CN117580708A

CN117580708A - Optical film with release film

Info

Publication number: CN117580708A
Application number: CN202280046737.XA
Authority: CN
Inventors: 野田美菜子; 三浦大生; 宝田翔
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-06-30
Filing date: 2022-06-14
Publication date: 2024-02-20
Also published as: JP2023006650A; TW202309562A; WO2023276653A1; KR20240028347A

Abstract

The optical film (X) with a release film of the present invention has an optical film (Y) with an adhesive layer, a light release film (40), and a heavy release film (50). An optical film (Y) with an adhesive layer, which has an optical film (10), an adhesive layer (20), and an adhesive layer (30), wherein the optical film (10) has a first surface (11) and a second surface (12) and has a thickness of 100 [ mu ] m or less; the adhesive layer (20) is adhered to the first surface (11) and has an adhesive surface (21); the adhesive layer (30) is affixed to the second face (12) and has an adhesive face (31). The light release film (40) is disposed on the adhesive surface (21), and the heavy release film (50) is disposed on the adhesive surface (31). At the side surface concave-convex end (E) of the optical film (X), the end edges (22, 32) of the adhesive layers (20, 30) are set back from the end edges of the films (10, 40, 50) in the in-plane direction (D), and the first set back length D1 of the end edges (22) is smaller than the second set back length D2 of the end edges (32).

Description

Optical film with release film

Technical Field

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

Background

The display panel has a laminated structure including a pixel panel, a touch panel, a transparent cover film, and the like, for example. An optical film having a predetermined optical function is provided in the laminated structure of the display panel. Examples of the optical film include a polarizing plate in a film form and a retardation film. The optical film is manufactured, for example, as a release film-attached optical film having an adhesive layer and a release film provided on both sides of the optical film. For example, patent document 1 below describes an optical film with a release film.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2020-190754

Disclosure of Invention

Problems to be solved by the invention

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 has 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. An adhesive layer 94 is attached to the other side of the optical film 93. The release film 91 is releasably adhered to the adhesive layer 92. The release film 95 is releasably adhered to the adhesive layer 94. At the end E' of the film Z, the end edge 91E of the release film 91, the end edge 92E of the adhesive layer 92, the end edge 93E of the optical film 93, the end edge 94E of the adhesive layer 94, and the end edge 95E of the release film 95 are flush with each other.

When such a film Z is used in the manufacturing process of the display panel, first, the release film 91 is peeled 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 the peeling. The load includes: a force required to sufficiently deform the release film 91 at the end E' and a force required to pull the adhesive layer 92 away from the release film 91 elastically deformed following the deformation of the release film 91. At the end E', by applying such a load, the end of the release film 91 is deformed so as to be pulled away from the end edge 92E of the adhesive layer 92. Then, the end portion of the release film 91 is pulled in a direction away from the end edge 92e so that the pulling-off between the release film 91 and the adhesive layer 92 is performed, thereby removing the release film 91 from the adhesive layer 92. Then, the optical film 93 is bonded to a first adherend (not shown) such as a pixel panel by the exposed adhesive layer 92. Next, the release film 95 is peeled from the adhesive layer 94 (second peeling step). Next, the optical film 93 is bonded to a second adherend (not shown) via the pressure-sensitive adhesive layer 94 exposed by the peeling.

On the other hand, development of a display panel that is foldable (foldable) repeatedly, for example, for a smart phone and a tablet computer terminal, is advancing. In a foldable display panel, each element in the laminated structure is required to be thin and flexible.

However, in the conventional film Z, the thinner the optical film 93 is, the more the load for starting the peeling in the first peeling step is likely to cause significant deformation of the optical film 93 at the end E' of the film Z. Such deformation of the optical film 93 causes deformation of the adhesive layer 94 attached to the optical film 93, and pulls the end edge 94e of the adhesive layer 94 away from the release film 95. Once the end edge 94e is detached from the release film 95, separation between the adhesive layer 94 and the release film 95 is easily performed. In the first peeling step, when separation between the adhesive layer 94 and the release film 95 is performed, the next step cannot be performed.

The present invention provides an optical film with a release film which is suitable for peeling a light release film from a thin optical film with an adhesive layer on both sides while suppressing peeling of a heavy release film.

Means for solving the problems

The invention [1] comprises an optical film with a release film having an optical film with an adhesive layer, a light release film and a heavy release film, the optical film with an adhesive layer having an optical film, a first adhesive layer and a second adhesive layer, the optical film having a first face and a second face on the opposite side from the first face; the first adhesive layer is adhered to the first surface and has a first adhesive surface on a side opposite to the optical film, the second adhesive layer is adhered to the second surface and has a second adhesive surface on a side opposite to the optical film, the light release film is disposed on the first adhesive surface, the heavy release film is disposed on the second adhesive surface, the optical film has a thickness of 100 [ mu ] m or less, and side concave-convex end portions are provided in an in-plane direction orthogonal to the thickness direction of the optical film, wherein a first end edge of the first adhesive layer and a second end edge of the second adhesive layer recede from each end edge of the optical film, the light release film, and the heavy release film, and a first receding length of the first end edge from an end edge of the light release film is smaller than a second receding length of the second end edge from an end edge of the heavy release film at the side concave-convex end portions.

At the side concave-convex end portion of the optical film with a release film of the present invention, as described above, the first end edge of the first adhesive layer is receded in the in-plane direction of the optical film compared to the respective end edges of the optical film, the light release film, and the heavy release film. At such side concave-convex end portions, the light release film has an empty portion to which the first adhesive layer is not attached. Therefore, at the side concave-convex end portion, when the light release film is peeled from the first adhesive layer, the free portion of the light release film is peeled first to deform it, and then the end portion of the light release film, which has peeled off the deformation, is pulled, whereby the light release film can be pulled away from the first end edge of the first adhesive layer. That is, in the peeling start process, it is not necessary to apply a force (first force) for sufficiently deforming the end portion of the light peeling film and a force (second force) for pulling the light peeling film away from the first end edge of the first adhesive layer elastically deformed following the deformation of the light peeling film at the same time (in contrast, in the film Z described above, it is necessary to apply the first force and the second force at the same time, and therefore the force required in the peeling start process is large). Such an optical film with a release film is suitable for reducing the force required for the peeling start process. The smaller the force, the more the deformation of the thin optical film having a thickness of 100 μm or less is suppressed during the peeling start of the light peeling film, and the more the deformation of the second adhesive layer is suppressed, and therefore the second edge of the second adhesive layer is suppressed from being peeled off from the heavy peeling film.

In addition, as described above, at the side concave-convex end portion of the present optical film with a release film, the first back length (distance from the end edge of the light release film to the first end edge of the first adhesive layer in the film in-plane direction) is smaller than the second back length (distance from the end edge of the heavy release film to the second end edge of the second adhesive layer in the film in-plane direction). That is, at the side surface concave-convex end portion, the second end edge of the second adhesive layer is receded from the first end edge of the first adhesive layer in the film in-plane direction. Such a configuration is suitable for suppressing deformation of the second adhesive layer when the above-described second force for pulling the light release film away from the first end edge of the first adhesive layer acts on the present optical film with release film during the start of the release of the light release film, and therefore is suitable for suppressing detachment of the second end edge of the second adhesive layer from the heavy release film.

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

Such a configuration is preferable for suppressing the deformation of the second adhesive layer during the peeling start of the light release film, and is therefore preferable for suppressing the separation of the second end edge of the second adhesive layer from the heavy release film.

The invention [3] comprises the optical film with a release film according to the above [1] or [2], wherein the first back length is 20 μm or more.

Such a configuration is suitable for sufficiently lifting up and deforming the end portion (the above-described free portion) of the light release film before the light release film is pulled away from the first end edge of the first adhesive layer in the peeling start process of the light release film, and is therefore preferable for reducing the force (total force) required for peeling start of the light release film.

The invention [4] comprises the optical film with a release film according to any one of [1] to [3], wherein the ratio of the first back length to the thickness of the first adhesive layer is 0.4 to 8.

Such a configuration is suitable for sufficiently lifting up and deforming the end portion (the above-described free portion) of the light release film before the light release film is pulled away from the first end edge of the first adhesive layer in the peeling start process of the light release film, and is therefore preferable for reducing the force required for peeling start of the light release film.

The invention [5] comprises the optical film with a release film of any one of [1] to [4], wherein a first release initiation force for initiating release of the light release film from the first adhesive surface is smaller than a second release initiation force for initiating release of the heavy release film from the second adhesive surface.

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

Such a configuration is preferable for suppressing the deformation of the second adhesive layer during the peeling start of the light release film, and is therefore preferable for suppressing the detachment of the second end edge of the second adhesive layer from the heavy release film.

