Note: Descriptions are shown in the official language in which they were submitted.
3135~ig
Title: REPOSITIONABLE WALL COVERING
Field of the Invention
This invention relates to a decorative sheet material for
applying to a wall, ceiling, floor, kitchen unit, table or other
surface within domestic or industrial premises or place of
amenity. In a preferred embodiment, this invention relates to
wall coverings, such as wallpaper which utilize a pressure
sensitive adhesive and a means to minimize initial adhesion of
the wall covering to a wall. Maximum adhesion is subsequently
attained after the wall covering has been repositioned as
desired.
Backcrround of the Invention
Decorative sheet material such as wall coverings are formed
typically of paper, plastic, metal foil, or fabric material
having a pattern or design printed or embossed on the front
surface, with the other surface, or back, being coated by the
consumer with a suitable adhesive, such as glue, cement, or the
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R.I.C-2285A 07-21-94
like (typically known as "wallpaper paste") by which the wall
covering may be secured to a wall, ceiling or other surface.
Other types of wall coverings include those having a plastic
decorative surface and a backing of woven or non-woven fabric or
paper. The backing or back surface is adapted to be coated by
the user with the aforementioned adhesive in order to secure the
wall covering to a surface. However, consumers dislike the
inconvenience of mixing and applying the paste. Additionally,
prepasted wall coverings need a water pan and this can be messy.
Generally, in conventional wall coverings, once the wall
covering is applied to the surface, it may be shifted or adjusted
thereon to a limited degree until the adhesive paste cures, or
dries.
Pressure sensitive adhesives, hereinafter "PSA" or "PSAs"
are known generally for their ability to provide adhesion
between two substrates upon contact. PSAs rely on high initial
tack and/or quick set-up reaction, or cure time for prompt or
instant adhesion. However, PSAs with sufficiently high tack to
hold a wall covering in place are very difficult to apply to a
wall and then reposition, as occurs for example, while matching
up patterns from one wallpaper strip to the next. Although
suitable pressure sensitive adhesives have in the past been
applied to wall coverings, attempts to reposition those same wall
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coverings generally have not met with success. Typically,
wall coverings having PSA have fallen from the walls to
which they were applied shortly after such application due
to poor permanent adhesion; the wall covering cannot be
slid and repositioned while in contact with the wall due to
adhesive tack; the outline of various spacer means used to
separate the adhesive from the wall in attempting to
introduce some slip until a permanent adhesion is attained
show through the decorative face of the wall covering;
spacer means are often on the surface or embedded in the
PSA so that upon development of slight adhesive contact
with the wall, the spacers loose their effectiveness;
manufacturing difficulties are encountered in placing the
correct thickness or otherwise positioning of spacers or
projections over an adhesive coating; and have other
shortcomings.
The following references are illustrative of the prior
art.
U.S. Patent No. 3,301,741 of January 31, 1967
discloses a self-adhering wall covering comprising: a
substrate such as paper; a pressure sensitive adhesive; and
a separation means secured to or a part of the backside of
the substrate. The spacer means are of a uniformly pebbly
contour of raised adhesive protrusions on the back
separated by intervening adhesive planar areas wherein the
tips of the protrusions are of a friable non-adhesive
material which crumble into particles upon the application
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r
of pressure to the substrate. Also, the tips of the
adhesive projections can be coated with a non-adhesive
coating.
U.S. Patent No. 3,331,729 of July 18, 1967 discloses
wall coverings which are allegedly repositionable and
slidable due to micro balloons over or imbedded in the PSA.
U.S. Patent No. 3,554,835 of January 12, 1971 shows an
allegedly slidable PSA film. When force is exerted on the
face of the film, PSA on its backside extrudes from below
the dots of release material and adheres to the receptive
surface, or the dots may be fractured or sink into the PSA.
U.S. Patent No. 3,663,269 of May 16, 1972 discloses a
wall covering having a coating of dry encapsulated adhesive
on its back surface which is made tacky by the application
of heat and/or pressure.
U.S. Patent No. 3,851,731 of December 31, 1974
discloses a reusable, rebondable sheet having PSA with
microspheres embedded in a binder.
