Splicing method of nickel mold for microprism type reflective film

Abstract

The invention relates to the technical field of precise optical mold manufacturing, in particular to a splicing method of a nickel mold for a microprism type reflective film, which comprises the following steps of: firstly, determining the width a of a welding damage band through laser welding; and then, during splicing in the 0-degree direction, the cutting position is positioned at the position which moves outwards for a / 2 along the 0-degree side line of the 0-degree pyramid, so that the welding damage area is prevented from influencing the effective pyramid. And during splicing in the 90-degree direction, according to the bottom edge length L of the effective pyramid and the distance b from the 90-degree damaged edge to the nearest effective pyramid, it is determined that invalid pyramids and effective pyramids with different areas are combined and alternately arranged on the two sides of the welding area, so that the retroreflection efficiency is maximized. And then, in the 0-degree direction and the 90-degree direction, precise cutting equipment is used for cutting correspondingly, and precise laser welding equipment is used for welding after alignment is conducted on the splicing platform. The technical problem that in the prior art, the retroreflection efficiency and the overall uniformity of the splicing area are poor is solved.

Description

Technical Field

[0001] The invention relates to the technical field of precision optical mold manufacturing, and in particular to a method for splicing a nickel mold for a micro-prismatic reflective film. Background Art

[0002] At present, micro-prismatic reflective structures have high retro-reflective properties, which can increase the brightness and directionality of reflected light, making it easier for drivers or pedestrians to detect and identify, improving visual guidance and safety at night or in low-visibility conditions, and are widely used in transportation, clothing and other fields. Figure 1 As shown, only the light reflected by the three sides can form effective retroreflection, and the light vertically incident from the bottom surface of the corner cone unit can be divided into three areas according to the vertical projection of the edge. Only within the area surrounded by the regular hexagon with the bottom center as the center and a side length of 1 / 3 of the side length of the corner cone (1-2, 1-3, 2-2, 2-3, 3-2, 3-3) can the incident light be reflected three times on the corner cone unit, and the light incident in the area (1-1, 1-4, 2-1, 2-4, 3-1, 3-4) exceeds the third side area after the second reflection, forming an invalid light effect. Therefore, the theoretical effective retroreflection efficiency of the microprismatic corner cone unit is about 66.7%.

[0003] In order to efficiently realize large-scale and continuous production of micro-prismatic reflective film, it is usually necessary to make the working mold into a large-area cylindrical roller. However, due to the limitations of the processable size of the copper mold engraving equipment and the uniformity caused by the loss of large-area engraving tools, it is generally necessary to recast the engraved copper master mold into a nickel mold through precision electroforming, and then process it into a working roller mold through splicing and recasting multiple times. The difference in splicing process and technology will have a great impact on the final reflective film. For example, Chinese Patent Publication No.: CN111055094A discloses a method for making a micro-prismatic mold that reduces the dark band in the seam. A method is proposed for splicing in the 0° direction after precision processing using a special tool to reduce the dark band in the seam, thereby improving the retroreflective performance of the splicing area of ​​the nickel mold in the 0° and 0° directions. Figure 2 However, the processing method is complicated, and the angle, cutting position, cutting depth, etc. of the special tool need to be micro-controlled to make the tool and the triangular pyramid processing knife line completely overlap. At the same time, the cutting depth must be controlled to prevent the problem of the invalid area of ​​the 180° angle pyramid from becoming larger due to overcutting.

