MXPA00002875A - Dual use reflective article - Google Patents

Abstract

A reflective article has a structured surface which includes a first and second array of reflective elements. The first array includes elements which have at least a first, second, and third reflecting face arranged to retroreflect incident light in a retroreflected beam. The second array includes elements which have at least a fourth, fifth, and sixth reflecting face arranged to reflect incident light in a second beam at an observation angle greater than 2 degrees. In signing applications, the second beam can be light originating from a stationary light source, thesecond beam having a direction and beam width suitable for illuminating an observation zone of interest. The retroreflected beam can be light originating from a moving light source such as a vehicule headlamp. Sheeting comprising such an article can be used both where external lighting from a suitable stationary light source is available and where it is not available.

Description

DOUBLE USE REFLECTIVE ARTICLE BACKGROUND The present invention relates generally to articles used in various applications such as road signs, and has particular application in situations where an off-axis stationary light source is used to illuminate such a signal. The use of retroreflective laminate for signaling applications is known. As used herein, the term "retroreflective" refers to the attribute of reflecting a beam of incident light in an antiparallel direction to its incident or near direction, so that it returns to the light source or the immediate vicinity thereof. . Known laminate constructions utilize miniature glass spheres in connection with reflective coatings, or alternatively, cube corner arrangements, to retroreflect incident light. They are designed to provide specified brightness values for a range of input angles. For design purposes a typical angular separation of the driver of a vehicle and the headlights of the vehicle is considered to be less than two degrees; Many laminate constructions specify retroreflective brilliance at an angle of observation REF .: 33011 narrow of 0.2 degrees. The terms "observation angle" and "entry angle" are defined together with other related terms at the end of the section of the detailed description. Figure IA shows a typical situation where a vehicle approaches a road sign 2 placed on the side of the road. A portion 4 of the light emitted from one of the headlights strikes an entrance angle ß on the retroreflective laminate 6 placed on the face of the signal 2. The laminate 6 may be, for example, one of a variety of reflective laminates. of the Scotchlite ™ brand available from 3M Company, such as the "Engineer Grade" or "High Intensity Grade" laminates. The laminate 6 retroreflects the incident light into a narrow cone 8 which includes the eyes 10 of the conductor. The cone 8 has an angular half-width 12, measured from the maximum central part to 10% maximum brightness, of approximately 1.7 degrees for the standard laminate "Engineer Grade" and approximately 0.75 degrees for the standard laminate "High Intensity Grade". As the vehicle advances along the direction 14 of the road, the entrance angle ß increases and the cone remains centered in the vehicle's headlights. Because the retroreflected light is confined to a relatively narrow cone, the perceived brightness of the signal may be relatively high, depending on the angular proximity of the observer's eye to the light source. US-A-3 833 825 shows a variation of this concept where a reflector has a plurality of reflector elements, each has three faces, the reflector elements have two dihedral angles substantially of 90 °, and at least one part it also has a third dihedral angle greater than the other two, so that the retroreflected light diverges in an elongated pattern. Figure IB shows an alternative arrangement similar to that described in PCT publication WO96 / 04638. A signal 2 is illuminated by a stationary light source 16, which is placed at an inlet angle of approximately 0 to 30 degrees relative to the portions of the signal. The retroreflective laminate 18 on the face of the -signal reflects light in a broad cone, defined by an observation angle ranging from 0 to about 40 degrees. The cone of reflected light is wide enough to include the observer or driver 10 traveling along the direction 14 of the road. The present application describes articles which can be used to take advantage of arrangements similar to those of Figure IB, and at the same time maintain desirable retroreflective properties like those in Figure IA. As shown in the figure IC, the light 4 of the light source 16 is incident at an inlet angle ß on a reflecting article 20. The reflective article 20 redirects the light preferentially within two beams 22, 24. The article 20 is designed so that one of the beams 24 is directed towards, and fills an observation zone 26. The light source 16, of conventional design, is located outside the observation zone. Efficiency is improved by reducing wasted light, which increases the amount of light available to illuminate the observation area. The brightness of the beam 24 observed in relation to the non-observed beam 22 can be increased by using reflective elements in the article which have highly non-orthogonal reflective surfaces in contrast to conventional corner corner elements.BRIEF DESCRIPTION OF THE INVENTION The present application describes a reflective article having a structured surface which includes a first and second arrays of reflective elements. The first array includes elements which have at least one first, second and third reflective faces arranged to retroreflect incident light in a retroreflected beam. The second array includes elements that have at least one fourth, fifth, and sixth reflecting faces arranged to reflect incident light in a second beam, at an observation angle greater than 2 degrees. When the article is used in the laminate for signaling applications, the second beam can be a light originating from a stationary light source, the second beam illuminates an observation area of interest, and the retroreflected beam can be light that is originates from a source of light in motion such as the headlights of a vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A-B show typical views and lighting scenarios for known retroreflective laminates. Figure IC shows a vision and lighting scenario for reflective articles described herein. Figure 2 is an enlarged plan view of a structured surface of the described reflective article. Figure 3 is a further enlarged representation of a side view of two reflective surfaces on the structured surface. Figures 4A-C show the reflective characteristics of an example reflector. Figure 5 shows an observation geometry for the example reflector.

