TW202237399A - Laminated film and use thereof comprising a base material layer, a release layer, and an adhesive layer sandwiched between the base material layer and the release layer - Google Patents

Abstract

The present invention provides a laminated film having die cut resistance. The laminated film of this invention is a laminated film comprising a base material layer, a release layer, and an adhesive layer sandwiched between the base material layer and the release layer, and the shear yield stress when a strain is applied at 5 mm/min to the adhesive layer in a direction parallel to the film surface is adjusted to 0.15 N/mm<SP>2</SP> or more. The shear yield stress may be 0.17 N/mm<SP>2</SP> or more. The laminated film may be a transparent film. The adhesive layer may include an optically transparent adhesive. The optically transparent adhesive may be a cured product of a curable composition. The curable composition may contain a (meth)acrylic polymer and a crosslinking agent. The base material layer may contain a transparent resin. The laminated film may be a film for die-cutting.

Description

Laminated films and their uses

The present invention relates to a laminated film with punching mark resistance and its application.

Conventionally, as described in Japanese Patent Application Laid-Open No. 2015-98123 (Patent Document 1), as an optical film provided on the display surface of various display devices such as personal computer (PC) monitors, TVs, and smartphones, A transparent laminated film including a substrate layer, an optical function layer, a cover layer, and an adhesive layer (or adhesive layer) is used. In the transparent laminated film, the adhesive layer is formed by an optically clear adhesive (OCA).

Die-cutting is used as a method of forming a transparent laminated film into a target display size. Conventionally, in the die-cutting process of a transparent laminated film, it is known that a slight deformation occurs inside the film edge along the die-cut shape. This deformation is called the edge line mark (TM; touring mark), for example, due to the temporary deformation of the adhesive layer during the die-cutting process, and near the end of the film (near the cut-off position), there is a linear mark along the end. produced in the form. Therefore, in the previous display device, the existence of the edge lines is hidden by the frame of the display, so it will not become a serious problem. However, in recent years, along with narrower borders (thinner borders) of displays (monitors), edge lines are conspicuously present on the display, causing image strain, and thus edge lines have become a problem. [Prior Art Literature]

[Patent Document] Patent Document 1: Japanese Patent Laid-Open No. 2015-98123

[Problem to be Solved by the Invention]

However, conventional adhesives (or adhesives) such as OCA have focused on optical properties, viscoelastic properties, and adhesiveness as design criteria, and there has been no design based on the viewpoint of suppressing punch marks. In addition, the present inventors studied the correlation between the occurrence of die-cut marks and the adhesiveness of the adhesive, and found that there is no correlation between these characteristics and the generation of die-cut marks.

Therefore, the object of the present invention is to provide a laminated film having die cut resistance and its use. [Technical means to solve the problem]

The present inventors found that by adjusting the shear yield stress (or yield shear stress) of the adhesive layer (or adhesive layer) of the laminated film to 0.15N/ ^mm2 or more, punching mark resistance was exhibited, thereby completing the invention.

That is to say, the laminated film of the present invention is a laminated film comprising a substrate layer, a release layer, and an adhesive layer interposed between the substrate layer and the release layer, and the adhesive layer along the film surface The shear yield stress when a strain is applied in a parallel direction at 5 mm/min is 0.15 N/mm ² or more. The aforementioned shear yield stress may be 0.17 N/mm ² or more. The aforementioned adhesive layer may include an optically transparent adhesive. The aforementioned optically transparent adhesive may be a cured product of a curable composition. The aforementioned curable composition may include a (meth)acrylic polymer and a crosslinking agent. The aforementioned base material layer may contain a transparent resin. The aforementioned laminated film may be a film to be subjected to die-cutting. The aforementioned laminated film may be a die-cut film obtained by die-cutting.

Also included in the present invention is a method of producing a die-cut film by performing a die-cut process on the aforementioned laminated film.

The present invention also includes a display device including the aforementioned die-cut film on a display surface. The display device can be a narrow frame display.

