Optical laminate and display member using the same

Abstract

To provide an optical laminate enabling efficient manufacturing while suppressing yellowness, and having excellent abrasion resistance even with a thinner hard coat layer, and a display member using the same.SOLUTION: An optical laminate includes: a transparent substrate including polyimide; and a hard coat layer formed on one side of the transparent substrate. The hard coat layer is composed of a cured film of a composition including a (meth)acrylate compound, an organic compound having a thiol group, a pigment configured to absorb light having a wavelength of 550-650 nm and a silsesquioxane compound. A yellowness index YI is 2.5 or lower, measured in accordance with JIS K 7373:2006. A mixture amount of the silsesquioxane compound is 1.0-30.0 mass% based on all components of the composition other than a solvent.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical laminate and a display member using the same.

Background Art

[0002] Electronic devices equipped with foldable display devices are commercially available. In conventional non-foldable electronic devices, glass has been used as the outermost protective film. However, in foldable electronic devices, it is necessary to form a protective film from a material that is resistant to repeated bending. In recent years, a glass film with excellent flexibility called ultra-thin glass has sometimes been used as the protective film for foldable electronic devices. However, due to the brittleness peculiar to glass, a hard coat film in which a hard coat layer is laminated on a transparent base material made of a resin film is often used. As the transparent base material of the hard coat film used for the foldable display device, a transparent polyimide (CPI) film with excellent mechanical strength is suitable.

[0003] For example, Patent Document 1 describes a configuration of an optical laminate that can be used for a foldable organic EL display device, which has a function of replacing the cover glass of the organic EL display device and includes a flexible surface protection layer, a polarizer, and an optical compensation layer in this order. As a specific example, Patent Document 1 describes a protective film in which a hard coat layer is formed from a composition for forming a hard coat layer containing an acrylate compound on a transparent polyimide film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The mechanical strength of the transparent polyimide film is in a trade-off relationship with the yellowness index YI. Considering the usage form of the foldable display device, when using a transparent polyimide film with high mechanical strength, the YI value of the transparent polyimide film also increases, which impairs the color tone of the displayed image. In order to reduce the YI value of the transparent polyimide film, it is necessary to add a layer colored blue separately from the hard coat layer. However, when providing a colored layer separately from the hard coat layer, there are problems that the manufacturing process and the amount of materials used increase, and the yield rate decreases as the manufacturing process increases.

[0006] In addition, with the improvement of the flexibility of the foldable display device, thinning of the hard coat film is desired. However, simply thinning it may deteriorate the scratch resistance, and it may not be possible to obtain the scratch resistance required for the outermost surface protection.

[0007] Therefore, an object of the present invention is to provide an optical laminate capable of efficiently manufacturing while suppressing the yellowness index, and having excellent scratch resistance even when the hard coat layer is thinned, and a display member using the same.

Means for Solving the Problems

[0008] The optical laminate according to the present invention includes a transparent base material made of polyimide and a hard coat layer formed on one surface of the transparent base material. The hard coat layer is composed of a cured film of a composition containing a (meth)acrylate compound, an organic compound having a thiol group, a dye that absorbs light having a wavelength of 550 to 650 nm, and a silsesquioxane compound. The yellowness index YI measured in accordance with JIS K 7373:2006 is 2.5 or less, and the blending amount of the silsesquioxane compound is 1.0 to 30.0% by mass of all components other than the solvent of the composition.

[0009] The display member according to the present invention includes the above optical laminate and is foldable.

Effects of the Invention

[0010] The present invention can provide an optical laminate that can be efficiently manufactured while suppressing yellowness and has excellent scratch resistance even when the hard coat layer is made thin, and a display member using the same.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] FIG. 1 is a cross-sectional view schematically showing an optical laminate according to an embodiment.

[0013] The optical laminate 10 includes a transparent substrate 1 and a hard coat layer 2 laminated on one surface of the transparent substrate 1. The optical laminate 10 can be used as a protective film provided on the outermost surface of an electronic device (such as a smartphone or a tablet) having a foldable display device.

