U.S. patent application number 10/243716 was filed with the patent office on 2003-05-08 for graffiti and/or environmental protective article having removable sheets.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Everaerts, Albert I., Janssen, Jeffrey R., O'Keefe, Donald R., Sheffield, William F..
Application Number | 20030087054 10/243716 |
Document ID | / |
Family ID | 22664688 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030087054 |
Kind Code |
A1 |
Janssen, Jeffrey R. ; et
al. |
May 8, 2003 |
Graffiti and/or environmental protective article having removable
sheets
Abstract
This invention relates to an article comprising a transparent
stack of sheets that may be applied, for example, to protect
substrates such as glass or plastic windows, signage or displays. A
topmost sheet can be peeled away after it is damaged to reveal an
undamaged sheet below. The invention also relates to the protected
substrates and a method of protecting substrates such as glass or
plastic windows, signage and displays from vandalism or other
surface damage by adhering the stack of sheets to the substrate to
be protected and subsequently pulling a topmost sheet away from the
stack after it becomes damaged.
Inventors: |
Janssen, Jeffrey R.;
(Woodbury, MN) ; Everaerts, Albert I.; (Oakdale,
MN) ; O'Keefe, Donald R.; (Roseville, MN) ;
Sheffield, William F.; (Oakdale, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
22664688 |
Appl. No.: |
10/243716 |
Filed: |
September 13, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10243716 |
Sep 13, 2002 |
|
|
|
09181532 |
Oct 28, 1998 |
|
|
|
6461709 |
|
|
|
|
Current U.S.
Class: |
428/40.1 |
Current CPC
Class: |
B32B 17/10009 20130101;
B32B 2556/00 20130101; B32B 27/08 20130101; Y10T 428/14 20150115;
B32B 2307/412 20130101; Y10T 156/1089 20150115; Y10T 428/2486
20150115; B32B 7/06 20130101; Y10T 428/1471 20150115; Y10T
428/24868 20150115; Y10T 156/1092 20150115 |
Class at
Publication: |
428/40.1 |
International
Class: |
B32B 009/00 |
Claims
What is claimed is:
1. An article comprising: a stack of sheets, wherein each sheet
independently comprises: (a) a film, the film having a first side
having a surface area and an opposite second side having a surface
area; (b) a bonding layer having a first side having a surface area
and an opposite second side having a surface area, wherein the
bonding layer is bonded via its first side to the second side of
the film such that at least a center of the surface area of the
second side of the film is in contact with the bonding layer,
wherein at least about 50 percent of the surface area of the second
side of the film has the bonding layer bonded thereto; wherein each
sheet is stacked upon another sheet such that except for a bottom
sheet of the stack of sheets, the bonding layer of a sheet is in
contact with the film, of a sheet below; wherein a topmost sheet
can be removed from the stack of sheets by pulling it away from the
stack such that the sheet being removed from the stack as well as
the sheets remaining with the stack do not delaminate; wherein the
stack of sheets when subjected to a visual acuity test using a 3
meter Snellen eye chart can allow an observer with 6 meter/6 meter
vision to read a line on the eye chart which is indicative of about
6 meter/9 meter vision or better.
2. The article of claim 1, wherein when subjected to a visual
acuity test using a 3 meter Snellen eye chart can allow an observer
with 6 meter/6 meter vision to read the line on the eye chart which
is indicative of about 6 meter/6 meter vision or better.
3. The article of claim 1, wherein the stack of sheets is
transparent.
4. The article of claim 1, wherein each sheet has a penetration
resistance of at least about 0.5 kg.
5. The article of claim 1 which comprises at least about 3
sheets.
6. The article of claim 1, wherein the film has a thickness ranging
from about 25 to about 4000 microns.
7. The article of claim 1, wherein the film comprises multiple
layers.
8. The article of claim 1, wherein the article further comprises a
plurality of tabs, wherein a separate tab is bonded to a portion of
the second side of the bonding layer of each of the sheets in a
manner such that the tab on the topmost sheet can be used to pull
the topmost sheet away from the stack of sheets.
9. The article of claim 1, wherein for each sheet at least a
portion of a margin of the film does not have bonding material
bonded thereto in a similar location such that the topmost sheet
can be removed by grasping the portion of the barrier film without
bonding material bonded thereto and pulling it away from the
stack.
10. The article of claim 9, wherein for each sheet the portion of
the margin which does not have bonding material bonded thereto is a
corner of the sheet.
11. The article of claim 1, wherein for each sheet at least a
portion of a margin of the bonding material is detackified in a
similar location wherein the topmost sheet can be removed by
grasping the sheet where the bonding material is detackified and
pulling it away from the stack.
12. The article of claim 11, wherein for each sheet the portion of
the margin where the bonding material is detackfied is a corner of
the sheet.
13. The article of claim 1, wherein each sheet has a hole which
extends through that sheet in a margin of the sheet, wherein the
holes in the sheets are staggered such that the holes do not
overlap and wherein the topmost sheet can be removed from the stack
of sheets by using a tool which can be inserted in the hole of the
topmost sheet and used to pull the topmost sheet away from the
stack.
Description
[0001] This application is a continuation of pending prior
application Ser. No. 09/181,532, filed Oct. 28, 1998, now
allowed.
FIELD OF THE INVENTION
[0002] This invention relates to an article comprising a
transparent stack of sheets that may be applied, for example, to
protect substrates such as glass or plastic windows, signage or
displays. A topmost sheet can be peeled away after it is damaged to
reveal an undamaged sheet below. The invention also relates to a
method of protecting substrates such as glass or plastic windows,
signage and displays from vandalism or other surface damage by
adhering the stack of sheets to the substrate to be protected and
subsequently pulling a topmost sheet away from the stack after it
becomes damaged.
BACKGROUND OF THE INVENTION
[0003] Windows and glass in public transportation vehicles such as
buses or subway trains can be subjected to a tremendous amount of
abuse. The windows can be damaged by both incidental scratching
during cleaning or they can be maliciously damaged by vandalism.
Vandals damage the windows by scratching or abrading the surface of
the window with items such as lava rock, diamonds, abrasive papers
or abrasive cloths. Vandals can also damage the window by painting
or coloring the surface of the window. Cleaning processes have been
defined to eliminate damage by painting or coloring. However,
scratching of glass by vandals presents a significant problem. In
one major city, for example, approximately 40 percent of the bus
windows have been vandalized by scratching and close to 80 percent
of the subway train windows. The public transportation officials
now call this type of graffiti "scratchiti". The best approach to
stopping graffiti historically has been to remove the graffiti
immediately once it appears. This graffiti prevention system which
is known as "zero tolerance", has been extremely successful in
eliminating the written and painted vandalism. Scratched glass,
however, is extremely difficult and expensive to repair and as a
result, the zero tolerance approach to scratchiti prevention and
elimination is cost prohibitive. The vandalism issue tarnishes the
overall image of an entire city's transportation system. The
vandalized glass leads to lower ridership because of the reduced
perception of safety on the vehicle by the public. The vandalism
ultimately leads to lost revenue for the public transportation
system and substantially high repair costs.
[0004] Several approaches have been evaluated to combat the
scrachiti problem. The first approach has been to repair the glass
by a multi-step abrasion/polishing method to remove the scrachiti.
The abrasion steps remove glass to the depth of the scratch with
diamond abrasives and then with subsequently finer grades of
diamond or aluminum oxide abrasives the surface of the glass is
polished to its original appearance. The abrasive materials are
expensive and the time required to completely abrade and polish the
surface of the glass can be several hours depending on the depth of
the damaged areas.
[0005] A second approach to eliminating the problem has been to
apply a single permanent adhesive coated polyester sheet onto the
surface of the window. The polyester sheet is thick enough to
protect the window from scratching by diamonds, lava rocks and most
abrasives. The sheet is typically applied onto the glass with a
water solution to eliminate any trapped air. The application
process takes about 5 to 10 minutes to complete. The sheet does a
good job of protecting the window from most of the damage but the
sheet is readily damaged and the damage is visible to the
passengers. Removing the sheet is very time consuming taking about
15 to about 60 minutes depending on the amount of residue left on
the window after removal of the sheet. Once the damaged sheet is
removed, a new permanent adhesive coated polyester sheet needs to
be applied. The time required to remove the adhesive coated
polyester sheet, remove the adhesive residue from the glass, and
apply a new permanent adhesive coated polyester sheet and reinstall
the window can be close to 2 hours. Examples of single permanent
adhesive coated polyester sheets which can be used to protect a
window are 3M.TM. Scotchshield.TM. Safety and Security Window Film
and 3M.TM. Sun Control Window Films, data sheet number
70-0703-7220-0 published in September 1996 by the 3M Company.
[0006] The replaced sheet can be quickly damaged once the vehicle
is used again in public thus necessitating another costly and time
consuming replacement.
[0007] The third approach commonly used to repair and protect
windows from scratches is to coat the damaged window with an epoxy
coating. (Enhancement of Vehicle Glazing for Vandal Resistance and
Durability, by Daniel R. Bowman, Mar. 25, 1996, available from the
United States Transportation Research Board). The damaged window is
typically first scrubbed clean before coating with an epoxy
coating. The epoxy coating can be used to fill the defects on the
windows and restore the window to a state of clarity where signs
can be read through the window. To apply the coating, the window
must be removed from the vehicle and the window must be cleaned and
primed. The coatings are applied and cured in a clean environment.
The coatings currently available however are easily scratched by
the same method used to scratch the glass. Once the coating is
damaged, it is difficult to apply a subsequent coating due to poor
adhesion of the coating to the first layer. The process to replace
the damaged coating with a new coating is time consuming and
expensive.
[0008] Another approach to the problem is to apply a sacrificial
window as a shield over an original non-damaged window. The
vehicle's window is modified with a frame that has a channel
designed for a sheet of polycarbonate or acrylic. The rigid
self-supporting sheet is inserted into the channel and acts as a
barrier to damage on the base window. The polycarbonate sheet can
be easily scratched by intentional methods being used to scratch
the glass. This approach requires extensive modification to the
window frame. Furthermore, the material cost per repair can be
excessive making this approach cost prohibitive.
