CN116333610A - Optical adhesive sheet - Google Patents

Optical adhesive sheet Download PDF

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Publication number
CN116333610A
CN116333610A CN202211658399.3A CN202211658399A CN116333610A CN 116333610 A CN116333610 A CN 116333610A CN 202211658399 A CN202211658399 A CN 202211658399A CN 116333610 A CN116333610 A CN 116333610A
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China
Prior art keywords
adhesive sheet
meth
acrylate
mass
strain stress
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Pending
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CN202211658399.3A
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Chinese (zh)
Inventor
山本真也
永田拓也
天野光
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Nitto Denko Corp
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Nitto Denko Corp
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    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/30Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38Pressure-sensitive adhesives [PSA]
    • C09J7/381Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
    • C09J7/385Acrylic polymers
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/10Adhesives in the form of films or foils without carriers
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02Non-macromolecular additives
    • C09J11/06Non-macromolecular additives organic
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/02Homopolymers or copolymers of acids; Metal or ammonium salts thereof
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J4/00Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • C09J4/06Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00Adhesives in the form of films or foils
    • C09J7/30Adhesives in the form of films or foils characterised by the adhesive composition
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/30Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/312Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier parameters being the characterizing feature
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00Additional features of adhesives in the form of films or foils
    • C09J2301/40Additional features of adhesives in the form of films or foils characterized by the presence of essential components
    • C09J2301/416Additional features of adhesives in the form of films or foils characterized by the presence of essential components use of irradiation
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Adhesive Tapes (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)

Abstract

An optical adhesive sheet suitable for flexible device applications is provided. The adhesive sheet (10) of the present invention is an optical adhesive sheet. The adhesive sheet (10) has strain stress S 200 (N/cm 2 ) As strain stress at 200% elongation in the 1 st tensile test at 25℃and a tensile speed of 50 mm/min, there was strain stress S' 200 (N/cm 2 ) As a film at 25℃and a drawing speed of 600mStrain stress at 200% elongation in the 2 nd tensile test under the condition of m/min, strain stress S 200 And strain stress S' 200 The ratio of (2) is 0.8 or less.

Description

Optical adhesive sheet
Technical Field
The present invention relates to an optical adhesive sheet.
Background
The display panel has a laminated structure including elements such as a pixel panel, a polarizing plate, a touch panel, and a cover film. In the manufacturing process of such a display panel, for example, an optically transparent adhesive sheet (optical adhesive sheet) is used for bonding elements included in the laminated structure to each other.
On the other hand, in smart phone applications and tablet terminal applications, display panels that can be repeatedly folded (foldable) have been developed. The foldable display panel is in particular repeatedly deformable between a curved shape and a flat non-curved shape. In such a foldable display panel, each element in the laminated structure is manufactured so as to be bendable repeatedly, and a thin optical adhesive sheet is used for bonding between the elements. An optical pressure-sensitive adhesive sheet for flexible devices such as a foldable display panel is described in patent document 1 below, for example.
Prior art literature
Patent literature
Patent document 1: japanese patent laid-open publication No. 2018-111754
Disclosure of Invention
Problems to be solved by the invention
In the conventional art, an optical pressure-sensitive adhesive sheet is easily peeled from an adherend as an element at a bending portion of a foldable display panel. This is because, when the display panel is bent, a large tensile stress is locally generated in the bent portion of the optical adhesive sheet. In the folded portion of the optical adhesive sheet, for example, the greater the tensile stress in the shearing direction to the element (adherend), the more easily peeling occurs between the optical adhesive sheet and the element. In addition, in the folding process of the foldable display panel, the faster the folding speed is, the greater the stress generated in the optical adhesive sheet is, and the peeling between the optical adhesive sheet and the element is liable to occur. The occurrence of such peeling is not preferable because it causes malfunction of the device. An optical pressure-sensitive adhesive sheet for a foldable display panel is required to be less likely to be peeled off from an element (adherend) at a high level.
On the other hand, as a flexible device, a rollable display panel has also been developed. The rollable display panel may be repeatedly deformed between a rolled shape after being rolled up in whole or in part and a flat shape after being unrolled in whole, for example. In such a rollable display panel, each element in the laminated structure is made to be repeatedly deformable, and a thin optical adhesive sheet is used for bonding between such elements. In the case of a rolled shape of a rollable display panel, the whole of the optical adhesive sheet joined to the element of the rolled shape is continuously subjected to tensile stress from the element. In addition, the faster the winding speed, the greater the stress generated in the optical adhesive sheet during winding of the rollable display panel, and the more easily peeling between the optical adhesive sheet and the element. Such an optical pressure-sensitive adhesive sheet is required to be less likely to be peeled off from the element (adherend) at a high level.
The present invention provides an optical adhesive sheet suitable for flexible device applications.
Solution for solving the problem
The invention [1 ]]Comprises an optical adhesive sheet having a strain stress S 200 (N/cm 2 ) As strain stress at 200% elongation in the 1 st tensile test at 25℃and a tensile speed of 50 mm/min, there was strain stress S' 200 (N/cm 2 ) As strain stress at 200% elongation in the 2 nd tensile test at 25℃and at a tensile speed of 600 mm/min, the strain stress S was the above 200 And the strain stress S 'is as described above' 200 The ratio of (2) is 0.8 or less.
The invention [2 ]]Comprises the above [1 ]]The optical adhesive sheet, wherein the strain stress S at 500% elongation in the 1 st tensile test 500 (N/cm 2 ) And the strain stress S 200 The ratio of (2) is 1.8 or less.
The invention [3 ]]Comprises the above [1 ]]Or [2 ]]The optical adhesive sheet, wherein the strain stress S at 1000% elongation in the 1 st tensile test 1000 Is 18N/cm 2 The following is given.
The invention [4 ]]Comprises the above [1 ]]~[3]The optical adhesive sheet according to any one of the above, wherein the strain stress S 'at 500% elongation in the 2 nd tensile test' 500 (N/cm 2 ) And front ofThe strain stress S' 200 The ratio of (2) is 1.7 or less.
