KR20230004281A - Optical pressure-sensitive adhesive layer - Google Patents

Abstract

An objective of the present invention is to provide an optical pressure-sensitive adhesive layer suitable for use in a flexible device. According to the present invention, the optical pressure-sensitive adhesive layer (10) comprises a first surface (10a) and a second surface (10b) disposed on the opposite side to the first surface (10a). The optical pressure-sensitive adhesive layer (10) has a shear storage modulus (G') of 180 kPa or less at -20℃. After 30 minutes at 23℃ from bonding to the polyimide film, At least one of the first surface (10a) and second surface (10b) of the optical pressure-sensitive adhesive layer (10) has a peeling adhesive force F of 5 N/25 mm or more under the conditions of a peeling angle of 180° and a peeling speed of 300 mm/min with respect to a polyimide film.

Description

Optical adhesive layer {OPTICAL PRESSURE-SENSITIVE ADHESIVE LAYER}

The present invention relates to an optical pressure-sensitive adhesive layer.

The display panel has a laminated structure including, for example, a pixel panel, a touch panel, a polarizing plate, and a cover film. In the manufacturing process of such a display panel, a pressure-sensitive adhesive layer (optical pressure-sensitive adhesive layer) formed from a transparent pressure-sensitive adhesive for optical use is used for bonding between elements included in the laminated structure. In the manufacturing process of a display panel, an optical adhesive layer is formed, for example by bonding the optical adhesive sheet formed from the optical adhesive composition to the object to be bonded. Alternatively, the optical adhesive layer is formed by applying an optical adhesive composition onto an object to be bonded or the like.

On the other hand, for example, for smartphones and tablet terminals, development of display panels capable of being repeatedly bent (foldable) is in progress. In the foldable display panel, each element in the laminated structure is manufactured to be able to be repeatedly bent, and an optical adhesive layer is used for bonding between such elements. About the optical adhesive layer for flexible devices, such as a foldable display panel, it describes, for example in patent document 1 below.

Japanese Unexamined Patent Publication No. 2018-111754

Conventionally, peeling of the optical adhesive layer from the adherend is likely to occur at the bent portion of the foldable display panel. It is because when a display panel is bent, stress, such as shear stress, acts locally with respect to the optical adhesive layer at the said bending location. Occurrence of the said peeling becomes a cause of malfunction of a device, and is not preferable. An optical adhesive layer for a foldable display panel is required to be easily bent and deformed together with an adherend when the display is bent, and to be compatible with peeling suppression from the adherend at a higher level.

As a flexible device, development of a rollable (rollable) display panel is also progressing. The optical pressure-sensitive adhesive layer for rollable display panels is required to be easily deformed (winding deformation) together with an adherend at the time of winding up the display, and to be compatible at a very high level with suppression of peeling from the adherend.

The present invention provides an optical pressure-sensitive adhesive layer suitable for use in flexible devices.

The present invention [1] is an optical pressure-sensitive adhesive layer having a first surface and a second surface opposite to the first surface, and has a shear storage modulus G' of 180 kPa or less at -20 ° C, and the first surface and At least one of the second surfaces is 5 N / 25 mm or more peeled from the polyimide film after 30 minutes at 23 ° C. from bonding to the polyimide film, under the conditions of a peel angle of 180 ° and a peel rate of 300 mm / min An optical pressure-sensitive adhesive layer having an adhesive strength F is included.

In the present invention [2], the shear storage modulus G' (kPa) and the peel adhesive force F (N/25 mm) at -20°C satisfy F≥0.4667×G'-58 at G'>135. The optical adhesive layer as described in said [1] which makes it is included.

In the present invention [3], the ratio of the shear storage modulus G' (kPa) at -20 ° C to the peel adhesive strength F (N / 25 mm) is 200 or less, the optics according to [1] or [2] above. Contains an adhesive layer.

In the present invention [4], the ratio of the shear storage modulus G' (kPa) at -40 ° C to the peel adhesive force F (N / 25 mm) is 200 or less, any one of the above [1] to [3] Including the optical pressure-sensitive adhesive layer described in.

This invention [5] contains the optical adhesive layer in any one of said [1]-[4] whose shear storage elastic modulus G' at -40 degreeC is 1200 kPa or less.

This invention [6] contains the optical adhesive layer in any one of said [1] - [5] whose difference of maximum thickness and minimum thickness is 3 micrometers or less.

The present invention [7] includes the optical pressure-sensitive adhesive layer according to any one of [1] to [6], wherein the change in transmittance at 1 hour after winding on a core having a cross-sectional diameter of 20 mm is 5% or less.

As described above, the optical pressure-sensitive adhesive layer of the present invention has a shear storage modulus G' of 180 kPa or less at -20°C. The optical pressure-sensitive adhesive layer having such a high level of softness follows the deformation of the adherend to a large curvature when the adherend to which the adhesive layer is bonded is deformed with a relatively large curvature (such as the aforementioned bending deformation and winding deformation). easy to deform The softness of the optical adhesive layer and its ability to deform to a large curvature (bending deformability) are suitable for realizing good repeated deformation (repeated bending deformation and winding deformation, etc.) of flexible devices in which the optical adhesive layer is used. In addition, as described above, the optical pressure-sensitive adhesive layer has a peel adhesive strength F of 5 N/25 mm or more under predetermined conditions on at least one of the first surface and the second surface. This configuration is suitable for ensuring good adhesion of the optical adhesive layer to the adherend, and therefore suitable for suppressing peeling of the optical adhesive layer from the adherend. An optical pressure-sensitive adhesive layer in which bending deformability and peeling suppression properties are compatible in this way is suitable for use in flexible devices.

[Fig. 1] It is a cross-sectional schematic diagram of an embodiment of an optical pressure-sensitive adhesive layer of the present invention.
Fig. 2 shows a case where the optical pressure-sensitive adhesive layer shown in Fig. 1 has a two-layer structure.
Fig. 3 shows a case where the optical pressure-sensitive adhesive layer shown in Fig. 1 has a three-layer structure.
[Fig. 4] An example of a method of using the optical pressure-sensitive adhesive layer of the present invention is shown. Fig. 4A shows a step of bonding an optical adhesive layer to a first adherend, Fig. 4B shows a step of bonding a first adherend and a second adherend with an optical adhesive layer interposed therebetween, and Fig. 4C shows aging represents the process.
5] It is a plot of the measurement results of the 1st shear storage modulus G' (horizontal axis) and the peel adhesive force F (vertical axis) measured for the optical adhesive layers of Examples 1-4 and Comparative Examples 2 and 3.

As shown in Fig. 1, the optical pressure-sensitive adhesive layer 10 as an embodiment of the optical pressure-sensitive adhesive layer of the present invention has a sheet shape with a predetermined thickness and spreads in a direction orthogonal to the thickness direction H (planar direction). The optical adhesive layer 10 has a first surface 10a and a second surface 10b opposite to the first surface 10a. Fig. 1 exemplarily shows a state in which the optical adhesive layer 10 is produced as an optical adhesive sheet S and release films L1 and L2 are bonded to both surfaces of the sheet. The optical adhesive sheet S with a release film is, for example, roll-shaped (not shown).

