JP7773849B2 - Adhesive film, foldable device, and rollable device - Google Patents

Description

The present invention relates to an adhesive film. The present invention also relates to a foldable device equipped with such an adhesive film, and a rollable device equipped with such an adhesive film.

Adhesive films are used to reinforce and protect the surfaces of components of various shapes.

For example, when joining an integrated circuit (IC) or a flexible printed circuit board (FPC) to a semiconductor element substrate (e.g., a TFT substrate), thermocompression bonding is typically performed using an anisotropic conductive film (ACF). Before performing this thermocompression bonding, an adhesive film may be attached to the backside of the semiconductor element substrate to reinforce it (see, for example, Patent Document 1).

Furthermore, manufacturing methods for flexible and rollable devices, which have been under development in recent years, generally involve forming a release layer and a flexible or rollable film substrate on a support substrate such as glass, then forming a TFT substrate on the film substrate, and an organic EL layer on top of that. The support substrate is then peeled off to produce the flexible or rollable device, but because the flexible or rollable display layer is very thin, handling can cause problems with the device. For this reason, an adhesive film is sometimes attached to the backside for reinforcement (see, for example, Patent Document 2).

Semiconductor element substrates, flexible devices, and rollable devices are often bent repeatedly, and if the adhesive film attached to the back of the substrate has poor bending properties, it may not recover well after bending, or in the worst case, may even break due to repeated bending. Specifically, when attempting to attach an adhesive film to a bending portion (such as a movable bending portion of a folding member), the following problems may arise:

When adhesive film is bent at an angle, a compressive force acts on the inner diameter of the bent part, and the adhesive film itself deforms in an attempt to relieve this force. Specifically, for example, it becomes more prone to wrinkling.

When an adhesive film is bent at an angle, tensile stress acts on the outer diameter side of the bent part. As a result, when this stress is released, the film lifts off the adherend.

When an adhesive film is bent at an angle, the thickness of the bent or stretched parts of the adhesive film changes significantly, making it more likely to wrinkle or lift. For example, when an adhesive film is stretched, the thickness of the adhesive film becomes significantly thinner, making it more likely to lift from the adherend.

As such, conventional adhesive films are unable to adequately conform to the unevenness of corners and bends.

In particular, when an adhesive film is attached to a movable bending section, repeated bending can cause the adhesive film to develop creases (known as "creases") on the movable bending section.

In addition, when joining an integrated circuit (IC) or flexible printed circuit board (FPC) to a semiconductor element substrate (such as a TFT substrate) by thermocompression bonding, the joining position is confirmed from the back of the substrate before pressure bonding. For this reason, the adhesive film that is attached to the back of the substrate must be transparent.

Patent No. 5600039 Patent No. 6376271

An object of the present invention is to provide an adhesive film with excellent flexibility and transparency. Another object of the present invention is to provide a foldable device and a rollable device with excellent flexibility.

The adhesive film of the present invention is
A pressure-sensitive adhesive film having a base layer and a pressure-sensitive adhesive layer,
the material of the substrate layer is at least one selected from polyimide and polyether ether ketone,
the pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive,
the adhesive strength of the pressure-sensitive adhesive layer to a glass plate at 23°C, a pulling speed of 300 mm/min, and a 180° peel angle is 1 N/25 mm or more;
The thickness of the substrate layer is 10 μm to 100 μm,
The thickness of the adhesive layer is 10 μm to 100 μm,
The tan δ (0.7%) at a strain of 0.7% measured in a tension mode with a viscoelasticity measuring device is 0.1 or less.

In one embodiment, the pressure-sensitive adhesive film of the present invention is bent at a 6Φ angle, maintained at 90°C for 48 hours, and then released from the bend. After being left at 23°C and 50% RH for 24 hours, the bend angle is 60 to 180 degrees.

In one embodiment, the pressure-sensitive adhesive film of the present invention has a top coat layer on the surface of the substrate layer opposite to the surface having the pressure-sensitive adhesive layer.

In one embodiment, the top coat layer contains a binder containing at least one selected from polyester resins and urethane resins.

In one embodiment, the binder contains a urethane resin.

In one embodiment, the top coat layer contains an antistatic component.

In one embodiment, the substrate layer has a Young's modulus at 23° C. of 6.0×10 ⁷ Pa or more .

In one embodiment, the pressure-sensitive adhesive film of the present invention has a topcoat layer on the surface of the substrate layer opposite to the surface having the pressure-sensitive adhesive layer, the topcoat layer containing a binder including a urethane resin and an antistatic component, and the material of the substrate layer is at least one selected from polyimide and polyether ether ketone.

In one embodiment, the pressure-sensitive adhesive film of the present invention has a total light transmittance of 20% or more.

In one embodiment, the PSA film of the present invention has a haze of 15% or less.

In one embodiment, the adhesive film of the present invention is attached to a foldable member.

In one embodiment, the foldable component is an OLED.

In one embodiment, the adhesive film of the present invention is attached to a rollable member.

In one embodiment, the rollable member is an OLED.

The foldable device of the present invention includes the above-mentioned adhesive film.

The rollable device of the present invention comprises the above-mentioned adhesive film.

The present invention can provide an adhesive film with excellent flexibility and transparency. The present invention can also provide foldable and rollable devices with excellent flexibility.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the foldable device of the present invention, and shows one mode of use of the pressure-sensitive adhesive film of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a method for evaluating flex recovery. FIG. 3 is a schematic cross-sectional view illustrating the evaluation method for peeling evaluation.

<<<Adhesive film>>>
The pressure-sensitive adhesive film of the present invention has a base layer and a pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive film of the present invention may have any appropriate other layer as long as the effects of the present invention are not impaired.

The substrate layer may be one layer or two or more layers. The substrate layer is preferably one layer, as this can better demonstrate the effects of the present invention.

The adhesive layer may be a single layer or two or more layers. A single adhesive layer is preferred, as this allows the effects of the present invention to be more effectively achieved.

The adhesive film of the present invention may be provided with any suitable release liner on the surface of the adhesive layer opposite the substrate layer for protection until use.

Examples of release liners include release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is silicone-treated, and release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin. Examples of plastic films that can be used as liner substrates include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene-vinyl acetate copolymer film.

The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, even more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

The total thickness d of the pressure-sensitive adhesive film of the present invention is preferably 1 μm to 500 μm, more preferably 5 μm to 200 μm, even more preferably 10 μm to 150 μm, particularly preferably 20 μm to 100 μm, and most preferably 30 μm to 80 μm. When the total thickness d of the pressure-sensitive adhesive film of the present invention is within the above range, the effects of the present invention can be more effectively exhibited.

The adhesive film of the present invention has a tan δ (0.7%) at a strain of 0.7%, measured in the tension mode of a viscoelasticity measuring device, of 0.1 or less, preferably 0.09 or less, more preferably 0.08 or less, even more preferably 0.07 or less, and particularly preferably 0.06 or less. If the tan δ (0.7%) at a strain of 0.7%, measured in the tension mode of a viscoelasticity measuring device, of the adhesive film of the present invention is within the above range, the effects of the present invention can be more effectively achieved.

Tan δ (0.7%) at a strain of 0.7%, measured in tension mode with a viscoelasticity measuring device, is an index showing the loss tangent when the adhesive film is bent significantly. In completing this invention, we found, based on various experimental data, that the effects of the invention can be more effectively achieved if this value is within the above range. The method for measuring tan δ (0.7%) at a strain of 0.7%, measured in tension mode with a viscoelasticity measuring device, is described in detail below.

The adhesive film of the present invention preferably has a tan δ (0.1%) at a strain of 0.1%, measured in the tension mode of a viscoelasticity measuring device, of 0.1 or less, more preferably 0.08 or less, even more preferably 0.06 or less, and particularly preferably 0.05 or less. If the tan δ (0.1%) at a strain of 0.1%, measured in the tension mode of a viscoelasticity measuring device, of the adhesive film of the present invention is within the above range, the effects of the present invention can be more effectively achieved.

Tan δ (0.1%) at a strain of 0.1%, measured in tension mode with a viscoelasticity measuring device, is an index showing the loss tangent when the adhesive film is bent slightly. In completing this invention, we found, based on various experimental data, that the effects of the invention can be more effectively achieved if this value is within the above range. The method for measuring tan δ (0.1%) at a strain of 0.1%, measured in tension mode with a viscoelasticity measuring device, is described in detail below.

The adhesive film of the present invention preferably has a difference (tan δ (0.7%) - tan δ (0.1%)) between tan δ at 0.7% strain and tan δ at 0.1% strain, measured in the tensile mode of a viscoelasticity measuring device, of 0.05 or less, more preferably 0.04 or less, and even more preferably 0.03 or less. When the difference (tan δ (0.7%) - tan δ (0.1%)) between tan δ at 0.7% strain and tan δ at 0.1% strain, measured in the tensile mode of a viscoelasticity measuring device, of the adhesive film of the present invention is within the above range, the effects of the present invention can be better achieved.

The difference between tan δ (0.7%) at a strain of 0.7% and tan δ (0.1%) at a strain of 0.1%, measured using a viscoelasticity measuring device in tension mode, is an index showing the difference between the loss tangent when the adhesive film is bent significantly and the loss tangent when the adhesive film is bent slightly. Upon completing the present invention, it was found, based on various experimental data, that the effects of the present invention can be more effectively achieved if this value is within the above range.

The adhesive film of the present invention, after being bent at 6Φ and held at 90°C for 48 hours, then released and left at 23°C and 50% RH for 24 hours, preferably exhibits a bending angle of 60 to 180 degrees, more preferably 80 to 180 degrees, even more preferably 100 to 180 degrees, particularly preferably 120 to 180 degrees, and most preferably 150 to 180 degrees. If the bending angle of the adhesive film of the present invention, after being bent at 6Φ and held at 90°C for 48 hours, then released and left at 23°C and 50% RH for 24 hours, is within the above range, the effects of the present invention can be more effectively achieved.

The bending angle after bending an adhesive film to 6Φ and holding it at 90°C for 48 hours, then releasing the bending, and leaving it at 23°C and 50% RH for 24 hours is an indicator of recovery after bending. The method for measuring the bending angle after bending to 6Φ and holding it at 90°C for 48 hours, then releasing the bending, and leaving it at 23°C and 50% RH for 24 hours is described in detail below.

The pressure-sensitive adhesive film of the present invention preferably has a total light transmittance of 20% or more, more preferably 30% or more, even more preferably 40% or more, particularly preferably 50% or more, and most preferably 60% or more. When the total light transmittance of the pressure-sensitive adhesive film of the present invention is within the above range, excellent transparency can be exhibited.

The adhesive film of the present invention preferably has a haze of 15% or less, more preferably 13% or less, even more preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less. When the haze of the adhesive film of the present invention is within the above range, excellent transparency can be more clearly exhibited.

The adhesive film of the present invention has excellent flexibility and transparency, and is therefore preferably attached to a foldable member. Any appropriate member can be used as the foldable member as long as it can be repeatedly bent. Examples of such foldable members include foldable optical members and foldable electronic members, and a representative example is a foldable OLED.

The adhesive film of the present invention has excellent flexibility and transparency, and is therefore preferably attached to a rollable member. Any appropriate member can be used as the rollable member as long as it can be repeatedly wound and unwound. Examples of such rollable members include rollable optical members and rollable electronic members, and a typical example is a rollable OLED.

