JP2001517808A - Reflective articles incorporating reflective surfaces with high non-orthogonality - Google Patents

Abstract

(57) Abstract: A reflective article comprises a structured surface comprising a plurality of reflective elements each having first, second and third mutually reflecting surfaces having a definable dihedral angle. Have. At least one of the dihedral angles differs from a right angle by an angle greater than two degrees. In one embodiment, one of the dihedral angles is exactly so characterized, and the remaining dihedral angles differ from right angles by less than two degrees. In one embodiment, the reflective element is bounded by a plurality of groove rows in the structured surface, the groove rows being preferably spaced apart by about 0.0004-0.002 inches (10-50 μm). It has a groove. Reflective elements having various sets of dihedral angles can be incorporated into the structured surface by tiling or providing one or more rows of grooves having various groove side angle pairs. The article reflects an oblique incident beam with two reflected beams on either side of the incident beam. One of the two beams has a beam width sufficient to illuminate a pre-defined viewing zone angularly offset from the incident light direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates generally to articles used in prominent applications such as highway signs, and to specific situations where an off-axis fixed light source is used to illuminate such signs. There are uses.

[0002] The use of retroreflective sheets for signage applications is known. When used here
"Retroreflection" refers to the property of reflecting an incident light beam in a direction anti-parallel to or near the direction of incidence, such that the incident light beam returns to or near the light source. Known sheet structures use fine glass beads with a reflective coating, or alternatively, cube corner arrays to retroreflect incident light. They are designed to provide specified intensity values for a range of angles of incidence. For design purposes, the typical angular separation between the vehicle driver and the vehicle headlight is taken to be less than 2 degrees, and many seat structures have a narrow retroreflective luminous intensity of 0.2 degrees. Specify the observation angle. The terms “viewing angle” and “incident angle” are defined at the end of the detailed description along with other related terms.

FIG. 1A shows a typical situation in which a vehicle approaches a highway sign 2 located on the side of the road. The portion 4 of the light emitted from the headlight strikes the retroreflective sheet 6 installed on the surface of the sign 2 at an incident angle β. The sheet 6 is, for example, 3M Compa
"Engine Grade" or "High"
Various Scotchlite ^T such as "Intensity Grade" sheet
It may be one of ^M brand reflection sheets. The seat 6 retroreflects the incident light with a narrow cone 8 containing the driver's eyes 10. This conical body 8 has the standard "Eng
1.7 degrees for the "ineer Grade" sheet, and the standard "High"
It has an angular half-width 12 of about 0.75 degrees for the "Intensity Grade" sheet, measured from the central maximum of maximum luminosity to a range of 10%. As the vehicle travels along the road direction 14, the angle of incidence β increases, but the cone remains centered on the vehicle headlight. Since the retroreflected light is limited to a relatively narrow cone, the luminous intensity at which the sign is perceived can be relatively high due to the angular proximity of the observer's eyes to the light source.

FIG. 1B shows an alternative device similar to that disclosed in PCT Publication WO 96/04638. The sign 2 is illuminated by a fixed light source 16 arranged at an angle of incidence of about 0 to 30 degrees with respect to the part of the sign. The retroreflective sheet 18 on the sign surface is 0
It reflects light into a wide cone defined by a viewing angle in the range of about 40 degrees. The cone of reflected light can be seen by the observer or driver 10 traveling along the road direction 14.
Is large enough to encompass

This application discloses an article that can be used to serve with the same device as that of FIG. 1B. As shown in FIG. 1C, the light 4 from the light source 16 is incident on the reflective article 20 at an incident angle β. The reflective article 20 selectively divides the light into two beams 22, 24.
Redirect to The article 20 is such that one of the beams 24 is
And designed to meet it. A conventionally designed light source 16 is located outside the viewing zone. Efficiency is increased by reducing wasted light, thereby increasing the amount of light available to illuminate the viewing zone. Significantly, the brightness of the viewing beam 24 relative to the non-viewing beam 22 is enhanced by using a reflective element in the article having a reflective surface with high non-orthogonality, as opposed to a conventional cube corner element. I know it can be done.

SUMMARY OF THE INVENTION [0006] This application discloses a reflective article having a structured surface that includes a plurality of reflective elements. Each reflective element has at least first, second and third reflective surfaces having a definable dihedral angle therebetween. At least one of the dihedral angles differs from a right angle by an angle greater than two degrees. In some embodiments, one of the dihedral angles is exactly so characterized, and the remaining dihedral angles differ from right angles by less than 2 degrees. In one aspect, the reflective element is bounded by a plurality of groove rows in the structured surface, the groove rows being spaced apart by about 0.0004-0.002 inches (10-51 μm). It has a suitable groove located. The article reflects an oblique incident beam and two reflected beams on either side of the incident beam. One of the two beams has a sufficient angular range to fill a pre-defined viewing zone angularly offset from its incident light, and may have a higher brightness than the other.

