Optical film with adhesive layer and image display device comprising the same

Abstract

This invention provides an optical film with an adhesive layer that significantly suppresses paste defects in irregularly shaped processing sections and exhibits excellent transparency. An embodiment of the optical film with an adhesive layer has an optical film and an adhesive layer on one side of the optical film, and the optical film with the adhesive layer has an irregular shape other than a rectangle. The adhesive composition constituting the adhesive layer comprises a (meth)acrylic acid-based polymer and an isocyanate crosslinking agent. The (meth)acrylic acid-based polymer comprises aromatic (meth)acrylic esters as monomer components. For every 100 parts by weight of the (meth)acrylic acid-based polymer, the adhesive comprises 2 to 20 parts by weight of the isocyanate crosslinking agent.

Description

Technical Field

[0001] The present invention relates to an optical film with an adhesive layer and an image display device comprising the optical film with the adhesive layer. Background Technology

[0002] Optical films are widely used in image display devices such as mobile phones and laptops for the purpose of displaying images and / or improving their performance. Optical films are typically constructed with an adhesive layer, allowing them to be bonded to the image display unit. In recent years, it has become desirable to process optical films into shapes other than rectangles (irregular shapes: for example, the formation of notches and / or through holes). However, there is a problem that adhesive defects (the phenomenon of the adhesive layer detaching from its ends) easily occur in the irregularly shaped portions of the optical film with the adhesive layer. To address this problem, adhesives capable of suppressing adhesive defects in the irregularly shaped portions have been explored; however, such adhesives have high haze, resulting in insufficient transparency of the resulting optical film with the adhesive layer.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-090896 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The present invention was made to solve the above-mentioned existing problems, and its main objective is to provide an optical film with an adhesive layer that can significantly suppress paste defects in irregularly shaped processing sections and has excellent transparency.

[0008] Problem Solving Methods

[0009] The optical film with an adhesive layer of the present invention has an optical film and an adhesive layer on one side of the optical film, and the optical film with the adhesive layer has an irregular shape other than a rectangle. The adhesive composition constituting the adhesive layer comprises a (meth)acrylic acid-based polymer and an isocyanate crosslinking agent. The (meth)acrylic acid-based polymer comprises aromatic (meth)acrylic acid esters as monomer components. Relative to 100 parts by weight of the (meth)acrylic acid-based polymer, the adhesive comprises 2 to 20 parts by weight of the isocyanate crosslinking agent.

[0010] In one embodiment, the isocyanate crosslinking agent is a toluene diisocyanate crosslinking agent.

[0011] In one embodiment, the above-mentioned (meth)acrylic acid-based polymer contains 10 to 30 parts by weight of the above-mentioned aromatic (meth)acrylic acid ester relative to 100 parts by weight of all monomer components.

[0012] In one embodiment, the above-mentioned (meth)acrylic acid-based polymer further comprises at least one monomer component selected from carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, amino-containing monomers, nitrile-containing monomers, and polyfunctional monomers. In one embodiment, the above-mentioned (meth)acrylic acid-based polymer contains 0.1 to 1 part by weight of the hydroxyl-containing monomer relative to 100 parts by weight of all monomer components. In one embodiment, the above-mentioned (meth)acrylic acid-based polymer contains 2 to 8 parts by weight of the carboxyl-containing monomer relative to 100 parts by weight of all monomer components.

[0013] In one embodiment, the weight-average molecular weight of the above-mentioned (meth)acrylic acid-based polymer is 2 million to 3 million.

[0014] In one embodiment, the optical film includes a polarizer. In another embodiment, the optical film further includes a phase retardation layer.

[0015] According to another aspect of the present invention, an image display device is provided. The image display device includes the aforementioned optical film with an adhesive layer.

[0016] The effects of the invention

[0017] According to an embodiment of the present invention, in an optical film with an adhesive layer having irregular shapes (irregularly shaped processing portions) other than rectangles, by incorporating an aromatic (meth) acrylate and a given amount of isocyanate crosslinking agent into the adhesive composition constituting the adhesive layer, it is possible to achieve an optical film with an adhesive layer that can significantly suppress paste defects in the irregularly shaped processing portions and has excellent transparency. Attached Figure Description

[0018] Figure 1 This is a top view schematic diagram illustrating an example of an irregularly shaped or irregularly shaped processing portion in an optical film with an adhesive layer according to an embodiment of the present invention.

[0019] Figure 2 This is a top view schematic diagram illustrating a modified example of an irregularly shaped or irregularly shaped processed portion in an optical film with an adhesive layer according to an embodiment of the present invention.

[0020] Figure 3 This is a top view schematic diagram illustrating another variation of the irregular or irregularly shaped processing portion in the optical film with adhesive layer according to an embodiment of the present invention.

[0021] Figure 4 This is a top view schematic diagram illustrating another variation of the irregular or irregularly shaped processing portion in the optical film with adhesive layer according to an embodiment of the present invention. Detailed Implementation

[0022] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. It should be noted that the drawings are shown schematically for ease of observation, and the ratios of length, width, thickness, etc., and angles in the drawings differ from the actual figures.

[0023] A. Overview of optical films with adhesive layers

[0024] An optical film with an adhesive layer according to an embodiment of the present invention has an optical film and an adhesive layer on one side of the optical film. In an embodiment of the present invention, the optical film with an adhesive layer has an irregular shape other than a rectangle. In this specification, "having an irregular shape other than a rectangle" means that the top view shape of the optical film with an adhesive layer has a shape other than a rectangle (a rectangle including cases where the diagonals are chamfered). Typically, the irregular shape is an irregularly shaped processing section. Therefore, "an optical film with an adhesive layer having an irregular shape other than a rectangle" (hereinafter, sometimes referred to as "irregularly shaped optical film") includes not only cases where the entire irregularly shaped optical film (i.e., the outer edge defining the top view shape of the film) is not rectangular, but also cases where irregularly shaped processing sections are formed in portions spaced inward from the outer edge of a rectangular optical film. In such irregularly shaped processing sections, paste defects are prone to occur, but according to an embodiment of the present invention, such paste defects can be significantly suppressed. Examples of irregular shapes (irregularly shaped processing sections) can be cited as... Figure 1 and Figure 2 The through hole shown is a machined section that appears as a concave portion when viewed from above. Representative examples of concave portions include shapes resembling a boat, V-shaped notches, and U-shaped notches. Other examples of irregular shapes (irregularly shaped machined portions) include... Figure 3 and Figure 4 The shape shown corresponds to that of a car dashboard. In this shape, the outer edge is formed as an arc along the direction of rotation of the instrument needle, and includes a V-shaped (including arc-shaped) portion where the outer edge convexes inward in the surface direction. Of course, the shape of the irregular shape (irregularly shaped processing part) is not limited to the example shown. For example, the shape of the through hole, in addition to the approximately circular shape shown in the example, can be any suitable shape (e.g., ellipse, triangle, quadrilateral, pentagon, hexagon, octagon) depending on the purpose. Furthermore, the through hole can be placed in any suitable position depending on the purpose. The through hole can be as follows... Figure 2As shown, it can be disposed approximately at the center of the longitudinal end of a rectangular optical film, or at a given position at the longitudinal end, or at a corner of the optical film; although not shown, it can also be disposed at the short side end of the rectangular optical film; or as... Figure 3 or Figure 4 It is positioned at the center of the irregularly shaped optical film as shown. Furthermore, the shapes illustrated in the figure can be appropriately combined according to the purpose. For example, it can be... Figure 1 A through-hole can be formed at any position on the irregularly shaped optical film; it can also be... Figure 3 or Figure 4 A V-shaped notch and / or a U-shaped notch are formed at any suitable position on the outer edge of the irregularly shaped optical film. Such irregularly shaped optical films are suitable for image display devices such as automotive dashboards, smartphones, tablet PCs, or smartwatches.

