Abstract:
The invention relates to a method for producing an optical lens element, in particular for illuminating purposes, in particular for producing a headlight lens for a vehicle headlight, in particular for a motor vehicle headlight. A preform made of a transparent plastic, which is amorphous in particular, is molded in an injection mold using an injection molding method. The preform is removed from the injection mold, in particular before the average temperature of the preform falls below the melting temperature of the plastic and/or the flow temperature of the plastic, and the preform is subsequently pressed into the lens element, in particular the blank, using a final contour mold.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a method for manufacturing a headlight lens for a vehicle headlight wherein a blank is molded from transparent, in particular amorphous, plastic material by means of an injection molding process in an injection mold, and wherein the blank is subsequently press-molded by means of a final shape/contour mold to form the lens element. 
       BACKGROUND INFORMATION 
       [0002]    An above mentioned process is known from DE 10 2007 037 204 A1. 
         [0003]    DE 699 23 847 T2 discloses a process for manufacturing an optical mold body from thermoplastic resin by injection pressure molding, wherein the volume of a mold cavity expands more strongly than the volume of the optical mold body in question, and wherein molten thermoplastic resin is injected into the mold cavity through an injection molding passage. 
         [0004]    According to DE 699 23 847 T2, a method for manufacturing an optical mold body from thermoplastic resin by injection pressure molding as described in U.S. Pat. No. 4,540,534, EP 0 640 460 and JP 9-057794 has to be distinguished therefrom, which method comprises
       expanding the volume of a mold cavity beyond the volume of the optical mold body in question,   injection molding of molten thermoplastic resin in(to) the mold cavity through an injection molding cylinder,   pressing the expanded cavity to a predetermined thickness of the mold body,   returning a surplus of the thermoplastic resin which has occurred by the molding step, into the injection molding cylinder,   leaving the molten thermoplastic resin in the mold cavity until the mold body in question has been shaped, and   removing the obtained mold body from the mold cavity.       
 
         [0011]    DE 102 20 671 A1 discloses a plastic lens consisting of a collective lens of plastic material having a high Abbé number, and a dispersion lens connected therewith integrally and in positive fit, of plastic material having a comparably low Abbé number regarding the plastic material of the collective lens, wherein the thermal expansion coefficients of the respective plastic materials are essentially the same. 
         [0012]    Headlight lenses are known e.g. from WO 02/31543 A1, U.S. Pat. No. 6,992,804 B2, WO 03/074251 A1 and DE 100 52 653 A1. Further vehicle headlights are known e.g. from DE 100 33 766 A1, EP 0 272 646 A1, DE 101 18 687 A1 and DE 198 29 586 A1. 
         [0013]    It is an object of the invention to reduce the costs for manufacturing lens elements, in particular for illumination purposes, particularly for the manufacturing of headlight lenses for vehicle headlights. In this context, it is, in particular, desirable to manufacture especially high-value lens elements, in particular headlight lenses. It is a further object of the invention to improve the process disclosed in DE 10 2007 037 204 A1. In this context, it is particularly desirable to achieve a higher accuracy of contour. It is, in particular, an object of the invention to specify an improved vehicle headlight including a plastic lens and/or a motor vehicle with a correspondingly improved vehicle headlight. 
       SUMMARY 
       [0014]    The aforementioned object is achieved by a method for manufacturing a headlight lens for a vehicle headlight, in particular for a motor vehicle headlight, wherein a blank of transparent, e.g. amorphous, plastic material is molded by means of an injection molding process in an injection mold, wherein the blank is removed from the injection mold, particularly before its mean temperature falls below the melting temperature/the melting temperature range of the plastic material and/or the flow temperature/the glass transition temperature of the plastic material, and wherein the blank is subsequently pressed (molded under pressure), in particular press-molded (on all sides, on both sides) to form the headlight lens by means of a final shape (final contour) mold (by moving together mold parts of the final shape or contour mold). Herein, the blank is, in particular, molded such that it has essentially the same mass as the headlight lens. It is, in particular, provided for that the temperature and/or the mean temperature of the blank between the molding thereof in the injection mold and the press-molding is, at no time, lower than 60° C., particularly at no time lower than 80° C. 
