Packaging curable materials

Disclosed is a packaged element containing (a) a substrate that transmits less than about 0.5% of actinic radiation and has at least one recess, (b) a cover that transmits less than about 0.5% of actinic radiation and transmits at least part of the visible light spectrum, (c) a structure for maintaining the cover in contact with the substrate such that the cover filters incident radiation entering the recess, and (d) an element located in the recess and having a substance thereon that is curable by exposure to the actinic radiation. Also disclosed is an article containing (a) a substrate having at least one recess with an interior surface, (b) an element having a tacky substance on a surface thereof, and (c) a structure for positioning the element inside the recess such that the tacky substance does not separate from the element upon removal from the recess.

The present invention relates to packaging an element having a curable 
material coated thereon. In particular it relates to such a packaging 
wherein the materials are light-reactive, tacky, or both, and the element 
is an orthodontic bracket. 
Orthodontic brackets are typically packaged in bulk or in single-patient 
trays. Orthodontic brackets having a layer of unactivated adhesive 
material covered with a protective liner are disclosed in U.S. Pat. No. 
4,205,325. 
The present invention provides a packaged element comprising (a) a 
substrate that transmits less than about 0.5% of selective actinic 
radiation and has at least one recess, (b) a cover that transmits less 
than about 0.5% of the actinic radiation and transmits at least part of 
the visible light spectrum, (c) a means for maintaining the cover in 
contact with the substrate such that the cover filters incident radiation 
entering the recess, and (d) an element located in the recess and having a 
substance thereon that is curable by exposure to the actinic radiation. 
The present invention also provides an article comprising (a) a substrate 
having at least one recess with an interior surface, (b) an element having 
a tacky substance thereon, and (c) a means for positioning the element 
inside the recess such that the tacky substance does not separate from the 
element upon removal from the recess.

In one embodiment of the present invention, a tray containing orthodontic 
brackets pre-coated with adhesive paste and placed into 
release-layer-coated recesses (wells) is provided. The adhesive paste is 
curable upon exposure to selective actinic radiation, i.e., wavelengths of 
light (electromagnetic radiation) that effect curing in a particular 
material. Referring to FIGS. 7, 8, and 9, the embodiment contains a tray 
11, such as a vacuum-formed 6.35.times.15.24 cm tray made from a black 
(opaque) semi-rigid 0.508-0.635 mm thick high-impact polystyrene sheet. 
The tray includes wells 12, each of which has a concave inner surface deep 
enough to accommodate a standard orthodontic bracket 13, which is coated 
with light-curable adhesive paste 15, completely below the rim of the 
well. The bottom of each well is coated with an excess (0.3-0.4 grams) of 
a non-adhesive release-coating material 16, e.g., a silicone, 
polyethylene, or fluoropolymer coating such as those commercially 
available under the names Teflon.TM. poly-tetrafluoroethylene and 
Teflon.TM. fluorinated ethylene-propylene (available from E.I. du Pont de 
Nemours, Wilmington, Del.) and Silicone Premium (a siloxane available from 
General Electric Company, Waterford, N. Y.). A blue-light-filtering film 
14 covers the wells and is secured to the tray with double-sided, 
repositionable pressure-sensitive adhesive tape 18. The cover 14 is cut to 
form individual flaps 20, which allow access to individual wells as shown 
in FIG. 7. Each flap 20 has a piece of double-sided, repositionable 
pressure-sensitive adhesive tape 18, which maintains the flap in contact 
with the tray. Alternatively, access to the brackets can be provided via a 
star-burst pattern of slits cut into the film above each well. Preferably, 
the film is a flexible, colored transparent film, opaque to the wavelength 
of light required to cure the paste, but sufficiently transparent to 
non-curing wavelengths to permit viewing the bracket through the film. 
In another embodiment of the present invention, orthodontic brackets coated 
with a light-curable adhesive paste are provided in a tray in which each 
bracket is suspended in a recess designed to keep the adhesive paste from 
contacting the surface of the recess. As shown in FIGS. 10 and 11, bracket 
1 is attached to a conventional long-axis indicator 2, the ends of which, 
by virtue of cooperation with complimentally-shaped, linearly-aligned 
grooves 7 on opposing sides of well 9 in tray 3, suspend the bracket above 
the bottom 6 of well 9 such that adhesive paste 4 on bracket 1 does not 
contact any part of the tray. Cover film 5 (not seen in FIG. 10) is 
attached to the tray 3 by a double-sided, repositionable, 
pressure-sensitive adhesive tape (not shown) sandwiched between the film 
and the tray. As demonstrated in the figures, groove 7 and long-axis 
indicator 2 are shaped to engage in such a way that the indicator rests 
loosely in the groove while preventing lateral or rotational movement of 
the bracket 1 within the well 9. Cover film 5 contacts the top of the 
long-axis indicator 2 to hold the indicator in the groove 7. In this 
manner, cover film 5 and groove 7 cooperate with the long-axis indicator 2 
to fix the bracket 1 loosely in the well 9. 