U.S. Patent No. 4,054,697 of October 18, 1977
discloses a wall covering having PSA on its back side. The
PSA has a coating of resilient non-adhesive particles
thereon or imbedded therein.
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U.S. Patent No. 4,376,151 of March 8, 1983 discloses
business forms having PSA on their back side and
superimposed thereover is a layer of microspheres which are
displaced by application of pressure.
U.S. Patent No. 4,556,575 of December 3,1985 discloses
a relocatable, multiple use adhesive sheet wherein the back
is entirely covered with PSA in which elastic microspheres
are embedded.
U.S. Patent No. 4,735,837 of April 5, 1988 discloses a
self-adhesive wall covering comprising: a substrate; PSA;
and elastic micro-balls embedded in the adhesive.
U.S. Patent No. 5,080,957 of January 14, 1992
discloses a reinforced tape having ribs on one side thereof
wherein a PSA is applied over either the front or back side
of the tape.
U.S. Patent No. 5,108,811 of April 28,1992 discloses a
removable, reusable window insulation comprising a thermal
insulating material such as polyethylene foam coated with
PSA.
CA 02135016 2005-08-23
U.S. Patent No. 5,141,790 of August 25, 1992 discloses
a repositionable PSA sheet wherein the PSA has clumps
thereon with non-adherent material distributed on the
clumps.
Japanese Patent No. 61-115981 of June 3,1986 discloses
a PSA sheet consisting of a base sheet having hollow
protrusions which are filled with PSA.
European Patent No 0367651 of May 9, 1990 discloses
strippable wallpaper having on its gluable surface, areas
of water activated adhesive applied over hydrophobic
release agent or areas of such release agent applied over
such adhesive for easy release from a wall.
PCT Publication No. 91/09725 of July 11, 1991
discloses a carpet cushion having PSA coated thereon and a
scrim webbing or other spacer element laid on or into the
PSA after the adhesive has been applied.
Our invention provides a decorative sheet such as a
wall covering that is manufactured with an adhesive on its
back or
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R.I.C-2285A 07-2I-94
working surface, thus resulting in a so-called self-adhesive or
PSA wall covering that may be applied to a support surface and
yet repositioned, and which does not require the use of
additional cement, glue or wallpaper paste. This invention also
provides a decorative sheet which can make adhesive contact on
slight initial pressure, yet which can be repositioned before and
until a final desired position is achieved.
A substantial area of the decorative sheet working surface is
provided with a tacky, pressure sensitive adhesive. However,
remaining on the working surface area are spaces which are not
covered by adhesive which provide uniformly distributed
discontinuities or spaces. Uniformly distributed non-adhesive
projections which have a height equal to or greater than the
thickness of the adhesive are provided within the discontinuities
on the back side and out of contact with the adhesive.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a
repositionable PSA decorative sheet such as a wall covering or
the like that avoids the disadvantages and defects of the prior
art.
Another object of the present invention is to provide a
single layered or laminated self-adhesive decorative sheet such
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CA 02135016 2006-08-21
as a wall covering comprising a fabric, plastic film, or paper
substrate, possessing a decorative printed or embossed front or
decorative side and a back side, a PSA applied over a
substantial portion of said back side, and projections applied
to said back side, said projections spaced apart from the
adhesive and having adhesive adjacent thereto wherein the
height (thickness) of the projections is at least equal to the
thickness of the adhesive for partially and temporarily
maintaining a separation or slight contact between the PSA and
a wall or other substrate to be covered, while the projections
contact and are moved along the wall or substrate until the
sheet is properly positioned whereupon pressure applied on the
decorative side will cause the adhesive to be anchored to the
wall.
Various other objects, advantages, and features of this
invention will be readily apparent from the following detailed
description and appended claims.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention there is
provided, a self-adhesive decorative sheet that is easily
repositioned after initial contact with a wall, comprising: a
sheet having a decorative front side and a back side; a tacky
pressure sensitive adhesive layer applied onto said back side,
said layer having gaps lacking adhesive; and projections which
are not sticky or tacky rising from said back side within said
gaps and having a height at least equal to the thickness of the
adhesive, said projections being separated from the adhesive by
a portion of said gaps.