The invention [5 ]]Comprises the above [1 ]]~[4]The optical adhesive sheet according to any one of the above, wherein the strain stress S 'at 1000% elongation in the 2 nd tensile test' 1000 25N/cm 2 The following is given.
ADVANTAGEOUS EFFECTS OF INVENTION
In the optical adhesive sheet of the present invention, as described above, the strain stress S at 200% elongation in the 1 st tensile test (25 ℃ C., tensile speed 50 mm/min) was as follows 200 (N/cm 2 ) Strain stress S 'at 200% elongation in the 2 nd tensile test (25 ℃ C., tensile speed 600 mm/min)' 200 (N/cm 2 ) The ratio of (2) is 0.8 or less and smaller. Such an optical adhesive sheet is suitable for suppressing internal stress such as tensile stress generated in the optical adhesive sheet when the adherend to which the adhesive sheet is attached is deformed, and therefore, is suitable for suppressing peeling of the optical adhesive sheet from the adherend. Such an optical adhesive sheet is suitable for flexible device use.
Drawings
Fig. 1 is a schematic cross-sectional view of an embodiment of the optical adhesive sheet of the present invention.
Fig. 2 shows an example of a method of using the optical adhesive sheet of the present invention. Fig. 2 a shows a step of bonding the optical adhesive sheet to the 1 st adherend, fig. 2B shows a step of bonding the 1 st adherend and the 2 nd adherend via the optical adhesive sheet, and fig. 2C shows a curing step.
Description of the reference numerals
10 pressure-sensitive adhesive sheet (optical pressure-sensitive adhesive sheet)
11 12 adhesive faces
H thickness direction
L1, L2 release liner
21 st component 1
22 nd component 2
Detailed Description
As shown in fig. 1, an adhesive sheet 10 as an embodiment of the optical adhesive sheet of the present invention has a sheet shape having a predetermined thickness, and extends in a direction (plane direction) orthogonal to the thickness direction H. The pressure-sensitive adhesive sheet 10 has a pressure-sensitive adhesive surface 11 on one surface in the thickness direction H and a pressure-sensitive adhesive surface 12 on the other surface in the thickness direction H. Fig. 1 exemplarily shows a state in which release liners L1, L2 are attached to the adhesive surfaces 11, 12 of the adhesive sheet 10. The release liner L1 is disposed on the adhesive surface 11. The release liner L2 is disposed on the adhesive surface 12. The release liners L1 and L2 are peeled off at predetermined timings when the adhesive sheet 10 is used.
The pressure-sensitive adhesive sheet 10 is an optically transparent pressure-sensitive adhesive sheet disposed at a light transmission portion of a flexible device. As the flexible device, for example, a flexible display panel can be cited. Examples of the flexible display panel include a foldable display panel and a rollable display panel. The flexible display panel has a laminated structure including elements such as a pixel panel, a film-like polarizing plate (polarizing film), a touch panel, and a cover film. The adhesive sheet 10 is used for bonding elements included in a laminated structure to each other, for example, in a manufacturing process of a flexible display panel.
The adhesive sheet 10 has a strain stress S 200 As strain stress at 200% elongation in the 1 st tensile test at 25℃and a tensile speed of 50 mm/min, there was strain stress S' 200 As strain stress at 200% elongation in the 2 nd tensile test at 25℃and at a tensile speed of 600 mm/min, strain stress S 200 And strain stress S' 200 Ratio (S) 200 /S' 200 ) Is 0.8 or less. The method for carrying out the 1 st tensile test and the 2 nd tensile test is specifically as described in examples described later. Ratio (S) 200 /S' 200 ) The configuration of 0.8 or less is suitable for suppressing internal stress such as tensile stress generated in the adhesive sheet 10 when the adherend to which the adhesive sheet 10 is attached is deformed, and therefore suitable for suppressing peeling of the adhesive sheet 10 from the adherend. Such an adhesive sheet 10 is suitable for flexible device applications.
From the viewpoint of suppressing the peeling, the ratio (S 200 /S' 200 ) Preferably 0.75 or less, more preferably 0.7 or less, further preferably 0.67 or less, further preferably 0.65 or less, further preferably 0.63 or less. Ratio (S) 200 /S' 200 ) For example, 0.1 or more or 0.3 or more.
From the viewpoint of suppressing the difference in the occurrence of stress due to the degree of deformation of the adhesive sheet 10 during low-speed deformation, the strain stress S at 500% elongation in the 1 st tensile test 500 (N/cm 2 ) And strain stress S 200 Ratio (S) 500 /S 200 ) Preferably 1.8 or less, more preferably 1.6 or less, still more preferably 1.5 or less, and still more preferably 1.4 or less. Ratio (S) 500 /S 200 ) For example, 0.1 or more, 0.5 or more, or 1 or more.
From the viewpoint of suppressing the difference in the occurrence of stress due to the degree of deformation of the adhesive sheet 10 during high-speed deformation, the strain stress S 'at 500% elongation in the 2 nd tensile test' 500 (N/cm 2 ) And strain stress S' 200 Ratio (S' 500 /S' 200 ) Preferably 1.7 or less, more preferably 1.5 or less, still more preferably 1.3 or less, still more preferably 1.2 or less. Ratio (S' 500 /S' 200 ) For example, 0.1 or more, 0.5 or more, or 0.8 or more.
From the viewpoint of suppressing the stress generated during and after the low-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, the strain stress S 200 Preferably 15N/cm 2 Below, more preferably 12N/cm 2 Hereinafter, 9N/cm is more preferable 2 Hereinafter, it is more preferably 6N/cm 2 Hereinafter, it is more preferably 4.5N/cm 2 Hereinafter, it is more preferably 4N/cm 2 The following is particularly preferred to be 3.8N/cm 2 The following is given. Stress S of strain 200 For example 0.5N/cm 2 Above, 1N/cm 2 Above, or 1.5N/cm 2 The above. As strain stress S 200 Examples of the method for adjusting the monomer composition of the base polymer in the pressure-sensitive adhesive sheet 10 include adjustment of the molecular weight, adjustment of the blending amount, and adjustment of the crosslinking degree. Such a method of adjusting the strain stress is specific to the strain stress S 500 、S 1000 The same applies to the above-described method.
