Optical Film with Release Film

Abstract

To provide an optical film having a release film suitable for separating a light release film from a thin optical film having an adhesive layer on both sides while preventing a heavy release film from separating.SOLUTION: An optical film X includes an optical film Y having an adhesive layer, a light release film 40 and a heavy release film 50. The optical film Y having an adhesive layer includes: an optical film 10 of thickness 100 μm or less having a first face 11 and a second face 12; an adhesive layer 20 adhered onto the first face 11 and having an adhesive face 21; and an adhesive layer 30 adhered onto the second face 12 and having an adhesive face 31. The light release film 40 is arranged on the adhesive face 21, and the heavy release film 50 is arranged on the adhesive face 31. In a side face irregular end part E of the optical film X, edges 22 and 32 of the adhesive layers 20 and 30 retract in comparison to edges of the films 10, 40 and 50 in an in-plane direction D. A first retraction length d1 of the edge 22 is shorter than a second retraction length d2 of the edge 32.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an optical film with a release film.

Background Art

[0002] A display panel has a laminated structure including, for example, a pixel panel, a touch panel, and a transparent cover film. In the laminated structure of the display panel, an optical film having a predetermined optical function is provided. 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 surfaces of the optical film. The optical film with a release film is described in, for example, Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 6 is a schematic cross-sectional view of a film Z as an example of a conventional optical film with a release film. The film Z includes a release film 91, an adhesive layer 92, an optical film 93, an adhesive layer 94, and a release film 95 in this order in the thickness direction T. The adhesive layer 92 is attached to one surface of the optical film 93. The adhesive layer 94 is attached to the other surface of the optical film 93. The release film 91 is detachably attached to the adhesive layer 92. The release film 95 is detachably attached to the adhesive layer 94. At the end E' of the 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.

[0005] 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 step). In this step, 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 adhesively deformable adhesive layer 92 following the deformation of the release film 91. At the end E', due to the application of such a load, the end of the release film 91 is deformed so as to be pulled away from the edge 92e of the adhesive layer 92. Subsequently, the end of the release film 91 is pulled in a direction away from the edge 92e so that the separation between the release film 91 and the adhesive layer 92 progresses, and the release film 91 is removed from the adhesive layer 92. Thereafter, through the exposed adhesive layer 92, the optical film 93 and a first adherend such as a pixel panel (not shown) are joined. Next, the release film 95 is peeled off from the adhesive layer 94 (second peeling step). Next, through the adhesive layer 94 exposed by the peeling, the optical film 93 and a second adherend (not shown) are joined.

[0006] On the other hand, for example, the development of foldable display panels for smartphones and tablet terminals is progressing. In a foldable display panel, each element in the laminated structure is required to be thin and flexible.

[0007] However, in the conventional film Z, the thinner the optical film 93 is, the more likely it is that the load for starting peeling in the above-described first peeling step causes 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 pressure-sensitive adhesive layer 94 adhered to the optical film 93, and pulls the edge 94e of the pressure-sensitive adhesive layer 94 away from the release film 95. Once the edge 94e is separated from the release film 95, the separation between the pressure-sensitive adhesive layer 94 and the release film 95 tends to progress. When the separation between the pressure-sensitive adhesive layer 94 and the release film 95 progresses in the first peeling step, the next step cannot be carried out.

[0008] The present invention provides an optical film with a release film suitable for peeling a light release film while suppressing peeling of a heavy release film from a thin optical film with pressure-sensitive adhesive layers on both sides.

Means for Solving the Problems

[0009] The present invention [1] includes an optical film having a first surface and a second surface opposite to the first surface, a first pressure-sensitive adhesive layer adhered to the first surface and having a first adhesive surface on the side opposite to the optical film, a second pressure-sensitive adhesive layer adhered to the second surface and having a second adhesive surface on the side opposite to the optical film, an optical film with a pressure-sensitive adhesive layer, a light release film disposed on the first adhesive surface, and a heavy release film disposed on the second adhesive surface. The optical film has a thickness of 100 μm or less, and in a plane direction orthogonal to the thickness direction of the optical film, the first edge of the first pressure-sensitive adhesive layer and the second edge of the second pressure-sensitive adhesive layer are recessed more than the edges of the optical film, the light release film, and the heavy release film. In the side surface uneven end portion, the first recessed length of the first edge from the edge of the light release film is smaller than the second recessed length of the second edge from the edge of the heavy release film. The optical film with a release film is included.

[0010] At the side concavo-convex end of the optical film with a release film of the present invention, as described above, in the in-plane direction of the optical film, the first edge of the first adhesive layer is retracted more than the respective edges of the optical film, the lightly releasable film, and the heavily releasable film. In such a side concavo-convex end, the lightly releasable film has a free portion to which the first adhesive layer is not adhered. Therefore, when peeling the lightly releasable film from the first adhesive layer at the side concavo-convex end, first, the free portion of the lightly releasable film is lifted and deformed, and then, the edge of the already lifted and deformed lightly releasable film is pulled, and the lightly releasable film can be separated from the first edge of the first adhesive layer. That is, in the peeling start process, the force (the first force) for sufficiently deforming the edge of the lightly releasable film and the force (the second force) for separating the lightly releasable film from the first edge of the first adhesive layer that elastically deforms following the deformation of the lightly releasable film are not required simultaneously (in contrast, in the above-described film Z, the first force and the second force are required simultaneously, 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 optical film as thin as 100 μm or less in thickness is suppressed and the deformation of the second adhesive layer is also suppressed in the peeling start process of the lightly releasable film. Therefore, the second edge of the second adhesive layer is suppressed from separating from the heavily releasable film.

[0011] Also, at the side concavo-convex end of the optical film with the present release film, as described above, the first retraction length (the distance from the edge of the lightly releasable film to the first edge of the first adhesive layer in the in-plane direction of the film) is smaller than the second retraction length (the distance from the edge of the heavily releasable film to the second edge of the second adhesive layer in the in-plane direction of the film). That is, at the side concavo-convex end, in the in-plane direction of the film, the second edge of the second adhesive layer is retracted more than the first edge of the first adhesive layer. Such a configuration is suitable for suppressing the deformation of the second adhesive layer when the second force for separating the lightly releasable film from the first edge of the first adhesive layer acts on the optical film with the present release film in the peeling start process of the lightly releasable film. Therefore, it is suitable for suppressing the second edge of the second adhesive layer from separating from the heavily releasable film.

[0012] The present invention [2] includes the optical film with a release film as described in [1] above, wherein the distance between the first edge and the second edge in the in-plane direction is 1 μm or more.

[0013] Such a configuration is preferable for suppressing the above-described deformation of the second adhesive layer in the process of starting to peel the light release film. Therefore, it is preferable for suppressing the second edge of the second adhesive layer from separating from the double release film.

[0014] The present invention [3] includes the optical film with a release film as described in [1] or [2] above, wherein the first retraction length is 20 μm or more.

[0015] Such a configuration is suitable for sufficiently turning up and deforming the end portion (the free portion) of the light release film before pulling the light release film away from the first edge of the first adhesive layer in the process of starting to peel the light release film. Therefore, it is preferable for reducing the net force required for starting to peel the light release film.

[0016] The present invention [4] includes the optical film with a release film as described in any one of [1] to [3] above, 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.

[0017] Such a configuration is suitable for sufficiently turning up and deforming the end portion (the free portion) of the light release film before pulling the light release film away from the first edge of the first adhesive layer in the process of starting to peel the light release film. Therefore, it is preferable for reducing the net force required for starting to peel the light release film.

[0018] The present invention [5] includes the optical film with a release film as described in any one of [1] to [4] above, wherein the first release start force for starting to peel the light release film from the first adhesive surface is smaller than the second release start force for starting to peel the double release film from the second adhesive surface.

[0019] Such a configuration is preferable for suppressing the above-described deformation of the second adhesive layer in the peeling start process of the light peeling film, and thus is preferable for suppressing the second edge of the second adhesive layer from separating from the heavy peeling film.

[0020] The present invention [6] includes the optical film with a peeling film described in the above [5], in which the ratio of the first peeling start force to the second peeling start force is 0.8 or less.

