U.S. patent application number 14/711362 was filed with the patent office on 2015-08-27 for adhesive film.
This patent application is currently assigned to HITACHI CHEMICAL COMPANY, LTD.. The applicant listed for this patent is HITACHI CHEMICAL COMPANY, LTD.. Invention is credited to KOUHEI HORIUCHI, Junichi Imaizumi, Yasushi Numaguchi, Seiji Sunohara, Michio Uruno.
Application Number | 20150239220 14/711362 |
Document ID | / |
Family ID | 47677710 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150239220 |
Kind Code |
A1 |
HORIUCHI; KOUHEI ; et
al. |
August 27, 2015 |
ADHESIVE FILM
Abstract
The adhesive film includes a film-like adhesive layer, a light
release separator and a heavy release separator that are laminated
on either side of the adhesive layer, and a carrier film further
laminated on the heavy release separator. The outer edges of the
light release separator and the carrier film forming the outer
layer extend outward beyond the outer edge of the adhesive layer
and the heavy release separator forming the inner layer. The outer
edge sections of the adhesive layer are thereby protected. The
outer edge section of the carrier film is gripped and released
first, after which the outer edge section of the light release
separator is gripped and released, and finally the heavy release
separator is released, thereby allowing each separator and the
carrier film to be reliably and easily released in the prescribed
order.
Inventors: |
HORIUCHI; KOUHEI;
(Chikusei-shi, JP) ; Uruno; Michio; (Chikusei-shi,
JP) ; Imaizumi; Junichi; (Chikusei-shi, JP) ;
Sunohara; Seiji; (Chikusei-shi, JP) ; Numaguchi;
Yasushi; (Chikusei-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI CHEMICAL COMPANY, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
HITACHI CHEMICAL COMPANY,
LTD.
|
Family ID: |
47677710 |
Appl. No.: |
14/711362 |
Filed: |
May 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13571792 |
Aug 10, 2012 |
9034449 |
|
|
14711362 |
|
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|
Current U.S.
Class: |
156/249 |
Current CPC
Class: |
C09J 2433/00 20130101;
Y10T 428/2839 20150115; B32B 2307/412 20130101; C09J 2203/318
20130101; B32B 2457/202 20130101; Y10T 428/24777 20150115; C09J
2301/302 20200801; G02F 1/1333 20130101; B32B 37/12 20130101; B32B
37/02 20130101; C09J 7/20 20180101; Y10T 428/1476 20150115; C09J
7/40 20180101; Y10T 428/2848 20150115; Y10T 428/14 20150115 |
International
Class: |
B32B 37/02 20060101
B32B037/02; G02F 1/1333 20060101 G02F001/1333; C09J 7/02 20060101
C09J007/02; B32B 37/12 20060101 B32B037/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 2011 |
JP |
2011-177039 |
Jun 28, 2012 |
JP |
2012-145801 |
Claims
1. A method of making a display, comprising: providing an adhesive
film and two adherends, the adhesive film comprising: an adhesive
layer; first and second base material layers laminated in a manner
sandwiching the adhesive layer; and a carrier layer further
laminated on the second base material layer, the carrier layer
being in direct contact with the second base material layer;
wherein the first base material layer and the carrier layer are at
opposite sides of the adhesive layer; and wherein the outer edges
of the first base material layer and the carrier layer extend
outward beyond the outer edges of the adhesive layer and the second
base material layer; releasing the carrier layer; after releasing
the carrier layer, releasing the first base material layer; after
releasing the first base material layer, attaching the adhesive
layer to one adherend of the two adherends; after attaching the
adhesive layer to the one adherend, releasing the second base
material layer from the adhesive layer; and thereafter, attaching
the adhesive layer to the other adherend of the two adherends, such
that the adhesive layer is disposed between the two adherends.
2. The method according to claim 1, wherein the outer edge of the
second base material layer is essentially flush with the outer edge
of the adhesive layer.
3. The method according to claim 1, wherein the outer edge of the
carrier layer extends outward beyond the outer edge of the first
base material layer.
