Patent Publication Number: US-2013251954-A1

Title: Multilayered carbonate sheets

Description:
This invention relates to light transmissive panels in general and, in particular, to a multilayer thermoplastic carbonate sheet or a multilayer thermoplastic carbonate film with improved thermal insulation. 
     BACKGROUND OF THE INVENTION 
     With an increased awareness of energy use and sustainability, it is important to limit heat loss for transparent panels and sheets in building and construction applications. In this regard, it is desirable to increase the thermal insulation for these panels or sheets and trend is to provide such panels and sheets with a U value smaller or equal to 1 W/m 2 K. (U=1/R, where R is the thermal resistance, R=R(radiation)+R(conduction)+R(convection)). 
     Another important problem concerns the resistance of the transparent structures to the weather. The mechanical characteristics of the transparent structures must be able to withstand the weather in all conditions. Thus, it would be desirable to provide a panel for use as transparent structures having increased light transmission with a combination of good insulating properties, improved durability, and reduced maintenance requirements. 
     One suggestion to these problems is polycarbonate multi-walled sheet structures. The typical multi-walled sheet structures have about 3 to 5 layers, e.g., a triple wall sheet. A triple wall sheet has two external walls and one internal wall. Each external wall has an exterior surface and an interior surface. For a multi-walled sheet with three or more walls, the interior wall&#39;s surfaces are generally designated as the interior upper surface or interior lower surface. Typically a series of ribs are provided along the length of the sheet structures to separate the layers, provide stability, and create an insulation layer between the walls. While the insulating effectiveness of such a structure may be acceptable, providing additional walls and thus greater insulation would be desirable. A limiting factor to the creation of sheets having more walls or layers, i.e., seven, eight or more is the processing of the material used to create the multi-walled sheets through the extruder and die. Thus, known plastic resins used to create three to five to seven layer multi-walled sheets will if they are used in an attempt to create a multi-walled sheet having seven eight or more walls, result in sagging of the sheet geometry and very low line speed. 
     SUMMARY 
     In one embodiment, the present invention includes an extruded thermoplastic multi-walled sheet structure formed from a thermoplastic polymer and includes at least two generally parallel walls. Each wall has a first and a second surface and is separated apart from one another by ribs extending the length of the sheet in the direction of extrusion. In another embodiment, the multi-walled sheet structure includes at least seven, eight, nine, or more generally parallel walls, horizontal or under a certain angle, sometimes ten, and other times, ten or more walls. Each wall has a first and a second surface separated apart from one another by ribs extending the length of the sheet in the direction of extrusion. 
     The sheet structure of the present invention comprises a thermoplastic selected from the group of PC, PET, PETG, and PMMA, and generally PC. 
     The sheet structure of the present invention may include one or more of a UV absorber, a near infrared absorption (“NIR”) absorber, a thermal stabilizer, a colorant, a dye, a processing aid, a lubricant, a filler, or a reinforcing aid. 
     In another embodiment, the sheet structure of the present invention can also include a laminated or a coextruded layer of one or more thermoplastic or thermoset resins to provide abrasion/scratch resistance, chemical resistance, ultra violet (UV) radiation resistance, NIR, light scattering reduction, light reflection reduction, dirt accumulation reduction, condensation reduction, antimicrobial, protection from discoloration, protection from haze formation, or protection from cracking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view along the direction of extrusion of a multi-layer sheet structure according to one embodiment of the present invention. 
         FIGS. 2A through 2E  show a cross-section of exemplary rib structures that can be used to separate adjacent walls of the multi-layer sheet structure according to the present invention. 
         FIG. 3  shows the results of the measurement of the viscosity versus the shear rate of a polycarbonate suitable for use in the embodiments of the present invention compared to known polycarbonates. The log of the viscosity is plotted versus the log of the shear rate. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     When a multi-wall sheet is viewed in cross-section (cut across or perpendicular to the plane of extrusion as shown in  FIG. 1 ) with the sheet flat and having the longest dimensions (length and width) in the horizontal plane, there are two or more generally parallel, horizontal walls, also referred to as “layers” or “faces”  10  and a series of ribs  20  that run between the layers along the length direction and separate the layers. These ribs  20  are also sometimes referred to as “webs” or “slats”. While the ribs  20  are shown as vertical or perpendicular to the layers  10 ,  FIGS. 2A to 2E  show several non-limiting alternative rib structures that may be perpendicular  21 , diagonal  22  or combinations of perpendicular and diagonal between and separating the parallel faces  10 . While it is contemplated that each of the illustrated rib designs can be used in combination with each other, for simplicity of manufacturing, it is desired to use a single rib structure throughout the multi-layer structure. 
       FIGS. 2A to 2D  show two layers  10  of the multi-layer sheet structure of  FIG. 1  with each illustrating alternative rib designs.  FIG. 2E  shows three layers of the multi-layer sheet structure of  FIG. 1 . As illustrated in  FIGS. 1 and 2 , the multi-layer sheet has generally flat walls shown as first or upper wall  11  and second or lower wall  12  that are generally parallel to each other. Sheet structures that have at least two or more layers, generally with smooth surfaces, are collectively referred to as “multi-walled” sheets. For example in the case of multi-layer sheets such as the seven layer sheet shown in  FIG. 1 , there are two external walls ( 11  and  12 ) and five internal wall  13 . Each external wall as an exterior surface  14  and an interior surface  15 . For multi-walled sheet with three or more walls, the interior wall&#39;s surfaces are designated as the interior upper surface  16  or interior lower surface  17 . 
     While the external and internal walls have been depicted as being generally flat, it is contemplated that they may have other shapes such as a corrugated shaped wall structure. The term corrugated means having alternating ridges and grooves. The corrugation is in the direction of extrusion and is sometimes referred to as the machine direction or the length of the extruded sheet. The multi-layer sheet structure of the present invention may include both external walls with a corrugated shape. 
     The thickness  50  of the wall is defined as the distance from a first surface of a wall to a second surface of the wall. For example, as depicted in  FIG. 2   a , the thickness  50  of one of the internal walls  13  is the distance between the interior upper surface  16  and the interior lower surface  17 . The wall thickness of the walls of a multi-walled sheet of the present invention independently is equal to or greater than about 0.1 mm, in some cases, equal to or greater than about 0.3 mm, and in other cases, equal to or greater than about 0.5 mm. The wall thickness of the walls of a multi-walled sheet of the present invention independently is equal to or less than about 10 mm, in some cases, equal to or less than about 5 mm, and in other cases, equal to or less than about 1 mm. 
     The rib thickness of a multi-walled sheet of the present invention is equal to or greater than about 0.1 mm, in some cases, equal to or greater than about 0.3 mm, and in other cases, equal to or greater than about 0.5 mm. The rib thickness of a multi-walled sheet of the present invention is equal to or less than about 8 mm, in some cases equal to or less than about 4 mm, and in other cases equal to or less than about 0.8 mm. 
     The desired overall sheet thickness, the number of walls (that is, layers or faces) and the spacing between walls or layers (for example, height of perpendicular ribs) can be selected accordingly to provide desired sheet performance properties. Embodiments of the present invention include at least two spaced apart walls, in some cases, at least five walls, in other cases, at least seven walls, and in still other cases at least ten walls. When more than three layers are used, the interior walls may be located an equal distance from each other and from the upper and lower layers (i.e., one of more are centered with respect to the exterior walls) or closer to one layer or another. 
     A multi-walled sheet of the present invention has a total thickness that is defined as the distance from the exterior surface  14  of the upper wall  11  to the exterior surface  14  of the lower wall  12 . The multi-layer sheet structure of the present invention has total thickness equal to or greater than about 30 mm, in some cases, equal to or greater than about 40 mm, and in other cases, equal to or greater than about 50 mm. A multi-layer sheet structure of the present invention has a total thickness equal to or less than about 100 mm, in some cases equal to or less than about 80 mm, and in other cases equal to or less than about 60 mm. 
     The number and design of the ribs may depend on the structural requirements of the sheet. As noted above and depicted in the figures, the ribs may be vertical  21  (that is, perpendicular the sheet walls), diagonal  22  (including crossing diagonals  23 ), or combinations thereof. When vertical and diagonal ribs are both employed, the diagonal ribs may intersect the wall(s) at the same point that where the vertical ribs intersect  24  or at different points  25  and  26 . When vertical ribs  21  are provided they are spaced from each other a distance equal to or greater than about 10 mm, in some cases, equal to or greater than about 15 mm, and in other cases, equal to or greater than about 20 mm. The rib spacing of vertical ribs is equal to or less than about 30 mm, in some cases, equal to or less than about 40 mm, and in other cases equal to or less than about 50 mm. 
     The multi-layer sheets will generally have an area weight equal to or greater than 3.5 kg/m 2 , in some cases equal to or greater than 4 kg/m 2 , and in other cases equal to or greater than 5 kg/m 2 . The area weight of suitable multi-layer sheets is equal to or less than 8 kg/m 2 , in some cases equal to or less than 7 kg/m 2 , and in other cases equal to or less than 6 kg/m 2 . 
     As recognized by the skilled practitioner, depending upon the need for rigidity, thermal insulation, light transmission, and weathering resistance, the structures of the present invention can be prepared from a broad range of plastic resins. In some embodiments, the multi-walled sheet of the present invention is prepared from one of the known rigid thermoplastic resins including polycarbonate (PC), polypropylene (PP), polystyrene (PS), polystyrene-acrylonitrile copolymer (SAN), butadiene modified SAN (ASS), poly(methyl-methacrylate) (PMMA), poly(ethylene-terephthalate) (PET), glycol-modified PET (PETG), and polyvinyl chloride (PVC). In certain embodiments, the sheet structures are prepared from PC, PET, PETG, and PMMA and in some cases the structure is prepared from PC. 
     The carbonate polymer of the present invention is a thermoplastic aromatic polycarbonate and/or aromatic polyester carbonate. Suitable aromatic polycarbonates and/or aromatic polyester carbonates according to the invention are known from the literature or can be produced by methods known from the literature (for example, for the production of aromatic polycarbonates, see Schnell, “Chemistry and Physics of Polycarbonates”, Interscience Publishers, 1964, as well as U.S. Pat. Nos. 3,028,365; 4,529,791; and 4,677,162; which are hereby incorporated by reference in their entirety. Suitable aromatic polyester carbonates are described in U.S. Pat. Nos. 3,169,121; 4,156,069; and 4,260,731; which are hereby incorporated by reference in their entirety. 
     The production of aromatic polycarbonates is effected, for example, by the reaction of diphenols with carbonic acid halides such as phosgene, and/or with aromatic dicarboxylic acid dihalides, suitably benzenedicarboxylic acid dihalides, by the phase boundary method, optionally with the use of chain terminators, e.g., monophenols, and optionally with the use of trifunctional branching agents or branching agents with a functionality higher than three, for example triphenols or tetraphenols. 
     Diphenols for the production of the aromatic polycarbonates and/or aromatic polyester carbonates may be those of formula II 
     
