JP2022110832A - Hard coat film for flexible display and flexible display using the same - Google Patents

Abstract

To provide a hard coat film for a flexible display, which has excellent pencil hardness even if the film has an adhesive layer, has flexibility that can withstand repetitive bending, and can maintain excellent adhesion to an adherend even at a high temperature, and a flexible display using the same.SOLUTION: There is provided a hard coat film for a flexible display, comprising: a base film 12; a hard coat layer 14 formed on one surface of the base film; and an adhesive layer 16 formed on the other surface of the base film. The base film 12 contains a polyimide resin, the adhesive layer 16 is formed from a cured adhesive composition containing a (meth)acrylic polymer, a cross-linking agent, and a triazine compound having a predetermined structure, and an indentation modulus E-IT(a) of the adhesive layer 16 measured through a polyether-ether-ketone film having a predetermined indentation modulus and thickness is 290 N/mm2 or more and 1600 N/mm2 or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a hard coat film for flexible displays and a flexible display using the same.

Hard coat films are used for the purpose of protecting displays of image display devices such as liquid crystal display devices and organic EL display devices. 2. Description of the Related Art In recent years, in the field of image display devices, attention has been focused on flexible displays that can maintain display functions even when bent and can be repeatedly bent for use. Foldable displays that can be folded, rollable displays that can be rolled into a cylinder, and the like are known as flexible displays. Flexible displays are expected to be used for portable terminals such as smart phones and tablet terminals, and stationary displays that can be stored. As the cover window of the flexible display, a flexible plastic film is used instead of the glass substrate. Since a plastic film is more easily scratched than a glass substrate, a hard coat layer may be formed on the surface of the plastic film.

For example, Patent Literature 1 describes a hard coat film for flexible displays. The hard coat film of Patent Document 1 comprises a hard coat layer having a thickness of 5 to 50 μm and a rigidity of 15 to 130 kPa·m on each surface of a transparent substrate. Moreover, Patent Literature 1 describes that a pressure-sensitive adhesive layer is provided on one surface of the hard coat layer.

Patent Document 2 also describes a hard coat film for flexible displays. The hard coat film of Patent Document 2 includes a base film and a hard coat layer laminated on one side of the base film, the base film is a polyimide film, and the hard coat layer has a thickness of It is described that the thickness is 0.5 μm or more and 10 μm or less. Moreover, Patent Document 2 describes laminating a pressure-sensitive adhesive layer on the other surface of the base film.

JP 2017-036439 A WO2018/037488

Although the hard coat film of Patent Literature 1 itself has high pencil hardness and excellent flexibility, the provision of the pressure-sensitive adhesive layer greatly reduces the pencil hardness. In addition, the hard coat film of Patent Document 2 uses a polyimide film as the base film, and the thickness of the hard coat layer is set to a predetermined thickness, thereby achieving both scratch resistance and flex resistance. The composition of the agent layer is not studied, and the problem of the pencil hardness of the hard coat film surface being greatly reduced by providing the pressure-sensitive adhesive layer is not solved.

The problem to be solved by the present invention is to have a high surface hardness that gives excellent pencil hardness even if it has an adhesive layer, and has flexibility to withstand repeated bending, and a high temperature environment such as 60 ° C. To provide a hard coat film for a flexible display and a flexible display using the same, which can maintain excellent adhesion to an adherend even under the condition of the film.

式（１）において、Ｘはアルキレン基を表し、Ｒ^１およびＲ^２はそれぞれ個別に水素原子または炭素数１以上４以下のアルキル基を表し、ｎは０以上２以下の整数を表す。Ｘのアルキレン基は、置換基が結合されている場合、および主鎖中にヘテロ原子を含有する場合も含む。 In order to solve the above problems, the flexible display hard coat film according to the present invention is arranged on the surface of the flexible display, and includes a base film, a hard coat layer formed on one surface of the base film, and a pressure-sensitive adhesive layer formed on the other surface of the base film, wherein the base film contains a polyimide resin, and the pressure-sensitive adhesive layer comprises a (meth)acrylic polymer and a cross-linking agent. , and a triazine compound represented by the following general formula ( ¹ ); The pressure-sensitive adhesive layer has an indentation elastic modulus E-IT(a) of 290 N/mm ² or more and 1600 N/mm ² or less measured by a nanoindentation method through an ether ketone film.

In formula (1), X represents an alkylene group, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 2. The alkylene group of X includes the case where a substituent is attached and the case where it contains a heteroatom in the main chain.

In the hard coat film for a flexible display according to the present invention, the indentation hardness H-IT (h) of the hard coat layer measured by a nanoindentation method is 300 N/mm ² or more and 550 N/mm ² or less. good. The hard coat layer preferably has a thickness of 0.5 μm or more and 10.0 μm or less. And the thickness of the said adhesive layer is good in it being 5.0 micrometers or more and 50.0 micrometers or less. It is preferable to have a protective film on the surface of the hard coat layer.

And the flexible display which concerns on this invention arrange|positions the hard-coat film for flexible displays which concerns on this invention on the display surface through the said adhesive layer.

According to the hard coat film for a flexible display according to the present invention, the base film contains a polyimide resin, and the indentation elastic modulus E-IT(a) of the adhesive layer is 290 N/mm ² or more and 1600 N/mm ² or less. Therefore, even if it has a pressure-sensitive adhesive layer, it has a high surface hardness that gives an excellent pencil hardness, and also has flexibility to withstand repeated bending. In addition, since the adhesive layer is formed from a cured adhesive composition containing a (meth)acrylic polymer, a cross-linking agent, and the triazine compound of formula (1), a high temperature such as 60 ° C. Excellent adhesion can be maintained even under environmental conditions.

At this time, when the indentation hardness H-IT (h) of the hard coat layer is 300 N/mm ² or more and 550 N/mm ² or less, the hard coat film for a flexible display has an excellent balance between pencil hardness and flexibility. And when the thickness of the hard coat layer is 10.0 μm or less, it is easy to ensure the flexibility of the hard coat film. When the thickness of the pressure-sensitive adhesive layer is 5.0 μm or more and 50.0 μm or less, sufficient adhesiveness to the adherend can be ensured, and the indentation elastic modulus E-IT(a) can be easily controlled. When a protective film is provided on the surface of the hard coat layer, the surface of the hard coat layer is protected during handling, and the occurrence of scratches can be suppressed.

And according to the flexible display according to the present invention, since the hard coat film for a flexible display according to the present invention is arranged on the display surface via the adhesive layer, it has excellent pencil hardness and can withstand repeated bending. It has the flexibility to be

1 is a cross-sectional view of a hard coat film for a flexible display according to one embodiment of the present invention; FIG. FIG. 3 is a cross-sectional view of a hard coat film for a flexible display according to another embodiment of the present invention;

The present invention will be described in detail below.

[First Embodiment]
FIG. 1 is a cross-sectional view of a hard coat film for a flexible display (hereinafter simply referred to as hard coat film) according to one embodiment of the present invention. As shown in FIG. 1, the hard coat film 10 according to one embodiment of the present invention includes a base film 12, a hard coat layer 14 formed on one surface of the base film 12, and the base film 12. and an adhesive layer 16 formed on the other surface. The hard coat film 10 has a release film 18 on the surface of the adhesive layer 16 (on the surface of the adhesive layer 16 on which the base film 12 is not arranged). The release film 18 functions as a protective layer for the adhesive layer 16 before the hard coat film 10 is used, and is peeled off from the adhesive layer 16 when the hard coat film 10 is used. The hard coat film 10 has a protective layer 18, an adhesive layer 16, a base film 12, and a hard coat layer 14 in this order.

In the hard coat film 10, the hard coat layer 14 is in contact with one surface of the base film 12, and the adhesive layer 16 is in contact with the other surface of the base film 12. Another layer may be interposed between the hard coat layer and the base film or between the adhesive layer and the base film.

(Base film)
The base film 12 is a film containing polyimide resin. The base film 12 may be a film containing only polyimide resin as a polymer component, or may be a film containing other polymer components, additives, and the like. However, in order to fully exhibit the physical properties of the polyimide resin, it is preferable that the base film 12 contains the polyimide resin as the main polymer component. A main component means a component that accounts for 50% by mass or more of the entire polymer component. It is preferable that 50% by mass or more, 70% by mass or more, or 90% by mass or more of the polymer component of the base film 12 is polyimide resin. A polyimide film etc. are mentioned as a film containing a polyimide resin.