Also included in the present invention is a method, which is for a laminated film comprising a substrate layer, a release layer, and an adhesive layer interposed between the aforementioned substrate layer and the aforementioned release layer, the aforementioned adhesive layer along the The shear yield stress is adjusted to 0.15 N/mm ² or more when a strain is applied at a rate of 5 mm/min in the direction parallel to the film surface, thereby improving the die cut resistance of the laminated film.

Furthermore, in this specification and the scope of the patent application, the so-called "die-cut resistance" refers to the following film characteristics, that is, no die-cut marks such as edge line marks are generated, or even if die-cut marks are generated, they are also produced. Near the end of the film, the image will not be strained even for a narrow bezel (thin bezel) display.

In addition, in this specification and the scope of the patent application, the so-called "narrow bezel display" refers to a display in which the width of the frame portion (border portion around the screen) of the display device is narrow.

Furthermore, in the description of this case and the scope of the patent application, the so-called "cutting surface" refers to the surface on the side where the punching knife first contacts the laminated film. [Effect of Invention]

In the present invention, the shear yield stress of the adhesive layer of the laminated film (specifically, the maximum stress when it is displaced in the direction of the film surface (transverse shear)) is adjusted to 0.15N/ ^mm2 or more, so Die cut resistance can be imparted to a laminated film.

[laminated film] The laminated film of the present invention includes a substrate layer, a release layer, and an adhesive layer (or adhesive layer) interposed between the substrate layer and the release layer.

(Adhesive layer or adhesive layer) In the laminated film of the present invention, the shear yield stress (or the maximum value of the stress) when a strain is applied to the above-mentioned adhesive layer in a direction parallel to the film surface at 5 mm/min is 0.15N /mm ² or more (eg 0.15N/mm ² ~1N/mm ² ), preferably 0.17N/mm ² or more (eg 0.17N/mm ² ~0.8N/mm ² ), more preferably 0.18N/mm ² or more (for example, 0.18N/mm ² ~0.5N/mm ² ), more preferably 0.19N/mm ² or more (for example, 0.19N/mm ² ~0.4N/mm ² ), most preferably 0.2N/mm ² or more (eg 0.2N/mm ² ~0.3N/mm ² ). If the shear yield stress is less than 0.15 N/mm ² , die cut resistance cannot be imparted to the laminated film. On the other hand, if the shear yield stress is at least 0.15 N/mm ² , die cut resistance can be imparted to the laminated film. That is, the occurrence of edge lines can be suppressed, and even if edge lines are generated, they are generated in the region near the end of the laminated film, so that even in a narrow bezel display, image strain can be suppressed. In particular, when the shear yield stress is 0.17 N/mm ² or more, the occurrence of edge lines can be fundamentally suppressed.

Furthermore, in this specification and the scope of the patent application, the aforementioned shear yield stress refers to the maximum stress when the adhesive layer is displaced along the film surface direction (transverse shear), which can be determined by the method described in the examples described later. Determination.

Regarding the adhesive layer (or adhesive layer), the aforementioned shear yield stress is ^sufficient to be 0.15 N/mm or more, and conventional adhesives and adhesives can be used, but edge lines are likely to be a problem, preferably Formed from optically clear adhesive (OCA) used in transparent optical applications.

Optically transparent adhesives can use conventional OCA, such as (meth)acrylic adhesives (or adhesives), urethane-based adhesives (or adhesives), silicone-based adhesives (or adhesives) ), rubber adhesives (or adhesives), etc. These adhesives (or adhesives) can be used alone or in combination of two or more.

As a preferred OCA, it is preferably a cured product of a curable composition, especially one containing a (meth)acrylic polymer and The cured product of the curable composition of the crosslinking agent.

The (meth)acrylic monomers that form (meth)acrylic polymers include crosslinkable (meth)acrylic monomers that have crosslinkable groups and non-crosslinkable (meth)acrylic monomers that do not have crosslinkable groups. Meth)acrylic monomers, etc.

In the (meth)acrylic-type monomer which has a crosslinkable group, a hydroxyl group, a carboxyl group, an epoxy group, an amide group etc. are mentioned as a crosslinkable group.