[0014] (Transparent Substrate) The transparent substrate 1 is a film that serves as the base of the optical laminate 10. A transparent polyimide film that is transparent and has excellent mechanical strength is used as the transparent substrate 1 so as to be suitable for use in foldable electronic devices. The thickness of the transparent substrate 1 is not particularly limited, but is preferably 10 to 200 μm.

[0015] The surface of the transparent substrate 1 may be subjected to a surface modification treatment in order to improve the adhesion to the hard coat layer 2. Examples of the surface modification treatment include alkali treatment, corona treatment, plasma treatment, sputtering treatment, application of a surfactant or a silane coupling agent, Si vapor deposition, and the like.

[0016] (Hard Coat Layer) The hard coat layer 2 is a layer for imparting hardness to the optical laminate, and can be formed by applying and curing a composition for forming a hard coat layer containing a (meth)acrylate compound, an organic compound having a thiol group, a dye that absorbs light having a wavelength of 550 to 650 nm (hereinafter also simply referred to as "dye"), and a silsesquioxane compound. In order to make the optical laminate 10 thinner, the thickness of the hard coat layer 2 is less than 10 μm, preferably 2 to 8 μm, and more preferably 2 to 5 μm. If the thickness of the hard coat layer 2 is less than 2 μm, the hardness of the hard coat layer may be insufficient. If the thickness of the hard coat layer 2 is 10 μm or more, it is not preferable because it is disadvantageous for thinning the optical laminate 10.

[0017] ((meth)acrylate compound) (meth)acrylate compounds are compounds that polymerize and cure upon irradiation with active energy rays such as ultraviolet rays and electron beams. For example, monofunctional, bifunctional, or trifunctional or higher (meth)acrylate monomers can be used. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryloyl" is a general term for both acryloyl and methacryloyl.

[0018] Examples of monofunctional (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphate (meth)acrylate, ethylene oxide-modified phosphate (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide-modified phenoxy (meth)acrylate, propylene oxide-modified phenoxy (meth)acrylate, nonylphenol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, propylene oxide-modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolythylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, 2-adamantane,Examples of adamantyl acrylate derivatives mono(meth)acrylates such as adamantyl acrylate having a monovalent mono(meth)acrylate derived from adamantane diol can be mentioned.

[0019] Examples of bifunctional (meth)acrylate compounds include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl glycol hydroxypivalate di(meth)acrylate and the like.

[0020] Examples of (meth)acrylate compounds having three or more functional groups include tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and glycerin tri(meth)acrylate; trifunctional (meth)acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate; polyfunctional (meth)acrylate compounds having three or more functional groups such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate; polyfunctional (meth)acrylate compounds in which a part of these (meth)acrylates is substituted with an alkyl group or ε-caprolactone; and acrylic polymers having a weight average molecular weight of 20,000 to 30,000 in which a plurality of (meth)acryloyl groups and hydroxyl groups are introduced into the main chain, and the like.

[0021] In addition, urethane (meth)acrylate can also be used as the active energy ray curable resin. Examples of urethane (meth)acrylate include those obtained by reacting a (meth)acrylate monomer having a hydroxyl group with a product obtained by reacting a polyester polyol with an isocyanate monomer or prepolymer.

[0022] Examples of urethane (meth)acrylate include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer, and the like.

[0023] The above-mentioned active energy ray-curable resin may be used alone or in combination of two or more. Further, it may be a monomer or a partially polymerized oligomer in the above-mentioned active energy ray-curable resin and the composition for forming a hard coat layer.

[0024] Examples of commercially available products that can be used as the (meth)acrylate compound include, for example, Light Acrylate PE-3, TMP-A, DPE-6A, UV-curable acrylic polymer SMP-250AP, SMP-550AP (manufactured by Kyoeisha Chemical Co., Ltd.).

[0025] (Organic compound having a thiol group) The organic compound having a thiol group functions as a curing aid, improves the curability of the (meth)acrylate compound, and contributes to the improvement of the surface hardness. By the organic compound having a thiol group, a sulfide bond is introduced into the resin matrix, so that the flexibility of the hard coat layer 2 can be improved and curl can be reduced.

