Composite microprism reflective film integrated with various triangular pyramids and mold manufacturing method thereof

Abstract

The invention relates to a composite microprism reflective film integrated with various triangular pyramids and a mold manufacturing method thereof, the surface of the microprism reflective film is formed by an array of identical parallelogram unit bodies, and each parallelogram unit body is composed of three identical triangular pyramids A, three identical triangular pyramids B, a triangular pyramid C and a triangular pyramid D, the bottom surfaces of the triangular pyramid A, the triangular pyramid B, the triangular pyramid C and the triangular pyramid D are identical equilateral triangles, the inclination angles of the three pyramid surfaces of the triangular pyramid A are alpha / 2 and alpha / 2 and beta / 2 + respectively, the inclination angles of the three pyramid surfaces of the triangular pyramid B are alpha / 2 and alpha / 2 and beta / 2-respectively, the inclination angles of the three pyramid surfaces of the triangular pyramid C are beta / 2 + respectively, and the inclination angles of the three pyramid surfaces of the triangular pyramid D are beta / 2-respectively. Greater than zero. According to the method, the performance under different application conditions can be reasonably optimized, so that wide-angle performance improvement and optimization and balance of overall comprehensive performance can be realized.

Description

Technical Field

[0001] The present invention relates to a manufacturing method of a composite microprism retroreflective film integrating multiple triangular pyramids and a mold thereof. Background Art

[0002] Design of a microprism retroreflective film based on a triangular pyramid unit structure: A tool is used to machine three pyramid surfaces of the triangular pyramid, and the inclination angles (angles with the vertical plane) of the three pyramid reflecting surfaces are the same, as Figure 1 shown. Such a design of the microprism retroreflective film is mainly used for Class III and Class IV retroreflective films with relatively low performance requirements. When used for Class V retroreflective films, under the conditions of large viewing angles and large incident angles, the retroreflective coefficient cannot meet the standard requirements. In order to meet the performance requirements of Class V retroreflective films, different design or manufacturing solutions have been proposed at home and abroad. The 3M Company in the United States has proposed an optical design of a retroreflective film using a full prism structure. However, this design has a complex structure, high requirements for the manufacturing accuracy of the mold, and a large impact of manufacturing errors on the performance of the retroreflective film, which limits its popularization and application in China.

[0003] Specifically, there is only one optical design variable for the microprism retroreflective film in the above Figure 1 , and it is difficult to simultaneously improve the retroreflective performance at different incident angles and viewing angles (especially wide angles), that is, different azimuth angles, and to balance the retroreflective performance between different incident angles and viewing angles (especially wide angles and small incident angles), and the balance of retroreflective performance between different azimuth angles (such as 0 degrees, 90 degrees, 180 degrees).

[0004] In the prior art, in order to obtain the anisotropic uniformity of the retroreflective performance of the retroreflective film at different azimuth angles, nickel molds for four types of retroreflective films are usually manufactured by mechanically splicing two nickel molds of the retroreflective film with different orientations of 0 degrees and 90 degrees to make a roller master mold; by slightly adjusting an angle to deviate from the standard pyramid reflector structure, the regulation of the retroreflective performance of the retroreflective film is realized (such as improving the wide-angle performance), but the above method is very cumbersome to manufacture and there is a mechanical seam error, making it difficult to achieve the expected effect.

[0005] Although the microprism retroreflective film using a full prism (3M in the United States) has a 50% higher retroreflective performance than the microprism retroreflective film using a triangular pyramid (or the effective reflection area of the triangular pyramid retroreflective film is 66.67% of the effective reflection area of the full prism retroreflective film), the mold structure of the full prism retroreflective film (such as Chinese Patent Nos. 2015107772604 and 201811202555.9) is very complex, the manufacturing difficulty is very high, and due to the manufacturing error of the mold, the reflective performance is much lower than expected, thus limiting its popularization and application.

[0006] In view of the above deficiencies, the applicant applied for "Retroreflective Microprism Array Structure and Its Manufacturing Method" (Publication No. CN 117930406 A) in March 2024 and "Manufacturing Method of Microprism Reflective Film with Double Triangular Pyramid Composite Structure and Its Mold" (Publication No. CN118759624B) in September 2024 respectively.

[0007] Among them, although the "Retroreflective Microprism Array Structure and Its Manufacturing Method" is more convenient for manufacturing compared with Patents 2015107772604 and 201811202555.9, it avoids the difficulty of secondary clamping and machining of special-shaped surfaces, and ensures the quality of the finished product. However, when making through holes on the second substrate in the processing procedure, it is necessary to drill holes one by one first, and then process them by wire cutting. The processing procedure is still relatively cumbersome. Moreover, each pyramid formed by its processing is a regular triangular pyramid, and the inclination angles of the pyramid surfaces are all the same. There is only one optical design variable for the microprism reflective film obtained, and it is difficult to obtain different incident angles and observation angles. That is, such a microprism reflective film design can meet the performance requirements of Class Ⅳ reflective films. When used for Class Ⅴ reflective films, under the conditions of large observation angles and large incident angles, the retroreflective coefficient cannot meet the standard requirements. Among them, the "Manufacturing Method of Microprism Reflective Film with Double Triangular Pyramid Composite Structure and Its Mold" proposes to use two types of tools with tool design angles of α and β to process a microprism reflective film with a double triangular pyramid composite structure on the same mold substrate. After using the first type of tool with a tool angle of α to process the large triangular pyramid, then use the second type of tool with a tool angle of β to process. According to the design requirements, adjust the tool orientation so that the inclination angles of the three pyramid surfaces of the central triangular pyramid are all β / 2. At this time, the inclination angles of the two pyramid surfaces of the corner triangular pyramid are α / 2, and the inclination angle of the third pyramid surface in the middle is β / 2. Although the wide-angle performance of the reflective film can be optimized to a certain extent by adjusting the angle variable of the triangular pyramid located in the center, or a certain degree of optimization of the 0-degree and 90-degree performance of the reflective film can be obtained, the microprism reflective film obtained still has the disadvantage of insufficient freedom of optical design optimization. Summary of the Invention

[0008] In view of the above problems, the purpose of the present invention is to propose a manufacturing method of a composite microprism reflective film integrating multiple triangular pyramids and its mold. The manufacturing method of the composite microprism reflective film integrating multiple triangular pyramids and its mold is reasonably designed, can further increase the freedom of optical design, is conducive to optimization design, and obtains better performance indicators under different application conditions.