Figure 6 shows a reflective article such as a reflective laminate mounted in position in relation to a light source and a viewing area of interest. Figure 7A is a graph of the joined divergence profile of the example reflector. Figure 7B is an enlarged portion of Figure 7A, with a representation of an observation zone superimposed thereon. Figure 8 is a graph of the predicted divergence profile of the example reflector. Figure 9 is a graph of the predicted divergence profile of another reflective article. Figures 10A-J are a series of graphs of the predicted divergence profile for certain reflective articles having reflective elements with a dihedral angle less than 90 degrees in increments of one degree. Figures 11A-J are a series of graphs of the predicted divergence profile for certain reflective articles having reflective elements with a dihedral angle greater than 90 degrees, in increments of one degree. Figures 12A-B are graphs of the predicted divergence profile for reflective articles having slot separations different from those of the example reflector. Figure 13 'is a graph of the predicted divergence profile for a reflective article similar to the example reflector, except that the structured surface has a coating thereon, with 90% reflectivity. Figure 14 is a plan view of the reflective article having at least two different arrays of reflective elements. Figure 15 shows a double-use reflective article mounted in position in relation to a light source and to an observation area. Figure 16 shows an enlarged plan view of the structure surface of the PREVIOUS TECHNIQUE which can be elaborated to incorporate both reflective and retroreflective elements. Figure 17 is an enlarged plan view of a portion of a structured surface incorporating a variety of reflective elements interspersed in a repeated pattern. Figure 18 is a simplified version of the view of Figure 17, which identifies different types of reflective elements. Figure 19 is a graph of the predicted divergence profile for an article having the surface structure of Figure 17 as a back surface. In the drawings, the same reference numbers are used for convenience, to indicate elements which are the same or which perform an equal or similar function.

The numbers enclosed in boxes represent brightness levels in units of cd / lx / m2.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE MODALITIES Reflector Example Figure 2 is a plan view of a back structured surface 28 of an example reflective article that is manufactured and whose reflective properties are measured. The article has a front surface 30 (see FIGS. 4A-C) opposite the back surface, through which the incident and reflected light passes. The arrays of solid tetrahedral prisms 32, 34 formed on the back surface 28 reflect the incident light. Each of the prisms 32, 34 has three mutually reflecting surfaces, as shown in 36b, 38b, 40b and 36a, 38a, 40a respectively placed around a base triangle. At least two reflecting surfaces of a given prism are arranged at a highly orthogonal dihedral angle to direct the reflected light preferentially in one of two beams of certain orientations of the incident light. Preferably, only two of the reflecting surfaces are arranged in this manner, and the remaining reflective surface pairs differ from the orthogonality by a relatively small amount. When the article is of unitary construction such as the base triangles that do not correspond to a physical boundary between two layers, the tetrahedral prisms can also be considered as trihedral prisms. The prisms 32, 34 are joined by a plurality of sets 36, 38, 40 of parallel grooves. The slot assemblies are preferably coplanar, and each slot assembly intercepts two other slot assemblies at an included angle of approximately 60 degrees to define equilateral base triangles for prisms 32, 34. If one wishes to form a truncated cube corner with the dihedral angle between each pair of adjacent faces equal to 90 degrees, all of the slots can have a full slot angle (the dihedral angle between two opposite prism faces, for example 36a, 36b that coincide at the bottom of the slot) of approximately 70.5288 degrees. (The slot side angles will therefore be approximately 35.2644 degrees). The example article instead uses slot angles which deviate radically from these orthogonally produced angles: the totality of the slots in the set 36 of slots use a full slot angle 10 degrees greater than the full slot angle produced orthogonally (ie, approximately 80.5288 degrees), and all of the slots in the slit assemblies 38, 40 use a full slot angle 10 degrees smaller than the full orthogonal produced slot angle (i.e., approximately 60.5288 degrees) . The resulting tetrahedral prisms 32, 34 have highly non-orthogonal reflective surfaces - notably the surfaces 38b and 40b of the prism 32 and the surfaces 38a and 40a of the prism 34 - as seen from a comparison of the dihedral angles between the example reflector and an ideal retroreflector cube corner in table 1 below.

TABLE 1 Figure 3 is a representation (not to scale) of highly non-orthogonal reflective surfaces 42, 44, such as surfaces 38a, 40a or surfaces 38b, 40b, compared to orthogonal cube corner surfaces 42 ', 44'. The dihedral angle 46 differs from 90 degrees by more than 2 degrees, and more preferably by at least approximately 4 degrees, and much more preferably by approximately 6 to 8 degrees, so that they show the beneficial asymmetric reflective properties described in the present. The tetrahedral prisms 32, 34 have a rotational symmetry of 180 degrees around each set of slots 36, 38, 40, thus forming "matched pairs" of prisms in relation to each set of slots. A matching pair comprises a prism 32 and a prism 34. The back surface is therefore observed to comprise pairs of densely packed matched prisms. The prisms 32, 34 also have mirror image symmetry around the slot assembly 36. The slot assembly 36 is designated a "primary" slot assembly because the prisms have rotational symmetry as to image the mirror around it. In addition to having highly non-orthogonal reflective surfaces, the example reflector uses a very small gap spacing of 25.4 μm (0.001 inches) for each of the slot sets 36"r38, 40. This dimension is approximately 50 wavelengths of visible light at 555 nm, in approximately half of the visible spectrum and in the peak sensitivity of the human eye. No reflective coating is applied to the back surface of the example reflector, as will be explained later, which leaves the faces of the prism exposed to the air so that the total internal reflection (TIR) can occur on the faces of the prism. The term "air" includes both atmospheric gases at standard pressures as well as vacuum. The prisms 32, 34 are initially formed on a master mold by machining directly on a substrate the plurality of sets of intersecting grooves 36, 38, 40 using a diamond tool or other suitable method. The master mold substrate is preferably a unitary substrate made of copper or other suitable material that resists milling. A reflective article is then produced in a conventional manner: first a negative copy of the master mold is produced, such a negative copy is referred to as a "die" and then a negative copy of the die is made on a surface, defined as the back or the structured surface which is a positive copy of the master mold. The reflective article of the example has a positive copy of the 0.41 mm thick polycarbonate master mold. Substrate thicknesses of less than about 1 mm are recommended for reflective laminates when it is desirable to roll the laminate on a roller for ease of storage and shipping. Such a laminate has an edge aligned in a perpendicular or parallel manner with one of the slot assemblies, preferably the primary slot assembly for ease of installation. The polycarbonate has a refractive index of about 1.6 on the visible portion of the spectrum, from about 400 to 700 nm. The polycarbonate has an Abbe dispersion of 34. Other transparent materials having various refractive indices and dispersion values in the wavelength range of interest can be used. For most applications, flexible and durable materials having a relatively low dispersion in the visible range are preferred. Polymers are generally preferred because of their low cost and ease of manufacture. In an alternative embodiment, the solid prisms may be composed of a material such as polycarbonate and the phase triangles of the prisms may make contact with a thin base layer made of a more flexible transparent material, the two-layer structure provides a laminate of increased flexibility. Such an article can be manufactured by molding and curing techniques such as those described in U.S. Patents 5,175,030 (Lu et al.) And 5,183,597 (Lu).

