ELECTRICALLY DIMMABLE GLAZING

Abstract

The present invention relates to a specific multilayer composite which is suitable as a constituent of liquid-crystal devices and which contains two specific polycarbonate layers inter alia. The invention further relates to a method of producing the multilayer composite. The invention further relates to a liquid-crystal device comprising a multilayer composite according to the present invention, to a method of production thereof, and to the use thereof as structural glazing, in automotive glass, as floodlight cover, in optical filters, in shutters, in flat visual display screens, in glazed advertising devices, in dividing walls of trains, and in point-of-interest devices.

Claims

1. A multilayer composite with sandwich structure which is suitable as a constituent of liquid-crystal devices, comprising: a core layer consisting of one of a polymer matrix with nematic liquid crystals dispersed therein or a liquid-crystal matrix with polymers dispersed therein; two conductive layers each disposed on one surface of the core layer and enclosing the core layer, wherein the conductive layers are transparent and electrically conductive; two polycarbonate layers each disposed on a surface of the conductive layers which is remote from the core layer and each layer having a clear hardcoat coating on a side facing the core layer, and wherein the polycarbonate layers are transparent; and optionally two antiblocking hardcoat layers each layer disposed on a surface of the polycarbonate layers which is remote from the core layer, wherein the antiblocking hardcoat layers are transparent; and/or two adhesive layers each layer disposed on a surface of the polycarbonate layers or, if present, of the antiblocking hardcoat layers which is remote from the core layer, where the adhesive layers are transparent.

2. The multilayer composite as claimed in claim 1, characterized in that the core layer (i) has a thickness of 100 to 200 μm; and/or (ii) has a polymer matrix produced from UV-curable polymerizable monomers; and/or (iii) has liquid crystals selected from one of the classes of nematic, smectic, ferroelectric or organometallic mesogens, including the class of polymerizable liquid crystals.

3. The multilayer composite as claimed in claim 1, characterized in that the conductive layers (i) have a thickness of 20 to 50 nm; (ii) are the same or different; (iii) one selected from the group consisting of ITO, IMITO, tin oxide, and gallium-doped tin oxide; (iv) have a maximum roughness of the surface of Ra<0.1 μm, determined to DIN EN ISO 1302:2002-06; and (v) have a specific sheet resistance R.sub.□ of less than 100 ohms.

4. The multilayer composite as claimed in claim 1, characterized in that the polycarbonate layers (i) have a thickness of 90 to 1000 μm; (ii) are the same or different; (iii) consist of amorphous polycarbonate; (iv) have a transmittance Ty of at least 86%; (v) have a haze of less than 2%; (vi) are extruded polycarbonate layers; (vii) have a clear hardcoat coating which is a lacquer coating; (viii) have a Vicat softening temperature of 145 to 160° C., determined by test method ISO 306:2014-03 and the B50 method (test load 50 N; heating rate 50 K/h; pressboard in oil); (ix) have a melting range of 220 to 230° C.; and/or (x) have a burn rate of ≤100 mm/min, determined by test method US-FMVSS 302.

5. The multilayer composite as claimed in claim 1, characterized in that the antiblocking hardcoat layers (i) have a thickness of 0.5 to 12 μm; (ii) are the same or different; and (iii) are selected from the group consisting of silicon oxide layers, admixed with silicas and wax additives.

6. A method of producing a multilayer composite as claimed in claim 1, comprising the following steps: (i) providing two conductive layers and two polycarbonate layers, wherein the polycarbonate layers have a clear hardcoat coating on a first side and optionally an antiblocking hardcoat layer on a second side, and applying a conductive layer to each polycarbonate layer, wherein the conductive layer is applied on the side of the polycarbonate layer having a clear hardcoat coating to produce a first composite; (ii) applying the core layer to the conductive layer of a first composite by one selected from the group consisting of knife coating, casting, and printing to produce a second composite; (iii) applying the first composite to the core layer of the second composite, wherein the conductive layer of the first composite is applied to the second composite by one selected from the group consisting of lamination and pressing, to produce a third composite; (iv) optionally applying two antiblocking hardcoat layers, if not already present in step (i), to two faces of the third composite to produce a fourth composite; and (vii) optionally applying two adhesive layers to two faces of the third or fourth composite to produce an alternative fourth or a fifth composite; and (viii) optionally subjecting one of the third, fourth or fifth composite to overmolding or in-mold coating by an injection molding method.

7. A liquid-crystal device comprising the multilayer composite as claimed in claim 1, disposed between two sheets, wherein the conductive layers have been bonded by a voltage source.

8. A method of producing a liquid-crystal device as claimed in claim 7, comprising the following steps: securing two sheets, each on one side of the multilayer composite as claimed in claim 1.

9. One selected from structural glazing, automotive glass, mirrors and glazing, floodlight covers, optical filters, shutters, flat visual display screens, glazed advertising devices, dividing walls of trains, and point-of-interest devices, comprising the liquid crystal device produced according to claim 7.

