JP7701202B2 - Optical film with release film - Google Patents

Description

The present invention relates to an optical film with a release film.

The display panel has a laminated structure including, for example, a pixel panel, a touch panel, and a transparent cover film. An optical film having a predetermined optical function is provided in the laminated structure of the display panel. Examples of the optical film include a film-like polarizing plate and a retardation film. The optical film is manufactured, for example, as an optical film with a release film, in which an adhesive layer and a release film are provided on each of both sides of the optical film. The optical film with a release film is described, for example, in Patent Document 1 below.

JP 2020-190754 A

Figure 6 is a schematic cross-sectional view of film Z as an example of a conventional optical film with a release film. Film Z includes a release film 91, an adhesive layer 92, an optical film 93, an adhesive layer 94, and a release film 95, arranged in that order in the thickness direction T. The adhesive layer 92 is attached to one side of the optical film 93. The adhesive layer 94 is attached to the other side of the optical film 93. The release film 91 is releasably attached to the adhesive layer 92. The release film 95 is releasably attached to the adhesive layer 94. At the end E' of film Z, the edge 91e of the release film 91, the edge 92e of the adhesive layer 92, the edge 93e of the optical film 93, the edge 94e of the adhesive layer 94, and the edge 95e of the release film 95 are flush with each other.

When such a film Z is used in the manufacturing process of a display panel, first, the release film 91 is peeled off from the adhesive layer 92 (first peeling process). In this process, first, at the end E' of the film Z, a force for lifting the release film 91 from the adhesive layer 92 is applied to the release film 91 as a load for starting peeling. This load includes both the force required to sufficiently deform the release film 91 at the end E' and the force required to pull the release film 91 away from the adhesive layer 92 that elastically deforms following the deformation of the release film 91. At the end E', the application of such a load causes the end of the release film 91 to deform so as to be pulled away from the edge 92e of the adhesive layer 92. Following this, the end of the release film 91 is pulled in a direction away from the edge 92e so that the peeling between the release film 91 and the adhesive layer 92 progresses, and the release film 91 is removed from the adhesive layer 92. After this, the optical film 93 is bonded to a first adherend (not shown) such as a pixel panel through the exposed adhesive layer 92. Next, the release film 95 is peeled off from the adhesive layer 94 (second peeling process). Next, the optical film 93 is bonded to a second adherend (not shown) through the adhesive layer 94 exposed by this peeling.

Meanwhile, progress is being made in the development of foldable display panels that can be repeatedly folded, for example for use in smartphones and tablet devices. In foldable display panels, each element in the laminated structure is required to be thin and flexible.

However, in the conventional film Z, the thinner the optical film 93, the more likely it is that the load for initiating peeling in the first peeling step described above will cause significant deformation of the optical film 93 at the end E' of the film Z. Such deformation of the optical film 93 causes deformation of the adhesive layer 94 attached to the optical film 93, and pulls the edge 94e of the adhesive layer 94 away from the release film 95. Once the edge 94e is separated from the release film 95, separation between the adhesive layer 94 and the release film 95 is likely to progress. If separation between the adhesive layer 94 and the release film 95 progresses in the first peeling step, the next step cannot be carried out.

The present invention provides an optical film with a release film that is suitable for peeling a light release film from a thin optical film with double-sided adhesive layers while suppressing peeling of the heavy release film.

The present invention [1] includes an optical film with an adhesive layer, the optical film including an optical film having a first surface and a second surface opposite to the first surface, a first adhesive layer attached to the first surface and having a first adhesive surface opposite to the optical film, and a second adhesive layer attached to the second surface and having a second adhesive surface opposite to the optical film, a light release film arranged on the first adhesive surface, and a heavy release film arranged on the second adhesive surface, the optical film having a thickness of 100 μm or less, a side uneven end portion in which the first edge of the first adhesive layer and the second edge of the second adhesive layer are recessed from the respective edges of the optical film, the light release film, and the heavy release film in an in-plane direction perpendicular to the thickness direction of the optical film, and the side uneven end portion has a first recession length of the first edge from the edge of the light release film smaller than a second recession length of the second edge from the edge of the heavy release film.

At the uneven side end of the optical film with release film of the present invention, as described above, the first edge of the first adhesive layer is retracted from the edges of the optical film, the light release film, and the heavy release film in the in-plane direction of the optical film. At such an uneven side end, the light release film has a free portion to which the first adhesive layer is not attached. Therefore, at the uneven side end, when peeling the light release film from the first adhesive layer, the free portion of the light release film is first turned up and deformed, and then the end of the light release film that has already been turned up and deformed is pulled to separate the light release film from the first edge of the first adhesive layer. That is, in the peeling start process, the force (first force) for sufficiently deforming the end of the light release film and the force (second force) for pulling the light release film away from the first edge of the first adhesive layer, which elastically deforms following the deformation of the light release film, are not required at the same time (in contrast, in the above-mentioned film Z, the first force and the second force are required at the same time, and therefore the force required in the peeling start process is large). Such an optical film with a release film is suitable for reducing the force required in the peeling start process. The smaller this force is, the more the deformation of the thin optical film with a thickness of 100 μm or less is suppressed in the peeling start process of the light release film, and the deformation of the second adhesive layer is also suppressed, and therefore the second edge of the second adhesive layer is suppressed from separating from the heavy release film.

In addition, as described above, at the side unevenness end of the optical film with the release film, the first retraction length (the distance from the edge of the light release film in the in-plane direction of the film to the first edge of the first adhesive layer) is smaller than the second retraction length (the distance from the edge of the heavy release film to the second edge of the second adhesive layer in the in-plane direction of the film). That is, at the side unevenness end, the second edge of the second adhesive layer is retracted from the first edge of the first adhesive layer in the in-plane direction of the film. This configuration is suitable for suppressing deformation of the second adhesive layer when the second force for pulling the light release film away from the first edge of the first adhesive layer acts on the optical film with the release film during the process of starting to release the light release film, and therefore is suitable for suppressing the second edge of the second adhesive layer from separating from the heavy release film.

The present invention [2] includes the optical film with a release film described in [1] above, in which the distance between the first edge and the second edge in the in-plane direction is 1 μm or more.

This configuration is preferable for suppressing the above-mentioned deformation of the second adhesive layer during the initiation of peeling of the light release film, and is therefore preferable for suppressing the second edge of the second adhesive layer from separating from the heavy release film.

The present invention [3] includes the optical film with release film described in [1] or [2] above, in which the first retraction length is 20 μm or more.

This configuration is suitable for sufficiently turning up and deforming the end portion (the free portion) of the light release film before the light release film is pulled away from the first edge of the first adhesive layer during the process of initiating peeling of the light release film, and is therefore preferable for reducing the net force required to initiate peeling of the light release film.

The present invention [4] includes an optical film with a release film according to any one of [1] to [3] above, in which the ratio of the first retraction length to the thickness of the first pressure-sensitive adhesive layer is 0.4 or more and 8 or less.

This configuration is suitable for sufficiently turning up and deforming the end portion (the free portion) of the light release film before the light release film is pulled away from the first edge of the first adhesive layer during the process of initiating peeling of the light release film, and is therefore preferable for reducing the net force required to initiate peeling of the light release film.

The present invention [5] includes an optical film with a release film according to any one of [1] to [4] above, in which a first peel initiation force for initiating peeling of the light release film from the first adhesive surface is smaller than a second peel initiation force for initiating peeling of the heavy release film from the second adhesive surface.

This configuration is preferable for suppressing the above-mentioned deformation of the second adhesive layer during the initiation of peeling of the light release film, and is therefore preferable for suppressing the second edge of the second adhesive layer from separating from the heavy release film.

The present invention [6] includes the optical film with a release film described in [5] above, in which the ratio of the first peel initiation force to the second peel initiation force is 0.8 or less.

This configuration is preferable for suppressing the above-mentioned deformation of the second adhesive layer during the initiation of peeling of the light release film, and is therefore preferable for suppressing the second edge of the second adhesive layer from separating from the heavy release film.

The present invention [7] includes the optical film with a release film described in [6] above, in which the first peel initiation force is less than 800 gf/25 mm.

This configuration is preferable for preventing the second edge of the second adhesive layer from separating from the heavy release film during the start of peeling of the light release film, and for reducing the load on the optical film.

The present invention [8] includes an optical film with a release film according to the above [6] or [7], in which the second peel initiation force is 800 gf/25 mm or less.

This configuration is preferable for preventing the second edge of the second adhesive layer from separating from the heavy release film during the process of initiating peeling of the light release film, while reducing the load on the optical film during the process of initiating peeling of the heavy release film from the second adhesive layer.