As used herein, a "negative copy" refers to a copy of a given surface where the copy has inverted characteristics complementary to the characteristics on the given surface so that the negative copy and the given surface can be placed on contact coincident with each other; a "positive copy" of the given surface refers to an article produced from an even number of successive negative copies of the given surface. Both positive and negative copies also include enlarged or reduced articles that differ from the previous description only by an isotropic scale factor.

Optical Properties of the Reflector Example Figures 4A-C illustrate in a simplified manner the results of the test of measuring the reflective properties of the example reflector. In the figures, a reference axis 48 is shown perpendicular to the flat front surface 30 of the example reflector 50. The primary groove assembly 36 on the rear surface 28 is oriented along the line 52. The arrow 4 represents a visible white light incident from a slide projector. The angle ß is the angle of entry of the incident light and a is the angle of observation of a given reflected beam. In Figure 4A, the light is incident at ß = 11.5 degrees from below in a plane perpendicular to the plane of the drawing and containing the reference axis 48. Two beams 54, 56 reflected at observation angles a of about 18 degrees are observed on opposite sides of the incident beam. The measured brightness of beams 54, 56 is the same within 10%: beam 54 has 2.07E + 4 cd / m2 and beam 56 has 1.87E + 4 cd / m2. In Figure 4B, the light is incident at an angle of entry ß = 25.5 degrees generally from the right of the reference axis 48, as shown. Again two reflected beams 58, 60 are observed but surprisingly one of the beams has a brilliance much greater than the other. The beam 58, at ~ 18 degrees, has a brightness measured about 7 times that of beam 60, which is placed at a = 21 degrees. The brightness measures were 1.17E + 4 and 1.49E + 3 cd / m2, respectively. In Figure 4C, the light is incident from the other side of the reference axis 48 again at an entry angle ß = 25.5 degrees. Again two reflected beams are observed, and again one beam is brighter more than 7 times the other. The beam 62 in Figure 4C, at a = 18 degrees has a measured brightness of 1.15E + 4 cd / m2, and beam 64, placed at a ~ 21 degrees, is measured at 1.46E + 3 cd / m2. Note that the reflected beams 54, 56, 58, 60, 62, 64 are not retroreflected beams directed back toward the source nor are they the "glow" that results from a simple specular reflection outside the front surface of the article. Note further that both figures 4B and 4C, the brightest reflected beam is close to the reference axis (ie, has a smaller deflection angle thereof) than each of the incident beams in the other reflected beam. In summary, it is observed that the example reflector divides the incident light into two main reflected beams directed away from the source. In addition, for certain oblique entrance angles, such as can be found when a light source mounted on the side of a road illuminates a signal placed above the road, the reflector produces a beam of greater brightness on one side of the source of light than on the other side. Advantageously, the beam of high brightness is directed towards the reference axis, where the path and the expected observers are usually located. The divergence profile of the article of the same example is measured at a different lighting geometry, which is shown in figure 5. The light source 16 is placed at an entrance angle ß ~ 18 degrees, and an angle of orientation? = 18 degrees in relation to a mark 65 of data parallel to the set 36 of primary slot. A visible light detector 66 scans an area to map the reflected brightness as a function of the angle of observation a and the angle? of presentation . The lighting geometry of Figure 5 is used to simulate the placement distribution of the signal in Figure 6. In Figure 6, a sign 68 is placed at a height Hl above a reference plane 70 corresponding to the path or to a plane above a path at the level of the angle of the observer's eyes. Three fixed observation zones Zl, Z2, Z3 are located in the reference plane 70 and may correspond to the traffic lanes on the road, with observers moving along the lengths thereof. These zones have equal widths and have front and rear limits at longitudinal distances DI, D2 of the projected sign position. The sign 68 is aligned with a longitudinal bisector of the middle zone Z2. The distances D3, D4 and the height H2 per holm of the specific reference plane 70 at the position of the light source 16, which is located on the road side outside the observation zones. Table 2 provides the design values in meters for the distances labels in Figure 6.

