THERMOPLASTIC COMPOSITION FOR LIDAR SENSOR SYSTEM WITH IMPROVED ABSORPTION PROPERTIES

Abstract

A sensor system comprises a LiDAR unit having an emitter for laser light having a wavelength of 900 nm to 1600 nm and a receiver for light over a wavelength range which is between 800 nm and 1600 nm and at least partly below the operating wavelength of the LiDAR sensor and a cover having a substrate layer made of thermoplastic material which is arranged such that IR light emitted by the LiDAR unit and received by the LiDAR unit passes through the cover.

Claims

1.-15. (canceled)

16. A sensor system comprising a LiDAR unit having an emitter for laser IR light having an operating wavelength of 900 nm to 1600 nm and a receiver for laser light over a wavelength range which is between 800 nm and 1600 nm and is at least partially below the operating wavelength of the LiDAR sensor and a cover having a substrate layer comprising a region made of a thermoplastic composition based on aromatic polycarbonate and/or polymethyl methacrylate which is arranged such that the IR light emitted by the LiDAR emitter and received by the LiDAR receiver passes through the region made of the thermoplastic composition, wherein the thermoplastic composition has a light transmission Ty (D65, 10°) determined according to DIN EN ISO 13468-2:2006 at a layer thickness of 4 mm of <0.5%, wherein the thermoplastic composition contains a) at least two colorants having an absorption maximum in the range from 400 nm to 650 nm  selected from the group consisting of anthraquinone and perinone dyes in a total concentration of 0.07% by weight to 0.5% by weight, and b) at least one colorant having an absorption maximum in the range from >650 nm to 800 nm  selected from the group consisting of the colorants of formulae (1) to (5) with ##STR00010##  in a concentration of 0.008% to 0.02% by weight,  wherein R1 and R2 independently of one another represent a linear or branched alkyl radical or halogen, n is a natural number between 0 and 4, ##STR00011##  in a concentration of 0.002% to 0.008% by weight, ##STR00012##  where ##STR00013##  and  n is from 1 to 3,  in a concentration of 0.002% to 0.008% by weight, wherein the total concentration of colorants of formulae (2) and (3) is up to 0.008% by weight, ##STR00014##  in a concentration of 0.04% to 0.3% by weight where R=n-butyl, iso-butyl, ##STR00015##  in a concentration of 0.04% to 0.3% by weight,  in a total concentration of 0.005% to 0.3% by weight  and wherein the composition contains <0.05% by weight of phthalocyanines.

17. The sensor system according to claim 16, wherein the cover comprises no further layers other than the substrate layer, one or more primer layers optionally present and one or more topcoat layers optionally present.

18. The sensor system according to claim 17, wherein the primer layer is based on polymethylmethacrylate and optionally contains a UV absorber and the topcoat layer is based on polysiloxane comprising a combination of an organo-modified silane with a silica sol, wherein the topcoat layer contains silicon dioxide particles having a D.sub.90 determined by scanning transmission electron microscopy of less than 0.50 μm and no further particles having a D.sub.90 determined by scanning transmission electron microscopy ≥0.50 μm.

19. The sensor system according to claim 16, wherein the thermoplastic composition of the substrate layer contains no further components other than optionally further thermoplastic polymers, colorants distinct from colorants of groups a and b, heat stabilizers, demoulding agents, UV absorbers, carbon black, flame retardants, antistats and/or flow improvers.

20. The sensor system according to claim 16, wherein the composition contains no further thermoplastic polymers.

21. The sensor system according to claim 16, wherein the composition of the substrate layer is free from phthalocyanines.

22. The sensor system according to claim 16, wherein the LiDAR unit has an emitter for laser light having an operating wavelength of 900 nm to 950 nm.

23. The sensor system according to claim 16, wherein the operating wavelength of the laser lights emitter of the LiDAR unit is 905 nm±5 nm.

24. The sensor system according to claim 16, wherein the cover attenuates the LiDAR signal only to the extent that the signal intensity of IR light emitted by the LiDAR unit and received thereby determined by reflection from a smooth surface painted with TiO.sub.2-containing white paint at a distance of 3.2 m is ≥65% of a reference intensity determined without the cover.

25. The sensor system according to claim 16, wherein the cover is a front panel, a rear panel, a bumper, a radiator grille, a vehicle roof, a vehicle roof module, a vehicle side part or an element of the aforementioned.

26. The sensor system according to claim 16, wherein the colorants of group a are selected so as to give a black colour impression.

27. The sensor system according to claim 16, wherein only one colorant of formula (2) is present as colorant of group b.

28. The sensor system according to a claim 16, wherein only one colorant of formula (4) is present as colorant of group b.

29. The sensor system according to claim 16, wherein the thickness of the substrate layer is 1.0 to 7.0 mm.

30. The sensor system according to a claim 16, wherein the CIELab color coordinates of the composition of the substrate layer determined at a thickness of 2 mm according to ISO 13468-2:2006 (D65, 10°) and measured in transmission are as follows: L* less than 40, a* less than 10 and more than −10 and b* less than 10 and more than −10.