Description

EXAMPLE 1 (INVENTIVE)

Measurement of Light Transmittance and Haze on a Test Specimen Made of a Multilayer Composite According to the Invention

[0093] A test specimen was produced from a multilayer composite according to the invention using a polycarbonate film of the commercially available Makrofol® HS340 G-1 020010 type manufactured at Covestro Deutschland AG, provided on one side (front side) with a high-gloss hardcoat layer of silicon oxide and shiny on the opposite side (reverse side). This film of thickness 385 μm (test method: ISO 4593:1993-11) was used in the form of roll material and was coated on the front side with indium tin oxide (ITO) in a sputtering method. The resistance of the ITO layer was (90±5) Ω/□. The film thus produced was cut into leaves, i.e. leaf material, in about 200 mm×300 mm format. The leaf material thus obtained is also referred to for short as “PC-ITO leaves”—“PC-ITO leaf” in the singular.

[0094] Two such PC-ITO leaves according to this example 1 were used hereinafter as substrates for the test specimen in the multilayer composite according to the invention. It has been found that the applying of a polymer-dispersed liquid-crystal paste (PDLC paste) led to production of a PDLC layer by means of knife-coating on the ITO layer on account of the good surface planarity of the PC-ITO leaf having high constancy of thickness with values around 150 μm. Methods of producing encapsulated liquid crystals and producing a continuous PDLC layer on a carrier material have been described before and were employed here. They are based on the photochemical polymerization of UV-curing mixtures consisting of monomers, crosslinkers, photoinitiators and liquid-crystal mixtures. Details of the processes can be gleaned, for example, in the patent specification U.S. Pat. No. 4,435,047 A by Fergason J. L., “Encapsulated liquid crystal and method” and in Kashima M, Cao H, Meng Q, Liu H, Wang D, Li F, et al., “The influence of crosslinking agents on the morphology and electro-optical performances of PDLC films”, J. Appl. Pol. Sci. 2010 (117), 3434-3440. The PDLC layer has been distributed up to the edge of the PC-ITO leaf. The PDLC layer was sealed by means of a second PC-ITO leaf according to this example 1. This was done in such a way that the respective ITO layers of the two PC-ITO leaves were disposed directly atop the PDLC layer, i.e. the ITO layers of the two PC-ITO leaves were separated from one another solely by the PDLC layer.

[0095] FIG. 1 shows the schematic construction of a multilayer structure according to the invention (not to scale). In this figure: [0096] 11a Polycarbonate layer of the first PC-ITO leaf [0097] 12a Hardcoat layer of the first PC-ITO leaf [0098] 13a ITO layer of the first PC-ITO leaf [0099] 14 PDLC layer [0100] 13b ITO layer of the second PC-ITO leaf [0101] 12b Hardcoat layer of the second PC-ITO leaf [0102] 11b Polycarbonate layer of the second PC-ITO leaf

[0103] The total thickness of the multilayer composite according to the invention thus obtained was 920 to 930 μm as measured with a micrometer screw. For electrical contact connection, wires were connected to an outer edge by means of metal spring clamps, one for each PC-ITO leaf. For the contact connection of the ITO layer 13a of the first PC-ITO leaf, the second PC-ITO leaf was lifted briefly with a scalpel, i.e. the composite was separated at the PDLC layer 14, and about 1 cm.sup.2 was cut away from the edge of the second PC-ITO leaf. At this point, it was possible to contact the ITO layer 13a of the first PC-ITO leaf with the spring clamp Electrical contact improves if the PDLC layer 14 above the ITO is rubbed away mechanically. The procedure is similar for the contacting of the ITO layer 14a of the second PC-ITO leaf; in this case, a portion of the first PC-ITO leaf is cut away. It is thus possible to establish the second contact with the second electrode. The two contacts are a few centimetres apart, for example, but on the same edge of the multilayer composite. It was thus possible to apply electrical fields to the PDLC via its two adjacent electrically conductive ITO layers by the principle of a plate capacitor. Further cutting-to-size of the multilayer composite according to the invention thus obtained was necessary for the measurement in the sample chambers of the optical measurement devices, and was done by cutting to size with scissors. A test specimen of the multilayer composite according to the invention was obtained.

[0104] A test specimen of width about 120 mm was analysed for haze and transmittance in a Hazemeter NDH 2000 (from Nippon Denshoku Industries Co., Ltd.) with D65 standard illuminant, once in each case without voltage applied (0 volts) and once with voltage (36 volts).

[0105] The measurement results can be found in table 1.

[0106] The test specimen of the multilayer composite according to the invention has high haze in the normal state of 97.26% and high transmittance of 88.87% with simultaneously low residual haze of 4.0% in the switched-on state.

[0107] Comparison with the haze value of the polycarbonate film Makrofol® HS340 G-1 020010 with a hardcoat layer that has neither an ITO layer nor a PDLC layer and otherwise corresponds to the film, which was used for production of the multilayer structure according to the invention, of 0.98% shows that the contribution of the PDLC layer to the total haze of the test specimen in the connected state is small.