Table 2 The graphing of the data obtained from the detector of Figure 5 provides the divergence profile shown in Figure 7A, for the example reflector. The isobrillant contours are separated equally in brightness value. A sufficient number of contours with brightness values are labeled in units of cd / lx / m2 to allow the reader to determine the brightness value of any other contour. Brilliance value labels are placed in boxes to differentiate them from ordinary reference numbers. The central point 72 of the graph corresponds to retroreflection directly back to the source. Another point 74 corresponds to the reference axis 48. A line segment 76 passes through center 72 and point 74 and serves as a reference from which the angle? of presentation. The concentric circles centered around point 72 are for reference and show the angle of observation a. The source is back-reflected back to the source little or no significant light -that is, without light above a selected background or a reference intensity level, such as 0.5 cd / lx / m2, the amount of diffuse reflectance from a surface lambertiana ideal-. Instead, the example reflector produces two distinct beams 78, 80 on opposite sides of the incident beam. The "lower" beam 78 shown in FIG. 7A overlaps and surrounds the reference axis 74. The lower beam 78 propagates to the right of the light source 16 in the general direction of the Z1-Z3 areas (see Figure 6), while the "upper" beam 80 propagates to the left of the light source 16 moving away from the observers in zones Z1-Z3. Consistent with the results shown in Figures 4B-C, the beam 78 has a peak brightness significantly greater than that of the beam 80. However, with the present lighting geometry, the observed ratio is approximately 2, less than the previously observed ratio greater than 7. The measured peak brightness is 21.6 cd / lx / m2 and approximately 10 cd / lx / m2. In comparison, the currently available spherical laminates (part number HV-8100, sold by 3M Company), which reflect the incident light within a broad observation cone as in figure IB, is specified at a brightness of approximately 0.5 cd / lx / m2 at an observation angle of 20 degrees. In addition to the brightness asymmetry between the beams 78, 80, there is an asymmetry of shape of the beams insofar as the beam 78 has a shape substantially different from the beam 80. The beam 80 has two relative maxima, both located approximately in observation angles alike but displaced at presentation angle to such an extent that two lobes can be defined, separated by a region having a brightness less than half its maximum. The beam 78 also has two relative maxima located at approximately equal viewing angles and displaced at presentation angle. However, the region between the relative maxima in the beam 78 differs in brightness from any maximum in less than 20%, resulting in a more uniform beam profile compared to the beam 80. Figure 7B superimposedly shows a enlarged portion in Figure 7A an outline Z of observation area. The contour Z is a representation, in coordinates a,?, Of the position of the automobile driver located anywhere within zones Z1, Z2 or Z3. As you can see, the reflector of the example fills the Z contour of the area with a minimum brightness of 4 cd / lx / m2 and up to 20 cd / lx / m2 or more in some positions. The extent or "width" of the beam 78 at an observation angle, measured at a brightness of 4 cd / lx / m2, is well within a factor of twice the extension in the observation angle of the Z contour of the area. The "width" of the beam 78 at the presentation angle, similarly measured, is generally two to three times that of the Z contour of the area. By this measurement, the size of beam 78 coincides reasonably well with the observation zone. The effectiveness of the reflector of the example is improved by such a coincidence of the size of the beam 78 with the observation zone, by the characteristic of asymmetric brilliance for oblique incidence angles and by the little or no retroreflectivity of the reflector. It is possible to shift the relative position of zone Z and beam 78 by making another reflector with a slightly modified structured surface, or instead of simply moving light source 16 if feasible, to a new position having an angle ß of different entry and / or an angle? of orientation. In this way, the illumination of the Z zone can be optimized for maximum average brightness or better uniformity when making minor adjustments to the placement of the light source. This will also allow the same laminate to be used in two different applications where the size or position of the observation zones in relation to the signal differ, for example higher versus mounting on the road side of a signal. To extend the light from the light source which is incident across the face of the reflector over a range of values ß,?, It is desirable to have a reflected beam 78, for any given value of ß,? within that interval, a little larger than that of zone Z.