       
         
         
             
             
         
       
     
     wherein A denotes a single bond, a C 1 -C 5  alkylene, a C 2 -C 5  alkylidene, a C 5 -C 6  cycloalkylidene, —O—, —SO—, —CO—, —S—, —SO 2 —, or a C 6 -C 12  arylene, on to which other aromatic rings, which optionally contain hetero atoms, can be condensed, or a radical of formula III or IV 
     
       
         
         
             
             
         
       
         
         B in each case is independently hydrogen, a C 1 -C 12  alkyl, suitably methyl, or a halogen, such as chlorine and/or bromine; 
         x in each case is mutually independently 0, 1, or 2; 
         p is 0 or 1; 
         R c  and R d  are mutually independent of each other and are individually selectable for each X 1  and are hydrogen or a C 1 -C 6  alkyl, suitably hydrogen, methyl or ethyl; 
         X 1  denotes carbon; and 
         m denotes an integer from 4 to 7, in some cases 4 or 5, with the proviso that R c  and R d  simultaneously denote an alkyl on at least one X 1  atom. 
       
    
     Suitable diphenols are hydroquinone, resorcinol, dihydroxybiphenyls, bis(hydroxyphenyl)-C 1 -C 5  alkanes, bis(hydroxyphenyl)-C 5 -C 6  cycloalkanes, bis(hydroxyphenyl)ethers, bis(hydroxyphenyl)sulfoxides, bis(hydroxyphenyl)ketones, bis(hydroxyphenyl)sulfones and alpha,alpha′-bis(hydroxyphenyl)diisopropylbenzenes, as well as derivatives thereof which have brominated and/or chlorinated nuclei. 
     Desirable diphenols include 4,4′-dihydroxybiphenyl, bisphenol A, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 1,1-bis(4-hydroxyphenyl)-cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4-dihydroxydiphenyl sulfide and 4,4-dihydroxydiphenyl sulfone, as well as di- and tetrabrominated or chlorinated derivatives thereof, such as 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane or 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane. 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A) is an example of a suitable diphenol. The diphenols can be used individually or as arbitrary mixtures. The diphenols are known from the literature or can be obtained by methods known from the literature. 
     Examples of suitable chain terminators for the production of the aromatic polycarbonates include phenol, p-chlorophenol, p-tert-butylphenol or 2,4,6-tribromophenol, as well as long chain alkylphenols such as 4-(1,3-dimethyl-butyl)-phenol or monoalkylphenols or dialkylphenols which contain a total of 8 to 20 C atoms in their alkyl substituents, such as 3,5-di-tert-butyl-phenol, p-iso-octylphenol, p-tert-octylphenol, p-dodecylphenol, 2-(3,5-dimethylheptyl)-phenol and 4-(3,5-dimethylheptyl)-phenol. The amount of chain terminators used is generally between 0.1 mole percent and 10 mole percent with respect to the molar sum of the diphenols used in each case. 
     The aromatic polycarbonates and/or aromatic polyester carbonates of the present invention may have a mean weight average molecular weights of from about 20,000 to about 200,000, in some cases from about 30,000 to about 50,000 and in other cases from about 32,000 to about 45,000 and in still other cases between about 35,000 to about 40,000. Unless otherwise indicated, the references to aromatic polycarbonate and/or aromatic polyester carbonate “molecular weight” herein refer to weight average molecular weights (M w ) determined by gel permeation chromatography (GPC) using laser scattering techniques with a bisphenol A polycarbonate standard and is given in units of grams per mole (g/mole). 
     The aromatic polycarbonates can be branched by incorporating suitable branching agents. Branched polycarbonates suitable for the present invention can be prepared by known techniques, for example several suitable methods are disclosed in U.S. Pat. Nos. 3,028,365; 4,529,791; and 4,677,162; which are hereby incorporated by reference in their entirety. 
     Suitable branching agents that may be used are tri- or multi-functional carboxylic acid chlorides, such as trimesic acid trichloride, cyanuric acid trichloride, 3,3′-,4,4′-benzophenonetetracarboxylic acid tetrachloride, 1,4,5,8-naphthalene-tetracarboxylic acid tetrachloride or pyromellitic acid tetrachloride for example, in amounts of 0.01 to 1.0 mole percent (with respect to the dicarboxylic acid dichlorides used) or tri- or multi-functional phenols such as phloroglucinol, 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)-2-heptene, 4,4-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptane, 1,3,5-tris(4-hydroxyphenyl)benzene, 1,1,1-tris(4-hydroxyphenyl)ethane (“THPE”), tris(4-hydroxyphenyl)-phenyl-methane, 2,2-bis[4,4-bis(4-hydroxyphenyl)cyclohexyl]-propane, 2,4-bis[1-(4-hydroxyphenyl)-1-methylethyl]phenol, tetrakis(4-hydroxyphenyl)-methane, 2,6-bis(2-hydroxy-5-methyl-benzyl)-4-methyl-phenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)propane, or tetrakis(4-[1-(4-hydroxyphenyl)-1-methylethyl]-phenoxy)-methane. A suitable branching agent is THPE. 
     The branching agents can be placed in the reaction vessel with the diphenols. Acid chloride branching agents can be introduced together with the acid chlorides. 
     The branching agents may be incorporated in amounts from about 0.2 wt % to about 1 wt %, in some cases from about 0.3 wt % to about 0.8 wt %, and in other cases from about 0.5 wt % to about 0.7%, and in another case from about 0.6 wt % to about 0.7 wt %, for example about 0.64 wt %. 
     Both homopolycarbonates and copolycarbonates are suitable. For the production of copolycarbonates according to component (i) in accordance with the invention, 1 to 25 parts by weight, suitably 2.5 to 25 parts by weight (with respect to the total amount of diphenols to be used) of polydiorganosiloxanes comprising hydroxy-aryloxy terminal groups can also be used. These are known (see, for example, U.S. Pat. No. 3,419,634) or can be produced by methods known from the literature. 
     Apart from bisphenol A homopolycarbonates, other polycarbonates include the copolycarbonates of bisphenol A with up to 15 mole percent, with respect to the molar sums of the diphenols, of other diphenols which are cited as preferred or particularly preferred, in particular 2,2-bis(3,5-dibromo-4-hydroxyphenyl)-propane. 
     Aromatic dicarboxylic acid dihalides suitable for the production of the aromatic polyester carbonates are the diacid dichlorides of isophthalic acid, terephthalic acid, diphenyl ether-4,4′-dicarboxylic acid and naphthalene-2,6-dicarboxylic acid. Mixtures of the diacid dichlorides of isophthalic acid and terephthalic in a ratio between 1:20 and 20:1 are exemplary. A carbonic acid halide, such as phosgene, is used in conjunction as a difunctional acid derivative during the production of the polyester carbonates. 
     Apart from the aforementioned monophenols, suitable chain terminators for the production of the aromatic polyester carbonates include chlorocarboxylic acid esters thereof, as well as the acid chlorides of aromatic monocarboxylic acids which may optionally be substituted by C 1 -C 22  alkyl groups, or by halogen atoms, and also include aliphatic C 2 -C 22  monocarboxylic acid chlorides. The amount of chain terminator is 0.1 to 10 mole percent in each case, with respect to the moles of diphenols in the case of phenolic chain terminators and with respect to the moles of dicarboxylic acid dichlorides in the case of monocarboxylic acid chloride chain terminators. 
     The aromatic polyester carbonates may also contain incorporated hydroxycarboxylic acids. The aromatic polyester carbonates may be either linear or may be branched. Suitable branching agents are disclosed hereinabove. 
     The proportion of carbonate structural units in the aromatic polyester carbonates can be arbitrarily varied. The content of carbonate groups may be up to 100 mole percent, particularly up to 80 mole percent, and in some cases up to 50 mole percent, with respect to the sum of ester groups and carbonate groups. Both the ester and the carbonate fraction of the aromatic polyester carbonates can be present in the form of blocks, or can be randomly distributed in the condensation polymer. 