The invention [7] comprises the optical film with a release film described in the above [6], wherein the first peeling starting force is less than 800gf/25mm.

Such a configuration is preferable for suppressing detachment of the second end edge of the second adhesive layer from the heavy release film during the start of peeling of the light release film and reducing the load on the optical film.

The invention [8] comprises the optical film with a release film according to the above [6] or [7], wherein the second peeling starting force is 800gf/25mm or less.

Such a configuration is preferable for suppressing detachment of the second edge of the second adhesive layer from the heavy release film during the start of peeling of the light release film, and for reducing the load on the optical film during the start of peeling of the heavy release film from the second adhesive layer.

Drawings

FIG. 1 is a schematic cross-sectional view of one embodiment of an optical film with a release film of the present invention.

Fig. 2 is an enlarged partial cross-sectional schematic view of the optical film with release film shown in fig. 1.

Fig. 3 shows an example of a method for using the optical film with a release film of the present invention. Fig. 3A shows a first peeling step of peeling the light release film, fig. 3B shows a first bonding step of bonding the optical film to the first adherend with the first adhesive layer, fig. 3C shows a second peeling step of peeling the heavy release film, and fig. 3D shows a second bonding step of bonding the optical film to the second adherend with the second adhesive layer.

Fig. 4 is a schematic view for explaining the cutting edge angle of the rotary blade used in the profile working process in the examples and the comparative examples.

Fig. 5 shows an example of a graph obtained by a peeling test of peeling a release film on an adhesive layer from the adhesive layer.

Fig. 6 is a schematic cross-sectional view of a conventional optical film with a release film.

Detailed Description

As shown in fig. 1, an optical film X as one embodiment of the optical film with a release film of the present invention has a light release film 40 (light release liner), an optical film Y with an adhesive layer, and a heavy release film 50 (heavy release liner) in this order in the thickness direction T. The optical film X extends in an in-plane direction D orthogonal to the thickness direction T. The optical film Y with the adhesive layer is an element to be arranged to a light passing portion in the foldable device. As the foldable device, for example, a foldable display panel can be cited. The foldable display panel has a laminated structure including, for example, a pixel panel, a touch panel, a cover film, and the like. 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 polarizing plate in a film form 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 above-described laminated structure in the manufacturing process of the foldable display panel.

The adhesive layer-equipped optical film Y has an optical film 10 having a thickness of 100 μm or less, an adhesive layer 20 (first adhesive layer), and an adhesive layer 30 (second adhesive layer). The optical film 10 has a first surface 11 and a second surface 12 opposite to the first surface 11. The adhesive layer 20 is attached to the first face 11 and has an adhesive face 21 (first adhesive face) on the opposite side to the optical film 10. The light release film 40 is disposed on the adhesive surface 21. The adhesive layer 30 is attached to the second face 12 and has an adhesive face 31 (second adhesive face) on the opposite side to the optical film 10. The re-release film 50 is disposed on the adhesive surface 31. In addition, as the end edge defining the top-view outer contour shape, the optical film 10 has an end edge 13, the adhesive layer 20 has an end edge 22 (first end edge), the adhesive layer 30 has an end edge 32 (second end edge), the light release film 40 has an end edge 42, and the heavy release film 50 has an end edge 52.

As shown in fig. 2, the optical film X has a side surface concave-convex end E on all or a part of the outer peripheral end of the film. At the side concave-convex end E, the end edges 22, 32 of the adhesive layers 20, 30 recede in the in-plane direction D compared to the end edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50. In addition, at the side surface concave-convex end portion E, the first receding length d1 of the end edge 22 of the adhesive layer 20 from the end edge 42 of the light release film 40 is smaller than the second receding length d2 of the end edge 32 of the adhesive layer 30 from the end edge 52 of the heavy release film 50. The first retreating length D1 is the distance between the end edges 22, 42 in the in-plane direction D. The second receding length D2 is the distance between the end edges 32, 52 in the in-plane direction D. As a method of adjusting the first back length d1, for example, the thickness of the adhesive layer 20 and the elastic modulus are adjusted. As a method of adjusting the second back length d2, for example, the thickness of the adhesive layer 30 and the elastic modulus are adjusted. As a method for adjusting the distance between the edges 22 and 32 in the in-plane direction D (i.e., the difference between the first retreated length D1 and the second retreated length D2), for example, adjustment of cutting conditions in a cutting process to be described later, which is performed using a rotary blade to form the side surface concave-convex end portion E, may be mentioned. Examples of the cutting conditions include: the taper angle of the edge of the rotary blade, the rotation speed of the rotary blade, the incidence direction of the rotary blade on the surface of the optical film laminate described later, and the displacement speed of the rotary blade for cutting the optical film laminate.

As described above, at the side concave-convex end E of the optical film X, the end edge 22 of the adhesive layer 20 is retreated in the in-plane direction D compared to the end edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50. At such side concave-convex end portion E, the light release film 40 has a free portion 40a to which the adhesive layer 20 is not attached. Therefore, at the side concave-convex end portion E, when the light release film 40 is peeled from the adhesive layer 20, first, as shown by a broken line in fig. 2, the free portion 40a of the light release film 40 is lifted up to be deformed, and then, the free portion 40a, which has lifted up to be deformed, is pulled, whereby the light release film 40 can be pulled away from the end edge 22 of the adhesive layer 20. That is, in the peeling start process, it is not necessary to apply both a force (first force) for sufficiently deforming the free portion 40a of the light peeling film 40 and a force (second force) for pulling the light peeling film 40 away from the end edge 22 of the adhesive layer 20 elastically deformed following the deformation of the light peeling film 40. Such an optical film X is suitable for reducing the force required for the peeling start process. The smaller the force, the more the deformation of the thin optical film 10 having a thickness of 100 μm or less is suppressed during the peeling start of the light peeling film 40, and the more the deformation of the adhesive layer 30 is suppressed, and therefore the detachment of the end edge 32 of the adhesive layer 30 from the heavy peeling film 50 is suppressed.

In addition, at the side concave-convex end portion E of the optical film X, as described above, the first receding length d1 is smaller than the second receding length d2. That is, at the side surface concave-convex end E, the end edge 32 of the adhesive layer 30 is retreated from the end edge 22 of the adhesive layer 20 in the in-plane direction D. Such a configuration is suitable for suppressing deformation of the adhesive layer 30 when the above-described second force for pulling the light release film 40 away from the end edge 22 of the adhesive layer 20 acts on the optical film X during the start of peeling of the light release film 40, and therefore is suitable for suppressing detachment of the end edge 32 of the adhesive layer 30 from the heavy release film 50.

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

The distance between the edges 22, 32 in the in-plane direction D of the optical film X 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 deformation of the adhesive layer 20 during the peeling start of the light peeling film 40, and is therefore preferable for suppressing the detachment of the edge 42 of the adhesive layer 40 from the heavy peeling film 50. The distance between the edges 22, 32 in the in-plane direction D is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 220 μm or less. Such a configuration is preferable for suppressing damage to the end portion of the optical film 10, and is preferable for suppressing a decrease in durability of the end portion of the optical film 10 due to a decrease in the tacky area between the optical film 10 and the adhesive layers 20, 30.

The first retreating 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 lifting off and deforming the free portion 40a of the light release film 40 before the light release film 40 is pulled away from the end edge 22 of the adhesive layer 20 in the above-described peeling start process of the light release film 40, and is therefore preferable for reducing the force (total force) required for peeling start of the light release film 40. The first retraction length d1 is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less. The second back length d2 is preferably 21 μm or more, more preferably 41 μm or more, and even more preferably 61 μm or more, as long as it is larger than the first back length d 1. The second back length d2 is preferably 550 μm or less, more preferably 450 μm or less, and even more preferably 350 μm or less, as long as it is larger than the first back length d 1. The ratio (d 2/d 1) of the second back-off length d2 to the first back-off length d1 is preferably 1.1 or more, more preferably 1.2 or more. The ratio (d 2/d 1) is preferably 5 or less, more preferably 4 or less.

The first peeling start force F1 for starting 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 peeling of the heavy 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 during the peeling start of the light release film 40, and therefore are preferable for suppressing the detachment of the end edge 32 of the adhesive layer 30 from the heavy release film 50.

