CN116478631A

CN116478631A - Optical adhesive sheet

Info

Publication number: CN116478631A
Application number: CN202310061353.1A
Authority: CN
Inventors: 设乐浩司; 山本真也
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2022-01-24
Filing date: 2023-01-19
Publication date: 2023-07-25
Also published as: JP2023107668A; TW202334360A; KR20230114199A

Abstract

Provided is an optical adhesive sheet which suppresses contamination around the optical adhesive sheet, improves handling properties, and has excellent adhesive reliability. The optical adhesive sheet (1) is provided with a release liner (2) and an adhesive layer (3) in this order on one side in the thickness direction. The maximum length (L) of the adhesive layer (3) in the direction perpendicular to the thickness direction is 200mm or more. The release liner (2) is larger than the adhesive layer (3) when viewed in the thickness direction, and contains a cover adhesive layer (3).

Description

Optical adhesive sheet

Technical Field

The present invention relates to an optical adhesive sheet, and more particularly, to an optical adhesive sheet suitable for use in adhering members for image display devices.

Background

An optical pressure-sensitive adhesive sheet comprising a release liner, a pressure-sensitive adhesive layer, and a 2 nd release liner in this order is known (for example, refer to patent document 1 below).

In the optical adhesive sheet described in patent document 1, a release liner is peeled from an adhesive layer, and then the adhesive layer is attached to a member of an image display device. The image display device includes a tablet terminal.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2020-122140

Disclosure of Invention

Problems to be solved by the invention

However, in the case of adhering the adhesive layer to the member of the flat terminal, the size of the adhesive layer is also increased due to the large size of the flat terminal. Thus, the optical adhesive sheet having the adhesive layer also increases in size. Thus, it is necessary to mechanically convey the optical adhesive sheet.

Here, in the case where the adhesive layer has the same dimensions as the release liner and the 2 nd release liner, respectively, the end portions of the adhesive layer are likely to overflow outward from the release liner and the 2 nd release liner. In this way, there is a problem that the adhesive composition of the adhesive layer contaminates the machine.

In addition, if the above-mentioned overflow occurs, the end portion of the optical adhesive sheet is undesirably adhered to the machine, and thus there is a problem in that the handling property of the optical adhesive sheet is lowered.

Further, if the above-mentioned overflow occurs, the adhesive layer becomes defective at the end portion, and the adhesive is lost. Thus, the adhesion reliability of the adhesive layer is lowered.

The invention provides an optical adhesive sheet which can inhibit surrounding pollution, improve handling property and have excellent adhesive reliability.

Solution for solving the problem

The present invention (1) comprises an optical adhesive sheet comprising a release liner and an adhesive layer in this order on one side in the thickness direction, wherein the maximum length L of the adhesive layer in the direction orthogonal to the thickness direction is 200mm or more, and the release liner is larger than the adhesive layer and covers the adhesive layer when viewed in the thickness direction.

In this optical pressure-sensitive adhesive sheet, the maximum length L of the pressure-sensitive adhesive layer is 200mm or more, and therefore the pressure-sensitive adhesive layer can be attached to a member in a large-sized image display device such as a flat panel terminal.

In the optical adhesive sheet of the present invention, even if the length L is 200mm or more, the release liner is larger than the adhesive layer and includes the cover adhesive layer when viewed in the thickness direction, and therefore, the release liner can suppress the overflow of the end portion of the adhesive layer. Therefore, contamination of the surroundings due to the adhesive layer can be suppressed.

Further, in this optical adhesive sheet, overflow of the end portion of the adhesive layer is suppressed, and thus the handling property is excellent.

In addition, in the optical adhesive sheet, since the overflow of the end portion of the adhesive layer is suppressed, the lack of the adhesive is suppressed, and the adhesive reliability of the adhesive layer is excellent.

The invention (2) comprises the optical adhesive sheet according to (1), wherein the bending amount D measured by the bending test described below is 7mm or less.

Bending test: the optical adhesive sheet was formed into a shape having a length of 100mm and a width of 25mm, to prepare a sample. A stage having an upper surface and a height of 50mm or more is prepared. The surface of the 1 st part of the sample including one end edge in the longitudinal direction having a length of 50mm was fixed to the upper surface, and the 2 nd part of the sample including the other end edge in the longitudinal direction having a length of 50mm was protruded laterally from one end edge of the upper surface. Then, the mixture was left at 23℃for 5 minutes. Then, a movement amount by which one end edge of the protruding aforementioned sample moves downward from the upper surface is obtained. And fixing the back surface of the 1 st part to the upper surface to obtain the moving amount. An average of 2 moving amounts was obtained as a bending amount D.

In this optical pressure-sensitive adhesive sheet, the bending amount D is 7mm or less, and therefore the optical pressure-sensitive adhesive sheet is more excellent in handling property.

The invention (3) comprises the optical adhesive sheet according to (1) or (2), wherein the area P, which is the product of the offset amount of the release liner and the thickness of the release liner defined as follows, is 90X 10 ^-8 m ² The above.

The foregoing offset: a length (mm) of an offset portion of the release liner that is offset from the adhesive layer when viewed in the thickness direction

The thickness of the foregoing: average thickness (μm) at 3 points in the aforementioned offset portion

In the optical pressure-sensitive adhesive sheet, the area P is 90×10 ^-8 m ² As described above, the adhesive layer can be prevented from floating from the release liner.

The present invention (4) includes the optical adhesive sheet according to (2), further comprising an adjacent layer adjacent to the side opposite to the release liner with respect to the adhesive layer in the thickness direction, wherein the release liner, the adhesive layer, and the adjacent layer satisfy the following expression [1 ].

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥2500

[1]

E1: tensile modulus (MPa) of the foregoing release liner at 23 DEG C

E2: tensile modulus (MPa) of the adjacent layer at 23 DEG C

T1: thickness (μm) of the release liner

T2: thickness (μm) of the adjacent layer

T0: thickness (μm) of the adhesive layer

When the above formula [1] is satisfied, at least one selected from the group consisting of the thickness T1 of the release liner, the tensile modulus E1 of the release liner, the thickness T2 of the adjacent layer, and the tensile modulus E2 of the adjacent layer is large. Therefore, even if the adhesive layer is thick, the release liner and/or the adjacent layer tends to be hard, and therefore the above-mentioned bending amount D of the optical adhesive sheet can be reduced.

Alternatively, when the above formula [1] is satisfied, the adhesive layer is thin. Therefore, even if at least any one selected from the group consisting of the thickness T1 of the release liner, the tensile modulus E1 of the release liner, the thickness T2 of the adjacent layer, and the tensile modulus E2 of the adjacent layer is small, the optical adhesive sheet can secure toughness, and thus the above-described bending amount D of the optical adhesive sheet can be reduced.

The invention (5) includes the optical adhesive sheet according to (4), wherein the adjacent layer is a 2 nd release liner.

The invention (6) includes the optical adhesive sheet according to (5), wherein the 2 nd release liner is larger than the adhesive layer when viewed in the thickness direction, and includes the adhesive layer.

In this optical pressure-sensitive adhesive sheet, the 2 nd release liner is larger than the pressure-sensitive adhesive layer and includes the pressure-sensitive adhesive layer when viewed in the thickness direction, and therefore, the overflow of the end portion of the pressure-sensitive adhesive layer is further suppressed by the 2 nd release liner, and the handling property is further excellent.

The invention (7) includes the optical adhesive sheet according to (6), wherein an area P2, which is a product of a 2 nd offset amount of the 2 nd release liner and a thickness of the 2 nd release liner defined as follows, is 90X 10 ^-8 m ² The above.

The foregoing offset: a length (mm) of a 2 nd offset portion of the 2 nd release liner which is offset from the adhesive layer when viewed in the thickness direction

The thickness of the foregoing: average thickness (μm) at 3 points in the aforementioned 2 nd offset portion

In the optical pressure-sensitive adhesive sheet, the area P2 is 90×10 ^-8 m ² As described above, the adhesive layer can be prevented from floating from the 2 nd release liner.

The invention (8) includes the optical adhesive sheet according to (4), wherein the adjacent layer is a member for an image display device.

The invention (9) includes the optical adhesive sheet according to (8), wherein a peripheral edge of the image display device member coincides with a peripheral edge of the adhesive layer when viewed in the thickness direction.

The present invention (10) includes the optical adhesive sheet according to any one of (1) to (9), wherein one surface of the release liner in the thickness direction has a concave portion recessed to the other side in the thickness direction around the peripheral edge of the adhesive layer, and the depth of the concave portion is 30 μm or less.

The invention (11) includes the optical adhesive sheet according to any one of (1) to (10), wherein the pressure-sensitive adhesive layer has an indentation hardness H of 10kPa or less at 23 ℃.

In this optical pressure-sensitive adhesive sheet, since the pressure-sensitive adhesive layer has an indentation hardness H of 10kPa or less at 23 ℃, the pressure-sensitive adhesive layer is suitably used for sticking members in an image display device that can be repeatedly folded (foldable).

The invention (12) includes the optical adhesive sheet according to any one of (1) to (11), wherein the shear storage modulus G' of the adhesive layer at 25 ℃ is 100kPa or less.