In the drawings, the same element or an element performing the same or similar function is denoted by the same reference numeral for convenience. Numerals surrounded by squares, represents the luminous intensity in units of cd / lx / ^{m 2.}

DETAILED DESCRIPTION OF THE INVENTION Exemplary Reflector FIG. 2 is a plan view of a rear structured surface 28 of a typical reflective article as manufactured and its reflective properties measured. This article has a front surface 30 (FIG. 4) opposite the rear surface.
A through C) through which incident and reflected light passes. An array of solid four-sided prisms 32, 34 formed in the rear surface 28 reflects incident light. Each of the prisms 32, 34 has 36b, 38b arranged around a base triangle,
It has three mutually reflecting surfaces as shown at 40b and 36a, 38a, 40a, respectively. At least two reflecting surfaces of a given prism are arranged at dihedral angles with high non-orthogonality to selectively direct the reflected light into one of two beams for a given direction of incident light. Preferably, only two of the reflective surfaces are so arranged, and the other remaining reflective surface pairs differ relatively slightly from orthogonality. Here, the article is of unitary construction such that the base triangle does not correspond to the physical boundary between the two layers, and the tetrahedral prism may be considered to be a trihedral prism.

The prisms 32, 34 are delimited by a plurality of parallel groove sets 36, 38, 40. These groove sets are preferably coplanar, each groove set being about 6
Intersecting the other two groove sets at an included angle of 0 degrees defines the equilateral base triangle of the prisms 32,34. If one wants to form a truncated cube corner where the dihedral angle between each pair of adjacent faces is equal to 90 degrees, then all the grooves will be about 70.5288 degrees full angle groove (two opposing prism faces meeting at the groove bottom, e.g., , 36a, 36b) (the groove side angle is therefore about 35.2644 degrees). Typical articles have instead used groove angles that essentially depart from these orthogonal generation angles,
That is, all grooves in groove set 36 used a full groove angle that was 10 degrees greater than the orthogonally generated full groove angle (ie, about 80.5288 degrees), and the groove sets 38,4
All zero grooves used a full groove angle that was 10 degrees less than the orthogonal generated full groove angle (ie, about 60.5288 degrees). The resulting tetrahedral prisms 32, 34
As can be seen from a comparison of the dihedral angles between the typical reflector and the ideal cube-corner retroreflector in Table 1 below, reflective surfaces with high non-orthogonality, especially the surfaces 38b, 40b, And the surfaces 34a and 40a of the prism 34.

[0010]

[Table 1]

FIG. 3 shows the surfaces 38 a, 4 a compared to the orthogonal cube corner surfaces 42 ′, 44 ′.
Reflective surfaces 42, 44 with high non-orthogonality, such as 0a or surfaces 38b, 40b
(Without scaling in a fixed proportion). The dihedral angle 46 is 90 degrees and greater than 2 degrees, more preferably at least about 4 degrees, and most preferably about 6 degrees.
Because they differ by ８8 degrees, they can exhibit the advantageous asymmetric reflection characteristics disclosed herein.

The tetrahedral prisms 32, 34 have a 180 degree rotational symmetry about each groove set 36, 38, 40, thus forming a "matched pair" of prisms for each such groove set. One matching pair includes one prism 32 and one prism 34
And It can be seen that the rear surface contains such a closely packed pair of matching prisms. The prisms 32, 34 also have mirror image symmetry about the groove set 36. Groove set 36 is referred to as a "primary" groove set because the prism has both rotation and mirror image symmetry about it.

In addition to having a reflective surface with high non-orthogonality, typical reflectors have very small grooves of 0.001 inch (25.4 μm) for each of the groove sets 36, 38, 40. Intervals were used. This dimension is in the middle of the visible spectrum, 5
It is about 50 wavelengths of visible light at 55 nm, which is the highest sensitivity of the human eye. As explained below, no reflective coating is applied to the rear surface of a typical reflector,
The prism face was exposed to air so that total internal reflection (TIR) occurred at the prism face. “Air” includes both atmospheric gases at standard pressure as well as vacuum.

The prisms 32, 34 are initially mastered by machining a plurality of intersecting groove sets 36, 38, 40 directly on the substrate using a diamond tool or other suitable processing step. It is formed. The master-type substrate is preferably a one-piece substrate made of copper or other suitable material that does not easily generate burrs. The reflective article is then manufactured in a conventional manner, first producing a negative copy of the master mold, such a negative copy being called a "stamper", and then the negative copy of the stamper being a transparent sheet of Made on one side, defined as a posterior or structured surface. Thus, the reflective article has a rear surface that is a positive copy of the master mold. The example reflective article was a master-type positive replica of a 0.41 mm thick substrate of polycarbonate. Substrate thicknesses of less than about 1 mm are suitable for reflective sheets where it is desired to wind the sheet into a roll to facilitate storage and shipping. Such a sheet has edges aligned vertically or parallel to one of the groove sets, preferably one of the primary groove sets, to facilitate installation. Polycarbonate is about 400
It has a refractive index of about 1.6 over the visible part of the spectrum at ７００700 nm. Polycarbonate has a relatively low dispersion with an Abbe value of 34. Other transparent materials having various refractive indices and dispersion values within the relevant wavelength range can be used. For most applications, a flexible and durable material having a relatively low dispersion in visible light is preferred. Polymers are generally preferred because of their low cost and ease of manufacture. In an alternative embodiment, the solid prism can be composed of one material, such as polycarbonate, and the base triangle of the prism can be in contact with a thin base layer composed of a more flexible transparent material to increase flexibility. It has a two-layer structure that results in an elevated sheet. Such articles are disclosed in U.S. Patent Nos. 5,175,030 (Lu et al.) And
183,597 (Lu).

As used herein, “negative replica” refers to a replica of a given surface, which has complementary inverted features to features on a given surface, and thus is a negative replica. And the given surfaces are in mating contact with each other, and a "positive replica" of a given surface refers to an article generated from an even number of successive negative replicas of a given surface. Both positive and negative reproductions include enlarged or reduced articles that differ from the above description by an isotropic scale.