[0009] U.S. Pat. No. 3,785,102 discloses a pad comprising a
plurality of very thin polyethylene or polypropylene removable
sheets, each sheet bearing a very thin coating of pressure
sensitive adhesive on its top surface for removing dirt from shoes
and an adhesive at the bottom surface so that each successive layer
is removably adhered to successive bottom layers and eventually to
the floor. There is no discussion regarding the clarity of such a
pad.
[0010] 3M Masking and Packaging Systems Division sells a stack of
sheets with adhesive that removes lint and pet hair under the trade
names Pat It.TM. Lint and Pet Hair Remover, product data sheet
numbers 70-0705-7091-9, 70-0705-0819-0 and 70-0705-7038-0 published
by 3M Company in 1994.
[0011] Research Disclosure 24109 (May 1984) discloses transmissive
strippable plastic sheets stacked on mirror surfaces or stacked
reflective (mirror surfaced) strippable plastic sheets that can be
removed successively as toner or dust build up on the mirrors used
in the optical imaging systems of electrophotographic reproduction
apparatus occurs. The adhesive joining the layers to one another
are provided only about the border areas of the sheets which are
outside the optical image path to minimize image quality
losses.
[0012] JP 10167765A describes a method of cleaning windows by the
application of an optically clear sheet of plastic film on the
inner and outer surface of the glass. The film is comprised of
polyvinyl chloride, polyacrylic acid, polyester or polycarbonate.
The plastic film is thin and only a single sheet of plastic is
described on each side of the glass. The sheet is removed when the
sheet becomes soiled.
[0013] U.S. Pat. No. 5,592,698 discloses a tear away lens stack for
maintaining visibility through a transparent protective eye and
face shield of a racing vehicle drivers helmet which includes a tab
portion having projections formed thereon to assist in grasping the
tab portion for rapid tear away. No adhesive is used in the stack;
rather the lenses are clipped together.
[0014] A need thus exists for an article and a method for
protecting windows, displays, and signage which is time and labor
saving as well as cost effective.
SUMMARY OF THE INVENTION
[0015] We have discovered such an article and a method. The present
invention provides an article comprising a stack of sheets wherein
the sheets are designed to be removable from each other such that a
fresh sheet can be exposed after a topmost sheet above is damaged
and then removed. The stack can be applied, for example, to the
interior of bus or train windows to provide protection for the
windows. As a sheet is damaged by graffiti artists, the topmost
sheet of the article can be removed by trained maintenance
personnel to reveal a clean undamaged sheet below. Preferably the
time for each sheet removal is very fast (less than about 5
minutes, more preferably less than about 3 minutes and most
preferably less than about 1 minute.) In addition, the articles of
the invention are preferably cost effective. Using a preferred
embodiment of the invention the speed of damage removal and low
cost of damage removal allows the public transportation authorities
to practice the "zero tolerance" scratchiti prevention system on
the windows of public transportation vehicles.
[0016] The article of the invention can optionally be applied to
backlit signage or highway/street signage that is in areas that
make it susceptible to damage by graffiti artists, weathering, or
normal wear and tear. It can, for example, preferably be used on
top of the typical plastic layer protecting a sign or in place of
it.
[0017] The present invention provides an article comprising:
[0018] a stack of sheets, wherein each sheet independently
comprises:
[0019] (a) a film, the film having a first side having a surface
area and an opposite second side having a surface area;
[0020] (b) a bonding layer having a first side having a surface
area and an opposite second side having a surface area, wherein the
bonding layer is bonded via its first side to the second side of
the film such that at least a center of the surface area of the
second side of the film is in contact with the bonding layer,
wherein at least about 50 percent of the surface area of the second
side of the film has the bonding layer bonded thereto;
[0021] (c) an optional release layer coated on the first side of
the film;
[0022] wherein each sheet is stacked upon another sheet such that
except for a bottom sheet of the stack of sheets, the bonding layer
of a sheet is in contact with the protective film or release layer,
if present, of a sheet below;
[0023] wherein a topmost sheet can be removed from the stack of
sheets by pulling it away from the stack such that the sheet being
removed from the stack as well as the sheets remaining with the
stack do not delaminate;
[0024] wherein the stack of sheets when subjected to a visual
acuity test using a 3 meter Snellen eye chart can allow an observer
with 6 meter/6 meter vision to read a line on the eye chart which
is indicative of about 6 meter/12 meter vision or better.
[0025] In a preferred embodiment of the article of the invention
the article when subjected to a visual acuity test using a 3 meter
Snellen eye chart can allow an observer with 6 meter/6 meter vision
to read the line on the eye chart which is indicative of about 6
meter/6 meter vision or better.
[0026] In a preferred embodiment the first side of the film is not
bonded to a bonding layer of the same sheet. In other words,
preferably each sheet has a bonding layer coated on the second side
of the film only.
[0027] In a preferred embodiment of the article of the invention
the bonding layer is continuous.
[0028] In a preferred embodiment, the article of the invention when
subjected to a 180.degree. Peel Adhesion to Glass test leaves
substantially no residue (more preferably no residue) on the
glass.
[0029] In a preferred embodiment of the article of the invention
the stack of sheets is transparent.
[0030] In a preferred embodiment of the article of the invention
each sheet has a penetration resistance of at least about 0.5 kg,
even more preferably at least about 1 kg, even more preferably at
least about 2 kg, even more preferably at least about 2.5, even
more preferably at least about 3 kg, even more preferably at least
about 3.5 kg, and most preferably about 4 kg.
[0031] With respect to the article of the invention preferably the
maximum haze value of the stack of sheets is less than about 10
percent, more preferably less than about 5 percent, and most
preferably less than about 3 percent.
[0032] In a preferred embodiment of the article of the invention at
least about 80 percent (more preferably at least about 90 percent,
and most preferably about 100 percent) of the surface area of the
second side of the film has the bonding layer bonded thereto.
[0033] In a preferred embodiment of the article of the invention
the bonding layer is continuous and any areas of the second side of
the film not bonded to the bonding layer are margin(s).
[0034] Preferably the article of the invention comprises at least
about 3 sheets, more preferably about 5 to about 10 sheets.
[0035] In a preferred embodiment of the article of the invention
the release layer is present and the release layer of each sheet
has a Taber abrasion resistance of about 25 percent or less, more
preferably about 10 or less, and most preferably about 2 or less
according to ASTM D1044-76 after 100 cycles.
[0036] In a preferred embodiment of the article of the invention
the bonding layer comprises a material selected from the group
consisting of acrylics, rubbers, polyolefins, and mixtures
thereof.
[0037] In a preferred embodiment of the article of the invention
the bonding layer comprises a pressure sensitive adhesive.
[0038] In a preferred embodiment of the article of the invntion the
bonding layer has a thickness ranging from about 5 to about 150
microns, more preferably about 10 to about 25 microns.
[0039] In a preferred embodiment of the article of the invention
the film has a thickness ranging from about 25 to about 4000
microns, more preferably about 50 to about 1000 microns.
[0040] In a preferred embodiment of the article of the invention
the film comprises a material selected from the group consisting of
polyester, polycarbonate, acrylic, polyurethanes, poly acetyl,
polyolefin based ionomers, ethylene vinyl acetate polymers,
polyethylene, polypropylene, polyvinyl chloride, polystyrene,
urethane acrylate polymers, epoxy polymers, epoxy acrylate
polymers, and blends thereof.
[0041] In a preferred embodiment of the article of the invention
the film further comprises of an additive selected from the group
consisting of ultraviolet lights absorbers, ultraviolet light
stabilizers, flame retardants, smoke suppressants, antioxidants,
and mixtures thereof.
[0042] In a preferred embodiment of the article of the invention
the film comprises multiple layers.
[0043] In a preferred embodiment of the article of the invention
each sheet has a tensile strength of about 20 to about 2000 kP, an
elongation of about 5 to about 1000% and a tear strength of about
0.05 to about 5 kg. Even more preferably each sheet has a tensile
strength of about 70 to about 1400 kP, an elongation of about 5 to
about 500% and a tear strength of about 0.5 to about 2.5 kg. Most
preferably each sheet has a tensile strength of about 350 to about
1000 kP, an elongation of about 20 to about 100% and a tear
strength of about 1.5 to about 2.5 kg.
[0044] In a preferred embodiment of the article of the invention
the release layer is present.
[0045] In a preferred embodiment of the article of the invention
the release layer has a thickness ranging from about 0.1 to about
25 microns, more preferably about 2.5 to about 5 microns.
[0046] In a preferred embodiment of the article of the invention
the release layer comprises a material selected from the group
consisting of acrylates, methacrylates, urethanes, silicones,
polyolefins, fluorocarbons and mixtures thereof.
[0047] In a preferred embodiment of the article of the invention
the bonding layer of each sheet further comprises a component
selected from the group consisting of flame retardants, smoke
suppressants, antioxidants ultraviolet light absorbers, ultraviolet
light stabilizers, and mixtures thereof.
[0048] In a preferred embodiment of the article of the invention
the topmost sheet is capable of being removed by gripping the sheet
with an adhesive wand and pulling the sheet away from the stack of
sheets of sheets.
[0049] In a preferred embodiment of the article of the invention
the article further comprises a plurality of tabs, wherein a
separate tab is bonded to a portion of the second side of the
bonding layer of each of the sheets in a manner such that the tab
on the topmost sheet can be used to pull the topmost sheet away
from the stack of sheets.
[0050] In a preferred embodiment of the article of the invention
for each sheet at least a portion of a margin of the film does not
have bonding material bonded thereto in a similar location such
that the topmost sheet can be removed by grasping the portion of
the barrier film without bonding material bonded thereto and
pulling it away from the stack. Most preferably for each sheet the
portion of the margin which does not have bonding material bonded
thereto is a corner of the sheet.
