Preliminary Products for Light Protection Devices with High-Precision Optics for Glare-Free Light Deflection

Abstract

The invention relates to a planar preliminary product for producing focusing light-directing slats having a top side and an underside. The top side and the underside are the largest sides in terms of area. The top side has a groove structure having parallel grooves and ridges in a longitudinal direction and having a multiplicity of sidewalls F.sub.1 and F.sub.2. A respective pair of sidewalls F.sub.1 and F.sub.2 forms a common ridge projecting on the top side. The sidewalls F.sub.1 and F.sub.2 are in each case at an angle with respect to one another which is at least approximately constant along the transverse direction and longitudinal direction of the groove structure. The top side has an overall contour defined by the vertices of the ridges. The sidewalls F.sub.1 and F.sub.2 of adjacent pairs are at an angle γ with respect to one another. The sidewalls F.sub.1 and F.sub.2 are symmetrical with respect to one another in relation to an area of symmetry, which is oriented at right angles with respect to the overall contour and is arranged at the location lying in the centre between the sidewalls F.sub.1 and F.sub.2. The angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is at least approximately constant. The sidewalls have a surface, which surfaces specularly reflect light substantially according to the law of reflection that angle of incidence is equal to angle of reflection.

Claims

1. Planar preliminary product for producing focusing light-directing slats having a top side and an underside, comprising a top side and an underside are the largest sides in terms of area, wherein at least the top side has a groove structure having parallel grooves and ridges in a longitudinal direction and having a multiplicity of sidewalls F.sub.1 and F.sub.2, wherein a respective pair of sidewalls F.sub.1 and F.sub.2 forms a common ridge sidewall projecting on the top side, wherein the sidewalls F.sub.1 and F.sub.2 are in each case at an angle with respect to one another which is at least approximately constant along the transverse direction and longitudinal direction of the groove structure, and wherein the top side has an overall contour defined by the vertices of the ridges, wherein the sidewalls F.sub.1 and F.sub.2 of adjacent pairs are at an angle γ with respect to one another, characterized in that the sidewalls F.sub.1 and F.sub.2 are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to the overall contour and is arranged at the location lying in the centre between the sidewalls F.sub.1 and F.sub.2, wherein the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is at least approximately constant, wherein the sidewalls each have a surface, which surfaces specularly reflect light substantially according to the law of reflection that angle of incidence is equal to angle of reflection.

2. Strip-shaped preliminary product for producing focusing light-directing slats according to claim 1, characterized in that the sidewalls F.sub.1 and F.sub.2 are embodied as smaller than 1/10 mm.

3. Strip-shaped preliminary product for producing focusing light-directing slats according to claim 1, characterized in that the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is greater than or equal to 70° and less than 1 10°, preferably 90°.

4. Strip-shaped preliminary product for producing focusing light-directing slats according to claim 1, characterized in that the sidewalls F.sub.1 and F.sub.2 of two adjacent pairs are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to the overall contour and is arranged at the location lying in the centre between the pairs.

5. Light-directing slat comprising a top side and an underside, wherein the top side and the underside are the largest sides in terms of area, wherein the top side has a groove structure having parallel grooves and ridges in a longitudinal direction and having a multiplicity of sidewalls F.sub.1 and F.sub.2, wherein a respective pair of sidewalls F.sub.1 and F.sub.2 forms a common ridge projecting on the top side, wherein the sidewalls F.sub.1 and F.sub.2 are in each case at an angle with respect to one another which is at least approximately constant along the transverse direction and longitudinal direction of the groove structure, and wherein the top side has an overall contour defined by the vertices of the ridges, wherein the sidewalls F.sub.1 and F.sub.2 of adjacent pairs are at an angle γ with respect to one another, characterized in that the sidewalls F.sub.1 and F.sub.2 are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to an overall contour and is arranged at the location lying in the centre between the sidewalls F.sub.1 and F.sub.2, wherein the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is at least approximately constant, and wherein the sidewalls have a surface, which surfaces specularly reflect light substantially according to the law of reflection that angle of incidence is equal to angle of reflection, wherein the light-directing slat has a first and a second slat longitudinal edge, and wherein the light-directing slat in particular is taken from a planar preliminary product according to claim 1 transversely with respect to the longitudinal direction of the groove structure.

