Metallized multilayer structure made of specific polycarbonates with low coefficient of thermal expansion

Abstract

The invention relates to multilayer structures made of at least one thermoplastic material and having at least one metal layer. The invention further relates to multilayer products encompassing at least three layers comprising a substrate layer made of a substrate comprising specific copolycarbonates and at least one inorganic filler, a metal layer and one or more further layers. The invention further relates to the process for producing the said multilayer structures.

Claims

1. A multilayer structure comprising at least one substrate layer, one metal layer bonded directly thereto, wherein the metal layer is applied in a plasma pretreatment comprising medium-frequency excitation with an air or argon-based plasma at a frequency of from 0 Hz to 10 MHz at a power rating of from 0.8 W/cm.sup.2 to 8.3 W/cm.sup.2, and a process gas pressure of from 0.04 to 0.15 mbar, and at least one protective layer on the metal layer, wherein the at least one substrate layer comprises a copolycarbonate, which has a Vicat softening point above 160° C. in accordance with DIN ISO 306, and an inorganic filler with lamellar geometry in an amount of from 10 to 40% by weight, based on the entirety of thermoplastics used, wherein the inorganic filler is synthetic graphite with a smallest dimension thickness smaller than 1 μm, and is moulded in an injection-moulding process which uses dynamic mould-temperature control and the mould temperature on injection is within +/−20° C. of the Vicat softening point of the substrate material used.

2. The multilayer structure according to claim 1, wherein, based on the entire amount of the bisphenol blocks, from 15% by weight to 95% by weight, is composed of bisphenol blocks derived from 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.

3. The multilayer structure according to claim 1, wherein the at least one substrate layer comprises, alongside the copolycarbonate, another thermoplastic selected from the group consisting of polysulphone, polyether sulphone, and polyetherimide.

4. The multilayer structure according to claim 1, wherein the at least one substrate layer has a thickness of from 0.1 mm to 6.0 mm, and the metal layer has a thickness of from 10 nm to 1000 nm, and also has a protective layer with a thickness in the range from 5 nm to 200 nm.

5. The multilayer structure according to claim 1, wherein the metal layer is an aluminium or silver layer.

6. The multilayer structure according to claim 1, wherein the multilayer structure also comprises a protective layer composed of one or more siloxanes with a thickness of from 5 nm to 200 nm.

7. A lamp holder, a lamp cover, a light-collector system, a light reflector, a collimator, a light-emitting diode, a metallized display, a windshield, a lens holder, an optical-waveguide element, a LED application optionally comprising a socket, a LED reflector, a heat sink, an automobile part, optionally comprising a head lamp, a bezel, an indicator, a reflector, and/or a solar reflector formed from the multilayer structure according to claim 1.

8. The multilayer structure according to claim 1, wherein, based on the entire amount of the bisphenol blocks, from 25% by weight to 90% by weight, is composed of bisphenol blocks derived from 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.

9. The multilayer structure according to claim 1, wherein the inorganic filler with lamellar geometry is present in the at least one substrate layer in an amount of from 15 to 35% by weight, based on the entirety of thermoplastics used.

10. The multilayer structure according to claim 1, wherein the smallest dimension thickness of the synthetic graphite is smaller than 500 nm.

11. The multilayer structure according to claim 1, wherein the smallest dimension thickness of the synthetic graphite is smaller than 200 nm.

12. The multilayer structure according to claim 1, wherein the smallest dimension thickness of the synthetic graphite is in a range from 0.4 to 1 nm.

13. The multilayer structure according to claim 1, wherein the copolycarbonate of the at least one substrate layer comprises at least one bisphenol unit of formula (2), ##STR00004## in which R2 is C1-C4-alkyl, n is 0,1,2 or 3, and also comprises, as terminal group chain terminator, a structural unit of the formula (1) ##STR00005## in which R1 are hydrogen or C1-C18-alkyl.

14. The multilayer structure according to claim 13, wherein R1 is tertbutyl.

15. A process for producing a multilayer structure according to claim 1, comprising forming a base layer by injection moulding or extrusion and, in a subsequent layer.

16. The process according to claim 15, wherein the plasma pretreatment uses medium-frequency excitation with an air- or argon-based plasma at a frequency of from 0 Hz to 10 MHz at a power rating of from 0.8 W/cm.sup.2 to 3.3 W/cm.sup.2.

Description

EXAMPLES

(1) The invention is described in more detail below on the basis of inventive examples, and the determination methods described here are used for all of the corresponding variables in the present invention unless otherwise described.

(2) Melt volume rate (MVR) is determined in accordance with ISO 1133 under the conditions stated below.