A film containing a polyimide resin is suitable as a base film for a hard coat film for a flexible display, which is repeatedly bent, because it has flexibility to withstand repeated bending. In addition, since a film containing a polyimide resin has excellent surface hardness, it is suitable as a base film for a hard coat film having excellent pencil hardness. By using a film containing a polyimide resin as the base film, it is possible to ensure the pencil hardness of the surface of the hard coat layer when the hard coat layer is laminated. For example, depending on the structure of the hard coat layer, the pencil hardness of the surface of the hard coat layer can be 3H or more when the hard coat layer is laminated. A film containing a polyimide resin is also excellent in heat resistance.

From the viewpoint of improving the pencil hardness of the hard coat film 10, the base film 12 preferably has an indentation elastic modulus E-IT(h) of 4500 N/mm ² or more according to the nanoindentation method. From the viewpoint of improving the pencil hardness of the hard coat film 10, the indentation modulus E-IT(h) is more preferably 5000 N/mm ² or more, and still more preferably 5400 N/mm ² or more. On the other hand, from the viewpoint of contributing to improvement in flexibility of the hard coat film 10, the indentation elastic modulus E-IT(h) is preferably 100000 N/mm ² or less. Further, from the viewpoint of improving the flexibility of the hard coat film 10, the indentation hardness H-IT(h) is more preferably 80000 N/mm ² or less, and still more preferably 10000 N/mm ² or less.

The base film 12 is preferably colorless and transparent. Colorless and transparent means that the total light transmittance in the visible light wavelength region measured in accordance with JIS K7361-1 (1997) is 50% or more, and yellow color measured in accordance with JIS K 7373 (2006) degree (YI value) is 20 or less. The total light transmittance is more preferably 70% or higher, still more preferably 85% or higher. The yellowness index (YI value) is more preferably 10 or less, more preferably 5 or less. This makes it possible to obtain a display that displays an image with high transparency and high color reproducibility.

As the colorless and transparent polyimide resin, a polyimide resin containing the following unit structures as a unit structure derived from a carboxylic acid anhydride and a unit structure derived from a diamine can be preferably exemplified.
・ Unit structure derived from carboxylic anhydride: 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (FDA), 4-(2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxyl dianhydride (6FCDA ), 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) (HBDA), pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA) and oxydiphthalic acid A unit structure derived from at least one aromatic dianhydride selected from dianhydrides (ODPA).
- Unit structure derived from diamine: 2,2-bis[4-(4-aminophenoxy)-phenyl]propane (6HMDA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl ( 2,2-TFDB), 3,3′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (3,3′-TFDB), 4,4′-bis(3-aminophenoxy)diphenylsulfone ( DBSDA), bis(3-aminophenyl)sulfone (3DDS), bis(4-aminophenyl)sulfone (4DDS), 1,3-bis(3-aminophenoxy)benzene (APB-133), 1,4-bis (4-aminophenoxy)benzene (APB-134), 2,2′-bis[3(3-aminophenoxy)phenyl]hexafluoropropane (3-BDAF), 2,2′-bis[4(4-amino phenoxy)phenyl]hexafluoropropane (4-BDAF), 2,2′-bis(3-aminophenyl)hexafluoropropane (3,3′-6F), 2,2′-bis(4-aminophenyl)hexafluoropropane A unit structure derived from at least one aromatic diamine selected from fluoropropane (4,4'-6F) and oxydianiline (ODA).
Alternatively, as another suitable example of a colorless and transparent polyimide resin, the unit structure derived from the above aromatic dianhydride, terephthaloyl chloride (TPC), terephthalic acid, isophthaloyl dichloride and 4,4'-benzoyl chloride A polyimide resin containing a unit structure derived from at least one aromatic dicarbonyl compound selected from among and a unit structure derived from the aromatic diamine can be mentioned.

Although the thickness of the base film 12 is not particularly limited, it is preferably in the range of 12 to 200 μm from the viewpoint of handleability, colorless transparency, and the like. It is more preferably 25 to 100 μm, particularly preferably 40 to 80 μm.

(Hard coat layer)
(1) Properties of Hard Coat Layer The hard coat layer 14 contributes to improving the pencil hardness of the hard coat film 10 . From the viewpoint of improving the pencil hardness of the hard coat film 10, the hard coat layer 14 preferably has an indentation hardness H-IT (h) of 300 N/mm ² or more according to the nanoindentation method. Further, from the viewpoint of improving the pencil hardness of the hard coat film 10, the indentation hardness H-IT(h) is more preferably 320 N/mm ² or more, and still more preferably 350 N/mm ² or more. On the other hand, the indentation hardness H-IT(h) is preferably 550 N/mm ² or less from the viewpoint of contributing to improvement in flexibility of the hard coat film 10 . From the viewpoint of improving the flexibility of the hard coat film 10, the indentation hardness H-IT(h) is more preferably 520 N/mm ² or less, and even more preferably 500 N/mm ² or less. The indentation hardness H-IT (h) of the hard coat layer 14 is the indentation hardness H-IT (h) of the surface of the hard coat layer 14 formed on one surface of the base film 12. Measurement is performed in a state where the pressure-sensitive adhesive layer 16 is not formed on the other surface.

The hard coat layer 14 is preferably adjusted so that the indentation hardness H-IT(h) is relatively small as described above. For this purpose, for example, the indentation hardness H-IT of the hard coat layer 14 is determined by the selection of materials, the thickness of the hard coat layer 14, the content of inorganic particles and organic particles that may be contained in the hard coat layer 14, and the like. (h) can be relatively small. For example, the choice of material may be a material that is relatively soft. Moreover, it is preferable to make the thickness of the hard coat layer 14 relatively thin. In addition, the content of organic particles and inorganic particles that may be contained in the hard coat layer 14 should be relatively small.

The hard coat layer 14 preferably has a pencil hardness of 3H or higher. More preferably, it is 4H or more. The pencil hardness of the hard coat layer 14 referred to here is the pencil hardness of the surface of the hard coat layer 14 formed on one side of the base film 12, and the adhesive layer 16 on the other side of the base film 12. It is measured in an unformed state. The pencil hardness of the hard coat layer 14 can be measured according to JIS K 5600-5-4.

The thickness of the hard coat layer 14 is such that the hard coat film 10 has sufficient flexibility to withstand repeated bending. The thickness is preferably 10.0 μm or less from the viewpoint that curling is easily suppressed. It is more preferably 8.0 μm or less, and still more preferably 6.0 μm or less. On the other hand, from the viewpoint of ensuring sufficient pencil hardness of the hard coat film 10, the thickness is preferably 0.5 μm or more. It is more preferably 1.0 μm or more, still more preferably 3.0 μm or more. The thickness of the hard coat layer 14 is the thickness of the smooth portion, and when the hard coat layer 14 contains particles, the thickness of the smooth portion in the thickness direction where there is no unevenness caused by the particles. is.

(2) Constituent Material of Hard Coat Layer From the viewpoint of high hardness, high flexibility, productivity, and the like, the hard coat layer 14 is preferably composed of a cured product of a curable composition containing an ultraviolet curable resin.

Examples of UV-curable resins include monomers, oligomers, and prepolymers having UV-reactive groups. Examples of the UV-reactive reactive group include a radical polymerization type reactive group having an ethylenically unsaturated bond such as a (meth)acryloyl group, an allyl group, and a vinyl group, and a cationic polymerization type reactive group such as an oxetanyl group. is mentioned. Among these, a (meth)acryloyl group and an oxetanyl group are more preferable, and a (meth)acryloyl group is particularly preferable. That is, (meth)acrylate is particularly preferable as the ultraviolet curable resin. In this specification, "(meth)acrylate" means "at least one of acrylate and methacrylate". "(Meth)acryloyl" means "at least one of acryloyl and methacryloyl". "(Meth)acrylic" means "at least one of acrylic and methacrylic".