[0025] In embodiments of the present invention, the adhesive composition constituting the adhesive layer (hereinafter, sometimes simply referred to as the adhesive) comprises a (meth)acrylate base polymer and an isocyanate crosslinking agent. The (meth)acrylate base polymer comprises an aromatic (meth)acrylate. The adhesive contains 2 to 20 parts by weight of isocyanate crosslinking agent relative to 100 parts by weight of the (meth)acrylate base polymer. By combining an aromatic (meth)acrylate and a given amount of isocyanate crosslinking agent in the adhesive constituting the adhesive layer in this manner, paste defects in the irregularly shaped processing section can be significantly suppressed, and the haze of the resulting adhesive layer can be reduced. As a result, an optical film with an adhesive layer exhibiting excellent transparency can be obtained. It should be noted that details of the composition of the adhesive layer are described in section C below.

[0026] The amount of paste loss in the adhesive layer of the optical film with adhesive layer (especially the adhesive layer in the irregularly shaped processing section) is preferably 55 μm or less, more preferably 52 μm or less, and even more preferably 50 μm or less. The smaller the amount of paste loss, the more preferred; the lower limit can be, for example, 5 μm. According to embodiments of the present invention, the amount of paste loss in the irregularly shaped processing section can be reduced to a very small value. In this specification, "paste loss" refers to the maximum value of the adhesive layer that detaches from the outer edge of the optical film (including the outer edge of the through hole) in the inward direction in that direction.

[0027] B. Optical film

[0028] Optical films can be single-layer films or laminates. Examples of single-layer optical films include: window films, polarizers, and phase retardation films. Examples of laminated optical films include: polarizers (typically a laminate of a polarizer and a protective film), conductive films for touch panels, surface treatment films, and laminates formed by appropriately stacking these single-layer and / or laminated optical films for various purposes (e.g., circular polarizers for anti-reflective applications, polarizers with conductive layers for touch panels). Below, polarizers and circular polarizers will be briefly described as representative examples of optical films.

[0029] B-1. Polarizing filter

[0030] Typically, a polarizer has a polarizing mirror and a protective layer disposed on one or both sides of the polarizing mirror.

[0031] B-1-1. Polarizer

[0032] Typically, the polarizer is formed of a resin film containing a dichroic substance. Any suitable resin film suitable for use as a polarizer can be used as the resin film. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA-based resin") film. The resin film can be a single-layer resin film or a laminate of two or more layers.

[0033] As a specific example of a polarizer composed of a single-layer resin film, a polarizer made by dyeing and stretching a PVA-type resin film using iodine (typically uniaxial stretching) can be cited. The dyeing using iodine can be performed, for example, by immersing the PVA-type film in an aqueous iodine solution. The stretching magnification of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or during dyeing. Alternatively, dyeing can be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc., as needed. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-type film be washed away, but the PVA-type resin film can also swell to prevent uneven dyeing.

[0034] Specific examples of polarizers obtained using laminates include: polarizers obtained using a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or polarizers obtained using a resin substrate and a laminate coated with a PVA-type resin layer formed on the resin substrate. Polarizers obtained using a laminate of a resin substrate and a PVA-type resin layer coated on the resin substrate can be manufactured by: for example, coating a PVA-type resin solution onto a resin substrate, allowing it to dry to form a PVA-type resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-type resin layer; stretching and dyeing the laminate to form a polarizer from the PVA-type resin layer. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching may, as needed, further include stretching the laminate in a gas atmosphere at a high temperature (e.g., above 95°C) before stretching in the aqueous boric acid solution. The resulting resin substrate / polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate, and any suitable protective layer conforming to the purpose can be laminated on the peeled surface for use. Detailed descriptions of such a polarizer manufacturing method are provided, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0035] The thickness of the polarizer is preferably 25 μm or less, more preferably 1 μm to 12 μm, even more preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. If the thickness of the polarizer is within this range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0036] The polarizer preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The single-unit transmittance of the polarizer is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0037] B-1-2. Protective layer

[0038] The protective layer can be formed from any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that form the main component of the film include: cellulose resins such as cellulose triacetate (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrene, polynorbornene, polyolefins, (meth)acrylic acids, acetates, and other transparent resins. Additionally, thermosetting resins or UV-curable resins such as (meth)acrylic acids, urethanes, (meth)acrylate urethanes, epoxy resins, and silicone resins can also be used. Furthermore, glassy polymers such as siloxane polymers can also be used. Additionally, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material for this membrane, resin compositions can be used, for example, thermoplastic resins containing substituted or unsubstituted imide groups on the side chains, and thermoplastic resins containing substituted or unsubstituted phenyl and nitrile groups on the side chains. Examples include resin compositions having alternating copolymers formed from isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer membrane can be, for example, an extruded product of the above-mentioned resin compositions.

[0039] Depending on the needs, the protective layer (outer protective layer) opposite to the adhesive layer can be subjected to surface treatments such as hard coating, anti-reflective treatment, anti-adhesion treatment, and anti-glare treatment.

[0040] In one embodiment, the protective layer (inner protective layer) on the adhesive layer side is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0 nm to 10 nm, and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm. In another embodiment, the inner protective layer can be a phase retardation film, a brightness enhancement film, a diffusion film, etc.

[0041] The thickness of the protective layer can be any suitable thickness. Preferably, the thickness of the protective layer is 5 μm to 200 μm, more preferably 15 μm to 45 μm, and even more preferably 20 μm to 40 μm. It should be noted that, in the case of surface treatment, the thickness of the protective layer includes the thickness of the surface treatment layer.

[0042] B-2. Circular polarizer

[0043] A circular polarizer typically comprises a polarizer and a phase retardation layer. In practice, the polarizer can be incorporated into the circular polarizer as a polarizer with protective layers on one or both sides. Typically, the phase retardation layer can be disposed between the polarizer and the adhesive layer. The polarizer and polarizer are as described in section B-1 above.

[0044] The phase difference layer can be a single layer or a stacked structure.

[0045] When the phase retardation layer is constructed as a single layer, it typically functions as λ / 4. In this case, the in-plane phase difference Re(550) of the phase retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. The angle between the slow axis of the phase retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably about 45°. The phase retardation layer can exhibit inverse wavelength dispersion characteristics where the phase difference value increases with the wavelength of the measurement light, positive wavelength dispersion characteristics where the phase difference value decreases with the wavelength of the measurement light, and flat wavelength dispersion characteristics where the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the phase retardation layer exhibits inverse wavelength dispersion characteristics. In this case, the Re(450) / Re(550) of the phase retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and less than 0.95.

[0046] In the case where the phase difference layer has a stacked structure, typically there is a two-layer structure with a first phase difference layer and a second phase difference layer. In this case, either the first or second phase difference layer can function as a λ / 2 waveplate, and the other can function as a λ / 4 waveplate. For example, when the first phase retardation layer can function as a λ / 2 waveplate and the second phase retardation layer can function as a λ / 4 waveplate, the Re(550) of the first phase retardation layer is preferably 200nm to 300nm, more preferably 230nm to 290nm, and even more preferably 250nm to 280nm, and the angle between its slow axis and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably about 15°; the Re(550) of the second phase retardation layer 22 is preferably 100nm to 190nm, more preferably 110nm to 170nm, and even more preferably 130nm to 160nm, and the angle between its slow axis and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably about 75°.

[0047] The retardation layer can be formed from any suitable material, provided it meets the characteristics described above. For example, the retardation layer can be a resin film (typically a stretched film) or an orientation-cured layer of a liquid crystal compound (a liquid crystal orientation-cured layer). Representative examples of resins constituting the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins can be used alone or in combination (e.g., blending, copolymerizing). When the retardation layer is composed of a resin film exhibiting inverse dispersion wavelength characteristics, polycarbonate resins or polyester carbonate resins (hereinafter also simply referred to as polycarbonate resins) can be appropriately used. Details of polycarbonate resins suitable for use in retardation layers and methods for forming retardation layers are described, for example, in Japanese Patent Application Publication Nos. 2014-10291, 2014-26266, 2015-212816, 2015-212817, and 2015-212818; specific examples of liquid crystal compounds and details of methods for forming alignment-cured layers are described, for example, in Japanese Patent Application Publication No. 2006-163343. These publications are incorporated herein by reference.