         [0015]    In the sense of the invention, a headlight lens is particularly a headlight lens for imaging a bright-dark boundary on a roadway. 
         [0016]    The term press-molding, also given as or blank-molding, is, in particular, to be understood in a manner that an optically operative (or effective) surface is to be pressed (i. e. molded under pressure) such that any subsequent post-treatment (or finishing) of the contour of this optically operative surface may be dispensed with or does not apply or will not have to be provided for, respectively. 
         [0017]    An injection pressing mold in the sense of DE 10 2007 037 204 A1 may act as an example of embodiment for an injection mold. An injection pressing process in the sense of DE 10 2007 037 204 A1 may act as an example of embodiment for an injection molding process. Thickness is, in particular, a maximum thickness. The thickness and the diameter extend, for example, orthogonally with respect to each other. A diameter of an injection mold cavity or of a headlight lens, respectively, particularly relates to the maximum circular cross sectional face of the injection mold cavity or of the headlight lens, respectively. A diameter of an injection mold cavity or of a headlight lens, respectively, is, in particular, the diameter of the maximum circular cross sectional face of the injection mold cavity or of the headlight lens, respectively. In the sense of the invention, a sprue is no part of the injection mold cavity. 
         [0018]    According to a further embodiment of the invention the thickness of the injection mold cavity is at least 55%, in particular at least 80%, in particular at least 100% of the diameter of the injection mold cavity. 
         [0019]    According to a further embodiment of the invention the blank is removed from the injection molding mold after 40 seconds, at the latest. According to a further embodiment of the invention the blank is taken out of the injection mold after 30 seconds, at the latest. 
         [0020]    By means of the injection molding process the blank is molded as a pointed gob. A pointed gob, in the sense of the invention, comprises, for example, a surface molded as a rotational paraboloid. A pointed gob, in the sense of the invention, comprises, for example, a surface molded as an aspherical paraboloid of rotation. A pointed gob, in the sense of the invention, comprises, in particular, a surface shaped as an elliptical paraboloid. In a further embodiment of the invention, the pointed gob or the blank, respectively, has no curvature having a radius of curvature of less than 3 mm. In a further embodiment of the invention, the pointed gob or the blank, respectively, has no curvature having a radius of curvature of less than 5 mm. 
         [0021]    In a yet further embodiment of the invention the blank, after having been removed from the injection mold is placed in a melt-killing mold. A melt-killing mold, in the sense of the invention, is, in particular, a semi-open mold. A melt-killing mold, in the sense of the invention, has, for example, a round or circular mold cross section, respectively. A melt-killing mold, in the sense of the invention, is, for example, an (interiorly) cylindrical mold closed on one side. A melt-killing mold, in the sense of the invention, is, for example, a cylindrical or coniform tub or tank having a continuous transition from the wall towards the bottom. A melt-killing mold, in the sense of the invention, is, for example, a cylindrical or coniform tub or tank having a transition from the wall towards the bottom having a continuous first derivative. In a still further embodiment of the invention the melt-killing mold has a temperature of no less than 100° C. In a still further embodiment of the invention the melt-killing mold has a temperature of no more than 140° C. For example, it is provided for that the blank remains in the melt-killing mold for at least 6 min. In a yet further embodiment of the invention the inner diameter of the melt-killing mold is smaller than the diameter of the headlight lens. In a yet further embodiment of the invention the inner diameter of the melt-killing mold is smaller than 70% of the diameter of the headlight lens. Herein, it is particularly provided for that the inner diameter of the melt-killing mold is no more than 60% of the diameter of the headlight lens. In a yet further embodiment of the invention the diameter of the melt-killing mold is no smaller than 50% of the diameter of the headlight lens. 
         [0022]    In a yet further embodiment of the invention the blank is heated (before press molding). In a yet further embodiment of the invention the blank is cooled (down) and heated again, i. e. reheated, or removed from the injection mold and subsequently and heated again (reheated), respectively. In this context, the temperature gradient of the blank is advantageously reversed. Thus, the core of the blank, when taken out of the injection mold, is warmer than the outer region of the blank. After the heating, however, and in contrast thereto the outer region of the blank is, advantageously, warmer than the core of the blank. 