≪Base material layer≫
The thickness of the substrate layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, even more preferably 10 μm to 100 μm, particularly preferably 15 μm to 80 μm, and most preferably 20 μm to 60 μm. When the thickness of the substrate layer is within the above range, the effects of the present invention can be more effectively exhibited.

The Young's modulus of the substrate layer at 23°C is preferably 6.0 x ¹⁰⁷ Pa or more, more preferably 1.0 x ¹⁰⁸ Pa or more, even more preferably 5.0 x ¹⁰⁸ Pa or more, particularly preferably 8.0 x ¹⁰⁸ Pa or more, and most preferably 1.0 x ¹⁰⁹ Pa or more. The upper limit of the Young's modulus of the substrate layer at 23°C is typically preferably 1.0 x ¹⁰¹¹ Pa or less. If the Young's modulus of the substrate layer at 23°C is within the above range, the effects of the present invention can be more effectively exhibited. If the Young's modulus of the substrate layer at 23°C is too low, when the PSA film is bent at an angle, the tension on the outer diameter side may not be sufficiently maintained against the compression on the inner diameter side, which may make the thickness more likely to change and cause the PSA film to lift off the adherend. If the Young's modulus of the substrate layer at 23°C is too high, the PSA film may not be easily deformed. The method for measuring the Young's modulus will be described in detail later.

Any suitable material may be used as the material for the substrate layer, as long as it does not impair the effects of the present invention. A typical example of such a material for the substrate layer is a resin material.

Examples of resin materials for the substrate layer include acrylic resins such as polyimide (PI), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polymethyl methacrylate (PMMA), as well as polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), wholly aromatic polyamide (aramid), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene sulfide (PPS), fluorine-based resins, and cyclic olefin polymers.

As a resin material for the substrate layer, at least one selected from polyimide (PI), polyether ether ketone (PEEK), and cyclic olefin polymer is preferred, as it can further enhance the effects of the present invention, and at least one selected from polyimide (PI) and polyether ether ketone (PEEK) is more preferred.

<Adhesive layer>
The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, even more preferably 10 μm to 100 μm, particularly preferably 15 μm to 80 μm, and most preferably 20 μm to 60 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, the effects of the present invention can be more effectively exhibited.

The adhesive strength of the adhesive layer to a glass plate at 23°C, a tensile speed of 300 mm/min, and a 180-degree peel is preferably 1 N/25 mm or more, more preferably 5 N/25 mm or more, even more preferably 10 N/25 mm or more, particularly preferably 12 N/25 mm or more, and most preferably 15 N/25 mm or more. The upper limit of the adhesive strength of the adhesive layer to a glass plate at 23°C, a tensile speed of 300 mm/min, and a 180-degree peel is typically preferably 1000 N/25 mm or less, more preferably 5000 N/25 mm or less, even more preferably 300 N/25 mm or less, particularly preferably 200 N/25 mm or less, and most preferably 100 N/25 mm or less. When the adhesive strength of the adhesive layer to a glass plate at 23°C, a tensile speed of 300 mm/min, and a 180-degree peel is within the above range, the effects of the present invention can be more effectively exhibited.

The adhesive layer contains a base polymer. The base polymer may be of only one type, or may be of two or more types. The content of the base polymer in the adhesive layer is preferably 20% to 100% by weight, more preferably 30% to 95% by weight, even more preferably 40% to 90% by weight, particularly preferably 45% to 85% by weight, and most preferably 50% to 80% by weight, in order to further demonstrate the effects of the present invention.

Any appropriate polymer may be used as the base polymer as long as it does not impair the effects of the present invention. In order to further enhance the effects of the present invention, the base polymer is preferably at least one selected from an acrylic polymer, a rubber polymer, a silicone polymer, and a urethane polymer. That is, the pressure-sensitive adhesive layer preferably contains at least one selected from an acrylic pressure-sensitive adhesive containing an acrylic polymer, a rubber pressure-sensitive adhesive containing a rubber polymer, a silicone pressure-sensitive adhesive containing a silicone polymer, and a urethane pressure-sensitive adhesive containing a urethane polymer. In order to further enhance the effects of the present invention, the pressure-sensitive adhesive layer preferably contains an acrylic pressure-sensitive adhesive. Acrylic pressure-sensitive adhesives are described in detail below as a representative example of pressure-sensitive adhesives that can be contained in the pressure-sensitive adhesive layer.

<Acrylic adhesive>
The acrylic pressure-sensitive adhesive contains an acrylic polymer as a base polymer, may contain a tackifying resin, and may contain a crosslinking agent.

When the acrylic adhesive contains an acrylic polymer, a tackifier resin, and a crosslinking agent, the combined content of the acrylic polymer, tackifier resin, and crosslinking agent relative to the total amount of the acrylic adhesive is preferably 95% by weight or more, more preferably 97% by weight or more, and even more preferably 99% by weight or more, in order to further demonstrate the effects of the present invention.

(acrylic polymer)
The acrylic polymer is preferably a polymer of monomer components that contains, for example, an alkyl(meth)acrylate as a main monomer and may further contain a secondary monomer copolymerizable with the main monomer, where the main monomer is a component that accounts for more than 50% by weight of the total monomer components.

As the alkyl(meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used.
CH ₂ =C(R ¹ )COOR ² (1)

Here, in the above formula (1), R ¹ is a hydrogen atom or a methyl group, and R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, this range of carbon atoms may be referred to as "C1-20"). From the viewpoint of the storage modulus of the pressure-sensitive adhesive layer, etc., R ² is preferably a chain alkyl group having 1-14 carbon atoms, more preferably a chain alkyl group having 2-10 carbon atoms, and even more preferably a chain alkyl group having 4-8 carbon atoms. Here, "chain" means to include linear and branched chains.

Examples of alkyl(meth)acrylates in which R ² is a C1-20 chain alkyl group include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, and isooctyl(meth)acrylate. Examples of alkyl (meth)acrylate include acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates may be used alone or in combination of two or more.

Preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), as they can further enhance the effects of the present invention.

The alkyl (meth)acrylate content of all monomer components used in the synthesis of the acrylic polymer is preferably 70% by weight or more, more preferably 85% by weight or more, and even more preferably 90% by weight or more, in order to further enhance the effects of the present invention. The upper limit of the alkyl (meth)acrylate content is preferably 99.5% by weight or less, more preferably 99% by weight or less. However, the acrylic polymer may be obtained by polymerizing essentially only alkyl (meth)acrylate.

When an alkyl(meth)acrylate in which ^R2 is a C4-8 linear alkyl group is used, the proportion of alkyl(meth)acrylates in which ^R2 is a C4-8 linear alkyl group among the alkyl(meth)acrylates contained in the monomer component is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, particularly preferably 95% by weight or more, and most preferably 99% by weight or more and 100% by weight, in terms of being able to further exhibit the effects of the present invention.

One embodiment of the acrylic polymer is an acrylic polymer in which 50% by weight or more of the total monomer components is n-butyl acrylate (BA). In this case, the content of n-butyl acrylate (BA) in the total monomer components is preferably greater than 50% by weight and less than 100% by weight, more preferably 55% to 95% by weight, even more preferably 60% to 90% by weight, particularly preferably 63% to 85% by weight, and most preferably 65% to 80% by weight, in order to further demonstrate the effects of the present invention. The total monomer components may further contain 2-ethylhexyl acrylate (2EHA) in a proportion less than n-butyl acrylate (BA).

One embodiment of the acrylic polymer is an acrylic polymer in which less than 50% by weight of the total monomer components is 2-ethylhexyl acrylate (2EHA). In this case, the content of 2-ethylhexyl acrylate (2EHA) in the total monomer components is preferably greater than 0% by weight and not more than 48% by weight, more preferably 5% to 45% by weight, even more preferably 10% to 43% by weight, particularly preferably 15% to 40% by weight, and most preferably 20% to 35% by weight, in order to further demonstrate the effects of the present invention. The total monomer components may also contain n-butyl acrylate (BA) in a proportion greater than 2-ethylhexyl acrylate (2EHA).

The acrylic polymer may be copolymerized with other monomers as long as the effects of the present invention are not impaired. Other monomers can be used, for example, to adjust the glass transition temperature (Tg) of the acrylic polymer or to adjust the adhesive performance. Examples of monomers that can improve the cohesive strength and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphate group-containing monomers, cyano group-containing monomers, vinyl esters, and aromatic vinyl compounds, with vinyl esters being preferred. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, and vinyl laurate, with vinyl acetate (VAc) being preferred.

The "other monomer" may be one type only, or two or more types. The content of other monomers in the total monomer components is preferably 0.001% to 40% by weight, more preferably 0.01% to 40% by weight, even more preferably 0.1% to 10% by weight, particularly preferably 0.5% to 5% by weight, and most preferably 1% to 3% by weight.

Other monomers that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or that can contribute to improving adhesive strength include, for example, hydroxyl group (OH group)-containing monomers, carboxy group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, epoxy group-containing monomers, (meth)acryloylmorpholine, and vinyl ethers.

One embodiment of the acrylic polymer is an acrylic polymer copolymerized with a carboxyl group-containing monomer as another monomer. Examples of carboxyl group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Among these, acrylic acid (AA) and methacrylic acid (MAA) are preferred as the carboxyl group-containing monomer, as they can further exhibit the effects of the present invention, and acrylic acid (AA) is more preferred.

When a carboxyl group-containing monomer is used as the other monomer, the content of the other monomer in the total monomer components is preferably 0.1% to 10% by weight, more preferably 0.2% to 8% by weight, even more preferably 0.5% to 5% by weight, particularly preferably 0.7% to 4% by weight, and most preferably 1% to 3% by weight, in order to further demonstrate the effects of the present invention.

One embodiment of the acrylic polymer is an acrylic polymer copolymerized with a hydroxyl group-containing monomer as an additional monomer. Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; and N-hydroxyethyl (meth)acrylamide. Among these, hydroxyl group-containing monomers are preferably hydroxyalkyl (meth)acrylates in which the alkyl group is linear and has 2 to 4 carbon atoms, as they can further enhance the effects of the present invention. Specific examples include 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), with 4-hydroxybutyl acrylate (4HBA) being more preferred.

When a hydroxyl group-containing monomer is used as the other monomer, the content of the other monomer in the total monomer components is preferably 0.001% by weight to 10% by weight, more preferably 0.01% by weight to 5% by weight, even more preferably 0.02% by weight to 2% by weight, particularly preferably 0.03% by weight to 1% by weight, and most preferably 0.05% by weight to 0.5% by weight, in order to further demonstrate the effects of the present invention.

The Tg of the base polymer may be, for example, -80°C or higher, which can further enhance the effects of the present invention. The base polymer (preferably an acrylic polymer) is designed to have a Tg of preferably -15°C or lower, from the viewpoint of enhancing the deformability of the PSA layer in the shear direction. In some embodiments, the Tg of the base polymer is, for example, preferably -25°C or lower, more preferably -40°C or lower, and even more preferably -50°C or lower. The Tg of the base polymer is designed to be, for example, preferably -70°C or higher (more preferably -65°C or higher, and even more preferably -60°C or higher), from the viewpoint of enhancing cohesion and shape recovery.

The Tg of the base polymer is a value calculated from the Fox equation based on the Tg of the homopolymer of each monomer constituting the base polymer and the weight fraction (copolymerization ratio by weight) of the monomer. The Fox equation, as shown below, is a relational expression between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1/Tg=Σ(Wi/Tgi)

In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio by weight), and Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i. The Tg of the homopolymer is determined from a value listed in publicly available documents.

