MXPA00000091A - Method of manufacturing a plurality of laminae for use in a mold for forming retroreflective cube corner articles, mold and articles formed therewith - Google Patents

Abstract

A method is disclosed for manufacturing a plurality of laminae for use in a mold suitablefor use in forming retroreflective cube corner articles. Each lamina has opposing first and second major surfaces defining therebetween a first reference plane. Each lamina further includes a working surface connecting the first and second major surfaces. The working surface defines a second reference plane substantially parallel to the working surface and perpendicular to the first reference plane and a third reference plane perpendicular to the first reference plane and the second reference plane. The method includes orienting a plurality of laminae to have their respective first reference planes parallel to each other and disposed at a first angle relative to a fixed reference axis. At least two groove sets are formed in the working surface. Each groove set includes at least two parallel adjacent V-shaped grooves in the working surface of the laminae. The at least two groove sets form first, second and third groove surfaces that intersect substantially orthogonally to form a plurality of cube corner elements. Each of the plurality of cube corner elements is preferably located on essentially one of the plurality of lamina. The plurality of laminae can be oriented at a second angle relative to the fixed reference axis prior to forming at least one of the groove sets. A mold according to the present invention and a retroreflective article made therefrom are also disclosed.

Description

METHOD TO MANUFACTURE A PLURALITY OF SHEETS FOR USE IN A MOLD TO FORM ARTICLES RETRORREFLECTORS OF CORNER OF CUBES, MOLD AND ARTICLES FORMED WITH THE SAME FIELD OF THE INVENTION The present invention relates generally to molds suitable for use in the formation of laminate corners of corner cube readers, to methods for making them, and to a re-reflective laminate formed from these molds. . In particular, the invention relates to molds formed from a plurality of thin sheets and methods for making them.

BACKGROUND OF THE INVENTION The reflecting materials are characterized by the ability to redirect incident light in the material back to the source of light source. This property has led to the widespread use of retroreflective laminate in a variety of conspicuous applications. Retreflective laminate is frequently applied to rigid, flat items, such as, for example, road signs and barricades; however, it is also used in REF .: 32543 irregular or flexible surfaces. For example, the reflective laminate may be adhered to the side of a truck trailer, which requires the laminate to pass over the ridges and protruding rivets, or the laminate may adhere to a flexible body portion such as a safety vest of the road worker or other safety garment. In situations, where the underlying surface is irregular or flexible, the retroreflective laminate reader desirably possesses the ability to conform to the underlying surfaces without sacrificing retrospective reflective performance. Additionally, the laminate retainer is frequently packaged and shipped in roll form, thus requiring the laminate to be flexible enough to be wound around a core. Two known types of laminate are the micro-spheres laminate and the cube corner laminate. The microsphere-based laminate, sometimes referred to as the "beaded" laminate employs a multitude of microspheres, typically, at least partially embedded in a binder layer and having associated specular or diffuse reflective materials (e.g. pigment particles, metal leaflets or vapor coatings, etc.) to reflect the incident light. United States Patent Nos. 3,190,178 (McKenzie), 4,025,159 (MacGrath), and 5,066,098 (Kult) illustrative examples are described. Advantageously, the microsphere-based laminate can generally adhere to corrugated or flexible surfaces. Also, due to the symmetry of the retrorefers of beads, the microsphere-based laminate exhibits a relatively uniform, uniform overall light return when rotated about an axis normal to the laminate surface. In this way, this laminate based on microspheres has a relatively low sensitivity to the orientation in which it is placed on a laminate surface. However, in general, this laminate has a lower re-re-reading efficiency than the cube corner laminate. The cube corners reflecting laminate comprises a body portion typically having a substantially planar base surface and a structured surface comprising a plurality of cube corner elements, opposite the base surface. Each cube corner element comprises three mutually substantially mutually perpendicular optical surfaces intersecting at an individual reference point, or apex. The base of the corner corner element acts as an opening through which light is transmitted in the corner corner element. In use, the incident light in the base surface of the laminate is reflected in the base surface of the laminate, it is transmitted through the bases of the corner corner elements placed in the laminate, it is reflected from each of the three optical surfaces, cube corner, perpendicular, and redirected to the light source. The symmetrical axis, also called the optical axis, of a cube corner element is the axis extending through the apex of the cube corner and at an equal angle with the three optical surfaces of the cube corner element. The cube corner elements typically exhibit the highest optical efficiency at incident light at the base of the element closely along the optical axis. The amount of light reflected by a cube corner reflector falls as the incident angle of the optical axis is deflected.

The maximum efficiency of rereflecting the laminate reorretrode cube corner reader, is a fusion of the geometry of the cube corner elements on the structured surface of the laminate. The terms "active area" and "effective aperture" are used in the technique of cube corners to characterize the portion of a cube corner element that reflects the light incident on the base of the element. A detailed teaching regarding the determination of the active aperture for a cube corner element design is beyond the scope of the present disclosure. In Ec hardt, Applied Optics, v. 10, n. July 7, 1971, pp. 1559-1566 a method for determining the effective opening of a cube corner geometry is presented. US Patent No. 835,648 to Straubel also discusses the concept of effective aperture. At a given angle of incidence, the active area can be determined by the topological intersection of the projection of the three cube corner surfaces, on a plane normal to the incident light reflected with the projection of the image surface for the three reflections in the same plane. The term "percent active area" is then defined as the active area divided by the total area of the projection of the cube corner surfaces. The retroreflective efficiency of the retroreflective laminate correlates directly to the percentage of active area of the cube corner elements in the laminate. The expected return of the total light (TLR) for an array of coupled pairs of cube corner can be calculated from a knowledge of the percent of the active area and intensity of the beam. The intensity of the beam can be reduced by the losses of the front surface and by the reflection from each of the three cube corner surfaces for a reflected beam. The total return of light is defined as the product of the percentage of active area and the intensity of the lightning, as a percentage of the total incident light that is reflected in the light. In US Patent No. 3,712,706 (Stamm) a description of the total return of light is presented for cube corner arrangements, directly machined. Additionally, the optical characteristics of the retroreflective pattern of the reflective laminate are, in part, a function of the geometry of the cube corner elements. In this way, distortions in the geometry of the cube corner elements can cause independent distortions in the optical characteristics of the laminate. To inhibit undesirable physical deformation, the cube corner elements of the retroreflective laminate are typically made of a material having a relatively high elastic modulus, sufficient to inhibit the physical distortion of the cube corner elements during elastomeric bending or elongation. of the laminate. As discussed above, it is often desirable that the reflective laminate be sufficiently flexible to allow the laminate to adhere to a substrate that is corrugated or that is self-flexing, or to allow the laminate to retract. read or roll on a roll for storage and sent. The cube corner retreflective laminate is manufactured by first manufacturing a master mold including an image, either negative or positive, of a desired geometry of a cube corner element. The mold can be replicated using nickel-plated electroplating, chemical vapor position or steam physical position to produce the tool to form the rolling laminate. U.S. Patent No. 5,156,863 to Pricone, et al., Provides an illustrative overview of a process for forming the tool used in the manufacture of the retorref laminate cube corner reader. Known methods for manufacturing the main mold include spiking techniques, techniques of direct machining, and rolling techniques. Each of these techniques has benefits and limitations. In spiked tying techniques, a plurality of spikes, each having a geometric shape at one end, are assembled together to form a cube-corner retraction-reading surface. U.S. Patent Nos. 1,591,572 (Stimson), 3,926,402 (Heenan), 3,541,606 (Heenan et al.), And 3,632,695 from Howell provide illustrative examples. Spike tying techniques offer the ability to manufacture a wide variety of cube corner geometry in an individual mold. However, spiked tying techniques are economically and technically practical for making small cube corner elements (e.g., less than about 1.0 millimeters).