In accordance with the present invention various materials are useful for 
the cover and substrate. Commercially available flexible films that are 
useful as the cover in accordance with the present invention include, 
e.g., polyester materials available from Rosco Labs, Inc., Port Chester, 
N.Y. under the name Roscolux.TM. 12 (38.1 .mu.m thick, straw color, % 
transmittance curve for electromagnetic radiation shown in FIG. 1), 
Roscolux.TM. 22 (99 .mu.m thick, deep-amber color, % transmittance curves 
for electromagnetic radiation shown in FIG. 2), Roscolux.TM. 23 (38.1 
.mu.m thick, orange color, % transmittance curves for electromagnetic 
radiation shown in FIG. 3), Roscolux.TM. 42 (38.1 .mu.m thick, deep-salmon 
color, % transmittance curves for electromagnetic radiation shown in FIG. 
4), and vinyl materials, such as a 0.343 mm thick film having % 
transmittance curves for electromagnetic radiation as shown in FIG. 5 
(available from Frommelt Industries, Inc. Dubuque, Iowa, under the 
designation Saf-T-Vu yellow, M1063). Flexible films useful as covers in 
accordance with the present invention have a preferable thickness between 
about 0.00254 and 2.54 mm, more preferably between about 0.0254 and 0.254 
mm. Alternatively, rigid sheets instead of flexible films can be used, 
which are attached to the tray so as to permit access to the individual 
brackets, e.g., such as by a hinge or by cooperating tongue-and-groove 
appendages that permit the plate to slide relative to the tray. Useful 
rigid sheets include, e.g., a poly(methyl methacrylate) acrylic material 
having % transmittance curves as shown in FIG. 6, which has a thickness of 
about 3.05 mm (available from Rohm & Haas, Philadelphia, Penna. under the 
designation Amber 2422). Other useful covers include polymeric materials, 
e.g., polyesters such as poly(cyclohexane-1,4-dimethylene terephthalate), 
poly(ethylene terephthalate), and poly(butylene terephthalate), 
polycarbonates such as poly(4,4'-isopropyl-diphenyl carbonate), poly(vinyl 
chloride), and polypropylene. Useful rigid materials include, e.g., 
poly(methyl methacrylate), polyethylene, and polystyrene. Other useful 
cover materials include acrylic polymers, polycarbonates, polyolefins, 
fluorocarbon polymers, and inorganic glasses. 
Various colorants (i.e., pigments, and/or dyes) are useful for making the 
cover absorb selective wavelengths of electromagnetic radiation. Colorants 
can be incorporated into both rigid sheets and flexible films according to 
well known methods, e.g., as disclosed in the Modern Plastics Encyclopedia 
Vol. 65, No. 11, pp. 148-150, McGraw-Hill, New York (1988). Generally, 
this involves blending the colorant with a molten resin and then forming 
the product into pellets. These pellets are then used as feed, e.g., in 
extruding films of desired thicknesses. The amount of colorant necessary 
per unit of resin to provide the desired protection will vary depending 
upon various factors, such as the particular colorant used, thickness of 
the resulting film or sheet, wavelength of light to be absorbed, and the 
capacity of the non-colorant-treated material to absorb light of the 
wavelength to be filtered. Preferably, the amount of colorant used is 
sufficient to enable the cover to absorb at least about 80%, preferably 
about 95-100%, of selective actinic radiation, i.e., light in the 
wavelength range useful in curing the packaged material. Alternatively, 
the colorant can be coated onto the cover after it has been formed. 
The particular colorant necessary to absorb actinic radiation from a 
selected range of the electromagnetic spectrum can be readily determined 
by the skilled artisan. Various commercially available colorants known by 
their color index (C.I.) identification (See Colour Index Third Edition, 
The Society of Dyers and Colourists, England, 1971) absorb (i.e., do not 
freely transmit) different wavelengths of the electromagnetic spectrum. 
For example, C.I. Disperse Yellow 201 (available from Mobay Corporation, 
New Jersey under the name Macrolex Yellow 6G), a styryl dye that absorbs 
wavelengths between about 415 and 480 nm; C.I. Solvent Blue 97 (available 
from Mobay Corporation under the name Macrolex Blue RR), an anthraquinone 
dye that absorbs wavelengths between about 550 and 650 nm; C.I. Solvent 
Red 135 (available from Mobay Corporation under the name Macrolex Red EG), 
a perinone dye that absorbs wavelengths between about 440 and 570 nm; C.I. 