In this optical pressure-sensitive adhesive sheet, the shear storage modulus G' of the pressure-sensitive adhesive layer at 25 ℃ is 100kPa or less, and therefore the pressure-sensitive adhesive layer is suitably used for adhesion of members in an image display device that can be repeatedly folded (foldable).

The present invention (13) includes the optical adhesive sheet according to any one of (1) to (12), which is an optical adhesive sheet provided with the adhesive layer and disposed in an image display device, the image display device comprising: the pressure-sensitive adhesive layer and a pair of members for an image display device formed on one surface and the other surface of the optical pressure-sensitive adhesive sheet in the thickness direction.

ADVANTAGEOUS EFFECTS OF INVENTION

The optical adhesive sheet of the present invention suppresses peripheral contamination, improves handling properties, and is excellent in adhesion reliability.

Drawings

Fig. 1 is a cross-sectional view of an optical adhesive sheet according to one embodiment of the present disclosure.

Fig. 2 is a sectional view illustrating measurement of the amount of bending of the optical adhesive sheet.

In fig. 3, a to D in fig. 3 are process charts illustrating a method of manufacturing the optical adhesive sheet. A in fig. 3 is a process for preparing a laminate. Fig. 3B shows a process of shaping the adhesive layer and the 3 rd release liner. C in fig. 3 is a step of removing unnecessary portions. Fig. 3D shows a step of attaching the 3 rd release liner as an adjacent layer instead and shaping the release liner.

Fig. 4 is a cross-sectional view of an optical adhesive sheet provided with an image display device member as an adjacent layer.

Fig. 5 is a sectional view of the image display apparatus.

Fig. 6 is a cross-sectional view of an optical adhesive sheet according to a modification.

Fig. 7 is another embodiment of an optical adhesive sheet.

Description of the reference numerals

1 optical pressure-sensitive adhesive sheet

2 Release liner

3 adhesive layer

4 adjacent layers

4A 2 nd Release liner

10. Optical adhesive sheet

11. Member for image display device

12. Member for image display device

21. Offset portion

25. Concave part

41 No. 2 offset portion

100 samples

Part 1 of 101

102 part 2

105 tables

D bending amount

E1 tensile modulus (Release liner)

E2 tensile modulus (Adjacent layer)

G' shear storage modulus (adhesive layer)

H indentation hardness (adhesive layer)

OL offset (release liner)

OL2 nd offset (adjacent layer)

P product (Release liner)

P2 product (adjoining layer)

Detailed Description

1. Optical adhesive sheet 1

An embodiment of the optical adhesive sheet of the present invention is described with reference to fig. 1.

As shown in fig. 1, the optical adhesive sheet 1 has a thickness. The optical adhesive sheet 1 is along the plane direction. The plane direction is an example of the orthogonal direction, and is orthogonal to the thickness direction. The shape of the optical adhesive sheet 1 as viewed from one side in the thickness direction is not particularly limited. Examples of the shape of the optical pressure-sensitive adhesive sheet 1 include a rectangular shape, an elliptical shape, and a circular shape.

The optical adhesive sheet 1 includes a release liner 2 and an adhesive layer 3 in this order on one side in the thickness direction. In the present embodiment, the optical adhesive sheet 1 includes a release liner 2, an adhesive layer 3, and an adjacent layer 4 in this order on one side in the thickness direction.

1.2 adhesive layer 3 and its dimensions

The adhesive layer 3 is along the face direction. The adhesive layer 3 has a sheet shape. Examples of the shape of the adhesive layer 3 as viewed from the thickness direction side include a rectangular shape, an elliptical shape, and a circular shape.

The maximum length L of the adhesive layer 3 in the plane direction is 200mm or more.

If the adhesive layer 3 is rectangular in shape, the maximum length L of the adhesive layer 3 in the planar direction is the length of a line segment connecting the opposing 2 corners. If the adhesive layer 3 has an elliptical shape, the maximum length L of the adhesive layer 3 in the planar direction is the length in the major axis direction. If the adhesive layer 3 is circular in shape, the maximum length L of the adhesive layer 3 in the plane direction is the diameter.

When the maximum length L of the adhesive layer 3 in the plane direction is less than 200mm, the adhesive layer 3 cannot be attached to a member in a large-sized image display device such as a flat panel terminal.

On the other hand, in the present invention, the maximum length L of the adhesive layer 3 in the plane direction is 200mm or more, and therefore, the adhesive layer 3 can be attached to a member in the large-sized image display device.

The maximum length L of the adhesive layer 3 in the plane direction is preferably 200mm or more, more preferably 250mm or more, and still more preferably 300mm or more. The maximum length L of the adhesive layer 3 in the plane direction is, for example, 3000mm or less, and is, for example, 2000mm or less.

The thickness T0 of the adhesive layer 3 is, for example, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 30 μm or more, and further preferably 40 μm or more, 50 μm or more, and 100 μm or more. The thickness T0 of the adhesive layer 3 is, for example, preferably 500 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less, and further preferably 50 μm or less, and 30 μm or less.

1.3 Release liner 2 and its dimensions

The release liner 2 forms the other surface of the optical adhesive sheet 1 in the thickness direction. The release liner 2 is located at the other end portion of the optical adhesive sheet 1 in the thickness direction.

The release liner 2 is larger than the adhesive layer 3 when viewed in the thickness direction. The release liner 2 contains a cover adhesive layer 3 when viewed in the thickness direction. For example, the peripheral end portion of the release liner 2 is exposed from the adhesive layer 3. The release liner 2 has, for example, a shape similar to that of the adhesive layer 3.

The length L1 of the release liner 2 in the 1 st direction is, for example, 200mm or more, preferably 201mm or more, more preferably 203mm or more, still more preferably 250mm or more, and still more preferably 300mm or more. The length L1 of the release liner 2 in the 1 st direction is 3020mm or less, for example, and 2020mm or less, for example. The 1 st direction is a direction included in the plane direction, and is a direction defining the maximum length L of the adhesive layer 3.

The value (L1-L) obtained by subtracting the maximum length L of the adhesive layer 3 in the plane direction from the length L1 of the release liner 2 in the 1 st direction is, for example, 1mm or more, preferably 3mm or more, more preferably 5mm or more, and still more preferably 10mm or more. When the value (L1-L) is equal to or greater than the lower limit, the optical pressure-sensitive adhesive sheet 1 can more reliably exhibit the effects of suppressing the contamination around, improving the handling properties, and being excellent in the adhesive reliability.

The upper limit of the value (L1-L) obtained by subtracting the maximum length L of the adhesive layer 3 in the plane direction from the length L1 of the release liner 2 in the 1 st direction is, for example, 100mm. When the value (L1-L) is equal to or less than the upper limit, the reduction in the handleability of the optical adhesive sheet 1 due to the excessively large offset portion 21 (described later) of the release liner 2 can be suppressed.

According to the above values (L1-L), the release liner 2 has offset portions (edge portions) 21. The offset portion 21 is a peripheral end portion along the outer periphery of the adhesive layer 3 in the release liner 2.

The thickness T1 of the release liner 2 is appropriately set so that the area P described later becomes a specific value and so that the relationship value with the tensile modulus E1 described later becomes a specific value. The thickness T1 of the release liner 2 is, for example, 10 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and still more preferably 70 μm or more. The thickness T1 of the release liner 2 is, for example, 200 μm or less, preferably 100 μm or less, more preferably 70 μm or less, and still more preferably 50 μm or less.

1.4 Adjacent layer 4 and its dimensions

In the present embodiment, the adjacent layer 4 forms one surface of the optical adhesive sheet 1 in the thickness direction. The adjoining layer 4 adjoins the side opposite to the release liner 2 with respect to the adhesive layer 3 in the thickness direction. The adjacent layer 4 is located at one end portion of the optical adhesive sheet 1 in the thickness direction.

As shown in fig. 1, the peripheral edge of the adjacent layer 4 coincides with the peripheral edge of the release liner 2 when viewed in the thickness direction. Alternatively, as shown in fig. 7, the adjacent layer 4 may be larger than the adhesive layer 3 and include the cover adhesive layer 3 when viewed in the thickness direction. The peripheral end portion of the adjacent layer 4 is exposed from the adhesive layer 3. At this time, the adjacent layer 4 has, for example, a shape similar to that of the adhesive layer 3. The adjacent layer 4 is, for example, the 2 nd release liner 4A or the image display device member 11 (see fig. 5), and in the present embodiment, the 2 nd release liner 4A is preferable.

The length L2 of the adjacent layer 4 in the 1 st direction is, for example, 200mm or more, preferably 250mm or more, more preferably 300mm or more, and still more preferably 500mm or more. The length L2 of the adjacent layer 4 in the 1 st direction is, for example, 3000mm or less, and is, for example, 2000mm or less.

The value (L2-L) obtained by subtracting the maximum length L of the adhesive layer 3 in the plane direction from the length L2 of the adjacent layer 4 in the 1 st direction is, for example, 0mm or more, preferably 1mm or more, preferably 3mm or more, more preferably 5mm or more, and still more preferably 10mm or more.

As shown in fig. 7, the upper limit of the value (L2-L) obtained by subtracting the maximum length L of the adhesive layer 3 in the plane direction from the length L2 of the adjacent layer 4 in the 1 st direction is, for example, 100mm. When the value (L2-L) is equal to or less than the upper limit, the optical adhesive sheet 1 can be prevented from being degraded in handleability due to the excessively large 2 nd offset portion 41 (described later) of the adjacent layer 4.