In the techniques of direct work to machine, a series of notches is formed in a unitary substrate to form a surface rorre f or cor corner corner. U.S. Patent Nos. 3, 712, 706 to Stamm and 4,588,258 to Hoopman provide illustrative examples. Direct machining techniques offer the ability to precisely machine, very small cube corner elements, which are compatible with flexible, retroreflective laminates. However, it is not currently possible to produce certain cube corner geometries having very high effective openings at low entry angles using direct machining techniques. By way of example, the theoretical, maximum total light return of the cube corner element geometry shown in U.S. Patent No. 3,712,706 is about 67%. In the rolling techniques, a plurality of sheets, each sheet having geometric shapes at one end, are stamped to form a retracting reading surface of the corner of the cube. German Provisional Publication (OS) 19 17 292, International Publications Nos. WO 94/18581 (Bohn, et al.), WO 97/04939 (Mimura et al.), And WO 97/04940 (Mimura et al.), each describes a molded reflector wherein a groove surface is formed in a plurality of plates. The plates are then inclined at a certain angle and each second plate is changed transversely. This process results in a plurality of cube corner elements, each element formed by two machined surfaces in a first plate and a side surface in a second plate. German Patent DE 42 36 799 to Gubela describes a method for producing a molding tool with a cubic surface for the production of cube corners. An oblique surface is milled or cut in a first direction over the entire length of a band edge. Frequently a plurality of notches are formed in a second direction to form cube corner reflectors in a band. Finally, a plurality of notches are formed vertically on the sides of the band. German Provisional Patent 44 10 994 C2 of Gubela is a related patent. The reflectors described in Patent 44 10 994 C2 are characterized by reflecting surfaces having a concave curvature.

Brief Description of the Invention The present invention relates to a main mold, suitable for use in the formation of the reflective laminate from a plurality of sheets and methods for making the same. Advantageously, the molds manufactured in accordance with the methods described herein allow the manufacture of the retroreflective cube corner reader laminate exhibiting levels of retroreflective efficiency that reach 100%. In order to facilitate the manufacture of the flexible retracting laminate, the described methods allow the manufacture of retracting elements of corner corner readers having a width as small as 0.010 millimeters. Additionally, the present application allows the manufacture of a laminate retorref cube corner reader that exhibits a symmetrical retreflective performance in at least two different orientations. Effective methods in cost, efficient to elaborate methods formed from a plurality of sheets are also described.

A plurality of sheets are machined simultaneously to form a plurality of corner corner elements. The three mutually perpendicular optical surfaces of each cube corner element are preferably formed in one of the plurality of sheets. That is, the cube corner elements, individual or discrete do not extend preferably through more than one sheet. The three optical surfaces are preferably formed by the machining process to ensure the optical quality surface. A flat skin is preferably maintained between the adjacent sheets during the machining phase and subsequent to this to minimize the problems of dimension and damage due to the handling of the sheets. A plurality of sheets are made for use in a mold suitable for use in the formation of corner items of retroref cube readers. Each sheet has a first and a second main surfaces, opposites that define among these a first reference plane. Each sheet further includes a work surface connecting the first and second major surfaces. The work surface defines a second reference plane substantially parallel to the work surface and perpendicular to the first reference plane and a third reference plane perpendicular to the first reference plane and the second reference plane. One method includes orienting a plurality of sheets, to make their respective first reference planes are parallel to each other and placed at a first angle relative to a fixed, reference axis. At least two sets of grooves are formed on the work surface. Each set of slots includes at least two adjacent V-shaped slots, parallel to the working surface of the sheets. The at least two sets of grooves form a first, a second and a third groove surface that intersect substantially orthogonally to form a plurality of corner corner elements. Each cube corner element is preferably located in essentially one of the plurality of sheets. The plurality of sheets can be oriented at a second angle relative to the fixed reference axis before forming at least one of the sets of slots.

In one embodiment, the step of forming at least two sets of slots includes forming a first set of slots that includes at least two V-shaped slots, adjacent, parallel to the working surface of each of the sheets. Each of the adjacent grooves defines a first groove surface and a second groove surface that intersect in a substantially orthogonal manner to form a first reference edge in each of the respective sheets. A second set of slots is formed which includes at least one slot in the working surfaces of the plurality of sheets. Each slot in the second set of grooves defines a third groove surface that intersects in a substantially orthogonal manner with the first and second groove surfaces to form at least a first corner corner element located in essentially a single sheet. The first cube corner element preferably comprises a plurality of cube corner elements. Each of the plurality of corner corner elements is located essentially in a sheet. An interface between the first and second main, adjacent surfaces is preferably flat. Each sheet is between about 0.025 millimeters and about 1.0 millimeters thick, and more preferably from about 0.1 to about 0.6 millimeters. The method includes the step of orienting the plurality of sheets that includes mounting the sheets in an attachment defining a base plane. The first angle measures between about 5 ° and about 85 ° from a fixed reference axis, normal to the base plane, and more preferably between about 10 ° and about 65 ° and more preferably between about 25 ° to about 45 ° . The step of forming the slit assemblies comprises forming at least one of the sets of slots parallel to the base plane defined by the attachment. Alternatively, the sets of grooves can be formed at an acute angle relative to the base plane defined by the attachment. Slot assemblies may also be formed to vary the distance between the adjacent slots at different depths on the working surface of the sheets.

The process of forming the slit assemblies may comprise removing portions of each of the plurality of sheets close to the working surface of the plurality of sheets using a material removal technique. The first, second and third groove surfaces are formed essentially from the material removal technique. The sets of grooves can be formed by inducing a relative movement between the plurality of sheets and a cutting tool. The step of forming the slit assemblies comprises a machining operation, selected from the group of machine operations consisting of scratching, diamond milling, milling and abrasion. The slots preferably have an included angle that measures between about 10 ° and about 170 °. In one embodiment, the plurality of sheets can be oriented to have their respective first reference planes, parallel to each other and placed at a second angle relative to the fixed reference axis before forming the second set of slots. The step of orienting the plurality of sheets to make their respective reference planes parallel to each other and placed at a second angle with respect to the reference axis, fixed comprises the re-assembly of the plurality of sheets in a suitable attachment. In one embodiment, the step of orienting the plurality of sheets to make their respective first reference planes, parallel to each other placed at a second angle with respect to the reference axis, fixed comprises rotating a plurality of the sheets at 180 ° around the an axis perpendicular to the second reference plane. The cube corner elements are typically arranged in opposite pairs. In a relative mode, the optical axes of the cube corner elements may be generally parallel to provide a total, symmetrical light return around a 360 ° range of orientation angles. Also disclosed is a method for reproducing the working surface of the mold to form a negative copy of the plurality of corner corner elements suitable for use as a mold for forming reflective articles, and a mold formed therefrom. . A retracting article can be formed from the mold by forming the negative copy.

Brief Description of the Drawings Figure 1 is a perspective view of a single sheet, suitable for use in the described methods.

Figure 2 is a perspective view of a plurality of sheets.

Figure 3 is a terminal view of the plurality of sheets oriented in a first orientation.

Figure 4 is a terminal view of the plurality of sheets after a first machining operation.

Figure 5 is a side view of the plurality of sheets after a first machining operation.

Figure 6 is a terminal view of the plurality of sheets presented in Figure 5 oriented in a second orientation.

Figure 7 is a terminal view of the plurality of sheets oriented in a second orientation, wherein the alternating sheet has been rotated through 180 °.

Figure 8 is a terminal view of the plurality of sheets after a second machining operation.

Figure 9 is a view of the upper part of the plurality of sheets after a second machining operation.