In the present embodiment, the peeling start force is a force required in the peeling start process when the peeling film peelably attached to the pressure-sensitive adhesive layer is peeled from the pressure-sensitive adhesive layer. During the peeling start, a force is applied to the peeling film to deform the peeling film in a direction away from the adhesive layer. Thus, the edge of the pressure-sensitive adhesive layer attached to the release film and the vicinity thereof are elastically deformed so as to follow the deformation of the release film. When the release film is pulled with a force sufficient to pull the release film away from the end of the pressure-sensitive adhesive layer that has been elastically deformed in this way, a crack is generated between the end edge of the pressure-sensitive adhesive layer and the release film is initiated. That is, the peeling start force is a force required to pull the peeling film away from the end portion of the pressure-sensitive adhesive layer, which is elastically deformed, and start peeling of the peeling film from the pressure-sensitive adhesive layer in the peeling start process. Such a peeling start force can be measured by a method described later with respect to examples described later. Examples of such a method for adjusting the peeling start force include adjusting the thickness of the release film and selecting the type of the peeling treatment agent on the pressure-sensitive adhesive layer side surface of the release film.

The first peeling start force F1 is preferably less than 800gf/25mm, more preferably 500gf/25mm or less, and still more preferably 400gf/25mm or less. Such a configuration is preferable for suppressing detachment of the end edge 32 of the adhesive layer 30 from the heavy release film 50 and reducing the load on the optical film 10 during the peeling start of the light release film 40. The first peeling start force F1 is preferably 5gf/25mm or more, more preferably 10gf/25mm or more, and still more preferably 20gf/25mm or more. Such a configuration is preferable for suppressing the lifting (partial peeling) of the light release film 40 from the adhesive layer 20 at the time of, for example, the transport and the operation of the optical film X.

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

The second peeling start force F2 is preferably 800gf/25mm or less, more preferably 700gf/25mm or less, and still more preferably 600gf/25mm or less. Such a configuration is preferable for suppressing separation of the edge 32 of the adhesive layer 30 from the heavy release film 50 during the start of peeling of the light release film 40, and for reducing the load on the optical film 10 during the start of peeling of the heavy release film 50 from the adhesive layer 30. The second peeling start force F2 is preferably 10gf/25mm or more, more preferably 20gf/25mm or more, and still more preferably 30gf/25mm or more. Such a configuration is preferable for suppressing the bulge (partial peeling) of the heavy release film 50 from the adhesive layer 30 at the time of, for example, the transport and the operation of the optical film X.

The peeling force f2 for peeling the heavy release film 50 from the adhesive surface 31 of the adhesive layer 30 after the peeling of the heavy release film 50 from the adhesive layer 30 is started is preferably 0.1gf/25mm or more, more preferably 0.3gf/25mm or more, and still more preferably 0.5gf/25mm or more. The peel force f2 is preferably 5gf/25mm or less, more preferably 4gf/25mm or less, and still more preferably 3gf/25mm or less. The ratio (f 1/f 2) of the peeling force f1 to the peeling force f2 is preferably 0.8 or less, more preferably 0.7 or less. The ratio (f 1/f 2) is preferably 0.1 or more, more preferably 0.2 or more.

In the case where the optical film 10 is a film-like polarizing plate (polarizing film), examples of the polarizing film include a polarizing film having a polarizer and a transparent protective film attached to one or both surfaces of the polarizer. Examples of the polarizer include: uniaxially stretched hydrophilic polymer films and polyene oriented films having adsorbed dichroic materials. Examples of the hydrophilic polymer film include: polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films. Examples of the dichroic substance include iodine and a dichroic dye. Examples of the polyene oriented film include a dehydrated polyvinyl alcohol and a dehydrochlorinated polyvinyl chloride.

As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. Examples of the thin polarizer include: polarizers described in Japanese patent application laid-open No. 51-069644, japanese patent application laid-open No. 2000-338329, WO2010/100917, japanese patent No. 4691205 and Japanese patent No. 4751481.

As the transparent protective film, a film excellent in transparency, mechanical strength, thermal stability, moisture blocking property, and optical isotropy is preferable. Examples of the material of such a transparent protective film include: cellulose resins, cyclic polyolefin resins, acrylic resins, N-phenylmaleimide resins, and polycarbonate resins.

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

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

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

The acrylic polymer is a copolymer containing a monomer component of an alkyl (meth) acrylate in a proportion of 50 mass% or more. "(meth) acrylic" refers to acrylic and/or methacrylic.

As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms can be suitably used. The alkyl (meth) acrylate may have a linear alkyl group or a branched alkyl group, or may have a cyclic alkyl group such as an alicyclic alkyl group.

Examples of the alkyl (meth) acrylate having a linear alkyl group or a branched alkyl group include: methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-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 (i.e., lauryl (meth) acrylate, isotridecyl (meth) acrylate, tetradecyl (meth) acrylate, isotetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, and nonadecyl (meth) acrylate.

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 an aliphatic hydrocarbon ring having three or more rings. 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 an aliphatic hydrocarbon ring having three or more rings include: tetrahydrodicyclopentadiene (meth) acrylate, tetrahydrodicyclopentadiene oxyethyl (meth) acrylate, tetrahydrotricyclopentadienyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate and 2-ethyl-2-adamantyl (meth) acrylate.

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

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 exhibiting basic characteristics such as adhesiveness in the adhesive layer 20. The ratio is, for example, 99 mass% or less.

The monomer component may comprise a copolymerizable monomer capable of copolymerizing with the alkyl (meth) acrylate. 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, hydroxyl group-containing monomers, and carboxyl group-containing monomers. The polar group-containing monomer contributes to the modification of the acrylic polymer such as introducing crosslinking points into the acrylic polymer and securing the cohesive force of the acrylic polymer.

Examples of the monomer having a nitrogen atom-containing ring include: n-vinyl-2-pyrrolidone, N-methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinylOxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholone, N-vinyl-2-caprolactam, N-vinyl-1, 3- >Oxazin-2-one, N-vinyl-3, 5-morpholinedione, N-vinylpyrazole, N-vinyli->Oxazole, N-vinylthiazole and N-vinylisothiazole. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

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

Examples of the hydroxyl 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 hydroxyl group-containing monomers, 4-hydroxybutyl (meth) acrylate is preferably used, and 4-hydroxybutyl acrylate is more preferably used.

The proportion of the hydroxyl group-containing monomer in the monomer component is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and even more preferably 0.8 mass% or more, from the viewpoints of introducing a crosslinked structure into the acrylic polymer and securing the cohesive force of the adhesive layer 20. From the viewpoint of adjusting the polarity of the acrylic polymer (regarding the compatibility of various additive components in the adhesive layer 20 with the acrylic polymer), this ratio is preferably 20 mass% or less, more preferably 10 mass% or less.

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

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

In order to prevent corrosion of metal elements such as electrodes in the foldable device by acid components, the adhesive layer 20 preferably has a small acid content. In the case where the adhesive layer 20 is used for adhesion of a polarizing plate, the adhesive layer 20 preferably contains a small amount of acid in order to suppress the polyvinyl alcohol polarizer from being multi-olefinated by the acid component. The content of the organic acid monomer (e.g., (meth) acrylic acid and carboxyl group-containing monomer) in the acid-free adhesive layer 20 is preferably 100ppm or less, more preferably 70ppm or less, and still more preferably 50ppm or less. The organic acid monomer content of the adhesive layer 20 can be determined by quantifying the acid monomer extracted into water by immersing the adhesive layer 20 in pure water and heating at 100 ℃ for 45 minutes using an ion chromatograph.

From the standpoint of acid-free, the base polymer in the adhesive layer 20 preferably contains substantially no organic acid monomer as a monomer component. The proportion of the organic acid monomer in the monomer component is preferably 0.5 mass% or less, more preferably 0.1 mass% or less, still more preferably 0.05 mass% or less, and still more preferably 0 mass% or less, from the viewpoint of acid-free.

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

In this embodiment, the base polymer has a crosslinked structure. As a method for introducing a crosslinked structure into the base polymer, there can be mentioned: a method (first method) of compounding a base polymer having a functional group capable of reacting with a crosslinking agent and a crosslinking agent into a first adhesive composition, and reacting the base polymer with the crosslinking agent in the adhesive layer 20; and a method (second method) of forming a base polymer having a branched structure (crosslinked structure) incorporated in a polymer chain by polymerization of a monomer component forming the base polymer, including a polyfunctional monomer. These methods may be used in combination.

Examples of the crosslinking agent used in the first method include compounds that react with functional groups (e.g., hydroxyl groups and carboxyl groups) contained in the base polymer. Examples of such a crosslinking agent include: isocyanate crosslinking agent, peroxide crosslinking agent, epoxy crosslinking agent,Oxazoline crosslinkers, aziridine crosslinkers, carbodiimide crosslinkers, and metal chelate crosslinkers. The crosslinking agent may be used alone, or two or more thereof may be used in combination. As the crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent and an epoxy crosslinking agent are preferably used because of high reactivity with hydroxyl groups and carboxyl groups in the base polymer and easy introduction of a crosslinked structure.