(Meth)acrylates include urethane (meth)acrylates, silicone (meth)acrylates, alkyl (meth)acrylates, and aryl (meth)acrylates. Among them, urethane (meth)acrylate is particularly preferable from the viewpoint of being relatively flexible and improving the flexibility of the hard coat film 10 .

A urethane (meth)acrylate is formed from a polyol, an isocyanate compound, and a (meth)acrylate having a hydroxyl group. Examples of polyols include polyether polyols, polyester polyols, polycarbonate polyols, and the like, and can be appropriately selected from the viewpoint of flexibility, heat resistance, chemical resistance, and the like. Examples of isocyanate compounds include diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI) and other aromatic diisocyanates; -cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethyl Alicyclic diisocyanates such as cyclohexane (hydrogenated XDI) and 4-methyl-1,3-cyclohexylene diisocyanate (hydrogenated TDI) can be used.

The (meth)acrylate as the ultraviolet curable resin may be composed of only monofunctional (meth)acrylate, may be composed of polyfunctional (meth)acrylate, or may be composed of monofunctional (meth)acrylate and It may be composed of a combination of polyfunctional (meth)acrylates. (Meth)acrylates more preferably include polyfunctional (meth)acrylates. In particular, it preferably contains polyfunctional urethane (meth)acrylate.

Monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, and isobutyl (meth)acrylate. , t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl ( meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate ) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, bornyl (meth) acrylate, tricyclodeca Nil (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, 2-naphthylmethyl (meth)acrylate ) acrylate, phenoxyethyl (meth) acrylate, phenoxy-2-methylethyl (meth) acrylate, phenoxyethoxyethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, 2-phenylphenoxyethyl (meth) Acrylates, 4-phenylphenoxyethyl (meth)acrylate, 3-(2-phenylphenyl)-2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2- Hydroxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol (meth) ) acrylates, ethoxylates Chill (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, methoxypolypropyleneglycol (meth)acrylate and the like.

Polyfunctional (meth)acrylates include bifunctional (meth)acrylates, trifunctional (meth)acrylates, tetrafunctional (meth)acrylates, and the like. More specifically, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, Diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate , pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tetra(meth)acrylate, tripentaerythritol penta(meth)acrylate ) acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate and the like.

The curable composition forming the hard coat layer 14 may or may not contain a non-UV curable resin in addition to the UV curable resin. Moreover, the curable composition forming the hard coat layer 14 may contain a photopolymerization initiator. Moreover, the additive etc. which are added to a curable composition may be contained as needed. Examples of such additives include dispersants, leveling agents, antifoaming agents, stabilizing agents, antifouling agents, antibacterial agents, flame retardants, slip agents, inorganic particles and resin particles. Moreover, a solvent may be contained as necessary.

Examples of non-ultraviolet curable resins include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include polyester resins, polyether resins, polyolefin resins, and polyamide resins. Thermosetting resins include unsaturated polyester resins, epoxy resins, alkyd resins, phenolic resins, and the like.

Examples of the photopolymerization initiator include alkylphenone-based, acylphosphine oxide-based, and oxime ester-based photopolymerization initiators. Alkylphenone-based photopolymerization initiators include 2,2′-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl- Propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-( 2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzylmethyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-morpholino phenyl)-1-butanone, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, N,N-dimethylaminoacetophenone and the like. Acylphosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2. , 4,4-trimethyl-pentylphosphine oxide. Examples of oxime ester photopolymerization initiators include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime), ethanone-1-[9-ethyl-6-(2- methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) and the like. These photopolymerization initiators may be used alone, or two or more of them may be used in combination.

The content of the photopolymerization initiator is preferably in the range of 0.1 to 10% by mass based on the total solid content of the curable composition. More preferably, it is in the range of 1 to 5% by mass.

The inorganic particles and resin particles are added for the purpose of, for example, preventing blocking of the hard coat layer 14, improving the hardness of the hard coat layer 14, and imparting antiglare properties.

Inorganic particles include metal oxide particles composed of oxides of metals such as titanium, zirconium, tin, zinc, silicon, niobium, aluminum, chromium, magnesium, germanium, gallium, antimony, and platinum. These may be used individually by 1 type as an inorganic particle, and may be used in combination of 2 or more types. Among these, silica, titanium oxide, zirconium oxide, and tin oxide are particularly preferable from the viewpoint of being excellent in both high hardness and transparency.

Examples of resin particles include (meth)acrylic resins, styrene resins, styrene-(meth)acrylic resins, urethane resins, polyamide resins, silicone resins, epoxy resins, phenolic resins, polyethylene resins, resin particles made of resins such as cellulose. is mentioned. These resin particles may be used singly or in combination of two or more.

Examples of antifouling agents include fluorine-containing compounds. Examples of fluorine-containing compounds include (meth)acrylates containing perfluoroalkyl groups. Such a fluorine-containing compound can suppress adhesion of stains and fingerprints and facilitate removal of stains and fingerprints.

The content of the fluorine-containing compound is preferably in the range of 0.01 to 15% by mass based on the total amount of the hard coat layer 14. It is more preferably in the range of 0.05 to 10% by mass, still more preferably in the range of 0.2 to 5% by mass. When the content of the fluorine-containing compound is within the preferred range, excellent antifouling properties and anti-fingerprint properties can be obtained.

Solvents used in the curable composition forming the hard coat layer 14 include ethanol, isopropyl alcohol (IPA), n-butyl alcohol (NBA), ethylene glycol monomethyl ether (EGM), and ethylene glycol monoisopropyl ether (IPG). , alcohol solvents such as propylene glycol monomethyl ether (PGM) and diethylene glycol monobutyl ether; ketone solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone and acetone; aromatic solvents such as toluene and xylene; Ester-based solvents such as ethyl acetate (EtAc), propyl acetate, isopropyl acetate and butyl acetate (BuAc), and amide-based solvents such as N-methylpyrrolidone, acetamide and dimethylformamide are included. These may be used individually by 1 type as a solvent, and may be used in combination of 2 or more types.

The solid content concentration (concentration of components other than the solvent) of the curable composition may be appropriately determined in consideration of coatability, film thickness, and the like. For example, it may be 1 to 90% by mass, 1.5 to 80% by mass, 2 to 70% by mass, and the like.

(Adhesive layer)
(1) Properties of Adhesive Layer The adhesive layer 16 is for bonding the hard coat film 10 to an adherend. The pressure-sensitive adhesive layer 16 has an indentation elastic modulus E-IT(a) of 290 N/mm ² or more and 1600 N/mm ² or less. The indentation elastic modulus E-IT(a) of the adhesive layer 16 is measured by a nanoindentation method through an 8 μm-thick polyetheretherketone film having an indentation elastic modulus of 5200 N/mm ² by the nanoindentation method. be done. When the indentation modulus E-IT(a) of the adhesive layer 16 is 290 N/mm ² or more, even if the adhesive layer 16 is provided, a decrease in the pencil hardness of the hard coat film 10 can be suppressed, and the hard coat film 10 can be hardened. Coated film 10 can have excellent pencil hardness. From this point of view, the indentation elastic modulus E-IT(a) of the pressure-sensitive adhesive layer 16 is more preferably 300 N/mm ² or more, still more preferably 320 N/mm ² or more. When the indentation elastic modulus E-IT(a) of the adhesive layer 16 is 1600 N/mm ² or less, when the hard coat film 10 is bonded to the adherend and bent, the pressure from the adherend is reduced. Prevents floating and peeling. In addition, the hard coat film 10 can have flexibility to withstand repeated bending. From this point of view, the indentation elastic modulus E-IT(a) of the adhesive layer 16 is more preferably 1580 N/mm ² or less. Here, bending refers to bending of the hard coat film 10 with the hard coat layer 14 on the outside. In this specification, the adherend refers to a material constituting a flexible display, such as a barrier film, a polarizing film, a retardation film, an optical compensation film, a brightness enhancement film, a diffusion film, an antireflection film, a transparent conductive film. , metal mesh film, cushion film, etc.

