Optical adhesive sheet with release liner

Abstract

To provide an optical adhesive sheet with a release liner which is suitable for satisfying both release suppression and step difference followability of a tight release liner when releasing an easy release liner.SOLUTION: An optical adhesive sheet X with a release liner of the present invention comprises: an adhesive sheet 10 (optical adhesive sheet); a release liner 20 (tight release liner) which releasably contacts a first surface 11 of the adhesive sheet 10; and a release liner 30 (easy release liner) which releasably contacts a second surface 12 of the adhesive sheet 10. The adhesive sheet 10 includes a base polymer, a photopolymerizable polyfunctional compound and a photopolymerization initiator. In a probe tack test under predetermined conditions for the second surface 12 after the release liner 30 is released from the adhesive sheet 10, a probe peeling distance when the stress becomes 0 gf during a probe peeling process is 200 μm or more and 900 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical adhesive sheet with a release liner.

Background Art

[0002] A display panel has a laminated structure including elements such as a pixel panel, a polarizing film, and a cover glass. In the manufacturing process of a display panel, for example, an optically transparent adhesive sheet (optical adhesive sheet) is used for joining the elements included in the laminated structure. The optical adhesive sheet is manufactured, for example, as an optical adhesive sheet with a release liner in which release liners are bonded to both surfaces of the optical adhesive sheet. In the optical adhesive sheet with a release liner, a heavy release liner is bonded to one surface of the optical adhesive sheet, and a light release liner is bonded to the other surface of the optical adhesive sheet. Such an optical adhesive sheet for display panel applications is described, for example, in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the laminated structure of a display panel, elements having surface steps are included. For example, a decorative or light-shielding printing layer is provided at the edge of the surface of the cover glass on the pixel panel side, and there is a step (printing step) between the surface of the cover glass and the surface of the printing layer. Therefore, for an optical adhesive sheet for display panel applications, in addition to the reliability of the bonding between adherends, softness (step followability) to the extent that it can follow the printing step is required. Insufficient step followability of the optical adhesive sheet causes, for example, bubbles to be formed along the printing layer between the optical adhesive sheet laminated on the surface of the cover glass with the printing layer and the same cover glass, which is not preferable.

[0005] From the viewpoint of step followability, it is preferable that the optical adhesive sheet is softer. However, in an optical adhesive sheet with a release liner, the softer the optical adhesive sheet is, the more likely it is that the heavy release liner will be unintentionally peeled off when the light release liner is peeled off from the optical adhesive sheet.

[0006] The present invention provides an optical adhesive sheet with a release liner suitable for achieving both suppression of peeling of the heavy release liner during peeling of the light release liner and step followability.

Means for Solving the Problems

[0007] The present invention [1] is an optical adhesive sheet with a release liner, comprising an optical adhesive sheet having a first surface and a second surface opposite to the first surface, a heavy release liner detachably contacting the first surface, and a light release liner detachably contacting the second surface, wherein the optical adhesive sheet contains a base polymer, a photopolymerizable polyfunctional compound, and a photoinitiator, and in a probe tack test under the following conditions on the second surface after peeling the light release liner from the optical adhesive sheet, the probe peel-off distance when the stress becomes 0 gf during the probe peel-off process is 200 μm or more and 900 μm or less.

[0008] [Conditions] Temperature: 25 °C Probe diameter: 2.5 mm Pressing load: 1000 gf Pressing time: 30 seconds Peeling speed: 0.08 mm / second

[0009] The present invention [2] includes the pressure-sensitive adhesive sheet with a release liner described in [1] above, wherein the photopolymerizable polyfunctional compound includes a photopolymerizable polyfunctional compound having an aromatic ring.

[0010] The present invention [3] includes the pressure-sensitive adhesive sheet with a release liner described in [1] or [2] above, wherein the weight average molecular weight of the photopolymerizable polyfunctional compound is 1000 or less.

[0011] The present invention [4] includes the pressure-sensitive adhesive sheet with a release liner described in any one of [1] to [3] above, wherein the gel fraction is 50% by mass or more.

Advantages of the Invention

[0012] As described above, the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive sheet with a release liner of the present invention includes a base polymer, a photopolymerizable polyfunctional compound, and a photoinitiator. In such a pressure-sensitive adhesive sheet, the softness of the pressure-sensitive adhesive sheet can be ensured when joining adherends by the pressure-sensitive adhesive sheet (before photocuring), and after joining, the photopolymerizable polyfunctional compound can be photocured to make the pressure-sensitive adhesive sheet highly elastic. Such a pressure-sensitive adhesive sheet is suitable for ensuring the followability to the steps on the surface of the adherend during joining of the adherends and the joining reliability after joining of the adherends. Further, in the probe tack test under predetermined conditions for the second surface after peeling the light release liner from the pressure-sensitive adhesive sheet with a release liner, the probe peeling distance when the stress becomes 0 gf in the probe peeling process is 200 μm or more and 900 μm or less. Such a pressure-sensitive adhesive sheet with a release liner is suitable for suppressing the unintentional peeling of the heavy release liner when peeling the light release liner from the pressure-sensitive adhesive sheet.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0014] As one embodiment of the present invention, the optical adhesive sheet X with a release liner includes an adhesive sheet 10, a release liner 20, and a release liner 30 as shown in FIG. 1. The adhesive sheet 10 has a first surface 11 and a second surface 12 on the side opposite to the first surface 11. The first surface 11 and the second surface 12 are adhesive surfaces. The release liner 20 has a release surface 21. The release liner 20 is detachably in contact with the first surface 11 of the adhesive sheet 10 on the side of the release surface 21. The release liner 30 has a release surface 31. The release liner 30 is detachably in contact with the second surface 12 of the adhesive sheet 10 on the side of the release surface 31. That is, the optical adhesive sheet X with a release liner includes the release liner 20, the adhesive sheet 10, and the release liner 30 in this order in the thickness direction H. The optical adhesive sheet X with a release liner extends in a direction (plane direction) orthogonal to the thickness direction H.

[0015] The adhesive sheet 10 is an optically transparent adhesive sheet (optical adhesive sheet). The adhesive sheet 10 is a sheet-like pressure-sensitive adhesive. The adhesive sheet 10 contains a base polymer, a photopolymerizable polyfunctional compound, and a photoinitiator, and has photocurability. The adhesive sheet 10 is, for example, an optical adhesive sheet disposed at a light passage portion in a display panel. Examples of the display panel include a liquid crystal display panel and an organic EL display panel. The display panel has a laminated structure including elements such as a pixel panel, a polarizing film, a touch panel, and a cover glass. The adhesive sheet 10 is used, for example, for bonding elements included in the laminated structure during the manufacturing process of the display panel.

[0016] The release liner 20 is a heavy release liner with a relatively large force required to peel it from the adhesive sheet 10, and the release liner 30 is a light release liner with a relatively small force required to peel it from the adhesive sheet 10. Specifically, in a peel test where it is peeled from the adhesive sheet 10 under the conditions of 25 °C, a peel angle of 180°, and a tensile speed of 300 mm / min, the release liner 20 has a greater peel force than the release liner 30. The method for measuring the peel force is more specifically as described later in the examples. The release liner 30 (light release liner) and the release liner 20 (heavy release liner) are peeled from the adhesive sheet 10 in this order when using the adhesive sheet 10.

[0017] In the probe tack test under the following conditions with respect to the second surface 12 after peeling the release liner 30 from the adhesive sheet 10, the probe peel distance d when the stress becomes 0 gf during the probe peel process is 200 μm or more and 900 μm or less.

[0018] [Conditions] Temperature: 25 °C Probe diameter: 2.5 mm Pressing load: 1000 gf Pressing time: 30 seconds Peel speed: 0.08 mm / second

[0019] Before the probe tack test, as shown in FIG. 2, the adhesive sheet 10 with the release liner 20 is set as the test piece Z on the measurement table W of the tack tester. Specifically, first, the release liner 20 side of the optically adhesive sheet X with the release liner is fixed to the measurement table W via an adhesive (not shown). Then, the release liner 30 is peeled off from the adhesive sheet 10 of the optically adhesive sheet X with the release liner on the measurement table W.

