KR100498822B1 - Retroreflective articles having microcubes, and t00ls and methods for forming microcubes - Google Patents

Abstract

The present invention provides a retroreflective article having a microcube and a method and tool for manufacturing the microcube. One of the retroreflective articles includes an array of microcubes in which at least one microcube in the array is rectangular 110.

Description

RETROREFLECTIVE ARTICLES HAVING MICROCUBES, AND T00LS AND METHODS FOR FORMING MICROCUBES}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool for manufacturing microcube retroreflective elements for use in the manufacture of retroreflective articles, and more particularly to articles comprising retroreflective sheeting, microcubes, and Sheet material and methods for making such tools and articles. The invention also relates to tools, articles and methods in which the microcube has a border shape other than a triangle.

Microcube retroreflective sheeting materials are now known as materials for making reflective road signs, safety reflectors, reflective vests and other garments, and other safety related products. Such a retroreflective sheet material is usually provided with a transparent resin layer such as acrylic or polycarbonate or vinyl having a plurality of retroreflective microcube elements on the flat front and back surfaces. Light incident through the sheet material and incident on the flat front surface impinges on the retroreflective element and is reflected back through the flat front surface in a nominal 180 ° direction with respect to the incident direction.

The back of the resin layer containing the microcube is further provided with layers of various materials that provide functionality to metals, hydrophobic silica, adhesives, release liners or other sheet materials that enhance the entrance angularity. do.

Cube corner retroreflectors have been used in automotive and road signs since the early 1900s. This conventional device is based on a macrocube corner element manufactured by a pin manufacturing technique. From the use of this macrocube, a number of optical principles have been disclosed using the cube corner technique, and several techniques are currently patented. Typically, these principles will involve a change in the size of the cube, the shape or inclination of the cube face, or the dihedral angle inherent between the cube faces, thereby realizing some recursive reflector performance. This known optical principle is

Increasing the efficiency of the large viewing angle recursive reflector by varying one or more of the three dihedral angles of the cube, as disclosed in US Pat. No. 3,833,285 to Heenan;

For example, as disclosed in US Pat. No. 2,055,298 to Leray and Brazilian Patent 423,464 to Heenan and US Pat. No. 3,332,327 to Heenan, the efficiency of the reflex reflector at large angles of incidence by tilting the cube axis relative to the normal ( Often referred to as "angled reflex");

As disclosed in Heenan 3,873,184 and 3,923,378, the inclusion of a cube axis incline in the array cube increases the angle of incidence of one or more planes, particularly as disclosed in US Pat. No. 3,541,606 to Heenan et al. Likewise, increasing the angle of incidence of two planes perpendicular to each other by arranging one side of each cube facing each other more parallel to the front face of the reflector;

Rotating some cubes by varying approximately normal to the front of the article, assembling the cubes in an array of variability as disclosed in U. S. Patent No. 785,139 to Uding Canadian, and as disclosed in U. S. Patent No. 3,923, 378. Increasing the uniformity of the retroreflectivity versus orientation by tilting the combined cube axis by multiple rotations.

These retroreflective optical design principles have been known in the prior art cube corner technology, but in recent years some of the prior art's applicability when applied to microcube retroreflective sheet materials could not be implemented in conventional macrocube technology. It is attempted to reclaim the patent on microcube sheet material technology because it chooses to ignore or limit it extremely.

Prior to Applicant's invention, substantially all microcube sheet materials were limited to using microcubes made by standardizing along parallel planes. Due to this limitation, the dimensions of the microcube are smaller than those obtainable by the cutting, polishing, and cleaning techniques used in pin manufacturing techniques. There is one exception to the use of conventional standardization techniques, with a limited percentage of effective openings of less than 100%, but it limits the application of known optical principles to microcubes.

According to the present invention, significant progress has been made in microcube sheet material technology. This advancement is improved both in the application possibilities for the microcube of the known retroreflective optical principle of the prior art and in the fabrication performance of microcubes of different base configurations. Prior to the description of these developments, the following further describes the information of the background art.

As a retroreflective sheet material and a method for manufacturing a microcube retroreflective element in such a sheet material is disclosed, for example, in US Pat. No. 4,486,363 to Princone et al., Assigned herein by the same assignee, and is incorporated by reference in its entirety. It is described herein. As disclosed in this US Pat. No. 4,486,363, the thickness of the resinous layer of sheet material may be 0.01 inch (0.25 mm) or less, and the retroreflective element formed on the backside of this resinous layer is plastically recursive. Triangular microcube as known in the manufacture of the reflective sheet material.

In order to produce such a microcube sheet material, a disc of a retroreflective triangular microcube is usually manufactured by normalizing the pattern of the retroreflective cube corner to the flat surface of this plate. This is described in US Pat. No. 3,712,706 to Stamm, assigned by the same assignee; 5,122,902; 5,122,902; 4,478,769, which is hereby incorporated by reference in its entirety.

As shown in Figures 1A, 2 and 3 of U. S. Patent No. 4,478, 769, the flat surface of the disc is standardized with a diamond tool that cuts a series of exactly parallel V-shaped grooves. In order to standardize an equilateral triangular microcube, three sets of parallel grooves intersecting with each other at an angle of 60 ° are formed, and each groove may have a tip angle of 70.53 ° substantially, and according to the height of a predetermined microcube, It can be standardized to the groove depth to be determined. It is automatically normalized in an array of pairs of equilateral triangular microcubes arranged to face each other with respect to the face of the master.

This standardized master can be used to make a series of replicas by electroforming and assembled with the replicas to form a single "mother" tool. This assembled "mother" tool is used for electroforming molds, which form a tool capable of providing microcube retroreflective elements on the sheet material by bumping, casting, or other means known in the art. To be assembled and ultimately used. Continuously raised methods are disclosed in the aforementioned US Pat. No. 4,478,769, and casting techniques for forming microcubes are disclosed, for example, in US Pat. Nos. 3,684,348 and 3,689,346 to Rowland.

As will be described below, triangular microcubes having a base different from an equilateral triangle are used to realize improved degree of irradiation angle by use of the known optical principle disclosed in the macrocube technique. Therefore, as disclosed in US Pat. No. 4,633,567 to Montalbano, assigned by the same assignee, the change in the triangular microcube changes the tool normalization angle to tilt the cube axis, whereby some conventional techniques for microcube technology It can be realized by adopting and applying the optical principle of the technology. For example, it is possible to realize arrays with different degrees of irradiation or azimuth. (Columns 10, 11. 1-18 of US Pat. No. 3,684,348 to cf Rowland; US Pat. 4,633,567, columns 6, 11.4-36).

As noted above, US Pat. No. 3,833,285 discloses that the viewing angle of the cube corner retroreflective can be increased in one plane by increasing or decreasing the angle of one of the three dihedral angles of the cube. U.S. Patent Nos. 3,873,184 and 3,923,378 disclose arrays of retroreflective elements in which the cube axes of adjacent cubes are inclined with respect to one another and are disposed opposite one another such that the irradiation angle is increased. It is disclosed that the degree of irradiation angle is increased in two planes perpendicular to each other when one cube face of cubes disposed opposite each other is more parallel to the front face. Each of the foregoing patents is described herein for reference.

The same optical principles used in microcubes to improve retroreflectivity can be applied to small size triangular cubes as used in retroreflective sheeting. Therefore, U. S. Patent No. 4,588, 258 to Hoopman discloses a novel angled retroreflective article, in which an array of triangular microcube elements has a pair of pairs that match the cube's cube axis in each pair inclined relative to each other. Although it includes a set, it is, for example, face-more-parallel (hereinafter referred to as facet-more-parallel; hereafter assigned to the same assignee of the present invention, US Pat. Nos. 3,541,606, 3,923,378 or 3,873,184). The structure is simply duplicated. In addition, matched pairs of triangles by Hoopman are limited to the case where triangles that are standardized at Hoopman's application are only used to make microcubes.

Similarly, US Pat. No. 4,775,219 to Appeldorn et al. Discloses a retroreflective article of varying viewing angles with an array of microcube retroreflective elements formed by three intersecting sets of parallel V-shaped grooves, At least one of the three sets of intersections includes at least two groove side angles different from each other in a repeating pattern. An article by Appeldorn clearly embodies the same principles disclosed in US Pat. No. 3,833,285, assigned by the same assignee of the present invention.

However, all triangular cubes have the drawback that essentially only 66% of these areas can be retroreflected for any particular angle of incidence while providing adequate retroreflectivity. In an attempt to overcome such deficiencies of triangular cubes, a series of international patent applications (published publications WO 95/11463: WO 95/11465; WO 95/11467; WO 95/11470) by Minnesota Mining and Manufacturing Company An array of microcubes containing some non-triangular cubes and techniques for standardizing such arrays are disclosed. However, the arrays disclosed in these patent applications have cubes of significantly different heights (which may pose manufacturing challenges) and greatly varying aperture sizes (affecting diffraction and impact in retroreflectivity). Even at best, the arrays disclosed in these patent applications provide 91% of the effective openings calculated, which, when considering the manufacturing method (see, eg, FIG. 12 of WO 95/11470), drops to about 87%. It can be seen as. If the cube is inclined by the disclosed standardization technique, its efficiency is lowered more evenly. The ability to form these cubes by intersecting normalized grooves parallel to a single plane is inherently limited in the results available.

Techniques and articles according to the present invention may be obtained by initial triangular microcube as shown in the figures of the present invention and described in detail herein, or in more recently standardized mixtures of triangular and non-triangular cubes. This has the advantage of being flat.

Unlike triangular cube corners, hexagonal and rectangular cube corners have the advantage that 100% of these areas can be uniformly retroreflected even at large angles of incidence. However, unlike triangular cube corners, hexagonal and rectangular microcubes are not defined as continuous straight lines extending along a flat plane, and thus cannot be standardized as an intersection set of all parallel lines parallel to the common plane. . Thus, the only exception to rectangular cubes is disclosed in U.S. Patent Nos. 4,349,598 and 4,895,428 (one of the valid cube faces is perpendicular to the front face of the reflector), whereby these patents produce straight lines in a single flat plane. By standardizing it is not possible to cut or standardize a master containing all hexagonal or all rectangular microcubes. In addition, due to geometric limitations in standardizing cubes for U.S. Patent Nos. 4,349,598 and 4,895,428, the cube structure disclosed herein is not useful when the main light source is incident at nearly zero angles of incidence, such as road sign sheet material. Will not.

Methods of making tools with macrocubes are known in the art. Such a tool is typically manufactured by assembling a cluster of metal pins, each pin having a single cube corner that is mechanized and polished on one end. Hexagonal pins may have dimensions in parallel planes of about 0.10 inch (2.5 mm). Rectangular pins may have short dimensions of about 0.07 inches (1.8 mm) and long dimensions of about 0.120 inches (3.0 mm). These clusters of pins are used as masters for electroforming molds. These large cubes are too large to be used in the manufacture of the thin plastic retroreflective sheeting materials required for microcube because of their height, but where large retroreflective elements such as plastic reflectors and automotive taillights cast for road signs are acceptable. Practicality can be found in

Due to manufacturing constraints, the known ones with the smallest fins have a cube shape of about 0.040 "square. The microcube used for plastic retroreflective sheeting material is no greater than about 0.016 inch (0.4 mm) on the side. The sheet edge product marketed by the same assignee of the present invention, the largest edge of the cube shape is about 0.010 inch (0.25 mm).

Microcubes (or small dimension cubes) are standardized, as opposed to retroreflective articles comprising macrocubes typically formed by grouping fins (or by other techniques used to form large cubes). It is used in other patents for sheet material manufactured by tools which are manufactured directly or indirectly from the master.

Other alternatives related to “pin cluster” fabrication techniques for finishing hexagonal cubes include Applied Optics, Vol. 20, No. 6, p, 1268 (April 15, 1981). In this document, a method is disclosed in which a hexagonal cube corner can realize assembling a plane at a desired angle while precisely glossing a groove on the edge surface of a stack of flat plates. Referring to this document, photographs of several plates are shown in which adjacent plates are displaced relative to one another so that the grooves are cut and the grooves are offset at one edge stacked on the vertex. Flat plates of inclined stacks assembled according to a set of hexagonal cubes can be used as masters for electroforming molds. However, this technique is disclosed in the above-mentioned ten documents by the same assignee and is an unsatisfactory technique for cleaning reflex reflectors, but see US Pat. No. 1,591,572 (FIG. 16, p. 5, 11. 85-99). Is discussed.