1.5 bending amount D of optical adhesive sheet 1

As shown in fig. 2, the bending amount D of the optical adhesive sheet 1 measured by the bending test described below is, for example, 20mm or less, preferably 15mm or less, more preferably 10mm or less, still more preferably 7mm or less, and particularly preferably 5mm or less. The lower limit of the bending amount D of the optical adhesive sheet 1 is 0mm, and further 1mm.

Bending test: the optical adhesive sheet 1 was formed into a shape having a length of 100mm and a width of 25mm, thereby producing a sample 100. Sample 100 has neither offset portion 21 (described below) nor offset portion 41 (described below). A stage 105 having a surface with an upper surface and a height of 50mm or more as shown in fig. 2 was prepared. A 1 st part 101 of the sample 100 having a length of 50mm including one end edge in the longitudinal direction is fixed to the upper surface, and a 2 nd part 102 of the sample 100 having a length of 50mm including the other end edge in the longitudinal direction is protruded laterally from one end edge of the upper surface. The weight 106 is disposed on the upper surface of the 1 st portion 101. Thereby, the 1 st part 101 is fixed to the upper surface of the 106 st part. Then, the mixture was left at 23℃for 5 minutes. Then, a movement amount D by which one end edge of the protruding sample 100 moves downward from the upper surface is obtained. The other line fixes the back surface of the 1 st portion 101 to the upper surface, and obtains the movement amount. An average of 2 moving amounts was obtained as a bending amount D.

When the bending amount D of the optical adhesive sheet 1 is equal to or less than the upper limit, the handling properties of the optical adhesive sheet 1 are improved.

The bending amount D is adjusted by adjusting the thickness T1 of the release liner 2, the tensile modulus E1 of the release liner 2 (described later), the thickness T2 of the adjacent layer 4, the tensile modulus E2 of the adjacent layer 4 (described later), the shear storage modulus G' (described later) of the adhesive layer 3, and the thickness T0 of the adhesive layer 3. The bending amount D may be adjusted by a relation value (left side of the following expressions [1] to [8 ]), an area P (described below), and/or an area P2 (described below).

1.6 physical Properties of the layers

1.6.1 indentation hardness H of adhesive layer 3

The indentation hardness H of the adhesive layer 3 at 23℃is, for example, 20kPa or less, preferably 10kPa or less, more preferably 5kPa or less, still more preferably 4kPa or less, and particularly preferably 3kPa or less. When the indentation hardness H of the adhesive layer 3 at 23 ℃ is equal to or lower than the upper limit, the adhesive layer 3 is suitably used for adhesion of members in an image display device that can be repeatedly folded (foldable). The lower limit of the indentation hardness H of the adhesive layer 3 at 23℃is, for example, 0.001kPa, preferably 0.01kPa, more preferably 0.1kPa. The indentation hardness H of the adhesive layer 3 is measured in examples later. The indentation hardness H of the adhesive layer 3 is adjusted by adjusting the formulation (type) of the adhesive composition to be described later.

1.6.2 shear storage modulus G 'of the adhesive layer 3'

The shear storage modulus G' of the adhesive layer 3 at 25℃is, for example, preferably 10kPa or more, more preferably 15kPa or more, still more preferably 20kPa or more, still more preferably 25kPa or more, and is, for example, 1000kPa or less, preferably 700kPa or less, still more preferably 500kPa or less, still more preferably 300kPa or less, still more preferably 200kPa or less, 100kPa or less, and 50kPa or less, and is preferably 1000kPa or less. When the shear storage modulus G' of the adhesive layer 3 is equal to or less than the upper limit, the adhesive layer 3 can achieve the softness required for the application of the flexible device. The shear storage modulus G' of the adhesive layer 3 was obtained by measuring the dynamic viscoelasticity at a temperature rising rate of 5 ℃/min and a frequency of 1 Hz. The shear storage modulus G' of the adhesive layer 3 is adjusted by adjusting the formulation (kind) of the adhesive composition to be described later.

1.6.3 area P as the product of offset OL and thickness T1 of release liner 2

The area P (=ol×t1) which is the product of the offset OL of the release liner 2 and the thickness T1 of the release liner 2 is, for example, 50×10 ^-8 m ² The above is preferably 90×10 ^-8 m ² The above, more preferably 150×10 ^-8 m ² The above is more preferably 200×10 ^-8 m ² The above is particularly preferably 300×10 ^-8 m ² The above. The upper limit of the area P, which is the product of the offset amount OL of the release liner 2 and the thickness T1 of the release liner 2, is 1000×10, for example ^-8 m ² Preferably 500X 10 ^-8 m ² 。

The offset OL and thickness T1 of the release liner 2 are defined as follows.

Offset OL of release liner 2: the length (mm) of the offset portion 21 offset from the adhesive layer 3 in the release liner 2 when viewed in the thickness direction

Thickness T1: average thickness (μm) at 3 points in offset portion 21

There are 2 offset portions 21 in the 1 st direction. The offset amounts OL of the 2 offset portions 21 are preferably identical to each other.

The 3 points are located at the same position in the 1 st direction in the offset portion 21, and are spaced apart from each other in the width direction. The width direction is orthogonal to the thickness direction and the 1 st direction.

When the area P is equal to or larger than the lower limit, the offset amount OL is large and/or thick.

When the offset amount OL of the release liner 2 is large, even if the offset portion 21 is deformed, the deformation is less likely to affect the adhesive layer 3. The deformation includes bending of the offset portion 21. Accordingly, the adhesive layer 3 can be suppressed from being undesirably peeled (lifted) from the release liner 2.

Alternatively, when the release liner 2 is thick, even if the offset portion 21 is in contact with the conveying mechanism, deformation of the release liner 2 is suppressed. Therefore, the floating of the adhesive layer 3 can be suppressed.

1.6.4 tensile modulus E1 of Release liner 2

The tensile modulus E1 of the release liner 2 at 23℃was obtained by the following relationship (E1×E2× (T1+T2)/[ T0) ^1/2 ×100000]) The specific value is set appropriately. The tensile modulus E1 of the release liner 2 at 23℃is, for example, 1000MPa or more, preferably 2000MPa or more, more preferably 3000MPa or more, and still more preferably 4000MPa or more. The upper limit of the tensile modulus E1 of the release liner 2 at 23℃is 10000MPa, for example.

The tensile modulus E1 of the release liner 2 at 23℃was determined based on the stress-strain curve. Details of the measurement are described in examples.

1.6.5 recesses 25 in release liner 2

One surface of the release liner 2 in the thickness direction is provided with a concave portion 25, for example. The concave portion 25 is recessed toward the other side in the thickness direction around the peripheral edge of the adhesive layer 3. The depth of the recess 25 is, for example, 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, and particularly preferably 1 μm or less. The lower limit of the depth of the recess 25 is, for example, 0.001 μm, and further 0 μm. When the depth of the concave portion 25 is equal to or less than the upper limit, the release liner 2 can be prevented from being cut from the concave portion 25.

1.6.6 tensile modulus E2 of the adjacent layer 4

The tensile modulus E2 of the adjacent layer 4 at 23 ℃ is appropriately set so that a relationship value described below becomes a specific value. The tensile modulus E2 of the adjacent layer 4 at 23℃is, for example, preferably 50MPa or more, more preferably 100MPa or more, still more preferably 150MPa or more, still more preferably 250MPa or more, particularly preferably 600MPa or more, still more preferably 1000MPa or more, 2000MPa or more, 3000MPa or more, 4000MPa or more, and is preferably at least. The upper limit of the tensile modulus E2 of the adjacent layer 4 at 23 ℃ is, for example, 15000MPa, preferably 10000MPa, more preferably 7500MPa, and even more preferably 5000MPa.

The tensile modulus E2 of the adjacent layer 4 at 23℃was determined based on the stress-strain curve.

Details of the measurement are described in examples.

The 2 nd release liner has flexibility.

1.6.7 relation value of adhesive layer 3, release liner 2 and adjacent layer 4

The pressure-sensitive adhesive layer 3, the release liner 2 and the adjacent layer 4 preferably satisfy the following formula [1], more preferably the following formula [2], still more preferably the following formula [3], still more preferably the following formula [4], yet still more preferably the following formula [5], yet still more preferably the following formula [6], the following formula [7] and the following formula [8], for example. The upper limit on the left side in the above formulas is 100000, for example, and 10000, for example.

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥500

[1]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥1000

[2]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥2500

[3]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥3000

[4]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥4000

[5]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥5000

[6]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥6000

[7]

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥7000

[8]

E1: tensile modulus (MPa) of Release liner 2 at 23 ℃C

E2: tensile modulus (MPa) of adjacent layer 4 at 23 DEG C

T1: thickness (μm) of release liner 2

T2: thickness (μm) of the adjacent layer 4

T0: thickness (μm) of the adhesive layer 3

When the above formula is satisfied, at least one selected from the group consisting of the thickness T1 of the release liner 2, the tensile modulus E1 of the release liner 2, the thickness T2 of the adjacent layer 4, and the tensile modulus E2 of the adjacent layer 4 is large. Therefore, even if the adhesive layer 3 is thick, in other words, even if the thickness T0 is large, the release liner 2 and/or the adjacent layer 4 tend to be hard, and the amount D of bending of the optical adhesive sheet 1 can be reduced.

