KR20230096891A - Optical laminate - Google Patents

Abstract

Provided is an optical laminate suitable for suppressing the deterioration of optical properties after repeated bending. The optical laminate (X) of the present invention sequentially comprises an optical member (11), an adhesive layer (21), an optical member (12), an adhesive layer (22), and an optical member (13) in a direction of thickness (H). The optical members (11, 12) adhere to each other by the adhesive layer (21). The optical members (12, 13) adhere to each other by the adhesive layer (22). For the optical laminate (X), after repeated bending tests at 25℃ under the first bending conditions of a bending angle of 180℃, a bending outer diameter of 4mm, a bending speed of 60 reciprocations/min, and a bending number of 10000, a first ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the corresponding test is 1.2 or less.

Description

Optical laminate {OPTICAL LAMINATE}

The present invention relates to an optical laminate.

A display panel has a laminated structure including, for example, a pixel panel, a polarizing plate, and an optical member such as a surface cover. In the manufacturing process of a display panel, a transparent adhesive layer is used for bonding between optical members included in a laminated structure. In addition, in the manufacturing process of a display panel, the optical laminated body which forms a part of a laminated structure is manufactured in advance, for example. Such an optical laminate is supplied to a manufacturing line of a display panel.

Meanwhile, for smartphones and tablet terminals, development of display panels capable of being repeatedly bent (foldable) is in progress. Specifically, the foldable display panel can be repeatedly deformed between a curved shape and a flat non-curved shape. In such a foldable display panel, each optical member in the laminated structure is manufactured as an optical member that can be repeatedly bent. For bonding between optical members, a thin adhesive layer is used. About an optical laminate for flexible devices, such as a foldable display panel, it describes, for example in patent document 1 below.

Japanese Unexamined Patent Publication No. 2021-91117

Conventionally, in a bending portion of a foldable display panel, optical properties are deteriorated due to multiple bending times. As a cause of the fall of an optical characteristic, peeling between an optical member and an adhesive layer is mentioned, for example. A decrease in optical properties is undesirable because it causes image defects in a display panel.

The present invention provides an optical laminate suitable for suppressing deterioration in optical properties after repeated bending.

In the present invention [1], a first optical member, a first adhesive layer, a second optical member, a second adhesive layer, and a third optical member are provided in order in the thickness direction, and the first and second An optical laminate in which optical members are bonded together by the first adhesive layer and between the second and third optical members are bonded by the second adhesive layer, with a bending angle of 180°, a bending outer diameter of 4 mm, and a bending speed of 60 round trips. After the repeated bending test at 25 ° C. under the first bending condition of / min and the number of bending times of 10000, the first ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.2 or less, an optical laminate include

In the present invention [2], after the repeated bending test at 85 ° C. under the first bending condition, the second ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.5 or less, [1 ].

This invention [3] includes the optical laminate according to [2] above, wherein the ratio of the second ratio to the first ratio is 0.95 or more and 1.3 or less.

In the present invention [4], after a repeated bending test at 25° C. under the second bending conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute and a bending number of 50000, the portion repeatedly bent in the test A third ratio of the maximum thickness to the minimum thickness in the optical laminate is 1.3 or less.

In the present invention [5], after the repeated bending test at 85 ° C. under the second bending condition, the fourth ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.6 or less, [4 ].

This invention [6] includes the optical laminate as described in said [5] whose ratio of the said 4th ratio to the said 3rd ratio is 0.95 or more and 1.3 or less.

In the present invention [7], after a repeated bending test at 25° C. under the third bending conditions of a bending angle of 180°, a bending outer diameter of 3 mm, a bending speed of 60 reciprocations/minute and a bending number of 50000, the portion repeatedly bent in the test A fifth ratio of the maximum thickness to the minimum thickness in the optical laminate is 1.4 or less.

In the present invention [8], after the repeated bending test at 85 ° C. under the third bending condition, the sixth ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.7 or less, [7 ].

This invention [9] includes the optical layered body described in [8] above, wherein the ratio of the sixth ratio to the fifth ratio is 0.95 or more and 1.3 or less.

The optical laminate of the present invention is the first ratio (maximum thickness) after repeated bending tests at 25 ° C. under the first bending conditions (bending angle 180 °, bending outer diameter 4 mm, bending speed 60 reciprocations / min, bending number 10000) /minimum thickness) is less than 1.2. Alternatively, the optical laminate of the present invention, the third ratio ( maximum thickness/minimum thickness) is 1.3 or less. Alternatively, the optical laminate of the present invention, the fifth ratio after repeated bending tests at 25 ° C. under the third bending conditions (bending angle 180 °, bending outer diameter 3 mm, bending speed 60 reciprocations / min, bending number 50000) maximum thickness/minimum thickness) is 1.4 or less. In the optical layered body of the present invention, the change in thickness after 10000 times or 50000 times of 180° bending is as small as these. Such an optical layered body is suitable for suppressing a decrease in optical properties after repeated bending.

1 is a schematic cross-sectional view of an embodiment of an optical laminate of the present invention.
Fig. 2A of Fig. 2 shows a flat state of the test piece in the repeated bending test, and Fig. 2B shows a curved state of the test piece in the repeated bending test.

An optical layered body (X) as an embodiment of the optical layered body of the present invention includes optical members 11, 12, and 13 and pressure-sensitive adhesive layers 21 and 22, as shown in FIG. Specifically, the optical layered body X includes an optical member 11 (first optical member), an adhesive layer 21 (first adhesive layer), and an optical member 12 (second optical member). , The adhesive layer 22 (2nd adhesive layer) and the optical member 13 (3rd optical member) are provided in order in the thickness direction H. The optical layered body X has a sheet shape with a predetermined thickness, and spreads in a direction (planar direction) orthogonal to the thickness direction H. Between the optical members 11 and 12, the pressure-sensitive adhesive layer 21 is bonded. Between the optical members 12 and 13, the pressure-sensitive adhesive layer 22 is bonded.

The optical laminate (X) is an optically transparent laminate. The optical layered body X is disposed at a light passage location in the flexible device. As a flexible device, a flexible display panel is mentioned, for example. As a flexible display panel, a foldable display panel and a rollable display panel are mentioned, for example. The optical members 11, 12, and 13 are optical members incorporated into the flexible device, respectively. The optical members 11, 12, and 13 are film-shaped optical members that can be repeatedly bent, respectively.