From the viewpoint of suppressing the stress generated during and after the low-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, the strain stress S 500 Preferably 16N/cm 2 The following is more preferablePreferably 12N/cm 2 Hereinafter, more preferably 8N/cm 2 Below, more preferably 6N/cm 2 Hereinafter, it is more preferably 5N/cm 2 The following is particularly preferred to be 4.8N/cm 2 The following is given. Stress S of strain 500 For example 0.5N/cm 2 Above, 1N/cm 2 Above, or 3N/cm 2 The above.
Strain stress S at 1000% elongation in the 1 st tensile test (25 ℃ C., tensile speed 50 mm/min) 1000 From the viewpoint of suppressing the stress generated during and after the low-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, it is preferably 18N/cm 2 Below, more preferably 15N/cm 2 Hereinafter, it is more preferably 12N/cm 2 The following is more preferably 10N/cm 2 Hereinafter, it is more preferably 8N/cm 2 The following is particularly preferred to be 7.5N/cm 2 The following is given. Stress S of strain 1000 For example 1N/cm 2 Above, 5N/cm 2 Above, or 7N/cm 2 The above.
From the viewpoint of suppressing the stress generated during and after the high-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, the strain stress S' 200 Preferably 14N/cm 2 Hereinafter, it is more preferably 11N/cm 2 Hereinafter, more preferably 8N/cm 2 Hereinafter, more preferably 7N/cm 2 Hereinafter, it is more preferably 6N/cm 2 The following is particularly preferred to be 5.5N/cm 2 The following is given. Stress S 'of strain' 200 For example 0.5N/cm 2 Above, 1N/cm 2 Above, or 2N/cm 2 The above. As strain stress S' 200 Examples of the method for adjusting the monomer composition of the base polymer in the pressure-sensitive adhesive sheet 10 include adjustment of the molecular weight, adjustment of the blending amount, and adjustment of the crosslinking degree. Such a method of adjusting the strain stress is specific to the strain stress S' 500 、S' 1000 The same applies to the above-described method.
From the viewpoint of suppressing the stress generated during and after the high-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, the strain stress S' 500 Preferably 20N/cm 2 Below, more preferably 15N/cm 2 Below, more preferably 12N/cm 2 The following are the followingMore preferably 10N/cm 2 Hereinafter, it is more preferably 8N/cm 2 The following is particularly preferred to be 7.5N/cm 2 The following is given. Stress S 'of strain' 500 For example 0.5N/cm 2 Above, 1N/cm 2 Above, or 3N/cm 2 The above.
From the viewpoint of suppressing the stress generated during and after the high-speed deformation of the adhesive sheet 10 and suppressing the peeling described above, the strain stress S 'at 1000% elongation in the 2 nd tensile test (25 ℃ C., tensile speed 600 mm/min) was suppressed' 1000 Preferably 25N/cm 2 Hereinafter, more preferably 22N/cm 2 Hereinafter, more preferably 20N/cm 2 Below, more preferably 18N/cm 2 Hereinafter, it is more preferably 17N/cm 2 Hereinafter, it is particularly preferably 15N/cm 2 The following is given. Stress S 'of strain' 1000 For example 1N/cm 2 Above, 5N/cm 2 Above, or 8N/cm 2 The above.
The adhesive sheet 10 preferably has an adhesive force of 2N/10mm or more, more preferably 3N/10mm or more, still more preferably 3.5N/10mm or more, still more preferably 4N/10mm or more, particularly preferably 4.5N/10cm, to a polyimide film in a peeling test under peeling conditions of 25℃and peeling angle 180℃and stretching speed 300 mm/min after undergoing lamination to the polyimide film 2 The above. The adhesive force is, for example, 20N/10mm or less.
The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive formed of an adhesive composition. The adhesive sheet 10 (adhesive composition) contains at least a base polymer.
The base polymer is an adhesive component that causes the adhesive sheet 10 to exhibit 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, fluoropolymers, and rubber polymers. The base polymer may be used alone or in combination of two or more. From the viewpoint of ensuring good transparency and adhesion of the adhesive sheet 10, 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 proportion 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 alkyl (meth) acrylates having a linear or branched alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, n-hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-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, a (meth) acrylate having a bicyclic aliphatic hydrocarbon ring, and a (meth) acrylate having an aliphatic hydrocarbon ring having three or more rings. Examples of cycloalkyl (meth) acrylates 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) acrylic acid ester having an aliphatic hydrocarbon ring having a tricyclic or higher group 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.
From the viewpoint of obtaining the balance between the soft property and the adhesive force required for the adhesive sheet for flexible device use in the adhesive sheet 10, at least one selected from alkyl (meth) acrylates having an alkyl group having 3 to 12 carbon atoms is preferably used, more preferably a combination of alkyl (meth) acrylates having an alkyl group having 3 to 12 carbon atoms, a 1 st alkyl (meth) acrylate having a relatively large carbon number of the alkyl group and a 2 nd alkyl (meth) acrylate having a relatively small carbon number of the alkyl group are used, and even more preferably a combination of alkyl (meth) acrylates having an alkyl group having 6 to 8 carbon atoms and alkyl (meth) acrylates having an alkyl group having 5 carbon atoms or less, and particularly preferably a combination of alkyl (meth) acrylates having a linear alkyl group having 6 to 8 carbon atoms and alkyl (meth) acrylates having an alkyl group having 5 carbon atoms or less.
The proportion of the alkyl (meth) acrylate in the monomer component is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, particularly preferably 92% by mass or more, from the viewpoint of appropriately exhibiting basic characteristics such as adhesiveness of the adhesive sheet 10. The ratio is, for example, 99 mass% or less. When the 1 st and 2 nd alkyl (meth) acrylates are used in combination, the proportion of the 1 st alkyl (meth) acrylate in the monomer component is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, particularly preferably 58% by mass or more, and further preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 65% by mass or less, particularly preferably 62% by mass, from the viewpoint of the balance between the soft property and the adhesive force of the adhesive sheet 10. The proportion of the alkyl (meth) acrylate 2 in the monomer component is preferably 20 mass% or more, more preferably 25 mass% or more, further preferably 28 mass% or more, and further preferably 40 mass% or less, more preferably 35 mass% or less, further preferably 32 mass% or less, from the viewpoint of balance between the soft nature and the adhesive force of the adhesive sheet 10.
