Note: Descriptions are shown in the official language in which they were submitted.
- `- 200~6 1 7
BACKGROUND OF THE lN V~N~ oN
The present invention relates to an adhesive tape which
is low in cost and the properties of which such as
unwindability, adhesiveness, trimmed clearance, printability
and transparency are improved without spoiling hand lateral
cutting characteristics and, more particularly, it relates to
an adhesive tape having improved longitll~; n~ 1 tearing
strength.
In conventional adhesive tape, as shown in FIG. 9, a
molten synthetic resin material 101 is extruded into a sheet
by an extruding machine 102, and the sheet is passed through
a rubber roll 103 and a drawing roll 104 to form a smooth
surface on one side and an uneven surface on the other side
and then prscesc~ by corona discharge so as to facilitate
the coating of an adhesive, thereafter a base film 107 is
produced by passing through an electrode 105 and a processing
roll 106.
As shown in FIG. 10, the base film 107 passing through
the electrode 105 and the processing roll 106 contacts the
former at the smooth surface 108 and contacts the latter at
the uneven surface 109. The base film 107 thus prepared is
coated with an adhesive on the smooth surface 108 to produce
the adhesive tape.
Prior art disclosing an adhesive tape, in which an
adhesive layer is provided on the smooth surface and the
other surface is formed to be uneven, includes Japanese
Publication Patent No. 13306/1975 entitled "Adhesive Tape"
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20056 1 7
and Japanese Publication Utility Model Patent No. 47907/1976
entitled "Plastic Adhesive Tape".
In the prior art an adhesive tape which is formed in a
body by providing a smooth adhesive layer on the smooth
surface and forming the other surface to be uneven, exhibits
the following disadvantages.
(1) As shown in FIG. 10, in order to improve adhesion
of the adhesive on the smooth surface 108 of ~he base film
107, the smooth surface 108 is processed by corona discharge
by ~iæchArging from the electrode 105. But the corona
discharge is struck through the uneven surface 109. That is,
the uneven surface 109 is also partly processed by the corona
discharge and susceptible to stick to the adhesives coated on
the smooth surface 108 at that partly processed portion, so
that the rolled adhesive tape is difficult to unwind and
blocking may occur.
(2) When using the adhesive tape, the adhesive layer
surface is deformed unevenly by the uneven surface on the
rear side, and the adhesive power is inevitably weakened
since the adhesive area is reduced.
(3) When utilizing the adhesive tape as a trimming tape
for obt~in;ng a distinct coating line, as shown in FIG. 11, a
coating material permeates into recesses 112 of the adhesive
layer 111 of the base film 107, and the coating line L cannot
be finished distinctly as shown in FIG. 12. That is, the
trimmed clearance of the coating is poor.
(4) Since the adhesive tape has an uneven rear surface,
printing, stamping or writing on the rear surface cannot be
20056 1 7
made clearly. That is, the printability properties of the
tape are poor.
(5) Since the rear surface of`the adhesive tape is
formed unevenly, light is reflected irregularly to cause poor
transparency.
As a result of research by the inventors carried out to
solve such properties as unwindability, adhesiveness, trimmed
clearance, printability and transparency, the inventors have
developed an adhesive tape comprising a polyolefin resin base
film formed with a smooth surface on one side and an uneven
surface on the other side, and an adhesive layer coated with
an adhesive on said uneven surface.
With regard to the unwindability property of an adhesive
tape, this characteristic is practically very important among
the various characteristics exhibited by the adhesive tape.
In order to facilitate the unwindability of a tape and
to increase the anchoring force of an adhesive, the surface
wetting tension of the adhesive coated surface must be larger
than that of the rear side.
Therefore, there are such means as coating an anchor
coating agent on the adhesive coated surface or corona
discharge processing in order to increase the difference of
surface wetting tension, and further a method of coating a
stripping agent on the rear side. Among them the corona
discharge processing is the best, because it is inexpensive
and suitable for mass production.