As the Tg of the homopolymer, for example, the following specific values can be used:
2-Ethylhexyl acrylate -70℃
n-Butyl acrylate -55°C
Acrylic acid 106℃
2-Hydroxyethyl acrylate -15°C
4-hydroxybutyl acrylate -40°C

For the Tg of homopolymers other than those listed above, the values listed in the "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values are listed in the "Polymer Handbook," the conventional value is used. For monomers not listed in the "Polymer Handbook," the catalog value from the monomer manufacturer is used. For homopolymer Tg of monomers not listed in the "Polymer Handbook" and for which no catalog value from the monomer manufacturer is provided, the value obtained by the measurement method described in JP 2007-51271 A should be used.

Acrylic polymers can be obtained by various polymerization methods known for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. Among these polymerization methods, solution polymerization is preferred. Monomer supply methods for solution polymerization include a batch feed method in which the entire amount of monomer components is supplied at once, a continuous feed (dropping) method, and a divided feed (dropping) method. The polymerization temperature can be selected appropriately depending on the types of monomers and solvents used, the type of polymerization initiator, and other factors. It is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, and preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower. Acrylic polymers can also be obtained by photopolymerization using UV or other light (typically in the presence of a photopolymerization initiator), or by radiation polymerization using β-rays, γ-rays, or other radiation.

The solvent (polymerization solvent) used in solution polymerization can be selected from any suitable organic solvent. Examples include aromatic compounds (typically aromatic hydrocarbons) such as toluene, acetate esters such as ethyl acetate, and aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane.

The initiator (polymerization initiator) used in the polymerization can be selected from any appropriate polymerization initiator depending on the type of polymerization method. A single polymerization initiator may be used, or two or more polymerization initiators may be used. Examples of such polymerization initiators include azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN); persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; and aromatic carbonyl compounds. Other examples of polymerization initiators include redox-based initiators formed by combining a peroxide with a reducing agent.

The amount of polymerization initiator used is preferably 0.005 to 1 part by weight, and more preferably 0.01 to 1 part by weight, per 100 parts by weight of all monomer components.

The Mw of the acrylic polymer is preferably 10×10 ⁴ to 500×10 ⁴ , more preferably 10×10 ⁴ to 150×10 ⁴ , even more preferably 20×10 ⁴ to 75×10 ⁴ , and particularly preferably 35×10 ⁴ to 65×10 ^4. Here, Mw refers to a value calculated in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC device, for example, a model "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used.

(Tackifying resin)
The acrylic pressure-sensitive adhesive may contain a tackifying resin, which can further enhance the effects of the present invention. Examples of tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins. The tackifying resin may be one type or two or more types.

The amount of tackifier resin used is preferably 5 to 70 parts by weight, more preferably 10 to 60 parts by weight, even more preferably 15 to 50 parts by weight, even more preferably 20 to 45 parts by weight, particularly preferably 25 to 40 parts by weight, and most preferably 25 to 35 parts by weight, per 100 parts by weight of base polymer, in order to further demonstrate the effects of the present invention.

The tackifier resin preferably contains a tackifier resin TL with a softening point of less than 105°C, as this can further enhance the effects of the present invention. The tackifier resin TL can effectively contribute to improving the deformability of the PSA layer in the planar direction (shear direction). From the perspective of achieving even greater deformability improvement effects, the softening point of the tackifier resin used as the tackifier resin TL is preferably 50°C to 103°C, more preferably 60°C to 100°C, even more preferably 65°C to 95°C, particularly preferably 70°C to 90°C, and most preferably 75°C to 85°C.

The softening point of a tackifying resin is defined as the value measured using the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, avoiding the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, is cut off with a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and glycerin is poured into it to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the glycerin temperature is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, align the center of the thermometer's mercury bulb with the center of the ring, and heat the container. The flame of the Bunsen burner used for heating should be midway between the center of the bottom and the edge of the container, and heat evenly. After heating begins and the temperature reaches 40°C, the rate of increase in bath temperature must be 5.0 ± 0.5°C per minute. The sample gradually softens and flows down the ring, and the temperature is read when it finally touches the bottom plate; this is the softening point. Two or more softening points should be measured at the same time, and the average value should be used.

The amount of tackifier resin TL used is preferably 5 to 50 parts by weight, more preferably 10 to 45 parts by weight, even more preferably 15 to 40 parts by weight, particularly preferably 20 to 35 parts by weight, and most preferably 25 to 32 parts by weight, per 100 parts by weight of base polymer, in order to further demonstrate the effects of the present invention.

As the tackifier resin TL, one or more types appropriately selected from the tackifier resins exemplified above, which have a softening point of less than 105°C, can be used. The tackifier resin TL preferably contains a rosin-based resin.

Examples of rosin-based resins that can be preferably used as the tackifier resin TL include rosin esters such as unmodified rosin ester and modified rosin ester. Examples of modified rosin esters include hydrogenated rosin ester.

The tackifier resin TL preferably contains a hydrogenated rosin ester, which can further demonstrate the effects of the present invention. The softening point of the hydrogenated rosin ester is preferably less than 105°C, more preferably 50°C to 100°C, even more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C, which can further demonstrate the effects of the present invention.

The tackifying resin TL may contain a non-hydrogenated rosin ester. Here, the term "non-hydrogenated rosin ester" refers to all of the rosin esters listed above except for the hydrogenated rosin ester. Examples of non-hydrogenated rosin esters include unmodified rosin ester, disproportionated rosin ester, and polymerized rosin ester.

The softening point of the non-hydrogenated rosin ester is preferably less than 105°C, more preferably 50°C to 100°C, even more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C, in order to better demonstrate the effects of the present invention.

The tackifier resin TL may contain other tackifier resins in addition to the rosin-based resin. As the other tackifier resins, one or more types appropriately selected from the tackifier resins exemplified above that have a softening point of less than 105°C may be used. The tackifier resin TL may contain, for example, a rosin-based resin and a terpene resin.

The rosin-based resin content of the total tackifier resin TL is preferably greater than 50% by weight, more preferably 55% to 100% by weight, even more preferably 60% to 99% by weight, particularly preferably 65% to 97% by weight, and most preferably 75% to 97% by weight, in order to further demonstrate the effects of the present invention.

The tackifier resin may contain a combination of tackifier resin TL and tackifier resin TH, which has a softening point of 105°C or higher (preferably 105°C to 170°C), in order to further enhance the effects of the present invention.

As the tackifier resin TH, one or more types appropriately selected from the tackifier resins exemplified above that have a softening point of 105°C or higher can be used. The tackifier resin TH can include at least one type selected from rosin-based tackifier resins (e.g., rosin esters) and terpene-based tackifier resins (e.g., terpene phenol resins).

(Crosslinking agent)
A crosslinking agent can be contained in the acrylic pressure-sensitive adhesive. The crosslinking agent may be one type or two or more types. The use of a crosslinking agent can impart appropriate cohesive strength to the acrylic pressure-sensitive adhesive. The crosslinking agent can also be useful for adjusting the slippage distance and return distance in a holding power test. An acrylic pressure-sensitive adhesive containing a crosslinking agent can be obtained, for example, by forming a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing the crosslinking agent. The crosslinking agent can be contained in the acrylic pressure-sensitive adhesive in a form after crosslinking reaction, a form before crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, or the like. The crosslinking agent is typically contained in the acrylic pressure-sensitive adhesive exclusively in a form after crosslinking reaction.

The amount of crosslinking agent used is preferably 0.005 to 10 parts by weight, more preferably 0.01 to 7 parts by weight, even more preferably 0.05 to 5 parts by weight, particularly preferably 0.1 to 4 parts by weight, and most preferably 1 to 3 parts by weight, per 100 parts by weight of base polymer, in order to further demonstrate the effects of the present invention.

Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and peroxide-based crosslinking agents. In terms of being able to further demonstrate the effects of the present invention, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred, and isocyanate-based crosslinking agents are more preferred.

Isocyanate-based crosslinking agents can be compounds that have two or more isocyanate groups per molecule (including isocyanate-regenerating functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization). Examples of isocyanate-based crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

Specific examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate; trimethylolpropane/tolylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate L), trimethylolpropane/hexamethylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate HL), and hexamethylene diisocyanate isocyanurate (e.g., manufactured by Tosoh Corporation, trade name: Coronate HL). Examples of the polyisocyanate include isocyanate adducts such as those manufactured by Mitsui Chemicals, Inc. under the trade name of Coronate HX; trimethylolpropane adducts of xylylene diisocyanate (for example, Mitsui Chemicals, Inc. under the trade name of Takenate D110N), trimethylolpropane adducts of xylylene diisocyanate (for example, Mitsui Chemicals, Inc. under the trade name of Takenate D120N), trimethylolpropane adducts of isophorone diisocyanate (for example, Mitsui Chemicals, Inc. under the trade name of Takenate D140N), and trimethylolpropane adducts of hexamethylene diisocyanate (for example, Mitsui Chemicals, Inc. under the trade name of Takenate D160N); polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols; and polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, aromatic isocyanates and alicyclic isocyanates are preferred because they can achieve a good balance between deformability and cohesive strength.

The amount of isocyanate-based crosslinking agent used is preferably 0.005 to 10 parts by weight, more preferably 0.01 to 7 parts by weight, even more preferably 0.05 to 5 parts by weight, particularly preferably 0.1 to 4 parts by weight, and most preferably 1 to 3 parts by weight, per 100 parts by weight of base polymer, in order to further demonstrate the effects of the present invention.

When the monomer components constituting the acrylic polymer include a hydroxyl group-containing monomer, the weight ratio of isocyanate-based crosslinking agent to hydroxyl group-containing monomer is preferably more than 20 and less than 50, more preferably 22 to 45, even more preferably 25 to 40, particularly preferably 27 to 40, and most preferably 30 to 35, in order to further demonstrate the effects of the present invention.

When the acrylic adhesive contains a tackifier resin TL with a softening point of 105°C or less, the weight ratio of tackifier resin TL to isocyanate-based crosslinker is preferably more than 2 and less than 15, more preferably 5 to 13, even more preferably 7 to 12, and particularly preferably 7 to 11, in order to further demonstrate the effects of the present invention.

Epoxy-based crosslinking agents can be multifunctional epoxy compounds with two or more epoxy groups per molecule. Examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polyglycidyl ether. Examples of epoxy crosslinking agents include glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Commercially available epoxy crosslinking agents include products manufactured by Mitsubishi Gas Chemical Company, Inc., under the trade names "Tetrad C" and "Tetrad X."

The amount of epoxy crosslinking agent used is preferably 0.005 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, even more preferably 0.015 to 1 part by weight, particularly preferably 0.15 to 0.5 parts by weight, and most preferably 0.015 to 0.3 parts by weight, per 100 parts by weight of base polymer, in order to further demonstrate the effects of the present invention.

(Other ingredients)
The acrylic pressure-sensitive adhesive may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesives, such as a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc. As for such various additives, conventionally known ones can be used in the usual manner.

<Antistatic layer>
The pressure-sensitive adhesive film of the present invention may have an antistatic layer on the surface of the base layer opposite to the surface having the pressure-sensitive adhesive layer. By having an antistatic layer on the surface of the base layer opposite to the surface having the pressure-sensitive adhesive layer, the pressure-sensitive adhesive film itself can be suppressed from becoming charged, making it less likely to adsorb dust, which is a preferred embodiment.