Previously, the "laminated flatbed" method described above for making macrocubes has not really attracted interest in producing molds for retroreflective products upon commercial sale. First, the mold for the macrocube can be satisfactorily produced by the aforementioned clustering of the hexagonal pins. Secondly, by using conventional mechanization and polishing techniques, as recognized in US Pat. No. 1,591,572, the internal intersections can be cut and polished with precise angular tolerances and the edges obtainable by fin technology It is impossible to sharpen it.

In particular, any irregularities in the cube surface that can be generated by either cutting or polishing operations can unreasonably increase the divergence of retroreflected light, thereby reducing the effective retroreflectivity of the cube formed by the prior art. Can be reduced. This perceived difficulty in polishing the inner angles in which the grooves are formed is further exacerbated in the microcube because areas that cannot be polished uniformly occupy a relatively large percentage of the cube surface area that will result.

As part of this application, Applicant discloses a method of making and using thin plates that can be ruled and assembled in a variety of ways to obtain microcubes that were previously unavailable.

It is an object of the present invention to provide an array of microcubes that cannot be produced by ruling in one plane.

Another object of the present invention is to provide an array of microcubes whose non-diagonal faceted edges are not all parallel to the common plane.

Another object of the present invention is a means of correlating three structural parameters (e.g. slippage, groove depth and plate thickness described below) that define a hexagonal microcube to optimize the desired optical properties of the microcube. To provide.

It is a further object of the present invention to provide a retroreflective article, in particular a retroreflective sheet material having a pattern of hexagonal retroreflective microcubes having desirable retroreflective properties.

It is a further object of the present invention to provide a method of manufacturing a retroreflective article, in particular a retroreflective sheet material, a tool comprising two or more adjacent hexagonal microcubes.

It is a further object of the present invention to fabricate and partially fabricate the plates to form an array of hexagonal microcubes with desirable retroreflective properties by ruling the set of grooves into the ends of the set of plates, It is to provide a method of manufacturing a tool having a pattern.

It is another object of the present invention to provide an article having a hexagonal microcube with all cube faces pentagonal, to provide a tool for making such an article, and to provide a method for making such an article and a tool.

It is a further object of the present invention to have a retroreflective microcube where the dihedral face edges of one cube are not collinear with the dihedral face edges of the other cube, in particular the retroreflective properties in which the microcube provides the desired retroreflective properties. It is to provide an article, in particular a retroreflective sheet material.

It is another object of the present invention to have a unique pattern of rectangular microcubes in which the cube axis tilt is not limited to the need for collinearity of the dihedral surface edges of adjacent cubes, and the retroreflective article, in particular the retroreflective sheet material To provide a tool that can be used to manufacture the.

Yet another object of the present invention is to provide a method of manufacturing a tool which has a pattern of rectangular microcubes whose dihedral face edges are not collinear and can be used to produce retroreflective articles having rectangular microcubes such as sheet material. It is.

It is a further object of the present invention to provide a method of manufacturing a tool having a pattern of rectangular microcubes and which can be used to partially fabricate grooves and slopes into an end to provide the desired rectangular cube shape and pattern.

It is yet another object of the present invention to provide a method of manufacturing a rectangular microcube tool by assembling a plate having a rectangular microcube formed on one end.

It is another object of the present invention to provide an article in which a square set of four cubes of microcubes has a cube axis inclined in four different directions and has a pattern of retroreflective square microcubes.

It is another object of the present invention to provide an article having a pattern of retroreflective pentagonal microcubes, to provide a tool for making such an article, and to provide a method of making such an article and a tool.

Another object of the present invention is to provide an article having a pattern of pentagonal microcubes with an inclined cube axis, an article having a pentagonal microcube with differently inclined cube axes, and providing a tool for manufacturing such an article, It is to provide a method of manufacturing such articles and tools.

It is a further object of the present invention to provide a retroreflective article having a cube shape and at least one triangular microcube whose projected position of the cube vertices within the cube shape is independent of the cube axis tilt.

It is yet another object of the present invention to provide a retroreflective article in which adjacent triangular microcubes can have cube axes of different inclinations and are unnecessarily matched pairs.

Other objects, advantages and novel features of the invention will be readily apparent to those skilled in the art from the following specification and the accompanying drawings.

1 is a perspective view of a steel block for forming an electroless nickel plate used in the present invention.

FIG. 2A is a cross-sectional view of the block of FIG. 1 seen in the direction of arrow 2-2 after depositing an electroless nickel layer on the top surface of the block.

FIG. 2B is a cross-sectional view of the block of FIG. 1 and the electroless nickel deposit after machining one of the top edges. FIG.

2C is a cross sectional view of a block in which the electroless nickel plate is separated and electroless nickel residue remains in one of the block lower cuts.

3 is a perspective view of a stack of electroless nickel plates before being ruled.

FIG. 3A is a view from a direction perpendicular to the face of one of the plates of FIG. 3 showing the arrangement of dowel holes used in one method of aligning the assembly of the plate for rubbing with the electroforming disc. FIG.

4 is a perspective view of the same plate stack after the groove is ruled.

5 is a perspective view of the plates of FIG. 4 with adjacent plates offset by groove depth in the vertical direction and by 1/2 groove width in the horizontal direction.

FIG. 6 is a side view of the plate stack of FIG. 5 with "L" (as shown in FIG. 4) equal to "t" and seen in the direction of arrows 6-6.

6A is a view from the direction of arrows 6A-6A in FIG. 6.

FIG. 6B is a view from arrow 6B-6B direction of FIG. 6 with different shades added to emphasize the offset between adjacent plates. FIG.

7A is a view of a portion of the front face of a cutting tool used to rule the groove of the plate end in a direction perpendicular to the front face in accordance with the present invention.

7B is a view from the direction of arrows 7B-7B in FIG. 7A, and is a side view of the cutting tool in FIG. 7A.

8A is a view of a portion of the front side of a cutting tool when tilted to cut a groove.

Fig. 8B is a side view of the cutting tool of Fig. 8A, showing the inclination e of the surface of the tool and viewed in the direction of arrows 8B-8B and cutting direction of Fig. 8A.

FIG. 9 shows one complete groove when cut into the plate at an inner groove angle c + Δc corresponding to the inclination e of the cutting tool.

FIG. 10 is a side view of a laminated plate similar to the laminated plate of FIG. 6 but with "L" greater than "t" and adjacent plates offset by groove depth d in the vertical direction and 1/2 groove width in the horizontal direction.

10A is a view from arrow 10A-10A in FIG. 10 along the diagonal of the cube formed by the plate to coincide with the principal reflected light beam.

10B is a view from arrow 10B-10B in FIG. 10 perpendicular to the plane passing through the cube vertex.

Figure 10C is a view from the direction perpendicular to the plane of the plates with different shades added to emphasize the offset between adjacent plates.

11 is a side view of a stack of plates ruled with grooves and set at a very exaggerated angle to show the cutting plane.

FIG. 11A is a side view of the stack of the plate of FIG. 11 after ruling and offset relative to adjacent plates by a groove depth in the vertical direction and 1/2 groove width in the horizontal direction.

11B is viewed in a direction perpendicular to the plane of the face of the plate illustrating that the edges of the grooves are angled with respect to the vertical line with respect to the face of the plate (only a portion of the plate is shaded differently for illustrative purposes) (see FIG. 11A Along the arrows 11B-11B).

FIG. 12 is a side view of a stack of plates laminated with offsets of adjacent plates of " L " equal to " t " but 1.64t vertically and 0.707t horizontally as in FIG.

12A is a view showing the projection viewed from the direction of arrows 12A-12A of FIG. 12 parallel to the diagonal of the cube.

12B is a front view of the plates of FIG. 12.

12C and 12D are diagrams illustrating the interrelationships of various cube parameters for different incident light rays.

FIG. 13 is a paired array of hexagonal microcubes, d = 0.55t and s = 0.45t, formed of a laminated plate similar to FIG. 12 and providing a face-more-parallel microcube of 9.74 °. Partial side view of the article comprising a.

14A and 14B are partial plan and side views, respectively, of the plate before machining the rectangular cube.

15 is a schematic side view of a cross section of a stack of spacers and replacement plates inclined at an angle X for machining inclined surfaces with a cutting tool.

16A and 16B are partial plan and side views, respectively, of the single plate of FIGS. 14A and 14B after machining the inclined surface.

FIG. 17 shows a cross section of a stack of spacers and a replacement plate after machining the inclined surface, similar to FIG. 15, wherein the space between the plates is filled with plastic in the manufacture of the working groove.

FIG. 18 shows a cutting tool (and subsequent grooves cut along the dotted line) moving towards the plane of the paper and machining the grooves and arrows 18-18 of FIG. 17 for the stack of spacers and plates after partial machining of the groove face; It is the figure seen from the direction.

FIG. 19 is a side view of a cross section of the single plane of FIG. 18 seen in the direction of arrows 19-19. FIG.

FIG. 20 shows a rectangular outline of the microcube corner and a representative microcube is shown in the circle of dotted line and is a plan view seen from the direction of arrows 20-20 of FIG. 19 after a single plane has been processed.

FIG. 21 is a stack of three plates machined as in FIG. 20 with adjacent plates oriented at 180 ° to each other, assembled and used as discs in electroforming, with representative individual coves represented by three sides dotted. Top view.

FIG. 22 shows a plate after cutting an inclined plane perpendicular to the plane of the pedestal of the ruling machine, in which the plates having a thickness twice as used in another method of the present invention constituting a rectangular microcube are positioned at an angle (90 ° -X). Partial side view of the.

FIG. 22A shows a cutting tool when positioned to cut the inclined surface of FIG. 22. FIG.

FIG. 22B is a view showing the temporary surface and the first inclined surface processed to the plate end by the cutting tool and viewed in the direction of arrows 22B-22B in FIG. 22.

FIG. 22C is a view showing the first inclined surface and the temporary surface in FIG. 22 filled in the manufacture of the cutting groove. FIG.

FIG. 23 is a view showing the plate of FIG. 22 during cutting of the groove face viewed in the direction substantially perpendicular to the direction of the first inclination cut by the second cutting tool.

FIG. 23A is a cross sectional view through FIG. 23 in the valley of the cutout for the groove face, seen in the direction of arrows 23A-23A in FIG.

FIG. 23B is a view from the direction of arrows 23B-23B in FIG. 23A after cutting the groove face to form a first-order rectangular cube in which one of the rectangular cubes is indicated by the dotted surface in the dotted circle;

FIG. 24 is a side view of the plate of FIG. 23A repositioned to cut a second sloped surface for the cube of the second row of cubes by the first cutting tool to remove the temporary surface (as shown by dashed lines).

FIG. 25 is a front view of the plate of FIG. 24 after removal of the second slope for the cubes of the second row and during machining of a new groove surface substantially perpendicular to the second slope.

25A is a cross sectional view of the cutout for the groove face of the second row of cubes seen in the direction of arrows 25A-25A of FIG. 25.

FIG. 25B is a plan view of a finished plate for use as a pole master, as seen from the direction of arrows 25B-25B in FIG. 25A, showing the slope and groove faces of the second row of cubes with one cube in the second row indicated in a dashed circle. It is a figure.

26 is a top view of two square microcubes.

FIG. 27 is a front view of the plate for forming the square microcube of FIG. 26 viewed in the direction of cutting the groove surface where the valleys of the grooves are parallel to the intersections of the inclined surfaces but offset above.

FIG. 27A is a cross sectional view taken from the direction of arrows 27A-27A in FIG. 27 taken through the groove of the groove; FIG.

FIG. 27B shows a finished plate for use as an electroforming disc and seen in the direction of arrows 27B-27B in FIG. 27A.

FIG. 27C is another partial side view illustrating an array of rectangular microcubes configured in a similar manner to FIGS. 27-27B except that H = 2W, the axis is tilted, and the vertex is lowered, similar to FIG. .

FIG. 28 is a diagram illustrating a rectangular cube in which three main optical parameters (vertical descent, boundary ratio and axial tilt) have been changed for illustration and not shown but the cube size is the fourth parameter.

FIG. 29 shows an improved rectangular cube with more parallel planes when used as a pavement sign at 55 ° incidence, for example.

