MXPA99000141A - Formulation of polycarbonate and carrier for semiconductor wheels that is opacial at certain wave lengths of the - Google Patents

Abstract

An aromatic polycarbonate composition and articles made therefrom having less than 300 parts per billion each of ionic impurities, particularly sulfate and chloride ions, which are prepared by devolatilizing the ionic impurities of a polycarbonate composition using an aqueous medium of about 1% by weight, based on the weight of the polycarbonate composition, the devolatilization is preferably carried out in an extruder during the combination of the polycarbonate composition and preferably under vacuum, the extracted polycarbonate resin strands are also cooled , in water bath that have a content of sulfate and chloride ions of less than 300 ppb each u

Description

FORMULATION OF POLYCARBONATE AND CARRIER FOR SEMICONDUCTOR OBLEAS WHICH IS OPACIOUS AT CERTAIN WAVE LENGTHS OF THE LIGHT INTERREFERENCE TO RELATED REQUESTS This application is a Request for continuation in part of the serial number of E.U.A. 08 / 832,722, filed on April 11, 1997.

FIELD OF THE INVENTION The present invention is directed to a thermoplastic aromatic polycarbonate composition having reduced ionic impurities while maintaining good processability properties. The product is a high quality polycarbonate resin for producing high quality molded articles, such as hard disk carriers for computer device or silicon wafer carriers for microcircuits for the computer industry. More specifically, this invention is directed to an improved process and to an improved product from such a process, as described herein.

BACKGROUND OF THE INVENTION The polycarbonate resin can often contain certain impurities which can at the same time affect its performance of 5 properties in the final molded article. For example, sulfate and chlorine ions, if present in sufficient amounts, will affect the color and processing capacity of polycarbonate resins to produce carriers of silicon wafers for pre-microcircuits or carriers of the hard drive for computer device. The sulfate ions can react with the residual ammonia on the surface of the silicon wafer to form ammonium sulfate which forms a white residue on the surface of a silicon wafer for pre-microcircuit. The wafer then requires cleaning before being transformed into a microcircuit for a computer. The additional exposure of the heat phase, such as injection molding, extrusion or combination of the B themselves can also induce the coloration of the polycarbonate resin. Even with phosphite stabilizers, you can The degradation of the polycarbonate and the hydrolysis of the phosphite occur at processing temperatures. It is believed that phosphites, which are susceptible to hydrolysis at elevated temperatures or processing, form acid species in situ that can then react with polycarbonate to increase Possibly the chain scission and produce side reactions that can finally generate color in the molded article. This undesirable process can also occur during the extrusion, the combination or the molding of the polycarbonate resin. In addition, to achieve or improve desirable properties, certain additives are typically employed with the polycarbonate resin during extrusion, blending or injection molding. It is desirable that such additives do not adversely affect processability. Additionally, it is known that they stabilize the polycarbonate resins against discoloration by using phosphites and / or epoxies as stabilizing additives. These stabilizing additives are extensively set forth in U.S.A. such as 4,381,358, 4,358,563 and 3,673,146. However, if certain known impurities can be removed without the use of additives to neutralize the impurities, the removal of the impurities would greatly enhance the properties of the polycarbonate composition. In addition, the elimination of the additives would avoid the possibility of reducing the processing capacity, as may occur with the additives. The typical processing of silicon wafers for microcircuit involves coating the silicon wafer of a photocurable substance polymerizable with ultraviolet radiation and irradiating the photocurable substance according to the image to decorate the wafer. Specifically, the wafer coated with a photohardenable substance is exposed to ultraviolet light through a mask, which is printed with a decorative pattern corresponding to the circuit system to be constructed on the silicon wafer. Ultraviolet light polymerizes the exposed areas of the photocurable substance. The silicon wafer is then washed with a solvent, which dissolves the coating areas of the photoresist that has not polymerized, but leaves the polymerized areas. The wafer was then decorated, for example, by metallizing the wafer. The polymerized photoresist is then removed, then leaving a wafer that is metallized in the areas where the ultraviolet light was allowed to penetrate through the mask. It is critically important to avoid dust or any other form of contamination when treating silicon wafers for pre-microcircuit. It is also desirable to make very large amounts of particular silicon microcircuits. Therefore, when possible, manufacturing separations are made with machines that maintain a dust-free atmosphere. It can therefore be advantageous if the silicon wafer carrier for the pre-microcircuit is transparent at some wavelengths of light, so that a robotic device can determine how many wafers there are in a particular carrier based on the reflected light. However, as indicated above, it is also desirable that the silicon wafer carrier for the microcircuit prior be opaque to the wavelengths of light that could cause the polymerization of the photocurable substance. Therefore, it is an object of this invention to provide a method for reducing ionic impurities in a polycarbonate resin. Another object of this invention is to reduce the ionic impurities in a polycarbonate resin during the melt mixing of the polycarbonate composition. Still another object of the invention is to reduce the sulfate and chloride ions in polycarbonate resins. Still another object of the invention is to produce a polycarbonate resin having reduced ionic impurities. Another object of the invention is to provide a silicon wafer carrier for a microcircuit which can be sealed with a clean atmosphere. It is a further object of the invention that a human being can see how many wafers are present in such a carrier without having to open the carrier in a properly clean atmosphere. It is another object of the invention to provide a polycarbonate resin composition having reduced ionic impurities wherein the polycarbonate resin composition is opaque at the wavelengths of light that may cause the polymerization of the photocurable substances useful in the manufacture of semiconductor microcircuits, wherein the same polycarbonate resin compositions are also transparent at certain wavelengths of visible light. It is still another object of this invention to provide a suitable hard disk carrier for a computer device or a silicon wafer carrier for a prior microcircuit that overcomes the disadvantages of the prior art. It is a further object of this invention to provide a silicon wafer carrier for a prior microcircuit that is opaque to the wavelengths of light that can cause the The polymerization of the photoresistible substances useful in the manufacture of semiconductor microcircuits, where the same carrier is also transparent at certain wavelengths of visible light.