Figure 10 is a terminal view of the plurality of sheets oriented in a first orientation.

Figure 11 is a terminal view of the plurality of sheets after a first machining operation.

Figure 12 is a side view of the plurality of sheets after a first machining operation.

Figure 13 is a terminal view of the plurality of oriented sheets of a second operation.

Figure 14 is a terminal view of the plurality of sheets after a second machining operation.

Figure 15 is a side view of the plurality of sheets after a second machining operation.

Figure 16 is a terminal view of the plurality of sheets after a third machining operation.

Figure 17 is a view of the upper part of the plurality of sheets after a third machining operation.

Figure 18 is a perspective view of a single sheet according to the method of Figures 10-17.

Figure 19 is a terminal view of the plurality of sheets oriented in a first orientation.

Figure 20 is a terminal view of the plurality of sheets after a first machining operation.

Figure 21 is a side view of the plurality of sheets after a first machining operation.

Figure 22 is a terminal view of the plurality of sheets oriented in a second orientation.

Figure 23 is a terminal view of the plurality of sheets after a second machining operation.

Figure 24 is a side view of the plurality of sheets after a second machining operation.

Figure 25 is a side view of the plurality of sheets after a third machining operation.

Figure 26 is a view of the upper part of the plurality of sheets after a third machining operation.

Figure 27 is a perspective view of a single sheet according to the method of Figures 19-26.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of sheets are machined in a simultaneous manner to form a plurality of complete cube corner elements. The three mutually perpendicular optical surfaces of each cube corner element are preferably formed in a single sheet. The three optical surfaces are preferably formed by the machining process to secure the optical quality surfaces. A flat skin is preferably maintained between the adjacent sheets during the machining phase and subsequent to this, to minimize alignment problems and damage due to the handling of the sheets. In the description of the various modalities, specific terminology will be used for safety and clarity. However, this terminology is not intended to be limiting and it is to be understood that each term selected in this manner includes all technical equivalents that function in a similar manner. The described methods can be used to form retroreflective elements of a variety of sizes and shapes, such as cube corner elements, complete and truncated cube corner elements. The base edges of the truncated, adjacent corner corner elements in an array are typically co-planar. The base edges of the complete, adjacent cube corner elements in an array are not in the same plane. Related requests filed on the same date with this include: Cube Corner Sheeting Mold and Meting Making the Same (Attorney's Document No. 51946USA9A); Retroreflve Cube Corner Sheeting Mold and Sheeting Formed Therefrom (Attorney's Document No. 53305USA5A); Retroreflve Cube Corner Sheeting, Molds Therefore, and Methods of Making the Same (Attorney's Document No. 53318USA8A); Tiled Retroreflve Sheeting Composed of Highly Canned Cube Corner Elements (Attorney's Document No. 53285USA9A); Dual Orientation Retroreflve Sheeting (Attorney's Document No. 52303USA8B). For description purposes, some Cartesian coordinates can be superimposed on the sheet 10. A first reference plane 24 is centered between the first main surface 12 and the second main surface 14. The first reference plane 24, referred to as the xz plane, It has the y-axis as its normal vr. A second reference plane 26, referred to as the x-y plane, extends substantially co-planar with the work surface 16 of the sheet 10 and has an axis z as its normal vr. A third reference plane 28, referred to as the y_z plane, is centered between the first terminal surface 20 and the second terminal surface 22 and has the x-axis as its normal vr. Although various geometrical attributes will be described herein with reference to the Cartesian reference planes, it will be appreciated that they can be described using other coordinate systems or with reference to the structure of the sheet.