[0051] In a preferred embodiment of the article of the invention
for each sheet at least a portion of a margin of the bonding
material is detackified in a similar location wherein the topmost
sheet can be removed by grasping the sheet where the bonding
material is detackified and pulling it away from the stack. Most
preferably for each sheet the portion of the margin where the
bonding material is detackfied is a corner of the sheet.
[0052] In a preferred embodiment of the article of the invention
each sheet has a hole which extends through that sheet in a margin
of the sheet, wherein the holes in the sheets are staggered such
that the holes do not overlap and wherein the topmost sheet can be
removed from the stack of sheets by using a tool which can be
inserted in the hole of the topmost sheet and used to pull the
topmost sheet away from the stack.
[0053] The present invention also provides a construction
comprising:
[0054] (i) an article comprising:
[0055] a stack of sheets, wherein each sheet independently
comprises:
[0056] (a) a film, the film having a first side having a surface
area and an opposite second side having a surface area;
[0057] (b) a bonding layer having a first side having a surface
area and an opposite second side having a surface area, wherein the
bonding layer is bonded via its first side to the second side of
the film such that at least a center of the surface area of the
second side of the film is in contact with the bonding layer,
wherein at least about 50 percent of the surface area of the second
side of the film has the bonding layer bonded thereto, wherein with
respect to each sheet the first side of the film is not bonded to a
bonding layer of the same sheet;
[0058] (c) an optional release layer coated on the first side of
the film;
[0059] wherein each sheet is stacked upon another sheet such that
except for a bottom sheet of the stack of sheets, the bonding layer
of a sheet is in contact with the protective film or release layer,
if present, of a sheet below;
[0060] wherein a topmost sheet can be removed from the stack of
sheets by pulling it away from the stack such that the sheet being
removed from the stack as well as the sheets remaining with the
stack do not delaminate;
[0061] wherein the stack of sheets when subjected to a visual
acuity test using a 3 meter Snellen eye chart can allow an observer
with 6 meter/6 meter vision to read a line on the eye chart which
is indicative of about 6 meter/12 meter vision or better; and
[0062] (ii) a substrate to which the article is bonded via the
bonding layer of the bottom sheet.
[0063] In a preferred embodiment of the article of the invention
the substrate comprises a material selected from the group
consisting of glass, metal, plastic, painted surfaces, wood,
fabric, wallpaper, ceramic, concrete, mirrored surfaces,
plastic/glass laminates, and combinations thereof.
[0064] In a preferred embodiment of the article of the invention
the substrate is part of a structure. Most preferably the structure
is selected from the group consisting of windows, walls,
partitions, signs, bill boards, artwork, buildings, elevators,
vehicles, furniture, and doors.
[0065] In a preferred embodiment the structure comprises a
window;
[0066] wherein the article is bonded via the bonding layer of the
bottom sheet to the window, wherein the article has at least one
edge;
[0067] and wherein the construction further comprises a frame which
is attached to a least a portion of the window such that it extends
over at least one edge of the article. Preferably the frame extends
over all the edge(s) of the article.
[0068] In another preferred embodiment the structure comprises a
window;
[0069] wherein the article further comprises a plurality of tabs,
wherein a separate tab is bonded to a portion of the second side of
the bonding layer of each of the sheets in a manner such that the
tab on the topmost sheet can be used to pull the topmost sheet away
from the stack of sheets;
[0070] wherein the article is bonded via the bonding layer of the
bottom sheet to the window, wherein the article has at least one
edge;
[0071] and wherein the structure further comprises a frame which is
attached to at least a portion of the window such that it extends
over at least one edge of the article in a manner which covers the
tabs.
[0072] In another preferred embodiment of the construction the
structure is a window;
[0073] wherein for each sheet at least a portion of a margin of the
film does not have bonding material bonded thereto in a similar
location such that the topmost sheet can be removed by grasping the
portion of the barrier film without bonding material bonded thereto
and pulling it away from the stack;
[0074] wherein the article is bonded via the bonding layer of the
bottom sheet to the window, wherein the article has at least one
edge;
[0075] and wherein the construction further comprises a frame which
is attached to at least a portion of the window such that it
extends over at least one edge of the article in a manner such that
it extends over the portion of the film margin that does not have
bonding material bonded thereto.
[0076] In another preferred embodiment of the construction
structure comprises a window;
[0077] wherein for each sheet of the article at least a portion of
a margin of the bonding material is detackified in a similar
location wherein the topmost sheet can be removed by grasping the
sheet where the bonding material is detackified and pulling it away
from the stack;
[0078] wherein the article is bonded via the bonding layer of the
bottom sheet to the window, wherein the article has at least one
edge; and wherein the construction further comprises a frame which
is attached to at least a portion of the window such that it
extends over at least one edge of the article such that it extends
at least over the portion of the sheet margin wherein the bonding
material is detackified.
[0079] In another preferred embodiment of the construction the
structure comprises
[0080] a window;
[0081] wherein each sheet of the article has a hole which extends
through that sheet in a margin of the sheet, wherein the holes in
the sheets are staggered such that the holes do not overlap and
wherein the topmost sheet can be removed from the stack of sheets
by using a tool which can be inserted in the hole of the topmost
sheet and used to pull the topmost sheet away from the stack;
[0082] wherein the article is bonded via the bonding layer of the
bottom sheet to the window, wherein the article has at least one
edge; and wherein the construction further comprises
[0083] a frame which is attached to at least a portion of the
window such that it extends over at least one edge of the article
such that it extends at least over the holes in the sheets.
[0084] In another preferred embodiment of the construction
[0085] the structure comprises a vehicle comprising a window;
[0086] and wherein the article is bonded via the bonding layer of
the bottom sheet to the window. Most preferably the vehicle is
selected from the group consisting of buses, trains, and
subways.
[0087] The present invention also provides a method comprising the
steps of:
[0088] (a) applying an article comprising:
[0089] a stack of sheets, wherein each sheet independently
comprises:
[0090] (i) a film, the film having a first side having a surface
area and an opposite second side having a surface area;
[0091] (ii) a bonding layer having a first side having a surface
area and an opposite second side having a surface area, wherein the
bonding layer is bonded via its first side to the second side of
the film such that at least a center of the surface area of the
second side of the film is in contact with the bonding layer,
wherein at least about 50 percent of the surface area of the second
side of the film has the bonding layer bonded thereto, wherein with
respect to each sheet the first side of the film is not bonded to a
bonding layer of the same sheet;
[0092] (iii) an optional release layer coated on the first side of
the film;
[0093] wherein each sheet is stacked upon another sheet such that
except for a bottom sheet of the stack of sheets, the bonding layer
of a sheet is in contact with the protective film or release layer,
if present, of a sheet below;
[0094] wherein a topmost sheet can be removed from the stack of
sheets by pulling it away from the stack such that the sheet being
removed from the stack as well as the sheets remaining with the
stack do not delaminate;
[0095] wherein the stack of sheets when subjected to a visual
acuity test using a 3 meter Snellen eye chart can allow an observer
with 6 meter/6 meter vision to read a line on the eye chart which
is indicative of about 6 meter/12 meter vision or better;
[0096] to a substrate via the bonding layer of the bottom sheet of
the article;
[0097] (b) allowing the topmost sheet of the article to be
damaged;
[0098] (c) removing the damaged topmost sheet of the article by
gripping the sheet and pulling it away from the stack, in a manner
such that neither the sheet being removed nor the stack of sheets
which remains delaminates, in order to expose a lower sheet of the
article which thence becomes the topmost sheet of the article.
[0099] In a preferred embodiment of the method, steps (b) and (c)
are repeated at least once. More preferably steps (b) and (c) are
repeated until the bottom sheet is removed, and the bottom sheet
upon removal leaves substantially no adhesive residue (most
preferably) on the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0100] In a preferred embodiment of the article of the invention
the sheets are rectangular sheets of the same length and width.
[0101] FIG. 1 is a cross-sectional view taken along line 1-1 of the
construction of FIG. 5.
[0102] FIG. 2 is a cross-sectional view taken along line 2-2 of the
construction of FIG. 6.
[0103] FIG. 3 is a cross-sectional view taken along line 3-3 of the
construction of FIG. 7 showing a person peeling away a damaged
topmost sheet to reveal a new topmost sheet.
[0104] FIG. 4 is a cross-sectional view of the construction of FIG.
8 taken along line 4-4 showing a stack of four sheets which is
undamaged. FIG. 4 is identical to FIG. 3 except that damaged
topmost sheet has been removed.
[0105] FIG. 5 is a plan view of a construction comprising an
article of the invention adhered to a window.
[0106] FIG. 6 illustrates a plan view of the construction of FIG. 5
wherein the topmost sheet of the article is being damaged by a
rock.
[0107] FIG. 7 illustrates a plan view of the construction of FIG. 6
wherein the damaged topmost sheet is being peeled away to reveal an
undamaged sheet.
[0108] FIG. 8 illustrates a plan view of the construction of FIG. 7
after the damaged sheet has been removed and an undamaged sheet has
been revealed.
[0109] FIG. 9 illustrates a plan view of a construction comprising
an article of the invention bonded to a window, wherein a frame
extends over the edge of the article.
[0110] FIG. 9A illustrates a plan view of the construction of FIG.
9 wherein the topmost sheet of the article is being damaged by a
rock.
[0111] FIG. 9B illustrates a plan view of the construction of FIG.
9A, with the frame removed, wherein the damaged topmost sheet is
about to be peeled away to reveal an undamaged sheet.
[0112] FIG. 10 is a plan view of a construction comprising an
article of the invention on a window and a frame covering an edge
of the article.
[0113] FIG. 10A illustrates a plan view of the construction of FIG.
10 wherein the topmost sheet of the article is being damaged by a
rock.
[0114] FIG. 10B illustrates a plan view of the construction of FIG.
10A wherein the frame has been removed and wherein the damaged
topmost sheet is about to be peeled away to reveal an undamaged
sheet.