         [0023]    In a yet further embodiment of the invention the blank is cooled in the melt-killing mold (before pressing). In a yet further embodiment of the invention the blank is cooled (down) in the melt-killing mold (before pressing) and is subsequently heated anew. 
         [0024]    In a yet further embodiment of the invention the sprue is placed such that the location at which it had been arranged lies centrally on the (lateral) margin of the blank, immediately before pressing. 
         [0025]    In a yet further embodiment of the invention heat from above is applied to the blank in the melt-killing mold before cooling in the melt-killing mold, and/or during heating in the melt-killing mold. Herein, it is, for example, provided for that heat is applied to the blank for at least 2 minutes and/or no longer than for 6 minutes. In a yet further embodiment of the invention the blank is cooled down subsequently in the melt-killing mold without heat being applied from above. 
         [0026]    In a yet further embodiment of the invention the blank, before being heated anew, is removed from the melt-killing mold. When being heated again, the blank is for example held lying on a cooled lance. An appropriate cooled lance has been disclosed in DE 101 00 515 A1. For example, the lance has an annular-shaped or annular-segment-shaped support, respectively, having a diameter of approximately 90% of the diameter of the blank. It is, for example, provided for that, in reheating, the blank will be heated for no less than 60 seconds and/no more than 90 seconds. The kiln temperature for reheating will be, for example, no less than 150° C. and/or no more than 300° C. It is, for example, provided for that reheating is performed at no less than 150° C. and/or at no more than 300° C. 
         [0027]    It is, for example, provided for that the blank be turned around before reheating. Herein, it is, at least for example, provided for that the blank be reheated with that side facing upwardly on which it had been placed in the melt-killing mold. It is, for example, provided for that the side of the gob which had been facing upwardly in the melt-killing mold will form the supported side in reheating. 
         [0028]    In a further embodiment of the invention the blank, for example immediately before press-molding, will have no curvature having a radius of curvature smaller than 3 mm. In an embodiment of the invention, the thickness of the blank immediately before press-molding will be larger than the thickness of the headlight lens by more than at least 1 mm, for example at least 3 mm. 
         [0029]    It is, for example, provided for that the thickness of the blank immediately after this has been removed from the injection mold is not smaller than 140% of the thickness of the blank immediately before press-molding. It is, for example, provided for that the thickness of the blank immediately after this has been taken out of the injection mold is not smaller than 145% of the thickness of the blank immediately before press-molding. 
         [0030]    In an embodiment of the invention the injection molding process may occur through direct injection of the blank without any sprue runner (hot runner mold). 
         [0031]    The injection mold cavity has, for example, a volume of more than 40 ccm. The injection mold cavity has, for example, a volume of up to 100 ccm. 
         [0032]    In a further embodiment of the invention, a light dispersing surface structure may be embossed, by means of the final shape (contour) mold, into an optically operative surface of the headlight lens. An appropriate light dispersing surface structure may e.g. comprise a modulation and/or a (surface) roughness of at least 0.05 μm, for example at least 0.08 μm, or it may be configured as a modulation, if necessary having a (surface) roughness of at least 0.05 μm, for example at least 0.08 μm, respectively. Roughness in the sense of the invention is to be defined particularly as Ra, for example according to ISO 4287. In a furthermore embodiment of the invention, the light dispersing surface structure may comprise a structure simulating the surface of a golf ball, or it may be configured itself as a structure imitating a golf ball surface. Appropriate surface structures dispersing light have e.g. been disclosed in DE 10 2005 009 556, DE 102 26 471 B4, and DE 299 14 114 U1. Further embodiments of surface structures dispersing light have been disclosed in German Letters Patent 1 009 964, DE 36 02 262 C2, DE 40 31 352 A1, U.S. Pat. No. 6,130,777, US 2001/0033726 A1, JP 10123307 A, JP 09159810A, and JP 01147403 A. 