After the repeated bending test at 25° C. under the first bending condition, the optical layered body X has a maximum thickness to a minimum thickness in a portion repeatedly bent in the test (a portion to be bent (P) described later). The ratio R1 (first ratio) is 1.2 or less. The first bending conditions are conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute, and a bending frequency of 10000. In the repeated bending test, the optical layered body X is bent with the first optical member side inside the bending or outside the bending (the same applies to the repeated bending test under other conditions described later). The repeated bending test can be performed with, for example, a U-shaped stretch tester (manufactured by Yuasa System Machinery).

2A and 2B schematically show repeated bending tests at a bending angle of 180°. In the repeated bending test, both ends of the test piece S of the optical layered body X are fixed to the gripping parts C1 and C2 of the testing machine. In the repeated bending test, a series of processes including the first process and the second process is set as one cycle (one reciprocation). In the first process, the test piece S is curved from a flat shape to a U shape. In the second process, the test piece S is returned to a flat shape after the first process. By adjusting the distance between both ends of the U-shaped test piece S, the outer diameter of the test piece can be adjusted. After the repeated bending test, the minimum thickness and maximum thickness in the repeatedly bent portion P (shown with cross hatching) of the test piece S are measured. The method of the repeated bending test is as described below in relation to Examples specifically.

As described above, in the optical layered body X, the ratio R1 (maximum thickness/minimum thickness) in the portion to be bent P after 10,000 times of 180° bending is suppressed to a range of 1.2 or less. Such an optical layered body (X) is suitable for suppressing a decrease in optical properties after repeated bending. Specifically, it is as shown with examples to be described later. The ratio R1 is preferably 1.15 or less, more preferably 1.1 or less, from the viewpoint of suppressing a decrease in the optical properties after repeated bending of the optical layered body (X). The ratio R1 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more.

After the repeated bending test at 85° C. under the first bending condition, the optical layered body (X) has a maximum thickness to minimum thickness ratio R2 (2nd ratio) is preferably 1.5 or less, more preferably 1.4 or less, still more preferably 1.3 or less, particularly preferably from the viewpoint of suppressing a decrease in optical properties after repeated bending of the optical layered body (X) in a high temperature environment. is 1.0. The ratio R2 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more. The ratio (R2/R1) of the ratio R2 to the ratio R1 is preferably 0.95 or more, more preferably 0.98 or more, and is preferably 1.3 or less, more preferably 1.2 or less, still more preferably 1.1 or less. , particularly preferably 1.0.

In the present embodiment, the optical layered body X has, in the present embodiment, after the repeated bending test at 25° C. under the second bending condition, the maximum thickness to the minimum thickness in the portion P to be bent repeatedly in the test. Ratio R3 (third ratio) is 1.3 or less. The second bending conditions are conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute, and a bending frequency of 50000. In the optical layered body X, the ratio R3 in the portion P to be bent after 50000 times of 180° bending is suppressed to a range of 1.3 or less. Therefore, the optical layered body (X) is suitable for suppressing a decrease in optical properties after repeated bending. Specifically, it is as shown with examples to be described later. Further, the ratio R3 is preferably 1.25 or less, more preferably 1.2 or less, from the viewpoint of suppressing a decrease in the optical properties after repeated bending of the optical layered body (X). The ratio R3 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more.

After the repeated bending test at 85° C. under the second bending condition, the optical layered body (X) has a maximum thickness to minimum thickness ratio R4 (fourth Ratio) is preferably 1.6 or less, more preferably 1.5 or less, still more preferably 1.4 or less from the viewpoint of suppressing a decrease in optical properties after repeated bending of the optical layered body (X) in a high temperature environment. The ratio R4 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more. The ratio (R4/R3) of the ratio R4 to the ratio R3 is preferably 0.95 or more, more preferably 0.98 or more, and is preferably 1.3 or less, more preferably 1.2 or less, still more preferably 1.15 or less. am.

In the present embodiment, the optical layered body X has a maximum thickness to a minimum thickness in a portion P to be bent repeatedly in the test after a repeated bending test at 25° C. under the third bending condition. The ratio R5 (fifth ratio) is 1.4 or less. The third bending conditions are conditions of a bending angle of 180°, a bending outer diameter of 3 mm, a bending speed of 60 reciprocations/minute, and a bending frequency of 50000. In the optical layered body X, the ratio R5 in the portion to be bent P after 50,000 times of 180° bending (outer diameter of bending is 3 mm) is suppressed to a range of 1.4 or less. Therefore, the optical layered body (X) is suitable for suppressing a decrease in optical properties after repeated bending. Specifically, it is as shown with examples to be described later. Further, the ratio R5 is preferably 1.3 or less, more preferably 1.2 or less, from the viewpoint of suppressing a decrease in optical properties after repeated bending of the optical layered body (X). The ratio R5 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more.

After the repeated bending test at 85° C. under the third bending condition, the optical layered body (X) has a maximum thickness to minimum thickness ratio R6 (6th Ratio) is preferably 1.7 or less, more preferably 1.6 or less, still more preferably 1.5 or less from the viewpoint of suppressing a decrease in optical properties after repeated bending of the optical layered body (X) in a high temperature environment. The ratio R6 is, for example, 0.9 or more, preferably 1.00 or more, 1.00 or more, or 1.05 or more. The ratio (R6/R5) of the ratio R6 to the ratio R5 is preferably 0.95 or more, more preferably 0.98 or more, and is preferably 1.3 or less, more preferably 1.25 or less, still more preferably 1.2 or less. am.

As an adjustment method of ratio R1-R6, adjustment of the adhesive force of the adhesive layers 21 and 22, adjustment of the shear storage elastic modulus, and adjustment of thickness are mentioned, for example. As a method for adjusting the adhesive strength of the pressure-sensitive adhesive layer, selection of the type of base polymer in the pressure-sensitive adhesive layer, adjustment of molecular weight, and adjustment of the compounding amount are exemplified. Selection of the type of base polymer includes selection of the type of main chain in the base polymer, and selection of the type and amount of functional groups. As a method for adjusting the adhesive force of the pressure-sensitive adhesive layer, selection of the kind of components other than the base polymer in the pressure-sensitive adhesive layer and adjustment of the compounding amount of the component are also mentioned. As said component, a crosslinking agent, a silane coupling agent, and an oligomer are mentioned. As the method for adjusting the shear storage modulus of the pressure-sensitive adhesive layer, for example, selection of the type of base polymer in the pressure-sensitive adhesive layer, adjustment of the molecular weight, and adjustment of the compounding amount, and selection of the type and compounding amount of the crosslinking agent for crosslinking the base polymer can be adjusted.