Optical Properties of Typical Reflectors FIGS. 4A-C schematically show the results of tests measuring the reflective properties of typical reflectors. In the drawing, reference axis 48 is shown normal to the flat front surface of exemplary reflector 50. The primary groove set 36 in the rear surface 28 is located along line 52. Arrow 4 represents the incident visible white light from the slide projector. Is the angle of incidence of the incident light, and α is the viewing angle of the given reflected beam. FIG. 4A It is shooting. The two reflected beams 54, 56 were observed at an observation angle α of about 18 degrees on either side of the incident beam. The measured luminosity of the beams 54 and 56 is 2
. 07E + 4 cd / m ² , the beam 56 is 1.87E + 4 cd / m ² and 1
Same within the 0% range. In FIG. 4B, the light is to the right of reference axis 48 as shown. Observed again, surprisingly one of the beams was much brighter than the other. Also had the measured luminosity. These measured magnitudes are 1.17E + 4 and 1.4, respectively. At the other side of the reference axis 48. Two reflected beams observed again 4C in FIG. 4C has a measured intensity of 1.15E + 4 cd / m ² and α The radiation beams 54, 56, 58, 60, 62, 64 are not only retroreflective beams directed back to the light source, but they are also not "glare" light, which results in simple specular reflection from the front surface of the article. Keep in mind that In both FIGS. 4B and 4C, the brighter reflected beam is closer to the reference axis (ie, a smaller angle from it) than each of the incident beam and the other reflected beam. Also keep in mind.

In summary, it has been observed that this typical reflector splits the incident light into two reflected beams in a direction away from the light source. Furthermore, for certain oblique angles of incidence, such as those encountered when a light source located on the side of a road illuminates a sign located above the road, this reflector is more effective than one side of the light source. A higher intensity beam was generated on the other side. It is advantageous to direct this high intensity beam towards a reference axis, since it is likely that there will normally be roads and expected observers.

[0018] The divergence profile of the same typical article has different illumination geometries as shown in FIG. The visible light detector 66 scanned the area mapping the reflected light intensity as a function of the viewing angle α and the presentation angle γ.

The lighting geometry of FIG. 5 was used to simulate the sign placement layout shown in FIG. In FIG. 6, the sign 68 is placed on the road or at a height H1 above a reference plane 70 corresponding to a plane on the road at the average observer's eye level. The three fixed observation zones Z1, Z2, Z3 located on the reference plane 70 can correspond to the traffic lanes on the road on which the observer moves along its length. These zones have equal width W and have front and rear boundaries at longitudinal distances D1, D2 from the protruding marker location. Marker 68 is aligned with the longitudinal bisector of intermediate zone Z2. The distances D3, D4 and the height H2 above the reference plane 70 define the position of the light source 16, which is located on the side of the road outside the observation zone. Table 2 shows the design value of the distance displayed in FIG. 6 in meters.

[0020]

[Table 2]

Plotting the data obtained from the detector of FIG. 5, a typical reflector, FIG. 7A
The divergence profile shown in is created. The equal luminosity contours are arranged at equal intervals in luminosity values. Sufficient number of contour lines are displayed in luminosity units of cd / lx / m ^2, the reader can verify the intensity value of any other contour. These intensity value labels are boxed to distinguish them from other reference numbers. The center point 72 of the plot corresponds to the retroreflection returning directly to the light source. The other point 74 corresponds to the reference axis 48. The line segment 76 passing through the center 72 and the point 74 serves as a reference from which the presentation angle γ is measured. Concentric circles centered on the point 72 are for reference and indicate the observation angle <.

Light with little or no significance, ie, light where there is no light above a selected background or reference intensity, such as 0.5 cd / lx / m ² , is retroreflected back to the light source You. Instead, typical reflectors produce two distinct beams 78, 80 on either side of the incident beam. The “lower” beam 78 seen in FIG. 7A overlaps and surrounds the reference axis 74. The lower beam 78 extends to the right of the light source 16 toward the general direction of the zones Z1-Z3 (see FIG. 6), while the “upper” beam 80 is further away from the observer in the zones Z1-Z3. It spreads to the left of the light source 16 toward it.
Consistent with the results shown in FIGS. 4B-C, beam 78 has a significantly higher peak intensity than beam 80. However, in this lighting geometry, the observed rate was about 2 and lower than the previously observed rate of greater than 7. The measured peak luminosity was 21.6 cd / lx / m ² and about 10 cd / lx / m ² . In contrast, a currently available beaded sheet (part number HV-8100, commercially available from 3M Company) that reflects incident light into a wide viewing cone as in FIG. 1B, has about 0 at a 20 degree viewing angle. specified in intensity of .5cd / lx / ^{m 2.}

In addition to the luminous asymmetry between the beams 78, 80, there is asymmetry in the shape of the beam as long as the beam 78 has a substantially different shape than the beam 80. Beam 8
0 indicates that both are located at approximately equal viewing angles, but the presentation angle has been moved to such an extent that two distinct annuluses separated by a region having a luminous intensity less than half of either maximum can be identified. With two relative maxima. Beam 78 is also located at approximately equal viewing angles and has two relative maxima shifted presentation angles. However, the area between the relative maximum values of the beam 78 is 20
The light intensity differs from any of the maximum values by less than%, resulting in a more uniform beam profile as compared to beam 80.