Antistatic layers can be formed, for example, by applying an antistatic resin consisting of an antistatic agent and a resin component, a conductive polymer, or a conductive resin containing a conductive substance, or by vapor-depositing or plating a conductive substance.

Examples of antistatic agents contained in antistatic resins include cationic antistatic agents having cationic functional groups such as quaternary ammonium salts, pyridinium salts, and primary, secondary, and tertiary amino groups; anionic antistatic agents having anionic functional groups such as sulfonates, sulfate ester salts, phosphonates, and phosphate ester salts; amphoteric antistatic agents such as alkylbetaine and its derivatives, imidazoline and its derivatives, and alanine and its derivatives; nonionic antistatic agents such as aminoalcohols and their derivatives, glycerin and its derivatives, and polyethylene glycol and its derivatives; and ionic conductive polymers obtained by polymerizing or copolymerizing monomers having the above-mentioned cationic, anionic, or amphoteric ionic conductive groups. These antistatic agents may be used alone or in combination.

Examples of cationic antistatic agents include alkyltrimethylammonium salts, acyloylamidopropyltrimethylammonium methosulfate, alkylbenzylmethylammonium salts, acylcholine chloride, (meth)acrylate copolymers having quaternary ammonium groups such as polydimethylaminoethyl methacrylate; styrene copolymers having quaternary ammonium groups such as polyvinylbenzyltrimethylammonium chloride; and diallylamine copolymers having quaternary ammonium groups such as polydiallyldimethylammonium chloride. These antistatic agents may be used alone or in combination of two or more types.

Examples of anionic antistatic agents include alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfates, alkyl ethoxy sulfates, alkyl phosphates, and sulfonic acid group-containing styrene copolymers. These antistatic agents may be used alone or in combination.

Examples of amphoteric antistatic agents include alkylbetaine, alkylimidazolium betaine, and carbobetaine graft copolymer. These antistatic agents may be used alone or in combination with two or more types.

Examples of nonionic antistatic agents include fatty acid alkylolamides, di(2-hydroxyethyl)alkylamines, polyoxyethylene alkylamines, fatty acid glycerin esters, polyoxyethylene glycol fatty acid esters, sorbitan fatty acid esters, polyoxysorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyethylene glycol, polyoxyethylene diamines, copolymers of polyether, polyester, and polyamide, and methoxypolyethylene glycol (meth)acrylate. These antistatic agents may be used alone or in combination of two or more types.

Examples of conductive polymers include polyaniline, polypyrrole, and polythiophene. These conductive polymers may be used alone or in combination of two or more types.

Examples of conductive substances include tin oxide, antimony oxide, indium oxide, cadmium oxide, titanium oxide, zinc oxide, indium, tin, antimony, gold, silver, copper, aluminum, nickel, chromium, titanium, iron, cobalt, copper iodide, and alloys or mixtures thereof. These conductive substances may be used alone or in combination of two or more types.

The resin components used in antistatic resins and conductive resins include general-purpose resins such as polyester resins, acrylic resins, polyvinyl resins, urethane resins, melamine resins, and epoxy resins. Polymer-type antistatic agents do not necessarily need to contain resin components. Antistatic resins can also contain crosslinking agents such as methylolated or alkylolated melamine compounds, urea compounds, glyoxal compounds, acrylamide compounds, epoxy compounds, and isocyanate compounds.

Antistatic layers can be formed, for example, by diluting the above-mentioned antistatic resin, conductive polymer, or conductive resin with a solvent such as an organic solvent or water, applying the resulting coating liquid to a substrate, and drying it.

Diluted solutions used to form the antistatic layer include, for example, methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol, n-propanol, isopropanol, and water. These solvents may be used alone or in combination.

Any suitable coating method can be used to form the antistatic layer. Examples of such coating methods include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, impregnation, and curtain coating.

Any suitable method can be used to deposit or plate the conductive material. Examples of such methods include vacuum deposition, sputtering, ion plating, chemical vapor deposition, spray pyrolysis, chemical plating, and electroplating.

The antistatic layer may have any appropriate thickness as long as it does not impair the effects of the present invention. To maximize the effects of the present invention, the thickness of the antistatic layer is preferably 0.001 μm to 5 μm, and more preferably 0.005 μm to 1 μm.

<Top coat layer>
The pressure-sensitive adhesive film of the present invention may have a top coat layer on the surface of the substrate layer opposite to the surface having the pressure-sensitive adhesive layer. The top coat layer preferably contains a binder, more preferably contains a binder and a slipping agent. By having the pressure-sensitive adhesive film of the present invention have a top coat layer, the scratch resistance of the pressure-sensitive adhesive film is improved, which is a preferred embodiment.

<Binder>
Any appropriate resin may be used as the binder as long as it does not impair the effects of the present invention. Such a resin is preferably at least one selected from the group consisting of polyester resins and urethane resins, in that it can further exhibit the effects of the present invention.

(Polyester resin)
When the binder contains a polyester resin, the polyester resin may be of only one type, or of two or more types.

The polyester resin is preferably a resin containing polyester as a main component. The polyester content in the polyester resin is preferably greater than 50% by weight, more preferably 75% by weight or more, and even more preferably 90% by weight or more.

The polyester preferably has a structure obtained by condensing at least one compound (polycarboxylic acid component) selected from polycarboxylic acids (preferably dicarboxylic acids) having two or more carboxyl groups per molecule and their derivatives (anhydrides, esters, halides, etc. of polycarboxylic acids) with at least one compound (polyhydric alcohol component) selected from polyhydric alcohols (preferably diols) having two or more hydroxyl groups per molecule.

Examples of compounds that can be used as polycarboxylic acid components include oxalic acid, malonic acid, difluoromalonic acid, alkylmalonic acid, succinic acid, tetrafluorosuccinic acid, alkylsuccinic acid, (±)-malic acid, meso-tartaric acid, itaconic acid, maleic acid, methylmaleic acid, fumaric acid, methylfumaric acid, acetylenedicarboxylic acid, glutaric acid, hexafluoroglutaric acid, methylglutaric acid, glutaconic acid, adipic acid, dithioadipic acid, methyladipic acid, dimethyladipic acid, tetramethyladipic acid, methyleneadipic acid, muconic acid, galactaric acid, pimelic acid, suberic acid, and perfluorosuberic acid. Aliphatic dicarboxylic acids such as phosphoric acid, 3,3,6,6-tetramethylsuberic acid, azelaic acid, sebacic acid, perfluorosebacic acid, brassylic acid, dodecyldicarboxylic acid, tridecyldicarboxylic acid, and tetradecyldicarboxylic acid; alicyclic dicarboxylic acids such as cycloalkyldicarboxylic acids (for example, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid), 1,4-(2-norbornene)dicarboxylic acid, 5-norbornene-2,3-dicarboxylic acid (himic acid), adamantanedicarboxylic acid, and spiroheptanedicarboxylic acid; phthalic acid, isophthalic acid, dithioisophthalic acid, methyl Dichloroisophthalic acid, terephthalic acid, methyl terephthalic acid, dimethyl terephthalic acid, chloro terephthalic acid, bromo terephthalic acid, naphthalenedicarboxylic acid, oxofluorene dicarboxylic acid, anthracene dicarboxylic acid, biphenyl dicarboxylic acid, biphenylenedicarboxylic acid, dimethyl biphenylenedicarboxylic acid, 4,4"-p-terephenylenedicarboxylic acid, 4,4"-p-quartetphenyl dicarboxylic acid, bibenzyl dicarboxylic acid, azobenzene dicarboxylic acid, homophthalic acid, phenylene diacetic acid, phenylenedipropionic acid, naphthalene Examples of suitable polycarboxylic acids include aromatic dicarboxylic acids such as 4,4'-bibenzyldiacetic acid, naphthalenedipropionic acid, biphenyldiacetic acid, biphenyldipropionic acid, 3,3'-[4,4'-(methylenedi-p-biphenylene)dipropionic acid, 4,4'-bibenzyldiacetic acid, 3,3'(4,4'-bibenzyl)dipropionic acid, and oxydi-p-phenylenediacetic acid; acid anhydrides of any of the above-mentioned polycarboxylic acids; esters of any of the above-mentioned polycarboxylic acids (e.g., alkyl esters, monoesters, diesters, etc.); and acid halides corresponding to any of the above-mentioned polycarboxylic acids (e.g., dicarboxylic acid chlorides, etc.).

Suitable examples of compounds that can be used as the polycarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and their acid anhydrides; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, himic acid, and 1,4-cyclohexanedicarboxylic acid, and their acid anhydrides; and lower alkyl esters of the above dicarboxylic acids (e.g., esters with monoalcohols having 1 to 3 carbon atoms).

Examples of compounds that can be used as the polyhydric alcohol component include diols such as ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentanediol, diethylene glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, xylylene glycol, hydrogenated bisphenol A, and bisphenol A. Other examples include alkylene oxide adducts of these compounds (e.g., ethylene oxide adducts, propylene oxide adducts, etc.).

The polyester resin preferably contains a water-dispersible polyester, and more preferably contains a water-dispersible polyester as a major component. Such a water-dispersible polyester may be, for example, a polyester whose water dispersibility has been enhanced by introducing a hydrophilic functional group (e.g., at least one selected from hydrophilic functional groups such as a metal sulfonate salt group, a carboxyl group, an ether group, or a phosphate group) into the polymer. Any appropriate method can be used to introduce a hydrophilic functional group into the polymer, such as copolymerizing a compound having a hydrophilic functional group or modifying a polyester or its precursor (e.g., a polycarboxylic acid component, a polyhydric alcohol component, or an oligomer thereof) to generate a hydrophilic functional group. A preferred water-dispersible polyester is a polyester copolymerized with a compound having a hydrophilic functional group (copolyester).

The polyester resin used as the binder may be primarily composed of saturated polyester or unsaturated polyester. The polyester resin is preferably primarily composed of saturated polyester, and more preferably a saturated polyester that has been given water dispersibility (e.g., saturated copolymer polyester). Such polyester resins (polyester resins that may be prepared in the form of an aqueous dispersion) can be synthesized by any suitable method, or are readily available commercially.

The molecular weight of the polyester resin is preferably 0.5×10 ⁴ to 15×10 ⁴ , more preferably 1×10 ⁴ to 6×10 ⁴ , in terms of a weight average molecular weight (Mw) converted into standard polystyrene as measured by gel permeation chromatography (GPC).

The glass transition temperature (Tg) of the polyester resin is preferably 0°C to 100°C, and more preferably 10°C to 80°C.

(urethane resin)
When the binder contains a urethane-based resin, the urethane-based resin may be of only one type or of two or more types.

The urethane resin is preferably a urethane resin obtained by curing a composition containing a polyol (A) and a polyfunctional isocyanate compound (B).

The polyol (A) may be one type only, or two or more types.

Any suitable polyol having two or more OH groups can be used as polyol (A). Examples of such polyols (A) include polyols (diols) having two OH groups, polyols (triols) having three OH groups, polyols (tetraols) having four OH groups, polyols (pentaols) having five OH groups, and polyols (hexaols) having six OH groups.

As the polyol (A), a glycol having two or more OH groups, such as ethylene glycol or propylene glycol, is preferably used as an essential component. Using a glycol as an essential component in this way makes it possible to provide a urethane-based cured resin that exhibits, for example, excellent coating film strength after curing, adhesion to the substrate, and retention of additives. The glycol content in the polyol (A) is preferably 30% to 100% by weight, more preferably 50% to 100% by weight, even more preferably 70% to 100% by weight, even more preferably 90% to 100% by weight, particularly preferably 95% to 100% by weight, and most preferably substantially 100% by weight.