The optical member 11 is a base film in this embodiment. As a base film, a resin film, a glass film, and a metal film are mentioned, for example. Examples of the material of the resin film include polyester, polyolefin, polyimide (PI), polyamide, cellulose, modified cellulose, polystyrene, and polycarbonate. As polyester, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate are mentioned, for example. Examples of the polyolefin include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of the polyamide include polyamide 6, polyamide 6 and 6, and partially aromatic polyamide. As modified cellulose, triacetyl cellulose (TAC) is mentioned, for example. These resin materials may be used independently, or two or more types may be used together. As a material of a glass film, aluminosilicate glass, soda-lime glass, borosilicate glass, and aluminoborosilicate glass are mentioned, for example. These glass materials may be used independently, or two or more types may be used together. As a material of a metal film, stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, and titanium are mentioned, for example. These metal materials may be used independently, or two or more types may be used together. In addition, the optical member 11 may be a base film that functions as a transparent cover film disposed on the viewing side of the display panel.

The thickness of the optical member 11 is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of ensuring the supporting function of the optical member 11 . The thickness of the optical member 11 is preferably 100 μm or less, more preferably 75 μm or less, from the viewpoint of reducing the thickness of the optical layered body X.

The optical member 12 is a functional optical member in this embodiment. As a functional optical member, a film-shaped polarizing plate (polarizing film) and a retardation plate are mentioned, for example. The functional optical member is preferably a film-shaped functional optical member. As such an optical member, a film-like polarizing plate (polarizing film) and retardation film are mentioned, for example.

Examples of the polarizing film include a hydrophilic polymer film that has undergone dyeing treatment with a dichroic substance and subsequent stretching treatment. Examples of dichroic substances include iodine and dichroic dyes. Examples of the hydrophilic polymer film include a polyvinyl alcohol (PVA) film, a partially foamed PVA film, and a partially saponified film of ethylene/vinyl acetate copolymer. As a polarizing film, a polyene oriented film is also mentioned. As a material of the polyene orientation film, for example, a dehydrated product of PVA and a dehydrochlorinated product of polyvinyl chloride are exemplified. The polarizing film may have a protective film bonded to one side and/or the other side of the thickness direction through an adhesive agent. The thickness of the optical member 12 as a polarizing film is preferably 1 μm or more, more preferably 5 μm or more, from the viewpoint of securing the function and strength of the optical member 12 . The thickness of the optical member 12 as a polarizing film is preferably 50 μm or less, more preferably 35 μm or less, from the viewpoint of reducing the thickness of the optical layered body (X).

Examples of the retardation film include a λ/2 wavelength film and a λ/4 wavelength film, and a viewing angle compensation film. Examples of the material of the retardation film include a polymer film birefringent by stretching treatment. As a polymer film, a cellulose film and a polyester film are mentioned, for example. As a cellulose film, a triacetyl cellulose film is mentioned, for example. As a polyester film, a polyethylene terephthalate film and a polyethylene naphthalate film are mentioned, for example. As the retardation film, a film comprising a substrate such as a cellulose film and an alignment layer of a liquid crystal compound such as a liquid crystal polymer on the substrate can also be preferably used. The thickness of the optical member 12 as the retardation film is preferably 1 μm or more, more preferably 2 μm or more, from the viewpoint of securing the function and strength of the optical member 12 . The thickness of the optical member 12 as the retardation film is preferably 50 μm or less, more preferably 40 μm or less, from the viewpoint of reducing the thickness of the optical layered body (X).

The optical member 13 is a film-shaped pixel panel in this embodiment. As a pixel panel, an organic electroluminescent panel and a liquid crystal panel are mentioned, for example. The thickness of the optical member 13 is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of ensuring the function of the optical member 13. The thickness of the optical member 13 is preferably 150 μm or less, more preferably 100 μm or less, from the viewpoint of reducing the thickness of the optical layered body X.

The pressure-sensitive adhesive layer 21 is a pressure-sensitive adhesive layer formed from the first pressure-sensitive adhesive composition. The adhesive layer 21 is an optically transparent adhesive layer (optical adhesive layer). The first pressure-sensitive adhesive composition contains at least a base polymer.

The base polymer is an adhesive component that causes the adhesive layer 21 to develop adhesiveness. Examples of the base polymer include acrylic polymers, silicone polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyvinyl ether polymers, vinyl acetate/vinyl chloride copolymers, modified polyolefin polymers, epoxy polymers, and fluoropolymers. , and rubber polymers. A base polymer may be used independently, and two or more types may be used together. From the viewpoint of ensuring good transparency and adhesiveness of the pressure-sensitive adhesive layer 21, an acrylic polymer is preferable as the base polymer.

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

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

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

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

As the (meth)acrylic acid alkyl ester, in the pressure-sensitive adhesive layer 21, from the viewpoint of balancing the softness and adhesive force required for the pressure-sensitive adhesive layer for flexible devices, preferably (meth) having an alkyl group having 3 to 15 carbon atoms. A first alkyl (meth)acrylate in which at least one selected from alkyl acrylate esters is used, more preferably selected from alkyl (meth)acrylates having an alkyl group having 3 to 15 carbon atoms and having a relatively small number of carbon atoms in the alkyl group An ester and a second (meth)acrylic acid alkyl ester having a relatively large number of carbon atoms in the alkyl group are used in combination, more preferably, a (meth)acrylic acid alkyl ester having an alkyl group having 4 to 8 carbon atoms and an alkyl group having 9 to 13 carbon atoms A (meth)acrylic acid alkyl ester having is used in combination, and more preferably, a (meth)acrylic acid alkyl ester having a C 4-8 linear alkyl group and a C 9-13 linear alkyl group (meth) An acrylic acid alkyl ester is used in combination.

The ratio of (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 70% by mass or more, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the pressure-sensitive adhesive layer 21 , More preferably, it is 90 mass % or more. The ratio is, for example, 99% by mass or less. When the first and second alkyl (meth)acrylates are used together, the ratio of the first alkyl (meth)acrylates in the monomer component is, from the viewpoint of the balance between the softness of the pressure-sensitive adhesive layer 21 and the adhesive force, It is preferably 40% by mass or more, more preferably 50% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less. The ratio of the second (meth)acrylic acid alkyl ester in the monomer component is preferably 20% by mass or more, more preferably 30% by mass or more, from the viewpoint of the balance between the softness of the pressure-sensitive adhesive layer 21 and the adhesive force. , and is also preferably 50% by mass or less, more preferably 45% by mass or less.