FIG. 29A shows the protrusion of the cube of FIG. 29 parallel to the main reflected beam.

30 is a rear isometric view of an array of cubes of the type shown by the indicator of FIG. 29.

FIG. 31 is a diagram illustrating the pores of a triangular microcube with bases that are not all parallel.

FIG. 32 is a diagram illustrating an array of square microcubes that provide four orientations without slippage walls.

33 is a plan view of a plate with a single row in the form of a square cube shown in FIG. 32 with three cutting steps indicated.

34A and 34B show a plate with a rectangular microcube having inclined surfaces ruled in a direction perpendicular to the front of the plate, as compared to the pore method described in FIGS. 15-21 in which the inclined surface is ruled in a direction parallel to the front of the plate. Top and side views showing parts.

35 is a plan view of a five-sided hexagonal cube array with the ends of the brightest one plate.

36 illustrates an array of pentagonal microcubes constructed in accordance with the plate processing technique of the present invention.

FIG. 36A shows two pentagonal microcubes with different slopes; FIG.

FIG. 37 shows micros with various refractive indices for incidence angles from -90 ° to + 90 ° for an array of hexagonal microcubes with d / t = 0.7071, s / t = 0 of the type shown in FIGS. 6-6B. Graph showing a group of curves comparing the retroreflectivity of cubes.

FIG. 38 shows the curve of retroreflectivity for incidence angle I from −90 ° to + 90 ° for an array of unpaired hexagonal microcubes with an index of refraction = 1.49 with d / t changed and s / t = 0. Graph showing group.

FIG. 39 is a graph showing a group of curves of effective aperture percentages (instead of retroreflectivity) for the angle of incidence I from -90 ° to + 90 ° for the same microcube used in FIG. 38.

FIG. 40 compares the effectiveness shown by the effective aperture percentage and the retroreflectivity and the effectiveness of the rectangular microcube paired with the paired array of hexagonal microcubes of FIGS. 13 and 27C at angles of incidence from 0 ° to 70 °. graph.

FIG. 41 shows the retroreflectivity versus the rectangular microcube of the present invention in FIGS. 29 and 30, compared to a rectangular microcube with a cube axis tilt angle of 1.9 ° for a non-square plane perpendicular to the front face of the reflector as in the prior art. Graph showing a group of curves of horizontal entrance angles.

42A-42E show zero for a paired array of hexagonal microcubes with a refractive index of 1.59 for each of the five cube axis tilt angles compared to the retroreflectivity of the triangular microcube retroreflective article of Hoopman, US Pat. No. 4,588,258. 3 groups of curves of entrance angle versus retroreflectivity between ° and 70 °.

FIG. 43 is an angle of incidence from 0 ° to 60 ° in a plane perpendicular to the plane of symmetry for the inclined hexagon of a paired array and the inclined hexagon paired in comparison to the US inclined Hoopman's US patent. Plot of vs retroreflectivity.

FIG. 44 shows an entrance angle of -20 ° to 20 ° for a paired rectangle and paired squares both without the angle of inclination, compared to the array of microcubes from FIG. 12 of the conventional published European patent WO 95/11470. Figure showing the effective opening percentage for.

FIG. 45 is an entrance of -70 ° to 70 ° for an array of inclined hexagonal microcubes paired with a pair of inclined rectangular microcubes, compared to FIG. 32 of conventional published European patent WO 95/11463. Graph showing each versus effective aperture percentage.

46A-C show diffraction effects on retroreflected light patterns for three different sizes of hexagonal microcubes.

These various drawings are not drawn to scale, are shown for illustrative purposes and are not limiting. The various graphs are likewise illustrative rather than limiting and shown for comparison. Other graphs and embodiments will be apparent from the detailed description below.

According to the present invention, a method of manufacturing a tool having a pattern of microcubes used to make a retroreflective article is disclosed. Each plate provides a plurality of plates having at least one end and two substantially parallel planes made of a material that can be cut by a cutting tool that will produce an optical surface, such as a cut. The plates have a thickness “t” of very small size, ie, similar to the width of one or two microcubes, depending on the shape of the microcube corners being drilled. The thickness need not be the same for all plates.

Various shapes of the microcube can be manufactured using the plate treatment process disclosed herein. The two shapes, hexagonal and rectangular, are discussed in more detail, and other shapes will be discussed more generically to illustrate the flexibility of the process.

Hexagonal Microcube

In order to produce a pattern of hexagonal microcubes, the plates are stacked one by one such that, in a preferred form, an end set of cutable material lying substantially on a single side is substantially perpendicular to the parallel plane of each plate. A series of parallel V-shaped grooves is ruled using a cutting tool with a set of cuttable ends. Ruled grooves preferably have a polished surface by cutting, thus eliminating the need for continuous lapping and polishing as in the pins used in microcube fabrication.

In one embodiment of the present invention, the direction of cutting the groove is nominally perpendicular to the plane of the plate, and the length "L" of each inclined surface of the groove perpendicular to the cutting direction is equal to the thickness "t" of the plate. Selected equally, the narrow angle between the inclined surfaces is about 90 °. The narrow angle can be varied from 90 ° by inclining the cutting surface of the cutting tool with respect to the surface to be cut.

In order that the upper edge of the groove of one plate coincides with the lower edge of the ruled groove of the adjacent plate, the grooved plates are horizontally one half of the groove width and vertically one groove vertically and possibly but not necessarily Are offset from each other by the depth "d", resulting in an array of two overlapping hexagonal cube corners. One array consists of female (concave) hexagonal cube corners each formed by the addition of two faces of one groove of a subsequent adjacent plate plus an exposed plane of one plate. The other array consists of male (convex) hexagonal cube corners each formed by the addition of two adjacent surfaces and an exposed plane of one plate from adjacent grooves on the same plate. In order to further improve the accuracy of the resulting retroreflective article, several cube corners are preferred because they can avoid any angular error between plates.

Rectangular microcube

In order to create a pattern of rectangular microcubes, in one embodiment plates of the selected thickness "t" are alternately stacked as a slightly shortened spacer. The assembly of plates and spacers is inclined at any desired angle to have a set of edges of the cuttable end lying on a plane parallel to the workbench of the ruling machine. Thereafter, the cuttable end of each plate is cut into the slope by the cutting tool such that the slope is perpendicular to the workbench of the machine defined above. Thereafter, a series of preferred narrow grooves are cut by the cutting tool in a direction substantially perpendicular to the slope. To create an electroform master comprising a rectangular microcube, the spacer is removed, and then the plate has a vertex of a rectangular cube corner that lies all in the same plane perpendicular to the side of the plate and into the grooves. Stacked together with adjacent plates rotated 180 ° relative to each other with the vertices of the cube in adjacent parallel plates.

Manufacture of articles

Laminated plates of grooved plates (for hexagonal cubes) or grooved bevel plates (for rectangular cubes) are US patents for the production of retroreflective articles, in particular retroreflective sheet materials that do not have the pattern of existing hexagonal or rectangular microcubes. It may be used as a disc for initiating a mothering process or for electroforming a mold insert for electroforming a larger mold insert or embossing belt as disclosed in 4,478,769. The use of a hexagonal or rectangular microcube instead of a triangular microcube advantageously increases the effective opening of the article as if projected in parallel to the principal refractive ray from less than 66% to essentially 100%.

Explanation of terms

For the purposes of the present application, Applicant uses any term in a special sense as defined herein, and also uses other terms according to the examples commonly used in the art, such as the definition of existing ASTM. Many of these definitions distinguish between cubes and cube shapes, which are each defined herein.

Adjacent-For a microcube, it means that some of the edges of one cube shape essentially coincide with some of the edges of the other cube shape.

Angle of incidence-The angle between the normal to the front of the retroreflective reflector and the illumination axis. See also "entrance angle".

Array active aperture-The sum of the effective openings of the individual microcube elements that form an array. (See also "effective opening percentage.")

Contiguous microcubes-The non-diagonal face edges of one microcube that coincide with the non-faceted face edges of another microcube. Compare with "Nearby Cube". The contactless microcube may be adjacent. The array of contact microcubes is one in which the non-diagonal face edges of each microcube (except the periphery of the array) coincide with the non-diagonal face edges of the other microcube.

Cube (or "cube corner")-an element consisting of three nominally perpendicular faces, regardless of the size or shape of the surface, referred to in the art or literature as "corner cube", "trihedron" or "tetrahedron" Collectively.

Cube Area-The area surrounded by the cube geometry.

Cube Axis-A central axis that is three quarters of the interior space defined by the three intersecting faces of the microcube. It is often called "symmetry axis" in the technical field.

Cube Axis Slope-The angle between the cube axis and the main refractive beam. The sign of the slope is more parallel to the face (hereinafter referred to as face parallelism) (negative for face-more-parallel) and more parallel to the edge (hereinafter referred to as edge parallelism) ( It is positive for edge-more-parallel). The cube is considered to be inclined if the cube axis slope is not zero.

Cube Diagonal-For any cube corner, at an angle to cause all lines through the vertex that terminate on both ends of the cube shape to be bisected by the vertex in projecting the contour of the cube corner parallel to the cube diagonal. An imaginary line passing through a vertex of a cube corner.

Perimeter of a cube-A closed spatial curve containing non-diagonal edges of the cube's surface. Where there is a continuous surface shared by two or more microcubes, the divided lines between the microcubes are considered to be the shortest lines that can be constructed to complete the polygon (see FIG. 27B).

Cube shape-A two-dimensional geometric shape defined by the projection around the cube in the direction of the principal refractive ray. Thus, the triangular cube has a triangular cube shape, and the hexagonal cube has a hexagonal cube shape.

Cube symmetry plane-A face that divides cube corners into mirror images. Not all cube corners have a plane of symmetry.

Design Rays-An imaginary line through the cube vertices in the tool, which coincides with the main refractive ray in the article.

Diagonal Face Edge-The intersection of two sides of a single cube.

Entrance angle-The angle between the light axis and the optical axis (recursive reflector axis). Note the distinction between the entrance angle and the angle of incidence. The angle of incidence is always measured between the normal to the surface (which may or may not be the reflex reflector axis) and the incident beam, while the entrance angle is measured between the incident light and the retroreflector axis (which may or may not be normal to the surface). The entrance angle is measured only in the amount that the incident light is angled with respect to the retroreflector axis and is not related to the normal: the angle of incidence is angled with respect to the normal and not related to the retroreflector axis. It is measured only in the amount of cases. For example, when a paver marker is designed perpendicular to the marker surface to make an angle of 60 ° to the optical axis; If the light of the approaching vehicle is incident on the beacon along the retroreflector axis, the entrance angle is 0 ° and the angle of incidence is 60 °, and the light of the approaching vehicle is at a horizontal angle of 20 ° relative to the retroreflector axis. If incident on the phase, the entrance angle is 20 ° and the angle of incidence is 61.98 ° = [cos ^-1 (cos60) (cos20)].

"Plane parallelism" and "edge parallelism" relate to the positioning of the cube in relation to the principal refractive ray. If the angle between the cube surface and the main refractive beam does not coincide with 35.26 °, the cube depends on whether the plane angle is greater than or equal to 35.26 ° or less for 35.26 ° and the most different main refractive beam, respectively. More parallel to "or" more parallel to edge ". If the main refracting ray is a sheet material or other retroreflector that is typically perpendicular to the front of the retroreflector, for the face parallelism microcube, the cube face selected is also more in front of the reflector than any face of the non-inclined microcube. Will be parallel.

Horizontal Entrance Angle-For pavement markings, the angle in the horizontal plane between the direction of incident light and the reflex reflector axis.

Microcube (or “microcube corner”) — cube corner with a maximum area of about 0.0016 square inches (1 mm 2).

Non-dihedral face-edge-An edge of a microcube face that is not a dihedral face-edge, that is, an edge that is a segment around a cube.

Optical axis-a designated line segment from the center of the retroreflective reflector selected from the center of the intended illumination direction, such as the direction of the road on which the retroreflective is to be mounted above or in relation to it.

Paired-oriented oppositely. Paired cubes as used herein refers to adjacent cubes oriented oppositely. In addition, the paired array as used herein refers to cubes in one array that are oriented opposite to the other cube.