[0026] The blending amount of the organic compound having a thiol group is preferably 0.5 to 9.0% by mass based on all components other than the solvent of the composition for forming the hard coat layer. When the blending amount of the organic compound having a thiol group is less than 0.5%, the improvement in surface hardness and flexibility and the effect of reducing curl become weak, which is not preferable. Further, when the blending amount of the organic compound having a thiol group exceeds 9.0%, the effect of improving flexibility and reducing curl is further improved, but the surface hardness decreases, which is not preferable.

[0027] Examples of the organic compound having a thiol group include 1,4-bis(3-mercaptobutyryloxy)butane, pentaerythritol tetrakis(3-mercaptobutyrate), 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione, trimethylolpropane tris(3-mercaptobutyrate), etc. Commercially available products that can be used as the organic compound having a thiol group include, for example, Karenz MT (registered trademark) BD-1 and PE-1 (manufactured by Showa Denko K.K.).

[0028] (Dye) The dye absorbs light with a wavelength of 550 to 650 nm to color the hard coat layer 2 blue, offset the yellowness of the transparent base material 1 made of polyimide, and reduce the yellowness index (YI) of the entire optical laminate 10. As the dye, dyes, pigments, nano metals, etc. can be used. The compound that can be used as the dye is not particularly limited, but for example, 1-hydroxy-4-toluidinoanthraquinone (quinizarin blue) can be used. The blending amount of the dye is 0.001 to 0.200 parts by mass, preferably 0.001 to 0.015 g, based on 100 parts by mass of the (meth)acrylate compound. When the blending amount of the dye is less than 0.001 part by mass based on 100 parts by mass of the (meth)acrylate compound, the coloring of the hard coat layer 2 becomes insufficient and the yellowness of the optical laminate 10 cannot be reduced. Further, when the blending amount of the dye exceeds 0.200 parts by mass based on 100 parts by mass of the (meth)acrylate compound, the blueness of the optical laminate 10 becomes too strong and the color tone of the displayed image is impaired.

[0029] (Silsesquioxane compound) The silsesquioxane compound is a polymer compound having a siloxane bond (-Si-O-Si-) as a main skeleton and having an organic group, and is represented by the composition formula of [(RSiO 1.5 ) n . In this embodiment, a silsesquioxane compound containing a (meth)acryloyl group is used as the organic group R. Since the silsesquioxane compound contains a (meth)acryloyl group, the (meth)acrylate compound and the silsesquioxane compound are bonded by radical polymerization to form a resin matrix. By using the (meth)acrylate compound and the silsesquioxane compound in combination, it is possible to obtain the scratch resistance required for the outermost surface protection while thinning the hard coat layer 2. The blending amount of the silsesquioxane compound is 1.0 to 30.0% by mass of all components other than the solvent of the composition for forming the hard coat layer. When the blending amount of the silsesquioxane compound is less than 1.0% by mass, the scratch resistance becomes insufficient when the hard coat layer 2 is thinned to 10 μm. When the blending amount of the silsesquioxane compound exceeds 30.0% by mass, the inorganic component increases too much, so the flexural resistance deteriorates. The compound that can be used as the silsesquioxane compound is not particularly limited, but commercially available products that can be used include, for example, AC-SQ SI-20, MAC-SQ SI-20, and MAC-SQHDM of Toagosei Co., Ltd.

[0030] (Leveling agent) In order to improve the surface flatness of the coating film of the composition for forming the hard coat layer, a leveling agent may be blended. The blending ratio of the leveling agent is preferably 0.05 to 5.0% by mass of all components other than the solvent of the composition for forming the hard coat layer. The compound that can be used as the leveling agent is not particularly limited, but commercially available products that can be used include, for example, KY-1203 (manufactured by Shin-Etsu Chemical Co., Ltd.), RS-75, and RS-56 (manufactured by DIC Corporation).