         [0033]    The aforementioned problem is, moreover, solved by a vehicle headlight having at least one light source, wherein the vehicle headlight includes a headlight lens manufactured according to a process as has been described in the foregoing. In a yet further embodiment of the invention the vehicle headlight comprises a shield, wherein an edge of said shield can be imaged, by means of the headlight lens or a part of the headlight lens, as a bright-dark-borderline. 
         [0034]    The aforementioned problem is, moreover, solved by a motor vehicle having a vehicle headlight, wherein it is, in particular, provided that the bright-dark-borderline can be imaged on the roadway on which the motor vehicle can be situated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]      FIG. 1  shows an example of embodiment of a motor vehicle; 
           [0036]      FIG. 2  shows a schematic representation of an exemplary vehicle headlight; 
           [0037]      FIG. 3  shows an exemplary distribution of illumination or light of the headlight according to  FIG. 2 ; 
           [0038]      FIG. 4  shows a cross-section through an example of embodiment of a headlight lens for a vehicle headlight according to  FIG. 2 ; 
           [0039]      FIG. 5  shows a cut-out of the cross-section according to  FIG. 4 ; 
           [0040]      FIG. 6  shows an example of embodiment of a process for manufacturing a headlight lens according to  FIG. 4 ; 
           [0041]      FIG. 7  shows an example of embodiment of an injection (molding) mold by way of a principle representation; 
           [0042]      FIG. 8  shows an injection mold according to  FIG. 7  in a filled state; 
           [0043]      FIG. 9  shows an example of embodiment of a blank produced by means of an injection mold according to  FIG. 7  immediately after having been removed from the injection mold; 
           [0044]      FIG. 10  shows an example of embodiment of a blank according to  FIG. 9  in a melt-killing mold; 
           [0045]      FIG. 11  shows the blank according to  FIG. 10  in the melt-killing mold after a change of contour caused by shrinkage; 
           [0046]      FIG. 12  shows an example of embodiment of a blank produced by means of an injection mold according to  FIG. 7  after having cooled down and after removal of a sprue; 
           [0047]      FIG. 13  shows an example of embodiment of a final contour mold by way of a cross sectional principle representation; and 
           [0048]      FIG. 14  shows the final contour mold according to  FIG. 13  after the closing movement. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]      FIG. 1  shows a motor vehicle  100  having a vehicle headlight  1  schematically depicted in  FIG. 2  including a light source  10  for generating light, a reflector  12  for reflecting light generated by means of the light source  10 , and a shield  14 . The vehicle headlight  1 , moreover, comprises a monolithic headlight lens  2  blank-molded (bright-pressed) on both sides, for changing the beam direction of light generated by means of the light source  10 , and in particular for imaging an edge of the shield  14 , which edge has been denominated by reference numeral  15  in  FIG. 2 , as a light (or bright) -dark-borderline  25 , as has been represented, by way of example, in  FIG. 3  in a diagram  20  and in a photograph  21 . Herein, the gradient G of the bright-dark-borderline  25  and the glare (value) HV of the vehicle headlight  1  in which the headlight lens  2  has been installed, are important photometric guide values. 
         [0050]    The headlight lens  2  comprises a lens body  3  made of transparent plastic material, which body comprises an essentially planar, optically effective (operative) surface  5  facing the light source  10 , and a convexly curved optically operative surface  4  facing away from the light source  10 . Moreover, the headlight lens  2  optionally comprises a rim  6 , by means of which the headlight lens  2  can be attached within the vehicle headlight 
         [0051]      FIG. 4  shows a cross-section through an example of embodiment of the headlight lens  2  for the vehicle headlight  1  according to  FIG. 2 .  FIG. 5  shows a cut-out of the headlight lens  2 , which cut-out has been marked by means of a dash-dotted circle in  FIG. 4 . The essentially planar, optically operative surface  5 , shaped as a cascade or step  60 , projects, in the direction of the optical axis  30  of the headlight lens  2 , beyond the rim  6  of the lens or beyond the surface  61  of the rim  6  of the lens, said surface  61  facing the light source  10 , with the height h of step  60  amounting to no more than 1 mm, for example no more than 0.5 mm. The effective value of height h of step  60  expediently amounts to 0.2 mm. 