Examples of (meth)acrylic monomers having a hydroxyl group include hydroxy C _2-4 alkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; (poly)ethylene glycol mono (Meth)acrylates and other (poly)C _2-4 alkylene glycol mono(meth)acrylates; glycerol di(meth)acrylate, trimethylolethane di(meth)acrylate, Trimethylolpropane di(meth)acrylate, pentaerythritol di- or tri(meth)acrylate, dipentaerythritol di- or penta(meth)acrylate, and the like.

Examples of (meth)acrylic monomers having a carboxyl group include: (meth)acrylic acid; (meth)acrylic acid carboxyl C _2-6 alkyl esters such as β-carboxyethyl (meth)acrylate; Monoesters of carboxylic acids and (meth)acrylic monomers having hydroxyl groups, etc.

As a (meth)acrylic-type monomer which has an epoxy group, glycidyl (meth)acrylate etc. are mentioned, for example.

Examples of (meth)acrylic monomers having an amide group include: (meth)acrylamide; N,N-diC _1-4 alkyl (meth)acrylamide, etc. (Meth)acrylamide, etc.

Examples of non-crosslinkable (meth)acrylic monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. , Isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylate (meth)acrylic acid linear or branched C _1-20 alkyl esters such as isooctyl acrylate and isononyl (meth)acrylate; (meth)acrylic acid such as cyclohexyl (meth)acrylate C _5-10 cycloalkyl esters; cross-linked cyclic (meth)acrylates such as isobornyl (meth)acrylate; C _6-10 aryl (meth)acrylates such as phenyl (meth)acrylate, etc.

These (meth)acrylic monomers can be used individually or in combination of 2 or more types. These (meth)acrylic monomers may be (meth)acrylic monomers having at least a crosslinkable group, or may be (meth)acrylic monomers having a crosslinkable group and non-crosslinkable A combination of (meth)acrylic monomers. As a combination of a (meth)acrylic monomer having a crosslinking group and a (meth)acrylic monomer having a non-crosslinking group, C _1-10 alkyl acrylate and acrylic acid having a hydroxyl group are preferred. A combination of monomers and/or acrylic monomers having a carboxyl group, especially a combination of C _2-8 alkyl acrylate and hydroxy C _2-6 alkyl acrylate.

The weight-average molecular weight of the (meth)acrylic polymer can be measured by gel permeation chromatography (GPC; Gel Permeation Chromatography), etc., and when converted to polystyrene, it is, for example, 1,000 to 1,000,000, preferably 3,000 ~800,000, more preferably 5,000~500,000, more preferably 10,000~500,000.

As a crosslinking agent, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, etc. are mentioned, for example. Among these, an isocyanate-based crosslinking agent is preferable.

The isocyanate-based crosslinking agent is not particularly limited as long as it has a plurality of isocyanate groups. For example, aliphatic polyisocyanates (for example, tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanates such as methyl diisocyanate and lysine diisocyanate; triisocyanates such as 1,3,6-hexamethylene triisocyanate, etc.), alicyclic polyisocyanates (for example, cyclohexane 1,4-diisocyanate, Diisocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated bis(isocyanatophenyl)methane; triisocyanates such as dicycloheptane triisocyanate, etc.), aromatic polyisocyanates (such as benzene Isocyanate, Toluene Diisocyanate, Xylylene Diisocyanate (XDI), Tetramethylxylylene Diisocyanate, Naphthalene Diisocyanate, Bis(isocyanatophenyl)methane (MDI), Toluidine Diisocyanate, 1 , diisocyanate such as 3-bis(isocyanatophenyl)propane; triisocyanate such as triphenylmethane triisocyanate, etc.), dimers, trimers, adducts, biurets, etc. of these polyisocyanates .

These isocyanate type crosslinking agents can be used individually or in combination of 2 or more types. Among these isocyanate-based crosslinking agents, aromatic polyisocyanate-based crosslinking agents are preferred (for example, aromatic polyisocyanates such as XDI and MDI, aromatic polyisocyanates modified with alkane polyols such as trimethylolpropane, etc.) .

