MXPA00000092A

MXPA00000092A - Retroreflective cube corner sheeting mold, lamina for creating such a mold and method for manufacturing such a lamina

Info

Publication number: MXPA00000092A
Application number: MXPA/A/2000/000092A
Authority: MX
Inventors: Gerald M Benson; Kenneth L Smith
Original assignee: 3M Innovative Properties Company
Priority date: 1997-07-02
Filing date: 2000-01-03
Publication date: 2001-11-21

Abstract

Laminae (12) suitable for use in a mold suitable for use in forming retroreflective sheeting and methods of making such laminae are disclosed. A representative lamina (12) includes a single row of optically opposing cube corner elements disposed on its working surface. The working surface of a lamina is provided with a plurality of cube corner elements formed by the optical surfaces defined by three groove sets. Corresponding surfaces of opposing groove sets intersect substantially orthogonally along a reference edge to define first and second optical surfaces (60, 70) of the respective cube corner elements. The third optical surface of each respective cube corner element is defined by one surface of the third groove set (46).

Description

MOLD FOR LAMINATING RETRORREFLECTORS CUBE CORNERS, PLATE FOR FORMING SUCH MOLDS AND METHOD FOR MAKING SUCH SHEET FIELD OF THE INVENTION The present invention relates generally to molds suitable for use in the formation of laminates, rorref corner-corner readers, to methods for making them, and to a laminate. re trorre f reader 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 Retreflective materials are characterized by the ability to redirect light incident on the material back to the source of source light. This property has led to widespread use of retreflector laminate in a variety of conspicuous applications. The retroreflective laminate is often applied to rigid, flat items, such as, for example, road signs and barricades; however, it is also used in irregular or flexible surfaces. For example, REF. : 32559 The laminate can be attached to the side of a truck trailer, which requires the laminate to pass over the ridges and protruding rivets, or the laminate can adhere to a flexible body portion such as a waistcoat. road worker safety 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 retroreflective reader performance. Additionally, the retroreflective laminate is frequently packaged and shipped in roll form, thereby requiring the laminate to be flexible enough to be wound around a core. Two known types of lamination are the micro-sphere based 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 retract 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 re-account readers, the microsphere-based laminate exhibits a return of total light, relatively uniform in an orientational manner, when it is rotated about an axis normal to the surface of the laminate. . In this way, this micro-sphere-based laminate has a relatively low sensitivity to the orientation in which it is placed on a surface of the laminate. However, in general, this laminate has a lower reflective return efficiency than the cube corner laminate. The laminate retorref cube corner reader 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 on the base surface of the laminate is reflected on the base surface of the laminate, is transmitted through the bases of the corner corner elements placed on the laminate, is reflected from each of the three surfaces optical, 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 reflected light reflected by a cube corner reflector falls as the incident angle of the optical axis is deflected.

The maximum re rereflective efficiency of the cube corner retreflector laminate 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. Additionally, the optical characteristics of the retroreflection pattern of the retroreflective 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 bending or elongation. elastomeric laminate. As discussed above, it is often desirable that the reflective reel 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 retrever reader to be wound up. on a roll for storage and shipping. The cube corner retroreflective 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 laminate retorre f corner cube reader. 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 laminate retorre f corner cube reader. Known methods for manufacturing the main mold include spiking techniques, direct machining techniques, 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 to Ho ell 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 (eg, less than about 1.0 millimeters). In direct machining techniques, a series of notches is formed in a unitary substrate to form a retracting surface of the corner marker. U.S. Patent Nos. 3, 712, 706 to Stamm and 4,588,258 to Hoopman provide illustrative examples. The direct machining techniques offer the ability to exactly machine, very small cube corner elements, which are compatible with the laminates retorref readers, flexible. 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 assembled to form a re-reading surface of the corner of the cube. The 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 discloses 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.

Brief Description of the Invention The present invention relates to a main mold, suitable for use in the formation of the retroreflective 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 laminate of corner of cube that exhibits levels of retroreflective efficiency that reach 100% to facilitate the manufacture of the laminate retorref reader, flexible, the described methods allow the manufacture of elements retorref readers of corner of cube that has a width as small as 0.010 millimeters. Additionally, the present application allows the fabrication of a cube corner retroreflective laminate exhibiting symmetrical bending performance in at least two different orientations. Effective methods in cost, efficient to elaborate methods formed from a plurality of sheets are also described. One embodiment refers to a sheet suitable for use in a mold for the use of the formation of cube corner articles, the removal of readers, the sheet having a first and a second, opposite major surfaces defining between them the first reference plane, the sheet having also a work surface connecting the first and second main surfaces, the work surface defining a second reference plane substantially parallel to the work surface perpendicular to the first reference frame and a third reference frame perpendicular to the first reference plane and the second reference plane. The sheet includes: (a) a first set of grooves that includes at least one V-shaped groove in the working surface of the sheet, the groove defining a first groove surface and a second groove surface that intersects for define a first slot vertex; (b) a second set of grooves including at least one V-shaped groove in the working surface in the sheet, the groove defining a third groove surface and a fourth groove surface that intersects to define a second groove slot, the third groove surface crossing the first groove surface in a substantially orthogonal manner to define a first reference edge; and (c) a third set of grooves including at least two V-shaped grooves, adjacent, parallel to the working surface of the sheet, each groove defining a fifth groove surface and a sixth groove surface intersecting to define a third groove vertex, the fifth groove surface that intersects in a substantially orthogonal manner with a first and third groove surfaces to form at least one corner of a cube positioned in a first orientation. In a modality, the first and second sets of grooves are formed such that the first and third groove surfaces, respectively, intersect in an approximately orthogonal manner to define the reference edges, and the second and fourth groove surfaces intersect in an approximately orthogonal manner to define reference edges, which are substantially parallel to the first reference plane. Finally, the third set of grooves comprises a plurality of grooves having respective vertices extending along an axis perpendicular to the first reference plane. In this embodiment, the sheet comprises a single row of optically opposite cube corner elements placed on the working surface of the sheet. The three mutually perpendicular optical surfaces of each cube corner element are preferably formed of 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 the problems of alignment and damage due to the handling of the sheets. A method for manufacturing a sheet for use in a mold suitable for use in the formation of cube corner articles, for ref readers, the sheet having a first and a second, opposite, major surfaces defining between they are a first reference plane, the sheet including additionally 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. The method includes: (a) forming a first set of grooves that includes at least one V-shaped groove in the working surface of the sheet, the groove defining a first groove surface and a second groove surface intersecting to define a first slot vertex; (b) forming a second set of grooves that includes at least one V-shaped groove in the working surface of the sheet, the groove defining a third groove surface and a fourth groove surface intersecting to define a second groove slot vertex, the third groove surface crossing the first groove surface in a substantially orthogonal manner to define a first reference edge; and (c) forming a third set of grooves that includes at least adjacent, parallel V-shaped grooves in the working surface of the sheet, each groove defining a fifth groove surface and a sixth groove surface that is they cross to define a third groove vertex, a fifth groove surface which cross substantially orthogonally with the first and third groove surfaces to form at least one corner of a cube placed in a first position. A preferred mold assembly includes a plurality of sheets, the sheets including first and second main, parallel, opposing surfaces including a first reference plane, each sheet including a work surface, connecting the first and second surfaces main, 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. The working surface of a plurality of sheets includes: (a) a first set of grooves that includes at least adjacent, parallel V-shaped grooves, a working surface of each of the sheets, a plurality of adjacent grooves defining a first groove surface and a second groove surface that intersect to define a first groove vertex; (b) a second set of grooves that includes at least V-shaped grooves, adjacent, parallel, on the working surface of each of the sheets, a plurality of the adjacent grooves defining a third groove surface and a fourth intersecting groove surface to define a second groove vertex, the third groove surface crossing the first groove surface in a substantially orthogonal manner to define a first difference edge; and (c) a third set of grooves that include at least V-shaped grooves, adjacent, parallel to the working surface of the sheets, the third groove defining a fifth groove surface and a sixth groove surface that is intersect to define a third groove apex, the fifth groove surface that intersects substantially orthogonally with the first and third groove surfaces to form at least one corner of a cube positioned in a first orientation. In one embodiment, the first and second sets of grooves are formed such that their respective vertices extend along axes, in a plan view of the upper part, they are perpendicular to the respective first reference planes. Finally, the third set of grooves comprises a plurality of grooves having respective vertices extending along the axes perpendicular to the first reference plane. In this embodiment, each sheet comprises a single row of optically opposed cube corner elements positioned on the working surface of the sheet. Also disclosed is a method for manufacturing a plurality of sheets for the use of a mold suitable for use in the formation of cube corner articles, reor rreref readers, each sheet having a first and a second, opposing main surfaces. they define between them 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 on the work surface and perpendicular to the first plane of reference. reference and a third reference plane perpendicular to the first reference plane and the second reference plane. The method includes: (a) 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 reference axis, fixed; (b) forming a first set of grooves that includes a plurality of V-shaped grooves in the working surface of the sheet, the respective grooves defining a first groove surface and a second groove surface that intersect to define a groove. first slot vertex; (c) orienting the plurality of sheets to make their respective first reference planes are parallel to each other placed at a second angle relative to the reference axis, fixed; (d) forming a second set of grooves that includes a plurality of V-shaped grooves in the working surface of the sheet, the respective grooves defining a third groove surface and a fourth groove surface that intersects to define a groove. second slot vertex, the respective third groove surfaces crossing the first groove surface in a substantially orthogonal manner to define a first reference edge; and (e) forming a third set of grooves that includes a plurality of V-shaped grooves in the working surface of the sheet, the respective third grooves defining a fifth groove surface and the sixth groove surface intersecting for defining a third groove vertex, the fifth groove surface that intersects in a substantially orthogonal manner with the first and third groove surfaces to form at least one corner of a cube positioned in a first orientation. In a described method, the plurality of sheets are assembled in a suitable attachment defining a basic plane. Preferably, the attachment secures the sheets such that their respective first reference planes are substantially parallel and are placed at a first angle which preferably measures between 45 ° and 90 °, and more preferably measures between 45 ° and 60 ° with relation to a reference axis, fixed that is a normal vector to the base plane. The first set of grooves is then formed by removing the portions of each of the plurality of sheets close to the working surface of the plurality of sheets by using a material removal technique, suitable such as for example as milling, milling with diamond, grinding with a grinding wheel, or grinding. The plurality of sheets are then reassembled in the attachment and secured such that their respective first reference planes are substantially parallel and placed at a second angle of between 45 ° and 90 °, more preferably between 45 ° and 60 ° in relation to a fixed reference axis that is a normal vector to the base plane. The second set of slots is then formed using suitable material ratio techniques as described above. The plurality of sheets are then reassembled in the attachment and secured such that their respective first reference planes are substantially parallel to the reference axis. The third set of grooves is then formed using material removal techniques, suitable as described above.