     The aromatic polycarbonates and aromatic polyester carbonates can be used individually or in any mixture with each other. 
     The structures according to the invention can also contain or have laminated or coextruded thereto further layers of other thermoplastic or thermoset resins to provide desired performance results, particularly where it is desired to modify the surface(s) of the sheet structure in some fashion, such as for abrasion/scratch resistance, chemical resistance, ultra violet (UV) radiation resistance, near infrared (NIR) absorption, light scattering reduction, light reflection reduction, dirt accumulation reduction, condensation reduction, antimicrobial, protection from discoloration, protection from haze formation, protection from cracking, or the like. The thermoplastic resin may contain the normal type of additives used for their known purposes for these types of resins and structures, including, but not limited to stabilizers such as UV absorbers, NIR absorbers or thermal stabilizers, colorants such as dyes, processing aids such as lubricants, fillers, reinforcing aids, optical brighteners, fluorescent additives, and the like. Such additives can be added to the resins that are used to prepare these structures and/or any layers that may be laminated or coextruded thereto for their known purpose. 
     In suitable embodiments of the present invention the polycarbonate has a melt viscosity measured at a temperature of 260° C. at a shear rate of 100 s −1  equal to or greater than about 10,000 Pa·s, in some cases greater than about 12,000 Pa·s, in other cases, greater than about 14,000 Pa·s, and in other cases greater than 16,000 Pa·s. 
     To achieve an appropriate balance between suitable flow processing considerations and desired structural strength when the resin exits extruder, the inventor has found that suitable polycarbonates useful in the present invention have a defined melt viscosity ratio. The term melt viscosity ratio as used in this specification, drawings and claims refers to the ratio of the viscosity at a shear rate of 100 s −1  to the viscosity at a shear rate of 0.1 s −1  measured at 260° C. When graphically depicted (as in  FIG. 3 ) it is often useful to use the log of the shear rate and log of the viscosity. According to the present invention, the melt viscosity ratio is equal to or greater than about 4.5. In some cases, the melt viscosity ratio is equal to or greater than about 5, in other cases, the melt viscosity ratio is equal to or greater than about 5.5, in other cases, the melt viscosity ratio is equal to or greater than about 6, in still other cases, the melt viscosity ratio is equal to or greater than about 6.5. 
     IR Absorbing Additive 
     Suitable IR absorbers to improve the heat shielding properties of the multilayered article of the present invention are, a metal boride, cesium tungsten oxide, antimony doped tin oxide particles, zinc oxide particles containing at least one element selected from In, Ga, Al, and Sb, tin doped indium oxide particles, other organic or inorganic IR absorbers such as phthalocyanine-based compositions, naphthalocyanine-based compositions, copper sulfide, or copper ion compounds which may be blended into the carbonate compositions of the present invention. 
     The inorganic IR absorbing additives are generally fine particles of a metal boride, particularly a boride such as lanthanum boride (LaB 6 ), praseodymium boride (PrB 6 ), neodymium boride (NdB 6 ), cerium boride (CeB 6 ), gadolinium boride (GdB 6 ), terbium boride (TbB 6 ), dysprosium boride (DyB 6 ), holmium boride (HoB 6 ), yttrium boride (YB 6 ), samarium boride (SmB 6 ), europium boride (EuB 6 ), erbium boride (ErB 6 ), thulium boride (TmB 6 ), ytterbium boride (YbB 6 ), lutetium boride (LuB 6 ), strontium boride (SrB 6 ), calcium boride (CaB 6 ), titanium boride (TiB 2 ), zirconium boride (ZrB 2 ), hafnium boride (HfB 2 ), vanadium boride (VB 2 ), tantalum boride (TaB 2 ), a chromium borides (CrB and CrB 2 ), a molybdenum borides (MoB 2 , Mo 2 B 5  and MoB), tungsten boride (W 2 B 5 ), or the like, or combinations comprising at least one of the foregoing borides. 
     It is desirable for the inorganic IR absorbing additives to be in the form of nanosized particles prior to the dispersion into the thermoplastic and/or thermosetting polymer. There is no particular limitation to the shape of the particles, which may be for example, spherical, irregular, plate-like or whisker like. The nanosized particles may generally have average largest dimensions of less than or equal to about 200 nanometers (nm). In one embodiment, the particles may have average largest dimensions of less than or equal to about 150 nm. In another embodiment, the particles may have average largest dimensions of less than or equal to about 100 nm. In yet another embodiment, the particles may have average largest dimensions of less than or equal to about 75 nm. In yet another embodiment, the particles may have average largest dimensions of less than or equal to about 50 nm. As stated above, the nanosized particles may generally have average largest dimensions of less than or equal to about 200 nm. In one embodiment, more than 90 percent of the particles have average largest dimensions less than or equal to about 200 nm. In another embodiment, more than 95 percent of the particles have average largest dimensions less than or equal to about 200 nm. In yet another embodiment, more than 99 percent of the particles have average largest dimensions less than or equal to about 200 nm. Bimodal or higher particle size distributions may be used. 
     The inorganic IR absorbing additives are generally used in amounts of about 1.2-10 −6  gram/square meter (g/m 2 ) to about 2.0 g/m 2 . In one embodiment, the inorganic IR absorbing additive may be used in amounts of about 6-10 −6  to about 1.0 g/m 2 . In another embodiment, the inorganic IR absorbing additive may be used in amounts of about 0.09 to about 0.36 g/m 2 . In yet another embodiment, the inorganic IR absorbing additive may be used in amounts of about 0.18 to about 0.9 g/m 2 . 
     The inorganic IR absorbing additives are generally used in amounts of equal to or less than about 3000 ppm, in some cases equal to or less than about 2000 ppm, in some cases equal to or less than about 1500 ppm, in some cases equal to or less than about 1250 ppm, in some cases equal to or less than about 1000 ppm, in some cases equal to or less than about 750 ppm, and in other cases equal to or less than about 500 ppm weight percent based on the total weight of the carbonate polymer composition for a specific layer. The inorganic IR absorbing additives are generally used in amounts of equal to or greater than about 0.02 ppm, in some cases equal to or greater than about 1 ppm, in some cases equal to or greater than about 1.5 ppm, and in other cases equal to or greater than about 2.5 ppm based on the total weight of the carbonate polymer composition for a specific layer. 
     UV Absorbing Additive 