Percent Active Aperture-The portion of the protruding area of the array that functions recursively for a specific selection direction of the protrusion (this definition assumes that the back side of the cube has 100% reflectivity. / Same as the definition used for lines 11 to 25 of pages 11 to 11470.)

Primary incident beam-A beam parallel to the optical axis selected so that the beam after reflection at the front of the article passes through the vertex of the cube corner.

Primary reflected beam-An extension of the main incident beam after reflection from the front of the retroreflective reflector.

Recursive reflectance-product of the effective aperture percentage and the reflectance of each cube face and the square of the transmittance of the front face (to offset the Fresnel loss), which includes the term "recursive reflectance" of the front face loss. / "Total67 return" as defined in lines 17 and 26, page 27 of 11467). Retroreflectivity is a measure of the total retroreflective accumulation over all suitably small observation angles and all rotation angles.

Recursive reflector axis-same as "optical axis"

Ruleable-can be generated by repeated linear movements of the forming tool along a path parallel to the common plane.

Zone of Retroreflective-Range of entrance angles in a given plane of plane where the retroreflective reflector maintains a predetermined minimum retroreflectivity

The method of the present invention for forming a microcube may utilize the principle of ruling the end of any plate in a particular form, and these plates may be specifically combined to form an array of microcubes. As used herein, "array" means a repeating pattern of geometric elements, including microcubes. Those skilled in the art will appreciate that retroreflective articles having desirable performance characteristics can be made by synthesizing different arrays. For example, such articles may comprise different arrays of each made by one or more techniques of this invention, or such articles may comprise a combination of the array of the invention and an array made by prior art machining methods. have. Means for combining different arrays into a single article are known to those skilled in the art, and one or more retroreflective articles having multiple arrays and made in accordance with the present invention are considered to be within the scope of application of the present invention. In all cases where different arrays are combined, it will be understood that the specification and claims relate to the array or portion of an array made by the technology of the present invention.

The various examples discussed below represent the simplest form of advancement in this technology, and provide specific embodiments in which the performance of the improved retroreflector can be achieved in the microcube using the same optical principles that have been adopted in the microcube. It is starting.

All embodiments of the present invention require the use of somewhat different plates for different types of microcubes. The thickness of this plate is about 0.004-0.040 inch (0.1-1.00 mm) fine size. The plate has four basic forms. The plate 10 suitable for the tooling of a hexagonal microcube with a rectangular cube face has flat and parallel faces and should have a polished surface because only one side of the plate becomes the face of the cube. Plates 110 and 210 suitable for the fine pores of rectangular and triangular microcubes have flat and parallel faces, and preferably no surface of the plate is the face of the microcube. The plates 710 and 810 suitable for ruling the pentagonal microcube of FIG. 36 have one flat side and one grooved side and do not become the face of any shaved microcube. A plate suitable for drilling a hexagonal microcube having a pentagonal face of FIG. 35 and cutting two rows of the pentagonal microcube with respect to one plate has grooves formed on both sides, and the gap between the grooves and the angle of the grooves are formed on both sides. It does not necessarily have to be the same for each other.

Plate manufacturing method

The plate should be formed of a material that is cleanly cut when ruled by something such as a diamond cutting tool as is known in the art. Electroless nickel is particularly suitable for the ruleable plates used in the process of the invention.

Although different from the plate described above, the method of making the plate is generally described by the method of forming the plate 10 used in the manufacture of the hexagonal microcube. For illustration purposes, the plate 10 may have dimensions of about 1.0 "x 4.0" and a thickness of about 0.010 ".

In FIG. 1, a stainless steel block 601 is provided having a flat top surface 602 of about 1.0 "x 4.0". This block 601 may be made of stainless steel of grade 440C. Surface 602 of block 601 is ground and polished. The undercut is machined into two 0.75 "x 4.0" sides. These two sides are tapered from 0 to 0.005 "on the polished surface 602 and the depth is 0.250" down from the polished surface 602. Block 601 is surface stabilized, for example, by precipitation in 30% nitric acid for 10 seconds, and electroless nickel 604 is preferred to the polished top surface 602 of the stainless block, as shown in FIG. 2A. In addition to the thickness of about 0.002 ", in this embodiment the overall thickness of the top surface of the block is 0.012 " and the deposition is approximately 0.25 " below the side of the block.

The 1.0 "x 4.0" surface 609 of the electroless nickel 604 is machined with a diamond tool to the desired thickness, 0.010 "in this embodiment. The electroless nickel is undercut at position 605 in Figure 2B. The side of the block is machined at position 605 in FIG. 2B using a diamond tool to cut from the top to the stainless, and frees the electroless nickel plate 606 of FIG. 2C to a thickness of 0.010 "to separate from the stainless block. The undercut in the block is removed by pulling the loose wedge 607 in FIG. 2C of electroless nickel in the undercut. The process for forming as many plates 606 as necessary is repeated. In a subsequent step, the plate 606 may be identified as 10, 110 or 210 in the pore of each of the hexagonal, single rectangular or bi-rectangular microcube.

In the pores of the hexagonal microcube, a portion of the surface (FIG. 2C) of the electroless nickel plate 606 in contact with the polished surface of the stainless block will be one side of the cube corner. A surface 609 having dimensions of approximately 1.0 "x 4.0" of electroless nickel may also be provided for optical finishing during the step of machining the size of the plate using a diamond tool, in which case the surface of the stainless steel block is polished. It will be unnecessary. For the pores of the rectangular microcube, since neither surface of the plate is the surface of the microcube, it will be unnecessary to polish the surface of the stainless steel block before electroforming.

Hexagonal microcube manufacturing method

As shown in FIG. 3, the plate 10 is preferably flat, with each plate having at least one flat end 12 having an end that can be cut by a diamond cutting tool. The plates 10 are joined together so that at least one set of ends 12 lies in the plane. It will be appreciated that the three plates shown in FIG. 3 are for clarity and that three or more plates may be included in a single stack. A set of V-grooves 14 are ruled in the end 12 set. 4 shows a stack of identical plates 10, with the V-shaped grooves 14 being ruled at the straight ends 12. The grooves 14 are preferably parallel to each other and substantially perpendicular to the front surface of the stack of plates 10. The V-shaped grooves have a narrow angle of approximately 90 °, each groove being formed of two top edges or ridges 20 and a bottom edge or valley 21. For optimal efficiency, the grooves 14 are spaced apart from each other and separated only by the upper edge 20 of adjacent grooves, so that there is no substantially flat surface between the grooves 14.

7A and 7B are front and side views showing a part of a cutting tool for rubbing a groove. Where C is the angle between the cutting edges perpendicular to the front of the tool, the angle C may be chosen to be smaller than the narrow angle C + ΔC required in FIG. 9 so that the fine adjustment of the angle of the groove is relatively large in FIG. 8B. It can be made by tilting the tool in positive amounts. "E" is an angle in which the plane of the cutting tool is inclined from the right angle with respect to the direction of cutting as in the following equation.

FIG. 8A shows a portion of the front face of a cutting tool inclined by "e" in FIG. 8B, where C + ΔC is the angle between cutting edges parallel to the direction of cutting. 9 shows each C + ΔC changed in the cutting groove.

To form the pattern of the hexagonal retroreflective microcube, the grooved plate 10 may be offset from another plate as shown in FIG. 5. Adjacent plates are offset from each other in the horizontal direction by a distance " a " that is 1/2 of the width of the groove, as shown in FIG. In addition, adjacent plates are offset in the horizontal direction by a distance "d", which is the depth of the groove, as shown in FIG. The manner in which the plates are offset from each other is shown in Figure 6B, where the intersecting plates are shaded differently for clarity. The expression "vertical" throughout this specification refers to the direction perpendicular to the valley plane of the groove of the single plate, and the expression "horizontal" refers to the direction perpendicular to the plane and the vertical of the plate.

By offsetting the plate in this manner, the "male" microcube is formed by the inclined walls of adjacent grooves abutting at the top edge 20 to form two surfaces 17, 18 of the microcube and the front of the same plate. The third surface 19 of the microcube is formed. As can be seen in FIG. 6A, three surfaces 17, 18, 19 of a single number cube (indicated by dots) are formed on a single plate 10. The "female" microcube may be formed by the two sides of the groove in one plate and the front of the adjacent plate. The advantage of several microcubes is that the accuracy of the angle between the faces of each microcube is only related to the accuracy of the ruling motion of the grooves and not to the accuracy of the plates stacked and assembled in the form of "originals". The “original” of the stacked and assembled plate will be subjected to an electroforming process for forming the tool described in more detail below.

Both the hexagonal contour of the cube corner and the quadrilateral contour of the cube face produced by the method described above are clearly shown in FIGS. 5 and 6A. In particular, the hexagonal cube corners are not formed by continuous straight lines extending along the entire surface of the ruled disc, as in the case of the triangular cube corners shown in the example of FIG. 1A of the aforementioned U.S. Patent 4,478,769. Not clearly shown in FIGS. 5 and 6A. Thus, it is clear that a tool having only hexagonal microcube corners cannot be machined by ruling three sets of parallel grooves as described in US Pat. No. 4,478,769.

In the embodiment of FIGS. 5 and 6, the side lengths of the grooves (“L” in FIGS. 4 and 6B) and the thickness of the plates (“t” in FIGS. 3 and 6) are the same, and the ruling direction is the plate 10. Is perpendicular to the surface of the For this embodiment, the cube axis is perpendicular to the plane of the cube axes and the angle X in FIG. 6 is typically 35.26 °.

In this embodiment all cube dihedral angles and all cube faces are the same, but for some applications the cube corner recursive reflector makes a variety of optics of the retroreflective article by making certain modifications to the cube angle and relative size and shape of each cube face. It will be appreciated that it is desirable to have the property changed. These modifications can be achieved using the method of the present invention. Thus, for example, the thickness "t" of the plate does not necessarily have to be equal to the length "L" of the side of the groove, and the floor of one groove does not have to match the valley of the groove in the adjacent plate, and the ruling direction is It does not necessarily have to be perpendicular to the surface of the plate 10.

For example, the various angles of the main incident light may vary the depth of the groove with respect to the thickness of the plate (FIG. 10), or incline the bisection so that two side lengths of a single groove are not equal (not shown), Or by varying the offset of adjacent plates (FIG. 12). In other embodiments, the entrance angle can be increased in a plane (Figs. 41 and 43) perpendicular to the plane of symmetry of the cube by tilting the cube axis more parallel to the plane, and further increasing the plane or edge. A pair oriented opposite to each other with any of the parallel left and right slopes can be used to increase in a plane perpendicular to and parallel to the cube symmetry plane (FIG. 42), or more parallel to the oppositely oriented pair and plane. The slopes can be combined to increase in either plane, parallel and perpendicular to the plane of symmetry (FIGS. 43 and 45). In another embodiment, the divergence (ie, viewing angle) of the retroreflected beam is cut equal to the small angle between the normal and the cutting path to the front surface of the plate, as shown by the exaggerated angle "b" in FIG. The path of the tool can be increased in one or multiple planes by making the angle of the normal to the face of the plate and by making the groove angle somewhat larger or smaller than 90 °. In FIG. 11, the angle “b” lies in the vertical plane, but by movement of another plate, it can be placed in any plane including the cutting path and the normal with respect to the face of the plate. 11A shows that the ridges of the grooves in one plate are offset to match the valleys of the grooves in adjacent plates. The manner in which the plates are offset from each other is shown in FIG. 11B, where the plates of intersection are shaded to distinguish from each other. 11B also shows the faces 17 and 18 to be visible due to the exaggerated cutting angle even if the field of view is perpendicular to the face 19.

Those skilled in the art will appreciate that the various methods of the present invention described above, which can control the angle of incidence, the angle of incidence, and the angle of observation, are not necessarily mutually exclusive. Can be combined to create an array with

Three structural variables determine the angle of incidence of the equally slotted regular plate assembly that produces an array of hexagonal cube corners. At this time, the thickness of the plate is t, the depth of the groove is d and the deviation of the plate is s (see Figs. 12C and 12D). The deviation is the distance between the ridge of one grooved plate and the valley of the next adjacent plate. For the assembly of FIG. 6 the deviation S is zero and for the assembly of FIG. 12 the deviation S is nearly zero. The entrance face is assumed to be parallel to the plane of symmetry of the cube corner.