The optical adhesive layer 10 has a single layer structure or a multilayer structure of two or more layers (not shown in FIG. 1). 2 is a partially enlarged view of an optical adhesive layer 10A as an example of the optical adhesive layer 10 having a two-layer structure. 10 A of optical adhesive layers are provided with the adhesive layer 11 (1st adhesive layer) and the adhesive layer 12 (2nd adhesive layer) sequentially in thickness direction H (two-layer structure). In the optical pressure-sensitive adhesive layer 10A, the exposed surface of the pressure-sensitive adhesive layer 11 (the surface of the pressure-sensitive adhesive layer 11 on the opposite side to the pressure-sensitive adhesive layer 12) is the first surface 10a, and the pressure-sensitive adhesive layer 12 ) is the second surface 10b. 3 is a partially enlarged view of an optical adhesive layer 10B as an example of the optical adhesive layer 10 having a three-layer structure. The optical adhesive layer 10B includes an adhesive layer 11 (first adhesive layer), an adhesive layer 12 (second adhesive layer), and an adhesive layer 13 (third adhesive layer) in the thickness direction H. Equipped sequentially (three-layer structure). In the optical pressure-sensitive adhesive layer 10B, the exposed surface of the pressure-sensitive adhesive layer 11 (the surface of the pressure-sensitive adhesive layer 11 on the opposite side to the pressure-sensitive adhesive layer 12) is the first surface 10a, and the pressure-sensitive adhesive layer 13 ) is the second surface 10b.

Such an optical pressure-sensitive adhesive layer 10 is a transparent pressure-sensitive adhesive layer disposed at a light passage location in a flexible device. As a flexible device, a flexible display panel is mentioned, for example. A flexible display panel has a laminated structure including, for example, a pixel panel, a touch panel, a polarizing plate, and a cover film. As a flexible display panel, a foldable display panel and a rollable display panel are mentioned, for example. The optical pressure-sensitive adhesive layer 10 is used, for example, for joining elements included in the laminated structure to each other in a manufacturing process of a flexible display panel.

The optical pressure-sensitive adhesive layer 10 has a shear storage modulus G' (first shear storage modulus G') of 180 kPa or less at -20°C. In the optical adhesive layer 10, from the viewpoint of ensuring flexibility and flexibility suitable for flexible devices, the first shear storage modulus G' is preferably 150 kPa or less, more preferably 130 kPa or less, still more preferably 100 kPa or less. , particularly preferably 90 kPa or less. From the viewpoint of securing the cohesive force of the optical pressure-sensitive adhesive layer 10, the first shear storage modulus G' is preferably 30 kPa or more, more preferably 40 kPa or more, still more preferably 50 kPa or more, and particularly preferably 60 kPa or more. . The first shear storage modulus G' of the optical pressure-sensitive adhesive layer 10 can be measured with a dynamic viscoelasticity measuring device. In the measurement, the measurement mode is the shear mode, the measurement temperature range is -60°C to 150°C, the heating rate is 5°C/min, and the frequency is 1 Hz (second shear storage modulus G described later). The same applies to the measurement of '). Specifically, it is as described later regarding an Example. As a method for adjusting the shear storage modulus G' of the pressure-sensitive adhesive layer, for example, selection of the type of base polymer in the pressure-sensitive adhesive layer, adjustment of molecular weight, and adjustment of the compounding amount, and type of crosslinking agent for crosslinking the base polymer and adjustment of the selection and blending amount. Selection of the type of base polymer includes selection of the type of main chain in the base polymer, and selection of the type and amount of functional groups. In addition, when the optical adhesive layer 10 has a multilayer structure, as a method for adjusting the shear storage modulus G' of the optical adhesive layer 10, for example, the shear of each adhesive layer in the optical adhesive layer 10 Adjustment of storage elastic modulus G' and adjustment of the thickness of each adhesive layer are mentioned.

At least one of the first surface 10a and the second surface 10b of the optical pressure-sensitive adhesive layer 10 (ie, one or both of the first surface 10a and the second surface 10b) is made of a polyimide film. After a lapse of 30 minutes at 23 ° C. from bonding of the polyimide film, it has a peel adhesive force F of 5 N / 25 mm or more on the conditions of a peel angle of 180 ° and a peel speed of 300 mm / min. The attachment of the optical pressure-sensitive adhesive layer 10 to the adherend is the attachment by a load of reciprocating a 2-kg roller once in a 23°C environment. From the viewpoint of ensuring good adhesion to the adherend, the peel adhesive strength F is preferably 7 N/25 mm or more, more preferably 9 N/25 mm or more, and still more preferably 11 N/25 mm or more. The peel adhesive strength F is, for example, 30 N/25 mm or less. As a method for adjusting the peeling adhesive force F on the surface of the pressure-sensitive adhesive layer, for example, selection of the type of base polymer in the pressure-sensitive adhesive layer, adjustment of molecular weight, and adjustment of the compounding amount are exemplified. As a method for adjusting the peeling adhesive force F on the surface of the pressure-sensitive adhesive layer, selection of the kind of components other than the base polymer in the pressure-sensitive adhesive layer and adjustment of the compounding amount of the component are also mentioned. As said component, a crosslinking agent, a silane coupling agent, and an oligomer are mentioned. In addition, when the optical adhesive layer 10 has a multilayer structure, as a method for adjusting the peel adhesive force F of the optical adhesive layer 10, for example, the peel adhesive force F of each adhesive layer in the optical adhesive layer 10 Adjustment of and adjustment of the thickness of each adhesive layer are mentioned.

As described above, the optical pressure-sensitive adhesive layer 10 has a shear storage modulus G' of 180 kPa or less at -20°C. The optical adhesive layer 10 having such a high degree of softness tends to deform with a large curvature following the deformation of the adherend when the adherend to which the optical adhesive layer 10 is bonded is deformed with a relatively large curvature. Examples of deformation with a relatively large curvature include bending deformation of a foldable display and deformation (winding deformation) during winding of a rollable display. The optical adhesive layer 10 is soft and easily deformable to a large curvature (bending deformability), which is suitable for realizing good repeated deformation (repeated bending deformation and winding deformation, etc.) of a flexible device in which the optical adhesive layer 10 is used. Do.

As described above, the optical pressure-sensitive adhesive layer 10 has a peel adhesive strength F of 5 N/25 mm or more under the above conditions on at least one of the first surface 10a and the second surface 10b. That is, the optical adhesive layer 10 has the following first configuration or second configuration regarding adhesive force. A structure in which both the first surface 10a and the second surface 10b have a peel adhesive force F of 5 N/25 mm or more under the above conditions (first structure), and the first surface 10a and the second surface 10b is a configuration (second configuration) in which one side has a peel adhesive force F of 5 N/25 mm or more under the above conditions. Such an optical pressure-sensitive adhesive layer 10 is suitable for securing good adhesion to an adherend on the first surface 10b and/or the second surface 10b having peel adhesive force F, and therefore It is suitable for suppressing peeling of the optical adhesive layer 10 from.

As described above, the optical pressure-sensitive adhesive layer 10 having both bending deformability and peeling suppression properties is suitable for use in flexible devices.

The optical adhesive layer 10 preferably has a multilayer structure of two or more layers as shown in FIGS. 2 and 3 . Such a configuration is preferable for sharing functions among the pressure-sensitive adhesive layers included in the optical pressure-sensitive adhesive layer 10 and achieving the above-described coexistence of bending deformability and peeling suppression properties. For example:

The optical pressure-sensitive adhesive layer 10A shown in FIG. 2, for example, has a pressure-sensitive adhesive layer having a higher shear storage modulus and higher adhesive strength than the pressure-sensitive adhesive layer 12 as the pressure-sensitive adhesive layer 11, and as the pressure-sensitive adhesive layer 12, It has a pressure-sensitive adhesive layer having a lower shear storage modulus than the pressure-sensitive adhesive layer 11 and a low adhesive strength. Such a configuration suppresses the overall shear storage modulus of the optical pressure-sensitive adhesive layer 10 (the pressure-sensitive adhesive layers 11 and 12) while suppressing the aforementioned peel adhesive force of the first surface 10a (exposed surface on the pressure-sensitive adhesive layer 11 side). It is suitable for securing F. The optical pressure-sensitive adhesive layer 10B shown in FIG. 3 , for example, has a pressure-sensitive adhesive layer having a higher shear storage modulus and higher adhesive strength than the pressure-sensitive adhesive layer 12 as the pressure-sensitive adhesive layers 11 and 13, and the pressure-sensitive adhesive layer 12 As such, it has a pressure-sensitive adhesive layer having a lower shear storage modulus and lower adhesive strength than the pressure-sensitive adhesive layers 11 and 13. Such a configuration suppresses the overall shear storage modulus of the optical pressure-sensitive adhesive layer 10 (the pressure-sensitive adhesive layer 11, 12, 13), while the first surface 10a (the surface on the side of the pressure-sensitive adhesive layer 11) and the second surface (10b) (surface on the side of the pressure-sensitive adhesive layer 13) is suitable for securing the above-mentioned peeling adhesive force F. As a method for adjusting the shear storage modulus and adhesive force of the pressure-sensitive adhesive layer, for example, adjustment of the molecular weight of the base polymer in the pressure-sensitive adhesive layer, adjustment of the glass transition temperature, and adjustment of the degree of crosslinking are effective. The larger the molecular weight of the base polymer, the higher the elastic modulus of the pressure-sensitive adhesive layer tends to be, and the higher the adhesive strength tends to be. The lower the glass transition temperature of the base polymer, the lower the elastic modulus of the pressure-sensitive adhesive layer, and the lower the adhesive strength. The higher the degree of crosslinking of the base polymer, the higher the elastic modulus of the pressure-sensitive adhesive layer tends to be. In addition, the adhesive force of the pressure-sensitive adhesive layer changes according to the degree of crosslinking so as to have a maximum value at a predetermined degree of crosslinking in the base polymer. Specifically, it is as follows. The higher the degree of crosslinking of the base polymer, the higher the degree of crosslinking, the higher the cohesive force inside the pressure-sensitive adhesive layer, and the higher the pressure-sensitive adhesive layer tends to be. If the degree of crosslinking exceeds a certain degree, the higher the degree of crosslinking of the base polymer, the higher the elasticity of the pressure-sensitive adhesive layer, and the lower the adhesive strength.

In the optical pressure-sensitive adhesive layer 10, when one of the first surface 10a and the second surface 10b is an adhesive surface (low-adhesive surface) that does not have a peel adhesive force F of 5 N / 25 mm or more under the above conditions, and Even if the adhesion between the optical adhesive layer 10 and the adherend is ensured by subjecting the surface of the adherend (planned bonding surface) to a plasma treatment before bonding the low-adhesive surface side of the same optical adhesive layer 10 to the adherend. do. In the case where both the first surface 10a and the second surface 10b have a peel adhesive force F of 5 N/25 mm or more under the above conditions, such a plasma treatment for the surface of the adherend is not necessarily required, which is preferable. .

In the optical pressure-sensitive adhesive layer 10, the shear storage modulus G' (kPa) and the peel adhesive strength F (N/25 mm) at -20 ° C. are preferably G'> 135, F≥ 0.4667 × G'- satisfies 58. Coexistence of such high degree of softness and high adhesive strength in the optical adhesive layer 10 is desirable for achieving both the flexibility and the adhesiveness of the adherend of the optical adhesive layer 10, and therefore, the above-described bending deformability and peeling suppression properties. It is desirable to achieve both.

The ratio of the shear storage modulus G' (kPa) at -20 ° C to the peel adhesion F (N / 25 mm) is preferably 30 or less, more preferably 25 or less, still more preferably 15 or less, and , is preferably 1 or more, more preferably 3 or more, still more preferably 5 or more. Such a configuration is preferable for balancing the adhesive strength, flexibility, and bendability of the optical pressure-sensitive adhesive layer 10 .

The ratio of the shear storage modulus G' (kPa) at -40°C to the peel adhesion F (N/25 mm) is preferably 200 or less, more preferably 180 or less, still more preferably 100 or less, and , is preferably 10 or more, more preferably 20 or more, still more preferably 30 or more. Such a configuration is preferable for balancing the adhesive strength, flexibility, and bendability of the optical pressure-sensitive adhesive layer 10 .

The shear storage modulus G' at -40°C is preferably 1200 kPa or less, more preferably 1000 kPa or less, still more preferably 800 kPa or less, particularly preferably 600 kPa or less, and is preferably 100 or more, more preferably Preferably it is 200 or more, more preferably 300 or more. Such a configuration is preferable for ensuring the flexibility and bendability of the optical pressure-sensitive adhesive layer 10 .

In the optical adhesive layer 10, the difference between the maximum thickness and the minimum thickness is preferably 3 µm or less, more preferably 2 µm or less, still more preferably 1 µm or less. Such a structure is preferable for suppressing stress concentration in the adherend to which the optical pressure-sensitive adhesive layer 10 is in contact when deforming the adherend. Moreover, the said structure regarding the difference in thickness is preferable also from a viewpoint of the visibility of the flexible device (optical device) which has the optical adhesive layer 10 in laminated structure.

The change in transmittance of the optical adhesive layer 10 after 1 hour elapsed after winding the optical adhesive layer 10 around a core having a cross-sectional diameter of 20 mm is preferably 5% or less, more preferably 4% or less, still more preferably It is less than 3%. Such a configuration is suitable for ensuring transparency as an optical pressure-sensitive adhesive layer for flexible devices. The change in transmittance of the optical pressure-sensitive adhesive layer 10 can be specifically measured by a method described later in the Examples.

The optical adhesive layer 10 is a pressure-sensitive adhesive layer formed from an adhesive composition. The optical pressure-sensitive adhesive layer 10 has transparency (visible light transmission). The optical adhesive layer 10 contains at least a base polymer.

The base polymer is an adhesive component that expresses adhesiveness in the optical adhesive layer 10 . Examples of the base polymer include acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, and fluoropolymers. , and rubber polymers. A base polymer may be used independently, and two or more types may be used together. From the viewpoint of ensuring good transparency and adhesiveness of the optical pressure-sensitive adhesive layer 10, an acrylic polymer is preferably used as the base polymer.

An acrylic polymer is a copolymer of monomer components containing an alkyl (meth)acrylate in a proportion of 50% by mass or more. "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

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

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

As the (meth)acrylic acid alkyl ester having an alicyclic alkyl group, for example, (meth)acrylic acid cycloalkyl ester, (meth)acrylic acid ester having a bicyclic aliphatic hydrocarbon ring, and having a tricyclic or more aliphatic hydrocarbon ring ( meth)acrylic acid esters are exemplified. Examples of the (meth)acrylate cycloalkyl ester include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. As (meth)acrylic acid ester which has a bicyclic aliphatic hydrocarbon ring, isobornyl (meth)acrylate is mentioned, for example. Examples of the (meth)acrylic acid ester having a tricyclic or higher aliphatic hydrocarbon ring include dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, and tricyclopentanyl (meth)acrylate. , 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

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

The ratio of the (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 60% by mass, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the optical pressure-sensitive adhesive layer 10 or more, more preferably 70% by mass or more. The same ratio is, for example, 99% by mass or less.

The monomer component may also contain a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. Examples of the polar group-containing monomer include a monomer having a nitrogen atom-containing ring, a hydroxyl group-containing monomer, and a carboxy group-containing monomer. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing a crosslinking point into the acrylic polymer and securing cohesive force of the acrylic polymer.

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

The ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferable from the viewpoint of ensuring the cohesive force in the optical adhesive layer 10 and the adhesive force of the adherend in the optical adhesive layer 10. It is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.55% by mass or more. The ratio is preferably from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the optical adhesive layer 10 and the acrylic polymer). It is 30 mass % or less, More preferably, it is 20 mass % or less.