The pressure-sensitive adhesive layer 16 is adjusted so that the indentation elastic modulus E-IT(a) is relatively large, as described above. The indentation elastic modulus E-IT(a) of the adhesive layer 16 can be made relatively large by selecting the material, cross-linking treatment of the material, thickness of the adhesive layer 16, and the like. For example, the material should be selected to have a relatively high glass transition temperature (Tg). Also, the thickness of the adhesive layer 16 should be relatively thin.

The thickness of the pressure-sensitive adhesive layer 16 is preferably 5.0 μm or more from the viewpoint of ensuring sufficient adhesion to the adherend. More preferably, it is 10 μm or more. Further, the thickness of the adhesive layer 16 is preferably 50 μm or less from the viewpoint of easily controlling the indentation modulus E-IT(a) of the adhesive layer 16 to be high. More preferably, it is 30 µm or less.

The adhesive layer 16 is preferably colorless and transparent. Colorless and transparent means that the total light transmittance in the visible light wavelength region measured in accordance with JIS K7361-1 (1997) is 50% or more, and yellow color measured in accordance with JIS K 7373 (2006) degree (YI value) is 20 or less. The total light transmittance is more preferably 70% or higher, still more preferably 85% or higher. The yellowness index (YI value) is more preferably 10 or less, more preferably 5 or less.

The glass transition temperature (Tg) of the adhesive layer 16 is not particularly limited, but is preferably -25°C or lower, more preferably -30°C or lower, and still more preferably -35°C or lower. On the other hand, the glass transition temperature of the adhesive layer 16 is preferably −70° C. or higher, more preferably −60° C. or higher, and still more preferably −50° C. or higher. The glass transition temperature (Tg) of the adhesive layer 16 is obtained from the temperature at which the peak of the principal dispersion of the loss tangent (tan δ) by dynamic viscoelasticity measurement appears. When the glass transition temperature (Tg) of the pressure-sensitive adhesive layer 16 is within the above range, troubles such as the pressure-sensitive adhesive sticking out from the pressure-sensitive adhesive layer 16 can be suppressed, and appropriate adhesiveness and indentation elastic modulus can be easily obtained.

(2) Constituent Material of Adhesive Layer The adhesive layer 16 is formed from a cured adhesive composition containing a (meth)acrylic polymer, a cross-linking agent, and a triazine compound having a predetermined structure.

(2-1) (Meth)acrylic polymer A (meth)acrylic polymer is a homopolymer of a (meth)acrylic monomer or (meth)acrylic oligomer, or a (meth)acrylic monomer or (meth)acrylic oligomer as a main component. It is a copolymer with a reactive functional group. Examples of reactive functional groups include carboxyl groups and/or hydroxyl groups.

The amount of reactive functional groups per 100 g of the polymer is preferably 0.5 mmol/100 g or more. If the amount of reactive functional groups is 0.5 mmol/100 g or more, the pressure-sensitive adhesive layer 16 will have excellent durability. The amount of reactive functional groups is more preferably 5 mmol/100 g or more, still more preferably 10 mmol/100 g or more, particularly preferably 15 mmol/100 g or more, most preferably 50 mmol/100 g or more. On the other hand, the amount of reactive functional groups is preferably 150 mmol/100 g or less. If the amount of reactive functional groups is 150 mmol/100 g or less, the adhesion of the pressure-sensitive adhesive layer 16 to the adherend is excellent. The amount of reactive functional groups is more preferably 120 mmol/100 g or less, still more preferably 90 mmol/100 g or less.

The (meth)acrylic monomers or (meth)acrylic oligomers used as the (meth)acrylic polymer include isostearyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, and dodecyl (meth)acrylate. , (meth) decyl acrylate, isononyl (meth) acrylate, nonyl (meth) acrylate, isooctyl (meth) acrylate, octyl (meth) acrylate, isobutyl (meth) acrylate, n-(meth) acrylate Butyl, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, propyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic Alkyl (meth)acrylate monomers such as methyl acid, carboxyl group-containing monomers such as carboxyethyl (meth)acrylate and carboxypentyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 10 (meth)acrylic acid -hydroxydecyl, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth)acrylic acid 2 - hydroxyl group-containing monomers such as hydroxyethyl, amino group-containing monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, (meth)acrylic acid, (meth)acrylamide, dimethyl (meth)acrylamide, etc. be done.

The (meth)acrylic polymer may contain monomers or oligomers other than (meth)acrylic monomers or (meth)acrylic oligomers as copolymer components. Examples of such monomers or oligomers include acetic acid esters such as vinyl acetate and styrene.

(2-2) Cross-linking agent The cross-linking agent contained in the pressure-sensitive adhesive composition has a reactive group or reactive structural unit that can react with the reactive functional group of the above-mentioned (meth)acrylic polymer in one molecule. It is a compound having two or more. Examples of reactive groups capable of reacting with the reactive functional groups of the (meth)acrylic polymer include isocyanate groups, epoxy groups, aziridine groups, alkoxy groups, carbodiimide groups, oxazoline groups, and the like. The type of cross-linking agent is not particularly limited. Examples include resin-based cross-linking agents and urea resin-based cross-linking agents. Among these, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, and aziridine-based cross-linking agents are preferable. agents are more preferred.

The content of the reactive group or reactive structural unit in the cross-linking agent is preferably 0.5 mmol/g or more, more preferably 1.0 mmol/g or more, still more preferably 3.0 mmol/g or more, and particularly preferably 6.0 mmol/g or more. Then, the cohesive force of the pressure-sensitive adhesive layer 16 becomes favorable. On the other hand, the content thereof is preferably 20 mmol/g or less, more preferably 15.0 mmol/g or less, still more preferably 12.0 mmol/g or less. Then, even if the hard coat film 10 is bent, it is possible to effectively suppress the occurrence of deformation at the bent portion.

The content of the cross-linking agent in the adhesive composition is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the (meth)acrylic polymer. When the content of the cross-linking agent is 0.01 parts by mass or more, the pressure-sensitive adhesive layer 16 exhibits sufficient cohesion and exhibits excellent flexibility. The content of the cross-linking agent is more preferably 0.03 parts by mass or more. On the other hand, the content of the cross-linking agent is preferably 1 part by mass or less. When the content of the cross-linking agent is 1 part by mass or less, the pressure-sensitive adhesive layer 16 exhibits high adhesion to the base film 12, and the occurrence of lifting and peeling during bending can be suppressed. The content of the cross-linking agent is more preferably 0.5 parts by mass or less.

The pressure-sensitive adhesive composition has a molar ratio of the reactive functional group of the (meth)acrylic polymer to the reactive group or reactive structural unit of the cross-linking agent (the molar amount of the reactive functional group of the (meth)acrylic polymer /molar amount of reactive groups of the cross-linking agent) is preferably 1 or more, more preferably 2 or more, and still more preferably 10 or more. On the other hand, the molar ratio is preferably 1000 or less, more preferably 200 or less, still more preferably 100 or less.

式（１）において、Ｘはアルキレン基を表し、Ｒ^１およびＲ^２はそれぞれ個別に水素原子または炭素数１以上４以下のアルキル基を表し、ｎは０以上２以下の整数を表す。Ｘのアルキレン基は、置換基が結合されている場合、および主鎖中にヘテロ原子を含有する場合も含む。 (2-3) Triazine compound The triazine compound contained in the pressure-sensitive adhesive composition is represented by the following general formula (1) and consists of a diaminotriazine derivative having an alkoxysilyl group.

In formula (1), X represents an alkylene group, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 2. The alkylene group of X includes the case where a substituent is attached and the case where it contains a heteroatom in the main chain.

The triazine compound represented by the above formula (1) has high heat resistance by containing a triazine ring, and exhibits high solubility in a pressure-sensitive adhesive composition by containing an alkoxysilyl group. Containing an amino group is considered to improve adhesion to an adherend. Since the pressure-sensitive adhesive composition contains a diaminotriazine derivative having an alkoxysilyl group represented by the above formula (1), it contributes to the improvement of adhesion to the adherend, Excellent adhesion can be maintained even in high-temperature environments.