         [0052]    The thickness r of the rim  6  of the lens amounts to at least 2 mm but to no more than 5 mm. The diameter DL of the headlight lens  2  amounts to at least 40 mm but to no more than 100 mm. The diameter DB of the essentially planar, optically operative surface  5  equals the diameter DA of the convexly curved, optically operative surface  4 . In an expedient embodiment, the diameter DB of the essentially planar, optically operative surface  5  amounts to no more than 110% of the diameter DA of the convexly curved, optically operative surface  4 . Moreover, the diameter DB of the essentially planar, optically operative surface  5  for example amounts to at least 90% of the diameter DA of the convexly curved, optically operative surface  4 . The diameter DL of the headlight lens  2  is for example approximately 5 mm larger than the diameter DB of the essentially planar, optically operative surface  5  or than the diameter DA of the convexly curved, optically operative surface  4 . 
         [0053]    In the interior of the transparent body  3  the headlight lens  2  optionally has a structure  35  dispersing light. The light dispersing structure  35  is for example a structure generated by means of a laser. In this context, it for example comprises a number of punctiform defects which are aligned with respect to a plane which is orthogonal with respect to the optical axis  30 . It may be provided for that the dispersing structure  35  is designed to be ring-shaped or comprises annular regions or that the punctiform defects are arranged in the manner of rings, respectively. It may be provided for that, for example within the selected structure, the punctiform defects are distributed at random. 
         [0054]    For example, appropriate methods for generating the light dispersing structure  35  in the interior of the transparent body  3  may be taken from SU 1838163 A3, from SU 1818307 A1, from the article “Optical applications of laser-induced gratings in Eu-doped glasses”, Edward G. Behrens, Richard C. Powell, Douglas H. Blackburn, 10 Apr. 1990/Vol. 29, No. 11/APPLIED OPTICS, from the article “Relationship between laser-induced gratings and vibrational properties of Eu-doped glasses”, Frederic M. Durville, Edward G. Behrens, Richard C. Powell, 35, 4109, 1987, The American Physical Society, from the article “Laser-induced refractive-index gratings in Eu-doped glasses”, Frederic M. Durville, Edward G. Behrens, Richard C. Powell, 34, 4213, 1986, The American Physical Society, from the article “Interior Treatment of Glass by means of Nd: YAG-Laser” (“Innenbearbeitung von Glas mit Nd: YAG-Laser”), Klaus Dickmann, Elena Dik, Laser Magazin, as well as from the state of the art cited in U.S. Pat. No. 6 992 804 B2. 
         [0055]    In an alternative embodiment of the headlight lens  2 , it may be provided that (instead of the rim  6 ) the lens comprises a projecting rim (projecting in a rearward direction or in the direction of the side facing the light source  10 ), as has e.g. been disclosed in WO/03/087893 A1, DE 203 20 546 U1, EP 1 495 347 A1, DE 102 16 706 A1, EP 1645545, and DE 10 2004 048 500 A1. 
         [0056]    It may be provided for the headlight lens  2  to have surface structures as have been disclosed in  FIGS. 6 to 10  of DE 10 2007 037 204 A1. 