The ratio of the crosslinking agent can be selected from the range of 0.01 to 10 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer, for example, 0.05 to 5 parts by mass, preferably 0.1 Parts by mass to 3 parts by mass, more preferably 0.2 parts by mass to 2 parts by mass, more preferably 0.3 parts by mass to 1.5 parts by mass, most preferably 0.5 parts by mass to 1 part by mass. In the curable composition of the present invention, by adjusting the ratio of the crosslinking agent within the aforementioned range, the shear yield stress of the adhesive layer can be adjusted. When the ratio of the crosslinking agent is too small, it may be difficult to adjust the shear yield stress to 0.15 N/mm ² or more.

The total ratio of the (meth)acrylic polymer and the crosslinking agent may be at least 50% by mass, preferably at least 80% by mass, and more preferably at least 90% by mass in the cured product of the curable composition , more preferably at least 95% by mass, and may be 100% by mass.

The curable composition may be any curable composition of a room temperature curable type, a heat curable type, or a light curable type. Among these, the room temperature hardening type is preferable at the point that the aforementioned shear yield stress can be easily adjusted.

The curable composition may further contain a solvent. Examples of the solvent include conventional solvents such as water, alcohols, ketones, ethers, esters, amides, nitriles, ethylene oxides, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, etc. . These solvents can be used alone or in combination of two or more. Among these solvents, esters such as ethyl acetate and isopropyl acetate are preferred. The ratio of the solvent is, for example, 10 to 1,000 parts by mass, preferably 50 to 500 parts by mass, and more preferably 100 to 400 parts by mass to 100 parts by mass of the (meth)acrylic polymer. parts, more preferably 200 parts by mass to 350 parts by mass.

In addition to a (meth)acrylic-type polymer and a crosslinking agent, a curable composition may further contain usual additives. Commonly used additives include, for example, adhesion imparting agents (adhesives), viscosity modifiers, thickeners, defoamers, fillers, lubricants, stabilizers (antioxidants, heat stabilizers, light stabilizers) etc.), flame retardants, etc. These additives may be used alone or in combination of two or more. The total ratio of other additives may be 50 parts by mass or less, for example, 0.1 to 30 parts by mass, preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the (meth)acrylic polymer.

The total light transmittance of the bonding layer may be above 70%, such as 70%-99.9%, preferably 75%-99%, further preferably 80%-98%. If the total light transmittance is lowered, punching marks are not a problem, but there is a possibility that the effect of the present invention may not be exhibited.

In addition, in this specification and the claims, the total light transmittance can be measured based on JIS K7361.

The average thickness of the bonding layer is, for example, 1 µm to 100 µm, preferably 3 µm to 80 µm, further preferably 5 µm to 50 µm, more preferably 10 µm to 40 µm, most preferably 20 µm to 30 µm. If the average thickness of the adhesive layer is too thin, the adhesiveness may be lowered, and if it is too thin or too thick, punching marks may be easily generated.

In addition, in this specification and the claims, the average thickness of each layer can be obtained by measuring arbitrary 10 locations using an adhesive film thickness gauge, and calculating the average value.

(substrate layer) The material of the substrate layer is not particularly limited, and may be any of organic materials and inorganic materials, but it is preferably formed of a transparent material in terms of edge marks that tend to become a problem.

The transparent material may be an inorganic material such as glass, but in many cases it is formed by die-cutting. When the adhesive layer is in contact with the base layer, an organic material is preferable in terms of excellent adhesiveness.

Examples of the organic material include transparent resins such as cellulose esters, polyester resins, polyamide resins, polyimide resins, polycarbonate resins, and (meth)acrylic polymers. Among these, cellulose ester, polyester-based resin, and polycarbonate-based resin are preferable.

Examples of the cellulose ester include cellulose acetate such as cellulose triacetate (TAC), cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate _C3-4 acylate.

As a polyester resin, polyalkylene arylate resins, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. are mentioned, for example.

As polycarbonate-type resin, bisphenol type polycarbonate, such as bisphenol A type polycarbonate, etc. are illustrated, for example.