MODELING BY COMPUTER OF ALTERNATIVE MODALITIES If it is desired to test alternative reflector geometries other than the reflector of the example discussed above, one can make new high precision molds with the desired geometries, manufacture reflective laminates from the molds and make direct measurements from the laminates. A convenient alternative of lower cost is to use a computer program or a model to predict the optical properties such as the divergence profile of a given desired geometry. This last solution is used to test alternative reflector designs. The computer model used takes into account the effects of reflection, refraction and diffraction. The reflections from the surfaces of the reflective elements take into account the differences between the polarized light s and p. The model establishes a model of individual stripes all with a desired entrance angle and a uniformity of orientation angle through the triangles that constitute the bases of the various prism elements. The calculated output rays are processed to provide a divergence profile. Unless indicated, a wavelength of light in approximately the middle part of the visible spectrum, -555 nm, is used, and a refractive index of 1.6 is used. Figure 8 shows the divergence profile calculated for the geometry of the example article as described above and for the lighting geometry ß = 18 °,? = 18 °. As in FIG. 7A, the central point 72 represents the perfect retroreflection, the point 74 represents the reference axis 48 normal to the reflector, and the line segment 76 corresponds to? = 0o. The comparison of the calculated divergence profile of Figure 8 with the observed profile of Figure 7A demonstrates that the computer model can be used to draw general conclusions about the divergence profile of a given structured surface geometry. First, the whole pattern of two beams, with the beams located on opposite sides of the incident light direction, closely approximate the observed pattern. Secondly, the coordinates of the observation angle of the dominant maximum for each beam are close to the observed values, at a ~ 18 °. Third, the coordinates of the angle of presentation of the beams generally agree with the observed beams, except for the elongated feature in the upper beam observed at a ~ 1 °,? = 90 °. Fourth, both figures show an asymmetry in relation to point 72 in the shape of the beam between the lower and upper beams. Although there are differences in detail between the shapes of the calculated and observed beams, the lower beams in both cases cover an angle? A between 10 and 15 degrees and an angle of presentation ?? between approximately 40 and 50 degrees, measured at a brightness level of 2 cd / lx / m2. This high level is equal to about 10% of the maximum brightness of the beam 78 in Figure 7A. Some differences between the observed and calculated beams include details regarding the precise position number of relative maximum within a beam. More significantly, the calculated divergent profile of Figure 8 shows an approximately equal maximum brightness of the two reflected beams in contrast to the factor of two that is seen in Figure 7A. With the capabilities and limitations of the computer model under consideration, the additional calculated divergence profiles will now be discussed for reflective elements that differ from those of the example baffle in order to demonstrate the effect of a change in the structured surface of the reflector. The lighting geometry is the same as that of Figure 8, unless otherwise indicated. Returning to Figure 9, there is shown a divergence profile for an article as a reflector of the example except that approximately full slot angles are used. { 81, 47, 60.28, 60.28-} degrees, resulting in dihedral angles between the faces of the tetrahedral prism of approximately. { 83, 90, 90.}. degrees. These values can be compared with approximately. { 83.2, 89.8, 89.8} dihedral degrees of the example. When comparing figure 9 with figure 8, the change of 0.2 degrees in the dihedral angles is observed to produce an article which again redirects the light into two general reflected beams, shaped asymmetrically one with respect to the other, on opposite sides of the direction of incident light. The beams of Figure 9 have coordinates a,? similar to those in Figure 8. However, the lower beam of Figure 9 is less spatially uniform than its counterpart in Figure 8. The lower beam of Figure 9 has a more pronounced two-lobe beam shape, where a lobe is generally almost centered on the reference axis 74. Returning now to FIGS. 10A-10J, the effect of decreasing the deviation of the dihedral angle of 90 degrees, in increments of 1 degree, is demonstrated. The slot angles are introduced so that FIG. 10A represents a structured surface with each tetrahedral prism having a unique degree of deflection, ie, the dihedral angles of. { 89, 90, 90.}. , Figure 10B represents a deviation of two degrees, that is, the dihedral angles of. { 88, 90, 90) and so on. Figure 10G is identical to Figure 9. As shown, a greater deviation of approximately 2 to 3 degrees is required before any perceptible asymmetry between the two reflected beams is observed. Therefore, the reflective articles of at least FIGS. 10D-J herein are mentioned as having reflective elements with "highly non-orthogonal" reflecting surfaces. Note that for deviations of approximately 7 degrees or greater, the lower beam degenerates (at a level of 2 cd / lx / m2) into two distinct lobes or secondary beams which, although not generally located for uniform illumination of an observation zone large single, can be useful for other applications. Figures 11A-J are similar to Figures 10A-J respectively, except that deviations of the 90 degree dihedral angle are of opposite polarity in 1 degree increments. Figure HA is therefore related to prisms with dihedral angles of. { 91, 90, 90.}. and Figure 11J, relates to prisms with dihedral angles of. { 100, 90, 90.}. . Again, a greater deviation of approximately 2 to 3 degrees is required before perceptible asymmetry is observed. Note that the lower reflected beam advantageously has a calculated brightness value greater than the upper beam. Similar to the behavior observed in Figures 10A-J, deviations exceeding about 8 degrees provide separation of the lobes of the lower beam at a light level of 2 cd / lx / m2. The angular extension or "width",? A, ?? The reflected beam is a function of the diffraction effects which in turn are a function of the relative size of the individual reflective elements with respect to the wavelength of the light used. Figures 12A-B show profiles of visible light divergence predicted for structured surfaces with groove separations other than 0.025 mm (0.001 inches). It has been found that a change in the slot separation also affects the direction of the reflected beam. Therefore, new full-slot angles and corresponding dihedral angles are selected to at least partially compensate for this effect. In Figure 12A, the slot separation of the three slot sets is increased to 38 μm (0.0015 inches). This separation is equal to approximately 75 wavelengths of visible light. The full slot angles are adjusted to. { 81.3621, 59.6955, 59.6955} degrees for the three sets of grooves respectively, which provide dihedral angles of. { 86.62, 89.745, 89,745} degrees. In Figure 12B, the gap spacing at 18 μm (0.0007 inches) or about 35 wavelengths of visible light is decreased. The dihedral angles are the same as in Figure 12A. A narrower spacing is observed to provide a generally wider lower beam with less variations in dramatic brightness through the beam, which will be advantageous in some applications. A larger gap provides a more concentrated and non-uniform lower beam which may not adequately illuminate a Z observation zone but may work well in other applications. For road geometries similar to those of Figure 6, a slot separation in the range of 10 to 50 μm (0.0004 a) is generally preferred. 0. 002 inches, or 20 to 100 wavelengths of visible light). It is known that by coating the side of the structured surface of the prismatic laminate with a thin reflective metal layer. In the case of laminate having elements with highly non-orthogonal reflective surfaces, the effect of such reflective coatings in contact with the reflective surfaces is a diminished overall brightness of the reflected beams and a reduced width of at least the lower beam. Figure 13 shows the predicted divergence profile for the reflector of Figure 8, except that a 90% reflectivity coating has been added to each of the three remotely reflecting prismatic surfaces. The comparison of the figures shows the advantage, if high brightness and spatial uniformity is desired, to keep the reflective surfaces uncoated and instead they are placed on TIR from the reflecting surfaces. It is contemplated that sets of grooves that intersect each other at different angles of 60 degrees may also be used in order to form reflective foods which are on their side. The slots can be arranged to define base triangles that have exactly one included angle greater than 60 degrees, or instead of that they have exactly one included angle less than 60 degrees. The base triangles of the reflective elements can be isosceles or scalene. The angles of the sides of the grooves are selected to form tetrahedral prisms having at least two highly non-orthogonal reflective surfaces, as described above. Alternatively, reflective elements which are not defined by sets of parallel slots, which are referred to in the art as complete cube corner elements, whether sideways or not sideways, can also be used. A reflective article such as a laminate made in accordance with the principles described herein may use conventional backing materials to seal the prismatic elements in air, as well as adhesive layers and release sheets. See, for example, U.S. Patent No. 4,938,563 (Nelson et al.), Incorporated herein by reference. A conventional top film covers the uniform front surface 30 of the reflective layer and can also be used to absorb ultraviolet light which can damage the reflective layer. Dyes can be added or mixed with the material of the reflective layer to impart a color appearance to the article.