[0021] Such a configuration is preferable for suppressing the above-described deformation of the second adhesive layer in the peeling start process of the light peeling film, and thus is preferable for suppressing the second edge of the second adhesive layer from separating from the heavy peeling film.

[0022] The present invention [7] includes the optical film with a peeling film described in the above [6], in which the first peeling start force is less than 800 gf / 25 mm.

[0023] Such a configuration is preferable for suppressing the second edge of the second adhesive layer from separating from the heavy peeling film in the peeling start process of the light peeling film, and for reducing the load on the optical film.

[0024] The present invention [8] includes the optical film with a peeling film described in the above [6] or [7], in which the second peeling start force is 800 gf / 25 mm or less.

[0025] Such a configuration is preferable for suppressing the second edge of the second adhesive layer from separating from the heavy peeling film in the peeling start process of the light peeling film, while reducing the load on the optical film in the peeling start process of the heavy peeling film from the second adhesive layer.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0027] As an embodiment of the optical film with a release film of the present invention, the optical film X 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 as shown in FIG. 1. The optical film X extends in the in-plane direction D orthogonal to the thickness direction T. The optical film Y with an adhesive layer is an element arranged at a light passing portion in the foldable device. Examples of the foldable device include a foldable display panel. The foldable display panel has a laminated structure including, for example, a pixel panel, a touch panel, and a cover film. In the laminated structure of the foldable display panel, an optical film having a predetermined optical function may be provided. 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 of the optical film included in the laminated structure in the manufacturing process of the foldable display panel.

[0028] The optical film Y with an adhesive layer includes 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 adhered to the first surface 11 and has an adhesive surface 21 (first adhesive surface) on the side opposite to the optical film 10. The easy-peel film 40 is disposed on the adhesive surface 21. The adhesive layer 30 is adhered to the second surface 12 and has an adhesive surface 31 (second adhesive surface) on the side opposite to the optical film 10. The heavy-peel film 50 is disposed on the adhesive surface 31. Further, as an edge defining the outer shape in plan view, the optical film 10 has an edge 13, the adhesive layer 20 has an edge 22 (first edge), the adhesive layer 30 has an edge 32 (second edge), the easy-peel film 40 has an edge 42, and the heavy-peel film 50 has an edge 52.

[0029] Optical film X has side surface concavo-convex end portions E at all or part of the outer peripheral ends of the film, as shown in FIG. 2. In the side surface concavo-convex end portions E, in the in-plane direction D, the edges 22 and 32 of the adhesive layers 20 and 30 are retracted more than the edges 13, 42, and 52 of the optical film 10, the lightly peeling film 40, and the heavily peeling film 50. Also, in the side surface concavo-convex end portions E, the first retraction length d1 of the edge 22 of the adhesive layer 20 from the edge 42 of the lightly peeling 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 heavily peeling film 50. The first retraction length d1 is the distance between the edges 22 and 42 in the in-plane direction D. The second retraction length d2 is the distance between the edges 32 and 52 in the in-plane direction D. Examples of the method for adjusting the first retraction length d1 include adjusting the thickness and elastic modulus of the adhesive layer 20. Examples of the method for adjusting the second retraction length d2 include adjusting the thickness and elastic modulus of the adhesive layer 30. Also, as a method for adjusting the distance between the edges 22 and 32 in the in-plane direction D (that is, the difference between the first retraction length d1 and the second retraction length d2), for example, adjustment of the cutting conditions in the cutting process described later, which is performed using a rotary blade to form the side surface concavo-convex end portions E, can be mentioned. Examples of the cutting conditions include the taper angle of the cutting edge of the rotary blade, the rotational speed of the rotary blade, the incident direction of the rotary blade with respect to the surface of the optical film laminate described later, and the displacement speed of the rotary blade for cutting the optical film laminate.

[0030] At the side concavo-convex end portion E of the optical film X, as described above, in the in-plane direction D, the edge 22 of the adhesive layer 20 is retracted more than the edges 13, 42, and 52 of the optical film 10, the light release film 40, and the heavy release film 50. In such a side concavo-convex end portion E, the light release film 40 has a free portion 40a where the adhesive layer 20 is not adhered. Therefore, when peeling the light release film 40 from the adhesive layer 20 at the side concavo-convex end portion E, first, the free portion 40a of the light release film 40 is lifted and deformed as indicated by the phantom line in FIG. 2, and then the already lifted and deformed free portion 40a 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, the force (first force) for sufficiently deforming the free portion 40a of the light release film 40 and the 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 simultaneously. 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 optical film 10 as thin as 100 μm or less is suppressed and the deformation of the adhesive layer 30 is also suppressed in the peeling start process of the light release film 40. Therefore, the separation of the edge 32 of the adhesive layer 30 from the heavy release film 50 is suppressed.

[0031] Also, at the side concavo-convex end portion 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 concavo-convex end portion E, in the in-plane direction D, the edge 32 of the adhesive layer 30 is retracted more than the edge 22 of the adhesive layer 20. Such a configuration is suitable for suppressing the 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 in the peeling start process of the light release film 40. Therefore, it is suitable for suppressing the separation of the edge 32 of the adhesive layer 30 from the heavy release film 50.

[0032] As described above, the optical film X is suitable for peeling the easy-peel film 40 while suppressing peeling of the heavy-peel film 50 from the thin optical film 10 with the adhesive layers 20 and 30.

[0033] In the optical film X, the distance between the edges 22 and 32 in the in-plane direction D is preferably 1 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more. Such a configuration is preferable for suppressing the above-described deformation of the adhesive layer 20 in the above-described peeling start process of the easy-peel film 40, and thus is preferable for suppressing the edge 42 of the adhesive layer 40 from separating from the heavy-peel film 50. Also, the distance between the edges 22 and 32 in the in-plane direction D is preferably 300 μm or less, more preferably 250 μm or less, and still more preferably 220 μm or less. Such a configuration is preferable for suppressing damage to the end portion of the optical film 10, and is also preferable for suppressing a decrease in the durability of the end portion of the optical film 10 due to a decrease in the adhesion area between the optical film 10 and the adhesive layers 20 and 30.

[0034] The first retraction length d1 is preferably 20 μm or more, more preferably 40 μm or more, and still more preferably 60 μm or more. Such a configuration is suitable for sufficiently turning up and deforming the free portion 40a of the easy-peel film 40 before pulling the easy-peel film 40 away from the edge 22 of the adhesive layer 20 in the above-described peeling start process of the easy-peel film 40, and thus is preferable for reducing the net force required for starting the peeling of the easy-peel film 40. Also, the first retraction length d1 is preferably 500 μm or less, more preferably 400 μm or less, and still more preferably 300 μm or less. The second retraction length d2 is preferably 21 μm or more, more preferably 41 μm or more, and still more preferably 61 μm or more as long as it is larger than the first retraction length d1. The second retraction length d2 is preferably 550 μm or less, more preferably 450 μm or less, and still more preferably 350 μm or less as long as it is larger 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, more preferably 1.2 or more. The ratio (d2 / d1) is preferably 5 or less, more preferably 4 or less.

[0035] The first peeling start force F1 for starting the peeling of the light peeling film 40 from the adhesive surface 21 of the adhesive layer 20 is preferably smaller than the second peeling start force F2 for starting the peeling of the double peeling film 50 from the adhesive surface 31 of the adhesive layer 30. The ratio (F1 / F2) of the first peeling start force F1 to the second peeling start 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-described deformation of the adhesive layer 20 in the process of starting the peeling of the light peeling film 40, and thus are preferable for suppressing the edge 32 of the adhesive layer 30 from separating from the double peeling film 50.

