Thermoplastic film for a laminated glass pane

Abstract

Thermoplastic film suitable as an intermediate layer for a laminated glass pane, wherein the thermoplastic film includes a defined region, which is provided for a camera window or an HUD (head-up display) region that has a non-zero wedge angle, and a region surrounding the defined region on all sides, in which the thermoplastic film has a substantially constant thickness, wherein the maximum thickness in the defined region of the thermoplastic film is less than the thickness in the surrounding region.

Claims

1. Thermoplastic film suitable as an intermediate layer for a laminated glass pane, wherein the thermoplastic film comprises a defined region that is provided for a camera window or an HUD region, said defined region having a non-zero wedge angle, and a region surrounding the defined region on all sides of said defined region, the thermoplastic film having a constant thickness in said region entirely surrounding the defined region on all sides of said defined region, wherein a maximum thickness in the defined region of the thermoplastic film is less than a thickness in the surrounding region.

2. The thermoplastic film according to claim 1, wherein the defined region has a variable wedge angle.

3. The thermoplastic film according to claim 1, wherein the thickness of the thermoplastic film in the surrounding region is between 50 m and 2000 m.

4. The thermoplastic film according to claim 1, wherein the thermoplastic film is made substantially of PVB.

5. The thermoplastic film according to claim 1, wherein the thermoplastic film has a noise-reducing effect.

6. The thermoplastic film according to claim 1, wherein the defined region extends over an area of 2000 mm.sup.2 to 200,000 mm.sup.2 for an HUD region and over an area of 2000 mm.sup.2 10,000 mm.sup.2 for a camera window.

7. The thermoplastic film according to claim 1, wherein the thermoplastic film has a first surface and an opposite second surface, whose planes are arranged parallel to one another in the surrounding region, and wherein the thermoplastic film has, in the defined region, a mirror plane/plane of symmetry, which is arranged parallel to the planes of the first surface and the second surface in the surrounding region centrally between these planes.

8. Method for producing a thermoplastic film suitable as an intermediate layer for a laminated glass pane, wherein the thermoplastic film comprises at least a defined region that is provided for a camera window or an HUD region, said defined region having a non-zero wedge angle, and the thermoplastic film comprises a surrounding region that surrounds the defined region on all sides of said defined region, the thermoplastic film having a constant thickness in said region entirely surrounding the defined region on all sides of said defined region, wherein a maximum thickness in the defined region of the thermoplastic film is less than a thickness in the surrounding region, the method comprising: providing a thermoplastic film having a constant thickness, ablating the thermoplastic film using a laser in at least one defined region.

9. The method according to claim 8, wherein the wedge angle in the defined region changes.

10. The method according to claim 8, wherein first, a first surface of the thermoplastic film having a constant thickness is treated with the laser in the defined region and then, the second surface of the thermoplastic film is treated with the laser in the same defined region.

11. The method according to claim 8, wherein an ablation depth is between 0.10 mm and 0.30 mm.

12. Laminated glass pane, comprising a first glass layer, a second glass layer, and a thermoplastic film according to claim 1, wherein the thermoplastic film is arranged between the first glass layer and the second glass layer.

13. Method for producing a laminated glass pane, comprising: providing a first glass pane providing a second glass pane placing a thermoplastic film according to claim 1 on the first glass pane, placing a second glass pane on the thermoplastic film, and joining the second glass pane to the thermoplastic film.

14. Head-up display arrangement, comprising a projector for illuminating a head-up display area of a laminated glass pane and a laminated glass pane according to claim 12, wherein, during operation, the projector substantially illuminates the defined region.

15. Camera arrangement, comprising a camera and a laminated glass pane according to claim 12, wherein the camera is directed at the defined region and records light beams that pass through the laminated glass pane.

16. A method comprising utilizing the laminated glass pane according to claim 12 as a front pane with a head-up display and/or camera window in means of transportation on water, on land, and in the air.

17. The thermoplastic film according to claim 3, wherein the thickness of the thermoplastic film in the surrounding region is between 300 m and 850 m.

18. The thermoplastic film according to claim 17, wherein the thickness of the thermoplastic film in the surrounding region is between 380 m and 760 m.

19. The thermoplastic film according to claim 6, wherein the defined region extends over an area of 10,000 mm.sup.2 to 200,000 mm.sup.2 for an HUD region.