Among these, polyalkylene arylate-based resins such as cellulose acetate such as TAC and PET are preferable, and poly C _2-4 alkylene resins are particularly preferable in terms of excellent balance between mechanical properties and transparency. Aryl ester resin.

The ratio of the transparent resin in the substrate layer may be at least 50% by mass, preferably at least 80% by mass, further preferably at least 90% by mass, more preferably at least 95% by mass, and may be 100% by mass .

When the base material layer contains a transparent resin, it may further contain the additives exemplified as usual additives in the curable composition of the above-mentioned adhesive layer. The ratio of the additives may be 50 parts by mass or less, for example, 0.1 parts by mass to 30 parts by mass, preferably 0.5 parts by mass to 10 parts by mass, based on 100 parts by mass of the transparent resin.

When the substrate layer is an organic material (especially polyester-based resin), it may be an unstretched film or a uniaxially or biaxially stretched film. When the organic material is a polyester resin, it may be a biaxially stretched film.

The substrate layer may be surface-treated (for example, corona discharge treatment, flame treatment, plasma treatment, ozone irradiation treatment, ultraviolet irradiation treatment, etc.), and may also have an easy-adhesive layer.

The total light transmittance of the substrate layer may be above 70%, such as 70%-99.9%, preferably 75%-99%, and more preferably 80%-98%. If the total light transmittance is lowered, punching marks are not a problem, but there is a possibility that the effect of the present invention may not be exhibited.

The average thickness of the substrate layer can be selected from a range of about 10 µm to 2000 µm, such as 20 µm to 1000 µm, preferably 30 µm to 300 µm, further preferably 50 µm to 200 µm, and most preferably 75 µm~150 µm. If the thickness of the base material layer is too thin, the mechanical properties of the laminated film may be reduced, and if it is too thick, it may be difficult to impart die cut resistance.

(release layer) The laminated film of the present invention has a release layer. Therefore, during the punching process, the release layer tends to be temporarily peeled off with the movement of the punching knife, and punching marks are easily generated due to the peeling of the release layer. In the laminated film of the present invention, die cut resistance can be improved despite having a release layer.

The release layer is not particularly limited as long as it adheres moderately to the above-mentioned adhesive layer and can be peeled off, and a commonly used release film or the like can be used.

In addition, the release layer may be formed of a resin composition including a thermoplastic resin and a release agent. Examples of thermoplastic resins include polyolefin-based resins, polyvinyl alcohol-based polymers, polyester-based resins, polyamide-based resins, polyimide-based resins, polycarbonate-based resins, and polyphenylene ether-based resins. , polyphenylene sulfide resin, cellulose ester, etc. These thermoplastic resins can be used individually or in combination of 2 or more types. Among these thermoplastic resins, poly C _2-4 alkylene arylate resins such as PET are preferable.

As the release agent, for example, silicone-based compounds such as silicone oil, silicone resin, and polyorganosiloxane having polyoxyalkylene units; vegetable wax, animal wax, paraffin wax, polyethylene wax, vinyl wax, etc. Copolymer wax, polypropylene wax and other waxes; C _8-35 fatty acid alkali metal salts and other higher fatty acid metal salts; C _8-35 fatty acid alkyl esters and other higher fatty acid alkyl esters; C _8-35 fatty acid amides, extension Higher fatty acid amide such as alkylbis fatty acid amide; fluorine compounds such as fluorine oil and fluorine resin, etc. These release agents can be used alone or in combination of two or more. Among these, silicone-based compounds are preferable.

The ratio of the release agent is, for example, 0.01 to 30 parts by mass, preferably 0.05 to 20 parts by mass, and more preferably about 0.1 to 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin.

The release layer may further contain the additives exemplified as usual additives in the curable composition of the above-mentioned adhesive layer. The ratio of the additives may be 50 parts by mass or less, for example, 0.1 parts by mass to 30 parts by mass, preferably 0.5 parts by mass to 10 parts by mass, based on 100 parts by mass of the thermoplastic resin.

The average thickness of the release layer can be selected from a range of about 1 µm to 2000 µm, for example, 5 µm to 1000 µm, preferably 10 µm to 300 µm, and more preferably 30 µm to 200 µm.