     The composition can further comprise one or more UV absorbing additive. Suitable UV absorbing additives are cyanoacrylate compounds, triazine compounds, benzophenone compounds such as 2,4 dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy-2 hydroxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone, 2,2′ dihydroxy-4 methoxybenzophenone, 2,2′ dihydroxy-4,4′dimethoxybenzophenone, 2,2′ dihydroxy-4 methoxybenzophenone, 2,2′,4,4′ tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-5 sulfobenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,2′ dihydroxy-4,4′ dimethoxy-5 sulfobenzophenone, 2-hydroxy-4-(2-hydroxy-3-methylaryloxy)propoxybenzophenone, 2-hydroxy-4 chlorobenzopheone, or the like; benzotriazole compounds such as 2-(2-hydroxy-5-tert-octylphenyl)-benzotriazole, 2-hydroxy-4-n-octoxy benzophenone 2-(2-hydroxy-5-methyl phenyl)benzotriazole, 2-(2-hydroxy-3′,5′-di-tert-butyl phenyl)benzotriazole, and 2-(2-hydroxy-X-tert, butyl-5′-methyl-phenyl)benzotriazole, or the like; salicylate compounds such as phenyl salicylate, carboxyphenyl salicylate, p-octylphenyl salicylate, strontium salicylate, p-tert butylphenyl salicylate, methyl salicylate, dodecyl salicylate, or the like; and also other ultraviolet absorbents such as resorcinol monobenzoate, 2 ethyl hexyl-2-cyano, 3-phenylcinnamate, 2-ethyl-hexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3,3-diphenyl acrylate, 2-2′-thiobis(4-t-octylphenolate)-1-n-butylamine, or the like, or combinations comprising at least one of the foregoing UV absorbing additives. Commercially available UV absorbing additives are TINUVIN™ 234, TINUVIN 329, TINUVIN 350 and TINUVIN 360, commercially available from Ciba Specialty Chemicals; CYASORB™ UV absorbing additives, available from Cytec Industries, such as 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)-phenol (CYASORB 5411); 2-hydroxy-4-n-octyloxybenzophenone (CYASORB 531); 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)-phenol (CYASORB 1164); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one) (CYASORB UV-3638); 1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenyl-acryloyl)oxy]methyl]propane (UVINUL™ 3030); 2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one); 1,3-bis[(2-cyano-3,3-diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenyl-acryloyl)oxy]methyl]propane; 2,2′-methylen-bis-(6-{2H-benzotriazol-2-yl}-4-{1,1,3,3-tetramethylbutyl}-phenol) (LA-31 from Adeka Argus); or 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol (Tinuvin 1577 from Ciba Geigy). For articles formed by extrusion, UVINUL 3030, commercially available from BASF, is specifically useful due to its low volatility. 
     The one or more UV absorbing additive can be used in the carbonate polymer composition independently in amounts of equal to or less than about 15 weight percent, in some cases equal to or less than about 10 weight percent, in some cases equal to or less than about 7.5 weight percent, and in other cases equal to or less than about 5 weight percent based on the total weight of the carbonate polymer composition for a specific layer. The one or more UV absorbing additive can be used in the carbonate polymer composition independently in amounts of equal to or greater than about 0.01 weight percent, in some cases equal to or greater than about 0.1 weight percent, in some cases equal to or greater than about 0.5 weight percent, in some cases equal to or greater than about 1 and in other cases equal to or greater than about 2 weight percent based on the total weight of the carbonate polymer composition for a specific layer. 
     Thermal Stabilizer 
     The composition can contain one or more thermal stabilizers to compensate for the increase in temperature brought on by the interaction of the IR light with the inorganic infrared shielding additives. Further, the addition of thermal stabilizers protects the material during processing operations such as melt blending. In general, an article comprising thermoplastic polymer containing the inorganic infrared shielding additives may experience an increase in temperature of up to about 20° C., upon exposure to light. The addition of thermal stabilizers to the composition improves the long term aging characteristics and increases the life cycle of the article. 
     In another embodiment thermal stabilizers may be optionally added to the composition to prevent degradation of the organic polymer during processing and to improve heat stability of the article. Suitable thermal stabilizers include phosphites, phosphonites, phosphines, hindered amines, hydroxylamines, phenols, acryloyl modified phenols, hydroperoxide decomposers, benzofuranone derivatives, or the like, or combinations comprising at least one of the foregoing thermal stabilizers. Examples include, but are not limited to, phosphites such as tris(nonyl phenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, distearyl pentaerythritol diphosphite or the like; alkylated monophenols or polyphenols; alkylated reaction products of polyphenols with dienes, such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, or the like; butylated reaction products of para-cresol or dicyclopentadiene; alkylated hydroquinones; hydroxylated thiodiphenyl ethers; alkylidene-bisphenols; benzyl compounds; esters of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydric or polyhydric alcohols; esters of beta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid with monohydric or polyhydric alcohols; esters of thioalkyl or thioaryl compounds such as distearylthiopropionate, dilaurylthiopropionate, ditridecylthiodipropionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or the like; tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite (IRGAPHOS™ PEPQ); amides of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid or the like, or combinations comprising at least one of the foregoing antioxidants. Suitable thermal stabilizers that are commercially available are IRGAPHOS 168, DOVERPHOS™ S-9228, ULTRANOX™ 641, or the like. If desirable, an optional co-stabilizer such as a aliphatic epoxy or a hindered phenol anti-oxidant such as IRGANOX™ 1076, IRGANOX 1010, both from Ciba Specialty chemicals may also be added to improve thermal stability of the composition. Desirable thermal stabilizers are phosphites. 
     The one or more thermal stabilizers can be used in the carbonate polymer composition in amounts of equal to or less than about 5 weight percent, in some cases equal to or less than about 3 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 0.5 weight percent, and in other cases equal to or less than about 0.1 weight percent based on the total weight of the carbonate polymer composition. The one or more thermal stabilizers can be used in the carbonate polymer composition in amounts of equal to or greater than about 0.001 weight percent, in some cases equal to or greater than about 0.002 weight percent, in some cases equal to or greater than about 0.005 weight percent, and in other cases equal to or greater than about 0.01 weight percent based on the total weight of the carbonate polymer composition for a specific layer. 
     Antioxidant 
     Examples of antioxidant that may be used in the present invention include hindered phenol-based antioxidants. Specific examples of the hindered phenol-based antioxidants may include pentaerythirtyl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxphenyl)propionate], N,N′-hexane-1,6-di-yl-bis[3-(3,5-di-t-butyl-4-hydroxphenylpropionamide), 2,4-dimethyl-6-(1-methylpentadecyl)phenol, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphate, 3,3′,3″,5,5′,5″-hexa-t-butyl-a,a′,a″-(mesitylene-2,4,6-tri-yl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, ethylene-bis(ox-yethylene)bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-t-butyl-4-dyroxybenzyl)-1,3,5-trazine-2,4,6(1H,3H,5H)-tri-one, 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine-2-yl-amino)phenol, or the like. Of these, pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate are especially preferred. These two phenol-based antioxidants are available as trade names of “IRGANOX 1010” and “IRGANOX 1076” respectively produced by Ciba Speciality Chemicals Corp. 
     One or more antioxidants can be used in used in the present invention. The amount of phenol-based antioxidant that can be used includes amounts of equal to or less than about 2 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 0.5 weight percent, in some cases equal to or less than about 0.4 weight percent, and in other cases equal to or less than about 0.2 weight percent based on the total weight of the carbonate polymer composition. The amount of phenol-based antioxidant can be used in amounts of equal to or greater than about 0.01 weight percent, in some cases equal to or greater than about 0.05 weight percent, and in other cases equal to or greater than about 0.1 weight percent based on the total weight of the carbonate polymer composition for a specific layer. When the content of the phenol-based antioxidant is less than 0.1 weight percent, the effect of antioxidant may be insufficient and when the content of the phenol-based antioxidant is more than 2 weight percent, the effect of antioxidant may be saturated. 
