Production method for paper disk case

Abstract

[Problem] To provide a production method for a paper disk case that comprises a cardboard base material that can be shaped to have a cylindrical holding protrusion that can removably fit into a circular hole in a disk-shaped optical disk. [Solution] Discontinuous first arc-shaped slits 3L that do not intersect the direction parallel or the direction orthogonal to the grain of a paper base material 1, as seen from the center point O of a narrow portion that is to be shaped into a cylindrical holding protrusion 2 by raising a center part of the paper base material, are formed at the outer periphery of the narrow portion, discontinuous second arc-shaped slits 4L that intersect the direction parallel and the direction orthogonal to the grain of the paper base material 1, as seen from the center point O, but do not intersect in the radial direction through each center portion of the discontinuous first arc-shaped slits 3L, as seen from the center point O, are formed at the outer periphery of the discontinuous first arc-shaped slits 3L, and then the narrow portion of the center part of the paper base material is raised to form the cylindrical holding protrusion 2.

Description

Manufacturing method for paper disc cases

[0001] The present invention relates to a method for manufacturing a paper disc case that can replace a plastic case for a CD or DVD.

[0002] Conventionally, plastic containers and polystyrene foam containers have been widely used as containers for daily necessities and food due to their good moldability. However, after these containers are mass-produced, consumed, and discarded, they turn into so-called microplastics, which cause marine pollution and other problems. From the viewpoint of environmental protection, paper containers, which are easy to dispose of after use, are attracting attention.

[0003] Therefore, a method has been proposed in which flat paper materials such as cardboard, which are more difficult to process than plastic, are press-molded to produce tray-shaped or cup-shaped containers while maintaining their strength (Patent Document 1).

[0004] According to the invention described in Patent Document 1, when a tray shape with a large capacity is formed using a general paper material, wrinkles occur in the flange and sidewall of the tray-shaped container. The occurrence of such wrinkles impairs the aesthetic appearance, and there is a problem that it is impossible to properly apply markings, such as by printing, to those areas. Furthermore, when attempting to seal the container, wrinkles, particularly in the flange, cause a problem that complete sealing cannot be achieved. Therefore, a manufacturing method to solve these problems has been proposed (Patent Document 2).

[0005] As such, various methods for manufacturing paper containers have been proposed with the aim of eliminating plastic, but the main products being produced are tray-shaped and cup-shaped ones for holding food, etc., and paper is gradually becoming popular as a replacement for these. Furthermore, plastic products used as cases for electronic devices, such as disc-shaped optical disks like CDs and DVDs, are also mass-produced and used, and with the demand for eliminating plastic for these plastic products as well, paper versions are now being sought.

[0006] However, a structural feature of disc-shaped optical discs such as CDs and DVDs is that they have a circular hole formed in the center, and plastic storage cases are generally used that have an engagement portion with a claw-like protrusion that slides up along the inner circumferential wall of the hole and engages with the upper edge of the hole. Even if an attempt was made to manufacture an alternative case using paper, the shape of the engagement portion with the claw-like protrusion is complex, and it was not possible to press-mold it into such a shape. Therefore, a paper disc case has been proposed in which, instead of an engagement portion with a claw-like protrusion, a cylindrical holding protrusion that can be fitted into and removed from the circular hole in the center of the disc is formed by press-mold from a sheet of paper (Patent Document 3).

[0007] JP 2002-347736 A JP 2023-121290 A JP 2005-193923 A

[0008] However, as in the invention described in Patent Document 3, it has not been possible to actually form a cylindrical holding protrusion with a diameter of 15 mm or less and a height of approximately 3 to 4 mm, corresponding to the 15 mm diameter of the circular hole in the center of the disc, by drawing a flat paper material of 10 cm or more square and laminated to maintain a certain level of strength. In other words, when attempting to form such a cylindrical holding protrusion, if a sheet of paper with a certain thickness to maintain strength is drawn in a narrow area of ​​the size corresponding to the diameter of the circular hole, the processing pressure is concentrated in this narrow area, causing breakage around the rising base of the cylindrical holding protrusion, and it has not been possible to actually provide a paper disc case of this shape.