6. Light-directing slat according to claim 5, characterized in that the angle σ.sub.H1 of the sidewall F.sub.1 in relation to a connecting line from the first slat longitudinal edge to the second slat longitudinal edge increases continuously over the width of the light-directing slat from the first slat longitudinal edge to the second slat longitudinal edge, wherein in particular an angle σ.sub.H2 of the sidewall F.sub.2 in relation to the connecting line increases continuously over the width from the second slat longitudinal edge to the first slat longitudinal edge of the light-directing slat, and wherein the light-directing slat is curved concavely at its top side and the underside is curved convexly.

7. Light-directing slat according to claim 5, characterized in that the overall contour is at least approximately in the shape of an arc of a circle.

8. Light-directing slat according to claim 7, wherein the overall contour has the shape of a circle sector having a circle sector angle β, characterized in that the angles of the tangents t to the overall contour at both slat longitudinal edges relative to a connecting line from a first slat longitudinal edge to a second slat longitudinal edge are at least approximately equal in magnitude, wherein the angles of the tangents t are in each case approximately equal to half the angle of the circle sector angle β, wherein half the angle of the circle sector angle β is preferably greater than 5° and less than 20° and particularly preferably between 12° and 18°, in particular 14°-16°.

9. Light-directing slat according to claim 5, characterized in that the sidewalls F.sub.1 and F.sub.2 of the legs of an isosceles triangle approximately form a right angle between the legs, wherein a sidewall F.sub.1 at the first slat longitudinal edge and a sidewall F.sub.2 at the second slat longitudinal edge in each case form an angle with respect to a connecting line in the transverse direction of the light-directing slat between the first and second slat longitudinal edges of 20° to 42°, preferably between 28° and 32°, wherein the tangents to the overall contour at the slat longitudinal edges are approximately half the circle sector angle β.

10. Sun protection device, characterized in that the sun protection device comprises at least one upper and one lower light-directing slat according to claim 5, wherein during operation with a maximum horizontal view between the light-directing slats in particular a shadow line of a slat longitudinal edge of an upper light-directing slat extends to a slat longitudinal edge of a lower light-directing slat on the shadow side, wherein the shadow line is at an angle α.sub.s with respect to the horizontal, wherein the angle as is at least approximately equal to the circle sector angle β, wherein the vertical distance D between the undersides of the upper and lower light-directing slats is equal to the width β multiplied by the tangent of the angle α.sub.s.

11. Sun protection device according to claim 10, characterized in that a radius r of curvature of the overall contour of the light-directing slat transversely with respect to the longitudinal direction is at least approximately equal to the width B of the light-directing slat divided by double the sine of half the circle sector angle β, preferably a ratio B/r being 0.5±0.05, with preference 0.51.

12. Sun protection device according to claim 10, characterized in that a preliminary material width b of a preliminary product of a light-directing slat that is curved transversely with respect to the longitudinal direction is equal to the radius r of curvature multiplied by the circle sector angle β in radians, with preference a ratio r/b being greater than 1.5 and less than 2.5, particularly preferably 1.9±0.2.

13. Method for producing a light-directing slat according to claim 5, wherein a preliminary product according to claim 1 is used, characterized in that the preliminary product is reshaped into a light-directing slat that is concave at the top side, wherein the angle γ is reduced by the reshaping process.

14. Method according to claim 13, characterized in that a planar preliminary product is embodied as wider on a strip-shaped preliminary product for slat production, wherein the width of the strip-shaped preliminary material is defined transversely with respect to the longitudinal direction of the groove structure, and the strip-shaped preliminary product with a width b of a light-directing slat is split from the starting material.