[0009] The technical solution of the present invention is as follows: A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: the surface of the microprism retroreflective film is formed by an array of identical parallelogram unit bodies, and each parallelogram unit body is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C and one triangular pyramid D. The bottom surfaces of the triangular pyramids A, B, C and D are all the same equilateral triangle. The bottom area ratios of the triangular pyramids A, B, C and D are 37.5%, 37.5%, 12.5% and 12.5% respectively; the three pyramid face inclination angles of the triangular pyramid A are respectively α / 2, α / 2 and β / 2 + △, the three pyramid face inclination angles of the triangular pyramid B are respectively α / 2, α / 2 and β / 2 - △, the three pyramid face inclination angles of the triangular pyramid C are all β / 2 + △, and the three pyramid face inclination angles of the triangular pyramid D are all β / 2 - △, and △ is greater than zero.

[0010] A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: the surface of the microprism retroreflective film is formed by an array of identical parallelogram unit bodies, and each parallelogram unit body is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C and one triangular pyramid D. The bottom surfaces of the triangular pyramids A, B, C and D are all the same equilateral triangle. The bottom area ratios of the triangular pyramids A, B, C and D are 37.5%, 37.5%, 12.5% and 12.5% respectively; the three pyramid face inclination angles of the triangular pyramid A are respectively α / 2, α / 2 and βL, the three pyramid face inclination angles of the triangular pyramid B are respectively α / 2, α / 2 and βR, the three pyramid face inclination angles of the triangular pyramid C are all βL, and the three pyramid face inclination angles of the triangular pyramid D are all βR, and βL is not equal to βR.

[0011] A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: the surface of the microprism retroreflective film is formed by an array of identical parallelogram unit bodies, and each parallelogram unit body is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D and one triangular pyramid E. The bottom surfaces of the triangular pyramids A, B, C, D and E are all the same equilateral triangle. The bottom area ratios of the triangular pyramids A, B, C, D and E are 25%, 25%, 25%, 12.5% and 12.5% respectively; the three pyramid face inclination angles of the triangular pyramid A are all α / 2, the three pyramid face inclination angles of the triangular pyramid B are respectively α / 2, α / 2 and β / 2 + △, the three pyramid face inclination angles of the triangular pyramid C are respectively α / 2, α / 2 and β / 2 - △, the three pyramid face inclination angles of the triangular pyramid D are respectively α / 2, β / 2 + △ and β / 2 + △, and the three pyramid face inclination angles of the triangular pyramid E are respectively α / 2, β / 2 - △ and β / 2 - △, and △ is greater than zero.

[0012] A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: the surface of the microprism retroreflective film is formed by an array of identical parallelogram unit bodies, and each parallelogram unit body is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D and one triangular pyramid E. The bottom surfaces of the triangular pyramids A, B, C, D and E are all identical equilateral triangles. The bottom area ratios of the triangular pyramids A, B, C, D and E are 25%, 25%, 25%, 12.5% and 12.5% respectively; the three pyramid surface inclinations of the triangular pyramid A are all α / 2, the three pyramid surface inclinations of the triangular pyramid B are α / 2, α / 2 and βL respectively, the three pyramid surface inclinations of the triangular pyramid C are α / 2, α / 2 and βR respectively, the three pyramid surface inclinations of the triangular pyramid D are α / 2, βL and βL respectively, and the three pyramid surface inclinations of the triangular pyramid E are α / 2, βR and βR respectively, and βL is not equal to βR.

[0013] A manufacturing method of a mold for a composite microprism retroreflective film integrating multiple triangular pyramids, which is used to manufacture the mold for the above-mentioned composite microprism retroreflective film integrating a combination structure of three triangular pyramids, characterized in that: The mold base material is horizontally installed on the workbench. The workbench can drive the mold base material to move along the X-axis and Y-axis in the horizontal direction, and the B-axis turntable on the workbench can drive the mold base material to rotate around the normal B-axis of the mold base material. Above the mold base material, there is a main shaft parallel to the upper surface of the mold base material and a fly cutter head fixedly connected to the main shaft. A cutter is installed on the fly cutter head, and the cutter can rotate around the Y-axis driven by the main shaft. The specific manufacturing steps are as follows: Step 1: Rotate the mold base material on the B-axis turntable by an angle to 0 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to process the two side pyramid surfaces of the parallelogram unit body, that is, the pyramid surface γ1-1 and the pyramid surface γ1-2, and their inclination angles are α / 2. The first type of cutter is a symmetric cutter, and the two side inclinations are the same; Step 2: Rotate the mold base material on the B-axis turntable by an angle to 120 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to process the other two side pyramid surfaces of the parallelogram unit body, the pyramid surface γ2-1 and the pyramid surface γ2-2, and their inclination angles are α / 2; Step 3: Rotate the mold base material on the B-axis turntable by an angle to 60 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to process the pyramid surfaces at the two diagonals of the parallelogram unit body, that is, the pyramid surface γ3-1 and the pyramid surface γ3-2, and their inclination angles are α / 2; Step 4: On the basis of the structure processed in Step 3, rotate the mold base material to the 0-degree position, and use the cutter to process and form the pyramid surface γ4-1 and the pyramid surface γ4-2; Step 5: Rotate the mold substrate sequentially by 120 degrees, and use a cutting tool to machine and form the pyramid surfaces γ5-1 and γ5-2; Step 6: Rotate the mold substrate sequentially by 60 degrees again, and use a cutting tool to machine and form the pyramid surfaces γ6-1 and γ6-2; In at least two of the steps 4, 5, and 6, the second cutting tool is used, and the first cutting tool is used in the remaining steps. The second cutting tool is a symmetric cutting tool with a tool angle of β. The second cutting tool is installed on the tool holder of the working spindle. There is an adjustable deflection angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second cutting tool are β / 2 + △ and β / 2 - △, and the inclination angles of the pyramid surfaces machined on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; Alternatively, the second cutting tool is an asymmetric cutting tool with a tool angle of β, and the inclination angles of the left and right cutting edges of the second cutting tool are βL and βR respectively, so that the inclination angles of the pyramid surfaces machined on the left and right sides of the cutting edge are βL and βR respectively.