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

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 0.1% by mass or more, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and securing the cohesive force in the optical pressure-sensitive adhesive layer 10. Preferably it is 0.5 mass % or more, More preferably, it is 0.8 mass % or more. The ratio is preferably 20% by mass or less, more preferably 10% by mass, from the viewpoint of adjusting the polarity of the acrylic polymer (related to the compatibility of the acrylic polymer with various additive components in the optical pressure-sensitive adhesive layer 10). less than %

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 ratio of the carboxyl group-containing monomer in the monomer component is the ratio of introduction of a crosslinked structure to the acrylic polymer, securing of cohesive force in the optical adhesive layer 10, and adhesion to the adherend in the optical adhesive layer 10. From the viewpoint of securing, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. The ratio is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid.

In order to prevent metal elements such as electrodes in a flexible device from being corroded by an acid component, the optical adhesive layer 10 preferably has a small acid content. In addition, when the optical adhesive layer 10 is used for bonding a polarizing plate, in order to suppress polyenization of the polyvinyl alcohol-based polarizer by an acid component, the optical adhesive layer 10 preferably has a small content of acid. . In such an acid-free optical pressure-sensitive adhesive layer 10, the content of organic acid monomers (for example, (meth)acrylic acid and carboxyl group-containing monomers) is preferably 100 ppm or less, more preferably 70 ppm or less, still more preferably is less than 50 ppm. The organic acid monomer content of the optical pressure-sensitive adhesive layer 10 was determined by quantifying the acid monomer extracted in water by immersing the optical pressure-sensitive adhesive layer 10 in pure water and heating at 100 ° C. for 45 minutes with an ion chromatograph. It happens.

From an acid-free viewpoint, it is preferable that the base polymer in the optical pressure-sensitive adhesive layer 10 does not substantially contain an organic acid monomer as a monomer component. From the viewpoint of acid-free, the ratio of the organic acid monomer in the monomer component is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.05% by mass, and ideally 0% by mass. .

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

The base polymer has a crosslinked structure in this embodiment. As a method for introducing a cross-linked structure into the base polymer, a base polymer having a functional group capable of reacting with the cross-linking agent and a cross-linking agent are blended into the pressure-sensitive adhesive composition, and the base polymer and the cross-linking agent are reacted in the optical pressure-sensitive adhesive layer 10 (first method); and a method (second method) of forming a base polymer having a branched structure (crosslinked structure) introduced into the polymer chain by polymerization of the monomer component by including a polyfunctional monomer in a monomer component forming the base polymer, can be heard These methods may be used together.

Examples of the crosslinking agent used in the first method include compounds that react with functional groups (such as hydroxyl and carboxyl groups) contained in the base polymer. Examples of such crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. A crosslinking agent may be used independently and two or more types may be used together. As the crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent, and an epoxy crosslinking agent are preferably used because they have high reactivity with the hydroxyl group and carboxy group in the base polymer and introduce a crosslinked structure easily.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. nate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate. Moreover, derivatives of these isocyanates are also mentioned as an isocyanate crosslinking agent. As the said isocyanate derivative, an isocyanurate modified body and a polyol modified body are mentioned, for example. As a commercially available isocyanate crosslinking agent, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (of hexamethylene diisocyanate) Trimethylolpropane adduct, manufactured by Tosoh), Coronate HX (isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethyl of xylylene diisocyanate) All-propane adducts, manufactured by Mitsui Chemicals) are exemplified.

As the peroxide crosslinking agent, dibenzoyl peroxide, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylper oxy neodecanoate, t-hexylperoxy pivalate, and t-butylperoxy pivalate.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6- Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamineglycidylamine, N,N,N',N'-tetraglycidyl-m-xyl relendiamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

An isocyanate crosslinking agent (particularly, a bifunctional isocyanate crosslinking agent) and a peroxide crosslinking agent are preferable from the viewpoint of ensuring appropriate flexibility (and therefore flexibility) of the optical pressure-sensitive adhesive layer 10 . An isocyanate crosslinking agent (particularly, a trifunctional isocyanate crosslinking agent) is preferable from the viewpoint of securing durability of the optical pressure-sensitive adhesive layer 10 . In the base polymer, difunctional isocyanate crosslinking agents and peroxide crosslinking agents form more flexible two-dimensional crosslinking, whereas trifunctional isocyanate crosslinking agents form stronger three-dimensional crosslinking. From the viewpoint of both durability and flexibility of the optical pressure-sensitive adhesive layer 10, combination use of a trifunctional isocyanate crosslinking agent, a peroxide crosslinking agent, and/or a bifunctional isocyanate crosslinking agent is preferred.

The compounding amount of the crosslinking agent is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass with respect to 100 parts by mass of the base polymer, from the viewpoint of securing the cohesive force of the optical pressure-sensitive adhesive layer 10. more than wealth From the viewpoint of ensuring good tackiness in the optical adhesive layer 10, the compounding amount of the crosslinking agent relative to 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less. below the mass part.

In the second method, the monomer component (including the polyfunctional monomer for introducing the crosslinked structure and other monomers) may be polymerized at once or in multiple steps. In the multi-stage polymerization method, first, a monofunctional monomer for forming a base polymer is polymerized (prepolymerization), thereby preparing a prepolymer composition containing a partially polymerized product (a mixture of a polymer having a low polymerization degree and an unreacted monomer) do. Next, after adding the polyfunctional monomer to the prepolymer composition, the partial polymer and the polyfunctional monomer are polymerized (main polymerization).

Examples of the polyfunctional monomer include polyfunctional (meth)acrylates containing two or more ethylenically unsaturated double bonds in one molecule. As a polyfunctional monomer, a polyfunctional acrylate is preferable from the viewpoint of being able to introduce a crosslinked structure by active energy ray polymerization (photopolymerization).

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

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

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

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

The molecular weight of the polyfunctional monomer is preferably 1500 or less, more preferably 1000 or less. In addition, the functional group equivalent (g/eq) of the polyfunctional monomer is preferably 50 or more, more preferably 70 or more, still more preferably 80 or more. The functional group equivalent is preferably 500 or less, more preferably 300 or less, still more preferably 200 or less. These structures are preferable from the viewpoint of appropriately adjusting the viscoelastic properties (eg, storage modulus G' and loss tangent tan δ) by introduction of a crosslinked structure in the base polymer.

An acrylic polymer can be formed by polymerizing the above-mentioned monomer components. As a polymerization method, solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization are mentioned, for example. From the viewpoints of transparency, water resistance, and cost of the optical pressure-sensitive adhesive layer 10, solution polymerization and UV polymerization are preferred. As a solvent for solution polymerization, ethyl acetate and toluene are used, for example. Moreover, as a polymerization initiator, a thermal polymerization initiator and a photoinitiator are used, for example. The usage amount of the polymerization initiator is, for example, 0.05 part by mass or more, and, for example, 1 part by mass or less, with respect to 100 parts by mass of the monomer component.

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

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

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

The molecular weight of the base polymer can be adjusted by adjusting the type and/or amount of the polymerization initiator. For example, in radical polymerization, since the radical concentration in the reaction system increases as the amount of the polymerization initiator increases, the density of reaction starting points tends to increase and the molecular weight of the base polymer formed tends to decrease. On the other hand, the smaller the amount of polymerization initiator, the lower the density of the reaction starting point, so the polymer chain tends to elongate and the molecular weight of the formed base polymer tends to increase.

The weight average molecular weight of the base polymer is preferably 100,000 or more, more preferably 300,000 or more, and still more preferably 500,000 or more, from the viewpoint of securing the cohesive force in the optical pressure-sensitive adhesive layer 10. The same weight average molecular weight is preferably 5 million or less, more preferably 3 million or less, still more preferably 2 million or less. The weight average molecular weight of the base polymer is measured by a gel permeation chromatograph (GPC) and calculated in terms of polystyrene.