15. Method for producing a preliminary product according to claim 1, characterized in that the preliminary product is produced by its being provided with the groove structure by a) the groove structure being embossed into the preliminary and subsequently being reflectively coated, in particular metallized, or b) a transparent lamination film structured with the sidewalls F.sub.1 and F.sub.2 being applied to a carrier material, wherein the sidewalls F.sub.1 and F.sub.2 are applied to the lamination film by a printing method, in particular in a rotary printing method, wherein in particular a polymerizing printing varnish is applied, wherein either the structure is deposited from a structured roller onto the film, or the structure is embossed into an applied printing varnish, wherein the structured printing varnish is preferably cured, in particular by means of UV radiation, wherein the UV radiation impinges on the printing varnish preferably from the rear side through the film and cures said printing varnish, wherein afterwards the lamination film is metallized on the printed side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further explanations will be given on the basis of the descriptions of the figures, in which:

[0034] FIG. 1 shows the cross section through a slat having identical, symmetrical prisms before the concave/convex shaping,

[0035] FIGS. 2.1 and 2.2 show the contour configuration before and after slat shaping,

[0036] FIGS. 3 and 4 show a pair of slats of a blind hanging with exemplary light guidance,

[0037] FIG. 5 shows the geometric principles of slat shaping,

[0038] FIG. 6 shows the determination of the tangent inclination and of the radii for slat shaping,

[0039] FIG. 7 shows the determination of the slat contour in relation to the slat distance.

[0040] FIGS. 8, 9 show the reflection behaviour of a circularly curved light-directing slat in the case of light incidence at the angle of the shadow line.

[0041] FIGS. 10, 11 show the ray tracing on slat segments.

[0042] FIG. 12 shows the mirror behaviour of reflected radiation at glazing.

[0043] FIG. 13 shows ray tracing between the sidewalls F.sub.1 and F.sub.2.

DETAILED DESCRIPTION OF THE INVENTION

[0044] FIG. 1 shows a preliminary product in cross section, consisting of a main body 11 and the triangular grooves 12. The grooves 12 are situated on or in a carrier film 10 combined with the slat body 11. The grooved furrows are either imprinted or embossed and reflectively coated/metallized in the preliminary product. The term preliminary product relates to a web-type material with any desired working width. The preliminary product can be split into narrow strips. The end product of a focusing slat arises as a result of curvature of the split-off preliminary product. The individual work steps are preferably carried out from the coil.

[0045] In the case of a film support, the bond between slats 11 and carrier film 10 is effected by adhesive bonding, preferably by means of hot melt adhesives in a continuous method between two heated rollers. The continuous method works from coil to coil. The main body 11 consists e.g. of aluminium or steel or else of plastic or wood veneer and can also be brought to a concave/convex shape already prior to roller feed-in or the slats are shaped after the splitting of a wide strip.

[0046] FIG. 2.1 shows the triangular, symmetrical shaping and arrangement of the grooves. In the preliminary product, all adjacent triangles are at the same angle with respect to one another, an angle γ of 90° resulting by way of example in FIG. 2.1. The focusing optical system in the end product is produced by means of a reduction of the angle γ, as illustrated in FIG. 2.2. This is achieved by means of a concave curvature of the slat base. The curvature results in angles σ.sub.H with respect to the horizontal at the prism sidewalls located towards the incidence of radiation.

[0047] In FIG. 3, σ.sub.H increases from the irradiation side towards the interior. In the slat centre, σ.sub.H≅σ.sub.p; at the slat edge located towards the interior, σ.sub.H>σ.sub.p results in an optimized manner. In accordance with the teaching of the innovation, the focusing optical system is the result of the subsequent slat curvature. Slat width, slat distance and the focusing properties are defined exclusively by way of the angle γ between the triangles and are checked e.g. by way of the tangents t of the slat contour.

[0048] The cathetus or prism sidewalls F are of an economic order of magnitude of between 1 μm and 60 μm, preferably 2-3 μm, thus resulting in an overall construction of the lamination film of just 10 to 50 μm. If the groove structure is embossed into a film, similar dimensions result. However, other dimensions and film thicknesses are possible. An ideal optical system can be realized in the case of an inclination of the triangle sidewalls of σp=45° with respect to the base.