Solvent Orange 60 (available from Mobay Corporation under the name 
Macrolex Orange 3G), a perinone dye that absorbs wavelengths between about 
380 and 515 nm; and C.I. Solvent Yellow 14 (available from Mobay 
Corporation under the name Ceres Orange RA), a monoazo dye that absorbs 
wavelengths between about 350 and 530 nm. Dyes that absorb wavelengths in 
the ultraviolet range (i.e., about 300-390 nm), but which impart very 
little color, e.g., hydroxyphenyl benzotriazoles, such as 
2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 
2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, and 
benzophenones, such as 2,4-dihydroxybenzophenone, 
2-hydroxy-4-methoxybenzophenone, and 
2,2'-dihydroxy-4,4'-dimethoxybenzophenone, are also commercially 
available, e.g., dyes available from Ciba-Geigy Corporation, New York, 
under the names Tinuvin.TM.- P, -324, -326, -327, and -328 and dyes 
available from BASF Wyandotte Corporation, New Jersey, under the names 
Uvinul.TM.-400, M-40, and D-49. The cover preferably transmits visible 
light outside the range of the actinic radiation that will cure the 
light-curable material. This allows the practitioner to see the 
material-coated element through the cover while retaining the 
light-curable material in an un-cured state. However, the cover can be 
opaque as well. 
Various substrate materials useful in accordance with the present invention 
include, e.g., plastics such as poly(acrylonitrile-butadiene-styrene) 
copolymers (ABS polymers), poly(vinyl chloride) (PVC), poly(methyl 
methacrylate) (PMMA), polyethylene (PE), polystyrene (PS), and 
polypropylene (PP); metals, e.g., carbon steel, 303 stainless steel, and 
316 stainless steel; wood, e.g., oak, maple, pine, and walnut; and other 
durable materials such as ceramics and glasses. In one embodiment, the 
substrate is an injection-molded, black polypropylene tray. Substrates 
made from transparent materials, such as many plastics and glasses, are 
preferably opacified, using pigments such as titanium dioxide and carbon 
black, or modified with colorants as previously detailed for use in the 
cover sheet, in order to prevent electromagnetic radiation from reaching 
the adhesive material packaged therein. The substrate can be designed in 
various ways in accordance with the present invention, e.g., as shown in 
the accompanying figures. Other substrate examples based on the specific 
embodiments presented include, e.g., providing recesses large enough to 
accommodate more than one element, modifying the contour of the interior 
surface of the recesses to accommodate different shaped elements, and 
having projections emanating from the interior surface of the recess from 
which an article can be suspended. Substrates useful in accordance with 
the present invention can be made according to known methods, e.g., as 
disclosed in the aforesaid Modern Plastics Enclopedia. 
Various means are useful for maintaining the cover in contact with the 
substrate in accordance with the present invention. Preferably, an 
adhesive is used, either by itself or as part of a double-sided or 
single-sided adhesive tape. The adhesive can be an aggressive (permanent) 
adhesive, e.g., as disclosed in U.S. Pat. Nos. 3,691,140, 3,873,638 
3,922,464, 4,379,883, 4,413,080, 4,599,265, or RE 24906, the disclosures 
of which are incorporated herein by reference. Alternatively, the adhesive 
can be a pressure-sensitive, repositionable adhesive, e.g., as disclosed 
in U.S. Pat. Nos. 3,620,988, 3,691,140, 3,857,731, 4,166,152, 4,587,152, 
4,645,783, 4,656,218, 4,735,837, and 4,786,696, the disclosures of which 
are incorporated herein by reference. In addition to adhesive means, other 
useful means include a hinge-and-clasp fastening arrangement, which 
permits lifting the cover to permit removal of a bracket and then lowering 
and fastening the cover to the substrate to protect the remaining 
brackets, or a tongue-and-groove arrangement, which permits sliding of the 
cover with respect to the substrate. The cover can also be heat-sealed to 
the substrate. Additionally, the cover can be in one piece covering all of 
the recesses in the substrate, or in several pieces, either completely 
separate or partially connected, each piece covering one or more substrate 
recesses. 
The present invention is useful for packaging a variety of elements in 
accordance with the present invention, e.g., adhesive-coated orthodontic 
brackets as discussed above. Useful adhesive-coated orthodontic brackets 
include, e.g., those disclosed in U.S. Pat. No. 4,204,325 and European 
Pat. Application No. 0 290 133, the disclosures of which are incorporated 
herein by reference. Other useful elements containing radiation-curable 
materials, tacky materials, or both will be apparent to the skilled 
artisan.