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

Regarding the glass transition temperature (Tg) of the base polymer, a glass transition temperature (theoretical value) obtained based on the following formula of Fox can be used. Fox's formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In Fox's formula below, Tg represents the glass transition temperature (°C) of a polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature of a homopolymer formed from monomer i. (°C) is shown. Literature values can be used for the glass transition temperature of the homopolymer. For example, in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Bunko 7 Introduction to Synthetic Resins for Paint" (authored by Kitaoka Kyojo, Polymer Publication Society, 1995), The glass transition temperature of various homopolymers is mentioned. On the other hand, about the glass transition temperature of the homopolymer of a monomer, it is also possible to obtain|require by the method specifically described in Unexamined-Japanese-Patent No. 2007-51271.

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

The pressure-sensitive adhesive composition may contain one type or two or more types of oligomers in addition to the base polymer. When an acrylic polymer is used as the base polymer, an acrylic oligomer is preferably used as the oligomer. The acrylic oligomer is a copolymer of monomer components containing an alkyl (meth)acrylate in a proportion of 50% by mass or more, and has a weight average molecular weight of, for example, 1000 or more and 30000 or less.

The glass transition temperature of the acrylic oligomer is preferably 60°C or higher, more preferably 80°C or higher, still more preferably 100°C or higher, and particularly preferably 110°C or higher. The glass transition temperature of the acrylic oligomer is, for example, 200°C or lower, preferably 180°C or lower, and more preferably 160°C or lower. The combined use of a low-Tg acrylic polymer (base polymer) and a high-Tg acrylic oligomer into which a crosslinked structure is introduced can increase the adhesive strength of the optical pressure-sensitive adhesive layer 10, particularly at high temperatures. The glass transition temperature of the acrylic oligomer is calculated by the formula of Fox described above.

The acrylic oligomer having a glass transition temperature of 60°C or higher is preferably composed of an alkyl (meth)acrylate having a chain alkyl group (chain alkyl (meth)acrylate) and an alkyl (meth)acrylate having an alicyclic alkyl group (alicyclic). It is a polymer of monomer components including alkyl (meth)acrylates. As a specific example of these alkyl (meth)acrylates, the above-mentioned alkyl (meth)acrylates as a monomer component of an acrylic polymer are mentioned, for example.

As the chain alkyl (meth)acrylate, methyl methacrylate is preferable because it has a high glass transition temperature and excellent compatibility with the base polymer. As an alicyclic alkyl (meth)acrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferable. That is, the acrylic oligomer is a monomer component containing at least one selected from the group consisting of dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and methyl methacrylate It is preferably a polymer of

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

The weight average molecular weight of the acrylic oligomer is preferably 1000 or more, more preferably 1500 or more, still more preferably 2000 or more. The molecular weight is preferably 30000 or less, more preferably 10000 or less, still more preferably 8000 or less. Such a molecular weight range of the acrylic oligomer is preferable to secure the adhesive force and adhesive retention force of the optical pressure-sensitive adhesive layer 10 .

An acrylic oligomer is obtained by polymerizing the monomer component of the said acrylic oligomer. As a polymerization method, solution polymerization, active energy ray polymerization (for example, UV polymerization), bulk polymerization, and emulsion polymerization are mentioned, for example. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, or a chain transfer agent may be used for the purpose of molecular weight adjustment.

The content of the acrylic oligomer in the optical pressure-sensitive adhesive layer 10 is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass with respect to 100 parts by mass of the base polymer, in order to sufficiently increase the adhesive strength of the optical pressure-sensitive adhesive layer 10. part or more, more preferably 1 part by mass or more. On the other hand, from the viewpoint of securing the transparency of the optical adhesive layer 10, the content of the acrylic oligomer in the optical adhesive layer 10 is preferably 5 parts by mass or less, more preferably 5 parts by mass or less with respect to 100 parts by mass of the base polymer. is 4 parts by mass or less, more preferably 3 parts by mass or less. In the optical pressure-sensitive adhesive layer 10, when the content of the acrylic oligomer is too large, the haze tends to rise due to the decrease in compatibility of the acrylic oligomer, resulting in a decrease in transparency.

The pressure-sensitive adhesive composition may contain a silane coupling agent. The content of the silane coupling agent in the pressure-sensitive 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 copper content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

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

The optical adhesive layer 10 of single-layer structure is manufactured, for example, by applying the above-mentioned adhesive composition on the peeling film L1 (1st peeling film) to form a coating film, and then drying the coating film. can do.

As a peeling film, the plastic film which has flexibility is mentioned, for example. As the said plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the peeling film is, for example, 3 µm or more, and is, for example, 200 µm or less. The surface of the peeling film is preferably subjected to peeling treatment.

As a method of applying the pressure-sensitive adhesive composition, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50°C to 200°C. Drying time is 5 seconds - 20 minutes, for example.

You may laminate|stack the peeling film L2 (2nd peeling film) further on the optical adhesive layer 10 on the 1st peeling film L1. The second peeling film is a flexible plastic film subjected to surface peeling treatment, and the same film as described above for the first peeling film can be used.

As described above, the optical adhesive layer 10 as the optical adhesive sheet S in which the adhesive face is coated and protected by the release films L1 and L2 can be manufactured. When using the optical adhesive sheet S, the peeling films L1 and L2 are peeled off from the optical adhesive sheet S as needed.

Examples of the method for forming the optical pressure-sensitive adhesive layer 10 having a multilayer structure include a dry-on-dry method, a wet-on-dry method, and a wet-on-wet method. In the dry-on-dry method, for example, after forming each of a plurality of pressure-sensitive adhesive layers by coating and drying the pressure-sensitive adhesive composition onto a peeling film, by bonding the plurality of pressure-sensitive adhesive layers together, a multilayer pressure-sensitive adhesive layers can be formed. In the wet-on-dry method, a multilayer adhesive layer can be formed by, for example, forming an adhesive layer by coating and drying an adhesive composition on a peeling film for each adhesive layer. In the wet-on-wet method, for example, a multilayer adhesive layer can be formed by applying a plurality of adhesive compositions in multiple stages on a peeling film to form a multilayer coating film, and then drying the multilayer coating film.

You may form the optical adhesive layer 10 of a single layer structure or multilayer structure by apply|coating and drying the adhesive composition on the object to be bonded by the optical adhesive layer 10.

The thickness of the optical adhesive layer 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the adherend. From the viewpoint of handleability of the optical adhesive layer 10, the thickness of the optical adhesive layer 10 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 haze of the optical adhesive layer 10 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The haze of the optical adhesive layer 10 can be measured using a haze meter based on JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Kogyo Co., Ltd. and "HM-150 type|mold" by Murakami Color Technology Laboratory Co., Ltd. are mentioned, for example.

The total light transmittance of the optical adhesive layer 10 is preferably 60% or more, more preferably 80% or more, still more preferably 85% or more. The total light transmittance of the optical adhesive layer 10 is, for example, 100% or less. The total light transmittance of the optical adhesive layer 10 can be measured based on JIS K 7375 (2008).

4A to 4C show an example of a method of using the optical pressure-sensitive adhesive layer 10.

In this method, first, as shown to FIG. 4A, the optical adhesive layer 10 is bonded to one side of the thickness direction H of the 1st member 21 (adhered body). The first member 21 is, for example, one element of a laminated structure of a flexible display panel. As the said element, a pixel panel, a touch panel, a polarizing plate, and a cover film are mentioned, for example (the same also applies to the 2nd member 22 mentioned later). According to this process, the optical adhesive layer 10 for bonding with another member is provided on the 1st member 21.

Next, as shown in FIG. 4B, the thickness direction H one side of the first member 21 and the thickness of the second member 22 are separated through the optical adhesive layer 10 on the first member 21. Join the other side in direction H. The second member 22 is, for example, another element in the laminated structure of the flexible display panel.