[0020] The probe tack test under the above conditions is specifically as follows. As the probe P, a columnar stainless steel probe with a tip diameter (probe diameter) of 2.5 mm is used. The area of the tip Pa of this probe P is 19.63 mm 2Then, after setting the environmental temperature and the temperature of the probe P to 25°C, the tip Pa of the probe P (diameter 2.5 mm) is pressed vertically against the adhesive sheet 10 from above the adhesive sheet 10 at a pressing speed of 0.08 mm / second until the pressing load reaches 1000 gf. Subsequently, the pressing load of 1000 gf of the probe P is maintained for 30 seconds. Subsequently, the probe P is peeled off upward from the second surface 12 of the adhesive sheet 10 at a peeling speed of 0.08 mm / second (peeling process). During this period, the load acting on the probe P is measured as the stress of the adhesive sheet 10. The method of the probe tack test is specifically as described later for the examples.

[0021] An example of a stress-peeling distance curve showing the stress (load acting downward on the probe P) after the start of peeling of the probe P is shown in FIG. 3. In the graph of FIG. 3, the horizontal axis represents the peeling distance (μm) of the probe P, and the vertical axis represents the stress (gf). The peeling distance of the probe P is the rising distance of the tip Pa of the probe P during the peeling process of the probe P (the moving distance in the height direction from the position of the second surface 12 at the start of peeling). During the probe peeling process, first, the adhesive sheet 10 elastically deforms and the stress increases. Subsequently, after the stress reaches the maximum stress Smax, the adhesive sheet 10 plastically deforms and the stress decreases. The stress of the adhesive sheet 10 drops to 0 gf. The probe peeling distance at the time of 0 gf stress is shown in FIG. 3 as the distance d. Examples of the method for adjusting the peeling distance d include selection of the type of base polymer in the adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. The selection of the type of base polymer includes adjustment of the composition of the monomers forming the base polymer. Examples of the method for adjusting the peeling distance d also include selection of the type, adjustment of the molecular weight, and adjustment of the blending amount of components other than the base polymer in the adhesive sheet 10. Examples of such components include a photopolymerizable polyfunctional compound and a silane coupling agent.

[0022] The pressure-sensitive adhesive sheet 10 of the optical pressure-sensitive adhesive sheet X with a release liner contains, as described above, a base polymer, a photopolymerizable polyfunctional compound, and a photoinitiator. In such a pressure-sensitive adhesive sheet 10, the softness of the pressure-sensitive adhesive sheet 10 can be ensured during the joining of adherends by the pressure-sensitive adhesive sheet 10 (before photocuring), and after joining, the photopolymerizable polyfunctional compound can be photopolymerized to make the pressure-sensitive adhesive sheet 10 highly elastic. Such a pressure-sensitive adhesive sheet 10 is suitable for ensuring the followability to the steps on the surface of the adherend during the joining of adherends and the joining reliability after the joining of adherends.

[0023] Further, in the probe tack test under the above conditions for the second surface 12 after peeling the release liner 30 (light release liner) from the pressure-sensitive adhesive sheet 10 of the optical pressure-sensitive adhesive sheet X with a release liner, the peeling distance d of the probe when the stress becomes 0 gf in the probe peeling process is 200 μm or more and 900 μm or less. The optical pressure-sensitive adhesive sheet with a release liner having the above peeling distance d of 900 μm or less is suitable for suppressing the unintentional peeling of the release liner 20 as a heavy release liner when peeling the release liner 30 as a light release liner from the pressure-sensitive adhesive sheet 10. Also, the optical pressure-sensitive adhesive sheet with a release liner having the above peeling distance d of 200 μm or more is suitable for ensuring the viscosity on the surface of the pressure-sensitive adhesive sheet 10 and ensuring the joining reliability after the joining of adherends by the pressure-sensitive adhesive sheet 10.

[0024] As described above, the optical pressure-sensitive adhesive sheet X with a release liner is suitable for achieving both the suppression of the peeling of the release liner 20 (heavy release liner) during the peeling of the release liner 30 (light release liner) and the step followability.

[0025] From the viewpoint of the above peeling suppression, the peeling distance d (stress 0 gf) is preferably 250 μm or more, more preferably 300 μm or more, still more preferably 400 μm or more, and is preferably 850 μm or less, more preferably 750 μm or less, still more preferably 650 μm or less.

[0026] The gel fraction of the pressure-sensitive adhesive sheet 10 (before photocuring) is preferably 50% by mass or more, more preferably 53% by mass or more, from the viewpoint of the storage stability of the optical pressure-sensitive adhesive sheet X with a release liner or the pressure-sensitive adhesive sheet 10. When the storage stability of the pressure-sensitive adhesive sheet 10 is low, for example, due to the flow of the pressure-sensitive adhesive sheet 10 during storage of the optical pressure-sensitive adhesive sheet X with a release liner, the product shape is likely to change, and when stored in a laminated state, indentations are likely to occur on the pressure-sensitive adhesive sheet 10. The gel fraction of the pressure-sensitive adhesive sheet 10 (before photocuring) is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, from the viewpoint of ensuring the above-described step followability. Examples of the method for adjusting the gel fraction of the pressure-sensitive adhesive sheet 10 include selection of the type of the base polymer in the pressure-sensitive adhesive sheet 10, adjustment of the molecular weight, and adjustment of the blending amount. The method for measuring the gel fraction is as described later in the examples.

[0027] The peeling force F1 for peeling the release liner 20 (heavy release liner) from the adhesive sheet 10 (before photocuring) is preferably 0.1 N / 25 mm or more, more preferably 0.3 N / 25 mm or more, and still more preferably 0.5 N / 25 mm or more, from the viewpoint of suppressing the unintentional peeling of the release liner 20 from the adhesive sheet 10. The peeling force F1 is preferably 3.0 N / 25 mm or less, more preferably 2.0 N / 25 mm or less, and still more preferably 1.0 N / 25 mm or less, from the viewpoint of ensuring the ease of peeling of the release liner 20 from the adhesive sheet 10. The peeling force F1 is a value measured by conducting a peeling test for peeling the release liner 20 from the adhesive sheet 10 under the conditions of a measurement temperature of 25°C, a peeling angle of 180°, and a tensile speed of 300 mm / min. The method for measuring the peeling force F1 is specifically as described later for the examples. Examples of the method for adjusting the peeling force F1 include the selection of the type of base polymer in the adhesive sheet 10, the adjustment of the molecular weight, and the adjustment of the blending amount. Examples of the method for adjusting the peeling force F1 also include the selection of the type of components other than the base polymer in the adhesive sheet 10 and the adjustment of the blending amount of the component. Examples of the component include a photopolymerizable polyfunctional compound and a silane coupling agent. These adjustment methods are the same for the peeling force F2 described later. Further, examples of the method for adjusting the peeling force F1 include the selection of the type of material forming the peeling surface 21 of the release liner 20.

[0028] The peeling force F2 for peeling the release liner 30 (light release liner) from the adhesive sheet 10 is preferably 0.001 N / 25 mm or more, more preferably 0.01 N / 25 mm or more, and still more preferably 0.015 N / 25 mm or more from the viewpoint of suppressing the unintentional peeling of the release liner 30 from the adhesive sheet 10. The peeling force F2 is preferably 10 N / 25 mm or less, more preferably 0.1 N / 25 mm or less, and still more preferably 0.05 N / 25 mm or less from the viewpoint of ensuring the easy peelability of the release liner 30 as a light release liner. The peeling force F2 is a value measured by performing a peeling test for peeling the release liner 30 from the adhesive sheet 10 under the conditions of a measurement temperature of 25°C, a peeling angle of 180°, and a tensile speed of 300 mm / min. The method for measuring the peeling force F2 is specifically as described later for the examples. As a method for adjusting the peeling force F2, there is a selection of the type of material forming the peeling surface 31 of the release liner 30.

[0029] The difference F1 - F2 between the peeling force F1 and the peeling force F2 is preferably 0.1 N / 25 mm or more, more preferably 0.3 N / 25 mm or more, and still more preferably 0.5 N / 25 mm or more from the viewpoint of suppressing the peeling of the release liner 20 when the release liner 30 is peeled. The difference F1 - F2 is preferably 2.0 N / 25 mm or less, more preferably 1.0 N / 25 mm or less, and still more preferably 0.6 N / 25 mm or less from the viewpoint of ensuring a well-balanced peelability of the release liners 20 and 30 from the adhesive sheet 10.

[0030] The ratio (F1 / F2) of the peeling force F1 to the peeling force F2 is preferably 1.1 or more, more preferably 1.2 or more, and still more preferably 1.3 or more from the viewpoint of suppressing the peeling of the release liner 20 when the release liner 30 is peeled. The ratio (F1 / F2) is preferably 100 or less, more preferably 60 or less, and still more preferably 40 or less from the viewpoint of ensuring a well-balanced peelability of the release liners 20 and 30 from the adhesive sheet 10.