[0036] In the present embodiment, the peeling start force is the force required in the peeling start process when peeling the peeling film that is peelably attached to the adhesive layer from the adhesive layer. In the peeling start process, a force is applied to the peeling film so that the peeling film deforms in a direction away from the adhesive layer. As a result, the edge of the adhesive layer and the vicinity thereof that are attached to the peeling film are once elastically deformed so as to follow the deformation of the peeling film. Then, when the peeling film is pulled with a force large enough to pull the peeling film away from the end of the adhesive layer elastically deformed in this way, a cleavage occurs between the edge of the adhesive layer and the vicinity thereof and the peeling film, and the peeling starts. That is, the peeling start force is the force required to start peeling the peeling film from the adhesive layer by pulling the peeling film away from the end of the elastically deformed adhesive layer in the peeling start process. Such a peeling start force can be measured by the method described later with respect to the examples described later. Examples of such a method for adjusting the peeling start force include adjusting the thickness of the peeling film and selecting the type of the peeling treatment agent on the surface of the peeling film on the adhesive layer side.

[0037] The first peeling start force F1 is preferably less than 800 gf / 25 mm, more preferably 500 gf / 25 mm or less, and still more preferably 400 gf / 25 mm or less. Such a configuration is preferable for suppressing the edge 32 of the adhesive layer 30 from separating from the double-sided peeling film 50 and reducing the load on the optical film 10 during the peeling start process of the easy-peeling film 40. Also, the first peeling start force F1 is preferably 5 gf / 25 mm or more, more preferably 10 gf / 25 mm or more, and still more preferably 20 gf / 25 mm or more. Such a configuration is preferable for suppressing the floating (partial peeling) of the easy-peeling film 40 from the adhesive layer 20, for example, during transportation and handling of the optical film X.

[0038] The peeling force f1 for peeling the easy-peeling film 40 from the adhesive surface 21 of the adhesive layer 20 after the start of peeling of the easy-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 still 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 still more preferably 3 gf / 25 mm or less.

[0039] The second peeling start force F2 is preferably 800 gf / 25 mm or less, more preferably 700 gf / 25 mm or less, and still more preferably 600 gf / 25 mm or less. Such a configuration is preferable for suppressing the edge 22 of the adhesive layer 20 from separating from the double-sided peeling film 50 during the peeling start process of the easy-peeling film 40, while reducing the load on the optical film 10 during the peeling start process of the double-sided peeling film 50 from the adhesive layer 20. Also, the second peeling start force F2 is preferably 10 gf / 25 mm or more, more preferably 20 gf / 25 mm or more, and still more preferably 30 gf / 25 mm or more. Such a configuration is preferable for suppressing the floating (partial peeling) of the double-sided peeling film 50 from the adhesive layer 30, for example, during transportation and handling of the optical film X.

[0040] After the start of peeling from the adhesive layer 30 of the double-release film 50, the peeling force f2 for peeling the double-release film 50 from the adhesive surface 31 of the adhesive layer 30 is preferably 0.1 gf / 25 mm or more, more preferably 0.3 gf / 25 mm or more, still 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, still more preferably 3 gf / 25 mm or less. Further, the ratio (f1 / f2) of the above-described first peeling force f1 to the second peeling force f2 is preferably 0.8 or less, more preferably 0.7 or less. The ratio (f1 / f2) is preferably 0.1 or more, more preferably 0.2 or more.

[0041] When the optical film 10 is a polarizing plate, examples of the polarizing plate include a polarizing plate including a polarizer and a transparent protective film laminated on one or both sides of the polarizer. Examples of the polarizer include a uniaxially stretched hydrophilic polymer film adsorbed with a dichroic substance, and a polyene alignment film. Examples of the hydrophilic polymer film include a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene-vinyl acetate copolymer partially saponified film. Examples of the dichroic substance include iodine and a dichroic dye. Examples of the polyene alignment film include a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride.

[0042] As the polarizer, a thin polarizer having a thickness of 10 μm or less may be used. Examples of the thin polarizer include the polarizers described in JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917, Patent No. 4691205, and Patent No. 4751481.

[0043] As the transparent protective film, a film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and optical isotropy is preferable. Examples of the material for such a transparent protective film include cellulose resin, cyclic polyolefin resin, acrylic resin, phenyl maleimide resin, and polycarbonate resin.

[0044] From the viewpoint of flexibility, the thickness of the polarizing plate is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 70 μm or less.

[0045] 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.

[0046] The base polymer is an adhesive component that exhibits adhesiveness in the adhesive layer 20. Examples of the base polymer include acrylic polymer, silicone polymer, polyester polymer, polyurethane polymer, polyamide polymer, polyvinyl ether polymer, vinyl acetate / vinyl chloride copolymer, modified polyolefin polymer, epoxy polymer, fluorine polymer, and rubber polymer. The base polymer may be used alone or in combination of two or more. From the viewpoint of ensuring good transparency and adhesiveness in the adhesive layer 20, an acrylic polymer is preferably used as the base polymer.

[0047] The acrylic polymer is a copolymer of a monomer component containing (meth)acrylic acid alkyl ester at a ratio of 50% by mass or more. "(Meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0048] As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group with 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.

[0049] Examples of the (meth)acrylic acid alkyl ester 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, 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.

[0050] Examples of the alkyl (meth)acrylate having an alicyclic alkyl group include cycloalkyl (meth)acrylates, (meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and (meth)acrylates having a tricyclic or higher aliphatic hydrocarbon ring. Examples of the cycloalkyl (meth)acrylate include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of the (meth)acrylate having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. Examples of the (meth)acrylate having a tricyclic or higher aliphatic hydrocarbon ring 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.

[0051] As the alkyl (meth)acrylate, an alkyl acrylate having an alkyl group with 3 to 15 carbon atoms is preferably used, and more preferably, at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl acrylate is used.

[0052] The proportion of the alkyl (meth)acrylate in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more from the viewpoint of appropriately expressing basic properties such as adhesiveness in the adhesive layer 20. The proportion is, for example, 99% by mass or less.

[0053] The monomer component may contain a copolymerizable monomer copolymerizable with an (meth)acrylic acid alkyl ester. Examples of the copolymerizable monomer include monomers having a polar group. Examples of the polar group-containing monomer include monomers 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.

[0054] Examples of the monomer 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-vinyl oxazole, 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-oxazine-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

[0055] From the viewpoints of ensuring the cohesive force in the adhesive layer 20 and ensuring the adhesion to the adherend in the adhesive layer 20, the proportion of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.55% by mass or more. 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 between various additive components in the adhesive layer 20 and the acrylic polymer), the proportion is preferably 30% by mass or less, more preferably 20% by mass or less.

[0056] Examples of the hydroxy group-containing monomer 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.

[0057] From the viewpoints of introducing a crosslinked structure into the acrylic polymer and ensuring the cohesive force in the pressure-sensitive adhesive layer 20, the proportion of the hydroxy group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility between various additive components in the pressure-sensitive adhesive layer 20 and the acrylic polymer), the proportion is preferably 20% by mass or less, more preferably 10% by mass or less.

[0058] Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0059] From the viewpoints of introducing a crosslinked structure into the acrylic polymer, ensuring the cohesive force in the pressure-sensitive adhesive layer 20, and ensuring the adhesion to the adherend in the pressure-sensitive adhesive layer 20, the proportion of the carboxy group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. From the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by an acid, the proportion is preferably 30% by mass or less, more preferably 20% by mass or less.

[0060] In order to prevent metal elements such as electrodes in a foldable device from being corroded by an acid component, it is preferable that the adhesive layer 20 has a low acid content. Further, when the adhesive layer 20 is used for bonding a polarizing plate, in order to suppress the polyene formation of the polyvinyl alcohol polarizer due to the acid component, it is preferable that the adhesive layer 20 has a low acid content. In such an acid-free adhesive layer 20, the content of the organic acid monomer (for example, (meth)acrylic acid and carboxyl group-containing monomer) is preferably 100 ppm or less, more preferably 70 ppm or less, still more preferably 50 ppm or less. The content of the organic acid monomer in the adhesive layer 20 is determined by quantifying the acid monomer extracted into water by immersing the adhesive layer 20 in pure water and heating it at 100 °C for 45 minutes using an ion chromatograph.

[0061] 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, still more preferably 0.05% by mass, and ideally 0% by mass.

[0062] The monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include acid anhydride monomers, sulfonic acid group-containing monomers, phosphate 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.