(Characteristics of laminated film) The laminated film of the present invention is a film to be subjected to die-cutting, and by adjusting the aforementioned shear yield stress of the adhesive layer to 0.15 N/mm ² or more, punching resistance can be imparted to the laminated film trace. As a method of adjusting the aforementioned shear yield stress of the adhesive layer, it can be adjusted by appropriately selecting the material of the adhesive layer. The material of the composition and/or the degree of hardening are adjusted.

The laminated film of the present invention only needs to interpose an adhesive layer between the base material layer and the release layer, and may include other layers in addition to the base material layer, the release layer, and the adhesive layer. Examples of other layers include hard coat layers, optical functional layers (anti-glare layer, polarizing layer, antireflection layer, refractive index adjustment layer, anti-Newton ring layer, etc.), surface protection layer (covering layer), and the like. Other layers can be arranged at any position between the release layer and the adhesive layer, between the substrate layer and the adhesive layer, or on the substrate layer (on the side opposite to the adhesive layer), but the substrate layer is preferred Between the bonding layer and on the substrate layer, especially preferably on the substrate layer. For example, a hard coat layer may be laminated on the substrate layer, and a cover layer for the die-cut surface may be laminated on the hard coat layer.

Among the laminated films, the laminated films other than the release layer are preferably excellent in transparency. The total light transmittance of the laminated film other than the release layer may be more than 70%, such as 70%-99.9%, preferably 75%-99%, and more preferably 80%-98%. If the total light transmittance is lowered, punching marks are not a problem, but there is a possibility that the effect of the present invention may not be exhibited.

When the adhesive layer is in contact with the release layer, the peel strength between the adhesive layer and the release layer is, for example, 0.001N/50mm~2N/50mm, preferably 0.01N/50mm~1N/50mm, more preferably 0.05 N/50mm~0.5N/50mm. When the peeling strength is too high, there is a possibility that the release property may be lowered, and conversely, when the peeling strength is too low, there is a possibility that the handleability may be lowered.

In addition, in this specification and the claims, the peel strength can be measured according to the method described in JIS Z 0237:2009.

The average thickness of the laminated film of the present invention from the die-cut surface to the bonding layer (or adhesive layer) (that is, the average thickness of the layer between the die-cut surface and the bonding layer) may be 150 µm or less (for example, 10 µm to 150 µm), Preferably less than 135 µm (eg 20 µm~135 µm), more preferably less than 130 µm (eg 30 µm~130 µm), more preferably less than 100 µm (eg 40 µm~100 µm), most preferably 80 Below µm (for example, 50 µm~80 µm). When the said average thickness exceeds 150 micrometers, there exists a possibility that punching mark resistance may fall.

(Manufacturing method of laminated film) The laminated film of the present invention can be manufactured by a conventional method, such as co-extrusion, coating, lamination, etc., and when the adhesive layer is formed of a cured product of a curable composition, by adjusting the curing of the adhesive layer In this way, the aforementioned shear yield stress of the adhesive layer can be adjusted. When the curable composition is a room temperature curable composition, for example, the aforementioned shear yield stress can be adjusted by controlling the curing time (curing time or aging time). In addition, when the curable composition is a thermosetting composition, the aforementioned shear yield stress can be adjusted, for example, by controlling the heating temperature and/or heating time. Furthermore, when the curable resin composition is a photocurable composition, for example, by controlling the light irradiation amount and/or irradiation time, the aforementioned shear yield stress can be adjusted. Furthermore, as mentioned above, regardless of any curable composition, when the curable composition contains a cross-linking agent, the aforementioned shear yield stress can be adjusted by controlling the ratio of the cross-linking agent.

[Die-cut film and its application] Die-cut films (formed films) are produced by die-cutting the aforementioned laminated film into the desired shape according to the application. As a method of punching the laminated film, a conventional method can be used, for example, a punching machine equipped with a Pinnacle knife or a Thomson knife can be used for punching. In the die-cutting process, the die-cutting process can be performed on the side of the adhesive layer on which the substrate layer is formed, or the die-cutting process can be performed on the side of the adhesive layer on which the release layer is formed. .