The monomer component may also 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 into a crosslinking point of 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.
The proportion of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and particularly preferably 7% by mass or more, from the viewpoints of introduction of the crosslinked structure into the acrylic polymer and securing of cohesive force of the adhesive sheet 10. From the viewpoint of adjustment of the polarity of the acrylic polymer (regarding compatibility of various additive components in the adhesive sheet 10 and the acrylic polymer), the ratio is preferably 30 mass% or less, more preferably 20 mass% or less.
Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.
The proportion of the carboxyl group-containing monomer in the monomer component is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, and still more preferably 0.8 mass% or more from the viewpoints of introduction of a crosslinked structure into the acrylic polymer, securing of cohesive force of the adhesive sheet 10, and securing of adhesion force of the adhesive sheet 10 to an adherend. From the viewpoint of adjustment of the glass transition temperature of the acrylic polymer and avoidance of corrosion risk of the adherend by the acid, the ratio is preferably 10 mass% or less, more preferably 5 mass% or less.
Examples of the monomer having a nitrogen atom-containing ring include: n-vinyl-2-pyrrolidone, N-methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl imidazole, N-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.
The proportion of the monomer having a nitrogen atom-containing ring in the monomer component is preferably 0.5 mass% or more, more preferably 1 mass% or more, and still more preferably 1.5 mass% or more, from the viewpoints of ensuring the cohesive force of the adhesive sheet 10 and ensuring the adhesion force of the adhesive sheet 10 to an adherend. From the viewpoints of adjustment of the glass transition temperature of the acrylic polymer and adjustment of the polarity of the acrylic polymer (regarding compatibility of various additive components in the adhesive sheet 10 with the acrylic polymer), the ratio is preferably 20 mass% or less, more preferably 10 mass% or less.
The monomer component may also comprise other copolymerizable monomers. Examples of the other copolymerizable monomer include an acid anhydride monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, an epoxy group-containing monomer, a cyano group-containing monomer, an alkoxy group-containing monomer, and an aromatic vinyl compound. These other copolymerizable monomers may be used alone or in combination of two or more.
The monomer component preferably contains an alkyl (meth) acrylate 1 (alkyl group having a relatively large carbon number), an alkyl (meth) acrylate 2 (alkyl group having a relatively small carbon number), a hydroxyl group-containing monomer, and a monomer having a nitrogen atom-containing ring, from the viewpoint of both securing the adhesive force of the adhesive sheet 10 and suppressing the occurrence of stress during deformation. The 1 st (meth) acrylic acid alkyl ester is more preferably an alkyl (meth) acrylic acid alkyl ester having an alkyl group having 6 to 8 carbon atoms, still more preferably an alkyl (meth) acrylic acid alkyl ester having a linear alkyl group having 6 to 8 carbon atoms, and particularly preferably at least one selected from the group consisting of n-butyl acrylate (NOAA) and n-hexyl acrylate (HxA). The 2 nd alkyl (meth) acrylate is more preferably an alkyl (meth) acrylate having an alkyl group having 5 or less carbon atoms, and still more preferably n-Butyl Acrylate (BA). More preferably, the hydroxyl group-containing monomer is at least one selected from the group consisting of 4-hydroxybutyl acrylate (4 HBA) and 2-hydroxyethyl acrylate (2 HEA). The monomer having a nitrogen atom-containing ring is more preferably N-vinyl-2-pyrrolidone (NVP) from the viewpoint of designing the elastic modulus of the adhesive sheet 10 to be high from room temperature to high temperature.
The base polymer preferably has a crosslinked structure. As a method for introducing a crosslinked structure into a base polymer, the following methods can be mentioned: a method of compounding a base polymer having a functional group capable of reacting with a crosslinking agent and a crosslinking agent into an adhesive composition to react the base polymer and the crosslinking agent in an adhesive sheet (method 1); and a method (method 2) in which a polyfunctional monomer as a crosslinking agent is contained in a monomer component for forming a base polymer, and a branched structure (crosslinked structure) is introduced into a polymer chain by polymerization of the monomer component. These methods may also be used in combination.
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 two or more. As the crosslinking agent, an isocyanate crosslinking agent, a peroxide crosslinking agent, and an epoxy crosslinking agent are preferably used because of their high reactivity with hydroxyl groups and carboxyl groups in the base polymer and easy introduction of a crosslinked structure.
Examples of the isocyanate crosslinking agent include toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate. 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 CORONATE L (trimethylolpropane adduct of toluene diisocyanate, east Cao Zhizao), CORONATE HL (trimethylolpropane adduct of hexamethylene diisocyanate, east Cao Zhizao), CORONATE HX (isocyanurate of hexamethylene diisocyanate, east Cao Zhizao), TAKENATE D N (trimethylolpropane adduct of xylylene diisocyanate, manufactured by three-well chemical), and TAKENATE 600 (1, 3-bis (isocyanatomethyl) cyclohexane, manufactured by three-well chemical).
Examples of the peroxide crosslinking agent include dibenzoyl peroxide, di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, and t-butyl peroxypivalate.
Examples of the epoxy crosslinking agent include bisphenol a, epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N' -tetraglycidyl m-xylylenediamine, and 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane.
Isocyanate crosslinking agents (particularly difunctional isocyanate crosslinking agents) and peroxide crosslinking agents are preferable from the viewpoint of ensuring the flexibility of the adhesive sheet 10. The isocyanate crosslinking agent (particularly, trifunctional isocyanate crosslinking agent) is preferable from the viewpoint of securing durability of the adhesive sheet 10. In the base polymer, the difunctional isocyanate crosslinker and the peroxide crosslinker form softer two-dimensional crosslinks, while the trifunctional isocyanate crosslinker forms stronger three-dimensional crosslinks. From the viewpoint of achieving both durability and flexibility of the adhesive sheet 10, it is preferable to use a trifunctional isocyanate crosslinking agent in combination with a peroxide crosslinking agent and/or a difunctional isocyanate crosslinking agent.