[0031] In the present embodiment, the base polymer in the pressure-sensitive adhesive sheet 10 is a polymer obtained by photopolymerization of a polymerizable component containing a monofunctional monomer and a crosslinking agent. Photopolymerization is a polymerization method in which a polymerization reaction of a polymerizable component proceeds by irradiation with active energy rays such as ultraviolet rays. The base polymer is, for example, a polymer obtained by photopolymerization of a partial polymer obtained by photopolymerization of a monofunctional monomer (a mixture of a polymer of a monofunctional monomer and an unreacted monofunctional monomer) and a crosslinking agent.

[0032] Such a base polymer includes a photopolymerized polymer having a photocrosslinked structure (first photopolymerized polymer). The photocrosslinked structure is a structure in which between linear structures formed by units derived from a monofunctional monomer are crosslinked by units derived from a crosslinking agent. The base polymer may include a photopolymerized polymer that does not have such a photocrosslinked structure (second photopolymerized polymer). The second photopolymerized polymer is a polymer of a monofunctional monomer. Further, the base polymer is preferably an acrylic polymer. The acrylic polymer is a copolymer of a polymerizable component containing an alkyl (meth)acrylate at a ratio of 50% by mass or more. "(Meth)acrylic" means acrylic and / or methacrylic.

[0033] The monofunctional monomer is preferably a monofunctional alkyl (meth)acrylate, and more preferably an alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms. The alkyl (meth)acrylate may have a linear or branched alkyl group, or may have a cyclic alkyl group (alicyclic alkyl group).

[0034] Examples of the linear or branched (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

[0035] Examples of the alkyl (meth)acrylate having an alicyclic alkyl group include cycloalkyl (meth)acrylates, alkyl (meth)acrylates having a bicyclic aliphatic hydrocarbon ring, and alkyl (meth)acrylates having a tricyclic or higher aliphatic hydrocarbon ring. Examples of the cycloalkyl (meth)acrylate include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. Examples of the alkyl (meth)acrylate having a bicyclic aliphatic hydrocarbon ring include isobornyl (meth)acrylate. Examples of the alkyl (meth)acrylate having a tricyclic or higher aliphatic hydrocarbon ring include dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0036] The monofunctional monomer may be used alone or in combination of two or more. The monofunctional monomer is preferably an alkyl acrylate having an alkyl group with 3 to 12 carbon atoms, more preferably at least one selected from the group consisting of n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl acrylate.

[0037] From the viewpoint of appropriately expressing basic properties such as adhesiveness in the pressure-sensitive adhesive sheet 10, the proportion of the monofunctional monomer in the polymerizable component forming the base polymer is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and even more preferably 75% by mass or more. The proportion is, for example, 99% by mass or less.

[0038] The polymerizable component may contain, as a monofunctional monomer, a copolymerizable monomer copolymerizable with a monofunctional (meth)acrylic acid alkyl ester. Examples of the copolymerizable monomer include polar group-containing monomers. Examples of the polar group-containing monomers include hydroxy group-containing monomers, carboxy group-containing monomers, and monomers having a nitrogen atom-containing ring. The polar group-containing monomers are useful for modifying the acrylic polymer, such as ensuring the cohesive force of the acrylic polymer.

[0039] Examples of the hydroxy group-containing monomers 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, and 12-hydroxylauryl (meth)acrylate. The hydroxy group-containing monomer is preferably at least one selected from the group consisting of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

[0040] From the viewpoint of ensuring the cohesive force in the pressure-sensitive adhesive sheet 10, the proportion of the hydroxy group-containing monomer in the polymerizable component is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more. From the viewpoint of adjusting the polarity of the acrylic polymer (relating to the compatibility between various additive components in the pressure-sensitive adhesive sheet 10 and the acrylic polymer), the proportion is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less.

[0041] Examples of the carboxy group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0042] The proportion of the carboxy group-containing monomer in the polymerizable component is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, from the viewpoints of ensuring the cohesive force in the pressure-sensitive adhesive sheet 10 and ensuring the adhesion strength to the adherend in the pressure-sensitive adhesive sheet 10. The said proportion is preferably 20% by mass or less, more preferably 10% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by an acid.

[0043] Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl oxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and acryloylmorpholine. The monomer having a nitrogen atom-containing ring is preferably at least one selected from the group consisting of N-vinyl-2-pyrrolidone and acryloylmorpholine.

[0044] The proportion of the monomer having a nitrogen atom-containing ring in the polymerizable component is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, from the viewpoints of ensuring the cohesive force in the pressure-sensitive adhesive sheet and ensuring the adhesion strength to the adherend in the pressure-sensitive adhesive sheet. The said proportion is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoints of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to the compatibility between various additive components in the pressure-sensitive adhesive sheet and the acrylic polymer).

[0045] Examples of the crosslinking agent include polyfunctional oligomers and polyfunctional monomers.

[0046] Examples of the polyfunctional oligomer include urethane acrylate oligomer (an oligomer having a urethane skeleton and two or more acryloyl groups), epoxy acrylate oligomer (an oligomer having an epoxy skeleton and two or more acryloyl groups), and silicone acrylate oligomer (an oligomer having a siloxane skeleton and two or more acryloyl groups). Examples of commercially available urethane acrylate oligomers include Art Resin UN-333, UN-350, UN-353, UN-5500, and UN-5590 manufactured by Negami Kogyo Co., Ltd.

[0047] From the viewpoint of appropriately adjusting the gel fraction of the pressure-sensitive adhesive sheet 10, the weight average molecular weight (Mw) of the polyfunctional oligomer is preferably 5000 or more, and preferably 20000 or less, more preferably 15000 or less. The weight average molecular weight is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

[0048] Examples of the polyfunctional monomer include polyfunctional (meth)acrylates containing two or more ethylenically unsaturated double bonds in one molecule. From the viewpoint of easily introducing a crosslinked structure by photopolymerization (active energy ray polymerization), polyfunctional (meth)acrylates are preferred. Examples of the polyfunctional (meth)acrylates include the polyfunctional (meth)acrylates described later with respect to the photopolymerizable polyfunctional compounds.

[0049] The crosslinking agent may be used alone or in combination of two or more. The crosslinking agent is preferably a polyfunctional oligomer, more preferably a urethane acrylate oligomer.

[0050] The proportion of the crosslinking agent in the polymerizable component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more. Such a configuration is preferable for maintaining the sheet shape of the pressure-sensitive adhesive sheet 10 before photocuring, and thus is preferable for ensuring the handleability of the pressure-sensitive adhesive sheet 10. The proportion of the crosslinking agent in the polymerizable component is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and even more preferably 1% by mass or less. Such a configuration is preferable for ensuring a high degree of softness and realizing good step-following properties in the pressure-sensitive adhesive sheet 10 before photocuring. Further, such a configuration is preferable for suppressing the unintentional peeling of the heavy release liner at the time of peeling of the light release liner.

[0051] Examples of the photopolymerizable polyfunctional compound include polyfunctional monomers and polyfunctional oligomers.

[0052] Examples of the polyfunctional monomer include polyfunctional (meth)acrylates. Examples of the polyfunctional (meth)acrylate include bifunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates having four or more functional groups.

[0053] Examples of the bifunctional (meth)acrylate include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, di(meth)acryloyl isocyanurate, and ethoxylated bisphenol A diacrylate (BPAEODE).

[0054] Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl)isocyanurate.

[0055] Examples of tetrafunctional or higher polyfunctional (meth)acrylates include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

[0056] Examples of polyfunctional oligomers include those polyfunctional oligomers described above with respect to the crosslinking agent.

[0057] The photopolymerizable polyfunctional compounds may be used alone or in combination of two or more kinds.

[0058] From the viewpoint of adjusting the peel distance d to 200 to 900 μm, the photopolymerizable multifunctional compound preferably contains a photopolymerizable multifunctional compound having an aromatic ring (first photopolymerizable multifunctional compound), and more preferably contains a first photopolymerizable multifunctional compound and a photopolymerizable multifunctional compound without an aromatic ring (second photopolymerizable multifunctional compound). Because the first photopolymerizable multifunctional compound has an aromatic ring within its molecular structure, the molecular motion of the compound itself is restricted, and the compounds may be π-conjugated with each other. Such first photopolymerizable multifunctional compounds tend to have high viscosity, and therefore have a small plasticizing effect on the pressure-sensitive adhesive sheet 10, which is thought to help prevent the peel distance d from becoming excessive.