In economical corona discharge processing, though the
processing roll and an electrode are maintained at a given
- 3 -
- _ 20056 1 7
interval and high voltage is applied to initiate the corona
~i~chArge while passing a plastic film therebetween, marks,
stains and dust stuck to the processing roll may frequently
cause corona discharge between the rear side of the base film
and the processing roll. Since the rear side is also
subjected to the corona discharge processing, the surface
wetting tension of the rear surface may increase. That is,
if the plastic film is not tightly contacted to the
processing roll, the corona discharge is struck through it.
In the prior art, however, since the smooth surface must
be processe~ by the corona discharge and the rear side is
uneven, the rear side of the base film is not contacted to
the processing roll tightly, thus the corona discharge is
struck through and the surface wetting tension is increased.
When the adhesive tape is produced by such a base film, its
practical use may be h; n~ered by poor unwindability and
blocking which occurs.
SUMMARY OF THE lNv~llON
According to the present invention, when the uneven
0 surface of the base film is processed by the corona
h~rge, since the smooth surface of the rear side is
contacted tightly to the processing roll, the corona
discharge is not struck through, so that the rear side of the
base film is not exposed to the corona discharge processing
and an adhesive tape with good unwinding properties can be
produced.
A significant feature of the present invention is that,
as a result of research on preventing the corona discharge
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20056 1 7
processing from striking through to improve the unwindability
of the adhesive tape in use, an adhesive layer is provided by
coating an adhesive on the uneven surface which is entirely
different from the prior art. By this method, such
properties as adhesiveness, trimmed clearance, printability
and transparency which were problematic in the prior art have
been improved un~Ypectedly.
That is, the present invention is directed to an
adhesive tape comprising a polyolefin resin base film formed
with a smooth surface on one side and an uneven surface on
the other side, and an adhesive layer coated with an adhesive
on the uneven surface. The present invention also includes
an adhesive tape having a strong longitudinal tearing
property, and comprising a base film made from a polyolefin
resin formed on one side with a smooth surface pressed by a
rubber roll, and on the other side with an uneven surface
pressed by a drawing roll, and an~adhesive layer coated with
an adhesive on said uneven surface, the base film comprising
a polyolefin resin having a specific melt index and/or the
uneven surface having a specific shape.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an adhesive tape rolled
on a reel;
FIG. 2 is an enlarged perspective view of an adhesive
tape:
FIG. 3 is a front view illustrating production of a base
film of an adhesive tape of the present invention;
~v .
`_ 2005617
FIG. 4 is an enlarged front view of an essential portion
of FIG. 3;
FIG. 5 is a plan view of a typical base film;
FIG. 6 is a perspective view of FIG. 5;
FIG. 7 is a plan view showing a state wherein a
reinforcing bridge is provided on a base film;
FIG. 8 is a perspective view of FIG. 7;
FIG. 9 is a front view illustrating production of a
base film of a conventional adhesive tape;
FIG. 10 is an enlarged front view of an essential
portion of FIG. 9;
FIG. 11 is a perspective view of a conventional adhesive
tape; and
FIG. 12 is a plan view showing a trimmed line of a
coating line when an adhesive tape of FIG. 11 is used.
DET~TT~n DESCRIPTION OF THE lNvh~llON
An adhesive tape of the present invention having good
properties such as unwindability, adhesiveness, trimmed
clearance, printability and transparency and which is capable
of being rolled on a reel 1 is shown in FIG. 1.
FIG. 2 is an enlarged perspective view of the adhesive
tape, wherein the numeral 2 indicates a base film and 3
denotes an adhesive layer. The base film 2 used may be
formed on one side with a smooth surface 4 and the other
side with an uneven surface 5.