[0048] C. Adhesive layer

[0049] C-1. Properties of the adhesive layer

[0050] The haze of the adhesive layer is preferably 2.0% or less, more preferably 1.8% or less, further preferably 1.5% or less, particularly preferably 1.2% or less, and especially preferably 1.0% or less. Lower haze is more preferred, with a lower limit of, for example, 0.05%. According to embodiments of the present invention, while reducing the haze of the adhesive layer in this way (resulting in an optical film with an adhesive layer exhibiting excellent transparency), paste defects in the irregularly shaped processing section can be suppressed as described above. It should be noted that the haze can be determined using JIS K 7136.

[0051] The creep value of the adhesive layer at 85°C is preferably 500 μm or less, more preferably 5 μm to 500 μm. In one embodiment, the creep value is preferably 200 μm to 450 μm, more preferably 220 μm to 420 μm. In another embodiment, the creep value is preferably 5 μm to 300 μm, more preferably 5 μm to 200 μm, further preferably 10 μm to 100 μm, particularly preferably 15 μm to 70 μm, and especially preferably 20 μm to 50 μm. If the creep value is within such a range, paste defects in irregularly shaped processing sections can be significantly suppressed, and peeling in high temperature and high humidity environments can be significantly suppressed. It can be inferred that even with relatively large creep values ​​(e.g., above 200 μm), paste defects can be suppressed by controlling the composition of the adhesive layer (e.g., type of base polymer (polarity, Tg, softness), molecular weight) and crosslinking structure (e.g., type of crosslinking agent, distance between crosslinking points (molecular weight between crosslinking points), crosslinking density, and uncrosslinked components (sol components)). It should be noted that the creep value can be determined, for example, by pasting a test sample cut from an optical film with an adhesive layer onto a support plate with a 10 mm × 10 mm joint surface. With the support plate with the test sample attached fixed, a load of 500 gf is applied vertically downwards. The offset from the support plate after 1 second and 3600 seconds of applying the load is measured and denoted as Cr1 and Cr, respectively. 3600 . Will be composed of Cr1 and Cr 3600 The creep value is calculated using the following formula: ΔCr.

[0052] ΔCr=Cr 3600 -Cr1

[0053] The energy storage modulus of the adhesive layer at 85°C is preferably 1.0 × 10⁻⁶. 4 Pa or higher, more preferably 2.0 × 10 Pa 4 Pa or higher, more preferably 5.0 × 10 Pa 4 Pa or higher, preferably 1.0 × 10 Pa 5 Pa or higher. If the energy storage modulus is within this range, the desired creep value can be easily achieved. On the other hand, the energy storage modulus is, for example, 3.0 × 10⁻⁶ Pa. 6 Below Pa. If the upper limit of the energy storage modulus is within such a range, the peeling of the adhesive layer in high temperature and high humidity environments can be significantly suppressed.

[0054] The gel fraction of the adhesive layer is preferably 55% to 95%. In one embodiment, the gel fraction is preferably 60% to 93%, more preferably 80% to 91%. In this case, the weight-average molecular weight (Mw) of the high molecular weight component from the base polymer in the uncrosslinked component (sol component) of the adhesive composition is, for example, 50,000 to 1,000,000, preferably 50,000 to 500,000, more preferably 100,000 to 400,000. It should be noted that the gel fraction can be determined by (dry weight after impregnation / dry weight before impregnation) × 100 when the crosslinked adhesive is dried after being impregnated in a given solvent (e.g., ethyl acetate) for 6 days. The weight-average molecular weight (Mw) of the high molecular weight component from the base polymer in the uncrosslinked component (sol component) of the adhesive composition can be determined, for example, by gel permeation chromatography (GPC) and calculated using polystyrene conversion.

[0055] The swelling degree of the adhesive layer is preferably 35 times or less, more preferably 10 to 30 times, even more preferably 11 to 28 times, and particularly preferably 12 to 20 times. If the swelling degree is within this range, paste defects in the irregularly shaped processing section can be significantly suppressed. It should be noted that the swelling degree can be determined by immersing the cross-linked adhesive in a given solvent (e.g., ethyl acetate) for 6 days, based on (weight after immersion / dry weight after immersion).

[0056] The storage modulus, gel fraction, and swelling degree of the adhesive layer can be controlled by adjusting the composition of the adhesive that constitutes the adhesive layer (e.g., the type of base polymer (polarity, Tg, softness), molecular weight) and the crosslinking structure (e.g., the type of crosslinking agent, the distance between crosslinking points (molecular weight between crosslinking points), and the crosslinking density). More specifically, the type and combination of monomer components of the base polymer, the polymerization conditions of the base polymer, and the type and amount of crosslinking agent can be appropriately set.

[0057] The thickness of the adhesive layer is preferably 2 μm to 55 μm, more preferably 2 μm to 30 μm, further preferably 2 μm to 20 μm, and particularly preferably 5 μm to 15 μm. If the thickness of the adhesive layer is within such a range, the paste defects in the irregularly shaped processing section can be significantly suppressed based on the synergistic effect of setting the adhesive to a given configuration.

[0058] Typically, the adhesive layer may be formed from an adhesive composition containing a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a rubber polymer as a base polymer. When using a (meth)acrylic polymer as the base polymer, the adhesive layer may be formed, for example, from an adhesive composition containing a (meth)acrylic polymer (A) as the base polymer. The (meth)acrylic polymer (A) contains an alkyl (meth)acrylic ester as a main component. In this specification, the (meth)acrylic polymer used as the base polymer is sometimes referred to as a (meth)acrylic base polymer.

[0059] C-2. (Meth)acrylic polymers (A)

[0060] As described above, the (meth)acrylic polymer (A) contains alkyl (meth)acrylate as a main component. From the viewpoint of improving the adhesion of the adhesive layer, the alkyl (meth)acrylate is preferably 50 parts by weight or more relative to 100 parts by weight of all monomer components forming the (meth)acrylic polymer (A). The remaining portion of the monomers other than the alkyl (meth)acrylate can be arbitrarily set. It should be noted that (meth)acrylate refers to acrylates and / or methacrylates.

[0061] Alkyl methacrylates, which form the main backbone of the (meth)acrylic polymer (A), can be exemplified by linear or branched alkyl groups having 1 to 18 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isotetradecyl, undecyl, tridecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, etc. Alkyl methacrylates can be used alone or in combination. The average number of carbon atoms in the alkyl group is preferably 3 to 10.

[0062] In embodiments of the present invention, the (meth)acrylic polymer (A) comprises an aromatic hydrocarbon monomer (a1) as a monomer component. The aromatic hydrocarbon monomer (a1) is a compound whose structure contains an aromatic hydrocarbon group and polymerizable unsaturated double bonds such as (meth)acryloyl group and vinyl group. Specific examples of the aromatic hydrocarbon monomer (a1) include aromatic (meth)acrylates such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. Aromatic (meth)acrylates can be used alone or in combination. By using the aromatic hydrocarbon monomer (a1) as a monomer component, paste defects can be suitably suppressed, and a low-haze adhesive layer can be formed. More specifically, by using a given amount or more of an isocyanate crosslinking agent as described below, paste defects can be significantly suppressed. On the other hand, if a large amount of an isocyanate crosslinking agent is used, the resulting adhesive layer may sometimes have increased haze due to its refractive index, dispersibility, etc. By using aromatic hydrocarbon monomers (a1) as monomer components, the refractive index difference with isocyanate crosslinking agents can be reduced, and the dispersibility of isocyanate crosslinking agents in the adhesive composition can be improved. As a result, an adhesive layer (ultimately an optical film with an adhesive layer) can be achieved that balances the suppression of paste defects and transparency (low haze).