[0059] The first photopolymerizable polyfunctional compound is preferably a polyfunctional monomer having an aromatic ring, more preferably BPAEODE. From the viewpoint of adjusting the peeling distance d described above to 200 to 900 μm, the molecular weight of the first photopolymerizable polyfunctional compound is preferably 1000 or less, more preferably 700 or less, still more preferably 500 or less, and is also preferably 300 or more, more preferably 400 or more, still more preferably 450 or more.

[0060] The second photopolymerizable polyfunctional compound is preferably a polyfunctional monomer having no aromatic ring, more preferably TMPTA. From the viewpoint of adjusting the peeling distance d described above to 200 to 900 μm, the molecular weight of the second photopolymerizable polyfunctional compound is preferably 1000 or less, more preferably 700 or less, still more preferably 500 or less, and is also preferably 200 or more, more preferably 250 or more, still more preferably 280 or more.

[0061] The content of the polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 (total content when the pressure-sensitive adhesive sheet 10 contains a plurality of polyfunctional photopolymerizable compounds) is preferably 1.2 parts by mass or more, more preferably 2 parts by mass or more, still more preferably 2.5 parts by mass or more per 100 parts by mass of the base polymer, from the viewpoint of ensuring good bonding reliability after photocuring in the pressure-sensitive adhesive sheet 10. The content of the polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3.5 parts by mass or less per 100 parts by mass of the base polymer, from the viewpoint of adjusting the above-mentioned peel-off distance d to 200 to 900 μm. The content of the first polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, still more preferably 0.5 parts by mass or more per 100 parts by mass of the base polymer, from the viewpoint of ensuring good bonding reliability after photocuring in the pressure-sensitive adhesive sheet 10. The content of the first polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 is preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, still more preferably 1 part by mass or less per 100 parts by mass of the base polymer, from the viewpoint of adjusting the above-mentioned peel-off distance d to 200 to 900 μm. The content of the second polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 is preferably 1 part by mass or more, more preferably 1.6 parts by mass or more, still more preferably 2 parts by mass or more per 100 parts by mass of the base polymer, from the viewpoint of ensuring good bonding reliability after photocuring in the pressure-sensitive adhesive sheet 10. The content of the second polyfunctional photopolymerizable compound in the pressure-sensitive adhesive sheet 10 is preferably 5 parts by mass or less, more preferably 3.5 parts by mass or less, still more preferably 2 parts by mass or less per 100 parts by mass of the base polymer, from the viewpoint of adjusting the above-mentioned peel-off distance d to 200 to 900 μm.

[0062] Examples of the photoinitiator in the pressure-sensitive adhesive sheet 10 include radical photoinitiators, cationic photoinitiators, and anionic photoinitiators.

[0063] Examples of the radical photopolymerization initiator include an acylphosphine oxide photopolymerization initiator, a benzoin ether photopolymerization initiator, an acetophenone photopolymerization initiator, an α-ketol photopolymerization initiator, an aromatic sulfonyl chloride photopolymerization initiator, a photoactive oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, and a thioxanthone photopolymerization initiator.

[0064] Examples of acylphosphine oxide photoinitiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Examples of benzoin ether photoinitiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and 2,2-dimethoxy-1,2-diphenylethane-1-one. Examples of acetophenone photoinitiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol photoinitiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride photoinitiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin photoinitiators include benzoin. Examples of benzyl photoinitiators include benzyl. Examples of benzophenone photoinitiators include benzophenone, benzoyl benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone. Examples of ketal photoinitiators include benzyldimethyl ketal. Examples of thioxanthone photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.The photoinitiator may be used alone or in combination of two or more kinds. The photoinitiator is preferably an acylphosphine oxide photoinitiator, more preferably at least one selected from the group consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-dimethoxy-1,2-diphenylethan-1-one, and 1-hydroxycyclohexyl phenyl ketone.

[0065] The content of the photoinitiator in the pressure-sensitive adhesive sheet 10 is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, still more preferably 0.25 part by mass or more, even more preferably 0.3 part by mass or more, and even more preferably 0.4 part by mass or more per 100 parts by mass of the base polymer. Such a configuration is preferable for forming a crosslinked network with a sufficient crosslink density in the pressure-sensitive adhesive sheet 10 by the photopolymerization reaction during light irradiation on the pressure-sensitive adhesive sheet 10, and significantly changing the viscoelasticity of the pressure-sensitive adhesive sheet 10. The content of the photoinitiator in the pressure-sensitive adhesive sheet 10 is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and still more preferably 1 part by mass or less per 100 parts by mass of the base polymer. Such a configuration is preferable for suppressing the generation of a large amount of polymerization initiator during light irradiation on the pressure-sensitive adhesive sheet 10 and forming a long-distance and continuous crosslinked network by the photopolymerization reaction.

[0066] The pressure-sensitive adhesive sheet 10 may contain other components. Examples of the other components include an ultraviolet absorber, an antioxidant, a silane coupling agent, and a rust inhibitor.

[0067] Examples of the ultraviolet absorber include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. As the ultraviolet absorber, a triazine-based ultraviolet absorber is preferable because it has high absorbability of ultraviolet rays in the wavelength range of 320 to 370 nm and excellent compatibility with the acrylic polymer. The ultraviolet absorber may be used alone or in combination of two or more kinds.

[0068] Examples of commercially available triazine-based ultraviolet absorbers include bis(ethylhexyl)oxyphenol methoxyphenyltriazine (product name "Chinosorb S", manufactured by BASF), the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(alkyloxy)methyl]oxirane (product name "TINUVIN 400", manufactured by BASF), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (product name "TINUVIN 405", manufactured by BASF), (2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (product name "TINUVIN 460", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (product name "TINUVIN 577", manufactured by BASF), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (product name "TINUVIN 479", manufactured by BASF), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol ("ADK STAB LA-46", manufactured by ADEKA).

[0069] The content of the ultraviolet absorber in the pressure-sensitive adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, more preferably 2 parts by mass or less, per 100 parts by mass of the base polymer. Such a configuration is preferable from the viewpoint of achieving both the ultraviolet cut function for device protection and photocurability in the pressure-sensitive adhesive sheet 10.

[0070] Examples of the antioxidant include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and amine-based antioxidants. The antioxidant may be used alone or in combination of two or more.

[0071] As the antioxidant, preferably, a phenolic antioxidant is used, and more preferably, a hindered phenolic antioxidant is used. Examples of the hindered phenolic antioxidant include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (product name "Irganox 1010", manufactured by BASF), and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (product name "Irganox 1076", manufactured by BASF).

[0072] The content of the antioxidant in the pressure-sensitive adhesive sheet 10 is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, per 100 parts by mass of the base polymer, and is preferably 3 parts by mass or less, more preferably 2 parts by mass or less. Such a configuration is preferable from the viewpoint of achieving both suppression of oxidative degradation and photocurability of the pressure-sensitive adhesive sheet 10.

[0073] Examples of the silane coupling agent include silane coupling agents containing an epoxy group. Examples of the epoxy group-containing silane coupling agent include 3-glycidoxy dialkyldialkoxysilane and 3-glycidoxyalkyltrialkoxysilane. Examples of 3-glycidoxy dialkyldialkoxysilane include 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. Examples of 3-glycidoxyalkyltrialkoxysilane include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. Preferably, a 3-glycidoxyalkyltrialkoxysilane is used as the silane coupling agent, and more preferably, 3-glycidoxypropyltrimethoxysilane is used. The silane coupling agent may be used alone or in combination of two or more. The content of the silane coupling agent in the pressure-sensitive adhesive sheet 10 is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, per 100 parts by mass of the base polymer, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

[0074] From the viewpoint of ensuring sufficient adhesiveness to the adherend, the thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 μm or more, more preferably 20 μm or more. From the viewpoints of the handleability of the pressure-sensitive adhesive sheet 10 and the ease of cutting process, the thickness of the pressure-sensitive adhesive sheet 10 is preferably 500 μm or less, more preferably 400 μm or less, still more preferably 300 μm or less, even more preferably 200 μm or less, and even more preferably 150 μm or less.

[0075] The total light transmittance of the pressure-sensitive adhesive sheet 10 is preferably 90% or more, more preferably 92% or more. Such a configuration is preferable for ensuring the transparency required for the pressure-sensitive adhesive sheet 10 for display panel applications. The total light transmittance of the pressure-sensitive adhesive sheet 10 is, for example, 100% or less. The total light transmittance can be measured in accordance with JIS K 7375 (2008).