As shown in FIG. 3, the uneven surface is formed by
extruding a molten polyolefin resin 11 by an extruding
machine 12 into a sheet, which is then passed through a
-- 6 --
` -
20056-1 7
drawing roll 13 and a rubber roll 14 so as to be pressed
against the former by the latter and transferred with an
uneven pattern thereon. As shown in FIG. 2, the uneven
pattern may be formed continuously by providing regular
uneven parallel indents which cross the adhesive tape
orthogonally with respect to its longitll~; n~ 1 direction to
direct the hand cutting, in a predetermined interval P and
depth W. Furthermore, a fine reticulated unevenness of about
60 to 250 meshes may be formed on the uneven surface. After
forming the uneven surface with the drawing roll 13 and the
rubber roll 14, the base film is passed through a processing
roll 6 and an electrode 7 for corona discharge processing to
facilitate anchoring of an adhesive on the uneven surface 5.
At this time, as shown enlarged in FIG. 4, the uneven surface
5 of the base film 2 is positioned on the electrode 7 side
and the smooth surface 5 thereof is contacting the processing
roll 6.
Though the base film 2 takes the form as shown in FIGS.
5 and 6, it may be provided with a reinforcing bridge 16
longitll~i n~ 1 ly as shown in FIGS. 7 and 8. Though the upper
face of the reinforcing bridge 16 may be flush with the
uneven projection 17 of the adhesive tape, it is preferably
below the uneven projection 17 to provide for easy tearing or
cutting of the adhesive tape by hand.
As polyolefin resins used in the present invention,
polyethylene, polypropylene and copolymers of ethylene or
propylene and other one or more kinds of alpha-olefins are
exemplified. As alpha-olefins, ethylene, propylene, butene-
-- 7 --
20056 1 7
1, pentene-l, hexene-l, heptene-l, octene-l, nonene-l,
4-methylpentene-1, decene-l, etc. are exemplified.
A molecular weight (related to melt index (Ml) of
resins) of the polyolefin resin used in a polyolefin resin
base film has some connection with strengthening the
longitudinal tearing property of the adhesive tape, so that
the melt index may be made smaller within a range in which
the resin film can be proce~c~ the range of melt index may
be 0.2 to 20 g/10 min., and preferably 1.0 to 10.0 g/10 min.
10In the present invention, as to the uneven surface of
the polyolefin resin base film, the uneven depth W and
interval P are related to the longitll~i n~ 1 tearing strength
of the adhesive tape, so that the uneven depth may be 0.03-
0.30 mm and preferably 0.04-0.12 mm. The longitll~; n~l
tearing strength may increase below 0.03 mm but the lateral
tearing property may be deteriorated. Considering the ease
of hand cutting the adhesive tape, the uneven interval
(longitl~inAl interval of the adhesive tape) may be 0.5-5.0
mm and preferably 0.6-1.4 mm.
The surface wetting tension of the polyolefin resin base
film used in the adhesive tape of the present invention is
preferably 30 Dyn/cm or less on the smooth surface, and 35
Dyn/cm or more on the uneven surface. When the surface
wetting tension of the smooth surface is more than 30 Dyn/cm,
the adhesive tape wound in a roll is difficult to unwind, and
moreover, unwanted blocking may occur, and when the surface
wetting tension of the uneven surface is less than 35 Dyn/cm,
anchoring of the adhesive on the uneven surface becomes
- 8
2no5~ 7
insufficient.
Though the smooth surface 4 of the base film 2 is
obtained by the rubber roll 14, a rubber roll which is as
smooth as possible and preferably a silicon rubber roll may
be used. Then, the uneven surface 5 of the base film 2 is
processed by the corona discharge so as to facilitate
anchoring of the adhesive and the adhesive layer 3 is
laminated thereon. Any known adhesive may be used such as
those in the yL~uy~ of acryl, vinyl ether and silicon. Also,
any laminating process may be employed such as a method of
coating a solution or emulsion of an adhesive and drying or
hot-melt coating. The adhesive tape in the present invention
includes a two-layer construction comprising the base film 2
and the adhesive layer 3, the thickness t of the base film 2
is, though dep~n~;nq upon use, 30 to 500 ~m and t1 of the
adhesive layer 3 is less than 300 ~m from the uneven
projection 17. Depen~;ng upon use of the adhesive tape, a
coloring agent, filler and so on may be added to the
respective layers.