         [0057]      FIG. 6  shows a process for manufacturing the headlight lens  2 . In this context, transparent thermoplastic plastic material is being made available, produced or liquefied, respectively, in a step  111 . The transparent thermoplastic plastic material is, for example, a polycarbonate, for example LED 2643, or a thermoplastic resin such as e.g. a polycarbonate resin, a polyacrylic resin or a modified polyolefin resin. Examples for appropriate thermoplastic plastic material or thermoplastic resin may be taken, for example, from DE 699 23 847 T2. As a polycarbonate resin, DE 699 23 847 T2 thus discloses the appropriate use of aromatic polycarbonate resin which has been obtained by processing a diphenol and a carbonate precursor. In this context, examples for the diphenol include bis-(hydroxylaryl)-alkanes such as 2,2-bis-(4-hydroxyphenyl)-propane (so-called bisphenol A), bis-(4-hydroxyphenyl)-methane, 1,1-bis-(4-hydroxyphenyl)-ethane, 2,2-bis-(4-hydroxyphenyl)-butane, 2,2-bis-(4-hydroxyphenyl)-octane, 2,2-bis-(4-hydroxyphenyl)-phenylmethane, 2,2-bis-(4-hydroxy-3-methylphenyl)-propane, 1,1-bis-(4-hydroxy-3-tert-butylphenyl)-propane, 2,2-bis-(4-hydroxy-3-bromophenyl)-propane, 2,2-bis-(4-hydroxy-3,5-dibromophenyl)-propane, and 2,2-bis-(4-hydroxy-3,5-dichlorophenyl)-propane; bis-(hydroxyphenyl)-cycloalkane such as 1,1-bis-(hydroxyphenyl)-cyclopentane and 1,1-bis-(hydroxyphenyl)-cyclohexane; dihydroxyarylethers such as 4,4′-dihydroxydi-phenyl-ether and 4,4′-dihydroxy-3,3′-dimethyldiphenylether; dihydrodiarylsulfides such as 4,4′-dihy-droxydiphenylsulfide and 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfide; dihydroxy-diaryl-sulfoxides such as 4,4′-dihydroxydiphenylsulfoxide and 4,4′-dihydroxy-3,3′-dimethyl-diphenylsulfoxide; and dihydroxydiarylsulfones such as 4,4′-dihydroxydiphenylsulfone and 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone. These diphenols may be used per se or by way of a combination of two or more products. 
         [0058]    Step  111  is followed by a step  112 , in which—as has been represented in FIGS.  7  and  8 —a blank  136  is molded from the transparent plastic material by means of an injection molding process in an injection mold. The injection mold represented by way of a principle representation in  FIG. 7  and  FIG. 8  comprises a partial mold (mold part/component)  131  and a partial mold (mold part/component)  132 . The partial mold  131  and the partial mold  132  together form, when in a closed state of the injection mold, an injection mold cavity  133 , whose thickness D133 amounts to at least 80%, in particular to at least 100% of the diameter Q133 of the injection mold cavity  133 . The portion of the injection mold cavity of the mold part  131  and the portion of the injection mold cavity  132  essentially form a transition with each other having a continuous first derivative or configured without any bend or kink, respectively. The partial mold  131  and the partial mold  132 , respectively, form an example of embodiment for injection mold parts or components in the sense of the claims. The injection cavity  133  has a volume of approximately 63 ccm. The injection cavity  133  has, in particular, no curvature having a radius of curvature of less than 3 mm, for example no curvature of a radius of curvature of less than 5 mm 
         [0059]    As has been depicted by arrow  135 , the essentially fluid transparent plastic material is pressed into the injection mold such that the blank  136  is molded with a sprue  137 . By opening the partial molds  131  and  132 , the blank  136 —as represented in FIG.  9 —may be removed. In this context, it is provided for that the blank  136  remains in the injection mold for a maximum of 30 to 40 seconds and is removed from the injection mold before its mean temperature falls below the melting temperature/the melting temperature range of the plastic material and/or below the flow temperature/the glass transition temperature of the plastic material. 
         [0060]    A step  113  (including the steps  133 A,  133 B,  133 C,  133 D, and  133 E) follows, in which the blank  136  is tempered and/or cooled off. In tempering, the blank  136  is first cooled down and subsequently heated, so that its gradient of temperature is inverted, which means that before tempering the core of the blank  136  is warmer than the outer region of the blank  136 , and that after tempering, the outer region of the blank  136  is warmer than the core of the blank  136 . Herein, the sprue  137  is first removed in a step  133 A, and, as has been represented in  FIG. 10 , the blank  136  is placed in a melt-killing mold  50 , wherein the melt-killing mold  50  has a temperature of between 100 and 140° C. A step  133 B follows, in which the blank, as has been represented in  FIG. 10 , is heated from above in the melt-killing mold  54  for between 2 and 6 minutes by means of an infrared heater  51 . Subsequently, the blank remains in the melt-killing mold  50  in a step  133 C without being heated by means of the infrared heater  51 . The blank  136  remains in the melt-killing mold  50  for at least 6 minutes. In the melt-killing mold  50  the contour of the blank changes due to shrinkage caused by cooling down. In this context,  FIG. 9  shows the blank  136  before its modification due to shrinkage, and  FIG. 12  shows the blank after its modification caused by shrinkage. 