20. The method according to claim 11, wherein the ablation depth is between 0.15 mm and 0.25 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention are described by way of example with reference to the appended drawings, which depict:

(2) FIG. 1 the basic context of the development of double images in transmittance,

(3) FIG. 2 the basic context of the development of ghost images in reflection,

(4) FIG. 3 an exemplary structure of a laminated glass pane with a wedge-shaped intermediate layer,

(5) FIG. 4 a cross-section through a region of a thermoplastic film according to the invention,

(6) FIG. 5 a plan view of a laminated glass pane according to the invention with a camera window,

(7) FIG. 6 the basic structure of a camera arrangement,

(8) FIG. 7 a plan view of a laminated glass pane according to the invention with an HUD region,

(9) FIG. 8 a schematic representation of a method according to the invention,

(10) FIG. 9 a schematic plan view of a defined region during the method,

(11) FIG. 10 a cross-section through a region of a thermoplastic film according to the invention, and

(12) FIG. 11 a cross-section through a region of a thermoplastic film according to the invention.

(13) FIG. 1 depicts the basic context of the development of double images in transmittance with reference to a beam image. A curved pane 1 is assumed. The curved pane has, at the point of entry of a beam into the curved glass pane 1 a radius of curvature (R+D). Light is now emitted from a light source 3. This light strikes the pane and is refracted in accordance with the known refraction laws at the transition from air to glass on the first boundary surface and from glass to air on the second boundary surface and reaches the eye 2 of an observer. This beam is depicted as a solid line P. From the perspective of the observer, the light source 3 appears to be situated at the location 3. This is depicted as beam P. In addition to this beam P referred to as the primary beam, the beam is, however, only partially refracted on the second gas/air boundary surface in the manner described above; a smaller fraction is reflected on the second boundary surface and is once again reflected on the first boundary surface before the beam now passes through the second boundary surface and reaches the eye 2 of the observer. This beam, the so-called secondary beam is depicted as a dashed line S. From the perspective of the observer, the light source 3 also appears to be situated at the location 3. The angle enclosed by the primary beam P and the secondary beam S is the so-called double image angle.

(14) In order to address this double image, provision can now be made to provide a wedge angle between the two boundary layers assumed to be substantially parallel in FIG. 1.

(15) According to J. P. Aclocque Doppelbilder als strender optischer Fehler der Windschutzscheibe [Double Images As Interfering Optical Errors in Windshields] in Z. Glastechn. Ber. 193 (1970) pp. 193-198, the double image angle can be calculated as a function of the radius of curvature of the glass pane and the angle of incidence of the light beam according to the following equation:

(16) $=\frac{2d}{R}.Math.\frac{\sin }{\sqrt{n^2-{\sin }^2}},$
where

(17) is the double image angle, n is the index of refraction of the glass, d is the thickness of the glass pane,

(18) R is the radius of curvature of the glass pane at the location of the incident light beam, and is the angle of incidence of the light beam relative to the perpendicular on the tangent to the pane.

(19) In the case of flat glass panes, the double image angle is, according to the following formula

(20) $=2.Math..Math.\frac{\sqrt{n^2-{\sin }^2}}{\cos }$
a function of the wedge angle formed by the glass surfaces.

(21) Thus, by setting the aforementioned formulas equal, the wedge angle necessary for the elimination of the double image can be calculated:

(22) $=\frac{d}{R}.Math.\frac{\cos .Math.\sin }{n^2-{\sin }^2}.$

(23) Usually, this wedge angle is realized in that in laminated glass panes 1, a wedge-shaped intermediate layer F is placed between a first glass layer GS.sub.1, and a second glass layer GS.sub.2, see FIG. 3. It can usually be assumed for the sake of simplicity that the index of refraction n is constant, since the difference in the index of refraction of the intermediate layer F and the glass panes GS.sub.1, GS.sub.2 is rather small such that there is hardly any effect due to the small difference.

(24) This idea can also be applied with curved windshields. Usually, for the sake of simplicity, the angle of incidence and the radius of curvature are assumed for a reference eye point, and the wedge angle determined therewith is used for the entire windshield.

(25) In the case of large laminated glass panes 1, so-called panorama panes, and/or more highly curved laminated glass panes 1, this approach is, however, no longer adequate such that here, usually, a wedge-angle progression variable in the vertical direction must be determined.

(26) Then, it is possible, for example, by pointwise calculation along an imaginary vertical center line of a laminated glass pane and possible interpolation, to determine a compensation wedge-angle profile . After determination of the compensation wedge angle profile, a corresponding intermediate layer F can be produced.

(27) With regard to head-up displays, a problem develops which is similar to the phenomenon of double images and is referred to as a ghost image.