The incidence of light on the front face of the article at the angle of incidence I will be retroreflected to 100% geometrical effectiveness (ie, the effective aperture percentage is 100%), with the following relationship:

I 'is the angle of incidence after refraction by the front surface of the article, where I' = sin ^-1 (sinI / n), where n is the refractive index of the material. I '= I for a hollow retroreflector. I and I 'are either negative or positive. That is, the negative and positive values of I and I 'are shown in Figures 12C and 12D, respectively. Since the cube size can be ignored, the dimensions d and s are related to t.

For each value of I from -90 ° to + 90 °, the result can be obtained from equation E using t, d and s. For small values of slip s / t, equation E identifies the amount of d / t, the single ratio of groove depth to plate thickness, for each angle of incidence. For example, Table B shows the results when there is no slip, i.e., s / t = 0 and when the refractive index is 1.49.

TABLE B

If the slip s / t is a large value, there is a result for equation E only for a large value of I. For example, Table C shows an example when s / t = .75 and when the refractive index is 1.49.

TABLE C

If the ratio of d / t is fixed in the case of an example for a set of manufactured plates, there may be a range of angles of incidence from which equation E can be solved with a positive value of s / t. For example, Table D is developed for d / t = .707 and a refractive index of 1.49.

TABLE D

The result of d / t = .707 and s / t = 0 shown in both Table B and Table D, L is equal to t so that the floor of the groove in one plate is matched with the valley of the groove of the adjacent plate while there is no slip. And the adjacent plate is offset in the vertical direction by the groove depth d as shown in FIG. 6.

The results of d / t = 1.423 and s / t = 0 shown in Table B correspond to the embodiment of FIG. 10 where L is increased to approximately twice the plate thickness. FIG. 10A shows the projection of the array of FIG. 10 parallel to the cube diagonal (approximately 35.54 ° with respect to the plane of the cube vertex corresponding to the incident angle I of 60 °). As can be seen at 35.54 ° with respect to the vertical as in FIG. 10A, the opening effectiveness of the microcube is 100%. FIG. 10B shows the protrusion of the microcube of FIG. 10 perpendicular to the plane of the cube vertex, showing that the opening effectiveness at this angle is low. Figure 10C shows the projection perpendicular to the side of the plate, where the plate of the intersection is shaded for distinction.

The results of d / t = 0.707 and s / t = 0.932 shown in Table D correspond to the example shown in FIG. 12, in which case the effective opening is 100% at the 60 ° incidence angle as shown in FIG. 12A. 12B is the protrusion of FIG. 12 perpendicular to the side of the plate, with the cross plates shaded for discrimination.

The results of d / t = 0.352 and s / t = 0.75 shown in Table C almost correspond to the embodiment with the performance shown at the top of FIG. Table C shows that this curve has 100% effectiveness at an angle of incidence I of 20 °. If this curve is a pair of arrays, as in the example of FIG. 45, the next time one cube array receives light at I = 20 °, the other array receives light at I = -20 °, Due to this angle of incidence, the cube array has a low effective aperture percentage. The rise and fall effectiveness of the two cube arrays is added to produce the performance curve of FIG. 45 that is flat for entrance angle values from -20 ° to 20 °.

When d / t and s / t solve equation E for any value I ', the hexagonal cube achieves 100% aperture effectiveness only for one internal angle of incidence. Depending on the refractive index, the aperture effectiveness corresponds to one external incident angle I. The effective aperture percentage of the hexagonal cube, ie, the retroreflectivity in general, for all other incident angles requires further calculation. Graphs of effective aperture percentage and retroreflectivity versus incident angle from −90 ° to + 90 ° are shown in FIGS. 38 and 39, respectively, for nine different unpaired hexagonal microcube arrays. Each microcube will have n = 1.49, s / t = 0 and selected d / t according to equation E, resulting in a 100% effective aperture percentage incremented by 20 ° at an angle of incidence between -80 ° and + 80 °. do.

The graph of retroreflectivity versus incident angle from −90 ° to + 90 ° is shown in FIG. 37 for an unpaired hexagonal microcube array with d / t = 0.707 and s / t = 0 and five different retroreflective indexes. It is. 37 is well known in the art, indicating that any analysis of retroreflectivity should include the refractive index of the material used.

If the slip is not zero, the cube corner is strictly no longer hexagonal. If there are continuous faces shared by two or more adjacent cube elements, the dividing lines between the elements should be considered to be the shortest image line (15 in FIG. 12A) that can be drawn to complete the polygon. . Covalent or continuous planes are optically beneficial at orientation and entrance angles, where the ray that first reflects the continuous planes within one hexagon at that angle will be the second reflection and wit reflection in the adjacent hexagon. To be able.

Slip is a useful parameter in optical design. For example, the results in Tables C and D ensure 100% geometric effectiveness at selected angles of incidence while hexagons of different shapes with different volumes, different diffraction openings, different spot "weights" and different cube axis left and right tilts. It involves a cube.

The cube axis left and right slopes measured with respect to the front side of the array simply depend on (s + d) / t according to the following equation.

If the hexagonal cube array assembled from the slotted plate from equation E has an effective opening percentage of 100% at 0 ° incidence angle, d, s and t must satisfy the following equation.

From this equation, the following equation is performed.

According to equation F, this equation corresponds to the left and right inclination range from 0 ° to -9.74 °. All left and right slopes can be obtained in a grooved plate structure while being selected to have an effective aperture percentage of 100% at 0 ° incidence angle only in the range from 0 ° to -9.74 °.

However, to further increase the degree of entrance, the designer may choose to accommodate less than 100% effectiveness at a 0 ° incidence angle. As shown by the series of retroreflectivity graphs of FIGS. 42A-42E, a useful performance including a 0 ° entrance angle yields (d + s) / t, which goes far beyond the limit of equation H, i.e., from 0.5 to 1.2. Grooves can be obtained from a fine plate.

Each of the five sets of curves in FIGS. 42A-42E represent individual values of d + s and the final axial left and right slopes. For example, in FIG. 42A, d + s for all three curves is equal to 0.5t, and the final left and right slopes are + 8.70 ° emp. This "emp" means more parallel to the edges. Each of the three curves in each set represents a different value of d and s, the sum of which is 0.5t in the 42a set. For one of three curves within each set, s is chosen to be equal to 0 (as illustrated by the curve d / t = .5, s / t = 0 in FIG. 42A), and 3 within each set. For other curves of the two curves, d is chosen to be equal to 0.1t (as illustrated by the curves d / t = .1, s / t = .4 in FIG. 42A). For comparison, the curve of retroreflectivity versus entrance angle for the Hoopman triangle described in PCT WO95 / 11463 is indicated by thicker lines in each figure. Hexagonal microcubes can also be zero designed to provide 40% to 100% recursion greater than Hoopman via a 34 ° incidence angle as illustrated in FIG. 42B, or d / t = 0.3, s / t in FIG. 42E. A constant of 40 ° total over 10% to 40 ° as shown by the curve of 10 ° to 40 ° or above 10 ° to 70 ° as in d / t = 0.1, s / t = 1.1 in FIG. It can be designed to provide retroreflectivity.

In FIG. 42, it should be noted that for an effective aperture percentage of 100%, the retroreflectivity can never exceed 0.9 for polycarbonate articles due to Fresnel losses of the front surface included in the calculation of the retroreflectivity. .

Rectangular microcube manufacturing method

The method of manufacturing a tool with a rectangular microcube according to the invention starts with a laminate 110 (shown in partial front view in FIG. 14A) whose thickness t is equal to the rectangular predetermined dimension H (FIG. 26). The plate 110 is preferably flat and has at least one flat end 112 shown on the side of Fig. 14B, each of which is cut by a diamond cutting tool.

Each plate 110 or laminated plate 115 is of the pore machine of FIG. 15 on a pore machine having a cuttable end 112 and a front surface 124 of the plate at a predetermined amount X, eg, by an angle of 35.26 °. It is located perpendicular to the cutting plane. If a laminated plate is used, the top edges 125 of the ends 112 all lie in a single plane, providing a gap for the cutting tool between the plates to be machined and recessed from the plates of the edge 125. A space or space 111 of cutable material is provided between the plates as shown in FIG. 15 so that the cutting tool is not in contact with any material that may be damaging. The cutting edge 119A of the cutting tool 119 projecting parallel to the cutting direction is positioned perpendicular to the plane of the machine bed, and the bottom edge of the cutable end 112 is the cutting tool of the end 112. It is cut along the length of the plate 110 until it reaches or exceeds the midpoint, creating the bevel face 113 of FIG. 15. 16A and 16B show the plane and side surfaces of the plate 110 after cutting the slope 113, respectively. This step is repeated for each plate 110 in the stack 115.

After the slope 113 has been cut, the space between the plates may be filled with a plastic composite as shown in FIG. 17 to avoid damage by the cutting tool in order to prevent the occurrence of rough spots due to cutting.

In Fig. 18, grooves of a predetermined narrow angle Y, for example, 90 °, are cut in directions parallel to each other, and are substantially perpendicular to the direction of the cut slope. Dotted line 116A represents the face 116 already cut. It will be appreciated that in the method described in FIGS. 7A, 7B, 8A and 8B, the angle Y can be adjusted by adjusting the inclination of the cutting tool 118 with respect to the groove angle C + ΔC. In this embodiment, the groove of the groove formed by face 116 intersects the lower edge of inclined face 113.

FIG. 19 shows a cross section (19-19 of FIG. 18) penetrating a finished plate taken at the groove of the groove and perpendicular to the second ruling direction of operation. FIG. 20 is a view cut in the direction of arrow 20-20 parallel to the plane of plate 110 and perpendicular to the line through the cube vertex, with micros formed in inclined planes 100A and planes 100B and 100C from adjacent grooves. The rectangular shape of the cube 100 is shown. The cube face 100A is the portion between the grooves of the inclined face 113, and the cube faces 100B and 100C are the groove faces from the adjacent grooves. The thinly ruled plates of FIG. 18 may be rotated 180 ° in the alternating plates of FIG. 21 and stacked together.

Although microcubes can be processed on one plate at a given time, it is desirable to group the plates in order to minimize cost during processing.

A change in the process that can be used to make small microcubes is to process two rows of microcubes in a single plate to double the thickness of the plate and increase the strength. As shown in FIG. 22, a thick plate 210 without spacers is disposed in a ruling machine having a cuttable end 212 and the front face 224 of the plate is, for example, 35.26 ° with respect to the vertical of the plane of the machine workbench. Tilt by the amount X of hope.

In the cutting edge 219A of the cutting tool 219 disposed perpendicular to the plane of the machine platform in FIG. 22A and parallel to the direction of tool movement, the point 222 at the midpoint of the thickness of the plate at the lower edge 223. Temporary surface 213A and first inclined surface 213 with respect to surface 213 at an angle X of 1 to 2 times the inclination angle X and extending from the upper edge 213 of the furnace plate to less than 25% of the width of the plate. The cutting is performed with a cuttable end 212 that produces a cut.

A first inclined surface 213 that fills the cut with a plastic composite 114 (FIG. 22C) that does not degrade the functionality of the diamond tool and then forms the groove face 216 using the diamond tool 118 (FIG. 23). Is cut into a groove of a V-shape having a predetermined narrow angle Y, for example, 90 °, in a direction substantially perpendicular to the cutting direction, and the valley of the groove is the lower edge 223 of the first inclined surface 213 (FIG. 23A). Pass through).

The inclined face 216 of the adjacent grooves that meet at the upper edge 200 forms two faces 200B, 200C of the microcube 200, and the first inclined face 213 has a third face 200A (FIG. 23B); The rectangular outline of the microcube 200 becomes apparent. According to the method of this point, the microcube of a 1st row is formed in the edge part of a board | plate.

The plate 210 is tilted so that the front surface 224 is tilted at an angle X with respect to the vertical of the plane of the machine workbench. Since the symbol "X" in the specification represents the angle between the front of the plate and the perpendicular of the plane of the machine workbench, the angle "X" in FIG. 22 is the angle of FIG. It may or may not be the same as X ". The cutting tool 219 is repositioned to be parallel to the tool movement direction and the edges perpendicular to the plane of the machine platform, and completely remove the temporary face 213A (FIG. 24) to create the second inclined face 313. FIG. Cutting is done at the cuttable end 212 of 210. The grooves refill the grooves with plastic composite (not described), and the additional grooves are cut by the tool 118 (FIG. 25) in a direction perpendicular to the cutting direction of the second sloped surface 313.