Description

EXAMPLES

[0098] Components

[0099] PC-1: Linear bisphenol A homopolycarbonate comprising end groups based on phenol having a melt volume rate MVR of 12 cm.sup.3/10 min (measured at 300° C. and a loading of 1.2 kg according to ISO 1133-1:2011) and containing as colorants of group a 0.031% by weight of Oracet Yellow 180, 0.12% by weight of Macrolex Violet B and 0.067% by weight of Macrolex Green 5B, further additives: 0.30% by weight of pentaerythritol tetrastearate and 0.05% by weight of Irganox B900.

[0100] PC-2: Linear bisphenol A homopolycarbonate comprising end groups based on phenol having a melt volume rate MVR of 6 cm.sup.3/10 min (measured at 300° C. and a loading of 1.2 kg according to ISO 1133-1:2011).

[0101] PC-3: Linear bisphenol A homopolycarbonate comprising end groups based on phenol having a melt volume rate MVR of 18 cm.sup.3/10 min (measured at 300° C. and a loading of 1.2 kg according to ISO 1133-1:2011) and containing as colorants from group a 0.005% by weight of Macrolex Yellow 3G, 0.06% by weight of Macrolex Red EG and 0.019% by weight of Amaplast Blue HB and as colorant from group b 0.032% by weight of colorant A (colorant of formula (4)), further additives: 0.04% by weight of pentaerythritol tetrastearate.

[0102] PC-4: Luminate 7276. Polycarbonates from Epolin containing two or more colorants of group a including Macrolex Violet B and Macrolex Orange R in a total concentration in the inventive range and two colorants of group b (colorants of formula (5) having an absorption maximum of 700 to 750 nm and Macrolex Green G (formula (4)) in individual concentrations and the total concentration in the inventive range)

[0103] PC-5: Linear bisphenol A hompolyocarbonate comprising end groups based on phenol having a melt volume rate MVR of 12 cm.sup.3/10 min (measured at 300° C. and a loading of 1.2 kg according to ISO 1133-1:2011) and containing as colorants of group a 0.1% by weight of Macrolex Yellow 6G, 0.1% by weight of Macrolex Violet B, 0.0001% by weight of Macrolex Violet 3R and 0.00006% by weight of Macrolex Blue RR and as colorant of group b 0.03% by weight of colorant of formula (2).

[0104] Colorants of Group b:

[0105] Colorants of group b are already present in the PC mixtures PC-3, PC-4 and PC-5.

[0106] Macrolex Green G: Solvent Green 28; CAS 4851-50-7 from Lanxess AG, Leverkusen (colorant of formula (4)); (absorption maximum approximately in the range 670-700 nm).

[0107] Paliogen Blue L6385: BASF SE, Ludwigshafen; colorant of formula (1), (referred to in the table only as Paliogen Blue) (absorption maximum approximately in the range of 660 to 770 nm).

[0108] Lumogen IR 765: BASF SE, Ludwigshafen; colorant of structure (2); absorption maximum approximately in the range 660-800 nm).

[0109] Colorant for comparative example: Heliogen Blue K7104. Phthalocyanine dye. Absorption maximum in the range of 670 to 680 nm (referred to in the table only as Heliogen Blue).

[0110] Compounding

[0111] The compounding of the materials was carried out in a KraussMaffei Berstorff ZE25 twin-screw extruder at a barrel temperature of 260° C., or a mass temperature of approximately 280° C. and a speed of 100 rpm. Unless otherwise stated the additives were mixed together with pulverulent polycarbonate PC-2 in the specified amounts and then compounded together with the polycarbonate PC-1.

[0112] Sample Preparation

[0113] The optical rectangle sheets having dimensions of 250 mm×105 mm×3.2 mm were manufactured on an Arburg 720S Allrounder injection moulding machine.

[0114] The mass temperature was between 280° C. and 290° C. and the mould temperature was 80° C.

[0115] The sheets were then flow-coated on both sides with the primer system SHP 470 FT 2050 from Momentive Performance Materials GmbH and with the topcoat AS4700 (silicone scratch-resistant coating).

Example 1 (Comparative Example)

[0116] PC-1 and PC-2 were compounded with one another as described above. This polycarbonate mixture contains no colorants of group b. The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 2 (According to the Invention)

[0117] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.05% by weight of Macrolex Green G (colorant of group b; formula (4)). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 3 (According to the Invention)

[0118] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.01% by weight of Paliogen Blue (colorant of group b; formula (1)). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 4 (Comparative Example)

[0119] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.1% by weight of Paliogen Blue (colorant of group b; formula (1)). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 5 (According to the Invention)

[0120] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.005% by weight of Lumogen IR765 (colorant of group b; structure 2). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 6 (According to the Invention)

[0121] A polycarbonate sheet containing the colorants from PC-4 was analyzed. This sheet was obtained directly from the manufacturer. The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 7 (Comparative Example)