[0031] (Ultraviolet absorber) In addition, in order to suppress the deterioration of the dye and improve the light resistance of the optical laminate 10, an ultraviolet absorber may be added to the composition for forming the hard coat layer. As the ultraviolet absorber, for example, compounds of benzophenone type, benzotriazole type, triazine type, oxalic acid anilide type, and cyanoacrylate type can be used. Since the ultraviolet absorber is added to suppress the deterioration of the dye, an absorber having absorbability to light in the wavelength range that contributes to the deterioration of the dye in the ultraviolet region is used. However, when the composition containing the ultraviolet absorber is cured, if the amount of ultraviolet absorption by the ultraviolet absorber becomes too large, the curing of the composition may be insufficient, and the surface hardness of the obtained optical film may be insufficient. Therefore, it is preferable to use an ultraviolet absorber whose absorption wavelength range in the ultraviolet region is different from the absorption wavelength range of the photoinitiator in the ultraviolet region. The blending ratio of the ultraviolet absorber is preferably 0.1 to 5.0% by mass of all components other than the solvent of the composition for forming the hard coat layer. The compounds that can be used as the ultraviolet absorber are not particularly limited, but commercially available products that can be used include, for example, Tinuvin (registered trademark) 477 and 479 (manufactured by BASF).

[0032] (Photoinitiator) In order to enable the composition for forming a hard coat layer to be polymerized and cured by ultraviolet irradiation, it is preferable to blend a photoinitiator in the composition for forming a hard coat layer. As the photoinitiator, radical polymerization initiators such as acetophenone-based, benzophenone-based, thioxanthone-based, benzoin, and benzoin methyl ether can be preferably used. Specific examples of the radical polymerization initiator include α-hydroxyalkylphenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,2-ethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothioxanthone, etc. Among these, one kind may be used alone, or two or more kinds may be used in combination. The blending ratio of the photoinitiator is preferably 0.1 to 10.0% by mass of all components other than the solvent of the composition for forming a hard coat layer. The compounds that can be used as the photoinitiator are not particularly limited, but commercially available products that can be used include, for example, Omnirad (registered trademark) 184, 651, and TPO H (manufactured by BASF).

[0033] In addition, a solvent may be added to the composition for forming the hard coat layer to adjust the viscosity. For example, it is preferable to dilute with a solvent so that the solid content concentration in the composition for forming the hard coat layer is 30 to 50%. Specific examples of the solvent include ethers such as dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, and phenetole; ketones such as acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, and methylcyclohexanone; esters such as ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, n-pentyl acetate, and γ-butyrolactone; and cellosolves such as methyl cellosolve, cellosolve, butyl cellosolve, and cellosolve acetate. These may be used alone or in combination of two or more kinds.

[0034] In addition, the composition for forming the hard coat layer may contain metal oxide fine particles for the purpose of adjusting the refractive index and imparting hardness. Examples of the metal oxide fine particles include zirconium oxide, titanium oxide, niobium oxide, antimony trioxide, antimony pentoxide, tin oxide, indium oxide, indium tin oxide, and zinc oxide.

[0035] In addition, the composition for forming the hard coat layer may contain any one of silicon oxide, a fluorine-containing silane compound, fluoroalkylsilazane, fluoroalkylsilane, a fluorine-containing silicon-based compound, and a perfluoropolyether group-containing silane coupling agent to impart water repellency and / or oil repellency and enhance antifouling properties.

[0036] As other additives, an antifouling agent, an antifoaming agent, an antioxidant, a light stabilizer, a photosensitizer, a conductive material, etc. may be added to the composition for forming the hard coat layer.

[0037] The coating method of the composition for forming the hard coat layer is not particularly limited. For example, it can be coated using a spin coater, roll coater, reverse roll coater, gravure coater, microgravure coater, knife coater, bar coater, wire bar coater, die coater, dip coater, spray coater, applicator, or the like.