One embodiment of a sheet, as well as a method for making the same, will now be described with reference to Figures 1-9. In Figure 1, a representative sheet 10 useful in making a mold suitable for forming the retroreflective laminate includes a first major surface 12 and a second opposing major surface 14. The sheet 10 additionally includes a work surface 16 and a surface bottom, opposite 18 extending between the first main surface 12 and the second main surface 14. The sheet 10 additionally includes a first end surface 20 and a second opposite end surface 22. In one embodiment, the sheet 10 can be a rectangular, straight polyhedron where the opposing surfaces are substantially parallel. However, it will be appreciated that the opposing surfaces of the sheet 10 need not be parallel. Figures 2-9 illustrate one embodiment of the formation of a structured surface comprising a plurality of optically opposite cube corner elements on the surface of the substrate. work 16 of sheet 10. In summary, the plurality of sheets 10 are oriented such that their respective first reference planes 24 are placed at a first angle? i, relative to a fixed reference axis (Figure 3) . A first set of grooves comprising a plurality of adjacent, parallel grooves 30a, 30b, 30c, etc. (collectively referred to by the reference number 30) is formed on the work surface 16 of the plurality of sheets 10 (Figures 3-5). The grooves of the first set of grooves 30 define the first respective groove surfaces 32a, 32b, 32c, etc., and their respective second groove surfaces 34b, 34c, 34d, etc. Importantly, the first respective groove surfaces 32a, 32b, 32c, etc., cross the second respective groove surfaces 34b, 34c, etc., in a substantially orthogonal manner to define the respective first reference edges 36a, 36b, 36c, etc. As used herein, the terms "in a substantially orthogonal manner" or "in an approximately orthogonal manner" should mean that the dihedral angle between the respective surfaces measures approximately 90 °, slight variations in orthogonality as described and claimed in U.S. Patent No. 4,775,219 to Appeldorn are contemplated by the present invention. A second set of grooves comprising a plurality of adjacent, parallel grooves 46a, 46b, 46c, etc., also forms the working surface 16 of the sheet 10 (Figures 6-8). The slots 46 divide and / or cross the first and second slot surfaces 32, 34. For clarity security, the slot surfaces on one side of the slot 46 are referred to as the first and second slot surfaces 32, 34 and the groove surfaces on the other side of the groove 46 are referred to as the third and fourth groove surfaces 40, 42. The grooves of the second set of grooves define the fifth respective groove surfaces 48a, 48b, 48c, etc. (collectively referred to by the reference number 48) and the sixth slot surfaces 50a, 50b, 50c, etc. (collectively referred to by reference number 50). The fifth slot surfaces 48a, 48b, 48c, etc., cross the first respective slot surfaces 32a, 32b, 32c, etc., and the second slot surfaces 34b, 34c, etc., in a substantially orthogonal manner to forming a plurality of corner corner elements 60a, 60b, 60c on the working surfaces 16 of the respective sheets. Similarly, the sixth groove surfaces 50a, 50b, 50c, etc., cross the first respective groove surfaces 40a, 40b, 40c, etc., and the second groove surfaces 42b, 42c, etc., of a substantially orthogonally to form a plurality of corner corner elements 70a, 70b, etc., on the working surface 16 of the respective sheets. As used herein the term "set of slots" refers to all parallel slots formed in the working surface 16 of As sheets 10. Now, the modality will be explained in greater detail. Returning to Figure 2, a plurality of thin sheets 10 are assembled together such that the first major surface 12 of a sheet 10 is adjacent to the second major surface 14 of an adjacent sheet 10. Preferably, the plurality of sheets 10 mounts in a conventional design attachment capable of securing the plurality of adjacent sheets together. The accessory preferably defines a base plane 80 (Figure 3) which is substantially parallel preferentially to the bottom surface 18 of the sheets 10 when the sheets 10 are placed as shown in Figure 2. The plurality of sheets 10 can be characterize by a system of Cartesian coordinates as described previously. Preferably, the work surface 16 of the plurality of sheets 10 is substantially co-planar, when the sheets are placed with their first reference planes 24 perpendicular to the base plane 80. In Figure 3, the plurality of sheets 10 they guide to make their first reference planes 24 placed at a first angle? i from a fixed reference axis 82, normal to the base plane 80. In one embodiment, the first angle? i is approximately 27.8 °. However, in practice it may be between about 1 ° and about 85 °, and more preferably between about 10 ° and about 60 °, and more preferably between about 25 ° and about 45 °. With reference to Figures 4-5, a first set of grooves comprising a plurality of adjacent, parallel, V-shaped grooves 30a, 30b, 30c, etc. (collectively referred to by the reference number 30) is formed on the work surface 16 of the plurality of sheets 10 with the sheet placed at an angle? i. At least two grooves 30 are formed on the work surface 16 of the plurality of sheets 10. The grooves 30 define the first groove surfaces 32a, 32b, 32c, etc. (collectively referred to by the reference number 32) and the second slot surfaces 34b, 34c, 34d, etc. (collectively referred to by the reference number 34) which is crossed as shown in the slot vertices 33b, 33c, 33d, etc. (collectively referred to by reference number 33). At the edge of the sheets, the slot forming operation can form a single slot surface 32a. The groove surfaces 32a and 34b of the adjacent grooves 30a, 30b intersect approximately orthogonally along a reference edge 36a. Similarly, the surfaces of adjacent grooves 32b and 34c intersect approximately orthogonally along the reference edge 36b. This can be achieved by forming the slots 30 using a cutting tool having an included angle of 90 °. Preferably, this pattern is repeated across the entire work surface 16 of the plurality of sheets 10. The groove vertices 33 are preferably separated for approximately 0.01 millimeters and approximately 1.0 millimeters, however, these values are not intended to be 1 imi tantes. The slots 30 are formed by removing the portions of the work surface 16 from the plurality of sheets, using suitable material removal techniques including precision machining techniques such as abrasive grinding, scratching, grooving and milling with Diamond. Laser abrasion or chemical etching techniques can also be used. In one embodiment, the slots 30 are formed in a high precision machining operation in which a diamond cutting tool having an included angle of 90 ° moves repetitively transversely through the working surface 16. of the plurality of sheets 10 along an axis that is substantially parallel to the base plane 80. The diamond cutting tool, however, it can be moved along an axis that is not parallel to the base plane 80, such that the cutting tool of variable depth through the plurality of sheets 10. Additionally, the machining tool can be kept stationary while the plurality of sheets is placed in motion; any relative movement between the sheets 10 and the machining tool is contemplated. In the embodiments of Figures 2-5, the slots 30 of the first set of slots are formed at a depth such that the first respective reference edges 36 cross the first major surface 12 and the second major surface 14 of each sheet. In this manner, in the terminal view shown in Figure 4, the reference edges 36 and the groove vertices 33 form substantially continuous lines extending along an axis parallel to the base plane 80. Additionally, the grooves 30 are they form such that the respective reference edges 36 are placed in a plane crossing the respective first reference planes 24 and the second reference plane 26 at orthogonal angles. Thus, in a top plan view, the respective first reference edges 36, will appear to be perpendicular to the respective first reference planes 24 of the plurality of sheets 10. However, the slots 30 may also have smaller depths. For example, if the depth of the tool is decreased, the groove vertices 33 will be formed closer to the work surface 16 and flat, transient regions will be formed. To finish the formation of the cube corner elements on the work surface 16 of the sheets 10, a second set of slots is formed by machining a single slot in each sheet 10 along an axis substantially parallel to the Reference plane 24. In the embodiment illustrated in Figures 6-8, the plurality of sheets 10 are removed from the assembly and the alternating sheets (10b, 10d, etc.) are rotated 180 ° about an axis perpendicular to the second plane reference 26. The plurality of sheets is then traced with their respective respective reference planes 24 arranged in a preferred manner in a manner shown in Figure 7. With reference to Figures 8 and 9, a second set of slots preferably includes the less a slot 46 in each sheet 10 is formed on the work surface 16 of the plurality of sheets 10. In the described embodiment, the second slots 46a, 46b, 46c etc. (collectively referred to as 46) define the fifth slot surfaces, respectively 48a, 48b, 48c, etc. (collectively referred to as 48) and the sixth slot surfaces 50a, 50b, 50c, etc. (collectively referred to as 50) intersecting at the groove vertices, respective 52a, 52b, 52c, etc. (collectively referred to as 52) along the axes that are perpendicular to the third reference plane 28. The second grooves 46 are formed such that the fifth groove surfaces 48 are substantially orthogonal to the first respective groove surfaces (e.g. 32a, 32b, etc.) and the second groove surfaces (for example 34a, 34b, etc.). The formation of the fifth groove surfaces 48, as described, produces a plurality of corner corner elements 60a, 60b, etc. (collectively referred to as 60) and a work surface 16 of the alternating sheets 10. Each corner element of cube 60 is defined by a first groove surface (32a, 32b, etc.), a second groove surface (34a, 34b, etc.) and a portion of the fifth groove surface 48 that intersect each other at a point to define a peak of corner of cube, or apex 62. Similarly, the sixth groove surfaces 50 are substantially orthogonal to the respective third groove surfaces (e.g. 40a, 40b, etc.) and the fourth groove surfaces (e.g. 42a, 42b, etc.). As noted above, the first and fourth slot surfaces 40, 42 were formed by the first set of slots 30. The formation of the sixth slot surface 50 also produces a plurality of corner corner elements 70a, 70b, and so on. (collectively referred to as 70) and a work surface 16 of the alternating laminate 10.