TILING; DOUBLE USE LAMINATE The spatial uniformity of the reflected beam from a stationary light source towards the observation zone can be improved or modified in some other way by incorporating more than one type of reflective element coincident in pairs on the surface of the structure of the reflecting article. By tiling or incorporating some other way of arranging different reflective elements in the same article, using known manufacturing methods, a laminate having a divergence profile which is the average (or other weighted combination, in accordance with the relative surface areas used) of the divergence profiles of the individual reflective element designs used. Figure 14 depicts a laminate 82 comprising adjacent listed areas 82a. Each area 82a is filled with an array of an element class, either reflective or retroreflective. The areas 82a preferably have a width of less than about 50 mm so that the individual areas are imperceptible from observation distances of about 30 • m or greater, which gives the laminate a uniform appearance. You can also use different patterns to the strips, such as rectangles, squares or other geometric shapes. A unique advantage is obtained by including retroreflective element areas in the laminate 82 as well as areas of elements such as those described above that are reflective but not retroreflective. Such laminates 82, which are shown in Figure 15, have double utility. First, the laminate 82 'directs the light 84 from a stationary light source 16 to a broad beam 86 that fills the observation Z zone. Secondly, the laminate 82 reflects the light 88 from a source in a moving vehicle in a narrower beam 90 which is centered on the source in motion. In this way, the laminate 82 can be installed in positions where a fixed light source will illuminate the signal at an appropriate angle, and in positions where such a light source is not available. Even in those positions where such a source is provided, the retroreflective areas ensure that the signal will remain visible to the drivers of the vehicle if the stationary source stops functioning. Since the retroreflecting beam 90 remains centered in the moving light source of the vehicle, such a beam 90 will have high visibility for the drivers of the vehicle even outside the Z zone when the angle of observation of the driver's eyes relative to that of the headlights of the vehicle is very small. The retroreflecting beam 90 is produced by conventional cube corner retroreflective elements such as those described in U.S. Patent Nos. 4,588,258 (Hoopman), 4,775,219 (Appledorn et al.) Or 5,138,488 (Szczech), and are generally confined to approximately an observation angle of two degrees in relation to the direction of the incident light 88. The beam 86, in contrast, is generally directed at observation angles exceeding two degrees. The beam 86 is preferably produced by reflective elements having highly non-orthogonal reflective surfaces as described above, although the elements that produce the mirrored reflected beams may also be usable in some circumstances. Table 3 shows a possible design for the article 82 of figure 14. The design is repeated every 7 strips. The structured surfaces of the areas 82a are defined in terms of the deviation in each pair of groove side angles from the lateral groove angle producing orthogonality of 35.2644 degrees (the groove assemblies intersect at included 60 degree angles). one seventh of the area is occupied by retroreflective elements and the rest is occupied by three different reflective element designs in order to produce a reflected beam 86 of improved uniformity of greater width. Such tiling increases the width of the reflected beam 86 where each array of reflective element alone can not fill the viewing area with an adequate amount of reflected light. TABLE 3 Table 4 shows a simpler alternative design that is repeated every two strips. The design comprises alternating areas of reflective elements associated with Figure 11 that they have. { 97, 90, 90.}. degrees of dihedral angles, and retroreflective elements of conventional cube corner.

TABLE 4 DEVIATION OF THE SLIDE ANGLE (IN ARCH MINUTES) Set Number of Slot Strips Set 36 Slots 38 Slots 40 0 0 0 -273 +289 -289 The structured surface of article 84 may have individual reflective and / or retroreflective elements of different sizes. For example, the reflective elements in a first area 82a may have a first slot separation and the reflective elements in a second area 82a adjacent to the first area may have a different slot separation so that the elements have different sizes. Similarly, the retroreflective elements may be larger or smaller than the reflective elements. The arrays of various reflective and / or retroreflective elements may also be interleaved with one another by modification of the configuration of the PREVIOUS TECHNIQUE shown in Figure 16 (see U.S. Patent 5,600,484). The enlarged plan view shows the designs of three arrays of different elements 92, 94, 96. The elements 94, 96 have the same set of dihedral angles since their reflecting surfaces are coplanar to each other. The reflective surfaces of the elements 92, however, are formed independently of the elements 94, 96. Advantageously, the slot angles can be selected so that the elements 94, 96 are retroreflective elements, having orthogonal dihedral angles, and the elements 92 are reflective elements, having at least a non-orthogonal dihedral angle, or vice versa. However, this arrangement has less flexibility in choosing the ratio of areas covered by the respective arrangements compared to the mode in Figure 14. It also has less flexibility in choosing the relative sizes of the individual elements.