[0049] FIGS. 3 and 4 show pairs of slats with lateral incidence of solar radiation and the reflections thereof. In the present case, the angle α.sub.s corresponds to the inclination of the shadow line S of an upper slat edge in relation to the inner edge of a lower slat. Since a ray reflected in the direction of the light incidence does not undershoot the angle α.sub.s, there is also no occurrence of glare on account of specular reflection in an exterior pane. This type of glare suppression is realized by the triangle contour and also the slat contour because individual specular reflections between the slats are prevented from reaching the observer's eye. In this respect, see also FIG. 11.

[0050] It is evident that the slat bodies differ considerably in their width B.sub.1 versus B.sub.2 and in their distance D.sub.1 versus D.sub.2 and in their radius r and in their curvature. Nevertheless, according to the invention, with a single groove contour, the shape and size of the individual triangles of which do not differ, it is possible to achieve an identical light guidance of reflected light rays provided that the ratio h/B and/or D/B is maintained. This is the case if the sidewalls F.sub.1 are at identical angles σ=σ′ with respect to the horizontal at least at the edges and in the slat centre.

[0051] For identical angles of incidence of solar radiation, the same angles ε.sub.1=ε.sub.2 of reflective rays result e.g. at the slat edges and in the slat centre in both of FIGS. 3 and 4. In order to realize this, the following rule or design methodology holds true for the slat contour:

[0052] In FIG. 7, a circle sector is formed at the angle β and the slat width b is thereby determined, such that for σ.sub.p for the slat contour a tangent angle β/2 arises in the slat edges. The radius r and/or the slat widths can then be chosen to be of any desired magnitude. Prisms where σ.sub.p=45° are depicted in each case, wherein the base of the curve tangent t is positioned at the angle β/2. Independently of the slat width B, the same optical relationships are always ensured. The slat distances D among one another change proportionally to the slat width and are preferably determined by the angle α.sub.s of the shadow line S in order that the specular reflection of the retroreflection in an exterior pane cannot penetrate between the slats into the interior (see also FIG. 12). The prism sidewall exposed to the incidence of radiation at the slat edge on the interior side is ideally formed at a right angle with respect to the shadow line S, as a result of which the inclination angle α.sub.s=30° of the shadow line S is also determined. The angle σ.sub.H of the prism sidewalls at the slat edge oriented towards the interior I thus results as σ.sub.H=σ.sub.p+β/2=60° for β=30°, and the angles of the slat tangents tin the edges result as β/2.

[0053] An optimum slat distance D results as D=B×tan α.sub.s.

[0054] The segment height h likewise varies proportionally to the slat width and is determined as h=B/2×tan (β/4).

[0055] The slat cut width b (FIG. 5) is determined as b=β/360°×2r×π.

[0056] If a slat width B is predefined, then the radius r of the slat contour is determined as r=B/2×sin (β/2).

[0057] The advantage of the innovation is that the constructor of blinds, using these simple dimensions, can carry out quality control, despite the triangle mirrors on the top side contour not being discernible to said constructor on account of the microstructure.

[0058] Deviations from ideal dimensions determined computationally should be afforded tolerance in a manner governed by manufacturing. A slat in the shape of an arc of a circle with mirror symmetry of the prisms by way of the slat centre enables a very good approximation to a Fresnel focusing optical system as shown in FIGS. 8 to 11.

[0059] The prisms are illustrated in a manner enlarged by a multiple in all the drawings. Nano- or microsizes of the prism sidewalls are involved in reality. The latter form mini fragments of curve progressions and make it possible, depending on shaping or curve progression of the slat body, to precisely reproduce any desired geometry by adaptation of the angles γ. The prism sidewalls irradiated by the sun complement one another as a result of the slat shaping in their minimum size to form a continuous mirror optical system by virtue of the matching of the angles γ between the prisms e.g. as a result of a minimum angle reduction from a desired focusing optical system.

[0060] The following applies to the innovative microstructures: the smaller the prisms are chosen to be, the more accurately the desired focusing effect is realized by means of the slat contour. Therefore, the size and sharp-edged embodiment of the prisms with sidewalls <60 μm, advantageously <5 μm, are of elementary importance for a precision of the light guidance.

