U.S. patent application number 14/762703 was filed with the patent office on 2015-11-12 for sticky cleaner for removing organic dirt.
This patent application is currently assigned to NITTO DENKO CORPORATION. The applicant listed for this patent is KABUSHIKI KAISHA NITOMS, NITTO DENKO CORPORATION. Invention is credited to Yumi KAWAI, Aya NAGATOMO, Teiji SAKASHITA, Satoshi TAGUCHI.
Application Number | 20150320293 14/762703 |
Document ID | / |
Family ID | 51227424 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150320293 |
Kind Code |
A1 |
SAKASHITA; Teiji ; et
al. |
November 12, 2015 |
STICKY CLEANER FOR REMOVING ORGANIC DIRT
Abstract
Provided is a sticky cleaner that can easily remove organic dirt
adsorbed on a surface of an article with greater dirt-removing
workability. The sticky cleaner provided by the present invention
is used for removing organic dirt adsorbed on a flat surface of an
article. The sticky cleaner comprises a dirt-collecting member that
collects the organic dirt as it makes contact with the flat
surface. In the dirt-collecting member, the part to make contact
with the surface is formed with a PSA. The surface-contacting part
of the dirt-collecting member exhibits an adhesive strength of less
than 1 N/25 mm as a measured value based on the 180.degree. peel
test specified in JIS Z0237.
Inventors: |
SAKASHITA; Teiji; (Tokyo,
JP) ; TAGUCHI; Satoshi; (Tokyo, JP) ; KAWAI;
Yumi; (Tokyo, JP) ; NAGATOMO; Aya;
(Ibaraki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA NITOMS
NITTO DENKO CORPORATION |
Tokyo
Ibaraki-shi, Osaka |
|
JP
JP |
|
|
Assignee: |
NITTO DENKO CORPORATION
Ibaraki-shi, Osaka
JP
KABUSHIKI KAISHA NITOMS
Tokyo
JP
|
Family ID: |
51227424 |
Appl. No.: |
14/762703 |
Filed: |
January 16, 2014 |
PCT Filed: |
January 16, 2014 |
PCT NO: |
PCT/JP2014/050662 |
371 Date: |
July 22, 2015 |
Current U.S.
Class: |
15/104.002 |
Current CPC
Class: |
B08B 7/0028 20130101;
B08B 1/00 20130101; A47L 25/005 20130101; C09J 2301/312 20200801;
C09J 7/385 20180101; C09J 133/08 20130101; C08F 220/1808 20200201;
C08F 220/06 20130101; C08F 220/1808 20200201; C08F 220/06
20130101 |
International
Class: |
A47L 25/00 20060101
A47L025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 25, 2013 |
JP |
2013-012473 |
Claims
1. A sticky cleaner used for removing organic dirt adsorbed on a
surface of an article, the sticky cleaner comprising a
dirt-collector that collects the organic dirt as the dirt-collector
makes contact with the surface of the article, the dirt-collector
has a surface-contacting part to make contact with the surface of
the article, the surface-contacting part being formed with a
pressure-sensitive adhesive, and the surface-contacting part of the
dirt-collector exhibits an adhesive strength of less than 1 N/25 mm
as a measured value based on the 180.degree. peel test specified by
JIS Z0237.
2. The sticky cleaner according to claim 1, wherein the
surface-contacting part of the dirt-collector exhibits an adhesive
strength of 0.01 N/25 mm to 0.5 N/25 mm as the measured value based
on the 180.degree. peel test specified in JIS Z0237.
3. The sticky cleaner according to claim 1, wherein the sticky
cleaner comprises a cylindrical rolling member, and the
dirt-collector is arranged along the lateral surface of the rolling
member.
4. The sticky cleaner according to claim 3, further comprising a
grip that rotatably supports the rolling member.
5. The sticky cleaner according to claim 1, wherein the
dirt-collector is an adhesively single-faced pressure-sensitive
adhesive sheet comprising a sheet of support substrate and a
pressure-sensitive adhesive layer placed above the support
substrate, and the single-faced pressure-sensitive adhesive sheet
is wound with the pressure-sensitive adhesive layer on the outside
to form a pressure-sensitive adhesive sheet roll.
6. The sticky cleaner according to claim 5, wherein the
pressure-sensitive adhesive layer comprises an acrylic polymer at a
ratio of 50% by mass or higher.
7. The sticky cleaner according to claim 6, wherein the acrylic
polymer is a crosslinked acrylic polymer.
8. The sticky cleaner according to claim 6, wherein the acrylic
polymer is a thermoplastic acrylic polymer.
9. The sticky cleaner according to claim 6, wherein the
pressure-sensitive adhesive layer further comprises a
plasticizer.
10. The sticky cleaner according to claim 1 used for removing human
sebum dirt as the organic dirt.
11. The sticky cleaner according to claim 1, wherein the article is
a portable device having a flat surface on which a glass or
synthetic resin display is present.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sticky cleaner used for
removing organic dirt. In particular, it relates to a sticky
cleaner used for removing sebum and other organic dirt from a flat
surface (e.g. a touch panel display/input screen) in a portable
device such as a tablet terminal, smartphone and the Eke. The
present application claims priority based on Japanese Patent
Application No. 2013-012473 filed on Jan. 25, 2013 and the entire
contents thereof are incorporated herein by reference.
BACKGROUND ART
[0002] A display typically formed of a liquid crystal panel or an
organic EL panel is placed on a flat surface in a portable device,
for instance, a portable personal computer (PC) such as notebook
PCs, etc.; tablet terminal such as electronic books, etc.; mobile
phone such as smartphones, etc.; mobile gaming device; various
types of PDA (personal digital assistant); and the Eke. These
portable devices are carried and used on a daily basis, and thus
easily attract dust and organic dirt such as finger marks,
cosmetics and sebum. In particular, recently wide-spread
touch-screen portable devices are operated with a direct finger
touch by a user to the display/input portion in which the display
functions also as an input device, and thus are more likely to
attract organic dirt such as finger marks, sebum, etc. Not just
these portable devices, but also show window glass, glass tables,
showcases and the like have flat surfaces. The organic dirt
adsorbed on their surfaces degrades their exteriors, making them
unsightly.
[0003] As means to remove organic dirt adsorbed on the display, a
wipe (waste cloth) made of paper, woven fabric or non-woven fabric
is used. For instance, when the dirt includes an oily component
such as sebum and the like, wiping off dirt with a wipe is not
necessarily easy to carry out, possibly spreading the dirt
depending on how it is done or requiring multiple times of wiping,
and so on. Dirt gradually accumulates with continuous use,
requiring regular cleaning or a replacement with a new piece, which
can be troublesome. Alternatively, there is a means where organic
dirt is removed by wiping the surface with a suitable material
(e.g. sponge or gauze) containing a suitable detergent (e.g. see
Patent Document 1). However, not only is careful handling of the
detergent necessary, but residual detergent can even affect the
surface. This method thus requires elimination of the detergent and
thus is not advantageous in terms of workability.
CITATION LIST
Patent Literature
[0004] [Patent Document 1] Japanese Patent Application Publication
No. 2009-503161
[0005] [Patent Document 2] Japanese Patent Application Publication
No. 2004-237023
SUMMARY OF INVENTION
Technical Problem
[0006] The present invention has been made to solve the
conventional problem. An objective thereof is to provide a sticky
cleaner that can easily remove organic dirt adsorbed on a surface
of an article with greater dirt-removing workability.
Solution to Problem
[0007] To achieve the objective, the present invention provides a
sticky cleaner used for removing organic dirt adsorbed on a flat
surface of an article. The sticky cleaner comprises a
dirt-collecting member that collects the organic dirt as it makes
contact with the flat surface. In the dirt-collecting member, the
part to make contact with the surface is formed with a
pressure-sensitive adhesive (PSA). The surface-contacting part of
the dirt-collecting member exhibits an adhesive strength of less
than 1 N/25 mm as a measured value based on the 180.degree. peel
test specified by JIS Z0237.