[0009] Therefore, the present invention aims to provide a manufacturing method that uses a cardboard sheet material with a certain strength as a base material, and can form a cylindrical holding protrusion that can be fitted into and removed from the circular hole of a circular optical disk even when press-molded using a commonly used drawing machine, and that can easily fit the disk into and remove it from the holding protrusion, thereby realizing a paper disk case that can be used as a substitute for conventional plastic storage cases.

[0010] In order to solve the above problems, the present invention is configured as follows: In a first aspect of the present invention, a manufacturing method of a paper case for discs is a manufacturing method of a paper case for discs in which a cylindrical holding protrusion that can be fitted into a circular hole of a disc to be stored is formed by drawing in the center of a square planar paper base material, and a discontinuous first arc-shaped notch is formed around the outer periphery of a narrow area where the cylindrical holding protrusion is formed by drawing in the center of the paper base material, so as not to intersect with directions parallel to and perpendicular to the grain of the paper base material when viewed from the center point of the narrow area, and A discontinuous second arc-shaped notch is formed around the outer periphery of the discontinuous first arc-shaped notch, so that when viewed from the center point, it intersects with the directions parallel to and perpendicular to the grain of the paper base material, but does not intersect with the radial direction passing through each central portion of the discontinuous first arc-shaped notch, and after forming these first and second discontinuous arc-shaped notches, a drawing process is performed on a narrow area in the center of the paper base material to form a cylindrical retaining protrusion that can be fitted into and removed from the circular hole in the disk.

[0011] In addition, the manufacturing method of the second invention, like the first invention, is characterized in that it comprises forming first and second discontinuous arc-shaped notches around the outer periphery of the narrowed area where the central part of the paper base material is drawn to form the cylindrical retaining protrusion, and forming a plurality of teardrop-shaped notches at equal intervals along the circumferential edge, starting from the circumferential edge that will become the base of the cylinder after molding of the narrowed circular area where the cylindrical retaining protrusion is formed, and ending at the circumferential edge that will become the flat surface of the cylinder after molding, with the leading end narrow and the trailing end slightly bulging, and after forming these first and second discontinuous arc-shaped notches and teardrop-shaped notches, drawing is performed on the narrowed area in the central part of the paper base material to form a cylindrical retaining protrusion that can be fitted into and removed from the circular hole of the disc.

[0012] In addition, in the first invention, when the size of the paper base material is 5 cm square or more, the paper thickness is 0.4 to 1.0 mm, and the diameter of the cylindrical holding protrusion in the narrow area in the center of the paper base material where drawing is performed is set to 15 mm or less and the height is 3 to 4 mm, the first arc-shaped notch is formed at a position 6 mm away from the outer periphery of the cylindrical holding protrusion, and the second arc-shaped notch is formed at a position 8 mm away from the outer periphery of the cylindrical holding protrusion, and in the second invention, the length of the waterdrop-shaped notch is formed to be 6.2 mm.

[0013] According to the manufacturing method of the first invention for a paper disc case, discontinuous first arc-shaped notches are formed around the outer periphery of the narrowed area where the central part of the paper base is drawn to form the cylindrical retaining protrusions, so that when viewed from the center point of the narrowed area, they do not intersect in directions parallel to or perpendicular to the grain of the paper base, and discontinuous second arc-shaped notches are formed around the outer periphery of the discontinuous first arc-shaped notches, so that they intersect in directions parallel to and perpendicular to the grain of the paper base, but do not intersect in radial directions passing through the central parts of the discontinuous first arc-shaped notches when viewed from the center point. After forming these first and second discontinuous arc-shaped notches, the narrowed area in the central part of the paper base is drawn using a press, so that when drawing pressure is applied to the narrowed area, this drawing pressure also affects the discontinuous first arc-shaped notches and second arc-shaped notches, causing tears in these notches and dispersing the drawing force.

[0014] As a result, the drawing pressure is not concentrated at the base of the cylindrical holding protrusion that is being drawn, and breakage around the rising base of the cylindrically formed holding protrusion, as occurred in the past, is eliminated. These arc-shaped notches are formed taking into consideration the grain of the paper base material, and the notched portions and discontinuous portions of the first and second discontinuous arc-shaped notches are formed so that they do not overlap with each other, so that the concentration and dispersion of the drawing pressure act in a balanced manner, and the base of the cylindrical holding protrusion is not broken, and the cylindrical holding protrusion can be formed while maintaining a certain strength.

