Master mold for manufacturing retro-reflective sheet mold and manufacturing method therefor

Abstract

Disclosed are a master mold for manufacturing a retro-reflective sheet mold and a manufacturing method therefor. The disclosed master mold used for manufacturing a mold for a retro-reflective sheet comprises: a lower layer; an upper layer provided on the lower layer; and a plurality of unit master molds provided on the upper layer. The plurality of unit master molds are continuously aligned without being spaced apart from each other in horizontal and vertical directions. Each unit master mold comprises: first and second surfaces in contact with each other to form a first angle; and third and fourth surfaces spaced apart from each other with the first and second surfaces interposed therebetween, wherein the third and fourth surfaces are surfaces inclined with respect to each other, and the first and second surfaces are in contact with the third and fourth surfaces.

Description

Master mold for manufacturing a recursive reflector mold and its manufacturing method

[0001] The present disclosure relates to the manufacture of a mold for manufacturing a light reflector or a light reflective band, and more specifically, to a master mold used to manufacture a mold for a retroreflective sheet capable of increasing the reflectivity for incident light, and a manufacturing method thereof.

[0002] A retroreflective sheet is a sheet that reflects incident light. A retroreflective sheet can also be expressed as a reflective band. Depending on the material of the retroreflective area, a retroreflective sheet can exhibit a variety of colors. Therefore, using a retroreflective sheet can enhance the identification and visibility of the object to which it is attached. These properties of a retroreflective sheet allow for diverse applications. For example, it can be used in transportation, such as automotive applications, transportation, safety, and security, and can also be applied to product design.

[0003] Retroreflective sheets, a type of light reflector, have a high light reflectance for vertically incident light that is perpendicular to the front of the retroreflector, but have a relatively low reflectance for obliquely incident light, which is light that is incident at an angle to the front of the retroreflector, making them impractical in some cases.

[0004] Accordingly, interest in retroreflective sheets with high reflectivity for incident light is growing. To manufacture retroreflective sheets with high reflectivity for incident light, a mold capable of producing such sheets is required.

[0005] One embodiment provides a master mold capable of increasing the manufacturing efficiency of a mold for manufacturing a retroreflective sheet having a relatively high reflectivity for incident light (hereinafter, a mold for a retroreflective sheet).

[0006] One embodiment provides a master mold that can improve the economic efficiency of a mold for a recursive reflector.

[0007] One embodiment provides a master mold that can reduce the manufacturing cost of a mold for a recursive reflector.

[0008] One embodiment provides a method for manufacturing such a master mold.

[0009] A master mold used in manufacturing a mold for a recursive reflector according to an exemplary embodiment includes a lower layer, an upper layer provided on the lower layer, and a plurality of unit master molds provided on the upper layer.

[0010] The above multiple unit master molds are arranged continuously without spacing in the horizontal and vertical directions,

[0011] Each unit master mold,

[0012] It includes first and second surfaces that are in contact with each other to form a first angle, and third and fourth surfaces that are spaced apart from each other with the first and second surfaces interposed therebetween, wherein the third and fourth surfaces are surfaces inclined with respect to each other, and the first and second surfaces are in contact with the third and fourth surfaces.

[0013] In one example, one of the third and fourth surfaces may be a vertical surface, and the other may form an acute angle with respect to the vertical surface.

[0014] In one example, the edge resulting from the contact between the first and second surfaces may be connected to the upper vertex of the third surface and the upper vertex of the fourth surface. One of the third and fourth surfaces may be a vertical surface, and the length of the edge may be equal to the height of the vertical surface.

[0015] In one example, the distance between the upper vertex of the vertical surface of the first unit master mold among the plurality of unit master molds and the upper vertex of a surface other than the vertical surface among the third and fourth surfaces of the second unit master mold adjacent to the first unit master mold may be equal to the length of the edge.

[0016] A method for manufacturing a master mold according to an exemplary embodiment includes a process of forming a first pattern symmetrically in a first direction on one surface of a substrate, and a process of asymmetrically removing a portion of the first pattern in a second direction perpendicular to the first direction, wherein the first pattern is a pattern that forms a second pattern having a triangular cross-section on the one surface of the substrate, and in the process of removing a portion of the first pattern, a portion of the second pattern is also removed, and a vertical plane and an inclined plane inclined thereto are formed by the removal of a portion of the second pattern.

[0017] In one example, after the process of forming a first pattern symmetrically in a first direction on one surface of the substrate is performed at least twice, a process of asymmetrically removing a portion of the first pattern can be performed.

[0018] In one example, the process of removing a portion of the first pattern may be performed at least twice.

[0019] In one example, a first carving machine may be used in the process of forming the first pattern, and the first pattern may be a V-shaped groove.

[0020] In one example, a second carving tool may be used in the process of asymmetrically removing a portion of the first pattern, and a tip of the second carving tool that contacts the substrate may include a vertical plane and an inclined plane forming an acute angle therewith.