[0014] Preferably, in steps 4, 5, and 6, the first cutting tool is used in step 4, and the second cutting tool is used in steps 5 and 6. The second cutting tool is installed on the tool holder of the working spindle. There is an adjustable deflection angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second cutting tool are β / 2 + △ and β / 2 - △, and the inclination angles of the pyramid surfaces machined on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; A triangular prism A with the inclination angles of the three pyramid surfaces all at α / 2 and an area ratio of 25% is obtained by machining. A triangular prism B with the inclination angles of the three pyramid surfaces being α / 2, α / 2, and β / 2 + △ respectively and an area ratio of 25%. A triangular prism C with the inclination angles of the three pyramid surfaces being α / 2, α / 2, and β / 2 - △ respectively and an area ratio of 25%. A triangular prism D with the inclination angles of the three pyramid surfaces being α / 2, β / 2 + △, and β / 2 + △ respectively and an area ratio of 12.5%. A triangular prism E with the inclination angles of the three pyramid surfaces being α / 2, β / 2 - △, and β / 2 - △ respectively and an area ratio of 12.5%. The triangular prisms A, B, C, D, and E form a microprism reflective film mold with five different triangular prism combination structures.

[0015] Preferably, in steps 4, 5, and 6, the first type of tool is used in step 4, and the second type of tool is used in steps 5 and 6. The second type of tool is an asymmetric tool with a tool angle of β. The left and right cutting edge inclinations of the second type of tool are βL and βR respectively, so that the inclinations of the pyramid side surfaces machined on the left and right sides of the cutting edge are βL and βR respectively. A triangular pyramid A with three pyramid side surface inclinations all at α / 2 and an area ratio of 25%, a triangular pyramid B with three pyramid side surface inclinations of α / 2, α / 2, and βL respectively and an area ratio of 25%, a triangular pyramid C with three pyramid side surface inclinations of α / 2, α / 2, and βR respectively and an area ratio of 25%, a triangular pyramid D with three pyramid side surface inclinations of α / 2, βL, and βL respectively and an area ratio of 12.5%, and a triangular pyramid E with three pyramid side surface inclinations of α / 2, βR, and βR respectively and an area ratio of 12.5% are machined. The triangular pyramid A, the triangular pyramid B, the triangular pyramid C, the triangular pyramid D, and the triangular pyramid E form a microprism retroreflective film mold with five different triangular pyramid combination structures.

[0016] Preferably, the second type of tool is used in all of steps 4, 5, and 6. The second type of tool is installed on the tool holder of the working spindle. There is an adjustable offset angle △ for the mechanical axis of the tool holder, so that the inclinations of the two sides of the cutting edge of the second type of tool are β / 2 + △ and β / 2 - △, and the inclinations of the pyramid side surfaces machined on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively. A triangular pyramid A with three pyramid side surface inclinations of α / 2, α / 2, and β / 2 + △ respectively and an area ratio of 37.55%, a triangular pyramid B with three pyramid side surface inclinations of α / 2, α / 2, and β / 2 - △ respectively and an area ratio of 37.5%, a triangular pyramid C with three pyramid side surface inclinations all at β / 2 + △ and an area ratio of 12.5%, and a triangular pyramid D with three pyramid side surface inclinations all at β / 2 - △ and an area ratio of 12.5% are machined. The triangular pyramid A, the triangular pyramid B, the triangular pyramid C, and the triangular pyramid D form a microprism retroreflective film mold with four different triangular pyramid combination structures.

[0017] Preferably, the second type of tool is used in all of steps 4, 5, and 6. The second type of tool is an asymmetric tool with a tool angle of β. The left and right cutting edge inclinations of the second type of tool are βL and βR respectively, so that the inclinations of the pyramid side surfaces machined on the left and right sides of the cutting edge are βL and βR respectively. A triangular pyramid A with three pyramid side surface inclinations of α / 2, α / 2, and βL respectively and an area ratio of 37.55%, a triangular pyramid B with three pyramid side surface inclinations of α / 2, α / 2, and βR respectively and an area ratio of 37.5%, a triangular pyramid C with three pyramid side surface inclinations all at βL and an area ratio of 12.5%, and a triangular pyramid D with three pyramid side surface inclinations all at βR and an area ratio of 12.5% are machined. The triangular pyramid A, the triangular pyramid B, the triangular pyramid C, and the triangular pyramid D form a microprism retroreflective film mold with four different triangular pyramid combination structures.

[0018] The present invention has the following technical advantages.

[0019] From the perspective of optical design, an increase in the degree of freedom of optical design means that an optical system is expected to simultaneously meet the performance indicators of more different application conditions. For Class V retroreflective films with high-performance requirements, improving their wide-angle performance at large viewing angles and large incident angles, as well as the performance in the 90-degree and 0-degree azimuth orientations and their optimization and balance, have always been the focus of the research and development of Class V retroreflective film technology; The performance for different application conditions can be reasonably optimized, thereby achieving an improvement in wide-angle performance that cannot be achieved by the microprism retroreflective films with traditional triangular pyramid unit structures and double triangular pyramid combined structures, as well as the optimization and balance of the overall comprehensive performance; the performance of the retroreflective film can be further improved while maintaining the advantages of a simple structure of the retroreflective film and effectively controlling the complexity of the manufacturing of the retroreflective film mold.