The inclined face 316 of the adjacent grooves that meet at the upper edge 320 forms two faces 300B and 300C of the microcube 300 and forms a second slope 300 and a third face 300A. . The microcube of the second row is formed on the other side of the same end of the plate on which the microcube of the first row is formed. As will be apparent from the dashed line in FIG. 25 showing the intersection of the microcube 200 planes, since the intersecting lines are not continuous, a disc containing all rectangular microcubes in the opposite direction by ruling a straight line on a single flat surface. You won't be able to rule.

How to position the plate for ruling

The method of fixing to obtain the above-mentioned cube corners is a technique already known to those skilled in the art. However, due to the apparent tolerances required for the microcube, the means for positioning the plate in the machining operation will be explained in more detail. For all types of microcubes, the two dowel holes R of FIG. 3A will be grounded through the front of each plate. For the hexagonal microcube, the dowel holes R assemble the plates for cutting the grooves and position each plate to polish another set of dowel holes M with respect to the assembly of the electroforming disc. Will be used. Dowel holes M are in different positions on each plate. Dowel holes M are moved vertically from dowel holes R (FIG. 3A) by the same amount as k1 + n (d + s), where k1 is a constant, n is the number of plates in the stack, d is the groove depth and s Is slip. All dowel holes M are moved from the reference hole R by the constant k2 of all the odd plates and by d + k2 of the even plates, d is the groove depth and equal to half the groove width. In groove cutting, the dowel is inserted only in the reference dowel hole R; In electroforming, the dowel is inserted only in dowel hole M. Errors in positioning grooves in one plate relative to the grooves of adjacent plates are expected to be less than 0.0002 "(5μ) in any direction. Negative inserts that cut the bottom part and increase the loss To avoid slipping, it is desirable to design the microcube so that the positive slip is at least 0.0005 "(12.5μ). In order to process a rectangular microcube of one plate for a given time, the plate is placed on the ruling machine by the dowel through the standard dowel hole R, matching the dowels provided on the fixture, the surface of which is the worktable of the ruling machine. Slope by X from perpendicular to After the inclined face and grooves have been machined, the reference dowel hole R is used to position the plate during electroforming. The maximum error when positioning the microcube vertex with respect to the center of the plate is expected to be 0.0001 "(2.5μ) or less. When multiple plates are run for a certain time, the secondary dowel holes are described for the hexagonal microcube. It may be provided for each plate in a manner somewhat similar to the procedure described; however, for a stack of ten plates, the error in positioning the vertices of the microcube is 0.0005 "(12.5μ in the direction perpendicular to the side of the plate). It is expected to increase by).

Preferred microcube processing methods are described in detail; However, other machining methods based on the plate concept are readily known to skilled tool manufacturers, and these descriptions will not be considered as limiting.

Recursive reflector performance

The rectangular microcube of the present invention differs from the hexagonal microcube of the present invention in two main ways. First, rectangular microcubes can be aligned as paired (mirror images) elements, while hexagonal microcubes created from a single cut plate are all the same in orientation; To pair a hexagonal microcube to show symmetrical behavior, you need to pair a small mirror image array of hexagonal microcubes with a large array. Second, the rectangular microcube is designed more freely than the hexagonal microcube produced from a single cutting plate; For rectangles, the axial oblique vertex center, rectangle size can be changed independently of each other (see FIG. 28), whereas for hexagons a change in one of the variables requires a change in one of the other two. Rectangular cubes have a 100% effective opening percentage at 0 ° incidence by centering on the vertices; The slope is then adjustable from -54.74 ° to + 35.26 °, the magnitude of which is still variable. In contrast, conventional direct ruled triangular cubes do not have any independent variables. Slope, vertex centering, and ratio are complex correlations.

For a triangular microcube that is directly ruled, the cube axis slope is determined by the shape of the triangle by the following equation.

Here, A and B are tangents of two acute angles of a triangle. For triangular microcube fabricated with the plate assembly technique of the present invention, the cube axis tilt is the combination of the angle computed above and the angle between the triangle bottom and the front face.

In the recent PCT Publication Nos. WO95 / 11463, WO95 / 11465, and WO95 / 11470 by Minnesota and Manufacturing Co., Ltd., various graphs show a comparison of the retroreflectivity according to the effective aperture percentage, which is total Internal reflection (TIR) limitations are not taken into account; If the front mirror loss is not taken into account, the loss is significant at high incidence angles.

In the graph of the present invention, the following parameters are selected for the measurement of retroreflective.

1. A prism object is considered to be a single material with a constant reflectance.

2. Internal reflection is calculated by the Fresnel equation under the assumption that light is not polarized (as opposed to true).

3. The front transmission is calculated by the Fresnel equation under the assumption that the light is not polarized.

4. The cosine loss due to the angle of incidence is not considered at all.

5. The entrance plane is parallel to the plane of symmetry of the cube corners.

6. The diffraction effect is ignored.

The variously illustrated curves for possible designs necessarily represent commercially practical articles, as well as account for the wide variety of outcomes that can be achieved by producing tools and microcube retroreflectors in accordance with various aspects of the present invention. have.

Most graphs are for non-metalized cubes and include the effect of total reflection (TIR). 39, 40, 44 and 45 show the results when the microcube is metallized [the term “metallized” is generally applied to the cube face to provide a specific reflection at the angle at which the TIR fails. Used in the sense of containing all metals]. The various concepts presented in the recent PCT application described above regarding measuring the effective rate openings are only relevant when the cube is metallized.

44 and 45 compare the performance of some articles and prior art, respectively, according to the present invention. These figures correspond to the article of the present invention as well as the curves provided by FIG. 12 of WO 95/11470 and FIG. 32 of WO 95/11463 and revealing the public geometric effectiveness (measured as the effective aperture percentage) known to the applicant. It includes a curve. FIG. 44 compares the efficiency of the very simple non-tilt rectangular cube design of the present invention with the effectiveness curve from FIG. 12 of WO 95/11470. 44 shows that at 0 ° the effective opening percentage of the microcube of the invention is 9% higher than the best curve of WO 95/11470 (curve 153) and 50% higher than the curve for Hoopman.

At 20 °, the effective aperture percentage for the microcube of the present invention is 29% higher than curve 153 and 19% higher than Hoopman's curve.

Example 1

Recursive Reflector for Increased Entrance Angle

S / t = 0, shown in FIG. 6, to increase the degree of entrance angle of the cube as disclosed in US Pat. Nos. 3,541,606, 3,873,184 and 3,923,378, incorporated herein by reference and granted to the same assignee. The solution d / t = 0.707 is s / t = 0.45 where the cube axis slip is -9.74 ° with respect to the front of the array as shown in FIG. 13; d / t = 0.55 solution, the effective aperture percentage is 72.5% at 0 ° angle of incidence and 100% at 19.6 ° (in this embodiment, the plane of incidence is aligned to the plane of symmetry of the cube corners, Refractive index is 1.59). However, if the hexagonal arrays are paired for each cube oriented advantageously for an angle of incidence of 19.6 °, then the mirror image will have only 45% effective aperture percentage for the same angle of incidence, thus the paired array will be 19.6. It has an average of 72.5% for light incident at an angle of degrees and is as high as an average at incidence of 0 °. The result of this average for the effective apertures is preferably very flat of the effective aperture percentage versus incidence angle extending from -20 ° to + 20 ° for the paired inclined rectangles and the paired inclined hexagons of FIG. 45. The curve, which spans the 20 ° entrance angle region, is at least 48% over the effective aperture percentage curve for Hoopman, and 16% over the effective aperture percentage curve of WO 95/11463, for example 460. Exemplary rectangular and hexagonal curves of the present invention continue to prevail over the curve for Hoopman up to an entrance angle of 50 °, for example up to 70 ° for the curve of 460, the ent in both cases. The clearance angle is all meaningful entrance angles or more than described above.

Directly paired rectangles have the same -9.74 ° and substantially equal 72.5% effective opening percentages at 0 ° and 19.6 ° incidence, as for the exemplary hexagon by off centering the cube vertices by 13.75% of the height of the rectangle. As shown in FIG. 27C, the ratio is 1: 2 (width: height). As shown by the curves in FIGS. 40 and 45, the average effective opening percentage of a paired hexagon and a pair of rectangles is surprising at all entrance angles for the case where the effective opening percentage matches at an angle of incidence of 0 °. As similar as can be.

Since the benefits of inclined cube axes are realized mainly in cubes that depend on total reflection, it is more appropriate to base them on considering the effectiveness for retroreflectivity than for the effective aperture percentage. In both cases of the rectangular and hexagonal embodiments, the total reflection is maintained for the pair of cubes (or arrays) at the effective opening when the angle of incidence is 19.6 ° but is lost for the cube missing at the effective opening (factor 0.898 Due to surface loss). 40 compares the retroreflectivity and effective aperture percentage of hexagonal arrays paired with these rectangular pairs over a wide range of angles of incidence with respect to the plane of incidence aligned with the plane of symmetry of the cube.

The curves of d / t = 0.55 and s / t = 0.45 in FIG. 42D show Hoopman's curves for the retroreflectivity of the paired hexagonal arrays (and the retroreflectivity of the rectangular pair of FIG. Compare with 43 shows the retroreflectivity versus incidence angle for the same rectangular pair and paired hexagonal arrays with respect to the plane of incidence perpendicular to the plane of symmetry. In the plane of symmetry, the paired hexagonal array, more parallel to the plane of FIG. 13, and the rectangular pair of FIG. 27C, dominates up to 47 ° with respect to Hoopman, while in the plane perpendicular to the plane of symmetry these pairs dominate up to 60 °.

The effective aperture percentage and retroreflectivity for paired pentagons (see FIG. 36) are the same as the hexagons and rectangles described above for the same axial tilt and effective aperture percentage at 0 ° incidence.

For a set of cubes oriented face to face, the advantages of the “face-more-parallel” structure are shown in lines 62 to 16 of column 15 of column 15 to column 16 of US Pat. No. 3,541,606 and FIGS. 18, 19 and 20 Is shown in.

The method outlined in Example 1 is intended to maximize the range of angles of incidence in one or more planes through which minimum retroreflectivity can be maintained, which is described in the above-mentioned patent and 3M's "Diamond Grade." What is needed is a cube (or cube array) with slanted cube axes oriented to face as shown in sheet material (US Pat. No. 4,588,258 to Hoopman).

Example 2

Retroreflective, for example, for large angles of incidence for pavement markings

Example 2 is entirely different from Example 1. The method of Example 2 is to maximize retroreflectivity for a relatively small range of angles of incidence with respect to the axis (major incident light rays) that is not perpendicular to the plane of the retroreflector. For example, an embossed retroreflective lane marker installed on a roadway may have a front slope inclined 60 ° back from a plane perpendicular to the plane of the pavement. Light rays from the headlights of the vehicle approaching the pavement substantially parallel are retroreflected (in acrylic) at an angle of 35.5 ° to the vertical line by projecting onto the face of the reflex reflector at an angle of 60 ° to the vertical line. For the sake of explanation, the rays parallel to the surface of the pavement and the centerline of the road are referred to as the main projection beam or optical axis, and the rays in the beacon after the retroreflection at the front side are called the main retroreflected beam.

The reflex reflector for the plate shown in FIG. 6 with respect to L = t is used as a pavement marker since the effective cube area is lost if the plate is loaded at the top edge of the groove of the neighboring plate as in Example 1, ie 6A. Not desirable to The retroreflected ray deviates from the cube corner at the same distance from the cube vertex and the vertex on the opposite side of the cube vertex from the projection point. If the main retroreflective ray is at an angle to the cube axis, some of the light projected onto the cube for L = t is lost because there is no corresponding point on the side opposite the cube center. In order to utilize 100% of the area of each cube in the direction of the optical axis, the intersection point of three virtual planes which are relatively parallel to each of the three plane surfaces from the intersection point 29 of the three plane surfaces of the cube corner in FIG. 12. The cube diagonal 28 drawn up should be parallel to the main reflected beam.

As shown in equation E, for the hexagonal microcube, the relationship between I ', d, s and t is as follows.

