Patent Publication Number: US-2023160027-A1

Title: Patterned natural leather sheet, and method for patterning natural leather

Description:
TECHNICAL FIELD 
     The present invention relates to a natural leather seat wherein a pattern having convex ridgeline is given, and its patterning method. 
     BACKGROUND ART 
     Conventionally, a natural leather wherein embossment is done has been used in many goods including car seats, sofa, bags, wallets and the like. By performing embossment to the natural leather and forming roughness to the surface, it can give suitable decorativeness and feel. 
     Techniques for embossing the natural leather are roughly classified into a flat plate embossing method and a roll embossing method. As the flat plate embossing method, a method wherein a die is pressed against the leather surface to make it concave (Patent Literature 1), and a method wherein the pattern is raised to the surface by pressing the leather using a male and female die (Patent Literature 2) and the like are known. In the method of Patent Document 1, when the natural leather  1  is pressed shallower than the depth of the die  2 , a gap is formed between the leather  1  and the die  2 , and the surface of the leather  2  swells round (see  FIG.  5 A ); when the natural leather  3  is pressed deeper than the depth of the die  4 , the surface of the leather  3  is crushed by the die  4  and becomes flat (see  FIG.  5 B ). In other words, for the concave portion, sharp lines in the shape of the die can be expressed by the pressure from above, but for the convex portion, sufficient pressure cannot be applied, and sharp lines could not be expressed. 
     Also, in the method of Patent Literature 2, although it is relatively easy to form a sharp line on the natural leather  5  in the shape of the die  6  in both the concave and convex portions (see  FIG.  6 A ), the bottom of the natural leather  5  was raised to protrude the surface, so the formed pattern was not permanent, and was easily lost by load or friction (see  FIG.  6 B ). 
     Therefore, as the patterns formed on the natural leather by embossment, there are various patterns including the imitations of reptiles such as alligators, crocodiles, ostriches and the like, and geometrical patterns, botanical patterns, etc., however, the conventional patterns have been all flat and lacked sharpness and three-dimensional appearance (Non-patent literature 1). 
     PRECEDING ART DOCUMENT 
     Patent Literature 
     PATENT LITERATURE 1 Publication of Japanese Laid-Open Patent Publication No. Hei 6 (1994)-100900 
     PATENT LITERATURE 2 Publication of Japanese Laid-Open Patent Publication No. Hei 7 (1995)-138600 
     NON-PATENT LITERATURE 1 EMBOSS CATALOG, Fall/Winter 2017, SUMIDA KAWASUKI CO., LTD. 
     The present invention has been done in view of aforementioned problems, and its objectives are to provide with a patterning method wherein a three-dimensional pattern with clear convex ridges is patterned to a natural leather, and a natural leather seat with a high design effect having the pattern. 
     Means for Solving the Problem 
     The present inventors came to complete the present invention as a result of various consideration, finding out that the above issues could be resolved by devising the method of forming the shape and pattern of the die, etc. 
     In other words, the present invention relates to:
         1) a patterned natural leather seat having one or more patterns with convex ridges on the surface,
           a patterned natural leather seat wherein:   the aforementioned pattern height is 0.5-2.0 mm,   the aforementioned pattern base angle is 0.2°-89°,   the backside of the leather seat is flat;   
           2) the patterned natural leather seat described in (1), wherein the pattern comprises a polygonal pyramid convex part;   3) the patterned natural leather seat described in (2), having a convex ridgeline of 3-100 mm a in the aforementioned polygonal pyramid convex part;   4) the patterned natural leather seat described in any one of (1)-(3), wherein the pattern is a pattern having the concave part on the outer periphery of the convex part;   5) a method of patterning on a natural leather comprising:
           the process of preparing a die having one or several concave parts, a die wherein the aforementioned concave part has a tilt angle of 0.2°-45° and a depth of 0.5-2 mm, and preparing a pressure receiver; the process of installing a natural leather wherein the thickness is 0.5-2.0 mm, in between the aforementioned pressure receiver and the aforementioned die;   the process of pressing the aforementioned natural leather with the aforementioned die at a pressure of 0.1-5.0 MPa, and applying one or more selected from heat, ultrasonic waves and high frequency;   
           6) a method described in (5), wherein the pressure receiver comprises a plane metal surface having a hardness of 25-722 and a cushioning material having a thickness of 0.5-20 mm on the aforementioned plane metal surface.   7) the method described (5) or (6), wherein the depth of the die is shallower than the thickness of the natural leather.       