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

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

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 0.1% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and ensuring cohesive force in the pressure-sensitive adhesive layer 21 is 1% by mass or more, more preferably 2% by mass or more. The ratio is preferably 20% by mass or less, more preferably 10% by mass, from the viewpoint of adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the pressure-sensitive adhesive layer 21 and the acrylic polymer). below

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 carboxy group-containing monomer in the monomer component is determined by the introduction of a crosslinked structure into the acrylic polymer, the securing of the cohesive force in the pressure-sensitive adhesive layer 21, and the adhesion to the adherend in the pressure-sensitive adhesive layer 21. From the viewpoint of ensuring, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and still more preferably 0.8% by mass or more. The ratio is preferably 10% by mass or less, more preferably 5% by mass or less, from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid.

Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, and N- Vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylphy Peridine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine- 2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole.

The ratio of the monomer having a nitrogen atom-containing ring in the monomer component is preferably, from the viewpoint of securing the cohesive force in the adhesive layer 21 and securing the adhesion of the adherend in the adhesive layer 21. It is 1 mass % or more, More preferably, it is 3 mass % or more, More preferably, it is 5 mass % or more. The ratio is preferably 30 mass from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the pressure-sensitive adhesive layer 21 and the acrylic polymer). % or less, more preferably 20% by mass or less.

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

The monomer component is preferably a first (meth)acrylic acid alkyl ester (the number of carbon atoms in the alkyl group is relatively small ), a second (meth)acrylic acid alkyl ester (the alkyl group has a relatively large number of carbon atoms), a hydroxy group-containing monomer, and a monomer having a nitrogen atom-containing ring. The first (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group of 4 to 8 carbon atoms, more preferably a (meth)acrylic acid alkyl ester having a linear alkyl group of 4 to 8 carbon atoms. It is an acrylic acid alkyl ester, More preferably, it is at least one selected from the group which consists of 2-ethylhexyl acrylate (2EHA) and n-butyl acrylate (BA). The second (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group having 9 or more carbon atoms, more preferably lauryl acrylate (LA). The hydroxy group-containing monomer is preferably at least one selected from the group consisting of 4-hydroxybutyl acrylate (4HBA) and 2-hydroxyethyl acrylate (2HEA). The monomer having a nitrogen atom-containing ring is preferably N-vinyl-2-pyrrolidone (NVP).

The base polymer preferably has a crosslinked structure. As a method for introducing a cross-linked structure into the base polymer, a base polymer having a functional group capable of reacting with the cross-linking agent and a cross-linking agent are mixed in an adhesive composition, and the base polymer and the cross-linking agent are reacted in the pressure-sensitive adhesive sheet (Method 1), and the base polymer A method (second method) of forming a base polymer having a branched structure (crosslinked structure) introduced into the polymer chain by including a polyfunctional monomer as a crosslinking agent in a monomer component that forms there is. These methods may be used together.

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

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. nate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthaline diisocyanate, triphenylmethane triisocyanate , and polymethylene polyphenyl isocyanate. Moreover, derivatives of these isocyanates are also mentioned as an isocyanate crosslinking agent. As the said isocyanate derivative, an isocyanurate modified body and a polyol modified body are mentioned, for example. As a commercially available isocyanate crosslinking agent, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (of hexamethylene diisocyanate) Trimethylolpropane adduct, manufactured by Tosoh), Coronate HX (isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), Takenate D110N (trimethylol of xylylene diisocyanate) propane adduct, manufactured by Mitsui Chemicals), and Takenate 600 (1,3-bis(isocyanatomethyl)cyclohexane, manufactured by Mitsui Chemicals).

As the peroxide crosslinking agent, dibenzoyl peroxide, di(2-ethylhexyl) peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl per oxyneodecanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidyl amine, N,N,N',N'-tetraglycy dil-m-xylylene diamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

An isocyanate crosslinking agent (particularly, a bifunctional isocyanate crosslinking agent) and a peroxide crosslinking agent are preferable from the viewpoint of securing the flexibility of the pressure-sensitive adhesive layer 21 . An isocyanate crosslinking agent (particularly, a trifunctional isocyanate crosslinking agent) is preferable from the viewpoint of securing durability of the pressure-sensitive adhesive layer 21 . In the base polymer, difunctional isocyanate crosslinking agents and peroxide crosslinking agents form more flexible two-dimensional crosslinking, whereas trifunctional isocyanate crosslinking agents form stronger three-dimensional crosslinking. From the viewpoint of both durability and flexibility of the pressure-sensitive adhesive layer 21, a combination of a trifunctional isocyanate crosslinking agent, a peroxide crosslinking agent, and/or a difunctional isocyanate crosslinking agent is preferred.

The blending amount of the crosslinking agent in the first method is, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, with respect to 100 parts by mass of the base polymer, from the viewpoint of securing the cohesive force of the pressure-sensitive adhesive layer 21. More preferably, it is 0.1 mass part or more, More preferably, it is 0.2 mass part or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 21, the compounding amount of the crosslinking agent relative to 100 parts by mass of the base polymer is, for example, 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 2 parts by mass. is less than

In the second method, the monomer component (including a monofunctional monomer and a polyfunctional monomer for introducing a crosslinked structure) may be polymerized at one time or in multiple stages. In the multi-stage polymerization method, first, a monofunctional monomer is polymerized (prepolymerization), thereby preparing a prepolymer composition containing a partially polymerized product (a mixture of a polymer having a low polymerization degree and an unreacted monomer). Next, after adding a polyfunctional monomer as a crosslinking agent to the prepolymer composition, the partially polymerized product and the polyfunctional monomer are polymerized (main polymerization).

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

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

Examples of the bifunctional (meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene. Glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neophene Tylglycol di(meth)acrylate, stearic acid modified pentaerythritol di(meth)acrylate, dicyclopentenyl di(meth)acrylate, di(meth)acryloylisocyanurate, and alkylene oxides Modified bisphenol di(meth)acrylate is mentioned.

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

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

As the polyfunctional (meth)acrylate as the crosslinking agent, preferably, a bifunctional (meth)acrylate is used, more preferably, 1,6-hexanediol di(meth)acrylate is used, More preferably, 1,6-hexanediol dimethacrylate is used.

In the monomer component, the compounding amount of the polyfunctional monomer as a crosslinking agent in the second method is, for example, 0.01 part by mass with respect to 100 parts by mass of the monofunctional monomer from the viewpoint of ensuring the cohesive force of the pressure-sensitive adhesive layer 21. or more, preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 21, the blending amount of the polyfunctional monomer is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and still more preferably, based on 100 parts by mass of the monofunctional monomer. It is preferably 1 part by mass or less.