1 is a schematic cross-sectional view of one embodiment of an optical film with a release film of the present invention. 2 is a partially enlarged schematic cross-sectional view of the optical film with a release film shown in FIG. 1. An example of a method of using the optical film with a release film of the present invention is shown in Fig. 3A, which shows a first peeling step of peeling off a light release film, Fig. 3B, which shows a first bonding step of bonding an optical film to a first adherend via a first pressure-sensitive adhesive layer, Fig. 3C, which shows a second peeling step of peeling off a heavy release film, and Fig. 3D, which shows a second bonding step of bonding an optical film to a second adherend via a second pressure-sensitive adhesive layer. FIG. 4 is a schematic diagram for explaining the blade angle of the rotary blade used in the external shaping process in the examples and comparative examples. 1 shows an example of a graph obtained by a peel test in which a release film on a pressure-sensitive adhesive layer is peeled off from the pressure-sensitive adhesive layer. FIG. 1 is a schematic cross-sectional view of a conventional optical film with a release film.

As shown in FIG. 1, the optical film X as an embodiment of the optical film with a release film of the present invention includes a light release film 40, an optical film Y with an adhesive layer, and a heavy release film 50 in this order in the thickness direction T. The optical film X extends in an in-plane direction D perpendicular to the thickness direction T. The optical film Y with an adhesive layer is an element disposed at a light passing portion in a foldable device. An example of a foldable device is a foldable display panel. The foldable display panel has a layered structure including, for example, a pixel panel, a touch panel, and a cover film. An optical film having a predetermined optical function may be provided in the layered structure of the foldable display panel. Examples of the optical film include a film-like polarizing plate and a retardation film. The optical film Y with an adhesive layer is used as a supply material for the optical film included in the layered structure in the manufacturing process of the foldable display panel.

The optical film Y with adhesive layer comprises an optical film 10 having a thickness of 100 μm or less, an adhesive layer 20 (first adhesive layer), and an adhesive layer 30 (second adhesive layer). The optical film 10 has a first surface 11 and a second surface 12 opposite to the first surface 11. The adhesive layer 20 is attached to the first surface 11 and has an adhesive surface 21 (first adhesive surface) opposite to the optical film 10. The light release film 40 is disposed on the adhesive surface 21. The adhesive layer 30 is attached to the second surface 12 and has an adhesive surface 31 (second adhesive surface) opposite to the optical film 10. The heavy release film 50 is disposed on the adhesive surface 31. In addition, as edges that define the planar outer shape, the optical film 10 has edge 13, the adhesive layer 20 has edge 22 (first edge), the adhesive layer 30 has edge 32 (second edge), the light release film 40 has edge 42, and the heavy release film 50 has edge 52.

As shown in FIG. 2, the optical film X has a side uneven end E at all or part of the outer periphery of the film. At the side uneven end E, the edges 22, 32 of the adhesive layer 20, 30 are retracted from the edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50 in the in-plane direction D. Also, at the side uneven end E, the first retraction length d1 of the edge 22 of the adhesive layer 20 from the edge 42 of the light release film 40 is smaller than the second retraction length d2 of the edge 32 of the adhesive layer 30 from the edge 52 of the heavy release film 50. The first retraction length d1 is the distance between the edges 22, 42 in the in-plane direction D. The second retraction length d2 is the distance between the edges 32, 52 in the in-plane direction D. Examples of methods for adjusting the first retraction length d1 include adjusting the thickness of the adhesive layer 20 and adjusting the elastic modulus. Examples of methods for adjusting the second retraction length d2 include adjusting the thickness and elastic modulus of the adhesive layer 30. Examples of methods for adjusting the distance between the edges 22, 32 in the in-plane direction D (i.e., the difference between the first retraction length d1 and the second retraction length d2) include adjusting the cutting conditions in the cutting process described below, which is performed using a rotary blade to form the side uneven end E. Examples of the cutting conditions include the taper angle of the blade tip of the rotary blade, the rotation speed of the rotary blade, the incidence direction of the rotary blade with respect to the surface of the optical film laminate described below, and the displacement speed of the rotary blade that cuts the optical film laminate.

At the side uneven end E of the optical film X, as described above, the edge 22 of the adhesive layer 20 is retracted from the edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50 in the in-plane direction D. At such a side uneven end E, the light release film 40 has a free portion 40a to which the adhesive layer 20 is not attached. Therefore, at the side uneven end E, when peeling the light release film 40 from the adhesive layer 20, first, the free portion 40a of the light release film 40 is turned up and deformed as shown by the imaginary line in FIG. 2, and then the free portion 40a that has already been turned up and deformed is pulled to separate the light release film 40 from the edge 22 of the adhesive layer 20. That is, in the peeling start process, a force (first force) for sufficiently deforming the free portion 40a of the light release film 40 and a force (second force) for pulling the light release film 40 away from the edge 22 of the adhesive layer 20 that elastically deforms following the deformation of the light release film 40 are not required at the same time. Such an optical film X is suitable for reducing the force required in the peeling start process. The smaller this force is, the more the deformation of the thin optical film 10 with a thickness of 100 μm or less is suppressed in the peeling start process of the light release film 40, and the deformation of the adhesive layer 30 is also suppressed, and therefore the edge 32 of the adhesive layer 30 is suppressed from separating from the heavy release film 50.

In addition, at the side unevenness end E of the optical film X, as described above, the first retraction length d1 is smaller than the second retraction length d2. That is, at the side unevenness end E, the edge 32 of the adhesive layer 30 is retracted from the edge 22 of the adhesive layer 20 in the in-plane direction D. This configuration is suitable for suppressing deformation of the adhesive layer 30 when the second force for pulling the light release film 40 away from the edge 22 of the adhesive layer 20 acts on the optical film X during the process of starting to release the light release film 40, and is therefore suitable for suppressing the edge 32 of the adhesive layer 30 from separating from the heavy release film 50.

As described above, the optical film X is suitable for peeling the light release film 40 from the thin optical film 10 with the pressure-sensitive adhesive layers 20, 30 while suppressing peeling of the heavy release film 50.

In the optical film X, the distance between the edges 22, 32 in the in-plane direction D is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. Such a configuration is preferable for suppressing the above-mentioned deformation of the adhesive layer 20 during the above-mentioned peeling start process of the light release film 40, and therefore is preferable for suppressing the edge 42 of the adhesive layer 40 from separating from the heavy release film 50. In addition, the distance between the edges 22, 32 in the in-plane direction D is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 220 μm or less. Such a configuration is preferable for suppressing damage to the edge of the optical film 10, and is also preferable for suppressing a decrease in durability of the edge of the optical film 10 due to a decrease in the adhesion area between the optical film 10 and the adhesive layers 20, 30.

The first retraction length d1 is preferably 20 μm or more, more preferably 40 μm or more, and even more preferably 60 μm or more. Such a configuration is suitable for sufficiently turning up and deforming the free portion 40a of the light release film 40 before the light release film 40 is pulled away from the edge 22 of the adhesive layer 20 during the above-mentioned peeling start process of the light release film 40, and is therefore preferable for reducing the net force required to start peeling of the light release film 40. In addition, the first retraction length d1 is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less. The second retraction length d2 is preferably 21 μm or more, more preferably 41 μm or more, and even more preferably 61 μm or more, as long as it is greater than the first retraction length d1. The second retraction length d2 is preferably 550 μm or less, more preferably 450 μm or less, and even more preferably 350 μm or less, as long as it is greater than the first retraction length d1. The ratio (d2/d1) of the second retraction length d2 to the first retraction length d1 is preferably 1.1 or more, and more preferably 1.2 or more. The ratio (d2/d1) is preferably 5 or less, and more preferably 4 or less.

The first peel initiation force F1 for initiating peeling of the light release film 40 from the adhesive surface 21 of the adhesive layer 20 is preferably smaller than the second peel initiation force F2 for initiating peeling of the heavy release film 50 from the adhesive surface 31 of the adhesive layer 30. The ratio (F1/F2) of the first peel initiation force F1 to the second peel initiation force F2 is preferably 0.8 or less, more preferably 0.78 or less. The ratio (F1/F2) is preferably 0.1 or more, more preferably 0.15 or more. These configurations are preferable for suppressing the above-mentioned deformation of the adhesive layer 20 during the peel initiation process of the light release film 40, and therefore are preferable for suppressing the edge 32 of the adhesive layer 30 from separating from the heavy release film 50.

In this embodiment, the peeling initiation force is the force required in the peeling initiation process when the release film releasably attached to the adhesive layer is peeled off from the adhesive layer. In the peeling initiation process, a force is applied to the release film so that the release film deforms in a direction away from the adhesive layer. As a result, the edge of the adhesive layer attached to the release film and its vicinity are elastically deformed once so as to follow the deformation of the release film. Then, when the release film is pulled with a force large enough to pull the release film away from the elastically deformed end of the adhesive layer, a cleavage occurs between the edge of the adhesive layer and its vicinity and the release film, and peeling begins. That is, the peeling initiation force is the force required in the peeling initiation process to pull the release film away from the elastically deformed end of the adhesive layer to start peeling the release film from the adhesive layer. Such a peeling initiation force can be measured by the method described later in the examples below. Examples of methods for adjusting such a peeling initiation force include, for example, adjusting the thickness of the release film and selecting the type of release treatment agent on the adhesive layer side surface of the release film.