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 terminal view of a single sheet after a first step of machining.

Figure 3 is a side view of a single sheet after a first step of machining.

Figure 4 is a view of the upper part of a single sheet after the first machining step.

Figure 5 is a terminal view of a single sheet after a second machining step.

Figure 6 is a side view of a single sheet after a second step of machining.

Figure 7 is a top view of a single sheet after a second step of machining.

Figure 8 is a perspective view of a single sheet after a second step of machining.

Figure 9 is a terminal view of a single sheet after a third machining step.

Figure 10 is a side view of a single sheet after a third step of machining.

Figure 11 is a view of the upper part of a single sheet after a third step of machining.

Figure 12 is a perspective view of a single sheet after a third step of machining.

Figure 13 is a perspective view of a plurality of sheets suitable for use in the described methods.

Figure 14 is a terminal view of the plurality of sheets oriented in a first orientation.

Figure 15 is a terminal view of the plurality of sheets after a first machining operation.

Figure 16 is a side view of the plurality of sheets after a first machining operation.

Figure 17 is a terminal view of the plurality of sheets oriented in a second orientation.

Figure 18 is a terminal view of the plurality of sheets after a second machining operation.

Figure 19 is a side view of a plurality of sheets after a second machining operation.

Figure 20 is a side view of the plurality of sheets after a third machining operation.

Figure 21 is a view of the upper part of the plurality of sheets after a third machining operation.

Figure 22 is a terminal view of a single sheet after a first machining operation according to a triple mode.

Figure 23 is a side elevation view of the embodiment shown in Figure 22.

Figure 24 is a plan view of the upper part of the sheet shown in Figure 22.

Figure 25 is a terminal view of a single sheet after a second machining operation according to an alternative mode.

Figure 26 is an elevation, side view of the embodiment shown in Figure 25.

Figure 27 is a plan view of the upper part of the sheet shown in Figure 25.

Figure 28 is an elevation, side view of a single sheet after a second machining operation according to an alternative embodiment.

Figure 29 is a terminal view of the embodiment shown in Figure 28.

Figure 30 is a plan view of the upper part of the sheet shown in Figure 28.

Figure 31 is a plan view of the upper portion of a portion of the working surface of a single sheet.

Figure 32 is an elevation, side view of the work surface shown in Figure 31.