[0115] FIG. 11 is a cross-sectional view of the construction of
FIG. 9B taken along line 11-11.
[0116] FIG. 12 is a cross-sectional view of the construction of
FIG. 10B taken along line 12-12.
[0117] FIG. 13 is a cross-sectional view of another embodiment of a
construction of the invention comprising a window having a
protective article bonded to each side.
DETAILED DESCRIPTION OF THE INVENTION
[0118] Article
[0119] With respect to the article of the invention, preferably the
stack of sheets has no effect on visual acuity. The test for the
effect on visual acuity appears later herein. This test can be used
to determine the effect of an observer to discern images when
looking through the article of the invention.
[0120] Preferably the article (as well as the stack of sheets and
each individual sheet) has a haze value of less than about 10
percent, more preferably less than about 5 percent, and most
preferably less than about 3 percent.
[0121] The article of the invention as well as the sheets making up
the article are typically colorless although they may optionally be
tinted. The sheets may optionally have a graphic thereon which
would typically be on the edge of each sheet.
[0122] Sheets
[0123] Preferably the article comprises at least about 3 sheets,
typically about 5 to about 10 sheets. Preferably each sheet has the
same length, width, and shape. In a preferred embodiment each sheet
is rectangular in shape.
[0124] Each sheet preferably provides a protective barrier to
preferably prevent damage to a substrate to be protected such as a
glass window as well as any sheets below the exposed topmost sheet.
The sheet preferably resists penetration and damage from
conventional scratching tools such as razor blades, knives, lava
rocks, abrasive cloths, diamonds and carbide tipped styli.
Preferably at least one (more preferably each) sheet has a
penetration resistance of at least about 0.5 kg, more preferably at
least about 2 kg, and most preferably at least about 4 kg.
[0125] Effect on visual acuity and color preferably remain stable
upon exposure to a variety of environmental conditions.
[0126] The sheet is preferably easily removable, preferably in a
continuous piece. The following tests which evaluate the integrity
and removability of a sheet can be used to help predict the
removability of a sheet.
[0127] Preferably at least one sheet (more preferably each sheet as
well as each film making up the sheet) has a tensile strength when
subjected to ASTM D882 of about 20 to about 2000 kP, more
preferably about 70 to about 1400 kP, and most preferably about 350
to about 1000 kP. Preferably at least one sheet (more preferably
each sheet as well as each film making up each) has an elongation
when subjected to ASTM D882 of about 5 to about 1000%, preferably
about 5 to about 500 percent, and most preferably about 20 to about
100 percent.
[0128] Preferably at least one sheet (preferably each sheet as well
as each film making up each sheet) has a tear strength when
subjected to ASTM D1004 of about 0.05 to about 5 kg, more
preferably about 0.5 to about 2.5 kg, and most preferably about 1.5
to about 2.5 kg.
[0129] Film
[0130] Preferably the film comprises a material selected from the
group consisting of polyester, polycarbonate, acrylic,
polyurethanes, poly acetyl, polyolefin based ionomers, ethylene
vinyl acetate polymers, polyethylene, polypropylene, polyvinyl
chloride, polystyrene, urethane acrylate polymers, epoxy polymers,
epoxy acrylate polymers, and blends thereof. In one embodiment the
film comprises multiple layers.
[0131] The thickness of the film depends on the type of damage that
the film may be subjected to and the composition of the film.
Typically the film has a thickness of about 25 to about 4000
microns for reasons of weight, visual acuity and economics,
preferably about 50 to about 1000 microns and most preferably about
50 to about 250 microns.
[0132] The film can optionally further comprise stabilizers and
fillers which enhance the durability of the film upon exposure to
ultraviolet light and/or heat. Additives can also be incorporated
into the film that reduce the flammability of the film or smoke
generation during combustion.
[0133] Bonding Layer
[0134] The bonding layer preferably provides a stable bond between
the film layers. It is intended to prevent premature separation of
the sheets under the environmental conditions anticipated in the
application. It preferably serves to act as an optically clear
interface between the films. However, it must bond more readily to
the film of the same sheet than to the film of the sheet below.
[0135] In a preferred embodiment the first side of the film is not
bonded to a bonding layer. The bonding layer as well as the other
layers making up a sheet preferably do not change color when
subjected to environmental conditions. Furthermore, the stability
of the bonding layer preferably should not change dramatically on
exposure to a wide range of conditions.
[0136] The bonding layer may comprise a pressure sensitive adhesive
system or a non-pressure sensitive adhesive system. Preferably the
bonding layer comprises a pressure sensitive adhesive. The bonding
layer preferably comprises a material selected from the group
consisting of acrylics, for example, which are thermally cured,
ultraviolet light cured, electron beam cured and can be solvent
based, waterbased or 100 percent solids; rubbers, for example,
which can be thermoplastic rubbers, block copolymers, natural
rubbers or silicone rubbers; and polyolefins which can, for
example, be ethylene vinyl acetate polymers, poly-alpha olefins
(C.sub.3-C.sub.10) copolymers or blends of poly-alpha olefins with
ethylene or propylene based polymers; and mixtures thereof.
[0137] The bonding layer may optionally further comprise a
component selected from the group consisting of tackifiers, oils,
stabilizers, flame retardants fillers, and mixtures thereof subject
to obtain the desired properties. Preferably the bonding layer
further comprises a component selected from the group consisting of
ultraviolet light absorbers, ultraviolet light stabilizers and
mixtures thereof. Preferably the component selected from the group
consisting of ultraviolet light absorbers, ultraviolet light
stabilizers and mixtures thereof is used in an amount to inhibit
degradation of the article from ultraviolet radiation, preferably
about 0.5 to about 1 percent by weight based on the total weight of
the bonding layer.
[0138] Preferably at least about 80 percent, more preferably at
least about 90 percent, and most preferably about 100 percent of
the surface area of the second side of the film has the bonding
layer bonded thereto. Preferably the bonding layer is continuous.
Preferably any areas of the film not covered by the bonding layer
are margin(s).
[0139] Preferably the bonding layer has a thickness ranging from
about 5 to about 150 microns, more preferably about 10 to about 50
microns, and most preferably about 10 to about 25 microns.
[0140] Optional Release Layer
[0141] The optional release layer preferably prevents light
scratching of the surface of the film and in addition can provide a
release surface for the bonding layer on the sheet above. This
optional release layer is preferably bonded to the film layer in a
manner so as to maintain the bond after a variety of environmental
exposures. In addition, the release layer preferably remains clear
after environmental exposures. It preferably maintains scratch
resistant over time. It preferably forms a stable adhesion to the
bonding layer and provides a consistent surface for removal of the
sheet above.
[0142] Preferably the release layer, if present has a thickness
ranging from about 0.1 to about 25 microns, more preferably about
2.5 to about 5 microns.
[0143] Preferably the release layer comprises a material selected
from the group consisting of acrylates, methacrylates, urethanes,
polyolefins, silicones, fluorochemicals such as fluorocarbons, and
mixtures thereof.
[0144] U.S. Pat. No. 5,633,049 describes a method of making a
protective coating for thermoplastic transparencies particularly
aircraft transparencies. The coating is prepared from a silica-free
protective coating precursor composition comprising a
multifunctional ethylenically unsaturated ester of acrylic acid, a
multifunctional ethylenically unsaturated ester of methacrylic
acid, or a combination thereof; and an acrylamide. Such a
protective coating may be useful as a release coating for the
article of the present invention.
[0145] The release layer may optionally further comprise a filler
such as ceramer particles, for example, as described in U.S. Pat.
No. 5,104,929, in order to provide enhanced abrasion resistance
properties.
[0146] The adhesion of the bonding layer to the release layer can
be adjusted, for example, by incorporation of flow additives such
as silicones, acrylics or fluorochemicals to the release layer.
[0147] The release layer can optionally be selected to improve the
Taber Abrasion Resistance of the sheet. Release materials which may
provide good Taber Abrasion Resistance properties include but are
not limited to multifunctional acrylates or methacrylates.
[0148] The release layer on the top surface of the film layer may
provide uniform release performance across the sheet. Optionally, a
differential release layer can be coated on the film surface. Such
a differential release layer can be used to make the initial
separation of a sheet from the stack of sheets easier. Differential
release can be obtained, for example, by coating a material
providing easy release at the edge and/or corner of the sheet and
coating a material providing tighter release on the balance of the
sheet surface.
[0149] Suitable multifunctional ethylenically unsaturated esters of
(meth)acrylic acid are the polyacrylic acid or polymethacrylic acid
esters of polyhydric alcohols including, for example, the diacrylic
acid and dimethylacrylic acid ester of aliphatic diols such as
ethyleneglycol, triethyleneglycol, 2,2-dimethyl-3,3-propanediol,
1,3-cyclopentanediol, 1-ethoxy-2,3-propanediol,
2-methyl-2,4-pentanediol, 1,4-cyclohexanediol,
1,6-hexamethylenediol, 1,2-cyclohexanediol,
1,6-cyclohexanedimethanol; the triacrylic acid and trimethacrylic
acid esters of aliphatic triols such as glycerin,
1,2,3-propanetrimethanol, 1,2,4-butanetriol, 1,2,5-pentanetriol,
1,3,6-hexanetriol, and 1,5,10-decanetriol; the triacrylic acid and
trimethacrylic acid esters of tris(hydroxyethyl) isocyanurate; the
tetraacrylic and tetramethacrylic acid esters of aliphatic triols,
such as 1,2,3,4-butanetetrol, 1,1,2,2,-tetramethyloleth- ane,
1,1,3,3-tetramethylolpropane, and pentaerythritol tetraacrylate;
the pentaacrylic acid and pentamethacrylic acid esters of aliphatic
pentols such as adonitol; the hexaacrylic acid and hexamethacrylic
acid esters of hexols.
