Cleaning and liquid contact with solids – Processes – Longitudinally traveling work of bar – strip – strand – sheet...
Reexamination Certificate
2003-09-17
2004-09-28
Barr, Michael (Department: 1746)
Cleaning and liquid contact with solids
Processes
Longitudinally traveling work of bar, strip, strand, sheet...
C134S018000, C134S021000, C134S022190, C134S023000, C134S032000, C360S015000, C360S137000, C510S167000, C510S421000, C510S506000
Reexamination Certificate
active
06797072
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for restoring magnetic recording tape damaged by “Sticky Shed” syndrome.
Tape recording technology had its first beginnings in the late 1930s and early 1940s, and has continued to this day with a stream of changes and improvements to magnetic tapes and also to tape machines. Various standards for both tape and machines have also developed over time. The appeal of tape-recording is that one is able to form an analogous magnetic memory bank of magnetic patterns and impulses that can capture all kinds of acoustic events when the tape is recorded and played back at another time. Thus, tape and tape-recording are invaluable for capturing all kinds of sounds from sound effects, speech, as well as acoustic or electronic music. Recordings contain a vast personal, cultural, artistic, and historical value as well as a substantial monetary value when these recordings are copied, sold and played.
Tape-recordings were a new and better technology that replaced the older cylinder methods, the older direct recording to acetate or wax discs, and wire tape recorders. Today, the tape-recording industry is large and active, but it is facing competition from the newer digital and computer technologies, which at least supplement tape-recording, and which may replace tapes, particularly so if the tape problem of “Sticky Shed” is not solved and if tape-recordings are damaged or lost due to improper handling or destructive restoration efforts by those who do not understand the problems inherent in restoration, or who do not use a restoration process that best preserves tape and program integrity.
The earliest tapes used paper as a base for the tape. This did not work very well and the paper base was soon replaced by an Acetate Base. The Acetate Base is somewhat fragile and can be easily broken. Also, Acetate tapes need proper storage conditions of temperature and humidity to remain in good playing condition. In the early 1960s, a new Mylar Base material was invented that replaced Acetate. The Mylar Base tapes are much stronger than Acetate, and do not easily break, and also do not require rigid temperature and humidity control conditions to remain in good condition.
The other main element of a tape is the Oxide material and the binder chemicals that hold the Oxide to the Base. These Oxides and binders have undergone constant improvement over time. The Oxides range from Ferric Oxide to Chromium Dioxide to many variations thereof. The aim has been to get better and more powerful magnetic performance, a longer wear life, smoother surfaces, better frequency response, less noise, etc. The Binder is a chemical brew mixed with the Oxides, which is then processed to evaporate the solvents, leaving the Oxide coating on the Base, which is then rolled and smoothed out. The large tape rolls are then slit to various widths, and then put on reels for use on tape machines.
The third element in tape manufacture is the Backcoating. Backcoating was developed by Ampex. (now Quantegy) and other tape makers in the late 1960s, and added to tapes to improve the mechanical handling qualities of tapes by providing for a smoother tape wind and for reducing static build-up due to friction in the tape path of tape machines. Prior to the introduction of Backcoating in the late 1960s, tapes did not have Backcoating. Although Backcoating helps with these mechanical problems of machines of the day, the fact is there is a price to pay for using Backcoating which is that, over time, it causes the chemical breakdown of the tape and leads to the tape problem of “Sticky Shed” which is damaging and is currently destroying many tapes which have Backcoating. The tape makers touted Backcoating as an improved product and thus customers demanded tapes that had Backcoating. Sales of Backcoated tapes increased, while the sales of non-Backcoated tapes decreased. Today, it is very difficult to even find non-Backcoated tape for purchase. Rarely, if ever, did any tape that did not have Backcoating exhibit the “Sticky Shed” problem. Nearly every tape that has Backcoating has “Sticky Shed” problems to a varying degree. Thus, Applicant has concluded that the Backcoating is the bad actor in this situation. While Backcoating may have helped with some mechanical issues in the 1960s, it left behind a chemical time bomb which is destroying tapes today and will do more destruction in the future until and unless a process is used to solve the “Sticky Shed” problem. Backcoating is no longer needed as the problems it addressed either no longer exist or can be dealt with in other ways. Tapes need to have a long, safe, archival life, free of the “Sticky Shed” problem, and the best way to do that is to end the manufacture of tapes with Backcoating. However, it is often necessary and/or desirable to play old Backcoated tapes and the “Sticky Shed” problem makes the playing of old tapes difficult and endangers their future use.
A number of years after Backcoating was first applied to tapes, a new problem, which came to be known as the “Sticky Shed” problem, arose. Tapes now became sticky, which meant they would not play properly and smoothly on a tape machine. Instead of normal playback, the tapes now would stick to various mechanical parts in the tape path of a tape machine. This sticking would not only cause noise, but as the problem got worse, tapes either would not play at all, or even worse, would shed debris on the playback head which greatly impaired getting the proper or full magnetic and sound signal off the tape. In the worst case situations, the sticking Backcoating would rip the Oxide off the base of the tape, thus completely destroying all the magnetic data on the tape. Also, the sticking would cause the tape speed to vary, causing “flutter” of the program during playback.
Tape companies, users, and owners of tapes went into a state of dread and panic about losing these tapes, which concerns continue to the present day. There are millions of tapes with the “Sticky Shed” problem which has caused owners and users of tapes to face the grim prospect of losing, entirely, the valuable magnetic information on the tapes, or in getting inferior playback sound from these tapes. The “Sticky Shed” problem has thus compelled the industry to commence an extensive and expensive effort to transfer the content of the “Sticky Shed” tapes onto either digital media or other analog tapes.
The problem of “Sticky Shed” is well known in the tape-recording industry and numerous articles have been published discussing the problem and proposed solutions.
In an article published in the Washington Post in May, 1989, Agfa Corporation was reported to have introduced a five step labor intensive process described as “Agfa-NXT” that “involves a variety of techniques ranging from cleaning to heat.” In the December, 1994, edition of Pro Sound News, it was reported by Eddie Giletti that:
“Tapes with shedding problems can be cured, at least long enough to get a good transfer. Several manufacturers offer this service, or it can be done in-house. A low-temperature (140 degrees F.) baking process was found to reactivate the binder. The pack must be perfectly smooth or the tape surface will become uneven. Baking time varies with tape width, starting with one hour for quarter-inch tapes up to several hours for two-inch tapes. Flipping the tapes every half-hour ensures that the heat is distributed evenly. Tapes must cool before use.”
In the Nov. 29, 1995 edition of Radio World, an article titled “Clean & Restore Old Analog Tapes” states the following:
“Hydrogen peroxide is the only solution recommended by Neuman for cleaning the surface or backcoat of a tape. It does not damage any of the tape's chemical components and is safe to the user. By all means, do not use alcohol or other solvents as they may permanently damage the tape.
Peroxide will effectively clean off the mold and its antiseptic properties will help inhibit future mold growth.”
In a publication dated Feb. 17, 2002, and issued by the Magnetic Reference Labora
Barr Michael
Spiegel H. Jay
Winter Gentle E.
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