Detailed Description of Preferred Modalities When describing various modalities, specific terminology will be used for clarity security. This terminology, however, 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. Related requests filed on the same date with this include: Cube Corner Sheeting Mold and Method Making the Same (Attorney's Document No. 51946USA9A); Retroreflective Cube Corner Sheeting, Molds Therefore, and Methods of Making the Same (Attorney's Document No. 53318USA8A), Tiled Retroreflective Sheeting Composed of Highly Canned Cube Corner Elements (Attorney's Document No. 5325USA9A); Retroreflective Cube Corner Sheeting, Mold and Method of Making the Same (Attorney's Document No. 51952USA6A), and Dual Orientation Retroreflective Sheeting (Attorney's Document No. 52303USA8B). The described modalities can use cube corner elements, complete of a variety of sizes and shapes. The base edges of the complete, adjacent corner corner elements in an array are not all in the same plane. In contrast, the base edges of the truncated, adjacent corner corner elements in an array are typically co-planar. The complete cube corner elements have a total light return, greater than cube corner elements, truncated for a given amount of corner, but full cubes lose the total light return more quickly at higher entry angles. For the benefit of the complete cube corner elements, it is a greater total light return at lower entry angles, without being too large of a loss in performance at higher entrance angles. The total, predicted light return (TLR) for an array of coupled pairs of cube corner can be incorporated from a knowledge of the percent active area and the intensity of the beam. The intensity of the beam can be reduced by the frontal surface losses in the repression of each of the three cube corner surfaces for a reordered beam. The total light return is defined as the product of the percent active area and the lightning intensity, or one percent of the total incident light that is reflected back. A discussion of the total light return for cube corner arrangements, directly machined, is presented in the United States Patent No. 3,712,706 (Stamm). One embodiment of a sheet, as well as a method for making the same, will now be described with reference in Figures 1-12. With reference to Figure 1, a representative sheet 10 useful in the manufacture of a suitable mold to form a rerecorder laminate is illustrated. The sheet 10 includes a first major surface 12 and a second major surface 14 opposite. The sheet 10 further includes a work surface 16 and an opposing bottom surface 18 extending between the first major surface 12 and a second major surface 14. The sheet 10 further includes a first end surface 20 and a second end surface 22 opposite . In a preferred embodiment, the sheet 10 is a rectangular, straight polyhedron wherein the opposing surfaces are substantially parallel. However, it will be appreciated that on the opposite surfaces of the sheet 10 they need not be parallel. For purposes of description, a Cartesian coordinate system may be superimposed on the sheet 10. A first reference plane 24 is centered between the first major surface 12 and the second major surface 14. The first reference frame 24, preferred as the plane xz, has the axis 10 as its normal vector. A second reference plane 26, referred to as the x-y plane, extends in substantially co-planar fashion from the work surface 16 of the sheet 10 and has the z-axis as its normal vector. 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 vector. For clarity security, various geometrical attributes of the present invention will be described with reference to the Cartesian reference planes as set forth herein. However, it will be appreciated that these attributes can be described using other coordinate systems or with reference to the structure of the sheet. The sheets are preferably formed from a dimensionally stable material capable of maintaining expression tolerances, such as machined plastics (e.g., polyethylene terephthalate, pol imet il-met acrylate, and polycarbonate) or metals (e.g., brass, nickel, copper or aluminum). The physical dimensions of the sheets are restricted mainly by the limitations of machining. The sheets are preferably at least 0.1 millimeters thick, between 5.0 and 100.0 millimeters high and between 10 and 500 millimeters high. These dimensions are provided for illustrative purposes only and are not intended to be limiting. Figures 2-12 illustrate the formation of a structured surface comprising a plurality of optically opposite cube corner elements on the work surface 16 of the sheet 10. In a brief summary, a first set of slots comprising a plurality of adjacent, parallel slots 30a, 30b, 30c, etc. (collectively referred to as 30) the work surface 16 of the sheet 10 is formed (Figures 2-4). The grooves 30 define first groove surfaces 321, 32b, 32c, and second groove surfaces 34b, 34c, 34d, etc. A second set of grooves comprising at least one, preferably a plurality of adjacent, parallel grooves 38a, 38b, 38c, etc. (collectively referred to as 38) the work surface 16 of the sheet 10 is also formed (Figures 5-7). Slot 38 defines the third slot surfaces 40a, 40b, 40c, etc. and the fourth slot surfaces 42b, 42c, 42d, etc. Importantly, the first groove surfaces 32a, 32b, 32c, etc., cross the respective third groove surfaces 40a, 40b, 40c, etc., in a substantially orthogonal manner to define the respective first reference edges 44a, 44b , 44c, etc., and the second slot surfaces 34b, 34c, 34d, etc., crosses the fourth respective slot surfaces 42b, 42c, 42d, etc., in a substantially orthogonal manner to define the respective second reference edges 45b, 45c, 45d, 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. A third set of grooves comprising a plurality of adjacent, parallel grooves 46a, 46b, 46c, etc., is then formed on the work surface 16 of the sheet 10 (Figures 9-11). The grooves of the third set of grooves define the fifth respective groove surfaces 48a, 48, 48c, etc., and the sixth groove surfaces 50a, 50b, 50c, etc. Importantly, the respective fifth slot surfaces, 48a, 48b, 48c, etc., intersect the respective first slot surfaces 32a, 32b, 32c, etc., and the third slot surfaces 40a, 40b, 40c, etc. , in a substantially orthogonal manner to form a plurality of cube corner elements. Additionally, the sixth respective groove surfaces 50a, 50b, 50c, etc., intersect the respective second groove surfaces 34b, 34c, 34d, etc., and the fourth groove surfaces 42b, 42c, 42d, etc., in a substantially orthogonal manner to form a plurality of cube corner elements. As used herein, the term "set of grooves" refers to a plurality of parallel grooves, although not necessarily co-planar, formed in the working surface 16 of the sheet 10. Refer now to FIGS. 4, a first set of grooves comprising at least one, and preferably a plurality of adjacent, parallel grooves 30a, 30b, 30c, etc., (collectively referred to as 30) the working surface 16 of the sheet 10 is formed The grooves define the first groove surfaces 32a, 32b, 32c, etc. (collectively referred to as 32) and the second slot surfaces 34b, 34c, 34d, etc. (collectively referred to as 34) crossing at the groove vertices 33a, 33b, 33c, 33d, etc. (collectively referred to as 33) and along the edges 36a, 36b, 36c, etc., as shown. At the edge of the sheet, a groove formation can form an individual groove surface, for example, 32a, 34d. Preferably, this pattern is repeated through the entire work surface 16 of the sheet 10 as illustrated in Figures 2-4. The groove vertices 33 are preferably separated by a distance measuring between approximately 0.01 millimeters and approximately 1.01 millimeters, however, it is not proposed to limit the present invention to these dimensions. With particular reference to Figure 2, the slots 30 are formed such that the respective slot vertex 33 extends along an axis crossing the first major surface 12, the second major surface 14, and the second plane of reference 26. In the embodiment represented by Figures 2-4, the slots 30 are formed such that each of the respective slot vertices 33, are placed in planes crossing the first reference plane 24 and the second reference plane 26. at orthogonal angles such that, in the list at the top of Figure 4, the respective slot vertices 33 appear perpendicular to the first reference plane 24. In Figures 2-4, the respective slot vertices 33 cross the second plane of reference 26 at an exact angle? i measuring approximately 54.74 °. However, it will be appreciated that the slots 30 may be formed such that the respective slot vertices 33 cross the second reference plane 26 at different angles of 54.74 °. In general, it is feasible to form the respective slot vertices 33 crossing the second reference planes at any angle between approximately 45 ° and close to 90 °. Additionally, the dihedral angle between the opposing surfaces of the slots 30 (e.g., 34b and 32b), measures 120 ° in the embodiment shown in Figures 2-4. More generally, this angle can vary between 90 ° and 180 °. Referring now to Figures 5-8, a second set of slots comprising at least two adjacent, parallel slots 38a, 38b, 38c, etc. (collectively referred to as 38) is formed on the work surface 16 of the sheet 10. The notches define the third groove surfaces 40a, 40b, 40c, etc. (collectively referred to as 40) and the fourth slot surfaces 42b, 42c, 42d, etc. (collectively referred to as 42) intersecting at a slot vertex 41b, 41c, 41d, etc. (collectively referred to as 41) and edges 47a, 47b, 47c, etc. At the edge of the sheet, the groove forming operation can form a single groove surface, for example 42a, 42d. the groove 38a is formed such that the groove surfaces 32a and 40a intersect approximately orthogonally along a first reference edge 44a. Similarly, the groove 38b is formed such that the groove surfaces 34b and 42b cross approximately orthogonally along a second reference edge 45b and the groove surfaces 42b and 40b cross in an approximately orthogonal fashion to along a reference edge 44b. Preferably, this pattern is repeated through the entire work surface 16 of the sheet 10. The respective slot vertices 41 are preferably separated from a distance measuring between about 0.01 millimeters and about 1.01 millimeters, however, they are not It is proposed to limit the present invention to these dimensions. Referring again to Figures 5-8, the slots 38 are formed such that the respective slot vertices 41 extend along an axis crossing the second major surface and the second reference plane 26. Similarly, the slots 38 are formed such that each of the respective slot vertices 41 are placed in planes crossing the first reference plane 24 and the second reference plane 26 at orthogonal angles such that, in the top view of Figure 7, the respective groove vertices 41 appear perpendicular to the first reference plane 24. Further, with particular reference to Figure 7, it can be seen that the grooves 38 in the second set of grooves are preferably formed such that the respective groove vertices 41a, 41b, 41c, etc., are substantially co-planar with the respective slot vertices 33a, 33b, 33c of the first set of slots 30. However, it will be appreciated that the vertices of nura respective opposites (eg, 33, 41) do not need to be co-planners. The respective slot vertices 41 cross the second reference plane 26 at an acute angle 2 2 which measures approximately 54.74 °. It will be appreciated, however, that the grooves 38 may be formed such that the respective groove vertices 41 cross the second reference plane 26 at different angles of 54.74 °. Additionally, although the described mode is manufactured such that? I is equal to? 2, these angles may differ from each other. The relationship between the angles 9? and? 2 are discussed in greater detail later. In general, it is feasible to form grooves such that the respective groove vertices 41 cross the second reference plane 26 at any angle between about 45 ° and about 90 °, however, more preferably the grooves are formed such that the angle? i is equal to? 2, and the angles preferably measure between about 45 ° and about 60 °. In the described embodiment, the dihedral angle between the opposing surfaces of the slots 38 (e.g., 42b and 40b), measures 120 °. In this way, the reference edges 44, 45 are placed at angles? I and? 2 respectively, which measure approximately 45 ° from the second reference plane 26. Fig. 8 presents a perspective view of a representative sheet 10 at the termination of the formation of the slots 38 in the second set of slots. The sheet 10 includes a series of slots 30, 38 formed on the work surface 16 thereof as described above. The respective groove vertices intersect approximately along the first reference frame 24 to define a plurality of V-shaped valleys in a substantial manner on the working surface 16 of the sheet 10. Figures 9-12 illustrate an embodiment of the sheet 10 after forming a third set of grooves comprising a plurality of grooves 46a, 46b, 46c, etc., the sheet 10. A described embodiment, the third grooves 46 define the fifth respective groove surfaces 48a, 48b, 48c, etc. and a sixth surface of respective slots 50a, 50b, 50c, etc., which intersect at the respective slot vertices 52a, 52b, 52c. The grooves 46 are formed such that the respective groove vertices 52 extend along an axis that is substantially perpendicular to the first reference plane 24. The third grooves 46 are formed such that the respective fifth groove surfaces 48 are placed. in planes that are substantially orthogonal to the first respective groove surfaces 32 and the respective third groove surfaces 40 and the respective sixth groove surfaces 50 are placed in planes that are substantially orthogonal to the second groove surface 34 and the four groove surfaces. respective grooves 42. In the described embodiment, the third grooves 46 are formed such that the respective groove surfaces 48, 50 are placed at angles OI, a2, respectively, which measure 45 ° from an axis 82 normal to the second reference plane. In general, the angle OI is equal to? I and the angle a2 is equal to? 2. The formation of the respective fifth groove surfaces 48 according to the invention produces the plurality of corner corner elements 60a, 60b, etc. (collectively referred to by the reference number 60) on the work surface 16 of the sheet 10 which has three mutually perpendicular optical surfaces. Each cube corner element 60 is defined by a respective first slot surface 32a, 32b, 32c, etc., a third respective slot surface 40a, 40b, 40c, etc., and a fifth target slot surface 48a, 48b , 48c, etc., which intersect each other at a point to define a corner peak of the respective hub, or apex 62a, 62b, 62c, etc. Similarly, the formation of the sixth respective groove surfaces 50 also produces a plurality of corner corner elements 70a, 70b, 70c, etc. (collectively referred to by the reference number 70) on the work surface 16 of the sheet 10. Each corner corner element 70 is defined by a respective second groove surface 34b, 34c, 34d, etc., a fourth surface of respective slot 42b, 42c, 42d, etc., and a respective sixth slot surface 50a, 50b, 50c, etc., mutually intersecting at a point to define a respective hub corner peak or apex 63a, 63b, 63c , etc. Preferably, both the fifth groove surface 48 and the sixth groove surface 50 form a plurality of corner corner elements on the working surface 16 of the sheet 10. However, it will be appreciated that in alternative embodiments, the third respective grooves 46 can be formed such that only the fifth groove surfaces 48 or the sixth groove surface 50 form the corner corner elements. Preferably, the work surface 16 is formed using precision machining tool, conventional, and techniques. Mat material removal techniques suitable for forming the slots in the sheet 10 include precision engineering techniques such as, for example, grating, abrading, grooving, and diamond milling. In one embodiment, the second major surface 14 of the sheet 10 can be aligned to a substantially flat surface such as the surface of a precision machined abutment and each slot 30a, 30b, 30c, etc., can be formed on the work surface 16 by moving a V-shaped cutting tool having an included angle of 120 ° along an axis crossing the first work surface 12 and the first reference plane 24 at an angle of approximately 35.26 ° (90 ° - ??). In the described embodiment, each respective groove 30 is formed at the same depth on the work surface 16 and the cutting tool moves laterally by the same distance between the adjacent grooves such that the grooves are substantially identical. Then, the first major surface 12 of the groove 10 can be aligned to the flat surface in each groove 38a, 38b, 38c, etc., can be formed on the working surface 16 by moving a V-shaped cutting tool that it has an included angle of 120 ° along an axis crossing the second work surface 14 and the first reference plane 24 at an angle of about 35.26 ° (90o- ??). Finally, the three slots 46a, 46b, 46c, etc., can form a work surface 16 by moving a V-shaped cutting tool having an angle of 90 ° included along an axis substantially perpendicular to the first plane reference 24. While the three steps of slit formation have been cited in a particular order, one skilled in the art will recognize that the order of the steps is not critical; the steps can be practiced in any order. Additionally, one skilled in the art will recognize that the three sets of grooves can be formed with the sheet aligned in one position; the present description contemplates this method. Additionally, the particular mechanism for securing the sheet to the precision machined attachment is critical; The physical, chemical and electromechanical mechanisms of securing the sheet can be used. In order to form a mold suitable for use in forming retroreflective articles, a plurality of sheets 10 having a work surface 16 including the corner corner element 60, 70 formed as described above can be assembled together in a conventional, adequate attachment. The work surface 16 can then be reproduced using precision techniques such as, for example, nickel-plated elect to form a negative copy of the work surface 16. The technique of electroplating is known to those skilled in the retroreflection art. See, for example, U.S. Patent Nos. 4,478,769 and 5,156,863 to Pricone et al. The negative copy of a work surface 16 can then be used as a mold to form the retorm articles that have a positive copy of the work surface 16. More commonly, additional generations of re-formed electre replicas are they form and assemble together in a larger mold. It will be noted that the original work surfaces 16 of the sheet 10, or positive copies thereof, can also be used as an embossing tool to form the retaining articles of the readers. See, JP 8-309851 and U.S. Patent No. 4,601,861 (Pricone). An expert in the retroreflective technique will recognize that the work surface 16 of each sheet 10 functions independently as a retroreflector. In this way, the adjacent sheet in the mold does not need to be placed at precise angles at distances, one relative to the other.

