KR-20260065733-A - High hardness micro prism mold for retroreflective film formation and its manufacturing method

Abstract

The present invention improves hardness characteristics by using an alloy of Ni-Co, Ni-W, Ni-Cr, Ni-Fe, Ni-Mo, Ni-P, or Ni-Cu as the material for a microprism mold.

Inventors

• 문성재
• 임태홍
• 추현수
• 김알맹
• 이승현

Assignees

• 주식회사 에스피이노베이션

Dates

Publication Date

20260511

Application Date

20251103

Claims (4)

1. A method for manufacturing a microprism mold for forming a retroreflective film made of any one of an alloy of Ni-Co, Ni-W, Ni-Mo, Ni-P, and Ni-Cu, wherein The above manufacturing method is an electric casting technology, and During the plating process, It makes the equipotential plane of the electric field formed between the anode and cathode installed in the plating bath constant as a horizontal plane, and A method for manufacturing a micro prism mold for forming a retroreflective film, characterized by stirring with a stirrer to maintain the uniformity of the solution, controlling the flow rate of the solution at a predetermined speed, sensing the real-time solution concentration to maintain a constant concentration of the solution, and adding the necessary chemicals to ensure that the plating is done with a uniform thickness.
2. A method for manufacturing a micro prism mold for forming a retroreflective film according to claim 1, characterized in that, in order to make the equipotential plane of the electric field formed between the positive and negative electrodes constant as a horizontal plane, a positive shielding plate is placed near the positive electrode and spaced apart from the positive electrode.
3. A method for manufacturing a micro prism mold for forming a retroreflective film according to claim 1, wherein the plating process is designed with a step coverage consisting of multiple steps for the final target thickness, and the applied current, stirrer speed, chemical supply amount, the positions of the anode and cathode, and the position of the anode shielding plate are organically controlled for each step coverage stage to uniformly form the thickness of the plating film over a large area.
4. A method for manufacturing a micro prism mold for retroreflective film molding, characterized in that, in claim 1, the flow rate of the solution supplied into the plating bath is controlled to 1 to 100 Liter/min (LPM).

Description

High hardness micro prism mold for retroreflective film formation and its manufacturing method The present invention relates to a high-hardness microprism mold and a method for manufacturing the same, and more specifically, to a manufacturing technology for a microprism mold required for forming a retroreflective film. Retroreflective film is a film (sheet) formed with microprisms and is used in road signs, vehicle license plates, industrial safety equipment, etc. Retroreflective film is manufactured through a continuous process using roll molds or belt molds based on the production of electric die molds. That is, retroreflective film is manufactured by extruding a film using a mold formed with microprisms (hereinafter referred to as a microprism mold). In the film extrusion process, a decrease in the thickness uniformity of the microprism mold leads to a deterioration in the quality of the retroreflective film. Specifically, when manufacturing large-area microprism molds, overall thickness uniformity is not achieved, and the thickness at both ends is made thicker than the center; consequently, when mounted on a roll, the mold takes on a shape where the ends bulge and the center is sunken. The film produced under these conditions has the problem of exhibiting a bulging shape in the center. Additionally, cracks form at the connection points of the mold, rendering the corresponding parts of the film unusable (see Fig. 1). Total or partial product defects (using only a portion of the film and discarding the rest) lower productivity. Meanwhile, the material used for these microprism molds is known to be Ni. Microprism molds made of Ni require replacement due to deformation of the original microprism shape after prolonged use. Replacing the mold implies the shutdown and restart of the production line, which also reduces productivity. Registered Patent No. 10-0495977 discloses a method for making a mold belt for manufacturing optical films by electroforming technology. In the above publication as well, the mold belt is formed of Ni. Figure 1 shows the problem of thickness non-uniformity and cracks occurring at the connection points of a micro-prism mold according to the prior art. Figure 2 shows a cross-sectional view of a microprism mold and an image of a retroreflective film according to the present invention. Figure 3 is a table showing the physical properties of Ni and Ni alloys. Figure 4 shows a defective image of a retroreflective film manufactured by a conventional microprism mold and an image of a product according to the present invention that improves upon it. Figure 5 shows the manufacturing equipment and product of the microprism mold of the present invention. Figure 6 shows graphs illustrating the reflective performance of a retroreflective film manufactured by the microprism mold of the present invention compared to the prior art. Figure 7 is a table showing the thickness variation of the entire large area compared with the prior art (left) when the thickness of the micro prism mold of the present invention is manufactured to be 343 µm. Figure 8 shows the three-dimensional shape of the microprism mold of the present invention as a contour graph compared with the prior art (left). Figure 9 shows that the composition ratio of the electroplating solution has been improved to be kept constant for thickness uniformity of a large-area microprism mold. Figure 10 is a table showing the physical properties of the alloy mold of the present invention compared to a conventional Ni mold. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. As shown in Fig. 1, the microprism mold manufactured according to the prior art has a non-uniform thickness, so when mounted on a roll and rolled to form a retroreflective film, defective products are produced. This is because the diameter of the cylindrical microprism mold is about 1000φ, and it is difficult to make it have a uniform thickness over the entire area, which is a large area of about 3140 mm in width and 1500 mm in length when the mold is unfolded. Since electroforming technology is mostly applied to small items, manufacturing large-area items is inherently difficult. Furthermore, micro-prism molds require thick films reaching 300 µm (with a margin of error of ±5%), making it very challenging to uniformly manufacture large-area thick films. If a mold with poor thickness uniformity is welded to form a cylindrical shape, cracks are generated at the welded area due to stress. Retroreflective films manufactured using such molds become defective products that fail to reflect light along the desired path. Therefore, there is a need to provide electroforming technology capable of manufacturing large-area thick films with uniform thickness. FIG. 2 shows a cross-sectional view of a microprism mold and a product image according to the present invention. By manufacturing the thickness of the micropri