[0008] According to a sticky cleaner (dirt remover) having such a
constitution, by allowing the PSA constituting the dirt-collecting
member to make contact with a flat surface of an article, organic
dirt (e.g. finger marks and sebum residue of a person or cosmetics)
adsorbed on the surface can be collected and easily removed
therefrom. The surface-contacting part of the dirt-collecting
member exhibits an adhesive strength of less than 1 N/25 mm as a
measured value based on the 180.degree. peel test specified by JIS
Z0237. This means that the dirt-collecting member is easily
releasable. Accordingly, when the cleaner is operated on a flat
surface of an article (e.g. moved on the surface or taken away from
the surface), it requires little force, thereby providing excellent
dirt-removing workability. Furthermore, even when the article's
surface (e.g. tablet terminal's display) is covered with removable
protection film, because of the easy-release nature, it can clean
the surface without removing the protection film (in other words,
while keeping the article surface covered with the protection
film). In addition, despite such easy-release nature, it can
sufficiently remove organic dirt. As described above, the organic
dirt includes sebum from the skin, and as evident from this, it may
include inorganic substances such as sodium and potassium as well
as their salts, etc.
[0009] In a preferable embodiment of the sticky cleaner disclosed
herein, the surface-contacting part of the dirt-collecting member
exhibits an adhesive strength of 0.01 N/25 mm to 0.5 N/25 mm as a
measured value based on the 180.degree. peel test specified in JIS
Z0237. Such an easy-release cleaner can sufficiently remove organic
dirt while providing greater dirt-removing workability.
[0010] In a preferable embodiment, the sticky cleaner disclosed
herein comprises a cylindrical rolling member and the
dirt-collecting member is arranged along the lateral surface of the
rolling member. According to a cleaner having such a constitution,
when the rolling member is allowed to rotate in the circumferential
direction of the cylinder, the dirt-collecting member on the
lateral surface can efficiently remove organic dirt on the flat
surface. Since the dirt-collecting member can be released easily,
the peel resistance during the rotation is low, leading to
excellent dirt-removing workability.
[0011] In a preferable embodiment, the sticky cleaner disclosed
herein further comprises a grip member that supports the rolling
member in a freely rotatable manner. With this constitution, a user
can hold the grip member and rotate the rolling member to
efficiently remove organic dirt from the flat surface.
[0012] In a preferable embodiment of the sticky cleaner disclosed
herein, the dirt-collecting member is constituted as an adhesively
single-faced PSA sheet comprising a sheet of support substrate and
a PSA layer placed above the support substrate, and the
single-faced PSA sheet is wound with the PSA layer on the outside
to form a PSA sheet roll. With a sticky cleaner having such a
constitution, the lateral surface of the PSA sheet roll can be used
to remove dirt from a flat surface. In accordance with the usage
and the amount of dirt caught on the PSA layer, the lateral surface
used for dirt removal can be eliminated from (typically peeled off)
the roll to expose an unused section of the PSA layer on the
lateral surface. In other words, the PSA layer can be easily
refreshed to expose an unused section to the outer surface.
Accordingly, a desirable level of dirt-removing ability can be
constantly maintained.
[0013] Preferably, the PSA sheet roll disclosed herein is
constituted to deter rail drawing phenomenon. Rail drawing herein
refers to a phenomenon such that when the sheet roll is rolled
(rotated) reversely to the winding direction (typically in a
direction in which the wound single-faced PSA sheet is peeled) on
the surface to be cleaned (a flat surface of an article), a band of
the PSA sheet stays adsorbed on the surface to be cleaned,
beginning from the outer circumferential end of the roll. Reduced
occurrence of rail drawing allows for stress-free, smooth rotation
of the roll on the flat surface, leading to great usability. In
addition, it can also prevent wasteful use of the PSA sheet due to
the occurrence of rail drawing (i.e. waste of the sheet due to
unintentional adhesion of the PSA sheet to the surface).
[0014] In a preferable embodiment of the sticky cleaner disclosed
herein, the PSA layer comprises an acrylic polymer at a ratio of
50% by mass or higher. The use of the acrylic polymer as the PSA
can preferably bring about both removal of organic dirt and easy
release. The acrylic polymer is preferably a crosslinked acrylic
polymer. This further increases the ease of release. Alternatively,
it is preferable that the acrylic polymer is a thermoplastic
acrylic polymer. This facilitates formation of PSA layers.
[0015] Preferably, the PSA layer further comprises a plasticizer.
The inclusion of the plasticizer can lighten the release and lead
to greater dirt-removing workability. Even when the dirt-collecting
ability is reduced as a result of use, it preferably exhibits an
effect of regaining its dirt-collecting ability in relatively short
time (e.g. several minutes or several hours) (dirt-collecting
ability recovery effect).
[0016] In a preferable embodiment, the sticky cleaner disclosed
herein is used for removing human sebum dirt as the organic dirt.
The sticky cleaner having the prescribed constitution disclosed
herein effectively removes human sebum dirt despite the
easy-release nature. This has been made possible for the first time
through the studies by the present inventors. The sticky cleaner is
particularly suitable for removing human sebum dirt.
[0017] In a preferable embodiment of the sticky cleaner disclosed
herein, the article is a portable device having a glass or
synthetic resin display on the flat surface. The portable device is
carried and used on a daily basis and is likely to attract organic
dirt such as sebum. In particular, a portable device having a touch
panel display (display/input member) is operated with a direct
finger touch to the display/input portion, and thus is more likely
to attract organic dirt such as finger marks, cosmetics, sebum
dirt, etc. The sticky cleaner disclosed herein can easily remove
such organic dirt; and therefore, it is particularly preferably
used for removing dirt from a portable device having a display as
described above (e.g. a touch panel display). Sticky cleaners have
been conventionally used (e.g. see Patent Document 2). However,
conventional roller cleaners are used for cleaning floors and
carpets, but not intended for cleaning flat surfaces (e.g. touch
panel display/input portions) of portable devices (e.g. tablet
terminals and smartphones) as described above.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 shows a front view schematically illustrating the
sticky cleaner according to an embodiment.
[0019] FIG. 2 shows a side view schematically illustrating the
sticky cleaner according to an embodiment.
[0020] FIG. 3 shows a cross-sectional view schematically
illustrating the dirt-collecting member constituting the sticky
cleaner according to an embodiment.
[0021] FIG. 4 shows a perspective view schematically illustrating
an example of usage of the sticky cleaner according to an
embodiment.
[0022] FIG. 5 shows a diagram schematically illustrating the
mechanism of dirt-removing ability recovery effect of the sticky
cleaner according to an embodiment.
DESCRIPTION OF EMBODIMENTS
[0023] Preferred embodiments of the present invention are described
below. Matters necessary to practice this invention other than
those specifically referred to in this description may be
understood as design matters to a person of ordinary skill in the
art based on the conventional art in the pertinent field. The
present invention can be practiced based on the contents disclosed
in this description and technical common knowledge in the subject
field.
[0024] The sticky cleaner disclosed herein is different from
conventional sticky cleaners used for cleaning floors and carpets.
It is used for removing organic dirt adsorbed on a flat surface of
an article such as a portable device. The article on which the
sticky cleaner disclosed herein is used is not particularly limited
as long as it has a flat surface. Examples include show window
glass, glass tables, showcases and the like. As organic dirt
adsorbed on their flat surfaces (typically transparent glass
surfaces) is unsightly, if found any, its quick removal is
desirable. Thus, on their surface, the sticky cleaner disclosed
herein can be preferably used.
[0025] Preferable examples of the article on which the sticky
cleaner disclosed herein is used include various portable devices.
The term portable device herein refers to a mobile device having a
flat surface at least partially on the outside and is not limited
to a particular device. Examples include portable devices such as
notebook PCs; tablet terminals such as electronic books, etc.;
smartphones and other mobile phones; mobile gaming devices; PDAs
(mobile terminals) such as electronic organizers, etc.; and the
like. Since these are carried and used on a daily basis, they are
likely to attract dust and especially organic dirt such as finger
marks, cosmetics and sebum. Some of these portable devices have
displays such as liquid crystal displays, organic EL displays and
the like on flat surfaces (typically glass or synthetic resin
surfaces). Organic dirt on the displays makes information displayed
thereon hard to see, thereby hindering the use. Moreover, depending
on the amount of organic dirt adsorbed thereon, it might give a
filthy impression. On portable devices having such displays, the
sticky cleaner disclosed herein can be preferably used.
[0026] In particular, portable devices having touch panel
display/input portions are likely to attract the organic dirt since
users directly touch the displays with fingers. Thus, the sticky
cleaner disclosed herein can be preferably used on them. Among
them, tablet terminals such as electronic books and the like have
relatively large displays; and therefore, they are considered as
particularly preferable articles on which the sticky cleaner is
used.