Next, as shown in FIG. 4C, the optical adhesive layer 10 between the first member 21 and the second member 22 is aged. By aging, a crosslinking reaction of the base polymer in the optical pressure-sensitive adhesive layer 10 proceeds, and bonding strength between the first member 21 and the second member 22 increases. The aging temperature is, for example, 20°C to 160°C. Aging time is 1 minute to 21 days, for example. In the case of autoclave treatment (heating and pressure treatment) as aging, the temperature is, for example, 30°C to 80°C, the pressure is, for example, 0.1 to 0.8 MPa, and the treatment time is, for example, 15 minutes or longer.

As described above, the optical pressure-sensitive adhesive layer 10 used in the manufacturing process of the flexible device has a shear storage modulus G' of 180 kPa or less at -20 ° C., and also has a first surface 10a and At least one side of the second surface 10b has a peel adhesive force F of 5 N/25 mm or more under the above conditions. As described above, such an optical pressure-sensitive adhesive layer 10 is suitable for achieving both bending deformability and peeling suppression, and therefore suitable for use in flexible devices.

Example

The present invention will be described concretely by showing examples below. However, this invention is not limited to an Example. In addition, the specific numerical values such as the compounding amount (content), physical property values, and parameters described below are the compounding amounts (content), physical property values, and parameters corresponding to them described in the above-mentioned “Specific Content for Carrying Out the Invention”. It can be substituted with the upper limit (numerical value defined as "below" or "less than") or the lower limit (numerical value defined as "greater than" or "exceeding") of the same.

<Preparation of Polymer P1>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 89 parts by mass of 2-ethylhexyl acrylate (2EHA) and 10 parts by mass of N-vinyl-2-pyrrolidone (NVP), A mixture (solid content) containing 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate and toluene as a solvent A concentration of 50% by mass, the ratio of toluene in the solvent was 5% by mass) was stirred at 55°C for 6 hours in a nitrogen atmosphere (polymerization reaction). In this way, a solution containing the acrylic polymer (polymer P1) was obtained. Then, ethyl acetate was added to this solution to adjust the polymer concentration of the solution to 30% by mass. In this way, a first polymer solution containing an acrylic polymer (polymer P1) was obtained. The weight average molecular weight of the acrylic polymer in the first polymer solution was 2,190,000.

<Preparation of Polymer P2>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 56 parts by mass of 2-ethylhexyl (2EHA) acrylic acid, 39 parts by mass of lauryl acrylate (LA), and 4-hydroxy acrylic acid A mixture (solid content concentration: 33% by mass) containing 5 parts by mass of butyl (4HBA), 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate as a solvent, It stirred at 58 degreeC for 5 hours in nitrogen atmosphere (polymerization reaction). This obtained a solution containing an acrylic polymer (polymer P2). Then, ethyl acetate was added to this solution to adjust the polymer concentration of the solution to 30% by mass. In this way, a second polymer solution containing an acrylic polymer (polymer P2) was obtained. The weight average molecular weight of the acrylic polymer in the second polymer solution was 830,000.

<Preparation of Polymer P3>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 70.3 parts by mass of 2-ethylhexyl acrylate (2EHA), 8.0 parts by mass of lauryl acrylate (LA), and n-butyl acrylate ( BA) 20.1 parts by mass, 4-hydroxybutyl acrylate (4HBA) 1.0 parts by mass, N-vinyl-2-pyrrolidone (NVP) 0.6 parts by mass, and 2,2'-azobisiso as a thermal polymerization initiator A mixture containing 0.1 part by mass of butyronitrile (AIBN) and ethyl acetate as a solvent (solid content concentration: 47% by mass) was stirred at 56°C for 6 hours in a nitrogen atmosphere (polymerization reaction). This obtained a solution containing an acrylic polymer (Polymer P3). Then, ethyl acetate was added to this solution to adjust the polymer concentration of the solution to 24% by mass. In this way, a third polymer solution containing an acrylic polymer (polymer P3) was obtained. The weight average molecular weight of the acrylic polymer in the third polymer solution was 2,100,000.

<Preparation of Polymer P4>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 97.3 parts by mass of 2-ethylhexyl acrylate (2EHA) and 1.7 parts by mass of N-vinyl-2-pyrrolidone (NVP), A mixture (solid content) containing 1.0 parts by mass of 4-hydroxybutyl acrylate (4HBA), 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and ethyl acetate and toluene as solvents A concentration of 50% by mass, the ratio of toluene in the solvent was 5% by mass) was stirred at 55°C for 6 hours in a nitrogen atmosphere (polymerization reaction). In this way, a solution containing the acrylic polymer (polymer P1) was obtained. Then, ethyl acetate was added to this solution to adjust the polymer concentration of the solution to 30% by mass. In this way, a fourth polymer solution containing an acrylic polymer (polymer P4) was obtained. The weight average molecular weight of the acrylic polymer in the fourth polymer solution was 2,000,000.

<Preparation of the first acrylic oligomer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), and a chain transfer agent A mixture containing 3.5 parts by mass of α-thioglycerol and 100 parts by mass of toluene as a solvent was stirred at 70°C for 1 hour in a nitrogen atmosphere. Thereafter, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, and in a nitrogen atmosphere at 70 ° C. for 2 hours, and then It was made to react at 80 degreeC for 2 hours (formation of the 1st acrylic oligomer). In this way, a solid first acrylic oligomer was obtained. The weight average molecular weight of the 1st acrylic oligomer was 5100. The glass transition temperature (Tg) of the first acrylic oligomer was 130°C.

<Preparation of the second acrylic oligomer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet pipe, 95 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of acrylic acid (AA), and α-methylstyrene as a chain transfer agent. A mixture containing 10 parts by mass of dimer (product name "Nopmer MSD", manufactured by Nippon Oil & Oil Co., Ltd.) and 120 parts by mass of toluene as a solvent was stirred at room temperature for 1 hour in a nitrogen atmosphere. Thereafter, 10 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added to the mixture to prepare a reaction solution, and in a nitrogen atmosphere, at 85 ° C. for 2 hours, and then It was made to react at 86 degreeC for 1.5 hours (formation of the 2nd acryl oligomer). In this way, a solid second acrylic oligomer was obtained. The weight average molecular weight of the second acrylic oligomer was 4000. The glass transition temperature (Tg) of the second acrylic oligomer was 67°C.

[Example 1]

<Preparation of the first pressure-sensitive adhesive composition>

Ethyl acetate was added to the first polymer solution to adjust the solid content concentration to 10% by mass, thereby obtaining the first pressure-sensitive adhesive composition.

<Preparation of the second pressure-sensitive adhesive composition>

To the second polymer solution, 0.5 parts by mass of a crosslinking agent (product name "Nyper BMT 40SV", dibenzoyl peroxide, manufactured by Nippon Yuji Co., Ltd.) per 100 parts by mass of the acrylic polymer (polymer P2) in the polymer solution was added and mixed, and then ethyl acetate It was added, the solid content concentration was adjusted to 23% by mass, and the second adhesive composition was obtained.