[0150] Preferably the release layer is present and the release
layer of at least one sheet (preferably each sheet) has a Taber
abrasion resistance of about 25 or less (more preferably about 10
or less and most preferably about 2 or less) as measured according
to ASTM D1044-76 after 100 cycles. The release layer is not
required if the bonding layer is anchored well to the film. For
example, the film surface coated with the bonding layer may be
chemically primed or oxidized with a corona discharge treatment or
flame treatment. The film surface not coated with the bonding layer
would be free of surface treatments. This adhesion differential
between the two sides of the film facilitates clean separation of
sheets from the stack. The film may also be soluble in the solvents
or monomers used for the bonding layer. By coating a bonding layer
on a soluble film and curing or evaporating, the bonding layer can
become entangled with the film. The adhesion of the bonding layer
to the coated film surface is greater than adhesion to the
laminated surface in the stack of sheets. due to the differential
in adhesion, clean separation of a sheet from a stack can be
obtained.
[0151] Optional Prime Layer
[0152] An optional prime layer can be used to provide an adhesion
promoting interface between the bonding layer and the film of the
same sheet. Alternatively the film surface can optionally be
modified via corona discharge treatments in a variety of
atmospheres or by using a flame in order to promote adhesion
between the bonding layer and the film of the same sheet. A prime
layer can be, for example, an aziridine based prime layer or a
grafted surface such as an acrylamide/multifunctional acrylate
polymerized into the film surface with high-energy radiation. Other
examples of prime layers include, for example, acrylics,
polyvinylidene chloride and solution coated polyesters.
[0153] A prime layer can be, for example, a high tack pressure
sensitive adhesive with a composition similar to the bonding layer.
It can also, for example, be a coextruded interface prepared as a
component of the film or resin solution coated on the film.
[0154] Preparation of the Article of the Invention
[0155] The article of the invention can be made in a number of
different ways. One method of making the article of the invention
is to apply the optional release coating on the surface of a film.
The release coating could be applied by roll coating, gravure
coating, or by an air knife coating process, for example. Any
solvent(s) present in the coating are evaporated in an oven. The
release coating can then be cured with ultraviolet (UV) light or
with an electron beam. Alternatively, the opposite surface of the
film may optionally be primed either with a surface treatment such
as corona treatment or a flame treatment. The prime could also be a
chemical prime. The chemical prime could be pre-applied by the film
supplier or applied, for example, by roll coating, gravure coating,
or by an air knife coating process. The solvent(s) are evaporated
from the priming layer. The prime layer may be coated with the
bonding layer by a variety of methods including notch bar coating,
curtain coating, or slot die coating of a solution or latex.
Another method of applying the bonding layer is extrusion coating
of a 100% solids bonding layer. Depending on the chemistry of the
coating, the bonding layer material is dried and/or cured to form a
finished polymer. When the bonding layer is tacky at room
temperature the bonding layer is preferably protected by a smooth
release film. A stack of sheets can be prepared by removing the
release liner from the bonding layer and laminating the bonding
layer to the release surface of an adjacent sheet. The end
application dictates the number of sheets in the stack. The stack
of sheets can be cut into a desired shape by die cutting with a
steel rule die, laser or with a water jet.
[0156] Another approach to forming a stack of sheets is to prepare
a film with a primed surface and an opposite release surface. An
ultraviolet curable liquid bonding layer is applied to the primed
surface of one film and laminated in the liquid state to the
release surface of a subsequent film. The liquid is cured. An
ultraviolet curable liquid bonding layer is applied to the primed
surface of a third film and laminated to the exposed release
surface of the first laminated sheets. The liquid is cured
resulting in a stack of three sheets. This lamination and curing
process can be repeated until the desired number of sheets in a
stack is obtained.
[0157] Other approaches to making the article of the invention are
also possible.
[0158] Application of Article to Substrate
[0159] The article of the invention can be applied to a substrate
in a number of different ways. For example, it can be applied by
spraying an alcohol/water solution such as a 25% isopropanol/75%
water solution on to the surface of the substrate. The release
liner is removed from the bottom sheet of the stack of sheets to
expose a bonding layer and the exposed bonding layer is also
sprayed with the same isopropanol/water solution. The substrate and
the saturated bonding layer are brought into contact and the excess
solution is removed from the interface with a roller or a squeegee.
The stack of sheets could also be applied to a substrate with a
dilute solution of dishwashing detergent in water such as for
example a 0.5% Joy.TM. dishwashing detergent 99.5% water solution.
The stack of sheets could also be applied directly to the substrate
with high pressure lamination without a liquid interface. The stack
of sheets could be applied to the substrate by applying an
ultraviolet light curable coating on the substrate as the liquid
interface. The stack of sheets is applied, the excess air is
removed by a roller or squeegee and the coating is cured.
[0160] Removal of Sheets
[0161] In one embodiment of the article of the invention the
topmost sheet is capable of being removed by gripping the sheet
with an adhesive wand and pulling the sheet away from the stack of
sheets.
[0162] In another embodiment the article further comprises a
plurality of tabs, wherein a separate tab is bonded to the second
side of the bonding layer of each of the sheets in a manner such
that the tab on the topmost sheet can be used to pull the topmost
sheet away from the stack of sheets.
[0163] In another embodiment of the article for each sheet at least
a portion of a margin of the film does not have bonding material
bonded thereto in a similar location such that the topmost sheet
can be removed by grasping the portion of the barrier film without
bonding material bonded thereto and pulling it away from the stack.
Preferably for each sheet the portion of the margin which does not
have bonding material bonded thereto is a corner of the sheet.
[0164] In another embodiment of the article for each sheet at least
a portion of a margin of the bonding material is detackified in a
similar location wherein the topmost sheet can be removed by
grasping the sheet where the bonding material is detackified and
pulling it away from the stack. Preferably for each sheet the
portion of the margin where the bonding material is detackfied is a
corner of the sheet.
[0165] In another embodiment of the article each sheet has a hole
which extends through that sheet in a margin of the sheet
(preferably the same margin), wherein the holes in the sheets are
staggered such that the holes do not overlap and wherein the
topmost sheet can be removed from the stack of sheets by using a
tool (such as a pick) which can be inserted in the hole of the
topmost sheet and used to pull the topmost sheet away from the
stack.
[0166] The article of the invention can be better understood by
referring to the following FIGS. 1 to 13. FIG. 1 is a
cross-sectional view taken along line 1-1 of the construction of
FIG. 5. The article 2 of the invention is bonded via bonding layer
44 to a glass window pane 4. The article 2 comprises a stack of
five sheets (6, 8, 10, 12, and 14) bonded together. Sheet 6, which
is the topmost sheet in FIG. 1, comprises top release layer 16,
inner film layer 18, and lower bonding layer 20. Sheet 8 comprises
top release layer 22, inner film layer 24, and lower bonding layer
26. Sheet 10 comprises top release layer 28, inner film layer 30,
and lower bonding layer 32. Sheet 12 comprises top release layer
34, inner film layer 36, and lower bonding layer 38. Sheet 14,
which is the bottom sheet of article 2, comprises top release layer
40, inner film layer 42, and lower bonding layer 44.
[0167] FIG. 2 is a cross-sectional view of the construction of FIG.
6. FIG. 2 shows the topmost sheet 6 being scratched 48 by rock
46.
[0168] FIG. 3 is a cross-sectional view of the construction of FIG.
7 showing a person peeling away the damaged topmost sheet 6 to
reveal a new topmost sheet 8. Since no bonding material is present
along a portion of a corner margin of each sheet a convenient place
for grasping 21 and removing the sheet is provided.
[0169] FIG. 4 is a cross-sectional view of the construction of FIG.
8 showing a now four sheet stack of sheets which is undamaged,
wherein the topmost sheet is now sheet 8. FIG. 8 is identical to
FIG. 7 except that damaged topmost sheet 6 has been removed.
[0170] FIG. 5 is a plan view of a construction comprising article 2
of the invention on a window. An observer 53 can view a tree 50
through the undamaged window 4 and article 2. A rim 52 extends
around the window 4.
[0171] FIG. 6 illustrates a plan view of the construction of FIG. 5
wherein the top sheet 6 of the article 2 is being damaged by a rock
46.
[0172] FIG. 7 illustrates a plan view of the construction of FIG. 6
wherein the damaged sheet 6 is being peeled away to reveal an
undamaged sheet 8.
[0173] FIG. 8 illustrates how the observer 53 can now clearly view
the tree 50 after the damaged sheet 6 of FIG. 7 has been removed
and undamaged sheet 8 has been revealed.
[0174] FIG. 9 is a plan view of a construction comprising the
article of the invention 60 bonded via bonding layer 94 (not shown)
to a glass window pane 62 (not shown) of a window. A window
comprises a window pane and the framework in which the window pane
is situated. (Articles of the invention are typically bonded to the
window pane, typically the entire window pane.) (Items not
illustrated in FIG. 9 are illustrated in FIG. 1) which is a
cross-sectional view of FIG. 9B taken along line 11-11. The article
60 comprises a stack of four sheets (64, 66, 68, and 70) bonded
together. Sheet 64, which is the topmost sheet, comprises top
release layer 72, inner film layer 74, and lower bonding layer 76.
Sheet 66, comprises top release layer 78, inner film layer 80, and
lower bonding layer 82. Sheet 68, comprises top release layer 84,
inner film layer 86, and lower bonding layer 88. Sheet 70, which is
the bottom layer of article 60, comprises top release layer 90,
inner film layer 92, and lower bonding layer 94. Tabs 96, 98, 100
and 102 are positioned between the sheets 64, 66, 68 and 70 between
such that they are bonded to the bonding layer of the sheet above
the tab. Frame 52 which covers the tabs is attached to the
framework of the window. An observer 53 can view a tree 50 through
the undamaged window 62 and article 60. A rim 52 extends around the
window.
[0175] FIG. 9A illustrates a plan view of the article construction
of FIG. 9 wherein the topmost sheet 64 of the article is being
damaged by a rock 46. Scratches 61 are shown.
[0176] FIG. 9B illustrates a plan view of the construction of FIG.