[0027] The sticky cleaner according to an embodiment is described
below with reference to drawings. As shown in FIGS. 1 and 2, a
sticky cleaner (or simply cleaner, hereinafter) 10 comprises a
cylindrical holding member (core) 20 and a PSA sheet roll 30 held
on the outer periphery of holding member 20. These holding member
20 and PSA sheet roll 30 are assembled to form a cylindrical
rolling member. The holding member material is not particularly
limited. A holding member made of a polyolefin or other synthetic
resin as well as paper can be preferably used.
[0028] Cleaner 10 further comprises a grip member 40 in a form of a
pole that supports holding member 20 in a freely rotatable manner.
In particular, holding member 20 has a center hole (not shown in
the drawings) formed where the central axis of the cylinder is
located. A terminal section (one end) of grip member 40 is inserted
through the center hole, whereby holding member 20 is installed on
grip member 40 in a freely rotatable manner. To the other end of
grip member 40, a handle 42 is attached. The materials of grip
member and handle are not particularly limited. For instance, metal
or synthetic resin pieces can be used.
[0029] PSA sheet roll 30 in cleaner 10 is formed by winding a PSA
sheet 31 that serves as the dirt-collecting member. In particular,
PSA sheet (dirt-collecting member) 31 is constituted as a
single-faced PSA sheet 31 comprising, as shown in FIG. 3, a support
substrate 36 in a form of a long sheet (band) and a PSA layer 32
placed on one face 36A of the support substrate 36. Single-faced
PSA sheet 31 is wound with the PSA layer 32 on the outside and
formed as a PSA sheet roll 30.
[0030] With respect to cleaner 10 having a constitution as
described above, some applications are now described. As shown in
FIG. 4, cleaner 10 is used for removing organic dirt adsorbed on a
display 2 of a portable device 1. Display 2 in portable device 1
has a flat surface. An operator places cleaner 10 on the display 2
of portable device 1, grip a handle 42, and applies a prescribed
amount of external force to cleaner 10. The force is then
transmitted from grip member 40 to holding member 20, and the PSA
layer 32 (a section of the dirt-collecting member that makes
contact with the flat surface) placed on the outer periphery of
holding member 20 rotationally moves on display 2. In FIG. 4, PSA
sheet roll 30 moves on display 2 in the direction shown by the
arrow. During this, the PSA layer 32 collects dust, fine particles,
and especially organic dirt such as human finger marks, sebum and
the like present on the display 2. By this means, cleaning (dirt
removal) of display 2 is easily and certainly accomplished in the
rotation direction of PSA sheet roll 30 (more specifically, the PSA
sheet (dirt-collecting member) 31). The portable device in this
embodiment is a tablet terminal whose display is entirely formed
with flat tempered glass such as aluminosilicate glass and the like
although it is not limited to this as indicated earlier.
[0031] The size of the cylindrical PSA sheet roll is not
particularly limited. When it is used on portable devices such as
tablet terminals, etc., its diameter (which refers to the diameter
(outer diameter) before used; the same applies hereinafter) is
preferably 4 mm or larger (e.g. 10 mm or larger, typically 20 mm or
larger). From the standpoint of the maneuverability and
portability, the diameter is preferably 50 mm or smaller (e.g. 35
mm or smaller, typically 30 mm or smaller).
[0032] In the PSA sheet roll, the PSA sheet preferably has cut
lines (not shown in the drawings) at an interval of approximately
the length of the circumference. The cut lines provide cutting
means for efficiently refresh the PSA layer surface (outer surface
of the dirt-collecting member) with a reduced cleaning
(dirt-removing) ability after the cleaner is used several times.
The cut lines can be, for instance, lines of long holes or wavy
slits; intermittent slits such as perforation; and the like. The
cut lines are preferably arranged to run across the PSA sheet in
the width direction (direction perpendicular to the length
direction). Refreshing the lateral surface of the dirt-collecting
member is not limited to the cutting means. For instance,
intermittent slits such as perforation can be spirally formed in a
direction intersecting the winding direction of the PSA sheet roll
(typically, in a direction intersecting the width direction at an
angle between 30.degree. and 60.degree.). Alternatively, instead of
intermittent slits such as perforation, the PSA sheet constituting
the PSA sheet roll may comprise slits (continuous cut lines) at a
prescribed interval. In this embodiment, the PSA sheet constituting
the PSA sheet roll is fully cut in advance at the prescribed
intervals in the winding direction of the roll. Thus, the outer
surface of the PSA sheet roll can be peeled over the length of the
prescribed interval to easily refresh the outer surface.
[0033] The cleaner 10 can be produced by suitably employing
heretofore known techniques. For instance, PSA sheet roll 30 of
cleaner 10 can be fabricated in the same manner as conventional
roller cleaners. In other words, a PSA composition is applied to
the surface 36A of a long sheet of support substrate 36 by various
heretofore known coating means and subsequently allowed to dry to
form a PSA layer 32. The PSA sheet 31 is wound around holding
member 20 with the PSA layer 32 on the outside to form PSA sheet
roll 30 in a form of a roll. A terminal section of grip member 40
is further attached to holding member 20 in a freely rotatable
manner to construct cleaner 10. The structure of attachment of grip
member 40 to holding member 20 can be similar to those in
conventional roller cleaners and does not characterize the present
invention. Accordingly, detailed description is omitted.
[0034] The sticky cleaner is not limited to the embodiment above.
The sticky cleaner may be formed, for instance, solely with a
dirt-collecting member. Examples of such a sticky cleaner include a
cleaner formed solely with a dirt-collecting member in a form of a
sphere, column, cylinder, hexahedron (e.g. cuboid), sheet, etc.
[0035] In this embodiment, the dirt-collecting member is formed
with, but not limited to, the support substrate and PSA layer. For
instance, the dirt-collecting member may be formed solely with a
PSA (substrate-free PSA). Alternatively, when the dirt-collecting
member has a support substrate, the shape of the support substrate
is not particularly limited. For instance, the dirt-collecting
member may have a PSA layer on the outer surface of a spherical
support substrate.
[0036] In this embodiment, the grip member supports the holding
member in a freely rotatable manner, but it is not limited to this.
For instance, the grip member may be directly or indirectly joined
(connected or detachably joined) to the dirt-collecting member. In
an example of such a sticky cleaner, a columnar or cuboid PSA body
is fastened to one end of a pole-shaped grip member. Alternatively,
the grip member may have a flat portion and the dirt-collecting
member may be fastened to one face of the flat portion.
[0037] The dirt-collecting member (e.g. PSA sheet) disclosed herein
is characterized by that the part (e.g. sticky surface) that makes
contact with a flat surface of an article exhibits an adhesive
strength of less than 1 N/25 mm as a measured value based on the
180.degree. peel test specified in JIS Z0237. This means that the
dirt-collecting member is easily releasable. A cleaner having such
an easily releasable dirt-collecting member requires little force
for the dirt-removing operation on the surface, providing excellent
dirt-removing workability. More specifically, the cleaner can be
moved more smoothly on a flat surface of an article and has
advantages such that the cleaner can be easily separated from the
surface after the dirt-removing operation. Even when the surface of
the article (e.g. display of a tablet terminal) is covered with
removable protection film (e.g. protection film made of a
silicone-based or polyester-based synthetic resin, etc.), because
of the easy-release nature, it can clean the surface without
removing the protection film (i.e. while keeping the article
surface covered with the protection film). In this case, the object
to be cleaned is the surface of the protection film and such a
surface is also included in the article's flat surface. From the
standpoint of the dirt-removing workability, the adhesive strength
is preferably 0.8 N/25 mm or less (e.g. 0.6 N/25 mm or less,
typically 0.5 N/25 mm or less) or more preferably 0.57 N/25 mm or
less (e.g. 0.55 N/25 mm or less, typically 0.4 N/25 mm or less).
From the standpoint of the dirt-collecting ability, the adhesive
strength is preferably 0.001 N/25 mm or greater (e.g. 0.01 N/25 mm
or greater, typically 0.02 N/25 mm or greater) or more preferably
0.03 N/25 mm or greater (e.g. 0.05 N/25 mm or greater, typically
0.08 N/25 mm or greater).
[0038] In particular, the adhesive strength is measured according
to the following procedures: The dirt-collecting member (typically
a PSA sheet) is cut to a rectangular sheet to prepare a test piece.
