Plastic lens or lens blank with a flat-steep facet

Abstract

One aspect relates to a plastic lens or lens blank for the manufacture of a plastic lens with a first surface (12) and a second surface (14) opposite the first surface (12), wherein the plastic lens or lens blank has an annular central region (10) and a plano-steep facet (20) surrounding the central region, wherein the plano-steep facet comprises a plano-facet (22) surrounding the central region (10) and a steep facet (24) adjoining and surrounding the plano-facet (22), the plano-facet (22) being formed as a projection of the central region (10), wherein at least one of the surfaces (12, 14) in the region of the plano-facet (22) is arranged substantially perpendicular to a central axis (16) of the plastic lens or lens blank, and the steep facet (24) being formed as a projection of the plano-facet having at least one tip (240).which points away from at least one of the surfaces (12, 14) of the plastic lens or the lens blank in the area of ​​the planar facet (22). Further aspects concern a casting package and a manufacturing process.

Description

The present invention relates to a finished unrimmed plastic lens, a lens blank for the production of a plastic lens (i.e. a lens semi-finished product with a finished surface, usually the front surface of the lens semi-finished product) and a casting package for the production of plastic lenses or semi-finished lens blanks. In the production of plastic lenses, for example for spectacle lenses, a plastic lens or a semi-finished lens blank is cast in a casting kit using a liquid or viscous plastic monomer mixture, a so-called casting resin, and then cured through a polymerization or polyaddition reaction. The corresponding casting kit has two mold shells, to which the front and back surfaces of the lens or lens blank are cast, respectively. The two molds can be sealed with tape to allow the casting kit to be filled and closed for subsequent curing of the lens or lens blank. During the curing process, the volume of the casting resin decreases, which can cause mechanical stresses within the lens or lens blank.For this reason, after the curing process and the removal of the tape, the molds usually adhere strongly to the lens or lens blank and must be removed from the surface of the lens or lens blank by a specially developed demolding process. For demolding, i.e., removing the molds from the lens or lens blank, the casting is first fixed in a fixture. A punch is then mechanically pressed into the edge of the lens or lens blank, causing the molds to deform and detach from the surface. A disadvantage of this demolding method lies in the mechanical deformation of the lens or lens blank caused by the punch. This can result in cracks or streaks in the lens or lens blank, which can be exacerbated by internal stresses that develop during curing. Furthermore, the localized pressure on the edge of the lens or lens blank can lead to inhomogeneity in the plastic structure, which is often visible as a coloring defect after the lens or the lens produced from the lens blank has been dyed. After casting the plastic lens or lens blank, a coating can be applied, for example, a lacquer such as a photochromic lacquer or its primer. After application of the coating, cracks may form on one or both surfaces of the cast plastic lens or lens blank during the coating curing process. Similarly, in a spin coating process, a "coating bead" may form that extends into the optically effective area of ​​the plastic lens or lens blank and can impair its optical properties. Additionally, finished plastic lenses can become contaminated on their typically concave rear surface (cv side) during coating (for example, using a spin coating process), and this contamination can only be removed with complex and expensive cleaning procedures. This occurs primarily with plus lenses, i.e., lenses with a strongly curved or convex front surface. The invention is therefore based on the objective of providing a plastic lens, a semi-finished lens blank for the production of a plastic lens and a corresponding casting package for the production of plastic lenses or semi-finished lens blanks, in which the aforementioned disadvantages are reduced. This task is solved by the subject matter of the independent claims. According to a first aspect, a plastic lens or lens blank is proposed for the manufacture of a plastic lens, wherein the plastic lens has a plano-steep facet, i.e. a combination of a plano facet and a steep facet. A lens blank (plastic blank) for the production of a plastic lens is a semi-finished plastic lens (also referred to as a semi-finished (HF) product or lens semi-finished product) in which only one surface (usually the front surface) is a finished surface, i.e., a surface that requires no further shaping. The opposite surface (usually the back surface) is an unfinished surface that still requires shaping (for example, using CNC machines) to achieve the desired effect of the plastic lens. Both the plastic lens and the lens blank can undergo further treatment after the shaping of the two surfaces, such as rounding, coating, edge finishing, etc. A "plastic lens" or "lens blank" in the context of this description therefore also includes plastic lenses or lens blanks after the shaping of the surfaces of the plastic lens or one of the surfaces of the lens blank and before any further treatments. In particular, the first aspect relates to a plastic lens or lens blank for the manufacture of a plastic lens having a first surface and a second surface opposite the first surface, wherein the plastic lens or lens blank has an annular central region and a plano-steep facet surrounding the central region, and wherein the plano-steep facet comprises a plano-facet surrounding the central region and a steep facet adjoining and surrounding the plano-facet, the plano-facet being formed as a projection of the central region, wherein at least one of the surfaces in the region of the plano-facet (i.e.,at least one of the surfaces of the planar facet) is arranged substantially perpendicular to a central axis of the plastic lens or lens blank, and the steep facet is designed as a projection of the planar facet, which has at least one tip pointing away from the at least one