4. The method according to claim 1, wherein the peel strength
between the first base material layer and the adhesive layer is
lower than the peel strength between the second base material layer
and the adhesive layer.
5. The method according to claim 1, wherein the peel strength
between the second base material layer and the carrier layer is
lower than the peel strength between the second base material layer
and the adhesive layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an adhesive film.
[0003] 2. Related Background Art
[0004] In recent years, touch panels are being incorporated in the
liquid crystal display devices of cellular phones, portable gaming
devices, digital cameras, car navigation systems, handheld
computers, portable data terminals (PDA) and the like. Such liquid
crystal display devices (hereunder also referred to as "touch panel
displays") are constructed in a layered manner, with a protective
panel, touch panel and liquid crystal panel in that order, there
being disposed transparent adhesive films between the protective
panel and touch panel and between the touch panel and liquid
crystal panel (see PTL 1, for example). Because such adhesive films
help increase the brightness and visibility of the display while
also functioning as a shock absorption material, they are
indispensable components of the display structure.
[0005] [PTL 1] Japanese Unexamined Patent Application Publication
No. 2008-83491
SUMMARY OF THE INVENTION
[0006] The adhesive films mentioned above are generally handled in
a three-layer structure form, with both sides of the adhesive layer
sandwiched between releasable base material layers. An adhesive
film of this type is produced by coating a liquid adhesive
composition onto one of the base material layers, irradiating it
with active light rays such as ultraviolet rays if necessary to
induce semi-curing or curing and form an adhesive layer, and then
layering the other base material layer on the adhesive layer. The
adhesive layer is preferably formed beforehand to the size of the
liquid crystal display device in which it is intended to be used.
However, it is difficult to coat adhesive layers to prescribed
sizes. It is therefore effective to use a blade or other tool to
cut out the adhesive layer formed on the base material layer during
the process of producing the adhesive film, so that the adhesive
layer can be obtained in the desired shape. Yet, adhesive films
formed in such a manner are considered to be responsible for
releasability problems of base material layers from the adhesive
layer. An example of the releasability problems is such that the
adhesive layer is pulled toward the first base material layer
during release of the first base material layer from the adhesive
layer, causing it to be peeled from the other base material layer.
This problem can be occur even in case where, the design is such
that, in order to allow release of first one base material layer
and then the other base material layer, the peel strength between
the first base material layer and the adhesive layer is made to be
lower than the peel strength between the other base material layer
and the adhesive layer.
[0007] Being the result of much effort toward finding a solution to
this problem, the invention provides an adhesive film that protects
the adhesive layer while facilitating reliable release of each base
material layer in order, without releasability problems.
[0008] The adhesive film of the invention comprises a film-like
adhesive layer, first and second base material layers laminated in
a manner sandwiching the adhesive layer, and a carrier layer
further laminated on the second base material layer, wherein the
outer edges of the first base material layer and the carrier layer
constituting the outer layer extend outward beyond the outer edges
of the adhesive layer and the second base material layer
constituting the inner layer.
[0009] In this type of adhesive film, the outer edges of the first
base material layer and carrier layer, which constitute the outer
layer, extend outward beyond the outer edges of the adhesive layer
and the second base material layer, which constitute the inner
layer. This reliably protects the outer edges of the adhesive layer
during storage and transport of the adhesive film. When the
adhesive layer is to be attached to an adherend, the outer edge
section of the carrier layer that is extended outward may be
gripped for easy release of the carrier layer. The outer edge
section of the first base material layer may then be gripped for
easy release of the first base material layer. Since the second
base material layer thus remains on one side of the adhesive layer,
protection of the adhesive layer is maintained by the second base
material layer when one side of the adhesive layer is to be
attached to an adherend. The second base material layer may then be
subsequently released and the other side of the adhesive layer
attached to a different adherend so that the adhesive layer is
disposed between the pair of adherends.