The test piece preferably has a length of about 100 mm to 200 mm
and a width of about 15 mm to 30 mm. When the width is not 25 mm,
the value in N/25 mm can be determined (by conversion) based on the
ratio of actual width to 25 mm. The thickness is not particularly
limited. The resulting test piece is adhered over its sticky face
(e.g. PSA layer-side surface) to a stainless steel (SUS304) plate
with a 2 kg roller moved back and forth once. When the test piece
is sticky on each face such as in a double-faced PSA sheet, etc.,
it is preferable to back the surface opposite the measured surface
with a polyethylene terephthalate (PET) film of about 25 .mu.m in
thickness. This is stored in an environment at 23.degree. C. and
50% RH for 30 minutes. Based on JIS Z0237, using a tensile tester,
in an environment at 23.degree. C. and 50% RH, the 180.degree. peel
strength (N/25 mm) to SUS is measured. The tensile tester is not
particularly limited and a heretofore known tensile tester can be
used. For instance, measurements can be made with trade name
"TENSILON" available from Shimadzu Corporation.
[0039] The dirt-collecting member (e.g. PSA sheet) disclosed herein
may be characterized by that, instead of or in addition to the
180.degree. peel strength to SUS, the part (e.g. sticky surface)
that comes in contact with the article's flat surface exhibits a
180.degree. peel strength of less than 1 N/25 mm to a glass plate.
A cleaner having such an easily releasable dirt-collecting member
provides excellent dirt-removing workability. From the standpoint
of the dirt-removing workability, the adhesive strength is
preferably 0.9 N/25 mm or less (e.g. 0.85 N/25 mm or less,
typically 0.5 N/25 mm or less) or more preferably 0.57 N/25 mm or
less (e.g. 0.55 N/25 mm or less, typically 0.4 N/25 mm or less).
From the standpoint of the dirt-collecting ability, the adhesive
strength is preferably 0.001 N/25 mm or greater (e.g. 0.01 N/25 mm
or greater, typically 0.02 N/25 mm or greater) or more preferably
0.03 N/25 mm or greater (e.g. 0.05 N/25 mm or greater, typically
0.06 N/25 mm or greater). The 180.degree. peel strength to the
glass plate (180.degree. peel strength to glass) can be measured
similarly to the measurement of the 180.degree. peel strength to
SUS except that the glass plate (e.g. a commercial float glass
plate) is used as the adherend.
[0040] The dirt-collecting member (e.g. PSA sheet) disclosed herein
may be characterized by that, instead of or in addition to the
180.degree. peel strength to SUS, the part (e.g. sticky surface)
that comes in contact with the article's flat surface exhibits a
180.degree. peel strength of less than 1 N/25 mm to polyethylene
terephthalate (PET) film. A cleaner having such an easily
releasable dirt-collecting member provides excellent dirt-removing
workability. From the standpoint of the dirt-removing workability,
the adhesive strength is preferably 0.9 N/25 mm or less (e.g. 0.8
N/25 mm or less, typically 0.6 N/25 mm or less) or more preferably
0.5 N/25 mm or less (e.g. 0.4 N/25 mm or less). From the standpoint
of the dirt-collecting ability, the adhesive strength is preferably
0.001 N/25 mm or greater (e.g. 0.01 N/25 mm or greater, typically
0.02 N/25 mm or greater). The 180.degree. peel strength to PET film
(180.degree. peel strength to PET) can be measured similarly to the
measurement of the 180.degree. peel strength to SUS except that PET
film is used as the adherend.
[0041] When the sticky cleaner disclosed herein has a PSA sheet
roll, the PSA sheet roll preferably has balanced adhesive strength
(e.g. the measured value based on the 180.degree. peel test) and
unwinding force so that the occurrence of rail drawing is reduced
on the article's flat surface (e.g. a surface formed of glass such
as aluminosilicate glass or synthetic resin). The unwinding force
herein refers to the force required to pull out the PSA sheet from
the PSA sheet roll (i.e. resistive force against unwinding, which
can be perceived as the adhesive strength to the back face of the
PSA sheet (typically the back face of the support substrate). For
instance, when the unwinding force is excessively low as compared
with the adhesive strength, when the PSA sheet roll is rotated on a
flat surface, the unwinding force may succumb to the adhesive
strength between the PSA sheet (typically the PSA layer) and the
surface to cause rail drawing. On the other hand, an excessively
high unwinding force tends to result in unsmooth unwinding of the
PSA sheet.
[0042] The unwinding force can be assessed as follows. In
particular, the PSA sheet roll is set in a prescribed tensile
tester. In an environment at a temperature of 23.degree. C. and 50%
RH, the outer circumferential end of the wound PSA sheet is mounted
to the chuck of the tester and pulled at a rate of 300 mm/min to
unwind the PSA sheet roll in the tangential direction. The
unwinding force during this can be converted to and determined as
the value per width (e.g. 150 mm) of PSA layer of the PSA sheet
(N/150 mm). For instance, a preferable PSA sheet roll has an
unwinding force of about 0.5 N/150 mm to 2.5 N/150 mm.
[0043] The PSA (e.g. PSA layer) constituting the dirt-collecting
member (e.g. PSA sheet) is not particularly limited as long as it
satisfies the peel strength to SUS. For instance, the PSA may be
formed from an aqueous PSA composition such as a water-soluble PSA
composition, water-dispersed PSA composition and the like or from a
PSA composition such as a solvent-based PSA composition and the
like. A solvent-free PSA formed from an active energy ray-curable
PSA composition or a hot melt PSA composition can be preferably
used as well. To remove human sebum dirt, a solvent-based PSA and
solvent-free PSA are preferable. From the standpoint of the
handling, a hot melt PSA is preferable.
[0044] The PSA can be an acrylic PSA, rubber-based PSA (e.g.
natural rubber-based PSA), urethane-based PSA, silicone-based PSA,
etc. From the standpoint of the adhesive properties and cost, a
rubber-based PSA or an acrylic PSA can be preferably used.
[0045] In particular, from the standpoint of controlling the
adhesive strength (ease of release), the PSA is preferably an
acrylic PSA comprising an acrylic polymer as a base polymer
(primary component among polymers, a primary adhesive component).
The acrylic polymer can be synthesized from starting monomer(s)
comprising, as the primary monomer, an alkyl (meth)acrylate having
an alkyl group. The primary monomer herein refers to a monomer that
accounts for 50% by mass or more of all the monomers. In the
present description, the term "(meth)acrylate" comprehensively
means acrylate and methacrylate. Similarly, the terms
"(meth)acryloyl" and "(meth)acryl" comprehensively mean acryloyl
and methacryloyl, and acryl and methacryl, respectively.
[0046] As the alkyl (meth)acrylate, for instance, a compound
represented by a formula can be preferably used:
CH.sub.2.dbd.CR.sup.1COOR.sup.2
Herein, R.sup.1 in the formula is a hydrogen atom or a methyl
group. R.sup.2 is an alkyl group having 1 to 20 carbon atoms
(hereinafter, such a range of the number of carbon atoms may be
indicated as "C.sub.1-20"). From the standpoint of the storage
elastic modulus of the PSA, etc., an alkyl (meth)acrylate having a
C.sub.1-14 (e.g., C.sub.1-10) alkyl group is preferable. The alkyl
group may be linear or branched.
[0047] Examples of the alkyl (meth)acrylate having a C.sub.1-20
alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate,
propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl
(meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate,
t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl
(meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate,
heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate,
isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl
(meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate,
undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl
(meth)acrylate, tetradecyl (meth)acrylate, pentadecyl
(meth)acrylate, hexadecyl (meth)acrylate, heptadecyl
(meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate
and eicosyl (meth)acrylate. These alkyl (meth)acrylates may be used
singly as one species or in a combination of two or more species.
In particular, an alkyl (meth)acrylate having a C.sub.4-9 alkyl
group is preferable. Preferable examples include n-butyl acrylate
(BA), 2-ethylhexyl acrylate (2EHA) and isononyl acrylate. Among
these, BA and 2EHA are more preferable.