<Formation of optical adhesive layer>

On the release-treated surface of the first release film (trade name "JT-50Wa", polyester film, thickness 50 μm, manufactured by Nitto Denko Co., Ltd.) to which one side has been subjected to silicone release treatment, by a wet-on-wet method, the first adhesive composition (lower) and the second pressure-sensitive adhesive composition (upper) were applied. Specifically, while applying the first adhesive composition on the first peeling film to form a coating film (thickness after drying of 2 μm), the second adhesive composition is applied on the coating film to form a coating film (thickness after drying of 23 μm). (formation of multilayer coating film). Next, the multilayer coating film on the first peeling film was dried by heating at 155°C for 2 minutes to form a multilayer pressure-sensitive adhesive layer having a thickness of 25 µm. Next, to the multilayer pressure-sensitive adhesive layer on the first release film, the release-treated side of the second release film (product name “MRQ25T100J”, polyester film, thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) having one side subjected to silicone release treatment was bonded. Thereafter, an aging treatment was performed at 50°C for 48 hours to promote a crosslinking reaction in the pressure-sensitive adhesive layer. As described above, the optical adhesive sheet (optical adhesive layer) of Example 1 was produced. The optical adhesive sheet of Example 1 has two layers of a first layer (thickness: 2 μm) as the first adhesive layer formed from the first adhesive composition, and a second layer (thickness: 23 μm) as the second adhesive layer formed from the second adhesive composition. have a structure The polymer monomer composition and the pressure-sensitive adhesive layer composition in the optical adhesive sheet of Example 1 are shown in Table 1 in parts by mass (the same applies to Examples and Comparative Examples described later).

[Example 2]

An optical adhesive sheet of Example 2 was produced in the same manner as the optical adhesive sheet of Example 1 except for the following. Preparation of the 2nd adhesive composition WHEREIN: The compounding quantity of the crosslinking agent (product name "Nyper BMT 40SV") was made into 1.0 mass part instead of 0.5 mass part.

The optical adhesive sheet of Example 2 has two layers of a first layer (thickness: 2 μm) as the first adhesive layer formed from the first adhesive composition, and a second layer (thickness: 23 μm) as the second adhesive layer formed from the second adhesive composition. have a structure The optical adhesive sheet of Example 2 and the optical adhesive sheet of Example 2 differ in the degree of crosslinking of the polymer component in the first adhesive layer and the second adhesive layer. As a result, between the optical adhesive sheets of Examples 1 and 2, there is a difference in the peel adhesive strength F described later. In the above-described wet-on-wet method in the optical adhesive sheet manufacturing process, a part of the crosslinking agent diffuses into the first PSA composition from the second PSA composition (upper) applied on the first PSA composition (lower). to be.

[Example 3]

<Preparation of the third pressure-sensitive adhesive composition>

To the third polymer solution, 0.28 parts by mass of a crosslinking agent (product name "Nyper BMT 40SV", dibenzoyl peroxide, manufactured by Nippon Oil Co., Ltd.) and 3 parts by mass of the first acrylic oligomer per 100 parts by mass of the acrylic polymer (polymer P3) in the polymer solution. And 0.3 parts by mass of an antioxidant (product name "Irganox1010", manufactured by BASF) was added and mixed, and then ethyl acetate was added to adjust the solid content concentration to 15% by mass to obtain a third adhesive composition. The first acrylic oligomer was obtained as follows.

<Formation of optical adhesive layer>

A coating film (thickness after drying of 25 μm) by applying the third adhesive composition on the release treated surface of the first release film (product name “JT-50Wa”, polyester film, thickness 50 μm, manufactured by Nitto Denko Co., Ltd.) to which one side has been subjected to silicone release treatment ) was formed. Next, the coating film on the 1st peeling film was dried by heating at 155 degreeC for 2 minutes, and the adhesive layer of 25 micrometers in thickness was formed. Next, to the pressure-sensitive adhesive layer on the first release film, the release-treated side of the second release film (trade name “MRQ25T100J”, polyester film, thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) having one side subjected to silicone release treatment was bonded. Thereafter, an aging treatment was performed at 50°C for 48 hours to promote a crosslinking reaction in the pressure-sensitive adhesive layer. As described above, the optical adhesive sheet of Example 3 (optical adhesive layer having a single-layer structure) was produced.

[Example 4]

To the above-described third polymer solution, 0.26 parts by mass of the first crosslinking agent (product name "Nyper BMT 40SV", dibenzoyl peroxide, manufactured by Nippon Yuji Co., Ltd.) per 100 parts by mass of the acrylic polymer (polymer P3) in the polymer solution, and the second crosslinking agent (product name "Coronate L", trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh Corporation) 0.02 parts by mass, 1.5 parts by mass of the second acrylic oligomer, and a silane coupling agent (product name "KBM403 , manufactured by Shin-Etsu Chemical Industry Co., Ltd.) 0.3 parts by mass was added and mixed, and then ethyl acetate was added to adjust the solid content concentration to 23% by mass to obtain a fourth adhesive composition. Then, in the formation of the optical adhesive layer, the optical adhesive sheet of Example 4 (single-layer optical adhesive layer) was carried out in the same manner as the optical adhesive sheet of Example 3 except that the fourth adhesive composition was used instead of the third adhesive composition. has produced

[Comparative Example 1]

To the first polymer solution described above, 0.5 part by mass of a crosslinking agent (product name "Nyper BMT 40SV", dibenzoyl peroxide, manufactured by Nippon Yuji Co., Ltd.) per 100 parts by mass of the acrylic polymer (polymer P1) in the polymer solution was added and mixed, followed by acetic acid Ethyl was added to adjust the solid content concentration to 15% by mass to obtain a fifth adhesive composition. Then, in the formation of the optical adhesive layer, the optical adhesive sheet of Comparative Example 1 (single-layer structure optical adhesive layer) was carried out in the same manner as the optical adhesive sheet of Example 3 except that the fifth adhesive composition was used instead of the third adhesive composition. has produced

[Comparative Example 2]

In the formation of the optical adhesive layer, the optical adhesive sheet of Comparative Example 2 (single-layer optical adhesive layer) in the same manner as the optical adhesive sheet of Example 3 except that the above-described second adhesive composition was used instead of the third adhesive composition has produced

[Comparative Example 3]

Ethyl acetate was added to the above-mentioned fourth polymer solution to adjust the solid content concentration to 10% by mass, thereby obtaining a sixth adhesive composition. And in formation of the optical adhesive layer, the optical adhesive sheet of comparative example 3 was produced like the optical adhesive sheet of Example 1 except having used the 6th adhesive composition instead of the 1st adhesive composition. The optical adhesive sheet of Comparative Example 3 consists of two layers: a first layer (thickness: 2 μm) as the first adhesive layer formed from the sixth adhesive composition, and a second layer (thickness: 23 μm) formed from the second adhesive composition as the second adhesive layer. have a structure

<Thickness of adhesive layer>

The thickness of each optical adhesive sheet of Examples 1 to 4 and Comparative Examples 1 to 3 was investigated. Specifically, first, an adhesive sheet piece (25 mm short side x 100 mm long side) was cut out from the optical adhesive sheet. Next, the thickness of each of the five measuring points on the pressure-sensitive adhesive sheet piece was measured with a dial gauge. The five measuring points are five points that divide the center of the pressure-sensitive adhesive sheet in the width direction into six equal parts in the long side direction. Table 1 shows the maximum thickness T ₁ (μm) and the minimum thickness T ₂ (μm) among the thickness measurements at the five measurement points. Table 1 also shows the difference between the maximum thickness and the minimum thickness (T ₁ -T ₂ ).

<Peel Adhesion>

The peel adhesive strength of each optical adhesive sheet of Examples 1 to 4 and Comparative Examples 1 to 3 was examined by a peel test.