[0063] In this embodiment, the base polymer has a crosslinked structure. As a method for introducing a crosslinked structure into the base polymer, a method (the first method) in which a base polymer having a functional group capable of reacting with a crosslinking agent and the crosslinking agent are blended in the first adhesive composition and the base polymer and the crosslinking agent are reacted in the adhesive layer 20, and a method (the 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 can be mentioned. These methods may be used in combination.

[0064] Examples of the crosslinking agent used in the first method include compounds that react with functional groups (such as hydroxy groups and carboxy 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 agent may be used alone or two or more kinds may be used in combination. As the crosslinking agent, isocyanate crosslinking agents, peroxide crosslinking agents, and epoxy crosslinking agents are preferably used because they have high reactivity with hydroxy groups and carboxy groups in the base polymer and it is easy to introduce a crosslinked structure.

[0065] Examples of the isocyanate crosslinking agent 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 polyphenyl isocyanate. Further, examples of the isocyanate crosslinking agent include derivatives of these isocyanates. Examples of the isocyanate derivative include isocyanurate-modified products and polyol-modified products. Examples of commercially available products of the isocyanate crosslinking agent include Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh Corporation), Coronate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh Corporation), Coronate HX (isocyanurate form of hexamethylene diisocyanate, manufactured by Tosoh Corporation), and Takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals, Inc.).

[0066] Examples of the peroxide crosslinking agent 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.

[0067] Examples of the epoxy crosslinking agent include bisphenol A, an epichlorohydrin-type epoxy resin, ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diaminoglycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0068] Isocyanate crosslinking agents (particularly bifunctional isocyanate crosslinking agents) and peroxide crosslinking agents are preferred from the viewpoint of ensuring appropriate flexibility (and thus bendability) of the pressure-sensitive adhesive layer 20. Isocyanate crosslinking agents (particularly trifunctional isocyanate crosslinking agents) are preferred from the viewpoint of ensuring the durability of the pressure-sensitive adhesive layer 20. In the base polymer, bifunctional isocyanate crosslinking agents and peroxide crosslinking agents form a more flexible two-dimensional crosslink, while trifunctional isocyanate crosslinking agents form a stronger three-dimensional crosslink. From the viewpoint of achieving both durability and flexibility of the pressure-sensitive adhesive layer 20, a combination of a trifunctional isocyanate crosslinking agent and a peroxide crosslinking agent and / or a bifunctional isocyanate crosslinking agent is preferred.

[0069] The blending amount of the crosslinking agent is, from the viewpoint of ensuring the cohesive force of the pressure-sensitive adhesive layer 20, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, more preferably 0.07 part by mass or more, based on 100 parts by mass of the base polymer. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 20, the blending amount of the crosslinking agent based on 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

[0070] In the above second method, the monomer components (including a polyfunctional monomer for introducing a crosslinked structure and other monomers) may be polymerized at once or may be polymerized in multiple steps. In the method of multi-step polymerization, first, a monofunctional monomer for forming the base polymer is polymerized (prepolymerization), thereby preparing a prepolymer composition containing a partial polymer (a mixture of a polymer with a low degree of polymerization and unreacted monomers). Next, after adding a polyfunctional monomer to the prepolymer composition, the partial polymer and the polyfunctional monomer are polymerized (main polymerization).

[0071] Examples of the polyfunctional monomer include polyfunctional (meth)acrylates containing two or more ethylenically unsaturated double bonds in one molecule. From the viewpoint of being able to introduce a crosslinked structure by active energy ray polymerization (photo polymerization), polyfunctional acrylates are preferred as the polyfunctional monomer.

[0072] Examples of the polyfunctional (meth)acrylate include difunctional (meth)acrylate, trifunctional (meth)acrylate, and polyfunctional (meth)acrylate having four or more functional groups.

[0073] Examples of the difunctional (meth)acrylate 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.

[0074] Examples of the trifunctional (meth)acrylate include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl) isocyanurate.

[0075] Examples of the polyfunctional (meth)acrylate having four or more functional groups include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, alkyl - modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

[0076] The molecular weight of the polyfunctional monomer is preferably 1500 or less, more preferably 1000 or less. Further, the functional group equivalent (g / eq) of the polyfunctional monomer is preferably 50 or more, more preferably 70 or more, still more preferably 80 or more. The functional group equivalent is preferably 500 or less, more preferably 300 or less, still more preferably 200 or less. These configurations are preferable from the viewpoint of appropriately adjusting the viscoelasticity (for example, storage elastic modulus G' and loss tangent tanδ) by introducing a crosslinked structure in the base polymer.

[0077] The acrylic polymer can be formed by polymerizing the above-described monomer components. Examples of the polymerization method include solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization. From the viewpoints of the transparency, water resistance, and cost of the adhesive layer 20, solution polymerization and UV polymerization are preferable. As the solvent for solution polymerization, for example, ethyl acetate and toluene are used. Further, as the polymerization initiator, for example, a thermal polymerization initiator and a photo polymerization initiator are used. The amount of the polymerization initiator used is, for example, 0.05 part by mass or more and, for example, 1 part by mass or less with respect to 100 parts by mass of the monomer component.

[0078] 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'-dimethylenebisobutylamidine)dihydrochloride. Examples of the peroxide polymerization initiator include dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

[0079] Examples of the photopolymerization initiator include benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, and acylphosphine oxide photopolymerization initiator.

[0080] In the polymerization, a chain transfer agent and / or a polymerization inhibitor (polymerization retarder) may be used for the purpose of molecular weight adjustment or the like. Examples of the chain transfer agent 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.

[0081] 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 higher the amount of the polymerization initiator, the higher the radical concentration in the reaction system, so the density of the reaction start points is high, and the molecular weight of the formed base polymer tends to be small. On the contrary, the lower the amount of the polymerization initiator, the lower the density of the reaction start points, so the polymer chains are likely to elongate, and the molecular weight of the formed base polymer tends to be large.

[0082] 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, still more preferably 500,000 or more. The same weight average molecular weight is preferably 5,000,000 or less, more preferably 3,000,000 or less, still more preferably 2,000,000 or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene conversion.

[0083] The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, and still more preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher.

[0084] Regarding the glass transition temperature (Tg) of the base polymer, the glass transition temperature (theoretical value) obtained based on the following Fox's equation can be used. Fox's equation is a relational equation between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of the homopolymer of the monomer constituting the polymer. In the following Fox's equation, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature (°C) of the homopolymer formed from monomer i. Literature values can be used for the glass transition temperature of the homopolymer. For example, "Polymer Handbook" (4th Edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Introduction to Synthetic Resins for Paints" (written by Kyozo Kitaoka, Polymer Publishing Society, 1995) list the glass transition temperatures of various homopolymers. On the other hand, the glass transition temperature of the homopolymer of the monomer can also be determined by the method specifically described in JP-A-2007-51271.

[0085] Fox's equation: 1 / (273 + Tg) = Σ[Wi / (273 + Tgi)]

[0086] The first adhesive composition may contain one or more kinds of oligomers in addition to the base polymer. When an acrylic polymer is used as the base polymer, preferably an acrylic oligomer is used as the oligomer. The acrylic oligomer is a copolymer of a monomer component containing 50% by mass or more of an alkyl (meth)acrylate, and has a weight average molecular weight of, for example, 1000 or more and 30000 or less.

[0087] The glass transition temperature of the acrylic oligomer is preferably 60°C or higher, more preferably 80°C or higher, still 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. By using a combination of a low-Tg acrylic polymer (base polymer) into which a crosslinked structure has been introduced and a high-Tg acrylic oligomer, the adhesive strength of the adhesive layer 20, particularly the adhesive strength at high temperatures, can be increased. The glass transition temperature of the acrylic oligomer is calculated by the above-mentioned Fox's formula.

[0088] The acrylic oligomer having a glass transition temperature of 60°C or higher is preferably a polymer of a monomer component containing an alkyl (meth)acrylate having a chain alkyl group (chain alkyl (meth)acrylate) and an alkyl (meth)acrylate having an alicyclic alkyl group (alicyclic alkyl (meth)acrylate). Specific examples of these alkyl (meth)acrylates include the alkyl (meth)acrylates described above as monomer components of the acrylic polymer.