Examples of the isocyanate crosslinking agent include: toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate and polymethylene polyphenyl isocyanates. In addition, as the isocyanate crosslinking agent, derivatives of these isocyanates can be mentioned. Examples of the isocyanate derivative include isocyanurate modified products and polyol modified products. Examples of the commercial products of the isocyanate crosslinking agent include: coronate L (trimethylolpropane adduct of toluene 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 Sanyo chemical corporation).

As peroxide crosslinking agents, there may be mentioned: dibenzoyl peroxide, bis (2-ethylhexyl) peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate and tert-butyl peroxypivalate.

As the epoxy crosslinking agent, there may be mentioned: bisphenol a, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N' -tetraglycidyl-m-xylylenediamine and 1, 3-bis (N, -diglycidyl aminomethyl) cyclohexane.

From the viewpoint of ensuring moderate flexibility (and thus bendability) of the adhesive layer 20, isocyanate crosslinking agents (particularly difunctional isocyanate crosslinking agents) and peroxide crosslinking agents are preferable. From the viewpoint of ensuring the durability of the adhesive layer 20, an isocyanate crosslinking agent (particularly, a trifunctional isocyanate crosslinking agent) is preferable. In contrast to the base polymer, which forms softer two-dimensional crosslinks, the difunctional isocyanate crosslinker and the peroxide crosslinker form stronger three-dimensional crosslinks. From the viewpoint of achieving both durability and flexibility of the adhesive layer 20, it is preferable to use a trifunctional isocyanate crosslinking agent in combination with a peroxide crosslinking agent and/or a difunctional isocyanate crosslinking agent.

From the viewpoint of ensuring the cohesive force of the adhesive layer 20, the amount of the crosslinking agent to be blended is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the base polymer. From the viewpoint of ensuring good adhesion in the pressure-sensitive adhesive layer 20, the amount of the crosslinking agent blended is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer.

In the above-described second method, the monomer component (including the polyfunctional monomer for introducing a crosslinked structure and other monomers) may be polymerized at one time or may be polymerized in multiple steps. In the multi-step polymerization method, first, a monofunctional monomer used for forming a base polymer is polymerized (prepolymerized), thereby producing a prepolymer composition containing a part of a polymer (a mixture of a polymer having a low degree of polymerization and an unreacted monomer). Next, a polyfunctional monomer is added to the prepolymer composition, and then a part of the polymer is polymerized with the polyfunctional monomer (main polymerization).

Examples of the polyfunctional monomer include polyfunctional (meth) acrylates having two or more ethylenically unsaturated double bonds in one molecule. As the polyfunctional monomer, a polyfunctional acrylate is preferable from the viewpoint that a crosslinked structure can be introduced by active energy ray polymerization (photopolymerization).

As the polyfunctional (meth) acrylate, there may be mentioned: difunctional (meth) acrylates, trifunctional (meth) acrylates and multifunctional (meth) acrylates of more than tetrafunctional.

Examples of the difunctional (meth) acrylate include: ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, stearic acid modified pentaerythritol di (meth) acrylate, dihydro-dicyclopentadiene acrylate, di (meth) acryl isocyanurate, and alkylene oxide modified bisphenol di (meth) acrylate.

Examples of the trifunctional (meth) acrylate include: trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and tris (acryloxyethyl) isocyanurate.

Examples of the polyfunctional (meth) acrylate having four or more functions include: di (trimethylolpropane) tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxy penta (meth) acrylate, alkyl modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa (meth) acrylate.

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

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

Examples of the thermal polymerization initiator include: azo polymerization initiator and peroxide polymerization initiator. Examples of the azo polymerization initiator include: 2,2' -azobisisobutyronitrile, 2' -azobis (2-methylbutyronitrile), dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), azobisisovaleronitrile, 2' -azobis (2-amidinopropane) dihydrochloride, 2' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2' -azobis (2-methylpropionamidine) disulfate and 2,2' -azobis (N, N ' -dimethylene isobutyl amidine) dihydrochloride. Examples of the peroxide polymerization initiator include: dibenzoyl peroxide, t-butylmaleic anhydride and lauroyl peroxide.

Examples of the photopolymerization initiator include: benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, alpha-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzil photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, and acylphosphine oxide photopolymerization initiator.

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. As the chain transfer agent, there may be mentioned: alpha-thioglycerol, dodecyl mercaptan, glycidyl mercaptan, thioglycollic acid, 2-mercaptoethanol, thioglycollic acid, 2-ethylhexyl thioglycolate, 2, 3-dimercapto-1-propanol, and alpha-methylstyrene dimer.

The molecular weight of the base polymer can be adjusted by adjusting the kind 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 of the reaction system, and thus the density at the start of the reaction is high, and the molecular weight of the base polymer to be formed tends to be small. In contrast, the smaller the amount of the polymerization initiator, the lower the density of the reaction initiation point, and therefore the polymer chain tends to be elongated, and the molecular weight of the base polymer to be formed tends to be large.

The weight average molecular weight of the acrylic polymer is preferably 10 ten thousand or more, more preferably 30 ten thousand or more, and even more preferably 50 ten thousand or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 20. The weight average molecular weight is preferably 500 ten thousand or less, more preferably 300 ten thousand or less, and still more preferably 200 ten thousand or less. The weight average molecular weight of the acrylic polymer may be determined by Gel Permeation Chromatography (GPC) and calculated by polystyrene conversion.

The glass transition temperature (Tg) of the base polymer is preferably 0℃or lower, more preferably-10℃or lower, and further preferably-20℃or lower. The glass transition temperature is, for example, at least-80 ℃.

As for the glass transition temperature (Tg) of the base polymer, a glass transition temperature (theoretical value) obtained based on the following Fox formula can be used. The Fox equation is a relation between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In the following Fox formula, tg represents the glass transition temperature (. Degree. C.) of the polymer, wi represents the weight fraction of the monomer i constituting the polymer, tgi represents the glass transition temperature (. Degree. C.) of the homopolymer formed from the monomer i. As regards the glass transition temperature of the homopolymer, literature values can be used. Examples include: glass transition temperatures of the various homopolymers in Polymer handbook (fourth edition, john Wiley & Sons, inc., 1999) and New Polymer library 7 coating synthetic resin Ind (North Korea, polymer journal, 1995). On the other hand, the glass transition temperature of the homopolymer of the monomer can be determined by a method specifically described in Japanese patent application laid-open No. 2007-51271.

Fox equation 1/(273+tg) =Σ [ Wi/(273+tgi) ]

The first adhesive composition may further comprise one or two or more oligomers in addition to the base polymer. In the case of using an acrylic polymer as a base polymer, an acrylic oligomer is preferable as the oligomer. The acrylic oligomer is a copolymer containing a monomer component of an alkyl (meth) acrylate in an amount of 50 mass% or more, and has a weight average molecular weight of, for example, 1000 to 30000.

The glass transition temperature of the acrylic oligomer is preferably 60℃or higher, more preferably 80℃or higher, still more preferably 100℃or higher, particularly preferably 110℃or higher. The glass transition temperature of the acrylic oligomer is, for example, 200℃or less, preferably 180℃or less, and more preferably 160℃or less. By using the low Tg acrylic polymer (base polymer) and the high Tg acrylic oligomer together, which introduce a crosslinked structure, the adhesive strength of the adhesive layer 20, particularly the adhesive strength at high temperature, can be improved. The glass transition temperature of the acrylic oligomer is calculated by the Fox equation above.

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

The chain alkyl (meth) acrylate is preferably methyl methacrylate because of its high glass transition temperature and excellent compatibility with the base polymer. As the alicyclic alkyl (meth) acrylate, tetrahydrodicyclopentadiene methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferable. That is, the acrylic oligomer is preferably a polymer containing one or more monomer components selected from the group consisting of tetrahydrodicyclopentadienyl acrylate, tetrahydrodicyclopentadienyl methacrylate, cyclohexyl acrylate and cyclohexyl methacrylate, and methyl methacrylate.

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, and still more preferably 30% by weight or more. The proportion is preferably 90% by weight or less, more preferably 80% by weight or less, and 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, and still more preferably 70% by weight or less. The proportion is preferably 10% by weight or more, more preferably 20% by weight or more, and still more preferably 30% by weight or more.

The weight average molecular weight of the acrylic oligomer is preferably 1000 or more, more preferably 1500 or more, and further preferably 2000 or more. The molecular weight is preferably 30000 or less, more preferably 10000 or less, and even more preferably 8000 or less. Such a molecular weight range of the acrylic oligomer is preferable for securing the adhesive force and adhesive holding force of the adhesive layer 20.