[0010] The outer edge of the second base material layer is
preferably flush with the outer edge of the adhesive layer. Since
this will accentuate the difference in releasability between the
first base material layer and the second base material layer, it
will be possible to more easily release the first base material
layer before releasing the second base material layer. Furthermore,
if the outer edge of the second base material layer is aligned with
the outer edge of the adhesive layer, the outer edge of the
adhesive layer will become more distinct, thus facilitating
positioning of the adhesive layer with the adherend.
[0011] The outer edge of the carrier layer preferably extends
outward beyond the outer edge of the first base material layer.
This will further facilitate gripping of the outer edge sections of
the carrier layer, allowing the carrier layer to be more easily
released.
[0012] The peel strength between the first base material layer and
the adhesive layer is also preferably lower than the peel strength
between the second base material layer and the adhesive layer. This
will accentuate the difference in releasability between the first
base material layer and the second base material layer, thus making
it be possible to more easily release the first base material layer
before releasing the second base material layer.
[0013] In addition, the peel strength between the second base
material layer and the carrier layer is preferably lower than the
peel strength between the second base material layer and the
adhesive layer. This will accentuate the difference in
releasability between the carrier layer and the second base
material layer, thus making the carrier layer more easily
releasable.
[0014] The adhesive film of the invention can protect the adhesive
layer while facilitating reliable release of each base material
layer in order, without releasability problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a side view of an embodiment of an adhesive film
according to the invention.
[0016] FIG. 2 is a perspective view of an embodiment of an adhesive
film according to the invention.
[0017] FIG. 3 is a side view of another embodiment of an adhesive
film according to the invention.
[0018] FIG. 4 is a cross-sectional view of a preliminary film.
[0019] FIG. 5 is a cross-sectional diagram illustrating a cutting
step.
[0020] FIG. 6 is a cross-sectional diagram illustrating a removal
step.
[0021] FIG. 7 is a cross-sectional diagram illustrating a removal
step.
[0022] FIG. 8 is a cross-sectional diagram illustrating a removal
step.
[0023] FIG. 9 is a cross-sectional diagram illustrating an
attachment step.
[0024] FIG. 10 is a cross-sectional diagram illustrating a carrier
film releasing step.
[0025] FIG. 11 is a cross-sectional diagram illustrating a light
release separator-releasing step.
[0026] FIG. 12 is a cross-sectional diagram illustrating a step of
attachment for a side of an adhesive layer onto an adherend.
[0027] FIG. 13 is a cross-sectional diagram illustrating a heavy
release separator-releasing step.
[0028] FIG. 14 is a cross-sectional diagram illustrating a step of
attachment for a side of an adhesive layer onto an adherend.
[0029] FIG. 15 is a schematic diagram illustrating a method of
setting a sample on a macrodynamic viscoelasticity meter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] As shown in FIGS. 1 and 2, the adhesive film 1 of the
invention comprises a transparent film-like adhesive layer 2, a
light release separator 3 (first base material layer) and a heavy
release separator 4 (second base material layer) that are laminated
on either side of the adhesive layer 2, and a carrier film 5
(carrier layer) further laminated on the heavy release separator 4.
For assembly of a touch panel display for a portable terminal, for
example, the adhesive film 1 serves to provide an adhesive layer 2
between a protective panel and a touch panel, and between the touch
panel and a liquid crystal panel.
[0031] The adhesive layer 2 is formed, for example, by an adhesive
composition that includes (A) an acrylic acid-based derivative
polymer, (B) an acrylic acid-based derivative and (C) a
polymerization initiator. The (A) acrylic acid-based derivative
polymer may be obtained by polymerizing the (B) acrylic acid-based
derivative, and preferably its weight-average molecular weight is
between 10,000 and 1,000,000 (as measured using a calibration curve
for standard polystyrene obtained by gel permeation
chromatography). The acrylic acid-based derivative polymer may be a
polymer obtained by polymerization in combination with a monomer
other than an acrylic acid-based derivative. The weight-average
molecular weight can be measured using the following apparatus and
measuring conditions.
Apparatus: HCL-8320GPC High-speed GPC (detector: differential
refractometer or UV) (Tosoh Corp.)
Solvent: Tetrahydrofuran (THF)
Column: TSKGEL SuperMultipore HZ-H (Tosoh Corp.)
[0032] Column size: Column length=15 cm, Inner column diameter: 4.6
mm Measuring temperature: 40.degree. C. Flow rate: 0.35 ml/min
Sample concentration: 10 mg/5 mL THF Injection rate: 20 .mu.l
[0033] The (B) acrylic acid-based derivative may be acrylic acid or
methacrylic acid, or any of their derivatives. Specifically, these
include (meth)acrylic acid alkyl having C1-20 alkyl, benzyl
(meth)acrylate, alkoxyalkyl (meth)acrylates, aminoalkyl
(meth)acrylates, (meth)acrylic acid esters of (diethyleneglycol
ethyl ether), (meth)acrylic acid esters of polyalkyleneglycol alkyl
ethers, (meth)acrylic acid esters of polyalkyleneglycol aryl
ethers, (meth)acrylic acid esters with alicyclic groups,
fluorinated alkyl acrylates, (meth)acrylic acid esters with
hydroxyl groups, such as 2-hydroxyethyl methacrylate,
3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate,
2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl
acrylate, glycerol methacrylate and glycerol acrylate, glycidyl
(meth)acrylates, acrylamides, (meth)acryloylmorpholine, and the
like, which have one polymerizable unsaturated bond in the
molecule. Any of these may be used alone or in mixtures of two or
more.
[0034] A monomer with 2 or more polymerizable unsaturated bonds in
the molecule may also be used together with the aforementioned
monomers that have one polymerizable unsaturated bond in the
molecule. Such monomers include bisphenol A di(meth)acrylate,
1,4-butanediol di(meth)acrylate, 1,3-butyleneglycol
di(meth)acrylate, diethyleneglycol di(meth)acrylate, glycerol
di(meth)acrylate, neopentyl glycol di(meth)acrylate,
polyethyleneglycol di(meth)acrylate, polypropyleneglycol
di(meth)acrylate, tetraethyleneglycol dimethacrylate,
trimethylolpropane trimethacrylate, pentaerythritol
tri(meth)acrylate, tris((meth)acryloxyethyl)isocyanurate,
pentaerythritol tetra(meth)acrylate, dipentaerythritol
tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
dipentaerythritol penta(meth)acrylate, and di(meth)acrylates with
urethane bonds. These monomers may also be used alone or in
combinations of two or more. From the viewpoint of shapeability of
the adhesive layer 2, it is preferred to use a monomer with 2 or
more polymerizable unsaturated bonds in the molecule in component
(B).
[0035] The term "(meth)acrylate" refers to the "acrylate" and its
corresponding "methacrylate". Similarly, the term "(meth)acrylic"
refers to the "acrylic" and its corresponding "methacrylic"
compound, and "(meth)acryloyl" refers to the "acryloyl" and its
corresponding "methacryloyl" compound.
[0036] The (C) polymerization initiator may employ a
photopolymerization initiator, which may be selected from among
known materials such as ketone-based, acetophenone-based,
benzophenone-based, anthraquinone-based, benzoin-based,
acylphosphine oxide-based, sulfonium salt, diazonium salt and onium
salt compounds. Particularly preferred are ketone-based compounds
such as 1-hydroxycyclohexylphenyl ketone, and acylphosphine
oxide-based compounds such as
bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide,
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide and
2,4,6-trimethylbenzoyl-diphenylphosphine oxide, from the viewpoint
of transparency and curing properties.
[0037] The content of component (A) is preferably 15-80 wt %, more
preferably 15-60 wt % and even more preferably 15-50 wt % with
respect to the total weight of the adhesive composition. The
content of component (B) is preferably 15-80 wt %, more preferably
30-80 wt % and even more preferably 40-80 wt % with respect to the
total weight of the adhesive composition. If the contents of
component (A) and component (B) are within these ranges, the
viscosity of the adhesive composition will be within the proper
viscosity range for formation of the adhesive layer, and the
moldability will be satisfactory. The adhesion and transparency of
the adhesive layer 2 will also be improved. The content of
component (C) is preferably 0.05-5 wt %, more preferably 0.1-3 wt %
and even more preferably 0.1-0.5 wt % with respect to the total
weight of the adhesive composition. By limiting the content of
component (C) to no greater than 5 wt % it is possible to increase
the light transmittance of the adhesive composition and avoid its
yellowing, to obtain a superior adhesive layer 2.
[0038] The adhesive layer 2 is obtained by, for example, coating a
liquid adhesive composition comprising components (A) to (C) on a
heavy release separator 4 to a desired film thickness, irradiating
it with an active energy beam for curing, and then shaping it by
cutting to the desired size. From the viewpoint of adhesion, the
adhesive layer 2 is preferably composed mainly of a structural unit
derived from a (meth)acrylic acid alkyl having C4-18 alkyl. Here,
"composed mainly of" refers to the most abundant component
constituting the adhesive layer 2. The coated adhesive composition
may be irradiated with active light rays such as ultraviolet rays.
The thickness of the adhesive layer 2 is preferably between 0.1 mm
and 1 mm, and more preferably between 0.15 mm (150 .mu.m) and 0.5
mm (500 .mu.m). With this range of thickness, the adhesive layer 2
will be able to exhibit an even more superior effect when applied
in a display.
[0039] The storage elastic modulus of the adhesive layer 2 at
25.degree. C. is preferably between 1.0.times.10.sup.3 Pa and
1.0.times.10.sup.6 Pa, and more preferably between
1.0.times.10.sup.4 Pa and 5.0.times.10.sup.5 Pa.
[0040] The storage elastic modulus may be measured as follows.
First, two adhesive layers 2 with thicknesses of 250 .mu.m are
stacked for a thickness of approximately 500 .mu.m, and the stack
is cut into a 10 mm square to form a sample S. Two samples S are
prepared and set on a macrodynamic viscoelasticity meter by means
of a jig 100. As shown in FIG. 15, the jig 100 comprises a pair of
mounting jigs 100A, 100B that are mounted on the macrodynamic
viscoelasticity meter so as to face each other. The mounting jig
100A is provided with a plate P1 that extends toward the mounting
jig 100B. The mounting jig 100B is provided with a pair of plates
P2, P2 each facing a side of the plate P1, and extending toward the
mounting jig 100A. Each plate P2 is attached to the plate P1
through a sample S. The mounting jigs 100A, 100B are thus moved
away from each other by the macrodynamic viscoelasticity meter, and
the storage elastic modulus is measured. The macrodynamic
viscoelasticity meter used was a Solids Analyzer RSA-II by
Rheometric Scientific, and the measuring conditions were shear
sandwich mode, 1.0 Hz frequency, with temperature increase at
5.degree. C./min in a measuring temperature range of -20.degree. C.
to 100.degree. C.
[0041] The peel strength of the adhesive layer 2 for a glass plate
is preferably between 5 N/10 mm and 20 N/10 mm, and more preferably
between 7 N/10 mm and 15 N/10 mm. The thickness of the adhesive
layer 2 is preferably between 100 .mu.m and 500 .mu.m and more
preferably between 150 .mu.m and 400 .mu.m. The planar shape of the
adhesive layer 2 may be appropriately designed depending on the
adherend to which it will be applied, and for example, the effect
of the invention will be prominently exhibited with a rectangular
shape having long sides between 50 mm and 500 mm and short sides
between 30 mm and 400 mm, and even more prominently exhibited with
a rectangular shape having long sides between 100 mm and 300 mm and
short sides between 80 mm and 280 mm. The light transmittance of
the adhesive layer 2 is preferably at least 80%, more preferably at
least 90% and most preferably at least 95% with respect to light
rays in the visible light range (wavelength: 380-780 nm). The light
transmittance may be measured using a spectrophotometer. As an
example, the spectrophotometer may be a Hitachi Model U-3310
spectrophotometer (with integrating sphere). The light
transmittance of the adhesive layer 2 can be calculated by using a
spectrophotometer to measure the light transmittance of an adhesive
layer-attached glass plate, comprising a 500 .mu.m-thick glass
plate and the adhesive layer 2 adjusted to a thickness of 175
.mu.m, and subtracting the light transmittance of the glass plate
from the light transmittance of the adhesive layer-attached glass
plate.