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In accordance with another aspect of the invention there
is provided, a self-adhesive wall covering that is easily
repositionable on a wall by sliding after initial contact with
the wall and which can be subsequently firmly adhered to the
wall, said covering having a decorative front side and a back
side, comprising: a tacky pressure sensitive adhesive on the
back side; projections having a height which is at least equal
to the thickness of the adhesive on the back, said projections
being out of contact with the adhesive and wherein the
projections enable the back side to slide over a wall by
inhibiting contact of the adhesive with said wall while the
back side can be firmly adhered to said wall by application of
pressure to its front side.
In accordance with another aspect of the invention there
is provided, a decorative sheet having a back surface and a
uniformly distributed printed pattern of non-tacky projections
having a tacky pressure sensitive adhesive adjacent each
projection on said back surface, the adhesive and projections
being separated from each other in the plane of the back
surface and wherein the projections have a height which is at
least equal to the thickness of the adhesive.
In accordance with another aspect of the invention there
is provided, a decorative sheet having a decorative surface and
a working surface, wherein said working surface comprises:
uniformly distributed printed projections rising above said
working surface and having a substantially diamond shaped cross
section wherein each square foot of working surface contains
from about 200 to 300 projections; uniformly distributed
adhesive adjacent the projections and spaced therefrom printed
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on at least 40% of said surface, the thickness of said
adhesive being substantially equal to or less than the height
of the projections; and wherein the combination of projections
and adhesive permit the sheet to be slidable over a wall and to
be subsequently permanently secured thereto by application of
force on the decorative surface.
In accordance with another aspect of the invention there
is provided, a self adhesive decorative sheet that can be
repositioned after initial contact with a wall, said sheet
having a decorative front and a back side, said back side
having non-adhesive projections and a tacky pressure sensitive
adhesive over its surface, wherein: the projections form a
uniform pattern and cover about 5% to 20% of the total surface
area of the back; the adhesive is in a uniform pattern and
covers about 40% to 90% of the total surface area of said back,
said adhesive being in side by side relationship with the
projections which spaced apart from said projections and having
a thickness equal to or less than the thickness of the
projections; and wherein the projections allow the back to
slide on a wall and the sheet to be finally firmly attached to
the wall by application of pressure to the decorative front of
the sheet.
In accordance with another aspect of the invention there
is provided, a method of manufacturing a decorative sheet
having a decorative front side and a glueable back side,
comprising the steps of: printing projections on the back side;
printing a tacky pressure sensitive adhesive on said back side
wherein the adhesive does not overlap with the projections and
has a thickness equal to or less than the thickness of the
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CA 02135016 2006-08-21
printed projections and wherein a distribution, area occupied
by the projects and adhesive, and the thickness of the
projections rising above the plane of the adhesive surface
allow the back side to slide by contact of the projections
along the surface of a wall in order to reposition the sheet
and finally be firmly attached to the wall by application of
pressure on the decorative front side.
In an exemplary embodiment of this invention, a PSA-backed
decorative sheet is provided which is decorated on one side and
has on the other or back side, PSA for adhesion, and
projections which act as spacers between the PSA and the wall
to prevent full contact between the wall and the PSA, whereby
the wall covering can be initially repositioned by sliding the
surface of the projections across the wall surface until a
desired location is achieved. Then by applying sufficient
pressure to the outer decorated surface the separation created
by the projections between the PSA and the wall is overcome and
the PSA, not otherwise in contact with the wall, contacts and
adheres to the wall. Thus, a wall covering is provided which
can slide freely against the surface of the wall and which
develops additional tack after pressure is applied. By "wall"
herein is meant a wall or partition as in a room or on the
inside or outside of a building. However, "wall" shall also
mean herein any solid surface which can receive a PSA-backed
decorative sheet, including and not by way of limitation,
cabinets, doors, floors, ceilings, shelves, signs, fences,
billboards, automotive vehicle siding, windows, stationary,
drawers, borders, waste baskets, lamps, pictures, movable
paneling, etc.