The alkoxysilyl group possessed by the triazine compound of formula (1) includes an alkoxydialkylsilyl group (n=2), an alkyldialkoxysilyl group (n=1), and a trialkoxysilyl group (n=0). Among them, an alkyldialkoxysilyl group (n=1) or a trialkoxysilyl group (n=0) is preferable. The alkyl group (R ¹ ) includes methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group and the like. Alkoxy groups (OR ² ) include methoxy, ethoxy, propoxy, isopropoxy, butoxy, and isobutoxy groups. Specific examples of the alkoxysilyl group include trimethoxysilyl group, methyldimethoxysilyl group, dimethylmethoxysilyl group, triethoxysilyl group, methyldiethoxysilyl group and dimethylethoxysilyl group.

In formula (1), the alkylene group represented by X may be linear or branched, may be unsubstituted or may be substituted, and preferably has 1 to 10 carbon atoms. In addition, the main chain of the alkylene group may contain heteroatoms (atoms of elements other than carbon and hydrogen, such as O, S, and N). Hetero atoms are ether bond (-O-), sulfide bond (-S-), imino group (-NH-), carbonyl group (-CO-), ester bond (-COO- or -OCO-), amide bond (-CONH- or -NHCO-), carbonate bond (-OCOO-), urethane bond (-NHCOO- or -OCONH-), urea bond (-NHCONH-) and other functional groups in the main chain may be One or more heteroatoms can be included in the main chain. However, in the alkylene group X, the atom adjacent to Si of the alkoxysilyl group is not a heteroatom but a carbon atom.

Substituents bonded to the alkylene group X include aryl groups or substituted aryl groups such as phenyl, naphthyl, 4-methylphenyl and 4-methoxyphenyl groups; methoxy, ethoxy, propoxy and isopropoxy groups. alkoxy or substituted alkoxy groups such as , butoxy, isobutoxy, sec-butoxy, tert-butoxy, trifluoromethoxy, benzyloxy; phenoxy, 2-methylphenoxy, 4-methylphenoxy, 4 -Aryloxy groups such as methoxyphenoxy group and 3-phenoxyphenoxy group or substituted aryloxy groups; and halogen atoms such as fluorine atom and chlorine atom.

The content of the triazine compound represented by formula (1) in the pressure-sensitive adhesive composition is preferably 0.5 parts by mass or more with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition. As a result, the pressure-sensitive adhesive layer 16 becomes excellent in adhesion to the adherend and adhesion in a high-temperature environment. The content of the triazine compound is more preferably 1 part by mass or more, still more preferably 3 parts by mass or more. On the other hand, the content of the triazine compound is preferably 20 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition. As a result, when the hard coat film 10 is attached to an adherend and bent, it is prevented from lifting or peeling off from the adherend. The content of the triazine compound is more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less.

(2-4) Other Components The pressure-sensitive adhesive composition may contain other additives in addition to the (meth)acrylic polymer, cross-linking agent, and triazine compound represented by formula (1). Other additives include known additives such as plasticizers, silane coupling agents, surfactants, antioxidants, fillers, curing accelerators and curing retarders. Moreover, from the viewpoint of productivity, etc., an organic solvent may be used to dilute the adhesive.

(Method for producing hard coat film)
The hard coat film 10 can be produced by forming the hard coat layer 14 on one side of the base film 12 and forming the adhesive layer 16 on the other side of the base film 12 .

(1) Formation of hard coat layer The hard coat layer 14 is formed by coating a composition for forming the hard coat layer 14 on one surface of the base film 12 and, if necessary, drying or irradiating with ultraviolet rays. can be formed. At this time, in order to improve the adhesion between the base film 12 and the hard coat layer 14, the surface of the base film 12 may be subjected to surface treatment before coating. Examples of surface treatment include corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment.

For coating the composition forming the hard coat layer 14, for example, a reverse gravure coating method, a direct gravure coating method, a die coating method, a bar coating method, a wire bar coating method, a roll coating method, a spin coating method, and a dip coating method. , a spray coating method, a knife coating method and a kiss coating method, and various printing methods such as an inkjet method, offset printing, screen printing and flexographic printing.

The drying process is not particularly limited as long as the solvent and the like used in the coating liquid can be removed, but it is preferably carried out at a temperature of 50 to 150° C. for about 10 to 180 seconds. Especially, the drying temperature is preferably 50 to 120°C.

A high-pressure mercury lamp, an electrodeless (microwave type) lamp, a xenon lamp, a metal halide lamp, or any other ultraviolet irradiation device can be used for ultraviolet irradiation. UV irradiation may be performed under an inert gas atmosphere such as nitrogen, if necessary. The amount of ultraviolet irradiation is not particularly limited, but is preferably 50-800 mJ/cm ^{2 , more preferably 100-300 mJ/cm 2 .}

(2) Formation of adhesive layer The adhesive layer 16 is formed by directly applying a composition that forms the adhesive layer 16 on the other surface of the base film 12, or by applying an adhesive layer on the surface of the release film 18. A method of applying and forming a composition that forms the adhesive layer 16 and then transferring it onto the other surface of the base film 12, and applying a composition that forms the adhesive layer 16 on the surface of the first release film. After the substrate film 12 is formed, a second release film is attached, and one of the release films is peeled off and transferred onto the other surface of the base film 12 . The pressure-sensitive adhesive layer 16 can be formed by forming a composition layer by each method and then drying and curing the composition. When the composition is cured, the reactive functional group of the (meth)acrylic polymer reacts with the reactive group of the cross-linking agent to form a cross-linked structure.

The same coating method as used for forming the hard coat layer 14 can be used to apply the composition for forming the pressure-sensitive adhesive layer 16 . In addition, surface treatments such as corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment may be applied before coating.

The drying and curing steps are not particularly limited as long as the solvent or the like used in the coating liquid can be removed and cured, but it is preferable to carry out at a temperature of 60 to 150° C. for about 20 to 300 seconds. In particular, the drying temperature is preferably 100-130°C. The adhesive layer 16 may be formed before or after the hard coat layer 14 is formed.

(Characteristics of hard coat film)
According to the hard coat film 10 having the above configuration, the base film 12 contains polyimide, and the pressure-sensitive adhesive layer 16 contains a (meth)acrylic polymer, a cross-linking agent, and a triazine compound represented by the above formula (1). and, and the indentation elastic modulus E-IT(a) of the adhesive layer 16 is 290 N/mm ² or more and 1600 N/mm ² or less, so that the adhesive layer It has a high surface hardness that gives an excellent pencil hardness even with a hardness of 16, and has flexibility to withstand repeated bending. In addition, even in a high-temperature environment such as 60° C., excellent adhesion to the adherend can be maintained.

The hard coat film 10 can be bent with an inner diameter (diameter) of 10 mm due to the above configuration. In addition, it can be bent with an inner diameter (diameter) of 8 mm. In addition, it can be bent with an inner diameter (diameter) of 6 mm. Therefore, the hard coat film 10 can be suitably used for a flexible display that is bent with an inner diameter (diameter) of 10 mm or less. Moreover, it can be suitably used for a flexible display that is bent with an inner diameter (diameter) of 8 mm or less. Moreover, it can be suitably used for a flexible display that is bent with an inner diameter (diameter) of 6 mm or less.

The hard coat film 10 can be used as a cover window of a flexible display as a substitute for a glass substrate that has been mainly used in the past. Examples of flexible displays include foldable displays and rollable displays that can be rolled into a cylinder.

The flexible display is composed of a hard coat film 10 arranged on the surface of the display with an adhesive layer 16 interposed therebetween. The flexible display is bendable with an inner diameter (diameter) of 10 mm before the hard coat film 10 is arranged. In addition, it can be bent with an inner diameter (diameter) of 8 mm. In addition, it can be bent with an inner diameter (diameter) of 6 mm. Even the flexible display provided with the hard coat film 10 can be bent with an inner diameter (diameter) of 10 mm. In addition, it can be bent with an inner diameter (diameter) of 8 mm. In addition, it can be bent with an inner diameter (diameter) of 6 mm.

[Other embodiments]
The hard coat film according to the present invention is not limited to the configuration of the hard coat film 10 according to the embodiment described above. Other embodiments will be described below.