     Effects of Invention 
     According to the present invention, it becomes possible to provide with a natural leather seat with a high design effect, having a three-dimensional pattern with sharp convex ridges. 
     Also, according to the present invention, it becomes possible to realize a further clarification of the convex portion of the pattern, by having the concave portion on the outer periphery of the convex portion of the pattern formed on the natural leather sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  A cross-sectional view of a patterned natural leather seat of the present invention. 
         FIG.  1 B  A cross-sectional view of a die used in a patterning method of natural leather of the present invention. 
         FIG.  2 A  It is a first embodiment of the patterned natural leather seat of the present invention. 
         FIG.  2 B  It is a second embodiment of the patterned natural leather seat of the present invention. 
         FIG.  2 C  It is a third embodiment of the patterned natural leather seat of the present invention. 
         FIG.  2 D  It is a fourth embodiment of the patterned natural leather seat of the present invention. 
         FIG.  2 E  It is a fifth embodiment of the patterned natural leather seat of the present invention. 
         FIG.  2 F  It is a sixth embodiment of the patterned natural leather seat of the present invention. 
         FIG.  3 A  It is a patterning method of the natural leather pertaining to the Working Example 1 of the present invention. 
         FIG.  3 B  It is a surface photo of the patterned natural leather seat pertaining to the Working Example 1 of the present invention. 
         FIG.  4 A  It is a patterning method of the natural leather pertaining to the Working Example 1 of the present invention. 
         FIG.  4 B  It is a surface photo of the patterned natural leather seat pertaining to the Comparative Example 1 of the present invention. 
         FIG.  5 A  It is a figure showing an example of the patterning method of the natural leather of a prior art. 
         FIG.  5 B  It is a figure showing an example of the patterning method of the natural leather of a prior art. 
         FIG.  6 A  It is a figure showing an example of the patterning method of the natural leather of a prior art. 
         FIG.  6 B  It is a figure showing an example of the patterning method of the natural leather of a prior art. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (Definition) 
     In the present invention, the term “embossing” refers to a processing method wherein an embossed pattern is created by pressing on a natural leather with a die having an uneven pattern. 
     In the present invention, the term “convex ridgeline” refers to a line segment (side) protruding like a mountain ridge formed by two adjacent faces of a pattern formed on a natural leather (See, for example,  103  in  FIG.  1 A ). 
     In the present invention, the term “pattern base angle” refers to an angle between the horizontal plane of the convex part of the pattern formed on the natural leather and the convex ridgeline in contact with the horizontal plane (See, for example,  104  in  FIG.  1 A ). 
     In the present invention, the term “pattern height” refers to the maximum height difference of the pattern formed on the natural leather (See, for example,  105  in  FIG.  1 A ). For example, when the pattern formed on the natural leather has only the polygonal pyramid convex part, “pattern height” indicates the distance between the top and the bottom of the polygonal pyramid. 
     In the present invention, the term “tilt angle” refers to an angle between the horizontal plane and the inclined plane of the die (See, for example,  112  in  FIG.  1 B ). 
     In the present invention, the term “die depth” refers to the maximum height difference of the die (See, for example,  114  in  FIG.  1 B ). 
     In the present invention, “natural leather” includes but is not limited to those originated from mammalian including cows, horses, pigs, goats, sheep, deer, kangaroos; birds including ostriches; reptiles including snakes and crocodiles. Especially, cowhide of large area with high versatility is preferred. The biological leather collection site to become the source of the natural leather is not especially limited. The leather is made by tanning the dermis of raw hides. As a method of tanning, Wet white, Wet blue and the combination of the two are used. 
     (Patterned Natural Leather Seat) 
     The patterned natural leather seat  100  of the present invention is illustrated in  FIG.  1 A , and has one or more patterns having convex ridgeline on the surface. 
     The pattern height  105  is 0.5-2 mm, is preferably 0.75-1.75 mm, is particularly preferably 1.0-1.5 mm. When the pattern height  105  is less than 0.5 mm, it does not become a three-dimensional pattern; when the pattern height  105  exceeds 2 mm, the convex ridgeline cannot be formed. 
     The pattern base angle  104  is 0.2°-89°, is preferably 0.5°-60°, is particularly preferably 1°-45°. When the pattern base angle  104  is less than 0.2°, it does not become a three-dimensional pattern; when the pattern base angle  104  exceeds 89°, the convex ridgeline  103  cannot be formed. 