[0063] The content of aromatic hydrocarbon monomer (a1) is preferably 10 to 50 parts by weight, more preferably 10 to 30 parts by weight, and even more preferably 11 to 25 parts by weight, relative to 100 parts by weight of all monomer components forming the (meth)acrylic polymer (A). If the content is too low, it may sometimes result in a higher haze in the resulting adhesive layer.

[0064] In addition to alkyl methacrylates and aromatic hydrocarbon monomers (a1), (meth)acrylic acid polymers (A) may also contain comonomers such as carboxyl-containing monomers (a2) and hydroxyl-containing monomers (a3). The comonomers can be used alone or in combination. When the adhesive composition contains a crosslinking agent (described later), the comonomers can become reaction sites with the crosslinking agent. Since carboxyl-containing and hydroxyl-containing monomers have high reactivity with intermolecular crosslinking agents, they are preferred for improving the cohesiveness and heat resistance of the resulting adhesive layer. Furthermore, carboxyl-containing monomers are preferred for their combination of durability and reworkability, while hydroxyl-containing monomers are preferred for improving reworkability.

[0065] Carboxyl-containing monomers (a2) are compounds whose structures contain a carbonyl group and polymerizable unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. Examples of carboxyl-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylic acid, carboxypentyl (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is preferred from the viewpoints of copolymerization, price, and improved adhesive properties of the adhesive layer.

[0066] When using a carboxyl-containing monomer (a2) as a monomer component, the content of the carboxyl-containing monomer (a2) is preferably 0.01 to 10 parts by weight, more preferably 2 to 8 parts by weight, relative to 100 parts by weight of all monomer components forming the (meth)acrylic polymer (A).

[0067] Hydroxyl-containing monomers (a3) ​​are compounds whose structures contain hydroxyl groups and polymerizable unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylaurate (meth)acrylate, and other hydroxyalkyl (meth)acrylates; methyl (4-hydroxymethylcyclohexyl)acrylate, etc. From the viewpoint of improving the durability of the adhesive layer, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is more preferred.

[0068] When using a hydroxyl-containing monomer (a3) ​​as a monomer component, the content of the hydroxyl-containing monomer (a3) ​​is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 1 part by weight, relative to 100 parts by weight of all monomer components forming the (meth)acrylic polymer (A).

[0069] As a monomer component, other comonomers (a4) can be further used. These other comonomers (a4) have polymerizable functional groups with unsaturated double bonds, such as (meth)acryloyl or vinyl groups. By using other comonomers (a4), the adhesion and heat resistance of the adhesive layer can be improved. These other comonomers (a4) can be used alone or in combination.

[0070] By using amino-containing monomers, amide-containing monomers, and nitrile-containing monomers as other comonomers (a4), the adhesion and durability of the adhesive layer can be improved. Examples of amino-containing monomers include N,N-dimethylaminoethyl methacrylate and N,N-dimethylaminopropyl methacrylate. Amide-containing monomers include, for example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethyl-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, mercaptoethyl(meth)acrylamide, and other acrylamide monomers; N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and other N-acryloyl heterocyclic monomers; and N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and other N-vinyl lactam monomers. Nitrile-containing monomers include, for example, (meth)acrylonitrile.

[0071] Other comonomers (a4) can also be multifunctional monomers. By using multifunctional monomers, it is possible to adjust the gel fraction of the adhesive layer and control the cohesiveness. Examples of multifunctional monomers include: hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl methacrylate, vinyl methacrylate, epoxy acrylate, polyester acrylate, urethane acrylate, and other multifunctional acrylates; and divinylbenzene. The preferred polyfunctional acrylates are 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

[0072] Other comonomers (a4) besides those mentioned above may include, for example: 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 3-methoxypropyl methacrylate, 3-ethoxypropyl methacrylate, 4-methoxybutyl methacrylate, 4-ethoxybutyl methacrylate, and other alkoxyalkyl esters of methacrylate; cyclizable monomers such as methyl 2-(allyloxymeth)acrylate; and condensed methacrylates. Monomers containing epoxy groups, such as hydroglycerol esters and methyl glycidyl acrylate; monomers containing sulfonic acid groups, such as sodium vinyl sulfonate; monomers containing phosphoric acid groups; methacrylates with alicyclic hydrocarbon groups, such as cyclopentyl acrylate, cyclohexyl acrylate, and isobornyl acrylate; vinyl esters, such as vinyl acetate and vinyl propionate; aromatic vinyl compounds, such as styrene and vinyltoluene; olefins or dienes, such as ethylene, propylene, butadiene, isoprene, and isobutylene; vinyl ethers, such as vinyl alkyl ethers; and vinyl chloride.

[0073] Relative to 100 parts by weight of all monomer components forming the (meth)acrylic polymer (A), the content of other comonomers (a4) in the (meth)acrylic polymer (A) is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, further preferably 8 parts by weight or less, and particularly preferably 5 parts by weight or less.

[0074] (Meth)acrylic acid polymers (A) may also contain monomers (a5) with a glass transition temperature of 0°C or higher and having unsaturated carbon double bonds as monomer components. Examples of monomers (a5) with a glass transition temperature of 0°C or higher and having unsaturated carbon double bonds include alkyl meth)acrylic acid monomers and (meth)acrylic acid. Monomer (a5) is preferably a monomer with a glass transition temperature of 20°C or higher and having unsaturated carbon double bonds, and more preferably a monomer with a glass transition temperature of 40°C or higher and having unsaturated carbon double bonds.

[0075] Examples of monomers (a5) include: methyl acrylate (Tg: 8℃), methyl methacrylate (Tg: 105℃), ethyl methacrylate (Tg: 65℃), n-propyl acrylate (Tg: 3℃), n-propyl methacrylate (Tg: 35℃), n-pentyl acrylate (Tg: 22℃), n-tetradecyl acrylate (Tg: 24℃), n-hexadecyl acrylate (Tg: 35℃), n-hexadecyl methacrylate (Tg: 15℃), n-stearyl acrylate (Tg: 30℃), and n-stearyl methacrylate (Tg: 15℃). Straight-chain alkyl esters of (meth)acrylate, such as tert-butyl acrylate (Tg: 43℃), tert-butyl methacrylate (Tg: 48℃), isopropyl methacrylate (Tg: 81℃), and isobutyl methacrylate (Tg: 48℃); branched-chain alkyl esters of (meth)acrylate, such as cyclohexyl acrylate (Tg: 19℃), cyclohexyl methacrylate (Tg: 65℃), isobornyl acrylate (Tg: 94℃), and isobornyl methacrylate (Tg: 180℃); acrylic acid (Tg: 106℃), etc. These can be used alone or in combination.

[0076] C-3. Method for manufacturing (A) (meth)acrylic acid polymers

[0077] (Meth)acrylic acid polymers (A) can be manufactured by any suitable method. Specific examples of manufacturing methods include: electron beam polymerization, UV radiation polymerization, solution polymerization, bulk polymerization, emulsion polymerization, and various free radical polymerizations. The resulting (meth)acrylic acid polymer (A) can be any copolymer, such as a random copolymer, block copolymer, or graft copolymer.

[0078] In solution polymerization, ethyl acetate or toluene can be used as the polymerization solvent. The reaction in solution polymerization can be carried out under a gas stream of inert gas such as nitrogen, with the polymerization initiator added to the monomer component, typically at around 50°C to 70°C for about 5 to 30 hours.

[0079] The polymerization initiators, chain transfer agents, emulsifiers, etc. used for free radical polymerization can be appropriately selected according to the purpose. The weight-average molecular weight of (meth)acrylic acid polymers (A) can be controlled according to the amount of polymerization initiator and chain transfer agent and the reaction conditions. The type and amount of these agents can be adjusted according to the desired weight-average molecular weight.