[0015] Furthermore, when the paper substrate size is 5 cm or more, the paper thickness is 0.4 to 1.0 mm, and the molding conditions are set so that the central portion of the paper substrate is drawn to form a cylindrical holding protrusion in the narrowed region with a diameter of 15 mm or less and a height of 3 to 4 mm, by forming a discontinuous first arc-shaped notch 6 mm away from the drawing position on the outer periphery of the base of the cylindrical holding protrusion, and by forming a discontinuous second arc-shaped notch 8 mm away from the drawing position on the outer periphery of the base of the cylindrical holding protrusion, as described above, the concentration and dispersion of the drawing force act in a balanced manner, thereby enabling the molding of a cylindrical holding protrusion that is adapted to the set conditions reliably and maintains practical strength. The positioning of the notches is based on knowledge and data obtained by the applicant through repeated trial and error.

[0016] According to the manufacturing method of the disc paper case of the second invention, as in the first invention, when drawing pressure is applied to the narrow area, the drawing pressure is exerted on the discontinuous first arc-shaped notch and second arc-shaped notch, causing cracks in these notches and dispersing the drawing force, so that the drawing pressure is no longer concentrated on the base of the cylindrical holding protrusion that is drawn and molded, and no breakage occurs around the rising base of the cylindrically molded holding protrusion as occurred in the past. Furthermore, multiple teardrop-shaped notches, which are narrow at the tip and slightly bulge at the rear end in the direction toward the center point of the narrow circular area portion where the cylindrical holding protrusion is molded, are formed at equal intervals, starting from the circumferential edge that will become the base of the cylinder after molding of the narrow circular area portion where the cylindrical holding protrusion is molded, and ending at the circumferential edge of the cylindrical plane after molding.When the cylindrical holding protrusion is squeezed and molded, tiny cracks also occur in these teardrop-shaped notches formed in the area that will become the cylindrical side wall surface of the cylindrical holding protrusion.As described above, the squeezing processing pressure acts in a dispersed manner as the cylindrical holding protrusion rises, eliminating fractures on the side wall surface of the cylindrical holding protrusion and allowing the cylindrical holding protrusion to be molded in a more stable state.

[0017] Furthermore, when inserting or removing a disc into or from the cylindrical holding protrusion, the microcracks close during insertion, making it easier to insert the disc, and then widen after insertion, making it difficult for the disc to come out.When removing the disc, if you lift the disc while pressing down on the upper surface of the cylindrical holding protrusion, the microcracks close, making it easy to remove the disc.

[0018] Furthermore, as in the first invention, when the size and other factors of the paper substrate are set to the same molding conditions, forming the teardrop-shaped notches to a length of 6.2 mm will result in a balanced effect between the concentration and dispersion of the drawing force, as described above, and will enable the molding of a cylindrical holding protrusion that is suited to the set conditions and that maintains practical strength. The position, number, and length of these notches are also based on knowledge and data obtained by the applicant through repeated trial and error.