From the viewpoint of ensuring cohesive force of the adhesive sheet 10, 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. From the viewpoint of ensuring good tackiness of the adhesive sheet 10, the amount of the crosslinking agent to be blended is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the base polymer.
In the method 2, the monomer component (including the polyfunctional monomer for introducing a crosslinked structure and other monomers) may be polymerized at one time or in multiple stages. In the multistage polymerization method, first, a monofunctional monomer used for forming a base polymer is polymerized (prepolymerized), thereby producing a prepolymer composition containing a part of a polymer (a mixture of a polymer having a low degree of polymerization and an unreacted monomer). Next, after adding a polyfunctional monomer as a crosslinking agent to the prepolymer composition, a part of the polymer is polymerized with the polyfunctional monomer (main polymerization).
Examples of the polyfunctional monomer include polyfunctional (meth) acrylates having 2 or more ethylenically unsaturated double bonds in 1 molecule. As the polyfunctional monomer, a polyfunctional acrylate is preferable from the viewpoint of being capable of introducing a crosslinked structure by active energy ray polymerization (photopolymerization).
Examples of the multifunctional (meth) acrylate include difunctional (meth) acrylate, trifunctional (meth) acrylate, and multifunctional (meth) acrylate having four or more functions.
Examples of the difunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol di (meth) acrylate, stearic acid modified pentaerythritol di (meth) acrylate, dicyclopentenyl di (meth) acrylate, di (meth) acryl isocyanurate, and alkylene oxide modified bisphenol di (meth) acrylate.
Examples of the trifunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and tris (acryloxyethyl) isocyanurate.
Examples of the polyfunctional (meth) acrylate having four or more functions include di (trimethylolpropane) tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, alkyl-modified dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate.
As the polyfunctional (meth) acrylate, a polyfunctional (meth) acrylate having four or more functions is preferably used, and dipentaerythritol hexaacrylate is more preferably used.
From the viewpoint of ensuring cohesive force of the adhesive sheet 10, the amount of the polyfunctional monomer as a crosslinking agent in the monomer component is, for example, 0.01 parts by mass or more, preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, and still more preferably 0.07 parts by mass or more, per 100 parts by mass of the monofunctional monomer. From the viewpoint of ensuring good tackiness of the adhesive sheet 10, the blending amount of the polyfunctional monomer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, still more preferably 0.2 parts by mass or less, and particularly preferably 0.1 part by mass or less relative to 100 parts by mass of the monofunctional monomer.
The acrylic polymer can be formed by polymerizing the above monomer components. Examples of the polymerization method include solution polymerization, photopolymerization in the absence of a solvent (for example, UV polymerization), bulk polymerization, and emulsion polymerization. As the solvent for the solution polymerization, for example, ethyl acetate and toluene are used. As the initiator for polymerization, for example, a thermal polymerization initiator and a photopolymerization initiator are used. The amount of the polymerization initiator used is, for example, 0.05 parts by mass or more, preferably 0.08 parts by mass or more, and 1 part by mass or less, preferably 0.5 parts by mass or less, based on 100 parts by mass of the monomer component.
Examples of the thermal polymerization initiator include azo polymerization initiators and peroxide polymerization initiators. Examples of the azo polymerization initiator include 2,2' -azobisisobutyronitrile, 2' -azobis-2-methylbutyronitrile, dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2' -azobis (2-amidinopropane) dihydrochloride, 2' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2' -azobis (2-methylpropionamidine) disulfate, and 2,2' -azobis (N, N ' -dimethyleneisobutyl amidine) dihydrochloride. Examples of the peroxide polymerization initiator include dibenzoyl peroxide, t-butyl peroxymaleate, and lauroyl peroxide.
Examples of the photopolymerization initiator include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α -ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzil-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators.
The weight average molecular weight of the base polymer is preferably 10 ten thousand or more, more preferably 30 ten thousand or more, and still more preferably 50 ten thousand or more from the viewpoint of securing cohesive force of the adhesive sheet 10. 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 preferably 0℃or lower, more preferably-10℃or lower, and still more preferably-20℃or lower. The glass transition temperature is, for example, at least-80 ℃.
As the glass transition temperature (Tg) of the base polymer, a glass transition temperature (theoretical value) obtained based on the following Fox formula can be used. The Fox formula is a relation between the glass transition temperature Tg of the polymer and the glass transition temperature Tgi of the homopolymer of the monomers constituting the polymer. In the following Fox formula, tg represents the glass transition temperature (. Degree. C.) of the polymer, wi represents the weight fraction of the monomer i constituting the polymer, tgi represents the glass transition temperature (. Degree. C.) of the homopolymer formed from the monomer i. For the glass transition temperature of the homopolymer, literature values can be used. For example, glass transition temperatures of various homopolymers are listed in "Polymer Handbook" (4 th edition, john Wiley & Sons, inc., 1999) and "synthetic resin entrance to New Polymer library 7 paint" (North Korea, polymer journal, congress, 1995). On the other hand, the glass transition temperature of a homopolymer of a monomer can be obtained by a method specifically described in JP-A2007-51271.
Fox 1/(273+tg) =Σ [ Wi/(273+tgi) ]
The adhesive composition may also 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 required. Examples of the other components include solvents, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents. Examples of the solvent include a polymerization solvent used when polymerizing an acrylic polymer, if necessary, and a solvent added to a polymerization reaction solution after polymerization. As the solvent, for example, ethyl acetate and toluene are used.
The pressure-sensitive adhesive sheet 10 can be produced, for example, by coating the pressure-sensitive adhesive composition described above on a release liner L1 (1 st release liner) to form a coating film, and then drying the coating film.
Examples of the release liner L1 include a flexible plastic film. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film, and polyester film. The thickness of the release liner L1 is, for example, 3 μm or more and, for example, 200 μm or less. The surface of the release liner L1 is preferably subjected to a release treatment.
Examples of the method for applying the adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50 to 200 ℃. The drying time is, for example, 5 seconds to 20 minutes.