[0038] (Yellowness) The yellowness YI of the optical laminate 10 according to the present embodiment is 2.5 or less, and does not impair the color tone of the display image when used in a display device. The yellowness YI is a value measured in accordance with JIS K 7373:2006. As a method for reducing the yellowness YI of the optical laminate, a method of providing a blue colored layer in addition to the transparent substrate and the hard coat layer, or a method of coloring the polyimide film itself blue can be considered. However, when a blue colored layer is provided in addition to the transparent substrate and the hard coat layer, there are problems that the manufacturing process and the amount of material used increase, and the yield rate decreases as the manufacturing process increases. Further, when coloring the polyimide film itself, an existing transparent polyimide film cannot be used, the choice of materials is limited, and the cost required for the polyimide film may increase. On the other hand, in the present embodiment, since the hard coat layer 2 contains a dye to reduce the yellowness, a colored layer other than the transparent substrate 1 and the hard coat layer 2 is unnecessary, and a polyimide film used as the transparent substrate 1 can be selected from existing products.

[0039] (Pencil hardness) The pencil hardness of the surface of the hard coat layer 2 of the optical laminate 10 according to the present embodiment is 4H or more. The pencil hardness is a value measured in accordance with the former JIS K 5400:1900. When the pencil hardness of the surface of the hard coat layer 2 is 4H or more, the optical laminate 10 can be suitably used as a protective film for a display device.

[0040] (Scratch resistance) The optical laminate 10 according to the present embodiment has steel wool on the surface of the hard coat layer 2 at 1.5 kg / cm 2After performing a scratch resistance test in which it was brought into contact at the pressure of and reciprocated 4,500 times, no scratches were visually observed on the hard coat layer 2, and the contact angle of pure water on the surface of the hard coat layer 2 after the scratch resistance test was 100° or more. The optical laminate 10 according to the present embodiment is less likely to be scratched even when the surface is rubbed with a finger, cloth, etc. during use, and has excellent scratch resistance.

[0041] (Flexural resistance) After a bending test in which the optical laminate 10 according to the present embodiment was bent 200,000 times with a radius of 1.5 mm so that the hard coat layer 2 was on the inside, and after a bending test in which it was bent 200,000 times with a radius of 2.5 mm so that the hard coat layer 2 was on the outside, no cracks occurred in the hard coat layer 2. Since the hard coat layer 2 of the optical laminate 10 according to the present embodiment has good flexural resistance, it is suitable as a protective film for a foldable display device.

[0042] As described above, the optical laminate 10 according to the present embodiment has a reduced yellowness by containing a dye that absorbs light with a wavelength of 550 to 650 nm in the hard coat layer 2. With this configuration, since there is no need to provide a coloring layer other than the transparent substrate 1 and the hard coat layer 2, the optical laminate 10 can be efficiently manufactured without increasing the manufacturing process and the materials used. Further, the optical laminate 10 according to the present embodiment has a hard coat layer 2 formed of a cured film of a hard coat layer-forming composition containing (meth)acrylate, a thiol compound, and a predetermined amount of a silsesquioxane compound on a transparent substrate 1 made of a polyimide film having excellent mechanical properties. As a result, even when the hard coat layer is made thinner than 10 μm, it is excellent in surface hardness, scratch resistance, and flexural resistance, so it is suitable for use as a protective film provided on the outermost surface of a foldable display device, and is effective for thinning the protective film and a display member using the same.

[0043] The optical laminate 10 according to this embodiment can be used to form a display member by laminating one or more of a polarizing plate, a retardation plate, a touch panel, and a display panel. As the display panel, for example, an organic EL panel can be preferably used. Further, the display member according to this embodiment can be used to form an electronic device including a foldable display device.

Example

[0044] Hereinafter, examples of specifically implementing the present invention will be described.