Alternatively, when the above formula is satisfied, the adhesive layer 3 is thin. Therefore, even if at least any one selected from the group consisting of the thickness T1 of the release liner 2, the tensile modulus E1 of the release liner 2, the thickness T2 of the adjacent layer 4, and the tensile modulus E2 of the adjacent layer 4 is small, the optical adhesive sheet 1 can secure toughness. Therefore, the bending amount D of the optical adhesive sheet 1 can be reduced.

1.7 Material of layers

1.7.1 materials for the adhesive layer 3

The adhesive layer 3 is a sheet-like pressure-sensitive adhesive formed of an adhesive composition. The adhesive composition comprises at least a base polymer.

The base polymer is an adhesive component that exhibits adhesiveness in the adhesive layer 3. 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, fluoropolymers, and rubber polymers. The base polymer may be used alone or in combination of 2 or more. From the viewpoint of ensuring good transparency and adhesion of the adhesive layer 3, an acrylic polymer is preferably used as the base polymer.

The acrylic polymer is a copolymer containing a monomer component of a (meth) acrylic acid ester in a ratio of 50 mass% or more. "(meth) acrylic" refers to acrylic and/or methacrylic.

As the (meth) acrylic acid ester, an alkyl (meth) acrylate is preferably used, and an alkyl (meth) acrylate having an alkyl group of 1 to 20 carbon atoms is more preferably used. The alkyl (meth) acrylate may have a linear or 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 or 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, cetyl (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) acrylate, alicyclic (meth) acrylate having a bicyclic aliphatic hydrocarbon ring, and alicyclic (meth) acrylate having a tricyclic or higher aliphatic hydrocarbon ring. Examples of the cycloalkyl (meth) acrylate include: cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate. Examples of the (meth) acrylic acid ester 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: dicyclopentyl (meth) acrylate, dicyclopentyloxyethyl (meth) acrylate, tricyclopentyl (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 of 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 ratio of the alkyl (meth) acrylate in the monomer component is, for example, 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more, and still more preferably 92 mass% or more, from the viewpoint of appropriately exhibiting the adhesion property in the adhesive layer 3.

The ratio is, for example, 99 mass% or less.

The monomer component may contain a copolymerizable monomer copolymerizable with the alkyl (meth) acrylate. Examples of the copolymerizable monomer include monomers having a polar group. Examples of the polar group-containing monomer include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a monomer having a nitrogen atom-containing ring. The polar group-containing monomer contributes to modification of the acrylic polymer such as introduction of a crosslinking point into the acrylic polymer and securing of cohesion of the acrylic polymer.

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 the hydroxyl group-containing monomer, at least one selected from the group consisting of 4-hydroxybutyl acrylate and 2-hydroxyethyl acrylate is preferably used.

The ratio of the hydroxyl group-containing monomer in the monomer component is, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more from the viewpoint of introducing a crosslinked structure into the acrylic polymer and securing cohesive force of the adhesive layer 3. From the viewpoint of adjusting the polarity of the acrylic polymer (regarding the compatibility of the various additive components in the adhesive layer 3 and the acrylic polymer), this ratio is preferably 20 mass% or less, 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 ratio of the carboxyl group-containing monomer in the monomer component is, for example, 0.1 mass% or more, preferably 0.5 mass% or more, and more preferably 0.8 mass% or more from the viewpoints of introducing a crosslinked structure into the acrylic polymer, securing cohesive force of the adhesive layer 3, and securing adhesion to an adherend of the adhesive layer 3. From the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid, the ratio is preferably 10 mass% or less, more preferably 5 mass% or less.

Examples of the monomer having a ring containing a nitrogen atom 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-vinyl oxazole, N- (meth) acryl-2-pyrrolidone, N- (meth) acryl piperidine, N- (meth) acryl pyrrolidine, N-vinyl morpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinedione, N-vinyl pyrazole, N-vinyl isoxazole, N-vinyl thiazole, and N-vinyl isothiazole. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

The ratio of the monomer having a ring containing a nitrogen atom in the monomer component is, for example, 0.1 mass% or more, preferably 0.5 mass% or more, and more preferably 1 mass% or more from the viewpoint of securing cohesive force of the adhesive layer 3 and securing adhesion force of the adhesive layer 3 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 the various additive components in the adhesive layer 3 with the acrylic polymer), the ratio is preferably 30 mass% or less, preferably 20 mass% or less.

The monomer component may comprise other copolymerizable monomers. Examples of the other copolymerizable monomer 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 2 or more.

The base polymer preferably has a crosslinked structure. The method of introducing the crosslinked structure into the base polymer includes the 1 st method and the 2 nd method. These methods may also be used in combination.

In the method 1, a base polymer having a functional group capable of reacting with a crosslinking agent and a crosslinking agent are compounded in an adhesive composition, and the base polymer and the crosslinking agent are reacted in the adhesive layer 3. In the method 2, a polyfunctional monomer is contained in a monomer component forming the base polymer, and the base polymer having a branched structure (crosslinked structure) introduced into a polymer chain is formed by polymerization of the monomer component.

Examples of the crosslinking agent used in the method 1 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 agents, peroxide crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. The crosslinking agent may be used alone or in combination of 2 or more.

As the crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent and an epoxy crosslinking agent are preferably used in view of high reactivity with hydroxyl groups and carboxyl groups in the base polymer and easiness of introducing 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. Further, 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 cornate L (trimethylolpropane adduct of toluene diisocyanate, manufactured by eastern corporation), cornate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by eastern corporation), cornate HX (isocyanurate of hexamethylene diisocyanate, manufactured by eastern corporation), takenate D110N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by tricyclopedia chemical Co., ltd.), and Takenate600 (1, 3-bis (isocyanatomethyl) cyclohexane, manufactured by tricyclopedia chemical Co., ltd.).

The peroxide crosslinking agent may be: dibenzoyl peroxide, di (2-ethylhexyl) peroxydicarbonate, di (4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxypivalate, and tert-butyl peroxypivalate.

Examples of the epoxy crosslinking agent include bisphenol a, epichlorohydrin type epoxy resin, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N' -tetraglycidyl m-xylylenediamine, and 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane.

From the viewpoint of ensuring cohesive force of the adhesive layer 3, the blending 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 or more, relative to 100 parts by mass of the base polymer. In the adhesive layer 3, the amount of the crosslinking agent blended per 100 parts by mass of the base polymer 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, from the viewpoint of securing good tackiness.

In the method 2, the monomer component may be polymerized at one time or in multiple stages. The monomer component contains a polyfunctional monomer for introducing a crosslinked structure and other monomers. In the multistage polymerization method, first, a monofunctional monomer 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, after adding a polyfunctional monomer to the prepolymer composition, a part of the polymer and the polyfunctional monomer are polymerized (main polymerization).

Examples of the polyfunctional monomer include polyfunctional (meth) acrylates having 2 or more ethylenically unsaturated double bonds in 1 molecule. The polyfunctional monomer is preferably a polyfunctional acrylate from the viewpoint of being capable of introducing a crosslinked structure by active energy ray polymerization (photopolymerization).

Examples of the polyfunctional (meth) acrylate include: difunctional (meth) acrylates, trifunctional (meth) acrylates, and multifunctional (meth) acrylates of four or more functionalities.

Examples of the difunctional (meth) acrylate include: ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol dimethacrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, stearic acid modified pentaerythritol di (meth) acrylate, dicyclopentadiene diacrylate, 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: ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxy penta (meth) acrylate, alkyl modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa (meth) acrylate.

The acrylic polymer is obtained by polymerizing the above monomer components by a known method.

In the polymerization, a chain transfer agent 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 (Mercaptoacetic acid), 2-mercaptoethanol, mercaptoacetic acid (Thioglycolic acid), 2-ethylhexyl thioglycolate, 2, 3-dimercapto-1-propanol, and α -methylstyrene dimer.

From the viewpoint of ensuring cohesive force of the adhesive layer 3, the weight average molecular weight of the base polymer is, for example, 10 ten thousand or more, preferably 30 ten thousand or more, more preferably 50 ten thousand or more. The weight average molecular weight is, for example, 500 ten thousand or less, preferably 300 ten thousand or less, and more preferably 200 ten thousand or less. The weight average molecular weight of the base polymer was measured by Gel Permeation Chromatography (GPC), and calculated by conversion to polystyrene.

The glass transition temperature (Tg) of the base polymer is, for example, 0℃or lower, preferably-10℃or lower, more preferably-20℃or lower. The glass transition temperature is, for example, at least-80 ℃. The glass transition temperature (Tg) of the base polymer was determined based on the Fox formula.

The adhesive composition may contain 1 or 2 or more kinds 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 containing a monomer component of an alkyl (meth) acrylate at a ratio 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, for example, 60℃or higher, preferably 80℃or higher, more preferably 100℃or higher, and still more preferably 110℃or higher. The glass transition temperature of the acrylic oligomer is, for example, 200℃or lower, preferably 180℃or lower, and preferably 160℃or lower. By using a combination of a low Tg acrylic polymer (base polymer) having a crosslinked structure and a high Tg acrylic oligomer, the adhesive force of the adhesive layer 3, particularly the adhesive force at high temperature, is improved. The glass transition temperature of the acrylic oligomer was determined based on the Fox formula.