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

In order to sufficiently improve the adhesive strength of the adhesive layer 20, the content of the acrylic oligomer in the adhesive layer 20 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and further preferably 1 part by mass or more, relative to 100 parts by mass of the base polymer. On the other hand, from the viewpoint of ensuring transparency of the pressure-sensitive adhesive layer 20, the content of the acrylic oligomer in the pressure-sensitive adhesive layer 20 is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and still more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer. In the case where the content of the acrylic oligomer in the pressure-sensitive adhesive layer 20 is too large, there is a tendency that the haze increases and the transparency decreases due to a decrease in the compatibility of the acrylic oligomer.

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

The first adhesive composition may contain other components as needed. Examples of the other components include: tackifiers, plasticizers, softeners, anti-deterioration agents, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents.

From the viewpoint of ensuring sufficient adhesion to an adherend, the thickness H of the pressure-sensitive adhesive layer 20 is preferably 10 μm or more, more preferably 15 μm or more. From the viewpoint of operability, the thickness H is preferably 300 μm or less, more preferably 200 μm or less, further preferably 100 μm or less, and particularly preferably 50 μm or less.

The ratio (d 1/H) of the first taper length d1 to the thickness H is preferably 0.4 or more, more preferably 0.6 or more. The ratio (d 1/H) is preferably 8 or less, more preferably 6 or less. These configurations are suitable for sufficiently lifting off and deforming the end portion (the above-described free portion 40 a) of the light release film 40 before the light release film 40 is pulled away from the end edge 22 of the adhesive layer 20 in the peeling start process of the light release film 40, and are therefore preferable for reducing the force required for peeling start of the light release film 40.

The haze of the adhesive layer 20 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The haze of the adhesive layer 20 can be measured according to JIS K7136 (year 2000) using a haze meter. Examples of the haze meter include "NDH2000" manufactured by Nippon electric color industry Co., ltd and "HM-150" manufactured by Country color technology research Co., ltd.

The total light transmittance of the adhesive layer 20 is preferably 60% or more, more preferably 80% or more, and further 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 according to JIS K7375 (2008).

The adhesive layer 30 is a pressure-sensitive adhesive layer formed of 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 for the first adhesive composition. The base polymer in the first adhesive composition and the base polymer in the second adhesive composition may be the same or different. The second adhesive composition may contain ingredients other than the base polymer. Examples of the component that may be contained in the second adhesive composition include components other than the base polymer described above for the first adhesive composition. The composition of the first adhesive composition and the composition of the second adhesive composition may be the same or different. From the standpoint of adjusting the above-described peeling start forces F1, F2 and peeling forces F1, F2, it is preferable that the composition of the first adhesive composition is different from the composition of the second adhesive composition.

The thickness of the adhesive layer 30 may be the same as or different from the thickness of the adhesive layer 20. The thickness of the pressure-sensitive adhesive layer 30 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of securing sufficient adhesiveness to an adherend. 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. The ratio of the thickness of the pressure-sensitive adhesive layer 30 to the thickness of the pressure-sensitive adhesive layer 20 is, for example, 0.2 or more, and is, for example, 5 or less.

The haze of the pressure-sensitive adhesive layer 30 is preferably 3% or less, more preferably 2% or less, and further preferably 1% or less. The haze of the adhesive layer 30 can be measured according to JIS K7136 (year 2000) using a haze meter.

The total light transmittance of the adhesive layer 30 is preferably 60% or more, more preferably 80% or more, and further 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 K7375 (2008).

As the light release film 40, for example, a plastic film having flexibility is cited. Examples of the plastic film include: polyester films such as polyethylene terephthalate films, polyethylene films and polypropylene films. The thickness of the light release film 40 is preferably 5 μm or more, more preferably 10 μm or more, and the thickness of the light release film 40 is preferably 200 μm or less, more preferably 150 μm or less. The surface of the light release film 40 is preferably subjected to a release treatment. Examples of the release treatment include a silicone release treatment and a fluorine-containing release agent release treatment (the same applies to the release treatment described later). The first peeling start force F1 and the peeling force F1 related to the peeling of the light peeling film 40 from the adhesive layer 20 can be adjusted by the presence or absence of the peeling treatment, the selection of the type and the adjustment of the conditions.

The heavy release film 50 includes, for example, the plastic film described above for the light release film 40. The thickness of the re-release film 50 is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 200 μm or less, more preferably 150 μm or less. The surface of the heavy release film 50 is preferably subjected to a release treatment. The second peeling start force F2 and the peeling force F2 related to peeling of the heavy release film 50 from the adhesive layer 30 can be adjusted by the presence or absence of the peeling treatment, the selection of the type and the adjustment of the conditions.

The optical laminate X can be manufactured, for example, as follows.

First, 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 are prepared (preparation process).

The adhesive layer 20 with the light release film 40 may be formed as follows: the first adhesive composition (varnish) is coated on the light release film 40 to form a coating film, and then the coating film is dried. Examples of the method for applying the first adhesive composition include: roll coating, roll licking coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip die coating, and die coating (the same applies to the coating of the second adhesive composition described below). Other release films may also be laminated on the adhesive layer 20 on the light release film 40. The release film is peeled off before the optical film 10 is bonded to the adhesive layer 20.

The adhesive layer 30 with the heavy release film 50 may be formed as follows: a second adhesive composition (varnish) is coated on the re-release film 50 to form a coating film, and then the coating film is dried. Other release films may also be laminated on the adhesive layer 30 on the re-release film 50. The release film is peeled off before the optical film 10 is bonded to the adhesive layer 30.

Next, the first surface 11 of the optical film 10 is bonded to the pressure-sensitive adhesive layer 20 side of the pressure-sensitive adhesive layer 20 with the light release film 40 (first bonding step). Next, the second surface 12 of the optical film 10 is bonded to the pressure-sensitive adhesive layer 30 side of the pressure-sensitive adhesive layer 30 with the heavy release film 50 (second bonding step). Thus, a laminate of the optical film X with an unprocessed outer peripheral end was obtained. The first face 11 and the second face 12 of the optical film 10, the exposed face of the adhesive layer 20 with the light release film 40, and the exposed face of the adhesive layer 30 with the heavy release film 50 are preferably subjected to plasma treatment prior to these bonding.

Next, the laminate is held by a jig that holds the laminate in the thickness direction, and the pressurizing force applied to the laminate in the thickness direction by the jig is adjusted so that each adhesive layer 20, 30 elastically deforms to protrude from the side end face of the laminate by a predetermined extent (pressurizing and holding step). By adjusting the pressing force, the degree of elastic deformation of the adhesive layers 20, 30 can be adjusted, and therefore the length of extension from the laminate-side end face can be adjusted.

Next, in a state where the adhesive layers 20, 30 are elastically deformed so as to protrude from the laminate-side end face, the inner side of a predetermined length from the laminate-side end face is cut by a rotary blade in the thickness direction so that all or a part of the outer peripheral end of the laminate is reformed (cutting step). The predetermined length is, for example, 0.1mm or more, and 1mm or less. Then, the pressing state of the jig against the laminate is released. As a result, the adhesive layers 20 and 30 are elastically restored, and the end edges 22 and 32 of the adhesive layers 20 and 30 recede inward in the in-plane direction D than the end edges 13, 42 and 52 of the optical film 10, the light release film 40 and the heavy release film 50. By doing so, the side surface concave-convex end portion E is formed.

In such a dicing step, by adjusting the pressing force applied to the laminate in the thickness direction, the lengths of the adhesive layers 20 and 30 extending from the side end surfaces of the laminate can be adjusted, and the retreated lengths d1 and d2 of the end edges 22 and 32 after the pressing state is released can be adjusted. As a method for adjusting the first retraction length d1, as described above, the thickness of the adhesive layer 20 and the elastic modulus can be adjusted. As the method of adjusting the second back length d2, as described above, there are also cited adjusting the thickness of the adhesive layer 30 and adjusting the elastic modulus. As a method for adjusting the distance between the edges 22 and 32 in the in-plane direction D (i.e., the difference between the first retreated length D1 and the second retreated length D2), there is mentioned the adjustment of the cutting conditions in the cutting process described later, which is performed using a rotary blade to form the side surface concave-convex end portion E. Examples of the cutting conditions include: the taper angle of the edge of the rotary blade, the rotation speed of the rotary blade, the incidence direction of the rotary blade on the surface of the optical film laminate described later, and the displacement speed of the rotary blade for cutting the optical film laminate.

By the above operation, the above-described optical film X (optical film with a release film) can be manufactured.