Each corner corner element 70 is defined by a third groove surface (40a, 40b, etc.), a fourth groove surface (42a, 42b, etc.) and a portion of the sixth groove surface 50 that intersects each other in a point to define a hub corner peak, or apex 72. Preferably, both groove surfaces 48 and 50 form a plurality of hub corner elements on the work surface 16 of sheet 10. However, it will be appreciated that the second groove 46 can be formed such that only the groove surface 48 or the groove surface 50 forms the corner corner elements. The cube corner elements 60, 70 are opposing pairs that generate opposite, reorreflexion patterns, although not necessarily identical. The corner corner elements 60, 70 preferably generate mirrored or symmetrical mirroring patterns, such as elements that are substantially identical but rotate 180 ° relative to each other. In an alternative embodiment, the second set of slots 46 can be cut in the stack of sheets shown in Figure 6 so that the resulting cube corner elements 60, 70 are all aligned in the same direction. That is, the axes of symmetry or optical axes of the corner corner elements 60, 70 are generally parallel. Similarly, the sheets 10b, 10d, etc. can be rotated 180 ° after the second set of slots 46 is cut (see figure 8). The total light return for the corner corner elements 60, 70, aligned in the same direction is symmetrical about a 360 ° interval of the orientation angles. A pattern of asymmetric torque reflection can be desired for some applications, such as pavement markers or other items that are viewed from a narrow range of orientation angles. One method of the present disclosure comprises simultaneously machining a plurality of sheets, each sheet comprising one or more discrete cube corner elements. The cube corner elements preferably do not extend through more than one sheet. For example, the three mutually perpendicular optical surfaces 32, 34, 48 of the cube corner elements 60 are machined in a single sheet. Similarly, the three optical surfaces 40, 42, 50 of the corner corner elements 70 are machined in a single sheet. The corner corner elements 60, 70 can be located on the same or different sheets. The corner corner elements 60, 70 are advantageously formed with only two sets of slots 30, 46 by the machining process to ensure an optical quality surface. A flat interface between the main surfaces 12, 14 is maintained between the adjacent sheets during the machining phase and in the subsequent mold formed therefrom to minimize the problems of alignment and damage due to the handling of the sheets, to minimize the separations between the adjacent sheets that would degrade the quality of the negative copies, and to minimize the flooding that migrates in the separations between the sheets. Figures 10-18 illustrate an alternative method for forming the mold of Figures 1-9 into a plurality of sheets as illustrated in Figure 2, using three sets of slots 130, 138, 146. Preferably, the surfaces of respective work 116 of the plurality of sheets 110 are substantially coplanar when the sheets are placed with their respective first reference planes 124 perpendicular to the base plane 180. The reference planes 124, 126, 128 correspond to the reference planes 24, 26, 28, respectively, discussed previously. With reference to Figure 10, the plurality of sheets 110 are oriented to have their first reference planes 124, placed at a first angle ßi, from a fixed reference axis 182 normal to the base plane 180. In a ßi mode it is approximately 27.8. °. However, ßi may alternatively be between 1 ° and about 85 °, and more preferably between about 10 ° and about 60 °. With reference to Figs. 11-12, a first set of grooves comprising a plurality of adjacent, parallel, V-shaped grooves 130a, 130b, 130c, and the like (collectively referred to as 130) is formed on work surfaces 116 of the plurality of sheets 110 with the sheet placed at the angle ßi. At least two grooves 130 are formed in the work surface 116 of the plurality of sheets 110. The grooves 130 define the first groove surfaces 132a, 132b, 132c, etcetera (collectively referred to as 132) and the second groove surfaces 134b, 134c, 134d, etc. (collectively referred to as 134) intersecting as shown in the groove vertices 133b, 133c, 133d, etc. (collectively referred to as 133) At the edge of the sheet, the groove forming operation can form an individual slot surface 132a. The groove surfaces 132a and 134b of the adjacent grooves intersect approximately orthogonally along a reference edge 136a. Similarly, the adjacent slot surfaces 132b and 134c intersect approximately orthogonally along the reference edge 136b. Preferably, this pattern is repeated through the entire work surfaces 116 and the plurality of the sheets 110. The grooves 130 are formed by removing portions of the work surface 116 from the plurality of sheets using surface removal techniques. Suitable materials, including precision machining techniques such as abrasion, scratching, grooving and diamond milling. Laser ablation or chemical etching techniques can also be used. In one embodiment, the slots 130 are formed in a high precision machining operation in which a diamond cutting tool having an included angle of 90 ° repeatedly moves transverse through the working surfaces 116. of the plurality of sheets 110 along an axis that is substantially parallel to the base plane 180. However, the diamond cutting tool could alternatively be moved along an axis that is not parallel to the base plane 180 such that the tool cuts at a variable depth through the plurality of sheets 110.

Additionally, the machining tool could be kept stationary while the plurality of blades are placed in motion; any relative movement between the blades 110 and the machining tool is contemplated. In the embodiment of Figures 11-12, the slots 130 are formed at a depth such that the respective first reference edges 136 cross the first major surface 112 and the second major surface 114 of each sheet. Thus, in the terminal view of Figure 11, the reference edge 136 and the groove vertices 133 form substantially continuous lines extending along an axis parallel to the base plane 180. Additionally, the grooves 130 are formed such that the respective reference edges 136 are placed in a plane that crosses the respective first reference planes 124 and the second reference plane 126 at orthogonal angles. In this manner, the first respective reference edges 136 will appear perpendicular to the respective first reference planes 124 of the plurality of sheets 110. However, the slots 130 may also have smaller units to form transmissible, flat regions.

With reference to Figure 13, the plurality of sheets 110 are then oriented to have their respective first reference planes 124 placed at a second angle ß2, from the fixed reference angle 182 normal to the base plane 180. In a β2 mode it is approximately 27.8 °. However, in practice ß2 may be between about 1 ° and about 85 °, but preferably between about 10 ° and about 60 °. The angle ß2 is independent of the angle ßi and does not need to be equal to ßi. To orient the plurality of sheets 110 in the angle ß2, the sheets 110 are preferably removed from the attachment and reassembled with their respective first reference planes placed at the angle ß2. With reference to Figures 14-15, a second set of grooves comprising a modality of adjacent, parallel, V-shaped grooves 138b, 138c, etc. (collectively referred to as 138) is formed on work surfaces 116 of the plurality of sheets 110 with the sheets placed at angle ß2. At least two adjacent grooves 138 are formed on the work surface 116 of the plurality of sheets 110. The grooves 138 define three groove surfaces 140a, 140b, 140c, etcetera (collectively referred to as 140) and on four groove surfaces 142b, 142c, 142d, etc. (collectively referred to as 142) they use as shown in slot vertices 141b, 141c, 141d, etc. (collectively referred to as 141). At the edge of the sheet, the groove forming operation can form an individual groove surface 140a. The groove surfaces 140a and 142b of the adjacent grooves cross approximately orthogonally along a reference edge 144a. Similarly, the adjacent slot surfaces 140b and 142c intersect approximately orthogonally along the reference edge 144b. Preferably, this pattern is repeated through the entire work surfaces 116 of the plurality of sheets 110. The slots 138 of the second set of slots are also preferably formed by a high precision machining operation in which a The diamond cutting tool having an included 90 ° angle repeatedly moves transverse through the work surface 116 of the plurality of sheets 110 along a cutting axis that is substantially parallel to the base plane 180. Again, it will be noted that it is important that the adjacent slot surfaces 138 cross along the reference edges 144 to form orthogonal, dihedral angles. The included angle of each slot can measure different from 90 °. The slots 138 are preferably formed at approximately the same depth on the work surface 116 of the plurality of sheets 110 as the slots 130 in the first set of slots. Additionally, the grooves 138 of the second set of grooves are preferably formed such that the respective groove vertices (e.g., 141a, 141b, etc.) and the respective reference edges (e.g. 144a, 144b, etc.) are substantially coplanar with the grooves. respective slot vertices (e.g., 133a, 133b, etc.) and the respective reference edges (e.g. 136a, 136b, etc.) of the slots 130 in the first set of slots. With reference to Figures 16-17, a third set of slots preferably including at least one slot 146 in each sheet 110, is formed on the work surface 116 of the plurality of sheets 110. In the embodiment described, the third slots 146a, 146b, 146c, et cetera (collectively referred to as 146) define the fifth slot surfaces, respectively 148a, 148b, 148c, etcetera (collectively referred to as 148) and the sixth respective slot surfaces 150a, 150b, 150c, etc. (collectively referred to as 150) crossing at the respective slot vertices 152a, 152b, 152c, etc. (collectively referred to as 152) along the axis which is parallel to the respective first reference planes 124. The third slots 146 are formed such that the fifth respective slot surfaces 148 are placed in a plane that is substantially orthogonal to the respective first slot surfaces, (e.g., 132a, 132b, etc.) and the respective second groove surfaces (for example 134a, 134b, etc.). The formation of the fifth groove surfaces 148 in this manner produces a plurality of corner corner elements 160a, 160b, and so on. (collectively referred to as 160) on the work surface 116 of the respective sheet 110.