[0021] The master mold for obtaining the mold for manufacturing the disclosed retroreflective sheet is formed by directly forming a mold pattern on one side of a flat substrate, and the method is also completed by simply moving two different carving machines in a mutually perpendicular direction to carve the pattern.

[0022] As such, the master mold manufacturing method illustrated herein forms a mold pattern on a plane by simply moving two carving machines in a direction perpendicular to each other, making pattern formation easy and the formed pattern simple. Therefore, transferring the mold pattern formed on the master mold to another mold substrate is easy, and the mold pattern can be transferred completely. Furthermore, since the mold pattern is simple and formed on a plane, the transferred mold pattern does not suffer damage even after repeated transfers, making it economical.

[0023] FIGS. 1 and 3 to 7 are perspective views showing, step by step, a method for manufacturing a master mold used in manufacturing a mold for manufacturing a retroreflective sheet having a high reflectivity for incident light, according to an exemplary embodiment.

[0024] FIG. 2 is a perspective view illustrating an example of a first carving machine used in a method for manufacturing a master mold according to one embodiment.

[0025] FIG. 8 is a perspective view illustrating an example of a second carving machine used in a method for manufacturing a master mold according to one embodiment.

[0026] Figure 9 is a perspective view of a unit master mold included in the master mold of Figure 7.

[0027] Figure 10 is a plan view of the master mold of Figure 7.

[0028] Figure 11 is a cross-sectional view taken along the 11-11' direction of Figure 10.

[0029] Figure 12 is a cross-sectional view taken along the 12-12' direction of Figure 10.

[0030] A master mold used in manufacturing a mold for a recursive reflector according to one embodiment includes a lower layer, an upper layer provided on the lower layer, and a plurality of unit master molds provided on the upper layer.

[0031] The above multiple unit master molds are arranged continuously without spacing in the horizontal and vertical directions,

[0032] Each unit master mold,

[0033] It includes first and second surfaces that are in contact with each other to form a first angle, and third and fourth surfaces that are spaced apart from each other with the first and second surfaces interposed therebetween, wherein the third and fourth surfaces are surfaces inclined with respect to each other, and the first and second surfaces are in contact with the third and fourth surfaces.

[0034] Hereinafter, a master mold for manufacturing a mold for manufacturing a retroreflective sheet capable of increasing the reflectivity of incident light and a manufacturing method thereof according to an exemplary embodiment will be described in detail with reference to the attached drawings. The sizes of each component or the thicknesses of layers or regions illustrated in each drawing may be exaggerated for clarity and convenience of explanation. In addition, the embodiments described below are merely exemplary, and various modifications are possible from these embodiments. In addition, in the layer structure described below, the expressions "upper" or "upper" may include not only a part directly above in direct contact, but also a part above another part in a non-contact manner.

[0035] FIGS. 1 to 8 are perspective views illustrating step-by-step a method for manufacturing a master mold used in manufacturing a mold for a retroreflective sheet capable of increasing reflectivity for incident light according to an exemplary embodiment, and perspective views illustrating components used in the manufacturing method.

[0036] To manufacture a master mold, first, as illustrated in FIG. 1, a mold substrate (40) is prepared. In one example, the mold substrate (40) may include a lower layer (40A) and an upper layer (40B) that are sequentially laminated. The lower layer (40A) may be referred to as a lower substrate. The upper layer (40B) may be referred to as an upper substrate. In one example, the lower layer (40A) may include a first metal layer, and the upper layer (40B) may include a material layer including a metal. In one example, the first metal layer may be or include a stainless steel layer. In one example, the upper layer (40B) may include a second metal layer or an alloy layer. In one example, the material of the second metal layer may be the same as or different from the material of the first metal layer. In one example, the second metal layer may include, but is not limited to, a copper (Cu) layer. In one example, the alloy layer may include, but is not limited to, nickel phosphorus (NiP).

[0037] In order to process the mold substrate (40) into a master mold, first, the first carving machine (100) is moved in a first direction (e.g., X-axis direction) on one surface of the upper layer (40B). In one example, the one surface of the upper layer (40B) may be a surface parallel to a plane (XY plane) formed by the X-axis and the Y-axis.

[0038] The first carving tool (100) can be moved from one end of the surface to the other end while in contact with one end of the upper layer (40B). In this movement, the state of contact between the first carving tool (100) and the upper layer (40B) can be set in consideration of the pattern formed on one end of the upper layer (40B). For example, if the pattern formed on one end of the upper layer (40B) is a first pattern (3G1) having a cross-section in the shape of an inverted triangle or a V as illustrated in FIG. 3, the degree of contact or contact condition between the tip (100b) of the first carving tool (100) and the upper layer (40B) can be set in consideration of the shape of the first pattern (3G1) to be formed on one end of the upper layer (40B). The shape of the first pattern (3G1) is determined by the shape of the tip (100b) of the first carving machine (100), but the size of the first pattern (3G1) can be determined by the degree of contact or contact conditions between the tip (100b) of the first carving machine (100) and the upper layer (40B).