First, samples for measurement were prepared for each optical adhesive sheet. In the production of samples for measurement of each optical adhesive sheet in Examples 1 and 2, first, the second release film was peeled off from the optical adhesive sheet, and the exposed surface thereby exposed was a polyimide substrate whose surface was plasma-treated. (product name "UPILEX 25RN", thickness 25 µm, manufactured by Ube Kosan Co., Ltd.) were bonded together to obtain a laminate. Next, a test piece (25 mm in width x 100 mm in length) was cut out from this layered product (polyimide base material/adhesive layer/1st peeling film). Next, the first peeling film is peeled off from the pressure-sensitive adhesive layer of this test piece, and a polyimide film (product name "Upilex 50S", thickness 50 μm, manufactured by Ube Kosan Co., Ltd.) was bonded. In this bonding, the test piece was crimped against the polyimide film by an operation in which a 2 kg hand roller was reciprocated once in a 23°C environment. As described above, samples for measurement of each optical adhesive sheet of Examples 1 and 2 and Comparative Example 3 were prepared. The samples for measurement of each optical adhesive sheet in Examples 3 and 4 and Comparative Examples 1 and 2 were made of a polyimide substrate (product name "UPIREX 25RN", It was produced in the same manner as the measurement sample in Examples 1 and 2 and Comparative Example 3, except that a thickness of 25 µm, manufactured by Ube Industries, Ltd.) was used.

Next, after the sample for measurement was left still at room temperature for 30 minutes, a peeling test was conducted in which a test piece was peeled from the polyimide film in the sample for measurement, and the peel strength was measured. In the samples for measurement in Examples 1 and 2 and Comparative Example 3, the peel strength from the surface of the polyimide film on the surface of the first layer was measured. For this measurement, a tensile tester (product name "Autograph AG-50NX plus", manufactured by Shimadzu Corporation) was used. In this measurement, the measurement temperature was 25°C, the peel angle of the test piece from the polyimide film was 180°, the tensile speed of the test piece was 300 mm/min, and the peel length was 50 mm. The average value of the measured peel strength is shown in Table 1 as the peel adhesive strength F (N/25 mm). The peel adhesive force F of the pressure-sensitive adhesive layer of the multilayer structure (first layer/second layer) is the adhesive force of the exposed surface of the first layer.

<Shear storage modulus>

About each optical adhesive sheet (optical adhesive layer) of Examples 1-4 and Comparative Examples 1-3, the shear storage elastic modulus was measured as follows.

First, samples for measurement were produced. Specifically, a plurality of PSA layer pieces cut out from the optical PSA sheet were bonded together to prepare a PSA sheet having a thickness of about 1 mm, and then the sheet was punched out to obtain a cylindrical pellet (9 mm in diameter) as a sample for measurement. And about the sample for a measurement, dynamic-viscoelasticity measurement was performed after fixing to the jig of a parallel plate with a diameter of 8 mm using the dynamic-viscoelasticity measuring apparatus (product name "ARES-G2", made by TA Instruments). In this measurement, the measurement mode was the shear mode, the measurement temperature range was -60°C to 150°C, the temperature increase rate was 5°C/min, and the frequency was 1 Hz. From the measurement results, the first shear storage modulus G' (kPa) at -20°C and the second shear storage modulus G' (kPa) at -40°C were read. The results are shown in Table 1. In Table 1, the ratio of the first shear storage modulus G' (kPa) to the peel adhesion force F (N / 25 mm) and the ratio of the second shear storage modulus G' (kPa) to the peel adhesion force F (N / 25 mm) also, indicate

In addition, the measurement results of the peel adhesive force F and the first shear storage modulus G' described above for each optical adhesive sheet (optical adhesive layer) of Examples 1 to 4 and Comparative Examples 2 and 3 are shown in the graph of FIG. 5 . In the graph of FIG. 5 , the abscissa axis represents the first shear storage modulus G' (kPa) as the shear storage modulus at -20°C, and the ordinate axis represents the peel adhesive force F (N/25 mm). 5, plot E1 shows the measurement results in Example 1, plot E2 shows the measurement results in Example 2, plot E3 shows the measurement results in Example 3, and plot E4 shows the measurement results in Example 3. The measurement results in Example 4 are shown, the plot C2 shows the measurement results in Comparative Example 2, and the plot C3 shows the measurement results in Comparative Example 3 (the measurement results in Comparative Example 1 are the vertical and horizontal axes). is outside the range of , and did not appear). In Fig. 5, the dashed-dotted line R1 represents a line of peel adhesive strength F = 5 N/25 mm in G' ≤ 135, and the dashed-dotted line R2 represents the line in G' > 135, F = 0.4667 x G'- Shows line 58. When the peel adhesive force F is 5 N/25 mm or more in G'≤135 and the peel adhesive force F satisfies F≥0.4667 × G'-58 in G'>135 (plots E1 to E4), the optical adhesive Coexistence of layer softness and high adhesion can be achieved.

<Change in transmittance>

The transmittance change was investigated for each optical adhesive sheet (optical adhesive layer) of Examples 1 to 4 and Comparative Examples 1 to 3 as follows.

First, samples for measurement were produced. Specifically, after peeling off the second peeling film from the optical adhesive sheet, the exposed adhesive layer side was bonded to a PET base material (product name "T100C50", thickness 50 µm, manufactured by Mitsubishi Chemical). Next, after peeling off the first peeling film from the optical adhesive sheet (adhesive layer), the surface of the adhesive layer thus exposed was bonded to a PET substrate (product name “T100C50”, thickness 50 μm, manufactured by Mitsubishi Chemical Corporation). In this way, a laminate having a laminate configuration of PET base material/optical pressure-sensitive adhesive layer/PET base material was obtained. Next, a sample for measurement having a size of 25 mm in width x 100 mm in length was cut out from this laminate.

Next, the transmittance (T1) of light having a wavelength of 550 nm was measured for the sample for measurement (first transmittance measurement). For the measurement, a transmittance measuring device (product name "U4100 type spectrophotometer", manufactured by Hitachi High-Technologies Corporation) was used.

Next, the sample for measurement, which had undergone the first transmittance measurement, was wound around a winding core with a diameter of 20 mm in such a way that the longitudinal direction of the sample was along the circumferential direction of the winding core (approximately 1.6 turns around the winding core). Next, the sample wound around the core in this way was stored at 23°C for 1 hour. Next, the transmittance (T2) of light having a wavelength of 550 nm was measured for the storage sample for measurement in the same manner as in the first transmittance measurement (second transmittance measurement).

And the change rate of transmittance T2 with respect to transmittance T1 was calculated|required based on the following formula. The values are shown in Table 1.

Transmittance change rate (%) = [(T2-T1) / T] × 100

S optical adhesive sheet
10 Optical adhesive layer
10a page 1
10b page 2
11 1st adhesive layer
12 2nd adhesive layer
13 2nd adhesive layer
H thickness direction
L1, L2 release film
21 first member
22 Second member

Claims (7)

An optical adhesive layer having a first surface and a second surface opposite to the first surface,
Has a shear storage modulus G' of 180 kPa or less at -20 ° C,
At least one of the first surface and the second surface is bonded to the polyimide film after 30 minutes at 23 ° C., with respect to the polyimide film, under the conditions of a peeling angle of 180 ° and a peeling speed of 300 mm / min. The optical adhesive layer which has peel adhesive force F of 5 N/25 mm or more. According to claim 1,
The shear storage modulus G' (kPa) and the peel adhesive force F (N / 25 mm) at -20 ° C. satisfy F≥ 0.4667 × G' -58 at G'> 135. The optical adhesive layer. According to claim 1,
The ratio of the shear storage modulus G' (kPa) at -20 ° C. to the peel adhesive strength F (N / 25 mm) is 30 or less, the optical adhesive layer. According to claim 1,
The ratio of the shear storage modulus G' (kPa) at -40 ° C. to the peel adhesive strength F (N / 25 mm) is 200 or less, the optical adhesive layer. According to any one of claims 1 to 4,
The optical adhesive layer whose shear storage elastic modulus G' at -40 degreeC is 1200 kPa or less. According to any one of claims 1 to 4,
An optical pressure-sensitive adhesive layer having a difference between the maximum thickness and the minimum thickness of 3 µm or less. According to any one of claims 1 to 4,
An optical adhesive layer having a change in transmittance of 5% or less over 1 hour after winding on a core having a cross-sectional diameter of 20 mm.

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