ADDITIONAL MODALITY In an effort to produce a reflected beam having a wider angular extent and improved spatial uniformity, without having to list a large number of structured surfaces of different reflective elements, a structured surface is designed which incorporates a variety of types of elements Different reflective elements interspersed with each other on the structured surface in a repeated pattern. The different types of reflective elements each have at least one dihedral angle which differs by more than about 2 degrees from a right angle. The elements are defined by a repeated sequence of different (large) deviations in the lateral angles of the groove in relation to the lateral angles of the groove that could produce dihedral angles of 90 degrees. For the elements having equilateral base angles, the deviations of the lateral groove angle are measured in relation to a nominal slot side angle of approximately 35.2644 degrees. For side elements, lateral groove angle deviations are measured in relation to the lateral groove angle that can produce a dihedral angle of 90 degrees.

A portion 104 of a structured surface, which is illustrated in Figure 17, is illustrative. A complete structured surface can be composed of duplicates of the portion 104 generated when the respective sequences of the slots 106a-h, 108a-d and llOa-d extend and repeat through the surface. The slot assemblies 106, 108, 110 intersect each other by 60 degrees. The lateral slot angle deviations are shown for each slot labeled in Figure 17 and are given in arc minutes. The pairs of lateral groove angles associated with a groove sequence in a set of grooves are different. For example, pair. { -350, -200} for slot 108a is different from the pair. { -200, -350} for the slots 108b and 108c. Or again, the pair. { 300, 150) for the slot 106a is different from the pair. { 300, 300.}. for the slot 106b which in turn is different from the pair. { 150, 300.}. for slot 106c. With the pattern defined in this way, six different types of reflective elements are formed, each type having a different set of dihedral angles that are different from the other types. The different combinations of groove side angle surfaces are included in table 5 together with the associated dihedral angles. The six types of reflective elements are assigned labels A to F.

TABLE 5 The different classes of reflective elements A-F are arranged in the structured surface portion 104 as shown in the simplified view of Figure 18, where the side groove surfaces are not shown. It should be noted that there are more than six different kinds of reflective elements in the portion 104 if the shape and orientation of the individual reflective elements are considered. For example, although all the elements marked "A" in Figure 18 have the same three dihedral angles shown in Table 5, some of these elements are rotated with respect to each other, and some are mirror images of others. (but not congruent with each other). The portion 104 of structured surface has a divergence profile which is a combination of the divergence profiles of the many different reflective elements that constitute it. The divergence profile is calculated using the aforementioned computer model for a laminate having as a back surface the structured surface of Figure 17, assuming: a slot separation of 25.4 μm (0.001 inches) for the entire set of slots; an optical length of -555 nm and a refractive index of 1.6; and a lighting geometry ß =? = 18 degrees. The result is shown in Figure 19, where the reference numbers 72, 74 and 76 have the same meanings as in the above. The two reflected beams, designated 112 and 114, are again observed on opposite sides of the retroreflection point 72. The peak brightness of both beams is relatively low (slightly higher than 4 cd / lx / m2) compared to the predicted results shown for some of the modalities previously described. However, the beams 112, 114 are generally more uniform than the previous units and have a more rounded (less elongated) shape, at least at a brightness level of 1 to 2 cd / lx / m2. A more rounded beam shape means that the laminate has the structured surface 104 which can illuminate a wider viewing area than a laminate having a more elongated reflected beam. It also means that widely spaced portions of a large sheet will have approximately the same apparent brightness at a given observation point, although the separated points are at entry angles and / or at substantially different orientation angles with respect to the light source. It should also be noted from Figure 19 that although the beams 112, 114 show certain asymmetries one in relation to the other, the total similarity of the beam shapes is surprising. The structured surface of Figure 17, and similar surfaces, may be incorporated into a double-use laminate or other article by the tiling techniques discussed above.

GLOSSARY OF SOME TERMS Beam: amount of light or reflectivity region characterized by having a peak brightness and decreasing below a given threshold such as 1% to 10% of the peak brightness surpassing a limiting region characterizable as a beam contour. Brilliance: when it refers to a beam of light, the amount of light expressed in candelas per square meter (cd / m2). When referring to a reflective article, the reflectivity of the article, that is, the luminous intensity reflected from the article divided by the normal illuminance and between the surface area of the article, expressed in candelas per lux per square meter and abbreviated cd / (lx- .m2) or cd / lx / m2. For light outside the visible spectrum, the corresponding quantities are expressed in radiometric rather than photometric terms. Data mark: a mark (real or hypothetical) on a reflective article that is used as a reference to indicate the orientation around the reference axis. Divergence profile: a representation, for a given lighting geometry of the brightness of the reflected light as a function of the angle of observation and the angle of presentation. Typically, the representation takes the form of an isobrillant contour plotted on (r, teta) polar coordinates, where the coordinate r represents the observation angle a and the theta coordinate represents the angle of presentation?. Input angle ß: the angle between the illumination axis and the reference axis. Entry half-plane: a half-plane which originates in the reference axis and contains the axis of illumination.

Slot side angle: the dihedral angle between a slot side and a plane extending parallel to the length of the slot and perpendicular to a base surface of the reflective article. Lighting axis: a line segment that extends between the reference center and the light source. Light: electromagnetic radiation, either in the visible, ultraviolet or infrared portion of the spectrum. Observation angle (o): the angle between the illumination axis and the observation axis. Observation axis: a line segment that extends between the reference center and the observation point that is selected.