Figures 13-21 present another method for forming a plurality of sheets suitable for use in a mold suitable for use in the formation of retroreflective articles. In the embodiment shown in Figures 13-21, a plurality of corner corner elements are formed on the working surface of a plurality of sheets while the sheets are secured in an assembly, rather than independently, as described before. The plurality of sheets 10 is preferably mounted such that respective work surfaces 16 are substantially co-planar. In brief summary, the plurality of sheets 10 are oriented such that their respective principal planes are placed at a first angle? I, relative to a fixed reference axis 82 (see Figure 14). A first set of grooves preferably comprising a plurality of adjacent, parallel, V-shaped grooves is formed in the working surface 16 of the plurality of sheets 10 (Figures 15-16). The plurality of sheets is then oriented such that their respective principal planes are placed at a second angle 2 2, relative to the reference axis 82 (see Figure 17). A second set of grooves comprising a plurality of adjacent, parallel, V-shaped grooves forming the work surface 16 of the plurality of sheets 10 (Figures 18-19). The plurality of slots is then oriented such that their respective first reference planes are placed in a substantially parallel manner to the reference axis and a third set of slots comprising a plurality of V-shaped slots in the working surface 16 at each sheet 10 is formed (Figure 20). The formation of the third set of grooves results in a structured surface having a plurality of cube corner elements on the working surface of the plurality of sheets 10 (Figure 21). The embodiment illustrated in Figures 13-21 will now be described in greater detail with reference to Figure 13, a plurality of thin sheets 10 assembled together being illustrated 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 is mounted on a conventional attachment capable of securing the plurality of adjacent sheets together. The details of the attachment are not critical. For purposes of description, however, the attachment preferably defines a base plane 80 which, in a preferred embodiment, is substantially parallel to the bottom surface 18 of the respective sheet 10 when the sheet 10 is placed as referred to in Figure 13. The plurality of sheets 10 can be characterized in the three-dimensional space by a Cartesian coordinate system as described above. Preferably, the respective work surfaces 16 of the plurality of sheets 10 are substantially coplanar when the sheet is placed with its respective first reference planes 74 perpendicular to the base plane 80. With reference to Figure 14, the plurality of sheets 10 they are oriented to have their respective first reference planes 24 placed at a first angle,? i, of a fixed reference axis 82 normal to the reference plane 80. In one embodiment, the angle 9? it measures approximately 54.74 °. In theory, the angle? I can be any angle between about 45 ° and about 90 °, however, in practice the angle? I can typically be measured between about 45 ° and about 60 °. With reference to Figures 15-16, 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 the angle 6 ?. The grooves 30 define the first respective groove surfaces 32a, 32b, 32c, etc. (collectively referred to by the reference number 32) and in the respective second slot surfaces 34b, 34c, 34d, etc. (collectively referred to by the reference number 34) which intersect at the respective slot vertices 33b, 33c, 33d, etc. (collectively referred to by reference number 33). It will be noted, that at the edge of the sheet, the groove forming operation can form on a single slot surface, for example, 32b, 34d. Preferably, this pattern is repeated through the entire work surfaces 16 of the plurality of sheet s 10. The slots 30 are formed by removing portions of the work surface 16 from the plurality of sheets using any of a wide variety of material removal techniques that include precision machining techniques such as joining, grating and diamond milling, or laser ablation or engraving techniques. According to one embodiment, the slots 30 of the first set of slots are formed in a high precision machining operation in which a diamond cutting tool having an included angle of 120 ° moves repetitively and transversely through the work surface 16 of the plurality of sheets 10 along an axis that is substantially parallel to the base plane 80. It will be appreciated, however, that the diamond cutting tool can be moved along a axis that is not parallel to the base plane 80 such that the tool cuts at a variable depth through the plurality of sheets 10. It will also be appreciated that the machining tool can be held stationary while the plurality of sheets is placed in movement; the present description contemplates the relative movement between the plurality of sheets 10 and the machining tool.