[0020] In the present invention, by selecting different deflection values △ of the second tool with a tool angle design of β (or an asymmetric tool design including different inclination angles βL and βR of the left and right cutting edges) and different combinations of the tool selections for the fourth to sixth cuts, a microprism retroreflective film design with a combination structure of a variety of different triangular pyramids (with the inclination angle of the pyramid surface changed) can be obtained, realizing the improvement of the overall performance of the retroreflective film, as well as the optimization of the wide-angle performance and small-angle performance, and the performance in the 90-degree and 0-degree orientations. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings; Figure 1 is the front view of a traditional triangular pyramid; Figure 2 is the three-dimensional schematic diagram of the mold substrate placed on the workbench for processing; Figure 3 is the sectional structure schematic diagram of a fly cutter for processing the mold substrate; Figure 4 is the sectional structure schematic diagram of another fly cutter for processing the mold substrate; Figure 5 is the front view of the microprism retroreflective film and the finished mold of the present invention; Figure 6 is the three-dimensional structure schematic diagram of the mold substrate before processing; Figure 7 is Figure 6 the front view of; Figure 8 is Figure 7 the front view of the mold substrate after being processed in step 1; Figure 9 is Figure 8 the front view of the mold substrate after being processed in step 2; Figure 10 is Figure 9 the front view of the mold substrate after being processed in step 3; Figure 11is Figure 10 isometric view; Figure 12 is Figure 10 front view of the mold substrate of Figure 10 after being processed in step 4; Figure 13 is Figure 12 isometric structure schematic diagram; Figure 14 is Figure 12 front view of the mold substrate of Figure 12 after being processed in step 5; Figure 15 is Figure 14 isometric structure schematic diagram; Figure 16 is Figure 15 front view of the mold substrate of Figure 15 after being processed in step 6. Specific Embodiments

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] The present invention integrates a microprism reflective film with a combination structure of multiple triangular pyramids. The reflective film is composed of four or more different triangular pyramid structures. Specific embodiments are as follows: One of the embodiments: The surface of the microprism reflective film is formed by an array of identical parallelogram unit bodies 1. Each parallelogram unit body 1 is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C, and one triangular pyramid D. The bases of the triangular pyramids A, B, C, and D are all identical equilateral triangles. The proportion of the base areas of the triangular pyramids A, B, C, and D is 37.5%, 37.5%, 12.5%, and 12.5% respectively; the inclination angles of the three pyramid faces of the triangular pyramid A are all α / 2, α / 2, and β / 2 + △ respectively, the inclination angles of the three pyramid faces of the triangular pyramid B are all α / 2, α / 2, and β / 2 - △ respectively, the inclination angles of the three pyramid faces of the triangular pyramid C are all β / 2 + △, and the inclination angles of the three pyramid faces of the triangular pyramid D are all β / 2 - △, where △ is greater than zero.

[0024] One of the embodiments: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells 1. Each parallelogram unit cell 1 is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C, and one triangular pyramid D. The bases of the triangular pyramids A, B, C, and D are all identical equilateral triangles. The proportions of the base areas of the triangular pyramids A, B, C, and D are 37.5%, 37.5%, 12.5%, and 12.5% respectively; the inclination angles of the three pyramidal faces of the triangular pyramid A are α / 2, α / 2, and βL respectively, the inclination angles of the three pyramidal faces of the triangular pyramid B are α / 2, α / 2, and βR respectively, the inclination angles of the three pyramidal faces of the triangular pyramid C are all βL, and the inclination angles of the three pyramidal faces of the triangular pyramid D are all βR, where βL is not equal to βR.

[0025] One of the embodiments: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells 1. Each parallelogram unit cell 1 is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D, and one triangular pyramid E. The bases of the triangular pyramids A, B, C, D, and E are all identical equilateral triangles. The proportions of the base areas of the triangular pyramids A, B, C, D, and E are 25%, 25%, 25%, 12.5%, and 12.5% respectively; the inclination angles of the three pyramidal faces of the triangular pyramid A are all α / 2, the inclination angles of the three pyramidal faces of the triangular pyramid B are α / 2, α / 2, and β / 2 + △ respectively, the inclination angles of the three pyramidal faces of the triangular pyramid C are α / 2, α / 2, and β / 2 - △ respectively, the inclination angles of the three pyramidal faces of the triangular pyramid D are α / 2, β / 2 + △, and β / 2 + △ respectively, and the inclination angles of the three pyramidal faces of the triangular pyramid E are α / 2, β / 2 - △, and β / 2 - △ respectively, where △ is greater than zero.

[0026] One of the embodiments: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells 1. Each parallelogram unit cell 1 is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D, and one triangular pyramid E. The bases of the triangular pyramids A, B, C, D, and E are all identical equilateral triangles. The proportions of the base areas of the triangular pyramids A, B, C, D, and E are 25%, 25%, 25%, 12.5%, and 12.5% respectively; the inclination angles of the three pyramidal faces of the triangular pyramid A are all α / 2, the inclination angles of the three pyramidal faces of the triangular pyramid B are α / 2, α / 2, and βL respectively, the inclination angles of the three pyramidal faces of the triangular pyramid C are α / 2, α / 2, and βR respectively, the inclination angles of the three pyramidal faces of the triangular pyramid D are α / 2, βL, and βL respectively, and the inclination angles of the three pyramidal faces of the triangular pyramid E are α / 2, βR, and βR respectively, where βL is not equal to βR.