     Although not limited to this, the pattern of the natural leather seat may have the concave part  102  on the outer periphery of the convex part  101 . With the above, the boundary of the convex part  101  becomes clear, and a pattern with sharp impression can be formed. The depth of the concave part  102  is preferably 0.01-1.0 mm, more preferably 0.03-0.5 mm, particularly preferably 0.05-0.1 mm. When the depth of the concave part is within the range, it is easier to further clarify the convex part. 
     The pattern shape is not particularly limited, but the examples thereof include a polygonal pyramid, a polygonal frustum, a truncated cone, and a shape obtained by deforming the top of the above, and the like. 
     “Polygonal pyramid” is a pyramid wherein the shape of the bottom surface is a polygon, and all sides are triangular. In the present invention, “polygonal pyramid” is not particularly limited, but is preferably from a triangular pyramid to a decagonal pyramid, more preferably a triangular pyramid to a hexagonal pyramid, and particularly preferably a triangular pyramid or a quadrangular pyramid. A pyramid wherein the bottom surface is a n-gon is called a n-gonal pyramid. 
     “Polygonal frustum” is a three-dimensional figure obtained by removing a polygonal pyramid that share vertices and are similarly reduced from a polygonal pyramid. In the present invention, the “polygonal frustum” is not particularly limited, but is preferably from a triangular frustum to a decagonal frustum, more preferably from a triangular frustum to a hexagonal frustum, and particularly preferably a triangular frustum or a square frustum. Note that a truncated pyramid wherein the bottom surface is an n-gon is called an n-gonal frustum. 
     “Circular truncated cone” is a frustum with a circle as the base, and a three-dimensional figure excluding the small circular cone part by cutting the cone with a plane parallel to the bottom surface. 
     The First Embodiment 
       FIG.  2 A  shows the first embodiment of the patterned natural leather seat of the present invention. In the present embodiment, the pattern formed on a natural leather seat  10  has a polygonal pyramid convex part. In this embodiment, a clear convex ridgeline  12  can be formed on the side surface of the polygonal pyramid. In this embodiment, the length of the convex ridgeline  12  is preferably 3-100 mm, is more preferably 10-80 mm, and particularly preferably 20-50 mm. If the length of the convex ridgeline is less than 3 mm, it is difficult to confirm a clear convex ridgeline, and it is difficult to form a convex ridgeline exceeding 100 mm. The length of one side of the bottom surface of the polygonal pyramid is preferably 2.0-70 mm, is more preferably 5.0-50 mm, and is particularly preferably 10-40 mm. If the length of one side is less than 2.0 mm, it may be difficult to confirm a sharp convex ridgeline, and if it exceeds 70 mm, it may be difficult to form a three-dimensional pattern. 
     The Second Embodiment 
       FIG.  2 B  shows the second embodiment of the patterned natural leather seat of the present invention. In the present embodiment, the pattern formed on a natural leather seat  20  has a polygonal frustum convex part or a truncated cone convex part. In this embodiment, a clear convex ridgeline  22  can be formed on the upper surface of the polygonal frustum or the circular truncated cone. Also, in a case of polygonal frustum convex part, a clear ridgeline  23  can be formed not only on the upper surface but also on the side surface of the polygonal frustum. In this embodiment, the length of one side of the bottom surface of the polygonal frustum is preferably 2.0-70 mm, is more preferably 5.0-50 mm, and particularly preferably 10-40 mm. If the length of one side is less than 2.0 mm, it is difficult to confirm a clear convex ridgeline, and if it exceeds 70 mm, it may be difficult to form a three-dimensional pattern. The length of the diameter of the bottom surface of the circular truncated cone is preferably 2.5-100 mm, is more preferably 7.0-75 mm, and is particularly preferably 15-60 mm. If the length of one side is less than 2.5 mm, it may be difficult to confirm a sharp convex ridgeline, and if it exceeds 100 mm, it may be difficult to form a three-dimensional pattern. 
     The Third Embodiment 
       FIG.  2 C  shows the third embodiment of the patterned natural leather seat of the present invention. In the present embodiment, the pattern formed on a natural leather seat  30  has a convex part wherein the top of the polygonal pyramid is depressed. In this embodiment, by modifying the die shape, it is possible to create a curved shape having a convex ridgeline  32  formed on the side surface, and a convex ridgeline  33  on the upper surface. In this embodiment, the length of one side of the bottom surface is preferably 2.0-70 mm, is more preferably 5.0-50 mm, and is particularly preferably 10-40 mm. If the length of one side is less than 2.0 mm, it is difficult to confirm a clear convex ridgeline, and if it exceeds 70 mm, it may be difficult to form a three-dimensional pattern. 