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BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed descriptions, are given by way of
example and are not intended to limit the present invention
which will be better understood in conjunction with the
following drawings in which:
Fig. 1 is a plan view of a preferred embodiment of a
single pattern of spaces, adhesive and projections on the back
of a r7r~rnratlTTP C~'laat of Chic in~rPnt-inn~
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R.I.C-2285A 07-21-94
Fig. 2 is a plan view of the back of a decorative sheet of
this invention showing a repeating pattern of FIG. 1;
Fig. 3 is a vertical cross section on line A-A of FIG. 1:
Fig. 4 is a plan view of another repeating pattern on the
back of a decorative sheet of this invention;
Fig. 5 is a vertical cross section on line B-B of Fig. 4;
and
Fig. 6 is a vertical cross section of the pattern of Fig. 1
as initially applied to a wall before contact with the PSA.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, the invention comprises a
decorated, printed or embossed decorative sheet 10 having a
decorative side l0A such as that of fabric, metal foil, plastic
film, such as vinyl, (i.e., polyvinyl chloride), or polyester,
cellulosic material, such as but not limited to paper, and
combinations thereof, to which has been applied on the back or
working side lOB a tacky PSA (pressure sensitive adhesive), in a
desired pattern.
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R.I.C-2285A 07-21-94
Referring now more specifically to Fig. 1, there is shown a
design on the back i0B which has a projection 18, of a diamond
shaped cross section, a diamond shaped gap or space 16
surrounding the projection 18, diamond shaped PSA 14, and a
diamond shaped space or gap 12 surrounds the PSA. The projection
18 occupies an area of about 0.03296 square inches which is about
9.4% of the design area on back lOB. The gap 16 occupies an area
of about 0.01394 square inches on back lOB which is about 4% of
the design area. PSA 14 occupies an area of about 0.23317 square
inches on back i0B which is about 66.7% of the design area. The
outer space or gap 12 occupies an area of about 0.06936 square
inches on the back lOB which is about 20% of the design area.
Fig. 2 shows repeating units of the design of Fig. 1 on the
back 10B of the rectangular decorative sheet with the acute
angles facing the longer dimension of the sheet. Outwardly of
adjacent adhesive diamonds 14 the diamond shaped gap is made up
of adjacent gaps 12 of Fig. 1 and thus the spacing between
adjacent adhesive diamonds 14 is twice as great as that set forth
in Fig. 1. The distance between the centers of adjacent
projections 18 on a line parallel to the long axis of the back
10, i.e. in the direction of the obtuse angles, is about 0.7
inches: whereas on a line along the short axis of the back lOB,
i.e. from the centers of the projections 18 along a straight line
between adjacent diamonds having acute angles facing each other
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R.I.C-2285A 07-21-94
the distance is about 1 inch; and finally the distance from the
centers of projections 18 in a straight line which is angled from
sides of back lOB such as in about a diagonal direction is about
0.6 inches. The back 10B has about 250 projections I8 for each
square foot of surf ace .
In the vertical cross section of Fig. 1, as shown in Fig. 3,
it can be seen that projection 18 rises from back lOB and extends
above the height or thickness of adhesive 14 and that there is
neither adhesive nor projections within gaps 12 and 16 on back
IOB so that a separation is provided between projections 18 and
adhesive 14. The thickness (height) of projections 18 rising
above the surface of the adhesive 14 as best shown in Fig 3 is
preferably about 2o to 30a more than the thickness of PSA 14.
The thickness of the PSA 14 on surface 10B is about 0.00125
inches, i.e., one and a quarter of a mil.
Fig. 4 and Fig. 5 show another embodiment of the invention
wherein the layer of PSA 22 is continuous on the back lOB except
for islands of projections 26 surrounded by gaps 24 which in turn
are surrounded by PSA 22. In Figs. 4 and 5, the dimensions of the
projections 26 and gaps 24 are the same as projections IS and
gaps 16 in Fig. 1.