[0039] After the first carving device (100) moves in a first direction on one side of the upper layer (40B) to form a pattern, the first carving device (100) is moved to its original position, the first carving device (100) is moved in a second direction (e.g., Y-axis direction) perpendicular to the first direction, and then moved again in the first direction to form a pattern on one side of the upper layer (40B). By repeating this process, a plurality of patterns parallel to the first direction, i.e., a plurality of V-shaped patterns (3G1), can be formed on the entire side of the upper layer (40B) as shown in FIG. 4.

[0040] Referring to FIG. 3 or FIG. 4, one V-shaped pattern (3G1) is formed in a straight line from one end of the upper layer (40B) to the other end in the first direction, and the width (3W1) of the upper end of the pattern (3G1) in the second direction may be constant or substantially constant over the entire length of the pattern (3G1).

[0041] “Substantially constant” may mean that the variation in width of the pattern (3G1) is within the allowable error range, or that the variation in width is within the range of variation in width that does not affect the operating characteristics of the result manufactured with the mold formed by the manufacturing method exemplified.

[0042] In one example, the width (3W1) of the top of the first pattern (3G1), that is, the maximum width of the first pattern (3G1), may be about 1 µm to 500 µm, but is not limited thereto. In one example, the width (3W1) of the top of the first pattern (3G1) may be about 100 µm, but is not limited thereto.

[0043] Since the first pattern (3G1) has a V-shaped groove in cross section, the width (3W1) of the first pattern (3G1) becomes narrower according to the depth of the first pattern (3G1). In other words, the width (3W1) of the first pattern (3G1) gradually becomes wider from the bottom to the top of the first pattern (3G1).

[0044] In one example, the depth (3D1) of the first pattern (3G1) may be approximately 50 μm to 150 μm, but is not limited thereto. In one example, the depth (3D1) of the first pattern (3G1) may be approximately 90 μm.

[0045] A plurality of first patterns (3G1) may be formed adjacent to each other, and two adjacent first patterns (3G1) may be formed to be in contact with each other. For example, two adjacent first patterns (3G1) may be formed such that their boundaries are in contact with each other.

[0046] Since the first pattern (3G1) is a groove with a V-shaped cross-section, when two adjacent first patterns (3G1) are formed, a second pattern (150) with a triangular cross-section is also naturally formed between the two first patterns (3G1). Consequently, when a plurality of first patterns (3G1) are formed on one surface of the upper layer (40B), a plurality of second patterns (150) with a triangular cross-section are also formed on one surface of the upper layer (40B). Accordingly, a plurality of second patterns (150) exist between a plurality of first patterns (3G1), and a plurality of first patterns (3G1) exist between a plurality of second patterns (150).

[0047] Since the second pattern (150) is a result of the formation of the V-shaped first pattern (3G1), the change in the width of the second pattern (150) is opposite to the change in the width (3W1) of the first pattern (3G1). That is, the width of the second pattern (150) is widest at the bottom of the second pattern (150) and becomes narrower as it goes upward. In addition, the width (maximum width) of the bottom of the second pattern (150) may be the same as the width (maximum width) of the top of the first pattern (3G1).

[0048] The second pattern (150) may include first and second inclined planes (3S1, 3S2). The first and second inclined planes (3S1, 3S2) may be planes parallel to the first direction (e.g., X-axis direction) and may be planes perpendicular to a plane formed by the Y-axis and the Z-axis (YZ plane).

[0049] The first and second inclined surfaces (3S1, 3S2) may be two inclined inner surfaces of the first pattern (3G1), which is a V-shaped groove. Consequently, the first and second inclined surfaces (3S1, 3S2) may be at the boundary of the first and second patterns (3G1, 150) and may be surfaces shared by the first and second patterns (3G1, 150).

[0050] In the first pattern (3G1), the two inclined inner surfaces (3S1, 3S2) are inclined at a first angle (θ1) with respect to each other. That is, the angle between the two inner surfaces (3S1, 3S2) is the first angle (θ1). This suggests that the angle between the first and second inclined surfaces (3S1, 3S2) in the second pattern (150) is also the first angle (θ1).

[0051] The areas of the first and second inclined surfaces (3S1, 3S2) may be equal or substantially equal to each other.

[0052] The first carving tool (100) may be expressed as a carving knife, a carving knife, a bite, or a cutting tool. The first carving tool (100) includes a body (100a) and a tip (100b) provided at the lower end of the body (100a). The body (100a) may be expressed as a handle. The tip (100b) may be expressed as a contact end, a contact portion, a blade, or the like. The body (100a) may be a part that is directly connected to a driving device (e.g., a machine tool) that moves the first carving tool (100). The tip (100b) is a part that is in direct contact with the upper layer (40B) and is a part that is directly used to form a pattern (3G1) on one surface of the substrate (40). The size of the cross-section of the pattern (3G1) formed on the substrate (40) may vary depending on the degree of initial contact between the tip (100b) and the upper layer (40B) (e.g., the degree of contact area).