[0045] The materials shown below were mixed at the ratios shown in Table 1 to prepare compositions for forming hard coat layers according to Combinations 1 to 6. The unit of the compounding ratio shown in Table 1 is mass%. · Acrylate compound: A mixture obtained by mixing Lite Acrylate PE-3A (pentaerythritol triacrylate, manufactured by Kyoeisha Chemical Co., Ltd.) and UV curable acrylic polymer SMP-250AP (manufactured by Kyoeisha Chemical Co., Ltd.) at a mass ratio of 7:1 · Organic compound having a thiol group: Karenz MT (registered trademark) PE1 (manufactured by Showa Denko K.K.) · Dye 1-Hydroxy-4-toluidinoanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd.) · Silsesquioxane compound MAC-SQ HDM (manufactured by Toagosei Co., Ltd.) · Levelling agent: KY-1203 (manufactured by Shin-Etsu Chemical Co., Ltd.) · Ultraviolet absorber Tinuvin 479 (manufactured by BASF) · Photoinitiator Omnirad 184 (manufactured by IGM RESIN)

[0046]

Table 1

[0047] (Examples 1 to 3, Comparative Examples 2, 4 to 7) The composition for forming a hard coat layer having the composition shown in Table 2 was diluted with methyl isobutyl ketone, applied to one surface of a clear polyimide film having a thickness of 50 μm so that the film thickness after curing became the value in Table 2, dried, and then irradiated with ultraviolet rays to form a hard coat layer.

[0048] (Comparative Example 1) The same clear polyimide film as that used in Example 1 was used as the film according to Comparative Example 1.

[0049] (Comparative Example 3) The composition for forming a hard coat layer according to Composition 2 in Table 1 was diluted with methyl isobutyl ketone, applied to one surface of a clear polyimide film having a thickness of 50 μm so that the film thickness after curing became the value in Table 2, dried, and then irradiated with ultraviolet rays to form a hard coat layer. Next, on the other surface of the clear polyimide film, a composition for forming a colored layer having the following composition diluted with a solvent was applied, dried, and then irradiated with ultraviolet rays to form a colored layer. The coating amount of the composition for forming a colored layer was adjusted so that the film thickness after curing of the colored layer became 0.5 μm. <Colored layer material composition> · Dimethylol dicyclopentane diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 72.5% by mass · 3-(acryloyloxy)-2-hydroxypropyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 24.2% by mass · 1-hydroxy-4-toluidinoanthraquinone (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.1% by mass, · Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 3.0% by mass, · PC4300 (manufactured by DIC Corporation) 0.2% by mass

[0050] (Total light transmittance, haze) The total light transmittance and haze were measured in accordance with JIS K 7105 using NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0051] (Yellowness) Using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation), the transmittance of the films according to each example and each comparative example was measured, and the yellowness index YI was calculated under the conditions of a C light source and a 2-degree field of view.

[0052] (Adhesion) Based on the cross-cut test specified in the former JIS K 5400 General Test Methods for Paints, 100 squares of 1 mm 2 were formed in each hard coat layer. An adhesive tape (CT405AP-24, manufactured by Nichiban Co., Ltd.) was attached to the formed squares, uniformly pressed using a spatula, and then the adhesive tape was peeled off in the 90° direction. The number of hard coat layers remaining without peeling was visually confirmed.

[0053] (Pencil hardness) Using a pencil (uni, manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens type scratching tester (HA-301, manufactured by Tester Sangyo Co., Ltd.), the pencil hardness of the surface of the hard coat layer was measured under the conditions of a load of 750 g and a scratching speed of 0.5 mm / sec. The test was repeated while changing the hardness of the pencil, and the surface of the hard coat layer was visually observed. The maximum hardness at which no scratches were observed was taken as the evaluation value.

[0054] (Scratch resistance) The prepared film was set on a Kagaku-Shinbun type friction fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.), and a scratch resistance test was performed by bringing a steel wool (Bonstar #0000) into contact with the surface of the hard coat layer at a pressure of 1.5 kg / cm 2 and reciprocating 4500 times. After the scratch resistance test, the surface of the hard coat layer was visually observed to confirm the presence or absence of scratches. Also, 1 μL of pure water was dropped onto the surface of the hard coat layer of the film before and after the scratch resistance test, and the angle formed between the surface of the hard coat layer and the surface of the droplet was measured. If the pure water contact angle after the scratch resistance test is 100° or more, the scratch resistance is good.

