Radiation imagery chemistry: process – composition – or product th – Transfer procedure between image and image layer – image... – Imagewise heating – element or image receiving layers...
Reexamination Certificate
1999-12-01
2002-05-28
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Transfer procedure between image and image layer, image...
Imagewise heating, element or image receiving layers...
C430S338000, C430S523000, C430S527000, C430S530000, C430S531000, C430S536000, C430S935000, C430S961000, C427S255500, C427S255230, C347S105000, C503S227000
Reexamination Certificate
active
06395448
ABSTRACT:
FIELD OF THE INVENTION
The present invention is a method to provide a lubricant layer to an imaging element. More particularly the present invention eliminates the use of solvent in applying the lubricant layer to an imaging element.
BACKGROUND OF THE INVENTION
Photographic and image or information recording media require adequate lubrication for the purposes of transport through recording devices and imaging devices (camera, photofinishing, thermal head, etc.), and for scratch protection. Also, backing layers on photographic negative film that can be used to magnetically record, and subsequently, to retrieve, information require excellent lubrication at their surface to improve the durability of the recording layer. Contact between the magnetic head and the outermost surface of the backing layers of the film is necessary, however, this imposes a great amount of stress to the backing layers and may result in rupture of the layer, and in loss of signal. Good lubrication allows for multiple transports of the film through various magnetic head-containing equipment. The lubricant must also remain effective after the film has been run through photographic processing solutions.
Polyethylenes, silicone waxes, natural waxes such as Carnauba, polytetrafluoroethylene (PTFE), and fluorinated ethylene propylene (FEP) are known to be lubricating agents. Some are not soluble, some are soluble in limited solvents which impose constraints and difficulties for the coating of these lubricants and on manufacturing. In addition, the solvents used as vehicles for the wax may attack or cause damage or undesirable changes in the surface of the layer or layers onto which the lubricant is being coated. In addition, these carrier solvents may not be environmentally friendly.
Imaging elements containing transparent magnetic oxide coatings on the side opposite the imaging emulsions have been well-documented. The need for lubricating layers on said magnetic oxide coatings have also been well-described. A variety of types of lubricants have been disclosed including fatty acids, fatty acid esters, silicones, waxes, etc. In general, the transparent magnetic layer and the lubricating layer are applied in separate coating steps. This reduces the manufacturing efficiency of the product by requiring several coating stations. Typically these layers have been applied by first coating a solution of the magnetic oxide layer onto a support using a bead coating technique. The coating is then dried and a lubricant layer is then coated over the magnetic layer using a similar technique. Thus, another disadvantage is that the lubricant containing layer is typically applied using a solvent as a carrier, thus, generating solvent and solvent vapor waste.
Alternatively, the lubricant can be added to the magnetic oxide coating solution such that both the magnetics and lubricant arc coated simultaneously. This is advantageous because less coating stations are required, likely reducing waste and simplifying the production. Unfortunately, in order for the lubricant to be effective it must primarily reside at the uppermost surface of the dry coating. When the lubricant is added to the magnetic oxide solution, it is difficult for the lubricant to get to the surface. As the solution dries rapidly, the polymeric binder for the magnetic oxide will vitrify or solidify, which retards the mobility of the lubricant. Additionally, the lubricant may also go to the support/magnetics interface instead of the desired magnetics/air interface. The result is an improperly lubricated surface, or a coating with a high coefficient of friction.
Another drawback of adding the lubricant directly to the magnetics layer is that phase separation can occur resulting in a translucent or opaque film. The lubricant can destabilize the magnetics dispersion, resulting in flocculation of the particles. Also, the lubricant may not be compatible with the magnetics binder, which can lead to gross phase separation and loss of optical transparency. It is desired to have the lubricant phase separate and migrate to the air interface, without the loss of optical transparency. Obviously a very selective phase separation is desired and is difficult to control. Alternatively, the lubricant may not be soluble, or dispersible in the same solvents as are needed for the components of the transparent magnetic layer.
Japanese Patent1251349 A (New Nippon Electric Co) discusses a magneto-optical recording medium that comprises an optically transparent substrate onto which a magnetic film is formed. A macromolecular film formed by plasma polymerization of tetrafluoroethylene monomer is formed on the surface-side dielectric substance film. Vacuum deposition of PTFE-like substances involve starting with gaseous monomers and doing a plasma polymerization. The present invention offers the advantage that the original lubricant materials are preformed polymers as opposed to monomers such as tetrafluoroethylene, thus avoiding complex handling of often toxic gases. In addition, exposing the surface to the plasma can degrade the magnetic and underlying layers and compromise the coefficient of friction, the durability, and the abrasion resistance of the element.
U.S. Pat. No. 4,863,762 describes a physical vapor deposition technique that deposits fluororesins onto a surface. However, in this process, there is a need to degrade the molecular weight of the initial resin sample prior to the vacuum deposition process. This is done by heating the resin in the presence of a fluorine source. U.S. Pat. No. 4,390,601 describes the vacuum deposition of a lubricant onto a (non-transparent) magnetic substrate. The lubricants described are paraffins, fatty-acids and soaps, which are not the subject of the present application. The deposition process described is for a stationary substrate, not a moving web.
What is needed in the art is a method that does not require solvents, does not require a solvent coating machine, and also ensures that the lubricant remains at the outermost surface of the transparent magnetic layer. Thus a manufacturing advantage would be obtained since a solvent coating machine would not be required for the application of this lubricant, which offers capacity advantages. Also, environmental benefits would be obtained due to the elimination of solvent waste and evaporation. A minimal amount of lubricant would be deposited by this method, so that lube transfer to the head would be minimized and head clogging problems reduced.
SUMMARY OF THE INVENTION
The present invention describes a means of obtaining a lubricated layer on an imaging element via deposition of the lubricant onto a dried magnetic layer via an evaporative process. The method includes providing a polymer or a wax selected from the group consisting of polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), fluorinated ethylene copolymers, polyethylenes, high density polyethylene, natural waxes such as Carnauba wax, synthetic waxes, and silicone waxes in a deposition chamber. The chamber is evacuated to a pressure of 10
−1
Torr or less A carrier gas is bled into the chamber while maintaining the pressure in the chamber to 100 mTorr or less. Preferred gases are selected from the group consisting of N
2
, O
2
, and Ar. The polymer or wax is heated to a temperature sufficient to vaporize the polymer or wax, and the imaging element is moved through the chamber on a continuously moving web, depositing the polymer or wax on the imaging element to form the lubricating layer.
The present invention provides low coefficient of friction and, in addition, provides durability for excellent performance under a magnetic head. The lubricant layer is transparent and does not interfere with the transmission of light through the imaging element.
DETAILED DESCRIPTION OF THE INVENTION
A support, coated with appropriate layers (e.g. subbing, antistat, and transparent magnetic oxide layers) on the side opposite to the emulsion layers, is exposed, under vacuum, to a lubricant vapor phase. The lubricant vapor phase is obtain
Freeman Dennis R.
Landry-Coltrain Christine J.
Schilling Richard L.
Wells Doreen M.
LandOfFree
Evaporated lubricants for imaging element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Evaporated lubricants for imaging element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evaporated lubricants for imaging element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2823119