Anti-reflection film and process for preparation thereof

Abstract

This invention provides an anti-reflection film for use in various displays which prevents the reflection of light on the surface and enables necessary visual information to be clearly discerned. The anti-reflection film has a hard coat layer 4 , an intermediate refractive index layer 3 , a high refractive index layer 2 and a low refractive index layer 1 formed in this sequence on a transparent base film 5 , such that the refractive indices of the adjacent layers satisfy the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer>1.40.

1 . An anti-reflection film having an intermediate refractive index layer, a high refractive index layer and a low refractive index layer formed in this order on a transparent base film via a hard coat layer, said anti-reflection film comprising: 
 the low refractive index layer comprising an SiO X  layer;    the intermediate refractive index layer constituted by a coating of a composition comprising a binder and ultrafine particles having a refractive index of 1.5 or more; and    the high refractive index layer; and    said anti-reflection film having: 
 the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer>1.40;  
 the thickness of each refractive index layer being 80 to 110 nm for the low refractive index layer, 30 to 110 nm for the high refractive index layer, and 50 to 100 nm for the intermediate refractive index layer; and  
 an optical film thickness D not larger than the wavelength of visible light (D=n·d wherein n is the refractive index of the intermediate refractive index layer and d is the thickness of the intermediate refractive index layer).  
   
     
     
         2 . An anti-reflection film as claimed in    claim 1   , wherein the hard coat layer has irregularities on its surface in contact with the intermediate refractive index layer.  
     
     
         3 . An anti-reflection film as claimed in    claim 1   , wherein the hard coat layer is provided on the transparent base film directly or via a primer layer and/or an adhesive layer.  
     
     
         4 . An anti-reflection film as claimed in    claim 1   , wherein the intermediate refractive index layer comprises 1 part by weight of a thermosetting resin and/or an ionizing radiation curing resin and 0.1 to 20 parts by weight of ultrafine particles of one or more kinds selected from the group consisting of ultrafine particles of ZnO, TiO 2 , CeO 2 , Sb 2 O 5 , SnO 2 , ITO, Y 2 O 3 , La 2 O 3 , Al 2 O 3 , Hf 2 O 3  and ZrO 2 .  
     
     
         5 . An anti-reflection film as claimed in    claim 1   , wherein the high refractive index layer and the low refractive index layer are each a layer provided by vacuum coating.  
     
     
         6 . An anti-reflection film as claimed in    claim 1   , wherein the low refractive index layer is formed by plasma CVD involving the discharge of the starting gas of an organosiloxane, and the undecomposed organosiloxane remains in an amount of 0.1 to 0.2 part based on the silicon.  
     
     
         7 . An anti-reflection film as claimed in    claim 1   , wherein an antifouling layer may be formed on the low refractive index layer.  
     
     
         8 . A process for preparation of an anti-reflection film having a hard coat layer, an intermediate refractive index layer, a high refractive index layer, and a low refractive index layer formed in this sequence on a transparent base film, comprising the steps of: 
 forming an uncured hard coat layer on a transparent base film;    forming an uncured intermediate refractive index layer on the transparent base film, said uncured intermediate refractive index layer comprising a composition containing a binder and fine particles having a higher refractive index than the refractive index of the binder;    laminating a mirror-shaped or finely irregular, matted shaped film on the uncured intermediate refractive index layer to shape the surface of the intermediate refractive index layer;    heat-treating and/or ionizing radiation treating the resulting laminate to cure the uncured layers;    removing the shaped film from the cured laminate to form an intermediate refractive index layer having a smooth or finely irregular surface on the transparent base film;    forming a high refractive index layer on the intermediate refractive index layer by vacuum deposition or sputtering; and    forming a low refractive index layer comprising an SiO X  layer on the high refractive index layer by vacuum deposition, sputtering or plasma CVD.    
     
     
         9 . A process for preparation of an anti-reflection film having a hard coat layer, an intermediate refractive index layer, a high refractive index layer, and a low refractive index layer formed in this sequence on a transparent base film, comprising the steps of: 
 forming an uncured intermediate refractive index layer on a mirror-shaped or matted shaped film having irregularities on the surface, said uncured intermediate refractive index layer comprising a composition containing a binder and fine particles having a higher refractive index than the refractive index of the binder;    laminating the uncured intermediate refractive index layer to an uncured hard coat layer provided on a transparent base film;    heat-treating and/or ionizing radiation treating the resulting laminate to cure the uncured layers;    stripping off the shaped film from the cured laminate to form an intermediate refractive index layer having a smooth or finely irregular surface on the transparent base film;    forming a high refractive index layer on the intermediate refractive index layer by vacuum deposition or sputtering; and    forming a low refractive index layer comprising an SiO X  layer on the high refractive index layer by sputtering or plasma CVD.    
     
     
         10 . A process for preparation of an anti-reflection film having an intermediate refractive index layer, a high refractive index layer, and a low refractive index layer formed in this sequence on a transparent base film via a hard coat layer, comprising the steps of: 
 coating a shaped film having a mirror- or mat-shaped surface with an uncured intermediate refractive index layer containing a binder and fine particles having a higher refractive index than the refractive index of the binder, and an uncured hard coat layer, followed by curing, to form an intermediate refractive index layer and a hard coat layer;    laminating an uncured surface of a reactive adhesive layer coated on a transparent base film to the cured hard coat layer;    heat-treating and/or ionizing radiation treating the resulting laminate to cure the adhesive layer;    stripping off the shaped film from the cured laminate to form the intermediate refractive index layer having a smooth or irregular surface and the hard coat layer on the transparent base film;    forming a high refractive index layer on the intermediate refractive index layer by vacuum deposition or sputtering; and    forming a low refractive index layer comprising an SiO X  layer on the high refractive index layer by sputtering or plasma CVD.    
     
     
         11 . An anti-reflection film as claimed in    claim 1   , wherein the high refractive index layer comprises a sputter film of ITO, and its surface resistance is 10 3 Ω/¤ or less.  
     
     
         12 . An anti-reflection film as claimed in    claim 1   , wherein the binder of the intermediate refractive index layer comprises a thermosetting and/or ionizing radiation curing organosilicon compound.  
     
     
         13 . An anti-reflection film as claimed in    claim 1   , wherein the ultrafine particles of the intermediate refractive index layer comprise ZrO 2  particles.  
     
     
         14 . An anti-reflection film having an intermediate refractive index layer, a high refractive index layer and a low refractive index layer formed in this sequence on a transparent base film via a hard coat layer, said anti-reflection film comprising: 
 the low refractive index layer comprising an SiO X  layer;    the intermediate refractive index layer constituted by coating a paint comprising a binder and ultrafine particles having a refractive index of 1.5 or more; and    the high refractive index layer having electric conductivity; and    said anti-reflection film having: 
 the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer>1.40; and  
   the ultrafine particles of the intermediate refractive index layer comprising ZrO 2  particles.    
     
     
         15 . An anti-reflection film as claimed in    claim 1   , wherein the high refractive index layer has electric conductivity.