[0061] The prism films are metallized with aluminium, for example, in a high vacuum. Colour designs are possible by means of metallic additives or else vapour depositions of gold or silver or later transparent, thin colour varnishes.

[0062] Since there is the occurrence of specular reflections in the exterior glazing in the event of reflections back into the fagade, said specular reflections, as already described, being trapped on the underside of the slats, it is possible also to reflectively coat the slat undersides and/or to equip them with mirror prism supports which reflect the impinging specular reflection back into the exterior glazing. At least bright coatings, e.g. white, are recommendable.

[0063] FIG. 5 elucidates the geometric interactions in the curvature of the basic contour. The figure shows the logic of the prism configuration as a consequence of the radii r. In the present case, the design is once again based on a mirror prism where σ.sub.p=45° and the contour configuration of the concave slat curvature is elucidated on the basis of four different radii r with circle centres M.sub.1 to M.sub.4.

[0064] Depending on the magnitude of the radii r, the result is different inclination angles σ.sub.H of the prisms in adaptation to the tangent inclination angles t.sub.1 to t.sub.4 in the slat edges. The prism sidewalls are indicatively assigned to M.sub.1 to M.sub.4. Upon complying with the requirement for freedom from glare owing to specular reflection of the reflection in an exterior glazing, the shadow line S.sub.1 to S.sub.4 is arranged at right angles with respect to the sunlit sidewall F.sub.1 of the prism at the slat edge towards the interior (enlarged view in FIG. 5.1), thus giving rise to the angles α.sub.s1 to α.sub.s4 of the shadow lines depending on the slat radius r and the position of the centres M.sub.1 to M.sub.4 on an axis γ of symmetry.

[0065] The exact curvature of the slats L.sub.1 to L.sub.4 varies with the centres M.sub.1, to M.sub.4 and is discernible in the basis contour b. The resulting segment heights h.sub.1 to h.sub.4 of the slats are all the smaller, the larger the radius r formed. At the same time, the smaller the radius r, the shallower the resulting angles α.sub.s1 to α.sub.s4 of the shadow lines S.sub.1 to S.sub.4 and the smaller the slat distance D.sub.1 to D.sub.4, too. The variations of the slat widths b are negligible in the case of microprisms.

[0066] FIG. 6 shows a greatly enlarged view of a triangular prism at the slat edge towards the interior from FIG. 5 and FIG. 5.1, the base of which prism, following the slat contour, is arranged at an angle β/2. Since the prism angles σ.sub.p and σ.sub.H are not verifiable on account of the minimal size, the prism angles σ.sub.H are determined by the angle of the tangent t with respect to the horizontal H e.g. with β/2, wherein β corresponds to the centre angle at M.

[0067] If the slats are formed symmetrically about a central axis γ, the prism inclination angles likewise turn out to be mirror-symmetrical. By virtue of the angle indication of the slat contour at the end points, the microstructure is also able to be controlled by a constructor of blinds easily with a template, for example, whereby a major objective of the innovation is fulfilled. All the triangular prisms are embodied at the angle of σ.sub.p=45° in FIGS. 5 and 6. This is not a condition, however. Optimal results are also achievable with angles σ.sub.p of 30° to 50°. σ.sub.p<45° results in larger slat distances D. σ.sub.p>45° results in smaller slat distances D.

[0068] In order to realize an optimum reflection optical system of a concave/convex light-deflecting slat taking account of freedom from glare in the exterior glazing in the event of the blinds being mounted behind glass in the interior, the following dependencies exist: For a ratio of

[0069] Slat distance D to slat width B

D/B=0.58±0.05

[0070] the prism angle is σ.sub.p>30°<50°, preferably σ.sub.p=45°.

[0071] The tangents tin the edges of the slat bodies are inclined 15°±5° with respect to the horizontal under the above conditions in the case of a horizontal slat position.

[0072] This results in a rise h of the curved slat body as a ratio to the slat width B

h/B>0.07<0.13, preferably h/B 0.1±0.01.