The first peel initiation force F1 is preferably less than 800 gf/25 mm, more preferably 500 gf/25 mm or less, and even more preferably 400 gf/25 mm or less. This configuration is preferable for preventing the edge 32 of the adhesive layer 30 from separating from the heavy release film 50 during the peel initiation process of the light release film 40, and for reducing the load on the optical film 10. In addition, the first peel initiation force F1 is preferably 5 gf/25 mm or more, more preferably 10 gf/25 mm or more, and even more preferably 20 gf/25 mm or more. This configuration is preferable for preventing the light release film 40 from floating (partial peeling) from the adhesive layer 20, for example, during transportation and handling of the optical film X.

The peeling force f1 for peeling the light peeling film 40 from the adhesive surface 21 of the adhesive layer 20 after the start of peeling of the light peeling film 40 from the adhesive layer 20 is preferably 0.1 gf/25 mm or more, more preferably 0.3 gf/25 mm or more, and even more preferably 0.5 gf/25 mm or more. The first peeling force f1 is preferably 5 gf/25 mm or less, more preferably 4 gf/25 mm or less, and even more preferably 3 gf/25 mm or less.

The second peel initiation force F2 is preferably 800 gf/25 mm or less, more preferably 700 gf/25 mm or less, and even more preferably 600 gf/25 mm or less. This configuration is preferable for suppressing the edge 22 of the adhesive layer 20 from separating from the heavy release film 50 during the peel initiation process of the light release film 40, while reducing the load on the optical film 10 during the peel initiation process of the heavy release film 50 from the adhesive layer 20. In addition, the second peel initiation force F2 is preferably 10 gf/25 mm or more, more preferably 20 gf/25 mm or more, and even more preferably 30 gf/25 mm or more. This configuration is preferable for suppressing the lifting (partial peeling) of the heavy release film 50 from the adhesive layer 30, for example, during transportation and handling of the optical film X.

The peeling force f2 for peeling the heavy release film 50 from the adhesive surface 31 of the adhesive layer 30 after the start of peeling of the heavy release film 50 from the adhesive layer 30 is preferably 0.1 gf/25 mm or more, more preferably 0.3 gf/25 mm or more, and even more preferably 0.5 gf/25 mm or more. The second peeling force f2 is preferably 5 gf/25 mm or less, more preferably 4 gf/25 mm or less, and even more preferably 3 gf/25 mm or less. The ratio (f1/f2) of the first peeling force f1 to the second peeling force f2 is preferably 0.8 or less, and more preferably 0.7 or less. The ratio (f1/f2) is preferably 0.1 or more, and more preferably 0.2 or more.

When the optical film 10 is a polarizing plate, the polarizing plate may be, for example, a polarizing plate including a polarizer and a transparent protective film attached to one or both sides of the polarizer. Examples of polarizers include uniaxially stretched hydrophilic polymer films with a dichroic substance adsorbed thereon, and polyene-oriented films. Examples of hydrophilic polymer films include polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films. Examples of dichroic substances include iodine and dichroic dyes. Examples of polyene-oriented films include dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

As the polarizer, a thin polarizer having a thickness of 10 μm or less may be used. Examples of thin polarizers include the polarizers described in JP-A-51-069644, JP-A-2000-338329, WO2010/100917, Japanese Patent No. 4691205, and Japanese Patent No. 4751481.

The transparent protective film is preferably a film that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and optical isotropy. Examples of materials for such transparent protective films include cellulose resins, cyclic polyolefin resins, acrylic resins, phenylmaleimide resins, and polycarbonate resins.

From the viewpoint of flexibility, the thickness of the polarizing plate is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less.

The adhesive layer 20 is a pressure-sensitive adhesive layer formed from a first adhesive composition. The adhesive layer 20 has transparency (visible light transmittance). The first adhesive composition contains at least a base polymer.

The base polymer is an adhesive component that exerts adhesiveness in the adhesive layer 20. Examples of base polymers include acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, fluoropolymers, and rubber polymers. The base polymers may be used alone or in combination of two or more types. From the viewpoint of ensuring good transparency and adhesiveness in the adhesive layer 20, an acrylic polymer is preferably used as the base polymer.

An acrylic polymer is a copolymer of monomer components containing 50% or more by weight of (meth)acrylic acid alkyl ester. "(Meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 20 carbon atoms is preferably used. The (meth)acrylic acid alkyl ester may have a linear or branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group.

Examples of (meth)acrylic acid alkyl esters having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, Examples of such acrylates include nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (i.e., lauryl acrylate), isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

Examples of (meth)acrylic acid alkyl esters having an alicyclic alkyl group include (meth)acrylic acid cycloalkyl esters, (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring, and (meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring. Examples of (meth)acrylic acid cycloalkyl esters include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. Examples of (meth)acrylic acid esters having three or more aliphatic hydrocarbon rings include dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

As the (meth)acrylic acid alkyl ester, preferably, an acrylic acid alkyl ester having an alkyl group having 3 to 15 carbon atoms is used, and more preferably, at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl acrylate is used.

The proportion of (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, from the viewpoint of adequately expressing basic properties such as adhesiveness in the adhesive layer 20. The proportion is, for example, 99% by mass or less.

The monomer component may include a copolymerizable monomer that is copolymerizable with the (meth)acrylic acid alkyl ester. Examples of the copolymerizable monomer include a monomer having a polar group. Examples of the polar group-containing monomer include a monomer having a nitrogen atom-containing ring, a hydroxy group-containing monomer, and a carboxy group-containing monomer. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing crosslinking points into the acrylic polymer and ensuring the cohesive force of the acrylic polymer.

Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole. As a monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

The proportion of the monomer having a nitrogen atom-containing ring in the monomer components is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.55% by mass or more, from the viewpoints of ensuring the cohesive strength of the adhesive layer 20 and ensuring the adhesive strength of the adhesive layer 20 to the adherend. The proportion is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to the compatibility of the various additive components in the adhesive layer 20 with the acrylic polymer).

Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxy group-containing monomer, 4-hydroxybutyl (meth)acrylate is preferably used, and 4-hydroxybutyl acrylate is more preferably used.

The proportion of the hydroxyl group-containing monomer in the monomer components is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and ensuring the cohesive strength in the adhesive layer 20. From the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility between the various additive components in the adhesive layer 20 and the acrylic polymer), the proportion is preferably 20% by mass or less, and more preferably 10% by mass or less.

Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

The proportion of the carboxyl group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.8% by mass or more, from the viewpoints of introducing a crosslinked structure into the acrylic polymer, ensuring the cohesive strength of the adhesive layer 20, and ensuring the adhesive strength of the adhesive layer 20 to the adherend. The proportion is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid.

In order to prevent metal elements such as electrodes in a foldable device from being corroded by acid components, it is preferable that the adhesive layer 20 has a small acid content. In addition, when the adhesive layer 20 is used to adhere a polarizing plate, it is preferable that the adhesive layer 20 has a small acid content in order to suppress polyenization of the polyvinyl alcohol polarizer by acid components. The content of organic acid monomers (e.g., (meth)acrylic acid and carboxyl group-containing monomers) in such an acid-free adhesive layer 20 is preferably 100 ppm or less, more preferably 70 ppm or less, and even more preferably 50 ppm or less. The organic acid monomer content of the adhesive layer 20 is determined by immersing the adhesive layer 20 in pure water and heating it at 100°C for 45 minutes, and quantifying the acid monomers extracted into the water using ion chromatography.

From the viewpoint of being acid-free, it is preferable that the base polymer in the adhesive layer 20 does not substantially contain an organic acid monomer as a monomer component. From the viewpoint of being acid-free, the ratio of the organic acid monomer in the monomer component is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, even more preferably 0.05% by mass, and ideally 0% by mass.

The monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and aromatic vinyl compounds. These other copolymerizable monomers may be used alone or in combination of two or more.

In this embodiment, the base polymer has a crosslinked structure. Methods for introducing a crosslinked structure into the base polymer include a method (first method) in which a base polymer having a functional group capable of reacting with a crosslinking agent and the crosslinking agent are mixed into a first adhesive composition, and the base polymer and the crosslinking agent are reacted in the adhesive layer 20, and a method (second method) in which a polyfunctional monomer is included in the monomer components forming the base polymer, and a base polymer having a branched structure (crosslinked structure) introduced into the polymer chain is formed by polymerization of the monomer components. These methods may be used in combination.

