Method for coloring a transparent article made of polycarbonate and resulting article

Abstract

The invention concerns a method which comprises irradiating at least one face of an article with UV radiation, causing the article to be photodegraded over a thickness of at least 1 μ.m. and contacting the irradiated face of the article with a coloring agent, so as to diffuse the coloring agent in the entire thickness of the photodegraded surface layer of the article. The invention is useful for optical and ophthalmologic articles.

1 . Method for colouring a transparent article made of polycarbonate not containing polyester groups and having two opposite principal faces, characterized in that it comprises: 
 a) the photodegradation of the polycarbonate material of the transparent article by irradiation of at least one of the principal faces of the article with a predetermined UV radiation, to produce in the article at least one photodegraded surface layer of the polycarbonate material with a thickness of at least 1 to 2 μm; and    b) placing in contact at least said principal face of the article with a colouring agent so as to diffuse the colouring agent within a thickness of at least 1 to 2 μm of the photodegraded surface layer.    
     
     
         2 . Method according to  claim 1 , characterized in that comprises the photodegradation by irradiation by a predetermined UV radiation of the two opposite principal faces of the article to produce in the article two photodegraded surface layers of the polycarbonate material, each having a thickness of at least 1 to 2 μm, and in that the two opposite principal faces of the article are placed in contact with the colouring agent so as to diffuse the colouring agent within a thickness of at least 1 to 2 μm for these two photodegraded surface layers.  
     
     
         3 . Method according to claims  1  or  2 , characterized in that the photodegraded surface layer or layers have a thickness of 2 to 20 μm, preferably 2 to 10 μm.  
     
     
         4 . Method according to any of  claims 1  to  3 , characterized in that the colouring agent is diffused throughout the entire thickness of the photodegraded surface layer or layers.  
     
     
         5 . Method according to any of  claims 1  to  4 , characterized in that the predetermined UV radiation is such that, during the irradiation, at least 50% of the energy of the irradiation originates from the part of the radiation with wavelength 320 nm.  
     
     
         6 . Method according to any of  claims 1  to  5 , characterized in that the energy of the irradiation due to the part of the radiation with wavelength 320 nm is from 2.4 J/cm 2  to 48 J/cm 2 , preferably 10 J/cm 2  to 30 J/cm 2 .  
     
     
         7 . Method according to any of  claims 1  to  6 , characterized in that the predetermined UV radiation contains a part of the radiation with wavelength>320 nm and is such that the energy of the irradiation due to the part of the radiation with wavelength>320 nm is from 0.9 J/cm 2  to 15 J/cm 2 , preferably 2 J/cm 2  to 8 J/cm 2 .  
     
     
         8 . Method according to any of  claims 1  to  7 , characterized in that the polycarbonate material is selected from the bisphenol A homopolycarbonates.  
     
     
         9 . Method according to any of  claims 1  to  8 , characterized in that the polycarbonate material contains a UV absorber.  
     
     
         10 . Method according to any of  claims 1  to  9 , characterized in that the contact of the opposite principal face or faces of the article with the colouring agent is performed by dipping in a colouring bath containing the colouring agent.  
     
     
         11 . Method according to  claim 10 , characterized in that the colouring bath contains a surface-active alkyl benzene sulfonate.  
     
     
         12 . Method according to any of  claims 1  to  11 , characterized in that it includes, after the step b), c) a thermal stabilization treatment to fix the colouring agent.  
     
     
         13 . Method according to  claim 12 , characterized in that the thermal stabilization treatment consists of heating the article to a temperature of 100 to 140° C. for 1 hour or more.  
     
     
         14 . Method according to  claim 13 , characterized in that the thermal stabilization treatment consists of heating the article to 130° C. for 2 hours.  
     
     
         15 . Method according to any of  claims 1  to  14 , characterized in that the colouring agent is selected from the azo dyes, the anthraquinone dyes and their mixtures.  
     
     
         16 . Method according to any of  claims 1  to  14 , characterized in that the colouring agent is selected from the photochromic compounds and their mixtures.  
     