[0080] Examples of polymerization initiators include: 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropanediamine) disulfate, 2,2'-azobis(N.N'-dimethyleneisobutyronitrile), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanediamine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057), potassium persulfate, ammonium persulfate, di(2-ethylhexyl) peroxide dicarbonate, and peroxide dicarbonate. Di(4-tert-butylcyclohexyl) carbonate, disec-butyl percarbonate, tert-butyl peroxynedecanoate, tert-hexyl peroxynepentanoate, dilauroyl peroxide, dioctanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxyne-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-di-tert-hexylcyclohexane peroxide, tert-butyl hydroperoxide, and other peroxide initiators; combinations of persulfate and sodium bisulfite; combinations of peroxide and sodium ascorbate, etc., are redox initiators that combine peroxides and reducing agents.

[0081] The polymerization initiator can be used alone or in combination. The total amount of polymerization initiator relative to 100 parts by weight of monomer is preferably about 0.005 parts by weight to 1 part by weight, more preferably about 0.01 parts by weight to 0.5 parts by weight.

[0082] Examples of chain transfer agents include: dodecyl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolic acid, and 2,3-dimercapto-1-propanol. Chain transfer agents can be used alone or in combination of two or more. The total amount of chain transfer agent used is approximately 0.1 parts by weight or less per 100 parts by weight of the monomer component.

[0083] Examples of emulsifiers used in emulsion polymerization include anionic emulsifiers such as sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecylbenzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkylphenyl ether sulfate; and nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene-polyoxypropylene block polymers. Emulsifiers can be used alone or in combination.

[0084] Examples of reactive emulsifiers include those incorporating free radical polymerizable functional groups such as propylene groups and allyl ether groups. Specific examples include AQUALON HS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (all manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), and ADEKA REASOAP SE10N (manufactured by ADEKA Corporation). Since reactive emulsifiers are incorporated into the polymer chain after polymerization, they exhibit improved water resistance and are therefore preferred. The amount of emulsifier used is preferably 0.3 to 5 parts by weight, more preferably 0.5 to 1 part by weight, relative to 100 parts by weight of the total monomer content. When the amount of emulsifier is within this range, the polymerization stability and the mechanical stability of the resulting adhesive layer are excellent.

[0085] (Meth)acrylic acid polymers (A) can be manufactured via radiation polymerization by irradiating the monomer components with radiation such as electron beams or UV light to induce polymerization. In the case of radiation polymerization via UV polymerization, a photoinitiator can be included in the monomer components, thereby shortening the polymerization time. In the case of radiation polymerization using electron beams, it is not necessary to specifically include a photoinitiator in the monomer components.

[0086] As a photopolymerization initiator, any suitable photopolymerization initiator can be used. Specific examples include: benzoin ethers, acetophenones, α-ol ketones, photoactive oximes, benzoin, benzoyl, benzophenones, ketals, and thioxanthones. The amount of photopolymerization initiator used is preferably 0.02 to 1.5 parts by weight, more preferably 0.1 to 1 part by weight, relative to 100 parts by weight of the total monomer components. The photopolymerization initiator can be used alone or in combination.

[0087] The weight-average molecular weight (Mw) of the (meth)acrylic acid polymer (A) is preferably 1,000,000 to 3,000,000, more preferably 2,000,000 to 3,000,000, and even more preferably 2,000,000 to 2,800,000. When the weight-average molecular weight (Mw) is less than 1,000,000, the suppression of paste defects may sometimes become insufficient. When the weight-average molecular weight (Mw) exceeds 3,000,000, it may sometimes lead to an increase in viscosity and / or gelation during polymer polymerization.

[0088] The polydispersity index (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of the (meth)acrylic acid polymer (A) is preferably 5.0 or less, more preferably 1.05 to 5.0, and even more preferably 1.05 to 4.0. When the polydispersity index (Mw / Mn) is large (e.g., exceeding 5.0), there are more low-molecular-weight polymers. Even if the adhesive layer is formed from the same constituent materials, the amount of uncrosslinked polymers and oligomers (sol components) will increase, resulting in lower toughness (increased fragility) of the adhesive layer. This can sometimes lead to paste defects during irregular processing and peeling in high-temperature and high-humidity environments. It should be noted that the polydispersity index (Mw / Mn), like the weight-average molecular weight, can be determined by measuring it using GPC (gel permeation chromatography) and calculating the value using polystyrene conversion.

[0089] C-4. Silane coupling agents containing functional groups

[0090] The adhesive composition may contain a silane coupling agent with a functional group. Examples of functional groups include: epoxy, mercapto, amino, isocyanate, isocyanurate, vinyl, styrene, acetoacetyl, acylurea, thiourea, (meth)acrylate, heterocyclic, anhydride, and combinations thereof. The silane coupling agent containing the functional group may be used alone or in combination.

[0091] Examples of functionalized silane coupling agents include: 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.; mercaptosilane coupling agents such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, etc.; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethyl... Coupling agents containing aminosilanes, such as oxysilyl-N-(1,3-dimethylbutylene)propylamine and N-phenyl-γ-aminopropyltrimethoxysilane; coupling agents containing isocyanate groups, such as 3-isocyanatepropyltriethoxysilane; coupling agents containing vinyl silanes, such as vinyltrimethoxysilane and vinyltriethoxysilane; coupling agents containing styryl silanes, such as p-styryltrimethoxysilane; and coupling agents containing (meth)acrylic acid silanes, such as 3-acryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyltriethoxysilane. Among these, coupling agents containing epoxy groups and coupling agents containing mercaptosilanes are preferred. Commercially available epoxy group silane coupling agents include, for example, "KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.

[0092] As functionalized silane coupling agents, silane coupling agents with multiple alkoxysilyl groups within the molecule (oligomeric silane coupling agents) can also be used. Specific examples include epoxy-containing oligomeric silane coupling agents manufactured by Shin-Etsu Chemical Co., Ltd., trade names “X-41-1053,” “X-41-1059A,” “X-41-1056,” and “X-40-2651”; and mercapto-containing oligomeric silane coupling agents “X-41-1818,” “X-41-1810,” and “X-41-1805.” Oligomeric silane coupling agents are less volatile and have multiple alkoxysilyl groups, thus effectively improving durability.

[0093] When a functionalized silane coupling agent is incorporated into an adhesive composition, the amount of the functionalized silane coupling agent is typically 0.001 parts by weight or more and 5 parts by weight or less relative to 100 parts by weight of the (meth)acrylic polymer (A).

[0094] C-5. Crosslinking agent

[0095] In embodiments of the present invention, the adhesive composition (adhesive) constituting the adhesive layer contains an isocyanate crosslinking agent. By containing an isocyanate crosslinking agent, paste defects can be suppressed. As an isocyanate crosslinking agent, for example, a compound having at least two isocyanate groups (including isocyanate regenerated functional groups whose isocyanate groups have been temporarily protected by end-capping agents or polymerization, etc.) can be used. For example, any suitable aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, etc., that can be used in carbamate reactions can be used.

[0096] Examples of aliphatic polyisocyanates include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylidene diisocyanate, 1,3-butylidene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0097] Examples of alicyclic isocyanates include: 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated phenyl dimethyl diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated tetramethylphenyl dimethyl diisocyanate.

[0098] Examples of aromatic diisocyanates include: phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-biphenyl diisocyanate, 1,5-naphthalene diisocyanate, and phenyl dimethyl diisocyanate.

[0099] Other examples of isocyanate crosslinking agents include the above-mentioned diisocyanate polymers (dimers, trimers, pentamers, etc.), urethane-modified products, urea-modified products, biuret-modified products, urethane-modified products, isocyanurate-modified products, and carbodiimide-modified products formed by reacting with polyols such as trimethylolpropane.