FIG. 7B shows the observation zone outline Z superimposed on the enlarged portion of FIG. 7A.
The outline Z represents the position of the car driver located somewhere in the zone Z1, Z2 or Z3 by α and γ coordinates. As can be seen, this typical reflector is 4 cd / lx / m
² minimum intensity, range or "breadth" of the beam 78 of the observation angle 4cd / lx / ^{m 2} intensity was measured to meet the zone outline Z at 20 cd / lx / ^{m 2} or more intensity in some places, suitably Are within the range of 2 magnifications of the range of the zone outline Z at the observation angle. Similarly measured, the "width" of beam 78 at the presentation angle is
It is approximately two to three times the zone Z. By this measurement, the size of the beam 78 is
Suitably and efficiently adapted to the observation zone. The efficiency of a typical reflector is such that the size of the beam 78 is adapted to the viewing zone, due to the asymmetric luminosity characteristic for oblique incident light, and due to the low or non-negligible retroreflectivity of the reflector. Enhanced.

Simply move the light source 16 by making another reflector with a slightly modified structured surface, or alternatively if it can be moved to a new position with a different angle of incidence β and / or orientation angle ω By doing so, it is also possible to shift the relative position between the zone Z and the beam 78. In this way, the illumination of zone Z can optimize the maximum average luminous intensity or the best uniformity by slightly adjusting the arrangement of the light sources. This means that the same sheet may have a different size or position of the observation zone for the sign, for example, for roadside installation versus overhead installation of the sign,
Make it available for two different uses. For any given β, ω value in the range, slightly larger than zone Z, to the extent that light from the light source is incident across the plane of the reflector in the range of β, ω values, the reflected beam It is desirable to have 78.

Computer Model of Alternative Embodiment If it is necessary to try alternative reflective element geometries different from the exemplary reflector described above, a new high precision mold having the desired geometry is manufactured and the mold is fabricated. Would make a reflective sheet from which the measurements would be made directly. A convenient and low cost alternative is to use a computer program or model to predict optical properties, such as the divergence profile of a given desired geometry. This latter method is
Used to test alternative reflector designs.

The computer used took into account reflection, refraction and diffraction effects. The reflection from the surface of the reflective element took into account the difference between s- and p-polarized light. This model set up an array of individual rays, all having the desired angle of incidence and orientation, that uniformly traverse the base triangle of the various prism elements. The calculated output rays were processed to obtain a divergence profile. Unless stated otherwise, light wavelengths approximately in the middle of the visible spectrum, 〜555 nm, were used, and a refractive index of 1.6 was used.

FIG. 8 shows the calculated divergence profile for the exemplary article geometry described above, with illumination geometry β = 18 °, ω = 18 °. As in FIG. 7A, center point 72 represents perfect retroreflection, point 74 represents reference axis 48 perpendicular to the reflector, and line segment 76 corresponds to γ = 0 °.

The comparison of the calculated divergence profile of FIG. 8 with the observed profile of FIG. 7A relies on the computer model drawing rough conclusions about the divergence profile of a given structured surface geometry. Prove that you can. First, the overall two-beam pattern is such that these beams are located on either side of the incident light direction,
It closely approximates the observed pattern. Second, a view of the dominant maximum for each beam Except for the elongated features in the beam, they are almost identical to the observed beam. Fourth,
Both figures show that the beam shape is asymmetric with respect to point 72 between the lower and upper beams. Although there is a slight difference between the calculated and observed beam shapes, in each case the lower beam is between 10 and 15 degrees measured at ² cd / lx / m ² light intensity levels. And a presentation angle Δγ between about 40 and 50 degrees. This level of light is equivalent to beam 78 in FIG. 7A.
Equal to about 10% of the maximum luminous intensity of

Some differences between the observed and calculated beams include details about the number or exact location of relative maxima in the beam. More importantly,
The calculated divergence profile of FIG. 8 shows approximately equal maximum luminosity of the two reflected beams as opposed to the two luminosity observed in FIG. 7A.

Taking into account the capabilities and limitations of the computer model, the additionally calculated divergence profile can be used to demonstrate a reflectivity different from that of a typical reflector to demonstrate the effects of changes in the structured surface of the reflector. Discuss the elements. Its illumination geometry is the same as that of FIG. 8 unless otherwise noted.

Referring to FIG. 9, the total groove angles of about {81.47, 60.28, 60.28 °}, which are the dihedral angles between the tetrahedral prism faces of about {83, 90, 90 °} The divergence profile for the same article as a typical reflector except that was used is shown there. These values are compared to the dihedral angles of a typical reflector of approximately {83.2, 89.8, 89.8 °}. 8 and 9, a 0.2 degree change in dihedral angle redirects light on two sides in the direction of incident light to two substantially reflected beams formed asymmetrically with respect to each other. Is generated. The beam in FIG. 9 has the same α and γ coordinates as in FIG. However, the lower beam of FIG. 9 is less spatially uniform than that of FIG. In the lower beam of FIG.
4 has a beam shape with a more pronounced two-wheeled portion with its center on.