[0089] As the chain 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. That is, the acrylic oligomer is preferably a polymer of a monomer component containing one or more selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate and methyl methacrylate.

[0090] The proportion of the 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, still more preferably 30% by weight or more. The proportion is preferably 90% by weight or less, more preferably 80% by weight or less, still more preferably 70% by weight or less. The proportion of the 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, still more preferably 70% by weight or less. The proportion is preferably 10% by weight or more, more preferably 20% by weight or more, still more preferably 30% by weight or more.

[0091] The weight average molecular weight of the acrylic oligomer is preferably 1000 or more, more preferably 1500 or more, still more preferably 2000 or more. The molecular weight is preferably 30000 or less, more preferably 10000 or less, still more preferably 8000 or less. Such a molecular weight range of the acrylic oligomer is preferable for ensuring the adhesive strength and adhesive holding power of the adhesive layer 20.

[0092] The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer. Examples of the polymerization method include solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, or a chain transfer agent may be used for the purpose of adjusting the molecular weight.

[0093] 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, still more preferably 1 part by mass or more, based on 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, still more preferably 3 parts by mass or less, based on 100 parts by mass of the base polymer. In the adhesive layer 20, when the content of the acrylic oligomer is too large, the haze tends to increase and the transparency tends to decrease due to the decrease in the compatibility of the acrylic oligomer.

[0094] 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, based on 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.

[0095] The first adhesive composition may contain other components as required. Examples of the other components include tackifiers, plasticizers, softeners, anti-degradants, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents.

[0096] From the viewpoint of ensuring sufficient adhesiveness to the adherend, the thickness H of the adhesive layer 20 is preferably 10 μm or more, more preferably 15 μm or more. From the viewpoint of handleability, the thickness H is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and particularly preferably 50 μm or less.

[0097] The ratio (d1 / H) of the above-described 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 release film 40 before the release film 40 is pulled away from the edge 22 of the adhesive layer 20 in the release start process of the release film 40. Therefore, it is preferable for reducing the net force required for the start of the release of the release film 40.

[0098] The haze of the adhesive layer 20 is preferably 3% or less, more preferably 2% or less, still 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 the haze meter include "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150 type" manufactured by Murakami Color Research Laboratory.

[0099] The total light transmittance of the adhesive layer 20 is preferably 60% or more, more preferably 80% or more, still 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).

[0100] The adhesive layer 30 is a pressure-sensitive adhesive layer formed from a 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 with respect to 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 components other than the base polymer. Examples of the same components contained in the second adhesive composition include the components other than the base polymer described above with respect to 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-described peel start 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.

[0101] 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 adhesiveness 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, still more preferably 100 μm or less, and particularly preferably 50 μm or less. Also, 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.

[0102] The haze of the adhesive layer 30 is preferably 3% or less, more preferably 2% or less, still 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).

[0103] The total light transmittance of the adhesive layer 30 is preferably 60% or more, more preferably 80% or more, still 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).

[0104] As the light release film 40, for example, a flexible plastic film can be mentioned. 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 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 later). By adjusting the presence or absence of the release treatment, the type selection, and the conditions, the above-described first release start force F1 and release force f1 related to the release of the light release film 40 from the adhesive layer 20 can be adjusted.

[0105] As the heavy release film 50, for example, the above-described plastic film for the light release film 40 can be mentioned. The thickness of the heavy release film 50 is preferably 5 μm or more, more preferably 10 μm or more, and 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. By adjusting the presence or absence of the release treatment, the type selection, and the conditions, the above-described second release start force F2 and release force f2 related to the release of the heavy release film 50 from the adhesive layer 30 can be adjusted.

[0106] The optical film X can be manufactured, for example, as follows.

[0107] First, prepare the optical film 10, the adhesive layer 20 with the light release film 40, and the adhesive layer 30 with the heavy release film 50 (preparation step).

[0108] The pressure-sensitive adhesive layer 20 with the light release film 40 can be formed by applying a first pressure-sensitive adhesive composition (varnish) onto the light release film 40 to form a coating film and then drying the coating film. Examples of the application method of the first pressure-sensitive adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, 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 pressure-sensitive adhesive composition described later). Another release film may be laminated on the pressure-sensitive adhesive layer 20 on the light release film 40. This release film is peeled off before the optical film 10 and the pressure-sensitive adhesive layer 20 are bonded together.

[0109] The pressure-sensitive adhesive layer 30 with the heavy release film 50 can be formed by applying a second pressure-sensitive 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 pressure-sensitive adhesive layer 30 on the heavy release film 50. This release film is peeled off before the optical film 10 and the pressure-sensitive adhesive layer 30 are bonded together.

[0110] Next, the first surface 11 of the optical film 10 and the pressure-sensitive adhesive layer 20 side of the pressure-sensitive adhesive layer 20 with the light release film 40 are bonded together (the first bonding step). Next, the second surface 12 of the optical film 10 and the pressure-sensitive adhesive layer 30 side of the pressure-sensitive adhesive layer 30 with the heavy release film 50 are bonded together (the second bonding step). Thereby, a laminate as the optical film X with an unprocessed outer peripheral end is obtained. Preferably, before these bondings, the first surface 11 and the second surface 12 of the optical film 10, the exposed surface of the pressure-sensitive adhesive layer 20 with the light release film 40, and the exposed surface of the pressure-sensitive adhesive layer 30 with the heavy release film 50 are subjected to plasma treatment.

[0111] Next, hold the laminate with a jig that sandwiches it in the thickness direction, and adjust the pressing force applied in the thickness direction to the laminate by the jig so that each adhesive layer 20, 30 elastically deforms and protrudes from the side end face of the laminate to a predetermined extent (pressing and holding step). By adjusting the pressing force, the degree of elastic deformation of the adhesive layers 20, 30 can be adjusted, and thus the length protruding from the side end face of the laminate can be adjusted.

[0112] Next, in a state where the adhesive layers 20, 30 are elastically deformed so as to protrude from the side end face of the laminate, cut in the thickness direction with a rotary blade so that all or part of the outer peripheral end of the laminate is newly formed within a predetermined length from the side end face of the laminate (cutting step). The predetermined length is, for example, 0.1 mm or more and, for example, 1 mm or less. Thereafter, the pressing state of the laminate by the jig is released. As a result, the adhesive layers 20, 30 elastically return, and the edges 22, 32 of the adhesive layers 20, 30 retract 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 surface uneven end portion E is formed.

[0113] In such a cutting step, by adjusting the above-described pressing force applied in the thickness direction to the laminate, the length by which the adhesive layers 20, 30 protrude from the side end face of the laminate can be adjusted, and the retraction lengths d1, d2 of the edges 22, 32 after the release of the pressing state can be adjusted. Further, as a method for adjusting the first retraction length d1, as described above, adjustment of the thickness and elastic modulus of the adhesive layer 20 can also be mentioned. As a method for adjusting the second retraction length d2, as described above, adjustment of the thickness and elastic modulus of the adhesive layer 30 can also be mentioned. Further, as a method for adjusting the distance between the edges 22, 32 in the in-plane direction D (that is, the difference between the first retraction length d1 and the second retraction length d2), as described above, adjustment of the cutting conditions in the following cutting step performed using a rotary blade to form the side surface uneven end portion E can be mentioned. Examples of the cutting conditions include the taper angle of the cutting edge of the rotary blade, the rotation speed of the rotary blade, the incident direction of the rotary blade with respect to the surface of the optical film laminate described later, and the displacement speed of the rotary blade for cutting the optical film laminate.

[0114] In the above manner, the above-described optical film X (optical film with a release film) can be manufactured.