The crosslinking agent used in the first method includes, for example, a compound that reacts with functional groups (such as hydroxyl groups and carboxyl groups) contained in the base polymer. Examples of such crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. The crosslinking agents may be used alone or in combination of two or more. As the crosslinking agent, isocyanate crosslinking agents, peroxide crosslinking agents, and epoxy crosslinking agents are preferably used because they are highly reactive with the hydroxyl groups and carboxyl groups in the base polymer and can easily introduce a crosslinked structure.

Examples of isocyanate crosslinking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenylisocyanate. In addition, examples of isocyanate crosslinking agents include derivatives of these isocyanates. Examples of the isocyanate derivatives include isocyanurate modified products and polyol modified products. Commercially available isocyanate crosslinking agents include, for example, Coronate L (a trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (a trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh), Coronate HX (an isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (a trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals).

Peroxide crosslinking agents include dibenzoyl peroxide, di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.

Epoxy crosslinkers include bisphenol A, epichlorohydrin type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

Isocyanate crosslinking agents (particularly bifunctional isocyanate crosslinking agents) and peroxide crosslinking agents are preferred from the viewpoint of ensuring the appropriate flexibility (hence the flexibility) of the adhesive layer 20. Isocyanate crosslinking agents (particularly trifunctional isocyanate crosslinking agents) are preferred from the viewpoint of ensuring the durability of the adhesive layer 20. In the base polymer, bifunctional isocyanate crosslinking agents and peroxide crosslinking agents form more flexible two-dimensional crosslinks, whereas trifunctional isocyanate crosslinking agents form stronger three-dimensional crosslinks. From the viewpoint of achieving both durability and flexibility of the adhesive layer 20, it is preferred to use a trifunctional isocyanate crosslinking agent in combination with a peroxide crosslinking agent and/or a bifunctional isocyanate crosslinking agent.

The amount of the crosslinking agent to be blended is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and more preferably 0.07 parts by mass or more, per 100 parts by mass of the base polymer, from the viewpoint of ensuring the cohesive strength of the adhesive layer 20. From the viewpoint of ensuring good tackiness in the adhesive layer 20, the amount of the crosslinking agent to be blended is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the base polymer.

In the second method, the monomer components (including a multifunctional monomer for introducing a crosslinked structure and other monomers) may be polymerized in one step or in multiple steps. In the multistep polymerization method, first, a monofunctional monomer for forming a base polymer is polymerized (preliminary polymerization), thereby preparing a prepolymer composition containing a partial polymer (a mixture of a polymer with a low degree of polymerization and unreacted monomer). Next, a multifunctional monomer is added to the prepolymer composition, and then the partial polymer and the multifunctional monomer are polymerized (main polymerization).

An example of a polyfunctional monomer is a polyfunctional (meth)acrylate that contains two or more ethylenically unsaturated double bonds in one molecule. As a polyfunctional monomer, a polyfunctional acrylate is preferred from the viewpoint of being able to introduce a crosslinked structure by active energy ray polymerization (photopolymerization).

Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and tetrafunctional or higher polyfunctional (meth)acrylates.

Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, stearic acid modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, di(meth)acryloyl isocyanurate, and alkylene oxide modified bisphenol di(meth)acrylate.

Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl)isocyanurate.

Examples of tetrafunctional or higher polyfunctional (meth)acrylates include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

The molecular weight of the polyfunctional monomer is preferably 1500 or less, more preferably 1000 or less. The functional group equivalent (g/eq) of the polyfunctional monomer is preferably 50 or more, more preferably 70 or more, and even more preferably 80 or more. The functional group equivalent is preferably 500 or less, more preferably 300 or less, and even more preferably 200 or less. These configurations are preferred from the viewpoint of appropriately adjusting the viscoelasticity (e.g., storage modulus G' and loss tangent tan δ) by introducing a crosslinked structure in the base polymer.

The acrylic polymer can be formed by polymerizing the above-mentioned monomer components. Examples of the polymerization method include solution polymerization, active energy ray polymerization (e.g., UV polymerization), bulk polymerization, and emulsion polymerization. From the viewpoints of transparency, water resistance, and cost of the adhesive layer 20, solution polymerization and UV polymerization are preferred. For example, ethyl acetate and toluene are used as the solvent for solution polymerization. For example, a thermal polymerization initiator and a photopolymerization initiator are used as the polymerization initiator. The amount of the polymerization initiator used is, for example, 0.05 parts by mass or more and, for example, 1 part by mass or less, per 100 parts by mass of the monomer components.

Examples of the thermal polymerization initiator include azo polymerization initiators and peroxide polymerization initiators. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine)dihydrochloride. Examples of peroxide polymerization initiators include dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

Examples of photopolymerization initiators include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, thioxanthone photopolymerization initiators, and acylphosphine oxide photopolymerization initiators.

In the polymerization, a chain transfer agent and/or a polymerization inhibitor (polymerization retarder) may be used for the purpose of adjusting the molecular weight, etc. Examples of chain transfer agents include α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene dimer.

The molecular weight of the base polymer can be adjusted by adjusting the type and/or amount of the polymerization initiator. For example, in radical polymerization, the greater the amount of polymerization initiator, the higher the radical concentration in the reaction system, so the higher the density of reaction initiation points, and the smaller the molecular weight of the base polymer formed tends to be. In contrast, the smaller the amount of polymerization initiator, the lower the density of reaction initiation points, so the easier it is for the polymer chains to extend, and the larger the molecular weight of the base polymer formed tends to be.

From the viewpoint of ensuring the cohesive force in the adhesive layer 20, the weight average molecular weight of the acrylic polymer is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 500,000 or more. The weight average molecular weight is preferably 5 million or less, more preferably 3 million or less, and even more preferably 2 million or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher.

For the glass transition temperature (Tg) of the base polymer, the glass transition temperature (theoretical value) calculated based on the Fox formula below can be used. The Fox formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of the monomer that constitutes the polymer. In the Fox formula below, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of the monomer i that constitutes the polymer, and Tgi represents the glass transition temperature (°C) of the homopolymer formed from the monomer i. For the glass transition temperature of the homopolymer, literature values can be used. For example, the glass transition temperatures of various homopolymers are listed in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7: Introduction to Synthetic Resins for Paints" (Kyozo Kitaoka, Polymer Publishing Association, 1995). On the other hand, the glass transition temperature of a homopolymer of a monomer can also be determined by the method specifically described in JP 2007-51271 A.

Fox formula 1/(273+Tg)=Σ[Wi/(273+Tgi)]

The first adhesive composition may contain one or more oligomers in addition to the base polymer. When an acrylic polymer is used as the base polymer, an acrylic oligomer is preferably used as the oligomer. The acrylic oligomer is a copolymer of monomer components containing 50% or more by mass of (meth)acrylic acid alkyl ester, and has a weight average molecular weight of, for example, 1,000 or more and 30,000 or less.

The glass transition temperature of the acrylic oligomer is preferably 60°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and particularly preferably 110°C or higher. The glass transition temperature of the acrylic oligomer is, for example, 200°C or lower, preferably 180°C or lower, and more preferably 160°C or lower. The combined use of a low Tg acrylic polymer (base polymer) into which a crosslinked structure has been introduced and a high Tg acrylic oligomer can increase the adhesive strength of the pressure-sensitive adhesive layer 20, particularly at high temperatures. The glass transition temperature of the acrylic oligomer is calculated using the above Fox formula.

The acrylic oligomer having a glass transition temperature of 60°C or higher is preferably a polymer of monomer components including an alkyl (meth)acrylate ester having a chain alkyl group (chain alkyl (meth)acrylate) and an alkyl (meth)acrylate ester having an alicyclic alkyl group (alicyclic alkyl (meth)acrylate). Specific examples of these alkyl (meth)acrylate esters include the alkyl (meth)acrylate esters listed above as monomer components of the acrylic polymer.

As the linear alkyl (meth)acrylate, methyl methacrylate is preferred because it has a high glass transition temperature and excellent compatibility with the base polymer. As the alicyclic alkyl (meth)acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferred. In other words, the acrylic oligomer is preferably a polymer of monomer components containing methyl methacrylate and one or more selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate.

The proportion of alicyclic alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 30% by weight or more. The proportion is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. The proportion of chain alkyl (meth)acrylate in the monomer component of the acrylic oligomer is preferably 90% by weight or less, more preferably 80% by weight or less, and even more preferably 70% by weight or less. The proportion is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 30% by weight or more.

The weight average molecular weight of the acrylic oligomer is preferably 1000 or more, more preferably 1500 or more, and even more preferably 2000 or more. The molecular weight is preferably 30000 or less, more preferably 10000 or less, and even more preferably 8000 or less. Such a molecular weight range of the acrylic oligomer is preferable for ensuring the adhesive strength and adhesive retention strength of the pressure-sensitive adhesive layer 20.