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, dicyclopentyl acrylate is preferable.

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

The weight average molecular weight of the acrylic oligomer is, for example, 1000 or more, preferably 1500 or more, and more preferably 2000 or more. The molecular weight is, for example, 30000 or less, preferably 10000 or less, more preferably 8000 or less. The molecular weight range of such an acrylic oligomer is preferable for securing the adhesion and adhesive holding power of the adhesive layer 3.

The acrylic oligomer is obtained by polymerizing the monomer component of the acrylic oligomer by a known method.

In order to sufficiently improve the adhesive strength of the adhesive layer 3, the content of the acrylic oligomer in the adhesive layer 3 is, for example, 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and still more preferably 1 part by mass or more, based on 100 parts by mass of the base polymer. On the other hand, from the viewpoint of ensuring transparency of the adhesive layer 3, the content of the acrylic oligomer in the adhesive layer 3 is, for example, 5 parts by mass or less, more preferably 4 parts by mass or less, and still more preferably 3 parts by mass or less, per 100 parts by mass of the base polymer. When the content of the acrylic oligomer in the adhesive layer 3 is too large, the haze tends to increase due to the decrease in the compatibility of the acrylic oligomer, and the transparency tends to decrease.

The adhesive composition may contain a silane coupling agent. The content of the silane coupling agent in the adhesive composition is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, relative 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 adhesive composition may contain other components as needed. Examples of the other components include: solvents, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, dyes, pigments, ultraviolet absorbers, antioxidants, infrared absorbers, surfactants, catalysts, particulates, UV-curable monomers, UV-curable oligomers, UV-curable resins, photopolymerization initiators, metals, fibers, conductive materials, and antistatic agents.

1.7.2 Material of Release liner 2

As a material of the release liner 2, a flexible material is exemplified. As the release liner 2, specifically, plastic is exemplified. Examples of the plastic include acrylic resins such as polyesters, polyolefins, polyimides, polyetheretherketones (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polymethyl methacrylate (PMMA), polycarbonates, cellulose Triacetate (TAC), polysulfones, polyarylates, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, ethylene-vinyl acetate copolymers (EVA), polyamides (nylon), wholly aromatic polyamides (aramid), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene Sulfide (PPs), fluorine resins, cyclic olefin polymers, cycloolefins, and polyurethanes.

As a material of the release liner 2, from the viewpoint of improving the tensile modulus E1, polyester is preferably exemplified.

A release layer, not shown, may be formed on one surface of the release liner 2 in the thickness direction. The release layer is a layer formed by a release treatment of one surface of the release liner 2 in the thickness direction with a release treatment agent. Examples of the release treatment include silicone release treatment, long-chain alkyl acrylate release treatment, and fluorine release treatment. That is, examples of the release layer include a silicone release layer, a long-chain alkyl acrylate release layer, and a fluorine release layer. The release layer is preferably a silicone release layer from the viewpoint of ease of adjusting the release force of the self-adhesive layer 3.

1.7.3 Material of adjoining layer 4

As a material of the adjacent layer 4, a flexible material is exemplified. As the adjacent layer 4, specifically, plastic is exemplified. The plastic may be exemplified as the release liner 2. The other surface of the adjacent layer 4 in the thickness direction may be formed with a release layer, not shown.

1.8 method for producing optical pressure-sensitive adhesive sheet 1

A method of manufacturing the optical adhesive sheet 1 will be described with reference to a to D of fig. 3. In this manufacturing method, first, the laminate 51 is manufactured (see a of fig. 3), then the adhesive layer 3 is subjected to the contour processing (see B of fig. 3), then the unnecessary portion 53 is removed (see C of fig. 3), then the release liner 2 is subjected to the contour processing (see D of fig. 3), and then the adjacent layer 4 is replaced by the 3 rd release liner 5 (see D of fig. 3).

As shown in a of fig. 3, the laminate 51 has, for example, a long sheet shape. The laminate 51 includes a release liner 2, an adhesive layer 3, and a 3 rd release liner 5 in this order on one side in the thickness direction.

The release liner 5 of the 3 rd step has a small release force. Specifically, the release force for releasing the 3 rd release liner 5 from the adhesive layer 3 is smaller than the release force for releasing the release liner 2 from the adhesive layer 3. The surface of the 3 rd release liner 5 is subjected to a known release treatment, for example. The 3 rd release liner 5 is also a protective material for protecting one surface of the adhesive layer 3 (coating film 31) in the manufacturing process.

In order to produce the laminate 51, for example, the release liner 2 is prepared, then the adhesive composition is applied to one surface of the release liner 2 in the thickness direction to form the coating film 31, then the 3 rd release liner 5 is disposed on one surface of the coating film 31 in the thickness direction, and then the coating film 31 is dried or irradiated with light.

Examples of the method for shaping the adhesive layer 3 include laser irradiation and cutting by a dicing blade. Laser light is irradiated to the laminate 51 from one side in the thickness direction, or a knife is inserted into the laminate 51.

As a method for shaping the adhesive layer 3, laser irradiation is preferably used from the viewpoint of making the concave portion 25 shallow.

Examples of the laser include a gas laser, a solid-state laser, and a semiconductor laser. Examples of the gas laser include excimer laser and CO ₂ Laser (10.6 μm).

By the above-described shaping, the adhesive layer 3 is shaped to have the above-described length L. Along with this, the 3 rd release liner 5 is also contoured to the same shape and size as the adhesive layer 3. Thereby, the notch 26 is formed in the adhesive layer 3 and the 3 rd release liner 5. The adhesive layer 3 has the length L described above.

Meanwhile, the concave portion 25 is formed unexpectedly (inevitably) on one face of the release liner 2 in the thickness direction. The recess 25 is the bottom of the cutout 26.

As shown in C of fig. 3, the unnecessary portion 53 is removed. The unnecessary portion 53 is a portion located outside the slit 26 in the adhesive layer 3 and the 3 rd release liner 5. As a method for removing the unnecessary portion 53, for example, removal by a take-up roller is mentioned.

As shown in fig. 3D, the 3 rd release liner 5 is replaced by the adjacent layer 4 and the release liner 2 is contoured.

In the replacement bonding of the adjacent layer 4, as shown by the virtual line C in fig. 3, the 3 rd release liner 5 is peeled off from one surface of the adhesive layer 3 in the thickness direction, and then the adjacent layer 4 is disposed on one surface of the adhesive layer 3.

The strip of release liner 2 is contoured to be larger than the adhesive layer 3 and to include a pattern of cover adhesive layer 3. The outline processing of the release liner 2 includes laser irradiation and cutting by a dicing blade.

Then, the adhesive layer 3 is cured as necessary. The curing temperature is, for example, 50℃to 100 ℃. The curing time is 30 minutes to 3 days.

Thereby, the optical adhesive sheet 1 having the release liner 2, the adhesive layer 3, and the adjacent layer 4 is produced.

As shown in fig. 4, the adhesive layer 3 in the optical adhesive sheet 1 is adhered to the member 11 for an image display device.

The image display device member 11 is along the plane direction. The member 11 for an image display device has a sheet shape. The image display device member 11 is an element disposed in the image display device 20 (see fig. 5). Specifically, examples of the member 11 for an image display device include an optical substrate, a pixel panel, a polarizing plate, a touch panel, and a cover film. Examples of the optical substrate include glass films (ultrathin glass and UTG), polyester films, polyolefin films, and polyimide films. Examples of the polyester film include polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film. Examples of the polyolefin film include polyethylene film, polypropylene film, and cycloolefin film. As the pixel panel, an LCD panel, an OLED panel, a miniLED, a μled panel, and the like can be cited.

The image display device member 11 has 1 or more layers. As shown by the virtual line in fig. 4, for example, the image display device member 11 includes a 1 st layer 111 and a 2 nd layer 112 in this order on one side in the thickness direction. Examples of the 1 st layer 111 include an optical substrate and a polarizing plate. The 2 nd layer 112 may be, for example, a cover film.

The member 11 for an image display device is another example of the adjacent layer 4. The optical pressure-sensitive adhesive sheet 1 includes a release liner 2, a pressure-sensitive adhesive layer 3, and an image display device member 11 in this order on one side in the thickness direction.

The peripheral edge of the image display device member 11 coincides with the peripheral edge of the adhesive layer 3.

The other surface of the image display device member 11 in the thickness direction may be formed with an undercoat layer, not shown. At this time, the image display device member 11 is bonded (formed) to one surface of the pressure-sensitive adhesive layer 3 in the thickness direction via the primer layer.

In order to manufacture the optical adhesive sheet 1 shown in fig. 4, the 3 rd release liner 5 is peeled from the adhesive layer 3 as shown by the virtual line in fig. 3C, and then, as shown in fig. 4, the image display device member 11 is attached to one face of the adhesive layer 3 in the thickness direction.

1.9 image display device 20

As shown in fig. 5, the adhesive layer 3 is further adhered to another member 12 for an image display device. Specifically, the image display device 20 includes the adhesive layer 3 and a pair of members 11 and 12 for the image display device.

The adhesive layer 3 and the member 11 for an image display device in fig. 5 are the same as the adhesive layer 3 and the member 11 for an image display device in the optical adhesive sheet 1 shown in fig. 4.