[0048] The ratio of primary monomer to all the monomers is
preferably 60% by mass or higher, more preferably 80% by mass or
higher, or yet more preferably 90% by mass or higher. The upper
Emit of the primary monomer ratio is not particularly limited. It
is preferably 99% by mass or less (e.g. 98% by mass or less,
typically 95% by mass or less). The acrylic polymer can be a
polymerization product of essentially just the primary monomer.
[0049] To improve various properties such as the ease of release,
etc., the starting monomers used in polymerization of the acrylic
polymer may comprise, in addition to the primary monomer, a
secondary monomer that can be copolymerized with the primary
monomer. The secondary monomer encompasses not only a monomer, but
also an oligomer. As such a secondary monomer, a monomer having a
functional group (or "functional group-containing monomer"
hereinafter) can be cited. The functional group-containing monomer
can be added to incorporate crosslinking points into the acrylic
polymer to increase the cohesive strength thereof. Examples of such
a functional group-containing monomer include
carboxyl-group-containing monomers, acid-anhydride-group-containing
monomers, hydroxyl-group-containing monomers,
amide-group-containing monomers, amino-group-containing monomers,
epoxy-group (glycidyl group)-containing monomers,
alkoxy-group-containing monomers, and alkoxysilyl-group-containing
monomers. These can be used as a single kind alone, or in
combination of two or more kinds. Among these, functional
group-containing monomers having a functional group of carboxyl
group, hydroxyl group, epoxy group, etc. are more preferable, and
carboxyl-group-containing monomers and hydroxyl-group-containing
monomers are yet more preferable because they can preferably
introduce crosslinking points into the acrylic polymer and achieve
an even higher cohesive strength in the acrylic polymer.
[0050] Examples of a carboxyl-group-containing monomer include
ethylenic unsaturated monocarboxylic acids such as acrylic acid,
methacrylic acid, crotonic acid, carboxyethyl (meth)acrylate,
carboxypentyl (meth)acrylate, etc.; ethylenic unsaturated
dicarboxylic acids such as itaconic acid, maleic acid, fumaric
acid, citraconic acid, etc.; and the like. Among these, acrylic
acid and/or methacrylic acid are preferable, and acrylic acid is
especially preferable.
[0051] Examples of an acid-anhydride-group-containing monomers
include acid anhydrides of the ethylenic unsaturated dicarboxylic
acids listed above such as maleic acid anhydride, itaconic acid
anhydride, etc.; and the like.
[0052] Examples of a hydroxyl-group-containing monomer include
hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate,
2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,
2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.;
unsaturated alcohols such as N-methylol(meth)acrylamide, vinyl
alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl
vinyl ether, diethylene glycol monovinyl ether, etc.; and the
like.
[0053] Examples of an amide-group-containing monomer include
(meth)acrylamide, N,N-dimethyl(meth)acrylamide,
N-butyl(meth)acrylamide, N-methylol(meth)acrylamide,
N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide,
N-butoxymethyl(meth)acrylamide, and the like.
[0054] Examples of an amino-group-containing monomer include
aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate,
t-butylaminoethyl (meth)acrylate, and the like.
[0055] Examples of an epoxy-group (glycidyl group)-containing
monomer include glycidyl (meth)acrylate, methylglycidyl
(meth)acrylate, allyl glycidyl ether, and the like.
[0056] Examples of an alkoxy-group-containing monomer include
methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and the
like.
[0057] Examples of an alkoxysilyl-group-containing monomer include
3-(meth)acryloxypropyltrimethoxysilane,
3-(meth)acryloxypropyltriethoxysilane,
3-(meth)acryloxypropylmethyldimethoxysilane,
3-(meth)acryloxypropylmethyldiethoxysilane, and the like.
[0058] When an aforementioned functional group-containing monomer
is used as a monomer constituting the acrylic polymer, the
functional group-containing monomer (preferably a carboxyl
group-containing monomer) is preferably added at 1 to 10% by mass
(e.g., 2 to 8% by mass, typically 3 to 7% by mass) of all the
monomers.
[0059] To increase the cohesive strength of the acrylic polymer,
etc., another monomer besides the functional-group-containing
monomer can be included as a secondary monomer. Examples of such a
monomer include vinyl-ester-based monomers such as vinyl acetate,
vinyl propionate, etc.; aromatic vinyl compounds such as styrene,
substituted styrenes (.alpha.-methylstyrene, etc.), vinyl toluene,
etc.; and the like.
[0060] The method for polymerizing the monomer or a monomer mixture
is not particularly limited, and a general polymerization method
heretofore known can be employed. Examples of such a polymerization
method include solution polymerization, emulsion polymerization,
bulk polymerization, and suspension polymerization. Among these,
solution polymerization is preferable. The embodiment of the
polymerization is not particularly limited and can be carried out
with suitable selection of a heretofore known monomer supply
method, polymerization conditions (temperature, time, pressure,
etc.), and other components (polymerization initiator, surfactant,
etc.) used besides the monomer. For instance, as the monomer supply
method, the monomer mixture can be supplied to a reaction vessel
all at once (all-at-once supply), or gradually supplied dropwise
(continuous supply), or the mixture can be divided in several
portions and each portion can be supplied at a prescribed time
interval (portionwise supply). The monomer or the monomer mixture
can be supplied as a solution or a dispersion containing part or
all thereof dissolved in a solvent or emulsified in water.
[0061] The polymerization initiator is not particularly limited.
Examples include azo-based initiators such as
2,2'-azobisisobutylonitrile, etc.; peroxide-based initiators such
as benzoyl peroxide, etc.; substituted ethane-based initiators such
as phenyl-substituted ethane, etc.; redox-based initiators
combining a peroxide and a reducing agent such as a combination of
a peroxide and sodium ascorbate, etc.; and the like. The amount of
polymerization initiator used can be suitably selected in
accordance with the type of polymerization initiator, types of
monomers (composition of the monomer mixture) and so on. It is
usually suitably selected from a range of, for instance, about
0.005 to 1 part by mass, relative to 100 parts by mass of all the
monomers. The polymerization temperature can be, for example,
around 20.degree. C. to 100.degree. C. (typically 40.degree. C. to
80.degree. C.).
[0062] A crosslinking agent is preferably added to the PSA
composition. Preferable examples of a crosslinking agent for an
acrylic PSA include organometallic salts such as zinc stearate,
barium stearate, etc.; epoxy-based crosslinking agents;
isocyanate-based crosslinking agents; and the like. Oxazoline-based
crosslinking agents, aziridine-based crosslinking agents,
metal-chelate-based crosslinking agents, and melamine-based
crosslinking agents can also be used. These crosslinking agents can
be used singly as one species or as two or more species together.
Among these, epoxy-based crosslinking agents and isocyanate-based
crosslinking agents are preferable because they can be preferably
crosslinked to carboxyl groups and are likely to produce good
maneuverability (typically easy-release nature) and even good acid
resistance as well. Combined use of an epoxy-based crosslinking
agent and an isocyanate-based crosslinking agent is particularly
preferable. The amount of crosslinking agent added is not
particularly limited. In order to achieve the adhesive strength in
the preferable numerical value range, it can be about 0.01 to 10
parts by mass (e.g. 0.05 to 5 parts by mass, typically 0.1 to 5
parts by mass) relative to 100 parts by mass of the base polymer
(e.g. an acrylic polymer). When an epoxy-based crosslinking agent
(C.sub.E) and an isocyanate-based crosslinking agent (C.sub.I) are
used together, their mass ratio value (C.sub.E/C.sub.I) is
preferably 0.01 to 1 (e.g. 0.05 to 0.5, typically 0.1 to 0.4).
[0063] When a solvent-based PSA is used, preferable examples of a
solvent for use include aliphatic hydrocarbons such as hexane,
heptane, mineral spirit, etc.; alicyclic hydrocarbons such as
cyclohexane, etc.; aromatic hydrocarbons such as toluene, xylene,
solvent naphtha, tetralin, dipentene, etc.; alcohols such as butyl
alcohol, isobutyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl
alcohol, tridecyl alcohol, etc.; esters such as methyl acetate,
ethyl acetate, isopropyl acetate, butyl acetate, etc.; ketones such
as acetone, methyl ethyl ketone, etc.