[0004] Generally, in the process of making a roller nickel mold, in addition to the splicing in the 0° and 0° direction, it is also necessary to splice the sub-molds at 90° and 90° or 0° and 90° (yin-yang grid). However, there is no reported research in this regard. When people cut in the 90° direction, they usually cut and splice along the center line of the pyramid. Affected by the precision of the splicing angle and position, the half pyramids on both sides of the seam cannot form a complete triangular pyramid structure, and the light cannot form effective retroreflection, resulting in large dark bands on both sides of the seam, which seriously affects the retroreflection efficiency and overall uniformity of the splicing area. Summary of the invention

[0005] Therefore, in response to the above-mentioned problems, the present invention proposes a splicing method for a nickel mold for a microprismatic reflective film, which reduces the invalid area of ​​the splicing area by changing the cutting position and improves the overall uniformity of the mold after splicing, thereby solving the technical problems of poor retroreflective efficiency and overall uniformity of the splicing area in the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solution: a method for splicing a nickel mold for a micro-prismatic reflective film, characterized in that it comprises the following steps:

[0007] The first step is to determine the width of the welding damage zone: take a nickel sub-mold that is the same as the nickel sub-mold to be cut and spliced, perform laser welding on the back, and then check the front of the welding position to determine the width a of the thermal damage zone caused by laser welding;

[0008] The second step is to determine the cutting position in the 0° direction: the micro-prismatic cone of the micro-prismatic reflective film is set to be a valid cone when it has a complete shape, and an invalid cone when it has an incomplete shape. The lowest valid cone is set to be a 0° cone, and the lowest edge of the 0° cone is set to be a 0° sideline. When splicing the nickel mold in the 0° direction, the cutting position is positioned at a position a / 2 away from the 0° sideline of the 0° cone to avoid the welding damage area affecting the valid cone.

[0009] The third step is to determine the cutting position in the 90° direction: set the length of the bottom side of the effective angle cone to L, set the distance between the 90° damaged edge and the nearest effective angle cone to b, 0<b≤L / 2, when the nickel mold is spliced ​​in the 90° direction, the two sides of the welding area are formed by the combination of effective angle cones with an area greater than 1 / 2 and invalid angle cones with an area less than 1 / 2 of the effective angle cone, where b is the value that maximizes the retroreflection efficiency of the effective angle cone unit and the invalid angle cone unit;

[0010] Step 4, 0° direction cutting and splicing: install the nickel sub-mold on the fixture of the precision cutting equipment, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then use the 0° edge line of the first row of effective angle cones to be retained as the reference, and cut the sub-mold along the X-axis at a distance a / 2 away from the 0° edge line. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment;

[0011] The fifth step is 90° cutting and splicing: install the nickel sub-mold on the precision cutting equipment fixing fixture, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then adjust the cutting tool to the best cutting position b and cut the sub-mold along the Y-axis. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment.

[0012] Preferably, the retroreflection efficiency of the combination of effective corner pyramid and invalid corner pyramid unit is set to η, and the retroreflection efficiency change formula of the unit combination is:

[0013]

[0014] Preferably, in the third step, when b is one quarter of the length L of the base of the micro-prismatic pyramid, the retroreflection efficiency of the effective pyramid units and the ineffective pyramid units reaches a maximum.

[0015] Preferably, in the third step, when cutting the nickel sub-mold in the 90° direction, the cutting position is set at a distance b+a / 2 from the nearest invalid corner point of the corner cone to minimize the dark area, thereby improving the retro-reflection efficiency of the corner cone in the welding area, thereby improving the uniformity of the overall spliced ​​nickel mold.

[0016] By adopting the above technical solution, the beneficial effect of the present invention is as follows: the present invention determines the optimal cutting position range by studying the relationship between the cutting position and the change of the retroreflection efficiency. The method provided by the present invention can effectively improve the retroreflection efficiency of the joint area by simply adjusting the cutting position to the calculated optimal position without changing the existing laser welding process conditions, and improve the overall uniformity of the joint nickel mold, and the operation method is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the light reflection path of the existing micro-prism corner cone unit.

[0018] Figure 2 It is a schematic diagram of the retroreflective performance of the splicing area of ​​the nickel mold at 0° and 0° directions.

[0019] Figure 3 It is a structural schematic diagram of the cutting position of the nickel mold at 0° direction.

[0020] Figure 4 It is a structural schematic diagram of the cutting position of the nickel mold at 90°.

[0021] Figure 5 It is a schematic diagram of different positions of the nickel mold cutting at 90°.