[0076] The shear storage modulus of the pressure-sensitive adhesive sheet 10 (before photocuring) at 25°C is preferably 1 MPa or less, more preferably 500 kPa or less, still more preferably 300 kPa or less, even more preferably 200 kPa or less, still even more preferably 180 kPa or less, and particularly preferably 150 kPa or less, from the viewpoint of ensuring the softness of the pressure-sensitive adhesive sheet 10. The shear storage modulus of the pressure-sensitive adhesive sheet 10 at 25°C is preferably 5 kPa or more, more preferably 10 kPa or more, still more preferably 15 kPa or more, and particularly preferably 20 kPa or more, from the viewpoint of ensuring the cohesive force of the pressure-sensitive adhesive sheet 10. The shear storage modulus of the pressure-sensitive adhesive sheet can be measured by a dynamic viscoelasticity measuring device. As the dynamic viscoelasticity measuring device, for example, the "Advanced Rheometric Expansion System" manufactured by Rheometric Scientific can be used. In the measurement, the measurement mode is set to the shear mode, the measurement temperature range is set to -50°C to 150°C, the temperature rising rate is set to 5°C / min, and the frequency is set to 1 Hz. The method for measuring the shear storage modulus is specifically as described later in the examples.

[0077] The release liner 20 is, for example, a flexible transparent resin film. Examples of the material of the release liner 20 include polyester resin, polyolefin resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, cellulose resin, and polystyrene resin. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer (COP). From the viewpoints of transparency and strength, the material of the release liner 20 is preferably a polyester resin, and more preferably PET.

[0078] The release surface 21 of the release liner 20 may be subjected to a release treatment with a release treatment agent. Examples of the release treatment include silicone release treatment, long-chain alkyl acrylate release treatment, and fluorine release treatment. From the viewpoint of ease of adjusting the release force from the adhesive sheet 10, silicone release treatment is preferable as the release treatment.

[0079] From the viewpoint of ensuring the protection function for the adhesive sheet 10, the thickness of the release liner 20 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. From the viewpoint of handleability, the thickness of the release liner 20 is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

[0080] The release liner 30 is a flexible transparent resin film. Examples of the material of the release liner 30 include the materials described above as the material of the release liner 20. From the viewpoints of transparency and strength, a polyester resin is preferably used as the material of the release liner 30, and more preferably PET is used.

[0081] In the present embodiment, the release surface 31 of the release liner 30 is subjected to a release treatment with a release treatment agent. Examples of the release treatment include silicone release treatment, long-chain alkyl acrylate release treatment, and fluorine release treatment. From the viewpoint of ease of adjusting the release force from the adhesive sheet 10, silicone release treatment is preferable as the release treatment. The release treatment for the release liner 30 is performed so that the release force F2 of the release liner 30 is smaller than the release force F1 of the release liner 20.

[0082] From the viewpoint of ensuring the protection function for the adhesive sheet 10, the thickness of the release liner 30 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more. From the viewpoint of handleability, the thickness of the release liner 30 is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

[0083] The optical adhesive sheet X with a release liner can be manufactured, for example, as follows.

[0084] First, a prepolymer composition is prepared (prepolymer composition preparation step). Specifically, first, a mixture (liquid) containing the above-mentioned monofunctional monomer for forming a base polymer and a photoinitiator is prepared. Next, by irradiating the mixture with ultraviolet rays, a part of the monofunctional monomer in the mixture is photopolymerized to obtain a prepolymer composition. Examples of the light source for ultraviolet irradiation include ultraviolet LED lights, black light lamps, high-pressure mercury lamps, and metal halide lamps. Also, in ultraviolet irradiation, a wavelength cut filter for cutting a part of the wavelength region of the light emitted from the light source may be used as necessary. In ultraviolet irradiation, the illuminance is, for example, 5 - 200 mW / cm 2 ², and the integrated light quantity of irradiation is, for example, 100 - 5000 mJ / cm 2 ². It is preferable to continue the ultraviolet irradiation until the viscosity of the composition reaches about 15 - 25 Pa·s. This viscosity is the value measured by a B-type viscometer under the conditions of rotor No. 5, rotor rotation speed 10 rpm, and temperature 30°C. The prepolymer composition contains a photopolymer of the monofunctional monomer (the second photopolymer) and a monofunctional monomer that has not undergone a polymerization reaction (residual monomer). Also, the prepolymer composition does not contain a solvent.

[0085] Next, a crosslinking agent, a photoinitiator, and, if necessary, other components are added to the prepolymer composition to prepare an adhesive composition (adhesive composition preparation step). Examples of other components include additional monofunctional monomers (additional monomers), antioxidants, silane coupling agents, and rust preventives. Since the adhesive composition does not contain a solvent, it is a solvent-free adhesive composition.

[0086] Next, as shown in FIG. 4A, a coating film 10A is formed between the release liners 20 and 30 (coating film forming step). Specifically, first, an adhesive composition is applied onto the release surface 21 of the release liner 20 to form the coating film 10A. Next, the release surface 31 side of the release liner 30 is bonded onto the coating film 10A on the release liner 20. 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, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0087] Next, as shown in FIG. 4B, the coating film 10A (FIG. 4A) between the release liners 20 and 30 is irradiated with ultraviolet rays to form a base adhesive sheet 10B (base adhesive sheet forming step). During the ultraviolet irradiation, in the coating film, a photopolymerization reaction proceeds in a reaction system containing a monofunctional monomer (residual monomer, additional monomer) and a crosslinking agent, and a base polymer is formed.

[0088] Next, as shown in FIG. 4C, the release liner 30 is peeled off from the base adhesive sheet 10B (peeling step).

[0089] Next, as shown in FIG. 4D, a post-added component is supplied to the base adhesive sheet 10B (post-added component supply step). For example, a post-added component solution (not shown) containing a post-added component and a solvent is applied to the exposed surface of the base adhesive sheet 10B. The post-added component contains the above-described photopolymerizable polyfunctional compound and the above-described photoinitiator, and may contain additives such as an ultraviolet absorber and an antioxidant. Next, while allowing the post-added component to penetrate into the base adhesive sheet 10B from the surface of the base adhesive sheet 10B, the solvent is vaporized by heating as necessary. Prior to this step, the base polymer already has a crosslinked structure and the base adhesive sheet 10B has been formed. Therefore, due to the vaporization of the solvent in this step, it is difficult (substantially not formed) to form a fish-skin surface on the base adhesive sheet 10B. Further, the photocurable adhesive sheet 10 is formed by the base adhesive sheet 10B and the post-added component. The amount of the photopolymerizable polyfunctional compound added in this step is, as described above, preferably 1.2 parts by mass or more, more preferably 2 parts by mass or more, still more preferably 2.5 parts by mass or more, per 100 parts by mass of the base polymer, and preferably 7 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3.5 parts by mass or less.

[0090] Next, as shown in FIG. 4E, another release liner 30 is bonded to the adhesive sheet 10 (bonding step).

[0091] As described above, the adhesive sheet 10 whose adhesive surface is covered and protected by the release liners 20 and 30 can be manufactured. The adhesive sheet 10 formed from the solvent-free adhesive composition is suitable for reducing the environmental load.

[0092] FIGS. 5A to 5C show an example of a method of using the adhesive sheet 10 of the optical adhesive sheet X with a release liner.

[0093] In this method, first, as shown in FIGS. 5A and 5B, the member 51 and the cover glass 52 are joined via the adhesive sheet 10. The member 51 is, for example, a pixel panel for a display panel, a polarizing film, or a touch panel. The cover glass 52 has a first surface 52a on the member 51 side and a second surface 52b on the side opposite to the first surface 52a. A printing layer 53 for decoration or light shielding is formed at the edge of the first surface 52a. The printing layer 53 is provided, for example, over the entire circumference of the edge of the cover glass 52. There is a step (printing step) between the first surface 52a and the surface of the printing layer 53 on the member 51 side of the cover glass 52. The member 51 and the cover glass 52 are joined via the adhesive sheet 10. Specifically, it is as follows: the first method or the second method.

[0094] In the first method, first, the release liner 30 is peeled off from the adhesive sheet 10 of the optically clear adhesive sheet X with a release liner (FIG. 1). Next, the adhesive sheet 10 exposed by the peeling is bonded to the member 51 (FIG. 5A). Next, the release liner 20 is peeled off from the adhesive sheet 10 on the member 51. Next, the adhesive sheet 10 exposed by the peeling is bonded to the first surface 52a of the cover glass 52. In the second method, first, the release liner 30 is peeled off from the adhesive sheet 10 of the optically clear adhesive sheet X with a release liner (FIG. 1). Next, the adhesive sheet 10 exposed by the peeling is bonded to the first surface 52a of the cover glass 52. Next, the release liner 20 is peeled off from the adhesive sheet 10 on the cover glass 52. Next, the adhesive sheet 10 exposed by the peeling is bonded to the member 51.