Referring to FIGS. 10A-10J, the effect of reducing the dihedral angle deviation from 90 degrees is demonstrated in one degree increments. The groove angles are shown in FIG. 10A for a structured surface with each tetrahedral prism having a one degree shift, ie, a dihedral angle of {89, 90, 90}, and FIG. 10B for a two degree shift. That is, they are introduced to represent the dihedral angles of {88, 90, 90} and so on. FIG. 10G is the same as FIG. 9. As shown, about 2
A deviation greater than ３3 is required before any visible asymmetry is observed between the two reflected beams. Thus, at least the reflective articles of FIGS. 10D-J refer herein to those having a reflective element with a “highly non-orthogonal” reflective surface. For deviations of about 7 degrees or more, the lower beam retreats into two distinct annular or daughter beams that would not be ideally suited for uniform illumination of one large viewing zone, but would be useful for other applications. (At a level of ² cd / lx / m ² ).

FIGS. 11A-J are identical to each of FIGS. 10A-J except that the dihedral angle deviation from 90 degrees is of opposite polarity in one degree increments. FIG. 11A therefore shows that $ 9
For prisms having dihedral angles of 1, 90, 90 °, FIG. 11J shows {100, 9
A prism having a dihedral angle of 0, 90 °. A deviation of more than about 2-3 degrees is needed again before significant asymmetry is observed. Note that the lower reflected beam advantageously has a larger calculated luminosity value than the upper beam. FIG.
Similar to the property seen in J, a deviation of more than about 8 degrees causes a lower beam ring separation at ² cd / lx / m2 luminous intensity.

The angular range or “width” Δα, Δγ of 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 light used. Become. 12A-B show the predicted visible light emission profile of a structured surface having a groove spacing different from 0.001 inches. It has been found that the change in the groove spacing also affects the reflected beam direction. Therefore, the new full groove angle and the corresponding dihedral angle have been selected to at least partially compensate for this effect. FIG.
In A, the groove spacing of all three groove sets was increased to 0.0015 inches (38 μm). This spacing is equal to about 75 wavelengths of visible light. The total groove angle is $ 81.3621, 59.6955, 59.695 for each of the three groove sets.
The dihedral angle was adjusted to 5 degrees, and dihedral angles of {82.62, 89.745, 89.745 degrees were obtained. In FIG. 12B, the groove spacing has been reduced to 0.0007 inches (18 μm), or about 35 wavelengths of visible light. The dihedral angles are the same as in FIG. 12A. Narrower spacing appears to result in a generally wider lower beam with less abrupt intensity changes across the beam, which may be advantageous in some applications. Wider spacing yields a more concentrated, non-uniform lower beam, which does not adequately illuminate the observation zone Z, but may be useful in other applications. For road geometry similar to FIG. 6,
0.0004-0.002 inch (10-50 μm, or 20-10
A groove spacing of 0 wavelength) is generally preferred.

It is well known to coat the structured surface side of a prismatic sheet with a thin reflective layer of metal. For sheets having elements with a reflective surface having high non-orthogonality, the effect of such a reflective coating in contact with the reflective surface is that the overall luminosity of the reflected beam is reduced, and at least the width of the lower beam is reduced It is to be. FIG. 13 shows the predicted divergence profile for the reflector of FIG. 8 except that a 90% reflective coating was applied to each of the three mutually reflecting prismatic surfaces. Comparing the figures shows the advantage of not coating the reflective surface and instead relying on TIR from the reflective surface if high luminosity and spatial uniformity are desired.

It is also contemplated that sets of grooves that intersect each other at angles other than 60 degrees can also be used to form the tiltable reflective element. These grooves may be arranged to define a base triangle having exactly one included angle of greater than 60 degrees, or alternatively, having exactly one included angle of less than 60 degrees. The base triangle of the reflective element is
It may be an isosceles side or an unequal side. The groove side angles are selected to form a tetrahedral prism having at least two highly non-orthogonal reflective surfaces, as described above. Alternatively, reflective elements, whether tilted or not, that are not defined by parallel groove sets, referred to in the art as full cube corner elements, can be used.

Reflective articles such as sheets made according to the principles disclosed herein can use conventional backing materials to seal the prismatic elements from the atmosphere, as well as adhesive layers and release sheets. For example, US Pat. No. 4,938,5, incorporated herein by reference.
See No. 63 (Nelson et al.). Conventional top films that cover the smooth front surface 30 of the reflective layer can also be used to absorb ultraviolet light that can damage the reflective layer. Dyes can be added to or mixed with the reflective layer material to provide a coloring effect to the article.

Tiling; Dual-purpose sheet The spatial uniformity of the beam reflected from the fixed light source towards the viewing zone is enhanced by incorporating more than one type of reflective element matching pair within the structured surface of the reflective article. Or amended. Tiling or incorporating different reflective element arrays on the same article utilizing well-known manufacturing methods allows for the average divergence profile of the individual reflective element designs used (or other relative surface areas depending on the relative surface area used). Sheets having a divergence profile that is a weighted combination of

FIG. 14 shows a sheet 82 having adjacent striped portions 82a. Each portion 82a, whether reflective or retroreflective, is filled with an array of one type of element.
The portions 82a preferably have a width of less than about 50 mm, so that the individual portions
The sheet cannot be perceived from a viewing distance of 0 m or more, and the sheet looks apparently uniform. Patterns other than stripes can also be used, such as rectangles, squares, and other geometric shapes.

A particular advantage is achieved by including portions of the retroreflective elements within sheet 82 as well as portions of the elements such as those described above that are reflective but not retroreflective. Such a sheet 82 shown in FIG. 15 has duality. First, the sheet 82 directs light 84 from the fixed light source 16 to a broad beam 86 that fills the viewing zone Z. Second, the sheet 82 retroreflects light 88 from a light source on the moving vehicle into a narrow beam 90 centered on the moving light source. This sheet 82 can therefore be installed in both cases, even where a fixed light source illuminates the sign at an appropriate angle or where such a light source is not available. Even in those locations where such a light source is provided, even if the fixed light source fails, the retroreflective portion makes the sign visible to the vehicle driver.