The acrylic oligomer is obtained by polymerizing the monomer components of the acrylic oligomer. Examples of the polymerization method include solution polymerization, active energy ray polymerization (e.g., UV polymerization), bulk polymerization, and emulsion polymerization. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, and a chain transfer agent may be used for the purpose of adjusting the molecular weight.

In order to sufficiently increase the adhesive strength of the adhesive layer 20, the content of the acrylic oligomer in the adhesive layer 20 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the base polymer. On the other hand, from the viewpoint of ensuring the transparency of the adhesive layer 20, the content of the acrylic oligomer in the adhesive layer 20 is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer. If the content of the acrylic oligomer in the adhesive layer 20 is too large, the haze tends to increase and the transparency tends to decrease due to a decrease in the compatibility of the acrylic oligomer.

The first adhesive composition may contain a silane coupling agent. The content of the silane coupling agent in the first adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, per 100 parts by mass of the base polymer. The content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

The first adhesive composition may contain other components as necessary. Examples of other components include tackifiers, plasticizers, softeners, anti-degradants, fillers, colorants, UV absorbers, antioxidants, surfactants, and antistatic agents.

The thickness H of the adhesive layer 20 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend. From the viewpoint of handling, the thickness H is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

The ratio (d1/H) of the first retraction length d1 to the thickness H is preferably 0.4 or more, more preferably 0.6 or more. The ratio (d1/H) is preferably 8 or less, more preferably 6 or less. These configurations are suitable for sufficiently turning up and deforming the end portion (the above-mentioned free portion 40a) of the light release film 40 before the light release film 40 is pulled away from the edge 22 of the adhesive layer 20 during the process of starting the peeling of the light release film 40, and are therefore suitable for reducing the net force required to start the peeling of the light release film 40.

The haze of the adhesive layer 20 is preferably 3% or less, more preferably 2% or less, and more preferably 1% or less. The haze of the adhesive layer 20 can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of haze meters include the "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and the "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.

The total light transmittance of the adhesive layer 20 is preferably 60% or more, more preferably 80% or more, and even more preferably 85% or more. The total light transmittance of the adhesive layer 20 is, for example, 100% or less. The total light transmittance of the adhesive layer 20 can be measured in accordance with JIS K 7375 (2008).

The adhesive layer 30 is a pressure-sensitive adhesive layer formed from the second adhesive composition. The adhesive layer 30 has transparency. The second adhesive composition contains at least a base polymer. Examples of the base polymer contained in the second adhesive composition include the base polymers described above for the first adhesive composition. The base polymer in the first adhesive composition and the base polymer in the second adhesive composition may be the same or different. The second adhesive composition may contain a component other than the base polymer. Examples of the same component contained in the second adhesive composition include the components other than the base polymer described above for the first adhesive composition. The composition of the first adhesive composition and the composition of the second adhesive composition may be the same or different. From the viewpoint of adjusting the above-mentioned peel initiation forces F1, F2 and peel forces f1, f2, it is preferable that the composition of the first adhesive composition and the composition of the second adhesive composition are different.

The thickness of the adhesive layer 30 may be the same as or different from the thickness of the adhesive layer 20. From the viewpoint of ensuring sufficient adhesion to the adherend, the thickness of the adhesive layer 30 is preferably 10 μm or more, more preferably 15 μm or more. From the viewpoint of handleability, the thickness of the adhesive layer 30 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. In addition, the ratio of the thickness of the adhesive layer 30 to the thickness of the adhesive layer 20 is, for example, 0.2 or more, and, for example, 5 or less.

The haze of the adhesive layer 30 is preferably 3% or less, more preferably 2% or less, and more preferably 1% or less. The haze of the adhesive layer 30 can be measured using a haze meter in accordance with JIS K7136 (2000).

The total light transmittance of the adhesive layer 30 is preferably 60% or more, more preferably 80% or more, and even more preferably 85% or more. The total light transmittance of the adhesive layer 30 is, for example, 100% or less. The total light transmittance of the adhesive layer 30 can be measured in accordance with JIS K 7375 (2008).

The light release film 40 may be, for example, a plastic film having flexibility. Examples of the plastic film include a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film. The thickness of the light release film 40 is preferably 5 μm or more, more preferably 10 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less. The surface of the light release film 40 is preferably subjected to a release treatment. Examples of the release treatment include a silicone release treatment and a fluorine release treatment (the same applies to the release treatment described below). The above-mentioned first release initiation force F1 and release force f1 for the release of the light release film 40 from the adhesive layer 20 can be adjusted by selecting the presence or absence of a release treatment, the type of treatment, and adjusting the conditions.

The heavy release film 50 may, for example, be the plastic film described above with respect to the light release film 40. The thickness of the heavy release film 50 is preferably 5 μm or more, more preferably 10 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less. The surface of the heavy release film 50 is preferably subjected to a release treatment. The above-mentioned second release initiation force F2 and release force f2 for the peeling of the heavy release film 50 from the adhesive layer 30 can be adjusted by selecting the presence or absence of release treatment, the type of treatment, and adjusting the conditions.

Optical film X can be produced, for example, as follows:

First, prepare an optical film 10, an adhesive layer 20 with a light release film 40, and an adhesive layer 30 with a heavy release film 50 (preparation process).

The adhesive layer 20 with the light release film 40 can be formed by applying a first adhesive composition (varnish) onto the light release film 40 to form a coating film, and then drying the coating film. Examples of methods for applying the first adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating (the same applies to the application method of the second adhesive composition described below). Another release film may be laminated on the adhesive layer 20 on the light release film 40. This release film is peeled off before the optical film 10 and the adhesive layer 20 are bonded together.

The adhesive layer 30 with the heavy release film 50 can be formed by applying a second adhesive composition (varnish) onto the heavy release film 50 to form a coating film, and then drying the coating film. Another release film may be laminated on the adhesive layer 30 on the heavy release film 50. This release film is peeled off before bonding the optical film 10 and the adhesive layer 30 together.

Next, the first surface 11 of the optical film 10 is bonded to the adhesive layer 20 side of the adhesive layer 20 with the light release film 40 (first bonding process). Next, the second surface 12 of the optical film 10 is bonded to the adhesive layer 30 side of the adhesive layer 30 with the heavy release film 50 (second bonding process). This results in a laminate as the optical film X with an unprocessed outer edge. Preferably, prior to bonding, the first surface 11 and the second surface 12 of the optical film 10, the exposed surface of the adhesive layer 20 with the light release film 40, and the exposed surface of the adhesive layer 30 with the heavy release film 50 are plasma treated.

Next, the laminate is held by a jig that clamps it in the thickness direction, and the pressure applied by the jig to the laminate in the thickness direction is adjusted so that each adhesive layer 20, 30 elastically deforms and protrudes a predetermined amount from the side end face of the laminate (pressure holding process). By adjusting the pressure, the degree of elastic deformation of the adhesive layers 20, 30 can be adjusted, and therefore the length that protrudes from the side end face of the laminate can be adjusted.

Next, while the adhesive layers 20, 30 are elastically deformed so as to protrude from the laminate side end face, a predetermined length inward from the laminate side end face is cut in the thickness direction with a rotary blade so that all or part of the outer peripheral edge of the laminate is newly formed (cutting process). The predetermined length is, for example, 0.1 mm or more and, for example, 1 mm or less. Thereafter, the pressure applied to the laminate by the jig is released. This causes the adhesive layers 20, 30 to elastically return to their original state, and the edges 22, 32 of the adhesive layers 20, 30 retreat inward in the in-plane direction D from the edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50. In this way, the side uneven end E is formed.

In such a cutting process, the length of the adhesive layer 20, 30 protruding from the side end surface of the laminate can be adjusted by adjusting the pressure applied to the laminate in the thickness direction, and the retracted length d1, d2 of the edge 22, 32 after the pressure is released can be adjusted. In addition, as described above, the adjustment of the thickness and elastic modulus of the adhesive layer 20 can be used as a method for adjusting the first retracted length d1. As described above, the adjustment of the thickness and elastic modulus of the adhesive layer 30 can be used as a method for adjusting the second retracted length d2. In addition, as described above, the adjustment of the distance between the edge 22, 32 in the in-plane direction D (i.e., the difference between the first retracted length d1 and the second retracted length d2) can be used as a method for adjusting the cutting conditions in the cutting process described below, which is performed using a rotary blade to form the side uneven end E. The cutting conditions include, for example, the taper angle of the cutting edge of the rotary blade, the rotation speed of the rotary blade, the incidence direction of the rotary blade with respect to the surface of the optical film laminate described below, and the displacement speed of the rotary blade that cuts the optical film laminate.

In this manner, the above-mentioned optical film X (optical film with release film) can be produced.