BRIEF DESCRIPTION OF THE INVENTION This invention is directed to a polycarbonate flfe composition having reduced ionic purities and a process for producing reduced ionic impurities in polycarbonate resins. This invention is also directed to an aromatic polycarbonate composition having reduced ionic impurities. The polycarbonate composition can be injection molded (e.g. to produce a silicon wafer carrier for pre-microcircuit), Extrude by forming sheet or film, extrude in profile, extrude in profile, or extrude by blow molding.

A polycarbonate formulation is also provided which has reduced ionic impurities * and has specific light transmission qualities that allow it to be transparent at least at certain wavelengths of visible light, or also be opaque to the wavelengths of the light that cause the polymerization of photocurable substances that are known to be useful in the manufacture of semi-circular microcircuits.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 depicts an ultraviolet-visible light spectrograph of a polycarbonate formulation according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION The process of this invention comprises the devolatilization of the impurities downstream in a melt mixing process, such as an extruder during the combination of the aromatic polycarbonate resin formulation using the aqueous medium. A small amount of the aqueous medium, preferably water, may be added to the formulation during melt mixing in an extruder, then removing the ionic impurities by devolatization, generally, under a downstream vacuum in an extruder. Although the removal of sulfate ions is the preferred ion removal, it has been found that other ions, such as chloride ions, are also removed. Each of the sulfate and chloride ions is preferably reduced to levels of less than 300 parts per billion (hereinafter, ppb). A fusion mixing process, the formulation is extruded through the mold to form strands that retransform into pellets. The strands, before forming the pellets, are passed through a cooling bath or extension of aqueous medium. Since water has a considerably high ionic strength, namely sulfate and chloride ions, polycarbonate resin stocks are re-contaminated with these ions. Therefore, the process of this invention further requires the use of an aqueous cooling bath through which extruded strands having low ion concentration, particularly a low content of chloride sulfate ions, are passed through. Therefore, the water bath should be analyzed at least in terms of concentration of chloride sulfate ions that should be less than each one or at least should be deionized water. The methods of blending or blending the aromatic polycarbonate resin as used herein are well known to those skilled in the art in combination and melt mixing giving aromatic polycarbonate formulation, respectively. In addition, these procedures will be disclosed in numerous articles and patents for preparing polycarbonate molding formulations. Preferably, the melt is at least melt blended or mixed with the additive materials, generally, in an extruder. The combined formulation is extruded into strands which are generally cooled in an aqueous bath, pelletized, dried and transformed with heat and pressure into the finished article. The finished item can be injection molded, extruding the profile, in film, coextruding or extruding by blow molding in hollow configurations, such as multiple plastic objects, such as bottles, hard disk carriers for computer devices carrying silicon microcircuit wafer for the industry of the computers. A small amount of an aqueous medium is added to the combination formulation to enhance the removal of ionic impurities. An aqueous cooling bath having a low concentration of ions is also used to prevent the reintroduction of ionic impurities. Such an aqueous medium, preferably water, uses sufficient amount to reduce the ionic impurities particularly the sulfate and chloride ions to less than about 300 ppb. The amount of aqueous medium added is from about 0.25 to about 2.0% by weight, based on the weight of the polycarbonate formation, and preferably from about 0.65 to about 1.5% by weight. It has been found that approximately 1.0% is optimal. Aqueous cooling or cooling should have a low concentration of ions, preferably in the concentration of sulfate and chloride ions are respectively less than about 300 ppb