TABLE-US-00001 TABLE 1 Optical properties of a multilayer composite according to the invention in the connected (voltage 36 volts) and unconnected initial state (0 volts) Voltage [V (DC)] Transmittance [%] Haze [%] 0 81.51 97.26 36 88.87 4.0

EXAMPLE 2 (COMPARATIVE)

Measurement of Light Transmittance and Haze on a PET-Based Test Specimen not According to the Invention

[0108] By comparison with the multilayer composite according to the invention from example 1, a test specimen composed of commercially available PET-ITO layer composite, TL42 from OPAK Smart Glas GmbH, was employed. The PET-ITO layer composite TL42 has a PDLC core layer, the chemical feedstocks and formulation of which are identical to the core layer from example 1. The two carrier films are 188 μm-thick PET with an ITO layer.

[0109] The respective ITO layers of the two carrier films of the PET-ITO layer composite TL42 are disposed directly atop the PDLC layer; in other words, the ITO layers of the two carrier films of the PET-ITO layer composite TL42 were separated from one another solely by the PDLC layer.

[0110] FIG. 2 shows the schematic structure of the PET-ITO layer composite TL42 (not to scale). In this figure: [0111] 21a PET layer [0112] 23a ITO layer [0113] 24 PDLC layer [0114] 23b ITO layer [0115] 21b PET layer

[0116] The measurement results for haze and transmittance can be found in table 2.

TABLE-US-00002 TABLE 2 Optical properties of the test specimen not according to the invention based on a PET-ITO layer composite TL42 (comparative test specimen) in the connected (voltage 65 volts) and unconnected initial state (0 volts) Voltage [V (DC)] Transmittance [%] Haze [%] 0 75.36 97.26 65 81.89 4.10

[0117] The comparative test specimen has high haze in the normal state of 97.26%. This is identical to the multilayer composite according to the invention.

[0118] The comparative test specimen in the connected state, in spite of the high voltage applied, has comparatively low transmittance of 81.89% and high residual haze of 4.10%.

[0119] Comparison with the haze value of an uncoated PET film of 0.8% shows that the contribution of the PDLC layer to the total haze of the comparative test specimen in the connected state is high, especially higher than in the multilayer composite according to the invention from example 1.

EXAMPLE 3 (COMPARATIVE)

Measurement of Light Transmittance and Haze on a Test Specimen not According to the Invention Based on Polycarbonate

[0120] By comparison with the multilayer composite according to the invention from example 1, a commercially available high-gloss polycarbonate film, Makrofol® DE 1-1 from Covestro Deutschland AG, was used in example 3 for the reverse side of the test specimen to be produced. This film was cut into leaves—here too called “PC-ITO leaves” or in the singular “PC-ITO leaf”—each with an about 150 mm×150 mm format, and these PC-ITO leaves were individually coated on the front side with indium tin oxide (ITO) in a sputtering method. The resistance of the ICO layer was (90±5) Ω/□.

[0121] Such a PC-ITO leaf not according to the invention according to this example 3 and a PC-ITO leaf according to the invention from example 1, produced according to example 1, were then respectively used for the reverse side and the front side of the PDLC specimen to be constructed. The process for producing the test specimen according to this example 3 corresponds to that from example 1.

[0122] FIG. 3 shows the schematic construction of a test specimen according to this example 3 (not to scale). In this figure: [0123] 31a Polycarbonate layer of the first PC-ITO leaf [0124] 33a ITO layer of the first PC-ITO leaf [0125] 34 PDLC layer [0126] 33b ITO layer of the second PC-ITO leaf [0127] 31b Polycarbonate layer of the second PC-ITO leaf

[0128] The Makrofol® DE 1-1 film was 385 μm thick (test method: ISO 4593:1993-11).

[0129] A test specimen of width about 50 mm was analysed for haze and transmittance in a Hazemeter NDH 2000 (from Nippon Denshoku Industries Co., Ltd.) with D65 standard illuminant, once in each case without voltage applied (0 volts) and once with voltage (36 volts).

[0130] The measurement results can be found in table 3.

[0131] The test specimen according to this example 3 in the opaque normal state has lower haze compared to the test specimen according to the invention from example 1 (91.39% compared to 97.26%).

[0132] The test specimen according to this example 3 in the transparent connected state has lower transmittance compared to the test specimen according to the invention from example 1 (84.83% compared to 88.87%) and simultaneously higher residual haze (3.99% compared to 3.74%). This demonstrates that the specimen not according to the invention (with a PC film lacking a scratch-resistant finish) in both connection states is worse in terms of optical properties than the specimen according to the invention.

TABLE-US-00003 TABLE 3 Optical properties of a noninventive PC-based PDLC test specimen in the connected (voltage 36 volts) and unconnected initial state (0 volts) Voltage [V (DC)] Transmittance [%] Haze [%] 0 75.42 91.39 36 84.83 3.99