Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2002-04-11
2004-03-09
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S354000, C428S447000, C428S448000, C428S066300, C428S351000, C428S401000, C525S477000, C525S478000, C528S015000, C528S035000, 48, 48, 48, 48
Reexamination Certificate
active
06703120
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to silicone adhesives, articles, and methods of making and using. The adhesives are particularly useful on articles such as cover tapes for analytical receptacles, such as microtiter plates, microfluidic devices, discrete or continuous multi-reservoir carriers, or other analytical receptacles, particularly those that are designed for holding a variety of liquids, in bioanalytical applications, for example.
BACKGROUND
Microtiter plates are well known for use in handling liquid materials in bioanalytical assays for multiple, rapid, low-volume analysis. A typical screening technique combines an assay plate, having multiple depressions or wells, with liquid handling hardware to provide a rapid, automated system of analysis. In a current, standard analytical system, each assay plate accommodates 96 wells, each well being addressable by suitably programmed hardware. The capacity of each of the 96 wells is about 0.2 milliliter (ml) to about 0.4 ml. Smaller capacity wells lead to assay plates that accommodate a larger number of samples. For example, assay plates containing 1536 wells, each with a capacity of less tan 5 microliters (&mgr;l) are known. These plates, with increased sampling capability, have demonstrated usefulness in a variety of assays, including enzyme assays, receptor-ligand assays, and even cell based assays. The increased number of sample wells, per assay plate, demands increased precision of the hardware associated with analysis using these assay plates.
Liquid handling for bioanalytical applications, using assay plates of either the 96-well, 384-well, or the 1536-well variety, may be viewed as a batch process with rate limitation due to the loading and positioning of the assay tray. Possible improvement in the rate of sample analysis results from the use of a continuous strip of material having sample wells molded along its length. U.S. Pat. No. 4,883,642 (Bisconte) suggests such a strip or tape. The patent teaches a continuous ribbon, which may be either smooth or suitably molded to incorporate a plurality of micro-wells. Fixed biological sample analysis uses smooth versions of the continuous ribbons while micro-well ribbons find use for analyzing living biological samples. Two tracks, positioned along opposite edges of the ribbon, provide addressable means for moving and positioning the ribbon in a selected, precise location with adjustment accurate to 10 micrometers (&mgr;m). The tracks may be coded using magnetic, optical, or computer methods, for example, which allow manipulation and positioning of the ribbon. A dosage syringe type of device, positioned using a step by step motor, distributes biological samples in the micro-wells.
This continuous multi-reservoir carrier is useful in the automated analysis of biological samples, such as histological sections. Protection of the samples, whether applied to a smooth ribbon or contained in micro-wells may use a self-adhesive film. The self-adhesive film covers the smooth film surface or seals the openings to the individual micro-wells. It may be permeable or impermeable to air.
U.S. Pat No. 5,721,136 (Finney et al.) teaches the use of a multiplayer sheet having a silicone adhesive thereon for use on vessels for biochemical reactions. One layer provides strength and integrity for the film. The second layer is a thick, in the range of about 2 mils. To about 40 mils (50 &mgr;m to 1016 &mgr;m), deformable material with a very low surface. The elastic nature of the second layer results in good seal when clamped down during thermal cycling. The rubbery materials also provide a very low level of adhesion. The peel force of the sheet from a Polypropylene surface is reported to be in the range of 1.1 N/dm to 5 N/dm (0.1 oz/in to 4.5 oz/in). Although a low tack adhesive is desirable to prevent the tape from sticking to rubber gloves commonly used in biological research, when applied to a microplate, for example, low adhesion of thick, elastic adhesive tapes is likely to cause a high evaporation rate and increase the incidence of cross-contamination during storage and handling.
To increase cohesive strength and reduce contamination due to residual adhesive, silicone may be cured or crosslinked by catalysts such as peroxide or metallic salts at elevated temperatures. For example, benzoyl peroxide requires a cure temperature of more than 150° C. for the catalyst to be functional. Consequently, a backing with low melting or softening point, such as a polyethylene film, may be overly stretched or distorted dimensionally during curing. To prepare a curable silicone tape, one common practice is to coat curable silicones on a release liner consisting of a fluorosilicone coating and PET (polyethylene terephthalate) backing. The tape is then laminated with the backings of low melting or softening point temperatures. Since release liners arm commonly used to process and to protect silicone adhesive surfaces, it is important that the release force to separate the tape from the release liner be kept at a low level to minimize distortion of the tape backing, particularly when the release liner is removed during an automatic process.
U.S. Pat. No. 5,082,706 (Tangney) describes a silicone PSA/fluorosilicone release laminate having a release force of less than 7.7 N/dm (7 oz/in) from the fluorosilicone release layer and a peel adhesion of at least 46.4 N/dm (42.2 oz/in). This adhesive includes a tackifying resin (often referred to as an MQ resin) containing two structural units, one of which is R
3
SiO
1/2
(often designated as M) and the other SiO
4/2
(often designated as Q). As discussed in The Handbook of Pressure-Adhesive Technology, 2
nd
Edition, (ed. D. Satas, 1989) p. 510, the peel adhesion of silicone pressure sensitive adhesives can be controlled by controlling the amount of tackifying resin. For example, increasing the amount of tackifying resin increases the peel adhesion; however, there is typically a point at which the peel adhesion maximizes. Thus, increasing the amount of tackifying resin beyond this point can cause peel adhesion to decrease.
SUMMARY OF THE INVENTION
What is needed are adhesives and adhesive articles, particularly cover tapes for analytical receptacles, that provide an effective peel strength from the materials that typically form analytical receptacles yet good release from a release liner and preferably sufficiently low tack as to be suitable for use with analytical receptacles. Such adhesives would be especially desirable if they are substantially resistant to liquids, particularly organic solvents such as dimethyl sulfoxide that are often used in bioanalytical applications.
The present invention provides adhesives, preferably pressure sensitive adhesives (PSAs), adhesive articles, and methods. Preferably, the articles are cover tapes for analytical receptacles, such as microtiter plates, microfluidic devices, and continuous multi-reservoir carriers, or other analytical receptacles or biosensors, for example. Typically, such analytical receptacles are used in bioanalytical applications and are designed for containing solids and fluids, including liquids, gases, powders, and gels, which may include biological samples or organic solvents, for example.
In preferred embodiments, cover tapes for such analytical receptacles provide a sealing membrane so that each reservoir, such as a well or channel, for example, is part of a sealed enclosure to retain the contents and/or reduce evaporation and contamination of the contents of the receptacle. Preferred cover tapes have sufficient transparency to allow for photometric analysis and/or visual inspection and are substantially resistant to solvents commonly used in bioanalytical applications, such as dimethyl sulfoxide (DMSO), water, acetonitrile/water, methanol, ethanol, or mixtures thereof, for example. As used herein, a substantially solvent-resistant cover tape, and particularly adhesive, is one that does not substantially swell or dissolve in the solvent used in the particular application and does maintain sufficie
Ko John H.
Melancon Kurt C.
Schulz Anita L.
3M Innovative Properties Company
Dawson Robert
Keehan Christopher
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