[0073] In order to shape the slat body correctly, an optimum ratio of the radius r to the slat width B of

r/B<2.5>1.5, preferably r/B=1.94±0.1

[0074] is defined.

[0075] The following holds true as a guideline value for the slat contour: the larger the distance D as a ratio to the slat width B is chosen and the larger the angle α.sub.s of the shadow line S is chosen, the shallower the prism angle σ.sub.p and/or σ.sub.H that can be determined at the slat edge located towards the interior. For a ratio D/B˜0.58 and a shadow line of 30°, the prism angle in the region of the slat edge on the irradiation side is σ=30° in order largely to avoid glare in the event of reflection back into the glazing.

[0076] FIG. 8 shows a radiation analysis of an end product curved in an arc of a circle from a flat preliminary product for an angle of incidence of solar radiation at the angle of the shadow line of 32°, specifically for a folding at the angle σ.sub.p=45°. FIG. 9 shows the light incidence at the angle of 32° from the opposite direction with an identical reflection behaviour. The advantage of the development is the symmetry of the structure, which precludes wrong incorporation of the slats in a hanging.

[0077] FIG. 10 shows an analysis of the ray tracing in the first slat segment, and FIG. 11 shows that in the second slat segment. By means of the circular rounding-off, only a concentration zone can be formed, but not an exact focus, wherein the first slat segment forms a focus zone F.sub.1, and the second segment a focus zone F.sub.2. The illustration does not show the second reflection at the slat underside, through which the radiation is reflected back into the exterior area.

[0078] What is crucial is that no glare occurs in the exterior glazing. This is precluded because a ray incident at the smaller angle <α.sub.s of the shadow line is reflected more steeply than the shadow line to the underside of the upper slat.

[0079] FIG. 12 shows the specular reflection in the exterior pane 100 for incidence of solar radiation of 65°. No ray 104 reflected back towards the outside can produce glare upon specular reflection at the exterior pane 100 between the slats in the interior since all rays 105 are trapped on the slat undersides. This is the realization of an innovation goal of the preliminary product and of the teaching for determining the curved basic contour and also for determining the correct slat distance D as a ratio to the slat width B.

[0080] FIG. 13 shows an enlarged view of the mirror structure and of the reflection behaviour in the case of incidence of solar radiation of 65°. The largest portion of radiation impinges on the sidewalls F.sub.1. A small part of the radiation impinges on the sidewall F.sub.2 and is deflected to the sidewall F.sub.1. In the first segment 101 it is shown that the radiation is reflected back from F.sub.1 in the direction of the incidence of solar radiation. Therefore, even a secondary reflection cannot initiate glare owing to an unavoidable specular reflection in the exterior pane.

[0081] The reason for this ray guidance is the merely minimal deviation γ from the right angle between F.sub.1 and F.sub.2. The advantage of the microstructures according to the invention is that the angle deviations, as explained with reference to FIGS. 2.1 and 2.2, turn out to be all the more minimal, the smaller the structures. An angle deviation of less than 1/1000th° is ultimately involved—that is to say an optically negligible order of magnitude.

[0082] In contrast to the prior art in accordance with DE 10 2014 005 480, the innovative preliminary product has achieved a significant technical advance as a result of a simplification of the microstructure, which nevertheless enables all differentiated requirements in respect of directing light and freedom from glare.

[0083] The following paragraphs list certain embodiments of the invention.

[0084] Paragraph 1

[0085] Planar preliminary product for producing focusing light-directing slats having a top side and an underside, wherein the top side and the underside are the largest sides in terms of area, wherein at least the top side has a groove structure having parallel grooves and ridges in a longitudinal direction and having a multiplicity of sidewalls F.sub.1 and F.sub.2, wherein a respective pair of sidewalls F.sub.1 and F.sub.2 forms a common ridge sidewalls projecting on the top side,

[0086] wherein the F.sub.1 and F.sub.2 are in each case at an angle with respect to one another which is at least approximately constant along the transverse direction and longitudinal direction of the groove structure, and wherein the top side has an overall contour defined by the vertices of the ridges,

[0087] wherein the sidewalls F.sub.1 and F.sub.2 of adjacent pairs are at an angle γ with respect to one another,

[0088] characterized in that

[0089] the sidewalls F.sub.1 and F.sub.2 are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to the overall contour and is arranged at the location lying in the centre between the sidewalls F.sub.1 and F.sub.2, wherein the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is at least approximately constant,

[0090] wherein the sidewalls each have a surface, which surfaces specularly reflect light substantially according to the law of reflection that angle of incidence is equal to angle of reflection.