Examples of polyol (A) include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, polyethylene glycol, polypropylene glycol, polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil-based polyol.

The polyester polyol can be obtained, for example, by an esterification reaction between a polyol component and an acid component.
Examples include:

Examples of acid components include succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anhydrides of these acids.

Examples of polyether polyols include those obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide using initiators such as water, low-molecular-weight polyols (propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (bisphenol A, etc.), and dihydroxybenzenes (catechol, resorcinol, hydroquinone, etc.). Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Examples of polycaprolactone polyols include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

Examples of polycarbonate polyols include polycarbonate polyols obtained by polycondensation of the above polyol components with phosgene; polycarbonate polyols obtained by transesterification of the above polyol components with carbonate diesters such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, and dibenzyl carbonate; copolymer polycarbonate polyols obtained by combining two or more of the above polyol components; polycarbonate polyols obtained by esterification of the above polycarbonate polyols with carboxyl group-containing compounds; and various polycarbonate polyols obtained by esterification of the above polycarbonate polyols with carboxyl group-containing compounds. Examples include polycarbonate polyols obtained by etherifying a recarbonate polyol with a hydroxyl group-containing compound; polycarbonate polyols obtained by transesterifying the above-mentioned various polycarbonate polyols with an ester compound; polycarbonate polyols obtained by transesterifying the above-mentioned various polycarbonate polyols with a hydroxyl group-containing compound; polyester-based polycarbonate polyols obtained by polycondensation of the above-mentioned various polycarbonate polyols with a dicarboxylic acid compound; and copolymer polyether-based polycarbonate polyols obtained by copolymerizing the above-mentioned various polycarbonate polyols with an alkylene oxide.

Examples of castor oil-based polyols include castor oil-based polyols obtained by reacting castor oil fatty acids with the above-mentioned polyol components. Specific examples include castor oil-based polyols obtained by reacting castor oil fatty acids with polypropylene glycol.

The polyfunctional isocyanate compound (B) may be a single type or two or more types.

As the polyfunctional isocyanate compound (B), any suitable polyfunctional isocyanate compound that can be used in a urethanization reaction can be used. Examples of such polyfunctional isocyanate compounds (B) include polyfunctional aliphatic isocyanate compounds, polyfunctional alicyclic isocyanates, and polyfunctional aromatic isocyanate compounds.

Examples of polyfunctional aliphatic isocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of polyfunctional alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of polyfunctional aromatic diisocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

Examples of the polyfunctional isocyanate compound (B) include trimethylolpropane adducts of the various polyfunctional isocyanate compounds described above, biuret compounds formed by reaction with water, and trimers having an isocyanurate ring. These may also be used in combination.

The content of the polyfunctional isocyanate compound (B) relative to the polyol (A) is preferably 5% to 60% by weight, more preferably 8% to 60% by weight, and even more preferably 10% to 60% by weight. By adjusting the content of the polyfunctional isocyanate compound (B) within the above range, the effects of the present invention can be further enhanced.

Urethane resins are typically obtained by curing a composition containing a polyol (A) and a polyfunctional isocyanate compound (B). Such compositions may contain any appropriate other components in addition to the polyol (A) and the polyfunctional isocyanate compound (B), provided that the effects of the present invention are not impaired. Examples of such other components include catalysts, resin components other than polyurethane resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, plasticizers, antioxidants, conductive agents, antioxidants, UV absorbers, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, and solvents.

As a method for curing a composition containing polyol (A) and polyfunctional isocyanate compound (B) to obtain a urethane resin, any appropriate method can be used as long as it does not impair the effects of the present invention, such as a urethane reaction method using bulk polymerization or solution polymerization.

(Other resins)
The top coat layer may further contain, as a binder, other resins than polyester resins and urethane-based resins (e.g., at least one resin selected from acrylic resins, acrylic-styrene resins, acrylic-silicone resins, silicone resins, polysilazane resins, fluororesins, and polyolefin resins), to the extent that the performance of the PSA film is not significantly impaired. In a preferred embodiment of the top coat layer, the binder of the top coat layer is essentially composed of at least one resin selected from the group consisting of polyester resins and urethane-based resins, and the proportion of at least one resin selected from the group consisting of polyester resins and urethane-based resins in the binder is preferably 98% by weight to 100% by weight, more preferably 99% by weight to 100% by weight, and even more preferably 99.5% by weight to 100% by weight. The proportion of the binder in the entire top coat layer is preferably 15% by weight to 95% by weight, and more preferably 25% by weight to 80% by weight.

<Slip agent>
The slip agent preferably contains an ester of a higher fatty acid and a higher alcohol (hereinafter sometimes referred to as "wax ester").

A "higher fatty acid" is preferably a carboxylic acid having 8 or more carbon atoms, more preferably 10 or more carbon atoms, and even more preferably 10 to 40 carbon atoms. The carboxylic acid is preferably a monocarboxylic acid.

A "higher alcohol" is preferably an alcohol having 6 or more carbon atoms, more preferably 10 or more carbon atoms, and even more preferably 10 to 40 carbon atoms. The alcohol is preferably a monohydric or dihydric alcohol, and more preferably a monohydric alcohol.

A top coat layer containing such a wax ester in combination with the aforementioned binder is resistant to whitening even when maintained under high-temperature, high-humidity conditions. Therefore, a pressure-sensitive adhesive film having a substrate with such a top coat layer can have a higher quality appearance.

The top coat layer with the above composition provides excellent whitening resistance (e.g., resistance to whitening even when maintained under high-temperature, high-humidity conditions) for the following reasons: Conventionally used silicone-based lubricants are thought to impart slipperiness to the surface of the top coat layer by bleeding onto the surface. However, the degree of bleeding of these silicone-based lubricants is prone to vary depending on storage conditions (temperature, humidity, age, etc.). For this reason, if the amount of silicone-based lubricant used is set so that adequate slipperiness is achieved over a relatively long period (e.g., approximately three months) from immediately after production of the PSA film when maintained under normal storage conditions (e.g., 25°C, 50% RH), excessive bleeding of the lubricant will occur when the PSA film is stored under high-temperature, high-humidity conditions (e.g., 60°C, 95% RH) for two weeks. Such excessive bleeding of the silicone-based lubricant may cause whitening of the top coat layer (and ultimately the PSA film).

A preferred embodiment of the top coat layer employs a specific combination of a wax ester as the slip agent and a polyester resin as the binder. This combination of slip agent and binder makes it less susceptible to storage conditions for bleeding of the wax ester from the top coat layer. This can improve the whitening resistance of the PSA film.

As the wax ester, one or more compounds represented by the general formula (W) can be preferably used.
X-COO-Y (W)

In formula (W), X and Y are each independently preferably a hydrocarbon group having 10 to 40 carbon atoms, more preferably 10 to 35 carbon atoms, even more preferably 14 to 35 carbon atoms, and particularly preferably 20 to 32 carbon atoms. If the number of carbon atoms is too small, the effect of imparting slipperiness to the top coat layer may be insufficient. The hydrocarbon group may be a saturated or unsaturated hydrocarbon group. The hydrocarbon group is preferably a saturated hydrocarbon group. Furthermore, the hydrocarbon group may have a structure containing an aromatic ring, a structure not containing an aromatic ring (aliphatic hydrocarbon group), a hydrocarbon group with a structure containing an aliphatic ring (alicyclic hydrocarbon group), or a chain (including linear and branched) hydrocarbon group.

The wax ester is preferably a compound in which X and Y in formula (W) are each independently a chain alkyl group having 10 to 40 carbon atoms, more preferably a linear alkyl group having 10 to 40 carbon atoms. Specific examples of such compounds include myricyl cerotate _{( CH3} ( _CH2 ) _24COO ( _CH2 ) _29CH3 ), myricyl palmitate ( _CH3 ( _CH2 ) _14COO ( _CH2 ) _29CH3 ), cetyl palmitate ( _CH3 ( _CH2 ) _14COO ( _CH2 ) _15CH3 ), _and stearyl stearate ( _CH3 ( _CH2 ) _{16COO ( CH2} ) _{17CH3 )} .

The wax ester preferably has a melting point of 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and particularly preferably 75°C or higher. Such wax esters can achieve higher blushing resistance. The wax ester preferably has a melting point of 100°C or lower. Such wax esters are highly effective in imparting slipperiness, making it possible to form a top coat layer with higher scratch resistance. A wax ester with a melting point of 100°C or lower is also preferred because it makes it easier to prepare an aqueous dispersion of the wax ester. For example, myricyl cerotate can be preferably used as such a wax ester.

Natural waxes containing such wax esters can be used as raw materials for the top coat layer. Such natural waxes preferably contain more than 50% by weight of the wax esters (the total content of two or more wax esters, if any) based on the nonvolatile content (NV). These natural waxes preferably contain more than 65% by weight, more preferably more than 75% by weight, and even more preferably more than 75% by weight. Examples of such natural waxes include carnauba wax (which generally contains myricyl cerotate in an amount of preferably more than 60% by weight, more preferably more than 70% by weight, and even more preferably more than 80% by weight), vegetable waxes such as palm wax, and animal waxes such as beeswax and spermaceti. The melting point of such natural waxes is preferably 50°C or higher, more preferably more than 60°C, even more preferably more than 70°C, and especially preferably more than 75°C. Chemically synthesized wax esters may be used as raw materials for the top coat layer, or natural waxes refined to increase the purity of the wax esters may be used. These raw materials may be used alone or in combination.

The proportion of slip agent in the entire top coat layer is preferably 5% to 50% by weight, and more preferably 10% to 40% by weight. If the slip agent content is too low, scratch resistance may be reduced. If the slip agent content is too high, the effect of improving whitening resistance may be insufficient.

The top coat layer may contain other slip agents in addition to the wax ester. Examples of other slip agents include various waxes other than wax esters, such as petroleum waxes (such as paraffin wax), mineral waxes (such as montan wax), higher fatty acids (such as cerotic acid), and neutral fats (such as palmitic acid triglyceride). In addition to the wax ester, silicone-based lubricants, fluorine-based lubricants, etc. may also be contained. A preferred embodiment of the top coat layer is one that is substantially free of silicone-based lubricants and fluorine-based lubricants. For example, the total content of silicone-based lubricants and fluorine-based lubricants is preferably 0.01% by weight or less of the entire top coat layer, and more preferably below the detection limit.

The top coat layer may contain additives such as antistatic components, crosslinking agents, antioxidants, colorants (pigments, dyes, etc.), flow control agents (thixotropic agents, thickeners, etc.), film-forming aids, surfactants (antifoaming agents, dispersants, etc.), and preservatives, as needed.

<Antistatic component of top coat layer>
A preferred embodiment of the top coat layer contains an antistatic component. The antistatic component is a component that can prevent or suppress static buildup in the PSA film. When the top coat layer contains an antistatic component, for example, organic or inorganic conductive substances, various antistatic agents, etc. can be used as the antistatic component. It is also possible to use antistatic agents that can be used in the above-mentioned antistatic layer.