[0095] According to the optically adhesive sheet X with a release liner, in either the first method or the second method, when the release liner 30 (light release liner) is peeled off from the adhesive sheet 10, the unintentional peeling of the release liner 20 (heavy release liner) from the adhesive sheet 10 is suppressed. Also, according to the optically adhesive sheet X with a release liner, in either the first method or the second method, the adhesive sheet 10 is bonded to the stepped surface (the first surface 52a of the cover glass 52) of the adherend in a soft state before photocuring. Therefore, the adhesive sheet 10 of the optically adhesive sheet X with a release liner is suitable for realizing good step following properties.

[0096] Next, as shown in FIG. 5C, the adhesive sheet 10 is photocured (photocuring step) between the member 51 and the cover glass 52 by ultraviolet irradiation. By ultraviolet irradiation, in the adhesive sheet 10, the photopolymerization reaction of the photopolymerizable polyfunctional compound proceeds, and a photopolymer of the photopolymerizable polyfunctional compound is formed. Since the photopolymerization reaction proceeds around the base polymer (the first photopolymer and the second photopolymer having a photocrosslinked structure), the photopolymer of the photopolymerizable polyfunctional compound is formed while forming an interpenetrating polymer network structure (IPN) with the base polymer. Thereby, the adhesive sheet 10 is highly elasticized, and the bonding force between the member 51 and the cover glass 52 is increased. Examples of the light source for ultraviolet irradiation include an ultraviolet LED lamp, a black light lamp, a high-pressure mercury lamp, and a metal halide lamp. Also, in ultraviolet irradiation, a wavelength cut filter for cutting a part of the wavelength region of the light emitted from the light source may be used. In ultraviolet irradiation, the irradiation integrated light amount is, for example, 50 to 10000 mJ / cm 2 is.

Example

[0097] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. Also, the specific numerical values such as the compounding amounts (contents), physical property values, parameters, etc. described below can be replaced with the upper limits (numerical values defined as "below" or "less than") or lower limits (numerical values defined as "above" or "exceeding") of the corresponding compounding amounts (contents), physical property values, parameters, etc. described in the above-mentioned "Mode for Carrying Out the Invention".

[0098] [Example 1] 〈Preparation of prepolymer composition〉 In a flask, after adding a total of 0.07 parts by mass of two types of first photopolymerization initiators to a monomer mixture of 78 parts by mass of n-butyl acrylate (BA), 16 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 6 parts by mass of 4-hydroxybutyl acrylate (4HBA), the mixture was irradiated with ultraviolet rays under a nitrogen atmosphere to polymerize a part of the monomer components in the mixture to obtain a prepolymer composition. As the first photopolymerization initiator, 0.035 parts by mass of "Omnirad184" (1-hydroxycyclohexyl phenyl ketone) manufactured by IGM Resins and 0.035 parts by mass of "Omnirad651" (2,2-dimethoxy-1,2-diphenylethane-1-one) manufactured by IGM Resins were used. The ultraviolet irradiation was continued until the viscosity of the composition reached about 20 Pa·s. This viscosity is a value measured with a B-type viscometer under the conditions of rotor No. 5, rotor rotation speed of 10 rpm, and temperature of 30°C (the same applies to the viscosities described later). The obtained prepolymer composition is a partial polymer containing a photopolymer (photopolymerized polymer P1a) and monomer components (residual monomers) that have not undergone a polymerization reaction.

[0099] 〈Preparation of adhesive composition〉 Next, 100 parts by mass of the prepolymer composition, 2 parts by mass of acryloylmorpholine (ACMO) as an additional monomer, 8 parts by mass of 4-hydroxybutyl acrylate (4HBA) as another additional monomer, 0.8 parts by mass of urethane acrylate oligomer (UAO) (product name "Art Resin UN-350 NDTN001BA", weight average molecular weight 12,500, manufactured by Negami Kogyo Co., Ltd.) as a crosslinking agent, 0.4 parts by mass of a second photoinitiator, 0.5 parts by mass of an antioxidant (product name "Irganox 1010", manufactured by BASF), 0.15 parts by mass of a rust inhibitor (product name "BT-120", benzotriazole, manufactured by Johoku Chemical Industry Co., Ltd.), and 0.35 parts by mass of a silane coupling agent (product name "KBM-403", 3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain an adhesive composition. As the second photoinitiator, "Omnirad 819" (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) manufactured by IGM Resins was used.

[0100] <Preparation of Base Adhesive Sheet> Next, the adhesive composition was applied onto the release-treated surface of a first release liner as a heavy release liner having a release-treated surface on one side (product name "Diafoil MRV", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) to form a coating film. Next, the release-treated surface of a second release liner as a light release liner having a release-treated surface on one side (product name "Diafoil MRE", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) was laminated onto the coating film on the first release liner. Next, ultraviolet rays were irradiated onto the coating film between the release liners from the side of the second release liner to photocure the coating film and form an adhesive layer with a thickness of 100 μm (ultraviolet irradiation step). In the ultraviolet irradiation, a black light lamp (manufactured by Toshiba) was used as the light source, the illuminance was 6.5 mW / cm 2 and the integrated light quantity of irradiation was 1500 mJ / cm 2It was set as such. In the ultraviolet irradiation step, in the coating film, the photopolymerization reaction in the reaction system containing the above-mentioned residual monomer, additional monomer, and crosslinking agent proceeds, and the photopolymer P1b having a photocrosslinked structure is formed. Further, since the photopolymerization reaction proceeds around the above-mentioned photopolymer P1a, the photopolymer P1b is formed around the photopolymer P1a. The pressure-sensitive adhesive layer formed in this step contains such photopolymer P1a and photopolymer P1b as base polymers. In the above manner, a base pressure-sensitive adhesive sheet with a release liner (first release liner / base pressure-sensitive adhesive sheet (thickness 100 μm) / second release liner) was produced.

[0101] <Preparation of Post-Added Component Solution> 1.8 parts by mass of ethoxylated bisphenol A diacrylate (BPAEODE) (product name "ABE-300", molecular weight: 468.0, manufactured by Shin-Nakamura Chemical Co., Ltd.) as the first photopolymerizable polyfunctional compound, 5.7 parts by mass of trimethylolpropane triacrylate (TMPTA) (product name "Viscote #295", molecular weight: 296.3, manufactured by Osaka Organic Chemical Industry Co., Ltd.) as the second photopolymerizable polyfunctional compound, 1.4 parts by mass of the third photoinitiator, 3.5 parts by mass of an ultraviolet absorber (product name "Tinosorb S", manufactured by BASF), and 49.1 parts by mass of ethyl acetate as a solvent were mixed to prepare a post-added component solution (components other than the solvent in the solution are post-added components). As the third photoinitiator, "Omnirad 819" manufactured by IGM Resins was used. The composition of the post-added component solution is shown in Table 1. In Table 1, the unit of the blending amount of each component is relative "parts by mass".

[0102] <Preparation of Optically Clear Adhesive Sheet> After peeling off the second release liner from the base adhesive sheet with the above-mentioned release liner, a post-addition component solution was applied to the exposed surface of the base adhesive sheet thus exposed to a thickness of 20 μm (coating process). For the coating, a bar coater RDS No. 10 manufactured by R.D. SPECIALTIES was used. Next, it was dried in a dryer at 110 °C for 60 seconds. By the coating process and the drying process, the post-addition components (photopolymerizable polyfunctional compound, third photoinitiator, ultraviolet absorber) were penetrated into the base adhesive sheet, and the solvent was vaporized. Due to the penetration of the post-addition components into the base adhesive sheet, a photocurable optical adhesive sheet was formed. The addition amount of BPAEODE per 100 parts by mass of the base polymer (a total of 100 parts by mass of the above-mentioned prepolymer composition, additional monomer, and crosslinking agent) is 0.6 parts by mass, the addition amount of TMPTA is 2.0 parts by mass, and the addition amount of the third photoinitiator (Omnirad 819) is 0.5 parts by mass (in Table 2, for the photopolymerizable polyfunctional compound and the third photoinitiator, the relative amounts with respect to 100 parts by mass of the base polymer are shown in parentheses attached to the components). Next, the release-treated surface of a third release liner (product name "Diafoil MRQ", thickness 50 μm, manufactured by Mitsubishi Chemical Corporation), which is a lightly releasable liner having a release-treated surface on one side, was bonded to the optical adhesive sheet on the first release liner.