         [0061]    The step  133 C is followed by a step  133 D, in which the blank  136  is removed from the melt-killing mold  50  and turned around so that the surface  138  of the blank  136  will be at the top and the surface  139  of the blank  136  is at the bottom.  FIG. 12  shows the blank  136  after step  133 D, in which context it should be recognised that, in the melt-killing mold  50 , the convex surface  139  of the blank  136  converted into a concave surface. The step  133 D is followed by a step  133 E in which the blank  136 , with its surface  139  forming a support face, is placed on an annular-shaped support and will be heated in a kiln for 60 to 90 seconds at 150 to 300° C. An appropriate annular-shaped support which has a through-flow of cooling temperature may be taken from DE 101 00 515 A1. Therein, the diameter of the ring-shaped support is approximately 90% of the diameter of the blank  136 . The reversing of the blank  136  has proved to be particularly appropriate for generating a particularly high-grade surface quality of the headlight lens  2 . 
         [0062]    A step  114  follows in which the blank (pre-form)  136  is (blank-) pressed—by means of a final-shape mold represented in  FIG. 13  and FIG.  14 —between a top mold  140  and a bottom mold, which comprises a first partial mold  141  and a second partial mold  142 , the latter being annular-shaped and enclosing the first partial mold  141 , to form a headlight lens  2  with an integrally molded rim  6  of the lens, wherein, by means of an offset  143  between the first partial mold  141  and the second partial mold  142  and depending on the volume of the blank  136 , the cascade or step  60  is pressed into the headlight lens  2 . 
         [0063]    For pressing, the blank  136  is placed—as has been depicted in FIG.  13 —on the bottom mold or on the partial mold  141  thereof, respectively, The pressing of the blank  136  is, for example, not performed in vacuum or under significant low-pressure. The pressing of the blank  136  to form the headlight lens  2  particularly occurs under atmospheric (air-)pressure. The first partial mold  141  and the second partial mold  142  are non-positively coupled together by means of springs  145  and  146 . Herein, the pressing is performed such that the distance between the first partial mold  141  and the top mold  140  is dependent on the volume of the blank or of the headlight lens  2  pressed from it, respectively, and the distance between the second partial mold  142  and the top mold  140  is independent of the volume of the blank or of the headlight lens  2 , respectively, pressed from it. After the pressing, the headlight lens  2  is cooled down and, if necessary, the essentially planar surface  5  is polished. 
         [0064]    Optionally, the step  114  may be followed by a step  115  in which the gradient of a headlight lens is measured and a structure corresponding to the light dispersing structure  35  is introduced in this or another headlight lens in dependency on the measured value of the gradient. 
         [0065]    In a step  116  following step  114  or step  115 , respectively, the headlight lens  2  is packaged in a transport container for the transport of headlight lenses together with further headlight lenses, designed corresponding to headlight lens  2 . 
         [0066]    The standard deviation of the gradient of the headlight lenses corresponding to headlight lens  2  is smaller than or equal to 0.005. The standard deviation of the glare (value) of the batch of headlight lenses  2  or of the vehicle headlights, respectively, in which the headlight lenses  2  are to be installed is for example smaller than or equal to 0.05 lux. In a yet further embodiment, there is provided that the standard deviation of the value 75R of the headlight lenses  2  or of the vehicle headlights, in which the headlight lenses  2  have been installed, be smaller than or equal to 0.5 lux. 
         [0067]    The elements in the figures have been drawn in consideration of simplicity and clearness and not necessarily to scale. Thus, for example, the order of magnitude of some elements has been exaggerated with respect to other elements in order to improve comprehension of the example of embodiment of the present invention.