[0064] The molecular weight (Mw: weight average molecular weight)
of the base polymer (e.g. an acrylic polymer) to be used
(synthesized) is not particularly limited, but a polymer (e.g., an
acrylic polymer) having a weight average molecular weight (Mw) of
approximately 30.times.10.sup.4 to 100.times.10.sup.4 can be used
preferably.
[0065] The acrylic polymer constituting the PSA in the art
disclosed herein can be a thermoplastic polymer. A typical example
thereof is an acrylic block copolymer. Can be preferably used an
acrylic block copolymer comprising at least one acrylate block
(which hereinafter may be referred to as an Ac block) and at least
one methacrylate block (which hereinafter may be referred to as an
MAc block). For instance, preferable is a block copolymer having a
structure in which Ac blocks and MAc blocks are positioned
alternately. The total number of Ac blocks and MAc blocks is
preferably 3 or larger (e.g., 3 to 5).
[0066] In typical, the Ac block preferably comprises an alkyl
acrylate as the primary monomer (i.e. the component that accounts
for 50% by mass or more among the block-constituting monomeric
units). Of the monomeric units, 75% by mass or more (e.g. 90% by
mass or more) can be an alkyl acrylate. In a preferable embodiment,
the monomeric units constituting the Ac block in the acrylic block
copolymer (in an acrylic block copolymer comprising two or more Ac
blocks, possibly at least one of the Ac blocks or all the Ac
blocks) essentially consist of one, two or more species (typically
one species) of alkyl acrylate. Alternatively, the Ac block may be
a copolymer of an alkyl acrylate and another monomer (e.g. an alkyl
methacrylate, etc.).
[0067] Examples of the Ac block-constituting alkyl acrylate include
methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl
acrylate, n-butyl acrylate (BA), isobutyl acrylate, tert-butyl
acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate,
n-octyl acrylate, 2-ethylhexyl acrylate (2EHA), nonyl acrylate,
isononyl acrylate, decyl acrylate, dodecyl acrylate, stearyl
acrylate, etc. For example, a constitution where the Ac
block-constituting monomers essentially consist of BA alone, 2EHA
alone, or both BA and 2EHA can be preferably used.
[0068] It is typically preferable that the MAc block comprises an
alkyl methacrylate as the primary monomer. Of all the monomers
constituting the MAc, 75% by mass or more (e.g. 90% by mass or
more) can be an alkyl methacrylate. In a preferable embodiment, the
monomeric units constituting the MAc block (in an acrylic block
copolymer comprising two or more MAc blocks, possibly at least one
of the MAc blocks or all the MAc blocks) contained in the acrylic
block copolymer essentially consist of only one, two or more
species (typically one species) of alkyl methacrylate.
Alternatively, the MAc block may be a copolymer of an alkyl
methacrylate and another monomer (e.g., an alkyl acrylate).
[0069] The alkyl methacrylate constituting the MAc block may be an
alkyl methacrylate whose alkyl group has 1 to 20 (preferably 1 to
14) carbon atoms. Specific examples thereof include methyl
methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl
methacrylate, n-butyl methacrylate, isobutyl methacrylate,
tert-butyl methacrylate, n-pentyl methacrylate, n-hexyl
methacrylate, n-heptyl methacrylate, n-octyl methacrylate,
2-ethylhexyl methacrylate, nonyl methacrylate, isononyl
methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl
methacrylate, etc.
[0070] In a preferable embodiment, of the monomers constituting the
MAc block, 50% by mass or greater (or 75% by mass or greater, or
essentially all) is an alkyl methacrylate having an alkyl group
with 1 to 4 carbon atoms. Especially preferable alkyl methacrylates
include methyl methacrylate (MMA) and ethyl methacrylate (EMA). For
example, the monomers preferably employed may consist essentially
of MMA alone, EMA alone, both MMA and EMA, or the like.
[0071] The acrylic block copolymer in the art disclosed herein may
be a copolymer comprising A blocks and B blocks positioned
alternately such as type AB, type ABA, type ABAB, type ABABA, etc.,
with the A block having been formed of a polymer having a rigid
structure with excellent cohesive strength and elasticity, and the
B block having been formed of a polymer having a flexible structure
with excellent viscosity. A PSA comprising as its base polymer an
acrylic block copolymer having such a structure may form a PSA
layer combining cohesive strength and elasticity as well as
viscosity at high levels. A PSA having such a composition can be
preferably used as a hot melt PSA. An acrylic block copolymer (such
as type ABA, type ABABA, etc.) having a structure with A blocks at
both termini of the molecule can be preferably used. An acrylic
block copolymer having such a structure is preferable because it is
likely to have a good balance of cohesion and thermoplasticity.
[0072] When the acrylic block copolymer comprises two or more A
blocks, the compositions, molecular weights (polymerization
degrees), structures, etc., of these A blocks can be the same with
or different from each other. When the acrylic block copolymer
comprises two or more B blocks, the same is true with the B
blocks.
[0073] As the A Nock, can be preferably used an MAc Nock as those
described above. As the B block, can be preferably used an Ac block
as those described above. In a preferable embodiment, the acrylic
block copolymer is a triblock copolymer having a structure of
MAc-Ac-MAc (type ABA). For instance, can be preferably used a
triblock copolymer with two MAc blocks having essentially identical
monomer compositions.
[0074] The ratio of mass of MAc block (when two or more MAc blocks
are contained, their total mass) to mass of Ac block (when two or
more Ac blocks are contained, their total mass) in the acrylic
block copolymer is not particularly limited, but can be preferably
in a range such that the mass ratio MAc block/Ac block is 4/96 to
90/10 (usually 7/93 to 80/20, preferably 10/90 to 70/30, e.g.,
20/80 to 50/50). At a large MAc block ratio, there is a tendency
for reduced adhesive strength, allowing for easy release. At a
large Ac block ratio, there is a tendency for an increased organic
dirt-collecting ability.
[0075] As the acrylic block copolymer, in usual, can be suitably
used an acrylic block copolymer having a weight average molecular
weight (Mw) of about 3.times.10.sup.4 to 30.times.10.sup.4. The
acrylic block copolymer has a Mw of preferably about
3.5.times.10.sup.4 to 25.times.10.sup.4 or more preferably about
4.times.10.sup.4 to 20.times.10.sup.4 (e.g., 5.times.10.sup.4 to
15.times.10.sup.4). Too small a Mw of the acrylic block copolymer
may decrease the adhesive properties (e.g., cohesion) or lower the
ease of release. Too large a Mw tends to lead to insufficient
thermoplasticity of the acrylic block copolymer. The Mw of the
acrylic block copolymer described here refers to a value based on
standard polystyrene that is determined by gel permeation
chromatography (GPC) with respect to a sample prepared by
dissolving the copolymer in a suitable solvent (e.g.,
tetrahydrofuran (THF)).
[0076] In the acrylic block copolymer in the art disclosed herein,
a monomer (other monomer) other than an alkyl acrylate and an alkyl
methacrylate may be copolymerized. Examples of the other monomer
include vinyl compounds having functional groups such as alkoxyl
group, epoxy group, hydroxyl group, amino group, amide group, cyano
group, carboxyl group, acid anhydride group, etc.; vinyl esters
such as vinyl acetate; aromatic vinyl compounds such as styrene;
vinyl group-containing heterocyclic compounds such as
N-vinylpyrrolidone and the like. Alternatively, it can be an alkyl
acrylate having a structure with an acryloyl group coupled to a
fluorinated alkyl group, a fluorinated alkyl acrylate and a
fluorinated alkyl methacrylate. The other monomer may be used, for
instance, to adjust the properties (adhesive properties, ease of
molding, etc.) of the PSA layer and its content is suitably 20% by
mass or less (e.g. 10% by mass or less, typically 5% by mass or
less) of all the monomers constituting the acrylic block copolymer.
In a preferable embodiment, the acrylic block copolymer is
essentially free of the other monomers.
[0077] Such an acrylic block copolymer can be readily synthesized
by a known method (e.g. see JP2001-234146, JPH11-323072), or a
commercial product is readily available. Examples of the commercial
product include trade name "LA POLYMER" series (e.g., those with
product numbers LA2140e, LA2250, etc.) available from Kraray Co.,
Ltd., trade name "NABSTAR" available from Kaneka Corporation, and
the like. As the method for synthesizing the acrylic block
copolymer, living polymerization can be preferably employed.