     Antistatic 
     The term “antistatic agent” refers to monomeric, oligomeric, or polymeric materials that can be processed into polymer resins and/or sprayed onto materials or articles to improve conductive properties and overall physical performance. Examples of monomeric antistatic agents include glycerol monostearate, glycerol distearate, glycerol tristearate, ethoxylated amines, primary, secondary and tertiary amines, ethoxylated alcohols, alkyl sulfates, alkylarylsulfates, alkylphosphates, alkylaminesulfates, alkyl sulfonate salts such as sodium stearyl sulfonate, sodium dodecylbenzenesulfonate or the like, quaternary ammonium salts, quaternary ammonium resins, imidazoline derivatives, sorbitan esters, ethanolamides, betaines, or the like, or combinations comprising at least one of the foregoing monomeric antistatic agents. 
     Exemplary polymeric antistatic agents include certain polyesteramides polyether-polyamide (polyetheramide) block copolymers, polyetheresteramide block copolymers, polyetheresters, or polyurethanes, each containing polyalkylene glycol moieties polyalkylene oxide units such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Such polymeric antistatic agents are commercially available, for example Pelestat™ 6321 (Sanyo) or Pebax™ MH1657 (Atofina), Irgastat™ P18 and P22 (Ciba-Geigy). Other polymeric materials that may be used as antistatic agents are inherently conducting polymers such as polyaniline (commercially available as PANIPOL™ EB from Panipol), polypyrrole and polythiophene (commercially available from Bayer), which retain some of their intrinsic conductivity after melt processing at elevated temperatures. In one embodiment, carbon fibers, carbon nanofibers, carbon nanotubes, carbon black, or any combination of the foregoing may be used in a polymeric resin containing chemical antistatic agents to render the composition electrostatically dissipative. 
     Antistatic agents that are suitable for use herein include onium salts of alkyl sulfonates, particularly alkylated and arylated onium salts of perfluorinated alkyl sulfonates. Exemplary onium salts are phosphonium, ammonium, sulfonium, imidazolinium, pyridinium or tropilium salt. Suitable examples are the alkylated ammonium and phosphonium salts of perfluorinated alkyl sulfonates, and particularly alkylated phosphonium sulfonates. Specifically useful phosphonium sulfonates include fluorinated phosphonium sulfonates which can comprise a fluorocarbon containing an organic sulfonate anion, and an organic phosphonium cation. Suitable examples of such organic sulfonate anions include, but are not limited to, perfluoro methane sulfonate, perfluoro butane sulfonate, perfluoro hexane sulfonate, perfluoro heptane sulfonate, perfluoro octane sulfonate, combinations comprising one or more of these, and the like. Suitable examples of the aforementioned phosphonium cation include, but are not limited to, aliphatic phosphonium such as tetramethyl phosphonium, tetraethyl phosphonium, tetrabutyl phosphonium, triethylmethyl phosphonium, tributylmethyl phosphonium, tributylethyl phosphonium, trioctylmethyl phosphonium, trimethylbutyl phosphonium trimethyloctyl phosphonium, trimethyllauryl phosphonium, trimethylstearyl phosphonium, triethyloctyl phosphonium and aromatic phosphoniums such as tetraphenyl phosphonium, triphenylmethyl phosphonium, triphenylbenzyl phosphonium, tributylbenzyl phosphonium, combinations comprising one or more of the foregoing, and the like. Suitable examples of the aforementioned ammonium cation include, but are not limited to, aliphatic ammonium such as tetramethyl ammonium, tetraethyl ammonium, tetrabutyl ammonium, triethylmethyl ammonium, tributylmethyl ammonium, tributylethyl ammonium, trioctylmethyl ammonium, trimethylbutyl ammonium trimethyloctyl ammonium, trimethyllauryl ammonium, trimethylstearyl ammonium, triethyloctyl ammonium and aromatic ammoniums such as tetraphenyl ammonium, triphenylmethyl ammonium, triphenylbenzyl ammonium, tributylbenzyl ammonium, combinations comprising one or more of the foregoing, and the like. A combination comprising at least one of the foregoing antistatic agents may also be used. 
     One or more antistatic agents can be used independently in amounts of about 0.0001 to about 5.0 weight percent, based on the total weight of the carbonate polymer composition for a specific layer. 
     Mold Release 
     Examples of mold release agents useful in the present invention may include at least one selected from aliphatic carboxylic acids, esters of aliphatic carboxylic acid and aliphatic alcohol, aliphatic hydrocarbon compounds having a number-average molecular weight of 200 to 15000 and polysiloxane-based silicone oils. 
     Examples of the above aliphatic carboxylic acids may include saturated or unsaturated aliphatic monocarboxylic acids, dicarboxylic acids and tricarboxylic acids. Here, the aliphatic carboxylic acids also involve alicyclic carboxylic acids. Of these aliphatic carboxylic acids, preferred are C 6  to C 36  mono- or di-carboxylic acids, and more preferred are C 6  to C 36  aliphatic saturated monocarboxylic acids. Specific examples of such aliphatic carboxylic acids may include palmitic acid, stearic acid, caproic acid, capric acid, lauric acid, arachic acid, behenic acid, lignoceric acid, cerotic acid, melissic acid, tetraiacontanioc acid, montanic acid, adipic acid and azelic acid. 
     As the aliphatic carboxylic acid components constituting the ester of aliphatic carboxylic acid and aliphatic alcohol, there may be used the same aliphatic carboxylic acids as described above. Also, as the aliphatic alcohol components constituting the aliphatic carboxylic acid esters, there may be used saturated or unsaturated monohydric alcohols, saturated or unsaturated polyhydric alcohols, etc. These alcohols may have substitute groups such as a fluorine atom, an aryl group or the like. Of these alcohols, preferred are saturated monohydric or polyhydric alcohols having not more than 30 carbon atoms, and more preferred are polyhydric alcohols or aliphatic saturated monohydric alcohols having not more than 30 carbon atoms. Here, the aliphatic alcohols also involve alicyclic alcohols. Specific examples of the alcohols may include octanol, decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol, diethylene glycol, glycerol, pentaerythritol, 2,2-dihydroxyperfluoropropanol, neopentylene glycol, ditrimethylol propane and dipentaerythritol. These ester of aliphatic carboxylic acid and aliphatic alcohol may contain aliphatic carboxylic acids and/or alcohols as impurities, or may be in the form of a mixture of a plurality of compounds. 
     Specific examples of the ester of aliphatic carboxylic acid and aliphatic alcohol may include bees wax (mixtures containing myricyl palmitate as a main component), stearyl stearate, behenyl behenate, stearyl behenate, glycerol monopalmitate, glycerol monostearate, glycerol distearate, glycerol tristearate, penaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate and pentaerythritol tetrastearate or the like. 
     As the aliphatic hydrocarbon compounds having a number-average molecular weight of 200 to 15000, there are exemplified liquid paraffins, paraffin waxes, microwaxes, polyethylene waxes, Fischer-Tropsch waxes, α-olefin oligomers having C 6  to C 12  or the like. Here, the aliphatic hydrocarbon compounds also involve alicyclic hydrocarbon compounds also involve alicyclic hydrocarbon compounds. Further, these hydrocarbon compounds may be partially oxidized. Of these, paraffin waxes, polyethylene waxes and partially oxidized products of polyethylene wax are preferred, and paraffin waxes and polyethylene waxes are more preferred. The number-average molecular weight of aliphatic hydrocarbon compounds is preferably 200 to 5000. These aliphatic hydrocarbon compounds may be used singly or as a mixture of two or more compounds having various components and molecular weights as long as the main constitution has the properties within the above range. 