Below, the present invention is specifically described
in the following examples.
EXAMPLE 1, COMPARATIVE EXAMPLE 1, COMPARATIVE EXAMPLE 2
With respect to the adhesive tape of the present
invention having a good unwinding property, adhesiveness and
trimmed clearance:
A masterbatch of polyethylene cont~;n;ng calcium
carbonate of 50% by weight was mixed with a polyethylene
resin (d=0.96 g/cm3: melt index of 7 g/10 min. at 190 C and
_ g
20056 1 7
2.16 kg/cm2) such that the calcium carbonate content became
20% by weight to the total resin, and was extruded at 160-
190 C to obtain a molten sheet. The molten sheet was
pressed by a rubber roll so as to be formed with a smooth
surface on one side, and by a drawing roll (a) (see Table 3)
having a surface capable of forming an uneven surface on the
other side, then the sheet was cooled and the uneven surface
was proc~sC~ by corona discharge at 45 Dyn/cm to obtain the
base film for adhesive tape.
On the uneven surface of an uneven polyethylene film
having the thickness of 130 ~m, a 40 wt % solution (about
4000 centipoise) of a copolymer of butyl acrylate (80 wt %)
and 2-ethylhexyl acrylate (20 wt %) in ethyl acetate-toluene
mixed solvent was coated with a roll coater, and the coated
film was passed through a drying oven at 80--100 C for 3
minutes to obtain the adhesive tape formed with an acryl
adhesive layer of 30 ~m thick on the polyethylene film.
In the comparative example 1, the smooth surface of the
base film was processed by the corona discharge at 45 Dyn/cm
by the same method as aforementioned, and coated with the
adhesive to obtain the adhesive tape.
In the comparative example 2, the uneven surface of the
2s base film was proc~cce~ by the corona discharge at 45
Dyn/cm by the same method as aforementioned except using a
rubber roll with a coarse surface, and coated with the
adhesive to obtain the adhesive tape.
Surface wetting tension of the smooth and uneven
surfaces of the base film, and adhesiveness, unwinding
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20056 1 7
property and trimmed clearance as a trimming tape of the
adhesive tape are shown in Table 1. Bonding strength was
tested by using stainless steel as a test plate at a peeling
angle of 180 and peeling speed of 300 mm/min. Peeling force
was tested by the same measuring method as the bonding
strength except using a polyolefin film as a test plate. The
surface wetting tension was measured according to JIS K6768.
-- 11 --
- 20056 1 7
-
a Ei ~
0
r~
t~
P~ ~n ~
o
o ~ ta
~~ ~o
'~ 3 C : _~
1~ 0 u ~ h m
1) ~ .C ~ O
tn
r
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_1 ' ~ 0
- l ~ o ~
c tn ~3
~ U
~ tv ~ ~r t
4 a ~ ~ ~c
2 0 ~ 5 ~ ~ 0 S 0 ) - u
~ ~ ~ ~ ~ 8 ~ ~ , o ~
~ 3 1 tn ~ 5 v'n
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s 15 ~ s ~
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r' cD S~ ~5 tV -~ t~ ~D hO
S F u'~ r~ s o tn v ~s o~ tn ~q
15 a) t~5 a)
rO~ X ~ r~ X ,~
,, .
-- 12 ~
200561 7
As shown in Table 1, it is apparent that an adhesive
tape of the present invention provided with an adhesive layer
on the uneven surface of a base film, is superior to the
conventional one provided with the adhesive layer on the
smooth surface in many respects.
When the surface wetting tension of the smooth surface
of the base film eYcee~ 30 Dyn/cm, the peeling strength is
increased, namely, it is difficult to unwind and to u~e in
practice. Besides, the bonding strength and the trimmed
clearance as a trimming tape is deteriorated. It is also
apparent regarding the adhesive tape of the present
invention, that the insufficient smooth surface in the
Comparative Examples results in a poor unwinding property,
adhesiveness and trimmed clearance.