In the preparation step, it is possible to: the adhesive layer 20 with the first step release film was prepared by using the first step release film in place of the light release film 40, and the adhesive layer 30 with the second step release film was prepared by using the second step release film in place of the heavy release film 50. In this case, in the first bonding step, the first surface 11 of the optical film 10 is bonded to the pressure-sensitive adhesive layer 20 side of the pressure-sensitive adhesive layer 20 having the release film for the first step. In the second bonding step, the second surface 12 of the optical film 10 is bonded to the pressure-sensitive adhesive layer 30 side of the pressure-sensitive adhesive layer 30 having the release film for the second step (the plasma treatment is preferably performed before bonding). Thus, a laminate having 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 was obtained. In the laminate, the first step release film is peeled off from the adhesive layer 20, the light release film 40 is then bonded to the exposed surface of the adhesive layer 20, the second step release film is peeled off from the adhesive layer 30, and the heavy release film 50 is then bonded to the exposed surface of the adhesive layer 30. By the above operation, a laminate of the optical film X with its outer peripheral end unprocessed can be obtained. Then, the laminate is subjected to the pressure-holding step and the dicing step, whereby the optical film X (the optical film with a release film) can be produced.

In the manufacturing process of the optical film X, it is possible to: in the first bonding step, the adhesive layer 20 with the release film for the first step is bonded to the first surface 11 of the optical film 10, while in the second bonding step, the adhesive layer 30 with the heavy release film 50 is bonded to the second surface 12 of the optical film 10 (the plasma treatment is preferably performed before bonding). Thus, a laminate having the first step release film, the pressure-sensitive adhesive layer 20, the optical film 10, the pressure-sensitive adhesive layer 30, and the re-release film 50 in this order in the thickness direction was obtained. Then, in the laminate, the first step release film is peeled from the adhesive layer 20, and then the light release film 40 is bonded to the exposed surface of the adhesive layer 20. By the above operation, a laminate of the optical film X with its outer peripheral end unprocessed can be obtained. Then, the laminate is subjected to the pressure-holding step and the dicing step, whereby the optical film X (the optical film with a release film) can be produced.

In the manufacturing process of the optical film X, it may be performed as follows: in the first bonding step, the adhesive layer 20 with the light release film 40 is bonded to the first surface 11 of the optical film 10, while in the second bonding step, the adhesive layer 30 with the release film for the second step is bonded to the second surface 12 of the optical film 10 (the plasma treatment is preferably performed before bonding). Thus, a laminate having the light release film 40, the pressure-sensitive adhesive layer 20, the optical film 10, the pressure-sensitive adhesive layer 30, and the release film for the second step in this order in the thickness direction was obtained. Then, in the laminate, the release film for the second step is peeled from the adhesive layer 30, and then the heavy release film 50 is bonded to the exposed surface of the adhesive layer 30. By the above operation, a laminate of the optical film X with its outer peripheral end unprocessed can be obtained. Then, the laminate is subjected to the pressure-holding step and the dicing step, whereby the optical film X (the optical film with a release film) can be produced.

In the process of manufacturing the optical film X, the adhesive layers 20, 30 may be formed using a photocurable adhesive composition as the adhesive composition. Examples of the photocurable adhesive composition include an ultraviolet curable adhesive composition which undergoes polymerization reaction containing a monomer component upon irradiation with ultraviolet rays. For example, in the case of using a photocurable adhesive composition as the second adhesive composition, first, the second adhesive composition is coated on a release film for the second step to form a coating film. Next, the heavy release film 50 is laminated on the coating film on the release film for the second step. Then, the coating film between the release films is irradiated with light (ultraviolet rays or the like) of a predetermined wavelength, whereby the coating film is photo-cured. Thereby, the adhesive layer 30 is formed between the release films. Next, the second step release film is peeled from the adhesive layer 30 on the heavy release film 50. The second bonding step may be performed using the pressure-sensitive adhesive layer 30 with the heavy release film 50 thus obtained.

Fig. 3A to 3D show an example of a method of using the optical film X.

In this method, first, as shown in fig. 3A, the light release film 40 is peeled from the adhesive layer 20 of the optical film X. For example, in a state where the heavy release film 50 side of the optical film X is fixed to the work table, a force is applied to the end portion of the light release film 40 of the side surface concave-convex end portion E, and the light release film 40 is peeled from the adhesive layer 20. Thereby, the adhesive surface 21 of the adhesive layer 20 is exposed.

At the side concave-convex end E, as described above, the end edge 22 of the adhesive layer 20 is retreated in the in-plane direction D compared to the end edges 13, 42, 52 of the optical film 10, the light release film 40, and the heavy release film 50. At such side concave-convex end E, as described above with reference to fig. 2, the light release film 40 has the free portion 40a to which the adhesive layer 20 is not attached. Therefore, at the side concave-convex end portion E, when the light release film 40 is peeled from the adhesive layer 20, first, as shown by a broken line in fig. 2, the free portion 40a of the light release film 40 is peeled off to be deformed, and then the free portion 40a, which has been peeled off to be deformed, is pulled, so that the light release film 40 can be pulled off from the end edge 22 of the adhesive layer 20. That is, in the peeling start process, it is not necessary to apply both a force (first force) for sufficiently deforming the free portion 40a of the light peeling film 40 and a force (second force) for pulling the light peeling film 40 away from the end edge 22 of the adhesive layer 20 elastically deformed following the deformation of the light peeling film 40. Such an optical film X is suitable for reducing the force required for the peeling start process. The smaller the force, the more the deformation of the thin optical film 10 having a thickness of 100 μm or less is suppressed during the peeling start of the light peeling film 40, and the more the deformation of the adhesive layer 30 is suppressed, and therefore the detachment of the end edge 32 of the adhesive layer 30 from the heavy peeling film 50 is suppressed.

In addition, at the side surface concave-convex end portion E, as shown in fig. 2, the first retreating length d1 is smaller than the second retreating length d2. That is, at the side surface concave-convex end E, the end edge 32 of the adhesive layer 30 is retreated from the end edge 22 of the adhesive layer 20 in the in-plane direction D. Such a configuration is suitable for suppressing deformation of the adhesive layer 30 when the above-described second force for pulling the light release film 40 away from the end edge 22 of the adhesive layer 20 acts on the optical film X during the peeling start of the light release film 40, and therefore is suitable for suppressing detachment of the end edge 32 of the adhesive layer 30 from the heavy release film 50.

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

Next, as shown in fig. 3C, the heavy release film 50 is peeled from the adhesive layer 30. Thereby, the adhesive surface 31 of the adhesive layer 30 is exposed.

Next, as shown in fig. 3D, the optical film 10 is bonded to the second member M2 (second adherend) via the adhesive layer 30.

For example, in the manufacture of flexible panels, the optical film X is used as shown above.

Examples

The present invention will be specifically described below with reference to examples. The present invention is not limited to the embodiments. In addition, specific numerical values such as the blending amount (content), physical property value, parameter and the like described below may be used instead of the upper limit (numerical value defined as "below" or "less" or the lower limit (numerical value defined as "above" or "greater") of the blending amount (content), physical property value, parameter and the like corresponding to these described in the above-described "specific embodiment".

Example 1

< first adhesive sheet production >

The first adhesive sheet in example 1 was produced by the following operation.

< preparation of acrylic oligomer >)

In a reaction vessel having a stirrer, a thermometer, a reflux condenser and a nitrogen introducing tube, a mixture comprising 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of Acrylic Acid (AA), 10 parts by mass of α -methylstyrene dimer as a chain transfer agent and 120 parts by mass of toluene as a solvent was stirred at room temperature under a nitrogen atmosphere for 1 hour. Then, 10 parts by mass of 2,2' -Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture and a reaction solution was prepared, and reacted at 85 ℃ for 5 hours under a nitrogen atmosphere (formation of an acrylic polymer). Thus, an oligomer solution (solid content concentration: 50 mass%) containing the acrylic oligomer was obtained. The acrylic oligomerization had a weight average molecular weight of 4300. In addition, the glass transition temperature (Tg) of the acrylic oligomer was 84 ℃.

< preparation of first acrylic base Polymer >

In a reaction vessel having a stirrer, a thermometer, a reflux condenser and a nitrogen introducing tube, a mixture (solid content concentration 47% by mass) containing 70 parts by mass of 2-ethylhexyl acrylate (2 EHA), 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 (4 HBA), 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 under a nitrogen atmosphere at 56 ℃ for 6 hours (polymerization reaction). Thus, a first polymer solution containing a first acrylic base polymer was obtained. The weight average molecular weight of the first acrylic base polymer in the polymer solution was about 200 ten thousand.