[0115] In the above-described preparation step, instead of the light release film 40, a pressure-sensitive adhesive layer 20 with a first-step release film may be prepared using a first-step release film, and instead of the heavy release film 50, a pressure-sensitive adhesive layer 30 with a second-step release film may be prepared using a second-step release film. In this case, in the above-described first laminating step, the first surface 11 of the optical film 10 and the pressure-sensitive adhesive layer 20 side of the pressure-sensitive adhesive layer 20 with the first-step release film are laminated. Further, in the second laminating step, the second surface 12 of the optical film 10 and the pressure-sensitive adhesive layer 30 side of the pressure-sensitive adhesive layer 30 with the second-step release film are laminated (preferably, the above-described plasma treatment is performed before lamination). Thereby, a laminate including the first-step release film, the pressure-sensitive adhesive layer 20, the optical film 10, the pressure-sensitive adhesive layer 30, and the second-step release film in this order in the thickness direction is obtained. Then, in the laminate, after peeling the first-step release film from the pressure-sensitive adhesive layer 20, the light release film 40 is laminated on the exposed surface of the pressure-sensitive adhesive layer 20, and after peeling the second-step release film from the pressure-sensitive adhesive layer 30, the heavy release film 50 is laminated on the exposed surface of the pressure-sensitive adhesive layer 30. In the above manner, a laminate as the optical film X with an unprocessed outer peripheral end may be obtained. Thereafter, by performing the above-described pressure holding step and cutting step on the laminate, the optical film X (optical film with a release film) can be manufactured.

[0116] In the manufacturing process of the optical film X, in the first laminating step, the adhesive layer 20 with the first process release film is laminated on the first surface 11 of the optical film 10, while in the second laminating step, the adhesive layer 30 with the double release film 50 may be laminated on the second surface 12 of the optical film 10 (before lamination, preferably, the above-mentioned plasma treatment is carried out). Thereby, a laminate including the first process release film, the adhesive layer 20, the optical film 10, the adhesive layer 30, and the double release film 50 in this order in the thickness direction is obtained. Then, in the laminate, after peeling the first process release film from the adhesive layer 20, the light release film 40 is laminated on the exposed surface of the adhesive layer 20. In this way, a laminate as the optical film X with an unprocessed outer peripheral end may be obtained. After that, by performing the above-mentioned pressure holding step and cutting step on the laminate, the optical film X (optical film with a release film) can be manufactured.

[0117] In the manufacturing process of the optical film X, in the first laminating step, the adhesive layer 20 with the light release film 40 is laminated on the first surface 11 of the optical film 10, while in the second laminating step, the adhesive layer 30 with the second process release film may be laminated on the second surface 12 of the optical film 10 (before lamination, preferably, the above-mentioned plasma treatment is carried out). Thereby, a laminate including the light release film 40, the adhesive layer 20, the optical film 10, the adhesive layer 30, and the second process release film in this order in the thickness direction is obtained. Then, in the laminate, after peeling the second process release film from the adhesive layer 30, the double release film 50 is laminated on the exposed surface of the adhesive layer 30. In this way, a laminate as the optical film X with an unprocessed outer peripheral end may be obtained. After that, by performing the above-mentioned pressure holding step and cutting step on the laminate, the optical film X (optical film with a release film) can be manufactured.

[0118] In the manufacturing process of the optical film X, a photocurable pressure-sensitive adhesive composition may be used as the pressure-sensitive adhesive composition to form the pressure-sensitive adhesive layers 20 and 30. Examples of the photocurable pressure-sensitive adhesive composition include a UV-curable type pressure-sensitive adhesive composition in which the polymerization reaction of the contained monomer components proceeds upon irradiation with ultraviolet light. For example, when a photocurable pressure-sensitive adhesive composition is used as the second pressure-sensitive adhesive composition, first, the second pressure-sensitive adhesive composition is applied onto the second process release film to form a coating film. Next, the double release film 50 is laminated on the coating film on the second process release film. Next, the coating film is photocured by irradiating the coating film between the release films with light (such as ultraviolet light) having a predetermined wavelength. Thereby, the pressure-sensitive adhesive layer 30 is formed between the release films. Next, the second process release film is peeled off from the pressure-sensitive adhesive layer 30 on the double release film 50. The second lamination step described above may be carried out using the pressure-sensitive adhesive layer 30 with the double release film 50 thus obtained. Each other

[0119] Figures 3A to 3D illustrate an example of the usage method of the optical film X.

[0120] In this method, first, as shown in Figure 3A, the light release film 40 is peeled off from the pressure-sensitive adhesive layer 20 of the optical film X. For example, with the double release film 50 side of the optical film X fixed on the work table, a force is applied to the end of the light release film 40 at the side surface uneven end E to peel off the light release film 40 from the pressure-sensitive adhesive layer 20. Thereby, the adhesive surface 21 of the pressure-sensitive adhesive layer 20 is exposed.

[0121] At the side concavo-convex end E, as described above, in the in-plane direction D, the edge 22 of the adhesive layer 20 is retracted more than the edges 13, 42, and 52 of the optical film 10, the light release film 40, and the heavy release film 50. In such a side concavo-convex end E, as described above with reference to FIG. 2, the light release film 40 has a free portion 40a where the adhesive layer 20 is not adhered. Therefore, when peeling the light release film 40 from the adhesive layer 20 at the side concavo-convex end E, first, the free portion 40a of the light release film 40 is turned up and deformed as shown by the virtual line in FIG. 2, and then the already turned-up and deformed free portion 40a 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, the force (the first force) for sufficiently deforming the free portion 40a of the light release film 40 and the force (the 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 simultaneously. 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 optical film 10 as thin as 100 μm or less is suppressed and the deformation of the adhesive layer 30 is also suppressed in the peeling start process of the light release film 40. Therefore, the separation of the edge 32 of the adhesive layer 30 from the heavy release film 50 is suppressed.

[0122] Also, at the side concavo-convex 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 concavo-convex end E, in the in-plane direction D, the edge 32 of the adhesive layer 30 is retracted more than the edge 22 of the adhesive layer 20. Such a configuration is suitable for suppressing the 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 in the peeling start process of the light release film 40. Therefore, it is suitable for suppressing the separation of the edge 32 of the adhesive layer 30 from the heavy release film 50.

[0123] Next, as shown in FIG. 3B, the optical film 10 and the first member M1 (first adherend) are joined via the adhesive layer 20. The first member M1 is, for example, an element in the laminated structure of the flexible panel. Examples of such an element include a pixel panel, a touch panel, and a transparent cover film (the same applies to the second member M2 described later).

[0124] Next, as shown in FIG. 3C, the release film 50 is peeled off from the adhesive layer 30. As a result, the adhesive surface 31 of the adhesive layer 30 is exposed.

[0125] Next, as shown in FIG. 3D, the optical film 10 and the second member M2 (second adherend) are joined via the adhesive layer 30.

[0126] For example, in the manufacturing process of a flexible panel, the optical film X is used as described above.

Example

[0127] The present invention will be specifically described below with reference to examples. The present invention is not limited to the examples. Also, specific numerical values such as the blending amounts (contents), physical property values, and parameters described below can be replaced with the upper limits (numerical values defined as "below" or "less than") or lower limits (numerical values defined as "above" or "more than") of the corresponding blending amounts (contents), physical property values, parameters, etc. described in the above "Mode for Carrying Out the Invention".

[0128] 〔Example 1〕 <Production of the first adhesive sheet> The first adhesive sheet in Example 1 was produced as follows.

[0129] 〈Preparation of acrylic oligomer〉 In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 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 were stirred at room temperature for 1 hour under a nitrogen atmosphere. Then, 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 an acrylic oligomer). As a result, an oligomer solution containing an acrylic oligomer (solid content concentration: 50% by mass) was obtained. The weight average molecular weight of the acrylic oligomer was 4300. Also, the glass transition temperature (Tg) of the acrylic oligomer was 84 °C.

[0130] 〈Preparation of the First Acrylic Base Polymer〉 In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, a mixture (solid content concentration: 47% by mass) 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 part by mass of N-vinyl-2-pyrrolidone (NVP), 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent was stirred at 56 °C for 6 hours under a nitrogen atmosphere (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.