In a embodiment shown in Figures 15-16, the slots 30 of the first set of slots are formed at a depth such that the respective slot vertices 33 cross the first major surface 12 and the second major surface 14 of each sheet. In this manner, the terminal view shown in Figure 13, the groove vertices 33 form substantially continuous lines extending along an axis parallel to the base plane 80. Additionally, the grooves 30 are formed such that the groove vertices 33 and the edges 36 are placed in plan and cross the respective first reference planes 24 and the second reference plane 26 at orthogonal angles. In this way, in a plan view of the upper part analogous to Figure 4, the respective groove vertices will appear perpendicular to the respective first reference planes 24 in the plurality of sheets 10. However, the grooves 30 can be formed alternatively at lower depths or along different axes. With reference to Figures 17-19, the plurality of sheets 10 are then oriented to cause their respective first reference planes 24 to be placed at a second angle, 2 2, of the fixed reference axis 82 normal to the base plane 80 and a second set of grooves comprising a plurality of adjacent, parallel V-shaped grooves 38b, 38c, etc. (collectively referred to by the reference numeral 38) the work surfaces 16 of the plurality of sheets 10 are formed. In the described embodiment, the angle 22 measures approximately 54.74 °. As discussed above, angle? 2 can be any angle between 45 ° and 90 °, however, in practice angle? 2 is preferably between about 45 ° and 60 °. In order to orient the plurality of sheets 10 at the angle? 2, the sheets 10 are preferably removed from the attachment 'and reassembled with their respective first reference planes placed at the angle? 2. The grooves 38 define the third groove surfaces, respective 40a, 40b, 40c, etc. (collectively referred to by the reference number 40) and the fourth respective slot surfaces 42a, 42b, 42c, 42d, etc. (collectively referred to by the reference number 42) crossing at the respective slot vertices 41b, 41c, 41d, etc. (collectively referred to by the reference number 41) and along the edges 47a, 47b, 47c, etc. It will be noted that, at the edge of the sheet, the groove forming operation can form an individual groove surface, for example, 40a, 42d. Preferably, this pattern is repeated through the entire work surface 16 of the plurality of sheets 10. The slots 38 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 120 ° moves repeatedly transversely through the working surface 16 of the plurality of sheets 10 along a cutting axis' which is substantially parallel to the base plane 80 The slots 38 are preferably formed at approximately the same depth on the work surface 16 of the plurality of sheets 10 as the slots 30 in the first set of slots. Additionally, the slots 38 in the second set of slots are preferably formed such that the respective slot vertices (e.g., 41a, 41b, etc.) are substantially co-planar with respective slot vertices (e.g. 33a, 33b). , etc.) of the slots 30 in the first set of slots. After forming the slots 38 in the second set of slots, each sheet 10 appears to be preferably substantially identical to the sheet shown in Figure 8. With reference to Figures 20-21, a third set of slots comprising a plurality of slots in the form of adjacent, parallel Vs 46a, 46b, 46c, etc. (collectively referred to by the reference number 46) is formed on the work surfaces 16 of the plurality of sheets 10. The third slots 46a, 46b, 46c, etc. (collectively referred to as 46) define the fifth respective groove surfaces 48a, 48b, 48c, etc. (collectively referred to as 48) and the sixth respective groove surfaces 50a, 50b, 50c, etc. (collectively referred to as 50) crossing at a respective slot vertex 52a, 52b, 52c, etc. (collectively referred to as 52). Significantly, the respective third grooves 46 are formed such that the respective fifth groove surfaces (e.g., 48a, 48b, 48c, etc.) are positioned substantially orthogonally to the respective first groove surfaces (e.g. 32a, 32b, etc.) and the respective third groove surfaces (eg, 40a, 40b, 40c, etc.). The formation of the fifth groove surfaces 48 as described, produces a plurality of corner corner elements (eg, 60a, 60b, 60c, etc.), collectively referred to by the reference number 60, on the work surface 16 of the respective sheet 10. Each corner corner element 60 is defined by a first groove surface 32, a third groove surface 40 and a fifth groove surface 48 that intersect each other at a point to define a corner peak Cube, or apex 62. Similarly, the sixth respective groove surfaces (e.g., 50a, 50b, 50c, etc.) are positioned substantially orthogonal to the respective second groove surfaces (e.g., 34a, 34b, 34c). , etc.) and the respective fourth slot surfaces (eg, 42a, 42b, 42c, etc.). The formation of the sixth groove surfaces 50 also produces a plurality of corner corner elements 70a, 70b, etc. (collectively referred to by the reference numeral 70) on the work surface 16 of the sheet 10. Each corner corner element 70 is defined by a second groove surface 34, a fourth groove surface 42 and a sixth groove surface. slot 50 mutually intersecting at a point to include a hub corner peak, or apex 72. Preferably, both the fifth slot surface 48 and the sixth slot surface 50 form a plurality of cube corner elements, optically opposed, on the work surface 16 of the sheet 10. However, it will be appreciated that the third groove 46 can be formed such that only the fifth groove surface 48 and the sixth groove surface 50 form the corner corner elements. An arrangement of the cube corner elements 60, 70 each having three mutually perpendicular optical surfaces 32, 40, 48, and 34, 42, 50, respectively, which preferably form a single sheet. The three optical surfaces are preferably formed for the machining process to stimulate the optical quality surfaces. A flat interliner 12, 14 is preferably held 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. In a preferred method, the plurality of slots 10 are reoriented to obtain their respective major planes 24 positioned approximately parallel to the reference axis 82 before forming the plurality of slots 46. In a preferred embodiment, a diamond cutting tool that has an included angle of 90 ° moves through the work surface 16 in the plurality of sheets 10 along an axis that is substantially parallel to the base plane 80. However, the grooves 46 can be formed with the sheet oriented so that their respective principal planes are placed at an angle relative to the reference axis 82. The slots 46 are preferably formed such that the respective slot vertices 52 are slightly deeper than the vertices of the slots in the first and second set of slots. The formation of the slots 46 results in a plurality of sheets 10 having a substantially structured surface as depicted in Figure 12. The work surface 16 exhibits several desirable characteristics in a reader scanner. The geometry of the cube corner element formed on the work surface 10 of the sheet 10 can be characterized as a "full" or "high efficiency" cube corner element geometry because the geometry exhibits a maximum objective aperture that reaches 100% with the condition that the peaks of the cube corner are placed approximately at the center of the cube corner element. It will be recognized by one skilled in the art that the corner elements of the cube can be designed with their respective peaks misaligned from the center to face the problems of performance of a wide angle of entry and other problems. In this wayA reader formed as a replica of the work surface 16 will exhibit a wide optical presence in response to the incident light in the reader, approximately along the axes of symmetry of the corner elements. of cube Additionally, the cube corner elements 60 and 70 are placed in opposite orientations and are symmetrical with respect to the first reference plane 24 and will exhibit a mirror-retentive performance symmetric reader in response to the incident light in the reader reorder in high entry angles. Figures 22-30 illustrate an alternative embodiment in which an individual sheet is provided with a plurality of corner corner elements that are not optically opposed in their orientation. In contrast, the cube corner elements shown in Figures 22-30 are placed in substantially the same orientation. In this way, the retroreflective laminate formed as a replica of the sheet presented in Figures 22-30 will exhibit the highly asymmetric input angularity performance. This may be desirable for unidirectional retroreflective applications, such as, for example, barricade markers or certain pavement marking applications. A method for forming this sheet is illustrated particularly with reference to a single sheet. However, it will be appreciated in the machining technique described in connection with Figures 13-21 that they are equally effective in producing a plurality of sheets. In brief, a first set of grooves comprising a plurality of adjacent, parallel grooves 130a, 130b, 130c, etc. (collectively referred to by the reference number 130) is formed on the work surface 116 of the sheet 110 (Figures 22-24). The grooves of the first set of grooves define the respective first groove surfaces 132a, 132b, 132c, etc., and the second groove surfaces, respectively 134a, 134b, 134c, etc. A second set of grooves comprising at least one, and preferably a plurality of adjacent, parallel grooves 138a, 138b, 138c, etc. (collectively referred to by the reference number 138) a work surface 116 of the sheet 110 is also formed (Figures 25-27). The grooves of the second set of grooves define the respective third groove surfaces 140a, 140b, 140c, etc., and the fourth groove surfaces 142a, 142b, 142c, etc. Importantly, the first surfaces of respective grooves 132a, 132b, 132c, etc., cross the respective third groove surfaces 140a, 140b, 140c, etc., in a substantially orthogonal manner to define the respective first reference edges 144a, 144b, 144c, 144d, etc. In the described embodiment, the respective second groove surface 134b, 134c, 134d, etc., is substantially co-planar with the fourth respective groove surfaces 142b, 142c, 142d, etc. The third set of grooves comprising a plurality of adjacent, parallel grooves 146a, 146b, 146c, etc., is then formed on the work surface 116 of the sheet 110 (Figures 28-30). The grooves of the third set of grooves define certain respective groove surfaces 150a, 150b, 150c, etc., which intersect the respective first groove surfaces 132a, 132b, 132c, etc., and the third groove surfaces 140a, 140b, 140c , etc., at an apex 162a, 162b, 162c, 162d, etc., in a substantially orthogonal manner to form a plurality of cube corner elements 160a, 160b, 160c, positioned in the same orientation on the sheet 110. The sheet shown in Figures 21-30 is formed preferentially using precision machining techniques as described above. One embodiment of a sheet can be manufactured by machining the first set of slots 130 using a cutting tool that is asymmetric about its vertical axis and having an included angle that measures approximately 66.1 ° along a crossing axis the second reference plane 26 at an angle? j which measures approximately 50.7 °. Similarly, the second set of slots 138 is preferably formed when machining with a cutting tool that is asymmetric about its vertical axis and having an included angle that measures approximately 66.1 °. Along an axis that crosses the second reference panel 26 at an angle 2 2 that measures approximately 50.7 °. Finally, the third set of grooves 146 is preferably formed by machining with a half-angle tool having an angle a that measures approximately 35 ° along an axis that is substantially perpendicular to the first reference panel 24. The edges 144a, 144b, 144c, 144d, etc., are placed at an angle? I, respectively, which measures approximately 35 ° from the second reference plane 26. In the embodiment of Fig. 28, a =? I. The above discussion has described several particular modalities of the allowed elements describe the cube and the associated coupling configurations required to reproduce the geometries. The methods of the present disclosure can be used to produce a wide variety of geometries of cube corner elements by altering the angles of the slots, (e.g., 2, 2), and the angle at which the sheets are formed. tilt (for example,? i and? i) to thereby change the orientation of the cube corner elements on the working surface of the sheets. Additionally, manufactured articles are included as replicas of the plates. The preceding discussion described several modalities of cube corner geometries. The following paragraphs provide a generic description of the angular relationships within the surfaces of the cube corner elements such that one skilled in the art can produce a wide variety and geometries of cube corner elements. Figures 31-32 present a plan view of the upper part and lateral elevation views of the work surface of a sheet 410 having a cube corner movement 460, individual formed in it. The sheet 410 can be characterized in a three-dimensional space by a first, a second and a third reference plane 424, 426 and 428, respectively. For purposes of illustration, the cube corner member 460 may be defined as a unitary cube consisting of three mutually substantially perpendicular optical surfaces 432, 434, 448. The optical surface 432 is formed by an optical surface of a first slot 430 formed in the working surface of the sheet 410 and the optical surface 434 is formed by an optical surface of a second slot 438 formed in the working surface of the sheet 410. The optical surface 448 is formed by a surface of the slot 446. The reference plane 456a is parallel to the apex of the slot 446 and perpendicular to the second reference plane 426. Similarly, the reference plane 456d is parallel to the vertex of the slot 456 'and perpendicular to the second reference plane . The reference planes 456a and 456b are placed at an angle f3 relative to the third reference plane 428. The angle f3 corresponds to the degree of angular retention of the corner corner element on the surface of the sheet. Subject to the limitations of machining, the angle f3 can vary from 0 °, such that the slot assemblies are formed along axes substantially coincident with the reference planes 424 and 428, about 90 °. However, preferably, the angle f3 measures between 0 ° and 45 °. The optical surface 448 is placed at an angle o? from reference plane 456a. similarly, the optical surface 432 is placed at an angle a2 from the reference plane 456b and the optical surface 434 is positioned at an angle 3 from the reference plane 456b. Preferably, the unit cube 460 is formed using conventional, precision machining techniques and the angles? I ?, a2 and 3 correspond to the angles included in the cutting tools used to form the grooves defining the element. Cube corner 460. Figure 32 shows a side elevational view of a unit cube 460 taken along lines 31-31. The apex 436 of the slot 430 is placed at a right angle ßx relative to the second reference plane 426. Similarly, the apex 441 of the slot 438 is placed at an acute angle ß2 relative to the second reference frame 426. The orientation in the space of the optical surface 432 is a function of the groove angle ax and the angle ßx. Similarly, the orientation in space of the optical surface 434 is a function of the groove angle OII and the angle ß2. A second Cartesian coordinate system can be established using the slot vertices forming the unit cube 460 as the reference axes. In particular, the x axis can be set parallel to the intersection of the panel 456 and the second reference plane 426, the y axis can be set parallel to the second reference plane 426 and perpendicular to the x axis, and the z axis extends perpendicularly to the second reference plane 426. Adopting this coordinate system, the unit normal vectors Ni, N2 and N3 can be defined for the unit cube surfaces 448, 432, and 434, respectively as s igue: N2 = Sen (a2) sin (ßx) i -cos (a) j + cos (ßx) sin (a2) k N3 = sin (ß222) sin (a3) i -eos (a) j + cos (ß2) sin (a3) k The surfaces 432 , 434 and 448 must be substantially mutually perpendicular. In this way, the dot products of the normal vectors is equal to zero. N? »N2 = N2 * N3 = N? * N3 = 0. Therefore, the following condition holds: t an (OII) t an (a2) cos (ßi) = 1 t an (OII) t an (a2) ) eos (ß2) = 1 tan (ßi) an (ß2) = l + tan2 (?) These equations define the geometric orientations specifically for the unit cube 46. The general approach can be applied by a knowledge in the corner techniques of cube with different orientations that include, for example, the cube corner 460. In the manufacture of the retroreflective articles such as retreflector laminate, the structured surface of the plurality of sheets is used as a main mold that can be reproduced using elect rformation techniques or other technology. of conventional reproduction. The plurality of sheets may include substantially identical cube corner elements, or may include cube corner elements of varying size, geometries, or varying orientations. The structured surface of the replica, referred to in the art as "stamping" contains a negative image of the cube corner elements. This replica can be used as a mold to form a retroreflector. However, most commonly a large number of positive or negative replicates are assembled to form a mold large enough to be useful and in the formation of retroreflective lamination. The retroreflective laminate can then be manufactured as an integral material, for example, by embossing the relief in a preformed sheet in an arrangement of corner corner elements as described above or by casting a fluid material in the mold. Alternatively, the retroreflective laminate may be manufactured as a laminated product by hanging the corner corner elements against a preformed film as taught in PCT Application No. WO 95/11464 and U.S. Patent No. .3,648,348 or by laminating a preformed film to the preformed corner corner elements. By way of example, this laminate can be etched using a nickel mold formed by electrolytic nickel deposition in a main mold. The formed elect mold can be used as a stamper for embossing the relief of the mold plate 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 at a temperature of about 175 ° to 200 ° C.