     As the polysiloxane-based silicone oils, there are exemplified dimethyl silicone oils, phenylmethyl silicone oils, diphenyl silicone oils, fluorinated alkyl silicone oils or the like. These may be used singly or as a mixture of two or more. 
     The amount of mold release agent can be used in the composition in amounts of equal to or less than about 2 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 1 weight percent, in some cases equal to or less than about 0.5 weight percent, in some cases equal to or less than about 0.4 weight percent, and in other cases equal to or less than about 0.2 weight percent based on the total weight of the carbonate polymer composition for a specific layer. The amount of mold release agent can be used in the composition in amounts of equal to or greater than about 0.01 weight percent, in some cases equal to or greater than about 0.05 weight percent, and in other cases equal to or greater than about 0.1 weight percent based on the total weight of the carbonate polymer composition for a specific layer. These mold release agents may be used singly or as a mixture of two or more. 
     Dyes 
     Polycarbonate compositions in optical uses typically are color-corrected, i.e. they contain dyes to adjust the color in order to compensate for the any slightly color shade of the polycarbonate, typically yellow. 
     Dyes that can be employed for adjustment of the color in polycarbonate are in principle all dyes which have a sufficiently high heat stability up to at least 300° C., so that they are not decomposed at the processing temperatures of the polycarbonate. Furthermore, the dyes should not have basic functionalities, which lead to a degradation of the polymer chain of the polycarbonate. 
     Suitable dyes include dyes of the following classes: anthanthrones, anthraquinones, benzimidazoles, diketopyrrolopyrroles, isoindolinols, perinones, perylenes, phthalocyanines, quinacridones and quinophthalones. 
     Dyes suitable for use in the present invention may be organic materials and include, for example, coumarin dyes such as coumarin 460 (blue), coumarin 6 (green), nile red or the like; lanthanide complexes; hydrocarbon and substituted hydrocarbon dyes; polycyclic aromatic hydrocarbon dyes; scintillation dyes such as oxazole or oxadiazole dyes; aryl- or heteroaryl-substituted poly(C 2-8 ) olefin dyes; carbocyanine dyes; indanthrone dyes; phthalocyanine dyes; oxazine dyes; carbostyryl dyes; napthalenetetracarboxylic acid dyes; porphyrin dyes; bis(styryl)biphenyl dyes; acridine dyes; anthraquinone dyes; cyanine dyes; methine dyes; arylmethane dyes; azo dyes; indigoid dyes, thioindigoid dyes, diazonium dyes; nitro dyes; quinone imine dyes; aminoketone dyes; tetrazolium dyes; thiazole dyes; perylene dyes, perinone dyes; bis-benzoxazolylthiophene (BBOT); triarylmethane dyes; xanthene dyes; thioxanthene dyes; naphthalimide dyes; lactone dyes; fluorophores such as anti-stokes shift dyes which absorb in the near infrared wavelength and emit in the visible wavelength, or the like; luminescent dyes such as 7-amino-4-methylcoumarin; 3-(2′-benzothiazolyl)-7-diethylaminocoumarin; 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole; 2,5-bis-(4-biphenylyl)-oxazole; 2,2′-dimethyl-p-quaterphenyl; 2,2-dimethyl-p-terphenyl; 3,5,3″″,5″″-tetra-t-butyl-p-quinquephenyl; 2,5-diphenylfuran; 2,5-diphenyloxazole; 4,4′-diphenylstilbene; 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran; 1,1′-diethyl-2,2′-carbocyanine iodide; 3,3′-diethyl-4,4′,5,5′-dibenzothiatricarbocyanine iodide; 7-dimethylamino-1-methyl-4-methoxy-8-azaquinolone-2; 7-dimethylamino-4-methylquinolone-2; 2-(4-(4-dimethylaminophenyl)-1,3-butadienyl)-3-ethylbenzothiazolium perchlorate; 3-diethylamino-7-diethyliminophenoxazonium perchlorate; 2-(1-naphthyl)-5-phenyloxazole; 2,2′-p-phenylen-bis(5-phenyloxazole); rhodamine 700; rhodamine 800; pyrene; chrysene; rubrene; coronene, or the like, or combinations comprising at least one of the foregoing dyes. 
     MACROLEX™ dyes from Lanxess can be very suitably employed for coloring polycarbonate. A large number of various dyes are available from this product line, e.g. the methine dyes MACROLEX Yellow 6G Gran, the azo dyes MACROLEX Yellow 4G, the pyrazolone dyes MACROLEX Yellow 3G Gran, the quinophthalone dyes MACROLEX Yellow G Gran, the perinone dyes MACROLEX Orange 3G Gran, the methine dyes MACROLEX Orange R Gran, the perinone dyes MACROLEX Red E2G Gran and MACROLEX Red EG Gran and the anthraquinone dyes MACROLEX Red G Gran, MACROLEX Red 5B Gran, MACROLEX Red Violet R Gran, MACROLEX Violet B Gran, MACROLEX Blue 3R Gran, MACROLEX Blue 2B Gran, MACROLEX Green 5B Gran and MACROLEX Green G Gran. 
     WO 99/13007 moreover describes e.g. indigo derivatives which are suitable for dyeing polycarbonate. 
     DE 19747395 describes e.g. benzo(de)isoquinolinobenzo(1,2-d:4,5-d′)diimidazole-2,12-diones which can be employed as polymer-soluble dyess, inter alia in polycarbonate. 
     Suitable dyes are violet and/or blue in color or produce violet and/or blue color in the carbonate polymer compositions of the invention, for example Macrolex Violet 3R Gran (which is a violet dye and sometimes called Solvent Violet 36) and 1,4-bis[(2,6-diethyl-4-methylphenyl)amino]-9,10-anthracenedione, available as Macrolex Blue RR Gran (which is a blue dye and is sometimes called Solvent Blue 97) which are anthraquinone dyes. Such violet and blue dyes may be used in combination in a ratio of from 25:75 to 75:25. 
     One or more dye can be used independently or in combination wherein each dye is independently present in an amount equal to or greater than about 1 ppm, in some cases equal to or greater than about 10 ppm, in some cases equal to or greater than about 25 ppm, and in other cases equal to or greater than about 50 ppm based on the total weight of the carbonate polymer composition for a specific layer. One or more dye can be used independently or in combination wherein each dye is independently present in an amount equal to or less than about 10,000 ppm, in some cases equal to or less than about 5,000 ppm, in some cases equal to or less than about 1,000 ppm, in some cases equal to or less than about 750 ppm, and in other cases equal to or less than about 500 ppm based on the total weight of the carbonate polymer composition for a specific layer. 
     Other Additives 
     In addition to the additives noted above, other additives typically used in transparent polycarbonate compositions can also be employed. For example, flame retardants, optical brighteners, anti-blocking agents, lubricants, anti-fog agents, natural oils, synthetic oils, waxes, or the like. For example, flame retardant additives that leave the composition transparent can be used in one or more layer composition. Preferred flame retardant additives are silicone based flame retardants, phosphorous based flame retardants, brominated flame retardants such as brominated bis-A oligomers (e.g., BC-52 available from CHEMTURA) at levels up to 20 weight percent, C4 charring salts (potassium perfluorobutane sulphonate, available form Lanxess) up to 1500 ppm, KSS (diphenyl sulfone-3-sulfonic acid, potassium salt, available from Seal Sands) up to 1.0 weight percent, alone or in combinations. Another additive that may be used when a UV stabilizer is present is an optical brightener. For example, 2,2′-(2,5-Thiophenediyl)bis[5-tert-butylbenzoxazole] available as UVITEX™ OB from CIBA, 2,2′-(1,2-ethenediyldi-4,1-phenylene)bisbenzoxazole available as EASTOBRITE™ OB-1 from EASTMAN, 2-[4-[4-(2-Benzoxazolyl)styryl]phenyl]-5-methylbenzoxazole, available as HOSTALUX KS-N from CLARIANT. Optical brighteners are typically employed in amounts from 1 to 10000 ppm, in some cases from 2 to 1000 ppm, and in other cases from 5 to 500 ppm. 