and if not 5 each in particular of not more than about 100 ppb and if not each more particularly of approximately 50 ppb. The aqueous medium is preferred to the ingredients in the extruder feed hopper or it may be added downstream to the molten bath. 10 Obviously, the aqueous medium must be added before the Devolatilization of the aqueous medium and elimination of ionic impurities. The aqueous medium can be added as a single or can be added in several increments, such as part in the feed hopper and the remainder down in the extruder or the increment is down from the feed hopper. The aromatic polycarbonate resin employed herein may be any of the known aromatic polycarbonates B or copolymers or terpolymers thereof, or mixtures of polycarbonates with other polymers, copolymers or terpolymers thereof. The aromatic polycarbonate used in the practice of this invention can be prepared by reacting a dihydric phenol with a carbonate precursor in the presence of an acid receptor and generally a molecular weight regulator. Any phenol can be used dihydric in the preparation of the polycarbonate resin disclosed herein. Preferably, they are mononuclear or polynuclear aromatic compounds which contain as functional groups two hydroxyl radicals, each of which is directly linked to a carbon atom of an aromatic nucleus. Examples of some of the dihydric phenols which can be employed in the practice of this invention are bisphenols, such as 1,1-bis- (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, 4,4, -bis (4-hydroxyphenyl) heptane, etc .; the dihydric phenol ethers, such as bis (4-hydroxyphenyl), bis (3,5-10-dichloro-4-hydroxyphenyl) ether, ether, dihydroxy diphenyl, such as p, p'-dihydroxyphenyl, 3,3'-dichloro -4,4'-dihydroxy diphenyl, etc., dihydroxyaryl sulfones, such as bis (4-hydroxyphenyl) sulfone, bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, bis (3-methyl-5-ethyl-4) -hydroxyphenyl) sulfone, etc., dihydroxy benzenes, resorcinol, hydroquinone; substituted with halogen and alkyl, such as 1,4-dihydroxy-2-chlorobenzene, 1,4-dihydroxy-2,3-dichlorobenzene, 1,4-dihydroxy-2-methylbenzenes, etc .; and dihydroxy and diphenyl sulfoxides, such as bis (4-hydroxyphenyl) sulfoxide, bis (3,5-dibromo-4-hydroxyphenyl) sulfoxide, sulfoxides, etc. The carbonate precursor used in the practice of this invention can be either halide or halogen carbonyl formate. The carbonyl halides that can be used herein are carbonyl bromide, carbonyl chloride, carbonyl fluoride, etc; or mixtures thereof. Suitable halogen formates for use herein include bishalogenoformates of dihydric phenols (hydrochloride bischloroformates, etc.) or glycols (bishaloformate ethylene glycol, neopentyl glycol, polyethylene glycol, etc.). Although other carbonate precursors will occur to those skilled in the art, it refers to carbonyl chloride, also known as phosgene. The reaction disclosed above is preferably known as a process or interfacial reaction between the dihydric compound and the carbonyl chloride / such as phosgene. Another method for preparing the aromatic polycarbonate of this invention is the transesterification process involving the transesterification of an aromatic hydroxy compound and a diester carbonate. This method is known as the interfacil fusion process. In the practice of this invention, the process for producing the aromatic polycarbonate is not critical. The critical aspect of this invention is to prepare the aromatic polycarbonate resin formulation by volatilization of aqueous medium containing ionic impurities as described above. As used herein, aromatic polycarbonate should include and include any of the aromatic polycarbonates and combinations thereof as set forth above. The polycarbonate composition of the invention may also include additives such as stabilizers or tablets, thermal stabilizers, release agents, Teflon, fillers and fillers, such as fiberglass (short or long glass fibers), carbon fibers, talc, silica and other known additives used in polycarbonate compositions. However, for applications in which it is important that the molded article has low content of volatile substances (for example, hard disk carriers for computer devices on silicon wafer carriers for prior microcircuits), it is necessary that the additives select carefully based on this criterion. For example, many fillers that form a matrix instead of a homogeneous