[0131] 〈Preparation of the First Pressure-Sensitive Adhesive Composition〉 To 100 parts by mass of the solid content of the first polymer solution, 1.5 parts by mass of an acrylic oligomer, 0.26 parts by mass of a first crosslinking agent (product name "Niper BMT-40SV", dibenzoyl peroxide, manufactured by NOF Corporation), 0.02 parts by mass of a second crosslinking agent (product name "Coronate L", trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation), 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 to prepare a first adhesive composition.

[0132] 〈Formation of the First Adhesive Sheet〉 The first adhesive composition was applied onto the release-treated surface of a release film L1 having one side silicone release-treated to form a coating film. The release film L1 is a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, manufactured by Mitsubishi Chemical Corporation) having one side silicone release-treated. Next, the release-treated surface of a release film L2 having one side silicone release-treated was bonded to the coating film on the release film L1. The release film L2 is a PET film (product name "Diafoil MRV75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) having one side silicone release-treated. 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 at 150°C for 3 minutes to form a first adhesive sheet composed of a transparent first adhesive layer with a thickness of 50 μm. In the above manner, a first adhesive sheet with release films L1 and L2 was produced.

[0133] <Production of the Second Adhesive Sheet> The second adhesive sheet in Example 1 was produced as follows.

[0134] 〈Preparation of the Second Acrylic Base Polymer〉 In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 99 parts by mass of butyl acrylate (BA), 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 0.3 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent were stirred at 60 °C for 4 hours under a nitrogen atmosphere (polymerization reaction). As a result, a second polymer solution containing a second acrylic-based polymer was obtained. The weight average molecular weight of the second acrylic-based polymer in this polymer solution was 1.65 million.

[0135] 〈Preparation of the second pressure-sensitive adhesive composition〉 To the second polymer solution, 0.3 part by mass of a first cross-linking agent (product name "Niper BMT-40SV", dibenzoyl peroxide, manufactured by NOF Corporation), 0.1 part by mass of a third cross-linking agent (product name "Takenate D110N", trimethylolpropane xylylene diisocyanate, manufactured by Mitsui Chemicals), and 0.3 part by mass of a silane coupling agent (product name "KBM403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added per 100 parts by mass of the solid content of the polymer solution and mixed to prepare a second pressure-sensitive adhesive composition.

[0136] 〈Formation of the second pressure-sensitive adhesive sheet〉 The second pressure-sensitive adhesive composition was applied onto the release-treated surface of a release film L3 having one side silicone release-treated to form a coating film. The release film L3 is a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, manufactured by Mitsubishi Chemical Corporation) having one side silicone release-treated. Next, the release-treated surface of a release film L4 having one side silicone release-treated was bonded to the coating film on the release film L3. The release film L4 is a PET film (product name "Diafoil MRV75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) having one side silicone release-treated. 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 at 150 °C for 3 minutes to form a second pressure-sensitive adhesive sheet composed of a transparent second pressure-sensitive adhesive layer with a thickness of 50 μm. In the above manner, a second pressure-sensitive adhesive sheet with release films L3 and L4 was produced.

[0137] <Manufacture of Optical Film with Release Film> First, the release film L2 was peeled off from the first adhesive sheet with double-sided release films, and the exposed surface thus exposed was subjected to plasma treatment. On the other hand, both surfaces (the first surface and the second surface) of a polarizing plate with a thickness of 31 μm were also subjected to plasma treatment. In each plasma treatment, a plasma irradiation device (product name "AP-TO5", manufactured by Sekisui Kogyo Co., Ltd.) was used, the voltage was set to 160 V, the frequency was set to 10 kHz, and the processing speed was set to 5000 mm / min (the same applies to the plasma treatment described later). Then, the exposed surface of the first adhesive sheet and the first surface of the polarizing plate were bonded together. In this bonding, in an environment of 25°C, the first adhesive sheet with the release film L1 and the polarizing plate were pressure-bonded by an operation of reciprocating a 2 kg roller once.

[0138] Next, the release film L3 was peeled off from the second adhesive sheet with release films L3 and L4, and the exposed surface thus exposed was subjected to plasma treatment. Then, the exposed surface of the second adhesive sheet and the second surface of the polarizing plate were bonded together. In this bonding, in an environment of 25°C, the second adhesive sheet with the release film L4 and the polarizing plate were pressure-bonded by an operation of reciprocating a 2 kg roller once. As a result, a laminated film having a laminated structure of the first adhesive sheet with the release film L1 (thickness: 50 μm), the polarizing plate, and the second adhesive sheet with the release film L4 (thickness: 75 μm) was obtained.

[0139] Next, using a punching machine and a Thomson blade, the laminated film was punched into a size of 150 mm × 120 mm (punching process).

[0140] Next, outer shape processing was performed as follows (outer shape processing step). First, 50 laminated films punched to the same size were stacked to obtain a laminate. Specifically, in adjacent laminated films, 50 laminated films were stacked so that the release film L1 (first release film) of one laminated film was in contact with the release film L4 (second release film) of the other laminated film, thereby obtaining a laminate. This laminate has a first surface in the thickness direction (first surface layer) where the first release film is disposed on the surface, and a second surface in the thickness direction (second surface layer) where the second release film is disposed on the surface. Next, the laminate was held by a jig that sandwiches the laminate in the thickness direction. Next, the pressing force 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 inside 0.5 mm from the end face of the laminate was cut in the thickness direction so that a new outer peripheral end of the laminate was formed. For the cutting, a predetermined cutting machine and a first rotating blade attached to the machine were used. This rotating blade has a disk portion and a plurality of protruding blades protruding in the disk diameter direction from the peripheral edge of the disk portion. As shown in FIG. 4, the protruding blade 70 has a linear knife edge 71 (length 6 mm) responsible for cutting the object to be cut 80 at the front edge during rotation of the rotating blade. In the outer shape processing step, the rotating blade was rotated with respect to the laminate so that each protruding blade 70 cut into the laminate from the first surface layer side of the laminate (object to be cut 80), the rotational speed of the rotating blade was set to 4500 rpm, the displacement speed of the rotating blade with respect to the laminate was set to 1000 mm / min, and the elevation angle (blade angle θ) of the knife edge 71 facing the laminate immediately before cutting with respect to the laminate surface (first surface layer) was set to -5° (FIG. 4B) (when the blade angle θ opens outward in the disk diameter direction as shown in FIG. 4A, it is defined as a positive blade angle θ, and when the blade angle θ opens inward in the disk diameter direction as shown in FIG. 4B, it is defined as a negative blade angle θ). Then, after the outer shape processing, the pressing state of the laminate by the jig was released.

[0141] As described above, the optical film with a release film of Example 1 was produced. This optical film with a release film includes, in the thickness direction, 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), and has side surface uneven end portions over the entire outer peripheral end. At these side surface uneven end portions, in the in-film surface direction, the edges of the first and second adhesive layers are recessed more than the edges of the respective films. Further, in the optical film with a release film produced as described above, in the in-film surface direction, the edges of the first release film, the optical film, and the second release film are substantially at the same position. That is, at the side surface uneven end portions of the optical film with a release film, the first recession length d1 of the first edge of the first adhesive layer from the edge of the first release film is substantially equal to the recession length d1' of the first edge of the first adhesive layer from the edge of the optical film, and the second recession length d2 of the second edge of the second adhesive layer from the edge of the second release film is substantially equal to the recession length d2' of the second edge of the second adhesive layer from the edge of the optical film.

[0142] 〔Examples 2 to 6〕 Except for the following, the optical films with release films of Examples 2 to 6 were produced in the same manner as the optical film with a release film of Example 1.

[0143] Regarding the above-described blade angle θ during external shape processing, in Examples 3 and 4, it was adjusted so that the absolute value becomes larger on the negative side than in Example 1, in Example 2, it was adjusted so that the absolute value becomes larger on the negative side than in Examples 3 and 4, and in Example 6, it was adjusted so that the absolute value becomes larger on the negative side than in Example 2. Further, in Example 5, the above-described blade angle θ during external shape processing was adjusted to change to the positive side from Example 1, and the above-described rotational blade displacement speed during the same processing was adjusted to be slower than in Example 1.

[0144] 〔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.

[0145] 〔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.