< preparation of first adhesive composition >

To the first polymer solution, 1.5 parts by mass of an acrylic oligomer, 0.26 parts by mass of a first crosslinking agent (product name "Nyper BMT-40SV", manufactured by japan oil and fat), 0.02 parts by mass of a second crosslinking agent (product name "cornate L", trimethylolpropane/toluene diisocyanate trimer adduct, east Cao Zhizao), and 0.3 parts by mass of a silane coupling agent (product name "KBM403", manufactured by the letter chemical industry) were added and mixed with respect to 100 parts by mass of the solid content of the polymer solution, thereby preparing a first adhesive composition.

< formation of first adhesive sheet >

The first adhesive composition was applied to the release treated surface of the release film L1 having one surface subjected to the silicone release treatment to form a coating film. The release film L1 was a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, mitsubishi chemical Co., ltd.) having one side subjected to silicone release treatment. Next, the release treated surface of the release film L2 having one surface subjected to the silicone release treatment was bonded to the coating film on the release film L1. The release film L2 was a PET film (product name "Diafoil MRV75", thickness 75 μm, mitsubishi chemical Co., ltd.) having one side subjected to silicone release treatment. Next, the coating film sandwiched between the release film L1 and the release film L2 was dried by heating at 100 ℃ for 1 minute and then at 150 ℃ for 3 minutes, thereby forming a first adhesive sheet containing a transparent first adhesive layer having a thickness of 50 μm. By the above operation, the first adhesive sheet with the release films L1, L2 was produced.

< production of second adhesive sheet >

The second adhesive sheet in example 1 was produced by the following operation.

< preparation of the second acrylic base Polymer >

In a reaction vessel having a stirrer, a thermometer, a reflux condenser and a nitrogen introducing tube, a mixture containing 99 parts by mass of Butyl Acrylate (BA), 1 part by mass of 4-hydroxybutyl acrylate (4 HBA), 0.3 part by mass of 2,2' -Azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent was stirred under a nitrogen atmosphere at 60 ℃ for 4 hours (polymerization reaction). Thus, a second polymer solution containing a second acrylic base polymer was obtained. The weight average molecular weight of the second acrylic base polymer in the polymer solution was 165 ten thousand.

< preparation of the second adhesive composition >

To the second polymer solution, 0.3 parts by mass of a first crosslinking agent (product name "Nyper BMT-40SV", manufactured by japan oil and fat manufacturing), 0.1 parts by mass of a third crosslinking agent (product name "Takenate D110N", manufactured by trimaran chemical manufacturing) and 0.3 parts by mass of a silane coupling agent (product name "KBM403", manufactured by the singe chemical industry manufacturing) were added and mixed with respect to 100 parts by mass of the solid content of the polymer solution, whereby a second adhesive composition was prepared.

< formation of second adhesive sheet >

The second adhesive composition was applied to the release treated surface of the release film L3 having one surface subjected to the silicone release treatment to form a coating film. The release film L3 was a polyethylene terephthalate (PET) film (product name "Diafoil MRF50", thickness 50 μm, mitsubishi chemical Co., ltd.) having a silicone release treatment on one side. Next, the release treated surface of the release film L4 having one surface subjected to the silicone release treatment was bonded to the coating film on the release film L3. The release film L4 was a PET film (product name "Diafoil MRV75", thickness 75 μm, mitsubishi chemical Co., ltd.) having one side subjected to silicone release treatment. Next, the coating film sandwiched between the release film L3 and the release film L4 was dried by heating at 100 ℃ for 1 minute and then at 150 ℃ for 3 minutes, thereby forming a second adhesive sheet containing a transparent second adhesive layer having a thickness of 50 μm. By the above operation, the second adhesive sheet with the release films L3, L4 was produced.

< preparation of optical film with Release film >

First, the release film L2 is peeled from the first adhesive sheet with release films on both sides, and the exposed surface thus exposed is subjected to plasma treatment. On the other hand, plasma treatment was also performed on both sides (first side, second side) of the polarizing plate having a thickness of 31 μm. In each plasma treatment, a plasma irradiation apparatus (product name "AP-TO5", manufactured by water industry Co., ltd.) was used, the voltage was set TO 160V, the frequency was set TO 10kHz, and the treatment 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 is bonded to the first surface of the polarizing plate. In this bonding, the first adhesive sheet with the release film L1 was pressure-bonded to the polarizing plate by one operation of reciprocating a 2kg roller at 25 ℃.

Then, the release film L3 is peeled off from the second adhesive sheet with release films L3, L4, and the exposed surface thus exposed is subjected to plasma treatment. Then, the exposed surface of the second adhesive sheet is bonded to the second surface of the polarizing plate. In this bonding, the second adhesive sheet with the release film L4 was pressure-bonded to the polarizing plate by one operation of reciprocating a 2kg roller at 25 ℃. Thus, a laminated film having a laminated structure of a first adhesive sheet with a release film L1 (thickness: 50 μm), a polarizing plate, and a second adhesive sheet with a release film L4 (thickness: 75 μm) was obtained.

Next, the laminated film was punched out to a size of 150mm×120mm using a punching machine and a thomson knife (punching step).

Next, outline processing (outline processing step) is performed by the following operation. First, 50 laminated films punched out to have the same size were laminated to obtain a laminated body. Specifically, 50 laminated films were laminated 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, among the adjacent laminated films, to obtain a laminated body. The laminate has one surface (first surface layer) in the thickness direction on which the first release film is disposed on the surface and the other surface (second surface layer) in the thickness direction on which the second release film is disposed on the surface. Next, the stacked body is held by a jig that clamps in the thickness direction. Next, the pressurizing force applied by the jig to the laminate in the thickness direction is adjusted so that each adhesive layer protrudes from the end face of the laminate by a prescribed extent. In this state, the inner side of 0.5mm from the end face of the laminate is cut in the thickness direction so that the outer peripheral end of the laminate is reformed. A predetermined cutting machine and a first rotary blade mounted on the cutting machine are used for cutting. The rotary blade has a disk portion and a plurality of projecting blades projecting radially from a peripheral end of the disk portion toward the disk. As shown in fig. 4A and 4B, the edge of the projecting blade 70 on the front side when the rotary blade rotates has a linear blade 71 (length 6 mm) for cutting the object to be cut 80. In the profile processing step, the rotary blade is rotated relative to the laminate such that each of the projecting blades 70 cuts into the laminate (the object to be cut 80) from the first surface side thereof, the rotational speed of the rotary blade is 4500rpm, the displacement speed of the rotary blade relative to the laminate is 1000 mm/min, the elevation angle (the blade angle θ) of the blade 71 facing the laminate immediately before cutting relative to the surface (the first surface side) of the laminate is-5 ° (fig. 4B) (the case where the blade angle θ opens to the outside in the disk radial direction as shown in fig. 4A is a positive blade angle θ), and the case where the blade angle θ opens to the inside in the disk radial direction as shown in fig. 4B is a negative blade angle θ). Then, after the shaping, the pressing state of the jig against the laminate is released.

By the above operation, the optical film with a release film of example 1 was produced. The optical film with a release film has, in order in the thickness direction, a first release film (release film L1) as a light release film, 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) as a heavy release film, and has side surface concave-convex end portions on the entire outer peripheral end. At the side concave-convex end portions, the respective end edges of the first and second adhesive layers recede with respect to the end edges of the respective films in the in-plane direction of the films. In the optical film with a release film produced by the above-described operation, the respective edges of the first release film, the optical film, and the second release film are located at substantially the same position in the in-plane direction of the film. That is, at the side surface concave-convex end portion of the optical film with a release film, the first receding length d1 of the first end edge of the first adhesive layer from the end edge of the first release film is substantially equal to the receding length d1 'of the first end edge of the first adhesive layer from the end edge of the optical film, and the second receding length d2 of the second end edge of the second adhesive layer from the end edge of the second release film is substantially equal to the receding length d2' of the second end edge of the second adhesive layer from the end edge of the optical film.

Examples 2 to 6

The optical films with release films of examples 2 to 6 were produced in the same manner as the optical film with release film of example 1, except for the following matters.

The above-mentioned cutting edge angle θ at the time of the profile processing was adjusted to be larger on the negative side than in example 1 in examples 3 and 4, was adjusted to be larger on the negative side than in examples 3 and 4 in example 2, and was adjusted to be larger on the negative side than in example 2 in example 6. In example 5, the edge angle θ was adjusted to be positive in the profile processing as compared with example 1, and the rotary blade displacement speed in the processing was adjusted to be slower than in example 1.

Example 7

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

Example 8

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

Comparative example 1

An optical film with a release film of comparative example 1 was produced in the same manner as the optical film with a release film of example 1, except that the operation after the punching process was not performed.