Examples of organic conductive substances include cationic antistatic agents having cationic functional groups such as quaternary ammonium salts, pyridinium salts, primary amino groups, secondary amino groups, and tertiary amino groups; anionic antistatic agents having anionic functional groups such as sulfonates, sulfate ester salts, phosphonates, and phosphate ester salts; amphoteric antistatic agents such as alkylbetaine and its derivatives, imidazoline and its derivatives, and alanine and its derivatives; nonionic antistatic agents such as aminoalcohols and their derivatives, glycerin and its derivatives, and polyethylene glycol and its derivatives; ionic conductive polymers obtained by polymerizing or copolymerizing monomers having the above-mentioned cationic, anionic, or amphoteric ionic conductive groups (e.g., quaternary ammonium salt groups); and conductive polymers such as polythiophene, polyaniline, polypyrrole, polyethyleneimine, and allylamine-based polymers. These antistatic agents may be used alone or in combination.

Examples of inorganic conductive substances include tin oxide, antimony oxide, indium oxide, cadmium oxide, titanium oxide, zinc oxide, indium, tin, antimony, gold, silver, copper, aluminum, nickel, chromium, titanium, iron, cobalt, copper iodide, ITO (indium oxide/tin oxide), and ATO (antimony oxide/tin oxide). Only one type of such inorganic conductive substance may be used, or two or more types may be used.

Examples of antistatic agents include cationic antistatic agents, anionic antistatic agents, amphoteric antistatic agents, nonionic antistatic agents, and ionic conductive polymers obtained by polymerizing or copolymerizing monomers having the above cationic, anionic, or amphoteric ionic conductive groups.

When the top coat layer contains an antistatic component, the antistatic component preferably contains an organic conductive substance. Various conductive polymers can be preferably used as the organic conductive substance. This configuration can achieve both good antistatic properties and high scratch resistance.

Examples of conductive polymers include polythiophene, polyaniline, polypyrrole, polyethyleneimine, and allylamine-based polymers. These conductive polymers may be used alone or in combination with two or more types. They may also be used in combination with other antistatic components (inorganic conductive substances, antistatic agents, etc.).

The amount of conductive polymer used is preferably 1 to 100 parts by weight, more preferably 2 to 70 parts by weight, and even more preferably 3 to 50 parts by weight, per 100 parts by weight of the binder contained in the top coat layer. If the amount of conductive polymer used is too small, the antistatic effect may be reduced. If the amount of conductive polymer used is too large, the compatibility of the conductive polymer in the top coat layer may be insufficient, which may result in a decrease in the appearance quality of the top coat layer or a decrease in solvent resistance.

Preferred examples of the conductive polymer include polythiophene and polyaniline. The polystyrene-equivalent weight average molecular weight Mw of the polythiophene is preferably 40 x 10 ⁴ or less, more preferably 30 x 10 ⁴ or less. The polystyrene-equivalent weight average molecular weight Mw of the polyaniline is preferably 50 x 10 ⁴ or less, more preferably 30 x 10 ⁴ or less. The polystyrene-equivalent weight average molecular weight Mw of the conductive polymer is preferably 0.1 x 10 ⁴ or more, more preferably 0.5 x 10 ⁴ or more. In this specification, polythiophene refers to a polymer of unsubstituted or substituted thiophene. Examples of substituted thiophene polymers include poly(3,4-ethylenedioxythiophene).

When a method for forming a top coat layer is employed in which a coating material for forming the top coat layer is applied to a substrate and then dried or cured, the conductive polymer used in preparing the coating material is preferably a conductive polymer dissolved or dispersed in water (a conductive polymer aqueous solution). Such a conductive polymer aqueous solution can be prepared, for example, by dissolving or dispersing a conductive polymer having a hydrophilic functional group (a conductive polymer that can be synthesized by copolymerizing a monomer having a hydrophilic functional group in its molecule) in water. Examples of the hydrophilic functional group include sulfo groups, amino groups, amido groups, imino groups, hydroxyl groups, mercapto groups, hydrazino groups, carboxyl groups, quaternary ammonium groups, sulfate ester groups (—O—SO ₃ H), and phosphate ester groups (e.g., —O—PO(OH) ₂ ). Such hydrophilic functional groups may form salts. Commercially available polythiophene aqueous solutions include the “Denatron” series manufactured by Nagase Chemtec Corporation. An example of a commercially available aqueous solution of polyaniline sulfonic acid is "aqua-PASS" manufactured by Mitsubishi Rayon Co., Ltd.

In preparing the coating material, a polythiophene aqueous solution is preferably used. The polythiophene aqueous solution is preferably a polythiophene aqueous solution containing polystyrene sulfonate (PSS) (e.g., a polythiophene solution in which PSS is added as a dopant). Such a polythiophene aqueous solution may contain polythiophene:PSS in a mass ratio of preferably 1:1 to 1:10. The total content of polythiophene and PSS in such a polythiophene aqueous solution is preferably 1% to 5% by weight. Commercially available polythiophene aqueous solutions include, for example, H. C. Stark's "Baytron" product. When using a polythiophene aqueous solution containing PSS as described above, the total amount of polythiophene and PSS is preferably 5 to 200 parts by weight, more preferably 10 to 100 parts by weight, and even more preferably 25 to 70 parts by weight, per 100 parts by weight of the binder.

The top coat layer may optionally contain both a conductive polymer and one or more other antistatic components (such as organic conductive substances other than conductive polymers, inorganic conductive substances, antistatic agents, etc.). Preferably, the top coat layer contains substantially no antistatic components other than the conductive polymer. In other words, it is preferable that the antistatic component contained in the top coat layer consists essentially of only the conductive polymer.

<Crosslinking agent>
The top coat layer preferably contains a crosslinking agent. The crosslinking agent can be appropriately selected from melamine-based crosslinking agents, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and other crosslinking agents commonly used for crosslinking resins. By using such a crosslinking agent, at least one of the following effects can be achieved: improved scratch resistance, improved solvent resistance, improved print adhesion, and reduced coefficient of friction (i.e., improved slipperiness). Preferably, the crosslinking agent contains a melamine-based crosslinking agent. The top coat layer may be one in which the crosslinking agent is essentially composed only of a melamine-based crosslinking agent (melamine-based resin) (i.e., the top coat layer does not substantially contain any crosslinking agent other than the melamine-based crosslinking agent).

<One Preferred Embodiment of the Top Coat Layer>
In a preferred embodiment of the top coat layer, when the material of the base layer is at least one selected from polyimide and polyether ether ketone, the top coat layer contains a binder containing a urethane resin and an antistatic component. By adopting a binder containing a urethane resin as the binder for the antistatic component of the top coat layer, the top coat layer can be easily applied to the surface of the base layer made of at least one selected from polyimide and polyether ether ketone, resulting in a good appearance and excellent antistatic properties.

Binders containing polyester resins are often preferred as binders for the antistatic component of the top coat layer. However, for certain substrate layers, such as those made of at least one material selected from polyimide and polyether ether ketone, binders containing polyester resins may have low affinity, potentially resulting in poor appearance after coating and failure to exhibit excellent antistatic properties. As described above, when the substrate layer is made of at least one material selected from polyimide and polyether ether ketone, if the top coat layer contains a binder containing a urethane resin and an antistatic component, the top coat layer can be easily coated onto the surface of the substrate layer, resulting in a good appearance and excellent antistatic properties.

<Formation of Top Coat Layer>
The top coat layer can be suitably formed by a method including applying to the substrate a liquid composition (top coat layer-forming coating material) in which the resin component and optional additives are dispersed or dissolved in an appropriate solvent. For example, a preferred method is to apply the coating material to the first surface of the substrate, dry it, and optionally perform a curing treatment (heat treatment, UV treatment, etc.). The NV (non-volatile content) of the coating material is preferably 5 wt % or less, more preferably 0.05 wt % to 5 wt %, even more preferably 0.05 wt % to 1 wt %, and particularly preferably 0.10 wt % to 1 wt %. When forming a thin top coat layer, the NV of the coating material is preferably 0.05 wt % to 0.50 wt %, more preferably 0.10 wt % to 0.30 wt %. Using a coating material with such a low NV can result in a more uniform top coat layer.

The solvent constituting the coating material for forming the top coat layer is preferably one that can stably dissolve or disperse the top coat layer-forming components. Such a solvent can be an organic solvent, water, or a mixture thereof. Examples of organic solvents include at least one selected from the following: esters such as ethyl acetate; ketones such as methyl ethyl ketone, acetone, and cyclohexanone; cyclic ethers such as tetrahydrofuran (THF) and dioxane; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic alcohols such as methanol, ethanol, n-propanol, isopropanol, and cyclohexanol; and glycol ethers such as alkylene glycol monoalkyl ethers (e.g., ethylene glycol monomethyl ether and ethylene glycol monoethyl ether) and dialkylene glycol monoalkyl ethers. Preferably, the solvent constituting the coating material for forming the top coat layer is water or a mixture of water as the main component (e.g., a mixture of water and ethanol).

<Properties of the top coat layer>
The thickness of the top coat layer is preferably 3 nm to 500 nm, more preferably 3 nm to 100 nm, and even more preferably 3 nm to 60 nm. If the thickness of the top coat layer is too large, the transparency (light transmittance) of the PSA film may be easily reduced. If the thickness of the top coat layer is too small, it may be difficult to form the top coat layer uniformly. For example, the thickness of the top coat layer may vary greatly depending on the location, which may result in unevenness in the appearance of the PSA film.

The thickness of the topcoat layer can be determined by observing the cross-section of the topcoat layer using a transmission electron microscope (TEM). For example, a target sample (such as a substrate with a topcoat layer or an adhesive film with a substrate) can be stained with heavy metals to clarify the topcoat layer, then embedded in resin. The results obtained by TEM observation of the sample cross-section using ultrathin sectioning can be used to determine the thickness of the topcoat layer. A Hitachi TEM (model "H-7650"), for example, can be used as the TEM. In the examples described below, cross-sectional images obtained at an accelerating voltage of 100 kV and a magnification of 60,000x are binarized, and the topcoat layer thickness (average thickness within the field of view) is measured by dividing the cross-sectional area of the topcoat by the sample length within the field of view. Note that heavy metal staining may be omitted if the topcoat layer can be observed clearly enough without it. Alternatively, the thickness of the topcoat layer can be determined by creating a calibration curve and performing calculations to correlate the thickness determined by TEM with the results of measurements using various thickness detection devices (e.g., surface roughness meter, interference thickness meter, infrared spectrometer, various X-ray diffraction devices, etc.).

The surface resistivity measured on the surface of the top coat layer is preferably 10 ^Ω or less, more preferably ¹⁰ Ω to ¹⁰ Ω, even more preferably 10 Ω to ¹⁰ Ω, particularly preferably 5× ^{10 Ω} to ¹⁰ Ω, and most preferably ¹⁰ Ω to ¹⁰ Ω. PSA films exhibiting such a surface resistivity can be suitably used, for example, as PSA films used in the processing or transport process of static-sensitive items such as liquid crystal cells and semiconductor devices. The surface resistivity value can be calculated from the surface resistance value measured in an atmosphere of 23°C and 50% RH using a commercially available insulation resistance measuring device.

The coefficient of friction of the top coat layer is preferably 0.4 or less. A top coat layer with such a low coefficient of friction allows the top coat layer to deflect a load (a load that could cause scratches) along its surface, reducing the frictional force caused by the load. This reduces the likelihood of cohesive failure (internal failure of the top coat layer) or interfacial failure (peel-off of the top coat layer from the back surface of the substrate) of the top coat layer. Therefore, scratches on the PSA film can be more effectively prevented. The lower limit of the coefficient of friction is preferably 0.1 or more, more preferably 0.15 or more, taking into account the balance with other properties (e.g., appearance quality and printability). The coefficient of friction can be determined, for example, by rubbing the surface of the top coat layer with a normal load of 40 mN under a measurement environment of 23°C and 50% RH. The amount of slip agent used should be set to achieve a desired coefficient of friction. To adjust the coefficient of friction, it is also effective to increase the crosslink density of the top coat layer by, for example, adding a crosslinking agent or adjusting the film formation conditions.