The image display device member 12 is disposed on the opposite side of the pressure-sensitive adhesive layer 3 from the image display device member 11 in the thickness direction. Specifically, the image display device member 12 is disposed on the other surface of the pressure-sensitive adhesive layer 3 in the thickness direction. An undercoat layer, not shown, may be formed on one surface of the image display device member 12 in the thickness direction. At this time, the image display device member 12 is bonded (formed) to the adhesive layer 3 via the primer layer. Examples of the image display device member 12 include the elements exemplified in the image display device member 11.

The peripheral edge of the image display device member 12 coincides with the peripheral edge of the adhesive layer 3 when viewed in the thickness direction. In the present embodiment, the peripheral end surfaces of the pair of image display device members 11, 12 are flush with the peripheral end surface of the adhesive layer 3.

2. Effects of one embodiment

In the optical pressure-sensitive adhesive sheet 1, since the maximum length L of the pressure-sensitive adhesive layer 3 is 200mm or more, the pressure-sensitive adhesive layer 3 can be attached to a member in a large-sized image display device such as a flat panel terminal.

In addition, even if the length L is 200mm or more, in the optical adhesive sheet 1, since the release liner 2 is larger than the adhesive layer 3 and includes the cover adhesive layer 3 when viewed in the thickness direction, the release liner 2 suppresses the overflow of the end portion of the adhesive layer 3. Therefore, contamination of the surroundings by the adhesive layer 3 can be suppressed.

Further, in the optical adhesive sheet 1, the overflow of the end portion of the adhesive layer 3 is suppressed, and thus the handling property is excellent.

In addition, in the optical adhesive sheet 1, since the overflow of the end portion of the adhesive layer 3 is suppressed, the lack of the adhesive is suppressed, and the adhesive reliability of the adhesive layer 3 is excellent.

When the bending amount D of the optical adhesive sheet 1 is 7mm or less, the optical adhesive sheet 1 is more excellent in handling property.

In the optical adhesive sheet 1, the area P, which is the product of the offset amount OL of the release liner 2 and the thickness T1 of the release liner 2, is 90×10 ^-8 m ² In this way, the pressure-sensitive adhesive layer 3 can be prevented from floating from the release liner 2.

Specifically, the area P is 90×10 ^-8 m ² In the above, even if the thickness T1 of the release liner 2 is small, the offset amount OL of the release liner 2 increases. Therefore, even if the offset portion 21 is deformed, the deformation does not easily affect the stickingAnd (3) laminating. Accordingly, the adhesive layer 3 can be suppressed from undesirably peeling off from the release liner 2.

Alternatively, the area P is 90×10 ^-8 m ² In the above, even if the offset amount OL of the release liner 2 is small, the release liner 2 is thick. At this time, even if the offset portion 21 is in contact with the conveying mechanism, deformation of the release liner 2 is suppressed. Therefore, the floating of the adhesive layer 3 can also be suppressed.

In addition, in the optical adhesive sheet 1, when the above formula [3] is satisfied, at least one selected from the group consisting of the thickness T1 of the release liner 2, the tensile modulus E1 of the release liner 2, the thickness T2 of the adjacent layer 4, and the tensile modulus E2 of the adjacent layer 4 is large.

Therefore, even if the adhesive layer 3 is thick, the release liner 2 and/or the adjacent layer 4 tend to be hard, and therefore the above-described bending amount D of the optical adhesive sheet 1 can be reduced.

Alternatively, when the above formula [3] is satisfied, the adhesive layer 3 is thin. Therefore, even if at least any one selected from the group consisting of the thickness T1 of the release liner 2, the tensile modulus E1 of the release liner 2, the thickness T2 of the adjacent layer 4, and the tensile modulus E2 of the adjacent layer 4 is small, the toughness of the optical adhesive sheet 1 can be ensured, and therefore, the above-described bending amount D of the optical adhesive sheet 1 can be reduced.

In the optical adhesive sheet 1, since the 2 nd release liner 4A, which is an example of the adjacent layer 4, is larger than the adhesive layer 3 and includes the cover adhesive layer 3 when viewed in the thickness direction, the overflow of the end portion of the adhesive layer 3 is further suppressed by the 2 nd release liner 4A, and the optical adhesive sheet 1 is more excellent in handling property.

In the optical adhesive sheet 1, the area P2, which is the product of the 2 nd offset amount OL2 of the 2 nd release liner 4A and the thickness T2 of the 2 nd release liner 4A, which is an example of the adjacent layer 4, is 90×10 ^-8 m ² In this way, the adhesive layer 3 can be prevented from floating from the 2 nd release liner 4A.

Specifically, the area P2 is 90×10 ^-8 m ² In the above, the 2 nd offset amount OL2 of the 2 nd release liner 4A is large, and even if the 2 nd offset portion 41 is deformed, the deformation is less likely to affect the adhesive layer 3. Thus, the adhesive layer 3 can be suppressed from unexpectedly peeling off the liner from the 2 nd4A peel.

Alternatively, the area P2 is 90×10 ^-8 m ² In the above, the 2 nd release liner 4A is thick. At this time, even if the offset portion 21 is in contact with the conveying mechanism, deformation of the 2 nd release liner 4A is suppressed. Therefore, the floating of the adhesive layer 3 can be suppressed.

In the optical pressure-sensitive adhesive sheet 1, when the depth of the concave portion 25 is 30 μm or less, the release liner 2 can be prevented from being cut from the concave portion 25 as a starting point.

In the optical pressure-sensitive adhesive sheet 1, when the indentation hardness H of the pressure-sensitive adhesive layer 3 at 23 ℃ is 10kPa or less, the pressure-sensitive adhesive layer 3 is suitably used for adhesion of members in an image display device that can be repeatedly folded (foldable).

In the optical pressure-sensitive adhesive sheet 1, when the shear storage modulus G' of the pressure-sensitive adhesive layer 3 at 25 ℃ is 100kPa or less, the pressure-sensitive adhesive layer 3 is suitably used for adhesion of members in an image display device that can be repeatedly folded (foldable).

3. Modification examples

In the following modifications, the same members and steps as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Each modification can exhibit the same operational effects as those of the first embodiment unless otherwise specified. Further, one embodiment and the modification can be appropriately combined.

As shown in fig. 6, the optical adhesive sheet 1 of the modification includes a release liner 2 and an adhesive layer 3 in this order on one side in the thickness direction. The optical adhesive sheet 1 does not include the adjacent layer 4. The optical adhesive sheet 1 of the modification includes only the release liner 2 and the adhesive layer 3.

To manufacture the optical adhesive sheet 1 of the modification, the 3 rd release liner 5 shown by the virtual line in fig. 3C is peeled from the adhesive layer 3.

When comparing one embodiment with the modification, one embodiment is preferable. According to one embodiment, the adjacent layer 4 can suppress contamination of one surface of the adhesive layer 3 in the thickness direction.

Although not shown, the adjacent layers 4 have the same size when viewed in the thickness direction. In this modification, the peripheral side surface of the adjacent layer 4 is flush with the peripheral side surface of the adhesive layer 3.

Examples

Hereinafter, the present invention will be described more specifically by way of examples. The present invention is not limited to any embodiment. Specific numerical values such as the compounding ratio (containing ratio), physical property value, and parameter used in the following description may be substituted for the upper limit (numerical value defined by "below", "less than") or the lower limit (numerical value defined by "above", "exceeding") of the compounding ratio (containing ratio), physical property value, and parameter described in the above-described "specific embodiment" corresponding thereto.

(preparation of adhesive composition A-adhesive composition E)

Preparation example A

60 parts by mass of dicyclopentyl methacrylate (DCPMA) and 40 parts by mass of Methyl Methacrylate (MMA) as monomer components, 3.5 parts by mass of alpha-thioglycerol as a chain transfer agent, and 100 parts by mass of toluene as a polymerization solvent were mixed, and stirred at 70℃for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of 2,2' -Azobisisobutyronitrile (AIBN) was charged as a thermal polymerization initiator, reacted at 70℃for 2 hours, then heated to 80℃and reacted for 2 hours. Then, the reaction solution was heated to 130 ℃, toluene and unreacted monomers were dried and removed, and a solid acrylic oligomer (1)) was obtained. The weight average molecular weight of the oligomer (1) was 5100, and the glass transition temperature (Tg) was 130 ℃.

Further, 40 parts by mass of Lauryl Acrylate (LA), 46 parts by mass of 2-ethylhexyl acrylate (2 EHA), 7 parts by mass of 4-hydroxybutyl acrylate (4 HBA), 7 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 0.015 part by mass of "IRGACURE184" manufactured by BASF as a photopolymerization initiator were blended, and polymerization was performed by irradiation with ultraviolet rays, to obtain a prepolymer composition a (polymerization rate about 10%).

Then, to 100 parts by mass of the prepolymer composition a, 0.07 parts by mass of 1, 6-hexanediol diacrylate (HDDA), 5 parts by mass of the oligomer (1), and 0.3 parts by mass of a silane coupling agent (KBM 403", believed to be a chemical system of surmounting) were added, and then they were uniformly mixed to prepare an adhesive composition a.