A release liner L2 (release liner 2) may be further laminated on the adhesive sheet 10 on the release liner L1. The release liner L2 is preferably a flexible plastic film having a release-treated surface. As the release liner L2, the plastic film described above with respect to the release liner L1 can be used.
In the above manner, the adhesive sheet 10 having the adhesive surfaces 11 and 12 covered and protected by the release liners L1 and L2 can be manufactured.
The thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of securing sufficient adhesiveness to an adherend and handling properties. The thickness of the pressure-sensitive adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, particularly preferably 50 μm or less, from the viewpoint of thinning of the flexible device.
The haze of the pressure-sensitive adhesive sheet 10 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. The haze of the pressure-sensitive adhesive sheet 10 can be measured by a haze meter based on JIS K7136 (year 2000). Examples of the haze meter include "NDH2000" manufactured by Nippon electric color industry Co., ltd., and "HM-150" manufactured by Toku Kogyo Co., ltd.
The total light transmittance of the pressure-sensitive adhesive sheet 10 is preferably 60% or more, more preferably 80% or more, and still more preferably 85% or more. The total light transmittance of the pressure-sensitive adhesive sheet 10 is, for example, 100% or less. The total light transmittance of the adhesive sheet 10 can be measured based on JIS K7375 (2008).
Fig. 2 a to 2C show an example of a method of using the adhesive sheet 10.
In this method, first, as shown in a of fig. 2, the adhesive sheet 10 is attached to one surface of the 1 st member 21 (adherend) in the thickness direction H. The 1 st member 21 is, for example, one element of a laminated structure of a flexible display panel. Examples of the element include a pixel panel, a film-like polarizing plate (polarizing film), a touch panel, and a cover film (the same applies to the 2 nd member 22 described later). In this step, the 1 st member 21 is provided with an adhesive sheet 10 for bonding with other members.
Next, as shown in fig. 2B, one surface side in the thickness direction H of the 1 st member 21 and the other surface side in the thickness direction H of the 2 nd member 22 are joined by the adhesive sheet 10 on the 1 st member 21. The 2 nd member 22 is, for example, other elements in the laminated structure of the flexible display panel.
Next, as shown in fig. 2C, the adhesive sheet 10 between the 1 st member 21 and the 2 nd member 22 is cured. By curing, the bonding force between the adhesive sheet 10 and the members 21, 22 is improved. The curing temperature is, for example, 20℃to 160 ℃. The curing time is, for example, 1 minute to 21 days. As curing, autoclave treatment (heat and pressure treatment) is carried out at a temperature of, for example, 30 to 80℃and a pressure of, for example, 0.1 to 0.8MPa for a treatment time of, for example, 15 minutes or more.
In the adhesive sheet 10 used in the manufacturing process of the flexible display panel, for example, as in the above operation, as described above, the ratio (S 200 /S' 200 ) Is less than 0.8 and smaller. Such a configuration is suitable for suppressing internal stress such as tensile stress generated in the adhesive sheet 10 when the adherend to which the adhesive sheet 10 is attached is deformed, and therefore, is suitable forThe peeling of the adhesive sheet 10 from the adherend is suppressed. Such an adhesive sheet 10 is suitable for flexible device applications.
Examples
The present invention will be specifically described with reference to the following examples. However, the present invention is not limited to the examples. Specific numerical values such as the compounding amount (content), physical property value, and parameter described below may be replaced with upper limits (numerical values defined as "below" or "less" or lower limits (numerical values defined as "above" or "exceeding") of the compounding amount (content), physical property value, and parameter described in the above-described "specific embodiment".
[ example 1 ]
Preparation of prepolymer composition
In a flask, after 60 parts by mass of N-octyl acrylate (NOAA), 30 parts by mass of N-Butyl Acrylate (BA), 8 parts by mass of 4-hydroxybutyl acrylate (4 HBA) and 2 parts by mass of N-vinyl-2-pyrrolidone (NVP) were added to a monomer mixture containing 0.05 parts by mass of 2, 2-dimethoxy-1, 2-diphenylethane-1-one (trade name "Omnirad651", manufactured by IGM Resins) as a 1 st photopolymerization initiator and 0.05 parts by mass of 1-hydroxycyclohexyl phenyl ketone (trade name "Omnirad184", manufactured by IGM Resins) as a 2 nd photopolymerization initiator, the mixture was irradiated with ultraviolet light under a nitrogen atmosphere to polymerize a part of monomer components in the mixture, thereby obtaining a 1 st prepolymer composition (containing monomer components which were not subjected to polymerization reaction).
Preparation of adhesive composition
100 parts by mass of the 1 st prepolymer composition, 0.08 part by mass of dipentaerythritol hexaacrylate (DPHA) as a crosslinking agent, 0.05 part by mass of 2, 2-dimethoxy-1, 2-diphenylethan-1-one (trade name "Omnirad651", manufactured by IGM Resins Co., ltd.) as a photopolymerization initiator, and 0.3 part by mass of a silane coupling agent (trade name "KBM-403", manufactured by the Xinyue chemical industry) were mixed to obtain a 1 st adhesive composition.
Formation of adhesive layer
1 st release liner having release treated surface on one side (trade name "Diadel MRF#38", thickness 38 μm, mitsubishi chemical corporation) was coated with the 1 st adhesive composition to form a coating film. Then, a release treated surface of a 2 nd release liner (trade name "diasol mrn#38", thickness 38 μm, manufactured by mitsubishi chemical corporation) having a release treated surface on one side was bonded to the coating film on the 1 st release liner. Then, the coating film between the release liners was irradiated with ultraviolet rays, and the coating film was photo-cured to form an adhesive layer (thickness: 50 μm). In the ultraviolet irradiation, a black light lamp was used as an irradiation light source, and the irradiation intensity was set to 5mW/cm 2
In the above manner, an adhesive sheet (thickness: 50 μm) of example 1 with a release liner on both sides was produced. The relevant composition of the adhesive sheet of example 1 is shown in table 1 in parts by mass (the same applies to examples and comparative examples described later).