[0146] 〔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 after the above punching process were not performed.

[0147] 〔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.

[0148] The second rotary blade was used instead of the first rotary blade. This rotary blade has a disk portion and a plurality of protruding blades protruding in the disk diameter direction from the peripheral edge of the disk portion. In the profiling process, the rotary blade was rotated with respect to the laminate so that each protruding blade 70 cut into the laminate from the second surface layer side thereof (that is, the arrangement mode of the laminate with respect to the rotary blade was made the opposite of that in Example 1). The rotational speed of the rotary blade was set to 4500 rpm, the displacement speed of the rotary blade with respect to the laminate was set to 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 layer) was set to +5° (FIG. 4A).

[0149] 〈Retreat length〉 Regarding each optical film with a release film (optical film with a double-sided release film) in Examples 1 to 8 and Comparative Examples 1 and 2, the first retreat length d1 of the first edge of the first adhesive layer and the second retreat length d2 of the second edge of the second adhesive layer were examined as follows.

[0150] First, after peeling the first release film from the optical film with a double-sided release film, an optical film with a single-sided release film was attached to a glass plate through the first adhesive layer exposed by the peeling. Next, the second release film was peeled from the optical film (optical film with a double-sided adhesive layer) on the glass plate. A predetermined position selected from the outer peripheral edge of the optical film with a double-sided adhesive layer on the glass plate was observed with an optical microscope. Specifically, the optical film with a 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 a 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 the retraction length d1 (μm) and the retraction length d2 (μm) (as described above, the retraction length d1' is substantially equal to the retraction length d1, and the retraction length d2' is substantially equal to the retraction length d2).

[0151] 〈Peeling start force and peeling force〉 Regarding each optical film with a release film in Examples 1 to 8 and Comparative Examples 1 and 2, the force required for peeling each release film (peeling start force and subsequent peeling force) was examined.

[0152] First, a test piece for measurement (about 25 mm in short side × 150 mm in long side) was cut out from the optical film with a release film. Specifically, a test piece having a length of about 150 mm and a width of 25 mm from the side concavo-convex end of the optical film with a release film was cut out from the same film.

[0153] Next, the test piece was fixed to the fixing table of a tensile testing machine (product name "Autograph", manufactured by Shimadzu Corporation). Specifically, after peeling and removing one release film (the first release film or the second release film) from the test piece, the test piece was attached to the fixing table through the adhesive layer exposed by the peeling.

[0154] Next, a gripping tape was attached to the short side on the side of the side surface uneven end portion of the other release film (the second release film or the first release film) located on the exposed surface side of the test piece. This gripping tape has a strong adhesive surface, and the gripping tape was attached to the release film of the test piece through the strong adhesive surface.

[0155] Next, a peeling test was carried out by a tensile testing machine to peel the release film of the adhesive layer from the adhesive layer in the test piece, and the force required for peeling was measured as the peeling strength. In this measurement, the measurement temperature was set to 25 °C, the release film was peeled by pulling the gripping tape, the peeling angle was set to 180 °, the pulling speed was set to 300 mm / min, and the peeling length was set to 100 mm. An example of a graph obtained by such a peeling test is shown in FIG. 5. In the graph of FIG. 5, the horizontal axis represents the peeling length (mm), the vertical axis represents the peeling strength (gf), and Fm represents the maximum value of the peeling strength.

[0156] The peeling start forces F1, F2 (gf / 25 mm) and the peeling forces f1, f2 (gf / 25 mm) obtained by the peeling test as described above are shown in Table 1 (however, for Examples 7 and 8, the peeling start forces F1, F2 were not measured). The peeling start force F1 is the maximum value of the peeling strength within a peeling length of 20 mm when the first release film is peeled from the first adhesive layer, and the peeling force f1 is the average value of the peeling strength at a peeling length of 20 to 100 mm (the peeling strength is stable after passing through the peeling start force F1 at the start of peeling). The peeling start force F2 is the maximum value of the peeling strength within a peeling length of 20 mm when the second release film is peeled from the second adhesive layer, and the peeling force f2 is the average value of the peeling strength at a peeling length of 20 to 100 mm (the peeling strength is stable after passing through the peeling start force F2 at the start of peeling).

[0157] <Suppression of peeling of the double release film when peeling the light release film> For each optical film with a release film in Examples 1 to 8 and Comparative Examples 1 and 2, the ease of peeling of the heavy release film when the light release film was peeled was examined. Specifically, first, 10 evaluation samples were prepared for each optical film with a release film. Next, the light release film of each evaluation sample was peeled off. For the peeling, a tensile testing machine (product name "Autograph", manufactured by Shimadzu Corporation) was used. In the peeling, the peeling angle was set to 180° and the tensile speed was set to 300 mm / min. Then, when the number of evaluation samples in which only the light release film could be appropriately peeled without peeling of 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.

[0158] 〈Suppression of Edge Cracks in Optical Film〉 For each optical film with a release film in Examples 1 to 8 and Comparative Examples 1 and 2, the ease of crack generation at the edge of the optical film when the light release film was peeled was examined. Specifically, first, evaluation samples were 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 peripheral portion (region 1 mm from the edge) of the optical film was observed with an optical microscope. Then, when no crack with a length of 200 μm or more occurred in the outer peripheral portion of the optical film after peeling of the light release film, it was evaluated as "excellent", and when a crack with a length of 200 μm or more occurred, it was evaluated as "poor".

[0159] 〈Blocking at Edge〉 For each of the optical films with a release film in Examples 1 to 8 and Comparative Examples 1 and 2, the difficulty of blocking at the edges 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, with respect to the optical film with a release film located at the top of the film pile, after pressing the adhesive surface at the tip of a cylindrical rod (diameter 10 mm) having an adhesive surface at the tip from above, the rod was pulled upward, and the number of optical films with a release film lifted along with the rod was counted (second step). The 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, when the number of trials in which only 1 optical film with a release film was lifted along with the rod was 10, it was evaluated as "excellent", when it was 6 to 9, it was evaluated as "good", and when it was 5 or less, it was evaluated as "poor". The evaluation results are shown in Table 1.

[0160] [Table 1] [Explanation of symbols]

[0161] X Optical film (optical film with a release film) Y Optical film with an adhesive layer E Side uneven edge T Thickness direction 10 Optical film 11 First surface 12 Second surface 13 Edge 20, 30 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

1. An optical film having a first surface and a second surface opposite to the first surface, a first adhesive layer adhered to the first surface and having a first adhesive surface on the side opposite to the optical film, a second adhesive layer adhered to the second surface and having a second adhesive surface on the side opposite to the optical film, an optical film with an adhesive layer, a light release film disposed on the first adhesive surface, a heavy release film disposed on the second adhesive surface, wherein the optical film has a thickness of 100 μm or less, in a plane direction orthogonal to the thickness direction of the optical film, the first edge of the first adhesive layer and the second edge of the second adhesive layer are recessed more than the edges of the optical film, the light release film, and the heavy release film, having a side surface uneven end portion, In the side surface uneven end portion, a first recess length of the first edge from the edge of the light release film is smaller than a second recess length of the second edge from the edge of the heavy release film, an optical film with a release film.

2. The optical film with a release film according to claim 1, wherein a distance between the first edge and the second edge in the plane direction is 1 μm or more.

3. The optical film with a release film according to claim 1 or 2, wherein the first recess length is 20 μm or more.

4. The optical film with a release film according to any one of claims 1 to 3, wherein a ratio of the first recess length to the thickness of the first adhesive layer is 0.4 or more and 8 or less.

5. The optical film with a release film according to any one of claims 1 to 4, wherein a first release start force for starting peeling of the light release film from the first adhesive surface is smaller than a second release start force for starting peeling of the heavy release film from the second adhesive surface.

6. The optical film with a release film according to claim 5, wherein a ratio of the first release start force to the second release start force is 0.8 or less.

7. The optical film with a release film according to claim 6, wherein the first release start force is less than 800 gf / 25 mm.

8. The optical film with a release film according to claim 6 or 7, wherein the second release start force is 800 gf / 25 mm or less.

Images