Apparatuses and methods for pre-erasing during manufacture of magnetic tape

Abstract

The present invention relates to direct current (“DC”) pre-erasing servo channels of a magnetic tape prior to writing servo data in a servo channel. The present invention particularly relates to those servo recordings which were written with a uni-polar current waveform. The DC pre-erase is performed using a uni-polar direct current of a polarity that is opposite to the polarity of the direct current used to write the servo data. This pre-erase may be done with one or more heads. Also, as will be described, the pre-erase of a servo channel and writing to a servo channel may be done by making two passes over a single head or by using two or more heads to perform both steps. Also, it is within the scope of the present invention to have the heads mounted on a single mount or have the heads on separate mounts and on separate tape decks.

1 . A method for making a magnetic media, the method comprising:
 pre-erasing at least one servo channel of the magnetic media, without direct current pre-erasing the data channels of the magnetic media, by applying a direct current of a first polarity; and   writing a servo pattern by applying a direct current of substantially opposite polarity of the first polarity.   
     
     
         2 . The method of  claim 1 , wherein the pre-erasing and the writing is performed using a compound magnetic recording head. 
     
     
         3 . The method of  claim 2 , wherein the compound magnetic recording head comprises:
 a first head comprising a magnetically permeable thin film layer comprising an erase gap pattern for pre-erasing a servo track of a magnetic media; and   a second head comprising a magnetically permeable thin film layer comprising a servo write gap pattern for writing a servo pattern in the servo track.   
     
     
         4 . The method of  claim 3 , wherein the erase gap pattern of the first head and the servo write gap pattern of the second head are lithographically printed using a single mask. 
     
     
         5 . The method of  claim 4 , wherein pre-erasing at least one servo channel is performed by passing a portion of the magnetic media over the erase gap pattern of the first head and writing a servo pattern is performed by then passing a portion of the magnetic media over the servo write gap pattern of the second head. 
     
     
         6 . The method of  claim 5 , wherein the servo write gap pattern of the second head is a timing-based servo pattern. 
     
     
         7 . The method of  claim 5 , wherein the servo write gap pattern of the second head is an amplitude-based servo pattern. 
     
     
         8 . The method of  claim 1 , wherein prior to pre-erasing at least one servo channel of the magnetic media, the magnetic media is alternating current erased. 
     
     
         9 . A magnetic tape having at least one servo channel that is direct current pre-erased and has servo data written in the at least one servo channel and at least one alternating current pre-erased data channel for receiving data subsequently written thereon, the magnetic tape made by a method comprising: writing a servo pattern using a direct current of a first polarity; prior to the act of writing a servo pattern, erasing at least one servo channel of the magnetic tape by applying a direct current of a substantially opposite polarity of the first polarity. 
     
     
         10 . The magnetic tape of  claim 9 , wherein the act of writing and erasing is performed using a first head. 
     
     
         11 . The magnetic tape of  claim 10 , wherein the first head comprises a time-based servo pattern. 
     
     
         12 . The magnetic tape of  claim 10 , wherein the first head comprises an amplitude-based servo pattern. 
     
     
         13 . The magnetic tape of  claim 10 , wherein the act of erasing at least one servo channel of the magnetic tape is performed by first passing a portion of the magnetic tape that includes the at least one servo channel to be erased over the first head. 
     
     
         14 . The magnetic tape of  claim 13 , wherein the act of writing a servo pattern in the at least one servo channel of the magnetic tape is performed by then passing a portion of the magnetic tape that includes the at least one servo channel to be written over the first head. 
     
     
         15 . The magnetic tape of  claim 9 , wherein the act of erasing is performed by a first head and the act of writing a servo pattern is performed by a second head. 
     
     
         16 . The magnetic tape of  claim 15 , wherein the second head includes a time based servo pattern. 
     
     
         17 . The magnetic tape of  claim 15 , wherein the second head includes an amplitude-based servo pattern. 
     
     
         18 . The magnetic tape of  claim 15 , wherein the first head includes an erase pattern having an erase gap track width that is substantially the same as the servo gap track width. 
     
     
         19 . The magnetic tape of  claim 15 , wherein the second head is one of a thin film head, ferrite based head, and surface thin film head. 
     
     
         20 . The magnetic tape of  claim 15 , wherein the two heads are located on a single mount. 
     
     
         21 . The magnetic tape of  claim 15 , wherein the two heads are located on separate mounts. 
     
     
         22 . The magnetic tape of  claim 15 , wherein the head used to erase is located on a separate tape deck from the head used to write a servo pattern.