According to living polymerization, while keeping the
weatherability inherent in the acrylic polymer, because of the
excellent structure control unique to the living polymerization, an
acrylic block copolymer having excellent thermoplasticity can be
synthesized. Since the molecular weight distribution can be
controlled in a narrow range, insufficient cohesion caused by the
presence of low molecular weight components can be reduced to
obtain an easily releasable PSA (even a PSA sheet (dirt-collecting
member)).
[0078] When the PSA (e.g. PSA layer) in the art disclosed herein
comprises an acrylic block copolymer, solely one species or a
combination of two or more species of acrylic block copolymer can
be used. In addition to the acrylic block copolymer, to control the
adhesive properties, etc., it may comprise, as an optional
component, a component other than an acrylic block copolymer.
Examples of the optional component include a polymer and an
oligomer excluding acrylic block copolymers. The amount of the
polymer or oligomer (or "optional polymer" hereinafter) is suitably
50 parts by mass or less relative to 100 parts by mass of the
acrylic block copolymer, preferably 10 parts by mass or smaller, or
more preferably 5 parts by mass or smaller. In a preferable
embodiment, the PSA layer may be essentially free of polymers other
than the acrylic block copolymer.
[0079] The PSA composition in the art disclosed herein preferably
comprises a plasticizer. The inclusion of plasticizer increases the
ease of release. It also lowers the viscosity of the composition
and thus the application is further facilitated. In yet another
aspect, the inclusion of plasticizer also increases the organic
dirt-collecting ability on the PSA surface. The organic dirt
collected on the PSA surface is absorbed into the PSA (e.g. PSA
layer) and dispersed therein. Thus, even when the dirt-collecting
ability is reduced by repeated use, the dirt-collecting ability
recovers in relatively short time (e.g. several minutes or several
hours) as a unique effect (dirt-collecting ability recovery
effect).
[0080] The dirt-collecting ability recovery effect is described
with reference to FIG. 5. As schematically illustrated in FIG. 5,
when the PSA layer 32 in dirt-collecting member (PSA sheet) 31 is
allowed to make contact with a flat surface 2 of an article 1 such
as a portable device, etc., the PSA layer 32 collects organic dirt
50 adsorbed on the surface 2. The PSA layer 32 has a property to
not only collect organic dirt 50, but also causes it to migrate
into the layer. Thus, the organic dirt 50 caught on the surface of
PSA layer 32 migrates with time into the PSA layer 32, leading to a
lower presence of organic dirt 50 on the surface of PSA layer 32;
and eventually, the surface of PSA layer 32 will be essentially
free of the presence of organic dirt 50. In other words, the
surface regains the same state as before the sticky cleaner is
used. Accordingly, the term "recovery effect" refers to an effect
such that when the PSA collects organic dirt and the
dirt-collecting ability is temporarily reduced, the dirt-collecting
ability recovers in a prescribed time period (e.g. several minutes,
preferably several hours) and the PSA (e.g. PSA layer) regains the
ability to collect dirt. It encompasses that the dirt-collecting
ability requires short time for recovery.
[0081] Examples of plasticizer include phthalic acid esters such as
dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate,
dibutyl phthalate, etc.; adipic acid esters such as dioctyl
adipate, diisononyl adipate, etc.; trimellitic acid esters such as
trioctyl trimellitate, etc.; sebacic acid esters; and the like.
Softeners such as processed oil are also included in the
plasticizer. These can be used singly as one species or in a
combination of two or more species. Among them, adipic acid esters
are preferable.
[0082] The amount of plasticizer added is not particularly limited.
For instance, it is suitably 1 part by mass or greater to 100 parts
by mass of the base polymer (e.g. an acrylic polymer). The amount
added is preferably 5 parts by mass or greater, more preferably 10
parts by mass or greater, yet more preferably 15 parts by mass or
greater, or particularly preferably 20 parts by mass or greater.
The amount added is suitably 100 parts by mass or less, preferably
80 parts by mass or less, more preferably 70 parts by mass or less,
yet more preferably 60 parts by mass or less, or particularly
preferably 50 parts by mass or less. From the standpoint of
balancing the dirt-collecting ability and dirt-collecting ability
recovery effect, the amount of plasticizer added is preferably 40
parts by mass or less (e.g. 20 to 40 parts by mass, typically 25 to
35 parts by mass) to 100 parts by mass of the base polymer.
[0083] The PSA composition (or PSA, PSA layer) in the art disclosed
herein can include, as other components, various additives known in
the PSA field, such as tackifier, surfactant, chain transfer agent,
anti-aging agent, antioxidant, UV ray absorber, photostabilizer,
antistatic agent, colorant (pigment, dye, etc.) and so on. The
types and amounts of these non-essential additives can be the same
as usual types and amounts in this type of PSA.
[0084] When the PSA (e.g. PSA layer) is formed from the PSA
composition disclosed herein, the formation method is not
particularly limited. For instance, it is possible to apply a
method where the PSA composition is directly provided (typically
applied) to a substrate, using a heretofore known application means
such as die coater, gravure roll coater and the like, and allowed
to dry.
[0085] The thickness of the PSA layer can be suitably selected in
accordance with the purpose and is not particularly limited. From
the standpoints of making sufficient use of the dirt-collecting
ability and increasing the recovery of the dirt-collecting ability,
the thickness of the PSA layer is preferably about 10 .mu.m or
larger (e.g. 30 .mu.m or larger, typically 50 .mu.m or larger).
When it is important to reduce the weight or size, etc., the
thickness of the PSA layer is preferably 300 .mu.m or smaller (e.g.
100 .mu.m or smaller, typically 70 .mu.m or smaller). The PSA layer
may be formed entirely over one face of the support substrate.
Alternatively, for instance, a non-sticky region (dry edge) free of
the PSA layer may be included along each edge of the support
substrate's width direction.
[0086] When the dirt-collecting member disclosed herein comprises a
support substrate as in this embodiment, as the support substrate,
materials formed with various types of synthetic resin, non-woven
fabric or paper can be used. The material of the support substrate
can be a fabric, rubber sheet, foam sheet, metal foil, a composite
of these, etc.
[0087] Examples of synthetic resin include a polyolefin
(polyethylene, polypropylene, ethylene-propylene copolymers, etc.),
polyester (polyethylene terephthalate, etc.), vinyl chloride resin,
vinyl acetate resin, polyimide resin, polyamide resin, fluorocarbon
resin, and the Eke. In particular, a support substrate made of
polyethylene terephthalate (PET) can be preferably used. Examples
of paper include Washi, kraft paper, glassine paper, high-grade
paper, synthetic paper, top-coated paper, and the Eke. Examples of
a fabric include a woven fabric and a non-woven fabric of a single
species or a blend, etc., of various fibrous substances. Examples
of the fibrous substance include cotton, staple fiber, Manila hemp,
pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol
fiber, polyamide fiber, polyolefin fiber, and the like. Examples of
a rubber sheet include a natural rubber sheet, a butyl rubber
sheet, and the Eke. Examples of a foam sheet include a polyurethane
foam sheet, a polychloroprene rubber foam sheet, and the like.
Examples of metal foil include aluminum foil, copper foil, and the
like. The support substrate may contain as necessary various
additives such as filler (inorganic filler, organic filler, etc.),
anti-aging agent, antioxidant, UV ray absorber, photostabilizer,
anti-static agent, lubricant, plasticizer, colorant (pigment, dye,
etc.), and the like.
[0088] When the dirt-collecting member is a single-faced PSA sheet
having a PSA layer formed on a single face of a support substrate,
the back face (PSA layer-free face) of the support substrate is
preferably subjected to a surface treatment such as coating of a
silicone-based release agent and the like to adjust the unwinding
force of the PSA sheet roll to a suitable range (typically a
release treatment to prevent the unwinding force from becoming
excessively high).
[0089] The thickness of the support substrate can be suitably
selected in accordance with the purpose and is not particularly
limited. In general, the thickness is preferably about 20 .mu.m or
larger (e.g. 30 .mu.m or larger, typically 40 .mu.m or larger), but
suitably about 200 .mu.m or smaller (e.g. 100 .mu.m or smaller,
typically 70 .mu.m or smaller).
[0090] Several working examples related to the present invention
are described below although the present invention is not to be
limited to these specific examples. In the following explanation,
the terms "parts" and "%" are based on the mass unless specifically
stated otherwise.