Each cube corner element 160 is defined by a first groove surface (132a, 132b, etc.) a second groove surface 134b, 134c, etc.) and a portion of a fifth groove surface 148 that intersect each other at a point to define a corner peak of cube or apex 162. Similarly, the sixth groove surface 150 is placed in a plane that is substantially orthogonal to the respective third groove surfaces (e.g. 140a, 140b, etc.) and fourths respective slot surfaces (e.g. 142b, 142c, etc.). The formation of the sixth surfaces 150 also produces a plurality of cube corner elements 170a, 170b, etc. (collectively referred to as 170) on the work surface 116 of the sheet 110. Each corner corner element 170 is defined by a third groove surface (140a, 140b, etc.), a fourth groove surface (142a, 142b, etc.) and a portion of the sixth groove surface 150 that mutually intersect at a point to define a cube corner peak, or apex 172. Preferably, both the fifth groove surface 148 and the sixth groove surface 150 form a plurality of corner corner elements on the work surface 116 of the sheet 110. However, it will be appreciated that the third Slot 146 may be formed such that only the fifth groove surface 148 or the sixth groove surface 150 forms the corner corner elements. In a preferred method, the plurality of sheets 110 are reoriented to have their respective first reference planes 124 placed approximately parallel to the reference axis 182 prior to the formation of the plurality of slots 146. However, the slots 146 can be forming with the oriented sheet such that its respective first reference planes are placed at an angle relative to the reference axis 182. In particular, in some embodiments, it may be advantageous to form the respective third slits 146 with the respective sheet 110 placed on the ß2 angle to avoid an additional orientation step in the manufacturing process. Preferably the slots 146 are also formed by a high precision machining operation. In the described embodiment, a diamond cutting tool having the included cut of approximately 55.6 ° moves through the work surface 116 of each sheet 110 along an axis that is substantially contained by the first reference plane 124 of the sheet 110 and which is parallel to the base plane 180. The groove 146 is preferably formed such that the respective groove vertices 152 are slightly deeper than the apexes of the grooves in the first and second groove assemblies. The formation of the slots 146 results in a plurality of sheets 110 having a structured surface substantially as depicted in Figure 18. As discussed in conjunction with Figures 1-9, the method of Figures 10-18 gives result a simultaneous machining of a sheet priority, each having cube corner elements 160 with three mutually perpendicular optical surfaces 132, 134, 148 in a single sheet. Similarly, on the three optical surfaces 140, 142, 150 of the corner corner elements 170 are machined into a single sheet. A flat interface between the main surfaces 112, 114 is maintained between the adjacent sheets during the machining phase and in the subsequent mold formed therefrom to minimize the problems of alignment and damage due to the handling of the sheets. Figures 19-27 illustrate an alternative embodiment of the simultaneous formation of a plurality of cube corner elements in a plurality of sheets, as illustrated in Figure 2. Preferably, the respective working surface 216 of the sheets 210 are substantially co-planar when the sheets are placed with their respective first reference planes 224, perpendicular to the base plane 280. The reference planes 224, 226, 228 correspond to the planes reference 24, 26, 28, respectively discussed above. With reference to Figure 19, the plurality of sheets 210 are oriented to have their first reference planes 224 placed at a first angle? I from a first reference axis 282 normal, to the base plane 280. In one embodiment,? I is approximately 54.74 °. In theory,? I. it can be any angle between about 45 ° and about 90 °, however, in practice it is typically between about 45 ° and about 60 °. With reference to Figures 20-21, a first set of grooves comprising a plurality of parallel adjacent V-shaped grooves 230a, 230b, 230c, etc. (collectively referred to as 230) are formed on work surfaces 216 of the plurality of sheets 210 with the sheet placed in the angle,? i. The slots 230 define the first slot surfaces 232a, 232b, 232c, etcetera (collectively referred to as 232) and the second slot surfaces 234b, 234c, 234d , etc. (collectively referred to as 234) intersecting at the groove vertices 233b, 233c, 233d, etc. (collectively referred to by reference numeral 233) as shown. At the edge of the sheet, the groove forming operation can form a single groove surface, for example, 232a, 234d. Preferably, this pattern is repeated through the concrete work surfaces 216 of the plurality of sheets 210. The slots 230 are formed by removing portions of the work surface 216, as discussed above. In one embodiment, the slots 230 are formed in a high precision machining operation in which a diamond cutting tool having an included angle of 120 ° moves repetitively transversely through the working surfaces 216 of the priority of sheets 210 along an axis that is substantially parallel to the base plane 280. However, it will be appreciated that the diamond cutting tool can move about an axis that is not parallel to the base plane 280 such that the tool cut to a variable depth through the sheet depth 210. In the embodiment of Figures 20-21, the slots 230 are formed at a depth such that the respective slot vertices 233 cross the first major surface 212 and the second main surface 214 of each sheet. In this manner, in the terminal view shown in FIG. 20, the groove vertices 233 form substantially continuous lines extending along an axis parallel to the base plane 280. Additionally, the grooves 230 are formed such that the vertices of slot 233 and edges 236 are placed in planes crossing the first reference planes 224 and the second reference planes 226 at orthogonal angles. The respective groove vertices appear perpendicular to the respective first reference planes 224 of the plurality of sheets 210. However, the grooves 230 can be formed at lower depths or along different axes. With reference to Figures 22-23, the plurality of sheets 210 are then oriented to have their respective first reference planes 224 placed at the second angle 2 2. from the fixed reference axis 282 normal to the base plane 280 and a second set of slots comprising a plurality of adjacent, parallel V-shaped slots 238a, 238b, 238c, etc. (collectively referred to as 238) a work surface is formed 216 of the plurality of sheets 210. In the embodiment described,? 2.is approximately 54.74 °. As discussed previously, in theory,? 2. it can be any angle between approximately 45 ° and approximately 90 °, however, in practice it is preferably between about 45 ° and about 60 °. To orient the plurality of sheets 210 at the angle? 2, the sheets 210 are preferably removed from the attachment and reassembled with their respective first reference planes placed at the angle? 2. The grooves 238 define the third groove surfaces 240a, 240b, 240c, etcetera (collectively referred to as 240) and the fourth groove surfaces 242b, 242c, 242d, and so on. (collectively referred to as 242) intersecting at the groove vertices 241b, 241c, 241d, etc. (collectively referred to as 241) and along the edges 247a, 247b, 247c, etc. as shown. At the edge of the sheet, the groove forming operation can form a single groove surface. Preferably, this pattern is repeated along the entire work surfaces 216 of the sheets 210. The slots 238 of the second set of slots are also preferably formed by a high precision machining operation in which a The diamond cutting tool having an included angle of approximately 120 ° moves repetitively transversely through the work surface 216 of the sheets 210 along a cutting axis substantially parallel to the base plane 280. The grooves 238 They are preferably formed at approximately the same depth as the slots 230. Additionally, the slots 238 are preferably formed such that the slot vertices (eg, 241a, 241b, etc.) are substantially co-planar with the respective slot vertices. (for example 233a, 233b, etc.) of the slots 230. After the formation of the slots 238 in the second set of slots Each sheet 210 preferably appears as shown in Figure 27. With reference to Figures 25-26 a third set of slots comprising a plurality of adjacent, parallel V-shaped slots 246a, 246b, 246c, etc. ( collectively referred to as 246) is formed on the work surfaces 216 of the plurality of sheets 210. The third slots 246 define the fifth slot surfaces 248a, 248b, 248c, etcetera (collectively referred to as 248) and the sixth slot surfaces. , respective 250a, 250b, 250c, etc. (collectively referred to as 250) crossing at the groove vertices 252a, 252b, 252c, etc. (collectively referred to as 252). The third grooves 246 are formed such that the fifth groove surfaces 248 are positioned substantially orthogonal to the respective first groove surfaces 232 of the respective third groove surfaces 240. The formation of the fifth groove surfaces 248 as described produces a plurality of cube corner elements (eg, 260a, 260b, 260c, etc.) collectively referred to as reference number 260, on the work surface 216 of the respective sheet 210. Each corner corner element 260 is defined by a first slot surface 232, a third slot surface 240 and a fifth slot surface 248 mutually intersecting a point to define a hub corner peak, or apex 262. Similarly, the sixth slot surfaces 250 are they place substantially orthogonal to the second groove surfaces 234 and the fourth groove surfaces 242. The formation of the sixth groove surfaces a 250 also produces a plurality of corner corner elements 270a, 270b, etc. (collectively referred to by the reference number 270) on the work surface 216 of the sheet 210. Each corner corner element 270 is defined by a second groove surface 234, a fourth groove surface 242 and a sixth groove surface 250 that intersect each other at a point to define a hub or apex corner peak 272. Preferably, both the fifth groove surface 248 and the sixth slot surface 250 forms a plurality of optically opposite cube corner elements on the work surface 216 of the sheet 210. However, it will be appreciated that the third slot 246 can be formed such that only the fifth slot surfaces 248 or the sixth groove surfaces 250 form the corner corner elements. In a preferred method, the plurality of sheets 210 are reoriented to make their respective major planes 224 positioned approximately parallel to the reference axis 282 before forming the plurality of slots 246. In a preferred embodiment, a diamond cutting tool having an included 90 ° angle moves through surfaces 216 of the plurality of sheets 210 along an axis that is substantially parallel to the base plane 280. However, the slots 246 are they can form with the oriented sheet such that the respective main planes are placed at an angle relative to the reference axis 282. The slots 246 are preferably formed such that the respective slot vertices 252 are slightly deeper than the apexes of the slots in FIG. The first and second slot sets. The formation of the slots 246 results in a plurality of sheets 210 having a substantially structured surface as depicted in Figure 27. The work surface 216 exhibits several desirable characteristics such as the re-reflective article. The geometry of the cube corner element formed on the work surface 216 and the sheet 210 can be characterized as a "high efficiency" or "full" cube corner element geometry because the geometry exhibits an opening of maximum effective that reaches 100%. In this manner, a retroreflective article formed as a replica of the work surface 216 will exhibit a high optical efficiency in response to incident light to the reflective retracting article approximately along the axes of symmetry of the elements of cube corner. Additionally, the corner corner elements 270 and 260 can be placed in opposite orientations and are symmetrical with respect to the first reference plane 24 and will exhibit a symmetrical reflectance reflective performance in response to incident light in the article. read at high entry angles. The sheets are preferably formed from a dimensionally stable material capable of maintaining precision tolerance, for example, machine-worked plastics (eg, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate) or metals. (for example, brass, nickel, copper, or aluminum). The physical dimensions of the sheets are restricted mainly by the limitations of machining. Each sheet is preferably between about 0.025 millimeters and about 1.0 millimeters thick and more preferably about 0.1 to about 0.6 millimeters, between about 5 and about 100 millimeters high and between about 10 and about 500 millimeters wide. These measurements are provided for illustrative purposes only and are not intended to be limiting. In the manufacture of reflective articles such as the retroreflective laminate, the structured surface of the plurality of sheet is used as a main mold that can be reproduced using elect rformation techniques or other conventional reproduction technology. The plurality of sheets may include substantially identical cube corner elements or may include cube corner elements of varying sizes, geometries or orientations. The structured surface of the replica, referred to in the art as the "stamper" contains negative image of the cube corner elements. This replica can be used as a mold to form a retroreflective article. More commonly, however, a large number of positive or negative replicas are assembled to form a mold large enough to be useful in forming retroreflective sheeting. The retroreflective laminate can then be manufactured as an integral material, for example, by embedding a preformed sheet with an arrangement of corner corner elements as described above or by casting a fluid material in a mold. See JP 8-309851 and U.S. Patent No. 4,601,861 (Pricone). Alternatively, the beret-lapping laminate can be manufactured as a stiffened product by casting the corner corner elements against a preformed film as taught in PCT application number WO 95/11464 and the United States patent number 3, 648,348 or by laminating a preformed film to the preformed corner corner elements. By way of example, the lamination can be made using a nickel mold formed by nickel electrolytic deposition on a main mold. The embossed elect mold can be used as a stamper to emboss the mold pattern on a polycarbonate film of approximately 500 μm thick having a Refractive Index of about 1.59. The mold can be used in a press with the pressing being carried out at a temperature of about 175 ° to about 200 ° C. The materials useful for making this reflective laminate are preferably materials that are dimensionally stable, durable, resistant to the weather and easily formables in the desired configuration. Examples of suitable materials include acrylics, which generally have a Refractive Index of about 1.5, such as the Plexiglas resin of Rohm and Hass.; thermosetting acrylates and epoxy acrylates, preferably radiation cured polycarbonates having an Index of about 1.6; polyethylene-based ionomers (sold under the name "SURLYN"); polyesters, and cellulose acetate butyrates. In general, any optically transmissive material that is formable can be used, typically under heat and pressure. Other materials suitable for forming the reflective back laminate are described in U.S. Patent No. 5,450,235 to Smith et al. The laminate may also include colorants, dyes, UV absorbers or other additives as needed. It is desirable in some circumstances to provide the retracting laminate with a backing layer. A backing layer is particularly useful for the reflective reflector laminate that reflects light in accordance with the principles of internal, total reflection. A suitable backing layer can be made of any transparent or opaque material, including colored materials that can be effectively coupled with the described reader retourine laminate. Suitable backing materials include aluminum laminate, galvanized steel, polymeric materials such as polymethyl methacrylates, polyesters, polyamides, polyvinyl fluoride, polycarbonates, polyvinyl chloride, polyurethanes, and a wide variety of rolled products made from these and other materials.