[0053] Figure 2 shows a three-dimensional example of the first carving machine (100).

[0054] Referring to FIG. 2, the body (100a) of the first carving device (100) may have a square pillar shape, and the tip (100b) is attached (connected) to the bottom surface of the square pillar. The body (100a) may have a first width (Wx) in the X-axis direction and a second width (Wy) in the Y-axis direction. In one example, the first and second widths (Wx, Wy) may have a constant ratio. In one example, the first and second widths (Wx, Wy) may be the same as each other, but may also be different. The tip (100b) may cover the entire bottom surface of the body (100a). The width of the tip (100b) in the X-axis direction may be constant, and may have the same width as the body (100a). The width of the tip (100b) in the Y-axis direction or in the direction parallel to the Y-axis is not constant, and may become narrower toward the bottom of the tip (100b). The change in the width of the tip (100b) in the Y-axis direction may become constant toward the bottom of the tip (100b). Accordingly, the tip (100b) may include two sides of a triangle spaced apart by a distance corresponding to a first width (Wx) in the X-axis direction, a first inclined plane (2S1) of a rectangle connecting corresponding first hypotenuses of the two triangles between the two triangles, and a second inclined plane (2S2) of a rectangle connecting corresponding second hypotenuses of the two triangles between the two triangles. At the bottom of the tip (100b), the corresponding sides of the first and second inclined planes (2S1, 2S2) are in contact with each other.

[0055] Soon, at the bottom of the tip (100b), the first and second inclined planes (2S1, 2S2) are in contact with each other and share one side with each other. This side is parallel to the X-axis and has a length corresponding to the first width (Wx). In addition, the vertices of the two sides of the triangle are connected to each other by the side shared by the first and second inclined planes (2S1, 2S2). Consequently, the first and second inclined planes (2S1, 2S2) are located between the two sides of the triangle and have a form that is spread (splayed out) from the bottom to the top of the tip (100b). In one example, the first inclined plane (2S1) and the second inclined plane (2S2) may be spread out at a first angle (θ1). The first angle (θ1) may also be expressed as an angle between the first and second inclined planes (2S1, 2S2). The first angle (θ1) is an acute angle and may be 90° or less. In one example, the first angle (θ1) may be greater than or equal to 45° and less than or equal to 90°.

[0056] Since the first and second patterns (3G1, 150) are formed on one surface of the upper layer (40B) by the first carving machine (100), the angle between the two inclined inner surfaces of the V-shaped first pattern (3G1) is determined by the first angle (θ1), and the angle between the first and second inclined surfaces (3S1, 3S2) of the second pattern (150) can also be determined.

[0057] The body (100a) may have a first length (h1) in a direction perpendicular to one surface of the upper layer (40B), that is, a direction perpendicular to the XY plane (e.g., the Z-axis direction), and the tip (100b) may have a second length (h2). The first and second lengths (h1, h2) may be the same as or different from each other. In one example, the second length (h2) may be shorter than the first length (h1). In one example, the second length (h2) may be determined in consideration of the size (depth, maximum width, etc.) of the pattern (3G1) to be formed on one surface of the upper layer (40B). In addition, since the angle (θ1) between the first and second inclined planes (2S1, 2S2) may vary depending on the second length (h2), the second length (h2) may be determined by considering the angle (θ1) between the first and second inclined planes (2S1, 2S2). In addition, when the second length (h2) is constant, the angle (θ1) between the first and second inclined planes (2S1, 2S2) varies depending on the width in the Y-axis direction of the upper end of the tip (100b) (the separation distance between the upper sides of the first and second inclined planes (2S1, 2S2)), so in a structure in which the second length (h2) is constant, the width in the Y-axis direction of the upper end of the tip (100b) may be determined by considering the angle between the first and second inclined planes (2S1, 2S2).

[0058] The second length (h2) can be determined by considering the depth (3D1) of the pattern (3G1), and in one example, the second length (h2) can be about 50 micrometers (㎛) to 150 ㎛, for example, about 90 ㎛. In one example, the width of the upper end of the tip (100b) that directly contacts the bottom surface of the body (100a) can be determined by considering the maximum width (3W1) of the pattern (3G1), and can be about 1 ㎛ to 500 ㎛, but is not limited thereto. In one example, the width of the upper end of the tip (100b) can be about 100 ㎛.

[0059] The tip (100b) may comprise a material harder than the material of the upper layer (40B). In one example, the tip (100b) may be a material containing carbon, such as a diamond tip, but is not limited thereto. In one example, the body (100a) may be made of a metal material or a material other than metal.