Observation half-plane: a half-plane which originates in the axis of illumination and which contains the axis of observation. Angle of orientation (?): The dihedral angle between the entry half-plane and the half-plane that originates in the reference axis and that contains the data mark. Angle of presentation (?): The dihedral angle between the entrance half-plane and the observation half-plane. Reference axis: a line segment that extends from the reference center away from the reflective article, and which is usually perpendicular to the reflective article in the reference center. Reference center: a point on or near the reflective article which is designated to be the center of the article to specify its performance. Visible light: light detected by the human eye are help, generally in the wavelength range of approximately 400 to 700 nm. Although the present invention has been described with reference to preferred embodiments, the skilled artisan will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one of the objects or products to which it refers.

Claims (19)

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

1. A double-use reflective article, characterized in that it comprises a layer having a structured surface, the structured surface includes first and second arrays of reflective elements, the first arrangement comprises elements which have at least one first, second and third reflecting faces arranged to retroreflect incident light in a retroreflected beam within approximately an observation angle of 2 degrees, the second array comprises elements which have at least one fourth, fifth and sixth reflecting faces arranged to reflect incident light in a second beam in a observation angle greater than 2 degrees, wherein the observation angle is measured between the respective incident light direction and an axis extending from the illuminated article to an observer of the respective beam.

2. The article according to claim 1, characterized in that the structured surface has a plurality of areas tiled thereon, the first arrangement is placed in a first set of tiled areas, and the second arrangement is placed in a second set of tiled areas .

3. The article according to claim 1, characterized in that the fourth, fifth and sixth reflecting faces have dihedral angles therebetween, at least one of the dihedral angles differs from a right angle by more than two degrees.

4. The article according to claim 3, characterized in that at least one of the dihedral angles differs from a right angle by approximately 6 to 8 degrees.

5. The article according to claim 1, characterized in that the structured surface further includes a third array of reflective elements different from the elements of the second array, the third array comprises reflective elements having a seventh, eighth and ninth reflective faces arranged to reflect light incident in a third beam, at an observation angle greater than 2 degrees.

6. The article according to claim 1, characterized in that the fourth, fifth and sixth reflecting faces are arranged so that the second beam has a beam width greater than the beam width of the retroreflected beam, wherein the beamwidths are measured at a level of 10% of the peak brilliance of the reflective beam.

7. The article according to claim 1, characterized in that the reflective faces are arranged so that the retroreflected beam has a first beam shape, when measured at 2 cd / lx / m2, and the second beam has a second beam form , when measured at 2 cd / lx / m2, the first and second beam forms are not superimposable.

8. The article according to claim 1, characterized in that the fourth, fifth and sixth reflective faces are arranged to reflect incident light from an angle of incidence between 18 and 26 degrees within the second beam so that the second beam has a beam shape , when measured at a brightness level of 2 cd / lx / m2, the shape of the beam has a beam width of observation angle? to greater than 5 degrees and less than 20 degrees.

9. The article according to claim 8, characterized in that? A is between 10 and 15 degrees.

10. The article according to claim 1, characterized in that at least the elements of the second array are joined by a plurality of sets of slots.

11. The article according to claim 10, characterized in that at least one of the slit assemblies has a slot spacing between about 10 and 50 μm.

12. The article according to claim 10, characterized in that at least one of the slit sets has a sequence of slots having different pairs of slot side angles.

13. The article according to claim 1, characterized in that at least the elements of the second array comprise solid prisms formed in the layer, the fourth, fifth and sixth reflecting faces are exposed to the air to allow total internal reflection in such faces.

14. The article according to claim 1, characterized in that the reflective elements have the same dihedral angles and are referred to as a kind of reflective element, wherein the reflective elements of the second array include at least three different kinds of elements reflective

15. An arrangement for displaying information in an extended observation zone comprising: a placeable signal next to an extended observation zone; and a stationary light source that illuminates the signal at an oblique angle; characterized in that the signal comprises: a double-use reflective article comprising a layer having a structured surface, the structured surface includes a first and second arrays of reflective elements, the first arrangement comprises elements which have at least one first, second and third reflective faces arranged to retroreflect incident light in a retroreflective beam within an observation angle of approximately 2 degrees, the second arrangement comprises elements which have at least one fourth, fifth and sixth reflecting faces arranged to reflect incident light in a second beam at an observation angle greater than 2 degrees, wherein the observation angle is measured between the respective incident light direction and an axis extending from the illuminated article to a respective beam observer.

16. The arrangement according to claim 15, characterized in that the second arrangement reflects the light from the stationary light source in a reflected beam that encompasses the extended observation zone and omits the stationary light source.

17. The arrangement according to claim 15, characterized in that the fourth, fifth and sixth reflecting faces have dihedral angles (46) therebetween, at least one of the dihedral angles differs from a right angle by approximately 6 to 8 degrees.

18. The arrangement according to claim 15, characterized in that the fourth, fifth and sixth reflective faces are arranged so that the second beam has a beam width greater than the beam width of the retroreflected beam, where the beamwidths are measured at a level of 10% of the peak brightness of the respective beam.

19. The arrangement according to claim 15, characterized in that at least the elements of the second array are joined by a plurality of slot assemblies. REFLECTIVE ARTICLE OF DOUBLE USE SUMMARY OF THE INVENTION A reflective article has a structured surface which includes a first and second array of reflective elements. The first array includes elements which have at least a first, second and third face reflective and arranged to retroreflect incident light in a retroreflected beam. The second array includes elements which have at least one fourth, fifth and sixth reflecting faces positioned to reflect incident light in a second beam at an observation angle greater than 2 degrees. In signaling applications, the second beam may be light originating from a stationary light source, the second beam having a direction and beam width suitable for illuminating a viewing area of interest. The retroreflective beam may be light that originates from a light source in motion such as the headlights of a vehicle. The laminate comprising such article can be used for external lighting from a stationary light source that is available, and when it is not available.