9B wherein the frame 52 has been removed to expose the tabs and
wherein the topmost damaged sheet 64 is being peeled away to reveal
an undamaged sheet 66.
[0177] FIG. 10 is a plan view of the construction comprising
article 110 on window pane 112 (shown in FIG. 12). An observer 53
can view a tree 50 through the undamaged window and article. A rim
52 extends around the window. Frame 56 is attached to the window
frame and extends over through holes 53, 55, 57, and 59 (not
shown).
[0178] FIG. 10A illustrates a plan view of the construction of FIG.
10 wherein the topmost sheet of the article is being damaged by a
rock 46. The scratches are identified as 47.
[0179] FIG. 10B illustrates a plan view of the construction of FIG.
10A wherein the frame 56 has been removed and the damaged topmost
sheet 114 is about to be peeled away to reveal an undamaged sheet
66 (not shown).
[0180] FIG. 12 is a cross-sectional view taken along line 12-12 of
FIG. 10B. The article of the invention 110 is bonded via bonding
layer 144 to a glass window 112. The article 110 comprises a stack
of four sheets (114, 116, 118, and 120) bonded together. Sheet 114,
which is the topmost sheet, comprises top release layer 122, inner
film layer 124, and lower bonding layer 126. Sheet 116, comprises
top release layer 128, inner film layer 130, and lower bonding
layer 132. Sheet 118, comprises top release layer 134, inner film
layer 136, and lower bonding layer 138. Sheet 120, which is the
bottom sheet, comprises top release layer 140, inner film layer
142, and lower bonding layer 144. Through holes 154, 156, 152, and
150 are created in the stack of sheets 114, 116, 118, and 120 after
the stack is prepared. They are staggered along a margin of the
article when viewed from above the topmost sheet.
[0181] FIG. 13 illustrates a cross-sectional view of a window pane
4 having an article 2 of the invention bonded to each side thereof.
Preferably such an article would have the preferred visual acuity
and haze values discussed elsewhere herein. Each article 2
comprises a topmost sheet 6 (the exposed sheet which is farthest
from the substrate being protected), and sheets 8, 10, 12, and 14.
Sheet 6 comprises top release layer 16, inner film layer 18, and
lower bonding layer 20. Sheet 8 comprises top release layer 22,
inner film layer 24, and lower bonding layer 26. Sheet 10 comprises
top release layer 28, inner film layer 30, and lower bonding layer
32. Sheet 12 comprises top release layer 34, inner film layer 36,
and lower bonding layer 38. Sheet 14 comprises top release layer
40, inner film layer 42, and lower bonding layer 44.
[0182] Test Methods
[0183] Penetration Resistance
[0184] A white painted steel panel from Advanced Coating
Technologies in Hillsdale Mich. is used as a base. A 50
mm.times.150 mm test sample is secured to the painted surface of
the steel panel using a 100 mm.times.50 mm piece of No. 232
Scotch.TM. Masking Tape from 3M Company along the long edges of the
sample such that a 125 mm.times.50 mm portion of the sample is in
direct contact with the painted panel. (In the case of a sheet or
stack of sheets the exposed adhesive layer is placed in contact
with the painted panel.) The panel with the sample on the top
surface is placed onto an electronic balance with a capacity of 20
kg. The balance is tared to the combined weight of the panel and
sample. Using a stainless steel coated industrial single edge razor
blade, apply a force of 0.5 kg to the test sample and hold for 2
seconds. Remove the blade from the test sample and repeat
identically the force application and removal at a site 0.5 cm away
from the original test site. Repeat the force application and
removal at a site 0.5 cm away from the second site and at least 0.5
cm away from the first site to thus obtain 3 replicates at this
force level. Color each force application test area with a black
Sharpie.TM. felt tipped permanent marker from the Sanford Corp. The
ink will flow through a penetrated area of the test sample and
produce a mark on the white metal panel. Remove the test sample
from the base panel and observe any marks on the base panel. If no
marks are present the sample has passed the test. If any marks are
present the sample has failed the test. Repeat the test using the
following forces in the test: 1 kg, 1.5 kg, 2 kg, 2.5 kg, 3 kg, 3.5
kg, and 4 kg. The force required to penetrate the sample is
recorded.
[0185] Effect of Sample on Visual Acuity of Observer
[0186] An observer with 6 meter/6 meter vision is positioned 3
meters from a 3 Meter Snellen eye chart, covers one eye and read
with the uncovered eye the line which corresponds to 6 meter/6
meter vision. The observer will be considered to have 6 meter/6
meter vision if the observer has that vision unaided or has that
vision with corrective lenses as long as the corrective lenses are
worn during the testing. A 75 mm.times.75 mm sample of the article
or material to be evaluated is then placed 3 centimeters in front
of the observer's uncovered eye while the other eye remains covered
to determine if the sample causes a loss of visual acuity. If the
sample has a protective release liner, the release liner is removed
prior to conducting the test. If the viewer can still read the line
of letters indicative of 6 meter/6 meter vision it is considered
that there is no interference with visual acuity caused by the
sample. If the line indicative of 6 meter/6 meter vision cannot
still be read the smallest line which can still be read is
recorded, (For example 6 meter/9 meter, 6 meter/12 meter, 6
meter/15 meter, 6 meter/18 meter, etc.).
[0187] Appearance After 120 hours at 23.degree. C. and 180 Degree
Peel Adhesion Between a Bonding Layer of a Sheet and the Surface of
an Adjacent Supported Film
[0188] A supported film is prepared as follows. A 105 mm.times.305
mm piece of 467 VHB.TM. Transfer Adhesive from 3M Company is
removed from a roll. The transfer adhesive is an acrylic adhesive
coated on a paper liner where both surfaces of the paper liner were
treated with a differential silicone release such that the adhesive
releases from one side of the liner easier than the other side. The
sheet of transfer adhesive was laminated with a rubber roller to
the entire surface of a 100 mm.times.300 mm rectangular painted
white metal panel from Advanced Coatings Technology of Hillsdale,
Mich. The release liner is removed from the transfer tape exposing
the adhesive on the entire surface of the metal panel. To the
adhesive is applied a 110 mm.times.320 mm film in such a way that
film/adhesive/panel laminate is free of bubbles. The film is
applied to the panel such that the release surface (the release
layer or the surface of the first side of the film if there is no
release layer present) is on the opposite surface of the film from
the adhesive coated panel. Any excess film and adhesive was trimmed
away.
[0189] To this panel supported film is laminated a 25 mm.times.150
mm sample of the sheet to be tested. (The sheet to be tested
typically comprises a film with a bonding layer coated on one
surface thereof.) The sample sheet is bonded to the panel supported
film via its bonding layer. A rubber roller is used and in such a
way that 100 mm of the sheet is bonded onto the panel supported
film and 50 mm of the sheet hangs freely over the edge of the panel
supported film. This assembly is allowed to dwell for 120 hours at
room temperature and about 50% relative humidity (R.H.).
[0190] The over-hanging edge of the sample sheet is clamped to a
sensor of a Slip-Peel Tester Model SP-102C-3090 adhesion tester
(IMASS Inc. Accord, Mass.). The rest of the assembly is firmly
clamped onto a carriage of the Slip-Peel Tester. As the carriage
moves upon operation of the tester the sheet sample is peeled from
the panel supported film at a rate of 228.6 cm/min and at an angle
of 180 degrees. The average force required to remove the sheet
sample from the panel-supported film over a 2-second test period is
recorded. The test was conducted at about 23.degree. C. and about
50% relative humidity.
[0191] Typical 180 degree peel adhesion values for a sheet of the
article of the invention range from about 50 to about 2000 g/2.54
cm. The 180 degree peel adhesion values at the lower end of the
range facilitate easy stripping of one sheet from another sheet.
The 180 degree peel adhesion values at the upper end of the range
make stripping of the sheets more challenging but the integrity of
the stack (the ability of the stack to resist premature separation)
can be maintained better when vandals scratch the surface of the
stack. The preferred 180 degree peel adhesion range is about 500 to
about 1500 .mu.l 2.54 cm. The most preferred 180 degree peel
adhesion range is about 750 to about 1250 g/2.54 cm.
[0192] Appearance After Heat Aging and 180 Degree Peel Adhesion
Between a Bonding Layer of a Sheet and the Surface of an Adjacent
Supported Film
[0193] The 180 degree peel adhesion force between a bonding layer
on a sheet sample and the surface of an adjacent supported film is
evaluated as described in the test method entitled "180 Degree Peel
Adhesion Between a Bonding Layer of a Sheet and the Surface of an
Adjacent Supported Film" except the assembly is aged for 5 days at
80.degree. C. The assembly is examined for discoloration,
blistering, and adhesive residue. Preferably the test sample is not
discolored or blistered. The test sample is allowed to equilibrate
to room temperature for 2 hours prior to testing. The test was
conducted at about 23.degree. C. and 50% relative humidity.
[0194] The 180 degree peel adhesion value of a sheet of the article
of the invention should preferably be stable compared to the room
temperature adhesion value measured according to the test entitled
"Appearance After 120 hours at 23.degree. C. and 180 Degree Peel
Adhesion Between a Bonding Layer of a Sheet and the Surface of an
Adjacent Supported Film". The 180 degree peel adhesion after heat
aging preferably should not increase more than about 50% and should
not decrease more than about 25%. The test sample preferably leaves
no residue such as adhesive residue upon removal.
[0195] Appearance After Continuous Exposure to Condensing Humidity
and 180 Degree Peel Adhesion Between a Bonding Layer of a Sheet and
the Surface of an Adjacent Supported Film
[0196] The adhesion force between a bonding layer of a sheet and
the surface of an adjacent supported film is evaluated as described
in the test method entitled "Appearance After 120 hours at
23.degree. C. and 180 Degree Peel Adhesion Between a Bonding Layer
of a Sheet and the Surface of an Adjacent Supported Film" except
that the assembly is first continuously aged in a chamber that is
maintained at 38.degree. C. and 100% relative humidity for 5 days
prior to appearance evaluation and 180 degree peel adhesion
testing. The assembly is examined for discoloration and blistering.