The backing layer or sheet may be sealed in a grid pattern or any other suitable configuration to the reflective elements. Sealing can be effected by the use of a number of methods including ultrasonic welding, adhesives, or by thermal seal in discrete lubrications in the arrangements of the reflective elements (see, for example, U.S. Patent No. 3,924,928). Sealing is desirable to inhibit the ingress of contaminants such as dirt and / or moisture and to preserve air spaces adjacent to the reflecting surfaces of the corner corner elements. If strength or roughness is required added to the composite product, the polycarbonate, polybutyrate or fiber reinforced plastic backing sheets can be used. Depending on the degree of flexibility of the resulting bending material, the material can be rolled or cut into strips or other suitable designs. The retroreflective material can also be backed with an adhesive and a release sheet can make it useful for application to any substrate without the additional step of applying an adhesive or using a fastening means.

The cube corner elements described herein may be individually adjusted to distribute the light re flected by the articles in a desired pattern or divergence profile, as taught by U.S. Patent No. 4,775,219. Typically, the half-angle error of the inserted slot will be less than + _20 minutes and frequently less than +5 minutes. All patents and patent applications referred to herein, including those described in the background of the invention, are hereby incorporated by reference. The present invention has now been described with reference to the various embodiments thereof. It will be apparent to those skilled in the art that many changes can be made in the described embodiments without departing from the scope of the invention. Thus, the scope of the present invention should not limit the preferred structures in methods described herein, but rather by the broad scope of the following indications.

It is noted that in relation to this date the best known method for the applicant to carry out the present invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property:

Claims (28)

1. A method for making a plurality of sheets for use in a mold suitable for the use of the formation of cube corner articles, retroreflectors, each sheet having a first and a second main, opposite surfaces defining between these a first reference plane, each sheet additionally including a work surface connecting the first and second main surfaces, the work surface defining a second reference plane substantially parallel to the work surface and perpendicular to the first reference plane and a third reference plane perpendicular to the first reference plane and the second reference plane, characterized in that it comprises: orienting a plurality of sheets to make their respective first reference planes are parallel to each other and placed at a first angle with respect to the axis of reference; reference, fixed; and forming at least two sets of grooves, each groove assembly including at least two parallel grooves in the working surface of the sheets, the at least two sets of grooves forming a first, a second and a third groove surface that they intersect in a substantially orthogonal manner to form a plurality of corner corner elements located in the plurality of sheets, each of the corner corner elements being located essentially in one of the plurality of sheets.

