Multilayer cholesteric pigments

• US 6,582,781 B1
• Filed: 03/02/2000
• Issued: 06/24/2003
• Est. Priority Date: 09/02/1997
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Meyer, Frank, Heilmann, Peter, Bettinger, Günter, Schneider, Norbert, Keller, Harald, Best, Wolfgang, Richter, Volker, Blaschka, Peter, Schuhmacher, Peter
• Primary Examiner(s): LE, HOA T
• Application Number:
  US09/486,694
• Time in Patent Office: 1,209 Days
• Field of Search: 428/403, 428/407, 428/1.1, 428/1.2
• US Class Current: 428/1.1
• CPC Class Codes: A61K 2800/412 Microsized, i.e. having sizes between 0.1 and 100 microns
• CPC Class Codes: A61K 2800/436 Interference pigments, e.g. Iridescent, Pearlescent
• CPC Class Codes: A61K 2800/622 by organic compounds
• CPC Class Codes: A61K 2800/63 More than one coating
• CPC Class Codes: A61K 2800/651 The particulate/core comprising inorganic material
• CPC Class Codes: A61K 8/0266 Characterized by the sequence of layers
• CPC Class Codes: A61K 8/0295 Liquid crystals
• CPC Class Codes: A61Q 1/02 Preparations containing skin colorants, e.g. pigments preparations in powder form A61Q1/12
• CPC Class Codes: C01P 2004/20 extending in two dimensions, e.g. plate-like
• CPC Class Codes: C08G 59/20 characterised by the epoxy compounds used
• CPC Class Codes: C09B 67/0098 Organic pigments exhibiting interference colours, e.g. nacrous pigments
• CPC Class Codes: C09C 1/0015 Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
• CPC Class Codes: C09C 1/48 Carbon black
• CPC Class Codes: C09C 2220/20 PVD, CVD methods or coating in a gas-phase using a fluidized bed
• CPC Class Codes: C09D 5/36 Pearl essence, e.g. coatings containing platelet-like pigments for pearl lustre
• CPC Class Codes: C09K 19/00 Liquid crystal materials
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

A platelet-shaped cholesteric multilayer pigment which comprises the layer sequence A¹/B/A²

where

A¹ and A² are identical or different and each comprise at least one cholesteric layer, and

B is at least one interlayer which separates the layers A¹ and A² from one another and which absorbs all or some of the light transmitted by the layers A¹ and A²,

processes for its preparation, and its use are all described.

Claims

1. A platelet-shaped cholesteric multilayer pigment which comprises the layer sequence A¹/B/A²,

wherein

A¹ and A² are identical or different and each comprise at least one cholesteric layer wherein the thickness of each cholesteric layer is about 0.5 to 2 μ

m, and

B is at least one interlayer which separates the layers A¹ and A² from one another and which absorbs all or some of the light transmitted by the layers A¹ and A².

2. A multilayer pigment as claimed in claim 1, wherein A¹ and A² possess identical or different optical properties.

3. A multilayer pigment as claimed in claim 2, wherein A¹ and A² reflect light of identical or different wavelength and/or are of identical or different handedness.

4. A multilayer pigment as claimed in claim 1, wherein B comprises at least one organic or inorganic absorption pigment, optionally bound in a binder matrix.

5. A multilayer pigment as claimed in claim 1, wherein A¹ and A² comprise cholesteric mixtures selected from the group consisting of

a) at least one cholesteric, polymerizable monomer,

b) at least one achiral, nematic, polymerizable monomer and one chiral compound,

c) at least one cholesteric, crosslinkable oligomer or polymer,

d) a cholesteric polymer in a polymerizable diluent, and

e) at least one cholesteric polymer whose cholesteric phase can be frozen in by rapid cooling to below the glass transition temperature, in the cured state.

6. A multilayer pigment as claimed in claim 1, wherein B comprises a binder matrix comprising at least one cholesteric mixture selected from the group consisting of

a) at least one cholesteric, polymerizable monomer,

b) at least one achiral, nematic, polymerizable monomer and one chiral compound,

c) at least one cholesteric, crosslinkable oligomer or polymer,

d) a cholesteric polymer in a polymerizable diluent, and

e) at least one cholesteric polymer whose cholesteric phase can be frozen in by rapid cooling to below the glass transition temperature, in the cured state.

7. A multilayer pigment as claimed in claim 6, where A¹, B and A2 comprise the same cholesteric mixtures.

8. A process for producing a multilayer pigment as claimed in claim 1, which comprises applying the layers A¹, B and A² atop one another to a substrate, simultaneously or with a time differential, curing the layers, simultaneously or with a time differential, removing the fully cured layers from the substrate and then comminuting them to produce multilayer pigments.

9. A process as claimed in claim 8, wherein the applied layers are dried prior to curing.

10. A process as claimed in claim 8, which comprises applying the layers A¹, B and A² to the substrate by means of a technique selected from the group consisting of air knife.

11. A process as claimed in claim 10, which comprises applying the layers A¹, B and A² to the substrate by means of letterpress (relief), intaglio, flexographic, or offset or screen printing.

12. A process as claimed in claim 10, wherein the layers A¹, B and A² are applied by means of casting or offset printing.

13. A composition comprising at least one multilayer pigment as claimed in claim 1.

14. A coating material comprising at least one multilayer pigment as claimed in claim 1.