surface of the plastic lens or lens blank in the area of ​​the planar facet. The plastic lens can be a spectacle lens, especially an unrimmed spectacle lens. Typically, the plastic lens or lens blank has a substantially cylindrical shape, with the bases of the cylinder forming the two opposing surfaces of the lens or blank, and the lateral surface of the cylinder forming the outer surface of the lens or blank. The cross-section of the lens or lens blank is usually circular in a plane perpendicular to the cylinder axis. In this case, the central axis of the lens or lens blank coincides with the cylinder axis. Other cross-sectional shapes are also possible, such as an elliptical shape. The first surface of the plastic lens or lens blank can be the surface facing an object (front surface) and the second surface the surface facing a user's eye (back surface). The central area can be, or encompass, an optically effective area of ​​the plastic lens or lens blank. The central area is typically circular and has a center point that usually coincides with the center point of the plastic lens or lens blank. The central area can also have other shapes, such as an elliptical shape. In the central region, the first surface, for example the front surface, is usually a convex surface and can be a spherical or rotationally symmetric aspherical surface whose axis of rotation coincides with the central axis or cylinder axis of the plastic lens or lens blank. The curvature of the front surface at the center of rotation of the plastic lens or lens blank, or, in the case of a non-rotationally symmetric aspherical surface, the curvature at a given reference point, such as the distance reference point of a spectacle lens, is also referred to as the "base curve". In both plastic lenses and semi-finished lens blanks, the front surface in the central area is typically a finished surface, meaning it requires no further shaping. Similarly, in a plastic lens, the second surface, such as the back surface, is also a finished surface in the central area. Together with the front surface, this surface provides the lens's optical effect. The second surface, such as the back surface, is usually convex or planar and can be, for example, spherical, toric, rotationally symmetric aspherical, atoric, progressive, or another type of freeform surface. The central area is surrounded by a plano-steep facet, which comprises a combination of a plano facet and a steep facet, or is formed by a combination of a plano facet and a steep facet. The plano-steep facet forms an arc-shaped, in particular ring-shaped (e.g., circular), lenticular or annular outer region of the plastic lens or lens blank. The plano-steep facet has two annular regions, with the plano facet forming the inner annular region and the steep facet the outer annular region in the radial direction. The radial direction is a direction from the center of the plastic lens or lens blank towards the periphery or edge of the plastic lens or lens blank. The plane facet is a circular arc-shaped, in particular a ring-shaped (for example, a circular) annular region that surrounds the central region (for example, completely) and connects to it directly or via a transition region. The plane facet can be formed as a projection extending substantially horizontally (i.e., in a direction perpendicular to the central axis or cylinder axis of the plastic lens or lens blank) beyond the central region or the base curve. The planar facet can connect to the central area without forming a kink or step. For example, the curvature of the front surface and / or the back surface can change continuously in a transition area between the central area and the planar facet to ensure a smooth, step-free, and kink-free transition from the central area to the planar facet. However, it is also possible to shape the plastic lens or lens blank so that the planar facet connects to the central area with a kink or step and / or without a transition area. The steep facet is a circular arc-shaped, especially ring-shaped (for example, circular), annular region that surrounds the planar facet (for example, completely). The outer edge of the steep facet in the radial direction forms the outermost edge of the plastic lens or lens blank. The steep facet is formed as a (pointed) extension of the planar facet, which has at least one tip pointing away from at least one surface of the plastic lens or lens blank in the area of ​​the planar facet. For example, the steep facet can be formed as a projection extending obliquely upwards and / or downwards, or away from at least one surface of the plastic lens or lens blank in the area of ​​the planar facet, following the planar facet. The tip of the steep facet can, for example, form the outermost edge of the plastic lens or lens blank and have a thickness greater than the thickness of the planar facet at the boundary between the planar and steep facets. In other words, the steep facet can be designed such that the thickness of the plastic lens or lens blank in the region of the steep facet increases radially towards the outer edge of the steep facet, with the increase in thickness being continuous, for example. The thickness can be measured, for example, in a direction parallel to the central axis or the cylinder axis of the plastic lens or lens blank. The steep facet can, for example, connect to the flat facet with a kink or step. It is also possible for the steep facet to connect to the flat facet without a kink or step. The boundary between the flat and steep facets can be designed as a predetermined breaking point to, for example, allow or facilitate the removal of the steep facet during the subsequent manufacturing process. To form the planar facet and the steep facet, at least one of the two surfaces of the plastic lens or lens blank can be designed as a "composite" surface, which has a plurality of zones in which the surface is shaped differently or has different basic shapes. The opposite surface can be a continuous surface or a surface that is also composite. In one example, the front surface of the plastic lens or lens blank can be a composite surface and the back surface a continuous surface. In this example, the front surface can have the following zones: an annular central zone, which together