Since the retroreflective beam 90 remains centered on the moving light source of the vehicle, such a beam 90 is located outside the zone Z where the driver's eye viewing angle with respect to the vehicle headlight is very small. But it has high visibility for the vehicle driver. This retroreflected beam 9
0 is U.S. Pat. No. 4,588,258 (Hoopman), 4,775,2.
No. 19 (other than Appledorn) or 5,138,488 (Szc
zech), produced by conventional cube-corner retroreflective elements, such as those disclosed in US Pat. In contrast, beam 86 is generally directed at a viewing angle of greater than 2 degrees. Beam 86 is preferably generated by a reflective element having a reflective surface with high non-orthogonality, as described above, but elements that produce a symmetrical reflected beam may be used in certain other situations.

Table 3 shows one possible design of the article 82 of FIG. This design repeats every seven stripes. The structured surface of portion 82a is defined for each pair of groove side angles offset from the orthogonality generating groove side angle of 35.2644 degrees (the groove sets intersect at an included angle of 60 degrees). One-seventh of that portion is occupied by a retroreflective element, and the remainder is occupied by three different reflective element designs to produce improved uniformity and a wider reflected beam 86. Such tiling increases the width of the reflected beam 86 where each reflective element array alone could not fill the viewing zone with a sufficient amount of reflected light.

[0044]

[Table 3]

Table 4 shows an alternative simple design that repeats every two stripes. This design costs $ 97
, 90, 90 ° and a conventional cube corner retroreflective element with an alternative part of the reflective element associated with FIG. 11G.

[0046]

[Table 4]

The structured surface of article 84 can have individual reflective and / or retroreflective elements of various sizes. For example, the reflective elements in the first portion 82a have a first groove spacing and the reflective elements in the second portion 82a adjacent to the first portion have different groove spacings, so that these elements may vary. Have a size. Similarly, the retroreflective element can be larger or smaller than the reflective element.

An array of various reflective and / or retroreflective elements can also be interspersed with one another by modifying the prior art configuration shown in FIG. 16 (US Pat.
, 600, 484). The enlarged plan view shown therein shows the different elements 92, 9
4, 96 three arrays are shown. Elements 94 and 96 have the same set of dihedral angles because two of their reflective surfaces are coplanar with each other and the third reflective surface is parallel to each other. However, the reflective surface of element 92 is formed independently of elements 94 and 96. Grooves such that elements 94, 96 are retroreflective elements having orthogonal dihedral angles and elements 92 are reflective elements having at least one non-orthogonal dihedral angle, or vice versa. The angle can be conveniently selected. However, this device lacks flexibility in choosing the proportion of the portion covered by each array as compared to the embodiment of FIG. It also lacks flexibility in choosing the relative size of individual elements.

Additional Embodiments Structured in a repeating pattern in an effort to produce a reflected beam with a wider angular range and improved spatial uniformity without having to tile a number of different reflective element structured surfaces. One structured surface was designed that incorporated a variety of different reflective elements interspersed on the surface. These various reflective elements have at least one dihedral angle, each differing from a right angle by more than about 2 degrees. The elements are defined by a repeating sequence of different (large) misalignment of the groove side angles with respect to the groove side angles that would have produced a 90 degree dihedral angle. For elements having an equilateral base triangle, the groove angle deviation is measured for a nominal groove angle of about 35.2644 degrees. For a tilting element (see previous discussion), the groove angle deviation is measured relative to the groove angle that would have produced a 90 degree dihedral angle.

The portion 104 of the structured surface shown in FIG. 17 is exemplary. A complete structured surface would consist of a replica of the portion 104 that would be created if each row of grooves 106a-h, 108a-d, and 110a-d were extended and repeated over the surface. The groove sets 106, 108, 110 cross each other at 60 degrees. The groove side angle shift is drawn for each labeled groove in FIG. 17 and is displayed in minutes. The groove side angle pairs associated with the groove rows in the groove set are different. For example, the groove 108a
Of the grooves 108b and 108c are {-350, -200}.
It is different from 350 °. Alternatively, the pair {300, 150} of the groove 106a is
06b, the pair {300, 300}, which, in turn, is the pair {150} of the groove 106c.
, 300 °. With the pattern so defined, six different classes of reflective elements are formed, each class having a different set of dihedral angles than the other classes. The different combinations of groove side corner surfaces are listed in Table 5, along with the associated dihedral angles. These six reflective element classes are assigned to labels A to F.

[0051]

[Table 5]

The different classes of reflective elements AF are arranged on the structured surface portion 104 as shown in the simplified diagram of FIG. 18, where the grooved surface is not shown. It should be noted that there are more than six different types of reflective elements in portion 104 given the shape and orientation of the individual reflective elements. For example, all of the elements labeled “A” in FIG. 18 have the same three dihedral angles as shown in Table 5, but some of these elements have been rotated with respect to others and Those are other mirror images (but not congruent with each other).