[0042] The light release separator 3 may be a polymer film such as
polyethylene terephthalate, polypropylene, polyethylene or
polyester, and is preferably a polyethylene terephthalate film (PET
film). The thickness of the light release separator 3 is preferably
between 25 .mu.m and 125 .mu.m, more preferably between 30 .mu.m
and 100 .mu.m and most preferably between 40 .mu.m and 75
.mu.m.
[0043] The heavy release separator 4 may also be a polymer film
such as polyethylene terephthalate, polypropylene, polyethylene or
polyester, and is preferably a polyethylene terephthalate film (PET
film). The thickness of the heavy release separator 4 is preferably
between 50 .mu.m and 150 .mu.m, more preferably between 60 .mu.m
and 125 .mu.m and most preferably between 70 .mu.m and 100
.mu.m.
[0044] The carrier film 5 may likewise be a polymer film such as
polyethylene terephthalate, polypropylene, polyethylene or
polyester, and is preferably a polyethylene terephthalate film (PET
film). The thickness of the carrier film 5 is preferably between 15
.mu.m and 100 .mu.m, more preferably between 20 .mu.m and 80 .mu.m
and most preferably between 20 .mu.m and 50 .mu.m.
[0045] The outer edge 4a of the heavy release separator 4 is
essentially flush with the outer edge 2a of the adhesive layer 2.
The outer edges 3a, 5a of the light release separator 3 and the
carrier film 5 extend outward beyond the outer edge 2a of the
adhesive layer 2. The outer edge 5a preferably extends outward even
beyond the outer edge 3a.
[0046] The amount by which the outer edge 3a extends outward beyond
the outer edge 2a is preferably between 2 mm and 15 mm and more
preferably between 4 mm and 10 mm. The amount by which the outer
edge 5a extends outward beyond the outer edge 2a is preferably
between 3 mm and 25 mm and more preferably between 5 mm and 20 mm.
Preferably, the inequality Q>P is satisfied, where P is the
amount by which the outer edge 3a extends outward beyond the outer
edge 2a, and Q is the amount by which the outer edge 5a extends
outward beyond the outer edge 3a.
[0047] The peel strength between the light release separator 3 and
the adhesive layer 2 is preferably lower than the peel strength
between the heavy release separator 4 and the adhesive layer 2. The
peel strength between the carrier film 5 and the heavy release
separator 4 is lower than the peel strength between the heavy
release separator 4 and the adhesive layer 2. The peel strength
between the carrier film 5 and the heavy release separator 4 is
even more preferably lower than the peel strength between the light
release separator 3 and the adhesive layer 2, but the effect of the
invention will not be impaired if it is higher.
[0048] The peel strength between the light release separator 3 and
the adhesive layer 2 is preferably 0.01 N/25 mm to 0.4 N/25 mm, the
peel strength between the heavy release separator 4 and the
adhesive layer 2 is preferably 0.3 N/25 mm to 1.5 N/25 mm, and the
peel strength between the carrier film 5 and the heavy release
separator 4 is preferably 0.005 N/25 mm to 0.3 N/25 mm. Also, the
inequalities T>S and T>U are preferably satisfied, where S is
the peel strength between the light release separator 3 and the
adhesive layer 2, T is the peel strength between the heavy release
separator 4 and the adhesive layer 2, and U is the peel strength
between the carrier film 5 and the heavy release separator 4. The
relationship between S and U may be either S>U or U>S, but
S>U is especially preferred.