An acrylic polymer can be formed by polymerizing the above-mentioned monomer components. Examples of the polymerization method include solution polymerization, photopolymerization in the absence of a solvent (for example, UV polymerization), block polymerization, and emulsion polymerization. As a solvent for solution polymerization, ethyl acetate and toluene are used, for example. Moreover, as a polymerization initiator, a thermal polymerization initiator and a photoinitiator are used, for example. A polymerization initiator may be used independently, and 2 or more types may be used together. The amount of polymerization initiator used is preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more, still more preferably 0.1 parts by mass or more, and preferably 1 part by mass or less, based on 100 parts by mass of the monomer component. , More preferably 0.5 parts by mass or less, and still more preferably 0.3 parts by mass or less.

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

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

The weight average molecular weight of the base polymer is preferably 100,000 or more, more preferably 300,000 or more, and still more preferably 500,000 or more, from the viewpoint of securing cohesive force in the pressure-sensitive adhesive layer 21. The weight average molecular weight of the base polymer is preferably 3 million or less, more preferably 2.5 million or less, still more preferably 2 million or less, from the viewpoint of ensuring the flexibility of the pressure-sensitive adhesive layer 21. The weight average molecular weight of the base polymer is measured by a gel permeation chromatograph (GPC) and calculated in terms of polystyrene.

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

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

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

The pressure-sensitive adhesive composition may contain an oligomer 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. In addition, an oligomer may be used independently and may use two or more types together.

The acrylic oligomer is a copolymer of monomer components containing an alkyl (meth)acrylate in a proportion of 50% by mass or more. The monomer component may also contain a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester. As an alkyl (meth)acrylate, the alkyl (meth)acrylate ester mentioned above regarding an acrylic polymer is mentioned, for example. As a copolymerizable monomer, the copolymerizable monomer (polar group containing monomer etc.) mentioned above regarding an acrylic polymer is mentioned, for example. The acrylic oligomer is preferably a copolymer of a (meth)acrylic acid alkyl ester having 3 to 8 carbon atoms in the alkyl group and a polar group-containing monomer. The alkyl (meth)acrylate is more preferably n-butyl (meth)acrylate, still more preferably n-butyl acrylate. The polar group-containing monomer is preferably a carboxy group-containing monomer, more preferably acrylic acid. The ratio of the (meth)acrylic acid alkyl ester in the monomer component of the acrylic oligomer is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more. The ratio is, for example, 99% by mass or less.

An acrylic oligomer can be formed by polymerizing the monomer component of the said acrylic oligomer. Examples of the polymerization method include solution polymerization, photopolymerization in the absence of a solvent (for example, UV polymerization), block polymerization, and emulsion polymerization. As a solvent for solution polymerization, ethyl acetate and toluene are used, for example. In the polymerization of the acrylic oligomer, a polymerization initiator may be used, or a chain transfer agent may be used for the purpose of molecular weight adjustment. As the polymerization initiator, a thermal polymerization initiator and a photopolymerization initiator are used, for example. The amount of the polymerization initiator used is preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more, and preferably 1 part by mass or less, and more preferably 0.5 parts by mass or less, based on 100 parts by mass of the monomer component. am.

The weight average molecular weight of the acrylic oligomer is preferably 1000 or more, more preferably 1500 or more, still more preferably 2000 or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 21. The molecular weight is preferably 30000 or less, more preferably 10000 or less, still more preferably 8000 or less, from the viewpoint of securing the flexibility of the pressure-sensitive adhesive layer 21.

The content of the acrylic oligomer in the first pressure-sensitive adhesive composition is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, based on 100 parts by mass of the base polymer, in order to sufficiently increase the adhesive strength of the pressure-sensitive adhesive layer 21. More preferably, it is 35 mass parts or more. On the other hand, from the viewpoint of securing the transparency of the pressure-sensitive adhesive layer 21, the content of the acrylic oligomer in the pressure-sensitive adhesive layer 21 is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, based on 100 parts by mass of the base polymer. below the mass part. In the pressure-sensitive adhesive layer 21, when the content of the acrylic oligomer is too large, the haze tends to rise and the transparency decreases due to a decrease in the compatibility of the acrylic oligomer.

The 1st adhesive composition may contain other components as needed. Examples of other components include silane coupling agents, solvents, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, ultraviolet absorbers, surfactants, and antistatic agents. As a solvent, the polymerization solvent used as needed at the time of polymerization of an acrylic polymer or an acrylic oligomer, and the solvent added to the polymerization reaction solution after polymerization are mentioned, for example. As such a solvent, ethyl acetate and toluene are used, for example.

The thickness of the pressure-sensitive adhesive layer 21 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the optical members 11 and 12 . The thickness of the pressure-sensitive adhesive layer 21 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and particularly preferably 50 μm or less, from the viewpoint of reducing the thickness of the flexible device.

The haze of the pressure-sensitive adhesive layer 21 is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less. The haze of the adhesive layer 21 can be measured using a haze meter based on JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Kogyo Co., Ltd. and "HM-150 type|mold" by Murakami Color Technology Laboratory Co., Ltd. are mentioned, for example.

The total light transmittance of the pressure-sensitive adhesive layer 21 is preferably 60% or more, more preferably 80% or more, still more preferably 85% or more. The total light transmittance of the pressure-sensitive adhesive layer 21 is, for example, 100% or less. The total light transmittance of the pressure-sensitive adhesive layer 21 can be measured based on JIS K 7375 (2008).

The pressure-sensitive adhesive layer 22 is a pressure-sensitive adhesive layer formed from the second pressure-sensitive adhesive composition. The adhesive layer 22 is an optical adhesive layer. The second pressure-sensitive adhesive composition contains at least a base polymer. As a base polymer contained in a 2nd adhesive composition, the base polymer mentioned above regarding a 1st adhesive composition is mentioned, for example. The base polymer in the first adhesive composition and the base polymer in the second adhesive composition may be the same or different. The 2nd adhesive composition may contain components other than a base polymer. Examples of the component contained in the second adhesive composition include components other than the base polymer described above in relation to the first adhesive composition. The composition of the 1st adhesive composition and the composition of the 2nd adhesive composition may be the same or different.

The thickness of the pressure-sensitive adhesive layer 22 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the optical members 12 and 13 . The thickness of the pressure-sensitive adhesive layer 22 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, and particularly preferably 50 μm or less, from the viewpoint of reducing the thickness of the flexible device.