When the transparency of the laminated film other than the release layer is high, it is preferable to arrange the obtained die-cut film on the display surface of the display device. As the display device, for example, a liquid crystal display (LCD; liquid crystal display) device, a cathode tube display device, an organic or inorganic electroluminescence (EL; electroluminescence) display, a field emission display (FED; field emission display), a surface Conduction electron emission display (SED; surface-conduction electron-emitter display), rear projection TV display, plasma display, display device with touch panel, touch panel display, touch sensor, etc. In these display devices, since the laminated film has die-cut resistance, it is preferable to be a narrow-frame display in which the width of the frame arranged on the display surface is narrow. In a narrow bezel display, the width of the frame may be, for example, less than 5 mm, preferably less than 3 mm.

Furthermore, various aspects disclosed in this specification can also be combined with any other features disclosed in this specification. [Example]

Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples. The raw materials used in the examples are as follows, and the obtained laminated film was evaluated by the following method.

[raw material] Acrylic adhesive: "Coponyl N-7520" manufactured by Mitsubishi Chemical Co., Ltd. Cross-linking agent: "Coronate L-45E" manufactured by Tosoh Co., Ltd. Release film: "COSMOPEEL TZ-600" manufactured by Toyobo Co., Ltd. Base film: "Diafoil O321E" manufactured by Mitsubishi Chemical Co., Ltd., with an average thickness of 75 µm to 140 µm.

[Shear characteristics] The obtained laminated film was processed into the shape shown in Fig. 1 and used as a measurement sample. As shown in the side view (a) and top view (b) of Fig. 1, the measurement sample was obtained by cutting the obtained laminated film into a width of 10 mm, and processing it so that only the central part in the longitudinal direction remained the laminated structure . Specifically, as shown in the side view (a) of Fig. 1, the measurement sample has a structure in which a laminated structure remains at a length of 10 mm in the central part in the longitudinal direction, and at one end of the central part , the substrate layer 1 and the bonding layer 2 are removed and the release layer 3 is exposed, and at the other end, the release layer 3 and the bonding layer 2 are removed and the substrate layer 1 is exposed.

Set the above-mentioned measurement sample on Tensilon ("AGS-X50N" manufactured by Shimadzu Corporation Co., Ltd.), as shown in the side view (a) of Fig. 1, and stretch the exposed base film The tensile test was performed by stretching along the film surface direction of the measurement sample, and the shear yield stress value applied to the adhesive layer was measured. Specifically, the maximum value or peak value of the stress when the tensile displacement is 0 mm to 1 mm is divided by the area of the bonding layer (the area of the bonding region), and the obtained value is regarded as the shear yield stress value.

[edge line marks] Using a punching machine ("PAC-HD" manufactured by DAITEX Co., Ltd.), the obtained laminated film is punched into 90 mm from the base film side under the conditions of a pinnacle knife, a knife height of 2.2 mm, and two knife angles of 30°. ×130mm. Using LED lighting ("HOLOLIGHT" manufactured by PiPhotonics Co., Ltd.) as a light source, light is transmitted through the die-cut film, and the shadow of the film is projected on a white board to generate edge lines inside the edge of the film. The following indicators evaluate the edge lines produced. The projection method is to place the die-cut laminated film between the whiteboard and the light source, and adjust the distance between the whiteboard and the light source to be 80 cm, and the distance between the laminated film and the whiteboard to be between 5 cm and 10 cm. Observe the position of the edge line marks.

○: No edge marks at all △: The edge line mark is located within 3 mm from the end of the die-cut film ×: Edge lines are located at a position of 3 mm or more from the end of the die-cut film.

Example 1 (Preparation of OCA coating solution) An OCA coating liquid was prepared by dissolving 35 parts by mass of an acrylic adhesive and 0.15 parts by mass of a crosslinking agent in 90 parts by mass of ethyl acetate.