mixture with polycarbonate should not be used, since they can produce dust, which should be avoided in the manufacture of hard drives to electronic microcircuits. In applications such as an optical filtration transport device used for storing and sending photosensitive electronic devices it is advantageous to add a radiation absorbing additive to the polycarbonate optical filtration obstacles. The transport device simultaneously avoids the contamination of photosensitive semiconductor device and deflects by filtering the wavelengths of the light that would react with the photosensitive device (for example light-cured a coating of photocurable substance). In a preferred embodiment of the transport device, less than 3% of the light having wavelengths between 250 and 450 nm is transmitted through the transport device, while at least 25% of a certain length of light is transmitted. light wave between 600 nm and 1500 nm. In this preferred embodiment, the level of degassing measured to an atmosphere is 100 ° C by the technique described above is less than 0.5% by weight of the polycarbonate and the chloride content and the lixibishable sulfate content is less than 300 ppb. In a more preferred embodiment of the invention, the transport device transports less than 25 of the light having a wavelength of 390 and 500 nm and transmitting at least 20% of a certain visible wavelength of the light. In a still more preferred embodiment of the invention, the transport device transmits less than 0.5% of light having a wavelength between 190 and 500 nm and the degassing level measured under the conditions described above is less than 0.1% in weight of the polycarbonate in the molded transport device. Degassing can be measured by several known techniques. In short, a method involves placing pellets of the product in a sealed container at specified temperature and pressure for a given time. At the conclusion of the specified time, the air space is then released above the pellets inside the container and taken as a sample and analyzed using gas chromatography and mass spectrometry. This method provides a semiquantitative indication of the levels of volatile species that are released at the given temperature and indicate the identity of said species. A more sensitive dynamic method employs an extremely cooled absorber to trap volatile substances that are being eliminated in light that is constantly purged with inert gas. After a while, the trapped materials are desorbed and analyzed for gas chromatography and mass spectrometry. In one measurement, this last test produced a desorption level of 0.5 ppm for a sample made in accordance with the present invention, while a commercial sample produced a desorption level of 31 ppm. The content of lexibiable chloride can also be determined by known methods. For example, the contents can be determined by soaking polycarbonate pellets in pure deionized water at elevated temperature (for example 50-80 ° C) for a predetermined time (for example 1-24 hours). At the end of that time, the pellets are removed and the water injected into a liquid chromatograph using ion exchange separation to detect the chloride ions at the level of parts per million. Alternatively, the ionic content can be determined by dissolving the polycarbonate in a chlorinated solvent, extracting with deionized water the ionic content level of the water as described in example 1. Typical photosensitive electronic devices that are protected by optical filtration transport devices they are the semiconducting wafers of microcricuito previous coated with a photocurable substance sensitive to ultra violet light, but other electronic photosensitive devices could be protected with the transport devices. In a preferred embodiment, the transport device contains a plurality of additives that absorb ultraviolet radiation. In a more preferred embodiment, the transport device contains one or more benzotriazole additives. Suitable benzotriazole additives include the "Tinuvin" additives sold by Ciba Geigy. A list of smooth additives, along with their chemical structures, is available from the Ciba Specialty Chemicals Corporation Catalog and the MSDS sheets and associated technical data sheets, which is incorporated herein by reference. In a highly preferred embodiment a transport device contains a dye together with a plurality of benzotriazole additives.