For an acrylic pavement sign with a front sloped 30 ° on the road, I '= 35.54 °. If slip is chosen to be zero (s / t = 0)

90 °-35.54 ° = tan ^-1 (t / d) + tan ^-1 (t / 2d),

From this equation, d / t = 1.42.

In order to produce a tool comprising a hexagonal microcube for the pavement markings, the plate is structured to be d / t = 1.42, with d = 1.42t in both the horizontal and vertical directions as shown in FIG. 10. Can be offset relative to each other.

Alternatively, the plate of FIG. 6 (d / t = 0.707) is used so that the plate is offset in the horizontal direction by d = 0.707t, and in the vertical direction d = 0.707 in addition to s = 0.932t as shown in FIG. Can be offset relative to each other. Irregular hexagons projected along the cube diagonal 28 are indicated by dashed line 15 in FIG. 12A. The microcube can be metallized to provide a better degree of horizontal incidence angle.

Pavement signs comprising rectangular microcubes structured by the plate method can be made with improved horizontal incidence angles compared to the directional controlled cube of Nelson's US Pat. No. 4,895,428. In order to structure a -9 ° face parallelism rectangular cube for use on acrylic pavement markings with a 55 ° front deviation, the plate thickness is parallel to the plane of symmetry projected parallel to the main reflected beam as in FIG. 29A. And the plate is selected to be equal to the dimension of H, the plate being at an angle to X which is a vertical line equal to 35.26 ° below the cube axis tilt (hereinafter referred to as "CAC") on the ruling machine (35.26 °-(-9 ° in this embodiment). Or at an angle X equal to 44.26 °), the inclined surface 113 is cut at the midpoint of the plate and the groove is structured to be perpendicular to the cutting direction of the inclined surface with a depth equal to 0.5 W, as shown in FIG. W in FIG. 29A is the dimension of the side of a rectangle perpendicular to H. FIG. The angle θ in FIG. 29 is the angle between the pentagonal plane and the vertical line with respect to the plane of the cube vertex, which is equal to the subtraction of sin ⁻¹ [(sinT) / n] from CAC plus 35.26 °, where T is It is the deviation of the front. In the direct structured cube of US Pat. No. 4,895,428 to Nelson, θ is necessarily 0 ° and the pentagonal face becomes a triangle. FIG. 29 shows the resulting rectangular cube in cross section, FIG. 30 is a perspective view of an array of such cubes, and FIG. 41 shows an improvement of about 11 ° in the horizontal angle of incidence compared to Nelson's patent, which is Heenan. In accordance with the theory disclosed in U.S. Patent No. 3,541,606, by a structure more parallel to the -9 ° plane.

The use of angles more parallel to the face, greater than -9 °, for acrylic pavement signs is problematic due to equipment tolerances. As in FIG. 41, the maximum retroreflectivity is limited to about 0.87 due to frontal loss at 55 ° incidence.

Example 3

Recursive reflector with increased divergence

The divergence (ie, viewing angle) of the retroreflected beam is determined by varying the half-angle between two or three planes and / or affecting diffraction, as disclosed in US Pat. No. 3,833,285 by the same applicant. It can be changed in one or many aspects by changing the size of which is incorporated herein by reference.

The upper half angle may be changed by forming a groove angle greater than 90 ° and / or by tilting the stack of plates 10 slightly perpendicular to the cutting plane before the groove is cut, as shown by the angle “b” in FIG. 11. Can be. The groove angle can be changed by changing the angle "C" (FIG. 7A) of the diamond tool or by adjusting the angle "e" (FIG. 8A) of the diamond tool with respect to the perpendicular to the structured surface according to Equation A described above. Can be.

The inclination angle "e" of the cutting tool can remain the same for all grooves. Alternatively, the inclination angle "e" of the cutting tool is cut as a function of the distance each groove is moved by the cutting tool along the structured surface, or the cutting tool is maintained at an angle "e" relative to the entire length of each groove. It can be adjusted continuously as it can be changed for each successive groove cutting into the surface. It is also possible to use these techniques in combination, ie vary the angle "e" of the cutting tool with respect to the surface along the length of each groove and from groove to groove.

Diffraction is the diffusion of a light beam generated by limiting the beam size. Diffraction is the major optical difference between macrocube and microcube. For observation angles associated with commercial applications such as highway markings, namely 0.1 ° to 1.5 °, the diffraction effect on the microcube may be important, while not on macrocube. With respect to the macrocube the degree of observation is entirely determined by the upper half angle, the planar view of the face and the cube shape, but for the microcube size they are additional determinants.

46A-46C show the effect of diffraction on the pattern of retroreflected light with respect to the square cube corners of d / t = 0.707 and s / t = 0 of refractive index 1.49 for 0 ° incidence and three different cube sizes. Indicates. The circumference of the figure shows a divergence of 0.5 °, and each gray band represents two factors in the retroreflected intensity. All cube corners preferably have an error of 0.103 ° in only one of the flat face and the upper half angle. Fig. 46A shows t = 0.866 mm, Fig. 46B shows t = 0.217m, and Fig. 46C shows t = 0.087 mm.

By forming the groove angle 90.103 [deg.] In the plate of FIG. 6, a prism article with an index of refraction 1.49 accurately replicated from the tool must have a divergence of 0.25 [deg.] Exactly by geometry only and all retroreflectives are directed at two points. In practice, the light pattern depends on the cube size. For the large microcube of FIG. 46A with a cube height of 1 mm and a plane width of 1.22 mm, the light pattern approximates the prediction of geometry (FIG. 46A). For the average size microcube of FIG. 46B with a cube height of 0.25 mm and a plane width of 0.306 mm, the light pattern is still the same as geometric prediction, but significantly wider (FIG. 46B). For the small microcube of FIG. 46C with a cube height of 0.1 mm and a plane width of 0.122 mm, the light pattern is its main at a divergence of 0 °, near two predicted points (FIG. 46C), as opposed to geometric prediction. Peaks and only weak secondary peaks at 3 ° divergence. Diffraction by the microcube advantageously flattens the light pattern, but diffraction must be calculated for every microcube because it can direct light in a non-functional direction. Suitable cube corner diffraction theory has been described in the optical literature for at least 35 years.

The plate used in the structuring method of the present invention may be formed of any material that is sufficiently strong and tightly organized when formed into a flat plate of the required thickness. The material must be able to be cut and polished with high precision. Some plastics, such as polymethylmethacrylate, may be suitable if they are metallized after mechanical treatment to impart electrical conductivity for electroforming. Suitable metals include hardened pure silver of purity 925, hardened aluminum 707T6, and electroless nickel. Electroless nickel is known to be very hard but is easily cut by diamond cutting tools. Electroless nickel applied on stainless steel is divided into plates having electroless nickel on one end, which is particularly suitable for use in the present invention. Alternatively, electroless nickel is a non-stick plate separated into a plate that functions as plate 10 to a thickness of about 0.012 inches on a surface stabilized stainless steel block (or block of other material such as aluminum or metalized plastic). It can be formed as.

In another form of the invention, an assembly of microcubes formed by a plate when structured, assembled and oriented as described above can be used as a disc for electroforming radiation. The radiation is assembled into clusters of adjacent devices and the clusters are repeated to provide a large number of replicas, and this process is repeated to create a flexible strip with a continuous pattern, which strips into cylindrical segments provided on the cylindrical mandrel. The assembled cylindrical segment is assembled to provide a cylinder of a predetermined dimension corresponding to the width of the web provided to the retroreflective element, and the assembled cylinder radiates to provide a flexible continuous disc cylinder with a pattern of microcubes. do. The disc cylinder can be copied to form a relatively thick mother cylinder and then to form an approximately cylindrical metal embossing tool.

Embossing tools formed as described above can be used to emboss the microcube on the surface of a continuous resinous sheet material to produce a retroreflective sheet material as disclosed in US Pat. No. 4,486,363. According to the method disclosed herein, the embossing tool described above is moved to a cooling section that is heated to a predetermined temperature while passing through the heating section along a closed path and then cooled to a predetermined temperature or less, wherein the resinous sheet material material is embossed through the heating section. Continuously supplied to the tool, the sheet material is in direct contact with the pattern of the cavity microcube, and the sheet material is pressed against the embossing tool until one surface of the sheet material copies the pattern of the pentagonal or rectangular microcube at one or more points of the heating section. After that, the embossing tool and the sheet material are transferred to the cooling unit so that the sheet material is cooled below its glass transition temperature, and the embossed sheet material is separated from the embossing tool.

Those skilled in the art will appreciate that in addition to the embossing tool and the foregoing technique, the aforementioned pentagonal or rectangular microcube embossing tool can be used to produce the retroreflective sheet material by other methods, such as the casting method, the press method, or the casting method. I understand. For example, an electroformed strip having a hollow pentagonal or rectangular microcube as described above may be provided with a suitable support and may be embossed or compression molded tools but in a discontinuous manner as disclosed in US Pat. No. 4,244,683 by Rowland. Can be used.

It is generally preferred that the reflective reflective sheet material produced according to the invention and having a precise optical pattern of various cube-shaped microcubes is formed with a triangular microcube on the sheet material. For small angles of incidence from 0 ° to 5 ° that are particularly relevant for retroreflective highway signs and signs, the full range of pentagonal or rectangular microcubes is substantially effective for retroreflective, while triangular microcubes have a 66% range only. This retroreflectivity is shown. Therefore, at these narrow angles of incidence, the five-sided or rectangular microcube retroreflective sheet material has a 50% increase in its retroreflectivity compared to conventional triangular microcubes.

Retroreflective articles, rather than sheet materials made with microcubes, are also advantageous for modifications to pentagonal or rectangular microcubes. For example, pavement markings incorporating the microcube of the present invention are less expensive due to reduced material costs, and are less degraded by abrasion because the existing light rays are closer to the projection light, reducing the effects of surface irregularities, and pavement The loss by shadow is minimized for road signs or pavement signs that may be slightly crumpled.

In the reflective sheet material art, it is well known that different sheet materials, such as acrylic, polycarbonate and vinyl, have different refractive indices " n " and exhibit different retroreflective properties even in the same cube form (see FIG. 37).

Modifications to the structured process of the present invention allow for various modifications to the cube.

(1) As shown in FIG. 26, the depths of the intersecting plane at 421 of the groove face 416 and the intersecting plane at 521 of the groove face 516 are as shown in FIGS. 27 and 27A and the inclined surfaces 413 and 513. The square cube can be made by decreasing it as compared to the depth of intersection at 423. The arrangement of the square microcube is consequently shown in plan view in FIG. 27B, where cube 500 is square, face 500A along elongated imaginary line 515 is pentagonal, and 500A and FIG. Compare the triangular face 300A of FIG. 25B. In addition, the quadrilateral faces 500B and 500C of FIG. 27B extend in comparison with the faces 300B and 300C of FIG. 25B. Square cubes or cubes that extend beyond the square range have several advantages when considering the spot pattern of retroreflected light.

(2) The angle of the cube axis proportional to the perpendicular to the cube vertex plane is selected for the angle X of the front face 124 or 224 of the plane proportional to the plane of the machine and / or proportional to the vertical of the machine platform. 25, 27 can be deformed by dividing the internal angle of the V-shaped grooves shown in FIG. See related patents such as

(3) For a rectangular or pentagonal microcube, the dihedral angle between the cube faces is the working table of the tool when viewed from the tool moving direction, for example, the cutting edge 119A of the tool 119 of FIG. Can be changed from 90 ° by setting it to an angle perpendicular to and / or increasing or decreasing the narrow angle Y of the V-shaped groove from 90 °, such that a change in the narrow angle between these cube planes is responsible for the divergence of the retroreflected beam. To control.

(4) The cube opening size can be changed by varying the plate thickness and groove depth or by processing a row of microcubes on a double thickness flat plate larger than a row of paired microcubes, and providing different cube opening size microcubes. In order to minimize the potential diffraction loss at any one viewing angle.

(5) Since one edge of the rectangular cube is a straight line, sets of opposing rectangular cube pairs having different characteristics can be joined without area loss or slip between the sets. Thus, the joining set may have different cube axes or different divergences, or different cube heights with no sharp edges between the non-active surfaces or sets. To move between planes with different cube heights, the cube vertices of different sized cube rows joining one or two may be off center. Move the vertices of the last cube row of one set of large cubes in the direction of one set of smaller cubes to equalize the volume of matter in the two sets of cubes.