In the above-mentioned preparation step, the first adhesive layer 20 with a release film for process may be prepared using a first release film instead of the light release film 40, and the second adhesive layer 30 with a release film for process may be prepared using a second release film instead of the heavy release film 50. In this case, in the above-mentioned first bonding step, the first surface 11 of the optical film 10 and the adhesive layer 20 side of the adhesive layer 20 with the first release film for process are bonded together. In addition, in the second bonding step, the second surface 12 of the optical film 10 and the adhesive layer 30 side of the adhesive layer 30 with the second release film for process are bonded together (preferably, the above-mentioned plasma treatment is performed before bonding). This results in a laminate having the first release film for process, the adhesive layer 20, the optical film 10, the adhesive layer 30, and the second release film for process in order in the thickness direction. Then, in the laminate, after the first process release film is peeled off from the adhesive layer 20, a light release film 40 is attached to the exposed surface of the adhesive layer 20, and after the second process release film is peeled off from the adhesive layer 30, a heavy release film 50 is attached to the exposed surface of the adhesive layer 30. In this manner, a laminate may be obtained as the optical film X whose outer peripheral edge is unprocessed. Thereafter, the optical film X (optical film with a release film) can be manufactured by carrying out the above-mentioned pressurizing and holding process and cutting process on the laminate.

In the manufacturing process of the optical film X, the first adhesive layer 20 with the first release film for process may be attached to the first surface 11 of the optical film 10 in the first lamination step, while the adhesive layer 30 with the heavy release film 50 may be attached to the second surface 12 of the optical film 10 in the second lamination step (preferably, the above-mentioned plasma treatment is performed before lamination). This results in a laminate having the first release film for process, the adhesive layer 20, the optical film 10, the adhesive layer 30, and the heavy release film 50 in order in the thickness direction. Then, in the laminate, after peeling the first release film for process from the adhesive layer 20, the light release film 40 is attached to the exposed surface of the adhesive layer 20. In this manner, a laminate as the optical film X with an unprocessed outer edge may be obtained. Thereafter, the above-mentioned pressurizing and holding step and cutting step are performed on the laminate to produce the optical film X (optical film with a release film).

In the manufacturing process of the optical film X, in the first lamination step, the adhesive layer 20 with the light release film 40 is laminated to the first surface 11 of the optical film 10, while in the second lamination step, the adhesive layer 30 with the second release film for process may be laminated to the second surface 12 of the optical film 10 (preferably, the above-mentioned plasma treatment is performed before lamination). This results in a laminate having the light release film 40, the adhesive layer 20, the optical film 10, the adhesive layer 30, and the second release film for process in that order in the thickness direction. Then, in the laminate, after the second release film for process is peeled off from the adhesive layer 30, the heavy release film 50 is laminated to the exposed surface of the adhesive layer 30. In this manner, a laminate as the optical film X with an unprocessed outer edge may be obtained. Thereafter, the above-mentioned pressurizing and holding step and cutting step are performed on the laminate to produce the optical film X (optical film with release film).

In the manufacturing process of the optical film X, the adhesive layers 20, 30 may be formed using a photocurable adhesive composition as the adhesive composition. An example of a photocurable adhesive composition is an ultraviolet-curable adhesive composition in which a polymerization reaction of the monomer components contained therein proceeds upon irradiation with ultraviolet light. For example, when a photocurable adhesive composition is used as the second adhesive composition, the second adhesive composition is first applied onto a second release film for process to form a coating film. Next, a double release film 50 is laminated onto the coating film on the second release film for process. Next, the coating film between the release films is photocured by irradiating the coating film with light of a predetermined wavelength (such as ultraviolet light). This forms an adhesive layer 30 between the release films. Next, the second release film for process is peeled off from the adhesive layer 30 on the double release film 50. The adhesive layer 30 with the double release film 50 thus obtained may be used to carry out the second lamination process described above.

Figures 3A to 3D show an example of how optical film X can be used.

In this method, first, as shown in FIG. 3A, the light release film 40 is peeled off from the adhesive layer 20 of the optical film X. For example, with the heavy release film 50 side of the optical film X fixed on a work table, a force is applied to the end of the light release film 40 at the side uneven end E to peel off the light release film 40 from the adhesive layer 20. This exposes the adhesive surface 21 of the adhesive layer 20.

At the side uneven end E, as described above, the edge 22 of the adhesive layer 20 is retracted from the edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50 in the in-plane direction D. At such a side uneven end E, as described above with reference to FIG. 2, the light release film 40 has a free portion 40a to which the adhesive layer 20 is not attached. Therefore, at the side uneven end E, when peeling the light release film 40 from the adhesive layer 20, first, the free portion 40a of the light release film 40 is turned up and deformed as shown by the imaginary line in FIG. 2, and then the free portion 40a that has already been turned up and deformed is pulled to pull the light release film 40 away from the edge 22 of the adhesive layer 20. That is, in the peeling start process, a force (first force) for sufficiently deforming the free portion 40a of the light release film 40 and a force (second force) for pulling the light release film 40 away from the edge 22 of the adhesive layer 20 that elastically deforms following the deformation of the light release film 40 are not required at the same time. Such an optical film X is suitable for reducing the force required in the peeling start process. The smaller this force is, the more the deformation of the thin optical film 10 with a thickness of 100 μm or less is suppressed in the peeling start process of the light release film 40, and the deformation of the adhesive layer 30 is also suppressed, and therefore the edge 32 of the adhesive layer 30 is suppressed from separating from the heavy release film 50.

In addition, at the side unevenness end E, as shown in FIG. 2, the first retraction length d1 is smaller than the second retraction length d2. That is, at the side unevenness end E, the edge 32 of the adhesive layer 30 is retracted from the edge 22 of the adhesive layer 20 in the in-plane direction D. This configuration is suitable for suppressing deformation of the adhesive layer 30 when the second force for pulling the light release film 40 away from the edge 22 of the adhesive layer 20 acts on the optical film X during the process of starting to release the light release film 40, and is therefore suitable for suppressing the edge 32 of the adhesive layer 30 from separating from the heavy release film 50.

Next, as shown in FIG. 3B, the optical film 10 and the first member M1 (first adherend) are bonded via the adhesive layer 20. The first member M1 is, for example, one element in the laminated structure of the flexible panel. Examples of such elements include a pixel panel, a touch panel, and a transparent cover film (the same applies to the second member M2 described below).

Next, as shown in FIG. 3C, the heavy release film 50 is peeled off from the adhesive layer 30. This exposes the adhesive surface 31 of the adhesive layer 30.

Next, as shown in FIG. 3D, the optical film 10 and the second member M2 (second adherend) are bonded via the pressure-sensitive adhesive layer 30.

For example, in the manufacturing process of a flexible panel, optical film X is used as described above.

The present invention will be specifically described below with reference to examples. The present invention is not limited to the examples. In addition, the specific numerical values of the compounding amounts (contents), physical property values, parameters, etc. described below can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than") of the corresponding compounding amounts (contents), physical property values, parameters, etc. described in the above-mentioned "Form for carrying out the invention."

Example 1
<Preparation of first adhesive sheet>
The first pressure-sensitive adhesive sheet in Example 1 was produced as follows.

Preparation of Acrylic Oligomer
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, a mixture containing 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of acrylic acid (AA), 10 parts by mass of α-methylstyrene dimer as a chain transfer agent, and 120 parts by mass of toluene as a solvent was stirred at room temperature for 1 hour under a nitrogen atmosphere. Thereafter, 10 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, which was reacted at 85°C for 5 hours under a nitrogen atmosphere (formation of acrylic oligomer). As a result, an oligomer solution containing acrylic oligomer (solid concentration 50% by mass) was obtained. The weight average molecular weight of the acrylic oligomer was 4300. The glass transition temperature (Tg) of the acrylic oligomer was 84°C.

Preparation of First Acrylic-Based Polymer
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, a mixture containing 70 parts by mass of 2-ethylhexyl acrylate (2EHA), 20 parts by mass of n-butyl acrylate (BA), 8 parts by mass of lauryl acrylate (LA), 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 0.6 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.1 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent (solid concentration 47% by mass) was stirred under a nitrogen atmosphere at 56°C for 6 hours (polymerization reaction). As a result, a first polymer solution containing a first acrylic base polymer was obtained. The weight average molecular weight of the first acrylic base polymer in this polymer solution was about 2 million.

Preparation of First Pressure-Sensitive Adhesive Composition
To the first polymer solution, 1.5 parts by mass of an acrylic oligomer, 0.26 parts by mass of a first crosslinking agent (trade name "Niper BMT-40SV", dibenzoyl peroxide, manufactured by Nippon Oil & Fats), 0.02 parts by mass of a second crosslinking agent (trade name "Coronate L", trimethylolpropane/tolylene diisocyanate trimer adduct, manufactured by Tosoh), and 0.3 parts by mass of a silane coupling agent (trade name "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed per 100 parts by mass of the solid content of the polymer solution to prepare a first pressure-sensitive adhesive composition.