It is preferable that the back surface of the adhesive film (the surface of the topcoat layer) be easily printable with oil-based ink (e.g., using an oil-based marking pen). Such an adhesive film is suitable for marking and displaying the identification number of the adherend (e.g., optical component) to be protected during processing, transportation, etc. of the adherend with the adhesive film attached. Therefore, a surface protection film that not only has excellent appearance quality but also excellent printability is preferred. For example, it is preferable that the film has high printability with oil-based inks that use alcoholic solvents and contain pigments. It is also preferable that the printed ink is resistant to rubbing or transfer (i.e., has excellent print adhesion). It is preferable that the adhesive film has solvent resistance to the extent that wiping the print with alcohol (e.g., ethyl alcohol) to correct or erase the print does not cause a noticeable change in appearance.

The top coat layer preferably contains a wax ester as a slip agent, so sufficient slip properties (e.g., the preferred friction coefficient described above) can be achieved even in an embodiment in which the surface of the top coat layer is not subjected to an additional release treatment (e.g., a treatment in which any appropriate release agent, such as a silicone-based release agent or a long-chain alkyl-based release agent, is applied and dried). This embodiment in which the surface of the top coat layer is not subjected to an additional release treatment is preferable in that it can prevent whitening caused by the release agent (e.g., whitening due to storage under heated and humidified conditions). It is also advantageous in terms of solvent resistance.

The PSA film may also be implemented in an embodiment that includes other layers in addition to the substrate, PSA layer, and top coat layer. Examples of the location of such "other layers" include between the first surface (back surface) of the substrate and the top coat layer, and between the second surface (front surface) of the substrate and the PSA layer. The layer located between the back surface of the substrate and the top coat layer may be, for example, a layer containing an antistatic component (antistatic layer). The layer located between the front surface of the substrate and the PSA layer may be, for example, an undercoat layer (anchor layer) or an antistatic layer that enhances the anchoring of the PSA layer to the second surface. The PSA film may also have a configuration in which an antistatic layer is located on the front surface of the substrate, an anchor layer is located on the antistatic layer, and an PSA layer is located on the anchor layer.

<<Foldable and rollable devices>>
The adhesive film of the present invention has excellent flexibility and transparency, and therefore can be suitably provided for, for example, bendable devices (devices that can be bent) having movable bending parts, foldable devices (devices that can be folded), and rollable devices (devices that can be rolled up). The adhesive film of the present invention is particularly excellent in flexibility and transparency, and therefore can be suitably provided for foldable devices (devices that can be folded) and rollable devices (devices that can be rolled up), which have been more difficult to apply until now.

The foldable device of the present invention comprises the adhesive film of the present invention. The foldable device of the present invention may also include any other appropriate components, as long as it comprises the adhesive film of the present invention.

The rollable device of the present invention comprises the adhesive film of the present invention. The rollable device of the present invention may also include any other appropriate components, as long as it comprises the adhesive film of the present invention.

Figure 1 is a schematic cross-sectional view showing one embodiment of a foldable device of the present invention, as a representative example of one usage form of the adhesive film of the present invention. In Figure 1, the foldable device 1000 of the present invention comprises a cover film 10, an adhesive layer 20, a polarizing plate 30, an adhesive layer 40, a touch sensor 50, an adhesive layer 60, an OLED 70, and an adhesive film 100 of the present invention. In Figure 1, the adhesive film 100 of the present invention is composed of an adhesive layer 80 and a substrate layer 90. The adhesive layer 20, the adhesive layer 40, and the adhesive layer 60 may be adhesive layers containing an adhesive of the same composition as the adhesive layer 80 constituting the adhesive film 100 of the present invention, or may be adhesive layers containing an adhesive of a different composition.

The adhesive film of the present invention has excellent flexibility and transparency, and can therefore be suitably provided on the back surface (the surface opposite the display surface) of, for example, a bendable device (a device that can be bent), a foldable device (a device that can be folded), or a rollable device (a device that can be rolled up). Figure 1 shows the adhesive film provided on the back surface (the surface opposite the display surface) of a foldable device (a device that can be folded).

The present invention will be explained in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the following explanation, "parts" and "%" are by weight unless otherwise specified.

<tan δ>
Measurements were performed using a viscoelasticity measuring device "RSA-G2" (manufactured by TA Instruments Japan Co., Ltd.) in tension mode, with a sample size of 5 mm wide x 15 mm distance and an axial force of 100 g. In strain sweep (oscillation amplitude) mode, the frequency was 1 Hz, the measurement temperature was 90 ° C, the immersion time was 60 seconds, and the strain measurement range was set to 0.01% to 1.0%, and measurements were performed at the strains in between. The tan δ values at each strain were graphed, and the tan δ values at 0.1% strain and 0.7% strain were calculated from the graph. Regarding thickness, the rigidity of the substrate was large in both the storage modulus and loss modulus relative to the adhesive film, and the influence of the adhesive was negligible. Measurements were performed by inputting only the thickness of the substrate excluding the thickness of the adhesive.
Tan δ was calculated using the following formula.
tan δ = loss modulus/storage modulus

<Bending test>
As shown in Figure 2, a flat pressure-sensitive adhesive film was bent to 6Φ with the pressure-sensitive adhesive layer facing outward, and sandwiched between the silicone-treated surfaces of a silicone-treated separator, and held at 90°C for 48 hours. The film was then released from the bend and left at 23°C and 50% RH for 24 hours, after which the angle of the bent film was measured. A film that had completely returned to its original state was recorded as 180°, and a film that maintained the bent state from the initial fixation was recorded as 0°.

<Peeling evaluation>
An adhesive film was attached to a 50 μm thick PET film (S10, manufactured by Toray Industries, Inc.), folded so that the adhesive film was on the inside as shown in Figure 3, and held at 90°C for 48 hours. After that, the fixed state was released and peeling of the adhesive film from the PET film was visually observed. Evaluation was performed according to the following criteria.
○: No peeling from the PET film was observed.
×: Peeling from the PET film was observed.

<Measurement of haze and total light transmittance>
Using a haze meter HM-150 (manufactured by Murakami Color Research Laboratory Co., Ltd.), calculation was performed in accordance with JIS-K-7136 using the formula: haze (%) = (Td/Tt) × 100 (Td: diffuse transmittance, Tt: total luminous transmittance). The total luminous transmittance was measured in accordance with JIS-K-7316.

<Young's modulus>
The sample pieces were cut into strips with a width of 10 mm, and the strip-shaped sample pieces were measured by pulling them in the longitudinal direction with a chuck distance of 100 mm using a universal tension and compression testing machine (Tensilon) in a temperature environment of 25°C, and the Young's modulus was determined from the resulting S-S (Strain-Strength) curve. The measurement conditions were a tensile speed of 200 mm/min and a chuck distance of 50 mm. The Young's modulus was determined from the S-S curve by creating a graph of the S-S curve, drawing a tangent (linear equation) to the graph in the displacement range of 1 mm to 2 mm, and determining the Young's modulus from the slope of the tangent.

<Adhesive strength>
The adhesive film was cut into a width of 25 mm and a length of 150 mm to prepare a sample for evaluation. The adhesive layer surface of the evaluation sample was attached to a glass plate (manufactured by Matsunami Glass Industrial Co., Ltd., product name: Microslide Glass S) using a 2.0 kg roller in one stroke in an atmosphere of 23°C and 50% RH. After aging for 30 minutes in an atmosphere of 23°C and 50% RH, the sample was peeled off at a peel angle of 180° and a pulling rate of 300 mm/min using a universal tensile tester (manufactured by Minebea Co., Ltd., product name: TCM-1kNB) to measure the adhesive strength.

<Applyability>
The number of circular irregularities that occurred on the applied top coat layer (containing an antistatic layer) was counted. Two A4 size sheets were prepared, and the average number was calculated.
A score of 2 or less was judged as good, and a score of 3 or more was judged as bad. The circular uneven areas were areas where the thickness of the top coat layer was thin, which was a defect in terms of appearance, and areas where the antistatic agent was repelled and could not be applied at all were judged as "repellent."

<Surface Resistivity (for Example 8)>
In Example 8, the layer on which the antistatic treatment layer was formed was measured at a voltage of 10 V using a volume resistivity meter Model 152-1 152P-2P probe (manufactured by Trek Japan Co., Ltd.).

<Surface Resistivity (for Examples 9 and 13 )>
In Examples 9 and 13 , a resistivity meter ("Hiresta UP MCP-HT450 type" manufactured by Mitsubishi Chemical Analytical Co., Ltd.) was used to measure the surface resistivity by contacting a URS probe with the surface of the PSA film on which the PSA layer was not attached, under the conditions of an applied voltage of 100 V and a voltage application time of 10 seconds.

[Production Example 1]: Preparation of Pressure-Sensitive Adhesive Composition A 63 parts by weight of 2-ethylhexyl acrylate (2EHA) as monomer components, 15 parts by weight of N-vinyl-2-pyrrolidone (NVP), 9 parts by weight of methyl methacrylate (MMA), 13 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 133 parts by weight of ethyl acetate as a polymerization solvent were placed in a separable flask and stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature was raised to 65 ° C. and the reaction was allowed to proceed for 10 hours. Thereafter, ethyl acetate was added to obtain a solution of acrylic polymer (a) with a solids concentration of 30 wt%.
Next, an isocyanate-based crosslinking agent (trade name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) was added to the solution of the acrylic polymer ( a ) so that the amount was 1 part by weight in terms of solid content per 100 parts by weight of the acrylic polymer (a) (solid content), thereby preparing a pressure-sensitive adhesive composition A.

[Production Example 2]: Preparation of Pressure-Sensitive Adhesive Composition B A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with 96.2 parts by weight of 2-ethylhexyl acrylate (2EHA), 3.8 parts by weight of hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 150 parts by weight of ethyl acetate, and nitrogen gas was introduced while gently stirring. The liquid temperature in the flask was maintained at around 60°C, and a polymerization reaction was carried out for 6 hours to prepare a solution (40 wt%) of acrylic polymer (b). The weight-average molecular weight of the acrylic polymer (b) was 540,000.
Next, a solution (40% by weight) of the acrylic polymer (b) was diluted to 25% by weight with ethyl acetate, and to 400 parts by weight (100 parts by weight of solids) of this solution were added 4 parts by weight (4 parts by weight of solids) of an isocyanurate of hexamethylene diisocyanate, a trifunctional isocyanate compound (Tosoh Corporation, Coronate HX) as a crosslinking agent, 2 parts by weight (0.02 parts by weight of solids) of dioctyltin dilaurate (Tokyo Fine Chemical Co., Ltd., Envirizer OL-1, 1% by weight ethyl acetate solution) as a crosslinking catalyst, and 3 parts by weight of acetylacetone, followed by mixing and stirring to prepare PSA composition B.