     
         17 . Method according to any of  claims 1  to  16 , characterized in that it comprises the application of a layer of a hard anti-abrasion material onto at least one of the opposite principal faces of the article on which the polycarbonate material has been photodegraded.  
     
     
         18 . Method according to  claim 17 , characterized in that the hard anti-abrasion material is a (meth)acrylic resin.  
     
     
         19 . Method according to  claim 17 , characterized in that it comprises, prior to the deposit of the layer of hard anti-abrasion material, a deposit on said face of the article of a primer layer favorizing the adhesion of the layer of hard anti-abrasion material.  
     
     
         20 . Method according to  claim 19 , characterized in that the primer is selected from the thermoplastic polyurethanes, the thermosetting polyurethanes, the poly(meth)acrylic latexes, and the polyurethane latexes.  
     
     
         21 . Method according to one of claims  19  or  20 , characterized in that the hard anti-abrasion material results from the setting of a hydrolysate of epoxysilane.  
     
     
         22 . Method according to  claim 21 , characterized in that the hydrolysate contains a colloidal filler, selected from SiO 2 , TiO 2  and Sb 2 O 5 .  
     
     
         23 . Method according to any of  claims 17  to  22 , characterized in that it comprises the deposit of a layer of an anti-reflection material onto the layer of hard anti-abrasion material.  
     
     
         24 . Method according to any of  claims 1  to  23 , characterized in that the article is an optical or ophthalmic article.  
     
     
         25 . Method according to  claim 24 , characterized in that the article is a spectacle lens.  
     
     
         26 . Transparent article made from polycarbonate not containing polyester groups, characterized in that it contains at least one photodegraded surface layer on one of the principal faces of the article and having a thickness of at least 1 to 2 μm in which is diffused a colouring agent, within a thickness of at least 1 to 2 μm.  
     
     
         27 . Transparent article according to  claim 26 , characterized in that it contains two photodegraded surface layers on two opposite principal faces of the article with a thickness of at least 1 to 2 μm in which are diffused a colouring agent, within a thickness of at least 1 to 2 μm.  
     
     
         28 . Article according to claims  26  or  27 , characterized in that the thickness of the photodegraded surface layer or layers is from 2 to 20 μm, preferably 2 to 10 μm.  
     
     
         29 . Article according to any of  claims 26  to  28 , characterized in that the colouring agent is diffused throughout the entire thickness of the photodegraded surface layer or layers.  
     
     
         30 . Article according to any of  claims 26  to  29 , characterized in that the polycarbonate material is a bisphenol A homopolycarbonate.  
     
     
         31 . Article according to any of  claims 26  to  30 , characterized in that the polycarbonate material contains a UV absorber.  
     
     
         32 . Article according to any of  claims 26  to  31 , characterized in that it contains a layer of a hard anti-abrasion material on at least the face corresponding to the photodegraded surface layer.  
     
     
         33 . Article according to  claim 32 , characterized in that it contains a primer layer favorizing the adhesion between said face of the article and the layer of hard anti-abrasion material.  
     
     
         34 . Article according to  claim 33 , characterized in that the hard anti-abrasion material results from the setting of a hydrolysate of epoxysilane  
     
     
         35 . Article according to claims  33  or  34 , characterized in that the primer layer is obtained from a thermoplastic polyurethane, a thermosetting polyurethane, a poly(meth)acrylic latex, a polyurethane latex or a mixture of these latexes.  
     
     
         36 . Article according to any of  claims 26  to  35 , characterized in that it contains a layer of primer and a layer of hard anti-abrasion coating on each of its principal faces.  
     
     
         37 . Article according to any of  claims 32  to  36 , characterized in that it contains an anti-reflection layer on the layer or layers of hard anti-abrasion material.  
     
     
         38 . Article according to any of  claims 26  to  37 , characterized in that the article is an optical or ophthalmic article.  
     
     
         39 . Article according to  claim 38 , characterized in that the article is a spectacle lens.