The haze of the pressure-sensitive adhesive layer 22 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The total light transmittance of the pressure-sensitive adhesive layer 22 is preferably 60% or more, more preferably 80% or more, still more preferably 85% or more. The total light transmittance of the pressure-sensitive adhesive layer 22 is, for example, 100% or less.

Optical laminated body (X) can be manufactured as follows, for example.

First, the optical members 11, 12, 13 and the pressure-sensitive adhesive layers 21, 22 are prepared.

The pressure-sensitive adhesive layer 21 can be prepared as, for example, the pressure-sensitive adhesive layer 21 with a release liner. The pressure-sensitive adhesive layer 21 with release liner can be formed by applying the first pressure-sensitive adhesive composition (varnish) onto the release liner to form a coating film, and then drying the coating film. As a method of applying the first pressure-sensitive adhesive composition, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating Coating, and die coating are mentioned (the same applies also to the method of application|coating of another adhesive composition mentioned later). You may laminate|stack another peeling liner further on the adhesive layer 21 on a peeling liner.

The pressure-sensitive adhesive layer 22 can be prepared as, for example, the pressure-sensitive adhesive layer 22 with a release liner. The pressure-sensitive adhesive layer 22 with a release liner can be formed by applying the second pressure-sensitive adhesive composition (varnish) onto the release liner to form a coating film, and then drying the coating film. On the pressure-sensitive adhesive layer 22 with a release liner, another release liner may be further laminated.

Next, the optical member 11 and the optical member 12 are bonded together by the pressure-sensitive adhesive layer 21 . For example, first, the pressure-sensitive adhesive layer 21 is bonded to one surface of the optical member 12 in the thickness direction (lower surface in FIG. 1 ). Before bonding, it is preferable to corona-treat or plasma-treat the surface of the optical member 12, and it is more preferable to also corona-treat or plasma-treat the surface of the pressure-sensitive adhesive layer 21 (described later between the optical member and the pressure-sensitive adhesive layer). The same applies to bonding). Next, the release liner is peeled from the pressure-sensitive adhesive layer 21 on the optical member 12 . Next, the optical member 11 is bonded to the exposed surface of the pressure-sensitive adhesive layer 21 exposed by the peeling.

Next, the optical member 12 and the optical member 13 are bonded together by the pressure-sensitive adhesive layer 22 . For example, first, the adhesive layer 22 is bonded to the other surface of the optical member 12 in the thickness direction (upper surface in FIG. 1 ). Next, the release liner is peeled from the pressure-sensitive adhesive layer 22 on the optical member 12 . Next, the optical member 13 is bonded to the exposed surface of the pressure-sensitive adhesive layer 22 exposed by the peeling.

As described above, the optical layered body (X) can be manufactured.

Example

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

[Example 1]

<Preparation of base polymer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 53 parts by mass of 2-ethylhexyl acrylate (2EHA), 40 parts by mass of lauryl acrylate (LA), and N-vinyl-2 - 5 parts by mass of pyrrolidone (NVP), 2 parts by mass of 4-hydroxybutyl acrylate (4HBA), and 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator; The 1st mixture (solid content concentration of 47 mass %) containing ethyl acetate as a solvent was stirred at 56 degreeC for 6 hours in nitrogen atmosphere (polymerization reaction). In this way, a first polymer solution containing an acrylic polymer was obtained. The weight average molecular weight of the acrylic polymer in the first polymer solution was about 1,800,000. The solid content concentration of the first mixture was adjusted by adjusting the amount of the solvent.

<Preparation of pressure-sensitive adhesive composition>

In the first polymer solution, the first crosslinking agent (trade name "Takenate D110N", trimethylolpropane adduct of xylylene diisocyanate, Mitsui Chemical agent) 0.03 mass part and the 2nd crosslinking agent (product name "Nipper BMT", dibenzoyl peroxide, Nippon Oil & Fats Co., Ltd. make) 0.4 mass part were added and mixed, and the 1st adhesive composition was prepared.

<Formation of pressure-sensitive adhesive layer>

On the release treated surface of a release liner (product name “Diafoil MRF#38”, thickness 38 μm, manufactured by Mitsubishi Chemical Corporation) having a release treatment surface on one side, the first pressure-sensitive adhesive composition was applied to form a coating film. Next, the coating film on the release liner was dried by heating at 100°C for 1 minute and then heating at 150°C for 3 minutes to form a transparent pressure-sensitive adhesive layer (pressure-sensitive adhesive layer A ₁ ) having a thickness of 50 μm. As described above, two first adhesive sheets (thickness: 50 µm) with release liner were produced.

<Production of optical laminate>

First, both sides of a polarizing film (thickness: 32 μm) having a liquid crystal retardation layer on one side were subjected to plasma treatment (the surface on the liquid crystal retardation layer side of the polarizing film was used as the first surface, and the opposite surface was used as the second surface). do). In each plasma treatment, a plasma irradiation device (product name "AP-TO5", manufactured by Sekisui Kogyo) was used, the voltage was set to 160 V, the frequency was set to 10 kHz, and the processing speed was set to 5000 mm/min (plasma treatment described later) the same for ). Next, the exposed surfaces of the first pressure sensitive adhesive sheets of the two sheets and the first and second surfaces of the polarizing films were bonded together. In this bonding, the first adhesive sheet with a peeling liner and the polarizing film were crimped by an operation of reciprocating a 2 kg roller once in a 25°C environment (the same applies to bonding described later). Next, the release liner was peeled from the first pressure-sensitive adhesive sheet on the first side of the polarizing film. Next, the exposed surface of the first pressure sensitive adhesive sheet exposed by this peeling was subjected to plasma treatment. On the other hand, a polyethylene terephthalate (PET) film (product name "Diafoil", thickness 125 µm, manufactured by Mitsubishi Chemical Corporation) as a third optical member was also subjected to plasma treatment. And the exposed surface of the 1st adhesive sheet on the 1st surface of a polarizing film, and the plasma-processed surface of a PET film were bonded together. Next, the release liner was peeled from the first pressure-sensitive adhesive sheet on the second side of the polarizing film. Next, the exposed surface of the first pressure sensitive adhesive sheet exposed by this peeling was subjected to plasma treatment. On the other hand, a polyimide (PI) film (product name "Kapton 300V", thickness 75 µm, manufactured by DuPont Toray) as the first optical member was also subjected to plasma treatment. Then, the exposed surface of the first pressure-sensitive adhesive sheet on the second surface of the polarizing film and the plasma-treated surface of the polyimide film were bonded together.