The materials useful for making the reflective laminate are preferably materials that are dimensionally stable, durable, weather-resistant and easily formable in the desired configuration. Examples of suitable materials include acrylics, which generally have a refractive index of about 1.5 such as Plexiglas resin from Rohm and Haas; thermosetting acrylates and epoxy acrylates, preferably radiation cured, polycarbonates, having a Refractive Index of about 1.6; and polyethylene-based ionomers (sold under the name "SURLYN"); polyesters; and cellulose acetate butyrates. In general, any optically transmitting material that can be formed, typically under heat and pressure, can be used. Other materials suitable for forming the retracting 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 necessary. It is desirable in some circumstances to provide retroreflective laminate with a backing layer. A backing layer is particularly useful for the reflector reflector laminate that reflects light in accordance with the principles of total internal reflection. A suitable backing layer can be made of any transparent or opaque material, including colored materials, which can be effectively coupled with the retreated reader laminate, described. Suitable backing materials include aluminum laminate, galvanized steel, polymeric materials such as polymethyl methacrylates, polyesters, polyamides, polyvinyl fluorides, polycarbonates, polyvinyl chlorides, polyurethanes, and a wide variety of laminates made from these and others. materials . The backing layer or sheet can be sealed in a grid pattern or any other suitable configuration for the reflective elements. Sealing can be effected by the use of a number of methods including ultrasonic welding, adhesives, or thermal sealing to discrete locations in the arrays of the reflective elements (see for example, U.S. Patent No. 3,924,928). The desirable seal 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 additional coarse consistency is required in the composite product, polycarbonate, polybutyrate or fiber reinforced plastic backing sheets can be used. Depending on the degree of flexibility of the resultant reading material, the material can be rolled or cut into strips of other suitable waste. The retroreflective material can also be backed with an adhesive and a release sheet to make it useful for application to any substrate without the additional step of applying an adhesive or using another fastening means. The cube corner elements described herein may be individually adjusted to distribute the retroreflected light 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, frequently less than ± 5 minutes.