[0027] The manufacturing method of the mold for the composite microprism retroreflective film integrating multiple triangular pyramids of the present invention is as follows (i.e., the mold for manufacturing the microprism retroreflective film with a combination structure of three triangular pyramids as described above, and this mold corresponds one-to-one with the above-mentioned retroreflective film structure. The mold for the retroreflective film with a combination structure of multiple triangular pyramids of the present invention is formed by the same parallelogram unit array. Each parallelogram unit is formed by 6 cuts with a cutting tool. The two corner pyramid surfaces formed by the first cut are respectively marked as γ1-1 and γ1-2, the two corner pyramid surfaces formed by the second cut are respectively marked as γ2-1 and γ2-2, and so on. The two corner pyramid surfaces formed by the sixth cut are respectively marked as γ6-1 and γ6-2, as Figure 6 shown, the microprism retroreflective films of the following several embodiments are obtained by the above processing): When the first to third cuts are formed by array processing, the first type of cutting tool with a tool angle designed as α is used. When the fourth to sixth cuts are formed by array processing, the first type of cutting tool with a tool angle designed as α or the second type of cutting tool with a tool angle designed as β and having a deflection angle Δ (or the left and right cutting edge inclination angles are βL and βR respectively) is selectively used.

[0028] 1. Four triangular pyramid structures: When the fourth, fifth, and sixth cuts are all formed by the second type of cutting tool β with a deflection angle Δ, it is composed of triangular pyramid A with three corner pyramid surface inclination angles of α / 2, α / 2, and β / 2 + △ (or βL) and an area ratio of 37.55%, triangular pyramid B with three corner pyramid surface inclination angles of α / 2, α / 2, and β / 2 - △ (or βR) and an area ratio of 37.5%, triangular pyramid C with three corner pyramid surface inclination angles all of β / 2 + △ (or βL) and an area ratio of 12.5%, and triangular pyramid D with three corner pyramid surface inclination angles all of β / 2 - △ (or βR) and an area ratio of 12.5%.

[0029] 2. Five triangular pyramid structures: When the fourth and fifth or the fifth and sixth or the fourth and sixth cuts are formed by the second type of cutting tool β with a deflection angle Δ, it is composed of triangular pyramid A with three corner pyramid surface inclination angles all at α / 2 and an area ratio of 25%, triangular pyramid B with three corner pyramid surface inclination angles of α / 2, α / 2, and β / 2 + △ (or βL) and an area ratio of 25%, triangular pyramid C with three corner pyramid surface inclination angles of α / 2, α / 2, and β / 2 - △ (or βR) and an area ratio of 25%, triangular pyramid C with three corner pyramid surface inclination angles of α / 2, β / 2 + △ (or βL), and β / 2 + △ (or βL) and an area ratio of 12.5%, and triangular pyramid E with three corner pyramid surface inclination angles of α / 2, β / 2 - △ (or βR), and β / 2 - △ (or βR) and an area ratio of 12.5%.

[0030] These two new designs increase the optical design freedom of the triangular pyramid reflective film. When only the 4th or 5th or 6th knife (only one of the 4th - 6th knives) uses the second type of tool with a tool angle of β having a deflection angle Δ (or the left and right blade inclination angles are βL and βR respectively) for processing and forming, it is a micro - prism reflective film with a three - triangular - pyramid combination structure.

[0031] The specific processing equipment and processing method are as follows: The mold substrate K1 for processing this mold is horizontally installed on the workbench K2. The workbench can drive the mold substrate to move along the X - axis and Y - axis in the horizontal direction, and the B - axis turntable on the workbench can drive the mold substrate to rotate around the normal B - axis of the mold substrate. Above the mold substrate, there is a main shaft K3 parallel to the upper surface of the mold substrate and a flying - cutter disk K4 fixedly connected to the main shaft. A tool K5 is installed on the flying - cutter disk. The tool can rotate around the Y - axis driven by the main shaft. The specific manufacturing steps are as follows: Step 1: Rotate the mold substrate on the B - axis turntable by an angle of 0 degrees, and use the first type of tool with a tool angle of α installed on the flying - cutter disk to process the two side conical surfaces of the parallelogram unit body, that is, the conical surface γ1 - 1 and the conical surface γ1 - 2, with an inclination angle of α / 2. The first type of tool is a symmetric tool, and the two side inclination angles are the same; Step 2: Rotate the mold substrate on the B - axis turntable by an angle of 120 degrees, and use the first type of tool with a tool angle of α installed on the flying - cutter disk to process the other two side conical surfaces of the parallelogram unit body, the conical surface γ2 - 1 and the conical surface γ2 - 2, with an inclination angle of α / 2; Step 3: Rotate the mold substrate on the B - axis turntable by an angle of 60 degrees, and use the first type of tool with a tool angle of α installed on the flying - cutter disk to process the conical surfaces of the two opposite corners of the parallelogram unit body 1, that is, the conical surface γ3 - 1 and the conical surface γ3 - 2, with an inclination angle of α / 2; Step 4: On the basis of the structure processed in Step 3, rotate the mold substrate to the 0 - degree position, and use the tool to process and form the conical surface γ4 - 1 and the conical surface γ4 - 2; Step 5: Sequentially rotate the mold substrate to 120 degrees, and use the tool to process and form the conical surface γ5 - 1 and the conical surface γ5 - 2; Step 6: Sequentially rotate the mold substrate to 60 degrees again, and use the tool to process and form the conical surface γ6 - 1 and the conical surface γ6 - 2; In at least two of the above - mentioned Steps 4, 5, and 6, the second type of tool is used, and the first type of tool is used in the remaining steps. The second type of tool is a symmetric tool with a tool angle of β. The second type of tool is installed on the tool holder of the working spindle, and there is an adjustable deflection angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second type of tool are β / 2 + △ and β / 2 - △, making the inclination angles of the conical surfaces processed on the left and right sides of the blade be β / 2 + △ and β / 2 - △ respectively (as shown in the figure); Another type, the second tool is an asymmetric tool with a tool angle of β. The left and right cutting edge inclination angles of the second tool are βL and βR respectively. The second tool is installed on the tool holder of the working spindle, and the mechanical axis of the tool holder is adjusted to be in a vertical state, so that the inclination angles of the conical surfaces machined on the left and right sides of the cutting edge are βL and βR respectively (as shown in the figure).