As described above, the optical laminate of Example 1 was produced. The optical layered body of Example 1 includes a PI film (thickness: 75 μm) as a first optical member, an adhesive layer _A1 (thickness: 50 μm) as a first adhesive layer, and a polarizing film (thickness: 32 μm) as a second optical member; A pressure-sensitive adhesive layer A ₁ (thickness: 50 μm) as the second pressure-sensitive adhesive layer and a PET film (thickness: 125 μm) as the third optical member are sequentially provided in the thickness direction. The PET film in this laminated structure is an element imitating the above-described film-like pixel panel (the same applies to Examples and Comparative Examples to be described later).

[Example 2]

<Preparation of base polymer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, 98 parts by mass of n-butyl (BA) acrylate and 2 parts by mass of 4-hydroxybutyl acrylate (4HBA) were used as a thermal polymerization initiator. A second mixture (solid content concentration: 47% by mass) containing 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) and ethyl acetate as a solvent was stirred at 56°C for 6 hours under a nitrogen atmosphere. (polymerization). In this way, a second polymer solution containing an acrylic polymer was obtained. The weight average molecular weight of the acrylic polymer in the second polymer solution was about 1,700,000. The solid content concentration of the second mixture was adjusted by adjusting the amount of the solvent.

<Preparation of oligomer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction pipe, 95 parts by mass of n-butyl (BA) acrylic acid, 5 parts by mass of acrylic acid (AA), 3 parts by mass of 2-mercaptoethanol, , A third mixture (solid content concentration: 40% by mass) containing 0.1 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator and toluene as a solvent was mixed with nitrogen at 70°C for 8 hours. It was stirred under atmosphere (polymerization reaction). As a result, an oligomer solution containing an oligomer having a weight average molecular weight of 5000 was obtained. The solid content concentration of the third mixture was adjusted by adjusting the amount of the solvent.

<Preparation of pressure-sensitive adhesive composition>

In the second polymer solution, 0.03 parts by mass of the first crosslinking agent (product name "Takenate D110N", manufactured by Mitsui Chemicals) per 100 parts by mass of the acrylic polymer (base polymer) of the polymer solution, and the second crosslinking agent (product name "Niper BMT") ", Nippon Oil & Fat Co., Ltd.) 1.5 parts by mass and 40 parts by mass of the oligomer were added and mixed to prepare a second adhesive composition.

<Formation of pressure-sensitive adhesive layer>

A second PSA sheet with a release liner (PSA layer A2 having a thickness of 50 _μm ) was prepared in the same manner as in the first PSA sheet with a release liner in Example 1, except that the second PSA composition was used instead of the first PSA composition. did.

<Production of optical laminate>

An optical laminate of Example 2 was produced in the same manner as in the optical laminate of Example 1, except that the second adhesive sheet with a release liner was used instead of the first adhesive sheet with a release liner. The optical laminate of Example 2 includes a PI film (thickness: 75 μm) as a first optical member, an adhesive layer _A2 (thickness: 50 μm) as a first adhesive layer, and a polarizing film (thickness: 32 μm) as a second optical member; A pressure-sensitive adhesive layer A ₂ (thickness: 50 μm) as a second pressure-sensitive adhesive layer and a PET film (thickness: 125 μm) as a third optical member are sequentially provided in the thickness direction.

[Comparative Example 1]

<Preparation of pressure-sensitive adhesive composition>

In the second polymer solution, 0.2 parts by mass of the first crosslinking agent (product name "Takenate D110N", manufactured by Mitsui Chemicals) per 100 parts by mass of the acrylic polymer (base polymer) of the polymer solution, and the second crosslinking agent (product name "Nipper BMT") ", Nippon Oil & Fat Co., Ltd.) 0.2 mass part was added and mixed, and the 3rd adhesive composition was prepared.

<Formation of pressure-sensitive adhesive layer>

Except for using the third PSA composition instead of the first PSA composition, a third PSA sheet with a release liner (PSA layer _A3 having a thickness of 50 μm) was produced in the same manner as in the first PSA sheet with a release liner in Example 1. did.

<Production of optical laminate>

An optical laminate of Comparative Example 1 was produced in the same manner as in the optical laminate of Example 1, except that the third adhesive sheet with a release liner was used instead of the first adhesive sheet with a release liner. The optical laminate of Comparative Example 1 includes a PI film (thickness: 75 μm) as a first optical member, an adhesive layer A ₃ (thickness: 50 μm) as a first adhesive layer, and a polarizing film (thickness: 32 μm) as a second optical member; A pressure-sensitive adhesive layer A ₃ (thickness: 50 μm) as a second pressure-sensitive adhesive layer and a PET film (thickness: 125 μm) as a third optical member are sequentially provided in the thickness direction.

<Repeated bending test, thickness measurement, reliability evaluation>

For each optical laminate of Examples 1 and 2 and Comparative Example 1, a repeated bending test, thickness measurement, and reliability evaluation were performed as follows.

First, a test piece (width 25 mm x length 100 mm) was cut out from the optical laminate. Five test pieces were prepared for each optical laminate of Examples 1 and 2 and Comparative Example 1. Next, in the test piece, the thickness of the portion where the bending in the repeated bending test is scheduled was measured with a scanning electron microscope (product name "JSM-7100F", manufactured by Nihon Denshi Co., Ltd.). The thickness was uniform (322 μm) (the same applies to the test piece described later before the repeated bending test). Next, as shown in Fig. 2A, both ends of the test piece S were fixed to gripping portions C1 and C2 of a U-shaped stretching tester (manufactured by Yuasa System Machinery). Next, under the conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute, and a bending number of 10000 (first bending condition) by the same tester in an environment of a temperature of 25 ° C. and a relative humidity of 55%. , a repeated bending test was conducted (first bending test). In the repeated bending test, a series of processes including the first process and the second process were set as one cycle (one reciprocation), and this one cycle was repeated a plurality of times (number of bends). In the first step, the test piece S was bent from a flat shape (FIG. 2A) to a U-shape (FIG. 2B) with the PI film side as the inside of the bend. In the second process, the test piece S was returned to a flat shape (FIG. 2A) after the first process.

After the repeated bending test, the minimum thickness and maximum thickness in the repeatedly bent portion P (cross-hatched in Figs. 2A and 2B) of the test piece S were determined by scanning electron microscope (product name "JSM- 7100F", manufactured by Nihon Denshi Co., Ltd.) (thickness measurement). The results are shown in Table 1 as the minimum thickness h ₁₁ and maximum thickness h ₁₂ after the test. Table 1 also shows the ratio R1 (first ratio) of the maximum thickness h ₁₂ to the minimum thickness h ₁₁ .