Preparation example B

30 parts by mass of Lauryl Acrylate (LA), 65 parts by mass of 2-ethylhexyl acrylate (2 EHA), 8 parts by mass of 4-hydroxybutyl acrylate (4 HBA) and 4 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 0.015 part by mass of "IRGACURE184" manufactured by BASF as a photopolymerization initiator were mixed and polymerized by irradiation of ultraviolet rays to obtain a prepolymer composition B (polymerization rate about 10%).

Then, 0.07 parts by mass of 1, 6-hexanediol diacrylate (HDDA) as a post-additive component, 5 parts by mass of the above oligomer (1), and 0.3 parts by mass of a silane coupling agent (KBM 403 by siemens chemical system) were added to 100 parts by mass of the prepolymer composition B, and then they were uniformly mixed to prepare an adhesive composition B.

Preparation example C

Into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler, 9 parts by mass of Lauryl Acrylate (LA), 68 parts by mass of 2-ethylhexyl acrylate (2 EHA), 21 parts by mass of N-Butyl Acrylate (BA), 1 part by mass of 4-hydroxybutyl acrylate (4 HBA), 1 part by mass of N-vinyl-2-pyrrolidone (NVP), and 0.1 part by mass of 2,2' -Azobisisobutyronitrile (AIBN) as a polymerization initiator were charged such that the total concentration thereof was 47% by weight, and the inside of the system was replaced with nitrogen gas for 1 hour while being slowly stirred, and polymerization was performed for 6 hours while maintaining the liquid temperature in the flask at about 56 ℃, and after the completion of the reaction, ethyl acetate was added so as to adjust the polymer concentration to 24% by weight, thereby obtaining a solution of acrylic polymer C. The weight average molecular weight of the acrylic polymer C was 200 ten thousand.

Next, 100 parts by mass of an acrylic polymer C, 0.25 part by mass of a peroxide (Nyper BMT-40SV, manufactured by Japanese fat and oil Co., ltd.) as a crosslinking agent, 3 parts by mass of the above-mentioned oligomer (1), 0.3 part by mass of IRGANOX1010 (manufactured by BASF) as an antioxidant, and a catalyst were mixed0.01 part by mass of IRON (III) (manufactured by Japanese chemical Co., ltd.) was mixed and stirred well, and the mixture was diluted with ethyl acetate so that the total solid content became 21% by weight, to prepare an adhesive composition C.

Preparation example D

A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer was charged with a monomer mixture containing 99 parts of Butyl Acrylate (BA) and 1 part of 4-hydroxybutyl acrylate (HBA). Further, 0.1 part of 2,2' -azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate with nitrogen gas being introduced thereto while being slowly stirred to replace the nitrogen gas with respect to 100 parts of the above-mentioned monomer mixture, and then, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at about 55℃to prepare a solution (solid content concentration: 30% by weight) of an acrylic polymer having a weight average molecular weight of 180 ten thousand. An adhesive composition D was prepared by mixing 100 parts of the solid content of the solution of the acrylic polymer (1) with 0.3 part of a radical generator (benzoyl peroxide, trade name Nyper BMT manufactured by Japanese fat and oil Co., ltd.), 0.1 part of an isocyanate-based crosslinking agent (trade name Takenate D110N manufactured by Sanyo chemical Co., ltd.) and 0.1 part of a silane coupling agent (KBM 403 manufactured by Xinyue chemical Co., ltd.).

Preparation example E

63 parts by mass of 2-ethylhexyl acrylate (2 EHA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 9 parts by mass of Methyl Methacrylate (MMA), 13 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.2 part by mass of 2,2' -azobisisobutyronitrile as a polymerization initiator, and 133 parts by mass of ethyl acetate as a polymerization solvent were put into a separable flask, and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this manner, the temperature was raised to 65℃and the reaction was carried out for 10 hours, and then ethyl acetate was added to obtain a solution of the acrylic polymer (f) having a solid content of 30% by weight.

Next, an isocyanate-based crosslinking agent (trade name "take D110N", manufactured by san-jing chemical company) was added to 100 parts by mass of the acrylic polymer (a) (solid content) in the solution of the acrylic polymer (a) so as to be 1 part by mass in terms of solid content conversion, to prepare an adhesive composition E.

< preparation of Release liner 2 and Adjacent layer 4 >

A release liner 2 and an adjacent layer 4 described in table 1 below were prepared. The materials and manufacturers of release liner 2 and adjacent layer 4 are shown in table 1.

(example of forming adhesive layer 3 from adhesive composition A)

(example 1-example 16, example 20-example 23, example 25-example 29)

Example 1

A release liner 2 made of MRF having a thickness T1 of 25 μm and a 3 rd release liner 5 having a thickness of 75 μm were prepared. The 3 rd release liner 5 is a single sided silicone release treated PET film (mitsubishi chemical "Diafoil MRE 75"). The release liners 2 and 3 rd release liner 5 have an elongated shape, respectively.

The adhesive composition a was applied to one surface of the release liner 2 so that the thickness thereof became 25 μm after drying, thereby forming a coating film 31. A 3 rd release liner 5 is attached to the coating film 31. As a result, a laminate 51 including the release liner 2, the coating film 31, and the 3 rd release liner 5 in this order is produced as shown in fig. 3A. By using the irradiation intensity on the irradiation surface directly under the lamp as 5mW/cm ² The black light lamp whose position was adjusted in this manner was used to irradiate the laminate 51 with ultraviolet light from one side of the laminate 51 in the thickness direction, and the laminate was subjected to photo-curing to produce the adhesive layer 3 having a thickness T0 of 25 μm.

Next, as shown in fig. 3B, the adhesive layer 3 of the laminate 51 is subjected to contour processing. Specifically, the laminate 51 is irradiated with CO from the 3 rd release liner 5 side to the thickness direction ₂ Laser to form incisions 26 in adhesive layer 3 and release liner 3, 5, respectively. Thereby, the adhesive layer 3 and the 3 rd release liner 5 are cut in the thickness direction. On one surface of the release liner 2, a recess 25 having a depth of 20 μm was formed. The length L of the adhesive layer 3 in the longitudinal direction was 250mm.

Next, as shown in fig. 3C, the outer portions of the cutouts 26 of the adhesive layer 3 and the 3 rd release liner 5 are wound up using a winding roller.

Then, as shown in fig. 3D, the release liner 2 is subjected to profile processing. The length L1 of the release liner 2 was 260mm. The offset OL of the release liner 2 is 5mm.

Next, the adjacent layer 4 having a length L2 of 250mm was laminated on one surface of the adhesive layer 3. The peripheral side of the abutment layer 4 is flush with the peripheral side of the adhesive layer 3.

The laminate was then cured in an oven at 50 ℃ for 1 day.

Thus, the optical adhesive sheet 1 having the release liner 2, the adhesive layer 3, and the adjacent layer 4 in this order was produced.

(example 2-example 16, example 20-example 23, example 25-example 29)

An optical adhesive sheet 1 was produced in the same manner as in example 1. The types, thicknesses, offsets, 2 nd offsets, and the like of the release liner 2, the adhesive layer 3, and the adjacent layer 4 were changed according to the descriptions in tables 2 and 3.

(example of forming adhesive layer 3 from adhesive composition B-adhesive composition E)

Example 17

An optical adhesive sheet 1 was produced in the same manner as in example 1. In this connection, the adhesive composition B was used instead of the adhesive composition a according to the description in table 3.

Example 18

An optical adhesive sheet 1 was produced in the same manner as in example 1. In this connection, adhesive composition C was used instead of adhesive composition A according to the description in Table 3. Further, in the production of the adhesive layer 3, heat curing is used instead of photo curing. Specifically, the coating film 31 before the 3 rd release liner 5 was disposed as the coating film 31 on the release liner 2, and the coating film 31 was dried at 130 ℃ for 3 minutes to form the adhesive layer 3. Curing was carried out in the same manner as in example 1.

Example 19

An optical adhesive sheet 1 was produced in the same manner as in example 1. In this connection, adhesive composition D was used instead of adhesive composition a according to the description in table 3. Further, in the production of the adhesive layer 3, heat curing is used instead of photo curing. Specifically, the coating film 31 before the 3 rd release liner 5 was disposed as the coating film 31 on the release liner 2, and the coating film 31 was dried at 130 ℃ for 3 minutes to form the adhesive layer 3. Curing was carried out in the same manner as in example 1.

(example of forming adhesive layer 3 from adhesive composition E)

Example 24

An optical adhesive sheet 1 was produced in the same manner as in example 1. In this connection, adhesive composition E was used instead of adhesive composition A according to the description in Table 3. Further, in the production of the adhesive layer 3, heat curing is used instead of photo curing. Specifically, the coating film 31 before the 3 rd release liner 5 was disposed as the coating film 31 on the release liner 2, and the coating film 31 was dried at 130 ℃ for 3 minutes to form the adhesive layer 3. Curing was carried out in the same manner as in example 1.

(evaluation)

The following items were evaluated for the optical adhesive sheets 1 of each of examples 1 to 29.

The results are set forth in tables 2 and 3.

(offset OL, 2 nd offset OL 2)

The offset amount OL of the release liner 2 in the optical adhesive sheet 1 and the 2 nd offset amount OL2 of the adjacent layer 4 were measured.

(thicknesses T0, T1, T2)

The thickness T0 of the adhesive layer 3, the thickness T1 of the release liner 2, and the thickness T2 of the adjacent layer 4 in the optical adhesive sheet 1 were measured.