(production of laminated film) The OCA coating solution was applied to the release surface of the release film with a Baker applicator, and dried in a drying oven at 120°C for 2 minutes to form an adhesive layer (adhesive layer) with an average thickness of 25 µm. A substrate film with an average thickness of 125 µm was bonded to the surface of the obtained adhesive layer using a pressure bonding roller to prepare a laminated film precursor. The obtained laminated film precursor was left to stand in an environment of 30° C. and 50% RH, and the subsequent layer was hardened to obtain a laminated film. At this time, the shear properties of the adhesive layer and the edge marks of the laminated film were evaluated after standing for 5 days and 10 days.

Example 2 Except having changed the crosslinking agent into 0.3 mass parts, the laminated|multilayer film was produced similarly to Example 1, and the shear characteristic of an adhesive layer and the edge line mark of a laminated film were evaluated.

The evaluation results are shown in Table 1 below.

[Table 1] (Evaluation of shear characteristics and edge marks) Hardening days of next layer 5 days 10 days Shear yield stress (N/mm ² ) edge line marks Shear yield stress (N/mm ² ) edge line marks Example 1 0.12 x 0.15 △ Example 2 0.16 △ 0.21 ○

From the results in Table 1, it can be clearly seen that if the shear yield stress of the adhesive layer is above 0.15N/mm ² , the occurrence of edge marks can be suppressed.

Example 3 Except for using a substrate film with an average thickness of 75 µm, a laminated film precursor was produced in the same manner as in Example 2, and the obtained laminated film precursor was left to stand at 30°C and 50%RH for 10 days. The subsequent layer is subjected to curing treatment to obtain a laminated film. The edge marks of the laminated film were evaluated, and the evaluation result was "◯".

Example 4 Except for using a substrate film with an average thickness of 140 µm, a laminated film precursor was produced in the same manner as in Example 2, and the obtained laminated film precursor was left to stand at 30°C and 50%RH for 10 days. The subsequent layer is subjected to curing treatment to obtain a laminated film. The edge marks of the laminated film were evaluated, and the evaluation result was "△". [Industrial availability]

The laminated film of the present invention can be used as a laminated film formed by punching, for example, it is useful as a film arranged on the display surface of various displays, and can be used as a PC monitor, TV, car navigation, smart phone, tablet The film provided on the display surface of PC, game machine, etc. can be pre-assembled to the display surface, or it can be a protective film for the aftermarket (aftermarket). The films are particularly useful where there are narrow bezel displays that are easily noticeable.

1: Substrate layer 2: Next layer 3: Release layer

[ Fig. 1 ] It is a schematic side view (a) and a top view (b) of a sample used to measure the shear yield stress of the adhesive layer in the examples.

none.

Claims (12)

A laminated film, which is a laminated film comprising a base material layer, a release layer, and an adhesive layer interposed between the aforementioned base material layer and the aforementioned release layer, and the aforementioned adhesive layer is aligned in a direction parallel to the film surface The shear yield stress when a strain is applied at 5 mm/min is 0.15 N/mm ² or more. The laminated film according to claim 1, wherein the shear yield stress is 0.17 N/mm ² or more. The laminated film according to claim 1 or 2, wherein the adhesive layer is formed of an optically transparent adhesive. The laminated film according to claim 3, wherein the optically transparent adhesive is a cured product of a curable composition. The laminated film according to claim 4, wherein the curable composition includes a (meth)acrylic polymer and a crosslinking agent. The laminated film according to claim 1 or 2, wherein the base material layer comprises a transparent resin. The laminated film of claim 1 or 2 is a film for die-cutting. The laminated film of claim 1 or 2 is a die-cut film obtained by die-cutting. A method for producing a die-cut film, comprising performing die-cut processing on the laminated film according to claim 1 or 2 to produce a die-cut film. A display device having the die-cut film according to claim 8 on the display surface. As the display device of claim 10, it is a narrow frame display. A method for improving the punching mark resistance of a laminated film, which is aimed at a laminated film comprising a base material layer, a release layer, and an adhesive layer interposed between the aforementioned base material layer and the aforementioned release layer. The shear yield stress of the subsequent layer when a strain is applied at 5 mm/min in a direction parallel to the film surface is adjusted to be 0.15 N/mm ² or more, thereby improving the die cut resistance of the laminated film.

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