In addition, the appearance of the portion to be bent (P) of the test piece (S) was observed. Regarding the bonding reliability between the optical members in the optical laminate, in all of the five test pieces, the case where the surface of the bent portion P is flat and there is no change in appearance is evaluated as "excellent", and 3 In one or four test pieces, the surface of the portion to be bent P is flat and there is no change in appearance (that is, in one or two test pieces, the surface of the portion P to be bent is slightly When unevenness was confirmed) was evaluated as "good", and in all five test pieces, when unevenness was confirmed on the surface of the portion to be bent P, it was evaluated as "poor" (reliability evaluation). The results are shown in Table 1.

With respect to another test piece (width 25 mm × length 100 mm) cut out from the optical laminate, as a repeated bending test, except that the second bending test was performed instead of the first bending test, the same repeated bending test as described above, thickness measurement, and reliability evaluation. conducted. The second bending test was conducted under the first bending condition at a temperature of 85°C and in a dry environment. The minimum thickness h ₂₁ and the maximum thickness h ₂₂ in the bent portion P after the test, the ratio R2 of the maximum thickness h ₂₂ to the minimum thickness h ₂₁ (second ratio), and the ratio of the ratio R2 to the ratio R1 (R2/R1) is shown in Table 1. Table 1 also shows the reliability evaluation results.

With respect to another test piece (width 25 mm × length 100 mm) cut out from the optical laminate, the same repeated bending test as described above, thickness measurement and reliability evaluation, except that the third bending test was performed instead of the first bending test as a repeated bending test. conducted. The third bending test was conducted under the conditions of a bending angle of 180 °, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute, and a bending frequency of 50000 (second bending condition) in an environment of a temperature of 25 ° C. and a relative humidity of 55%. . Table 1 shows the minimum thickness h ₃₁ and maximum thickness h ₃₂ and the ratio R3 (third ratio) of the maximum thickness h ₃₂ to the minimum thickness h ₃₁ in the bent portion P after the test. Table 1 also shows the reliability evaluation results.

With respect to another test piece (25 mm in width x 100 mm in length) cut out from the optical laminate, the same repeated bending test as described above, thickness measurement and reliability evaluation, except that the fourth bending test was performed instead of the first bending test as a repeated bending test. conducted. The fourth bending test was conducted under the second bending condition at a temperature of 85°C and in a dry environment. The minimum thickness h ₄₁ and the maximum thickness h ₄₂ in the bent portion P after the test, the ratio R4 of the maximum thickness h ₄₂ to the minimum thickness h ₄₁ (fourth ratio), and the ratio of the ratio R4 to the ratio R3 (R4/R3) is shown in Table 1. Table 1 also shows the reliability evaluation results.

With respect to another test piece (25 mm in width x 100 mm in length) cut out from the optical laminate, the same repeated bending test as described above, thickness measurement and reliability evaluation, except that the fifth bending test was performed instead of the first bending test as a repeated bending test. conducted. The fifth bending test was conducted under the conditions of a bending angle of 180 °, a bending outer diameter of 3 mm, a bending speed of 60 reciprocations/minute, and a bending frequency of 50000 (third bending condition) in an environment of a temperature of 25 ° C. and a relative humidity of 55%. . Table 1 shows the minimum thickness h ₅₁ and maximum thickness h ₅₂ and the ratio R5 (fifth ratio) of the maximum thickness h ₅₂ to the minimum thickness h ₅₁ in the bent portion P after the test. Table 1 also shows the reliability evaluation results.

With respect to the other test piece (25 mm in width x 100 mm in length) cut out from the optical laminate, the same repeated bending test as described above, thickness measurement and reliability evaluation, except that the sixth bending test was performed instead of the first bending test as a repeated bending test. conducted. The sixth bending test was conducted under the third bending condition at a temperature of 85°C and in a dry environment. The minimum thickness h ₆₁ and the maximum thickness h ₆₂ in the bent portion P after the test, the ratio R6 of the maximum thickness h ₆₂ to the minimum thickness h ₆₁ (sixth ratio), and the ratio of the ratio R6 to the ratio R5 (R6/R5) is shown in Table 1. Table 1 also shows the reliability evaluation results.

X: optical stack
11: optical member (first optical member)
12: optical member (second optical member)
13: optical member (third optical member)
21: pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer)
22: pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer)
H: thickness direction

Claims (9)

A first optical member, a first pressure sensitive adhesive layer, a second optical member, a second pressure sensitive adhesive layer, and a third optical member are provided in order in the thickness direction, and the first pressure sensitive adhesive is provided between the first and second optical members. An optical laminated body bonded by layers and bonded between the second and third optical members by the second pressure-sensitive adhesive layer,
After a repeated bending test at 25° C. under the first bending conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute and a bending number of 10000, the maximum for the minimum thickness in the repeatedly bent portion in the test The optical laminate, wherein the first ratio of the thickness is 1.2 or less. According to claim 1,
After the repeated bending test at 85 ° C. under the first bending condition, the second ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.5 or less, the optical laminate. According to claim 2,
The optical laminate, wherein the ratio of the second ratio to the first ratio is 0.95 or more and 1.3 or less. After a repeated bending test at 25°C under the second bending conditions of a bending angle of 180°, a bending outer diameter of 4 mm, a bending speed of 60 reciprocations/minute and a bending number of 50000, the maximum for the minimum thickness in the repeatedly bent portion in the test The third ratio of the thickness is 1.3 or less, the optical laminate. According to claim 4,
After the repeated bending test at 85 ° C. under the second bending condition, the fourth ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.6 or less, the optical laminate. According to claim 5,
The optical laminate, wherein the ratio of the fourth ratio to the third ratio is 0.95 or more and 1.3 or less. After a repeated bending test at 25°C under the third bending conditions of a bending angle of 180°, a bending outer diameter of 3 mm, a bending speed of 60 reciprocations/minute and a bending number of 50000, the maximum for the minimum thickness in the repeatedly bent portion in the test The fifth ratio of the thickness is 1.4 or less, the optical laminate. According to claim 7,
After the repeated bending test at 85 ° C. under the third bending condition, the sixth ratio of the maximum thickness to the minimum thickness in the repeatedly bent portion in the test is 1.7 or less, the optical laminate. According to claim 8,
The optical laminate, wherein the ratio of the sixth ratio to the fifth ratio is 0.95 or more and 1.3 or less.

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