The assembly is allowed to equilibrate to room temperature for 2
hours prior to testing for 180 degree peel adhesion. The test was
conducted at about 23.degree. C. and 50% relative humidity.
[0197] The 180 degree peel adhesion value of a sheet of the article
of the invention should preferably be stable compared to the room
temperature 180 degree peel adhesion value as measured according to
the test method entitled "Appearance After 120 hours at 23.degree.
C. and 180 Degree Peel Adhesion Between a Bonding Layer of a Sheet
and the Surface of an Adjacent Supported Film". The level of 180
degree peel adhesion after condensing humidity exposure preferably
should not increase more than about 50% or decrease more than about
25%. The test sample preferably leaves no residue such as adhesive
residue upon removal.
[0198] Appearance After an Environmental Cycling Test and 180
Degree Peel Adhesion Between a Bonding Layer on a Sheet Sample and
the Surface of a Supported Adjacent Film
[0199] The adhesion force between a bonding layer on a sheet sample
and the surface of a supported adjacent film is evaluated as
described in the test method entitled "Appearance After 120 hours
at 23.degree. C. and 180 Degree Peel Adhesion Between a Bonding
Layer of a Sheet and the Surface of an Adjacent Supported Film"
except that prior to testing the assembly is first aged in a
controlled environmental chamber that is programmed to conduct the
following continuous cycle: 4 hours at 40.degree. C./100% relative
humidity (RH), followed by 4 hours at 80.degree. C. and then
followed by 16 hours at -40.degree. C. The sample is exposed 10
times to this cycle. The sample is examined for discoloration and
blistering. Preferably the aged sample does not experience
discoloration or blistering. The sample is allowed to equilibrate
to room temperature for 2 hours before 180 degree peel adhesion
testing. The peel adhesion test was conducted at about 23.degree.
C. and about 50% humidity.
[0200] The 180 degree peel adhesion value of a sheet of the article
of the invention should preferably be stable compared to the room
temperature adhesion value as evaluated in the test method entitled
"Appearance After 120 hours at 23.degree. C. and 180 Degree Peel
Adhesion Between a Bonding Layer of a Sheet and the Surface of an
Adjacent Supported Film". The level of 180 degree peel adhesion of
a sheet of the article of the invention after thermal cycling
preferably should not increase more than about 50% or decrease more
than about 25%. The test sample preferably leaves no residue such
as adhesive residue on removal.
[0201] 180 Degree Peel Adhesion to Glass
[0202] A 100 mm.times.200 mm flat glass plate is cleaned with
toluene and allowed to air dry prior to application of a sheet
sample to be tested. (The sheet to be tested typically comprises a
film and a bonding layer bonded to one side thereof.) The adhesion
to glass is measured by bonding a 25 mm.times.150 mm of the sheet
sample to be tested using a rubber roller such that no trapped air
and 25 mm.times.50 mm of the sheet is hanging over the edge of the
glass. The sheet is applied such that the bonding layer of the
sheet is in contact with the glass. The sheet is allowed to dwell
on the glass at least 10 minutes but less than 60 minutes. The
glass plate is clamped onto the carriage of a Slip-Peel Tester
Model SP-102C-3090 adhesion tester (IMASS Inc., Accord Mass.). The
overhang of the sheet is clamped to a sensor of the tester. As the
carriage moves upon operation of the tester the force to peel the
sheet is measured at 228.6 cm/min at an angle of 180 degrees. The
average force over a 2 second period is recorded. The test is
conducted at about 23.degree. C. and about 50% R.H.
[0203] Typically the 180 degree peel adhesion to glass of a sheet
of an article of the invention is about 100 g/2.54 cm to about 5000
g/2.54 cm, preferably about 500 g/2.54 cm to about 3000 g/2.54 cm,
and most preferably about 1500 g/2.54 cm to about 2500 g/2.54 cm.
One hundred eighty degree peel adhesion above about 5000 g/2.54 cm
is less preferred, because the sheet may be difficult to remove
after a prolonged time on the glass. One hundred eighty degree peel
adhesion below about 100 g/2.54 cm is less preferred, because the
bond to the glass could potentially be disrupted when the
individual sheets are removed from the stack.
[0204] The glass panel is inspected for residue left after the
sheet sample is peeled from the glass. Preferably substantially no
residue (such as adhesive residue) remains on the glass. Most
preferably no visible residue (such as adhesive residue) remains on
the glass. The percentage of the area of the test panel where the
sample was initially applied on which any residue remained is
recorded.
[0205] Haze Test
[0206] The haze of a sample is measured by using a Garner XL211
Hazeguard device. The procedure used is in accordance to ASTM
D1003-95 with the following exceptions
[0207] 1. The sample size is rectangular with a minimum size of 40
mm.times.40 mm.
[0208] 2. The sample is scanned for areas of the maximum haze.
These selected areas are measured and the maximum haze value is
reported.
[0209] 3. The sample is allowed equilibrate at 23.degree. C. and
50% R.H. for 72 hours prior to testing.
[0210] 4. If printed or embossed images or graphics are contained
on the sample, those areas of the sample should be avoided when
measuring the maximum haze of the sample.
[0211] 5. Prior to conducting the haze test, the release liner (if
any) is removed from the sample.
[0212] Scratch Resistance
[0213] A 1.2 kg hammer manufactured by Collins Axe Company is
provided. A tungsten carbide tipped stylus from General Tools
Manufacturing Co. Inc. New York, N.Y. is taped securely to the very
top of the metal head of the hammer such that the tip of the nail
points in substantially the same downward direction as does the
hitting end of the hammer head. The nail is positioned such that it
is substantially perpendicular to the handle of the hammer. The
stylus protrudes from the hammer 2.5 cm. The tape used is No 471
tape from 3M Company. The sheet sample is attached to a 100
mm.times.300 mm white painted metal panel and held securely in
place. The hammer is held at the end of the handle while the
carbide stylus bears the weight of the hammer. A straight edge is
taped to the sheet sample as a guide. The hammer is pulled down the
length of the panel at about 200 cm/min such that the weight of the
hammer is on the stylus. The hammer is pushed back up the length of
the panel. Each up and down motion consisted of one cycle. The
number of cycles needed to scratch through the sample and into the
white paint is reported.
[0214] The scratch resistance of a sheet or a film layer of an
article of the invention typically ranges from about 5 to more than
about 500 cycles, preferably greater than about 10 cycles, more
preferably greater than 50 cycles and most preferably greater than
about 100 cycles.
[0215] Taber Abrasion Resistance
[0216] A 7.5 cm diameter non-abraded circular sample of the
material to be tested is cut such that a 1.25 cm hole is provided
in the center of the sample. The haze of the non-abraded sample is
then measured using a Gardner XL211 Hazeguard system. The Gardner
XL211 Hazeguard system is balanced and calibrated to zero using the
non-abraded sample. The sample is clamped in a fixture of a Taber
abrader. The sample is abraded using the Taber Abrader with CS10
wheels and a 500 gram load for 100 cycles. The haze of the abraded
sample is measured using the Gardner XL211 Hazeguard system. The
difference in haze of the abraded surface and the non-abraded
surface is recorded.
[0217] The Taber abrasion resistance value is the percentage
difference between the haze value of the abraded sample and the
non-abraded sample. Preferably the Taber abrasion resistance of the
sample of the material being tested after 100 cycles is less than
about 25 percent, more preferably less than about 10 percent, and
most preferably less than about 2 percent.
EXAMPLES
[0218] The present invention will be better understood by referring
to the following non-limiting examples. All parts, percentages,
ratios, etc. in the examples are by weight unless indicated
otherwise.
Example 1
[0219] A bonding material solution comprising 96 parts by weight of
isooctyl acrylate and 4 parts by weight of acrylamide was prepared
in a 50% heptane/50% ethyl acetate solution using
2,2'-azobis(isobutyronitrile- ) free radical initiator available
under the trademark "VAZO" 64 from the E. I. DuPont Company, of
Wilmington, Del.
[0220] The following components were added to a reaction vessel:
19.2 kg of isooctyl acrylate, 0.8 kg of acrylamide, 40 kg of
heptane and 40 kg of ethyl acetate. While constantly stirring under
a nitrogen atmosphere and controlling the temperature between
70-100.degree. C., 270 grams of VAZO.TM. 64 was added to the vessel
in three 90-gram increments. The resulting polymer had a conversion
of 98%. The Brookfield viscosity was measured (#3 spindle at 12
rpm) at 2000-2800 cps at a solids level of 19-23%. The inherent
viscosity of the polymer was 1.25-1.40 di/gram.
[0221] A first sheet of film with a tacky bonding layer was
prepared by coating the bonding material solution onto a second
surface of a 15 cm.times.100 cm.times.125 micron thick optically
clear biaxially oriented corona treated polyester film using a
knife coater at a wet thickness of 175 microns. The second surface
of the film was the corona treated surface of the film. The coated
film was dried in an air convection oven for 10 minutes at
82.degree. C. The dry thickness of the coating of the coated film
was 20-25 microns. The tacky bonding layer of this first sheet was
protected by laminating an optically clear silicone coated
polyester film to the tacky bonding layer. The silicone coated
polyester film was 1-2 PESTRD (P1)-7200 available from DCP Lohja
Inc. of Lohja Calif. The surface opposite the bonding layer coated
surface of the film will be referred to herein as the release
surface.
[0222] A second sheet of film with a tacky bonding layer was
prepared in a similar manner. The bonding layer of the second sheet
was laminated to the release surface of the first sheet using a
laminator with a steel roll and a rubber backup roll having a shore
A hardness of 75 at a pressure of 32 N/cm.sup.2 such that the
bonding layer of the second sheet was in contact with the release
surface of the first sheet. This sheet preparation and lamination
process was repeated until a stack of four sheets was
completed.