All the patents and patent applications referred to, including that described without the background of the invention, are hereby incorporated by reference. The present invention has now been described with reference to 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 be limited to the preferred structures and methods described herein, but rather to the broad scope of the claims that follow.

Claims

1. A sheet suitable for the use of a mold for use in the formation of cube corner articles, reorbent readers, the sheet having a first and a second, opposite major surfaces defining between this a first reference plane, the sheet further including a work surface connecting the first and second major surfaces, the work surface defining a second reference plane substantially parallel to the work surface perpendicular to the first reference plane and a third reference plane perpendicular to the reference plane. reference plane and the second reference plane, comprising: a first set of grooves including at least one V-shaped groove a work surface of the foil, the groove defining a first groove surface and a second surface intersecting slots to define a first slot vertex; a second set of slots that includes at least one V-shaped groove in the working surface of the sheet, the groove defining a third groove surface and a fourth groove surface intersecting to define a second groove apex, characterized in that the third groove surface crosses the first groove surface in a substantially orthogonal manner to define a first reference edge; and further characterized by a third set of grooves including at least two V-shaped grooves, parallel to the working surface of the sheet, each groove defining a fifth groove surface and a sixth groove surface intersecting to define a third groove vertex, the fifth groove surface of one of the at least two parallel grooves that intersect in a substantially orthogonal manner with the first and third groove surfaces to form a first corner corner element positioned in a first orientation .