Fig. 6 shows a cross section of the pattern of Fig. 1 as it
is positioned against a wall 30 with only the surface of the
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' ' R.I.C-2285A 07-21-94
projection 18 facing the wall 30 in contact therewith and the PSA
14 spaced from the wall with gaps 16 between the projection 18
and the adhesive 14, 14 on either side of the projection as well
as spaces or gap 12, 12 outwardly of adhesive 14, 14 wherein the
projection 18 and adhesive 14 extend outwardly from the back 10B
of sheet 10.
The Material of the Decorative Sheet
The decorative sheet can be, without limitation, any
natural or synthetic cloth fabric, plastic, paper, or paper-like
material, copolymer, laminate, metallic foil, or the like or
combination thereof, which can be manufactured in a layer, sheet,
web or film and printed upan, embossed, or otherwise decorated on
at least the front surface and which is printable on the back
surface. This can include, for example, wallcoverings, billboard
advertising, home and commercial decorations, and the like.
There is no limitation on the thickness of the decorative sheet.
Preferably the decorative sheet is flexible so that it adjusts to
the contour of slight projections or dimples on the underlying
wall to which it is applied even though at times such underlying
surface imperfections may not be visible from the decorative side
of the sheet after it is apglied to the wall. The sheet material
of decorative sheet 10 can be produced by any manufacturing
technique known to those skilled in the art, including and not by
way of limitation, extruding, co-extruding, molding and blow
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' R.I.C-2285A 07-21-94
molding, sheeting, rolling, stamping, calendering laminating, or
by the use of paper or foil making machines, and the like.
The decorative sheet is sufficiently colored, patterned,
printed or embossed as to be at least opaque and preferably not
transmissive so that the projections on the back side are not
visible through the face side. Particularly preferred decorative
surfaces are manufactured from paper, embossed paper, and vinyl
film.
The PSA
The PSA useful in the present invention can be any adhesive
known to those in the industry provided it exhibits sufficient
initial tackiness to cause the decorative sheet to aggressively
adhere to the wall.
Of the preferred elastomeric-type PSA, many chemical
compositions are known to those skilled in the art and without
limitation these are useful in the present invention. Thus, for
example, elastomeric-type PSAs comprising natural rubber,
reclaimed rubber, styrene-isoprene-styrene rubber, butadiene-
acrylonitrile rubber, polyvinyl ether rubber, styrene-butadiene-
styrene rubber, butyl rubber, polyisobutylene rubber, nitrile
rubber, styrene-butadiene rubber, polyurethane, polysulfide,
polyesters, silicone resins and gums, neoprene rubber, acrylic,
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R.I.C-2285A 07-21-94
methacrylic, polyacrylate ester rubber, and vinyl and mixtures
thereof are useful in the present invention.
Room temperature curing PSAs are predominately based on the
use of metal chelates or diisocynates to obtain cross-linking.
Particularly preferred herein as PSAs are compositions
comprising silicone, including copolymers comprised of vinylidene
fluoride and/or tetrafluoroethylene with organopolysiloxane and
an organohydrogenpolysiloxane. Silicone PSAs have good thermal
resistance, cold resistance, chemical resistance, electrical
insulating properties, and controllable tack and hence are used
for extensive purposes. Silicone cross-linking agents for
optional use herein include organic peroxides and alkoxysilanes.
Preferred organic PSAs herein are the acrylate adhesives,
which are normally a copolymer of a higher alkyl acrylate, such
as 2-ethyl hexyl acrylate, copolymerized with a small amount of a
polar comonomer. Suitable comonomers include acrylic acid,
acrylamide, malefic anhydride, diacetone acrylamide, and long
chain alkyl acrylamide. Additional preferred organic PSAs
include polyvinyl acetate, vinyl acetate copolymer including
comonomers of acrylate and maleate or ethylene, and acrylics.
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R.I.C-2285A 07-21-94
The silicone adhesive and/or organic adhesive composite may
be applied to the printed substrate 10 from solution, emulsion or
solventless.
Solution application of the PSA composite to the back of
the decorative sheet requires only an amount of solvent that is
capable of dissolving the adhesive. Such solvents are preferably
non-polar and include toluene, dimethyl ether, xylene, etc.
Aromatic solvents are preferred. Aqueous emulsions of PSA
without organic solvent are even more preferred herein.