(28) FIG. 2 presents the basic context of the development of ghost images in reflection with reference to a beam image. Here, a curved glass pane 1 is assumed. The curved glass pane 1 has a radius of curvature R at the point of entry of a beam into the curved glass pane 1. Light is now emitted from a light source 3, which is representative of a head-up display HUD. This light impinges on the glass pane 1 along the beam R.sub.i from the inside at an angle and is reflected there at the same angle . The reflected beam R.sub.r reaches the eye 2 of an observer. This beam path is depicted as a solid line. From the perspective of the observer, the light source 3 appears to be situated virtually at the location 3, i.e., in front of the glass pane 1. This is depicted as beam R.sub.v. In addition to this first beam, another beam reaches the eye 2 of the observer. This beam R.sub.i likewise originates from the light source 3. However, this beam R.sub.i penetrates, in accordance to the known laws of refraction, into the glass pane 1 on the inner air/glass boundary surface and is reflected on the outer glass/air boundary surface before the beam passes through the inner boundary surface and reaches the eye 2 of the observer as beam R.sub.r. The term inner boundary surface thus refers to the boundary surface that is situated closer to the observer, whereas the term outer boundary surface refers to the boundary surface that is farther away from the observer. This beam path is depicted as a dashed line. From the perspective of the observer, the light source 3 appears to be situated virtually at the location 3, i.e., likewise in front of the glass pane 1. This is depicted as beam R.sub.v.

(29) To address this problem, the wedge angle can now be altered such that the beam R.sub.r reflected on the outer boundary surface and the beam R.sub.r reflected on the inner boundary surface overlap relative to the eye 2 of the observer, i.e., the beam reflected on the outer boundary surface exits at the point of reflection of the beam impinging on the inner boundary surface.

(30) However, if this is done only for a single eye position, the wedge angle determined therefrom can yield non-optimum results. This can be explained, among other things, by the fact that both the body sizes of drivers for whom the HUD displays are primarily intended and the seating position are very different such that there are a large number of possible eye position. This results in the fact that the virtual display is situated in different places depending on the eye position; and, accordingly, there is, for each of these eye positions, a sometimes different value for an optimized wedge angle. In addition, a wedge angle optimized exclusively for ghost images usually results in an overcompensation of double images such that the double images thus caused are again problematic relative to the perception of the observer and/or compliance with regulatory test specifications and/or compliance with customer specifications relative to double images.

(31) Wedge angle profiles that take into account both the different eye positions, i.e., also the compensation of double images in the HUD region are not constant in either the horizontal or the vertical direction. The resultant thickness profiles for the intermediate layer F cannot be produced by simple extrusion processes.

(32) FIG. 4 depicts a region of a thermoplastic film according to the invention F in cross-section. The plastic film F is made of PVB in the example. In the surrounding region A, the thickness h1 is 0.76 mm and is substantially constant. In the defined region K, the thickness decreases. At the thinnest point, the thermoplastic film F is 0.56 mm thick. In other words, the thickness difference h2.sub.min between the thicknesses in the surrounding region and at the thinnest point in the defined region is 0.76 mm-0.56 mm=0.20 mm=h2.sub.min. The film F is thinner in the defined region than in the surrounding region, in other words, even at its thickest point, the thickness h2.sub.max is less than the thickness h1. In the defined region K, the wedge angle in the first boundary region g1 first increases slowly and, then, increases in a central region corresponding to a previously optimized profile. After that, the wedge angle decreases again slowly in a second boundary region g2 in order to make the transition to the surrounding region A as little visible as possible. Accordingly, the thickness of the film first decreases slowly in the first boundary region g1, then changes in a central region according to a previously optimized profile, and then decreases again slowly in the second boundary region g2. This arrangement with two boundary regions with a slowly rising or falling wedge angle above and below or to the right and to the left relative to an installed windshield is particularly advantageous to minimize the optical defect at the transition between the surrounding region A and the defined region K. It can be seen in cross-section that no material ablation occurred along the second surface 10.2, in other words, in the defined region, the second surface continues in the same plane as in the surrounding region A parallel to the first surface 10.1 in the surrounding region. Thus, in the defined region, material was ablated only from the side of the first surface 10.1.

(33) FIG. 5 depicts a plan view of a laminated glass pane 1 according to the invention. The laminated glass pane is provided as a windshield of a passenger car. The upper edge in the figure borders the roof edge in the vehicle, and the lower edge borders the engine edge. A camera window K is arranged in the upper third of the laminated glass pane outside the through-vision area. The windshield preferably has, in the upper edge region, a masking print 9. Masking prints are common for vehicle panes outside the central field of vision to conceal attachment parts or to protect the adhesive with which the vehicle pane is connected to the car body against UV radiation. The masking print typically consists of a black or dark enamel applied and fired in a screen printing process. In the example, the masking print 9 frames the camera window K of the vehicle pane circumferentially to conceal the camera positioned therebehind. The laminating glass pane consists of two glass layers, GS1 and GS2, and a thermoplastic film F, which is arranged between these glass layers. The glass layers GS1 and GS2 are made of soda lime glass and have a thickness of 2.1 mm. The thermoplastic film F is formed as described in FIG. 4. The fixed area K forms the camera window.