2. The sheet according to claim 1, characterized in that the third set of grooves includes at least three V-shaped grooves, parallel to the working surface of the sheet, each sheet defining a fifth groove surface and a sixth groove surface. 7í intersecting groove to define a third groove vertex, the fifth groove surface of one of the at least three parallel grooves that cross in a substantially orthogonal manner with the first and third groove surfaces to form the first groove corner element. Cube.

3. The sheet according to claim 1, characterized in that the fourth groove surface crosses the second groove surface in a substantially orthogonal manner to define a second reference edge.

4. The sheet in accordance with the rei indication 3, characterized in that the sixth groove surface of the at least two parallel grooves is crossed substantially orthogonally by the second and fourth groove surface to form a second corner corner element placed in a groove. second orientation different from the first orientation.

5. The sheet according to claim 1, characterized in that the first groove vertex and the second groove vertex are placed in a plane that crosses the first reference plane at an orthogonal angle and that crosses the second reference plane in an orthogonal plane .

6. The sheet according to claim 1, characterized in that the first groove vertex and the second groove vertex are placed in a plane that crosses the first reference plane in an oblique plane and that crosses the second reference plane at an orthogonal angle .

7. The sheet according to claim 1, characterized in that the first groove vertex extends along a first axis that crosses the first main surface of the sheet and the second reference plane, the first axis that makes an angle? with respect to the second reference plane.

8. The sheet in accordance with the rei indication 7, characterized in that the second slot vertex extends along a second axis that crosses the second main surface of the sheet and the second reference plane, the second axis that makes an angle? 2 with respect to the second reference plane,? 2 which is different from? I.

9. The sheet according to claim 1, characterized in that the first groove vertex and the second groove vertex are placed in planes crossing the third reference plane at an orthogonal angle and crossing the second reference plane at angles measuring between approximately 45 ° and approximately 90 °.

10. The sheet according to claim 1, characterized in that the first groove vertex and the second groove vertex are placed in planes crossing the third reference plane at an orthogonal angle and crossing the second reference plane at angles measuring between approximately 45 ° and approximately 60 °.

11. The sheet according to claim The sheet according to claim 1, characterized in that the first set of grooves and the second set of grooves comprise a plurality of grooves, each groove having an included angle * measuring between approximately 10 ° and approximately 170 °.

12. The sheet according to claim 1, characterized in that the third groove apex extends along an axis that crosses the first major surface of the sheet to the second major surface of the sheet and extends deeper with the surface of the sheet. work that the first and second vertices of slot.

13. The sheet according to claim 1, characterized in that the first reference edge extends along an axis crossing the second reference plane at an acute angle? I and the slot surface machine is placed in a plane crossing the plane. third reference plane at an acute angle to OÍI =? x.

14. The sheet according to claim 3, characterized in that the second reference edge extends along an axis crossing the second reference plane at an acute angle? 2 and the sixth groove surface is placed in a plane crossing the third reference plane at an acute angle 2 = 2 -

15. The sheet according to claim 1, characterized in that the first, second and third sets of grooves form a plurality of discrete cube corner elements, each of the discrete cube corner elements that is located on the sheet.

16. The sheet according to claim 1, characterized in that the first and second main surfaces are substantially planar.

17. A mold suitable for use in the formation of retroreflective laminate comprising a plurality of sheets, including the sheet of any of claims 1, 2, 4, or 12.

18. A method for manufacturing a sheet for the use of a mold suitable for use in the formation of cube corner articles, retracting readers, the sheet having a first and a second, opposite major surfaces, which define between them a reference plane, the sheet also includes a work surface connecting the first and second main surfaces, the work surface defining a second reference plane substantially parallel to the work surface perpendicular to the first reference plane and a third reference plane perpendicular to the third reference plane and the second reference plane, comprising: forming a first set of grooves including at least one V-shaped groove in the working surface of the sheet, the groove defining a first slot surface and a second groove surface that intersects to define a first slot vertex; forming a second set of grooves including at least one V-shaped groove in the working surface of the sheet, the groove defining a third groove surface and a fourth groove surface crossing to define a second groove apex, characterized in that the third groove surface that intersects the first groove surface in a substantially orthogonal manner to define a first reference edge; further characterized in that: forming a third set of grooves including at least two V-shaped grooves, parallel to the working surface of the sheet, each slot defining a fifth groove surface and a sixth groove surface intersecting to defining a third groove vertex, the fifth groove surface of one of at least two parallel grooves that intersect in a substantially orthogonal manner with the first and third groove surfaces to form a first corner corner element positioned in a first orientation .

19. The method according to claim 18, characterized in that the third set of grooves is formed to include at least three V-shaped grooves, parallel to the working surface of the sheet, each groove defining a fifth groove surface and one sixth intersecting groove surface to define the third groove vertex, the fifth groove surface of one of at least three parallel grooves that intersect in a substantially orthogonal manner with the first and third groove surfaces to form a first groove element. cube corner.

20. The method according to claim 18, characterized in that the sixth groove surface of another of at least two parallel grooves cross in a substantially orthogonal manner with the second and fourth groove surfaces, to form a second corner corner element placed in a groove. second orientation different from the first orientation.

21. The method according to claim 18, characterized in that the steps of forming the groove assemblies comprises removing portions of the sheet close to the work surface using a material removal technique.

22. The method according to claim 18, characterized in that at least one of the forming steps comprises forming grooves having groove vertices that form, from a plan view of the upper part of the work surface, they are placed at an angle oblique to the foreground of reference.

23. A sheet manufactured according to the method of claim 18.

24. A mold suitable for use in the formation of the retroreflective laminate reader comprising a plurality of sheets, including the sheet of claim 23.

25. The reader retorref laminate formed using a mold derived from the mold set forth in either of claims 17 or 24.

26. A foil suitable for use in a mold for use in corner articles of bucket re torore readers, the foil having a first and a second opposing main surfaces including among them a first reference plane, the sheet including in addition 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 plane of reference. reference and the second reference plane, comprising: a plurality of adjacent geometric structures formed on the work surface, characterized in that each geometric structure comprises three optical surfaces arranged as a cube corner element and at least one additional surface. further characterized by a set of grooves including at least two V-shaped grooves, parallel to the working surface of the sheet, each groove having one of the three optical surfaces a geometric structure and at least one additional surface of a structure adjacent geometry as side groove surfaces.

27. The sheets according to claim 26, characterized in that the first and second main surfaces are substantially planar.

28. The sheet according to claim 26, characterized in that the plurality of adjacent geometric structures are arranged in a single row that substantially fills the work surface.

29. The sheet according to claim 26, characterized in that each groove in the groove assembly extends from the first and second main surfaces.

30. The sheet according to claim 26, characterized in that the corner corner elements in the adjacent geometric structures are placed in substantially the same orientation.

31. The sheet according to claim 30, characterized in that the corner corner elements in adjacent geometric structures are substantially identical.

32. The sheet according to claim 26, characterized in that the sheet has an impedance-rich input angularity associated with it.

33. A mold suitable for use in the formation of a laminate retorre f reader comprising a plurality of sheets exposed in claim 26.

34. A retroreflective laminate formed using a mold derived from the mold of claim 33.