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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 > ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( D ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( D ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Delaware ( State or Other Jurisdiction of Incorporation or Organization ) FORM 10 - K 900 East Green Street Bensenville , Illinois ( Address of Principal Executive Offices ) or RUBICON TECHNOLOGY , INC . ( Exact Name of Registrant as Specified in Its Charter ) Title of each class Common Stock , par value $ .001 per share Preferred Shares Purchase Rights Commission file number 001-33834 Large accelerated filer Non - accelerated filer Emerging growth company to ooo 36-4419301 ( I.R.S. Employer Identification No. ) Registrant's Telephone Number , Including Area Code : ( 847 ) 295-7000 Securities registered pursuant to Section 12 ( b ) of the Act : 60106 ( Zip Code ) Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes □ No - Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No □ Name of each exchange on which registered The NASDAQ Capital Market Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S - K is not contained herein , and will not be contained , to the best of registrant's knowledge , in definitive proxy or information statements incorporated by reference in Part III of this Form 10 - K or any amendment to this Form 10 - K Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , ” “ smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Accelerated filer Smaller reporting company □ 区 X If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act .