[0032] Specific Embodiment 1: In steps 4, 5, and 6, the second tool is used. The second tool is installed on the tool holder of the working spindle. There is an adjustable deflection angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the cutting edge of the second tool are β / 2 + △ and β / 2 - △, and the inclination angles of the conical surfaces machined on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; a triangular pyramid A with three conical surface inclination angles of α / 2, α / 2, and β / 2 + △ and an area ratio of 37.55% is obtained by machining, a triangular pyramid B with three conical surface inclination angles of α / 2, α / 2, and β / 2 - △ and an area ratio of 37.5%, a triangular pyramid C with three conical surface inclination angles of β / 2 + △ and an area ratio of 12.5%, and a triangular pyramid D with three conical surface inclination angles of β / 2 - △ and an area ratio of 12.5%. The triangular pyramids A, B, C, and D form a microprismatic retroreflective film mold with four different triangular pyramid combination structures.

[0033] Specific Embodiment 2: In steps 4, 5, and 6, the second tool is used. The second tool is an asymmetric tool with a tool angle of β. The left and right cutting edge inclination angles of the second tool are βL and βR respectively, so that the inclination angles of the conical surfaces machined on the left and right sides of the cutting edge are βL and βR respectively; a triangular pyramid A with three conical surface inclination angles of α / 2, α / 2, and βL and an area ratio of 37.55% is obtained by machining, a triangular pyramid B with three conical surface inclination angles of α / 2, α / 2, and βR and an area ratio of 37.5%, a triangular pyramid C with three conical surface inclination angles of βL and an area ratio of 12.5%, and a triangular pyramid D with three conical surface inclination angles of βR and an area ratio of 12.5%. The triangular pyramids A, B, C, and D form a microprismatic retroreflective film mold with four different triangular pyramid combination structures.

[0034] The above-mentioned Embodiments 1 and 2 obtain a microprismatic retroreflective film mold with four different triangular pyramid combination structures.

[0035] Specific Embodiment 3: In Steps 4, 5, and 6, the first type of tool is used in Step 4, and the second type of tool is used in Steps 5 and 6. The second type of tool is installed on the tool holder of the working spindle. There is an adjustable deflection angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second type of tool are β / 2 + △ and β / 2 - △, and the inclination angles of the conical surfaces processed on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; a triangular pyramid A with three conical surface inclination angles all at α / 2 and an area ratio of 25% is obtained by machining, a triangular pyramid B with three conical surface inclination angles of α / 2, α / 2, and β / 2 + △ respectively and an area ratio of 25%, a triangular pyramid C with three conical surface inclination angles of α / 2, α / 2, and β / 2 - △ respectively and an area ratio of 25%, a triangular pyramid D with three conical surface inclination angles of α / 2, β / 2 + △, and β / 2 + △ respectively and an area ratio of 12.5%, and a triangular pyramid E with three conical surface inclination angles of α / 2, β / 2 - △, and β / 2 - △ respectively and an area ratio of 12.5%. The triangular pyramid A, triangular pyramid B, triangular pyramid C, triangular pyramid D, and triangular pyramid E form a microprism retroreflective film mold with five different triangular pyramid combination structures.

[0036] Specific Embodiment 4: In Steps 4, 5, and 6, the first type of tool is used in Step 4, and the second type of tool is used in Steps 5 and 6. The second type of tool is an asymmetric tool with a tool angle of β, and the inclination angles of the left and right cutting edges of the second type of tool are βL and βR respectively, so that the inclination angles of the conical surfaces processed on the left and right sides of the cutting edge are βL and βR respectively; a triangular pyramid A with three conical surface inclination angles all at α / 2 and an area ratio of 25% is obtained by machining, a triangular pyramid B with three conical surface inclination angles of α / 2, α / 2, and βL respectively and an area ratio of 25%, a triangular pyramid C with three conical surface inclination angles of α / 2, α / 2, and βR respectively and an area ratio of 25%, a triangular pyramid D with three conical surface inclination angles of α / 2, βL, and βL respectively and an area ratio of 12.5%, and a triangular pyramid E with three conical surface inclination angles of α / 2, βR, and βR respectively and an area ratio of 12.5%. The triangular pyramid A, triangular pyramid B, triangular pyramid C, triangular pyramid D, and triangular pyramid E form a microprism retroreflective film mold with five different triangular pyramid combination structures.

[0037] The above-mentioned Embodiments 3 and 4 obtain a microprism retroreflective film mold with five different triangular pyramid combination structures.

[0038] The mold obtained by the above-mentioned machining is further processed by existing conventional technical means to obtain a retroreflective film (which is prior art and will not be elaborated here).

[0039] "Manufacturing Method of Microprism Reflective Film with Double Triangular Pyramid Composite Structure and Its Mould" (Publication No. CN118759624B) After machining the large triangular pyramid with the first type of cutting tool with a tool angle of α, then use the second type of cutting tool with a tool angle of β for machining (a total of 6 machining operations and 6 steps). Although by adjusting the angle variable of the triangular pyramid located at the center, the wide-angle performance of the reflective film can be optimized to a certain extent, or a certain degree of optimization of the performance at 0 degrees and 90 degrees of the reflective film can be obtained. However, under the same machining steps (this application also has 6 machining operations and 6 steps), although the microprism reflective film obtained by this patent has the design freedom of two types of triangular pyramids, there is still a lack of freedom in optical design optimization.

[0040] In summary, the present invention has the following technical advantages.

[0041] From the perspective of optical design, an increase in the degree of freedom of optical design means that the optical system is expected to simultaneously meet the performance indicators of more different application conditions. For Class V reflective films with high performance requirements, improving their wide-angle performance at large viewing angles and large incident angles, as well as the performance, optimization, and balance at 90-degree and 0-degree azimuth orientations, have always been the focus of the research and development of Class V reflective film technology. The performance under different application conditions can be reasonably optimized, thereby achieving an improvement in wide-angle performance that cannot be achieved by traditional triangular pyramid unit structures and microprism reflective films with double triangular pyramid composite structures, as well as the optimization and balance of overall comprehensive performance. The performance of the reflective film can be further improved, while maintaining the simplicity of the reflective film structure and effectively controlling the complexity of manufacturing the reflective film mould.