[0022] Figure 6 It is a schematic diagram of the nickel mold splicing in the 0° direction.

[0023] Figure 7 This is the first schematic diagram of the 90° splicing of the nickel mold.

[0024] Figure 8 This is the second schematic diagram of the nickel mold splicing at 90°.

[0025] Fig. 9 This is the first reflective effect picture of the nickel mold surface after cutting and splicing.

[0026] Fig.10 This is the reflective effect picture of the nickel mold surface after the second cutting and splicing.

[0027] Fig.11 This is the reflective effect picture of the nickel mold surface after the third cutting and splicing.

[0028] Fig.12 This is the fourth type of reflective effect picture of the nickel mold surface after cutting and splicing. DETAILED DESCRIPTION

[0029] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0030] refer to Figures 3 to 8 This embodiment provides a method for splicing a nickel mold for a micro-prismatic reflective film, which is characterized by comprising the following steps:

[0031] The first step is to determine the width of the welding damage zone: take a nickel sub-mold that is the same as the nickel sub-mold to be cut and spliced, perform laser welding on the back, and then check the front of the welding position to determine the width a of the thermal damage zone caused by laser welding;

[0032] The second step is to determine the cutting position in the 0° direction: the micro-prismatic cone of the micro-prismatic reflective film is set to be a valid cone when it has a complete shape, and an invalid cone when it has an incomplete shape. The lowest valid cone is set to be a 0° cone, and the lowest edge of the 0° cone is set to be a 0° sideline. When splicing the nickel mold in the 0° direction, the cutting position is positioned at a position a / 2 away from the 0° sideline of the 0° cone to avoid the welding damage area affecting the valid cone.

[0033] The third step is to determine the cutting position in the 90° direction: set the length of the bottom side of the effective angle cone to L, set the distance between the 90° damaged edge and the nearest effective angle cone to b, 0<b≤L / 2, when the nickel mold is spliced ​​in the 90° direction, the two sides of the welding area are formed by the combination of effective angle cones with an area greater than 1 / 2 and invalid angle cones with an area less than 1 / 2 of the effective angle cone, where b is the value that maximizes the retroreflection efficiency of the effective angle cone unit and the invalid angle cone unit;

[0034] Step 4, 0° direction cutting and splicing: install the nickel sub-mold on the fixture of the precision cutting equipment, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then use the 0° edge line of the first row of effective angle cones to be retained as the reference, and cut the sub-mold along the X-axis at a distance a / 2 away from the 0° edge line. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment;

[0035] The fifth step is 90° cutting and splicing: install the nickel sub-mold on the precision cutting equipment fixing fixture, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then adjust the cutting tool to the best cutting position b and cut the sub-mold along the Y-axis. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment.

[0036] Among them, in the first step, the size of a can be optimized and controlled by process parameters such as laser spot size, welding power, welding speed, laser frequency, sub-mold thickness, etc. Its 0° cutting position, such as Figure 3 shown.

[0037] In the second step, when the nickel mold is spliced ​​in the 0° direction, if the splicing welding damage area exceeds the 0° edge line of the 0° pyramid, the light in the pyramid unit damage area and the symmetrical area cannot form effective retroreflection, resulting in a significant decrease in the pyramid retroreflection efficiency on both sides of the splicing area, making the width of the dark area significantly larger than the welding damage width. The position of its b value is as follows Figure 4 shown.

[0038] In the third step, the retroreflection efficiency of the combination of effective corner cones and invalid corner cones is set to η, and the retroreflection efficiency change formula of the unit combination is:

[0039]

[0040] When b is one-fourth of the length of the bottom side L of the micro-prism corner cone, the retroreflection efficiency of the effective corner cone unit and the invalid corner cone unit reaches the maximum, η≈61.11%, which is close to the retroreflection efficiency of the complete corner cone unit; at the same time, we performed theoretical calculations and TracePro software modeling simulations for the cases of b=1 / 2, b=1 / 3, b=1 / 4, and b=1 / 5, and the simulation results are basically consistent with the calculated values, as shown in Table 1.

