Manufacturing method for paper disc cases

Abstract

A method for manufacturing a paper disc case using cardboard as a base material, capable of forming a cylindrical holding protrusion that can be fitted into and removed from a circular hole in a circular optical disc, is provided. [Solution] The central part of the paper base material 1 is drawn to form the cylindrical holding protrusion 2, and around the outer periphery of the narrowed area, discontinuous first arc-shaped notches 3L are formed so that they do not intersect with directions parallel to or perpendicular to the grain of the paper base material when viewed from the center point O of the narrowed area, and around the outer periphery of the discontinuous first arc-shaped notches 3L, discontinuous second arc-shaped notches 4L are formed so that they intersect with directions parallel to or perpendicular to the grain of the paper base material when viewed from the center point O, but do not intersect in the radial direction passing through each central part of the discontinuous first arc-shaped notches 3L when viewed from the center point O, and then the narrowed area in the central part of the paper base material is drawn to form the cylindrical holding protrusion 2.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a paper disc case that can be used as an alternative to plastic cases for CDs and DVDs. [Background technology]

[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 ordinary paper materials are molded into a tray shape with a large capacity, 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 not possible to properly apply markings by printing or the like to those areas. Furthermore, when attempting to seal the container, wrinkles, particularly in the flange, cause a problem that it is not possible to completely seal it. Therefore, a manufacturing method to solve these problems has also 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 more popular as a replacement for these. Plastic cases for electronic devices, such as disc-shaped optical discs 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 part 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 part 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 part 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). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-347736 [Patent Document 2] Japanese Patent Application Publication No. 2023-121290 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-193923 Summary of the Invention [Problem to be solved by the invention]

[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, etc., 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. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention is configured as follows: That is, the manufacturing method of the paper case for discs according to the first invention is a manufacturing method of the paper case for discs in which a cylindrical holding protrusion that can be fitted into a circular hole of the disc to be stored is formed by drawing in the center of a paper base material having a rectangular plane, in which a disc is formed by drawing in the center of the paper base material, a discontinuous first circular arc-shaped notch is formed around the outer periphery of the narrow area where the cylindrical holding protrusion is formed by drawing in the center of the paper base material, so that the disc does not intersect with the direction parallel to the grain of the paper base material and the direction perpendicular to the grain, as viewed from the center point of the narrow area, 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 processing is performed is set to 15 mm or less and the height to 3 to 4 mm, the first arc-shaped notch is formed at a position 6 mm away from the outer circumference of the cylindrical holding protrusion, and the second arc-shaped notch is formed at a position 8 mm away from the outer circumference of the cylindrical holding protrusion, and in the second invention, the length of the waterdrop-shaped notch is formed to be 6.2 mm. [Effects of the Invention]

[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 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. 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 drawn and molded, and breakage around the rising base of the cylindrically molded 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 molded while maintaining a certain strength.

[0015] Furthermore, when the paper substrate is 5 cm square or larger, the 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 projection with a diameter of 15 mm or less and a height of 3 to 4 mm in the narrowed region, forming a discontinuous first arc-shaped notch 6 mm from the drawing position on the outer periphery of the base of the cylindrical projection, and forming a discontinuous second arc-shaped notch 8 mm from the drawing position on the outer periphery of the base of the cylindrical projection, as described above, achieves a good balance between the concentration and dispersion of the drawing force, thereby enabling the molding of a cylindrical projection that meets the set conditions reliably and maintains practical strength. The positioning of the notches is based on knowledge and data obtained through repeated trial and error by the applicant.