[0042] By selecting different deviation values △ of the second type of cutting tool with a tool angle designed as β (or an asymmetric tool design including different inclinations βL and βR of the left and right cutting edges) and different combinations of the cutting tools used for the 4th - 6th operations, the present invention can obtain a microprism reflective film design with a composite structure of multiple different triangular pyramids (changing the inclination angle of the pyramid surface), realizing the improvement of the overall performance of the reflective film, as well as the optimization of wide-angle performance, small-angle performance, and 90-degree and 0-degree orientation performance.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that modifications can still be made to the specific implementation manners of the present invention or equivalent replacements can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells (1). Each parallelogram unit cell (1) is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C, and one triangular pyramid D. The bases of triangular pyramids A, B, C, and D are all identical equilateral triangles. The bottom area ratios of triangular pyramids A, B, C, and D are 37.5%, 37.5%, 12.5%, and 12.5% respectively. The inclination angles of the three pyramid faces of triangular pyramid A are α / 2, α / 2, and β / 2 + △ respectively. The inclination angles of the three pyramid faces of triangular pyramid B are α / 2, α / 2, and β / 2 - △ respectively. The inclination angles of the three pyramid faces of triangular pyramid C are all β / 2 + △. The inclination angles of the three pyramid faces of triangular pyramid D are all β / 2 - △, and △ is greater than zero.

2. A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells (1). Each parallelogram unit cell (1) is composed of three identical triangular pyramids A, three identical triangular pyramids B, one triangular pyramid C, and one triangular pyramid D. The bases of triangular pyramids A, B, C, and D are all identical equilateral triangles. The bottom area ratios of triangular pyramids A, B, C, and D are 37.5%, 37.5%, 12.5%, and 12.5% respectively. The inclination angles of the three pyramid faces of triangular pyramid A are α / 2, α / 2, and βL respectively. The inclination angles of the three pyramid faces of triangular pyramid B are α / 2, α / 2, and βR respectively. The inclination angles of the three pyramid faces of triangular pyramid C are all βL. The inclination angles of the three pyramid faces of triangular pyramid D are all βR, and βL is not equal to βR.

3. A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells (1). Each parallelogram unit cell (1) is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D, and one triangular pyramid E. The bases of triangular pyramids A, B, C, D, and E are all identical equilateral triangles. The bottom area ratios of triangular pyramids A, B, C, D, and E are 25%, 25%, 25%, 12.5%, and 12.5% respectively. The inclination angles of the three pyramid faces of triangular pyramid A are all α / 2. The inclination angles of the three pyramid faces of triangular pyramid B are α / 2, α / 2, and β / 2 + △ respectively. The inclination angles of the three pyramid faces of triangular pyramid C are α / 2, α / 2, and β / 2 - △ respectively. The inclination angles of the three pyramid faces of triangular pyramid D are α / 2, β / 2 + △, and β / 2 + △ respectively. The inclination angles of the three pyramid faces of triangular pyramid E are α / 2, β / 2 - △, and β / 2 - △ respectively, and △ is greater than zero.

4. A composite microprism retroreflective film integrating multiple triangular pyramids, characterized in that: The surface of the microprism retroreflective film is formed by an array of identical parallelogram unit cells (1). Each parallelogram unit cell (1) is composed of two identical triangular pyramids A, two identical triangular pyramids B, two triangular pyramids C, one triangular pyramid D, and one triangular pyramid E. The bases of triangular pyramids A, B, C, D, and E are all identical equilateral triangles. The proportion of the base areas of triangular pyramids A, B, C, D, and E is 25%, 25%, 25%, 12.5%, and 12.5% respectively. The inclination angles of the three pyramid faces of triangular pyramid A are all α / 2. The inclination angles of the three pyramid faces of triangular pyramid B are α / 2, α / 2, and βL respectively. The inclination angles of the three pyramid faces of triangular pyramid C are α / 2, α / 2, and βR respectively. The inclination angles of the three pyramid faces of triangular pyramid D are α / 2, βL, and βL respectively. The inclination angles of the three pyramid faces of triangular pyramid E are α / 2, βR, and βR respectively, and βL is not equal to βR.

5. A manufacturing method of a mold for a composite microprism retroreflective film integrating multiple triangular pyramids. The mold is used to manufacture a composite microprism retroreflective film integrating multiple triangular pyramids as described in any one of claims 1-4. It is characterized in that: The mold substrate (K1) is horizontally installed on the workbench (K2). The workbench can drive the mold substrate to move along the X-axis and Y-axis in the horizontal direction, and the B-axis turntable on the workbench can drive the mold substrate to rotate around the normal B-axis of the mold substrate. Above the mold substrate, there is a main shaft (K3) parallel to the upper surface of the mold substrate and a fly cutter head (K4) fixedly connected to the main shaft. A cutter (K5) is installed on the fly cutter head. The cutter can rotate around the Y-axis driven by the main shaft. The specific manufacturing steps are as follows: Step 1: Rotate the mold substrate on the B-axis turntable by an angle to 0 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to machine the two side pyramid faces of the parallelogram unit cell, that is, the pyramid faces γ1-1 and γ1-2, with an inclination angle of α / 2. The first type of cutter is a symmetric cutter with the same inclination angles on both sides. Step 2: Rotate the mold substrate on the B-axis turntable by an angle to 120 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to machine the other two side pyramid faces of the parallelogram unit cell, the pyramid faces γ2-1 and γ2-2, with an inclination angle of α / 2. Step 3: Rotate the mold substrate on the B-axis turntable by an angle to 60 degrees, and use the first type of cutter with a cutter angle of α installed on the fly cutter head to machine the pyramid faces at two opposite corners of the parallelogram unit cell (1), that is, the pyramid faces γ3-1 and γ3-2, with an inclination angle of α / 2. Step 4: On the basis of the structure machined in Step 3, rotate the mold substrate to the 0-degree position, and use the cutter to machine and form the pyramid faces γ4-1 and γ4-2. Step 5: Rotate the mold substrate to the 120-degree position in sequence, and use the cutter to machine and form the pyramid faces γ5-1 and γ5-2. Step 6: Rotate the mold substrate to the 60-degree position in sequence again, and use the cutter to machine and form the pyramid faces γ6-1 and γ6-2. In at least two of the steps 4, 5, and 6, the second type of cutting tool is used, and the first type of cutting tool is used in the remaining steps. The second type of cutting tool is a symmetric cutting tool with a tool angle of β. The second type of cutting tool is installed on the tool holder of the working spindle. There is an adjustable offset angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second type of cutting tool are β / 2 + △ and β / 2 - △, and the inclination angles of the angular conical surfaces processed on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; Alternatively, the second type of cutting tool is an asymmetric cutting tool with a tool angle of β. The inclination angles of the left and right cutting edges of the second type of cutting tool are βL and βR respectively, so that the inclination angles of the angular conical surfaces processed on the left and right sides of the cutting edge are βL and βR respectively.