2. The method according to claim 1, characterized in that the step of forming at least two sets of grooves comprises: forming a first set of grooves that includes at least two adjacent, parallel V-shaped grooves in the working surface of each one of the sheets, each of the adjacent grooves defining a first groove surface and a second groove surface that intersect substantially orthogonally to form a first reference edge in each of the respective sheets; and forming a second set of grooves that includes at least one groove in the working surface of the plurality of sheets, each groove in the second set of grooves defining a third groove surface that intersects in a substantially orthogonal manner with the first groove. and second groove surface to form a plurality of first corner corner elements.

3. The method according to claim 1, characterized in that the first and second main surfaces, adjacent, comprise a substantially flat interface.

4. The method according to claim 1, characterized in that the sheets comprise a spacing between approximately 0.025 millimeters and approximately 1.0 millimeters.

5. The method according to claim 1, characterized in that the step of orienting the plurality of sheets to make their respective first reference planes parallel to each other and placed at a first angle with respect to a fixed reference axis comprises mounting the plurality of sheets in an attachment that defines a base plane.

6. The method according to claim 5, characterized in that the first angle measures approximately and approximately 85 ° from a fixed reference axis normal to the base plane.

7. The method according to claim 5, characterized in that the first angle measures between approximately 10 ° and approximately 65 ° from a fixed reference axis normal to the base plane.

8. The method according to the rei indication 5, characterized in that the step of forming the sets of grooves comprises forming at least one of the sets of grooves parallel to the base plane.

9. The method according to claim 5, characterized in that the step of forming the sets of grooves comprises forming at least one of the sets of grooves at an acute angle relative to the base plane.

10. The method according to claim 1, characterized in that the step of forming the sets of grooves comprises varying the distance between the adjacent grooves at different depths in the work surface of the sheets.

11. The method according to claim 1, characterized in that the step of forming the sets of grooves comprises removing portions of each of the plurality of sheets close to the working surface of the plurality of sheets using a material removal technique.

12. The method according to the rei indication 11, characterized in that the first, second and third groove surfaces are formed essentially from the technique of material removal.

13. The method according to claim 11, characterized in that the step of forming the sets of grooves comprises inducing relative movement between the plurality of sheets and the cutting tool.

14. The method according to claim 1, characterized in that it additionally comprises the step of orienting the plurality of sheets at a second angle relative to the fixed reference axis before forming at least one of the sets of grooves.

15. The method according to the rei indication 1, characterized in that the step of forming the slit assemblies comprises the machining operation selected from the group of machining operations consisting of scratching, diamond milling, milling and abrasion .

16. The method according to claim 1, characterized in that the grooves have an included angle that measure between approximately 10 ° and approximately 170 °.

17. The method according to claim 2, characterized in that the plurality of sheets are oriented to have their respective reference planes parallel to each other placed at a second angle relative to the fixed reference axis before forming the second set of slots.

18. The method according to claim 17, characterized in that the step of orienting the plurality of sheets to make their respective first reference planes parallel to each other and placed at a second angle with respect to the fixed reference axis comprises tracing the plurality of sheets in an adequate attachment.

19. The method according to claim 17, characterized in that the step of orienting the plurality of sheets to make their respective first reference planes parallel to each other and placed at a second angle with respect to the reference axis, fixed comprises rotating a plurality of blades, 180 ° around an axis perpendicular to the second reference plane.

20. The method according to claim 1, characterized in that the optical axes of the corner corner elements are generally parallel.

21. The method according to claim 1, characterized in that the step of forming at least two sets of grooves comprises: forming a first set of grooves that includes at least two adjacent V-shaped grooves, parallel to the working surface of the sheets, each of the adjacent grooves defining a first and a second groove surface forming a first reference edge; forming a second set of grooves that includes at least two V-shaped grooves, adjacent, parallel to the working surface of the sheets, each of the adjacent grooves defining a fourth groove surface and a fifth groove surface that is cross in a substantially orthogonal manner to form a second reference edge; and forming a third set of grooves that includes at least one groove in the working surface of the sheets, the groove defining the third groove surface and a sixth groove surface, in the first, second and third groove surfaces forming a groove. at least one first cube corner positioned in a first orientation and the sixth groove surface intersecting in a substantially orthogonal manner with the fourth and fifth groove surface to form at least one second cube corner positioned in a second different orientation of the first orientation.

22. The method according to the rei indication 1, characterized in that the step of forming at least two sets of grooves comprises: forming a first set of grooves that includes at least one V-shaped groove in the working surface of the sheets, the slot defining the first groove surface and a fourth groove surface that intersects to define a first corner edge; forming a second set of grooves that includes at least one V-shaped groove in the working surface of the sheets, the groove defining the second groove surface and a fifth groove surface that intersects to define a second groove apex, the first and second groove surface intersecting to define a first reference edge; and forming a third set of grooves that include at least one V-shaped groove in the working surface of the sheets, the groove defining the third groove surface and a sixth groove surface that intersects to define a third groove of the groove. slot, first, second and third groove surface forming at least one corner of a cube placed in a first orientation.

23. A plurality of sheets manufactured according to the method of claim 1.

24. The method according to claim 1, characterized in that it further comprises the step of reproducing the work surface of the mold to form a negative copy of the plurality of corner corner elements suitable for use as a mold for forming articles rorre f lect ores.

25. A mold comprising a negative copy of the plurality of corner corner elements made in accordance with the method of claim 1.

26. A retreflective article formed from the mold that forms the negative copy according to claim 25.

27. A method for manufacturing a plurality of sheets for use in a mold suitable for the use of the formation of cube corner articles, retaining reflectors, each sheet having a first and second opposing main surfaces defining between them a first reference p, each sheet additionally including a work surface connecting the first and second main surfaces, the work surface defining a second reference p substantially parallel to the work surface and perpendicular to the first reference p while the reference p perpendicular to the first reference p and the second reference p characterized in that it comprises: assembling a plurality of sheets in a suitable attachment, the attachment defining a base p; orienting the plurality of sheets in the attachment to make their respective first reference ps are parallel to each other and placed at a first angle relative to a reference axis normal to the base p; machining a first set of grooves including a plurality of adjacent V-shaped grooves in the working surface of each of the sheets, each of the adjacent grooves defining a first groove surface and a second groove surface which intersect substantially orthogonally to form a first reference edge in each of the respective sheets; and machining a second set of grooves that includes at least one groove in the working surface of the plurality of sheets, each groove in the second set of grooves defining a third groove surface that crosses the first reference p in a angle equal to the first angle to form a plurality of corner corner elements on the working surface of the plurality of sheets, each of the plurality of corner corner elements which is located essentially on one of the plurality of sheets.

28. The method according to claim 27, characterized in that the first and second major surfaces comprise a substantially pr interface. SUMMARY OF THE INVENTION A method for making a plurality of sheets for use in a mold suitable for use in the formation of corner items of retroreflective cubes is disclosed. Each sheet has a first and a second, opposite principal surfaces defining between them, a first reference plane. Each sheet, furthermore, includes a work surface connecting the first and second major surfaces. The work surface defines a second reference plane substantially parallel to the work surface and perpendicular to the first reference plane and a third reference plane perpendicular to the first reference plane and to the second reference plane. The method includes orienting a plurality of sheets having their respective first reference planes, parallel to each other and placed at a first angle relative to a fixed reference axis. At least two sets of grooves are formed on the work surface. Each set of slots includes at least two V-shaped slots, adjacent, parallel, on the working surface of the sheets. The at least two sets of grooves form a first, second and third groove surfaces that intersect substantially orthogonally to form a plurality of corner corner elements. Each of the plurality of the cube corner elements is preferably located in essentially one of the plurality of sheets. The plurality of sheets can be oriented at a second angle relative to the fixed reference axis before forming the at least one of the sets of slots. Also described is a mold according to the present invention and a re-reflective article made therefrom.