[0100] Commercially available isocyanate crosslinking agents include, for example: those manufactured by Tosoh Corporation under the trade names "Millionate MT", "Millionate MTL", "Millionate MR-200", "Millionate MR-400", "Coronate L", "Coronate HL", and "Coronate HX"; and those manufactured by Mitsui Chemicals Corporation under the trade names "Takenate D-110N", "Takenate D-120N", "Takenate D-140N", "Takenate D-160N", "Takenate D-165N", "Takenate D-170HN", "Takenate D-178N", "Takenate 500", and "Takenate 600".

[0101] As isocyanate crosslinking agents, aromatic polyisocyanates and their modified aromatic polyisocyanates, as well as aliphatic polyisocyanates and their modified aliphatic polyisocyanates, are preferred. Aromatic polyisocyanates offer a good balance between crosslinking speed and pot life, and are therefore preferred. Toluene diisocyanate and its modified derivatives (sometimes collectively referred to as toluene diisocyanate crosslinking agents) are particularly preferred as aromatic polyisocyanates.

[0102] The amount of isocyanate crosslinking agent in the adhesive composition is 2 to 20 parts by weight, preferably 2 to 18 parts by weight, and more preferably 2 to 15 parts by weight, relative to 100 parts by weight of (meth)acrylic polymer (A). When the amount of isocyanate crosslinking agent is within this range, an adhesive layer with an excellent balance between paste defects and haze can be formed. If the amount of isocyanate crosslinking agent is too small, paste defects may not be sufficiently suppressed. If the amount of isocyanate crosslinking agent is too large, the resulting adhesive layer may have increased haze.

[0103] In one embodiment, isocyanate crosslinking agents and peroxide crosslinking agents can be used in combination as crosslinking agents in the adhesive composition.

[0104] As peroxide-based crosslinking agents, any suitable peroxide-based crosslinking agent can be used, as long as it generates free radical active species through heating or light irradiation to crosslink the base polymer ((meth)acrylic acid polymer (A)) of the adhesive composition. Peroxides with a 1-minute half-life temperature of 80°C to 160°C are preferred, and peroxides with a 1-minute half-life temperature of 90°C to 140°C are more preferred. Such peroxides exhibit excellent workability and stability.

[0105] Examples of peroxides as described above include: di(2-ethylhexyl) peroxide dicarbonate (1-minute half-life temperature: 90.6°C), di(4-tert-butylcyclohexyl) peroxide dicarbonate (1-minute half-life temperature: 92.1°C), disec-butyl peroxide dicarbonate (1-minute half-life temperature: 92.4°C), tert-butyl peroxyneodecanate (1-minute half-life temperature: 103.5°C), tert-hexyl peroxynepentanoate (1-minute half-life temperature: 109.1°C), tert-butyl peroxynepentanoate (1-minute half-life temperature: 110.3°C), and dilauryl peroxide. The following compounds have half-life temperatures: (1 minute half-life temperature: 116.4℃), dioctanoyl peroxide (1 minute half-life temperature: 117.4℃), 1,1,3,3-tetramethylbutyl peroxide-2-ethylhexanoate (1 minute half-life temperature: 124.3℃), di(4-methylbenzoyl peroxide) (1 minute half-life temperature: 128.2℃), benzoyl peroxide (1 minute half-life temperature: 130.0℃), tert-butyl peroxide isobutyrate (1 minute half-life temperature: 136.1℃), and 1,1-di(tert-hexylperoxide)cyclohexane (1 minute half-life temperature: 149.2℃). Among these, di(4-tert-butylcyclohexyl) peroxide dicarbonate, dilauryl peroxide, and benzoyl peroxide are preferred due to their particularly excellent cross-linking efficiency.

[0106] It should be noted that the half-life of a peroxide is an indicator of the rate of decomposition of the peroxide, referring to the time until half of the peroxide remains. Information regarding the decomposition temperature used to obtain the half-life at any given time, and the half-life time at any given temperature, is available in manufacturer catalogs, such as the "Organic Peroxide Catalog, 9th Edition (May 2003)" published by Nippon Oils & Fats Co., Ltd.

[0107] When a peroxide-based crosslinking agent is incorporated into the adhesive composition, the amount of the peroxide-based crosslinking agent is preferably 0.01 to 2 parts by weight, more preferably 0.1 to 0.5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer (A). Within this range, processability and crosslinking stability are easily adjustable.

[0108] Other crosslinking agents can be used in combination with isocyanate crosslinking agents to replace peroxide crosslinking agents, or used together with peroxide crosslinking agents. Examples of other crosslinking agents include: polyfunctional metal chelates, epoxy crosslinking agents, and imine crosslinking agents. Polyfunctional metal chelates are chelates formed by covalent or coordinate bonds between multivalent metals and organic compounds. Examples of multivalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compounds forming covalent or coordinate bonds include oxygen atoms. Examples of organic compounds include: alkyl esters, alcohols, carboxylic acids, ethers, and ketones.

[0109] C-6 Other ingredients

[0110] The adhesive composition may also contain (meth)acrylic acid oligomers. (Meth)acrylic acid oligomers can be obtained by homopolymerizing or copolymerizing two or more of the monomer components described in section C-2 concerning (meth)acrylic acid polymers. The type, quantity, combination, and molar ratio of the monomer components can be appropriately set according to the purpose and desired characteristics. The weight-average molecular weight (Mw) of the (meth)acrylic acid oligomer is preferably 1000 to 8000, more preferably 2000 to 7000, and even more preferably 3000 to 6000. When (meth)acrylic acid oligomers are incorporated into the adhesive composition, the amount of (meth)acrylic acid oligomer is preferably 5 to 35 parts by weight relative to 100 parts by weight of the (meth)acrylic acid polymer (A).

[0111] The adhesive composition may also contain an ionic compound. Any suitable ionic compound can be used. Examples of suitable ionic compounds include those described in Japanese Patent Application Publication No. 2015-4861, among which lithium (perfluoroalkyl sulfonyl)imide is preferred, and lithium bis(trifluoromethanesulfonyl)imide is more preferred. The amount of the ionic compound can be appropriately set according to the purpose. For example, relative to 100 parts by weight of the (meth)acrylic polymer (A), the amount of the ionic compound is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, further preferably 3 parts by weight or less, and particularly preferably 1 part by weight or less.

[0112] The adhesive composition may also contain additives. Specific examples of additives include colorants, pigments and other powders, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, granular or foil-like materials. Additionally, a redox system with added reducing agents can be used within a controllable range. The type, quantity, combination, and content of additives can be appropriately set according to the purpose. The content of additives is preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A).

[0113] D. Image display device

[0114] The optical film with an adhesive layer according to embodiments of the present invention, as described above, can be suitably applied to image display devices. Therefore, image display devices comprising an optical film with an adhesive layer are also included in embodiments of the present invention. An image display device typically includes an image display unit and an optical film with an adhesive layer bonded to the image display unit via an adhesive layer. Examples of image display devices include liquid crystal display devices, organic electroluminescent (EL) display devices, and quantum dot display devices. Organic EL display devices are preferred because of the significant effects provided by the optical film with an adhesive layer.

[0115] Example

[0116] The present invention will now be specifically described with reference to embodiments, but the present invention is not limited to these embodiments. The evaluation items in the embodiments are described below. Furthermore, unless otherwise specified, "parts" and "%" in the embodiments are based on weight.

[0117] (1) Paste loss

[0118] The cross-sectional state of the adhesive layer in the irregularly shaped processing part of the optical film with adhesive layer obtained in the examples and comparative examples was observed using an optical microscope. The length of the portion where the adhesive layer detached to the maximum from the outer edge to the inner side of the surface was measured and this length was taken as the paste loss amount (μm).

[0119] (2) Haze

[0120] Measurements were performed using a haze meter (manufactured by Murakami Color Science Research Institute Co., Ltd., trade name "HM-150") according to the method specified in JIS K 7136.