The structured surface portion 104 has a divergence profile that is a combination of the divergence profiles of the many different reflective elements that comprise it. This divergence profile is
As a posterior surface, assume 0.001 inch (25.4 μm) for all of the groove sets, an optical wavelength of ５５555 nm and a refractive index of 1.6, and illumination geometry β = ω = 18 degrees. Calculated using the computer model described above for a sheet with 17 structured surfaces. The result is shown in FIG. 19, where reference numerals 72, 74, 76 have the same meaning as described. The two reflected beams, indicated at 112 and 114, are again seen on either side of the retroreflective point 72. Peak intensity of both beams is relatively low compared with the predicted results shown for some of the embodiments described previously (above slightly 4cd / lx / m ^2). However, beam 11
2,114 are generally more uniform than such previous embodiments, at least
At a luminosity level of ² cd / lx / m ² it has a more rounded (less elongated) shape. A more rounded beam shape means that a sheet with a structured surface 104 can illuminate a larger viewing zone than a sheet with a more elongated, reflected beam. Widely separated portions of a large sheet will have approximately the same apparent luminous intensity at a given viewing point, even if the separated portions are at substantially different angles of incidence and / or orientation with respect to the light source. It also means something. It should be noted from FIG. 19 that the beams 112, 114 show some geometric asymmetry with respect to each other, but surprisingly the overall beam shape is similar.

The structured surface of FIG. 17, and the same plurality of surfaces, can be incorporated into a dual-purpose sheet or other article by the tiling techniques described above.

Glossary of Terms Beam: A light of reflectivity characterized by having a peak luminosity and falling below a given threshold, such as 1% to 10% of the peak luminosity over a boundary region characterized as a beam contour. Quantity or area. Luminous intensity: When referring to a beam, the amount of light expressed in candela per square meter (cd / m ² ). When referring to a reflective article, the reflectivity of the article, expressed in candelas per lux per square meter, is cd / (lx · m ² ).
Or abbreviated cd / lx / m ^2, mean illumination and reflection intensity of the article divided by the surface area of the article. For light outside the visible light spectrum, the corresponding quantities are expressed in radiometer terms rather than photometer terms. Data mark: A mark (real or hypothetical) on a reflective article that is used as a reference to support orientation about a reference axis. Divergence Profile: An expression, for a given illumination geometry, of the luminosity of reflected light as a function of viewing angle and presentation angle. Typically, this representation comprises r coordinates representing the viewing angle α and theta coordinates representing the presentation angle γ (
r, Theta) Takes the form of an isoluminous contour plotted in polar coordinates. Incident angle (β): the angle between the illumination axis and the reference axis. Incident half surface: Half surface starting from the reference axis and including the illumination axis. Groove side angle: The dihedral angle between the groove side and a surface extending parallel to the length of the groove and perpendicular to the base surface of the reflective article. Illumination axis: A line segment that extends between the reference center and the illumination source. Light: Electromagnetic radiation in the visible, ultraviolet, or infrared portions of the spectrum. Observation angle (α): The angle between the illumination axis and the observation axis. View axis: A line segment that extends between the reference center and the selected view point. Observation half: the half that begins with the illumination axis and includes the observation axis. Orientation angle (ω): The dihedral angle between the entrance half and the half starting at the reference axis and including the data mark. Presentation angle (γ): dihedral angle between the entrance half surface and the observation half surface. Reference axis: a line segment that extends away from the reflective article from the reference center and is usually perpendicular to the reflective article at the reference center. Reference center: A point on or near the reflective article specified as its center for specifying the performance of the reflective article. Visible light: Light visible to the naked eye, typically at a wavelength in the range of about 400-700 nm.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1A shows an exemplary observation and illumination model for a known retroreflective sheet.

FIG. 1B shows an exemplary observation and illumination model for a known retroreflective sheeting.

FIG. 1C illustrates an observation and illumination model for the reflective articles disclosed herein.

FIG. 2 is an enlarged plan view of the structured surface of the disclosed reflective article.

FIG. 3 is an enlarged side view of two reflective surfaces within a structured surface.

FIG. 4A shows the reflection characteristics of a typical reflector.

FIG. 4B shows the reflection characteristics of a typical reflector.

FIG. 4C shows the reflection characteristics of a typical reflector.

FIG. 5 shows illumination and observational geometric diagrams of a typical reflector.

FIG. 6 illustrates a reflective article, such as a reflective sheet, located at a location relative to an associated light source and viewing zone.

FIG. 7A is a plot of a measured divergence profile of a typical reflector.

7B is an enlarged portion of FIG. 7A in which the views of the observation zone are superimposed from above.

FIG. 8 is a plot of the predicted divergence profile of a typical reflector.

FIG. 9 is a plot of the predicted divergence profile of another reflective article.

FIG. 10A is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10B is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements having one dihedral angle of less than 90 degrees in one degree increments.

FIG. 10C is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10D is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10E is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10F is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements having one dihedral angle of less than 90 degrees in one degree increments.

FIG. 10G is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements having one dihedral angle of less than 90 degrees in one degree increments.

FIG. 10H is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10I is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 10J is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle less than 90 degrees in one degree increments.

FIG. 11A is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11B is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11C is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11D is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11E is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11F is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11G is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11H is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11I is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements having one dihedral angle greater than 90 degrees in one degree increments.

FIG. 11J is a series of plots of predicted divergence profiles for certain reflective articles having reflective elements with one dihedral angle greater than 90 degrees in one degree increments.

FIG. 12A is a plot of the predicted divergence profile of a reflective article having a different groove spacing than a typical reflector.

FIG. 12B is a plot of the predicted divergence profile of a reflective article having a different groove spacing than a typical reflector.