[ example 2 ]
An adhesive sheet of example 2 was produced in the same manner as the adhesive sheet of example 1, except that the blending amount of the crosslinking agent was changed from 0.08 parts by mass to 0.04 parts by mass and no photopolymerization initiator was added in the preparation of the adhesive composition.
[ example 3 ]
An adhesive sheet of example 3 was produced in the same manner as the adhesive sheet of example 1, except for the following. In the preparation of the prepolymer composition, the compounding amount of the 1 st photopolymerization initiator (trade name "Omnirad 651") was replaced with 0.035 parts by mass, and the compounding amount of the 2 nd photopolymerization initiator (trade name "Omnirad 184") was replaced with 0.05 parts by mass. In the preparation of the adhesive composition, the compounding amount of the crosslinking agent was replaced with 0.02 parts by mass from 0.08 parts by mass, and no photopolymerization initiator was added.
[ example 4 ]
An adhesive sheet of example 4 was produced in the same manner as the adhesive sheet of example 1, except for the following. In the preparation of the prepolymer composition, the compounding amount of the 1 st photopolymerization initiator (trade name "Omnirad 651") was replaced with 0.07 parts by mass, and the compounding amount of the 2 nd photopolymerization initiator (trade name "Omnirad 184") was replaced with 0.05 parts by mass. In the preparation of the adhesive composition, the compounding amount of the crosslinking agent was replaced with 0.04 parts by mass from 0.08 parts by mass, and no photopolymerization initiator was added.
[ example 5 ]
An adhesive sheet of example 5 was produced in the same manner as the adhesive sheet of example 1, except for the following. In the preparation of the prepolymer composition, the compounding amount of NOAA was replaced with 70 parts by mass, and the compounding amount of BA was replaced with 20 parts by mass, from 60 parts by mass. In the preparation of the adhesive composition, the compounding amount of the crosslinking agent was replaced with 0.05 parts by mass from 0.08 parts by mass.
[ example 6 ]
An adhesive sheet of example 6 was produced in the same manner as the adhesive sheet of example 1, except for the following. In the preparation of the adhesive composition, the compounding amount of the crosslinking agent was replaced with 0.05 parts by mass from 0.08 parts by mass.
Comparative example 1
Preparation of prepolymer composition
In a flask, to a monomer mixture containing 57 parts by mass of n-Butyl Acrylate (BA), 12 parts by mass of cyclohexyl acrylate (CHA) and 31 parts by mass of 4-hydroxybutyl acrylate (2 HBA), 0.09 parts by mass of a 1 st photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins) and 0.09 parts by mass of a 2 nd photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins) were added, and after that, the mixture was irradiated with ultraviolet rays under a nitrogen atmosphere, whereby a part of monomer components in the mixture was polymerized to obtain a 2 nd prepolymer composition having a polymerization rate of about 10%.
Preparation of adhesive composition
100 parts by mass of the 2 nd prepolymer composition, 0.12 parts by mass of DPHA as a crosslinking agent, and 0.3 parts by mass of a silane coupling agent (trade name "KBM-403", manufactured by Xinyue chemical industry) were mixed to obtain a 2 nd adhesive composition.
Formation of adhesive layer
An adhesive layer (thickness: 50 μm) sandwiched by the 1 st/2 nd release liners was formed in the same manner as in the formation of the adhesive layer (including ultraviolet irradiation) in example 1, except that the 2 nd adhesive composition was used instead of the 1 st adhesive composition.
As described above, an adhesive sheet (thickness: 50 μm) of comparative example 1 having a release liner on both sides was produced.
Tensile test
For each of the adhesive sheets of examples 1 to 6 and comparative example 1, strain stress generated in the following 1 st tensile test and 2 nd tensile test was studied.
Specifically, first, a necessary number of measurement samples are prepared for each adhesive sheet. In the production of the test sample, first, a small piece (30 mm wide by 100mm long) of the pressure-sensitive adhesive sheet with a release liner on both sides was cut out from the pressure-sensitive adhesive sheet with a release liner on both sides. Then, after one release liner was peeled off from the adhesive sheet small piece, the adhesive sheet small piece was wound on the other release liner in the longitudinal direction so as not to enter air bubbles, and a cylindrical shape (cylindrical height 30 mm) was formed. Thus, a cylindrical pressure-sensitive adhesive sheet chip as a measurement sample was obtained. Next, a tensile test was performed on the test specimen at 25℃and a relative humidity of 50% using a tensile tester (trade name "Autograph AG-50NX plus", manufactured by Shimadzu corporation), and tensile stress generated during the tensile process was measured (No. 1 tensile test). Thus, a stress-strain curve (load-elongation curve) was obtained. In the tensile test, the distance between the initial jigs was set to 10mm, and the measurement sample (cylindrical adhesive sheet small piece) was stretched in the height direction of the cylindrical shape, and the stretching speed was set to 50 mm/min. As a result of measurement in such a 1 st tensile test, the strain stress S at 200% elongation was measured 200 (N/cm 2 ) Strain stress S at 500% elongation 500 (N/cm 2 ) And strain stress S at 1000% elongation 1000 (N/cm 2 ) Table 1 shows the results (the adhesive sheet of comparative example 1 breaks before elongation of 1000% in the 1 st tensile test). In addition, strain stress S 500 And strain stress S 200 The ratio of (2) is also shown in Table 1.
On the other hand, for the measurement sample, the stretching speed was set to beThe tensile test was performed in the same manner as the 1 st tensile test except for 600 mm/min, and the tensile stress generated during the stretching was measured (2 nd tensile test). Thus, a stress-strain curve (load-elongation curve) was obtained. As a result of measurement in such a 2 nd tensile test, the strain stress S 'at 200% elongation was measured' 200 (N/cm 2 ) Strain stress S 'at 500% elongation' 500 (N/cm 2 ) And strain stress S 'at 1000% elongation' 1000 (N/cm 2 ) Table 1 shows the results (the adhesive sheet of comparative example 1 was broken before elongation of 1000% in the 2 nd tensile test). In addition, strain stress S 200 And strain stress S' 200 Ratio (S) 200 /S' 200 ) S 'S' 500 And strain stress S' 200 (ratio S' 500 /S' 200 ) Also shown in Table 1.