(3) Materials:

(4) Substrate Material 1 (for Comparative Example)

(5) Copolycarbonate comprising 70% by weight of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 30% by weight of bisphenol A with phenol as chain terminator and MVR 8 cm.sup.3/(10 min) (330° C.; 2.16 kg) in accordance with ISO 1133. The Vicat softening point of the material is 208° C. (ISO 306; 50 N; 120 K/h).

(6) Substrate Material 2 (for Multilayer Structure According to the Invention)

(7) Copolycarbonate comprising 70% by weight of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 30% by weight of bisphenol A with phenol as chain terminator and MVR 8 cm.sup.3/(10 min) (330° C.; 2.16 kg) in accordance with ISO 1133 is compounded with 20% by weight of graphite (Timrex KS 44 from Timcal AG, CH-6743 Bodio, Switzerland) under conditions described below. The Vicat softening point of the resultant material is 203° C. (ISO 306; 50 N; 120 K/h).

(8) Substrate Material 3 (for Comparative Example)

(9) Copolycarbonate comprising 70% by weight of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and 30% by weight of bisphenol A with phenol as chain terminator and MVR 8 cm.sup.3/(10 min) (330° C.; 2.16 kg) in accordance with ISO 1133 is compounded with 20% by weight of talc powder (Finntalc M05SL-AW from Mondo Minerals B.V.; NL-1041 Amsterdam) under conditions described below. The Vicat softening point of the resultant material is 198° C. (ISO 306; 50 N; 120 K/h).

(10) Compounding

(11) The materials were compounded in a ZE25 twin-screw extruder from KraussMaffei Berstorff, at a barrel temperature of 320° C./a melt temperature of about 340° C. and a rotation rate of 100 rpm, with the amounts stated in the examples of components.

(12) Production of Test Specimens:

(13) To produce moulded parts (rectangular sample sheets with side gating in optical quality with thickness 2 mm) used in Examples 1 and 2 for metallization, dynamic mould-temperature control was used. The injection-moulding process used a Battenfeld HM 210 at a melt temperature of about 350° C. and a mould temperature of about 201° C. The granulated material was dried for 5 hours in a vacuum drying oven at 120° C. prior to processing. Substrate material used comprises Substrate material 2.

(14) Measurement of Heat Resistance by Way of Vicat Softening Point:

(15) Vicat softening point in accordance with DIN EN ISO 306 is measured with a needle (with circular area of 1 mm.sup.2) A test force of 50 N (test force B) is applied to the needle. The abovementioned test specimen is exposed to a defined heating rate of 120 K/h. The Vicat point has been reached when the penetration depth of the probe is 1 mm This is measured in accordance with DIN ISO 306.

(16) Gloss Measurement:

(17) Gloss was measured in accordance with ASTM D523 on metallized sample sheets at various angles of incidence in BYK haze-gloss equipment.

(18) Measurement of Thermal Expansion:

(19) Longitudinal coefficients of expansion are determined under nitrogen by using Mettler TMA 841 measurement equipment (measurement range from 23 to 55° C.). ASTM E831 is used as standard.

(20) The test specimens (rectangular sample sheet) needed for the measurement are produced by injection moulding after drying of the granulated material at 130° C. overnight. In each case, the test specimen is measured transversely and longitudinally.

(21) Melt Stability

(22) Melt stability is evaluated by measuring melt volume rate (MVR) after various preheating times.

(23) Metallization Process:

(24) All of the sheets were stored for 21 days for 50% humidity and 23° C. prior to coating.

(25) The coating system was composed of a vacuum chamber, where the specimens were positioned on a rotating specimen holder. The specimen holder rotated at about 20 rpm. Before the test specimens were introduced into the vacuum chamber, ionized air was blown onto them in order to free them from dust. The vacuum chamber with the specimen was then evacuated to a pressure p≦1.Math.10.sup.−5 mbar. Argon gas was then allowed to enter until a particular pressure described in the inventive examples (process pressure 1) was reached, and for 2 minutes a plasma was ignited at a certain power rating described in the inventive examples (process power rating 1), and the specimens were exposed to the said plasma (plasma pretreatment). A diode arrangement composed of two parallel metal electrodes was used as plasma source and was operated at an AC frequency of 40 kHz and with a voltage greater than 1000 V. The specimens were then metallized. For this, Ar gas was allowed to enter with a pressure of 5.Math.10.sup.−3 mbar. An aluminium layer of thickness about 100 nm was applied to the specimens by means of a DC magnetron, using a power density of 6.4 W/cm.sup.2. The sputtering time was 2.5 minutes. Plasma polymerization was then used to apply a corrosion-protection layer made of HMDSO (hexamethyldisiloxane; CAS 107-46-0). For this, HMDSO was vaporized, and the vapour was allowed to enter the vacuum chamber until the resultant pressure of about 0.04 mbar. A plasma was then ignited by the diode arrangement described above at 1500 W for 1 minute, the corrosion-protection layer was applied.