FIG. 2 shows a hard coat film 20 according to another embodiment. The hard coat film 20 has a base film 12, a hard coat layer 14 formed on one surface of the base film 12, and an adhesive layer 16 formed on the other surface of the base film 12. . The hard coat film 20 has a release film 18 on the surface of the adhesive layer 16 (on the surface of the adhesive layer 16 on which the base film 12 is not arranged). The hard coat film 20 has a protective film 24 arranged on the surface of the hard coat layer 14 (on the surface of the hard coat layer 14 on which the base film 12 is not arranged) with an adhesive layer 22 interposed therebetween. When the protective film 24 is provided on the surface of the hard coat layer 14, the surface of the hard coat layer 14 is protected during handling and the occurrence of scratches can be suppressed.

The hard coat film 20 differs from the hard coat film 10 in that it has a protective film 24 on the surface of the hard coat layer 14 via the pressure-sensitive adhesive layer 22, and is otherwise the same as the hard coat film 10. , and the description of the same configuration is omitted.

(Protective film)
The protective film 24 can prevent the surface of the hard coat layer 14 from being scratched during handling such as continuous processing by a roll process or bonding of the hard coat film 20 to a flexible display. be. The protective film 24 is attached to the surface of the hard coat layer 14 via the adhesive layer 22 . The protective film 24 is peeled off from the surface of the hard coat layer 14 together with the adhesive layer 22 after processing. Therefore, in the adhesive layer 22, the adhesive force between the protective film 24 and the adhesive layer 22 is stronger than the adhesive force between the hard coat layer 14 and the adhesive layer 22. 22 is adjusted to allow interfacial peelable adhesion.

Materials constituting the protective film 24 include, for example, polyethylene terephthalate resin, polyester resin such as polyethylene naphthalate resin, polycarbonate resin, poly(meth)acrylate resin, polystyrene resin, polyamide resin, polyimide resin, polyacrylonitrile resin, polypropylene resin, Polyolefin resins such as polyethylene resins, polycycloolefin resins, and cycloolefin copolymer resins, polyphenylene sulfide resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl alcohol resins, and the like. The material that constitutes the protective film 24 may be composed of only one of these, or may be composed of a combination of two or more. Among these resins, polyethylene terephthalate resins, polyimide resins, polycarbonate resins, poly(meth)acrylate resins, polycycloolefin resins, and cycloolefin copolymer resins are more preferable from the viewpoint of optical properties, durability, and the like.

The protective film 24 may be composed of a single layer composed of a layer containing one or more of the above polymeric materials, or a layer containing one or more of the above polymeric materials and a layer containing this layer. It may be composed of two or more layers, such as a layer containing one or more polymeric materials different from.

The thickness of the protective film 24 is not particularly limited, but may be in the range of 2-500 μm, or in the range of 2-200 μm.

(Adhesive layer for protective film)
The adhesive that forms the adhesive layer 22 is not particularly limited, and an acrylic adhesive, a silicone adhesive, a urethane adhesive, or the like can be preferably used. In particular, an acrylic pressure-sensitive adhesive is suitable as a pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer 22 because of its excellent transparency and heat resistance. The acrylic pressure-sensitive adhesive is preferably formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a cross-linking agent.

(Meth)acrylic polymers are homopolymers or copolymers of (meth)acrylic monomers. (Meth)acrylic monomers include alkyl group-containing (meth)acrylic monomers, carboxyl group-containing (meth)acrylic monomers, and hydroxyl group-containing (meth)acrylic monomers.

Examples of alkyl group-containing (meth)acrylic monomers include (meth)acrylic monomers having an alkyl group having 2 to 30 carbon atoms. The alkyl group having 2 to 30 carbon atoms may be linear, branched, or cyclic. More specifically, the alkyl group-containing (meth)acrylic monomer includes, for example, isostearyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylic acid ) Decyl acrylate, isononyl (meth) acrylate, nonyl (meth) acrylate, isooctyl (meth) acrylate, octyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, ( meth)pentyl acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, propyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, etc. is mentioned.

Carboxyl group-containing (meth)acrylic monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate. The carboxyl group may be located at the end of the alkyl chain or in the middle of the alkyl chain.

Examples of hydroxyl group-containing (meth)acrylic monomers include hydroxyllauryl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxyhexyl (meth)acrylate, and hydroxybutyl (meth)acrylate. , hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, and the like. The hydroxyl group may be located at the end of the alkyl chain or in the middle of the alkyl chain.

The (meth)acrylic monomer forming the (meth)acrylic polymer may be one of the above, or may be a combination of two or more.

Examples of cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, metal chelate-based cross-linking agents, metal alkoxide-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, and melamine-based cross-linking agents. . The cross-linking agent may be used alone or in combination of two or more.

The pressure-sensitive adhesive composition may contain other additives in addition to the (meth)acrylic polymer and the cross-linking agent. Other additives include cross-linking accelerators, cross-linking retarders, tackifying resins (tackifiers), antistatic agents, silane coupling agents, plasticizers, release aids, pigments, dyes, wetting agents, thickeners. , ultraviolet absorbers, preservatives, antioxidants, metal deactivators, alkylating agents, flame retardants and the like. These are appropriately selected and used according to the application and purpose of use of the pressure-sensitive adhesive.

Although the thickness of the adhesive layer 22 is not particularly limited, it is preferably in the range of 1 to 10 μm. More preferably, it is in the range of 2-7 μm.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the above-described embodiment, the surface of the base film 12 may be subjected to surface treatment. good too. Various functional layers such as a gas barrier property improving layer, an antistatic layer, and an oligomer block layer may be provided in advance on the surface of the base film 12 before forming each layer. Further, another hard coat layer may be provided between the base film 12 and the adhesive layer 16 .

The present invention will be described in detail below using examples and comparative examples.

[Preparation of sample]
<Preparation of composition 1 for forming hard coat layer>
UV curable resin composition "Unidic ESS-620" (manufactured by DIC, urethane acrylate resin, solvent: ethyl acetate, solid content concentration 79.3% by mass) per 100 parts by mass, photopolymerization initiator "Omnirad 127" (IGM Resins B.V.) was added, and ethyl acetate was added so as to give a solid content concentration of 31% by mass, thereby preparing composition 1 for forming a hard coat layer.

<Preparation of composition 2 for hard coat layer formation>
Ultraviolet curable resin composition "Z-878-17HL" (manufactured by Aica Kogyo, urethane acrylate resin, solvent: propylene glycol monomethyl ether, solid content concentration 50% by mass) fluorine-containing compound "X-71-1203M" (Shin-Etsu Chemical Industrial product, perfluoroalkyl group-containing (meth)acrylate, solid content concentration 20%) is added, and propylene glycol monomethyl ether is added so that the solid content concentration is 33% by mass, to prepare composition 2 for forming a hard coat layer. did. The solid content of the fluorine-containing compound was 0.1% by mass with respect to the total 100% by mass of the solid content of the UV-curable resin composition and the solid content of the fluorine-containing compound.

<Preparation of adhesive layer-forming composition 1>
(Meth)acrylic polymer solution 1 (solvent: ethyl acetate, solid content concentration: 24.2% by mass, reactive functional group: carboxyl group, amount of reactive functional group per 100 g of polymer: 83.0 mmol/100 g) Per 100 parts by mass, 0.03 parts by mass of an epoxy-based cross-linking agent (Mitsubishi Gas Chemical "TETRAD-C", epoxy equivalent: 10.25 g / eq), a triazine compound (Shikoku Kasei "VD-5", 5.0 parts by mass of a diaminotriazine derivative having a triethoxysilyl group) was added, and butyl acetate was added so that the solid content concentration was 18% by mass, thereby preparing a composition 1 for forming an adhesive layer.

<Preparation of adhesive layer forming composition 2>
(Meth) acrylic polymer solution 2 (solvent: ethyl acetate, solid content concentration 33.9% by mass, reactive functional group: carboxyl group, amount of reactive functional group per 100 g of polymer: 55.4 mmol/100 g) 100 0.05 parts by mass of an epoxy cross-linking agent ("TETRAD-C" above) and 5.0 parts by mass of a triazine compound ("VD-5" above) are added to the parts by mass, and the solid content concentration is Butyl acetate was added so as to be 18% by mass to prepare a composition 2 for forming an adhesive layer.