with the continuous back surface forms the central area; a first zone, which surrounds the central zone and together with the continuous back surface forms the planar facet; and a second zone, which surrounds the first zone and together with the continuous back surface forms the steep facet. It is also possible to design the front surface as a continuous surface and the back surface as a composite surface with the three zones mentioned above. Furthermore, it is possible to design both the front and back surfaces as single composite surfaces. In this case, it is not necessary for both the front and back surfaces to exhibit all three of the aforementioned zones. For example, the front and back surfaces can each have a central annular zone, which, together with the central annular zone of the opposite surface, forms the central area. The planar facet can be formed simply by modifying the shape of either the front or back surface, and the steep facet can be formed simply by modifying either the back or front surface. Other combinations are also possible. The plastic lens or lens blank for manufacturing a plastic lens with a planar-steep facet features an improved design that enables efficient production without compromising the optical properties of the plastic lens or lens blank. In particular, the introduction of a combination of a planar and a steep facet ensures reliable demolding of the plastic lens or lens blank and reduces the occurrence of cracks in the material and / or prevents crack propagation. By incorporating a steep facet, cracks can be prevented from forming during demolding in the area of ​​the (usually thin) flat facet. Simultaneously, improved coating of the plastic lens or lens blank, for example with a photoresist or its primer, is ensured. The steep facet can be completely primed away after casting, with the rounding of the steep facet being carried out in such a way that the lens blank or plastic lens no longer exhibits any waviness ("wavy edge") at the edge. It is also possible to round off or remove part of the flat facet after casting and coating. This reduces demolding defects (such as cracks, stresses, etc.) in subsequent processing steps, thus increasing the optical quality of the finished plastic lens.This applies in particular to plastic lenses or lens blanks made of a high-refractive-index optical material with a refractive index of 1.60 and higher, whereby the refractive index of an optical material is usually determined at a wavelength of about 550 nm. The flat facet contributes to a reliable reduction of coating cracks (e.g., paint cracks) during coating curing. The flat facet also ensures that a coating bead (such as a paint bead from a photoresist coating), which is unavoidable in spin coating processes, forms on the flat facet and not on the convex front surface. This prevents the coating bead from restricting or interfering with the effective area of ​​the final plastic lens or lens blank. Similarly, when rounding the steep facet, it is possible to form a bevel, steep bevel, or chamfer on the surface opposite the remaining flat facet, in particular, to avoid the formation of a sharp edge on the plastic lens or lens blank. Preferably, the edge of the plastic lens or lens blank...of the lens blank and the convex or concave surface thereof form an obtuse angle or an angle of 90 degrees or more, preferably 100 degrees or more, more preferably 135 degrees or more. Besides the problem of coating ridges forming in the effective area of ​​the coated plastic lens or lens blank, contamination of the concave rear surface (cv side) can occur during spin coating (for example, with photoresist or its primer). With a finished plastic lens, such contamination can only be removed using complex and expensive cleaning processes. This is especially true for plus lenses, i.e., plastic lenses with a positive effect in the optically effective central area. The planar facet ensures that contamination from the coating (for example, the photoresist primer and / or the photoresist) does not extend into the area of ​​the finished concave rear surface.Rounding the flat facet, typically the final manufacturing step of an unrimmed plastic lens, ensures that any contamination on the back surface, occurring only in the area of ​​the flat facet, is automatically removed, thus eliminating the need for complex and costly cleaning after the final production step. The flat facet can therefore prevent both the problem of paint bulge and contamination of the back surface of the optically active part of the plastic lens or lens blank. By advantageously combining a planar facet with a steep facet, it is therefore possible to improve the optical properties of the plastic lens or lens blank while simultaneously increasing the efficiency of the manufacturing process. The flat facet and the steep facet can have different shapes and / or dimensions. Thus, at least one of the surfaces of the plastic lens or lens blank in the area of ​​the planar facet can be a planar surface (i.e., a surface with an infinite radius of curvature). It is also possible to design at least one of the surfaces of the plastic lens or lens blank in the area of ​​the planar facet as a curved (for example, spherical) convex or concave surface. The curved surface in the area of ​​the planar facet can, for example, have a curvature that is (for example, significantly) greater in magnitude than the curvature of at least one of the surfaces of the plastic lens or lens blank at the boundary of the central area with the planar facet. The at least one planar or curved surface can be the front surface. In one example, the planar facet can be designed such that it has a substantially constant thickness. However, it is also possible to design the planar facet as an area with changing thickness, for example, increasing radially outwards. The starting or inner diameter of the facet can be approximately 70 to 80 mm, depending on the nominal diameter of the central area, the plastic lens, or the lens blank. The width of the facet in the radial direction of the plastic lens or lens blank can, for example, be approximately 1 mm to 3 mm, or approximately 1.5 mm to 2.5 mm. The width of the facet is essentially half the difference between the end or outer diameter of