[0019] FIG. 1 is an external perspective view showing the molded form of a paper disc case to be manufactured. FIG. 2 is an explanatory diagram illustrating a cutting process, which is a step before drawing is performed in an embodiment of the first invention. FIG. 3 is an external perspective view showing a state in which a cylindrical holding protrusion that can be fitted into a circular hole in the center of the disc is molded by the manufacturing method of the first embodiment. FIG. 4 is an external perspective view showing a state in which a storage case of a general disc size is molded by the manufacturing method of the first invention. FIG. 5 is an external perspective view showing a state in which a disc-shaped paper disc case of the first embodiment is about to be accommodated in the disc-shaped paper disc case. FIG. 6 is an explanatory diagram illustrating a cutting and notching process, which is a step before drawing is performed in an embodiment of the second invention. FIG. 7 is an external perspective view showing a state in which a cylindrical holding protrusion that can be fitted into a circular hole in the center of the disc is molded by the manufacturing method of the second embodiment. FIG. 8 is an external perspective view showing a state in which a storage case of a general disc size is molded by the manufacturing method of the second invention.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] 1 is an external perspective view showing the basic form of a paper disc case to be manufactured, in which, for example, a sheet-like paper substrate 1 is 5 cm square or larger and 0.4 to 1.0 mm thick (in this example, a 5 cm square, 1.0 mm thick case is targeted, and a case is assumed for storing a 5 cm diameter disc) and an example is shown in which a narrow area in the center of this paper substrate 1 is drawn using a press molding machine to form a cylindrical holding protrusion 2 having a diameter of 15 mm or less and a height of 3 to 4 mm. By forming the cylindrical holding protrusion 2 having a diameter of 15 mm or less and a height of 3 to 4 mm, the cylindrical holding protrusion 2 can be inserted into and engaged with the hole (usually 15 mm in diameter) of the disc to store the disc. However, when a conventional press molding machine is used to squeeze the paper base material 1 into such a shape, the intermolecular bonds of the paper base material 1 are strong, and it is not malleable or ductile enough to withstand external forces like metals. Therefore, when a strong external force is applied, the cylindrical holding protrusion 2 that is being molded breaks around the base 2B, and in reality, it was not possible to mold the paper base material into such a shape.

[0022] As shown in Figure 2, in a manufacturing method according to an embodiment of the first invention, as a preliminary step to molding a cylindrical holding protrusion 2 in a narrow area in the center of the paper base material 1, a discontinuous first arc-shaped notch 3L is formed around the outer periphery of the area to be molded upright to form the base 2B of the cylindrical holding protrusion 2, so that when viewed from the center point O of the narrow area, it does not intersect with the direction parallel to or perpendicular to the grain of the paper base material 1.

[0023] Furthermore, discontinuous second arc-shaped notches 4L are formed around the outer periphery of these discontinuous first arc-shaped notches 3L so as to intersect in directions parallel to and perpendicular to the grain of the paper substrate 1 but not in radial directions passing through each central portion of the discontinuous first arc-shaped notches 3L when viewed from the center point O. As shown in the figure, the discontinuous first arc-shaped notches 3L are formed at a position 6 mm away from the narrowed position that becomes the base 2B of the cylindrical holding protrusion 2, and the discontinuous second arc-shaped notches 4L are formed at a position 8 mm away from the narrowed position that becomes the base 2B of the cylindrical holding protrusion 2.

[0024] In the manufacturing method of the embodiment, after forming the first arc-shaped incision 3L and the second arc-shaped incision 4L as a pre-process, a drawing process is carried out using a press molding machine in a narrow area in the center of the paper base material 1. The drawing process using the press molding machine is not performed using a specially specified machine for carrying out the present invention, but rather using a conventional machine, so a description of the drawing process itself will be omitted.

[0025] Figure 3 is an external oblique view showing the state in which the desired cylindrical holding protrusion 2 has been molded in the center of the paper base material 1 by carrying out the manufacturing method of the embodiment as described above.As shown in the figure, crescent-shaped cracks 3LH and 4LH have been formed around the base 2B of the molded cylindrical holding protrusion 2 at the locations of the discontinuous first arc-shaped notch 3L and second arc-shaped notch 4L.

[0026] These crescent-shaped cracks 3LH and 4LH have occurred because, when a press molding machine is used to draw a narrow area in the center of the paper base material 1, the drawing pressure extends to the discontinuous first arc-shaped cut 3L and second arc-shaped cut 4L, causing cracks 3LH and 4LH at these cuts 3L and 4L, indicating that the drawing force is not concentrated on the base 2B but is dispersed around it.

[0027] In this way, the drawing pressure is not concentrated on the base 2B of the drawn cylindrical holding protrusion 2, and no breakage occurs around the rising base 2B of the cylindrical holding protrusion 2. These arc-shaped notches are formed taking into consideration the grain of the paper base material, and are formed so that the notched portions and discontinuous portions of the first and second discontinuous arc-shaped notches do not overlap with each other, so the concentration and dispersion of the drawing pressure acts in a more balanced manner, and the cylindrical holding protrusion 2 can be formed while maintaining a constant strength without breaking the base 2B of the cylindrical holding protrusion 2. A disc can be placed on the paper base material 1 by inserting and engaging this molded cylindrical holding protrusion 2 into the hole in the disc.

