91  US 7,511,179 B2  92  A transmitting spectrum at a wavelength of 200 to 100 nm  in a coating film formed by applying each coating composi- For an optical system, refer to Rev. Sic. Instrum., 60(7),  1917 (1989) by H. Namba, et al.  A 100 ml autoclave was charged with 5.5 g of the cyclo› pentene having----C(CF $_{3}$ ) $_{2}$OH group obtained in Example 12,  40 ml ofHCFC-141b and0.7 g ofbis(4-tert-butylcyclohexyl) 65  peroxydicarbonate (TCP), and the inside of a system was  sufficiently replaced with nitrogen gas while cooling with dry  The coating thickness was measured with a AFM device  (SPI3800 available from SEIKO DENSHI KABUSHIKI  KAISHA). The results are shown in Table 1.  Coating films were formed by applying the respective coat› ing compositions under the same conditions as above except  that a silicon wafer was used instead of the MgF $_{2 }$ substrate.  Each coating composition was applied on a MgF $_{2 }$substrate  at room temperature with a spin coater under the condition of  1,000 rpm. After the coating, the coating composition was  baked at 100°  C. for 15 minutes to form transparent coating  films.  (i) Coating on a Substrate (MgF$_{2}$ )  for Measuring Transpar› ency  (ii) Measurement of Coating Thickness  (i) Measuring Device  (ii) Measurement of Transmitting Spectrum  Synthesis of Copolymer Comprising  tetrafluoroethylene and cyclopentene Having  -C(CF$_{3}$ ) $_{2}$OH Group)  having a boiling point of from 62°  to 64°  C./45 mmHg was  obtained. The monomer obtained above was determined by  $^{19}$F-NMR, $^{1}$H-NMR, $^{13}$C-NMR and IR analyses.  Magnesium was put in an amount of 24 g into a I-liter  four-necked glass flask equipped with a blowing tube, dry ice  condenser and dropping funnel and was dried by heating in  vacuo. Thereto was added 200 ml ofTHF, followed by cool- ing in ice bath. A solution obtained by mixing 31 g of previ› ously prepared 3-chlorocyclopentene to 150 ml of THF was  slowly added dropwise through the dropping funnel in a state  of the solution temperature being 10°  to 15°  C. After comple› tion of the addition, hexafluoroacetone was introduced slowly  through the gas feeding tube so that the solution temperature  did not exceed 20°  C. Hexafluoroacetone was introduced  until generation of heat was not recognized. After completion  of the introduction ofhexafluoroacetone, stirring was further  continued at room temperature for three hours. The reaction  mixture was put in 500 ml of 1 N hydrochloric acid, followed  by separating an organic layer, washing with water, drying  and distilling after concentration. As a result, 56.0 g of fluo› rine-containing alcohol represented by the formula:  The fluorine-containing polymers prepared in Examples 1  to 3, 6 to 10 and 13 were dissolved in butyl acetate so that the  concentration thereofbecame 3%, respectively. Thus coating  compositions were prepared.  (3) Measurement of Transparency in Vacuum Ultraviolet  Region  (2) Coating  (1) Preparation of Coating Composition  Measurement of Transparency at a Wavelength of  157 nm  As aresultof1H-NMRand $^{19}$F-NMRanalyses, the copoly› mer  was  one  comprising  TFE/cyclopentene  having  ----C(CF $_{3}$ ) $_{2}$OH group in a percent by mole ratio of 50/50.  A 500 ml four-necked glass flask equipped with a blowing  tube was charged with 100 g of cyclopentadiene, followed by  stirring in nitrogen gas atmosphere while cooling in dry ice/  acetone bath. HCl gas was slowly introduced at a solution  temperature of not more than 0°  C. through a gas feeding tube  and sometimes the flask was separated to measure the weight  thereof. HCl gas was introduced up to 90% of theoretical  amount to synthesize 3-chlorocyclopentene which was not  isolated and used for the following reaction.  Synthesis of cyclopentene Having -C(CF  3 ) $_{2}$OH  Group  This copolymer was dissolved uniformly in the solvents  such as acetone, THF, DMF and HFC-225.  After releasing the un-reacted monomer, the polymeriza› tion solution was removed, followed by re-precipitation with  hexane to separate a copolymer. Until a constant weight was  reached, vacuum drying was continued and 1.2 g of a copoly› mer having a structure represented by the following formula  was obtained.  ice/methanol solution. Then 10.0 g of tetrafluoroethylene  (TFE) was introduced through a valve, followed by shaking  for reaction at 40°  C. for 18 hours. With the advance of the  reaction, a gauge pressure was decreased from 0.88 MPaG  (9.0 kgf/cm $^{2}$G) before the reaction to 0.85 MPaG (8.7 kgf/  cm $^{2}$G).  Example 12  Example 14  Example  13  Setani-Namioka type spectrometer (BL-7B available from  HIGH ENERGY KENKYU KIKO)  Slit: 7 /8-7 /8  Detector: PMT  Grating (GII: Blaze wavelength 160 nm, 1,200 gratings/  mm) 