[0121] <Manufacturing Example 1: Preparation of Acrylic Polymer A1>

[0122] A monomer mixture containing 74.9 parts butyl acrylate, 20 parts benzyl acrylate, 5 parts acrylic acid, and 0.1 parts 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser. Further, 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-Azobisisobutyronitrile) as a polymerization initiator was added along with 100 parts ethyl acetate to 100 parts of this monomer mixture. After nitrogen purging by slowly stirring and introducing nitrogen gas, the liquid temperature in the flask was maintained at approximately 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of acrylic polymer A1 with a weight-average molecular weight (Mw) of 2.1 million.

[0123] <Manufacturing Example 2: Preparation of Acrylic Polymer A2>

[0124] A monomer mixture containing 82.9 parts of butyl acrylate, 12 parts of benzyl acrylate, 5 parts of acrylic acid and 0.1 parts of 4-hydroxybutyl acrylate was used. Otherwise, a solution of acrylic polymer A2 with a Mw of 2.05 million was prepared in the same manner as in Manufacturing Example 1.

[0125] <Manufacturing Example 3: Preparation of Acrylic Polymer A3>

[0126] A monomer mixture containing 79.9 parts butyl acrylate, 15 parts phenoxyethyl acrylate, 5 parts acrylic acid and 0.1 parts 4-hydroxybutyl acrylate was used. Otherwise, a solution of acrylic polymer A3 with a Mw of 2.6 million was prepared in the same manner as in Manufacturing Example 1.

[0127] <Manufacturing Example 4: Preparation of Acrylic Polymer A4>

[0128] A solution of acrylic polymer A4 with a Mw of 1.2 million was prepared in the same manner as in Manufacturing Example 1, except that a portion of the ethyl acetate added during polymerization was replaced with toluene.

[0129] <Manufacturing Example 5: Preparation of Acrylic Polymer A5>

[0130] A monomer mixture containing 94.9 parts butyl acrylate, 5 parts acrylic acid and 0.1 parts 4-hydroxybutyl acrylate was used. Otherwise, a solution of acrylic polymer A5 with a Mw of 2.2 million was prepared in the same manner as in Manufacturing Example 1.

[0131] <Example 6: Fabrication of Polarizing Film>

[0132] (Preparation of TAC membrane with HC)

[0133] A hard coating forming material was prepared by dissolving a UV-curable resin monomer or oligomer with urethane acrylate as the main component in butyl acetate to obtain a resin solution (manufactured by DIC Corporation, trade name: UNIDIC 17-806, solids concentration: 80%), with 5 parts of photopolymerization initiator (manufactured by BASF Corporation, trade name: IRGACURE 907) and 0.1 parts of leveling agent (manufactured by DIC Corporation, trade name: GRANDIC PC4100) per 100 parts of solids in the solution. Cyclopentanone and propylene glycol monomethyl ether were added to the solution at a ratio of 45:55 to achieve a solids concentration of 36%. This hard coating forming material was then coated onto a TAC film (manufactured by Fujifilm, product name: TJ40UL, thickness: 40 μm) to achieve a cured hard coating thickness of 7 μm, thus forming a coating film. The coating was dried at 90°C for 1 minute, and then further irradiated with a high-pressure mercury lamp with a cumulative light intensity of 300 mJ / cm². 2 Ultraviolet light was used to cure the coating, forming a hard coating layer, thus producing a TAC film with HC. The obtained TAC film with HC was then subjected to saponification treatment.

[0134] (Making of polarizing filters)

[0135] A 45 μm thick polyvinyl alcohol film was dyed for 1 minute at 30°C in a 0.3% iodine solution between rollers with different speed ratios, while being stretched to 3 times its original length. Then, it was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C for 0.5 minutes, while being stretched to a total stretch ratio of 6 times. Next, it was cleaned by immersion in an aqueous solution containing 1.5% potassium iodide at 30°C for 10 seconds, and then dried at 50°C for 4 minutes to obtain a polarizer with a thickness of 18 μm. A polarizer was fabricated by bonding the aforementioned HC-coated TAC film to one side of the polarizer using a polyvinyl alcohol adhesive, and a 40 μm thick TAC film (KC4CT, manufactured by Konica Minolta Co., Ltd.) after saponification to the other side.

[0136] <Example 1>

[0137] (Preparation of the adhesive composition)

[0138] A solution of an acrylic adhesive composition was prepared by combining 100 parts of the solid component of the acrylic polymer A1 solution obtained in Manufacturing Example 1 with 2 parts of an isocyanate crosslinking agent (trimethylolpropane / toluene diisocyanate adduct: manufactured by Tosoh Corporation, trade name "Coronate L"), 0.2 parts of a peroxide crosslinking agent (manufactured by Nippon Yushi Co., Ltd., trade name "NYPER BMT"), and 0.2 parts of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403").

[0139] (Fabrication of a polarizer with an adhesive layer)

[0140] The solution of the acrylic adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film, trade name "MRF38", separator) treated with an organosilicon release agent to achieve a dry adhesive layer thickness of 20 μm. The film was dried at 155°C for 1 minute, forming an adhesive layer on the surface of the separator. Next, the adhesive layer formed on the separator was transferred to the TAC film (KC4CT) side of the polarizer produced in Manufacturing Example 6, creating an optical film with an adhesive layer (polarizer with an adhesive layer). The obtained polarizer with an adhesive layer underwent irregular shaping. At this time, a laminate with a surface protective film (manufactured by Nitto Denko, trade name "PPF-100T") laminated on the HC-side of the obtained polarizer with an adhesive layer was used as the workpiece for irregular shaping. More specifically, the bundle, formed by stacking layers to a cumulative height of 10mm, was secured using clamps. A 2.0mm diameter end mill was used to open a through hole from the surface protective film side, cutting to achieve a hole diameter of 2.5mm (machining to the same level as...). Figure 2 (The shape corresponding to the center of the lower section). The cutting was performed under the conditions of a cutting tool speed of 2500 rpm and a feed rate of 50 mm / min. The polarizer with adhesive layer after irregular processing was submitted to the evaluation of (1) above, and the adhesive layer used for the fabrication of the optical film with adhesive layer was submitted to the evaluation of (2) above. The results are shown in Table 1.

[0141] <Examples 2-9 and Comparative Examples 1-2>

[0142] The composition of the adhesive composition forming the adhesive layer was modified as shown in Table 1. Otherwise, an optical film with an adhesive layer was fabricated using the same shaped process as in Example 1. The adhesive layer used to fabricate the optical film with the adhesive layer and the polarizer with the adhesive layer after shaped processing were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0143] [Table 1]

[0144]

[0145] A1: BA / BzA / AA / HBA=74.9 / 20 / 5 / 0.1 (wt%), Mw2.1 million

[0146] A2: BA / BzA / AA / HBA=82.9 / 12 / 5 / 0.1 (wt%), Mw2.05 million

[0147] A3: BA / PEA / AA / HBA=79.9 / 15 / 5 / 0.1(wt%), Mw2.6 million

[0148] A4:BA / BzA / AA / HBA=74.9 / 20 / 5 / 0.1(wt%), Mw1.2 million

[0149] A5: BA / HBA / AA=94.9 / 0.1 / 5(wt%), Mw2.2 million

[0150] The abbreviations in Table 1 are as follows. Additionally, the proportions of each component in Table 1 are relative to 100 parts of the polymer.

[0151] BA: Butyl acrylate

[0152] BzA: Benzyl acrylate

[0153] PEA: Phenoxyethyl acrylate

[0154] AA: Acrylic acid

[0155] HBA: 4-Hydroxybutyl acrylate

[0156] C / L: Trimethylolpropane / toluene diisocyanate adduct (manufactured by Tosoh Corporation, trade name "Coronate L")

[0157] Peroxide: Peroxide crosslinking agent (manufactured by Nippon Yushi Co., Ltd., trade name "NYPER BMT")

[0158] Si-cup agent: epoxy-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403")

[0159] <Example 9>

[0160] (Making of polarizing filters)

[0161] A 12μm thick polarizer was produced by unidirectionally stretching a 30μm thick polyvinyl alcohol film (KURARAY product name "PE3000") in the length direction by a roller stretching machine at a length ratio of 5.9 times. Simultaneously, swelling, dyeing, crosslinking, and cleaning processes were carried out, and finally, drying was performed.