(34) FIG. 6 depicts a possible camera arrangement 6 consisting of the laminated glass pane 1 described and a camera 7. The glass layer GS1 of the laminating glass pane 1 is directed toward the outside of the vehicle and the glass layer GS2 toward the inside. The camera 7 is arranged in the interior of the vehicle and records the light beams that pass through the laminated glass pane 1 from the outside inward. The camera is aimed at the defined region; this means that it is mounted such that the light beams pass through the region with the optimized wedge angle profile. Thus, the double images in transmittance are efficiently reduced. This can, for example, be used successfully in the area of lane assistance systems.

(35) FIG. 7 depicts a view of a laminated glass pane 1 according to the invention with an HUD region that is surrounded on all sides by the surrounding region A. The HUD region is situated in the defined region K, in which a wedge angle profile optimized to avoid ghost images and double images is arranged. In the example depicted, the HUD region is situated on the left side of the windshield in the through-vision region. During the production of the laminated glass pane 1 from the glass layer GS1, the glass layer GS2, and a thermoplastic film F according to the invention, this design can be readily adapted for a right-hand drive vehicle by ablating thermoplastic polymer on the right-hand side in the defined region K according to a previously optimized wedge angle profile.

(36) FIG. 8 represents, by way of example, a method cycle according to the invention. In step I., A thermoplastic film having a substantially constant thickness 4 is provided. In step II., the laser 8 is positioned at a distance a of approx. 1700 mm from the surface 10 of the thermoplastic film having a constant thickness 4 in the defined region K. Suitable as a laser is, for example, a CO.sub.2 laser with a wavelength of 10.6 m, and a power of 250 W. The defined region was traversed in lines 11 with the laser (see FIG. 9). FIG. 9 depicts a plan view of a defined region K that is treated in lines with a laser. The laser power was low at the beginning and was gradually increased. At a speed v of 10 m/s, polymer was ablated in lines in the defined region. The laser was offset by 0.1 mm after a line in each case and then polymer was ablated along the next line. After approx. 50 lines (5 mm), the power P of the laser was increased in order to increase the polymer ablation. This also increases the ablation depth.

(37) This operation is carried out until the desired profile is obtained. By means of this stepped increase in power, it was possible to specifically obtain the desired wedge angle.

(38) FIG. 10 depicts a thermoplastic film F that was processed with a laser in the defined region on its first surface 10.1 and on its second surface 10.2. There, mirror symmetrical ablation of thermoplastic polymer was done. Thus, it is possible to obtain larger wedge angles, while the absolute ablation depths on the surfaces are smaller than when ablation is done on only one surface.

(39) FIG. 11 depicts a thermoplastic film F that was processed with a laser in the defined region as in FIG. 10 on the first surface 10.1 and on the second surface 10.2. Only the wedge angle progression in the defined region K is different. In this case, the same amount of material was ablated on each surface 10.1 and 10.2. This results in a mirror symmetrical arrangement of the two surfaces 10.1 and 10.2 in the defined region K. Here, the mirror plane plane of symmetry S is the plane that runs parallel to the planes of the first surface 10.1 and the second surface 10.2 in the surrounding region centrally between them. The mirror plane S runs, accordingly, at a distance of h1 parallel to the plane of the first surface 10.1 and parallel to the plane of the second surface 10.2 in the surrounding region A.

LIST OF REFERENCE CHARACTERS

(40) GS1 glass layer 1, glass pane 1

(41) GS2 glass layer 2, glass pane 2

(42) F thermoplastic film

(43) K defined region

(44) A surrounding region

(45) g1 first boundary region

(46) g2 second boundary region

(47) h1 thickness of the unprocessed thermoplastic film, thickness of the thermoplastic film in the surrounding region A

(48) h2 thickness of the thermoplastic film in the defined region

(49) h2.sub.max maximum thickness of the thermoplastic film in the defined region

(50) S plane of symmetry, mirror plane

(51) 1 glass pane

(52) 2 eye

(53) 3 light source, HUD projector

(54) 4 thermoplastic film having a constant thickness, unprocessed thermoplastic film

(55) 5 HUD arrangement

(56) 6 camera arrangement

(57) 7 camera

(58) 8 laser

(59) 9 masking print

(60) 10 surface of the thermoplastic film

(61) 10.1 first surface of the thermoplastic film

(62) 10.2 second surface of the thermoplastic film

(63) 11 line