     The multi-walled sheet structures of the present invention are prepared by the extrusion through profile dies. Corrugated surfaces may be produced on multi-walled sheet structures of the present invention during the extrusion process for example by using a corrugated calibrator unit or by post embossing the sheet by using an embossing roller. Alternatively, a corrugated film may be laminated or coextruded onto one or more surfaces of one or more walls of a multi-walled sheet. 
     For example, the one or more additives (i.e., IR absorbing additive, UV absorbing additive, mold release, antioxidant, thermal stabilizer, dye, other additives, etc.) may be mixed in the polymerization stage of the carbonate polymer or at the end of the polymerization of the carbonate polymer, or the additives may be mixed in a kneading step under melting conditions of the carbonate polymer, or the additives may be mixed (with a mixer or other means) which is sometimes referred to as dry blended (in either solid or liquid form depending on the particular additive) with the solid state carbonate polymer (usually in the form of powder, pellets, or flake), the mixture melted, and kneaded by use of an extruder (single and twin screw), Buss-kneaders, helicones, WARING BLENDER™, HENSCHEL™ mixer, BANBURY™ mixer, roll mill, or the like and either converted directly into an article, e.g., a (multilayer) extruded sheet, a (multilayer) extruded structural sheet, or comminuted to pellets and subsequently converted into an article, e.g., a (multilayer) extruded sheet. 
     Alternatively, the additives for each carbonate polymer layer composition may be compounded into a masterbatch. A masterbatch can be prepared for use with a carbonate base polymer to prepare the multi-layer structure. As used herein, the term “masterbatch” refers to a dispersion of particles in a carrier resin, and typically is in the form of a pellet or bead formed using a mixing process such as a compounding/extrusion process. Preparing the masterbatch includes melt combining a mixture or dry blend comprising a carrier resin and one or more desired additional components such as, for example, the IR absorbing additive, the UV absorbing additive, antioxidant, mold release, dyes, thermal stabilizer and the like. In one embodiment, the carrier resin is a polycarbonate resin. The masterbatch can be melt combined with a carbonate base polymer and other additives to form the carbonate polymer layer composition. In one embodiment, the base polymer is a polycarbonate resin. In another embodiment, the base polymer is the same as the carrier resin used to prepare the masterbatch. The masterbatch can be combined with the base polymer as described above using a mixer, and extruded. In one embodiment, the masterbatch and base polymer are combined in the hopper at the feedthroat of an extruder. In another embodiment, the base polymer is added to the hopper at the feedthroat of the extruder, and the masterbatch is added to a downstream feedport of the extruder. 
     One process for producing the multi-layer sheet structure from a carbonate polymer layer composition is to independently make a mixture or dry blend of the carbonate polymer and the desired additives using carbonate polymer pellets and the solid/liquid state form of the additive(s) then co-extruding the multiple layer compositions into a multilayer article, such as a multilayer sheet. These mixtures or dry blends may be made and isolated as a physical melt blended mixture of pellets/additives prior to co-extrusion or the mixture may be made in situ and not isolated, for example by metering the components into a feed hopper at the throat of an extruder (via a dosing machine or feeder) and, without isolating the mixture, co-extruding the mixture directly into a multilayer article. 
     Multilayered films, multilayered sheets, or a combination of one or more film with one or more sheet may generally be produced by extrusion followed by laminating the films or sheets in a roll mill or a roll stack (this if for solid film/sheet; for structural sheet, extrusion is followed by calibration through opposite pairs of calibration plates). The extrusion for the identified layers of the multilayered film or multilayered sheet may be performed in a single screw extruder or in a twin screw extruder. It is desirable to extrude the layers in a single or twin screw extruder and to laminate the layers in a roll mill. It is more desirable to co-extrude the layers in a single screw extruder or twin screw extruder. Co-extrusion equipment can simultaneously co-extrude multilayered articles having at least 2, 3, 4, 5, 6, 7, 8, 9, 10, or more layers. Alternatively, a multilayered article having two or more layers may be co-extruded and one or more layer further laminated to said multilayered article, for example in a roll mill. The roll mill may be either a two roll, three roll mill, or four roll mill, as is desired. The opposite pairs of calibration plates can consist out of a single pair, a double pair or a triple pair. Where desired, the layers can be co-extruded using single screw extruders for manufacturing of the multilayered film or sheet. 
     In one method to produce the multilayered article of the present invention, the layers of the multilayered articles are co-extruded (i.e., prepared by multilayer coextrusion). In one embodiment, in one manner of co-extruding of the multilayered sheet, the melt streams (extrudates) from the various extruders are fed into a feed block die where the various melt streams are combined before entering the die. In another embodiment, the melt streams from the various extruders are fed into a multi-manifold internal combining die. The different melt streams enter the die separately and join just inside the final die orifice. In yet another embodiment, the melt streams from the various extruders are fed into a multi-manifold external combining die. The external combining dies have completely separate manifolds for the different melt streams as well as distinct orifices through which the streams leave the die separately, joining just beyond the die exit. The layers are combined while still molten and just downstream of the die. An exemplary die used in the production of the multilayered sheet is a feed block die. In an exemplary embodiment, the extruders used for the co-extrusion of the respective layers of the multilayer sheet are single screw extruders respectively. The co-extruded sheet may optionally be calendared in a roll mill if desired. 
     In the extrusion methods described above, the line speed of the process should be equal to or greater than about 0.5 m/min, in some cases greater than about 1 m/min, in some cases greater than 2 m/min, in some cases greater than 2.5 m/min. The line speed should be equal to or less than about 5 m/min, in some cases less than about 4 m/min, in some cases less than about 3 m/min. 
     In the extrusion methods described above the temperature of the die should be equal of greater than 245° C., in some cases greater than about 255° C., in some cases greater than about 265° C. The temperature in the die should be equal or lower than about 300° C., in some cases less than about 290° C., in some cases less than about 280° C. 
     EXAMPLES 
     A polycarbonate designated as XZR-993 was prepared according to the present invention using 0.64 wt % THPE to provide a polycarbonate having a molecular weight of 37,000, a melt viscosity of 14,800 Pa·s at 260° C., a shear rate of 0.1 s −1 , and a melt viscosity ratio at 260° C. of 6.4. The melt viscosity ratio of the polycarbonate XZR-993 was compared to the following commercially available polycarbonates, which are not part of the present invention. The results are shown in Table 1 and depicted in the graph in  FIG. 3 . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Polycarbonate 
                 Melt Viscosity Ratio 
               