Example 1
[0091] To a three-neck flask, were placed 2-ethylhexyl acrylate
(2EHA) and acrylic acid (AA) at a mass ratio 2EHA:AA=95:5. Toluene
was used as the solvent. Under a nitrogen flow, benzoyl peroxide
was added as a polymerization initiator. The reaction mixture was
heated to 60.degree. C. and the reaction was carried out for 2
hours. The reaction mixture was further heated to 80.degree. C. and
the reaction was carried out for 1 hour to prepare a solution of an
acrylic polymer A having a weight average molecular weight (Mw) of
about 50.times.10.sup.4 to 60.times.10.sup.4. Subsequently, to 100
parts of polymeric non-volatiles of the acrylic polymer solution,
were mixed 30 parts of a plasticizer (diisononyl adipate "MONOCIZER
W-242" available from DIC Corporation), 0.1 part of an epoxy-based
crosslinking agent ("TETRAD-C" available from Mitsubishi Gas
Chemical Inc.) and 2 parts of an isocyanate-based crosslinking
agent ("CORONATE L" available from Nippon Polyurethane Industry
Co., Ltd.) to prepare an acrylic PSA composition.
[0092] The resulting acrylic PSA composition was applied to a
surface of a 38 .mu.m thick PET support substrate sheet (width:
approximately 8 cm) and allowed to dry to fabricate a single-faced
PSA sheet having a PSA layer of about 80 .mu.m in thickness
(adhesive thickness) formed on the single face of the support
substrate. The resulting single-faced PSA sheet was wound around
the surface of a drum-shaped holding member (20 mm diameter) to
form a PSA sheet roll. The holding member was installed on an end
of a grip member in a freely rotatable (rolling) manner to
construct a cleaner as schematically shown in FIGS. 1 and 2.
Example 2
[0093] The amount of epoxy-based crosslinking agent was increased
to 0.5 part relative to 100 parts of polymeric non-volatiles of the
acrylic polymer solution. Otherwise, in the same manner as Example
1, a cleaner according to Example 2 was constructed.
Example 3
[0094] The amount of plasticizer added was increased to 60 parts
relative to 100 parts of polymeric non-volatiles of the acrylic
polymer solution. Otherwise, in the same manner as Example 2, a
cleaner according to Example 3 was constructed.
Example 4
[0095] Were mixed 100 parts (non-volatiles) of a commercial acrylic
Nock copolymer (acrylic polymer B) and 30 parts of a plasticizer
(diisononyl adipate "MONOCIZER W-242" available from DIC
Corporation) to prepare a hot melt acrylic PSA. The resulting
acrylic PSA was melted and applied to a surface of a 38 .mu.m thick
PET support substrate sheet (width: approximately 8 cm) to
fabricate a single-faced PSA sheet having a PSA layer of about 50
.mu.m in thickness (adhesive thickness) formed on the support
substrate. Using the resulting single-faced PSA sheet, otherwise in
the same manner as Example 1, a cleaner according to Example 4 was
constructed.
Example 5
[0096] The amount of plasticizer added was increased to 100 parts
relative to 100 parts (non-volatiles) of the acrylic Nock
copolymer. Otherwise, in the same manner as Example 4, a cleaner
according to Example 5 was constructed.
Example 6
[0097] A commercial roller floor cleaner (trade name "COLOCOLO"
available from Nitoms, Inc.) was used as Example 6.
[Measurement of 180.degree. Peel Strength to SUS]
[0098] The PSA sheet according to each example was cut to 200 mm by
25 mm to obtain a rectangular test piece. The test piece was
adhered over the sticky surface (PSA layer-side surface) to a
stainless steel (SUS304) plate with a 2 kg roller moved back and
forth once. The resultant was stored in an environment at
23.degree. C. and 50% RH for 30 minutes. Based on JIS Z0237, using
a tensile tester, in an environment at 23.degree. C. and 50% RH,
the 180.degree. peel strength (N/25 mm) to SUS was measured at a
peel angle of 180.degree. and at a tensile speed of 300 mm/min.
Measurements were made with "TENSILON" available from Shimadzu
Corporation. The results are shown in Table 1.
[Measurement of 180.degree. Peel Strength to Glass]
[0099] With respect to the PSA sheets according to Examples 1 to 3,
using a glass plate as the adherend, otherwise in the same manner
as the 180.degree. peel strength to SUS, the 180.degree. peel
strength (N/25 mm) to glass was measured. As the glass plate, a
commercial float glass plate was used. The results are shown in
Table 1.
[Measurement of 180.degree. Peel Strength to PET]
[0100] With respect to the PSA sheets according to Examples 1 to 3,
using a PET film (50 .mu.m thick) as the adherend, otherwise in the
same manner as the 180.degree. peel strength to SUS, the
180.degree. peel strength (N/25 mm) to PET was measured. The
results are shown in Table 1.
[Assessment of Dirt Removal Rate]
[0101] A tablet terminal (iPad.RTM., a product of Apple Inc.) was
obtained and the display (flat surface made of aluminosilicate
glass) was thoroughly cleaned with each cleaner and subjected to a
measurement of gloss value G0 (60.degree. measurement angle), using
a handy gloss meter "Gloss Checker IG-331" available from Horiba,
Ltd. Subsequently, sebum on the tester's face and other body skin
was rubbed on fingers and the organic sebum dirt on the fingers was
rubbed on and transferred to an area of the display of the tablet
terminal. The organic dirt was transferred in an amount to yield a
gloss value of about 60 (G1). The display's surface having the
sebum dirt was cleaned with the cleaner according to each example.
In particular, the PSA sheet roll of the cleaner according to each
example was allowed to rotate once. The rolling speed was about 0.5
msec. The pressure applied by the operator for the rotation was
about 700 g. The display was then subjected to a measurement of
gloss value G2 (60.degree. measurement angle) to determine the dirt
removal rate (%) based on an equation: dirt removal rate
(%)=(G2-G1)/(G0-G1).times.100. Two measurements were taken and
their average value was recorded. The results are shown in Table
1.
TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
Composition (parts) Acrylic polymer A 100 100 100 -- -- -- Acrylic
polymer B -- -- -- 100 100 Plasticizer 30 30 60 30 100 Epoxy-based
crosslinking agent 0.1 0.5 0.5 -- -- Isocyanate-based crosslinking
agent 2 2 2 -- -- 180.degree. Peel strength (N/25 mm) To SUS 0.80
0.16 0.09 0.04 0.02 9.7 To Glass 0.82 0.11 0.06 -- -- -- To PET
0.36 0.08 0.02 -- -- -- Dirt removal rate (%) 100 99 99 100 93
89
[0102] As shown in Table 1, the cleaners according to Examples 1 to
5 were easily releasable, exhibiting adhesive strengths of less
than 1 N/25 mm as measured values based on the 180.degree. peel
test specified in JIS Z0237. Despite the easy-release nature as
described above, the cleaners according to these examples achieved
greater organic dirt-removing abilities than the cleaner according
to Example 6 having relatively strong adhesive strength. Similarly
to usual dirt, at least a certain adhesive strength has been
considered necessary also with respect to organic dirt such as
human sebum dirt and the like. It has been validated, however, that
even a PSA as poorly adhesive as the PSA sheets of the respective
examples can even exhibit sufficient dirt-removing abilities. This
has been revealed for the first time through the studies by the
present inventors. For instance, even on a portable device surface
covered with removable protection film, because of the easy-release
nature, a sticky cleaner as easily releasable as those described
above can be expected to clean the surface (in this case, the
surface of the protection film) without removing the protection
film. A person skilled in the art would recognize this because of
the low peel strength to PET which is a synthetic resin.
[0103] Although specific embodiments of the present invention have
been described in detail above, these are merely for illustrations
and do not limit the scope of claims. The art according to the
claims includes various modifications and changes made to the
specific embodiments illustrated above.
REFERENCE SIGNS LIST
[0104] 1 portable device (article) [0105] 2 surface (display)
[0106] 10 sticky cleaner [0107] 20 holding member [0108] 30 PSA
sheet roll [0109] 31 PSA sheet (dirt-collecting member) [0110] 32
PSA layer [0111] 36 substrate [0112] 40 grip member [0113] 42
handle [0114] 50 organic dirt
* * * * *