[0055] (Flexural resistance) Samples were prepared by cutting the fabricated film into 30-mm widths, and these samples were set in a clam shell type bending tester (DR11MR-CS-t, manufactured by Yuasa System Devices Co., Ltd.) so that the hard coat layer faced inward, and a bending test was performed 200,000 times with a radius of 1.5 mm. After the bending test, the surface of the hard coat layer was visually observed to evaluate the presence or absence of cracks. Similarly, samples prepared in the same manner were set in the tester so that the hard coat layer faced outward, and after a bending test was performed 200,000 times with a radius of 2.5 mm, the surface of the hard coat layer was visually observed to evaluate the presence or absence of cracks.

[0056] Table 2 shows the configurations and evaluation results of each example and each comparative example.

[0057]

Table 2

[0058] For the hard coat films according to Examples 1 to 3, although the thickness of the hard coat layer was thinned to 5 μm, both the scratch resistance and the abrasion resistance were excellent. Further, for the hard coat films according to Examples 1 to 3, the yellowness index YI was suppressed to 2.5% or less, and the bending resistance, the surface hardness, and the adhesion of the hard coat layer to the transparent substrate were all good.

[0059] On the other hand, for the hard coat film according to Comparative Example 2, since the layer containing the dye was not provided, the yellowness index YI could not be reduced.

[0060] For the hard coat film according to Comparative Example 3, the layer containing the dye is provided separately from the transparent substrate and the hard coat layer, and since it is necessary to laminate the cured film on each of both surfaces of the transparent substrate, compared with the examples, the manufacturing process and the materials used increase, which is disadvantageous in terms of manufacturing efficiency.

[0061] The hard coat films according to Comparative Examples 4 and 5 were formed using a composition for forming a hard coat layer (Composition 3) that does not contain a silsesquioxane compound. As in Comparative Example 4, when the thickness of the hard coat layer was 10 μm, the scratch resistance was good. However, as in Comparative Example 5, when the thickness of the hard coat layer was reduced to 5 μm to form a thin film, the scratch resistance deteriorated. In addition, in the hard coat film according to Comparative Example 8, more than 10 scratches were confirmed on the surface of the hard coat layer after the scratch resistance test.

[0062] The hard coat film according to Comparative Example 6 was formed using a composition for forming a hard coat layer containing a silsesquioxane compound. However, since the blending amount of the silsesquioxane compound was small, both the scratch resistance and the abrasion resistance deteriorated.

[0063] The hard coat film according to Comparative Example 7 had deteriorated flex resistance because the blending amount of the silsesquioxane compound contained in the composition for forming the hard coat layer was too large.

Industrial Applicability

[0064] The present invention can be used as a hard coat film for a display device, and is particularly suitable as a protective film for a foldable display device.

Explanation of Symbols

[0065] 1 Transparent substrate 2 Hard coat layer 10 Optical laminate

Claims

1. a transparent substrate made of polyimide, and a hard coat layer formed on one surface of the transparent substrate, the hard coat layer is composed of a cured film of a composition containing a (meth)acrylate compound, an organic compound having a thiol group, a dye that absorbs light having a wavelength of 550 to 650 nm, and a silsesquioxane compound, the yellowness index YI measured in accordance with JIS K 7373:2006 is 2.5 or less, an optical laminate, wherein the blending amount of the silsesquioxane compound is 1.0 to 30.0% by mass of all components other than the solvent of the composition.

2. the pencil hardness of the surface of the hard coat layer is 4H or more, After the abrasion resistance test in which steel wool is brought into contact with the surface of the hard coat layer at a pressure of 1.5 kg / cm ２ and reciprocated 4,500 times, there is no scratch on the hard coat layer, and the pure water contact angle on the surface of the hard coat layer is 100° or more. the hard coat layer does not crack after a bending test of being bent 200,000 times at a radius of 1.5 mm so that the hard coat layer is on the inside, and after a bending test of being bent 200,000 times at a radius of 2.5 mm so that the hard coat layer is on the outside, the optical laminate according to Claim 1.

3. a foldable display member including the optical laminate according to Claim 1 or 2.

Images