               
                   
                   
               
             
            
               
                   
                 XZR-993 
                 6.4 
               
               
                   
                 Lexan ML3324 
                 3.7 
               
               
                   
                 Makrolon 1143 
                 4.1 
               
               
                   
                 Calibre 603-3 
                 3.7 
               
               
                   
                   
               
            
           
         
       
     
     The suitability of the XZR-993 described above for making a multi wall sheet was investigated. The XZR-993 was extruded on a 150 mm Omipa extruder with Bexsol die and calibrator plates using a melt temperature of 260° C. at a line speed of 0.9 m/min where the die produced a ten wall sheet with vertical ribs that had a total thickness of 55 mm and an area weight of 5 kg/m 2 . The resulting product did not exhibit any sagging, the ribs were vertical (i.e., straight), and the sheet structure was symmetrical. 
     A mixture of two commercially available polycarbonates, 50% Calibre 603-3 and 503-5 was prepared using 0.2 wt % THPE to provide a polycarbonate having a molecular weight of 31,500, a melt viscosity of 4,800 Pa·s at 260° C., a shear rate of 0.1 s −1 , and a melt viscosity ratio of 2.5. This polycarbonate was extruded under the same conditions as the XZR-993, described above. This polycarbonate, however, completely collapsed and no viable sheet structure was produced. 
     A commercially available polycarbonate, Calibre 603-3 was produced with 0.4 wt % THPE, a molecular weight of 33,500, a melt viscosity of 6,500 4,800 Pa·s at 260° C. a shear rate of 0.1 s −1 , and a melt viscosity ratio of 3.7. This polycarbonate was extruded under the same conditions as the XZR-993, described above. The 603-3 exhibited sagging of the sheet structure, ribs that were not vertical, and diamond shaped walls such that the sheet structure was not symmetrical. This sheet structure was not suitable for commercial use. 
     While the invention has been disclosed in several forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims.