JP5420138B2 - Method for inspecting adhesive film, and method for producing adhesive film using the same - Google Patents

Description

The present invention relates to a method for inspecting an adhesive film excellent in removability that can be adhered to various adherends, and a method for producing an adhesive film using the same. More specifically, a pressure-sensitive adhesive for producing a pressure-sensitive adhesive film provided with a pressure-sensitive adhesive layer that can be applied for the production of flexible printed wiring boards (hereinafter referred to as “FPC” where appropriate) used in electronic and electrical equipment, etc. inspection method of the film, and related to the production method of the adhesive film using the same. More specifically, even if other components such as a reinforcing plate are bonded to the release surface while suppressing the migration of trace components derived from the pressure-sensitive adhesive to the peeled FPC surface, the reinforcing plate, etc. may float or peel off. The present invention relates to a method for inspecting an adhesive film and a method for producing an adhesive film using the same .

Conventionally, as a so-called re-peelable adhesive film that adheres to and peels off various articles, a masking film that covers unnecessary parts while leaving a required part, a protective film that protects articles from external factors, and an article A carrier film or the like that is conveyed is known. Specifically, for example, the FPC is manufactured by being subjected to processing such as etching, punching, punching, and the like while being fixed on the protective film via an adhesive layer. In recent years, for example, a case in which a FPC is reinforced by adhering a reinforcing plate made of a polyimide film to a polyimide surface from which a protective film is peeled off after the manufacturing process has been increasing. However, in this case, the adhesive strength of the reinforcing plate to the FPC is reduced by attaching the protective film, and as a result, there are cases where problems such as floating and peeling of the reinforcing plate occur in the subsequent process.
One of the causes of the decrease in the adhesive strength of the reinforcing plate is due to the pressure-sensitive adhesive that has moved to the release surface (hereinafter, this component is also referred to as “glue residue”). The development of a pressure-sensitive adhesive that solves this problem has been strongly desired.

In order to solve these problems, for example, it contains a copolymer composition of (meth) acrylic acid alkyl ester, (meth) acrylic acid alkyl ester having a hydroxy group, an isocyanate curing agent and a melamine curing agent. Patent Document 1 describes that the adhesive residue on the release surface of the polyimide film was not found by microscopic observation at a magnification of 100 times. However, even if this pressure-sensitive adhesive is used, the reinforcing plate may float or peel off from the peeled surface.
In addition, the adhesive layer containing the acrylic adhesive polymer, the thermally expandable microsphere, the tackifier, and the epoxy crosslinking agent was attached to SUS304, and then the adhesive residue on the peeled surface was visually observed. It has been described in Patent Document 2 that there was no such thing. However, after actually attaching the protective film using this adhesive layer to the polyimide film, if the reinforcing plate is bonded to the peeled surface from which the protective film has been peeled off, the adhesive strength to the reinforcing plate is reduced, and the reinforcing plate floats.・ Peeling may occur.
JP 2005-75884 A JP 2003-160765 A

  Conventionally, the adhesive residue which the adhesive itself transfers to the polyimide film after peeling off the protective film has been recognized. The adhesive residue analysis of the pressure-sensitive adhesive is confirmed visually or with an optical microscope, or in recent years by a method using XPS or the like. However, in these methods, for example, a very small amount of a component derived from a pressure-sensitive adhesive (hereinafter, this component is also referred to as a “trace component”) such as a low-molecular-weight component generated by decomposition of a part of the polymer that is the base of the pressure-sensitive adhesive .) Could not be fully confirmed, and the presence or absence of trace components that could cause problems in the adhesion of the reinforcing plate could not be determined. As a result, a pressure-sensitive adhesive that can sufficiently maintain the adhesive strength of the reinforcing plate to the peeled surface cannot be accurately evaluated, and it has been difficult to develop such a pressure-sensitive adhesive.

When the present invention is attached to an adherend and peeled off from the adherend, it does not cause migration of trace components to the adherend and floats due to a decrease in adhesive strength when a reinforcing plate is bonded to the peeled surface. -It aims at providing the inspection method of the adhesive film which does not peel, and the manufacturing method of an adhesive film using the same.

  If the adherend has migration of trace components derived from the pressure-sensitive adhesive, the wetting tension on the surface of the adherend is lowered. And in adhesion | attachment by an adhesive, in order to enlarge the wet surface area of the to-be-adhered body by an adhesive and to obtain high adhesive force, the adhesive which has a surface tension lower than the wetting tension of an to-be-adhered body is needed. That is, the wetting tension of the adherend is related to the adhesive strength of the pressure-sensitive adhesive. Based on such knowledge, the inventor of the present invention analyzes the presence or absence of a trace component derived from the pressure sensitive adhesive by the TOF-SIMS method on the surface of the adherend from which the pressure sensitive adhesive layer has been peeled off. As a result of examining the correlation between the pressure-sensitive adhesive and the adhesive layer, the pressure-sensitive adhesive layer was peeled off from the pressure-sensitive adhesive layer in the TOF-SIMS analysis, if the wetting tension of the peeled surface was a specific value or more. The present inventors have found a relationship that when other members such as a reinforcing plate are bonded to the surface, the bonding strength does not decrease and the float / peel does not occur. In addition, the combination of the polymer used as the base of the pressure-sensitive adhesive and the cross-linking agent has also been intensively studied. It was found that when other members such as a plate were bonded, the bonding strength did not decrease, and floating and peeling were less likely to occur. That is, the inventor of the present invention has completed the present invention based on these findings.

That is, in the present invention, an adhesive layer made of an adhesive obtained by crosslinking an acrylic copolymer obtained by copolymerizing an alkyl (meth) acrylate and a vinyl monomer having a carboxyl group with an epoxy crosslinking agent is laminated on a substrate. A method for inspecting an adhesive film, wherein after the adhesive layer of the adhesive film is bonded to a polyimide film surface, the wetting tension of the polyimide film surface from which the adhesive layer has been peeled is measured by the following wetting tension evaluation method When the wetting tension is 40 dyne / cm or more, it is more preferably 60 dyne / cm or more, and the acrylic copolymer further includes polymerized units of 2-ethylhexyl acrylate, butyl acrylate and acrylic acid. It is the inspection method of the adhesive film characterized by determining with pass in case.
Moreover, this invention is a manufacturing method of the adhesive film which has an inspection process including the inspection method of the said adhesive film .
The “wetting tension evaluation method” is a method in which a pressure-sensitive adhesive layer of a pressure-sensitive adhesive film is bonded to a polyimide film, press-treated at 180 ° C. and 40 kg / cm ² for 30 minutes, and then the pressure-sensitive adhesive layer is peeled off. 1 ml each of the wetting tension test solution having a larger surface tension is dropped with a dropper from a height of 3 cm onto the surface of the test piece that is horizontally positioned according to JIS K 6768. When the test piece is immediately tilted by 90 degrees and the dropping surface is set in the vertical direction, the surface tension (dyne) of the wetting tension test liquid having the maximum surface tension when the droplet flows while wetting the test piece surface without being repelled. / Cm) is the wetting tension of the test piece.

In the present invention, a pressure-sensitive adhesive obtained by crosslinking an acrylic copolymer obtained by copolymerizing an alkyl (meth) acrylate and a vinyl monomer having a carboxyl group with an epoxy-based crosslinking agent, and a polyimide film from which the pressure-sensitive adhesive layer has been peeled off The surface has a wetting tension of 40 dyne / cm or more. The second configuration “wetting tension is 40 dyne / cm or more” is a desirable value that the adherend has in order for an ordinary adhesive to function effectively, and the adhesive of the adhesive film and the adhesive film are Practical adhesive strength can be obtained regardless of the combination with the pressure-sensitive adhesive of other members that are pasted after being peeled. On the other hand, if the wetting tension of the adherend is less than 40 dyne / cm, depending on the combination of the pressure-sensitive adhesive of the pressure-sensitive adhesive film and the pressure-sensitive adhesive of other members to be pasted after the pressure-sensitive adhesive film is peeled off, adhesion may be insufficient. is there.
The invention of the present application is that the wetting tension of the polyimide film surface is 60 dyne / cm or more, regardless of the combination of the adhesive of the adhesive film and the adhesive of other members applied after the adhesive film is peeled off Adhesion of these members is sufficient.
In the present invention, the upper limit of the wetting tension of the polyimide film surface is the wetting tension of the blank (original) polyimide. Since wetting tension test liquids with a wetting tension of 67 dyne / cm or more cannot be obtained, if wetting liquid for wetting tension test is tested as water, droplets will repel and flow on the surface of the test piece. The wetting tension of polyimide is less than 73 dyne / cm.

The method for inspecting an adhesive film of the present invention can easily inspect contamination due to a trace amount component derived from an adhesive on the surface of the adherend from which the adhesive film has been peeled off by a simple operation. And by incorporating such a method for inspecting an adhesive film into the production process of an adhesive film, if the adhesive film is an adhesive film that adheres another film to the adhesive film peeling surface of the adherend with another adhesive layer, An excellent pressure-sensitive adhesive film that does not cause lifting or peeling due to a decrease in force can be efficiently produced.
When the pressure-sensitive adhesive film of the present invention is peeled from the adherend, the transfer from the pressure-sensitive adhesive is suppressed on the surface of the adherend from which the pressure-sensitive adhesive film has been peeled off. Therefore, when the adherend is not contaminated by trace components, and other members are bonded to the adhesive film peeling surface of the adherend with other adhesives, floating / peeling due to a decrease in adhesive strength may occur. Absent.
In particular, when the adhesive film is a protective film that adheres to a surface on which an FPC conductive circuit having a polyimide resin layer as an insulating layer is not formed, an FPC manufacturing process using a resin layer conductor foil laminate with a protective film attached thereto Thus, it is possible to effectively protect the polyimide resin layer surface from various chemicals during the transport and processing of the resin layer conductor foil laminate with the protective film attached, and to peel off after the completion of the process to firmly bond the reinforcing plate.

The polymer for pressure-sensitive adhesives in the present invention is an acrylic copolymer that is self-adhesive. This acrylic copolymer can be obtained by copolymerizing an alkyl (meth) acrylate and a vinyl monomer containing a carboxyl group or the like. Moreover, the other monomer copolymerizable with these monomers can be used together.
As said alkyl (meth) acrylate, the C3-C14 thing of an alkyl group is preferable. When the carbon number of the alkyl group is outside this range, the properties as a pressure-sensitive adhesive are impaired, and the alkyl group having 4 to 9 carbon atoms is more preferable. As such, for example, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclobutyl (meth) acrylate, Examples thereof include n-octyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. Of these, butyl acrylate and 2-ethylhexyl acrylate are particularly preferably used.
In the acrylic copolymer, the other monomer copolymerizable with the alkyl (meth) acrylate is not particularly limited, and examples thereof include (meth) acrylonitrile, (meth) acrylamide, styrene, vinyl acetate and the like.

The vinyl monomer having a carboxyl group capable of reacting with an epoxy-based cross-linking agent is not only involved as a cross-linking point, but also improves the adhesive force by increasing the polarity of the surface, adjusting the glass transition point of the polymer, etc. Can also be involved.
Examples of the vinyl monomer having such a carboxyl group include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid and the like. Of these, acrylic acid is particularly preferred.
In the acrylic copolymer, the blending amount of the vinyl monomer having a carboxyl group is preferably 0.5 to 10% by weight. If it is less than this range, the degree of cross-linking of the pressure-sensitive adhesive will not increase, and sufficient cohesive force will not be obtained. More preferably, it is 1 to 5% by weight.

The weight average molecular weight (Mw) by GPC (gel permeation chromatography) of the acrylic copolymer is preferably in the range of 102 to 2,000,000. If the weight average molecular weight is smaller than this range, the necessary cohesive force cannot be obtained unless the functional group amount is increased. If the functional group amount is increased, the curing reaction takes time, resulting in a decrease in productivity. If this range is exceeded, the viscosity will increase and the productivity in the coating process will deteriorate. More preferably, it is 300 to 1,500,000.
The glass transition temperature of the acrylic copolymer is desirably −85 to 20 ° C., and more desirably 0 ° C. or less. When the glass transition temperature is higher than the temperature of the use environment, the adhesive strength with the adherend is reduced.
The method for producing the acrylic copolymer is not particularly limited, and examples thereof include known polymerization methods such as emulsion polymerization, solution polymerization, bulk polymerization, and suspension polymerization. The polymerization initiation method is not particularly limited, and examples thereof include a method using a thermal polymerization initiator such as benzoyl peroxide and azobisisobutylnitrile, and a photopolymerization initiator. A chain transfer agent may be added to adjust the molecular weight. As the chain transfer agent, one having a high chain transfer property such as a thiol compound or a halogen compound can be used.

  Among the crosslinking agents used in the present invention, as an epoxy crosslinking agent capable of reacting with a carboxyl group of an acrylic copolymer, for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, Glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, N, N, N ′, N′— Examples thereof include epoxy compounds such as tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N, N-diglycidylaminophenyl glycidyl ether, N, N-diglycidyl toluidine, N, N-diglycidyl aniline.

  In the pressure-sensitive adhesive, various additives that are usually used as desired, for example, a tackifier, an antioxidant, an ultraviolet absorber, a softener, a filler, a crosslinking accelerator, as long as the object of the present invention is not impaired. Etc. can be added as appropriate, but from the viewpoint of component transfer, it is desirable not to add additives as much as possible.

In the pressure-sensitive adhesive film of the present invention, a known method can be adopted as a method of providing a pressure-sensitive adhesive layer on a substrate. Specifically, a pressure-sensitive adhesive is applied to a release film, release paper, etc., dried, then a method for creating a laminated adhesive film on a substrate, a pressure-sensitive adhesive is applied to a substrate, dried, and then stuck to a release film. Examples include a method for producing a film. Specific coating means may be appropriately selected from known methods such as gravure coating, Mayer bar coating, air knife coating, doctor knife coating, reverse coating, and comma doctor coating.
Dissolve or disperse acrylic copolymer and epoxy-based crosslinking agent in an appropriate solvent, and apply and dry a coating solution with a solid content adjusted so that the adhesive layer forming coating solution has an appropriate viscosity. The pressure-sensitive adhesive layer is preferably provided at about 0.1 to 30 μm. If the pressure-sensitive adhesive layer is thicker than this range, for example, in a processing step such as FPC, the pressure-sensitive adhesive layer tends to cause cohesive failure at the time of peeling after heat treatment, and good peelability cannot be obtained. As a result, sufficient adhesion to the adherend cannot be obtained.

Examples of the substrate used for the adhesive film of the present invention include polyester films such as polybutylene terephthalate and polyethylene terephthalate, polyamide films such as nylon 6 and nylon 66, polyphenylene sulfide films, polyether ether ketone films, polyimide films, and polyolefin films. , Polyethylene naphthalate film, fluororesin film and the like. These films are preferably excellent in strength when stretched uniaxially or biaxially. In the case of stretching, it is preferable to heat-set by annealing or the like because shrinkage during heating is unlikely to occur and the laminate formed on the adherend is unlikely to curl. These films may be used alone, or two or more kinds of laminate films may be used. However, it is preferable to use a single film from the viewpoint of suppressing curling during heating. Of these base materials, a polyethylene terephthalate film is preferably used from the viewpoints of excellent mechanical properties, heat resistance, chemical resistance, etc., easy availability, and excellent economic efficiency. From the viewpoint of dimensional stability during heating, a biaxially stretched film is preferred. From the viewpoint of improving the lamination strength (adhesive strength) of the pressure-sensitive adhesive layer, a known method such as corona discharge treatment or plasma treatment is used. A surface-treated product is more preferable.
The thickness of the base material is the strength required depending on the type of film used as the base material (in this specification, the sheet and the film are not distinguished by thickness, and both are referred to as a film) and the application of the adhesive film. For example, when a polyethylene terephthalate film is used as a protective film for FPC processing, it is preferably about 12 to 125 μm.

  When a release film is further provided on the pressure-sensitive adhesive layer, examples of the release film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefin films such as polypropylene and polyethylene, and aminoalkyd resins. And those coated with a release agent such as silicone resin. When the pressure-sensitive adhesive film of the present invention is used as a protective film for FPC, it is desirable that this release agent does not use a silicone resin. This is because when a silicone resin is used, a part of the silicone resin moves to the surface of the pressure-sensitive adhesive in contact with the release film surface, which may further migrate to the polyimide surface. Although the thickness of these peeling films is not specifically limited, Usually, it is about 12-150 micrometers.

  The adhesive strength of the adhesive is not particularly limited, but the measurement method is in accordance with the test method described in JIS Z 0237. The adhesive strength with respect to the adherend surface is preferably about 0.03 to 2 N / inch under the conditions of a peeling angle of 180 ° peel and a peeling speed of 300 mm / min. When the adhesive strength is less than 0.03 N / inch, for example, the protective film may be peeled off or floated during work in the FPC manufacturing process. Moreover, when it exceeds 2 N / inch, it may be difficult to peel off the protective film, or a trace component derived from the adhesive may remain on the surface of the polyimide from which the protective film has been peeled off.

Here, when a polyimide reinforcing plate for reinforcing FPC is adhered to the polyimide surface of the FPC after the protective film has been peeled off, if the trace component derived from the adhesive migrates to the polyimide surface and becomes contaminated, adhesion Strength decreases. At this time, the wetting tension of the polyimide surface has decreased, and as a result, it is difficult to sufficiently cover the adhesive so that the adhesive wets the polyimide surface, and the adhesive strength is considered to decrease. In order to reinforce partially, various materials are used depending on the application. Usually, a polyimide film or a polyester film is often used for a thinned FPC. The thickness of the reinforcing plate is generally 25 μm or more for polyimide and 25 to 240 μm for polyester.

  The TOF-SIMS (time-of-flight secondary ion mass spectrometer) analysis method used to complete the present invention is suitable for the identification and structural analysis of organic contaminants adhering to the sample surface, and there are defects on the surface. Although it is a method that can be preferably used for local (about several μm) analysis in a clear area, it is not suitable as a method for detecting whether or not a surface defect exists. That is, it is not suitable for determining whether or not the adhesive strength is reduced when the surface is bonded to the reinforcing plate. Then, the protective film using various adhesives was prepared, the polyimide surface state after peeling the protective film which adhered the protective film, and the polyimide surface state of the blank were confirmed by TOF-SIMS analysis. For those in which the two are almost the same or different, a reinforcing plate is bonded to the polyimide surface from which the protective film has been peeled off, whether the reinforcing plate is lifted or peeled off, and the wetting of the peeled surface. The characteristics were evaluated by “wetting tension evaluation method” according to JIS K 6768 “plastic-film and sheet-wetting tension test method”, and the correlation was examined. As a result, a specific polymer is selected as the base of the pressure-sensitive adhesive and a crosslinking agent. If the wetting tension is a specific value or more, the polyimide surface state after peeling the protective film and the blank polyimide It was found that the surface state corresponds to a substantially equivalent state by TOF-SIMS analysis, and no problem occurs with the adhesion of the reinforcing plate.

According to JIS K 6768, a test solution with a higher surface tension is sequentially dropped onto the test surface, and the droplet is immediately spread to 6 cm ² or more using a wire bar or cotton swab and wetted for 2 seconds. Select a test solution that can be used. Of the test liquids selected in this way, the surface tension of the liquid with the largest surface tension is defined as the wetting tension of the polyimide surface. On the other hand, the wetting tension evaluation method in the present invention spreads a droplet by naturally hanging a test piece vertically without using a wire bar or a cotton swab. Compared to the JIS method, this method has no risk of affecting the surface condition due to the contact of the wire bar or the like on the surface of the test material. In addition, since multiple test solutions can be tested simultaneously in parallel, the method can be simplified in a short time. Features such as being able to evaluate.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the evaluation method of the test piece in the acryl-type copolymer used in a following example, an Example, and a comparative example is as follows.
"Wetting tension evaluation method"
The above method according to JIS K 6768 was used.
"Reinforcement plate adhesion test"
As an evaluation of the adhesion of the reinforcing plate, assuming that handling of the laminated product after attaching the reinforcing plate was performed, whether or not floating occurred when the reinforcing plate laminated product was bent at a predetermined bending angle was measured.
Specifically, a protective film (20 cm × 20 cm) was bonded to a 100 μm polyimide film (20 cm × 20 cm), and press treatment was performed at 180 ° C. and 40 kg / cm ² for 30 minutes.
Then, the protective film is peeled off, and a polyimide reinforcing plate (polyimide surface size = 15 cm × 15 cm, thickness = polyimide film 75 μm + acrylic adhesive 25 μm) is adhered to the surface from which the protective film has been peeled off, and polyimide film / reinforcement A board laminate was created. After standing at room temperature for 1 hour, the laminate was wound around a resin tube having a diameter of 3 inches with a polyimide film inside. Then, it was rewound and reversed, and the laminate was wound around the resin tube with the reinforcing plate surface inside. After rewinding and repeating the same operation five times, the reinforcing plate was visually observed for lifting and peeling.
"TOF-SIMS analysis"
Using a device manufactured by ION TOF, the surface from which the protective film of the polyimide film assumed on the back surface of the FPC was peeled off was used as measurement conditions: Au primary ion irradiation, measurement range 200 μm × 200 μm, detection range 0 to 1,000 a. m. I went with u. As comparison data, data obtained by measuring a blank polyimide film surface under the same conditions was used.
Note that the polyimide film on the back surface of the FPC is Kapton 100H manufactured by Toray DuPont Co., Ltd., which is currently widely used as a base material for FPC. In the present invention, the wetting tension of the FPC surface from which the adhesive film has been peeled is measured. When the Kapton 100H is not available, any polyimide film generally used as a base material for FPC is equivalent. Alternatives are possible.

Example 1
An acrylic copolymer composition adjusted to a solid content of 40% by weight of an acrylic copolymer comprising polymerized units of butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid was obtained. The weight average molecular weight Mw of the acrylic copolymer was 500,000, and the glass transition temperature was −54 ° C.
3 parts by weight of an epoxy crosslinking agent (N, N, N ′, N′-tetraglycidyl-m-xylenediamine (solid content 60% by weight)) is added to 100 parts by weight of the acrylic copolymer composition. Then, after applying to the annealed biaxially stretched polyethylene terephthalate film having a thickness of 50 μm by a comma doctor method so that the thickness of the pressure-sensitive adhesive layer after drying becomes 10 μm, the protective film is dried at 130 ° C. for 3 minutes. Obtained.
A 20 cm × 20 cm sample of the obtained protective film was used as a sample, and a polyimide film having the same dimensions as an FPC substitute was subjected to a press treatment at 180 ° C. and 40 kg / cm ² for 30 minutes and bonded to the adhesive layer surface. Then, the polyimide surface which peeled the protective film was confirmed by TOF-SIMS analysis.
As a result, a trace component derived from the pressure-sensitive adhesive was not detected, and the wetting tension according to the maximum wetting tension evaluation method was 67 dyne / cm or more. In addition, the wetting tension test solution with a wetting tension of 67 dyne / cm or more was not available, and the wetting tension could not be measured more specifically.
A polyimide reinforcing plate (size = 15 cm × 15 cm, thickness = polyimide film 75 μm + acrylic adhesive 25 μm) is adhered to the surface from which the protective film has been peeled off, and left at room temperature for 1 hour. An adhesion test was conducted and the appearance was visually inspected, but no occurrence of lifting or peeling of the reinforcing plate was observed.

Example 2
An acrylic copolymer composition adjusted to a solid content of 40% by weight of an acrylic copolymer comprising polymerized units of butyl acrylate, 2-ethylhexyl acrylate, acrylic acid and cyclobutyl acrylate was obtained. The weight average molecular weight Mw of the acrylic copolymer was 740,000, and the glass transition temperature was −23 ° C.
3 parts by weight of an epoxy crosslinking agent (N, N, N ′, N′-tetraglycidyl-m-xylenediamine (solid content 60% by weight)) is added to 100 parts by weight of the acrylic copolymer composition. The protective film prepared in the same manner as in Example 1 was evaluated in the same manner as in Example 1.
As a result of confirmation by TOF-SIMS analysis, the trace component derived from the pressure-sensitive adhesive was not detected, and the maximum wetting tension by the wetting tension evaluation method was 67 dyne / cm or more as in Example 1.
Also in the visual appearance inspection after the reinforcing plate adhesion test, no occurrence of floating / peeling of the polyimide reinforcing plate adhered to the peeled surface was observed.