[0016] According to the manufacturing method of the disc paper case of the second invention, as with the first invention, when drawing pressure is applied to the narrow area, the drawing pressure is exerted on the discontinuous first and second arc-shaped notches, causing cracks in these notches and dispersing the drawing force, preventing the drawing pressure from concentrating on the base of the cylindrical holding protrusion that is drawn and molding, and eliminating breaks that previously occurred around the rising base of the cylindrically molded holding protrusion. 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 with the first invention, when the size and other factors of the paper base material are set to the same molding conditions, forming the teardrop-shaped notches to a length of 6.2 mm will achieve a good balance 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. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view showing the external appearance of a molded paper disc case to be manufactured. [Figure 2] FIG. 3 is an explanatory view illustrating a cutting step prior to drawing in the embodiment of the first invention. [Figure 3] 1 is a perspective view showing the appearance of a state in which a columnar holding protrusion that can be fitted into and removed from a circular hole in the center of the disc is formed by the manufacturing method of the first embodiment. FIG. [Figure 4] 1 is a perspective view showing the appearance of a case molded into the shape of a general disc-sized case by the manufacturing method of the first invention. FIG. [Figure 5] 1 is a perspective view showing the appearance of a paper disc case according to a first embodiment, showing a state in which a circular optical disc is about to be placed in the paper disc case. FIG. [Figure 6] FIG. 10 is an explanatory view illustrating a cutting and notching step prior to drawing in an embodiment of the second invention. [Figure 7] FIG. 10 is an external perspective view showing a state in which a columnar holding protrusion that can be fitted into and removed from a circular hole in the center of the disc is molded by a manufacturing method according to a second embodiment. [Figure 8] FIG. 10 is an external perspective view showing a state in which the product is molded into the shape of a storage case of a general disc size by the manufacturing method of the second invention. [Figure 9] FIG. 10 is a perspective view showing the appearance of a paper disc case according to a second embodiment, showing a state in which a circular optical disc is about to be placed in the paper disc case. DETAILED DESCRIPTION OF THE INVENTION

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

[0021] 1 is an external perspective view showing the basic form of the paper disc case to be manufactured, in which, for example, the 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 it is assumed that a 5 cm diameter disc will be stored), 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 with a diameter of 15 mm or less and a height of 3 to 4 mm. By forming the cylindrical holding protrusion 2 with a diameter of 15 mm or less and a height of 3 to 4 mm in this way, 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 this 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 it into this 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 it does not intersect with the direction parallel to or perpendicular to the grain of the paper base material 1 when viewed from the center point O of the narrow area.

[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 with the directions parallel to and perpendicular to the grain of the paper substrate 1, but not with the radial direction 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 drawn 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 drawn position that will become 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 is 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, 4LH have occurred 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 occurred because when a press molding machine was used to draw a narrow area in the center of the paper base material 1, the drawing pressure extended 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 was not concentrated on the base 2B but was dispersed around it.

[0027] In this way, the drawing pressure is not concentrated on the base 2B of the drawn columnar holding protrusion 2, and no breakage occurs around the rising base 2B of the columnar 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 columnar holding protrusion 2 can be formed while maintaining a constant strength without breaking the base 2B of the columnar holding protrusion 2. A disc can be placed on the paper base material 1 by inserting and engaging this molded columnar 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, making it possible to reliably form the cylindrical holding projection 2 that is suited to the set conditions of the paper base material 1 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] FIG. 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 disc 20 is 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 disc 20, allowing the entire disc to be stored in the storage recess 11. The stored disc-shaped optical disc 20 can be easily removed by inserting a finger 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 retaining protrusion that can fit into and remove 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. [Example]

[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 with the directions parallel to and perpendicular to the grain of the paper substrate 1, but not with the radial direction 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 drawn 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 drawn 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 area 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 front end toward the center point O of the narrow area 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 performed 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 performed 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 of the cylinder, each have an ultra-thin convex lens-shaped crack 2LH.

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

[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, if the disc is lifted while pressing down on the upper surface of the cylindrical holding protrusion 2, the microcracks 2LH close, making it easy to remove the disc. 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 the removal operation 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 arc-shaped notch 3L and second arc-shaped notch 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 cleft 2LH is quickly closed, making it easier to remove the disc. Furthermore, as in the first embodiment, the crescent-shaped clefts 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 support 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 support projection 2. Eight equally spaced teardrop-shaped notches 2L are formed extending from the circumferential edge of the base 2B to the circumferential edge 2C, which forms the flat cylindrical edge, toward the center point O. The length of each teardrop-shaped notch 2L is 6.2 mm. This setting ensures a good balance between the concentration and dispersion of the drawing force, enabling the cylindrical support projection 2 to be formed reliably and with practical strength, tailored to the specified 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 acquired 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. The remaining areas are shown in dashed lines as an example of a suitable housing configuration, since various housing configurations proposed for different disc sizes are applicable. As shown in the figure, the 15-cm square paper substrate 10 is formed with a storage 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 storage recess 11, and a peripheral wall 13 formed along the disc's outer shape, forming the storage recess 11 and the ejection recess 12. These are molded into the paper substrate 10 using a press molding machine using a single pattern to form the desired shape.