[0049] The peel strength was measured using a TENSILON RTG-1210
Universal Tester by A&D. The measuring conditions were with 90
degree peeling for the peel strength between the light release
separator 3 and the adhesive layer 2, the peel strength between the
heavy release separator 4 and the adhesive layer 2 and the peel
strength between the carrier film 5 and the heavy release separator
4. The peel strength between the glass plate and the adhesive layer
2 was measured with 180 degree peeling.
[0050] Since the outer edges 3a, 5a of the light release separator
3 and the carrier film 5 forming the outer layer thus extend
outward beyond the outer edges 2a, 4a of the adhesive layer 2 and
the heavy release separator 4 forming the inner layer, the outer
edge sections of the adhesive layer 2 are reliably protected during
storage and transport of the adhesive film 1.
[0051] The peel strength between the separators 3,4 and the
adhesive layer 2 may be adjusted by surface treatment of the
separators 3,4, for example. Surface treatment of the separators
3,4 can be accomplished by release treatment with a silicone-based
compound or fluorine-based compound. Also, the peel strength
between the carrier film 5 and the heavy release separator 4 may be
adjusted by the type and thickness of glue formed between the
carrier film 5 and the heavy release separator 4. The type of the
glue formed between the carrier film 5 and the heavy release
separator 4 may be an acrylic adhesive, for example. The thickness
of the glue formed between the carrier film 5 and the heavy release
separator 4 is preferably 0.1 to 10 .mu.m and more preferably 1 to
5 .mu.m.
[0052] When the glue is formed over the entire region of the
surface 5b on the adhesive layer 2 side of the carrier film 5, the
glue will be exposed at an outer side of the outer edge 4a of the
heavy release separator 4. In this case, it is preferred to provide
a film 4A covering the surface 5b at the outer side of the outer
edge 4a of the heavy release separator 4, as shown in FIG. 3. The
film 4A may be made of the same material as the heavy release
separator 4, for example. Providing a film 4A will cover the glue
over the entire region of the surface 5b, thus effectively
preventing the exposed glue from becoming attached to other
sections, or foreign matter from becoming attached to the exposed
glue, so that the usability of the adhesive film 1 can be
improved.
[0053] The adhesive film 1 described above may be produced in the
following manner. First, a preliminary film 10 is prepared
comprising the heavy release separator 4, the adhesive layer 2 and
a temporary separator 6 laminated on the carrier film 5, as shown
in FIG. 4. The temporary separator 6 is a layer made of the same
material as the light release separator 3, for example.
[0054] Next, a die cutter (not shown) equipped with a blade B is
used to cut the temporary separator 6, the adhesive layer 2 and the
heavy release separator 4 into the desired shape. The die cutter
may be a crank-type die cutter or a rotary-type die cutter. In this
step, the blade B is passed through the temporary separator 6, the
adhesive layer 2 and the heavy release separator 4 to a depth
reaching the carrier film 5, as shown in FIG. 5. This forms a notch
5c on the surface 5b on the adhesive layer 2 side of the carrier
film 5. Since the blade B reaches from the temporary separator 6 to
the carrier film 5, it is possible to completely cut the adhesive
layer 2 and heavy release separator 4. When it is possible to cut
the heavy release separator 4 without forming a notch 5c, formation
of the notch 5c may be omitted.
[0055] Next, the outer sections of the temporary separator 6,
adhesive layer 2 and heavy release separator 4 are removed, as
shown in FIG. 6. As this is done, the film 4A may be formed by
removing only the outer sections of the temporary separator 6 and
adhesive layer 2, without removing the outer section of the heavy
release separator 4 so that it is left on the carrier film 5, as
shown in FIG. 7. Next, the temporary separator 6 is released from
the adhesive layer 2, as shown in FIG. 8, and the light release
separator 3 is attached to the adhesive layer 2, as shown in FIG.