[0028] In this embodiment, to facilitate easier disc insertion and removal when the hole of the disc is inserted into and engaged with the cylindrical holding projection 2, the cylindrical holding projection 2 and the step 5 are molded simultaneously so that a step 5 is formed on the outer periphery of the disc-shaped discontinuous first arcuate notch 3L and second arcuate notch 4L. By molding the step 5, the disc engaged with the cylindrical holding projection 2 is slightly raised, making it easier to remove. Furthermore, considering that the crescent-shaped cracks 3LH and 4LH formed on the outer periphery of the cylindrical holding projection 2 reduce the peripheral strength of the base 2B when the hole of the disc is inserted into and engaged with the cylindrical holding projection 2, a slight recess 6 is molded simultaneously around the periphery of the base 2B to maintain strength.

[0029] As described above, by forming the discontinuous first arc-shaped notch 3L at a position 6 mm away from the drawing position on the outer periphery of the base 2B of the cylindrical holding projection 2, and by forming the discontinuous second arc-shaped notch 4L at a position 8 mm away from the drawing position on the outer periphery of the base 2B of the cylindrical holding projection 2, the concentration and dispersion of the drawing force are balanced, and the cylindrical holding projection 2 that is adapted to the set conditions of the paper base material 1 can be reliably formed while maintaining practical strength. The positioning of the notches is based on knowledge and data obtained by the applicant through repeated trial and error.

[0030] Figure 4 is a perspective view showing the appearance of a paper case manufactured using a paper substrate 10 according to the manufacturing method of the present invention, capable of housing a 12 cm diameter disc. The area surrounding the cylindrical retaining projection 2, molded as described above, is shown in solid lines, while the remaining areas are shown in dashed lines as an example of a suitable housing configuration, since various housing configurations previously proposed for different disc sizes can be applied. As shown in the figure, the 15 cm square paper substrate 10 is formed with a housing recess 11, which becomes the housing for the entire disc when the hole of the disc is inserted and engaged with the cylindrical retaining projection 2, a disc ejection recess 12 connected to the housing recess 11, and a peripheral wall 13 formed along the disc's outer shape, forming the housing recess 11 and the ejection recess 12. These are molded into the paper substrate 10 using a single pattern using a press molding machine to form the desired shape.

[0031] 5 is an external perspective view showing a state in which a disc-shaped optical disk 20 is about to be stored in a paper storage case molded and manufactured by applying the manufacturing method of the present invention to a paper substrate 10, and the cylindrical holding protrusions 2 are inserted into and engaged with the holes 21 of the disc-shaped optical disk 20, allowing the entire disk to be stored in the storage recess 11. The stored disc-shaped optical disk 20 can be easily removed by inserting a fingertip into the removal recess 12 to release the engagement.

[0032] As described above, according to the manufacturing method of the first invention, even if a sheet of cardboard having a certain strength is used as the base material and press-molded using a commonly used drawing machine, it is possible to form a cylindrical holding protrusion that can be fitted into and removed from the circular hole of a circular optical disk, making it possible to actually provide a paper case for disks that can be used as a substitute for plastic storage cases, which was previously impossible to achieve.

[0033] Next, an embodiment of the second invention will be described. The paper disc case to be manufactured is the same as the basic form shown in the external perspective view of Figure 1, and therefore a description thereof will be omitted.

[0034] As with the first embodiment, the manufacturing method of the second invention involves first, as a preliminary step to molding a cylindrical holding protrusion 2 in a narrow area in the center of the paper base material 1, as shown in Figure 6, forming a discontinuous first arc-shaped notch 3L around the outer periphery of the area to be molded upright to become the base 2B of the cylindrical holding protrusion 2, so that when viewed from the center point O of the narrow area, it does not intersect with the direction parallel to or perpendicular to the grain of the paper base material 1.