(26) Test for Surface Quality after Heat-Ageing:

(27) The test is carried out directly after metallization. This means that after metallization the sheets were subjected to the said test within one hour.

(28) The metallized sheets here are stored in a conditioning chamber for 2 hours at 45° C. and 100% relative humidity. Directly after conditioning, the sheets are aged for one hour in an oven at 170/180° C.

(29) The metal surface is then assessed.

(30) Visual Assessment:

(31) The surface is studied to reveal elevations in the form of bubbles, clouding of the metal layer, or iridescence. Sheets exhibiting no iridescence, no clouding, and no bubbles are characterized as “defect free”.

Example 1

According to the Invention

(32) Rectangular injection-moulded sheets of Substrate material 2 component are prepared as described above.

(33) The test specimens were then metallized as described above. Process pressure 1 here is 0.09 mbar and process power rating 1 is 1.67 W/cm.sup.2. All of the other parameters for producing the metal layer/producing the topcoat are set as described above.

(34) Table 1 shows the result of the test (heat ageing).

Example 2

Comparative Example

(35) Rectangular injection-moulded sheets of Substrate material 2 component are prepared as described above.

(36) The test specimens were then metallized as described above. Process pressure 1 here is 0.09 mbar and process power rating 1 is 0.17 W/cm.sup.2. All of the other parameters for producing the metal layer/producing the topcoat are set as described above.

(37) Table 1 shows the result of the test (heat ageing).

(38) TABLE-US-00001 TABLE 1 Visual Pretreatment Heat-ageing assess- Ex. Substrate Sputter process temperature ment 1 Substrate Process power rating 170° C. Defect- According to material 2 1: 1.67 W/cm.sup.2 free the invention Process pressure 1: 0.09 mbar 1 Substrate Process power rating 180° C. Defect- According to material 2 1: 1.67 W/cm.sup.2 free the invention Process pressure 1: 0.09 mbar 2 Substrate Process power rating 170° C. Bubbles Comparison material 2 1: 0.17 W/cm.sup.2 Process pressure 1: 0.09 mbar 2 Substrate Process power rating 180° C. Bubbles Comparison material 2 1: 0.17 W/cm.sup.2 Process pressure 1: 0.09 mbar

(39) Example 1 according to the invention shows that very good surface qualities can be obtained at specific pressures and specific sputter energies. In contrast, there are metallization conditions which lead to defects in the surface in a subsequent stress test.

Example 3

Comparison

(40) Substrate material 2 is processed under conventional conditions to give sample sheets—no dynamic mould-temperature control is used here, i.e. sample sheets are prepared in optical quality, with side-gating. The melt temperature was from 300 to 330° C. and the mould temperature was 100° C. The granulated material was dried at 120° C. for 5 hours in a vacuum drying oven, prior to processing.

(41) The moulded part was then metallized as described in Example 1.

(42) TABLE-US-00002 TABLE 2 Gloss measurement Example Gloss at 20° Gloss at 60° 1 (According to the invention) 1449 784 3 (Comparison) 39 143

(43) The moulding not produced under the conditions stated for dynamic mould-temperature control is seen not to exhibit high gloss levels. In contrast, Example 1, which used dynamic mould-temperature control (mould temperature close to Vicat softening point) exhibits the high gloss level needed for reflectors.

(44) TABLE-US-00003 TABLE 3 Thermal expansion Example Transverse Longitudinal Substrate 65.2 × 10.sup.−6/K 65.2 × 10.sup.−6/K material 1 Substrate 52.4 × 10.sup.−6/K 40.9 × 10.sup.−6/K material 2 Substrate 49.3 × 10.sup.−6/K 36.8 × 10.sup.−6/K material 3

(45) Substrate material 2 serving for production of the multilayer structures according to the invention is seen to exhibit markedly less thermal expansion.

(46) TABLE-US-00004 TABLE 4 Melt stability MVR (330° C.; IMVR (330° C.; applied weight 2.2 kg); applied weight 2.2 kg); Example Preheat time: 6 min Preheat time: 19 min Substrate 8.0 cm.sup.3/[10 min] material 1 Substrate 2.7 cm.sup.3/[10 min]  3.0 cm.sup.3/[10 min] material 2 Substrate 59.8 cm.sup.3/[10 min]  67.7 cm.sup.3/[10 min] material 3

(47) Surprisingly, Substrate material 2, suitable for the invention exhibits markedly high melt stability in comparison with Substrate material 3.

(48) Overall, it has been shown that the multilayer structures according to the invention are obtained only by using the substrate material according to the invention in combination with replication in the injection-moulding process with dynamic mould-temperature control and with the specific coating process.