the facet and its starting or inner diameter. The maximum thickness of the facet parallel to the central axis or cylinder axis can, for example, be 0.5 mm to 20 mm. A planar facet designed in this way has particularly advantageous properties with regard to avoiding and / or reducing the aforementioned disadvantages in the manufacture of plastic lenses or lens blanks. At least one of the surfaces in the area of ​​the steep facet (i.e., at least one of the surfaces of the steep facet) can be curved, for example, a spherical concave or convex surface. The radius of curvature of the front and / or back surface in the area of ​​the steep facet can, for example, be from approximately 55 to 150 mm. It is also possible to design the front surface and / or the back surface in the area of ​​the steep facet as an essentially flat surface, which is arranged at an angle of, for example, 15° to 45° to the front surface and / or back surface in the area of ​​the flat facet. In other words, the front and / or back surface can be designed as a slope with an angle of 15° to 45°. This corresponds to a radius of 55 to 150 mm. The dimensions of the steep bevel can vary. For example, the width of the steep bevel in the radial direction of the plastic lens or lens blank can range from approximately 1 mm to 3.5 mm. The maximum thickness of the steep bevel in the direction parallel to the central axis can, for example, range from 0.5 mm to 5.0 mm. The maximum thickness of the steep bevel is generally the thickness measured at the outermost edge of the steep bevel, the plastic lens, or the lens blank. A steep facet designed in this way has particularly advantageous properties with regard to avoiding and / or reducing the aforementioned disadvantages in the manufacture of plastic lenses or lens blanks. The plastic lens or lens blank can be made of a suitable optical material, for example, an optical material with a refractive index of 1.50 or higher (such as 1.6, 1.67, etc.). The plastic lens can be a positive or negative lens, i.e., a lens with a positive or negative refractive power. The lens blank can accordingly be used to manufacture a negative or positive plastic lens. The plastic lens can be, in particular, a spectacle lens, such as a single-vision lens, a progressive lens, etc. The lens blank can accordingly be a lens blank for the manufacture of a spectacle lens. In this case, the front surface in the central area is usually a finished convex surface, specifically a spherical or rotationally symmetric convex surface. The back surface in the central area is shaped according to the desired prescription effect for the spectacle wearer and can be spherical, rotationally symmetric aspheric, or another aspheric surface (such as a progressive lens surface). According to a second aspect, a casting package is proposed comprising a first mold and a second mold, wherein the casting package is designed to form a plastic lens or lens blank for the production of a plastic lens with a plano-steep facet according to the first aspect and / or its variations and examples by curing a casting resin that can be introduced into the casting package. In particular, the casting package is designed such that, after casting, polymerization, and demolding of the lens blank or plastic lens, the plano-steep facet described above is transferred from the mold (=negative) to the lens blank or plastic lens (=positive). For this purpose, a recess can be formed on at least one of the two molds in an outer area of ​​the casting package such that the plano-steep facet described above can be cured during the production of the plastic lens or lens blank with the casting package. Optionally, after subsequent rounding or rounding of the lens blank or plastic lens to eliminate production-typical material defects, a flat facet or part of the flat facet may remain. The plastic lens or lens blank according to the first aspect and / or variation and / or examples thereof can be subjected to further processing steps to obtain, for example, a coated and optionally edged or shaped edged or edge-machined plastic lens or a coated lens blank. According to a third aspect, a method for producing a plastic lens or lens blank, in particular a plastic lens or lens blank according to a preceding aspect, is proposed, comprising the following steps: - providing two mold shells for forming a plastic blank, wherein the two mold shells are designed such that a plastic blank or a plastic lens can be formed, having a first side having a flat facet and having, on the same side and / or on a second side opposite it, a steep facet, in particular providing a casting package according to a second aspect, or providing a lens blank or lens blank designed in this way.of a plastic lens;- Rounding off the steep facet that is no longer needed after demolding the plastic blank or plastic lens, whereby a plastic blank or plastic lens then has a planar facet, in particular to obtain a spectacle lens blank which, when using a tape method, no longer has any waviness ("wavy edge") at the edge (i.e. a smooth edge surface) due to the rounding. Using the proposed method, a plastic lens or lens blank can be produced or formed which has the advantages described in the preceding paragraphs. In a first step, two mold shells or casting molds are provided for forming a plastic blank, wherein the two mold shells or casting molds are designed such that a plastic blank or a plastic lens can be formed, having a first side with a flat facet and having, on the same side and / or on a second side opposite it, a steep facet. In a further development, this step comprises providing such a casting package, comprising at least two mold shells or casting molds for forming such a plastic blank, in particular according to the preceding second aspect. The preparation or training process typically includes filling, curing, and demolding. Typically, and especially in a manner familiar to those skilled in the art, the cavity or space formed between the mold shells or casting molds is filled with a liquid or viscous plastic monomer mixture, a so-called casting resin, and then cured by a polymerization or polyaddition reaction in order to cast a plastic lens or lens blank. Advantageously, the two molds can be sealed with tape so that filling