DETAILED DESCRIPTION OF THE EXAMPLES OF THIS INVENTION This invention can be described in more detail by means of the following examples; it being understood, however, that this invention will not be restricted in any way by these examples. In the examples, where the amounts are in terms of percent, they will be in percent by weight.

EXAMPLE 1 Four samples, each of approximately 100 g of a polycarbonate resin, were prepared as follows: Sample A was an aromatic polycarbonate powder having an intrinsic viscosity of approximately 0.50 deciliters / gram (dl / g), as measured at 20 ° C in methylene chloride. The polycarbonate powder was not melt extruded in an extruder. Sample B was prepared using the polycarbonate powder of sample A by melt blending in an extruder a polycarbonate powder formulation of sample A and common mold release additives, thermal stabilizers and colorants. This sample was melted in a vented extruder at approximately 330 ° C and at an extrusion pressure of approximately 84.35 kg / cm 2. The strands extracted from sample B are cooled in a water bath, using regular water from the city. Sample C is also an aromatic polycarbonate powder but had an intrinsic viscosity of about 0.45 dl / g which was determined under the conditions used with sample A. The sample C was not extruded either by melting in an extruder. Sample B was prepared using a polycarbonate powder from sample C and melt-blended in an extruder under the same conditions as the extruder used with sample B. The formation was essentially the same as The formulation of sample B except that 1.0% by weight of water of the formulation was added, based on the weight of the formulation. Downstream of the extruder, the formulation is devolatilized at a vacuum greater than about 50.8 cm of mercury through the vent hole of the extruder. The water bath used to cool the extracted polycarbonate strands of the deionized water that had a content of sulphate of approximately 12 ppb and a chloride content of B approximately 12 ppb. Each formulation contained the same weight percentage of common additives. Each formulation was analyzed by analysis of ion chromatography (IC) in terms of the content of sulfate and dichloride ions. The results obtained were as follows in Table 1 below. The test method consists of dissolving B about 4-5 g of the polycarbonate sample in 25 ml of methylene chloride. Then, lotions were extracted with 15 a 20 ml of deionized water. A 5 ml aliquot of deionized water extracted on an ion chromatograph is injected to determine total free lotions in the sample.

TABLE 1 Sample Free content Total ion content of tota 1 of chloride sulfate A 565 1945 B 450 550 C 525 1555 D 276 156 EXAMPLE 2 This example is exposed to show the amount of leachable sulfate and dichloride ions that accumulate on the surface of the polycarbonate resin strands by the city's simple water compared to the deionized water after passing the strands of the resin polycarbonate through an aqueous cooling medium. The amount of leachable ions is totally that of those ions on the surface of the polycarbonate strands collected from the water bath. In this test procedure, 25 ml of deionized water is added to 9 comparison with the deionized water after passing the strands of the polycarbonate resin through an aqueous cooling medium. The amount of leachable ions is totally that of those ions on the surface of the polycarbonate strands collected from the water bath. In this test procedure, 25 ml of deionized water is added to approximately 10 g of the polycarbonate sample. The sample is then kept in an oven at 55 ° C for approximately 16-20 hours. A 5 ml aliquot of deionized water extracted from the sample is injected onto an ion chromatograph to determine leachable free lotions on the surface of the polycarbonate as it is collected in the cooling water bath. Close pellets of D of example 1 above and pellets of sample E which is prepared according to the procedure for preparing sample D above, except that the cooling water bath uses common water from the city instead of deionized water. The results obtained were as follows: TABLE 2 Ixible leachable Ions of sulfate chloride Pellets of the 10 20 sample D Pellets of the 50 100 sample E As can be seen from the examples, a polycarbonate composition employs some formulation during the combination, then the devolatilization of the water is probably in the form of water vapor after the cooling of the extracted cells in a water bath having low ion concentration, reduces the ionic impurities of polycarbonate formulations, particularly sulfate and dichloride ions.

EXAMPLE 3 This example is set forth to show the elaboration of a polycarbonate formulation that is transparent to at least a visible range of wavelengths of light, but that is opaque at wavelengths of light that could cause the polymerization of solidifiable self-reversing substances with ultraviolet light. A sample of approximately 3000 g of a polycarbonate formulation was prepared by melt blending in an extruder the following formulation: TABLE 3 Component Parts by weight Linear polycarbonate, Pm-30, 000-60, 000 100.0 Organic Phosphite Stabilizer 0.03 Organic ester mold release 0.30 Benzotriazole UV max 312,353 nm 1.00 Benzotriazole UV max 300,34053 nm 2.00 Organic phthaloperinone solvent 380-520 nm 0.08 The extruder produces a polycarbonate formulation transformed into pellets. A visible ultraviolet scan of this formulation was then prepared by the following procedure. First, a color microcircuit having the dimensions of 50.8 mm x 76.2 mm x 2.3 mm was prepared in a machine for injection molding at a temperature of 287.7 ° C. Second, the microcircuit was placed on a sample holder and inserted into the analyzer beam of a Varian Cary-5 Scanning UV-Visible spectrometer. The microcircuit was scanned over a range of wavelengths between 190 and 830 nm. Figure 1 represents the spectrogram of the formulation. Note that the formulation has very low transmission for wavelengths shorter than 500 nm.