[0060] After forming the first and second patterns (3G1, 150), in order to form a third pattern on one surface of the upper layer (40B) on which the first and second patterns (3G1, 150) are formed, as illustrated in Fig. 5, a second carving device (200) having a different structure from the first carving device (100) is moved in a direction perpendicular to the length of the first and second patterns (3G1, 150) (a direction perpendicular to the X-axis or a direction parallel to the Y-axis). The second carving device (200) can be moved from one end of the upper layer (40B) in the perpendicular direction across the first and second patterns (3G1, 150) to the other end of the upper layer (40B). The second carving device (200) can start at a height at which the first and second patterns (3G1, 150) can be cut and maintain the height until reaching the other end of the upper layer (40B). The second carving device (200) can be moved in the vertical direction at a height at which the first and second patterns (3G1, 150) can be cut to a depth corresponding to the depth (3D1) of the first pattern (3G1).

[0061] By moving the second carving device (200) in this manner, as illustrated in FIG. 6, a third pattern (7G1) is formed on one surface of the upper layer (40B) by removing parts of the first and second patterns (3G1, 150). After the third pattern (7G1) is formed, the second carving device (200) is moved to the original position, and then the second carving device (200) is moved to the second position in the first direction (X-axis direction) according to the set movement value. In one example, after forming the third pattern (7G1), the second carving device (200) may be moved directly to the second position without being moved to the original position.

[0062] The second carving device (200) moved to the second position can be moved in a direction perpendicular to the length of the first and second patterns (3G1, 150) under the same movement conditions as when forming one third pattern (7G1) to form another third pattern (7G1). In one example, the second position can be a position where the third pattern (7G1) formed immediately before and the third pattern (7G1) to be formed by the second carving device (200) starting from the second position can be spaced apart from each other in a direction parallel to the first and second patterns (3G1, 150) (e.g., X-axis direction).

[0063] By repeating this process, a plurality of third patterns (7G1) are formed on one entire surface of the upper layer (40B), as shown in FIG. 7, and as a result, a master mold (700) is formed to obtain a mold for manufacturing a retroreflective sheet capable of increasing the reflectivity for incident light.

[0064] In the master mold (700), a plurality of third patterns (7G1) are formed to be spaced apart from each other in the X-axis direction. The spacing (interval) between the plurality of third patterns (7G1) in the X-axis direction may be constant or substantially constant, but may not be so.

[0065] The third pattern (7G1) may be formed on each of the plurality of second patterns (150). The third pattern (7G1) is a portion of the second pattern (150) where a portion thereof is removed, and may be viewed as a groove formed in the second pattern (150). The third pattern (7G1) includes a third surface (7S1) inclined with respect to the XY plane and the YZ plane, and a fourth surface (7S2) that is parallel to the YZ plane, perpendicular to the X-axis, and perpendicular to the XZ plane. Therefore, the fourth surface (7S2) may be a vertical surface perpendicular to one surface of the upper layer (40B). The third and fourth surfaces (7S1, 7S2) may share a base with each other. The third surface (7S1) may be a surface inclined at a second angle (θ2) with respect to the fourth surface (7S2). In other words, the angle between the third and fourth surfaces (7S1, 7S2) may be the second angle (θ2). The second angle (θ2) may be determined by the structure of the tip (200b) used to directly contact the first and second patterns (3G1, 150) in the second carving tool (200) and remove portions of the first and second patterns (3G1, 150). In other words, the tip (200b) of the second carving tool (200) may be designed considering the shape of the third pattern (7G1). The second angle (θ2) may be an acute angle. For example, the second angle (θ2) may be 30° or more and less than 90°.

[0066] Each second pattern (150) has a plurality of third patterns (7G1), and the third patterns (7G1) are spaced apart from each other by a first distance (DS1). The first distance (DS1) corresponds to the distance between the third face (7S1) of a selected third pattern (7G1) and the fourth face (7S2) of a third pattern (7G1) adjacent to the selected third pattern (7G1). In one example, the first distance (DS1) may be equal to or substantially equal to the depth (3D1) of the first pattern (3G1), but is not limited thereto. In one example, the second distance (DS2) between the upper vertex of the third face (7S1) of one third pattern (7G1) and the vertex of the corresponding fourth face (7S2) may be equal to or substantially equal to the first distance (DS1), but is not limited thereto.

[0067] Since the third and fourth faces (7S1, 7S2) in a third pattern (7G1) are faces formed by cutting the second pattern (150) whose cross-section is triangular in a direction perpendicular to its length, the geometric shapes of the third and fourth faces (7S1, 7S2) may also be triangular. However, the size (or area) of the third face (7S1) may be different from the size (or area) of the fourth face (7S2).

[0068] The depth of the third pattern (7G1) may be the same as or substantially the same as the depth of the first pattern (3G1) or the height of the second pattern (150). The depth of the third pattern (7G1) may refer to the height of the fourth side (7S2) of the third pattern (7G1).

[0069] The second carving tool (200) may include a body (200a) and a tip (200b). The body (200a) may be a portion that is fastened to or directly connected to a driving device (e.g., a machine tool) of the second carving tool (200). The tip (200b) may be a portion that directly contacts the upper layer (40B) and may be a tip made of a material having a higher hardness than the upper layer (40B). For example, the material of the tip (200b) may be the same as that of the tip (100b) of the first carving tool (100), but may also be different. For example, the tip (100b) of the first carving tool (100) may include a carbon crystal tip (e.g., a diamond tip) having a first hardness, and the tip (200b) of the second carving tool (200) may include a tip of carbon crystal or another material having a second hardness different from the first hardness. The above first and second hardnesses may be greater than the hardness of the upper layer (40B).

[0070] Figure 8 shows an example of a second carving machine (200).

[0071] Referring to Fig. 8, the body (200a) of the second carving device (200) may have a square pillar shape, but is not limited thereto. The tip (200b) of the second carving device (200) is attached (connected) to the bottom surface of the body (200a). The body (200a) may have a third width (8Wx) in the X-axis direction and a fourth width (8Wy) in the Y-axis direction. In one example, the third and fourth widths (8Wx, 8Wy) may have a constant ratio. In one example, the third and fourth widths (8Wx, 8Wy) may be the same as each other, but may also be different from each other. The widths (8Wx, 8Wy) of the body (200a) in each direction may be constant from the top to the bottom of the body (200a).

[0072] The upper surface of the tip (200b) may cover the entire lower surface of the body (200a), but the opposite may also be true and may not be limited thereto. For example, the area of ​​the upper surface of the tip (200b) may be equal to or different from the area of ​​the lower surface of the body (200a). In one example, the area of ​​the upper surface of the tip (200b) may be smaller or larger than the area of ​​the lower surface of the body (200a).

[0073] The width in the X-axis direction and the width in the Y-axis direction of the tip (200b) can both vary in the longitudinal direction of the tip (200b). For example, the width in the X-axis direction of the tip (200b) can become narrower from the top to the bottom of the tip (200b), and the width in the Y-axis direction of the tip (200b) can also become narrower from the top to the bottom of the tip (200b). Accordingly, the tip (200b) has an overall shape that is pointed downwards, but the bottom (20T) of the tip (200b) does not have a pointed point but includes a straight edge (20E) like a blade. The edge (20E) is a portion where the first and second surfaces (5S1, 5S2) of the tip (200b) meet. The first and second surfaces (5S1, 5S2) are inclined relative to each other, and their widths gradually narrow toward the lower end (20T) of the tip (200b). The widths of the first and second surfaces (5S1, 5S2) are narrowest at the lower end (20T) of the tip (200b). The edge (20E) can be viewed as being formed where the narrowest portions of the first and second surfaces (5S1, 5S2) meet. Therefore, the edge (20E) can be a sharp part like a blade of a knife. The second surface (5S2) of the tip (200b) can be a surface parallel to the YZ plane, a surface perpendicular to the X axis, and a surface perpendicular to the XZ plane. The first and second surfaces (5S1, 5S2) of the tip (200b) are spread out (spread out) from the edge (20E) to the top of the tip (200b), and thus the first and second surfaces (5S1, 5S2) are inclined with respect to each other. The first surface (5S1) and the second surface (5S2) are spread out at a third angle (θ3). That is, the angle between the first surface (5S1) and the second surface (5S2) is a third angle (θ3). In other words, with the second surface (5S2) as a reference, the first surface (5S1) is inclined at a third angle (θ3) with respect to the second surface (5S2) and is also inclined at the same angle with respect to the YZ plane. In one example, the third angle (θ3) may be an acute angle, for example, 30° or more and less than 90°, but is not limited thereto.The angle (θ2) between the third surface (7S1) and the fourth surface (7S2) of the third pattern (7G1) can be determined by the third angle (θ3). Therefore, the third angle (θ3), which is the angle between the first and second surfaces (5S1, 5S2) of the tip (200b), can be equal to the second angle (θ2), which is the angle between the third and fourth surfaces (7S1, 7S2) of the third pattern (7G1).

[0074] The tip (200b) includes third and fourth faces (8S1, 8S2) that are spaced apart from each other between the first face (5S1) and the second face (5S2) and are inclined to each other. The third face (8S1) is a face that is forward in the direction of travel of the second carving machine (200) (- direction of the Y-axis) and has a geometric shape of a triangle. One side of the third face (8S1) forms one side of the upper surface of the tip (200b), and a vertex of the third face (8S1) that is apart from this side is connected to the edge (20E). The third face (8S1) may be a face that is perpendicular to the first and second faces (5S1, 5S2) and may be a face that is inclined with respect to the XZ plane.

[0075] The fourth surface (8S2) may be a surface located at the rear in the direction of travel of the second carving machine (200), and may be provided to be symmetrical with the third surface (8S1). The geometric shape of the fourth surface (8S2) may be a triangle. One side of the fourth surface (8S2) forms the other side of the upper surface of the tip (200b), and a vertex of the fourth surface (8S2) spaced apart from this side is connected to the corner (20E). The fourth surface (8S2) may be a surface perpendicular to the first and second surfaces (5S1, 5S2), and may be a surface inclined with respect to the XZ plane. The inclination angles of the third and fourth surfaces (8S1, 8S2) with respect to the XZ plane may be different from each other.

[0076] The body (200a) may have a first length (8h1) in a direction perpendicular to one surface of the upper layer (40B), that is, a direction perpendicular to the XY plane (e.g., the Z-axis direction), and the tip (200b) may have a second length (8h2). The first and second lengths (8h1, 8h2) may be the same or different. In one example, the second length (8h2) may be shorter than the first length (8h1). In one example, the second length (8h2) may be the same as or substantially the same as the second length (h2) of the tip (100b) of the first carving tool (100).

[0077] The master mold (700) illustrated in Fig. 7 includes a plurality of unit master molds (70U) formed on one surface (e.g., XY surface) of the upper layer (40B). The plurality of unit master molds (70U) can be aligned to have a constant period or pitch in the horizontal (e.g., Y-axis) and vertical (e.g., X-axis) directions.

[0078] Fig. 9 is a three-dimensional view of a unit master mold (70U). The fourth side (7S2) on the left in Fig. 9 is illustrated for convenience of explanation and may not be included in the unit master mold (70U).

[0079] Referring to Fig. 9, the unit master mold (70U) includes four faces (7S1, 7S2, 3S1, 3S2). Two of these faces (3S1, 3S2) are faces formed in the process of forming the first pattern (3G1) using the first carving machine (100), and are two inclined faces of the second pattern (150) having a triangular cross-section, and the remaining two faces (7S1, 7S2) are faces formed in the process of forming the third pattern (7G1) using the second carving machine (200), and are a fourth face (7S2) that is a vertical face and a third face (7S1) that is inclined at an acute angle thereto. The fourth face (7S2) is a face that is perpendicular to one face (e.g., XY plane) of the upper layer (40B). The fourth face (7S2) is perpendicular to the X-axis and parallel to the YZ plane. The direction of the fourth surface (7S2), that is, the direction perpendicular to the fourth surface (7S2), may be parallel to the X-axis. Since the fourth surface (7S2) is a surface formed as a result of the second pattern (150) being cut by the second cutter (200) in a direction perpendicular to the length of the second pattern (150), the geometric shape of the fourth surface (7S2) becomes a triangle.

[0080] In the unit master mold (70U), the third surface (7S1) is spaced apart from the fourth surface (7S2) by a first distance (DS1), but can be connected to the fourth surface (7S2) of another adjacent unit master mold through the bottom surface. In other words, two adjacent unit master molds (70U) can be formed in a structure in which the fourth surface (7S2) and the third surface (7S1) share a bottom. The second distance (DS2) between the upper vertex of the third surface (7S1) of one unit master mold (70U) and the upper vertex of the fourth surface (7S2 on the left) of the adjacent unit master mold can be equal to or different from the first distance (DS1). In one example, the height (9H1) of the fourth surface (7S2) of the unit master mold (70U) can be equal to or different from the first distance (DS1) or the second distance (DS2). The relationship between these dimensions (DS1, DS2, 9H1) can be set in a direction that increases the oblique light reflectance of the retroreflective sheet.

[0081] Since the third side (7S1) and the fourth side (7S2) are formed simultaneously by the second carving machine (200) as described above, the geometric shape of the third side (7S1) may also be a triangle like the fourth side (7S2). However, since the third side (7S1) is an inclined plane with respect to the fourth side (7S2), the geometric shapes of the third and fourth sides (7S1, 7S2) are both triangles, but the shapes and areas of the triangles may be different. For example, the area of ​​the third side (7S1) may be larger than that of the fourth side (7S2). In the unit master mold (70U), the first and second sides (3S1, 3S2) are located between the third and fourth sides (7S1, 7S2). The first and second sides (7S1, 7S2) may be perpendicular to the fourth side (7S2). The upper edges of the first and second faces (7S1, 7S2) are in contact with each other to form a corner. This corner is between the upper vertices of the third and fourth faces (7S1, 7S2) and is connected to the upper vertices. The lower edges of the first and second faces (7S1, 7S2) are spaced apart from each other and are connected to this side and that side of the bottom of the third and fourth faces (7S1, 7S2). The first and second faces (7S1, 7S2) are formed in a shape that is splayed downward. In one example, the first and second faces (7S1, 7S2) may be arranged to be inclined to each other at a first angle (θ1). Since the unit master mold (70U) corresponds to a unit mold of the retroreflective sheet mold, the first angle (θ1) may be set in a direction in which the reflectivity of the retroreflective sheet for incident light can be increased.