[0041] Table 1. Calculation and simulation values ​​of the variation of the retroreflection efficiency of the adjacent pyramidal units in the welding area with the position of b

[0042] Serial number The value of b η calculated value ηSimulation value 1 L / 2 44.44％ 44.66％ 2 L / 3 57.14％ 57.42％ 3 L / 4 61.11％ 61.53％ 4 L / 4 58.27％ 58.68％

[0043] When cutting the nickel sub-mold at 90°, the cutting position is set at a distance b+a / 2 from the nearest invalid corner point of the pyramid to minimize the dark area, thereby improving the retro-reflective efficiency of the pyramid in the welding area and improving the uniformity of the overall spliced ​​nickel mold.

[0044] like Figure 5 As shown, two 90° cutting positions are provided, such as 90° cutting position 1 and 90° cutting position 2 shown in the figure.

[0045] Refer to Figure 6 As shown, the nickel molds are spliced ​​at 0° to obtain a spliced ​​nickel mold with good retroreflective performance and uniformity. It can be seen that the dark area at the splicing position is basically not much different from the effective pyramid position at other positions, achieving good uniformity.

[0046] Refer to Figure 7 As shown, it is Figure 5 The splicing diagram of the 90° cutting position 1 is shown. Although the two dark areas are also spliced ​​together at the splicing point, overall, it has no effect on the effective retroreflection, achieving good uniformity.

[0047] Refer to Figure 8 As shown, it is Figure 5 The splicing diagram of the 90° cutting position 2 is shown. At the splicing, the dark areas are misaligned, but overall, it has no effect on the effective retroreflection, achieving good uniformity.

[0048] Specifically, take a real case as an example, refer to Figures 9 to 12 .

[0049] A micro-prismatic nickel mold with a bottom side length of L = 0.3 mm was used. Under the process condition of a = 0.01 mm in the splicing damage area, the nickel mold was cut and laser welded under the conditions of b = 0.175 mm, b = 0.10 mm, b = 0.075 mm and b = 0.06 mm respectively. The spliced ​​nickel mold was as follows Figures 9 to 12 As shown in the figure, it can be seen that at different cutting positions, the dark areas on both sides of the splicing area will have obvious changes. The dark area when b = 0.075mm is obviously smaller than the other three groups of splicing cases, such as Fig.11 shown.

[0050] Fig. 9, The first type of nickel mold surface reflection effect after cutting and splicing, where L = 0.3mm, a = 0.01mm, b = 0.175mm;

[0051] Fig.10 This is the second type of nickel mold surface reflection effect diagram after cutting and splicing, where L = 0.3mm, a = 0.01mm, b = 0.1mm;

[0052] Fig.11 This is the reflective effect diagram of the nickel mold surface after the third cutting and splicing, where L = 0.3mm, a = 0.01mm, b = 0.075mm;

[0053] Fig.12 This is the fourth type of nickel mold surface reflective effect diagram after cutting and splicing, where L = 0.3mm, a = 0.01mm, b = 0.06mm.

[0054] In the manufacturing process of micro-prismatic reflective sheeting, the quality of the splicing of the nickel mold directly affects the optical performance of the final product, especially the retroreflective efficiency, which is a key indicator that determines the visibility and safety of the reflective sheeting at night or in low light conditions. Traditional splicing methods often ignore the specific impact of the cutting position on the retroreflective efficiency, resulting in the problem of decreased optical performance in the splicing area, affecting the overall uniformity and use effect of the reflective sheeting.

[0055] Compared with the closest existing technology, the significant technical advantage of the present invention lies in its in-depth exploration and application of the scientific relationship between cutting position and retroreflective efficiency. Through precise experiments and data analysis, the present invention determines the optimal cutting position range in the 0° and 90° directions. This innovation not only reflects a deep understanding of the structural characteristics of microprisms, but also demonstrates the advanced concept that the splicing quality can be greatly improved by slightly adjusting the cutting position while maintaining the existing laser welding process unchanged.

[0056] In the 0° direction, by positioning the cutting position a / 2 outward from the edge of the 0° angle cone (a is the width of the laser welding heat damage zone), the welding heat affected zone is effectively avoided from directly covering the effective angle cone, thereby protecting the key optical structure of the reflective film and ensuring that the retroreflective efficiency is not damaged.

[0057] In the 90° direction, by accurately calculating the b value (i.e., the distance between the 90° damage edge and the nearest valid angle cone), the optimal combination arrangement of the effective angle cone and the invalid angle cone in the splicing area is achieved. This design utilizes the principle of optical interference and adjusts the size and distribution of the invalid angle cone to minimize the interference of the splicing area on the light reflection path and improve the overall retroreflection efficiency.

[0058] This method does not require changing the existing laser welding process, and only requires fine-tuning during the cutting stage. Therefore, it is easy to promote and implement on existing production lines, reducing the cost and risk of technology upgrades. By improving the splicing quality, it directly improves the product performance and market competitiveness of the reflective film, bringing significant economic benefits to the company.

[0059] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A method for splicing a nickel mold for a microprismatic reflective film, characterized in that: The following steps are involved: The first step is to determine the width of the welding damage zone: take a nickel sub-mold that is the same as the nickel sub-mold to be cut and spliced, perform laser welding on the back, and then check the front of the welding position to determine the width a of the thermal damage zone caused by laser welding; The second step is to determine the cutting position in the 0° direction: the micro-prismatic cone of the micro-prismatic reflective film is set to be a valid cone when it has a complete shape, and an invalid cone when it has an incomplete shape. The lowest valid cone is set to be a 0° cone, and the lowest edge of the 0° cone is set to be a 0° sideline. When splicing the nickel mold in the 0° direction, the cutting position is positioned at a position a / 2 away from the 0° sideline of the 0° cone to avoid the welding damage area affecting the valid cone. The third step is to determine the cutting position in the 90° direction: set the length of the bottom side of the effective angle cone to L, set the distance between the 90° damaged edge and the nearest effective angle cone to b, 0<b≤L / 2, when the nickel mold is spliced ​​in the 90° direction, the two sides of the welding area are formed by the combination of effective angle cones with an area greater than 1 / 2 and invalid angle cones with an area less than 1 / 2 of the effective angle cone, where b is the value that maximizes the retroreflection efficiency of the effective angle cone unit and the invalid angle cone unit; Step 4, 0° direction cutting and splicing: install the nickel sub-mold on the fixture of the precision cutting equipment, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then use the 0° edge line of the first row of effective angle cones to be retained as the reference, and cut the sub-mold along the X-axis at a distance a / 2 away from the 0° edge line. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment; The fifth step is 90° cutting and splicing: install the nickel sub-mold on the precision cutting equipment fixing fixture, adjust the mold direction so that the 0° direction of the sub-mold is parallel to the X-axis of the equipment, and then adjust the cutting tool to the best cutting position b and cut the sub-mold along the Y-axis. After the cut sub-mold is aligned on the splicing platform, it is welded using precision laser welding equipment.

2. The method for splicing a nickel mold for a microprismatic reflective film according to claim 1, characterized in that: Assuming the retroreflection efficiency of the effective corner cone and the invalid corner cone unit combination is η, the retroreflection efficiency change formula of the unit combination is:

3. The method for splicing a nickel mold for a microprismatic reflective film according to claim 2, characterized in that: In the third step, when b is one-fourth of the length L of the base side of the micro-prism corner cube, the retroreflection efficiency of the effective corner cube unit and the invalid corner cube unit reaches the maximum.

4. The method for splicing a nickel mold for a microprismatic reflective film according to claim 1, characterized in that: In the third step, when cutting the nickel sub-mold at 90°, the cutting position is set at a distance b+a / 2 from the nearest invalid corner point of the pyramid to minimize the dark area, thereby improving the retro-reflection efficiency of the pyramid in the welding area and improving the uniformity of the overall spliced ​​nickel mold.

Images