     The Fourth Embodiment 
       FIG.  2 D  shows the fourth embodiment of the patterned natural leather seat of the present invention. In the present embodiment, the pattern formed on a natural leather seat  40  has a convex part wherein the top of the polygonal pyramid is naturally curled up. In this embodiment, by performing embossment by not letting the surface of the natural leather  40  touch the deep part of the die, it is possible to form a convex ridgeline  42  on the side surface, also to leave a natural texture of the natural leather on the top of the convex part. In this embodiment, the length of one side of the bottom surface is preferably 2.0-70 mm, is more preferably 5.0-50 mm, and is particularly preferably 10-40 mm. If the length of one side is less than 2.0 mm, it is difficult to confirm a clear convex ridgeline, and if it exceeds 70 mm, it may be difficult to form a three-dimensional pattern. 
     The Fifth Embodiment 
     In the present embodiment, a pattern formed on a natural leather seat  10  is shown in  FIG.  2 E . In this embodiment, it is possible to form a clear convex ridgeline  52  on the upper surface. In this embodiment, the length of the convex ridgeline is preferably 2.0-70 mm, is more preferably 5.0-50 mm, and is particularly preferably 10-40 mm. When the length of the convex ridgeline is less than 2.0 mm, it is difficult to confirm a clear convex ridgeline, and it is difficult to form a convex ridgeline exceeding 70 mm. 
     The Sixth Embodiment 
       FIG.  2 F  shows the sixth embodiment of the patterned natural leather seat of the present invention. In the present embodiment, the pattern formed on a natural leather seat  60  has a polygonal frustum concave part. In this embodiment, it is possible to form a clear convex ridgeline  62  on the upper surface. Thus, even if it has only a concave part, as long as it has a convex ridgeline, it is equivalent to the pattern in the present invention. 
     As the backside of the patterned natural leather seat of the present invention is flat, the formed pattern does not easily disappear due to load or friction. 
     (Patterning Method of Natural Leather) 
     As shown in  FIG.  3 A , the embossing method of a natural leather of the present invention is a method wherein a natural leather  100  is installed and pressed between a die  110  and a pressure receiver  120 , and by adding one or more selected from heat, ultrasonic waves and high frequency waves, a pattern of the die  110  is formed on the surface of the natural leather  100 . 
     The die used in the patterning method of the present invention is exemplified in  FIG.  1 B . As shown in  FIG.  1 B , the die  110  has one or more concave part  111 . The tilt angle  112  of the concave part  111  is 0.2°-89°, is preferably 0.5°-60°, and is particularly preferably 1°-45°. If the tilt angle  112  of the concave part  111  of the die  110  is less than 0.2°, a three-dimensional pattern cannot be obtained, and if it exceeds 89°, a convex ridgeline cannot be formed. 
     The depth  114  of the die  110  is 0.5-2 mm, is preferably 0.75-1.75 cm, and is particularly preferably 1.0-1.5 cm. If the depth  114  is less than 0.5 mm, a three-dimensional pattern is not formed, and if it exceeds 2 mm, a convex ridgeline cannot be formed. However, this does not apply to the case wherein the surface of the natural leather does not touch the deep part of the die as in the aforementioned fourth embodiment. 
     Although not limited to this, the outer periphery of the concave part  111  of the die  110  may have a convex part  113 . By having the convex part  113 , a pattern of clear and sharp impression can be formed by the natural leather. The height of the convex part  113  is preferably 0.01-1 mm, is more preferably 0.03-0.5 cm, and is particularly preferably 0.05-0.1 cm. When the height of the convex part is within the range, the pattern can be further clarified. 
     If desired, the surface of the die  110  can be blasted to form fine concavity and convexity (scratches) on the surface of the die. As a result, not only can the light on the natural leather surface be pressed by the die be irregularly reflected to give a high-quality appearance, but also improvements on the functional aspects such as the touch or dirt prevention can be expected. 
     The pressure receiver  120  is preferably, but not limited to, a plane metal surface  122  having a hardness of 25 to 722 and a cushioning material  121  on the plane metal surface. More preferably, the cushioning material  121  is a wool felt having a thickness of 0.5 to 20 mm. By using the pressure receiver  120  having the above-described constitution, it becomes easier to secure a design property wherein a clear convex ridgeline is expressed even in a three-dimensional shape having a pattern height of 0.5-2.0 mm. 