<Formation of the first adhesive sheet>
A first adhesive composition was applied onto the release-treated surface of a release film L1, one side of which had been treated with silicone release, to form a coating film. The release film L1 was a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, manufactured by Mitsubishi Chemical) with one side treated with silicone release. Next, the release-treated surface of a release film L2, one side of which had been treated with silicone release, was attached to the coating film on the release film L1. The release film L2 was a PET film (product name "Diafoil MRV75", thickness 75 μm, manufactured by Mitsubishi Chemical) with one side treated with silicone release. Next, the coating film sandwiched between the release film L1 and the release film L2 was dried by heating at 100° C. for 1 minute and then heating at 150° C. for 3 minutes to form a first adhesive sheet consisting of a transparent first adhesive layer having a thickness of 50 μm. In this manner, a first adhesive sheet with release films L1 and L2 was produced.

<Preparation of second adhesive sheet>
The second adhesive sheet in Example 1 was produced as follows.

Preparation of the Second Acrylic-Based Polymer
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, a mixture containing 99 parts by mass of butyl acrylate (BA), 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 0.3 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent was stirred under a nitrogen atmosphere at 60°C for 4 hours (polymerization reaction). This resulted in a second polymer solution containing a second acrylic-based polymer. The weight average molecular weight of the second acrylic-based polymer in this polymer solution was 1.65 million.

Preparation of second pressure-sensitive adhesive composition
To the second polymer solution, 0.3 parts by mass of a first crosslinking agent (product name "Niper BMT-40SV", dibenzoyl peroxide, manufactured by Nippon Oil & Fats), 0.1 parts by mass of a third crosslinking agent (product name "Takenate D110N", trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Chemicals), and 0.3 parts by mass of a silane coupling agent (product name "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added and mixed per 100 parts by mass of the solid content of the polymer solution to prepare a second pressure-sensitive adhesive composition.

<Formation of second adhesive sheet>
A second adhesive composition was applied to the release-treated surface of the release film L3, one side of which was treated with silicone release, to form a coating film. The release film L3 was a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, manufactured by Mitsubishi Chemical) with one side treated with silicone release. Next, the release-treated surface of the release film L4, one side of which was treated with silicone release, was attached to the coating film on the release film L3. The release film L4 was a PET film (product name "Diafoil MRV75", thickness 75 μm, manufactured by Mitsubishi Chemical) with one side treated with silicone release. Next, the coating film sandwiched between the release film L3 and the release film L4 was dried by heating at 100 ° C for 1 minute and then heating at 150 ° C for 3 minutes, to form a second adhesive sheet consisting of a transparent second adhesive layer with a thickness of 50 μm. In this manner, a second adhesive sheet with release films L3 and L4 was produced.

<Preparation of Optical Film with Release Film>
First, the release film L2 was peeled off from the first pressure-sensitive adhesive sheet with double-sided release film, and the exposed surface was plasma-treated. Meanwhile, both sides (first surface, second surface) of a polarizing plate with a thickness of 31 μm were also plasma-treated. In each plasma treatment, a plasma irradiation device (name "AP-TO5", manufactured by Sekisui Kogyo Co., Ltd.) was used, and the voltage was set to 160 V, the frequency was set to 10 kHz, and the treatment speed was set to 5000 mm/min (the same applies to the plasma treatment described below). Then, the above-mentioned exposed surface of the first pressure-sensitive adhesive sheet and the first surface of the polarizing plate were bonded together. In this bonding, the first pressure-sensitive adhesive sheet with the release film L1 and the polarizing plate were pressure-bonded together by moving a 2 kg roller back and forth once in an environment of 25°C.

Next, release film L3 was peeled off from the second adhesive sheet with release films L3 and L4, and the surface thus exposed was subjected to plasma treatment. The exposed surface of the second adhesive sheet was then bonded to the second surface of the polarizing plate. In this bonding, the second adhesive sheet with release film L4 and the polarizing plate were pressed together by moving a 2 kg roller back and forth once in an environment of 25°C. This resulted in a laminated film having a laminated configuration of the first adhesive sheet with release film L1 (thickness 50 μm), the polarizing plate, and the second adhesive sheet with release film L4 (thickness 75 μm).

Next, the laminated film was punched out to a size of 150 mm x 120 mm using a punching machine and a Thompson blade (punching process).

Next, the outer shape processing was carried out as follows (outer shape processing step). First, 50 sheets of laminated film punched to the same size were stacked to obtain a laminate. Specifically, 50 sheets of laminated film were stacked so that the release film L1 (first release film) of one laminated film and the release film L4 (second release film) of the other laminated film were in contact with each other in adjacent laminated films to obtain a laminate. This laminate has one surface in the thickness direction (first surface) on which the first release film is disposed, and the other surface in the thickness direction (second surface) on which the second release film is disposed. Next, this laminate was held by a jig that sandwiched it in the thickness direction. Next, the pressure applied to the laminate in the thickness direction by the jig was adjusted so that each adhesive layer protruded from the end face of the laminate to a predetermined extent. In this state, the laminate was cut in the thickness direction 0.5 mm inward from the end face so that the outer peripheral edge of the laminate was newly formed. A specified cutting machine and a first rotary blade attached to the machine were used for cutting. This rotary blade has a disk portion and a plurality of protruding blades protruding from the peripheral edge of the disk portion in the disk radial direction. As shown in FIG. 4, the protruding blade 70 has a linear knife edge 71 (length 6 mm) for cutting the cutting object 80 at the edge on the front side when the rotary blade rotates. In the external shape processing step, the rotary blade is rotated relative to the laminate so that each protruding blade 70 cuts into the laminate (cutting object 80) from its first surface side, the rotation speed of the rotary blade is 4500 rpm, the displacement speed of the rotary blade relative to the laminate is 1000 mm/min, and the elevation angle (blade angle θ) of the knife edge 71 facing the laminate immediately before cutting is set to −5° (FIG. 4B) with respect to the laminate surface (first surface) (the blade angle θ is positive when the blade angle θ opens outward in the disk radial direction as shown in FIG. 4A, and is negative when the blade angle θ opens inward in the disk radial direction as shown in FIG. 4B). After the outer shape was processed, the pressure applied to the laminate by the jig was released.

In this manner, the optical film with a release film of Example 1 was prepared. This optical film with a release film includes a first release film (release film L1), a first adhesive layer (first adhesive sheet), a polarizing plate as an optical film, a second adhesive layer (second adhesive sheet), and a second release film (release film L4) in that order in the thickness direction, and has an uneven side end over the entire outer periphery. At this uneven side end, the edges of the first and second adhesive layers are retracted from the edges of each film in the in-plane direction of the film. In addition, in the optical film with a release film prepared as described above, the edges of the first release film, the optical film, and the second release film are substantially at the same position in the in-plane direction of the film. That is, at the side uneven end of the optical film with the release film, the first retraction length d1 of the first edge of the first adhesive layer from the edge of the first release film is substantially equal to the retraction length d1' of the first edge of the first adhesive layer from the edge of the optical film, and the second retraction length d2 of the second edge of the second adhesive layer from the edge of the second release film is substantially equal to the retraction length d2' of the second edge of the second adhesive layer from the edge of the optical film.

[Examples 2 to 6]
Each of the optical films with a release film of Examples 2 to 6 was produced in the same manner as the optical film with a release film of Example 1, except for the following.

The blade angle θ during external processing was adjusted in Examples 3 and 4 so that its absolute value was greater on the negative side than in Example 1, in Example 2 so that its absolute value was even greater on the negative side than in Examples 3 and 4, and in Example 6 so that its absolute value was even greater on the negative side than in Example 2. In Example 5, the blade angle θ during external processing was adjusted so that it was greater on the positive side than in Example 1, and the rotary blade displacement speed during the same processing was adjusted to be slower than in Example 1.

Example 7
An optical film with a release film of Example 7 was produced in the same manner as the optical film with a release film of Example 1, except that a polarizing plate with a thickness of 80 μm was used instead of the polarizing plate with a thickness of 31 μm.

Example 8
An optical film with a release film of Example 7 was produced in the same manner as the optical film with a release film of Example 1, except that a polarizing plate with a thickness of 100 μm was used instead of the polarizing plate with a thickness of 31 μm.

Comparative Example 1
An optical film with a release film of Comparative Example 1 was produced in the same manner as the optical film with a release film of Example 1, except that the operations subsequent to the above-mentioned punching process were not carried out.

Comparative Example 2
An optical film with a release film of Comparative Example 2 was produced in the same manner as the optical film with a release film of Example 1, except for the following.