Similarly, rectangular cubes of opposed sets of pairs may be combined with planar, cylindrical or lenticular components with optics other than microcubes. Such a sheet material composed of a retroreflective portion and other optical portions is known in the art as a sheet material to be transmitted. The rectangular edges of the planar or cylindrical optical surfaces can be set at the same height as the rectangular edges of the rectangular microcube, thereby preventing any slip wall between the two types of planes.

(6) For large angles of incidence, in the cubecube technique, rectangular cubes of a plurality of pins may be joined in all directions in one direction when exemplified using hexagonal cubes for pavement markings, parallel to the cube axis in use. And there will be a slip wall corresponding to one exposed side of the pin. Similarly for microcube technology, the plane for machining a rectangular microcube is a reference plane set at an angle of 90 ° -R to the side of the plane opposite to an adjacent plane oriented oppositely (or for a large angle of inclination optionally oriented in the same direction). It can be combined with the cube vertices that are in contact with R, where R is the angle between the main and normal beams.

(7) As shown in FIG. 32, rectangular cubes closely grouped in four directions can be generated by making a plane as shown in FIG. No order is required but the three sets of grooves are cut as shown. Two faces for each of the three grooves are formed for two different cubes, respectively. Each groove set requires a different angle of inclination X with respect to the plane and different narrow angles of the cutting tool, all of which can be calculated by trigonometry. Table J below shows the narrow angle and planar tilt angle of the cutting tool used to generate cubes of various cube axis tilts. For example, if the cube axis inclination is 0 °, then the plane angle will be 45 ° to make cutting number # 1 with the angle X to be tilted, and the narrow angle of the first cutting tool will be 109.47 °. To generate the four cube directions shown in FIG. 32, the finished planes alternately join opposite planes, for example rotated 180 ° relative to one another. When the cube axis inclination is other than 0 °, the values of the inclination angle of the plane and the narrow angle of the cutting tool can be calculated as shown in Table J below for each of the three sets of grooves, respectively.

The cube axis tilt values recorded above are for illustration only and do not limit the scope of the present invention or limit the range of cube axis tilts obtainable by the method of the present invention.

(8) In order to generate a pentagonal microcube as shown in FIG. 36, plates 710 and 810 are provided, each plate being flat on one side and the other on the same narrow angle as in the following equation: The groove is dug into a V-shaped groove having a width spaced apart from the cube by a predetermined interval on the plane.

Where g is the narrow angle of the groove, and u and v are the inclination angles of the cubes formed on the plates 710 and 810, respectively (FIG. 36A). Flat plates 710 and 810 do not necessarily require the same thickness. The inclined surface 813 and the grooved surface 716 are cut into the flat and grooved surfaces of the flat plate 810, respectively, in the same procedure as described in detail for the rectangular cube. The inclined surface 713 and the groove surface 816 are cut into the grooved surface and the flat surface of the flat plate 710. These plates are then paired with two plates 710 in pairs and two plates 810 in pairs facing each other at the intersection as shown in FIG. 36. The equivalent of assembly of two pairs of oppositely oriented plates 710 can be made by cutting two rows of cubes onto one thicker plate as shown by the square cubes of FIGS. 22-25A. Grooves are formed on both sides of the plate for this structure. Inclined surfaces 713 and 813 continue as long as the plates 710 and 810, respectively. Since the contiguous faces shared by two or more adjacent cube components exist with the hexagonal cube, the dividing lines between the components are considered the shortest lines that can be drawn to complete the polygon (lines 715 and 815 in FIG. 36). In order to prevent damaging the edges of the grooves on the side of the plate, the plate is assembled to equally face the grooved side of the grooved dummy plate.

(9) In order to produce a triangular microcube as shown in FIG. 31, the inclined and active regions do not depend only on the shape of the cube, and the flat plate 110 or stack of the plate has a predetermined amount X relative to the perpendicular of the rubbing machine cutting plane. As long as the angle is placed on the ruling machine having the side of the plate. The pattern of the triangular microcube is controlled on the cuttable end of the plate in a manner similar to limiting the continuous surface and disclosed in Stamm, US Pat. No. 3,712,706 or in Applicant's US Pat. No. 4,478,769. The controlled plates are then assembled as shown in FIG. 31 and the plates face each other at 180 ° to each other. The assembly of FIG. 31 is also made using a double-thick plate 210 and individually controls two arrangements of triangular microcubes on the ends of the plate, with the rectangular microcube shown in FIGS. 22-25. Shown. The inclination of the triangular microcube processed by one of the above two methods combines the X-axis and the inclination of the cube axis generated at the selected control angle. In most cases, rows of cubes are formed alternately with flat faces and edges.

(10) A retroreflective array consisting of a pentagonal face and a hexagonal cube as shown in FIG. 35 is made of a plurality of plates, each plate having a plurality of V-shaped grooves parallel to two opposing surfaces. To form a plate, first a plate is formed by plating adhesive non-electromagnetic nickel on the surface of a stainless steel block approximately 0.010 "thick. The non-electromagnetic nickel disc is a set of parallel Vs with a narrow angle of 120 °. It is controlled to form a groove, for example, to form a groove width equivalent to the dimension of the predetermined both ends of the hexagonal microcube, that is, 0.006 ". The groove surface is passivated and applied to the disc with non-electromagnetic nickel to a depth of approximately 0.010 ". Before removing the non-electromagnetic nickel deposit from the disc, the surfaces of the precipitate are machined into the same set of 120 ° V grooves, Arranged with the first set of V-shaped grooves on the disc, the largest thickness of nickel in the precipitate is the same depth as 1.155, which is the dimension of both ends, the precipitate is separated from the disc like a groove plane.

The plate is arranged so that the grooves are perpendicular to the workbench of the ruling machine. Face A is machined with a cutting tool with a narrow angle of 70.52 ° (when projecting in the cutting direction), and two halves of the narrow angle are perpendicular to the workbench of the machine. The plate is then inclined so that the groove side is angled so that each X is equal to 50.77 ° with respect to the machine's workbench, and face B1 is a cutting tool with a narrow angle of 131.81 ° with two halves of the angle perpendicular to the machine workbench. Is cut. This process is repeated for face B2.

The finished plates are stacked for electroforming with the groove interlock and become adjacent plates replacing 1/2 cube width to the side. One plate in the assembly is shown by the bold line.

For each microcube, one small triangular vertical wall portion remains exposed in the assembly of plates, and as shown by the circled C in FIG. 35, the cube dihedral angle of one plane is adjacent to the cube plane of the adjacent plate. These exposed walls eliminate the problem by electroforming or embossing, but the exposed walls can be drafted if necessary.

Those skilled in the art will recognize how to create an array of hexagonal cubes with pentagonal faces in accordance with the present invention. However, the method shown is preferred for each work plate.

It will be appreciated that embodiments will be disclosed that machining with diamond tools to form grooves and edges is disclosed, and that other linear forming techniques such as laser cutting, EDM, or ion processing may be used. In addition, various known ruling techniques can be used without departing from the scope of the present invention. For example, a plane may cut out grooves that are not flat, but may have some curvature.

Claims (34)

In an article comprising a microcube array, for every plane in the space there are two adjacent microcubes without face edges parallel to the plane at adjacent locations, At least one of the microcubes has a protruding area of about 1 mm ² or less, Wherein the at least one microcube is inclined with edge-more-parellel. An article characterized in that all regions of 3x3 microcubes contain an array of non-ruling microcubes. And a continuous microcube array, wherein at least one microcube in the array is not triangular. 3. The article of claim 1 or 2, wherein at least one microcube of the array is triangular. The article of claim 1, wherein at least one microcube of the array comprises at least one face that is a triangle and at least one face that is not a triangle. The article of claim 1, wherein the array is retroreflective. The article of claim 6, wherein the article comprises a retroreflective sheet. 8. The article of claim 7, wherein at least one microcube of the array has a protruding area of about 0.35 mm ² or less. The article of claim 8, wherein at least one microcube of the array has a protruding region of about 0.04 to 0.12 mm ² . 8. The article of claim 7, wherein the sheet comprises a polymer resin. The article of claim 10, wherein the polymer resin is selected from the group consisting of acrylics, polycarbonates, vinyls, polyesters, and polyethylenes. The article of claim 1, wherein all cube axes of the array are not parallel to each other. The method of claim 1, wherein the at least one microcube of the array has a plane of symmetry in which the cube axis of the microcube is disposed, and thus the angle of incidence of the array in a plane perpendicular to the plane of symmetry. an article characterized by an increased entrance angularity. The article of claim 1, wherein the retroreflectivity in the plane of symmetry of the microcubes of the array is substantially constant and is at least about 50% for all angles of incidence of about 30 ° or less. The article of claim 1, wherein the array is a retroreflective part of a pavement sign. The method of claim 13, wherein the plurality of microcubes are face parallel and the face parallel microcubes are provided as paired microcubes or paired microcube arrays, thus being perpendicular to and perpendicular to the plane of symmetry. An article characterized by increasing both the angle of incidence in one direction. 17. The article of claim 16, wherein the article has a surface for receiving incident light and the retroreflector axis of the article is perpendicular to the surface. And an array of microcubes wherein at least some of the microcubes are rectangular in shape and at least one side of the rectangular microcube is pentagonal. An array of rectangular microcubes, at least a portion of which has no dihedral face edge collinear with respect to any dihedral face edge of any adjacent microcube, At least one of the microcubes has a protruding area of about 1 mm ² or less, Wherein the at least one microcube is inclined with edge-more-parellel. 20. The article of claim 19, wherein the array comprises a rectangular subarray of four adjacent rectangular microcubes, each microcube rotated 90 [deg.] Relative to an adjacent microcube. The article of claim 1, wherein the article is a master used in the production of a tool for making a retroreflective article. The article of claim 1, wherein the article is of electroforming type used in the production of a tool for making a retroreflective article. 8. The article of claim 7, wherein the sheet member is transparent. A pavement marking for installing a marking visible from an approaching vehicle on a completed road surface, comprising: an array of foundation members suitable for mounting on the finished road surface, and the microcube of claim 1. Pavement road sign comprising a retroreflective signal means comprising a. 25. The apparatus of claim 24, wherein the front face of the retroreflective signaling means comprises an array of inclined rectangular microcubes that are inclined about 30 to 40 degrees with respect to the road surface, wherein the cube axis inclination is about -5 degrees to -13. A pavement sign characterized in that it is in the range of °. 26. The pavement sign of claim 25, having a horizontal angle of incidence of at least 30 degrees at least. 26. The pavement marker of claim 25, wherein the cube axis slope is about -9 degrees. In an article comprising an array of microcubes, all 3x3 subarrays of the microcube are non-ruleable, and at least one microcube in the 3x3 subarrays of the microcube is rectangular or pentagonal, and the at least one The microcube is inclined to plane parallelism, wherein at least one of the microcubes has a protruding area of 1 mm ² or less. 29. The system of claim 28, wherein at least one microcube of the array has a symmetry plane in which the cube axis of the microcube is disposed, such that the entrance angularity of the array is in a plane perpendicular to the plane of symmetry. An article characterized by increasing. In an article comprising an array of microcubes, there are two adjacent microcubes with no front edge parallel to the plane at a location adjacent to all planes in the space, At least one microcube of the array is rectangular or pentagonal, At least one microcube of the array is face-more-parallel, Wherein said at least one microcube has a protruding area of 1 mm ² or less. 31. The method of claim 30, wherein at least one microcube of the array has a symmetry plane in which the cube axis of the microcube is disposed, such that the entrance angularity of the array is in a plane perpendicular to the symmetry plane. An article characterized by increasing. In an article comprising an array of microcubes, there are two adjacent microcubes with no front edge parallel to the plane at a location adjacent to all planes in the space, The at least one microcube of the microcube shape is rectangular, At least one side of the rectangular microcube is pentagonal. In an article comprising an array of microcubes, all 3x3 subarrays of the microcube are non-ruleable, and at least one microcube in the 3x3 subarrays of the microcube is rectangular or pentagonal, and the at least one The microcube is inclined to plane parallelism, wherein the at least one microcube has a protruding area of 1 mm ² or less. 34. The method of claim 33, wherein the at least one microcube of the array has a symmetry plane in which the cube axis of the microcube is disposed so that the entrance angularity of the array is in a plane perpendicular to the plane of symmetry. An article characterized by increasing.