<Preparation of adhesive layer forming composition 3>
To 100 parts by mass of the above (meth)acrylic polymer solution 2, 0.05 parts by mass of an epoxy-based cross-linking agent (the above "TETRAD-C") is added so that the solid content concentration is 18% by mass. Butyl acetate was added to prepare a composition 3 for forming an adhesive layer. No triazine-based compound was used.

(Example 1)
<Preparation of base film with hard coat layer>
Polyimide film "OT2(h)" (manufactured by TAIMIDE TECH. INC., indentation modulus of elasticity 6070 N/mm ² , thickness 50 µm) was coated with composition 1 for forming a hard coat layer using a wire bar so as to have a predetermined thickness. After coating and drying at 80° C. for 60 seconds, an electrodeless (microwave) lamp was used to irradiate ultraviolet light at a light intensity of 110 mJ/cm ² to form a hard coat layer. Thus, a base film with a hard coat layer of Example 1 was produced.

<Production of adhesive film>
On the release surface of release film 1 ("HY-US20A" manufactured by Higashiyama Film Co., Ltd., silicone-based PET release film, thickness 50 μm), a baker-type film applicator is used to form a pressure-sensitive adhesive layer to a predetermined thickness. After applying composition 1 and heating at 120 ° C. for 2 minutes, release film 2 (Higashiyama Film "HY-S10", silicone A release surface of a PET release film (thickness: 50 μm) was attached. After that, it was cured at 40° C. for 3 days to prepare an adhesive film of Example 1 having an adhesive layer between the release film 1 and the release film 2 .

<Preparation of hard coat film>
By peeling off one release film of the prepared adhesive film and bonding the adhesive layer of the adhesive film to the surface of the polyimide film in the prepared base film with a hard coat layer, the hard of Example 1 having an adhesive layer A coated film was produced.

(Examples 2-3)
A hard coat film of Example 2 having an adhesive layer was produced in the same manner as in Example 1, except that the thickness of the adhesive layer was changed in the production of the adhesive film. The base film with a hard coat layer has the same structure as in Example 1.

(Examples 4-5)
In the preparation of the adhesive film, the adhesive layer-forming composition 2 was used instead of the adhesive layer-forming composition 1, the thickness of the adhesive layer-forming composition 2 was set to a predetermined thickness, and the heating conditions were 110°C. Hard coat films of Examples 4 and 5 having an adhesive layer were produced in the same manner as in Example 1 except that the curing conditions were set to room temperature (23° C.) for 7 days. The base film with a hard coat layer has the same structure as in Examples 1-3.

(Examples 6-7)
A substrate film with a hard coat layer was produced in the same manner as in Examples 2 and 3, except that Hard Coat Layer-Forming Composition 2 was used instead of Hard Coat Layer-Forming Composition 1. Drying conditions for the hard coat layer were 80° C.×60 seconds, and irradiation conditions were a high-pressure mercury lamp (light intensity 190 mJ/cm ² ). Hard coat films of Examples 6 and 7 having an adhesive layer were produced by laminating together in the same manner as in Example 1 using the prepared base film with a hard coat layer and an adhesive film. The pressure-sensitive adhesive layer has the same structure as in Examples 2-3.

(Examples 8-9)
In the preparation of the adhesive film, the adhesive layer-forming composition 2 was used instead of the adhesive layer-forming composition 1, the thickness of the adhesive layer-forming composition 2 was set to a predetermined thickness, and the heating conditions were 110°C. A pressure-sensitive adhesive film was produced in the same manner as in Examples 6 and 7, except that the curing conditions were set at room temperature (23° C.) for 7 days. Hard coat films of Examples 8 and 9 having an adhesive layer were produced by laminating together in the same manner as in Example 1 using the produced base film with a hard coat layer and an adhesive film. The base film with a hard coat layer has the same structure as in Examples 6-7, and the pressure-sensitive adhesive layer has the same structure as in Examples 4-5.

(Comparative example 1)
A hard coat film of Comparative Example 1 having an adhesive layer was produced in the same manner as in Example 4, except that the thickness of the adhesive layer was changed. The base film with a hard coat layer has the same structure as in Examples 1-5.

(Comparative example 2)
A hard coat film of Comparative Example 2 having an adhesive layer was produced in the same manner as in Example 1, except that the thickness of the adhesive layer was changed. The base film with a hard coat layer has the same structure as in Examples 1-5.

(Comparative Example 3)
A hard coat film of Comparative Example 3 having an adhesive layer was prepared in the same manner as in Example 3, except that the adhesive layer-forming composition 3 was used instead of the adhesive layer-forming composition 2 in the production of the adhesive film. was made. The base film with a hard coat layer has the same structure as in Examples 1-5.

[Evaluation method]
Using the prepared base film with a hard coat layer (no adhesive layer), the thickness of the hard coat layer, the indentation hardness H-IT (h) of the hard coat layer, the pencil hardness of the hard coat layer, the minimum hard coat layer Bending diameter was measured. Also, using the produced adhesive film, the thickness of the adhesive layer and the indentation elastic modulus E-IT(a) of the adhesive layer were measured. Further, using the prepared hard coat film (with an adhesive layer), the adhesive strength of the adhesive layer and the pencil hardness of the hard coat film were measured to examine the bending resistance of the hard coat film.

(Thickness of hard coat layer)
The thickness of the hard coat layer of the prepared substrate film with the hard coat layer was measured by spectral interferometry using a thickness measurement system "Filmetrics F20" manufactured by Filmetrics.

(Indentation hardness H-IT (h) of hard coat layer)
The prepared base film with a hard coat layer was cut into 15 mm × 15 mm, and an instant adhesive (“Aron Alpha Fast-acting Versatile” manufactured by Toagosei Co., Ltd.) was applied to a glass plate (20 mm × 20 mm, thickness 2 mm). A measurement sample was obtained by adhering the film side to the glass. The obtained measurement sample is fixed to a dedicated sample fixing table so that the hard coat layer side is in contact with the indenter. A Berkovich indenter (triangular pyramidal diamond indenter, edge-to-edge angle of 115°) was pressed into the measurement sample, and a load-unload test was performed. Then, the indentation hardness (H-IT(h)) of the hard coat layer was obtained by analyzing the test data. The maximum indentation load was 0.2 mN, the maximum load holding time was 10 seconds, and the unloading ratio used in the analysis was 70%.

(Pencil hardness of hard coat layer)
The prepared base film with a hard coat layer was cut into 15 mm × 15 mm, and an instant adhesive (“Aron Alpha Fast-acting Versatile” manufactured by Toagosei Co., Ltd.) was applied to a glass plate (20 mm × 20 mm, thickness 2 mm). A measurement sample was obtained by adhering the film side to the glass. The pencil hardness of the hard coat layer surface of the obtained measurement sample was measured. It was measured by the method specified in JIS K 5600-5-4 using a pencil hardness tester (manufactured by Tester Sangyo). The test load was 1 kg, and the test was repeated while changing the hardness of the pencil.

(Minimum bending diameter of hard coat layer)
A measurement sample was obtained by cutting the produced substrate film with a hard coat layer into a size of 30 mm×90 mm.
Both short sides of the obtained measurement sample were fixed to a durability tester "DLDM111LH" (manufactured by Yuasa System Equipment Co., Ltd., a U-shaped stretch tester with no load on the upper body) so that the hard coat layer side was bent to the outside. , flexed 100,000 times at a reciprocating speed of 60 spm (60 times of flexing per minute), and then visually confirmed. A bending test was repeated with an initial bending diameter (inner diameter/diameter) of 2 mm, and after bending 100,000 times, the measurement sample was visually checked for whitening or cracking. When whitening or cracking occurred in the measurement sample, the bending diameter was increased by 1 mm. This was repeated, and the maximum bending diameter at which no whitening or cracks occurred in the measurement sample was taken as the evaluation value. However, a new measurement sample was used each time the bending diameter was changed.

(Thickness of adhesive layer)
The thickness of the pressure-sensitive adhesive layer was obtained by subtracting the thickness of the release film from the total thickness of the pressure-sensitive adhesive film using a thickness measuring machine "TH-104" manufactured by Tester Sangyo.