[0045] 9 is an external perspective view showing a state in which a disc-shaped optical disc 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 into and engaged with the hole 21 of the disc-shaped optical disc 20 to store the entire disc in the storage recess 11, the engaged state prevents the disc from easily falling out, ensuring stable storage. The stored disc-shaped optical disc 20 can be more easily and smoothly removed by inserting a fingertip into the removal recess 12 to release the engagement and pressing in 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 fit 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 achieve. [Industrial Applicability]

[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. [Explanation of symbols]

[0048] 1 Paper base material 2 Cylindrical retaining protrusion 2B base 2C Circumference 2L water droplet notch 2LH Crack 3L Discontinuous first arc cut 3LH Crack 4L Discontinuous second circular arc cut 4LH Crack 5 Step 6. Recess O center point

Claims

1. A method for manufacturing a paper disc case, which is made by forming a cylindrical holding protrusion in the center of a square, flat paper base material by drawing, the cylindrical holding protrusion being capable of fitting into a circular hole in the disc to be stored, A discontinuous first arc-shaped cut is formed around the outer periphery of the narrowed area where the central part of the paper base material is drawn to form a cylindrical holding protrusion, so that the cut does not intersect with the direction parallel to the grain of the paper base material and the direction perpendicular to the grain when viewed from the center point of the narrowed area, and forming discontinuous second arc-shaped incisions around the outer periphery of the discontinuous first arc-shaped incisions such that, as viewed from the center point, they intersect with directions parallel to and perpendicular to the grain of the paper substrate, but do not intersect with each other in radial directions passing through the central portions of the discontinuous first arc-shaped incisions as viewed from the center point; This method of manufacturing a paper case for a disc is characterized in that, after forming these first and second discontinuous arc-shaped notches, a narrow area in the center of the paper base material is drawn to form a cylindrical retaining protrusion that can be fitted into and removed from the circular hole in the disc.

2. A method for manufacturing a paper disc case, which is made by forming a cylindrical holding protrusion in the center of a square, flat paper base material by drawing, the cylindrical holding protrusion being capable of fitting into a circular hole in the disc to be stored, A discontinuous first arc-shaped cut is formed around the outer periphery of the narrow circular area where the central portion of the paper base material is drawn to form the cylindrical holding protrusion, so that the cut does not intersect with the direction parallel to the grain of the paper base material and the direction perpendicular to the grain, as viewed from the center point of the narrow area. forming discontinuous second arc-shaped incisions around the outer periphery of the discontinuous first arc-shaped incisions such that, as viewed from the center point, they intersect with directions parallel to and perpendicular to the grain of the paper substrate, but do not intersect with each other in radial directions passing through the central portions of the discontinuous first arc-shaped incisions as viewed from the center point; A plurality of teardrop-shaped notches are formed at equal intervals along the circumferential edge, starting from the circumferential edge that will become the base of the cylinder after molding of the narrow circular area portion that molds the cylindrical holding protrusion, and ending from the circumferential edge that will become the flat surface of the cylinder after molding, with the tip side narrower in the direction toward the center point of the narrow area portion and the rear end slightly bulging, and A method for manufacturing a paper case for a disc, characterized in that after forming the first and second discontinuous arc-shaped notches and the teardrop-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 disc.

3. The method for manufacturing a disc paper case as described in claim 1, characterized in that 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 where the drawing process is performed is set to 15 mm or less and the height is 3 to 4 mm, the discontinuous first circular arc-shaped notch is formed at a position 6 mm away from the drawing position which is the outer periphery of the base of the cylindrical holding protrusion, and the discontinuous second circular arc-shaped notch is formed at a position 8 mm away from the drawing position which is the outer periphery of the base of the cylindrical holding protrusion.

4. The method for manufacturing a disc paper case described in claim 2, characterized in that 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 where the drawing process is performed in the center of the paper base material is set to 15 mm or less and the height is 3 to 4 mm, the discontinuous first circular arc-shaped notch is formed at a position 6 mm away from the drawing position on the outer periphery of the base of the cylindrical holding protrusion, the discontinuous second circular arc-shaped notch is formed at a position 8 mm away from the drawing position on the outer periphery of the base of the cylindrical holding protrusion, and the length of the waterdrop-shaped notch is formed to be 6.2 mm.

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