[0103] As described above, an optical adhesive sheet with a release liner of Example 1 (first release liner / optical adhesive sheet (thickness 100 μm) / third release liner) was produced. The optical adhesive sheet is a photocurable optical adhesive sheet containing a base polymer, a photopolymerizable polyfunctional compound, and a third photoinitiator.

[0104] 〔Example 2〕 An optical adhesive sheet with a release liner of Example 2 was produced in the same manner as the optical adhesive sheet with a release liner of Example 1, except for the following.

[0105] In the preparation of the post-added component solution, the compounding amount of BPAEODE was 3.0 parts by mass, and the compounding amount of ethyl acetate was 47.9 parts by mass. In the optical adhesive sheet of Example 2, the addition amount of BPAEODE as the first photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer was 1.0 part by mass, the addition amount of TMPTA as the second photopolymerizable polyfunctional compound was 2.0 parts by mass, and the addition amount of the third photoinitiator (Omnirad 819) was 0.5 part by mass (shown in Table 2).

[0106] [Example 3] An optical adhesive sheet with a release liner of Example 3 was produced in the same manner as the optical adhesive sheet with a release liner of Example 1, except for the following.

[0107] In the preparation of the post-added component solution, the addition amount of the third photoinitiator (Omnirad 819) was 1.8 parts by mass, and the compounding amount of ethyl acetate was 49.1 parts by mass. In the optical adhesive sheet of Example 3, the addition amount of BPAEODE as the first photopolymerizable polyfunctional compound per 100 parts by mass of the base polymer was 0.6 part by mass, the addition amount of TMPTA as the second photopolymerizable polyfunctional compound was 2.0 parts by mass, and the addition amount of the third photoinitiator (Omnirad 819) was 1.0 part by mass (shown in Table 2).

[0108] [Comparative Example 1] An optical adhesive sheet with a release liner of Comparative Example 1 was produced in the same manner as the optical adhesive sheet with a release liner of Example 1, except for the following.

[0109] In the preparation of the adhesive composition, the compounding amount of the crosslinking agent (UAO) was 1.2 parts by mass. In the preparation of the post-added component solution, BPAEODE was not compounded, the compounding amount of TMPTA (a photopolymerizable polyfunctional compound) was 16.1 parts by mass, the compounding amount of the third photoinitiator (Omnirad819) was 0.68 parts by mass, and the compounding amount of ethyl acetate was 39.7 parts by mass. In the optical adhesive sheet of Comparative Example 1, the addition amount of the photopolymerizable polyfunctional compound (TMPTA) per 100 parts by mass of the base polymer was 5.6 parts by mass, and the addition amount of the third photoinitiator (Omnirad819) was 0.24 parts by mass (shown in Table 2).

[0110] 〔Comparative Example 2〕 An optical adhesive sheet with a release liner of Comparative Example 2 was produced in the same manner as the optical adhesive sheet with a release liner of Example 1, except for the following.

[0111] In the preparation of the adhesive composition, the compounding amount of the crosslinking agent (UAO) was 1.2 parts by mass. In the preparation of the post-added component solution, BPAEODE was not compounded, the compounding amount of TMPTA (a photopolymerizable polyfunctional compound) was 16.1 parts by mass, and the compounding amount of ethyl acetate was 39.0 parts by mass. In the optical adhesive sheet of Comparative Example 2, the addition amount of the photopolymerizable polyfunctional compound (TMPTA) per 100 parts by mass of the base polymer was 5.6 parts by mass, and the addition amount of the third photoinitiator (Omnirad819) was 0.5 parts by mass (shown in Table 2).

[0112] 〈Total light transmittance〉 For each of the optical adhesive sheets in Examples 1 to 3 and Comparative Examples 1 and 2, the total light transmittance was measured as follows.

[0113] First, a sample for measurement was prepared. Specifically, after peeling off the third release liner from the optical adhesive sheet, the exposed surface of the optical adhesive sheet was bonded to non-alkali glass (manufactured by Matsunami Glass Industry Co., Ltd.), and then the first release liner was peeled off from the optical adhesive sheet on the glass. Thus, a sample for measurement was obtained. Next, for this sample, the total light transmittance was measured in accordance with JIS K7136 (2000) using a haze meter "HM-150N" manufactured by Murakami Color Research Institute. In this measurement, the measurement results obtained by measuring only the non-alkali glass under the same conditions were used as the baseline. The total light transmittance (%) of each optical adhesive sheet is shown in Table 2.

[0114] 〈Gel fraction〉 The gel fractions of the optical adhesive sheets in Examples 1 to 3 and Comparative Examples 1 and 2 were measured. Specifically, it was as follows.

[0115] First, about 1 g of an adhesive sample was collected from the optical adhesive sheet. Next, the mass (W1) of the adhesive sample was measured. Next, the adhesive sample was immersed in 40 g of ethyl acetate in a container for 7 days. Next, all the components (insoluble parts) insoluble in ethyl acetate were recovered. Next, the insoluble part was dried at 130 °C for 2 hours (removal of ethyl acetate). Next, the mass (W2) of the insoluble part was measured. Then, based on the following formula, the gel fraction G (mass %) of the optical adhesive sheet after photocuring was calculated. The value is shown in Table 2. The gel fraction G shown in Table 2 for each optical adhesive sheet (having photocurability) in Examples 1 to 3 and Comparative Examples 1 and 2 is the gel fraction before photocuring of the optical adhesive sheet.

[0116] Gel fraction (mass %) = (W2 / W1) × 100

[0117] 〈Shear storage modulus〉 For each optical adhesive sheet in Examples 1 to 3 and Comparative Examples 1 and 2, the dynamic viscoelasticity was measured. Specifically, it was as follows.

[0118] First, for each optical adhesive sheet, the required number of measurement samples were prepared. Specifically, first, 20 optical adhesive sheets cut out from the optical adhesive sheet were laminated to produce a sample sheet with a thickness of about 2 mm. Next, this sheet was punched to obtain columnar pellets (diameter 7.9 mm) as measurement samples.

[0119] Then, for the measurement samples, using a dynamic viscoelasticity measuring device (product name "Advanced Rheometric Expansion System (ARES)", manufactured by Rheometric Scientific), after fixing them to a jig of parallel plates with a diameter of 7.9 mm, dynamic viscoelasticity measurement was performed. In this measurement, the measurement mode was set to the shear mode, the measurement temperature range was -50°C to 150°C, the heating rate was 5°C / min, and the frequency was 1 Hz. From the measurement results, the shear storage modulus (MPa) at 25°C was read. The values are shown in Table 2. The shear storage moduli shown in Table 2 for each optical adhesive sheet (having photocurability) in Examples 1 to 3 and Comparative Examples 1 and 2 are the shear storage moduli before photocuring of the optical adhesive sheet.

[0120] 〈Peeling force of release liner〉 For each optical adhesive sheet with a release liner in Examples 1 to 3 and Comparative Examples 1 and 2, the peeling force for peeling the heavy release liner from the optical adhesive sheet was measured (First Measurement).

[0121] In the preparation of the test piece for the First Measurement, first, a sample sheet (length 100 mm × width 25 mm) was cut out from the optical adhesive sheet with a release liner. Next, the third release liner (light release liner) was peeled off from the sample sheet, and the exposed surface of the optical adhesive sheet thus exposed was bonded to a glass plate to obtain a test piece.

[0122] Next, after allowing the test piece to stand at 25°C for 60 minutes, a peel test was performed to peel the first release liner (heavy release liner) on the test piece from the pressure-sensitive adhesive sheet, and the force required for peeling was measured as the peel force. In this measurement, a tensile testing machine (product name: "Autograph AG-50NX plus", manufactured by Shimadzu Corporation) was used, the measurement temperature was 25°C, the peel angle was 180°, and the tensile speed was 300 mm / min (the same applies to the second measurement described below). The measured peel force F1 (N / 25 mm) is shown in Table 2.

[0123] On the other hand, for each of the optically pressure-sensitive adhesive sheets with a release liner of Examples 1 to 3 and Comparative Examples 1 and 2, the peel force for peeling the light release liner from the optically pressure-sensitive adhesive sheet was measured (second measurement).

[0124] In the preparation of the test piece for the second measurement, first, a sample sheet (length 100 mm × width 25 mm) was cut out from the optically pressure-sensitive adhesive sheet with a release liner. Next, the first release liner (heavy release liner) side of the sample sheet was bonded to a glass plate with a double-sided strong adhesive tape to obtain a test piece.