A second rotary blade was used instead of the first rotary blade. This rotary blade has a disk portion and a number of protruding blades protruding from the peripheral edge of the disk portion in the disk radial direction. In the external processing step, the rotary blade was rotated relative to the laminate so that each protruding blade 70 cuts into the laminate (object to be cut 80) from its second surface side (i.e., the arrangement of the laminate relative to the rotary blade was reversed from that in Example 1), the rotation speed of the rotary blade was 4500 rpm, the displacement speed of the rotary blade relative to the laminate was 1000 mm/min, and the elevation angle (blade angle θ) of the knife edge 71 (length 6 mm) facing the laminate immediately before cutting with respect to the laminate surface (second surface) was +5° (Figure 4A).

<Retraction length>
For each optical film with a release film (optical film with double-sided release film) in Examples 1 to 8 and Comparative Examples 1 and 2, the first retraction length d1 of the first edge of the first adhesive layer and the second retraction length d2 of the second edge of the second adhesive layer were examined as follows.

First, the first release film was peeled off from the optical film with double-sided release film, and then the optical film with one-sided release film was attached to a glass plate via the first adhesive layer exposed by the peeling. Next, the second release film was peeled off from the optical film on the glass plate (optical film with double-sided adhesive layer). A predetermined portion selected from the outer peripheral edge of the optical film with double-sided adhesive layer on the glass plate was observed with an optical microscope. Specifically, the optical film with double-sided adhesive layer was observed and photographed with an optical microscope from the side opposite to the glass plate in the thickness direction of the optical film with double-sided adhesive layer. Then, in the photographed image, the retraction length d1' of the first edge of the first adhesive layer from the edge of the optical film and the retraction length d2' of the second edge of the second adhesive layer from the same edge of the optical film were measured. The measurement results are shown in Table 1 as retraction length d1 (μm) and retraction length d2 (μm) (as described above, retraction length d1' is substantially equal to retraction length d1, and retraction length d2' is substantially equal to retraction length d2).

<Peel initiation force and peel force>
For each of the optical films with a release film in Examples 1 to 8 and Comparative Examples 1 and 2, the force required to peel each release film (the peel initiation force and the subsequent peel force) was examined.

First, a test piece for measurement (approximately 25 mm short side x 150 mm long side) was cut out from the optical film with a release film. Specifically, a test piece having a length of approximately 150 mm from the uneven side end of the optical film with a release film and a width of 25 mm was cut out from the same film.

Next, the test specimen was fixed to the fixing table of a tensile testing machine (product name "Autograph", manufactured by Shimadzu Corporation). Specifically, one of the release films (the first release film or the second release film) was peeled off from the test specimen, and then the test specimen was attached to the fixing table via the adhesive layer exposed by the peeling.

Next, a gripping tape was attached to the short side of the other release film (the second release film or the first release film) located on the exposed surface side of the test piece, on the side of the uneven side end. This gripping tape has a strong adhesive surface, and the gripping tape was attached to the release film of the test piece via this strong adhesive surface.

Next, a peel test was conducted using a tensile tester to peel the release film of the adhesive layer of the test piece from the adhesive layer, and the force required for peeling was measured as the peel strength. In this measurement, the measurement temperature was 25°C, the release film was peeled off by pulling the gripping tape, the peel angle was 180°, the tensile speed was 300 mm/min, and the peel length was 100 mm. An example of a graph obtained by such a peel test is shown in Figure 5. In the graph of Figure 5, the horizontal axis represents the peel length (mm), the vertical axis represents the peel strength (gf), and Fm represents the maximum peel strength.

The peel initiation forces F1, F2 (gf/25 mm) and peel forces f1, f2 (gf/25 mm) obtained by the above peel test are shown in Table 1 (however, peel initiation forces F1, F2 were not measured for Examples 7 and 8). Peel initiation force F1 is the maximum peel strength within a peel length of 20 mm when the first release film is peeled from the first adhesive layer, and peel force f1 is the average peel strength within a peel length of 20 to 100 mm (where the peel strength is stable after passing the peel initiation force F1 at the start of peeling). Peel initiation force F2 is the maximum peel strength within a peel length of 20 mm when the second release film is peeled from the second adhesive layer, and peel force f2 is the average peel strength within a peel length of 20 to 100 mm (where the peel strength is stable after passing the peel initiation force F2 at the start of peeling).

(Prevention of peeling of heavy release film when peeling off light release film)
The optical films with release films in Examples 1 to 8 and Comparative Examples 1 and 2 were examined for the difficulty of peeling the heavy release film when the light release film was peeled off. Specifically, first, 10 evaluation samples were prepared for each optical film with release film. Next, the light release film of each evaluation sample was peeled off. A tensile tester (product name "Autograph", manufactured by Shimadzu Corporation) was used for peeling. In the peeling, the peeling angle was 180° and the tensile speed was 300 mm/min. Then, when the number of evaluation samples in which only the light release film could be properly peeled off without peeling off the heavy release film was 10, it was evaluated as "excellent", when it was 7 to 9, it was evaluated as "good", and when it was 0 to 6, it was evaluated as "poor". The evaluation results are shown in Table 1.

(Suppression of edge cracks in optical films)
The optical films with release films in Examples 1 to 8 and Comparative Examples 1 and 2 were examined for the resistance to cracking at the edge of the optical film after the light release film was peeled off. Specifically, an evaluation sample was prepared for each optical film with a release film. Next, the light release film of the evaluation sample was peeled off manually. Next, the outer periphery of the optical film (a region 1 mm from the edge) was observed with an optical microscope. Then, the optical film was evaluated as "excellent" when no cracks of 200 μm or more were generated in the outer periphery of the optical film after the light release film was peeled off, and was evaluated as "poor" when cracks of 200 μm or more were generated in the outer periphery.

<End Blocking>
The resistance to blocking at the end of each of the optical films with a release film in Examples 1 to 8 and Comparative Examples 1 and 2 was examined. Specifically, first, 10 evaluation samples were prepared for each optical film with a release film, and the 10 evaluation samples were stacked to form a film pile (first step). Next, the adhesive surface at the tip of a cylindrical rod (diameter 10 mm) having an adhesive surface at the tip was pressed from above against the optical film with a release film located at the top of the film pile, and the rod was then pulled up, and the number of optical films with a release film that were lifted up with the rod was counted (second step). A trial consisting of the first step and the subsequent second step was performed 10 times for each optical film with a release film. In the 10 trials, if the number of trials in which only one optical film with a release film was lifted up with the rod was 10, it was evaluated as "excellent", if it was 6 to 9, it was evaluated as "good", and if it was 5 or less, it was evaluated as "poor". The evaluation results are shown in Table 1.

X Optical film (optical film with release film)
Y: Optical film with pressure-sensitive adhesive layer E: Side uneven end T: Thickness direction 10: Optical film 11: First surface 12: Second surface 13: Edge 20, 30: Pressure-sensitive adhesive layer 21, 31: Adhesive surface 22: Edge (first edge)
32 Edge (second edge)
40 Light release film 42 Edge 50 Heavy release film 52 Edge

Claims (8)

an optical film having a first surface and a second surface opposite to the first surface;
a first pressure-sensitive adhesive layer attached to the first surface and having a first pressure-sensitive adhesive surface on an opposite side to the optical film;
a second pressure-sensitive adhesive layer attached to the second surface and having a second pressure-sensitive adhesive surface on the opposite side to the optical film; and
A light release film disposed on the first adhesive surface;
a heavy release film disposed on the second adhesive surface,
The optical film has a thickness of 100 μm or less,
a side uneven end portion in which a first edge of the first pressure-sensitive adhesive layer and a second edge of the second pressure-sensitive adhesive layer are recessed from respective edges of the optical film, the light release film, and the heavy release film in an in-plane direction perpendicular to the thickness direction of the optical film,
An optical film with a release film, wherein at the side uneven end, a first retraction length of the first edge from the edge of the light release film is smaller than a second retraction length of the second edge from the edge of the heavy release film. The optical film with release film according to claim 1, wherein the distance between the first edge and the second edge in the in-plane direction is 1 μm or more. The optical film with release film according to claim 1 or 2, wherein the first retraction length is 20 μm or more. The optical film with release film according to any one of claims 1 to 3, wherein the ratio of the first retraction length to the thickness of the first adhesive layer is 0.4 or more and 8 or less. An optical film with a release film according to any one of claims 1 to 4, wherein a first peel initiation force for initiating peeling of the light release film from the first adhesive surface is smaller than a second peel initiation force for initiating peeling of the heavy release film from the second adhesive surface. The optical film with release film according to claim 5, wherein the ratio of the first peel initiation force to the second peel initiation force is 0.8 or less. The optical film with release film according to claim 6, wherein the first peel initiation force is less than 800 gf/25 mm. The optical film with release film according to claim 6 or 7, wherein the second peel initiation force is 800 gf/25 mm or less.

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