and closing of the casting package is possible for the subsequent curing of the lens or lens blank. During the curing process, the volume of the casting resin decreases, which is why, after the curing process and the removal of the tape, the casting molds usually adhere strongly to the lens or lens blank and are removed from the surface of the lens or lens blank by a demolding process. Typically, and especially in a manner familiar to those skilled in the art, a punch is mechanically pressed into the edge of the lens or lens blank for demolding, so that the molds detach from the surface of the lens or lens blank by deformation. In another further development, the provision can also include the provision of a lens blank or a plastic lens of such a nature, in particular a lens blank or a plastic lens that has already been manufactured, preferably as described above. As already explained in the preceding paragraphs, especially regarding the first aspect, the provision of a steep facet can prevent cracks from occurring during demolding, particularly in the area of ​​a (usually thin) flat facet. In a subsequent, second step, the steep bevel, no longer needed after demolding the plastic blank or lens, can be rounded off. Preferably, the steep bevel is completely primed away after casting, and the rounding can be carried out in such a way that the lens blank or plastic lens no longer exhibits any waviness ("wavy edge") at the edge after rounding. Optionally, a portion of the flat bevel can be rounded off. For example, the remaining portion of the flat bevel can be approximately 1 mm. Other dimensions are also possible. After rounding, particularly as the final process step, a plastic blank or lens with a planar facet is obtained. In other words, the proposed method allows for the improved production of a plastic lens or lens blank that exhibits a planar facet. Further developing this process can include rounding the steep bevel, and in further development, rounding a portion of the flat bevel, as well as forming a new or additional bevel, preferably a steep bevel, on the surface opposite the rounded steep bevel and the remaining flat bevel. Such a bevel prevents the formation of a sharp edge or edge area, which is disadvantageous in subsequent manufacturing or processing steps because such a sharp edge or edge area is difficult (or more difficult) to grip mechanically with manufacturing tools. In particular, (machine) handling can cause the edge to be subjected to such high mechanical stress that damage to the blank occurs. This damage can be advantageously avoided by an obtuse angle between the edge and the surface with properties as described above. Preferably, and in particular alternatively or additionally, the width of this facet in the radial direction of the plastic lens or lens blank is equal to the width of the opposite, and in particular remaining, planar facet, and preferably has a value of approximately 1 mm to 3 mm, particularly preferably approximately 1.5 mm to 2.5 mm. This ensures that the formed facet does not project into the central area of ​​the plastic lens or lens blank. Preferably, and in particular alternatively or additionally, the maximum thickness of this facet, formed during rounding, in the direction parallel to the central axis is between 0.5 mm and 5.0 mm. The maximum thickness is generally measured at the outermost edge of the steep facet, the plastic lens, or the lens blank, and is not initially limited further. Preferably, and in particular alternatively or additionally, this formed facet has an angle of inclination of 15° to 45° to the radial direction of the plastic lens or the lens blank. In contrast to a method in which a plastic lens or lens blank is formed with only a flat facet, the method according to the invention first proposes forming a plastic lens or lens blank with a flat-steep facet. That is, a plastic lens or lens blank with a flat-steep facet is initially formed or produced as an intermediate product, in order to overcome the disadvantages known from the prior art. In a subsequent process step, the steep facet is then removed or rounded off, and is no longer needed after demolding. A plastic lens or lens blank produced in this way, having a planar facet, can serve as a starting product and be further processed or treated in subsequent, in particular downstream, process steps, preferably provided with at least one coating and / or edge-processed or edge-finished. A preferred method for producing a further processed (such as coated and optionally edged) plastic lens or a further processed (such as coated) lens blank using a plastic lens or lens blank produced as described above, additionally comprises the following further steps: - Applying a coating to the lens blank having the planar facet or a part of the planar facet, or to the plastic lens having the planar facet or a part of the planar facet; and - Curing the applied coating, preferably thermally and / or UV-induced, to obtain a polymerized, permanently adhering coating. In further training, particularly before the application of a coating, a portion of the flat bevel can optionally be rounded off. For example, the remaining portion of the flat bevel can be approximately 1 mm. Other dimensions are also possible. A preferred method for producing a final (for example, coated and optionally edged) plastic lens or a final (such as a coated) lens blank using a plastic lens or lens blank as described above, additionally comprises the following further steps: - Applying a coating to the plastic blank having a flat facet, preferably a photoresist coating to obtain a photochromic object, particularly preferably by means of rotary coating; and - Curing the applied coating, preferably thermally and / or UV-induced, to obtain a (fully) polymerized, permanently adhering coating, wherein the flat facet contributes to improved curing behavior. Optionally, the process can include further rounding, for example to remove photoresist residues at the edge and / or around the planar facet or a remaining part of the planar facet, in particular to remove them completely, preferably in such a way that only the central area remains which forms or comprises the optically effective area. Further optional steps include: - Annealing of the