FIG. 13 is a plot of the predicted divergence profile of the same reflective article as a typical reflector, except that the structured surface has a 90% reflectivity coating thereon.

FIG. 14 is a plan view of a reflective article having at least two different arrays of reflective elements.

FIG. 15 shows a dual-purpose reflective article installed at a position relative to a light source and an observation zone.

FIG. 16 is an enlarged plan view of a prior art structured surface that can be manufactured to incorporate both reflective and retroreflective elements.

FIG. 17 is an enlarged plan view of a portion of a structured surface incorporating various reflective elements interspersed in a repeating pattern.

FIG. 18 is a simplified diagram of FIG. 17 so as to distinguish different types of reflective elements.

FIG. 19 is a plot of the predicted divergence profile of an article having the structured surface of FIG. 17 as a back surface.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, GW, HU, ID, IL, IS, JP, KE, KG, KP, KR , KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZWF term (reference) 2H042 EA03 EA17 5C096 AA01 BA03 BB22 BB23 CA02 CA12 CB01 CE03 CE04 CE14 CE19 CE24 CG12 CG14 CG17 EB03 FA FA07

Claims (29)

[Claims] 1. A reflective article comprising a layer having a structured surface, wherein the structured surface has at least a first, a second, and a second surface having a definable dihedral angle therebetween.
And a plurality of reflective elements each having a third reflective surface, wherein at least one of the dihedral angles differs from a right angle by more than two degrees. 2. The reflective article of claim 1, wherein at least one of said dihedral angles differs from a right angle by no more than about 10 degrees. 3. The reflective article according to claim 1, wherein only one of said dihedral angles differs by more than two degrees from a right angle. 4. The reflective article according to claim 3, wherein the remaining dihedral angles differ from a right angle by an angle greater than 0 degrees and less than 2 degrees. 5. The reflective article according to claim 4, wherein said remaining dihedral angles are substantially the same. 6. The reflective article according to claim 3, wherein said remaining dihedral angle is substantially a right angle. 7. The reflective article according to claim 1, wherein at least one of said dihedral angles differs from a right angle by at least 4 degrees. 8. The reflective article according to claim 7, wherein at least one of said dihedral angles differs from a right angle by approximately 6 to 8 degrees. 9. The reflective article according to claim 1, wherein said plurality of reflective elements comprises a solid four-sided prism. 10. The reflective article of claim 9, wherein said first, second, and third reflective surfaces are exposed to a medium that allows total internal reflection. 11. The reflective article according to claim 1, wherein said plurality of reflective elements are arranged as a plurality of pairs of opposing reflective elements. 12. The reflective article according to claim 1, wherein said plurality of reflective elements are bounded by a plurality of groove sets in said structured surface. 13. A reflective sheet comprising the reflective article of claim 12, wherein the reflective sheet has an edge aligned with one of the groove sets. 14. The reflective article of claim 12, wherein at least one of said groove sets has a groove spacing of about 10-50 μm. 15. The method according to claim 15, wherein at least one of said groove sets has an associated light wavelength of about 20.
13. The reflective article of claim 12, having a groove spacing of up to 100 times. 16. The reflective article of claim 12, wherein at least one of said groove sets has a series of grooves having different pairs of groove side angles. 17. The reflective article of claim 16, wherein each of the groove sets has a series of grooves having a different pair of groove side angles. 18. The method of claim 1, wherein the reflective elements having the same dihedral angle are referred to as a class of reflective elements, and wherein the plurality of reflective elements include at least three different classes of reflective elements. Item 6. The reflective article according to item 1. 19. The reflective article according to claim 18, wherein said different classes of reflective elements are individually discretely arranged with respect to each other. 20. The reflective article of claim 18, wherein said plurality of reflective elements comprises at least six different classes of reflective elements. 21. The first, second, and third reflecting surfaces convert light incident from an incident angle of 18 to 26 degrees into a reflected beam having an observation angle beam width Δα of greater than 5 degrees and less than 20 degrees. The reflective article according to claim 1, wherein the reflective article is arranged to be at least reflective. 22. The beam width is measured at a light intensity of ² cd / lx / m ² ,
A reflective article according to claim 21. 23. An apparatus for displaying information in an extended observation zone, comprising: a sign that can be disposed in proximity to the extended observation zone; and a fixed light source that illuminates the sign at an oblique angle. An apparatus configured such that the indicia comprises the reflective article of claim 1. 24. The method of claim 23, wherein at least one of the dihedral angles differs by at least 4 degrees from a right angle, and the remaining dihedral angles differ by an angle greater than 0 degrees and less than 2 degrees from a right angle. apparatus. 25. The apparatus according to claim 24, wherein said element has a lateral dimension of about 10-50 μm. 26. A reflective article comprising a layer having a structured surface, wherein the structured surface includes a plurality of elements each having at least first, second, and third reflective surfaces. A reflective article wherein the first, second and third reflective surfaces are arranged to reflect oblique incident light into first and second reflected beams asymmetrically distributed on opposite sides of the incident light direction. 27. The first and second reflected beams have maximum beam intensities B1 and B2, respectively, and the first, second and third reflecting surfaces are arranged such that B1 is at least twice B2. 27. The reflective article of claim 26, wherein 28. The reflective article of claim 27, wherein B1 is at least twice B2 for incident light at an incident angle of 18-26 degrees. 29. The reflective article of claim 26, wherein said elements have a lateral dimension of about 10-50 μm.