     The thickness of the natural leather is preferably 0.5-2.0 mm, is more preferably 0.7-1.5 mm, and is particularly preferably 0.8-1.2 mm. When the thickness of the natural leather exceeds the above range or is less than the above range, a clear convex ridgeline may not be formed. 
     In the present invention, the thickness of the natural leather is determined by measuring the thickness of ten points on the cross section and taking the mean value. 
     In the present invention, the depth of the die is preferably shallower than the thickness of the natural leather. By making the die shape wherein there is no gap between the natural leather and the die, the shape according to the die can be given to the surface of the natural leather. However, it is not limited to the above in a case wherein the die is purposefully deepened in order to round the convex top of the natural leather pattern, as in the aforementioned fourth embodiment. In addition, on the back surface of the natural leather, a backing material may be pasted with an adhesive in advance or simultaneously with the present method. When the hardness of the backing material is lower than the hardness of the natural leather (for example, urethane foam), the depth of the die is still shallower than the thickness of the natural leather. On the other hand, when the hardness of the backing material is close to or higher than that of the genuine leather, and is made of a thermoplastic material (for example, vinyl chloride), the objective can be similarly achieved when the depth of the die is shallower than the thickness determined by adding the natural leather and the backing material. 
     The pressure at the time of pressing is 0.1-5.0 MPa, is preferably 0.3-4.0 MPa, and is more preferably 0.4-3.0 MPa. When the pressure is within the above range, a clear convex ridgeline is likely to be formed. 
     As the backside of the patterned natural leather seat of the present invention is flat, the formed pattern does not easily disappear due to load or friction. 
     WORKING EXAMPLES 
     The present invention will be described in more detail with reference to a working example, but the present invention is not limited to only the working example. In the following working example, % indicates % by mass. 
     Working Example 1 
     On a metal table  122 , a wool felt  121  having a thickness of 3.0 mm was placed, and a natural leather  100  having a thickness of 2.0 mm was placed. On the surface of the natural leather  100 , embossment was performed by pressing (pressure 2 MPa) a 25 cm square iron die  110  for patterning while heating (die surface temperature 100° C.) (see  FIG.  3 A ). 
     The embossed natural leather pattern has a triangular pyramid convex part (height: 1.5 mm) and a concave part (depth: 0.1 mm) on its outer periphery; the concavity and convexity form, and convex ridgeline were clearly formed (pattern height: 1.6 mm) (see  FIG.  3 B ). 
     In addition, a car seat was created using a patterned natural leather seat as the surface material, and a 8000-times durability test (at 23° C. and 50% RH) was performed using a seat getting-on-and-off durability tester manufactured by TM TEC. Even in the seat after the durability test, the concavity and convexity form, and convex ridgeline clearly remained. 
     Comparative Example 1 
     On a metal table  122 , a natural leather  200  of the thickness of 2.0 mm was placed. On the surface of the natural leather  200 , embossment was performed by pressing (pressure 2 MPa) a 25 cm square iron die  210  for patterning while heating (die surface temperature 100° C.) (see  FIG.  4 A ). 
     The embossed natural leather pattern is a flat triangle expressed by a concave part having the depth of 0.1 mm, had no sharpness, and had a poor three-dimensional appearance (see  FIG.  4 B ). 
     INDUSTRIAL APPLICABILITY 
     The patterned natural leather seat of the present invention can be used as interior materials and seats for railway vehicles, automobiles, aircrafts, ships, and the like, industrial materials, interior materials, clothing, clothing materials, and the like. 
     EXPLANATION OF REFERENCES 
       1 ,  3 ,  5 ,  10 ,  20 ,  30 ,  40 ,  60 ,  100 ,  200  Natural Leather 
       11 ,  21 ,  31 ,  41 ,  61 ,  110  Patterning die of the present invention 
       2 ,  4 ,  6 ,  210  Conventional patterning die 
       101  Convex part of the pattern 
       102  Concave part of the pattern 
       12 ,  22 ,  23 ,  32 ,  33 ,  42 ,  52 ,  62 ,  103  Convex ridgeline 
       104  Pattern base angle 
       105  Pattern height 
       111  Concave part of the die 
       112  Tilt angle of the die 
       113  Convex part of the die 
       114  Die depth 
       120  Pressure receiver 
       121  Cushioning material 
       122  Plane metal surface