Bending retention test
For each of the adhesive sheets of examples 1 to 6 and comparative example 1, a bending retention test was performed as follows.
First, the 2 nd release liner was peeled from the adhesive sheet with release liners on both sides, and the exposed surface thus exposed was subjected to plasma treatment. On the other hand, both sides (1 st side, 2 nd side) of the polarizing film having a thickness of 51 μm were also subjected to plasma treatment. The surface of the transparent polyimide film having a thickness of 80 μm and the surface of the polyethylene terephthalate (PET) film having a thickness of 125 μm were also subjected to plasma treatment. In each plasma treatment, a plasma irradiation apparatus (trade name "AP-TO5", manufactured by water accumulation industry Co., ltd.) was used, the voltage was set TO 160V, the frequency was set TO 10kHz, and the treatment speed was set TO 5000 mm/min. Then, the exposed surface of the pressure-sensitive adhesive sheet is bonded to the 1 st surface of the polarizing film. In this bonding, the adhesive sheet with the 1 st release liner was pressed against the polarizing film by reversing a 2kg roller 1 time in an environment of 23 ℃. Then, the 1 st release liner was peeled off from the adhesive sheet with a polarizing film, and then the transparent polyimide film was bonded to the exposed surface of the adhesive sheet thus exposed. Then, the PET film was bonded to the 2 nd surface of the polarizing film via a thin adhesive sheet having a thickness of 15. Mu.m. In this bonding, the polarizing film and the PET film were pressure-bonded by reciprocating a 2kg roller 1 time in an environment of 23 ℃. Thus, a laminated film comprising a laminate of a PET film (thickness: 125 μm), a thin adhesive sheet (thickness: 15 μm), a polarizing film (thickness: 51 μm), an adhesive sheet (thickness: 50 μm) and a transparent polyimide film (thickness: 80 μm) was obtained.
Then, a sample for evaluation was cut out from the laminated film thus prepared. Specifically, a rectangular sample of 35mm×100mm was cut from the laminated film so that the absorption axis direction of the polarizing film was parallel to the longitudinal direction among the cut samples. Next, the sample was autoclaved at 35℃and 0.50MPa for 15 minutes.
Then, for this sample, a bending test was performed by using a planar body no-load U-shaped expansion and contraction tester (manufactured by YUASA SYSTEM co., ltd.). In this test, bending jigs were attached to both ends in the longitudinal direction of the sample at a distance of 20mm from the edge of the sample, and the sample was fixed to the tester (the region 60mm in the center in the longitudinal direction of the sample was left unfixed). In this test, the sample was repeatedly deformed (bent) 20 ten thousand times at a bending speed of 60rpm between a bent state and a non-bent state in which the surface of the PET film side was inside in a constant temperature and humidity tank under conditions of a temperature of 60 ℃ and a relative humidity of 95%. Specifically, the bending mode in this test is a mode in which the axial direction of the bending moment acting on the sample is perpendicular to the absorption axis direction of the polarizing film. In this bent form, the bending radius of the sample was set to 1.3mm and the bending angle was set to 180 °. In such a bending test, the adhesion of the adhesive sheet to the adherend was evaluated as "good" when no peeling occurred between the adhesive sheet and the adherend (transparent polyimide film, polarizing film), and as "poor" when peeling occurred. The evaluation results are shown in table 1.
TABLE 1
TABLE 1
Figure BDA0004012581460000221

Claims (9)

1. An optical adhesive sheet having strain stress S 200 (N/cm 2 ) As strain stress at 200% elongation in the 1 st tensile test at 25℃and a tensile speed of 50 mm/min,
with strain stress S' 200 (N/cm 2 ) As strain stress at 200% elongation in the 2 nd tensile test at 25℃and a tensile speed of 600 mm/min,
the strain stress S 200 And the strain stress S' 200 The ratio of (2) is 0.8 or less.
2. The optical adhesive sheet according to claim 1, wherein the strain stress S at 500% elongation in the 1 st tensile test 500 (N/cm 2 ) And the strain stress S 200 The ratio of (2) is 1.8 or less.
3. The optical adhesive sheet according to claim 1, wherein the strain stress S at 1000% elongation in the 1 st tensile test 1000 Is 18N/cm 2 The following is given.
4. The optical adhesive sheet according to claim 2, wherein the strain stress S at 1000% elongation in the 1 st tensile test 1000 Is 18N/cm 2 The following is given.
5. The optical adhesive sheet according to claim 1, wherein the strain stress S 'at 500% elongation in the 2 nd tensile test' 500 (N/cm 2 ) And the strain stress S' 200 The ratio of (2) is 1.7 or less.
6. The optical adhesive sheet according to claim 2, wherein the strain stress S 'at 500% elongation in the 2 nd tensile test' 500 (N/cm 2 ) And the strain stress S' 200 The ratio of (2) is 1.7 or less.
7. The optical adhesive sheet according to claim 3, which isIn the 2 nd tensile test, strain stress S 'at 500% elongation' 500 (N/cm 2 ) And the strain stress S' 200 The ratio of (2) is 1.7 or less.
8. The optical adhesive sheet according to claim 4, wherein the strain stress S 'at 500% elongation in the 2 nd tensile test' 500 (N/cm 2 ) And the strain stress S' 200 The ratio of (2) is 1.7 or less.
9. The optical adhesive sheet according to any one of claims 1 to 8, wherein the strain stress S 'at 1000% elongation in the 2 nd tensile test' 1000 25N/cm 2 The following is given.
CN202211658399.3A 2021-12-24 2022-12-22 Optical adhesive sheet Pending CN116333610A (en)

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JP2021210728A JP2023095067A (en) 2021-12-24 2021-12-24 optical adhesive sheet
JP2021-210728 2021-12-24

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CN116333610A true CN116333610A (en) 2023-06-27

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Publication number Priority date Publication date Assignee Title
JP6807234B2 (en) 2017-01-10 2021-01-06 日東電工株式会社 Adhesive sheet

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JP2023095067A (en) 2023-07-06
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