formed plastic blank or the formed plastic lens for complete polymerization and / or stress relief; and / or - (surface) processing, in particular to obtain an object or a finished plastic lens having the desired optical properties, preferably, in the case of a lens blank, back surface processing; and / or - Application of at least one further coating, wherein the at least one further coating may be a coating of hard lacquer, buffer and / or primer lacquer, anti-reflective and / or mirrored coating, anti-fog and / or easy-to-clean coating; and / or - Edge forming to obtain a rimmed plastic lens, such as a spectacle lens, having a desired edge shape or geometry, in particular for installation in a spectacle frame provided for this purpose. The invention is explained in more detail below with reference to exemplary embodiments shown in the accompanying figures. Individual features shown in the figures can be combined with features from the exemplary embodiments shown in other figures. The figures show: Fig. 1: a schematic sectional view of an exemplary lens blank with a cast flat-steep facet; Fig. 2: a schematic sectional view of an exemplary plastic lens with a cast flat-steep facet; Fig. 3: a schematic sectional view of an exemplary lens blank; Fig. 4: a schematic sectional view with dimensions of the lens blank shown in Fig. 3; Fig. 5: a schematic sectional view of an exemplary transition between a flat facet and a steep facet; Fig. 6: a schematic representation of an embodiment of a manufacturing process; Fig. 7: a schematic sectional view of an embodiment of a lens blank.a plastic lens as a product of an embodiment of the manufacturing process; Fig. 8 a schematic sectional view of a further or different embodiment of a lens blank or a plastic lens as a product of an embodiment of the manufacturing process. The sectional view in Figs. 1 to 4 and 7 to 8 is in a plane through a central axis or cylinder axis 16 of the lens blank or the finished plastic lens. The exemplary plastic lens shown in the figures is a spectacle lens, and the exemplary lens blanks are lens blanks for the manufacture of a spectacle lens. In particular, Fig. 1 shows a schematic sectional view of an exemplary lens blank for the production of a spectacle lens with a cast plano-steep facet 20. Fig. 2 shows a schematic sectional view of a finished spectacle lens with a cast plano-steep facet 20, which can be produced from the lens blank shown in Fig. 1 by machining the concave back surface 14 (for example, using CNC machines). The front surface 12 is a finished convex, for example, spherical surface. In the example shown, the back surface 14 can be the side facing the eye of a spectacle wearer, particularly in a typical position when used as a spectacle lens, and can therefore be designated as the eye side A, whereas the front surface 12 can face an object and can therefore be designated as the object side B. The exemplary lens blank and the finished plastic lens each have a central region 10 surrounded by a planar steep facet 20. The central region 10 forms or comprises the optically effective area of ​​the exemplary lens blank or plastic lens. The diameter D1 of the central region can vary. For example, in a spectacle lens or a lens blank for a spectacle lens, the diameter of the central region can be approximately 70 to 80 mm. The front surface 12 in the central region 10 (i.e., the front surface of the central region) is typically a spherical or rotationally symmetric aspherical surface. The planar steep facet 20 is formed from a planar facet 22 and a steep facet 24. The planar facet 22 is a round, ring-shaped annular area that adjoins and completely surrounds the central area 10. The diameter D1 of the central area thus also represents the starting or inner diameter of the planar facet 22. The steep facet 24 is a round, ring-shaped, annular area that adjoins and completely surrounds the flat facet 22. The end or outer diameter D2 of the flat facet D2 thus also represents the starting or inner diameter of the steep facet. The diameter D3 of the lens blank or plastic lens also represents the end or outer diameter of the steep facet 24. The width BS of the steep facet 24 (which is at least half the difference between D3 and D2) can, for example, be in the range of approximately 1 to 3.5 mm. The width of the flat facet 22 is half the difference between D2 and D1 and can, for example, be in the range of approximately 1 to 3.5 mm. Alternatively, the width of the flat facet 22 can also be a resultant or remaining width derived from the specified values ​​for D1, D3, and BS.For example, it may be useful to specify a value D1 for the diameter of the central area and a value for the width BS of the steep facet 24, as well as a value for the total width D3 of the finished plastic lens or lens blank, from which the width of the flat facet 22 then results as the remaining width. The planar facet 22 is formed as an essentially horizontal projection extending beyond the central area 10 or the base curve. The steep facet 24 is formed as an obliquely upward-sloping projection extending beyond the planar facet 22. The steep facet has a tip 240, which points away from the lens blank or the plastic lens. In the examples shown in Figs. 1 and 2, only the front surface 12 has correspondingly configured annular ring-shaped zones in which the shape of the front surface differs from the shape of the front surface in the central region 10. The back surface 14 is a continuous concave spherical surface. In other words, in the examples shown in Figs. 1 and 2, the planar facet 22 and the steep facet 24 are formed by a special shaping of the front surface 12. The front surface 12 in the region of the planar facet 22 (i.e., the front surface of the planar facet 22) is a substantially planar surface that runs substantially horizontally or perpendicularly to the central axis or cylinder axis 16 of the lens blank or the plastic lens. The front surface 12 in the region of the steep facet 24 (i.e., the front surface of the steep facet 24) is a spherical surface with a radius that can be, for example, in the range of approximately 55 mm to 150 mm. Alternatively, the front surface of the steep facet can be a planar surface. The angle W between (i) the front surface of the planar