Typically, a solventless silicone PSA can be prepared with a
viscosity of from 100 to 100,000 centipoise at 25° C. An organic
solvent is typically used when the polydiorganosiloxane has a
viscosity of at least one million centipoise, a so-called
silicone gum.
The solvent should not have such a low vapor pressure that
it is difficult to remove from the adhesive in a drying process.
If the solvent is too difficult to remove then phase separation
may occur following precipitation but prior to complete solvent
removal.
Adhesive emulsions or solutions for application to the back
of the decorative sheet generally contain from about 10 to 400
parts by weight of adhesive solids, i.e. micelles of adhesive or
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R.I.C-2285A 07-21-94
solute, for each 100 parts by weight water or organic solvent.
Preferably, the solids should range from about 15 to about 200
parts and more preferably from about 20 to about 100 parts by
weight for each 100 parts by weight of water or organic solvent.
Following application and drying of the PSA, the adhesive
can be cross-linked as needed. Where an alkoxysilane is utilized
as the cross-linking agent, cross-linking will occur by simply
exposing the composite to atmospheric moisture. Heating may be
used to speed the cure. However, where a peroxide cross-linking
agent is utilized, then a heat cure is often necessary. Thus,
the composite must be exposed to temperatures ranging from about
80° to about 200° C., for times varying between about 5 minutes
to about 1 hour. Persons skilled in the art are readily familiar
with cross-linking these systems.
In a more preferred embodiment, the PSA is high solids,
with little or no water or solvent and is applied directly to the
back side.
The PSA is generally applied over at least 40% and
preferably over at least 50% or 60% of the decorative sheet back
side. The adhesive must be applied in a layer thick enough to
adhere to both smooth and rough surfaces. The thickness of the
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adhesive layer on the back is preferably about 0.00125 of an
inch, i.e. 1.25 mils, but will generally vary from about one
quarter of a mil to 2 mils or more. However, thicknesses of more
than 2 mils are generally a waste of adhesive.
The percent of back surface area occupied by the PSA as well
as the percent of the back surface area occupied by the
projections and the height of the projections rising above the
plane of the adhesive surface are selected to allow the back
side to be slidably moved on the surface of a wall to reposition
the sheet and finally to be firmly attached to the wall by
application of pressure on the decorative side of the sheet.
A particularly preferred ratio of area of adhesive covering
the back side of the decorative sheet to area of projections is
about 6 to 9 times greater for the adhesive for every unit of
area covered by the projections. However, such ratio can vary
over a wide range such as from about a ratio of 4 times mare
adhesive area than area of the surface of the projections on the
back to about 15 times mare adhesive area than the area of the
surface of the projections attached to the back side with a
preferred range of such areas being in a ratio of about 5:1 to
10:1. More adhesive area generally reduces the slip to much
less. Less adhesive area can negatively impact adhesion to the
wall.
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R_I.C-2285A 07-21-94
The total area of the decorative sheet back covered by PSA
can vary from about 40% to 90% of the back and preferably from
50% to 85% thereof.
The Protections or Separation Means
The height (thickness) of the projections are sufficient to
allow the PSA-backed wall covering to be moved while the
projections are in contact with the wall without a significant
surface of the PSA contacting the wall. When the desired
location for the wall covering is attained, increased pressure on
the decorative or front side of the wall covering causes slight
deformation of the decorative sheet, compression of the
projections, or a combination thereof sufficient to cause a
significant area of the PSA to contact the wall surface to
thereby firmly anchor the wall covering to the wall permanently.
The size, location, repeating design and surface area of the
projections can also be varied to match or register with the
printed or embossed patterns on the face of the decorative sheet.
In this manner, the deductibility of the projections can be
significantly reduced.
The projections on the back of the decorative sheet can be
circles, diamonds, squares, ellipses, rectangles or other shapes,
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R.I.C-2285A 07-21-94
including irregular shapes such as wavy lines. Although many
patterns were tested, it was found that the pattern of a diamond
shaped projection, as shown in the drawings, gives the best
positionability and still allows adhesive to be maximized at the
edges even when trimming or cutting the decorative sheeting.