EXAMPLE 2, COMPARATIVE EXAMPLE 3
With respect to the adhesive tape of the present
invention having a good unwinding property, adhesiveness,
trimmed clearance, transparency and printability:
A mixture of an equal amount of polyethylene resin (1)
(d=0.96 g/cm=3: melt index of 5 g/10 min. at 190 C and 2.16
kg/cm2) and polyethylene resin (2) (d=o.s6 g/cm3: melt index
of 2 g/10 min. at 190 C and 2.16 kg/cm2) was extruded at
160 a C-190 C to obtain a molten sheet. The molten sheet was
pressed by a rubber roll to form a smooth surface on one
side, and by a drawing roll (1) having the surface to form an
uneven surface on the other side, then the sheet was cooled
and the uneven surface was processed by corona discharge at
45 Dyn/cm to obtain the base film for adhesive tape.
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200561 7
On the uneven surface of an uneven polyethylene film
having a thickness of 130 ~m, a 40 wt % solution (about 4000
centipoise) of a copolymer of butyl acrylate (80 wt %) and 2-
ethylhexyl acrylate (20 wt %) in ethyl acetate-toluene mixed
solvent was coated with a roll coater, and the coated film
was p~Fe~ through a drying oven at 80-100- C for 3 minutes
to obtain the adhesive tape formed with an acryl adhesive
layer of 30 ~m thick on the polyethylene film.
In comparative example (3), the smooth surface of the
base film was processed by corona discharge at 45 Dyn/cm by
the same method as aforementioned, and coated with the
adhesive to obtain the adhesive tape.
The peeling property, adhesiveness, transparency,
printability and the trimmed clearance as a trimming tape for
the adhesive tape thus obtained are shown in Table 2.
o o
TAB~ 2
Ba~e film
Surface wettlng Surface wQttlng ~h~Rlve Ta~ Trimmed *l
tension of tenslon o~ Bon~ng p~ ng clearance trans- *2
uneven surface smooth surface ~L~el.yLh s~enyLh as trimmlng parency print-
Content~Dyn/cm Dyn/cm g/25 m~ g/25 mm tape (%) ability
I Example Coated with 45 30 or less 1200 460 good 30 good
2 the adhesive
on the uneven
surface
Comparatlve Coated with 34 45 900 750 poor 54 poor o
example ths adhe~ive o
3 on the smooth C~
surface
*1 Transparency: MQasurQd by a hazs meter
*2 Prlntabllity: Det~rm~ned by printing condition exhibited u~lng a water ba~e stamp
20056 1 7
As shown in Table 2, it is apparent that the adhesive
tape of the present invention provided with an adhesive layer
on the uneven surface of the base film, is superior to the
conventional one provided with an adhesive layer on the
smooth surface of the base film in many respects.
EXAMPLES 3 AND 4
With respect to the adhesive tape of the present
invention in which a longitll~;n~l tearing strength is
improved:
A masterbatch of polyethylene cont~in;ng calcium
carbonate of 50~ by weight was mixed with a mixture of equal
amount of polyethylene resin (1) (d=0.96 g/cm=3: melt index
of 5 g/10 min. at 190 C and 2.16 kg/cm2~ and polyethylene
resin (2) (d=0.92 g/cm3: melt index of 5 g/10 min. at 190 C
and 2.16 kg/cm2) such that the calcium carbonate content
became 10% by weight to the total resin, and extruded at
160-190 C to obtain a molten sheet. ~he molten sheet was
pressed by a rubber roll to form a smooth surface on one
side, and by drawing rolls (a), (b) having the surface to
form an uneven surface on the other side, then the sheet was
cooled and the uneven surface was processed by the corona
discharge at 45 Dyn/cm to obtain the base film for adhesive
tape having a thickness of 0.13 mm.