[0122] This example employed the polycarbonate mixture PC-3 which in a departure from example 1 contained the colorants from group a 0.005% by weight of Macrolex Yellow 3G, 0.06% by weight of Macrolex Red EG and 0.019% by weight of Amaplast Blue HB and from group b 0.032% by weight of the colorant Macrolex Green G (formula (4)). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 8 (According to the Invention)

[0123] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.20% by weight of Macrolex Green G (colorant of group b; formula (4)). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 9 (Comparative Example)

[0124] The mixing of polycarbonates PC-1 and PC-2 was performed as described in example 1. In a departure from example 1 the powder component PC-2 was admixed with 0.05% by weight of Heliogen Blue (absorption maximum at approximately 670 to 680 nm). The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

Example 10 (Comparative Example)

[0125] This example employed the polycarbonate mixture PC-3 which in a departure from example 1 contained the colorants from group a 0.1% by weight of Macrolex Yellow 6G, 0.1% by weight of Macrolex Violet B, 0.0001% by weight of Macrolex Violet 3R and 0.00006% by weight of Macrolex Blue RR and as colorant from group b 0.03% by weight of Lumogen IR 765 (colorant of formula (2)) The results for LiDAR signal strength, light transmission and hiding power are summarized in the table.

[0126] Measurement of LiDAR Signal Strength

[0127] To reduce the scattered-light signals, the sensor head of the LiDAR sensor was shielded on the side away from the measurement path. Only lasers 1, 3, 5, 7, 8, 10, 12 and 14 were used. Furthermore, the field of view (FOV) of the sensor in the sensor interface was limited to 20° (350°-10°). The reflection surface used was a smooth white surface coated with TiO.sub.2-containing paint. The wall was at a distance of 3.2 m from the LiDAR sensor.

[0128] The test specimens were tested using a sample holder parallel to the LiDAR, wherein the back side of the sample was arranged about 10 mm in front of the LiDAR sensor so that both the output signal and the reflected input signal had to pass through the wall thickness of the test sheet. Analysis was carried out using the “VeloView” software from the manufacturer of the LiDAR sensor, Velodyne. The average value of the intensities measured for a sample was determined. This average sample value was divided by the average value of the reference measurement (air) to determine the relative intensity.

[0129] The lower the attenuation (weakening) of the signal, i.e. the higher the intensity of the signal measured, the more suitable the cover for LiDAR-assisted sensor applications in the automotive sector. The intensities measured in the examples are documented in the column “LiDAR signal strength”.

[0130] Values of ≥65% are considered sufficient intensities.

[0131] Visual Assessment of Hiding Power (Opacity) with Respect to LED Light:

[0132] Hiding power was determined by visual assessment of the samples using a white LED having a colour temperature of 4600 K and an irradiation intensity of 180 mW/cm.sup.2 (on the sample).

[0133] Light transmission: Ty (D65, 10°), determined according to DIN EN ISO 13468-2:2006

TABLE-US-00001 TABLE 1 Compositions and results 1V 2E 3E 4V 5E 6E 7V 8E 9V 10V Composition [% by wt.] PC-1 95.0 95.0 95.0 95.0 95.0 95.0 95.0 PC-2 5.0 4.95 4.99 4.90 4.995 4.80 4.95 PC-3 100 PC-4 100 PC-5 100 Macrolex Green G 0.05 0.20 Paliogen Blue 0.01 0.10 Lumogen IR 765 0.005 Heliogen Blue 0.05 Results Thickness [mm] 3.2 3.2 3.2 3.2 3.2 2.5 3.2 3.2 3.2 3.2 LiDAR signal 76 76 71 7 76 66 68 70 21 61 strength [%] Ty 0.02 0.01 0.01 0.01 0.01 0.01 0.0 0.0 0.0 0.0 LED light + 0 − 0 − 0 + 0 − − +: LED visible; −: LED weakly visible; 0: LED invisible

[0134] Example 1 shows that without colorants of the claimed group b the desired “cutoff” in spectrum is not achievable—the LED, as used in automotive headlights, is thus clearly visible and would thus likewise be captured by the LiDAR Sensor. Examples 2, 3, 5 and 6 contain colorants from the group b and thus exhibit the desired “cutoff characteristics”. Despite the use of colorants absorbent at longer wavelengths the attenuation of the LiDAR signal remains low. Example 4 shows that concentrations of colorants from group b which are outside the inventive concentration range, presently an excessively high concentration, result in a surprisingly severe increase in attenuation of the LiDAR signal. This also applies to example 10. Example 7 does not show the desired attenuation of the LED light despite the use of a colorant whose absorption maximum is between 650 and 700 nm. Example 9 also employed a colorant that exhibits an absorption maximum in the range from >650 nm bis 800 nm and shows practically no absorption above 750 nm but significantly attenuates the LiDAR signal. It could thus be demonstrated that not all colorants having their absorption maximum in the range from >650 nm to 800 nm were able to achieve the desired “cutoff characteristics” coupled with low attenuation of the LiDAR signal. It is apparent that only the compositions according to the invention allow a high residual signal strength and achieve the required covering of the LED light.