Illustratively, use of circular patterns are not a preferred
embodiment since they materially cut down on surface area for
adhesive on the back. Squares or rectangles can be used but there
is a risk that the sheet edges will be cut on a line adjacent the
squares or rectangles which is devoid of adhesive.
It is desirable to use projections which have a height equal
to or slightly more than the thickness of the adhesive to thereby
minimize the deformation of the face of the decorative sheet when
it is pressed to engage the PSA to the wall. The higher the
projections above the adhesive thickness, the more noticeable can
be the strike through, i.e., conspicuous visibility of the
projections or separation means on the decorative side after
final adherence to a wall. However, if the projections are not
sufficiently high, insufficient separation is provided to allow
the wall covering to slide over the wall on the surface of the
projections without the PSA firmly adhering to the wall.
Projections having a height greater than about twice the
thickness of the adhesive should be avoided since the projections
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213016
R.I:C-2285A 07-21-94
can generally be visible on the face of the wallcovering, i.e.,
strike through, when it is permanently secured to a wall.
Scrim and long strands generally provide strike through.
One reason for this is that the scrim is often too thick and thus
shows an imprint and if it is made thinner it is inoperable. The
other and main reason is that it follows a continuous line
pattern instead of being in the shape of projections having a
relatively small cross section and thickness. Normally, the wail
has random bumps or dimples on its surface, but the scrim
netting or straight strands, are symmetrical and thus show up.
The projections can be individual projections or a clump of
closely spaced projections.
The cross section of each projection will generally vary
from about 0.01 to about 0.5 square inches, preferably 0.02 to
0.1 square inches, and particularly about 0.02 to 0.06 square
inches. The total area of the back of the decorative sheet
covered by the projections can vary from about 5% to 20% and
preferably from about 7% to 15%.
The projections are preferably spaced so that there are
about 200 to 300 projections per square foot of surface area on
the back of the decorative sheet. This is equivalent to about
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R.I.C-2285A 07-21-94
1.5 to about 2 projections per sguare inch on the back of the
decorative sheet.
Anything that can be used as the ink on a printing machine
can be used for fabricating the projections so long as it is not
sticky or tacky upon drying so that they can slide over the
surface of a wall. Thus, any plastic, including resinous
material, which can be placed in solution, dispersion or emulsion
and which is not sticky or tacky on drying can be used. The
projections can be made of organic polymeric material such as
polyurethane, polyvinyl chloride, polyethylene, polypropylene or
polystyrene and the like. PVC plastisols are a preferred raw
material for the projections. Projections of such polymeric
material generally possess some resiliency. The solvent or
dispersing agent can be any one or a combinations of conventional
solvents, e.g. organic solvent or dispersing agents for plastic
or resinous material such as mineral spirits, various esters,
ketones, etc.
An expandable or foamable product, such as Expancel~ from
Nobel Industries can be used on the back of the sheet as the
projections. Other deformable plastic foams can be selected from
the group consisting of urethanes, polyvinylidene chloride,
polyethylene, polypropylene, polystyrene, rubber latices (natural
and synthetic), and polyvinyl chloride. The decorative sheet of
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this embodiment will be able to slide along a wall as the foam
contacts the wall surface, and without significantly contacting
the PSA with the wall and yet can be permanently adhered by the
application of sufficient pressure to deform the foam and thereby
place the PSA in substantially full contact with the wall.
Spaces Between the PSA and Projections
In positioning the projections and adhesive on the back of
the decorative sheet, e.g., by printing, care needs to be
exercised to prevent contact of the projections with the
adhesive. Projections which are contacted with adhesive will
interfere with slidability of the projections on a wall surface.
To prevent such contact the adhesive and projections are
generally separated by a space on the back surface. In practice
such space can vary over a wide range but it is desirable in
order to obtain maximum area of adhesive coverage on the back
that such space be as little as possible such as that of from
about one-sixtyfourth (1/64) of an inch to one sixteenth of an
inch although such space can be larger, e.g. one-eighth or one-
quarter or more of an inch.
The total area of the back which is not covered by
projections or PSA, i.e., the spaces on the back side, can vary
over a wide range such as that of about 3% to 30% of the back and
preferably from about 4% to 25% of the back.