EXAMPLE 4 This example is presented to show how an optical filtration transport device will be used to transport photosensitive electronic devices. The pellets of the polycarbonate formulation this were injected by injection according to example 3, by means of known methods to produce a transport device having a plurality of vertical spacers suitable for holding the discs. Although the invention has been described with reference to particular illustrative embodiments thereof, many variations and modifications of this invention are for the sake of those skilled in the art, the spirit and scope of this invention is desired, as set out in the appended claims. the same,

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. - A polycarbonate formulation containing: polycarbonate having less than 300 parts per billion - of sulfate ions and less than 300 parts per billion of chloride ions and a radiation absorbing additive, characterized in that the formulation transmits less than 3% of light having any band length between 250 and 450 nm, and transmitting at least 25% of a certain wavelength of light between 600 nm and 1500 nm, and because said formulation exhibits degassing levels of 1 atm and 100 ° C of less than 0.5% by weight of polycarbonate.

2. A polycarbonate formulation according to claim 1, further characterized in that the formulation transmits less than 2% of light having any wavelength between 190 and 500 nm, and transmits at least 70% of a certain length of visible wave of light.

3. A polycarbonate formulation according to claim 2, further characterized in that the formation transmits less than 0.5% of light having a wavelength range of between 190 and 500 nm.

4. - A polycarbonate formulation according to claim 3, further characterized in that the formulation exhibits degassing levels at 1 atm and 100 ° C of less than 0.1 wt% polycarbonate.

5. - A polycarbonate formulation according to claim 1, further characterized in that the formulation contains a plurality of absorbing additives of 5 radiations.

6. A polycarbonate formulation containing: a greater part of polycarbonate and a radiation absorbing additive, characterized in that the formulation transmits less than 3% of light having any length of 10 wave between 250 and 450 nm and transmits at least 25% of a certain wavelength of light between 600 nm and 1500 nm and because the formulation exhibits degassing levels at 1 atm and 100 ° C of less than 0.5% by weight of polycarbonate, which formulation is made of a process comprising: mixing by Melting a polycarbonate resin with sufficient aqueous medium to reduce the concentration of ionic impurities, the greater part of which consists of sulfate and chloride ions, of j? K less than about 300 parts per billion of sulfate ions and ions of chloride as determined by 20 ion chromatography; devolatilize the water with ionic impurities from the composition; extruding the polycarbonate resin together with the radiation absorbing additive into a cooling bath in an aqueous medium, bath having an ionic impurity concentration ionic.

7. An optical filtration transport device having a plurality of spacers suitable for holding a plurality of disks, a device that includes a polycarbonate formulation containing polycarbonate with less than 300 parts per billion of sulfate ions and less than 300 parts per billion chloride ions, and a radiation absorbing additive; because the formulation transmits less than 3% light having any wavelength between 250 and 450 nm and transmits at least 25% of a certain wavelength of light between 600 nm and 1500 nm, and because the formulation exhibits degassing levels at 1 atm and 100 ° C of less than 0.5% by weight polycarbonate.

8. A polycarbonate formulation containing: polycarbonate having less than 300 parts per trillion sulfate ions and less than 300 parts per trillion chloride ions, and a radiation absorbing additive; because the formulation is transparent to at least a certain range of wavelengths of visible light, but is opaque to wavelengths of light that can cause the polymerization of photocurable substances that are useful in the fabrication of semiconductor microcircuits.

9. A polycarbonate formulation according to claim 8, further characterized in that the formulation is opaque

10. - A polycarbonate formulation according to claim 9, further characterized in that the radiation absorbing additive is a benzotriazole.

11. A polycarbonate formulation according to claim 9, which contains a plurality of radiation absorbing additives.