EXAMPLE 5
A masterbatch of polyethylene cont~; n; ng calcium
carbonate of 50% by weight was mixed with a mixture of equal
amount of polyethylene resin (1) (d=0.96 g/cm3: melt index
of 5 g/10 min. at 190~ C and 2.16 kg/cm2 and polyethylene
,Q~
~ 16
20056 1 7
resin (3) (d=0.92 g/cm3: melt index of 2 g/10 min. at 190 C
and 2.16 kg/cm2) such that the calcium carbonate content
became 10% by weight to the total resin, and extruded at
160-190 C to obtain a molten sheet.
The molten sheet was pressed by a rubber roll to form a
smooth surface on one side and a drawing roll (a) having the
surface to form an uneven surface on the other side, then the
sheet was cooled and the uneven surface was processed by the
corona discharge at 45 ~yn/cm to obtain the base film for
adhesive tape having a thickness of 0.13 mm.
EXAMPLES 6 AND 7
A masterbatch of polyethylene containing calcium
carbonate of 50% by weight was mixed with a mixture of equal
amount of polyethylene resin (1) (d=0.96 g/cm3: melt index
of 5 g/10 min. at 190 C and 2.16 kg/cm2 and polyethylene
resin (3) (d=0.92 g/cm3: melt index of 2 g/10 min. at 190 C
and 2.16 kg/cm2) such that the calcium carbonate content
became 10% by weight to the total resin, and extruded at
190 C to obtain a molten sheet.
The molten sheet was pressed by a rubber roll to form a
smooth surface on one side, and by drawing rolls (a), (b)
having the surface to form an uneven surface on the other
side, then the sheet was cooled and the uneven surface was
processed by the corona discharge at 45 Dyn/cm to obtain the
base film for adhesive tape having a thickness of 0.13 mm.
, --
- 17 -
20056 1 7
COMPARATIVE EXAMPLE 4
A molten sheet was obtained by using the same
polyethylene resins (1) and (2) and masterbatch as the
examples 3, 4 and by the same extruding process.
The molten sheet was pressed by a rubber roll to form a
smooth surface on one side, and by drawing roll (d) having
the surface to form an uneven surface on the other side, the
sheet was cooled and the uneven surface was processed by the
corona discharge at 45 Dyn/cm to obtain the base film for
adhesive tape having the thickness of 0.13 mm.
For the base film thus obtained, a lateral hand cutting
strength and a longi~ in~l tearing strength of the adhesive
tapes were measured, the results of which are shown in Table
3.
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20056 1 7
TABLE 3
- Ml of polyethylene
Shape of drawing roll resin
Uneven
Uneven interval d = 0.96 d = 0.92
Type depth (mm) (mm) g/cm=3 g/cm=3
Examples
3 (a) 0.12 1.2 s s
4 (b) 0.08 1.2 5 5
(a) 0.12 1.2 5 2
6 (b) 0.08 1.2 s 2
7 (c) 0.04 1.2 5 2
Comparative (d) 0.14 0.4 5 5
Example 4
Film Lateral hand cut- Longitudinal tearing
thickness ting strength of strength of film
(mm) film (kg)* (kg)*
Examples
3 0.13 0.19 0.70
4 0.13 0.30 0-97
0.13 0.25 0.92
6 0.13 0.3s 1.22
7 0.13 0.38 1.67
Comparative 0.13 0.18 0.45
example 4
*Measured at 500 mm/min. according to Ermendorf Method.
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20056 1 7
Advantages of the Invention
According to the present invention, as described
heretofore, by forming one side of a polyolefin resin base
film into a smooth surface and the other side into an uneven
surface, and coating an adhesive on the uneven surface to
provide an adhesive layer, an adhesive tape having superb
properties such as unwindability, adhesiveness, trimmed
clearance, printability and transparency can be obtained
without spoiling its lateral hand-cutting characteristics.
An adhesive tape obtained by the present invention can
be broadly used, as an adhesive tape for trimming, for
light-, medium-, and heavy-packaging and for temporary
bonding.
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