9. This step completes the adhesive film 1.
[0056] The adhesive film 1 may be used in the following manner for
assembly of a display. First, the carrier film 5 is released from
the heavy release separator 4, as shown in FIG. 10. The outer edge
5a of the carrier film 5 extends outward beyond the outer edges 2a,
4a of the adhesive layer 2 and the heavy release separator 4, as
described above. Thus, the outer edge section of the carrier film 5
that is extended outward may be gripped for easy release of the
carrier film 5. The outer edge 5a of the carrier film 5 preferably
extends outward beyond the outer edge 3a of the light release
separator 3. This will further facilitate gripping of the outer
edge sections of the carrier film 5, allowing the carrier film 5 to
be more easily released. The peel strength between the carrier film
5 and the heavy release separator 4 is lower than the peel strength
between the heavy release separator 4 and the adhesive layer 2.
This will accentuate the difference in releasability between the
carrier film 5 and the heavy release separator 4, thus making the
carrier film 5 more releasable from the heavy release separator
4.
[0057] Next, as shown in FIG. 11, the light release separator 3 is
released from the adhesive layer 2 to expose the adhesive side 2b
of the adhesive layer 2. As mentioned above, the peel strength
between the light release separator 3 and the adhesive layer 2 is
lower than the peel strength between the heavy release separator 4
and the adhesive layer 2. In a conventional adhesive film, release
often cannot be accomplished as designed even when the peel
strengths are different. However, since the outer edge 3a of the
light release separator 3 extends outward beyond the outer edges
2a, 4a of the adhesive layer 2 and the heavy release separator 4,
the outer edge 3a of the light release separator 3 becomes the
outwardmost extended edge after the carrier film 5 has been
released. This will render the outer edge 3a of the light release
separator 3 more easy to grip than the outer edge 4a of the heavy
release separator 4, so that the light release separator 3 will be
easier to release than the heavy release separator 4. Therefore,
gripping the outer edge section of the light release separator 3
allows the light release separator 3 to be easily released before
release of the heavy release separator 4.
[0058] In the adhesive film 1, the outer edge 4a of the heavy
release separator 4 is essentially flush with the outer edge 2a of
the adhesive layer 2. With this construction, the difference in
releasability between the light release separator 3 and the heavy
release separator 4 will become even more prominent. Therefore, the
light release separator 3 can be easily released before release of
the heavy release separator 4.
[0059] In addition, since the heavy release separator 4 is
protected by the carrier film 5 up to the immediately previous
step, damage to the surface of the heavy release separator 4 is
minimized. This renders damage to the adhesive layer 2 highly
visible, so that any damage in the adhesive layer 2 can be easily
eliminated before attachment to an adherend.
[0060] Next, as shown in FIG. 12, the adhesive side 2b of the
adhesive layer 2 is attached to the adherend A1 and pressed with a
roller R, for example. The adherend A1 may be, for example, a
liquid crystal panel, a protective panel (glass plate, acrylic
resin board, polycarbonate board or the like), or a touch panel.
Since the heavy release separator 4 remains on the adhesive side 2c
of the adhesive layer 2, protection of the adhesive layer 2 is
maintained by the heavy release separator 4 when the adhesive side
2b of the adhesive layer 2 is attached to an adherend A1. In
addition, since the outer edge 4a of the heavy release separator 4
and the outer edge 2a of the adhesive layer 2 are aligned, the
position of the outer edge 2a of the adhesive layer 2 becomes more
definite and positioning between the adhesive layer 2 and adherend
A1 is facilitated.
[0061] Next, as shown in FIG. 13, the heavy release separator 4 is
released from the adhesive layer 2 to expose the adhesive side 2c
of the adhesive layer 2. Then, as shown in FIG. 14, the adhesive
side 2c of the adhesive layer 2 is attached to the adherend A2 and
heated and pressed. The adherend A2 may be, for example, a liquid
crystal panel, a protective panel or a touch panel. In the steps
described above, the adhesive layer 2 is disposed between the
adherend A1 and the adherend A2.
[0062] Thus, the adhesive film 1 can protect the adhesive layer 2
while facilitating reliable release of each separator 3,4 and the
carrier film 5 in the prescribed order, without releasability
problems.
[0063] The embodiments described above are preferred embodiments of
the invention, but the invention is not necessarily limited thereto
and may incorporate various modifications within the scope of the
gist thereof.
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