[0035] Next, discontinuous second arc-shaped notches 4L are formed around the outer periphery of these discontinuous first arc-shaped notches 3L so as to intersect in directions parallel to and perpendicular to the grain of the paper substrate 1, but not in radial directions passing through each central portion of the discontinuous first arc-shaped notches 3L when viewed from the center point O. As shown in the figure, the discontinuous first arc-shaped notches 3L are formed at a position 6 mm away from the narrowed position that will become the base 2B of the cylindrical holding protrusion 2, and the discontinuous second arc-shaped notches 4L are formed at a position 8 mm away from the narrowed position that will become the base 2B of the cylindrical holding protrusion 2.

[0036] Next, starting from the circumferential edge that will become the cylindrical base 2B after molding of the narrow circular region that will form the cylindrical holding protrusion 2, and ending at the circumferential edge 2C that will become the cylindrical flat edge after molding, eight teardrop-shaped notches 2L that are narrow at the tip end toward the center point O of the narrow region and slightly bulge at the rear end are formed at equal intervals along the circumferential edge. The length of these teardrop-shaped notches 2L is 6.2 mm.

[0037] In the second embodiment, after the first and second arc-shaped incisions 3L, 4L, and teardrop-shaped incisions 2L are formed as a pre-process, a drawing process is carried out using a press molding machine in a narrow area in the center of the paper base material 1. As with the first embodiment, the drawing process using the press molding machine is carried out using a conventional machine, and therefore a description of the drawing process itself will be omitted.

[0038] Figure 7 is an external oblique view showing the state in which the desired cylindrical holding protrusion 2 has been molded in the center of the paper base material 1 by carrying out the manufacturing method of the second embodiment as described above. As shown in the figure, crescent-shaped cracks 3LH and 4LH are formed around the base 2B of the molded cylindrical holding protrusion 2 at the locations of the discontinuous first arc-shaped notch 3L and second arc-shaped notch 4L, and eight teardrop-shaped notches 2L formed in the area that will become the cylindrical side wall surface after formation from the base 2B of the cylindrical holding protrusion 2 to the circumferential edge 2C, which becomes the flat edge on the cylinder, each have an ultra-thin convex lens-shaped crack 2LH.

[0039] These crescent-shaped cracks 3LH, 4LH and ultra-thin convex lens-like crack 2LH have occurred because, when a press molding machine is used to draw a narrow area in the center of the paper base material 1, the drawing pressure extends to the discontinuous first arc-shaped notch 3L and second arc-shaped notch 4L, and to the teardrop-shaped notch 2L, causing cracks 2LH, 3LH, and 4LH in these notches 2L and notches 3L and 4L. This shows that the drawing force is not concentrated on the base 2B, or even from the base 2B to the circumferential edge 2C, but is dispersed around the periphery.

[0040] In this way, the concentration and dispersion of the drawing pressure acts in a more balanced manner on the first arc-shaped notch 3L, the second arc-shaped notch 4L, and the teardrop-shaped notch 2L, and the cylindrical holding protrusion 2 is molded while maintaining a constant strength without breaking the periphery or side wall surface of the base 2B of the cylindrical holding protrusion 2.

[0041] Because the cylindrical holding protrusion 2 in the second embodiment is molded as described above, when inserting or removing a disc into or from the cylindrical holding protrusion 2, the microcracks 2LH close during insertion, making it easier to insert the disc, and then widen after insertion, making it difficult for the disc to fall out. When removing the disc, simply lifting the disc while pressing down on the upper surface of the cylindrical holding protrusion 2 closes the microcracks 2LH, allowing the disc to be easily removed. In this way, by inserting and engaging the molded cylindrical holding protrusion 2 into the hole in the disc, the disc can be stably stored on the paper substrate 1 in a state where it is difficult for it to fall out, and removal can be performed easily and reliably.

