curve of a bonding position. For example, in an example shown in  FIG. 8 , a surface of the dashboard  24  is curved, and the decorative sheet  10  is bent to conform to the curved shape. As shown in  FIG. 9 , in the decorative sheet  10 , the lenticular lens sheet  11  and the image forming layer  13  are integrally bent. 
     Second Embodiment 
       FIG. 10  shows a lighting device  31  in which the decorative sheet  10  according to the first embodiment is used as a lamp shade. The lighting device  31  includes the decorative sheet  10 , a stand  32 , a plurality of light sources  33 , and a light emitting controller (not shown) that controls light emission of each of the light sources  33 . 
     The decorative sheet  10  is bent in a cylindrical shape such that the convex portions  15 A of the cylindrical lenses  15  are positioned on the outer circumferential surface side. A bending direction is a direction perpendicular to a longitudinal direction (Y direction) of the cylindrical lenses  15 . The decorative sheet  10  is supported by the stand  32 . 
     Each of the light sources  33  is formed of, for example, a light emitting diode (LED) and is supported by a columnar support (not shown). The light sources  33  are disposed in an inner space of the cylindrical decorative sheet  10  at a predetermined interval parallel to each other in the longitudinal direction of the cylindrical lenses  15 . 
     In addition, in the embodiment, it is preferable that the image forming layer  13  is directly formed on the flat surface  11 A of the lenticular lens sheet  11  and a light-transmitting material is used as the material of the image forming layer  13 . Alternatively, it is preferable that a transparent resin sheet is used as the image forming medium  12  and the image forming layer  13  is formed on the transparent resin sheet using a light-transmitting material. 
     As a result, light emitted from each of the light sources  33  is diffused in a ring shape in the direction (the bending direction of the decorative sheet  10 ), in which the cylindrical lenses  15  are disposed, when passing through the decorative sheet  10 . In the lighting device  31 , light is emitted in a ring shape from each of the light sources  33  through the decorative sheet  10 . Therefore, the decorativeness of illumination light is high. 
     In each of the embodiments, the example in which the decorative sheet according to the present invention is applied to, for example, an interior part or an exterior part of an automobile, or a lighting device has been described, but the present invention is not limited thereto. The decorative sheet according to the present invention is applicable to electric appliances such as smartphones or tablets or to goods such as furniture. 
     EXPLANATION OF REFERENCES 
     
         
           10 : decorative sheet 
           11 : lenticular lens sheet 
           12 : image forming medium 
           13 : image forming layer 
           15 : cylindrical lens 
           15 A: convex portion 
         P 1 : first design 
         P 2 : second design 
         PG: gradation design 
         S 1 : first sub-divided region 
         S 2 : second sub-divided region 
         SM: intermediate region 
           21 : automobile 
           31 : lighting device