6. The manufacturing method of the mold for the composite microprism reflective film integrating multiple triangular pyramids according to claim 5, characterized in that: In step 4 of the steps 4, 5, and 6, the first type of cutting tool is used, and the second type of cutting tool is used in steps 5 and 6. The second type of cutting tool is installed on the tool holder of the working spindle. There is an adjustable offset angle △ for the mechanical axis of the tool holder, so that the inclination angles of the two sides of the second type of cutting tool are β / 2 + △ and β / 2 - △, and the inclination angles of the angular conical surfaces processed on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; A triangular pyramid A with three angular conical surface inclination angles all at α / 2 and an area ratio of 25% is obtained, a triangular pyramid B with three angular conical surface inclination angles of α / 2, α / 2, and β / 2 + △ respectively and an area ratio of 25%, a triangular pyramid C with three angular conical surface inclination angles of α / 2, α / 2, and β / 2 - △ respectively and an area ratio of 25%, a triangular pyramid D with three angular conical surface inclination angles of α / 2, β / 2 + △, and β / 2 + △ respectively and an area ratio of 12.5%, and a triangular pyramid E with three angular conical surface inclination angles of α / 2, β / 2 - △, and β / 2 - △ respectively and an area ratio of 12.5%. The triangular pyramids A, B, C, D, and E form a microprism retroreflective film mold with five different triangular pyramid combination structures.

7. The manufacturing method of the mold for the composite microprism retroreflective film integrating multiple triangular pyramids according to claim 5, characterized in that: In step 4 of the steps 4, 5, and 6, the first type of cutting tool is used, and the second type of cutting tool is used in steps 5 and 6. The second type of cutting tool is an asymmetric cutting tool with a tool angle of β. The inclination angles of the left and right cutting edges of the second type of cutting tool are βL and βR respectively, so that the inclination angles of the angular conical surfaces processed on the left and right sides of the cutting edge are βL and βR respectively; A triangular pyramid A with three angular conical surface inclination angles all at α / 2 and an area ratio of 25% is obtained, a triangular pyramid B with three angular conical surface inclination angles of α / 2, α / 2, and βL respectively and an area ratio of 25%, a triangular pyramid C with three angular conical surface inclination angles of α / 2, α / 2, and βR respectively and an area ratio of 25%, a triangular pyramid D with three angular conical surface inclination angles of α / 2, βL, and βL respectively and an area ratio of 12.5%, and a triangular pyramid E with three angular conical surface inclination angles of α / 2, βR, and βR respectively and an area ratio of 12.5%. The triangular pyramids A, B, C, D, and E form a microprism retroreflective film mold with five different triangular pyramid combination structures.

8. The manufacturing method of the mold for the composite micro prism reflective film integrating multiple triangular pyramids according to claim 5, characterized in that: In steps 4, 5, and 6, the second type of tool is used. The second type of tool is installed on the tool holder of the working spindle. There is an adjustable deflection angle △ for the mechanical axis of the tool holder, such that the inclination angles of the two sides of the second type of tool are β / 2 + △ and β / 2 - △, so that the inclination angles of the pyramid surfaces machined on the left and right sides of the cutting edge are β / 2 + △ and β / 2 - △ respectively; a triangular pyramid A with three pyramid surface inclination angles of α / 2, α / 2, and β / 2 + △ and an area ratio of 37.55% is obtained by machining, a triangular pyramid B with three pyramid surface inclination angles of α / 2, α / 2, and β / 2 - △ and an area ratio of 37.5%, a triangular pyramid C with three pyramid surface inclination angles of β / 2 + △ and an area ratio of 12.5%, and a triangular pyramid D with three pyramid surface inclination angles of β / 2 - △ and an area ratio of 12.5%. Triangular pyramid A, triangular pyramid B, triangular pyramid C, and triangular pyramid D form a microprismatic retroreflective film mold with four different triangular pyramid combination structures.

9. The manufacturing method of the mold for the composite microprism retroreflective film integrating multiple triangular pyramids according to claim 5, characterized in that: In steps 4, 5, and 6, the second type of tool is used. The second type of tool is an asymmetric tool with a tool angle of β. The inclination angles of the left and right cutting edges of the second type of tool are βL and βR respectively, so that the inclination angles of the pyramid surfaces machined on the left and right sides of the cutting edge are βL and βR respectively; a triangular pyramid A with three pyramid surface inclination angles of α / 2, α / 2, and βL and an area ratio of 37.55% is obtained by machining, a triangular pyramid B with three pyramid surface inclination angles of α / 2, α / 2, and βR and an area ratio of 37.5%, a triangular pyramid C with three pyramid surface inclination angles of βL and an area ratio of 12.5%, and a triangular pyramid D with three pyramid surface inclination angles of βR and an area ratio of 12.5%. Triangular pyramid A, triangular pyramid B, triangular pyramid C, and triangular pyramid D form a microprismatic retroreflective film mold with four different triangular pyramid combination structures.

Images