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R.I.C-2285A 07-2L-g4
Placement of the Projections and PSA on the Decorative Sheets.
The PSA and projections can be placed on the decorative
sheets by various techniques although printing is the preferred
method. Generally, the projections are first printed in a pattern
onto the back side. In the areas that do not have printed
projections, there is printed adhesive while a space is
maintained on the back between projection and adhesive. Such
printing allows for independent control of the adhesive thickness
(laydown) and the thickness or height of the projections, thus
allowing for infinite ratios of one height to the other. It also
allows unique and accurate control of the pattern or geometry of
each. Although many printing processes such as gravure,
flexographic, ink jet, or lithographic can be used, screen
printing is preferred. Screen printing can be flat screen
(silk screen) or rotary screen. The rotary screen process is
preferred since it lends itself to long production runs, allows
for a controlled pattern or design, is capable or controlling the
amounts of inks or adhesive, i.e. thickness or laydown rates, and
is capable or in-register or side-by-side pattern printing.
In practice, it may be necessary to cover the back side of
the decorative sheet containing the PSA and the projections with
a suitable release paper which, when the sheet material is rolled
up for storage purposes, prevents adhesion to the decorative
surface of the sheet material. Immediately prior to the sheet
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R.I.C-2285A 07-21-94
material being applied to a support surface the release paper can
be removed, exposing the adhesive and projections. Alternatively,
the decorative surface can have a release coating thereon so that
the adhesive does not stick to the decorative surface when the
sheet is rolled.
To further demonstrate and explain the present invention,
and not by way of limitation, the following examples are
presented.
Example I
In a preferred mode of placing the PSA and the projections
on the back of a paper decorative sheet as shown in Fig. I and
Fig. 2, the paper is hung on an unwind stand. The paper had a
decorative printed pattern on its face side and a silicone
release top coat applied over the decorative face side. The
paper is then fed onto a creeper table that allows each roll to
be spliced without shutting down the line. Next, the paper is
conditioned in an oven that removes all excess moisture, and then
into a tensioning device that controls the web tension through
the printing process. There are two print stations. The first
is a rotary screen station in which the projections are printed
on to the back of the decorative sheet. A 40 mesh screen that
was engraved in a diamond pattern as shown in Fig. 1 was used.
Brant 2031 PVC plastisol was used at 4,000 cps. The squeegee was
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CA 02135016 2005-08-23
rubber and the oven set at 300°F. Press speed was 31 yards
per minute. The plastisol height laid down was 1 mil (+ or
- 0.25 mils) dry. The second station printed the PSA on
the back of the decorative sheet. Dauber DC 7009 EMTM was
used. Another preferred pressure sensitive adhesive is 3M
4224-NFTM. The PSA was at a viscosity of 3,000 cps. A 40
mesh screen was used with a rubber squeegee. The oven was
set at 300°F. The adhesive height was approximately the
same or slightly lower than the projections. After the
adhesive is applied, the printed paper is wound into a
master roll for later slitting and trimming to the proper
width and length for use as a wall covering. The resulting
wallcovering will have excellent slideability,
removeability and initial tack with no visual detection of
the projections after it is secured to the wall.
Example 2
Printed and embossed paper decorative sheet, 70 pounds
per ream, measuring 20.5 inches across is printed by
gravure with a pattern of squares by a dispersion of
polyvinyl acetate. The squares are uniformly positioned
over the back side. An acrylic PSA (C800TM) obtained from
Century Adhesive, Columbus, Ohio is then printed by gravure
on the back of the decorative sheet so that about 55% of
the back surface adjacent the squares but not in contact
therewith is covered by the adhesive. The thickness of
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R.I.C-2285A 07-21-94
the adhesive is about 15% less than the thickness or height of
the polyvinyl acetate. The total area of the back covered by the
projections is about 12%. Area adjacent an edge of the resulting
wall covering is lightly brought in contacted with a wall and
then slid on the wall surface on the projections for accurate
positioning. Then pressure from a person's hand or a roller tool
is used to press the PSA into contacting the wall for permanent
adhesion.
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