[Example 1]
A commercially available release liner (Diafoil MRF-38, Mitsubishi Plastics, Inc.) was prepared. Pressure-sensitive adhesive composition A was applied to one surface (release surface) of the release liner so that the thickness after drying would be 25 μm, and the coating was dried at 130° C. for 3 minutes. In this way, a pressure-sensitive adhesive layer having a thickness of 25 μm and composed of acrylic pressure-sensitive adhesive A corresponding to pressure-sensitive adhesive composition A was formed on the release surface of the release liner.
A 50 μm thick polyimide substrate (trade name "Kapton", manufactured by DuPont-Toray Co., Ltd.) was prepared as the substrate layer. The pressure-sensitive adhesive layer formed on the release liner was attached to one side of this substrate layer. The release liner was left on the pressure-sensitive adhesive layer and used to protect the surface of the pressure-sensitive adhesive layer (pressure-sensitive adhesive layer surface). The obtained structure was passed through a laminator (0.3 MPa, speed 0.5 m/min) at 80°C once, and then aged in an oven at 50°C for 1 day. In this way, a pressure-sensitive adhesive film (1) was obtained.
The results are shown in Table 1.

[Example 2]
An adhesive film (2) was obtained in the same manner as in Example 1, except that a polyimide-based substrate (trade name "UPILEX-50S", manufactured by Ube Industries, Ltd.) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Example 3]
An adhesive film (3) was obtained in the same manner as in Example 1, except that a polyimide-based substrate (trade name "Pixio BP", manufactured by Kaneka Corporation) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Example 4]
An adhesive film (4) was obtained in the same manner as in Example 1, except that a polyimide-based substrate (trade name "UPILEX-50RN", manufactured by Ube Industries, Ltd.) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Example 5]
The same procedure as in Example 1 was carried out except that a 50 μm thick polyether ether ketone (PEEK)-based substrate (trade name “Shin-Etsu Sepla Film”, non-stretched film formation, highly crystalline, manufactured by Shin-Etsu Polymer Co., Ltd.) was used as the substrate layer. An adhesive film (5) was obtained.
The results are shown in Table 1.

[Example 6]
An adhesive film (6) was obtained in the same manner as in Example 1, except that a polyimide-based substrate (trade name "Neoprim S100", manufactured by Mitsubishi Gas Chemical Company, Inc.) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Example 7]
An adhesive film (7) was obtained in the same manner as in Example 1, except that a polyether ether ketone (PEEK)-based substrate (trade name "Expeak", manufactured by Kurabo Industries, Ltd.) having a thickness of 25 μm was used as the substrate layer.
The results are shown in Table 1.

[Comparative Example 1]
An adhesive film (C1) was obtained in the same manner as in Example 1, except that a polyester-based substrate (trade name "Lumirror S10", manufactured by Toray Industries, Inc.) having a thickness of 25 μm was used as the substrate layer.
The results are shown in Table 1.

[Comparative Example 2]
A pressure-sensitive adhesive film (C2) was obtained in the same manner as in Example 1, except that a polyester-based substrate (trade name "Lumirror S10", manufactured by Toray Industries, Inc.) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Comparative Example 3]
An adhesive film (C3) was obtained in the same manner as in Example 1, except that adhesive composition B was used instead of adhesive composition A, and a polyester-based substrate (product name "Lumirror S10", manufactured by Toray Industries, Inc.) having a thickness of 50 μm was used as the substrate layer.
The results are shown in Table 1.

[Comparative Example 4]
A PSA film (C4) was obtained in the same manner as in Example 6, except that PSA composition B was used instead of PSA composition A.
The results are shown in Table 1.

[Comparative Example 5]
A PSA film (C5) was obtained in the same manner as in Example 7, except that PSA composition B was used instead of PSA composition A.
The results are shown in Table 1.

[Production Example 3]: Preparation of Antistatic Treated Polyimide Film A An antistatic agent solution was prepared by diluting 10 parts by weight of an antistatic agent (Microsolver RMd-142 manufactured by Solvex, mainly composed of tin oxide and polyester resin) with a mixed solvent consisting of 30 parts by weight of water and 70 parts by weight of methanol. The obtained antistatic agent solution was applied to a 50 μm-thick polyimide substrate (trade name "Kapton", manufactured by DuPont-Toray Co., Ltd.) using a Meyer bar, and the solvent was removed by drying at 130°C for 1 minute to form an antistatic layer (thickness: 0.2 μm), thereby preparing antistatic treated polyimide film A.

[Example 8]
An adhesive film (8) was obtained in the same manner as in Example 1, except that antistatic treated polyimide film A was used as the substrate, and the surface resistance was 5×10 ⁶ Ω.

[Production Example 4]: Preparation of topcoat layer-forming polyimide film B <Preparation of coating material B>
A dispersion containing 25% by weight of a polyester resin (binder) was prepared (manufactured by Toyobo Co., Ltd., trade name "Binalol MD-1480" (aqueous dispersion of saturated copolymer polyester resin); hereinafter also referred to as "binder dispersion").
As a slipping agent, an aqueous dispersion of carnauba wax (manufactured by Nippon Wax Co., Ltd., trade name "Refined Carnauba Wax No. 2 Powder") (hereinafter also referred to as "slipping agent dispersion") was prepared.
Furthermore, an aqueous solution containing 0.5 wt % of poly(3,4-dioxythiophene) (PEDOT) and 0.8 wt % of polystyrene sulfonate (number average molecular weight 150,000) (PSS) (manufactured by H.C. Stark, trade name "Baytron P"; hereinafter also referred to as "aqueous conductive polymer solution") was prepared as a conductive polymer.
To a mixed solvent of water and ethanol (weight ratio 50:50), 100 parts by weight (solid content) of the binder dispersion, 30 parts by weight (solid content) of the slip agent dispersion, 50 parts by weight (solid content) of the conductive polymer aqueous solution, and 7 parts by weight of the melamine-based crosslinking agent were added, and the mixture was stirred for about 20 minutes to thoroughly mix. In this way, a coating material B with an NV of about 0.15% by weight was prepared.
<Preparation of Topcoat Layer-Forming Polyimide Film B>
The coating material B was applied to a 50 μm-thick polyimide substrate (trade name "Kapton", manufactured by DuPont-Toray Co., Ltd.) using a bar coater, and then dried by heating at 130° C. for 2 minutes. In this way, a substrate (topcoat layer-formed polyimide film B) having a 10 nm-thick transparent topcoat layer on one side of the polyimide substrate was produced.

[Production Example 5]: Preparation of topcoat layer-forming polyimide film C <Preparation of coating material C>
As a binder, an aqueous solution containing 25% by weight of a polyester urethane resin composed of 25 mol% ethylene glycol, 25 mol% neopentyne glycol, 30 mol% terephthalic acid, 10 mol% adipic acid, and 10 mol% tolylene diisocyanate (hereinafter also referred to as "binder dispersion") was prepared.
As a slipping agent, an aqueous dispersion of carnauba wax (manufactured by Nippon Wax Co., Ltd., trade name "Refined Carnauba Wax No. 2 Powder") (hereinafter also referred to as "slipping agent dispersion") was prepared.
Furthermore, an aqueous solution containing 0.5 wt % of poly(3,4-dioxythiophene) (PEDOT) and 0.8 wt % of polystyrene sulfonate (number average molecular weight 150,000) (PSS) (manufactured by H.C. Stark, trade name "Baytron P"; hereinafter also referred to as "aqueous conductive polymer solution") was prepared as a conductive polymer.
Furthermore, an aqueous solution containing 10% by weight of polyethylene glycol (PEG) alkyl ether and 10% by weight of polyvinyl alcohol was prepared as a dispersant.
To a mixed solvent of water and ethanol (weight ratio 50:50), 40 parts by weight of the binder dispersion, 5 parts by weight of the lubricant dispersion, 8 parts by weight of the conductive polymer aqueous solution, 40 parts by weight of the dispersant, and 7 parts by weight of the melamine-based crosslinking agent were added, and the mixture was stirred for about 20 minutes to thoroughly mix. In this way, a coating material C with an NV of about 0.30% by weight was prepared.
<Preparation of Topcoat Layer-Forming Polyimide Film C>
The coating material C was applied to a 50 μm-thick polyimide substrate (trade name "Kapton", manufactured by DuPont-Toray Co., Ltd.) using a bar coater, and then dried by heating at 130° C. for 2 minutes. In this way, a substrate (topcoat layer-formed polyimide film C) having a 50 nm-thick transparent topcoat layer on one side of the polyimide substrate was produced.

[Example 9]
An adhesive film (9) was obtained in the same manner as in Example 1, except that the topcoat layer-forming polyimide film B was used as the substrate.
The results are shown in Table 2 .

[Example 13]
An adhesive film (13) was obtained in the same manner as in Example 1, except that the topcoat layer-forming polyimide film C was used as the substrate.
The results are shown in Table 2 .

The adhesive film of the present invention has excellent flexibility and transparency, making it suitable for use in, for example, bendable devices (devices that can be bent) with movable bending portions, foldable devices (devices that can be folded), and rollable devices (devices that can be rolled up).

1000 Foldable device 100 Adhesive film 10 Cover film 20 Adhesive layer 30 Polarizer 40 Adhesive layer 50 Touch sensor 60 Adhesive layer 70 OLED
80 adhesive layer 90 substrate layer 1 6Φ glass rod 2 silicone treated separator 3 adhesive layer 4 fixing glass 5 PET film

Claims (16)

A pressure-sensitive adhesive film having a base layer and a pressure-sensitive adhesive layer,
the material of the substrate layer is at least one selected from polyimide and polyether ether ketone,
the pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive,
the adhesive strength of the pressure-sensitive adhesive layer to a glass plate at 23°C, a pulling speed of 300 mm/min, and a 180° peel angle is 1 N/25 mm or more;
The thickness of the substrate layer is 10 μm to 100 μm,
The thickness of the adhesive layer is 10 μm to 100 μm,
tanδ (0.7%) at a strain of 0.7% measured in a tensile mode of a viscoelasticity measuring device is 0.1 or less;
Adhesive film. The pressure-sensitive adhesive film according to claim 1, wherein the film is bent at 6Φ, held at 90 ° C. for 48 hours, then released from the bend, and left at 23 ° C. and 50% RH for 24 hours. The bending angle after this is 60 degrees to 180 degrees. The pressure-sensitive adhesive film according to claim 1 or 2 , further comprising a top coat layer on the surface of the substrate layer opposite to the surface having the pressure-sensitive adhesive layer. The pressure-sensitive adhesive film according to claim 3 , wherein the top coat layer contains a binder containing at least one selected from a polyester resin and a urethane resin. The pressure-sensitive adhesive film according to claim 4 , wherein the binder comprises a urethane resin. The pressure-sensitive adhesive film according to claim 3 , wherein the top coat layer contains an antistatic component. The pressure-sensitive adhesive film according to any one of claims 1 to 6 , wherein the base layer has a Young's modulus at 23°C of 6.0 x 10 ⁷ Pa or more. 3. The pressure-sensitive adhesive film according to claim 1 or 2, further comprising a top coat layer on the surface of the base layer opposite to the surface having the pressure-sensitive adhesive layer, the top coat layer containing a binder containing a urethane resin and an antistatic component, and the material of the base layer is at least one selected from polyimide and polyether ether ketone. The pressure-sensitive adhesive film according to any one of claims 1 to 8 , which has a total light transmittance of 20% or more. The adhesive film according to any one of claims 1 to 9, having a haze of 15% or less. The adhesive film according to claim 1 , which is attached to a foldable member. The adhesive film according to claim 11 , wherein the foldable member is an OLED. The adhesive film according to any one of claims 1 to 10 , which is attached to a rollable member. The adhesive film of claim 13 , wherein the rollable member is an OLED. A foldable device comprising the adhesive film according to any one of claims 1 to 10 . A rollable device comprising the adhesive film according to any one of claims 1 to 10 .