Example 2
[0223] Example 2 was identical to Example 1 except that the corona
treated polyester film was 170 microns in thickness.
Example 3
[0224] Example 3 was identical to Example 1 except that the corona
treated polyester film was 75 microns in thickness.
Example 4
[0225] Example 4 was identical to Example 1 except that the corona
treated polyester film was 250 microns in thickness and the size of
the corona treated polyester film was 15 cm.times.25 cm.
Example 5
[0226] Example 5 was identical to Example 1 except that a
sufficient number of sheets were made and laminated together until
a stack of 10 sheets was prepared.
Example 6
[0227] Example 6 was identical to Example 1 except that the film
onto which the bonding material solution was coated was a 175
micron polyester film with a hard coating on the first surface
which served as the release layer. This film and coating was
obtained from the Furon Corporation of Worcester, Mass. under the
product name 007 PET/0270x Hard coat. In addition, the side of the
film opposite the release layer was corona treated prior to coating
with the bonding material described in Example 1.
Example 7
[0228] A polished 22 cm.times.28 cm.times.250 micron thick film of
clear transparent polycarbonate was obtained from General Electric
under the tradename Lexan.TM. FR60. The film had a first surface
and an opposite second surface. The film was coated on its first
surface with a solution of 3M 906 hard coat, an acid-resistant
acrylic based protective coating available from 3M Company, St
Paul, Minn. in order to provide a release layer and an abrasion
resistant surface on one side of the film. The coating solution was
made by diluting to 16% solids 906 hard coat with a 50/50 mixture
of isopropanol and n-butanol. To 100 grams of the diluted hardcoat
solution, 0.075 gram of a leveling agent Dow 57, an alkoxy
terminated polysilicone available from Dow Corning of Midland,
Mich. was added. The coating was applied with a syringe to the
first surface of the film in a vertical position approximately 10
microns wet. The sheet was dried 10 minutes at 82 degrees C. The
coating on the film was cured with a 300 Watt high pressure mercury
vapor lamps at a belt speed of approximately 30 meters per minute.
The reflective parabolic lamp housing focused the light source on
the coating. The curing unit was Model II 180133 AN from RPC
Industries of Plainview, Ill. The resulting thickness of the hard
coat was 1-2 microns.
[0229] A bonding material was prepared from 96 parts by weight of
isooctyl acrylate and 4 parts by weight of acrylamide in a 50%
heptane/50% ethyl acetate solution using VAZO.TM. 64 initiator as
follows.
[0230] To a reaction vessel the following materials were added:
19.2 kg of isooctyl acrylate, 0.8 kg of acrylamide, 40 kg of
heptane and 40 kg of ethyl acetate. While constantly stirring under
a nitrogen atmosphere and controlling the temperature between
70-100.degree. C., 270 grams of VAZO.TM. 64 was added to vessel in
three 90 gram increments. The resulting polymer solution had a
conversion of 98%. The Brookfield viscosity was measured (#3
spindle at 12 rpm) at 2000-2800 cps at a solids level of 20%. The
inherent viscosity of the polymer solution was 1.40 dl/gram.
[0231] The polymer solution was coated on 15 cm.times.30
cm.times.50 micron thick optically clear biaxially oriented
silicone coated optically clear polyester film (transfer film)
using a knife coater at a wet thickness of 175 microns. The
silicone coated polyester was 1-2 PESTRD (P1)-7200 from DCP Lohja
Inc. of Lohja Calif. The coated film was dried in an air convection
oven for 10 minutes at 82.degree. C. in order to form a transfer
tape. The dry thickness of the coated layer was 20-25 microns. The
coating was considered to be a bonding layer. The transfer tape was
laminated to the non-hard coated surface of the Lexan.TM. FR60
sheet via the bonding layer of the transfer tape. Any excess
Lexan.TM. FR60 sheet and transfer tape were trimmed so that the
trimmed laminate had areas with complete coating of the bonding
layer. Four of these trimmed laminates were prepared.
[0232] A stack of sheets was produced by removing the optically
clear polyester release film from the bonding layer of the first
trimmed laminate and laminating it to the release coated surface of
the second trimmed laminate using a laminator with a steel roll and
a rubber backup roll with a shore A hardness of 75 at a pressure of
32 N/cm.sup.2. The optically clear polyester release film was
removed from the third trimmed laminate and the third trimmed
laminate was laminated to the release coated surface of the first
two trimmed laminates. This was repeated until a stack of four
trimmed laminates was produced.
Example 8
[0233] Example 6 was repeated except the bonding layer was
comprised of polyhexene. The film onto which the bonding material
layer was coated was a 175 micron thick optically clear polyester
with a 0270x hard coat as described in Example 6 from the Furon
Corporation of Worcester, Mass.
[0234] A bonding material was prepared using a polyhexene with an
inherent viscosity of 3.0 dl/gram. The polyhexene was prepared
using a process described in U.S. Pat. No. 5,644,007 issued on Jul.
1, 1997 and assigned to 3M Company. The polyhexene was prepared
using 0.2-0.3 g of a Ziegler-Natta catalyst Lynx.TM. 715 per kg of
monomer. Lynx.TM. 715 is TiCl.sub.4 supported on MgCl.sub.2 powder
which is commercially available from Catalyst Resources Inc. This
catalyst is discussed in Boor, Ziegler-Natta Catalysts and
Polymerizations, "Polymerization of Monomers," Ch. 19, pp. 512-562,
Academic. The conversion rate was 15%. The bonding material was
coated on the surface of the film opposite the release layer of the
film.
Comparative Example 9
[0235] Four layers of Scotch.TM. 375 packaging tape from 3M Company
in St. Paul, Minn. were laminated together using a laminator with a
steel roll and a rubber backup roll with a shore A hardness of 75
at a pressure of 32 N/cm.sup.2. Each layer of tape was 10
cm.times.15 cm and comprised a 50 micron biaxially oriented
polypropylene backing and a 37 micron rubber based adhesive coated
on one surface thereof. The adhesive on the bottom sheet of the
stack was protected by a silicone coated optically clear polyester
release liner. The polyester release liner was 1-2 PESTRD(P1)-7200
from DCP Lohja Inc. of Lohja Calif. The liner was removed from each
tape and the tapes were laminated together such that the adhesive
layer of one tape was in contact with the film layer of the tape
below except for the bottom piece of tape.
[0236] Example 1-8 and Comparative Example 9 were subjected to
various tests. The tests and the results obtained are reported in
the table below.
1 TABLE Comparative Example Example Example Example Example Example
Example Example Example 1 2 3 4 5 6 7 8 9 1. Effect of Sample of
6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/12 Visual Acuity (meter/meter) 2.
Penetration Resistance 1.0 1.0 0.5 1.5 1.0 1.0 1.5 1.5 0.5 (kg) 3.
Taber Abrasion Resis- 18 18 18 18 18 2 2 0.3 17 tance (% haze
difference between abraded and non abraded samples after 100 cycles
of abrasion on a Tabor Abrader) 4. Scratch Resistance 59 110 10 208
59 115 125 115 3 (cycles) 5. Haze % 3.8 2.8 2.3 4.1 3.3 2.9 3.0 2.9
7.5 6a. Appearance After 120 735 585 940 Not 735 207 889 73 207
hours at 23.degree. C. and 180 tested Degree Peel Adhesion be-
tween Bonding Layer of a Sheet and the Surface of an Adjacent
Supported Film. (grams/2.54 cm) 6b. Appearance of sample No No No
Not No No No No No after 120 hours at 23.degree. C. change change
change tested change change change change change and observations
of the sur- face where sheet was removed. (No change = no residue
on removal, no blisters in the sam- ple and no discoloration) 7a.
Appearance after Heat 833 695 980 Not 833 683 889 132 683 Aging
(120 hours at 23.degree. C.) tested and 180 Degree Peel Adhe- sion
Between a Bonding Layer of a Sheet and the Surface of an Adjacent
Supported Film. (g/2.54 cm) 7b. Appearance of sample No No No Not
No 5% residue 15% residue No 5% residue after 120 hours at
80.degree. C. change change change tested change small blisters
large blisters change small blisters and observation of surface no
dis- no dis- no dis- where sheet was removed. coloring coloring
coloring (No change = no residue on removal, no blisters in the
sample and no dis- coloration) 8a. Appearance After Con- 865 685
1025 Not 865 268 927 69 268 tinuous Exposure to Con- tested densing
Humidity (120 hours at 33.degree. C. and 100% R.H.) and 180 Degree
Peel Adhesion be- tween a Bonding Layer of a Sheet and the Surface
of an Adjacent Supported Film. (g/2.54 cm) 8b. Appearance of sample
No No No Not No No Small No No after 120 hours at 38.degree. C.
change change change tested change change blisters change change
C/100% RH and observa- tion of surface where sheet was removed. (No
change = residue on removal, no blisters in the sample and no
discol- oration). 9a. Appearance After an 815 655 1120 Not 815 357
575 73 357 Environmental Cycling Test tested and 180 Degrees Peel
Ad- hesion between a Bonding Layer on a Sheet Sample and the
Surface of a Supp- orted Adjacent Film. Adhe- sion between sheets
after 5 thermal cycles (g/2.54 cm) One thermal cycle consists of 4
hours at 80.degree. C., 4 hours at 38.degree. C. and 100% R.H. and
16 hours at -40.degree. C. 9b. Appearance of sample No No No Not No
5% residue 15% residue No 5% residue after 5 thermal cycles and
change change change tested change small blisters large blisters
change small blisters observation of surface no no dis- no dis-
where sheet was removed discoloring coloring coloring (No change =
no res- idue on removal, no blis- ters in the sample and no
discoloration).
[0237] The foregoing detailed description and Examples have been
given for clarity of understanding only. No unnecessary limitations
are to be understood therefrom. The invention is not limited to the
exact details shown and described, for variations obvious to one
skilled in the art will be included within the invention defined by
the claims.
* * * * *