[0082] Figure 10 is a plan view of Figure 7.

[0083] Referring to Fig. 10, a plurality of unit master molds (70U) are aligned in the horizontal and vertical directions in a master mold (700). Unit master molds (70U) adjacent in the horizontal and vertical directions are attached to each other and do not overlap each other.

[0084] Figure 11 shows a cross-section of Figure 10 taken along the 11-11' direction.

[0085] Referring to Fig. 11, it can be seen that the unit master molds (70U) are repeated in the X-axis direction. The unit master molds (70U) are arranged continuously without gaps, and adjacent unit master molds (70U) do not overlap.

[0086] Figure 12 shows a cross-section of Figure 10 taken in the 12-12' direction.

[0087] Referring to Fig. 12, the second pattern (150) is repeated continuously without gaps in the Y-axis direction.

[0088] In FIGS. 1 to 12, six second patterns (150) are shown to be formed on the upper layer (40B), and 20 or fewer unit master molds (70U) are shown to be formed. However, this is only for convenience of illustration and explanation, and is not intended to limit the number of second patterns (150) and the number of unit master molds (70U). More than six second patterns (150) may be formed on the upper layer (40B), and more than 20 unit master molds (70U) may be formed.

[0089] While the above description contains many specific details, they should be construed as illustrative examples of preferred embodiments rather than limiting the scope of the invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but rather by the technical concepts set forth in the claims.

[0090] A master mold for obtaining a mold for manufacturing a recursive reflector according to one embodiment of the present invention forms a mold pattern directly on one side of a flat substrate, and the method is also completed by simply moving two different carving machines in a mutually perpendicular direction to carve the pattern.

[0091] As such, the exemplified master mold manufacturing method forms a mold pattern on a plane by simply moving two carving machines in a direction perpendicular to each other, making pattern formation easy and the formed pattern simple. Therefore, the mold pattern formed on the master mold is easily transferred to another mold substrate, and the transfer of the mold pattern can also be accomplished completely. In addition, since the mold pattern is simple and formed on a plane, damage to the transferred mold pattern does not appear even after repeated transfer, making it economical for producing a mold for manufacturing a retroreflective sheet.

Claims

1. Lower layer; an upper layer provided on the lower layer; and including a plurality of unit master molds provided on the upper layer; The above multiple unit master molds are arranged continuously without spacing in the horizontal and vertical directions, Each unit master mold, First and second surfaces contacting each other to form a first angle; and including third and fourth surfaces spaced apart from each other with the first and second surfaces interposed therebetween; The third and fourth surfaces are inclined relative to each other, The first and second surfaces are a master mold in contact with the third and fourth surfaces.

2. In paragraph 1, A master mold wherein one of the third and fourth surfaces is a vertical surface and the other forms an acute angle with respect to the vertical surface.

3. In paragraph 1, A master mold in which the corners appearing from the contact of the first and second surfaces are connected to the upper vertex of the third surface and the upper vertex of the fourth surface.

4. In paragraph 3, A master mold wherein one of the third and fourth surfaces is a vertical surface, and the length of the edge is equal to the height of the vertical surface.

5. In paragraph 3, A master mold in which the distance between the upper vertex of the vertical surface of the first unit master mold among the plurality of unit master molds and the upper vertex of the non-vertical surface among the first and second surfaces of the second unit master mold adjacent to the first unit master mold is equal to the length of the edge.

6. A step of forming a first pattern symmetrical in a first direction on one side of the substrate; and A step of asymmetrically removing a portion of the first pattern in a second direction perpendicular to the first direction; The above first pattern is a pattern that causes a second pattern having a triangular cross-section to be formed on the one surface of the substrate, In the step of removing a part of the first pattern, a part of the second pattern is also removed. A method for manufacturing a master mold in which a vertical surface and an inclined surface thereof are formed by removing a portion of the above second pattern.

7. In paragraph 6, A method for manufacturing a master mold, comprising: performing a step of forming a first pattern symmetrically in a first direction on one side of a substrate at least twice; and then performing a step of asymmetrically removing a portion of the first pattern.

8. In paragraph 6 or paragraph 7, A method for manufacturing a master mold, wherein the step of removing a portion of the first pattern is performed at least twice.

9. In paragraph 6, A method for manufacturing a master mold, wherein a first carving machine is used in the step of forming the first pattern, and the first pattern is a V-shaped groove.

10. In paragraph 6, A method for manufacturing a master mold, wherein a second carving machine is used in the step of asymmetrically removing a portion of the first pattern, and a tip of the second carving machine that contacts the substrate includes a vertical plane and an inclined plane forming an acute angle therewith.

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