Low reflective films

Abstract

An anti-reflecting film is made from a polymeric film substrate consisting of cellulose acetate, polyamide or polyester. The substrate is coated with at least two polymeric layers. An outer layer is comprised of a fluorine containing polymer. Between the outer layer and the substrate is an intermediate layer of an organometallic polymeric layer. The organometallic polymeric layer is comprised of the condensation product of a metal alkoxide and a polymer reactive with the metal oxide.

1 . An anti-reflective film comprising a transparent polymeric film substrate coated with at least two polymeric layers, the two layers being an exposed outer polymeric layer comprising a fluorine containing polymer and immediately adjacent thereto an inner organometallic polymeric layer adjacent the exposed outer layer comprising the condensation product of a metal alkoxide and a polymer reactive with the metal alkoxide.  
     
     
         2 . Anti-reflective film as claimed in    claim 1    wherein said inner polymeric layer comprises the reaction product of a metal alkoxide and a polymer having silane group therein.  
     
     
         3 . Anti reflective film as claimed in    claim 2    wherein the metal alkoxide is a titanium alkoxide, preferably titanium isopropoxide.  
     
     
         4 . Anti reflective film as claimed in    claim 2    wherein the silane containing polymer is a silane modified polyester.  
     
     
         5 . Anti reflective film as claimed in    claim 1   , wherein the exposed outer polymeric layer is a crosslinked fluorine containing polymer.  
     
     
         6 . Anti reflective film as claimed in    claim 1    wherein the exposed outer polymeric layer is an acrylate modified perfluoropolyether.  
     
     
         7 . Anti reflective film as claimed in    claim 1    wherein the film further comprises at least one further optically active layer between the substrate and said inner layer.  
     
     
         8 . Anti reflective film as claimed in    claim 1    wherein the film substrate has a hard abrasion resistant coating immediately adjacent thereto.  
     
     
         9 . Anti-reflective film as claimed in    claim 1    wherein the inner polymer layer has a refractive index of at least 1.60 and a thickness of about {fraction (1/4)} wavelength and the exposed polymeric layer has a refractive index not greater than 1.45 and a thickness of about {fraction (1/4)} wavelength.  
     
     
         10 . Anti-reflective film as claimed in    claim 2    wherein the inner layer comprises as an additive a carbodiimide functional silane.  
     
     
         11 . An anti-reflective film comprising a transparent polymeric film substrate, an exposed outer polymeric layer comprising fluoro-containing polymers having a refractive index not greater than 1.45 and a thickness of about {fraction (1/4)} wavelength and an inner polymeric layer adjacent the exposed outer layer containing metal oxide and having a refractive index of at least about 1.6 and a thickness of about {fraction (1/4)} wavelength.  
     
     
         12 . A multilayer anti-reflective film comprising a transparent polymeric film substrate and including as one of its layers a transparent polymeric layer containing inorganic powder particles having a refractive index greater than 2.6.  
     
     
         13 . An anti-reflective film as claimed in    claim 12   , wherein the powder particles are coloured powders having an average equivalent diameter of less than 100 nm (100−10 −9  m).  
     
     
         14 . An anti-reflective film as claimed in    claim 12   , wherein the powder particles are metal compounds, in particular metal oxides.  
     
     
         15 . An anti-reflective film as claimed in    claim 14   , wherein the metal compound is preferably an iron oxide, in particular haematite.  
     
     
         16 . A multilayer anti-reflective film comprising a transparent polymeric film substrate and including as one of its layers a transparent coloured polymeric layer containing inorganic powdered particles which impart the coloration to said layer, and raise the refractive index of said layer to at least 1.6.  
     
     
         17 . A method of manufacture of an anti-reflective film in which method a reaction mixture of a metal alkoxide and a silane modified polymer is coated onto a transparent film substrate and cured to form an inner polymeric layer, and a further layer of a fluorine containing polymer is coated over the inner layer, and is cured to form an exposed outer polymeric layer.  
     
     
         18 . A method as claimed in    claim 17   , wherein the inner layer is a reaction mixture of a metal alkoxide and a silane modified polymer which is cured at 180° C. for at least one minute, and the second layer is a fluorine containing polymer coated over the first layer directly in contact therewith.  
     
     
         19 . A method as claimed in    claim 17    wherein the silane modified polymer is a polyester having silane groups on the polymer chain.  
     
     
         20 . A method as claimed in    claim 17    where the first layer is applied as a solution in a volatile solvent which is removed from the layer prior to curing.  
     
     
         21 . A method as claimed in    claim 19    wherein up to 10% by weight of a carbodiimide functional silane is added as a crosslinking agent to said reaction mixture.  
     
     
         22 . A method of manufacture of an anti-reflective film laminate in which method particles of metal oxide are dispersed in a liquid polymeric material, and the polymeric material is coated onto a polymeric film substrate and cured to give a transparent inner polymeric layer having a refractive index of at least about 1.6 and a thickness of about {fraction (1/4)} wavelength, and the inner polymeric layer is overcoated by a further transparent polymeric layer of fluorine containing polymer which is cured to give an outer polymeric layer having a refractive index of not greater than 1.45 and a thickness of about {fraction (1/4)} wavelength.  
     
     
         23 . A method as claimed in    claim 22   , wherein the inner polymeric layer is formed from a mixture of polymerisable monomers including a triacrylate, or a tetra acrylate and acrylic acid and photo initiators into which finely ground metal oxide is dispersed.  
     
     
         24 . A method as claimed in    claim 20   , wherein the metal oxide is preferably an iron oxide which has been ground to a particle size having an average equivalent diameter of less than 100 nm (100× 10   −9  m).  
     
     
         25 . A method of making a multilayer anti-reflective film in which a polymeric film substrate is coated with a transparent polymer layer containing inorganic powdered material dispersed within the layer, the powder particles having a high refractive index of greater than 2.6, the film having a haze value of less than 20%.  
     
     
         26 . A method of making an antireflective film as claimed in    claim 25    wherein the haze value of the film is less than 3%.  
     
     
         27 . A method as claimed in    claim 25    wherein the transparent layer is also coloured by means of the powder particles to form a transparent coloured layer.  
     
     
         28 . A method as claimed in    claim 25    wherein the transparent layer is an inner layer which is overcoated by an outer polymeric layer, the outer layer being coated onto the inner layer by either vacuum deposition, or by coating the inner layer with a solution of the second polymer, followed by removal of the solvent.  
     
     
         29 . A method of manufacture of a multilayer anti-reflective polymeric film having at least a two layer anti-reflective coating, wherein the inner layer of said two layers has a refractive index of at least 1.69 and comprises particles of iron oxide dispersed in a curable polymeric resin to form a transparent high refractive index layer.  
     
     
         30 . A method as claimed in    claim 29   , wherein the refractive index of said layer may be altered by varying the iron oxide content of the polymeric layer.  
     
     
         31 . A method of making an anti-reflective film in which a polymeric film substrate is coated with a transparent polymer layer containing inorganic powdered material dispersed within the layer to form a coloured transparent film, having a refractive index of at least 1.6.  
     
     
         32 . A multilayer antireflection film as claimed in    claim 16    wherein the coloration of the transparent coloured polymeric layer is neutralised by including a suitable dye in the polymeric film substrate, or other layer of said layers.