[0091] Paragraph 2

[0092] Strip-shaped preliminary product for producing focusing light-directing slats according to paragraph 1, characterized in that the sidewalls F.sub.1 and F.sub.2 are embodied as smaller than 1/10 mm.

[0093] Paragraph 3

[0094] Strip-shaped preliminary product for producing focusing light-directing slats according to either of the preceding paragraphs, characterized in that the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is greater than or equal to 70° and less than 110°, preferably 90°.

[0095] Paragraph 4

[0096] Strip-shaped preliminary product for producing focusing light-directing slats according to any of the preceding paragraphs, characterized in that the sidewalls F.sub.1 and F.sub.2 of two adjacent pairs are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to the overall contour and is arranged at the location lying in the centre between the pairs.

[0097] Paragraph 5

[0098] Light-directing slat having a top side and an underside, wherein the top side and the underside are the largest sides in terms of area, wherein the top side has a groove structure having parallel grooves and ridges in a longitudinal direction and having a multiplicity of sidewalls F.sub.1 and F.sub.2, wherein a respective pair of sidewalls F.sub.1 and F.sub.2 forms a common ridge projecting on the top side,

[0099] wherein the sidewalls F.sub.1 and F.sub.2 are in each case at an angle with respect to one another which is at least approximately constant along the transverse direction and longitudinal direction of the groove structure, and

[0100] wherein the top side has an overall contour defined by the vertices of the ridges, wherein the sidewalls F.sub.1 and F.sub.2 of adjacent pairs are at an angle γ with respect to one another,

[0101] characterized in that

[0102] the sidewalls F.sub.1 and F.sub.2 are symmetrical with respect to one another in relation to an area of symmetry which is oriented at right angles with respect to an overall contour and is arranged at the location lying in the centre between the sidewalls F.sub.1 and F.sub.2, wherein the angle γ between all pairs of sidewalls F.sub.1 and F.sub.2 is at least approximately constant, and

[0103] wherein the sidewalls have a surface, which surfaces specularly reflect light substantially according to the law of reflection that angle of incidence is equal to angle of reflection, wherein the light-directing slat has a first and a second slat longitudinal edge, and wherein the light-directing slat in particular is taken from a planar preliminary product according to claim 1 and/or is separated from a strip-shaped preliminary product according to any of claims 1 to 4 transversely with respect to the longitudinal direction of the groove structure.

[0104] Paragraph 6

[0105] Light-directing slat according to paragraph 5, characterized in that the angle σ.sub.H1 of the sidewall F.sub.1 in relation to a connecting line from the first slat longitudinal edge to the second slat longitudinal edge increases continuously over the width of the light-directing slat from the first slat longitudinal edge to the second slat longitudinal edge, wherein in particular an angle σ.sub.H2 of the sidewall F.sub.2 in relation to the connecting line increases continuously over the width from the second slat longitudinal edge to the first slat longitudinal edge of the light-directing slat, and wherein the light-directing slat is curved concavely at its top side and the underside is curved convexly.

[0106] Paragraph 7

[0107] Light-directing slat according to either of paragraphs 5 and 6, characterized in that the overall contour is at least approximately in the shape of an arc of a circle.

[0108] Paragraph 8

[0109] Light-directing slat according to paragraph 7, wherein the overall contour has the shape of a circle sector having a circle sector angle β,

[0110] characterized in that the angles of the tangents t to the overall contour at both slat longitudinal edges relative to a connecting line from a first slat longitudinal edge to a second slat longitudinal edge are at least approximately equal in magnitude, wherein the angles of the tangents t are in each case approximately equal to half the angle of the circle sector angle β, wherein half the angle of the circle sector angle β is preferably greater than 5° and less than 20° and particularly preferably between 12° and 18°, in particular 14°-16°.