Comparative Example 1
An acrylic copolymer composition adjusted to a solid content of 40% by weight of an acrylic copolymer comprising polymerized units of butyl acrylate and 2-ethylhexyl acrylate was obtained. The weight average molecular weight Mw of the acrylic copolymer was 600,000, and the glass transition temperature was −45 ° C.
Example 1 except that the isocyanate-based crosslinking agent (Coronate L-45 (manufactured by Nippon Polyurethane Industry Co., Ltd., solid content: 45% by weight)) was changed to 6 parts by weight with respect to 100 parts by weight of the acrylic copolymer composition. A protective film prepared in the same manner was evaluated in the same manner as in Example 1.
No adhesive residue was observed by visual inspection, but as a result of confirmation by TOF-SIMS analysis, a trace component derived from the adhesive was detected, and the maximum wetting tension by the wetting tension evaluation method was 32 dyne / cm.
In the visual appearance inspection after the reinforcing plate adhesion test, the occurrence of floating / peeling of the polyimide reinforcing plate adhered to the peeled surface was observed.

The method for inspecting the pressure-sensitive adhesive film of the present invention and the method for producing a pressure-sensitive adhesive film using the pressure-sensitive adhesive film can be used, for example, during the FPC manufacturing process, and transfer of trace components derived from the pressure-sensitive adhesive onto the FPC polyimide surface from which the pressure-sensitive adhesive film has been peeled off. It is possible to produce a pressure-sensitive adhesive film that suppresses the occurrence of lifting and peeling of the reinforcing plate that adheres to the peeled surface. In addition, the method for inspecting an adhesive film of the present invention , and the method for producing an adhesive film using the same , can easily evaluate whether or not a trace component can be suppressed after peeling off the protective film for an FPC processing / manufacturing adhesive. In addition, the FPC can be processed and manufactured.

Claims (4)

A method for inspecting an adhesive film in which an adhesive layer made of an adhesive obtained by cross-linking an acrylic copolymer obtained by copolymerizing an alkyl (meth) acrylate and a vinyl monomer having a carboxyl group with an epoxy-based cross-linking agent is laminated on a substrate. There,
After the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film was bonded to the polyimide film surface, the wet tension of the polyimide film surface from which the pressure-sensitive adhesive layer was peeled was measured by the following wet tension evaluation method, and the wet tension was 40 dyne / cm. When it is above, it determines with a pass, The inspection method of the adhesive film characterized by the above-mentioned.
Wet tension evaluation method The pressure-sensitive adhesive layer of the pressure-sensitive adhesive film was bonded to the polyimide film and pressed at 180 ° C. and 40 kg / cm ² for 30 minutes, and then the pressure-sensitive adhesive layer was peeled off. 1 ml each of a wetting tension test liquid having a larger surface tension is dropped on the surface of the test piece in a horizontal position according to JIS K 6768 with a dropper from a height of 3 cm. The surface tension (dyne / cm) of the wetting tension test liquid having the maximum surface tension when the drop surface is tilted 90 degrees and the drop surface is vertical and flows while wetting the test piece surface without being repelled. The wetting tension of the specimen.   The pressure-sensitive adhesive film inspection method according to claim 1, wherein the wetting tension of the polyimide film surface is determined to be acceptable when it is 60 dyne / cm or more.   The method for inspecting an adhesive film according to claim 1 or 2, wherein the acrylic copolymer contains polymerization units of 2-ethylhexyl acrylate, butyl acrylate, and acrylic acid.   The manufacturing method of the adhesive film which has an inspection process including the inspection method of the adhesive film in any one of Claim 1 thru | or 3.