[0042] In the second embodiment, to facilitate easier and more reliable disc insertion and removal when the hole of the disc is inserted into and engaged with the cylindrical holding projection 2, a step 5 is molded at the outer periphery of the discontinuous first and second arcuate notches 3L and 4L, and a recessed surface 2D is molded simultaneously on the upper surface of the cylindrical holding projection 2. By molding the step 5, the disc engaged with the cylindrical holding projection 2 is slightly raised, and by pressing the recessed surface 2D of the cylindrical holding projection 2, the crack 2LH is quickly closed, making disc removal easier. Also, as in the first embodiment, the crescent-shaped cracks 3LH and 4LH formed around the outer periphery of the cylindrical holding projection 2 reduce the peripheral strength of the base 2B when the hole of the disc is inserted into and engaged with the cylindrical holding projection 2. Therefore, a slight recess 6 is molded simultaneously around the periphery of the base 2B to maintain strength.

[0043] As in the first embodiment, the discontinuous first arc-shaped notch 3L is formed 6 mm away from the drawn position on the outer periphery of the base 2B of the cylindrical holding projection 2, and the discontinuous second arc-shaped notch 4L is formed 8 mm away from the drawn position on the outer periphery of the base 2B of the cylindrical holding projection 2. Eight equally spaced teardrop-shaped notches 2L are formed in the direction toward the center point O, extending from the circumferential edge of the base 2B to the circumferential edge 2C, which forms the flat cylindrical edge. The length of these teardrop-shaped notches 2L is 6.2 mm. This setting ensures a balanced concentration and dispersion of the drawing force, allowing the cylindrical holding projection 2 to be molded reliably and with practical strength, adapting to the set conditions of the paper substrate 1. The positioning of each notch and the number and positioning of the notches are based on knowledge and data obtained through repeated trial and error by the applicant.

[0044] FIG. 8 is a perspective view showing the appearance of a paper case manufactured using a paper substrate 10 according to the manufacturing method of the second invention, capable of housing a 12 cm diameter disc. As in the first embodiment, the area surrounding the cylindrical retaining projection 2 is shown in solid lines, while the remaining areas are shown in dashed lines as an example of a suitable housing configuration, since various housing configurations previously proposed for different disc sizes can be applied. As shown in the figure, the 15 cm square paper substrate 10 is formed with a housing recess 11 that serves as a housing for the entire disc when the disc hole is inserted and engaged with the cylindrical retaining projection 2, a disc ejection recess 12 connected to the housing recess 11, and a peripheral wall 13 formed along the disc's outer shape, forming the housing recess 11 and the ejection recess 12. These are molded into the paper substrate 10 using a single pattern using a press molding machine to form the desired shape.

[0045] 9 is an external perspective view showing a state in which a disc-shaped optical disk 20 is about to be stored in a paper storage case molded by applying the manufacturing method of the second invention to a paper substrate 10. When the cylindrical holding protrusion 2 is fitted and engaged with the hole 21 of the disc-shaped optical disk 20 to store the entire disc in the storage recess 11, the engaged state prevents the disc from easily falling out, allowing for stable storage. The stored disc-shaped optical disk 20 can be more easily and smoothly removed by inserting a fingertip into the removal recess 12 to release the engagement and pressing the recessed surface 2D of the cylindrical holding protrusion as described above.

[0046] As described above, according to the manufacturing methods of the first and second inventions, even if a sheet of cardboard having a certain strength is used as a base material and press-molded using a commonly used drawing machine, it is possible to form a cylindrical holding protrusion that can be fitted into the circular hole of a circular optical disk, and therefore it is now possible to actually provide a paper disk case that can be used as a substitute for plastic storage cases, which was previously impossible to realize.

[0047] In the above-described embodiment, when a narrow area in the center of a paper substrate is drawn using a press molding machine to form a cylindrical retaining protrusion with a small diameter, several cuts and notches are formed around the narrow area to prevent the drawing pressure from being concentrated in the narrow area. The drawing pressure also extends to the cuts and notches, and tears are created in the cuts and notches to disperse the drawing force. This manufacturing method provides a paper case for a disc-shaped optical disc, such as a CD or DVD. However, the key cuts and notches can be formed in various patterns. If similar protrusions can be molded into plastic containers used for other electronic products to form storage compartments, the range of paper cases that can be used as a replacement is expanded. Furthermore, the manufacturing method of the present invention can also provide paper storage cases as replacements for plastic cases with similarly shaped retaining sections, such as cosmetic cases and miscellaneous goods cases.