[0162] Specifically, the swelling treatment was carried out in pure water at 20°C while stretching to 2.2 times its original size. Next, the dyeing treatment was carried out in an aqueous solution at 30°C with an iodine to potassium iodide weight ratio of 1:7 (adjusted iodine concentration) to achieve a transmittance of 45.0% for the fabricated polarizing film, while stretching to 1.4 times its original size. Further, the crosslinking treatment employed a two-stage process. In the first stage, the crosslinking treatment was carried out in an aqueous solution containing boric acid and potassium iodide at 40°C while stretching to 1.2 times its original size. The aqueous solution for the first stage of crosslinking treatment contained 5.0% by weight of boric acid and 3.0% by weight of potassium iodide. In the second stage, the crosslinking treatment was carried out in an aqueous solution containing boric acid and potassium iodide at 65°C while stretching to 1.6 times its original size. The aqueous solution for the second stage of crosslinking treatment contained 4.3% by weight of boric acid and 5.0% by weight of potassium iodide. Finally, the cleaning treatment was carried out in an aqueous solution of potassium iodide at 20°C. The potassium iodide content of the cleaning solution was set to 2.6% by weight. Finally, the polarizing mirror was obtained by drying at 70°C for 5 minutes.

[0163] On both sides of the obtained polarizer, a TAC film (product name: KC2UA, thickness: 25μm) manufactured by Konica Minolta Corporation and an HC-TAC film (thickness: 32μm) with an HC layer on one side of the TAC film are respectively bonded by polyvinyl alcohol adhesive, resulting in a polarizer 1 with protective films bonded on both sides of the polarizer.

[0164] (Fabrication of phase difference layer A)

[0165] A liquid crystal composition (coating solution) was prepared by dissolving 10g of a polymerizable liquid crystal (manufactured by BASF, product name "Paliocolor LC242", represented by the following formula) and 3g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by Ciba Specialty Chemicals, product name "IRGACURE907") in 40g of toluene.

[0166] [Chemical Formula 1]

[0167]

[0168] Orientation treatment was performed by rubbing the surface of a polyethylene terephthalate (PET) film (38 μm thick) with a friction cloth. The conditions for orientation treatment were: 1 rubbing cycle (number of rubbing rollers), 76.89 mm radius of the rubbing rollers (r), 1500 rpm rotation speed of the rubbing rollers (nr), and 83 mm / sec film conveying speed (v).

[0169] The orientation treatment was set such that, when viewed from the visible side, it would be at -75° relative to the absorption axis of the polarizer when bonded to the polarizer. The aforementioned coating solution was applied to the orientation-treated surface using a wire-bar coater, and the surface was heated and dried at 90°C for 2 minutes, thereby aligning the liquid crystal compound. The liquid crystal layer thus formed was irradiated with a metal halide lamp at 1 mJ / cm². 2 The light is used to solidify the liquid crystal layer, thereby forming a phase retardation layer A on the PET film. The phase retardation layer A has a thickness of 2 μm and an in-plane phase retardation Re of 270 nm. In addition, the phase retardation layer A has a refractive index distribution of nx > ny = nz.

[0170] (Fabrication of phase difference layer B)

[0171] An alignment treatment was performed by rubbing the surface of a polyethylene terephthalate (PET) film (38 μm thick) with a rubbing cloth. The orientation direction was set such that it would be -15° relative to the absorption axis of the polarizer when viewed from the visible side when bonded to a polarizer. The same liquid crystal coating as described above was applied to the alignment-treated surface, and the liquid crystal was aligned and cured in the same manner to form a retardation layer B on the PET film. The retardation layer B has a thickness of 1.2 μm and an in-plane phase difference Re of 140 nm. Furthermore, the retardation layer B has a refractive index distribution of nx > ny = nz.

[0172] (Fabrication of a polarizer with a phase retardation layer)

[0173] The TAC film surface of the polarizer was bonded to the retardation layer A using a UV-curable adhesive, such that the absorption axis of the polarizer and the slow axis of the retardation layer A were at a 75° angle. Next, the retardation layer A and the retardation layer B were bonded together using the same adhesive (5 μm thick) as in Example 14, such that the absorption axis of the polarizer and the slow axis of the retardation layer B were at a 15° angle, thus obtaining a polarizer with a retardation layer. Furthermore, the same adhesive layer as in Examples 1-8 and Comparative Examples 1-2 was formed on the outer side of the retardation layer B. The obtained polarizer with a retardation layer was subjected to irregular shaping as in Example 1, and evaluated in the same manner as in Example 1. As a result, it was confirmed that for the polarizer with a retardation layer: when using the adhesive layer corresponding to Examples 1-8, the paste defects and haze were good; when using the adhesive layer corresponding to Comparative Example 1, the haze was high; and when using the adhesive layer corresponding to Comparative Example 2, the paste defects were large.

[0174] <Evaluation>

[0175] As can be clearly seen from Table 1, according to the embodiments of the present invention, it is practically possible to obtain an optical film with an adhesive layer that can significantly suppress paste defects in irregularly shaped processing areas and has excellent transparency. In Comparative Example 1, where aromatic (meth)acrylates were not used in the adhesive constituting the adhesive layer, the adhesive layer had high haze, and the resulting optical film with the adhesive layer had insufficient transparency. In Comparative Example 2, where the amount of isocyanate crosslinking agent was small, paste defects were large.

[0176] Industrial applicability

[0177] The optical film with adhesive layer of the present invention is suitable for use in image display devices, and in particular, it is suitable for use in image display devices with irregularly shaped parts, such as car dashboards, smartphones, tablet PCs or smartwatches.

Claims

1. An optical film with an adhesive layer, comprising an optical film and an adhesive layer on one side of the optical film, wherein, The optical film with an adhesive layer has irregular shapes other than rectangular. The adhesive composition constituting this adhesive layer comprises a (meth)acrylic base polymer and an isocyanate crosslinking agent. This (meth)acrylic acid-based polymer contains aromatic (meth)acrylic acid esters as monomer components. Relative to 100 parts by weight of the (meth)acrylic base polymer, the adhesive contains 8 to 20 parts by weight of the isocyanate crosslinking agent. The weight-average molecular weight of the (meth)acrylic acid-based polymer is 2.1 million to 3 million.

2. The optical film with an adhesive layer according to claim 1, wherein, The isocyanate crosslinking agent is a toluene diisocyanate crosslinking agent.

3. The optical film with an adhesive layer according to claim 1 or 2, wherein, In the (meth)acrylic base polymer, the aromatic (meth)acrylate is contained in 10 to 30 parts by weight relative to 100 parts by weight of all monomer components.

4. The optical film with an adhesive layer according to claim 3, wherein, The (meth)acrylic acid-based basic polymer contains at least one monomer component selected from carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, amino-containing monomers, nitrile-containing monomers, and polyfunctional monomers.

5. The optical film with an adhesive layer according to claim 4, wherein, In the (meth)acrylic acid-based polymer, 0.1 to 1 part by weight of the hydroxyl-containing monomer is included relative to 100 parts by weight of all monomer components.

6. The optical film with an adhesive layer according to claim 5, wherein, In the (meth)acrylic acid-based polymer, 2 to 8 parts by weight of the carboxyl-containing monomer are included relative to 100 parts by weight of all monomer components.

7. The optical film with an adhesive layer according to claim 1 or 2, wherein, The optical film includes a polarizer.

8. The optical film with an adhesive layer according to claim 7, wherein, The optical film further includes a phase retardation layer.

9. An image display device comprising an optical film with an adhesive layer as described in any one of claims 1 to 8.

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