[0125] Next, after allowing the test piece to stand at 25°C for 60 minutes, a peel test was performed to peel the third release liner (light release liner) on the test piece from the pressure-sensitive adhesive sheet, and the force required for peeling was measured as the peel force. The measured peel force F2 (N / 25 mm) is shown in Table 2. The difference F1 - F2 (N / 25 mm) between the peel force F1 and the peel force F2, and the ratio (F1 / F2) of the peel force F1 to the peel force F2 are also shown in Table 2.

[0126] 〈Probe Tack Test〉 For each of the optically pressure-sensitive adhesive sheets with a release liner of Examples 1 to 3 and Comparative Examples 1 and 2, the probe tack test was performed as follows.

[0127] First, an optically adhesive sheet with a release liner having a size of 20 mm × 40 mm was cut out as a test piece from an adhesive sheet with a release liner. Next, the test piece was set on the measurement table of a tack tester (product name: "TAC-1000", manufactured by Resca Co., Ltd.). Specifically, the first release liner side of the test piece was attached to the measurement table via a predetermined strong adhesive. Next, the third release liner was peeled off from the optically adhesive sheet in the test piece to expose one side (the second side) of the optically adhesive sheet. Then, a probe tack test was performed using the same tester.

[0128] In the probe tack test, a cylindrical stainless steel probe with a tip diameter (probe diameter) of 2.5 mm was used as the probe to be pressed against the optically adhesive sheet. The tip area of this probe is 19.63 mm 2 ². Also, in this test, the environmental temperature and the temperature of the probe were set to 25°C, the pressing speed was set to 0.08 mm / second, the pressing load was set to 1000 gf, the pressing time was set to 30 seconds, and the peeling speed was set to 0.08 mm / second. That is, in this test, first, the tip of the probe (diameter 2.5 mm) was vertically pressed against the optically adhesive sheet from above the optically adhesive sheet at a pressing speed of 0.08 mm / second until the pressing load reached 1000 gf. Subsequently, the pressing load of 1000 gf was maintained for 30 seconds. Subsequently, the probe was peeled off upward from the optically adhesive sheet at a peeling speed of 0.08 mm / second (peeling process). During this period, the load acting on the probe was measured as the stress of the optically adhesive sheet.

[0129] The measurement results of Examples 1 to 3 and Comparative Example 1 are shown in FIGS. 6 to 9. FIG. 6 represents the stress - peel distance curve obtained by the probe tack test of the optical adhesive sheet with a release liner of Example 1. In the graph of FIG. 6, the horizontal axis represents the peel distance (μm) of the probe, and the vertical axis represents the stress (gf) (the same applies to the graphs of FIGS. 7 to 9). The peel distance of the probe is the rising distance of the tip surface of the probe during the peel process of the probe (the moving distance in the height direction from the position of the second surface of the optical adhesive sheet at the start of peeling). FIG. 7 represents the stress - peel distance curve obtained by the probe tack test of the optical adhesive sheet with a release liner of Example 2. FIG. 8 represents the stress - peel distance curve obtained by the probe tack test of the optical adhesive sheet with a release liner of Example 3. FIG. 9 represents the stress - peel distance curve obtained by the probe tack test of the optical adhesive sheet with a release liner of Comparative Example 1. Regarding the probe tack tests of the optical adhesive sheets with release liners of Examples 1 to 3 and Comparative Examples 1 and 2, Table 2 shows the probe peel distance d (μm) when the stress becomes 0 gf during the probe peel process.

[0130] 〈Suppression of the release of the heavy release liner during the release of the light release liner〉 Regarding each of the optical adhesive sheets with release liners of Examples 1 to 3 and Comparative Examples 1 and 2, the difficulty of releasing the heavy release liner during the release of the light release liner was examined.

[0131] Specifically, first, 10 evaluation samples were prepared for each optical adhesive sheet with a release liner. Next, the evaluation samples were fixed on a predetermined stage. Specifically, the first release liner (heavy release liner) side of the evaluation sample was fixed to the stage via a double-sided adhesive tape (product name "TESA68547", manufactured by TESA). Next, the end of the third release liner (light release liner) of the evaluation sample on the stage was pinched with a fingertip, and the third release liner was peeled off. At the time of peeling, the peeling angle was set to approximately 45°, and the pulling speed was set to approximately 300 mm / min. Then, regarding the peeling suppression of the first release liner (heavy release liner) when the third release liner (light release liner) was peeled off, when the number of evaluation samples in which only the third release liner could be appropriately peeled off without causing peeling of the first release liner was 10, it was evaluated as "excellent", when it was 7 to 9, it was evaluated as "good", and when it was 0 to 6, it was evaluated as "poor". The evaluation results are shown in Table 2.

[0132] 〈Step following property test〉 The step following properties of each optical adhesive sheet in Examples 1 to 3 and Comparative Examples 1 and 2 were examined as follows.

[0133] First, a second sample sheet (75 mm × 45 mm) was cut out from the optical adhesive sheet with a release liner. Next, the third release liner (light release liner) was peeled off from the optical adhesive sheet in the second sample sheet, and the exposed surface of the optical adhesive sheet thus exposed was bonded to the center of a PET film (thickness 125 μm, 100 mm × 50 mm). For the bonding, a roll laminator was used, the pressure between the rolls was set to 0.2 MPa, and the feed rate was set to 100 mm / min (the same applies to the bonding described later). Next, the first release liner (heavy release liner) was peeled off from the optical adhesive sheet on the PET film, and the exposed surface of the optical adhesive sheet thus exposed was bonded to a glass plate with a printed layer (thickness 500 μm, length 100 mm × width 50 mm) to obtain a joined body. FIG. 11 shows the positional relationship between the glass plate 71 in the joined body and the optical adhesive sheet 72 derived from the second sample sheet. On one side in the thickness direction of the glass plate 71, a printed layer 73 (thickness 45 μm, black ink) is formed over the entire periphery of the edge of the glass plate 71. The printed layer 73 is formed in the range 15 mm inward from each end of the glass plate 71 in the length direction D1, and is formed in the range 5 mm inward from each end of the glass plate 71 in the width direction D2. The optical adhesive sheet 72 is bonded to the center of one side in the thickness direction of such a glass plate 71 and is in contact with the printed layer 73 over the entire periphery of the edge of the sheet. That is, the printed layer 73 on the glass plate 71 is sandwiched between the glass plate 71 and the optical adhesive sheet 72 in the range 2.5 mm outward from the inner edge of the layer.

[0134] Next, the joined body was autoclave-treated at 50°C and 0.5 MPa for 30 minutes. After that, the vicinity of the inner edge of the printed layer in the joined body was observed. Specifically, the inside of the inner edge of the printed layer (the region where the optical adhesive sheet should be in close contact with the glass plate) was observed at a magnification of 20 from the PET film side of the joined body using a digital microscope. Then, regarding the step followability of the optical adhesive sheet, when no bubbles were confirmed in the observation range, it was evaluated as "excellent", and when bubbles were confirmed, it was evaluated as "defective". The results are shown in Table 2.

[0135]

Table 1

[0136]

Table 2

Explanation of Symbols

[0137] X is an optical adhesive sheet with a release liner H In the thickness direction 10 Adhesive sheet (optical adhesive sheet) 11 First surface 12 Second surface 20 Release liner (heavy release liner) 21, 31 Release surface 30 Release liner (light release liner)

Claims

1. An optically adhesive sheet having a first surface and a second surface opposite to the first surface, a release liner that is removably adhered to the first surface, a light release liner that is removably adhered to the second surface, and an optically adhesive sheet with a release liner, wherein the optically adhesive sheet contains a base polymer, a photopolymerizable polyfunctional compound, and a photoinitiator, in a probe tack test under the following conditions on the second surface after peeling the light release liner from the optically adhesive sheet, the probe peel distance when the stress becomes 0 gf during the probe peeling process is 200 μm or more and 900 μm or less, an optically adhesive sheet with a release liner. [Conditions] Temperature: 25°C Probe diameter: 2.5 mm Pressing load: 1000 gf Pressing time: 30 seconds Peeling speed: 0.08 mm / second

2. The optically adhesive sheet with a release liner according to claim 1, wherein the photopolymerizable polyfunctional compound contains a photopolymerizable polyfunctional compound having an aromatic ring.

3. The optically adhesive sheet with a release liner according to claim 1, wherein the weight average molecular weight of the photopolymerizable polyfunctional compound is 1000 or less.

4. The optically adhesive sheet with a release liner according to any one of claims 1 to 3, wherein the gel fraction is 50% by mass or more.

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