[0111] Paragraph 9

[0112] Light-directing slat according to any of paragraphs 5 to 8, characterized in that the sidewalls F.sub.1 and F.sub.2 of the legs of an isosceles triangle approximately form a right angle between the legs, wherein a sidewall F.sub.1 at the first slat longitudinal edge and a sidewall F.sub.2 at the second slat longitudinal edge in each case form an angle with respect to a connecting line in the transverse direction of the light-directing slat between the first and second slat longitudinal edges of 20° to 42°, preferably between 28° and 32°, wherein the tangents to the overall contour at the slat longitudinal edges are approximately half the circle sector angle β.

[0113] Paragraph 10

[0114] Sun protection device, characterized in that the sun protection device comprises at least one upper and one lower light-directing slat according to one or more of paragraphs 5-9, wherein during operation with a maximum horizontal view between the light-directing slats in particular a shadow line of a slat longitudinal edge of an upper light-directing slat extends to a slat longitudinal edge of a lower light-directing slat on the shadow side, wherein the shadow line is at an angle α.sub.s with respect to the horizontal, wherein the angle α.sub.s is at least approximately equal to the circle sector angle β, wherein the vertical distance D between the undersides of the upper and lower light-directing slats is equal to the width β multiplied by the tangent of the angle α.sub.s.

[0115] Paragraph 11

[0116] Sun protection device according to paragraph 10, characterized in that a radius r of curvature of the overall contour of the light-directing slat transversely with respect to the longitudinal direction is at least approximately equal to the width b of the light-directing slat divided by double the sine of half the circle sector angle β, preferably a ratio B/r being 0.5±0.05, with preference 0.51.

[0117] Paragraph 12

[0118] Sun protection device according to paragraph 10 or 11, characterized in that a preliminary material width β of a preliminary product of a light-directing slat that is curved transversely with respect to the longitudinal direction is equal to the radius r of curvature multiplied by the circle sector angle β in radians, with preference a ratio r/b being greater than 1.5 and less than 2.5, particularly preferably 1.9±0.2.

[0119] Paragraph 13

[0120] Method for producing a light-directing slat according to at least one of paragraphs 5 to 9, wherein a preliminary product according to any of claims 1 to 5 is used, characterized in that the preliminary product is reshaped into a light-directing slat that is concave at the top side, wherein the angle γ is reduced by the reshaping process.

[0121] Paragraph 14

[0122] Method according to paragraph 13, characterized

[0123] in that a planar preliminary product is embodied as wider on a strip-shaped preliminary product for slat production,

[0124] wherein the width of the strip-shaped preliminary material is defined transversely with respect to the longitudinal direction of the groove structure,

[0125] and the strip-shaped preliminary product with a width β of a light-directing slat is split from the starting material.

[0126] Paragraph 15

[0127] Method for producing a preliminary product according to any of paragraphs 1 to 4 or a light directing slat according to any of claims 5 to 9, characterized in that the preliminary product or the light-directing slat is produced by its being provided with the groove structure by

[0128] a) the groove structure being embossed into the preliminary product or the light-directing slat and subsequently being reflectively coated, in particular metallized, or

[0129] b) a transparent lamination film structured with the sidewalls F.sub.1 and F.sub.2 being applied to a carrier material,

[0130] wherein the sidewalls F.sub.1 and F.sub.2 are applied to the lamination film by a printing method, in particular in a rotary printing method,

[0131] wherein in particular a polymerizing printing varnish is applied,

[0132] wherein either the structure is deposited from a structured roller onto the film, or the structure is embossed into an applied printing varnish,

[0133] wherein the structured printing varnish is preferably cured, in particular by means of UV radiation, wherein the UV radiation impinges on the printing varnish preferably from the rear side through the film and cures said printing varnish, wherein afterwards the lamination film is metallized on the printed side.