(Indentation modulus E-IT (a) of adhesive layer)
First, the indentation modulus of a PEEK (polyetheretherketone) film was measured. A PEEK film with a thickness of 8 μm (“APTIV2000” manufactured by VICTREX) was cut into 15 mm × 15 mm, and an instant adhesive (“Aron Alpha Fast-acting Versatile” manufactured by Toagosei Co., Ltd.) was applied to a glass plate (20 mm × 20 mm, thickness 2 mm). After coating and adhering to the glass, the PEEK film is brought into contact with the indenter, fixed to a dedicated sample fixing table, and using "Nanoindenter G200" manufactured by Agilent Technologies, based on the ISO14577 Standard method, A Berkovich indenter (triangular pyramidal diamond indenter, edge-to-edge angle of 115°) was indented at room temperature to perform a load-unload test, and the indentation elastic modulus of the PEEK film was obtained by analyzing the test data. The maximum indentation load was 2 mN, the maximum load holding time was 30 seconds, and the unloading ratio used in the analysis was 70%. The indentation modulus of the PEEK film was 5200 N/mm ² .

Next, one of the release films is peeled off from the produced adhesive film, and the exposed adhesive layer is covered with PEEK (polyetheretherketone) having a thickness of 8 μm and an indentation elastic modulus of 5200 N/mm ² by the nanoindentation method. After affixing to a film (“APTIV2000” manufactured by VICTREX), the other release film was peeled off, and the exposed adhesive layer was affixed to a glass plate (20 mm×20 mm, thickness 2 mm). A sample size of 20 mm×20 mm was cut to match the glass plate to obtain a measurement sample.
The obtained measurement sample is fixed to a dedicated sample fixing table so that the PEEK film is in contact with the indenter, and using Agilent Technologies "Nanoindenter G200", Berkovich at room temperature based on ISO14577 Standard method. An indenter (triangular pyramidal diamond indenter, edge-to-edge angle of 115°) was pushed into the upper surface of the measurement sample to perform a load-unload test. Then, the indentation elastic modulus (E-IT(a)) of the pressure-sensitive adhesive layer was obtained by analyzing the test data. The maximum indentation load was 2 mN, the maximum load holding time was 30 seconds, and the unloading ratio used in the analysis was 70%.

(Adhesive strength of adhesive layer)
The prepared hard coat film was cut into a size of 25 mm in width and 150 mm in length, and after peeling off the release film, a hand roller was applied to the polyimide film (manufactured by Toray DuPont "Kapton 200V", thickness 50 μm) with the adhesive layer. It was crimped using After storing the cut sample for 1 hour, according to the method of JIS Z 0237 (2009), using Shimadzu Corporation's precision universal testing machine "AUTOGRAPH AGS-1kNX, 50N load cell", peel speed 300 mm / min, peel angle 180 °. The adhesive strength of the adhesive layer to the polyimide film was measured under the conditions of .
Two conditions were adopted for storage and measurement. In the first condition, the sample was stored at room temperature (23°C) for 1 hour and then measured at 23°C. In the second condition, after storing the sample at 60°C for 1 hour using a constant temperature dryer, it was immediately placed in a precision universal testing machine without cooling, and the measurement was performed under the environment of 60°C.

(Pencil hardness of hard coat film)
Peel off the release film on the surface of the pressure-sensitive adhesive layer of the prepared hard coat film, attach it to a test table (glass plate, thickness 5 mm), and use a pencil hardness tester (manufactured by Tester Sangyo) to measure JIS K 5600-5. -4 by the method specified. The test load was 1 kg, and the test was repeated while changing the hardness of the pencil.

(Flex resistance of hard coat film)
The release film on the surface of the pressure-sensitive adhesive layer of the prepared hard coat film was peeled off, attached to a super birefringent PET film "SRF" (manufactured by Toyobo, thickness 80 μm), and cut into 30 mm × 90 mm to obtain a measurement sample. .
Both short sides of the obtained measurement sample were fixed to a durability tester "DLDM111LH" (manufactured by Yuasa System Equipment Co., Ltd., a U-shaped stretch tester with no load on the upper body) so that the hard coat layer side was bent to the outside. , bending diameter (inner diameter/diameter) of 10 mm, reciprocating speed of 60 spm (60 bendings per minute), and repeated bending test of 100,000 times. Visually confirm the measurement sample after the test, no whitening or cracking, and no peeling or peeling of the adhesive layer. The occurrence of was marked with "x".
[Evaluation results]

Table 1 below shows the results of each evaluation along with the configurations of the hard coat layer and the pressure-sensitive adhesive layer.

In Comparative Example 1, the indentation modulus E-IT (a) of the pressure-sensitive adhesive layer is less than 290 N/mm ² , and the indentation hardness H-IT (h) of the hard coat layer in the base film with the hard coat layer and the hard coat Even if the pencil hardness of the layer is high, the provision of the adhesive layer reduces the pencil hardness of the hard coat layer (from 3H to 2H). On the other hand, in each example, the indentation elastic modulus E-IT(a) of the adhesive layer was 290 N/mm ² or more, and a large decrease in the pencil hardness of the hard coat layer was suppressed even when the adhesive layer was provided. , and has excellent pencil hardness even with an adhesive layer.

In Comparative Example 2, the indentation elastic modulus E-IT (a) of the adhesive layer exceeded 1600 N/mm ² , and accordingly, the adhesive layer lifted in the bending resistance test (the bending resistance was x). On the other hand, in each example, the indentation elastic modulus E-IT(a) of the pressure-sensitive adhesive layer is 1600 N/mm ² or less, and the flex resistance is also excellent.

Since Comparative Example 3 does not contain a triazine compound in the adhesive composition, the adhesive force remains at a small value of less than 9.0 N/25 mm at 23°C and 60°C. In particular, the adhesive strength at 60°C is significantly reduced. On the other hand, in each example, the adhesive layer was composed of a cured product of a composition containing a triazine compound, and a large adhesive strength of 9.0 N/25 mm or more was obtained at both 23°C and 60°C. It is

On the other hand, in each example, the pressure-sensitive adhesive layer contains a diaminotriazine derivative having an alkoxysilyl group, and the indentation elastic modulus E-IT(a) is 290 N/mm ² or more and 1600 N/mm ² or less. . Correspondingly, the base film with a hard coat layer provided with an adhesive layer maintains a high pencil hardness of 3H or more as well as a high resistance to heat, like the base film with a hard coat layer before the adhesive is provided. Shows flexibility. In addition, the adhesive layer exhibits high adhesive strength and maintains high adhesive strength even in a high temperature environment such as 60°C.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.

10 Hard coat film 12 Base film 14 Hard coat layer 16 Adhesive layer 18 Release film 20 Hard coat film 22 Adhesive layer 24 Protective film

Claims (6)

placed on the surface of the flexible display,
a base film, a hard coat layer formed on one surface of the base film, and a pressure-sensitive adhesive layer formed on the other surface of the base film,
The base film contains a polyimide resin,
The pressure-sensitive adhesive layer is formed from a cured product of a pressure-sensitive adhesive composition containing a (meth)acrylic polymer, a cross-linking agent, and a triazine compound represented by the following general formula (1),
^The indentation modulus E-IT (a ) is 290 N/mm ² or more and 1600 N/mm ² or less.

In formula (1), X represents an alkylene group, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 2. The alkylene group of X includes the case where a substituent is attached and the case where it contains a heteroatom in the main chain. 2. The hard coat film for a flexible display according to claim 1, wherein the hard coat layer has an indentation hardness H-IT (h) of 300 N/mm ² or more and 550 N/mm ² or less, measured by a nanoindentation method. . 3. The hard coat film for a flexible display according to claim 1, wherein the hard coat layer has a thickness of 0.5 [mu]m or more and 10.0 [mu]m or less. The hard coat film for a flexible display according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer has a thickness of 5.0 µm or more and 50.0 µm or less. The hard coat film for a flexible display according to any one of claims 1 to 4, which has a protective film on the surface of the hard coat layer. A flexible display, wherein the hard coat film for a flexible display according to any one of claims 1 to 5 is arranged on the surface of the display via the pressure-sensitive adhesive layer.

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