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 matters.

A second rotary knife is used instead of the first rotary knife. The rotary blade has a disk portion and a plurality of projecting blades projecting radially from a peripheral end of the disk portion toward the disk. In the profile processing step, the rotary blade was rotated relative to the laminate such that each projecting blade 70 cut into the laminate (the object to be cut 80) from the second surface side thereof (i.e., the arrangement of the laminate relative to the rotary blade was reversed from that of example 1), the rotational speed of the rotary blade was set to 4500rpm, the displacement speed of the rotary blade relative to the laminate was set to 1000 mm/min, and the elevation angle (the blade angle θ) of the opposing blade 71 (length 6 mm) to the laminate surface (the second surface side) immediately before cutting the laminate was set to +5° (fig. 4A).

< backoff Length >)

For each of the optical films with release films (optical films with release films on both sides) in examples 1 to 8 and comparative examples 1 and 2, the first receding length d1 of the first end edge of the first adhesive layer and the second receding length d2 of the second end edge of the second adhesive layer were examined as follows.

First, the first release film is peeled from the optical film with a release film on both sides, and then the optical film with a release film on one side is stuck to a glass plate via the first adhesive layer exposed by the peeling. Next, the second release film was peeled from the optical film (optical film with adhesive layer on both sides) on the glass plate. The predetermined portion selected from the outer peripheral end of the optical film having the adhesive layer on both sides thereof on the glass plate was observed by an optical microscope. Specifically, the optical film with the adhesive layer on both sides was observed and photographed by an optical microscope in the thickness direction of the optical film with the adhesive layer on both sides from the side opposite to the glass plate. Then, in the captured image, the receding length d1 'of the first end edge of the first adhesive layer from the end edge of the optical film and the receding length d2' of the second end edge of the second adhesive layer from the end edge of the optical film were measured. The measurement results are shown in table 1 as a back length d1 (μm) and a back length d2 (μm) (as described above, the back length d1 'and the back length d1 are substantially equal, and the back length d2' and the back length d2 are substantially equal).

< peeling Start force and Peel force >)

The optical films with release films of examples 1 to 8 and comparative examples 1 and 2 were examined for the force (release initiation force and release force after) required for the release of each release film.

First, a test piece for measurement (short side about 25 mm. Times. Long side about 150 mm) was cut out from an optical film with a release film. Specifically, a test piece having a length of about 150mm from the side surface concave-convex end portion of the optical film with the release film and a width of 25mm was cut out from the film.

Next, the test piece was fixed to a fixing stand of a tensile tester (product name "Autograph", manufactured by shimadzu corporation). Specifically, one release film (first release film or second release film) was peeled off and removed from the test piece, and then the test piece was stuck to the fixing stage via the adhesive layer exposed by the peeling.

Next, the grip tape was stuck to the short side of the side surface concave-convex end portion side of the other release film (the second release film or the first release film) located on the exposed surface side of the test piece. The holding tape has a strong adhesive surface, and the holding tape is stuck to a release film of a test piece via the strong adhesive surface.

Next, a peel test was performed by a tensile tester 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 peel strength. In this measurement, the measurement temperature was set to 25 ℃, the peeling film was peeled off by pulling the holding tape, the peeling angle was set to 180 °, the pulling speed was set to 300 mm/min, and the peeling length was set to 100mm. Fig. 5 shows an example of a graph obtained by such a peel test. In the graph of fig. 5, the horizontal axis represents the peel length (mm), the vertical axis represents the peel strength (gf), and Fm represents the maximum value of the peel strength.

The peel start forces F1 and F2 (gf/25 mm) and the peel forces F1 and F2 (gf/25 mm) obtained by the peel test described above are shown in Table 1 (wherein, in examples 7 and 8, the peel start forces F1 and F2 were not measured). The peel start force F1 is the maximum value of peel strength within 20mm in peel length when the first release film is peeled from the first adhesive layer, and the peel force F1 is the average value of peel strength within the range of 20mm to 100mm in peel length (the peel strength is stabilized after the peel start force F1 at the start of peeling). The peel start force F2 is the maximum value of the peel strength within 20mm in peel length when the second release film is peeled from the second adhesive layer, and the peel force F2 is the average value of the peel strengths within the range of 20mm to 100mm in peel length (the peel strength is stabilized after the peel start force F2 at the time of peeling start).

< inhibition of peeling of heavy Release film at light Release film peeling >)

The optical films with release films in examples 1 to 8 and comparative examples 1 and 2 were examined for the ease of release of the heavy release film when the light release film was released. 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. A tensile tester (product name "Autograph", manufactured by shimadzu corporation) was used for the peeling. In peeling, the peeling angle was set to 180 °, and the pulling speed was set to 300 mm/min. Then, the number of evaluation samples in which peeling of the heavy peeling film did not occur and only the light peeling film could be peeled appropriately was evaluated as 10 as "excellent", the number of evaluation samples in which the number was 7 to 9 as "good", and the number of evaluation samples in which the number was 0 to 6 as "poor". The evaluation results are shown in table 1.

< inhibition of end crack of optical film >

The optical films with release films in examples 1 to 8 and comparative examples 1 and 2 were examined for the difficulty of occurrence of cracks at the end of the optical film when the optical film was peeled off by a light release film. Specifically, first, an evaluation sample was prepared for each optical film with a release film. Next, the light release film of the evaluation sample was peeled off by a manual operation. Then, the outer peripheral portion (region 1mm from the edge) of the optical film was observed by an optical microscope. Then, the case where a crack having a length of 200 μm or more was not generated in the outer peripheral portion of the optical film after the light release film was peeled off was evaluated as "excellent", and the case where a crack having a length of 200 μm or more was generated was evaluated as "poor".

< adhesion of end >)

The optical films with release films in examples 1 to 8 and comparative examples 1 and 2 were examined for the ease of blocking at the ends. Specifically, first, 10 evaluation samples were prepared for each optical film with a release film, and 10 evaluation samples were stacked to form a film stack (first step). Next, the tip adhesive surface of a cylindrical rod (diameter 10 mm) having an adhesive surface at the tip thereof was pressed against the uppermost optical film with a release film in the film stack from above, and the rod was lifted upward, and the number of optical films with release films accompanied by the lifting of the rod was counted (second step). Each of the optical films with a release film was subjected to 10 tests consisting of the first step and the subsequent second step. Of the 10 tests, the number of tests in which the number of times of the test in which the optical film with the release film lifted up along with the rod was 1 sheet was 10 was evaluated as "excellent", the number of tests in the range of 6 to 9 was evaluated as "good", and the number of tests in the range of 5 or less was evaluated as "poor". The evaluation results are shown in table 1.

The above-described embodiments are examples of the present invention, and the present invention is not to be interpreted in a limiting manner by using the embodiments. With respect to the present invention, variations obvious to those skilled in the art are included within the scope of the claims of the present invention.

Industrial applicability

The optical film with a release film of the present invention is used as a supply material of an optical film contained in a laminated structure of a foldable display panel, for example, in a process of manufacturing the panel.

Description of the reference numerals

X: optical film (optical film with stripping film)

Y: optical film with adhesive layer

E: end with concave-convex side surface

T: in the thickness direction

10: optical film

11: first surface

12: a second surface

13: end edge

20. 30: adhesive layer

21. 31: adhesive surface

22: end margin (first end margin)

32: end margin (second end margin)

40: light release film

42: end edge

50: heavy release film

52: end edge

Claims

1. An optical film with a release film having an optical film with an adhesive layer, a light release film and a heavy release film,

the adhesive layer-carrying optical film has an optical film, a first adhesive layer, and a second adhesive layer,

the optical film has a first face and a second face opposite to the first face;

The first adhesive layer is adhered to the first face and has a first adhesive face on a side opposite to the optical film,

the second adhesive layer is adhered to the second face and has a second adhesive face on the opposite side to the optical film,

the light release film is disposed on the first adhesive face,

the re-release film is disposed on the second adhesive surface,

the optical film has a thickness of 100 μm or less,

having side surface concave-convex end portions in an in-plane direction orthogonal to the thickness direction of the optical film, wherein a first end edge of the first adhesive layer and a second end edge of the second adhesive layer recede from each end edge of the optical film, the light release film, and the heavy release film,

at the side surface concave-convex end portion, a first retreating length of the first end edge from an end edge of the light release film is smaller than a second retreating length of the second end edge from an end edge of the heavy release film.

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

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

4. The optical film with a release film according to claim 1, wherein a ratio of the first receding length to a 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 initiation force for initiating release of the light release film from the first adhesive surface is smaller than a second release initiation force for initiating release 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 initiation force is less than 800gf/25mm.

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