Method for making multilayer optical films

• US 20010013668A1
• Filed: 03/16/2001
• Published: 08/16/2001
• Est. Priority Date: 01/13/1998
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Ouderkirk, Andrew J., Neavin, Terence D., Liu, Yaoqi J.
• Granted Patent: US 6,827,886 B2
• Time in Patent Office: Days
• US Class Current: 264/1.7
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/22 with means connecting the layers, e.g. tie layers or undercuts
• CPC Class Codes: B29C 48/495 Feed-blocks extrusion moulding of multi-component articles B29C48/16
• CPC Class Codes: B29C 48/71 for layer multiplication extrusion of multi-component articles B29C48/16
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree

Abstract

Methods and apparatuses are provided for the manufacture of coextruded polymeric multilayer optical films. The multilayer optical films have an ordered arrangement of layers of two or more materials having particular layer thicknesses and a prescribed layer thickness gradient throughout the multilayer optical stack. The methods and apparatuses described allow improved control over individual layer thicknesses, layer thickness gradients, indices of refraction, interlayer adhesion, and surface characteristics of the optical films. The methods and apparatuses described are useful for making interference polarizers, mirrors, and colored fihns that are optically effective over diverse portions of the ultraviolet, visible, and infrared spectra.

Claims

1. A feedblock for making a multilayer optical film, comprising:

(a) a gradient plate comprising at least first and second flow channels, wherein at least one of said flow channel has a cross-sectional area that changes from a first position to a second position along said flow channel;

(b) a feeder tube plate having a first plurality of conduits in fluid communication with said first flow channel and a second plurality of conduits in fluid communication with said second flow channel, each conduit feeding its own respective slot die, each conduit having a first end and a second end and, said first end of said conduits being in fluid communication with said flow channels, and said second end of said conduits being in fluid communication with said slot die; and

(c) an axial rod heater located proximal to said conduits.

2. A method for making a multilayered optical film, said method comprising the steps of:

(a) providing at least a first and a second stream of resin;

(b) dividing said first and said second streams into a plurality of layers using the feedblock of

claim 1

such that said layers of said first stream are interleaved with said layers of said second stream to yield a composite stream;

(c) passing said composite stream through an extrusion die to form a multilayer web in which each layer is generally parallel to the major surface of adjacent layers; and

(d) casting said multilayer web onto a casting roll to form a cast multilayer film.