[0048] REFERENCE SIGNS LIST 1 Paper base material 2 Cylindrical holding protrusion 2B Base 2C Circumferential edge 2L Teardrop-shaped notch 2LH Crack 3L Discontinuous first circular arc-shaped cut 3LH Crack 4L Discontinuous second circular arc-shaped cut 4LH Crack 5 Step portion 6 Depression portion O Center point

Claims

1. In a method for manufacturing a paper case for a disc, in which a columnar holding projection that can be fitted into and removed from a circular hole of a disc to be accommodated is formed by drawing in the central portion of a square planar paper base material, around the outer periphery of a narrow region where the central portion of the paper base material is drawn to form the columnar holding projection, a discontinuous first arc-shaped cut is formed so as not to intersect with the directions parallel and perpendicular to the paper grain of the paper base material as viewed from the center point of the narrow region, and around the outer periphery of the discontinuous first arc-shaped cut, a discontinuous second arc-shaped cut is formed so as to intersect with the directions parallel and perpendicular to the paper grain of the paper base material as viewed from the center point, and not to intersect in the radial direction passing through each central portion of the discontinuous first arc-shaped cut as viewed from the center point. After forming these first and second discontinuous arc-shaped cuts, the narrow region of the central portion of the paper base material is drawn to form a columnar holding projection that can be fitted into and removed from the circular hole of the disc. A method for manufacturing a paper case for a disc, characterized in that.

2. In a method for manufacturing a paper case for a disc, in which a columnar holding projection that can be fitted into and removed from a circular hole of a disc to be accommodated is formed by drawing in the central portion of a square planar paper base material, around the outer periphery of a narrow circular region where the central portion of the paper base material is drawn to form the columnar holding projection, a discontinuous first arc-shaped cut is formed so as not to intersect with the directions parallel and perpendicular to the paper grain of the paper base material as viewed from the center point of the narrow region, and around the outer periphery of the discontinuous first arc-shaped cut, a discontinuous second arc-shaped cut is formed so as to intersect with the directions parallel and perpendicular to the paper grain of the paper base material as viewed from the center point, and not to intersect in the radial direction passing through each central portion of the discontinuous first arc-shaped cut as viewed from the center point. After forming the columnar holding projection, starting from the circumferential edge that becomes the column base after molding and ending at the circumferential edge that becomes the upper plane of the column after molding, a plurality of water-drop-shaped notches are formed at equal intervals along the circumferential edge, with the tip side in the direction towards the center point of the narrow region being thin and the rear end side being slightly bulged. After forming the first and second discontinuous arc-shaped cuts and the water-drop-shaped notches, the narrow region of the central portion of the paper base material is drawn to form a columnar holding projection that can be fitted into and removed from the circular hole of the disc. A method for manufacturing a paper case for a disc, characterized in that.

3. When the size of the paper base material is 5 cm square or more, the paper thickness is 0.4 to 1.0 mm, and the diameter of the columnar holding protrusion in the narrow area where the drawing process is performed on the central part of the paper base material is 15 mm or less and the height is 3 to 4 mm, the discontinuous first arc-shaped cut is formed at a position 6 mm away from the constriction position that becomes the outer periphery of the base of the columnar holding protrusion, and the discontinuous second arc-shaped cut is formed at a position 8 mm away from the constriction position that becomes the outer periphery of the base of the columnar holding protrusion. The method for manufacturing a paper case for a disk according to claim 1, characterized in that it is formed.

4. When the size of the paper base material is 5 cm square or more, the paper thickness is 0.4 to 1.0 mm, and the diameter of the columnar holding protrusion in the narrow area where the drawing process is performed on the central part of the paper base material is 15 mm or less and the height is 3 to 4 mm, the discontinuous first arc-shaped cut is formed at a position 6 mm away from the constriction position that becomes the outer periphery of the base of the columnar holding protrusion, and the discontinuous second arc-shaped cut is formed at a position 8 mm away from the constriction position that becomes the outer periphery of the base of the columnar holding protrusion, and the length of the water droplet-shaped notch is formed to be 6.2 mm. The method for manufacturing a paper case for a disk according to claim 2, characterized in that it is formed.

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