The thickness T1 of the release liner 2 was obtained as the average thickness (μm) at 3 points in the offset portion. The thickness T2 of the adjacent layer 4 was found as the average thickness (μm) at 3 points in the offset portion.

Next, the area P, which is the product of the offset OL of the release liner 2 and the thickness T1, is obtained. The area P2 is obtained as the product of the 2 nd offset OL2 of the adjacent layer 4 and the thickness T2.

(bending amount D)

The following bending test was performed to determine the bending amount D of the optical adhesive sheet 1.

Bending test: the optical adhesive sheet 1 was formed into a size of 100mm in length and 100mm in width, thereby producing a sample 100. As shown in fig. 2, a stage 105 having an upper surface and a height of 50mm or more is prepared. The surface of the 1 st part 101 of the sample 100 including the length of 50mm of one end edge in the longitudinal direction was fixed to the upper surface. A 200g weight 106 formed of a glass plate was disposed on the upper surface of the 1 st part 101. The 2 nd portion 102 of the sample 100 having a length of 50mm including the other end edge in the longitudinal direction was protruded laterally from one end edge of the upper surface. Then, the mixture was left at 23℃for 5 minutes. Then, the amount of movement of one end edge of the protruding sample 100 from the upper surface downward is obtained. The back surface of the 1 st portion 101 is fixed to the upper surface, and the movement amount D is obtained. An average of 2 moving amounts was obtained as a bending amount D.

(indentation hardness H of adhesive layer 3)

In the optical adhesive sheet 1, the release liner 2 or the adjacent layer 4 is peeled from the adhesive layer 3. Subsequently, a press-in test according to ISO14577 using a triboindenor (manufactured by Hysitron corporation) was performed on the surface of the adhesive layer 3 in an environment of 23 ℃. In the press-in test, a press head having a diameter of 20 μm was used to press the press head into the adhesive layer 3 at a press-in depth of 2.5. Mu.m. The indentation hardness H of the adhesive layer 3 was calculated from the maximum vertical load and the contact area.

(tensile modulus E1 of Release liner 2, tensile modulus E2 of adjacent layer 4)

The measurement of the tensile modulus E1 of the release liner 2 and the tensile modulus E2 of the adjacent layer 4 in the optical adhesive sheet 1 will be described.

First, the outer shape of the central portion of the optical adhesive sheet 1 was processed to a size of 10mm in width and 150mm in length, thereby preparing a sample. Note that the sample has neither the offset portion 21 nor the 2 nd offset portion 41. The peripheral end surfaces of the release liner 2, the adhesive layer 3 and the adjacent layer 4 in the sample are flush.

Then, either one of the release liner 2 and the adjacent layer 4 is peeled from the adhesive layer 3. Thus, a sample formed of one and a laminated sample formed of the other and the adhesive layer 3 are prepared.

The samples were fixed to a tensile tester at a distance of 100mm between clamps. The sample was stretched at a speed of 200 mm/min to produce a stress-strain curve. The tensile modulus of the release liner alone or the adjacent layer 4 was calculated by determining the slope of the stress-strain curve at the 2 point where the strain was 0.05% and 0.25%.

The tensile modulus E2 of the laminated sample was calculated in the same manner as the tensile modulus E1 of the sample. In the tensile test of the laminated sample, the tensile modulus of the adhesive layer 3 (as a reference, the storage shear modulus G' of the adhesive layer 3 at 25 ℃ in example 1 is 0.03 MPa) was very small compared with the tensile modulus E1 of only the adjacent layer 4, and thus, the tensile modulus of only the release liner 2 or the adjacent layer 4 was calculated by the tensile test of the laminated sample.

(values of the relation between the thickness T0 of the adhesive layer 3, the thickness T1 of the release liner 2, and the tensile modulus E1 and the thickness T2 and the tensile modulus E2 of the adjacent layer 4)

Substituting the thickness T0 of the adhesive layer 3, the thickness T1 and tensile modulus E1 of the release liner 2, and the thickness T2 and tensile modulus E2 of the adjacent layer 4 into the left side (E1×E2× (T1+T2)/[ T0) ^1/2 ×100000])。

(shear storage modulus G' of adhesive layer 3)

The shear storage modulus G' of the adhesive layer 3 was obtained by dynamic viscoelasticity measurement.

First, a necessary number of measurement samples were prepared for each adhesive layer 3. Specifically, first, a plurality of sheets cut out from the adhesive layer 3 were stuck together to prepare a sample sheet having a thickness of about 1.5 mm. Subsequently, the sheet was die-cut to obtain columnar particles (diameter: 7.9 mm) as a sample for measurement.

Then, a dynamic viscoelasticity measurement device (product name "Advanced Rheometric Expansion System (ARES)", manufactured by Rheometric Scientific corporation) was used for the measurement sample, and the dynamic viscoelasticity measurement was performed after being fixed to a jig having a parallel plate with a diameter of 7.9 mm. In the dynamic viscoelasticity measurement, the measurement mode is set to the shear mode, the measurement temperature range is set to-40 ℃ to 100 ℃, the temperature rise rate is set to 5 ℃/min, and the frequency is set to 1Hz. The shear storage modulus at 25℃was read from the measurement results.

TABLE 1

TABLE 2

TABLE 3

The present invention is provided by way of example embodiments of the present invention, but this is merely illustrative and not to be construed as limiting. Variations of the present invention that are obvious to a person skilled in the art are included within the scope of the foregoing claims.

Claims

1. An optical adhesive sheet comprising a release liner and an adhesive layer in this order on one side in the thickness direction,

the maximum length L of the adhesive layer in the orthogonal direction orthogonal to the thickness direction is 200mm or more,

the release liner is larger than the adhesive layer when viewed in the thickness direction, and includes a cover for the adhesive layer.

2. The optical adhesive sheet according to claim 1, wherein the bending amount D measured by the following bending test is 7mm or less,

bending test: processing the optical adhesive sheet profile into dimensions of 100mm length and 25mm width to produce a sample; providing a table having an upper surface and a height of 50mm or more; fixing a 1 st part of the sample having a length of 50mm including one end edge in the longitudinal direction to the upper surface, and projecting a 2 nd part of the sample having a length of 50mm including the other end edge in the longitudinal direction laterally from one end edge of the upper surface; then, the mixture was left at 23℃for 5 minutes; then, the amount of movement of the protruding one end edge of the sample from the upper surface to the lower side was obtained as the bending amount D.

3. The optical adhesive sheet according to claim 1 or claim 2, wherein an area P which is a product of an offset amount of the release liner and a thickness of the release liner defined as follows is 90 x 10 ^-8 m ² The above-mentioned steps are carried out,

the offset is: a length (mm) of an offset portion of the release liner that is offset from the adhesive layer when viewed in the thickness direction,

the thickness is as follows: average thickness (μm) at 3 points in the offset portion.

4. The optical adhesive sheet according to claim 2, further comprising an adjacent layer adjacent to a side opposite to the release liner with respect to the adhesive layer in the thickness direction,

the release liner, the adhesive layer and the adjacent layer satisfy the following formula [1],

E1×E2×(T1+T2)/[T0 ^1/2 ×100000]≥2500

[1]

e1: tensile modulus (MPa) of the release liner at 23 ℃,

e2: tensile modulus (MPa) of the adjoining layer at 23 ℃,

t1: the thickness (μm) of the release liner,

t2: the thickness (μm) of the adjacent layer,

t0: the thickness (μm) of the adhesive layer.

5. The optical adhesive sheet according to claim 4, wherein the adjacent layer is a 2 nd release liner.

6. The optical adhesive sheet according to claim 5, wherein the 2 nd release liner is larger than the adhesive layer when viewed in the thickness direction, and comprises a cover for the adhesive layer.

7. The optical adhesive sheet according to claim 6, wherein the 2 nd release layer is defined as followsThe area P2 of the product of the offset and thickness of the pad is 90×10 ^-8 m ² The above-mentioned steps are carried out,

the 2 nd offset: a length (mm) of a 2 nd offset portion of the 2 nd release liner offset from the adhesive layer when viewed in the thickness direction,

the thickness is as follows: average thickness (μm) at 3 points in the 2 nd offset portion.

8. The optical adhesive sheet according to claim 4, wherein the adjacent layer is a member for an image display device.

9. The optical adhesive sheet according to claim 8, wherein a peripheral edge of the member for an image display device coincides with a peripheral edge of the adhesive layer when viewed in the thickness direction.

10. The optical adhesive sheet according to claim 1 or claim 2, wherein one surface of the release liner in the thickness direction has a concave portion recessed to the other side in the thickness direction around the peripheral edge of the adhesive layer,

the depth of the recess is 30 μm or less.

11. The optical adhesive sheet according to claim 1 or claim 2, wherein the adhesive layer has an indentation hardness H at 23 ℃ of 10kPa or less.

12. The optical adhesive sheet according to claim 1 or claim 2, wherein the shear storage modulus G' of the adhesive layer at 25 ℃ is 100kPa or less.

13. The optical adhesive sheet according to claim 1 or claim 2, which is an optical adhesive sheet provided with the adhesive layer and provided in an image display device,

the image display device includes: the pressure-sensitive adhesive layer and a pair of members for an image display device formed on one surface and the other surface of the optical pressure-sensitive adhesive sheet in the thickness direction, respectively.