facet 22 or a planar approximation 222 of the front surface of the planar facet 22 and (ii) the front surface of the steep facet 24 or a planar approximation of the front surface of the steep facet 24 can, for example, take a value between 15° and 45°. In the case of a curved surface (such as a curved front or back surface of the steep facet), the angle W can be defined as the angle formed between (i) the front surface of the planar facet 22 or a planar approximation 222 of the front surface of the planar facet 22 and (ii) a connecting line V that links the tip 240 of the steep facet 24 with the starting point or starting diameter D2 of the steep facet 24, or in particular a secant through the points D2 and the tip of the steep facet 240. Fig. 5 shows the angle W at an exemplary transition between a planar facet and a steep facet with a curved front surface. Figures 3 and 4 show a schematic sectional view of another exemplary lens blank for the production of a plastic lens with a cast plano-steep facet 20. The structure of this lens blank corresponds to the structure of the lens blank shown in Figure 1. In the example shown in Figs. 3 and 4, the front surface in the central region 10 is a convex spherical surface with a curvature (base curve) of 6.00 diopters. The diameter D1 of the central region 10, which is also the starting diameter of the planar facet 22, is 70.6 mm. The angle W is 27°. The radius of the front surface of the steep facet is 86 mm. The width of the steep facet is 1.81 mm. These dimensions are only examples and may vary, for example depending on the diameter and / or material of the lens blank, the base curve, etc. Fig. 6 shows a schematic representation of an embodiment of a manufacturing process for a plastic lens or lens blank. In Fig. 6, steps of the manufacturing process shown with solid lines are mandatory, whereas steps shown with dashed lines represent optional developments of the process, in particular further or subsequent steps for the production of a plastic lens using the lens blank or plastic lens produced, in particular in the preceding steps, especially with a plano-steep facet. The process comprises the following steps: - Providing S100 an exemplary lens blank or an exemplary plastic lens with a flat-steep facet. Providing a lens blank or a plastic lens with a flat-steep facet may include providing a casting package with two mold shells for casting such a lens blank or plastic lens and casting and demolding the lens blank or plastic lens; - Rounding S110 the steep facet of the lens blank or plastic lens, which is no longer needed after demolding from the mold shells, to obtain a lens blank or a plastic lens having, in particular, at least one flat facet, and in particular to obtain a lens blank or a plastic lens which, when using a tape method, no longer exhibits any waviness ("wavy edge") at the edge due to the rounding.In preferred embodiments, the method may further comprise the following additional steps: - Applying a coating (S120) to the lens blank or plastic lens having the planar facet. The coating may, for example, be a photoresist coating to obtain a photochromic object. The coating may be applied, for example, by rotary coating; and / or - Curing (S130) the applied coating, preferably thermally and / or UV-induced, to obtain a fully polymerized, permanently adhering coating, wherein the planar facet contributes to improved curing behavior.and / or- Rounding S140, in particular to remove photoresist residues at the edge and / or the remaining flat facet; and / or- (surface) processing S150, in particular back surface processing, to obtain desired optical properties, especially in the case of a semi-finished plastic blank; and / or- Application S160 of at least one further coating, such as a coating of hard lacquer, buffer and / or primer lacquer, and / or an anti-reflective and / or mirrored coating, and / or an anti-fog and / or easy-to-clean coating; and / or- Forming S170 to obtain a rimmed plastic lens, such as a rimmed spectacle lens, having the desired edge shape or geometry, in particular for installation in a spectacle frame provided for this purpose. Figs. 7 and 8 show schematic sectional views of different embodiments of a lens blank or a plastic lens as a product of different embodiments of the manufacturing process from Fig. 6. In the embodiment of a lens blank or plastic lens shown in Fig. 7, the product of the manufacturing process is a lens blank or plastic lens having a flat facet 22, since the steep facet 24, which was initially formed, particularly by casting, was rounded off or removed in process step S110. The plastic lens or lens blank shown is particularly suitable for the (further) production of a spectacle lens, since the flat facet 22, which in this case is formed or remains on the object side B, is advantageously useful in optional further manufacturing steps, such as steps S120 and / or S130. In the embodiment of a lens blank or plastic lens shown in Fig. 8, the product of the manufacturing process is a lens blank or plastic lens having a flat facet 22, since the steep facet 24, which was initially formed, in particular by casting, was rounded off or removed in process step S110. In contrast to the embodiment in Fig. 7, during the rounding of the steep facet 24, a facet 25, preferably a steep facet 25, was formed on the eye side A, in the case shown, in particular an additional facet 25, wherein this facet is located in the area of ​​the planar facet on the object side B, in particular with regard to the radial arrangement and extent. In this way it is ensured that the facet does not project into or engage in the central area. The plastic lens or lens blank shown is particularly suitable for the (further) manufacture of a spectacle lens, since, on the one hand, the formed or remaining flat facet, located in this case on the object side B, is advantageously useful in optional, further manufacturing steps, such as steps S120 and / or S130, and, on the other hand, the facet or steep facet 25 formed in this case on the eye side A is advantageously useful, especially in machine processing steps, preferably enabling machine gripping and / or fixing or holding of the plastic lens or lens blank, as in steps S120 to S160, since the additional facet 25, preferably a steep facet 25, enables improved gripping, fixing, or holding. Reference symbol list 10 Central area of ​​a plastic lens or lens blank 12 Front surface of the plastic lens or lens blank 14 Rear surface of the plastic lens or lens blank 20 Plane-steep facet 22 Plane facet 222 Plane approximation of a surface (e.g., the front surface) of the plane facet 24 Steep facet 240 Tip of the steep facet 25 Facet A Eye side B Object side D1 Starting diameter of the plane facet D2 End diameter of the plane facet D3 Diameter of the plastic lens or lens blank W Angle between a surface of the plane facet and a surface of the steep facet V Connecting line R Radius of a surface of the steep facet BS Width of the steep facet

Claims

Plastic lens or lens blank for the manufacture of a plastic lens with a first surface (12) and a second surface (14) opposite the first surface (12), wherein the plastic lens or lens blank has an annular central region (10) and a plano-steep facet (20) surrounding the central region, wherein the plano-steep facet comprises a plano-facet (22) surrounding the central region (10) and a steep facet (24) adjoining and surrounding the plano-facet (22), the plano-facet (22) being formed as a projection of the central region (10), wherein at least one of the surfaces (12, 14) in the region of the plano-facet (22) is arranged substantially perpendicular to a central axis (16) of the plastic lens or lens blank, and the steep facet (24) being formed as a projection of the plano-facet having at least one tip (240) pointing away from at least one the surfaces (12,14) of the plastic lens or lens blank in the area of ​​the planar facet (22)., Plastic lens or lens blank for the manufacture of a plastic lens according to claim 1, wherein at least one of the surfaces (12, 14) in the region of the planar facet (22) is a planar surface; or at least one of the surfaces (12, 14) in the region of the planar facet (22) is a curved surface which has a curvature which is greater in magnitude than a curvature of the at least one surface (12, 14) at a point on the boundary of the central region (10) to the planar facet (22). Plastic lens or lens blank for the manufacture of a plastic lens according to claim 1 or 2, wherein the thickness of the planar facet (22) is substantially constant or increases radially outwards. Plastic lens or lens blank for the manufacture of a plastic lens according to one of the preceding claims, wherein; the starting diameter (D1) of the planar facet (22) is in the range of 70 to 80 mm; and / or the width of the planar facet (22) in the radial direction of the plastic lens or lens blank is in the range of 1 mm to 3 mm. Plastic lens or lens blank for the manufacture of a plastic lens according to one of the preceding claims, wherein at least one of the surfaces (12, 14) in the region of the steep facet (24) is a curved surface, wherein the radius of curvature (R) of the at least one surface (12, 14) in the region of the steep facet (24) is in the range of 55 to 150 mm; and / or at least one of the surfaces (12, 14) in the region of the steep facet (22) is a substantially planar surface, which is arranged at an angle (W) of 15° to 45° to the front surface (14) and / or back surface (14) in the region of the planar facet (22). Plastic lens or lens blank for the manufacture of a plastic lens according to one of the preceding claims, wherein the width (BS) of the steep facet (24) in the radial direction of the plastic lens or lens blank is in the range of 1 mm to 3.5 mm. Plastic lens or lens blank for the manufacture of a plastic lens according to any of the preceding claims, wherein the plastic lens or lens blank is made of an optical material having a refractive index of 1.50 or higher; and / or wherein the plastic lens is a positive or a negative lens. Plastic lens or lens blank for the manufacture of a plastic lens according to any of the preceding claims, wherein the plastic lens is a spectacle lens. Casting package comprising a first mold and a second mold, wherein the casting package is configured to form a plastic lens or lens blank for the production of a plastic lens according to one of the preceding claims by curing a casting resin that can be introduced into the casting package. Method for producing a plastic lens or lens blank, in particular a plastic lens or lens blank according to any one of claims 1 to 9, comprising the following steps: - providing (S100) two mold shells for forming a plastic blank, wherein the two mold shells are designed such that a plastic blank or a plastic lens can be formed, having a first side having a planar facet and having, on the same side and / or on a second side arranged opposite it, a steep facet, in particular providing a casting package according to claim 9, or providing a lens blank or lens blank constructed in this manner.a plastic lens;- Rounding (S110) of the steep facet (24) which is no longer needed after demolding the plastic blank or plastic lens, wherein a plastic blank or plastic lens then has a planar facet (22), in particular to obtain a spectacle lens blank which, when using a tape process, no longer has any waviness (“wavy edge”) at the edge due to the rounding. Method according to claim 10, wherein the step of providing (S100) alternatively comprises providing a casting package according to claim 9; or providing a lens blank or plastic lens of such a nature. Method according to claim 10 or 11, wherein step S110 of rounding additionally comprises forming a facet or steep facet (25) on the side opposite the rounded steep facet (24) and remaining flat facet (22). A method according to any one of claims 10 to 12, wherein the formation of the facet or steep facet (25) is carried out such that this facet or steep facet (25) has: - a width in the radial direction of the plastic lens or lens blank corresponding to the width of the planar facet (22); and / or - a width in the radial direction of the plastic lens or lens blank of 1 mm to 3 mm; and / or - a maximum thickness in the direction parallel to the central axis of the plastic lens or lens blank of 0.5 mm to 5.0 mm; and / or - an angle or inclination angle to the radial direction of the plastic lens or lens blank of 15° to 45°.

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